DESlGfl OF 

smw cm 

STRUCTURES 

1978 

Engineering Technology Pertaining 

Primarily to the Design of Small 

Canal Structures of Less Than 

100-Cubic-Feet-Per-Second Capacity 

UNITED STATES 

DEPARTMENT OF THE INTERIOR 

BUREAU OF RECLAMATION 

A. J. Aisenbrey, Jr. 

R. B. Hayes 

H. J. Warren 

D. L. Winsett 

R. B. Young 

Denver, Colorado 
“As the Nation’s principal conservation agency, the Department of the 

Interior has basic responsibilities for the wise use and conservation of 

our land and water, energy and minerals, fish and wildlife, and park 

and recreation resources. The Department also has a major 

responsibility for American Indian reservation communities and for 

people who live in Island Territories under U.S. administration.” 

REVISED REPRINT 1978 

UNITED STATES GOVERNMENT PRINTING OFFICE 

DENVER : 1974 

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 

and the Bureau of Reclamation, Denver Federal Center, Denver, Colorado 80225, Attention: 922, 

Stock Number 024-003-00126-l 

IV 
Preface 

“Let man have dominion over the earth and 

let the earth bring forth grass, the herb yielding 

seed, and the fruit tree yielding fruit after its 

kind.” So is it written in the Book of Genesis. 

The availability of water has determined the 

course of empires in many civilizations. When 

made available, its use for irrigating crops has 

been practiced for thousands of years by many 

peoples of the world. But only since the late 

1800’s has man applied scientific knowledge to 

watering drylands to increase crop production. 

The wise use of soil and water resources has 

changed millions of acres of once barren 

wasteland and desert into productive farms 

supporting prosperous communities. 

Development of water resources by the 

Government to provide irrigation water for the 

arid lands of the western United States was 

initiated when the Reclamation Act of 1902 

was passed during President Theodore 

Roosevelt’s administration. Because of his 

strong leadership ability and contempt for 

abusive exploitation of our natural resources, 

he became regarded as the steward of the 

public’s welfare. 

Reclamation engineers and scientists through 

the years have developed canal structures for 

i rriga tion systems which can effectively 

perform their intended functions. This 

publication has been prepared to illustrate the 

application of canal structures having design 

discharge capacities up to 100 cubic feet per 

second. Several types of canal structures have 

been standardized for this capacity range and 

are presented herein. Structure sizes required 

to discharge these flows are relatively small; 

however, engineering principles used in their 

design are also applicable to canal structures of 

greater capacity. 

The need for this publication became 

apparent by the number of requests received, 

both foreign and domestic, during the past 

years. It is intended that this book provide the 

design engineer with a source of condensed 

information for use as a guide in efficiently 

designing small canal structures. The design 

engineer must realize, however, that sound 

engineering principles and judgment must be 

exercised in the selection and utilization of the 

structures, and that the use of design methods, 

procedures, and other information herein 

remains his responsibility. 

There are occasional references to 

proprietary materials or products in this 

publication. These must not be construed in 

any way as an endorsement by the Bureau of 

Reclamation since such endorsement cannot be 

made for proprietary products or processes of 

manufacturers or the services of commercial 

finns for advertising, publicity, sales, or other 

purposes. 

The text of this publication was prepared by 

a design team comprised of Bureau of 

Reclamation engineers from the Engineering 

and Research Center at Denver, Colorado, 

under the overall direction of H. G. Arthur, 

Director of Design and Construction. 

The text was coordinated and edited by A. 

J. Aisenbrey, Jr., Civil Engineer, Hydraulic 

Structures Branch. Team members who 

authored the presentations for the canal 

structures were R. B. Hayes, D. L. Winsett, and 

R. B. Young, Civil Engineers, Hydraulic 

Structures Branch and H. J. Warren, General 

Engineer, Engineering Reference Branch. 

Editorial guidance, final review, and 

preparation of the manuscript for publication 
VI PREFACE 

was performed by W. E. Foote, General 

Engineer, of the Technical Services Branch. 

The revised reprint was edited by R. D. 

Mohrbacher, General Engineer, Technical 

Services and Publications Branch. 

Many photographs used in the book were 

obtained through the cooperation of various 

Bureau of Reclamation offices and assembled 

for selection by R. S. Dinsmore, Civil 

Engineering Technician, Hydraulic Structures 

Branch under the guidance of D. L. Winsett. 

Illustrations were prepared in the Drafting 

Branch, Division of Engineering Support by L. 

L. McGhghy and W. D. Anderson under the 

guidance of W. W. Groom and direction of B. 

F. Wilson. 

Special recognition is given to Dr. J. W. Hilf, 

Chief, Division of Design, G. N. Thorsky, 

Chief, Division of Engineering Support; A. T. 

Lewis, Chief, Hydraulic Structures Branch; G. 

W. Birch, Head, Canal Structures and Bridges 

Section and engineers in this section for their 

support, guidance, and counsel. 

The engineers who authored and edited this 

publication wish to express a special thanks to 

the staff of the Media Unit who worked many 

long and hard hours to obtain a quality 

publication. Other thanks are directed to the 

printing assistants, production unit personnel, 

and those who coordinated the work flow. 

Food and fiber, essential to the well-being 

of mankind begins with the smallest viable 

seed, which when its fruit is harvested may 

provide substance to placate the hunger of 

man. 

To believe that even the smallest seed will grow 

is 

To believe in the force of will. 

To transform the desert into a living oasis is 

To transform despair into hope, 

That all mankind may be enriched 

And share in the power of Charity. 
Contents 

Preface . . . . . . . . . . . . . . . . 

Chapter 

A. 

SW riotI 

I-General Requirements 

Design Considerations 

GENERAL REQUIREMENTS 

l-l. Purpose . . . . . . . . . . . . . 

l-2. Structures . . . . . . . . . . . . 

(a) Conveyance structures . . . 

(b) Regulating structures . . . 

(c) Water measurement structures 

(d) Protective structures’ : : : : 

(e) Structure components and 

appurtenances . . . . . . 

l-3. 0 ther requirements . . . . . . . 

(a) Canal . . . . . . . . . . . 

(b) Other structures . . . . . . 

(c) Soils exploration . . . . 

(d) Hydrology 

(e) Sedimentation : : : : : : : 

(f) Operation and maintenance . . . . . . . . . 

B. DESIGN CONSIDERATIONS 

l-4. General . . . . . . . . . 

1. Loads 

l-5. General . . . . . . . . . 

l-6. Dead load weights . . . . 

l-7. Operating deck uniform live 

loads . . . . . . . . . 

. . 

Page 

V 

and 

2 

2 

6 

6 

Chapter I-General Requirements and 

Design Considerations-Continued 

Sectiot2 

1-8. Lateral pressures ......... 

(a) Water ........... 

(b) Earth ........... 

(c) Construction and operating equipment wheel 

surcharge ........ 

(d) Ice ............ 

(e) Wind ........... 

l-9. Other pressures ......... 

(a) Uplift ........... 

(b) Hydraulic transients .... 

(c) Seismic .......... 

l-10. Wheel loads transmitted to 

buried conduit ......... 

(a) Highways ......... 

(b) Railroads ......... 

2. Stabilit.) 

l-l 1. Bearing capacity ......... 

1- 12. Sliding coefficient ........ 

1-13. Overturning ........... 

l-l 4. Percolation ........... 

3, Hydraulics 

l-l 5. Hydraulic control ........ 

1- 16. Hydraulic head losses ...... 

(a) Friction .......... 

(b) Transitions and bends ... 

1- 17. Discharge coefficients ...... 

(a) Orifice .......... 

(b) Weir ........... 

4. Structural Considerations 

Page 

7 

7 

7 

l-l 8. Reinforced concrete ....... 

(a) Allowable stresses ..... 

8 

8 

8 

9 

9 

9 

9 

9 

10 

10 

10 

10 

10 

10 

10 

10 

VII 
VIII 

Chapter I-General Requirements and 

Design Considerations-Continued 

Section 

l-l 9. 

(c) Minimum wall thickness’ 

(d) Fillets . . . . . . . 

(e) Cutoffs . . . . . . . . 

Structural steel and welding 

5. Cunul 

11 

11 

14 

14 

14 

l-20. Freeboard . . . . . . . . . 14 

l-21. Winter operation . . . . . 14 

l-22. Profile sheet . . . . . . . . . 14 

l-23. 

l-24. 

6. Forms ji~r Structures 

Monolithic concrete . . . . 

Precast concrete . . . . . . 

16 

16 

C. BIBLIOGRAPHY 

l-25. Bibliography . . . . . 17 

(b) Minimum reinforcement 

requirements 

Chapter II-Conveyance Structures 

A. GENERAL 

2-l. Purpose . , . . . . . _ . . . 

B. ROAD CROSSINGS 

2-2. Purpose and description . . . 

2-3. Application . . . . . . . . 

2-4. Advantages . . . . . . . . . 

2-5. Design considerations . . . . 

(a) Pipe 

(b) Transitions ’ : : : : : : 

(c) Pipe collars . . . . . 

(d) Canal erosion protection . . . . . . . 

2-6. Design example . . . . . 

(a) Given . . . . . . . . 

(b) Determine 

(c) Check of design. : : : : 

C. INVERTED SIPHONS 

2-7. Purpose and description . . . 

2-8. Application . . . . . . . . 

2-9. Advantages and disadvantages 

of inverted siphons . . . . . 

19 

19 

19 

21 

21 

21 

22 

22 

23 

23 

23 

23 

24 

24 

24 

26 

CONTENTS 

Chapter II-Conveyance StructuresContinued 

Section 

2-l 0. Structure components ...... 

(a) Pipe ........... 

(b) Transitions ........ 

(c) Pipe collars ........ 

(d) Blowoff structures ..... 

(e) Canal freeboard and 

erosion protection .... 

(f) Wasteways 

(g) Safety features ’ 1 1 1 1 1 1 

2-l 1. Hydraulic design considerations ............. 

2-l 2. Design procedure ........ 

2-l 3. Design example ......... 

(a) Given ........... 

(b) Determine ........ 

D. BENCH AND ELEVATED FLUMES 

2-14. Purpose and description ..... 

(a) General .......... 

(b) Bench flumes ....... 

(c) Elevated flumes ...... 

1. Hydraulic Considerations 

2-l 5. Flume section .......... 

b (a) Ratio- d .......... 

(b) Slope and velocity ..... 

(c) Freeboard ......... 

2-l 6. Transitions 

(a) Genera; : : : : : : : : : : 

(b) Inlet ........... 

(c) Outlet .......... 

(d) Freeboard ......... 

(e) Cutoffs .......... 

2. Structural Considerutions of a 

Rectangular Bench Flume 

2-l 7. Flume section .......... 

(a) Stability 

(b) Wall loads : : : : : : : : : 

(c) Concrete thickness ..... 

(d) Drainage ......... 

(e) Joints ........... 

(f) Safety requirements .... 

2-l 8. Design example ......... 

(a) Given ........... 

(b) Determine ........ 

Page 

26 

26 

27 

27 

27 

28 

28 

28 

28 

29 

29 

32 

32 

38 

38 

38 

38 

39 

39 

39 

40 

40 

40 

40 

41 

41 

41 

41 

41 

41 

41 

41 

41 

42 

42 

42 

42 
CONTENTS IX 

Chapter II-Conveyance Structures- Chapter II-Conveyance StructuresContinued Continued 

E. DROPS 

Section 

2-19. Function . . . . . . . . 

2-20. Hydraulic design . . . . . . . . 

2. Rectungular Inclined Drops 

2-21. Purpose and description . . . 

2-22. Advantages and disadvantages 

2-23. Structure components . . . . . 

(a) Upstream transitions . . . 

(b) Inlet to drop . . . . . 

(c) Rectangular inclined 

channel . . . . . . . . 

(d) Stilling pool . . . . . . . 

(e) Outlet . . . . . . . . . 

2-24. Percolation . . . . . . . . . . 

2-25. Design example of R. I. drop 

with control inlet and stilling pool outlet . . . . . . . 

(a) Given . . . . . . . . 

(b) Determine control inlet dimensions . . . 

(c) Determine hydraulic 

setting for stilling 

pool by using table 

2-1 

(d) Alternative method for ’ ’ . 

determining stilling 

pool invert elevation . . . . . . . . . 

2-26. Design example of R. 1. drop 

with check inlet and stilling pool outlet . . . . . . . . 

(a) Given . . . . . . . . . . 

(b) Determine check inlet 

dimensions 

(c) Determine hydraulic’ . . 

setting for stilling 

pool . . . . . . . . . 

(d) Determine additional 

dimensions . . . . . . 

2-27. Purpose and description . . 

(a) Type 1 

(b) Type 2 : : : : : : : : : : 

2-28. Advantages and disadvantages . . 

Page 

48 

50 

2-29. Type 1 pipe drop structure 

components . . . . . . . 

(a) Upstream transition . 

(b) Inlet . . . . . . . . . 

(c) Pipe 

50 

59 

59 

59 

59 

61 

61 

61 

61 

(d) Outlet transitions ’ : : : : : 

2-30. Type 1 pipe drop design considerations . . . . . . . . . 

(a) Bends . . . . . . . . . 

(b) Pipe cover . . . . . . . . 

(c) Percolation . . . . . . . 

(d) Freeboard . . . . . . 

2-3 1. Type 2 pipe drop structure 

components and design considerations 

(a) Baffled’outlkts ’ : : : : : : 

(b) Stilling pools 

62 

62 

62 

(c) Outlet transition 1 1 1 1 : 1 

(d) Design layout . . . . . . 

(e) Freeboard . . . . . . . 

2-32. Design example of a type 1 

pipe drop with a control and 

pipe inlet . . . . . . . . . . 

(a) Given . . . . . . . . . . 

(b) Determine . . . . . . . . 

63 F. CHUTES 

63 

64 

64 

64 

2-33. Purpose and description . . . . . 

1 . Open Channel Chute 

2-34. Design considerations . . . . . . 

(a) Manning’s coefficient 

of roughness(n) . . . . . 

(b) Transitions . . . . . . 

(c) Chute section . . . . 

(d) Trajectory 

65 

65 

(e) Stilling pool 1 : 1 1 1 1 1 1 

(f) Wave formation . . . . . . 

2-3 5. Design procedure . . . . . . . 

2-36. Design example . . . . . . . . . 

2. Pipe Chute 

65 

65 

65 

65 

2-37. Pipe chute . . . . . . . . . 

G. BIBLIOGRAPHY 

2-38. Bibliography . . . . . . . 

Scctiofz Page 

66 

66 

66 

66 

66 

66 

67 

67 

67 

96 

96 

98 

98 

98 

98 

98 

98 

99 

99 

101 

104 

104 

104 

105 

105 

106 

108 

115 

116 

121 

131 
X CONTENTS 

Chapter Ill-Regulating Structures Chapter Ill-Regulating StructuresContinued 

A. GENERAL 

secrion Page 

3-1. Regulating structures . . . . . 133 F. CHECK AND PIPE INLETS 

Set lion 

3-l 9. Description and purpose . . . 

3-20. Application . . . . . . . . . 

3-2 1. Design considerations 

(a) Upstream transitions 1 1 

(b) Protection . . . . . . 

(c) Inlet opening . . . . . 

(d) Sidewalls . . . . . . . 

(e) Headwall . . . . . . . 

(f) Floor of inlet box and 

pipe invert . . . . . 

(g) Walk planks . . . . . 

(h) Pipe diameter . . . . . 

(i) Pipe vents . . . . . . . 

3-22. Structure numbering . . . . 

3-23. Design example . . . . . . . 

(a) Assumptions . . . . . 

(b) Determine . . . . . . 

Page 

. 166 

. 166 

. 166 

. 166 

. 166 

. 166 

. 166 

. 168 

B. CHECKS 

3-2. Purpose and description . . . . 134 

3-3. Combination structures . . . . . 134 

3-4. Spacing . . . . . . . . . . . . 135 

3-5. Design considerations 

(a) Stability and percolation. : : 

136 

136 

(b) Stoplogs, gates, and 

deck . . . . . . . . . . 136 

(c) Head loss . . . . . . . . 136 

3-6. Design example . . . . . . . 136 

. 168 

. 168 

. 168 

. 168 

. 168 

. 168 

. 169 

. 169 

C. CHECK-DROPS 

3-7. Purpose and description . . . 139 

3-8. Design considerations . . . . . 139 

3-9. Application . . . . . . . . . . 140 

3-l 0. Design example . . . . . . . . 140 

G. CONTROL AND PIPE INLETS 

3-24. Description and purpose . 

3-25. Application . . . . . . . 

3-26. Design considerations 

(a) Upstream earth transition . . . . . . 

(b) Erosion protection . 

(c) Control notch . . . 

(d) Overflow sidewalls . 

(e) Headwall . . . . . 

(f) Width of inlet box . 

(g) Inlet invert elevation 

(h) Pipe diameter . . . 

3-27. Structure numbering . . . 

3-28. Design example . . . . . 

(a) Given . . . . . . 

(b) Determine . . 

. . . 170 

. . . 170 

. . . 170 

. . . 170 

. . . 171 

. . 171 

. . . 171 

. . . 171 

. . . 171 

. . . 171 

. . . 171 

. . 171 

. . . 173 

. . . 173 

. . . 173 

D. TURNOUTS 

3- 1 1. Purpose and description . 

3-l 2. Design considerations . . 

(a) Velocity . . . . 

(b) Percolation and stability 

(c) Hydraulics 

(d) Miscellaneous’ : : : : 

3-l 3. Turnouts without water measuremen t . . . . . . . 

3-14. Design example . . . . . 

3-l 5. Turnouts with measurement 

(a) Flow meters . . . . 

(b) Parshall flumes and 

weirs . . . . . . . 

(c) Constant-head orifice 

structures . . . . 

3-16. Design considerations . . . 

3-l 7. Design example . . . . . 

. 146 

. . 146 

. . 146 

. . 146 

. . 146 

. . 146 

. 146 

. . 146 

. . 149 

. . 149 

. . 150 

H. BIBLIOGRAPHY 

. . 150 

. . 151 

. . 154 

3-29. Bibliography . . . . . . . . . 178 

Chapter IV-Protective Structures 

E. DIVISION STRUCTURES A. GENERAL 

3-l 8. Purpose and description . . . . . 162 4-l. Purpose . . . . . . . . . . . . . 179 
CONTENTS 

Chapter IV-Protective StructuresContinued 

B. WASTEWAYS 

See tion PZgC 

4-2. Description . . . . . . . . . . 179 

4-3. 

4-4. 

4-5. 

4-6. 

4-7. 

4-8. 

4-9. 

4-10 

(a) Wasteway inlets ...... 179 

(b) Wasteway outlets ..... 180 

(c) Wasteway channel and 

channel structures .... 180 

(d) Appurtenant canal 

structures ........ 181 

Location and number ...... 181 

Wasteway capacity considerations 181 

(a) Spillway ’ : : : : : : : : : 181 

(b) Wasteway turnout gate ... 181 

(c) Wasteway outlet ...... 181 

(d) Natural drainage channels ........... 182 

Limitations ........... 182 

1. Side Channel Spillways 

General ............. 182 

Design considerations ...... 182 

(a) Overflow crest ....... 182 

(b) Side channel ....... 184 

(c) Wasteway turnout gate ... 184 

(d) Pool ........... 184 

(e) Pipe ........... 184 

(f) Wasteway outlet structure ........... 185 

(g) Percolation ........ 185 

(h) Protection ........ 185 

(i) Operation ......... 185 

Design example ......... 185 

(a) Assumptions ....... 185 

(b) Solution 185 

(c) Check of hydraulics’ : : : : 187 

2. Gated Wasteway Turnouts 

General ............. 189 

(a) Usage ........... 189 

(b) Wasteway capacity ..... 189 

(c) Types of gates ....... 189 

Hydraulics 

(a) Inlet 1 1 1 1 1 1 1 1 1 1 1 

190 

190 

(b) Slide gates ........ 190 

(c) Radial gates ........ 190 

(d) Trajectory ........ 191 

(e) Outlet .......... 192 

XI 

Chapter IV-Protective StructuresContinued 

SEC tion P+?tT 

4-l 1. Lifts and hoists ......... 192 

(a) Manually operated 

lifts ........... 192 

(b) Power-operated lifts 

or hoists ........ 192 

(c) Hydraulically controlled ......... 192 

4-l 2. Miscellaneous considerations ... 192 

(a) Protection ........ 192 

(b) Percolation ........ 192 

(c) Operation ......... 192 

4-l 3. Design example ......... 192 

(a) Assumptions ....... 192 

(b) Solution ......... 193 

3. Siphon Spillways 

4-14. General ............. 195 

(a) Usage ........... 195 

(b) Description ........ 195 

(c) Function 195 

(d) Appurtenances . : : : : : : 196 

4- 15. Design considerations ...... 196 

(a) General .......... 196 

(b) Capacity ......... 196 

(c) Head ........... 196 

(d) Entrance ......... 197 

(e) Crest ........... 197 

(f) Throat .......... 197 

(g) Downstream leg ...... 197 

(h) Siphon breaker ...... 197 

(i) Pool 197 

(j) Outlet transition 1 1 1 1 1 1 197 

(k) Protection ........ 197 

(1) Percolation ........ 198 

4-l 6. Design example ......... 198 

(a) Assumptions ....... 198 

(b) Solution ......... 198 

4. Check Inlet Wasteway 

Turnouts 

4-17. General ............. 201 

4-l 8. Design considerations ...... 202 

C. CROSS-DRAINAGE STRUCTURES 

4-l 9. General ............. 202 

(a) Siphon crossings ...... 202 

(b) Cross-drainage alternatives .......... 202 
XII 

Chapter IV-Protective StructuresContinued 

4-20. 

4-2 1. 

4-22. 

4-23. 

4-24. 

4-25. 

4-26. 

4-27. 

4-28. 

4-29. 

4-30. 

4-3 I. 

4-32. 

4-33. 

4-34. 

4-35. 

4-36. 

(c) Cross-drainage capacity 

1 . Culverts 

General . . . . . . . . . 

Alinemen t . . . . . . . . 

Profile . . . . . . . . . 

Conduit . . . . . . . . 

Inlet 

(a) Type’1 ’ 1 1 1 1 1 1 1 

(b) Type 2 . . . . . 

(c) Type 3 . . . . . . 

(d) Type 4 . . . . . 

(e) Precast concrete transitions 

(f) Earth transitions : : . 

Outlet . . . . . . . . . 

(a) Concrete transitions . 

(b) Outlet energy dissipators . . . . . . 

Hydraulics . . . . . . . 

(a) Design capacity . 

(b) Pipe velocity . . . 

(c) Pipe diameter . . . 

(d) Hydraulic control . . 

(e) Determination of inlet 

or outlet control . . 

(f) Inlet control hydraulics 

(g) Outlet control hydraulics . . . . . . . . 

Pipe collars . . . . . . . . 

Protection . . . . . . 

Design example . . . . . . 

(a) Assumptions . . . . 

(b) Solution . . . . . 

(c) Verification of hydraulics by the Bernoulli 

method . . . . . . 

2. Overchutes 

General . . . . . . . . . . . 215 

Alinemen t . . . . . . . . 216 

Profile . . . . . . . . . . . 216 

Capacity . . . . . . . . . 216 

Conduit . . . . . . . . . . . 216 

(a) Rectangular conduit . . 216 

(b) Pipe conduit . . . . 218 

Inlet types . . . . . _ . . 218 

Outlet types . . . . . . . . . 218 

Page 

203 

203 

203 

203 

204 

205 

205 

205 

205 

205 

205 

205 

206 

206 

206 

207 

207 

207 

207 

207 

209 

209 

209 

210 

210 

210 

211 

211 

213 

CONTENTS 

Chapter IV-Protective StructuresContinued 

SW rim Page 

(a) Concrete transitions .... 218 

(b) Outlet energy dissipators ........... 218 

4-37. Pipe overchute hydraulics .... 218 

(a) Inlet transition ...... 218 

(b) Pipe velocity ....... 220 

(c) Pipe diameter ....... 220 

(d) Pipe outlet ........ 220 

4-38. Concrete overchute hydraulics . . 221 

(a) Rectangular section .... 221 

(b) Critical flow ........ 221 

(c) Inlet transition ...... 221 

(d) Chute hydraulics ..... 221 

(e) Stilling pool ........ 222 

4-39. Other considerations ....... 224 

(a) Bank heights ....... 224 

(b) Protection ........ 224 

(c) Percolation ........ 224 

4-40. Design example ......... 224 

(a) Assumptions ....... 224 

(b) Solution ......... 225 

3. Druin In lets 

4-41. General ............. 230 

(a) Location ......... 230 

(b) Types ........... 231 

(c) Design capacity ...... 231 

(d) Canal bank ........ 232 

4-42. Pipe drain inlets ......... 232 

(a) Inlet ........... 232 

(b) Conduit .......... 233 

(c) Outlet 233 

(d) Percolation’ : : : : : : : : 233 

(e) Protection ........ 234 

4-43. Rectangular concrete drain 

inlet to earth section ...... 234 

(a) Inlet ........... 234 

(b) Flume .......... 236 

(c) Chute ........... 236 

(d) Outlet pool ........ 236 

(e) Percolation ........ 237 

(f) Protection ........ 237 

4-44. Other types of drain inlets .... 237 

(a) Rectangular concrete 

drain inlets to a 

concrete-lined canal ... 237 

(b) Gravel blanket drain 

inlet .......... 237 
CONTENTS 

Chapter IV-Protective StructuresContinued 

Section Pap 

4-45. Design example . . . . . . 237 

(a) Assumptions . . . . . 237 

(b) Solution . . . . . . . . 238 

D. BIBLIOGRAPHY 

4-46. Bibliography . . . . . . . . . 24 1 

Chapter V-Water Measurement 

Structures 

A. GENERAL 5-20. 

5-1. Types of measuring structures . . 243 

B. PARSHALL FLUMES 5-2 1. 

5-2. Description . . . . . . 

5-3. Advantages . . . . . . . . . . 

5-4. Disadvantages . . . . . . . . 

5-5. Size selection . . . . . . 

5-6. Design example with freeflow discharge . . . . . . . 

5-7. Design example with 

submerged-flow discharge . . 

5-8. Use of tables and figures 

for discharge and free-flow 

determinations . . . . . . . . 

(a) Free-flow discharge . . . 

(b) Submerged-flow discharge . . , . . . . 

(c) Head losses . . . . . 

C. MODIFIED PARSHALL FLUMES 

5-9. Description . . . . , . . . . . 

5-10. Determination of upstream 

canal water surface . . . . . . 

D. STILLING WELLS 

5-I 1. Description .......... 260 5-27. 

5-l 2. Design criteria ......... 260 5-28. 

E. WEIRS H. BIBLIOGRAPHY 

5- 13. Purpose and description . . . 260 5-29. Bibliography .......... 297 

244 

245 

245 

245 

246 

247 

248 

248 

248 

248 

259 

259 

XIII 

Chapter V-Water Measurement 

Sectiorl 

5-14. 

5-l 5. 

5-l 6. 

5-l 7. 

5-l 8. 

5-19. 

5-22. 

5-23. 

5-24. 

5-25. 

5-26. 

Structures-Continued 

PLlgCY 

Types of weirs .......... 260 

Types of flow .......... 261 

Application ........... 26 1 

Adjustable weirs ......... 262 

Advantages and disadvantages . . 262 

Requirements for accurate 

measurement .......... 266 

(a) Weir blade ........ 266 

(b) Wve 

(c) Approach’channelk- .... 

266 

weir relationship ..... 266 

(d) Head on weir ....... 273 

Head-discharge relationship .... 273 

(a) Rectangular and Cipolletti weirs ........ 273 

(b) V-notch weirs ....... 273 

Design example of selecting 

and setting a weir ........ 273 

(a) Requirements ....... 273 

(b) Weir selection ....... 273 

(c) Weir setting ........ 273 

F. WEIR BOXES 

Purpose and descrjption ..... 291 

Design considerations .... 291 

(a) Head discharge rela- ’ 

tionship ......... 29 1 

(b) Head losses ........ 291 

Design example ......... 291 

(a) Solution ......... 291 

G. OPEN-FLOW METERS 

Purpose and description ..... 295 

Design considerations ...... 295 

(a) Velocity 

(b) Requirements’for accu: ’ ’ ’ 

295 

rate flow measurement .......... 295 

(c) Size determination ..... 295 

(d) Head loss ......... 295 

Advantages ........... 296 

Disadvantages .......... 296 
XIV 

Chapter VI-Energy Dissipators 

A. GENERAL 

Section 

6-1. Energy dissipators . . . . . . . . 

B. BAFFLED APRON DROPS 

6-2. General . . . . . . . . . . . . . 

(a) Usage . . . . . . . . . . 

(b) Inlet control features . . . 

(c) Miscellaneous features . . . 

6-3. Design considerations . . . . . 

(a) General . . . . . . . . . . 

(b) Capacity . . . . . . . . . 

(c) Inlet . . . . . . . . . . . 

(d) Baffled apron dimensions . . . 

(e) Uplift stability . : : 1 . . . 

(f) Sliding stability . . . . . . 

(g) Miscellaneous considerations 

6-4. Design example . . . . . . . . . 

(a) Assumptions . . . . . . . 

(b) Solution . . . . . . . . . 

C. BAFFLED OUTLETS 

6-5. Purpose and description . . 

6-6. Hydraulic considerations . . . 

6-7. Sediment and debris . . . . . 

6-8. Protection . . . . . . . . 

6-9. Basin width design procedure . 

6-10. Design example . . . . . . . 

(a) Given . . . . . . . . . 

(b) Determination of the 

basin dimensions . . . 

(c) Determination of erosion protection re308 

309 

321 

321 

321 

321 

321 

321 

quirements . . . . . 322 

D. VERTICAL SLEEVE VALVE 

STILLING WELLS 

6-l 1. General . . . . . . . . . . . 

(a) Description . . . . . 

(b) Types of vertical sleeve 

valves . . . . . . . . 

(c) Usage of vertical sleeve 

valve stilling wells . . 

(d) Limitations . . . . . . 

6-12. Design considerations . . . . 

Page 

299 

299 

299 

300 

300 

301 

301 

301 

301 

(a) Inlet conditions . . . 

(b) Sleeve valve design . . 

(c) Hydraulic requirements 

(d) Well dimensions . . . 

(e) Armor plating . . _ . 

(f) Outlet transition . . . 

(g) Outlet protection . . 

6-l 3. Design example . . . . . . 

(a) Assumptions . . . . 

(b) Solution . . . . . . 

Page 

. . . 326 

. . . 327 

. . 327 

. . . 328 

. . . 330 

. . 330 

. . 330 

. . . 330 

. . . 330 

. . . 331 

302 

303 

303 

304 

304 

304 

304 

E. BIBLIOGRAPHY 

6- 14. Bibliography . . . . . . . 

Chapter VII-Transitions 

Erosion Protection 

. . 333 

and 

A. TRANSITIONS 

1. General 

7-l. 

7-2. 

Purpose and description ..... 335 

Types .............. 335 

(a) Inline canal structure 

transitions ........ 335 

(b) Cross-drainage pipe 

structure transitions ... 336 

2. Design Considerations for Pipe 

Structure Transitions 

7-3. 

7-4. 

7-5. 

7-6. 

322 

322 

323 

7-7. 

7-8. 

7-9. 

7-10. 

7-l 1. 

Hydraulic design ......... 336 

(a) Pipe submergence ..... 336 

(b) Head losses ........ 336 

(c) Water surface angle .... 342 

(d) Channel erosion ...... 342 

Cutoffs ............. 3 42 

Standardization ......... 342 

Type 1 transitions (brokenback) ............. 342 

Type 2 transition ........ 343 

Type 3 transitions ........ 344 

Type 4 transitions ........ 344 

Type 5 transitions ........ 345 

Earth transitions ......... 345 

B. EROSION PROTECTION 325 

325 

326 7-l 2. Purpose and description . . . . . 345 

Chapter VI-Energy DissipatorsCONTENTS 

Continued 

Section 
Chapter VII-Transitions and 

Erosion Protection-Continued 

Section Page 

7-l 3. Inverted siphons . . . . . . . 345 

7-14. Cross-drainage structures . . . 347 

7-15. Other structures . . . . . . . 347 

7-16 

C. BIBLIOGRAPHY 

Bibliography . . . . . . . . 347 

Chapter VIII-Pipe and 

Pipe Appurtenances 

A. GENERAL 

8-l. Pipe and pipe appurtenances 349 

8-2. Hydraulic head losses . . . 349 

6. PIPE 

8-3. 

8-4. 

8-5. 

8-6. 

8-7. 

8-8. 

8-9. 

Precast reinforced concrete 

pressure pipe . . . . . . _ 

Precast reinforced concrete 

culvert pipe . . . . . . . 

Corrugated-metal pipe . . . 

Asbestos-cement pressure 

pipe . . . . . . . . . . . 

Reinforced plastic mortar 

pressure pipe . . . . . . . 

Welded steel pipe . . . . . 

Other pipe . . . . . . . 

3.59 

359 

. 359 

. 359 

. 359 

. 361 

. 362 

C. PIPE APPURTENANCES 

8-10. 

8-l 1. 

Pipe collars and percolation . . . 362 

Pipe bends 

(a) Purpose and design con-. . . 

364 

siderations 

(b) Bends for precast con-’ f ’ ’ 

364 

8-12. 

8-13. 

Crete pipe . . . . . _ . . 365 

(c) Bends for asbestoscement pipe . . . . . . . 365 

(d) Bends for reinforced 

plastic mortar pipe . . . . 371 

(e) Bends for corrugatedmetal pipe . . . . . . . . 371 

Pipe embedment . . . . . . . . . 371 

Pipe joints . . . . . . . . . . 371 

CONTENTS xv 

Chapter VIII-Pipe and 

Pipe Appurtenances-Continued 

Section Pdge 

8-14. 

8-l 5. 

8-l 6. 

8-l 7. 

8-l 8. 

pressurepipe . . . . . . 371 

(c) Joints for culvert pipe . . . 372 

(d) Joints for corrugatedmetal pipe . . . . . . . . 373 

(e) Joints for asbestoscement pressure pipe . . . 373 

(f) Joints for reinforced 

plastic mortar pipe . . . . 373 

(g) Joints for welded 

steel pipe . . . . . . . . 373 

Pipe safety barrier . . . . . . . . 373 

Blowoff structures . . . . . . . . 375 

Air vents . . . . . . . . . . . . 375 

Step-type pipe tapers . . . . . 379 

Pipe earthwork . . . . . . . 379 

D. BIBLIOGRAPHY 

8-19. Bibliography . . . . . . . . . . 382 

Chapter IX-Safety 

9-1. 

9-2. 

General . . , . . . . . . . . . . 383 

Hazard exposure classification . . . . . . . . . . . . . . 383 

A. SAFETY DEVICES 

9-3. Types . . . . . . . . . . . . . 383 

Fencing . . . . . . . 

Guardrails . . . . . 

Warning signs . . . . 

Pipe safety barrier . . 

Safety nets . . . . . 

Safety cables . . . . 

Safety racks . . . . . 

Safety ladders . . . . 

. 384 

. 384 

. 393 

. 393 

. 393 

. 394 

. 394 

. 396 

(a) Purpose and design considerations . . . . . . . 371 

(b) Joints for precast reinforced concrete 

B. BIBLIOGRAPHY 

9-4. Bibliography . . . . . . . . . . 3 98 
XVI CONTENTS 

Appendix A-Glossary of Terms Appendix C-Computer Program 

SCCtiOtl Page See tion Page 

A- 1. List of symbols and abbrevia- C-l. Program 223-E3WSP . . . . . . . 413 

tions . . . . . . . . . . . . . 401 

Appendix B-Conversion Factors 

B-l. International System (SI 

metric)/U.S. Customary 

Conversion Factors . . . . . 409 

LIST OF TABLES 

Table 

2-l. 

2-2. 

2-3. 

2-4. 

2-5. 

2-6. 

2-7. 

3-1. 

3-2. 

5-1. 

Page Table 

Canal and lateral rectangular in- 5-2. 

clined drop dimensions and reinforcement . . . . . . . . 53 

Wasteway and drain rectangular 

inclined drop dimensions and 5-3. 

reinforcement . . . . . . . 56 

Type 1 pipe drop with earth outlet transition . . . . . . . . 70 

Type 1 pipe drop with concrete 5-4. 

outlet transition . . . . . . . 8 1 

Uniform flow in trapezoidal channels by Manning’s formula . . . 124 5-5. 

Uniform flow in trapezoidal channels by Manning’s formula . . . 127 

Uniform flow in circular sec- 5-6. 

tions flowing partly full . . . . 130 

Discharge of constant-head orifice turnout in cubic feet per 5-7. 

second, capacity 20 cfs . . . . . 155 

Discharge of constant-head ori- 6-1. 

fice turnout in cubic feet per 8-l. 

second, capacity 10 cfs . . . . . 156 

Free-flow discharge through 9-l. 

6-inch Parshail measuring 

flume in cubic feet per 

second . . . . . . . . . . . . 252 

Free-flow discharge through 

9-inch Parshall measuring 

flume in cubic feet per 

second . . . . . . . . . 

Free-flow discharge through 

Parshall measuring flumes, 

l- through g-foot size, in 

cubic feet per second . . . . 

Discharge of standard contracted 

rectangular weirs in cubic 

feet per second . . . . . . 

Discharge of standard Cipolletti 

weirs in cubic feet per 

second . . . . . . . . . . 

Discharge of standard suppressed 

rectangular weirs in cubic 

feet per second . . . . . . 

Discharge of 90’ V-notch weirs 

in cubic feet per second . . 

Recommended discharge . . . 

Friction losses for circular 

conduits . . . . . . . . . 

Safety fence classification . . 

Page 

253 

254 

275 

281 

288 

290 

301 

350 

384 

LIST OF FIGURES 

Figure Page Figure Page 

l-l. Open canal system supplying l-4. Fishing on Hungry Horse Reserirrigation water to citrus voir, Montana . . . . . . . . . 3 

groves, Gila Project, l-5. Irrigating sugar beets on the 

Arizona . . . . . . . . 2 Boise Project, Idaho . . . . . . 5 

l-2. Irrigating corn using siphon l-6. Sprinkler irrigation in the 

tubes, Red Willow Unit, Coachella Valley, California . . 5 

Nebraska . . . . . . . . 3 l-7. Irrigating fruit on the Yakima 

l-3. Boating on the Rogue River Project, Washington . . . . . . 5 

Project, Oregon . . . . . 3 
CONTENTS 

Figure 

1-8. General notes and minimum requirements for detailing 

reinforcement . . . . . . . 

1-9. Freeboard for canal banks and 

freeboard for hard surface, 

buried membrane, and earth 

linings . . . . . . . . . . 

1-I 0. Precast concrete transitions 

in various stages of comple tion . . . . . . . . . . 

l-1 1. Placing precast concrete transition . . . . . . . . . . . 

l-l 2. In-place precast concrete transition, partially backfilled . 

l-l 3. Precast concrete turnout inlet 

being lowered into position 

on mortar pad . . . . . . . 

1-14. Slide gate being operated to 

control flow through turnout 

2-l. Road crossing . . . . . 

2-2. Road crossing plan and section 

2-3. Jacking and threading pipe 

under roadway . . . . . . 

2-4. Inverted siphon plan and 

section . . . . . . . . . . 

2-5. Inverted siphon under construction . . . . . . . . . . . . 

2-6. Inverted siphon inlet transition and 60-inch-diameter 

precast concrete pipe . . . . 

2-7. Design of free-flow siphon 

inlets . . . . . . . . 

2-8. Preliminary layout of inverted siphon . . . . . . . 

2-9. Final layout of inverted 

siphon . . . . . . . . . . 

2-10. Concrete bench flume . . . . 

2-11. Concrete bench flume . . . 

2-l 2. Elevated flume crossing natural drainage . . . . . . . . 

2-13. Early day elevated flume . . . 

2-14. Concrete pipeline for bench 

construction . . . . . . . . 

2-l 5. Transition lengths . . . . . 

2- 16. Schematic profile of bench 

flume . . . . . . . . . . . 

2-l 7. Cross section of bench flume . 

2-18. Series of rectangular inclined 

drops . . . . . . . . . . . 

2-l 9. Rectangular inclined drop with 

. . 

. . 

. . 

. . 

. . 

. 

. . 

. . 

. . 

. . 

. . 

. . 

. . 

. . 

. 

. . 

. . 

. . 

. . 

. . 

. . 

. . 

. . 

. . 

. . 

control notch inlet . . . . . . . 48 

Page Figure 

12 

15 

16 

16 

16 

17 

17 

19 

20 

21 

25 

26 

2-20. Rectangular inclined drop . . . 

2-2 1. Rectangular inclined drop 

under construction . . . . . . . 

2-22. Rectangular inclined drop in 

operation . . . . . . . . . . . 

2-23. Pipe drop with baffled outlet 

and pipe collars . . . . . . . . 

2-24. Pipe drops . . . . . . . . . . 

2-25. Pipe drop with baffled outlet . . . 

2-26. Rectangular inclined droptype 1 . . . . . . . . . 

2-27. Rectangular inclined dropp 

type 2 . . . . . . . . 

2-28. Determination of sump elevation for type 1 pipe drop . . . 

2-29. Type 1 pipe drop with earth 

outlet transition . . . . . . . 

2-30. Type 1 pipe drop with concrete 

outlet transition 

26 

30 

31 

36 

39 

39 

39 

39 

40 

45 

46 

47 

48 

2-3 1. Type 1 pipe drop-plan and ’ ’ ’ 

sections . . . . . . . . . . . . 

2-32. Type 2 pipe drop-plan and 

sections . . . . . . . . . . . 

2-33. Typical rectangular chutes . . . 

2-34. Rectangular concrete chute on 

a steep slope . . . . . . . . 

2-35. Terminal wasteway with a rectangular inclined drop into 

a stilling pool . . . . . . . . 

2-36. Stilling pool and outlet portions of a spillway 

structure . . . . . . . . . . 

2-37. Energy loss in hydraulic jump . 

2-38. Tailwater and jump elevation 

curve . . . . . . . . . . . . 

2-39. Weep hole with gravel pocket . . 

2-40. Stilling pool with end sill . . . . . 

2-4 1. Surging in a stilling pool 

caused by unstable flow in 

a chute structure . . . . . . _ . 

2-42. Pulsating flow in steep chute . . . 

2-43. Unstable flow at shallow depth . . 

2-44. Theoretical waveless chute 

section . . . . . . . . . . . 

2-45. Criteria for slug flow . . . . . . . 

2-46. Shape and slope criteria for 

slug flow . . . . . . . . . . . 

2-47. Invert, water surface, and 

energy profiles of a chute 

strut ture . . . . . . . . . . . 

XVII 

Page 

48 

49 

49 

49 

50 

50 

51 

52 

68 

69 

80 

96 

97 

102 

103 

103 

103 

107 

109 

110 

111 

111 

112 

112 

112 

113 

114 

115 
XVIII CONTENTS 

Figure 

2-48. 

2-49. 

2-50. 

2-5 1. 

3-l. 

3-2. 

3-3. 

3-4. 

3-5. 

3-6. 

3-7. 

3-8. 

3-9. 

3-10. 

3-l 1. 

3-l 2. 

3-l 3. 

3-14. 

3-15. 

3-16. 

3-l 7. 

3-18. 

3-l 9. 

3-20. 

3-21. 

3-22. 

3-23. 

3-24. 

3-25. 

3-26. 

3-27. 

Wave sweeping through the outlet transition of a stilling pool . . . . . . . . . . 

Chute with stilling pool . . . 

Pipe chutes . . . . _ . . . . 

Stilling pool on pipe chute _ . 

Control notch maintains water 

surface above a drop inlet 

to a pipe structure . . . . . 

Concrete check structure . . . 

Check inlet to pipe structure . 

Check inlet to pipe structure . 

Standard check structures . . 

Standard check structures . . 

Operator removing stoplogs 

from a check-drop structure 

Drop structure using a weir 

for regulation . . . . . . 

Concrete check with slide gate 

Concrete check-drop . . . . . 

Check-drop maintaining an upstream water surface . . . 

Standard check-drop structures 

Standard check-drop structures 

Standard dimensions for a 

3-foot check-drop structure . 

Turnout . . . . . . . . . . 

Precast concrete turnout 

inlets . . . _ . . . . . . . 

Completed turnout inlets in 

casting yard _ . . . . . . . 

Lateral turnout gates . . . . . 

Turnout structure in earth 

channel . . . . . . . . . . 

Precast turnout inlet in place 

in canal bank . . . . . . , 

Completed turnout structure 

ready for backfilling . . . . 

Flow through turnout being 

measured with an open-flow 

meter . . . . . . . . . . _ 

Farm turnout outlet . . . . . 

Constant-head orifice turnout 

with stilling wells . . . . . 

Constant-head orifice turnout 

inlet . . . . . . . . _ . _ 

Operator adjusting orifice 

gate on a constant-head orifice turnout . . . . . . . . 

Dimensions for a constant-head 

orifice . . . . . . . . . . 

Page Figure Page 

3-28. Constant-head orifice structure used as a check . . . . . . 158 

. . 115 3-29. Constant-head orifice turnout . . 159 

. . 117 3-30. Two-barrel constant-head ori- 

. . 121 fice turnout . . . . . . . . . . 160 

. . 123 3-3 1. Division structure using 

2-foot adjustable weirs . . . . . 162 

3-32. Pipe division box . . . . . . . . 163 

. . 133 3-33. Division structure with flow 

. . 134 over 18-inch weir in fore- 

. . 134 ground . . . . . . . . . . . 163 

. . 135 3-34. Division structure used as out- 

. . 137 let to turnout . . . . . . . . . 163 

. . 138 3-35. Division structure . . . . . . . . 164 

3-36. Division structure with pipe 

. . 139 inlet . . . . . . . . . . . . . 165 

3-37. Check inlet to 42-inch- 

. . 140 diameter pipe siphon . . . . . . 166 

. . 140 3-38. Check and pipe inlet . . . . . . . 167 

. . 140 3-39. Control and pipe inlet . . . . . . 172 

3-40. Control notch graphs . . . . . . 176 

. . 

140 

141 

142 

144 

147 

149 

149 

149 

150 

151 

151 

151 

152 

152 

152 

153 

157 

4-l. 

4-2. 

4-3. 

4-4. 

4-5. 

4-6. 

4-7. 

4-8. 

Wasteway turnout with side channel spillway and slide gate . . . 

Check and pipe inlet in operation . . . . . . . . . . . . . . 

Side channel spillway in operation in foreground, and 

wasteway gate at far end of 

spillway crest . . _ . . . . . . 

Side channel spillway used as 

a wasteway turnout . . . . . . 

General plan of typical canal 

with side channel spillway . . . 

Side channel spillway-typical 

sections . . . . _ . . . . . . . 

Side channel spillway-outlet 

hydraulics . . . . . . . . . . . 

Wasteway turnout at left, and 

radial gate check structure 

at right side of photograph . . . 

Radial gate used in combination with overflow spillway . . 

Radial gate wasteway turnoutsubmerged flow . . . . . . . . 

General plan of typical canal 

with wasteway turnout . . . . . 

Radial gate wasteway turnouttypical sections . . . . . . _ . 

Siphon spillway with siphon 

breaker pan . . . . . . . . . . 

4-9. 

4-l 0. 

4-l 1. 

4-12. 

4-13. 

180 

180 

182 

183 

185 

186 

187 

189 

190 

191 

192 

193 

195 
CONTENTS 

Figure 

4-14. Siphon spillway hood at left, 

radial gate for wasteway 

turnout in center, and hoist 

for radial gate check at 

right side of photograph . . . 

4-l 5. Siphon spillway with 

siphon breaker pan 

in place . . . . . . . . . . . 

4-l 6. General plan of typical canal 

with siphon spillway . . . , . 

4-l 7. Siphon spillway-typical sections . . . . . . . . . . . . 

4-l 8. Check and pipe inlet spilling 

over crest . . . . . . . . 

4-l 9. Culvert, constructed prior to 

construction of canal . . . . . 

4-20. Double-barreled pipe culvert 

with concrete percolation 

collars . . . . . . . . . . 

4-2 1. Concrete box culvert with con196 

198 

198 

199 

201 

203 

204 

4-22. 

4-23. 

4-24. 

4-25. 

4-26. 

4-27. 

4-28. 

4-29. 

4-30. 

4-3 1. 

4-32. 

4-33. 

4-34. 

4-35. 

4-36. 

4-37. 

Crete percolation collars . . . . 204 

Precast concrete pipe culvert 

with type 3 inlet transition . . . _ . . . . . . . 205 

Precast concrete pipe culvert 

with precast concrete inlet 

transition . . . . . . . . . . 205 

Baffled outlet at end of a 

culvert . . . . . . . . . . 206 

Concrete box culvert with baffled apron drop at outlet . . . 207 

Plan and profile of typical 

culverts . . . . . . . . . . . . 208 

Weighted-creep method . . . . . 210 

Culvert-typical profile _ . . . . . 211 

Culvert hydraulics . . . . . . . . 2 14 

Rectangular concrete overchute . . 2 15 

Steel pipe overchute on the 

Colorado-Big Thompson 

Project . . . . . . . . . . . . 2 16 

Overchute- typical plan and 

sections . . . . . . . . . . . . 217 

Overchutes- typical plan and 

sections . . . . . . . . . . . . 219 

Overchuteevertical drop hydraulics . . . . . . . . . . . . . 222 

Overchute-typical profile . . . _ 225 

Overchute-chute hydraulics . . . 226 

Drain inlet on far bank of 

earth section canal, and 

motor-operated gate hoist 

for turnout gate in foreground . . . . _ . . . . _ . . 231 

Figure 

XIX 

Pafit2 

4-38. Rectangular inclined drain 

inlet to earth section . . . . 

4-39. Rectangular concrete dram inlet to a concrete-lined 

canal section . . . . . . . 

4-40. Drain inlet with flap gate to 

prevent reverse flow . . . . 

4-41. Drain inlet-plan and sections . . 

4-42. Drain inlets-plan and sections . 

4-43. Concrete drain inlet dimensions . . . . . , . . . . . . 

4-44. Pipe drain inlet-plan, profile, 

and nomenclature . . . . 

5-l. Flow through a 9-inch Parshall 

flume . . . . . . . . . . . . . 

5-2. Recently constructed Parshall 

flume . . . . . . . . . . . . 

5-3. Concrete weir structure with 

standard con tracted 

Cipolletti weir . . . . . . . . 

5-4. Open-flow meter attached to a 

concrete pipe 

231 

232 

233 

234 

235 

236 

238 

243 

243 

5-5. Artist sketch showing Parshail ’ ’ ’ 

flume in a canal . . . . . . . . 

5-6. Relationship of flow depth to 

the flume crest elevation . . . 

5-7. Standard Parshall flume dimcnsions . . . . . . . . . . . . . 

5-8. Head loss through Parshall 

flumes, 1 through 8 feet 

wide . . . . . . . . . , . 

5-9. Diagram for determining rate 

of submerged flow in a 

6-inch Parshall flume . . . . . 

5-l 0. Diagram for determining rate 

of submerged flow in a 

9-inch Parshall flume . . . . . . 

5-l 1. Diagram for detemrining correction to be subtracted from 

free-flow discharge to 

obtain rate of submergedflow discharge through 

Parshall flumes, 1 through 

8 feet wide . . . . . . . . . . 

5-l 2. Modified Parshall flume . . . . 

5- 13. Standard contracted weir discharging at free flow . . . . . . 

5-l 4. Typical suppressed weir in a 

flume drop . . . . . . . . . . 

5-l 5. Water flowing over a standard 

Cipolle t ti weir . . . . . . . . . 

244 

244 

244 

248 

249 

250 

250 

251 

251 

259 

261 

262 

263 
xx 

Figure 

5-16. Cipolletti weir in a permanent 

bulkhead-free-flow conditions . . . . . . . . . . . 

5-l 7. Cipolletti weir structures12 inches to 4 feet . . . . 

5-18. Cipolletti weir stmctures5 feet to 16 feet . . . . . . 

5-l 9. Division structure with adjustable weirs . . . . . . . . . 

5-20. Adjustable weirs-2 and 3 feet 

wide 

5-2 1. Handwheels- ; 2: ;4, lk,‘and’i 

inches . . . . . . . . . 

5-22. Two-foot movable weir . . . 

5-23. Three-foot movable weir . . . 

5-24. Staff or weir gage installation . . . . . . . . . . . 

5-25. Staff or weir gage . . . . . . 

5-26. Longitudinal section turnout 

and weir box . . . . 

5-27. Three-foot weir box . . . . . 

5-28. Four-foot weir box . . . . . 

5-29. Water surface drop and total 

head loss across baffles 

and weir gage stilling well 

of 4-foot weir box . . . . . 

5-30. Artist sketch of turnout with 

open-flow meter attached . 

5-3 1. Outlet transition for open6-l. 

flow meter 

Baffled apron d;op defo;e ba$- . ’ 

296 

filling ............. 300 

Typical inlet types ........ 301 

Baffled apron drop with inlet 

control notches ........ 301 

Baffled apron drop with wingwalls located upstream from 

the outlet end ......... 301 

Baffled apron drop design .... 305 

Sill curve dimensions ....... 306 

Upstream wingwalls ....... 307 

Downstream wingwalls ...... 308 

Large baffled outlet ....... 309 

Design width of basin ...... 3 10 

Type 1 baffled outlet ...... 3 11 

Type 2 baffled outlet ...... 3 12 

Type 3 baffled outlet ...... 3 13 

Type 4 baffled outlet ...... 3 14 

Type 5 baffled outlet ...... 3 15 

Type 6 baffled outlet ...... 3 16 

Type 7 baffled outlet ...... 3 17 

6-28. Typical sleeve valve and still-. ’ ’ ’ 

ing well . . . . . . . . . . . 

7-l. Type 1 concrete transition . . . . 

7-2. Concrete transitions-type 1 . . . 

7-3. Concrete transitions-type 5 . . . 

7-4. Concrete transitions-type 2 . . . 

7-5. Concrete inlet transitionstype 3 . . . . . . . . . . 

7-6. Concrete inlet transitionstype 4 . . . . . . . . . . . 

7-7. Type 4 inlet concrete transition . . . . . . . . . . . . 

7-8. Erosion protection . . . . . . . 

8-l. Head loss coefficients for 

pipe bends . . . . . . . . . . 

8-2. Precast reinforced concrete 

pressure pipe in trench 

prior to backfilling . . . . . . . 

8-3. Precast reinforced concrete 

pressure pipe used for 

inverted siphon . . . . . . . . 

8-4. Corrugated-metal pipe used for 

road crossing . . . . . . . . 

8-5. Installation of corrugatedmetal-pipe road crossing . . . . 

8-6. Welded steel pipe flume . . . . . 

8-7. Overhead welded steel pipe 

crossing . . . _ . . . . 

8-8. Pipe collars . . . . . . . . . . . 

8-9. Forms for thrust block on 

54-inch-diameter precast 

concrete pipe . . . . . . . . 

8-10. Precast concrete pressure pipe 

bends . . . . . . , . . . . 

8-l 1. Precast concrete culvert pipe 

bends . . . . . . . . . . . . . 

8-l 2. Asbestos-cement pressure pipe 

361 

6-2. 

6-3. 

361 

6-4. 

361 

6-5. 

6-6. 

6-7. 

6-8. 

6-9. 

6-10. 

6-l 1. 

6-l 2. 

6-l 3. 

6-14. 

6-l 5. 

6-16. 

6-l 7. 

6-l 8. 

361 

362 

362 

363 

364 

366 

367 

Type 8 baffled outlet . . . . . . 3 18 bends . . . . . . . . . . . . . 368 

Page 

263 

264 

265 

266 

267 

268 

269 

270 

271 

272 

291 

292 

293 

294 

295 

Figure 

CONTENTS 

Page 

6-l 9. Type 9 baffled outlet . . . . . . 

(i-20. Type 10 baffled outlet . . . . . . 

6-2 1. Sleeve valve stilling well 

arrangements . . . . . . . . 

6-22. Typical sleeve valve installation for pipe turnout . . . . . 

6-23. Typical vertical sleeve valves . . . 

6-24. Thrust forces on bend . . . . . . 

6-25. Orifice of the standard sleeve 

valve . . . . . . . . . . . . 

6-26. Head loss coefficient for the 

standard sleeve valve . . . . . 

6-27. Vertical sleeve valve stilling 

well dimensions 

319 

320 

323 

324 

325 

327 

328 

328 

329 

329 

335 

337 

338 

339 

340 

341 

342 

346 

360 
CONTENTS 

Figure 

8- 13. Asbestos-cement pressure pipe 

and reinforced plastic mortar 

pressure pipe bends . . . . . . 

8-14. Precast concrete pipe embedment . . . . . . . . . . 

8-15. Precast concrete pipe jointstypes B and B-l . . . . . . . . 

8-l 6. Precast concrete pipe joint& 

copper seal-type D . . . . . . 

8-17. Pipe safety barrier . . . . . . . . 

8-l 8. Blowoff for precast concrete 

pipe . . . . . . . . . . 

8-l 9. Manhole and blowoff for concrete pressure pipe . . . . . . . 

8-20. 16-inch steel ladder . . . . . 

8-2 I . Concrete pipe air vent . . . . . 

8-22. Step-type pipe taper . . . . . . . 

8-23. Pipe earthwork details-precast 

concrete or asbestos-cement 

pipe-earth or rock excavation . . . . . . . . . . . . . 

8-24. Pipe earthwork detailsreinforced plastic mortar 

pipe-earth and rock excavation . . . . . . . . . . . . 

9-l. School and urban fence . . . . . 

9-2. Rural fence . . . . . . . 

9-3. Stock fence with wood posts . . 

94. Stock fence with steel posts . . . 

9-5. Deer fence . . . . . . . . . 

9-6. Warning sign, safety cable, 

and safety fence at siphon 

inlet . . . . . . . . . . . . . 

369 

370 

372 

373 

374 

376 

3 77 

378 

380 

381 

382 

382 

385 

386 

387 

388 

389 

390 

XXI 

Figure Page 

9-7. Safety fence, handrail, and 

safety rack at siphon inlet . . . 390 

9-8. Safety fence along a chute . . . . 390 

9-9. Typical pipe handrail installation along sides of inclined 

drop and stilling pool . . . . 390 

9-l 0. Two-rail handrail-42 inches 

high . . . . . . . . . . . 391 

9-l 1. Three-rail handrail-42 inches 

high . . . . . . . . . 392 

9-12. Check inlet with safety fence, 

safety net, and having handrails on both sides of 

walkway . . . , . . . . . 393 

9-13. Rope safety net upstream of 

checked siphon inlet . . . . . 394 

9-14. Wire mesh safety net at siphon 

inlet . . . . . . . . . 394 

9-15. Safety net and cable . . . . . . 395 

9-16. Safety net and cable at siphon 

inlet . . . . . . . . 395 

9-17. Safety cable with floats upstream of a siphon inlet . . . . 395 

9-18. Safety cable with floats . . . . 396 

9-19. Safety rack . . . . . . . . . . 397 

9-20. Safety rack on inlet transition . . . . . . . . . . . . 398 

9-2 1. Safety ladder and safety cable 

with floats upstream of a 

siphon inlet . . . . . . . . . . 398 

9-22. Safety ladder . . . . . . . . . 399 

< Chapter I 

General Requirements and 

Design Considerations 

A. J. AISENBREY, JR.’ 

A. GENERAL REQUIREMENTS 

l-l. Purpose.-To fulfill a project purpose 

o f p reducing crops or increasing crop 

production, water delivery to the land must be 

provided by a reliable and efficient irrigation 

system. A sun-drenched, parched soil may need 

only water to change it from a sparsely 

vegetated, thirsty desert to a high-yield crop, 

farmland oasis as illustrated in figure 1-l. An 

increased crop yield of premium quality is very 

likely if the proper amount of moisture is made 

available to the crop when needed. (See fig. 

l-2). 

A canal is frequently used to convey water 

for farmland irrigation. In addition to 

transporting irrigation water, a canal may also 

transport water to meet requirements for 

municipal, industrial, and outdoor recreational 

uses. A variety of recreation is provided by 

reservoirs as shown in figures l-3 and 1-4. 

The conveyance canal and its related 

structures should perform their functions 

efficiently and competently with minimum 

maintenance, ease of operation, and minimum 

water loss. 

l-2. Structures. -Many different types of 

canal structures are required in an irrigation 

system to effectively and efficiently convey, 

regulate, and measure the canal discharge and 

also to protect the canal from storm runoff 

damage. 

The design capacity of the conveyance, 

regulating, and water measurement structures 

‘Civil Engineer, Hydraulic Structures Branch, Bureau of 

Reclamation. 

discussed throughout this publication is limited 

to 100 cubic feet per second. 

(a) Corz veyance Structures. -In addition to 

the canal itself, it is usually necessary, because 

of topography or existing manmade features, 

to use inline canal structures to convey water 

along the canal route. Such structures include: 

(1) inverted siphons to convey canal water 

under natural channels, (2) road crossings to 

carry canal water under roadways, (3) bench 

flumes to conduct the water along a steep 

hillside, and (4) drop or chute structures to 

safely lower the canal water down a hillside. 

(b) Regulating Structures. -Regulation of 

canal discharge begins at the source of water 

supply. This may be a canal headworks 

structure adjacent to a diversion dam on a 

stream or river, a turnout from a larger canal, 

or a pumping plant located on a reservoir or 

large canal. Downstream from the source of 

water supply, regulation of canal discharge is 

primarily controlled by outflow through 

turnout structures. Where canal flow is to be 

divided and directed in several directions, 

division structures are used to regulate the 

discharge in each direction. Wasteway 

structures also are used to control flow in a 

canal; however, they are more commonly 

thought of as protective structures as their 

primary function is to discharge excess canal 

flows and thereby protect the canal from 

damage. 

Regulating structures are also capable of 

raising the canal water surface higher than 

would normally exist when the canal is flowing 

1 
2 SMALL CANAL STRUCTURES

Figure 1-1. Open canal system supplying irrigation water to citrus groves, Gila Project, Arizona. PSO-300-l0S86

at less than design capacity. A check structure,

for example, is used to raise the canal water

surface when the canal is flowing at partial

capacity so that a turnout structure may still

deliver its designed capacity. Check structures

are spaced at appropriate intervals along a canal

to provide this capa bili ty .

(c) Water Measurement

Structures.-Efficient management of an

irrigation system insists that measurement of

the rate-of-flow and volume delivered be made.

Equitable water distribution to the users is a

primary consideration. Water measurement also

tends to prevent unnecessary wasteful water

management practices, thereby enhancing the

conservation of this great natural resource.

Several types of water measurement

structures or devices are used. Parshall flumes,

weirs, weir boxes, open-flow meters, and

constant head orifices are the more common

types.

The constant head orifice, although

sometimes used as an inline canal water

measurement structure, is more commonly

used in conjunction with a turnout and

therefore is discussed in detail with regulating

structures.

Selection of the type of structure best suited

for a particular installation is discussed in

chapter V.

(d) Protective Structures.-Provisions must

be made in an open irrigation system to
GENERAL REQUIREMENTS AND DESIGN CONSIDERATIONS 3

Figure 1-2. Irrigating corn using siphon tubes, Red Willow Unit, Nebraska. P328-701-6140

Figure 1-3. Boating on the Rogue River Project, Oregon.

C448-100-148

Figure 1-4. Fishing on Hungry Horse Reservoir, Montana.

C447-100-S0
I 

4 

externally protect 

from damage by 

the canal on the uphill side 

storm runoff water, and 

internally protect the canal from excess canal 

flows caused by storm waters entering the 

canal, or by misoperation of the canal system. 

Cross-drainage structures and wasteways 

provide this protection. 

Cross-drainage structures are used to direct 

storm runoff flows under the canal through 

culverts, over the canal in overchutes, or into 

the canal by drain inlets. 

Wasteways evacuate excess canal flows over 

side channel spillways., through radial gated 

spillways, or through siphon spillways. 

(e) Structure Components and 

Appurtcnamzs. -Nearly all canal structures are 

made of several different structural parts which 

together make up the complete structure. 

These parts, (components and appurtenances) 

include: 

(1) Pipe.-Pipe is commonly used for 

that part of a structure placed 

underground and which may or may not 

be subjected to internal hydrostatic 

bursting pressure. Pipe is made from one 

of several different materials such as 

reinforced concrete, asbestos cement, 

welded steel, corrugated metal, or 

reinforced plastic mortar. Selection of the 

appropriate pipe material is dependent on 

several considerations discussed later in 

chapter VIII. 

(2) Pipe app ur tenawes. -Appurtenances include such items as pipe collars, 

air vents, blowoffs, manholes, and are 

discussed later in chapter VIII. 

(3) Tratzsitions. -Transitions connect a 

canal or natural channel to a structure 

inlet or structure outlet. Several different 

transition configurations of reinforced 

concrete are used. Earth transitions are 

used as required to vary base widths and 

invert slopes. See chapter VII for a 

detailed discussion of transitions. 

(4) Etzergy dissipators. -Energy 

dissipators are used at the outlet ends of 

drop or chute structures to dissipate 

excess energy. Energy dissipation may be 

achieved by a hydraulic jump in a stilling 

pool or by impact in a baffled outlet. 

Excess energy may also be dissipated by a 

hydraulic jump within a pipe; by impact 

SMALL CANAL STRUCTURES 

on a baffled apron; by impact and valve 

losses in a high-head vertical energy 

dissipator; or simply by a vertical drop of 

a few feet into a pool of water. Energy 

dissipators are discussed in detail in 

chapter VI. 

(5) Safety features. -Safety features 

are used to prevent humans, livestock, and 

wildlife from entering a canal and canal 

structures, and also to assist in their 

escape if inadvertently entered. Various 

types of fencing, guardrail, nets, racks, 

ladders, and signs are used as safety 

precautions. See chapter IX for a more 

detailed discussion of canal safety 

features. 

l-3. Other Requirements.-Many 

requirements vital to a complete and 

competent design of a canal water-delivery 

system are beyond the scope of this 

publication. However, the more basic 

considerations are briefly discussed in this 

section to remind or acquaint the reader of 

other essential design data requirements. 

(a) Canal.-Design capacity for an irrigation 

canal is determined by the maximum water 

demand which is primarily dependent on the 

following considerations: (1) the area to be 

irrigated, (2) crops to be grown, (3) rotation or 

demand system for turnout deliveries, (4) 

water losses from evaporation and seepage, and 

(5) anticipated efficiency of water application 

to the crops. Records of actual water use for 

conditions similar to the system to be designed 

are valuable guides for estimating the quantity 

of water required for each acre. Soil 

characteristics and climatic conditions should 

also be evaluated. Figure l-5 shows furrow 

irrigation of crops from a header ditch, and 

sprinkler irrigation is shown in figure l-6. 

Location of the canal with respect to the 

land to be irrigated is primarily influenced by 

topography and economic considerations. If, 

for example, water delivery cannot be made by 

gravity, the additional cost of pumping would 

be included in an economic study. Figure l-7 

shows water delivery by gravity from the canal, 

through a turnout, to the farmland. 

Considerations for the selection of the canal 

hydraulic properties include erosion resistance 

for the banks and invert of an earth canal, 

sideslope stability, hydraulic efficiency, 
GENERAL REQUIREMENTS AND DESIGN CONSIDERATIONS 5

Figure 1-5. Irrigating sugar beets on the Boise

Project, Idaho. C4-10o-I88

~'"

Figure 1-6. Sprinkler irrigation in the Coachella

Valley, California. LC830

(b) Other Structures. -Detailed discussions

of structures such as tunnels, bridges, utility

crossings, and fish screens and fish ladders are

not included herein.

Tunnels are used where it is more

economical to convey canal water through a

ridge or hill than to: (I) pump water over the

obstruction, (2) convey the water along the

hillside or around the ridge, or (3) construct a

canal section requiring a very deep cut.

Bridges for roadway traffic over a canal are

generally used for canals of much greater

capacity than 100 cubic feet per second.

However, if the monetary value of hydraulic

head in the canal system is particularly high, a

cost comparison of a bridge and a road crossing

structure may be warranted as the head loss

through a pipe road crossing could be

significant.

Utility crossing structures are provided for

existing utilities such as gas, oil, water, sewage,

electricity , and communication lines. Utility

lines may cross over or under the canal, and

frequently require special design considerations

to comply with the utility owner's

requirements and the canal design criteria.

Fish screens and ladders are special

structures at or near the source of canal water

supply. Screens exclude fish from a canal

whereas ladders permit migration in the natural

channel.

(c) Soils Exploration. -The following very

generally and briefly discusses some of the

more important considerations associated with

a soils exploration program. Methods and

procedures for drilling, sampling, and testing

are also very important [ I] .2

Soils investigation along a canal and at

structure sites is required to: ( I) identify the

soil materials to be excavated, (2) identify the

soil for potential use as canal embankment, (3)

determine the foundation adequacy for canal

structures and lining, ( 4) determine the need

for canal lining, (5) determine canal sideslope

stability, (6) assess erosion resistance

characteristics, (7) determine underdrain

requirements for lined canals, and (8)

Figure J -7. Irrigating frJ.rit on the Yakima Project,

Washington. C-33-IOO-80

operational flexibility, and economics. The

need for canal lining and selection of the type

of lining are also determinations which must be

made.

2Numbers in brackets refer to items in the bibliography

sec. 1-25.
6 

determine water-soluble sulfate ion 

concentrations. 

Soil material to be excavated has one of two 

classifications: rock or common (soil). The 

materials remolded and used for canal 

embankment construction should ideally be 

nonexpansive, possess adequate remolded 

shearing strength, be relatively impervious, and 

relatively erosion resistant if hard-surface canal 

lining is not used. The soil in its natural state 

should also possess these qualities. It is 

somctimcs necessary to locate a source of 

borrow material for canal embankment, for 

backfill adjacent to structures, and for 

foundation pads under the structures. 

The reaches of a canal which travcrsc low 

density soils highly susceptible to 

hydrocompaction should be well delineated. In 

addition, the depth to subsurface water levels if 

present in any exploration hole should be 

rccordcd. 

Canal structures discussed in this publication 

are relatively small and consequently 

foundation pressures are quite low. Therefore, 

structure settlement caused by foundation 

consolidation will usually be small in 

magnitude. Foundation treatment however, 

may be required to protect the structure from 

expansive soils or from undesirable settlement 

of low-density material. 

Sulfate concentrations in the soil samples 

and water samples indicate the relative degree 

of potential sulfate attack on concrete [ 21. 

Specifying the appropriate type of cement used 

in the concrete mix is usually all that is 

required to safeguard the concrete. Fly ash is 

also sometimes used in the concrete mix for 

sulfate resistance [ 31 . 

Although a well planned and executed soils 

exploration program may be conducted, an 

SMALL CANAL STRUCTURES 

admonishment by the eminent soils engineer 

Karl Terzaghi must always be borne in mind: .‘ 

. results of subsurface exploration still 

le&e a wide margin for interpretation. “[41 

Sound judgment is a requisite in all soil 

exploration programs. 

(d) Hydrology.-The canal system should be 

reasonably well protected from damage which 

could occur from storm runoff. The runoff 

area contributing to a natural drainage channel, 

the ground slope and vegetative density of the 

area, and storm frequency to be used for design 

are all infiuential in determining the design 

capacity for cross drainage structures. 

(e) Sedirnerztution. -Aggradation and 

degradation studies for a natural drainage 

channel provide the necessary data to 

determine earth cover required, for example, 

over the top of the pipe for an inverted siphon 

extending under the drainage channel. 

Degradation, if extensive enough could cause 

an empty pipe to float; whereas aggradation 

could create external earth loads great enough 

to crack or otherwise damage the pipe. 

( f) Operation md Muirzterzarzcc. -In a 

Bureau of Reclamation designed system, a 

designers’ operating criteria (DOC) is usually 

provided to assist operation and maintenance 

(O&M) personnel in adequately protecting the 

canal system from unnecessary damage which 

could otherwise be caused by misoperation or 

inadequate maintenance. A rigorous 

maintenance program should include control of 

weeds, aquatic growths, insects, and pests. 

Experience has shown that a well maintained 

and operated canal system usually has 

dedicated personnel-people who are justly 

proud of their work and take pride in what 

they do---people who curt. 

B. DESIGN CONSIDERATIONS 

l-4. General. -Canal structures which have discharge capacity for inline canal structures, 

been standardized in this publication, show when properly selected and hydraulically set, 

concrete dimensions and reinforcement steel, to convey the flow at normal canal water 

and are appropriately sized to provide for depths, (2) adequate built-in overflow capacity 

hydraulic, structural, and stability design for inline canal structures to limit infringement 

considerations. on the canal bank freeboard for emergency 

Ifydruzrlic desiglz provides: ( 1) adequate operation or misoperation of the canal, (3) 
GENERAL REQUIREMENTS AND DESIGN CONSIDERATIONS 7 

adequate structural proportioning and Loads.-Operating decks for structures using 

appropriate hydraulic setting of structures to stoplogs are designed for a uniform live load of 

permit excess energy dissipation with minimum 150 pounds per square foot; otherwise a 

water turbulence at the downstream ends of uniform live load of 100 pounds per square 

the structures, and (4) structural proportioning foot is used. Decks for radial gate hoists require 

of certain transitions to minimize hydraulic special structural design considerations which 

head loss. are not included herein. 

Structural design provides: appropriate 

concrete thicknesses and reinforcement steel 

patterns for structural members to resist 

bending moment, thrust, and shear stresses 

imposed by reasonable loads on the structure. 

Stability design pro vidcs: adequate 

structure dimensions so that for most soil 

foundation materials, the structure will: (1) 

resist sliding and overturning, (2) prevent 

percolating water from removing foundation 

materials, and (3) provide foundation pressures 

less than the maximum allowable bearing 

pressure. 

1-8. Lateral Pressures. -Lateral pressures 

from several different sources are imposed on 

walls of structures. Resultant forces from these 

pressures must be adequately resisted by the 

reinforced concrete. 

(a) Water. -A fluid pressure of 62.4 pounds 

per square foot (psf) per foot of depth is 

caused by water. The pressure diagram is 

triangular with the resultant force acting at 

one-third the height above the base of the 

pressure diagram. 

Design examples for structures which have 

not been standardized illustrate a 

recommended hydraulic design procedure, but 

exclude structural design and stability analysis. 

1. Loads 

(b) Eurtk.-Active earth pressures may be 

determined using Rankine’s solution of 

Coulomb’s equation [ 51 . The pressure diagram 

is assumed to be triangular, the same as for 

water, with the resultant force acting at 

one-third the height above the base of the 

pressure diagram. Because of this similarity 

with the fluid pressure of water, the pressure 

caused by earth is sometimes referred to as an 

equivalent fluid pressure. 

l-5. General.-Loads which canal structures 

must capably resist include dead load weights, 

live loads on operating decks, lateral pressures, 

bursting and uplift pressures, and wheel loads. 

l-6. Dead Load Weights.-Commonly used 

dead load weights for small canal structures are 

presented in the following tabulation: 

Load 

Water 

Backfill 

Dry 

Saturated 

Compacted backfill 

Dry 

Saturated 

Concrete 

Weight, 

(Ibs./cu. ft.) 

62.4 

100 

125 

120 

135 

150 

Standardized canal structures have been 

structurally designed to resist moist earth 

active lateral pressure equal to 30 psf per foot 

of depth and saturated earth active lateral 

pressure of 85 psf per foot of depth. Unless 

unusual soil properties exist, these values are 

considered adequate for design of small canal 

structures. For a detailed discussion of earth 

pressures on concrete retaining walls, see 

bibliography reference [ 5 1. 

To conveniently differentiate between soils 

which are above and below the water level in a 

soil mass, the terms dry and saturated are used. 

Obviously the soil adjacent to a structure is not 

ovendry and does possess a certain moisture 

content. 

(c) Construction a17d Operutirzg Equipment 

Wheel Surcharge. -Walls of structures should be 

designed to withstand construction and 

operating equipment wheel loads which are 

transmitted through the earth adjacent to the 

structure. An additional lateral load equivalent 

to 2 feet of earth surcharge is usually used. 

This results in an additional uniformly 

distributed lateral pressure (rectangular 

pressure diagram) of 60 psf from the backfill 

surface to the bottom of the wall. Standardized 

canal structures are designed to withstand this 

additional load. 

1-7. Operating Deck Uniform Live (d) /cc.-Ice loads on structures should be 
8 SMALL CANAL STRUCTURES 

Officials [6] (AASHO). The following 

tabulation shows total equivalent earth cover 

for various heights of earth cover over the top 

of the pipe with H-15 and H-20 truck wheel 

loads. 

considered if wintertime canal operation is 

required. The magnitudes for ice thrust 

presented in bibliography reference [ 51 may be 

used. 

(e) Wind.-Wind loads on small irrigation 

structures are not included in the structural 

and stability analyses. 

l-9. Other Pressures. -(a) U#ift. -Uplift 

pressures, which may be caused by water 

percolating under or along the sides of 

hydraulic structures, reduce the effective 

weight of a structure and are therefore 

particularly significant in the stability analysis. 

Stilling pool floors, for example, are 

subjected to uplift pressure from downstream 

water levels which may saturate the soil behind 

the wall to a significantly higher elevation than 

the water depth in the pool just upstream from 

the hydraulic jump. Weep holes are used to 

lower the saturation level. 

(b) Hydrudic Trarzsients. -Pressure surges in 

a pipe and bore waves in a canal accompany 

any change of flow in the system. These 

transients are u s ually of insignificant 

consequence in a small, open irrigation system 

and are therefore generally omitted from 

structural design considerations. A gradual rate 

of change of flow minimizes the magnitude of 

hydraulic transients. 

(c) Seismic. -Additional earth and water 

pressures imparted to small canal structures by 

earthquakes are not included in the design 

considerations. The increased loads are minor 

since the earth, water, and concrete masses are 

all small. Temporary stress increases caused by 

seismic loads would therefore be minor. 

l-l 0. Wheel Loads Transmitted to Buried 

Conduit. -Pipelines crossing under highways 

and railroads must be designed to withstand 

surcharge loads from trucks and locomotives. 

Concentrated wheel loads are transmitted 

through earth cover and distributed at the top 

of pipe where they are considered to be 

uniform loads. For design convenience, the 

uniform loads are converted to equivalent 

heights of compacted earth cover and added to 

the actual earth cover. Pipe is selected to 

withstand this total equivalent earth cover. 

(a) Highways.-Equivalent earth cover for 

highway wheel loads is based on criteria of the 

American Association of State Highway 

Height of 

earth cover, 

feet 

2 11.8 

1.5 

6.9 

1.3 

8.0 

8.7 

9.4 

Total equivalent earth cover for 

wheel loads shown, 

I 9.1 7.8 

8.1 

8.6 

9.2 

9.9 

For earth covers less than 2 feet, special 

provisions such as concrete encasement of the 

pipe or slab covers are required. Wheel load 

effect is negligible when the earth cover is more 

than 8 feet. 

Wheel load impact factors used for earth 

covers less than 3 feet are as follows: (1) 10 

percent for earth covers of 2 feet 1 inch to 2 

feet 11 inches, (2) 20 percent for earth covers 

of 1 foot 1 inch to 2 feet, and (3) 30 percent if 

the earth cover is 1 foot or less. 

Special provisions, such as detours and 

safety precautions, as may be required by a 

highway commission should be included in the 

design specifications. 

(b) Railroads. -Design and installation of 

pipe under a railroad often requires special 

provisions to comply with the railroad 

company requirements. Jacking casing pipe 

through the railroad embankment is a common 

requirement. Pipe used to convey the canal 

water (carrier pipe) is then installed in the 

casing pipe. 

The top of pipe installed under a railroad 

roadbed is usually at least 3 feet below the top 

of the railroad tie unless otherwise specified by 

the railroad. 

For an E-72 railroad loading [ 71, usual 

Reclamation practice is to provide a pipe class 

to withstand a total equivalent cover of 20 feet 

when the top of pipe is 3 to 15 feet below the 

top of the railroad tie. Additional load caused 

by impact is included in the total equivalent 

cover previously discussed. 
GENERAL REQUIREMENTS AND DESIGN CONSIDERATIONS 9 

2. Stability 

1-l 1. Bearing Capacity. -Foundation 

bearing pressures for small structures are of 

small magnitude and will ordinarily be less than 

allowable bearing pressures for the various soil 

types [51. 

Foundation treatment may be required, 

however, for low-density or expansive 

foundation soils. Ordinarily, hydrocompaction 

by ponding will sufficiently consolidate soils of 

low density. Overexcavation of the foundation 

soil and replacement with compacted, 

nonexpansive soil is a usual treatment for 

expansive soil foundations. The nonexpansive 

soil surcharges the underlying expansive soil 

and thereby can adequately reduce the 

foundation movement. Overexcavation is also 

sometimes used for foundation treatment of 

low-density soils. 

When installing pipe in rock, the foundation 

should be overexcavated and replaced with a 

gravel or earth cushion to permit a more 

uniform bearing pressure for the pipe. This is 

essential to effectively utilize the design 

strength of the pipe, and to preclude unequal 

settlement and resultant cracking of pipe. 

l-1 2. Sliding Coefficient. -Any structure 

subjected to differential lateral pressures must 

capably resist the tendency to slide. Resistance 

to sliding is developed by shearing strength 

along the contact surface of the structure base 

and the foundation, or by shearing strength 

within the foundation material itself. Shearing 

strength developed by cohesion is omitted and 

only that developed by mechanical friction at 

the base and foundation interface is used for 

sliding analysis of small structures. An 

allowable sliding coefficient equal to 0.35 is 

used unless unusual soil conditions exist. This 

may be expressed as: 

g= 0.35 

where: 

CH = summation of lateral forces acting 

parallel to the assumed sliding 

plane, and 

EN = summation of forces, reduced by 

uplift, acting normal to the 

assumed sliding plane. 

l- 13. Overturning. -To prevent overturning, 

the sum of the stabilizing moments must 

exceed the sum of the overturning moments on 

the structure. Checks and check-drop 

structures are perhaps the most critically 

loaded small canal structures subject to 

overturning. Maximum upstream and minimum 

downstream water surfaces subject these 

structures to unsymmetrical loads which tend 

to cause overturning. 

The resultant of all forces acting on the 

structure should fall within the middle third of 

the structure base to provide safety against 

overturning. This location of the resultant also 

provides a more uniform bearing pressure on 

the foundation. 

1-14. Percolation. -All standardized canal 

structures have sufficient cutoff and structural 

lengths to provide a percolation factor of 2.5 

or more. This is considered adequate for most 

soils to prevent piping of foundation materials 

from beneath or adjacent to small structures. 

Under ordinary operation, the maximum 

differential hydraulic head across the structure 

causing percolation is of short duration. For a 

more detailed discussion of percolation, see 

subchapter VIII C. 

3. Hydraulics 

1-15. Hydraulic Control-In the competent 

hydraulic design of any hydraulic structure it is 

necessary to first determine the location of the 

water surface control. 

Hydraulic control is at the downstream end 

of a structure if the downstream water surface 

influences the height to which the upstream 

water surface must rise. If the downstream 

water surface does not influence the upstream 

water surface, the control is at the upstream 

end of the structure. 

Upstream control for example will usually 

exist for a relatively short culvert conveying 

storm runoff under a small canal where the 

outlet channel water surface is several feet 

below the upstream pipe invert. In this 

instance, the downstream water surface does 

not control the upstream water surface; 

instead, the upstream water surface is 

controlled at the inlet end. The upstream pipe 

invert elevation, the size of pipe, and the 
10 SMALL CANAL STRUCTURES 

A change in the direction of flow causes 

bend losses. The magnitude of the loss is 

dependent on the water velocity, and the angle 

for a miter bend or the degree of curvature of a 

circular curve. Pipe bend losses are discussed in 

chapter VIII. 

1- 17. Discharge Coefficients. -(a) Orifice.-For a conduit flowing full, the discharge 

coefficient, C, used in the orifice equation [8], 

Q = CAdm, indicates the magnitude of the 

assumed entrance loss. Values of C may be 

related to an entrance loss coefficient, K, in 

the expression K,h,, by the relationship 

- 1. Values commonly used are: 

assumed entrance loss are all factors which 

determine the height to which the upstream 

water surface must rise to discharge the flow. 

Downstream hydraulic control exists for a 

properly designed inverted siphon when flow is 

at design capacity. The canal water surface at 

the downstream end of the siphon controls the 

upstream canal water surface. For partial 

discharges, hydraulic control is at the siphon 

inlet if the downstream water surface is low 

enough to permit the water to enter the siphon 

at minimum energy, which is at critical depth. 

For many structures, location of the 

hydraulic control may be determined by 

inspection of the structure profile and the 

normal channel or canal water surfaces at each 

end of the structure. In other cases the 

Bernoulli theorem [ 81 should be used to 

determine the hydraulic control location. 

Beginning from a known downstream water 

surface, a Bernoulli equation can be written 

between pairs of consecutive points. If a 

Bernoulli balance is attainable between all pairs 

of points from the outlet through the inlet, 

downstream control exists. If, however, a 

Bernoulli balance is not attainable between two 

consecutive points, a hydraulic jump between 

the points is indicated and hydraulic control 

will be at the inlet. It may then be assumed 

that the water depth in the pipe at the inlet is 

at critical depth; that is, at minimum energy. 

l- 16. Hydraulic Head 

Losses. -(a) Friction. -The Manning formula, 

[8] V = L$!S r2/3 sl/z, is used to determine 

friction losses in a canal system. For all 

monolithic concrete canal structures, a 

roughness coefficient n = 0.014 is used. 

Roughness (friction) coefficients used for pipe 

are n = 0.013 for precast concrete, asbestos 

cement, reinforced plastic mortar, and steel, 

while n = 0.024 is used for corrugated-metal 

pipe. A 20 percent reduction in the n value is 

used as a safety factor in the hydraulic analysis 

of excess energy dissipation for those 

structures which perform this function. 

(b) Trunsitions and Bends. -Transitions are 

used to geometrically change the water prism 

shape and cause acceleration or deceleration of 

the flow. Losses associated with convergence 

and divergence of the water prism are discussed 

in chapter VII. 

c Ko - 

0.6 1.78 

0.7 1.04 

0.75 0.78 

0.8 0.56 

0.82 0.50 

The value for C in the orifice equation is 

primarily dependent on the hydraulic entrance 

conditions. Subsequent chapters of canal 

structures using the orifice equation indicate ar 

appropriate C value for a specific design. 

(b) Weir. -Weirs are commonly used to 

measure the rate of flow of water. The basic 

weir equation [8] is Q = CLH3/‘. The 

appropriate value for the discharge coefficient, 

C, is primarily dependent on the geometric 

shape of the weir and contraction of the sheet 

of water flowing over the weir. 

Values for C and equations for the more 

commonly used weirs are: 

Weir 

- 

Weir equation 

Rectangular suppressed Q = 3.33 L H3i2 

Rectangular contracted 

Cipolletti 

Q = 3.33 (L - O.TH) H312 

Q = 3.367 L H3 2. 

For a comprehensive discussion of weirs, see 

chapter V. 

4. Structural Considerations 

l-l 8. Reinforced Concrete. -(a) Allowable 

Stresses. -Standardized canal structures 

included herein, which show concrete 
GENERAL REQUIREMENTS AND DESIGN CONSIDERATIONS 11 

thicknesses and size and spacing of 

reinforcement bars, were designed by the 

working stress method based on a ccncrete 

strength of 4,000 pounds per square inch (psi) 

at 28 days (fb ), and reinforcement steel having 

a specified minimum yield strength of 60,000 

psi (f,). Allowable working stresses used were 

1,800 psi compression (f,) for concrete and 

24,000 psi tension (f,) for reinforcement steel. 

For many of the smaller standardized 

structures, nominal minimum concrete 

thicknesses and minimal reinforcement steel 

patterns control the design. In these cases the 

concrete and steel strengths indicated could be 

reduced without jeopardizing structural 

integrity. 

Reinforced precast concrete pressure pipe 

was designed by the ultimate strength method 

using fb = 4,500 psi, fY = 40,000 psi, and an LF 

= 1.8 as a load factor. 

( b ) M i 11 im u m Reinforcement 

Requirements. -The minimum reinforcement 

used for canal structures should be No. 4 bars 

(l/2-inch diameter) at 12-inch spacing when 

reinforcement is placed in a single layer, or 

where exposed faces of concrete are reinforced. 

In unexposed faces of concrete having 

two-layer reinforcement. the minimum 

reinforcement should be No. 4 bars at 18 

inches. 

The following criteria should be used to 

determine the cross-sectional area for 

temperature or minimum reinforcement. The 

percentages of reinforcement steel areas listed 

are percentages of the gross cross-sectional area 

of the concrete to be reinforced: 

(1) Single-layer reinforcement.-For slabs 

with joint spacing not exceeding 30 feet 

and: 

Not exposed to freezing 

temperatures or direct 

sun . . . . . . . . . . . . . . . . . 0.25 percent 

Exposed to freezing 

temperatures or direct 

sun . . . . . .._......... 0.30 percent 

For slabs with joint spacing greater than 

30 feet and: 

Not exposed to freezing 

temperatures or direct 

sun . . . . . . . . . . . . . . . . . 0.35 percent 

Exposed to freezing 

temperatures or direct 

sun . . . . . . . . . . . . . . . . . 0.40 percent 

Walls and other structural members 

should have a total percentage of horizontal 

reinforcement equal to the sum of the 

percentages required for both faces as 

determined for double-layer reinforccmcnt. 

(2) Douhlc-layc‘r reinforcement.-For 

joint spacing not exceeding 30 feet and 

with: 

Face adjacent to earth . . . . 0.10 percent 

Face not adjacent to earth 

nor exposed to freezing 

temperatures or direct 

sun . . . . . . . . . . 0.15 percent 

Face not adjacent to earth 

but exposed to freezing 

temperatures or direct 

sun . . . . . . . . . . . . . 0.20 percent 

If a structural member exceeds 30 feet in 

any direction parallel to the reinforcement, an 

additional 0.05 percent of reinforcement steel 

area is required in that direction. 

If a slab is fixed along any line, the 

dimension from the line of fixity to the free 

end is doubled to determine if the 

reinforcement requirement should bc based on 

a length not exceeding 30 feet or a length 

greater than 30 feet. 

Reinforcement spacing should not exceed 

three times the thickness of the member for 

temperature reinforcement and twice the 

thickness of the member for stress bars. 

Other minimum requirements and general 

notes for designing, showing, and detailing 

reinforcement steel are indicated on figure l-8. 

When using the illustrations of standardized 

canal structures presented herein as 

construction drawings, figure l-8 should be 

used for general notes and minimum 

requirements for detailing reinforcement. 

(c) Minimum Wall Thickness.--To provide 

ease of concrete placement and insure good 

bond between the reinforcement and concrete, 

the minimum concrete thickness of cantilever 

walls should be 1 inch per foot of height (5 

inches minimum) for walls up to 8 feet high. 

For walls exceeding 8 feet in height, the 

minimum concrete thickness should be 8 

inches plus 3/4 inch for each foot of wall 

height greater than 8 feet. 
12 SMALL CANAL STRUCTURES 

coocrete Str”ct”rei’,Acl ifs, 

Figure I-8. General notes and minimum requirements for detailing reinforcement (Sheet 1 of 2). 103-D-1 194 
GENERAL REQUIREMENTS AND DESIGN CONSIDERATIONS 13 

FILLET IP”OR GREATER FILLET ‘ES.5 THAN /P” 

TYPICAL CORNER DETAILS 

TYPICAL OFFSET DETAILS 

TYPICAL BLOCKOUT RECESS DETAILS 

:Seco”d r*ope concrete Shown ) 

SECTION A-A 

Figure l-8. General notes and minimum requirements for detailing reinforcement (Sheet 2 of 2). 103-D-1 194 
14 SMALL CANAL STRUCTURES 

(d) I;illcf,s.~Fillcts are used to relieve stress 

concentrations, provide increased strength, 

facilitate concrete placement, and to 

accommodate removal of forms. For small 

canal structures, fillets are not ordinarily 

required for these purposes. However, 6inch 

fillets which may be formed by excavation 

lines for the structure are commonly used at 

the junctions of cutoff walls and floor slabs. 

Fillets used at the base of cantilever walls are 

usually 3 inches for walls up to 8 feet tall. 

(e) Clrtojjs. -- The primary purpose of cutoff 

walls is to increase the percolation path to 

prevent piping of foundation material and 

reduce percolation. Cutoffs should be used for 

structures in a concrete-lined canal as well as 

earth canals. Cutoffs also protect a structure 

from undermining, if excessive erosion should 

occur in an earth canal. Erosion protection of 

coarse gravel or riprap is frequently required at 

the ends of structures in an earth channel to 

control erosion. Criteria to determine if erosion 

protection is required, and the type of 

protection required, are discussed later in 

subchapter VII B and shown on figure 7-8. 

These criteria should be used where protection 

is indicated on structure illustrations. The 

passive resistance of earth behind a cutoff 

increases the resistance of the structure to 

sliding, although this resistance is usually 

omitted in the stability analysis. Criteria for 

lengths and thicknesses of cutoffs are also 

included in subchapter VII B. 

1- 19. Structural Steel and 

Welding. -Structural steel used with small canal 

structures is primarily for stoplog and gate 

frame guides. Nominal size members are used 

to provide sufficient rigidity. Strength 

requirements for steel shapes used to fabricate 

safety devices such as handrail and ladders are 

also nominal. All dimensions and strengths of 

metalwork used in standard canal structures are 

included on the illustrations. 

Many illustrations in subsequent chapters 

show welding requirements for metal parts. 

Explanations of the welding symbols and 

required welding procedures are included in 

bibliography reference [ 91 

5. Carnal 

l-20. Freeboard. Xanal lining and canal 

banks are extended above the canal normal 

water surface as a safety measure to protect the 

conveyance system from overtopping. 

Freeboard provides for a canal water surface 

higher than normal which may be caused by 

sedimentation in the canal, temporary 

misoperation of the canal system, excess flows 

caused by storm runoff entering the canal 

through drain inlets, additional water depth 

resulting from a rougher friction coefficient 

than used for design, and waves produced by 

wind or surges which accompany sudden 

changes in flow. 

Figure l-9 shows the vertical distance which 

canal lining and canal banks should be 

extended above the canal normal water surface 

to provide adequate freeboard. Special 

requirements for canal bank freeboard at 

structures such as inverted siphons and drain 

inlets are discussed in the appropriate 

subchapters for each particular structure. 

Freeboard requirements for the canal 

structures are also discussed with each 

structure. 

1-21. Winter Operation. --Winter operation 

of a canal system where temperatures are 

subfreezing may require additional canal and 

structure freeboard to permit wintertime 

design capacity to flow under an ice cover. At 

subfreezing temperatures an ice cover readily 

forms when velocities are less than 2.2 feet per 

second. If velocities are fast enough to prevent 

formation of an ice cover, frazil ice may form, 

and if allowed to accumulate on racks at inlets 

to structures will cause backwater. Additional 

forces caused by expansion of the ice cover or 

by ice lenses in clayey foundation materials 

should be considered. 

l-22. Profile Sheet. -Many design examples 

of structures in this publication refer to a canal 

profile sheet. The development of the canal 

profile requires close coordination of data 

obtained from several different studies 

including: (1) canal design capacity, (2) canal 

water surface requirements for turnout 

deliveries, (3) canal location with respect to 

topography within and adjacent to the canal 

prism, (4) canal location to minimize 

disturbance or relocation of existing features, 

and (5) the canal cross section. 

Data from canal plan and profile sheets are 

essential for design of the canal structures. 
$61 r-a-r01 Gk~!u~f qma pue ‘aueJquram pa!mq ‘ax3ms pmq 103 preoqaar3 pue syueq leuua 103 pmoqaald ‘6-I J.&II 

ooucn OcKm 0009 oooc 0002 ODOI 009 00, oo+ 002 001 09 09 

I 

’ I 

anoqo 6u!u1l au 
16 SMALL CANAL STRUCTURES

6. Forms tor Structures

1-23. Mono/ithic Concrete.-It is sometimes

advantageous to use "knock-down," reusable

steel forms for monolithic concrete

construction of small irrigation structures. A

construction procedure that has been used

successfully is to assemble the specially

designed forms in an area remote from the

construction site, place and tie the

reinforcement steel in the forms, and then haul

the unit to the jobsite. After carefully placing

the structure-form into position, concrete is

placed for the entire structure.

1-24. Precast Concrete. -If a sufficient

number of structures for a small canal system

are identical, it may be economically

advantageous to precast them in a yard and

haul them to the jobsite for installation.

Figure 1-10 shows concrete being placed for

a transition, and completed transitions in the

precasting yard. Slings are frequently used to

lower precast concrete structures into position

at the jobsite, as shown in figure I-II, for

placing a precast concrete transition. Figure

1-12 shows an inplace, broken-back transition

as a component part of a road crossing

structure.

To provide a uniform bearing surface for

precast concrete structures, a thin layer of

mortar at least an inch thick should be placed

on the foundation surfaces just prior to placing

the structure. A mortar bedding for a precast

concrete inlet to a turnout structure is shown

in figure 1-13.

S t an d ard structures discussed in this

publication which require a deck for

operational purposes, show either precast walk

planks or a precast deck. Precast decks are used

for the longer spans and are not mechanically

connected to the basic structure. The bearing

area at one end should have a very smooth

surface to permit temperature-induced

elongation or contraction of the deck without

causing additional shear and bending moment

stresses on the structure. Two asbestos sheets

each having graphite on one side only and with

the graphite surfaces in contact are sometimes

used to provide such a surface.

Figure 1.10. Precast concrete transitions in various

stages of completion. P-707-729-1763

Figure 1-12. In-place precast concrete transition,

partially backfilled. PX-D-72830

Figure 1-11. Placing precast concrete transition.

P-707-729-2134
GENERAL REQUIREMENTS AND DESIGN CONSIDERATIONS 17

Figure 1-13. Precast concrete turnout inlet being

lowered into position on mortar pad. p- 707- 729-1769

Figure 1 -14. Slide gate being operated to control

flow through turnout. P(F)-200-5717 NA

c. BIBLIOGRAPHY

1-25. Bibliography.

[1] "Earth Manual," Bureau of Reclamation, Second Edition,

1974.

[2] "Concrete Manual," Bureau of Reclamation, Eighth

Edition,1975.

[3] "Fly Ash Increases Resistance of Concrete to Sulfate

Attack," Report No. C-1224, Bureau of Reclamation,

January 1967.

[4] Terzaghi, Karl, "Does Foundation Technology Really

Lag?" Engineering News-Record, February 15,1962, p.

59.

[5] "Design Criteria for Concrete Retaining Walls," Bureau of

Reclamation, August 1971.

[6] "Standard Specifications for Highway Bridges," American

Association of State Highway Officials, Tenth Edition,

1969.

[7] "Manual for Railway Engineering," American Railway

Engineering Association, Vol. 1, Current to March 13,

1971.

[8] King, H. W. and Brater, E. F ., "Handbook of Hydraulics,"

Fifth Edition, McGraw-Hill Book Co., N.V., 1963.

[9] "Structural Welding Code," American Welding Society,

lQ7.'

«Chapter II

A. GENERAL

features along the way. Canals and pipelines

will not be discussed in detail in this

publication and the technical dissertation of

the other conveyance structures will be

restricted to those having a capacity of 100 cfs

or less.

2-1. Purpose. -Conveyance structures are

those structures such as road crossings, inverted

siphons, drops, chutes, flumes, canals, and

pjpelines that are used to safely transport water

from one location to another traversing various

existing natural and manmade topographic

B. ROAD CROSSINGS

1

R. B. YOUNG

Figure 2-1. Road crossing.

2-2. Purpose and Description. -Road

crossings are used to convey canal water under

roads or railroads (fig. 2-1 ). Pipe conduit is

generally used for these purposes. In

accomplishing these objectives the road

crossing conduit may have a straight line

profile (see fig. 2-2), as discussed in these

sections, or a profile like that shown in figure

2-4 with vertical bends as discussed later in

subchapters II C, II E, and II F. Road crossings

which have vertical bends in their profile

function either as inverted siphons, drops, or

chutes.

The straight line profile conduit (road

crossing) is designed for flow with little or no

internal hydrostatic pressure; that is, the

hydraulic gradient is near or below the top of

the pipe.

2-3. Application. -Available hydraulic head

and cost considerations usually determine the

feasibility of using pipe for conveying water

under a roadway or using a bridge over the

waterway. Generally, for capacities up to 100

1 Civil Engineer, Hydraulic Structures Branch, Bureau of

Reclamation.

19
SMALL CANAL STRUCTURES 

Figure 2-2. Road crossing plan and section. 103-D-1253. 
CONVEYANCE STRUCTURES 21

Testing and Materials [ 3] provided that the

design of the joints in the pipe is such that the

taper on the tongue and groove is not more

than 3-1/2° measured from a longitudinal trace

on the inside surface of the pipe.

cfs, it is more economical to use pipe rather

than a bridge. Bridge design is beyond the

scope of this publication and consequently is

not included.

2-4. Advantages. -Pipe road crossings are

relatively economical, easily designed and built,

and have proven a reliable means of conveying

water under a roadway. Normally, canal

erosion at the ends of the road crossing in earth

canals is minor and can be controlled by

transitions and rip rap or gravel protection.

Road crossings usually cause less roadway

interference than a bridge both during and

after construction. Pipe installation is

sometimes accomplished by jacking the pipe

through the roadway foundation (fig. 2-3). A

road crossing permits both continuous roadbed

and continuous side drain ditches which

otherwise might drain into the canal.

2-5. Design Considerations.-(a) Pipe.-

The pipe may be steel corrugated-metal pipe

(CMP), precast reinforced concrete culvert pipe

(RCCP), asbestos-cement pressure pipe (AC),

or precast reinforced concrete pressure pipe

(PCP). Where watertightness of the pipe is of

m in or concern, the selection of either

corrugated-metal pipe, asbestos-cement, or

concrete pipe is often established by past

experience. However, considerations involved

with the selection include hydraulic efficiency,

corrosion environment, and cost

considerations.

The required gage (wall thickness) of CMP

for a given height of earth cover and surcharge

load from vehicles can be determined from

manufacturers' tables. A typical set of tables is

provided in bibliography reference [ I] .2 If

RCCP is used, this pipe design may also be

determined from manufacturers' tables. A

typical set of tables is provided in bibliography

reference [2] .In Reclamation RCCP pipe is

used for roadway crossings having little or no

internal water pressure. Type B pipe joints (fig.

8-15) are generally used where RCCP pipe is

permitted. However, type F joints may be

substituted for type B joints. Type F joint

design and gaskets for type F joints should be

in accordance with the American Society for

Figure 2-3. Jacking and threading pipe under roadway

P-707-729-2007.

All pipe subjected to internal pressure

should have rubber gasket joints to insure

positive watertightness. Under some roadways,

watertight joints may be necessary irrespective

of internal pressure. Precast concrete pressure

pipe with type R joints (rubber gasket joints)

or asbestos-cement pressure pipe with rubber

gasket joints is used to insure watertightness.

The minimum pressure pipe class permitted for

each is B 25 [ 4] [ 5] .Selection of the

appropriate pipe class is explained later in the

discussion of Inverted Siphons, subchapter II

C.

The hydraulic design of a road crossing pipe

consists of selecting a pipe diameter that will

2Numbers in brackets refer to items in the bibliography, see

section 2-38.
22 SMALL CANAL STRUCTURES 

result in either: (1) a maximum allowable 

velocity of 3.5 feet per second for a pipe with 

earth transitions or, (2) a maximum allowable 

velocity of 5 feet per second for a pipe with 

concrete transitions or other concrete inlet and 

outlet structures. The maximum upstream 

invert elevation of the pipe is then determined 

by subtracting the pipe diameter and 1.5 times 

the velocity head of the pipe flowing full 

(diameter + 1.5 hvp) from the upstream normal 

water surface elevation in the canal. The pipe is 

set on a minimum slope of 0.005 from this 

upstream invert elevation. This provides a low 

point at the end of the pipe to facilitate 

draining should it become necessary. 

The pipe hydraulic design should be 

examined to determine if the resulting earth 

cover from the top of the roadway to the top 

of the pipe meets the following minimum 

requirements: 

(1) At all railroad and road crossings 

(except farm roads) a minimum of 3 feet of 

earth cover should be provided. If roadway 

ditches exist and are extended over the pipe, 

the minimum distance from the ditch invert 

to the top of the pipe should be 2 feet. 

(2) At farm road crossings a minimum 

earth cover of 2 feet should be provided for 

both the roadway and the ditches. Farm 

roads are frequently ramped using 10 to 1 

slopes (10 percent grade) when necessary to 

provide minimum earth cover requirements. 

Another alternative available to the designer 

for achieving minimum cover requirements is 

to set the upstream pipe invert a distance 

greater than the pipe diameter plus 1.5 11, 

P 

below the upstream normal water surface 

elevation. However, the maximum vertical 

distance from the canal invert to the pipe 

invert should not exceed one-half the pipe 

diameter, except where a control structure is 

required. Pipe with bends in its profile to 

provide the required earth cover, or sagged for 

any other reason, is discussed with Inverted 

Siphons, subchapter Ii C. 

Roadway widths and side slopes at the 

crossings should match existing roadway 

widths and side slopes, or as otherwise 

specified. Side slopes should not be steeper 

than l-1/2 to 1. 

(b) Tmuifiom. -Transitions are generally 

used both at the inlet and outlet of structures. 

An accelerating water velocity usually occurs at 

the inlet of a structure and a decclcrating 

velocity at the outlet. Transitions reduce head 

losses and prcvcnt canal erosion by making the 

velocity changes less abrupt. Concrete, earth, 

and combination concrete-earth transitions are 

used for this purpose. 

The following road crossings require either a 

concrete transition or some type of concrete 

control structure at the inlet and a concrete 

transition at the outlet: 

All railroad and state highway crossings. 

All crossings with 36inch-diameter pipe or 

larger. 

All pipe crossings with velocities in excess of 

3.5 feet per second discharging in to an 

earth canal. 

Standardization of concrete transitions is a 

means of reducing costs. This is accomplished 

by a transition being designed for a range of 

canal and structure conditions. As might be 

expected, if concrete transitions are 

standardized, the base width and invert will 

seldom match that of the canal. Therefore, 

additional transitioning is then accomplished 

by an earth transition for an earth canal and by 

transitioning concrete lining for a 

concrete-lined canal. For relatively short 

structures, such as road crossings, it is generally 

more economical to omit concrete transitions 

if established design criteria will permit the 

omission. For the design of transitions see the 

discussion on Transitions, subchapter VII A. 

If there is a need for controlling the water 

surface elevation upstream from the road 

crossing, a check inlet or a control inlet is used. 

(See discussion of Check and Pipe Inlet and 

Control and Pipe Inlet subchapters III F and III 

G.) If one of these structures is required, it is 

usually economically desirable to also use a 

concrete outlet structure and size the pipe 

based on a maximum velocity of 5 feet per 

second. 

(c) Pi/w Colluvs. -~Pipc collars may be 

required to reduce the velocity of the water 

moving along the outside of the pipe or 

through the surrounding earth thcrcby 

preventing removal of soil particles at the point 

of cmcrgence. Any road crossing where the 
CONVEYANCE STRUCTURES 23 

canal water surface is significantly higher than 

a potential point of relief for the percolating 

water, should be examined to determine if 

collars are required. Pipe collars may also be 

necessary to discourage rodents from 

burrowing along the pipe. A detailed discussion 

of the design of pipe collars and cutoffs as 

related to percolation may be found in 

subchapter VIII C. 

(d) Cutd Erosiorl Protcctiorz. -Protection is 

often used adjacent to structures in earth 

canals where erosion may occur. For design of 

protection see the discussion on Protection, 

subchapter VII B. 

2-6. Design Example (see fig. 

2-2). -(a) Giver1 : 

(1) Type of waterway = earth canal. 

(2) Type of roadway = farm road. 

(3) Canal Q = 15 cfs. 

(4) El. A = 5406.52 (from a profile 

sheet). 

(5) d, = 1.58 ft. (normal depth at Sta. 

A). 

(6) NWS at Sta. A= El. A+ d, = 5406.52 

+ 1.58 = 5408.10. 

(7) El. D = 5406.22 (from a profile 

sheet). 

(8) dz = 1.58 ft. (normal depth at Sta. 

D>. 

(9) NWS at Sta. D = El. D + d, = 5406.22 

+ 1.58 = 5407.80. 

(10) F (water surface differential) 

= Upstream canal NWS 

El. - Downstream 

canal NWS El. 

= 5408.10 - 5407.80 

= 0.30 ft. 

(11) Width of roadway = 18 ft. 

(12) Side slopes of roadway = l-1/2: 1. 

(13) El. top of roadway = El. F = 

5411 .oo. 

(14) Control structure at inlet not 

required. 

(b) De tcrmirze: 

( 1) Pipe size (see table on fig. 2-2). 

(2) Need for concrete transitions. 

(3) Pipe type: CMP, RCCP, or PCP. 

For a pipe discharge of 1.5 cfs, the table 

shows that either a 24-inch-diameter pipe with 

concrete transitions (max. V = 5 fps) or a 

30-inch-diameter pipe with earth transitions 

(max. V = 3.5 fps) will be hydraulically 

acceptable. Since the crossing is for a farm road 

and both diameters are less than 36 inches, 

either the 24-inch-diameter pipe with concrete 

transitions or the 30-inch-diameter pipe with 

earth transitions may be used. Material costs 

and other considerations previously discussed 

will determine which pipe diameter to select, 

and in addition whether the pipe should be 

CMP, RCCP, or PCP. In this example the 

30-inch-diameter concrete culvert pipe, class III 

with type B joints, and with earth transitions 

will be used. 

(4) Hydraulic properties of 

30-inch-diameter pipe for Q of 15 cfs: 

A = area of pipe = 0.785 x dia.’ 

= 4.91 ft.2 

Q 15 V = velocity in pipe = A= 491 

= 3.06 f.p.s. 

h V2 3.06’ 

vP = velocity head in pipe zZ = 64.4 

= 0.15 ft. 

where g = gravitational acceleration 

wp = wetted perimeter = 71 x dia. 

= 7.85 ft. 

A 4.91 R = hydraulic radius =wp =7.85 

= 0.63 ft. 

n = assumed roughness coefficient3 

= 0.013 

sf = friction slope of pipe 

1 = ( > n2 V2 = 0.00133 

2.2r4 I3 

(from Manning’s equation [ 61) 

Pipe hydraulic properties may also be 

taken from table 8- 1. 

(5) El. B = NWS El. at A - (pipe 

diameter + 1.5 hvp) = 5408.10 ~ (2.50 + 

0.22) = 5405.38. 

(6) Approximate length of pipe (see fig. 

2-2) = 1.5 (El. F - El. B) x 2 + roadway 

3See section l-16 
24 

width = 3(541 1.00 - 5405.38) + 18 = 34.9 

ft. The 1.5 represents a l-1/2 to 1 side slope. 

If the side slope is 2 to 1 use 2 instead of 1.5 

in the previous equation. 

(7) Drop in pipe = length of pipe x slope 

of pipe = 34.9 x 0.005 = 0.17 ft 

(8) El. C = El. B - drop in pipe 

= 5405.38 - 0.17 = 5405.21. 

(9) Length of earth transitions = 3 x dia. 

of pipe = 3 x 2.5 = 7.5 ft. 

(10) Drop in transitions 

Upstream = El. A - El. B 

= 5406.52 - 5405.38 

= 1.14ft. 

Downstream = El. D - El. C 

= 5406.22 - 5405.21 

=-1.01 ft. 

(1 1) Assume losses in road crossing are 

1.5 pipe velocity heads for inlet and outlet 

loss combined plus pipe friction loss, or 

1.5 hvp + h, = 0.22 + 35 x 0.00133 

= 0.27 ft. 

where h, = length of pipe x friction slope. 

( 1 2) P~okctiolr.-Use figure 7-8 to 

determine if protection is required. If 

required, select type, length, and height of 

protection. 

For d, or d, = 1.58 ft. and for road 

crossings without concrete transitions: 

Inlet protection = none 

Outlet protection = 12-m. coarse gravel 

(type 2) 

Length = 4d or 5 ft. min. = 4 x 1.58 ft. = 

6.3 ft. 

SMALL CANAL STRUCTURES 

Because the transition length of 7.5 feet is 

not much greater than the required protection 

length, extend protection for full length of 

transition. Extend protection to 12 inches 

above canal water surface. 

(c) Check of Desigrf. ~ 

(1) Compare computed losses with the 

loss provided on profile sheet. Computed 

losses = 0.27 foot. Loss provided, F = 0.30 

foot. The excess head of 0.03 foot (0.30 - 

0.27) provided on the profile sheet is 

inconsequential and the hydraulic design is 

considered adequate. 

(2) Trunsition slopes. -To reduce 

turbulence and provide for relatively smooth 

transitioning of the water prism, the 

maximum length to drop ratio of 4 to 1 is 

used. The design ratio of the upstream 

transition is 7.5 to 1.14 or 6.6 to 1. This is 

flatter than 4 to 1 and therefore within the 

criteria limits. By inspection, the slope of 

the downstream transition is also 

satisfactory. 

(3) Cover on I.‘i[le.-Minimum earth cover 

for farm road crossing is 2 feet. 

Approximate cover on pipe = El. F - (El. B 

+ dia. of pipe) = 5411.00 ~ (5405.38 + 

2.50) = 3.12 feet. As 3.12 feet is greater 

than the minimum required 2.0 feet the 

cover is satisfactory. 

If concrete transitions are required for a 

road crossing the inlet and outlet transitions 

will usually be identical. Refer to subchapter 

VII A and design example of inverted 

siphons subchapter II C for procedure used 

in design of type 1 concrete transitions. 

C. INVERTED SIPHONS 

R. B. YOUNG’ 

2-7. Purpose and Description. -Inverted excess head when flowing at design capacity. 

siphons figures 2-4, 2-5, and 2-6 (sometimes Closed conduits with excess head are 

called sag pipes or sag lines) are used to convey discussed in subchapters II E Drops and II F 

canal water by gravity under roads, railroads, Chu tcs. 

other structures, various types of drainage Closed conduits with straight profiles under 

channels, and depressions. A siphon is a closed roadways and railroads may also function as 

conduit designed to run full and under inverted siphons with internal pressure. 

pressure. The structure should operate without 2-8. Application. -Economics and other 

considerations determine the feasibility of 

‘Op. cit., p. 19. using a siphon or another type of structure to 
CONVEYANCE STRUCTURES 

Figure 24. Inverted siphon plan and section. 103-D-1254. 
26 SMALL CANAL STRUCTURES

accomplish the previous objectives. The use of

an elevated flume would be an alternative to a

siphon crossing a depression, drain channel or

another manmade channel. The use of a bridge

over a canal would be an alternative to a siphon

under a road or a railroad. Generally, for

capacities up to 100 cfs, it is more economical

to use a siphon rather than a bridge. Bridge

design is beyond the scope of this publication

and consequently is not included.

where the value of the head required to operate

a siphon may justify the use of another

structure such as a bridge.

An inverted siphon may present a hazard to

life, especially in high population density areas.

See chapter IX for safety features.

2-10. Structure Components.-(a) Pipe.-

The closed conduits discussed in this

publication are generally pipe. All pipe

subjected to internal pressure should have

watertight joints. Precast reinforced concrete

pressure pipe (PCP), asbestos-cement pressure

pipe (AC), or reinforced plastic mortar pressure

pipe (RPM), all with rubber gasket joints, are

used to insure watertightness. For heads up to

150 feet precast reinforced concrete pressure

pipe is most frequently used but any of the

above types may be used depending on their

availability and cost considerations.

Figure 2-6. Inverted siphon inlet transition and

60-inch~iameter precast concrete pipe. p 499-700-520.

Figure 2-5. Inverted siphon under construction,

P-328-701-7259A.

These pressure pipes are classed as to their

capacity to withstand external loads of cover

and wheel (equivalent earth cover) and internal

hydrostatic head measured to the centerline of

the pipe. Designations of A, B, C, and D

represent 5, 10, 15, and 20 feet of cover

respectively, while the associated number such

as 25, 50, 75, 100, 125, and 150 represents

feet of hydrostatic head. As an example, C 50

would be pressure pipe for 15-foot maximum

cover and 50-foot maximum head.

Additional information regarding pipe, pipe

joints, pipe bends, and other pipe

appurtenances may be found in chapter VIII.

2-9. Advantages and Disadvantages of

Inverted Siphons.-Inverted siphons are

economical, easily designed and built, and have

proven a reliable means of water conveyance.

Normally, canal erosion at the ends of the

siphon is inconsequential if the structures in

earth waterways have properly designed and

constructed transitions and erosion protection.

Costs of design, construction, and

maintenance are factors that may make an

inverted siphon more feasible than another

structure that might be used for the same

purpose. There may be, however, instances
CONVEYANCE STRUCTURES 

The pipe profile is determined in such a way 

as to satisfy certain requirements of cover, pipe 

slopes, bend angles, and submergence of inlet 

and outlet. Pipe cover requirements are: 

(1) At all siphons crossing under roads 

other than farm roads and siphons crossing 

under railroads, a minimum of 3 feet of 

earth cover should be provided. Farm roads 

require only 2 feet of earth cover and are 

frequently ramped using 10 to 1 slopes ( 10 

percent grade) when necessary to provide 

minimum cover requirements. If roadway 

ditches exist and are extended over the pipe, 

the minimum distance from the ditch to the 

top of the pipe should be 2 feet. 

(2) At siphons crossing under 

cross-drainage channels, a minimum of 3 feet 

of earth cover should be provided unless 

studies indicate more cover is required 

because of projected future retrogressions of 

the channel. 

(3) At siphons crossing under an earth 

canal, a minimum of 24 inches of earth 

cover should be provided. 

(4) At siphons crossing under a lined 

canal, a minimum of 6 inches of earth cover 

should be provided between the canal lining 

and the top of pipe. 

Roadway widths and side slopes at road 

and railroad siphon crossings should match 

existing roadway widths and side slopes, or 

as otherwise specified. Side slopes should 

not be steeper than l-1/2 to 1. 

Pipe slopes should not be steeper than 2 

to 1 and should not be flatter than a slope of 

0.005. 

Changes in PCP pipe grade and alinement 

(bends) may be made with precast elbows, 

with beveled end pipe, by miter cutting pipe, 

or by pulling joints. Changes in AC and RPM 

pipe grade and alinement may be made by 

miter cutting pipe or by pulling joints. See 

chapter VIII for further information on 

bends. 

(b) Trunsitiom -Transitions are nearly 

always used at the inlet and outlet of a siphon 

to reduce head losses and prevent canal erosion 

in unlined canals by causing the velocity 

change between the canal and pipe to be less 

abrupt. Concrete, earth, or a combination of 

concrete and earth transitions are used for this 

purpose. 

27 

The following siphons require either a 

concrete inlet transition or some type of 

concrete inlet control structure, and a concrete 

outlet transition: 

All siphons crossing railroads and state 

highways. 

All 36-inch-diameter and larger siphons 

crossing roads. 

All siphons in unlined canals with water 

velocities in excess of 3.5 feet per second 

in the pipe. 

Standardization of concrete transitions is a 

means of reducing costs. This is accomplished 

by having a single transition cover a range of 

canal and structure conditions. The base width 

and invert of standardized transitions will 

seldom match those of the canal. Additional 

transitioning is then accomplished with an 

earth transition where earth canals are involved 

and with a concrete lining transition where 

concrete-lined canals are involved. 

For relatively short structures, such as 

siphons crossing roads, it is frequently more 

economical to omit concrete transitions even 

though the length of pipe will increase and size 

of pipe and protection may also increase. For 

further discussion on Transitions see chapter 

VII. 

If there is a need for controlling the water 

surface elevation upstream from the siphon, a 

check and pipe inlet or a control and pipe inlet 

is used. (See discussion of Check and Pipe Inlet 

and Control and Pipe Inlet, subchapters III F 

and III G.) 

(c) Pipe Collars.-Pipe collars are not 

normally required on siphons but they may be 

needed to reduce the velocity of the water 

moving along the outside of the pipe or 

through the surrounding earth thereby 

preventing removal of soil particles (piping) at 

the point of emergence. Pipe collars may also 

be necessary to discourage rodents from 

burrowing along the pipe. A detailed discussion 

for design of pipe collars and cutoffs as related 

to percolation may be found in chapter VIII. 

(d) BlowofT Structures. -Blowoff structures 

are provided at or near the low point of 

relatively long inverted siphons to permit 

draining the pipe for inspection and 

maintenance or wintertime shutdown. 

Essentially the blowoff structure consists of a 
28 

valved steel pipe tapped into the siphon barrel. 

Blowoffs may also be used in an emergency in 

conjunction with wasteways for evacuating 

water from canals. Short siphons are usually 

dewatered when necessary by pumping from 

either end of the siphon. If annual wintertime 

draining is not required, breaking into pipe 

smaller than 24-inch diameter for emergency 

draining is an economical alternative to 

providing a blowoff. 

A manhole is often included with a blowoff 

on long siphons 36 inches and larger in 

diameter to provide an intermediate access 

point for inspection and maintenance. 

A detailed discussion for design of blowoff 

structures and manholes may be found in 

chapter VIII. 

(e) CaauI Freehourd urzd Erosion 

Protection-The canal bank freeboard 

upstream from siphons should be increased 50 

percent (1.0 foot maximum) to prevent 

washouts at these locations due to more storm 

runoff being taken into the canal than 

anticipated or by improper operation. The 

increased freeboard should extend a distance 

from the structure such that damage caused by 

overtopping the canal banks would be minimal; 

but in any event a minimum distance of 50 feet 

from the structure. 

Erosion protection is often used adjacent to 

siphons in earth canals. A discussion of 

Protection is presented in chapter VII. 

(f) Wustewuys. --Wasteways are often placed 

upstream from a siphon for the purpose of 

diverting the canal flow in case of emergency. 

For design of wasteways see the discussion on 

Wasteways, subchapter IV B. 

(g) Sufkty Features. -Safety measures must 

be taken near siphons to protect persons and 

animals from injury and loss of life. Safety 

features are discussed in chapter IX. 

2- 11. Hydraulic Design Considerations. - 

Available head, economy, and allowable pipe 

velocities determine the size of the siphon pipe. 

Thus, it is necessary to assume internal 

dimensions for the siphon and compute head 

losses such as entrance, pipe friction, pipe 

bend, and exit. The sum of all the computed 

losses should approximate the difference in 

energy grade elevation between the upstream 

and downstream ends of the siphon (available 

head). 

SMALL CANAL STRUCTURES 

In general, siphon velocities should range 

from 3.5 to 10 feet per second, depending on 

available head and economic considerations. 

The following velocity criteria may be used 

in determining the diameter of the siphon: 

(1) 3.5 feet per second or less for a 

relatively short siphon with only earth 

transitions provided at entrance and exit. 

(2) 5 feet per second or less for a 

relatively short siphon with either a concrete 

transition or a control structure provided at 

the inlet and a concrete transition provided 

at the outlet. 

(3) 10 feet per second or less for a 

relatively long siphon with either a concrete 

transition or a control structure provided at 

the inlet and a concrete transition provided 

at the outlet. 

The velocity or pipe size of a long siphon is 

of particular importance. economically, 

because a slight change in pipe size can make a 

great change in the structure cost. 

Head losses which should be considered are 

as follows: 

( 1) Convergence loss in the inlet 

transition. 

(2) Check structure losses when a check 

is installed in the inlet. 

(3) Control structure losses when a 

control is installed in the inlet. 

(4) Friction and bend losses in the pipe. 

(5) Divergence loss in the outlet 

transition. 

(6) Transition friction losses are usually 

ignored for the size of structures in this 

publication. 

(7) Convergence and divergence head 

losses in earth transitions when required 

between the canal and concrete transition 

are usually small and are usually ignored. 

The total computed head loss is usually 

increased by 10 percent as a safety factor to 

insure against the possibility of the siphon 

causing backwater in the canal upstream from 

the siphon. 

The hydraulic head loss in a transition is 

dependent on the difference of the velocity 

heads in the canal and the normal to centerline 

section of the closed conduit. Coefficients of 

velocity head considered adequate for 

determining head losses in a broken-back type 

of transition are 0.4 for the inlet and 0.7 for 
CONVEYANCE STRUCTURES 

the outlet, therefore the losses would be 

0.4Ah, for inlet and 0.7Ah, for the outlet 

transitions. 

Coefficients of velocity head considered 

adequate for determining head losses in earth 

transitions from the canal to a pipe are 0.5 for 

the inlet and 1.0 for the outlet. Therefore, the 

losses would be 0.5Ah, for the inlet and 

l.OAh, for the outlet transitions. 

For minimum hydraulic loss, it is desirable 

to provide a seal of 1.5Ah, with 3-inch 

minimum at pipe inlet and no submergence at 

the pipe outlet. The seal is equal in height to 

the vertical drop from the normal canal water 

surface to the top of the siphon opening. If the 

siphon has both upstream and downstream 

concrete transitions it may be economically 

desirable to construct the downstream 

transition the same as the upstream transition. 

If the outlet seal is greater than one-sixth the 

height of opening at the outlet, the head loss 

should be computed on the basis of a sudden 

enlargement and the loss for both earth and 

concrete outlet transitions would be 1 .OAh, . 

For additional discussion on Transitions SW 

chapter VII. 

If there is a check and pipe inlet or a control 

and pipe inlet for the siphon see subchapters 

III F and III G for their hydraulic design. 

. Pipe friction losses arc determined by using 

Manning’s formula as is explained in section 

2- 13 or by using table 8- 1. 

Pipe bend losses are detcrmincd by using 

figure 8-l as is explained in chapter VIII. 

Special hydraulic considerations must be 

given to the inlets on long siphons where, 

under certain conditions, the inlet will not 

be come sealed. On long siphons, such 

conditions may result when the canal is being 

operated at partial flows (flows less than design 

flow) or at full design flow when the actual 

coefficient of friction is less than assumed in 

design. Under such conditions, a hydraulic 

jump occurs in the pipe and may cause 

blowback and very unsatisfactory operating 

conditions. Figure 2-7, which is 

self-explanatory, should be used to determine 

proper performance of inlets to long siphons. 

Pipe slope or diameter should be changed to 

meet the requirements noted on the figure. 

Another way of solving the air problem is to 

29 

place properly designed air vents at locations 

where air might accumulate. This procedure is 

ordinarily used only as a remedial mcasurc for 

an existing siphon with blowback problems. 

See discussion on Air Vents in chapter VIII. 

2-12. Design Procedure. amSteps required for 

design of a siphon include the following: 

( 1 ) Determine what inlet and outlet 

structures are required, and the type and 

approximate size of pipe. 

(2) Make a preliminary layout of the siphon 

profile (siphon and required inlet and outlet 

structures) using the existing ground line, the 

canal properties, and the canal stations and 

elevations at the siphon ends (fig. 2-8). This 

layout should provide pipe requirements of 

cover, slope, bend angles, and provide pipe 

submergence requirements at transitions, check 

and pipe inlets, or control and pipe inlets. 

(3) Compute the siphon head losses in this 

preliminary layout. If the head losses as 

computed arc in disagrcemcn t with the 

available head, it may be necessary to make 

some adjustment such as pipe size or even the 

canal profile. 

If the computed losses are greater than the 

difference in upstream and downstream canal 

water surface, the siphon will probably cause 

backwater in the canal upstream from the 

siphon. If backwater exists, the pipe size 

should be increased or the canal profile revised 

to provide adequate head. 

If the computed losses are appreciably less 

than the difference in upstream and 

downstream canal water surface it may bc 

possible to decrease the size of pipe, or the 

canal profile may be revised so the available 

head is approximately the same as the head 

losses. 

(4) On long siphons where the inlet may not 

be sealed there is the possibility of blowback 

and unsatisfactory operating conditions. The 

inlet should be checked for proper 

performance and adjustments made if 

necessary. 

(5) Determine the pipe class. The pipe class 

can be determined from the amount of 

external load and internal head shown on the 

pipe profile. 

2- 13. Design Example (see fig. 

2-4.)-Assume that an earth canal crosses a 
30 SMALL CANAL STRUCTURES 

SECTION A-A “, I I FREE FLOW SIPHON INLET 

“, Velociry for free flow, ‘Feit/sec 

y, : Water depth for free flow, feet 

r; Surface width for free flow. feef 

i, : Hydraulic radius for free flow, feet 

C : Diameter of pipe. feet 

s z Siooe of oioe 

Fxperfmentol curves of cri+icol Froude 

numbers see A SC E lronscct:on ,943 

En’ro,nment of Air rn F:owrnq Waler-Closed 

Condrts page ,435 

So?Diego Sta 1hi3+50 N 

San Diego sio PPO*+OP Id 

1 

54" 012 61 P60 1490 

54' 010 0033 567 i 25 

54' Cl0 029 305 4 10 

54* 010 ,T 194 10 0 

54- OS0 2716 171 /I 90 

72> 010 ,935 134 9 95 

48" 010 3053 POP iz 15 

54' 010 2198 185 10 95 

48 0'0 3643 192 13 70 

48" 010 2563 PI2 Ii 35 

48" 010 3714 19 1383 

48" o/2 3114 211 ii 20 

48" 010 104 262 733 

48" 010 0336 355 4 17 

48" 010 377 190 I3 80 

26" 010 535 264 15 00 

24: Cl3 367 349 895 

24" 016 208 378 543 

tt I t 

NOTES 

Stphon inlets marked thus Q, hove g!ven trouble rn 

operation and nir outlets were instoiied in some cases to 

reireve the blowing bock of o/r and wafer 

Ailother siphons hove not given trouble in operotlon 

Study made indrcotes that free flow si 

so that Froude number WI// not /oil o ff eve the critical 

hon miets designed 

curves established by experiments WI// give sotrsfoctory 

performance 

Procedure to determine Froude number 

For o given 0 ,diometer D, slope S. ond coeff n, colculote 

the following 

o y, Using Monningk Formula 

b 4 

c v; 

Figure 2-7. Design of free-flow siphon inlets. 103-D-1255. 
CONVEYANCE ST ‘RIJCTIIRFS 1 

Os‘sots = H ‘I3 

,SZ’I =‘p 1, 

6f*OS1= H .VlS P’ 

Ill 

$ I’ 

-0 Lo 

G 

-2 

w 

IE’SOPS = 3 .I3 

f9+6tl= 3 271’5 

ZS~9OPS = v ‘I3 

LP+6PI = v ‘VlS 

z (1 

,SZ’I =‘P 

31 
32 SMALL CANAL STRUCTURES 

state highway and an inverted siphon is the 

most feasible type of structure for conveying 

water past the highway. 

(a) Giwn; (Refer to preliminary layout, fig. 

2-8.) 

(1) Type of waterway = earth canal. 

(2) Feature being crossed = state highway 

at right angles with canal E. 

(3) Q = 15 cfs. 

(4) Sta. A = 149 + 47 and Canal Invert 

El. A = 5406.52 (from a canal profile sheet). 

(5) d, = 1.25 feet (d,, normal depth in 

canal). 

V, = 2.1 f.p.s., hvl = 0.07 ft. 

(6) NWS El. at Sta. A = El. A + d, = 

5406.52 + 1.25 = 5407.77. 

(7) Sta. H = 150 + 49 and Canal Invert 

El. H = 5405.50 (from a canal profile sheet). 

(8) d, = 1.25 ft. (d,, , normal depth in 

callal). 

v2 = 2.1 f.p.s.. h,Z = 0.07 ft. 

(9) NWS El. at Sta. H = El. H + d, = 

5405.50 + 1.25 = 5406.75. 

(10) Width of roadway = 26 ft. 

(11) Side slopes of roadway ditch and 

canal embankment = l-1/2 to 1. 

(12) El. top of roadway = El. J = 

5407.26. 

(13) El. edge of roadway shoulders = 

5407.00. 

(14) Control structure at inlet not 

required for turnout delivery. 

( 15) 1 LX-inch-deep roadway ditches. 

(16) Canal Sta. J at ($ roadway = Sta. 

150+00. 

(17) Canal bank width = 10.0 ft. 

(18) Canal bank freeboard at outlet = 

normal canal bank freeboard = 1.3 ft. 

(b) Determirw. 

(1) Inlet and outlet structure 

requirements.-The siphon crosses under a 

state highway; therefore, some kind of 

concrete inlet and outlet structures are 

required. Since a control structure is not 

needed at the inlet, use a concrete transition 

for both the inlet and the outlet. Use type 1 

transitions (fig. 7-2, chapter VII) and use the 

same transition for both inlet and outlet. 

(2) Tvpc o,t’ pipe. -This pipe will have 

internal pressure and will be passing under a 

state highway, therefore, it should be either 

precast reinforced concrete pressure pipe 

(PCP), asbestos-cement pressure pipe (AC), 

or reinforced plastic mortar pressure pipe 

(RPM) each having rubber gasket joints. In 

this example assume that because of 

availability and costs it is advantageous to 

use PCP. 

(3) Pipe size. (SW tuble on fig. 2-4.)-For 

a relatively short siphon having concrete 

inlet and outlet transitions, the pipe would 

be sized for velocity of about 5 feet per 

second. Then for a discharge of 15 cfs the 

table suggests that a 24-inch-diameter pipe 

may he used. 

(4) Hydraulic properties of 

24-inch-diameter pipe for Q of 15 cfs. 

A = area of pipe = 0.785 x (dia.)2 

= 3.14 ft.* 

Q 15 V = velocity in pipe =A=-~ 

= 4.77 f.p.s. 2 

11 

V2 4.77 

vP 

= velocity head in pipe =- =m 

& 

= 0.35 ft. 

whcrc g = gravitational acceleration. 

wp = wetted perimeter = 71 dia. 

= 6.28 ft. 

3.14 r = hydraulic radius =$=-- 6.28 

= 0.5 ft. 

n = assumed roughness coefficient3 

= 0.013 

sf = friction slope of pipe 

Hydraulic properties of pipe may also be 

taken from table 8-l in chapter VIII. 

(5) Additional canal bank freeboard at 

upstream end of siphon.-Additional canal 

bank freeboard = 0.5 of normal 

3See section 1 -I 6 
CONVEYANCE STRUCTURES 33 

freeboard = 0.5 x 1.3 = 0.65 ft., use 0.7 ft. 

(6) Canal bank El. at Sta. A = NWS El. + 

regular freeboard + additional freeboard = 

5407.77 + 1.3 ft. + 0.7 ft. = 5409.77. 

Extend the bank at this elevation a distance 

of 50 feet upstream from the siphon to 

minimize damage which could be caused by 

overtopping. 

(7) Canal bank El. at Sta. H = NWS El. + 

freeboard = 5406.75 + 1.3 ft. = 5408.05. 

(8) Illlet trailsitioil hydraulic 

setting. -The transition invert elevation at 

the headwall (Sta. C) is based on the 

hydraulic seal required at the top of the 

headwall opening and the vertical height of 

the opening, Ht. Pipe slope affects this 

D vertical dimension since Ht = - where COScyl 

D = pipe diameter and 01~ = angle of pipe 

slope at headwall. The scaled value of cy, is 

usually adequate since a small error in o(~ 

will not significantly affect Ht. The scaled 

value ofa, is 12O. 

Ht =so =os= 2.04 ft 

Hydraulic seal required = 1.5 Ah, = 1 .5(hvp 

- h,,) = 1.5 (0.35 - 0.07) = 0.42 ft. which 

is greater than 3 inches (0.25 ft.) minimum 

seal required, therefore, 0.42 foot should be 

used. Transition invert El. C = NWS El. at 

Sta. A ~ (1.5 Ah, + Ht) = 5407.77 - (0.42 + 

2.04) = 5405.31 

If the transition invert at the cutoff (Sta. 

B) is set at the canal invert, the difference in 

invert elevations of the transition (p) is 

5406.52 - 5405.31 = 1.21 ft. = p. See figure 

7-2 for p. The maximum p value for the inlet 

is-$ D and the maximum p value for the 

outlet is $D. Therefore, by making the inlet 

and outlet identical, p cannot exceed+D 

which isiof 2 or 1 .O ft. (see subchapter VII 

A). Use a p value of 1.0 foot, then the inlet 

transition invert El. B will not be the same as 

the canal but will be El. C + p or 5405.31 + 

1.00 foot = 5406.3 1 which is 0.21 foot 

lower than the canal invert at Sta. A. The 

invert slope for a IO-foot-long earth 

transition resulting from the use of p = 1.0 

foot should not be steeper than 4 to 1 (see 

sec. 7-l 1). The actual slope = 10 to n Inv. of 

earth transition = 10 to 0.2 1 = 48 to 1 which 

is flatter than 4 to 1 and therefore 

permissible. 

(9) Outlet trausitiorz hydraulic 

setting. -To minimize headwall 

submergence, set the downstream invert 

elevation (Sta. G) of the transition at canal 

invert. Then the transition invert El. G = 

canal invert El. H = 5405.50. For the inlet 

and outlet transitions to be identical, p = 1.0 

foot. Then transition invert El. F = El. G - p 

= 5405.50 - 1.00 = 5404.50. 

The height of headwall opening (Ht) at 

station F is, 

Ht-!?v 2 00 2.00 = A ------= 2.04 ft. 

cos a2 cos 12O - 0.978 

Submergence of top of opening = 

(dz + p) - D 

cos a2 = (1.25 + 1.00) - 2.04 

= 0.21 ft. 

This submergence should not exceed 

one-sixth Ht for minimum head loss. 

One-sixth Ht = y = 0.34 foot which is 

greater than the submergence of 0.21 foot. 

Therefore, the loss for the outlet transition 

is minimum and may be calculated using the 

equation 0.7nh,. 

(10) Drop in water surface elevation 

(available head) = NWS El. Sta. A - NWS El. 

Sta. H = 5407.77 - 5406.75 = 1.02 ft. 

(1 1) Before establishing detailed siphon 

elevations and dimensions, use a preliminary 

siphon layout (fig. 2-8) and determine 

approximate total head loss and compare 

with head provided. Scale the dimensions 

and angles as required. This study will 

indicate if the pipe diameter or canal profile 

should be revised. 

Total siphon head loss with 10 percent 

safety factor = 1.1 (inlet transition 

convergence loss + pipe friction loss + bend 

losses + outlet transition divergence loss). 
34 SMALL CANAL STRUCTURES 

Pipe length scaled = about 72 feet. 

Pipe bend angles scaled = about 12’ 

(assume single angle bends). 

Approximate total head loss H, = 1.1 (hi 

+ h,- + h, + h,) where hi is inlet loss, h, is 

pipe friction loss, h, is pipe bend loss, and 

h, is outlet loss. 

H, = I. I[ 0.4nh, + pipe length x sf 

+ Ch, x 2 + 0.7nh,] 

H, = 1.1,0.:(0.35 ~ 0.07) + 72 x 0.0044 

+ (0.04 x 0.35) 2 

+ 0.7(0.35 ~ 0.07)] 

= 1.1 [ 0.1 1 + 0.32 + 0.03 + 0.201 

= I. 1 (0.66) = 0.73 foot 

Head provided by canal profile = 1.02 feet 

which is 0.29 foot more than the 0.73 foot 

required for this preliminary layout. This 

excess head will cause a slight drawdown in 

the canal upstream from the siphon and will 

result in faster than normal velocities for a 

short distance. For this design example 

assume that this velocity is noneroding so it 

is not necessary that the profile of the canal 

or the size of pipe be revised. 

( 1 2) Trurlsitiofl dime~zsioll, J’ (jig. 

7-2). -Dimension y should be determined so 

that the freeboard provided at the cutoff 

will be 0.5 foot as indicated in subchapter 

VII A. 

y = (NWS El. Sta. A - El. B) + F, 

= (5407.77 - 5406.3 I) + 0.5 

= 1.46 + 0.5 = 1.96 ft. 

Therefore. use 2 feet 0 inch. 

( 13) Trarlsitiorl dirnerlsion, u (jig. 

7-J). -Freeboard at the transition headwall 

for pipe diameters 24 inches and smaller 

may be the same as the freeboard at the 

cutoff. Therefore the top of the headwall is 

set at the same elevation as the top of the 

wall at the cutoff and is equal to: 

El. B + y = 5406.3 i + 2.00 = 5408.3 1 

a = El. top of wall - El. C 

= 5408.31 ~ 5405.31 = 3 ft. 0 in. 

( 14) Trutlsitiofl dinzerzsiorl, C. -Refer to 

the table on figure 7-2, to determine C. For 

identical upstream and downstream 

transitions, the column for water surface 

angle of 25’ should be used. 

The relationship of pipe diameter D to 

normal depth d in the canal is determined 

for use in the table and is equal to 

3.00 

D= 1.25 --x d= 1.6d. 

By interpolating in the table between D = 

1.5d and D = 2.0d, dimension C would be 

C= ,.,D+(;:;; $,,:,D - 1.8D) 

= 1.8D +++(0.5D) = 1.8D + O.lD 

= 1.9D ’ 

Then C = 1.9D = 1.9 x 2 = 3.8 feet 

Use C = 4 feet 0 inch. This may or may 

not match the canal bottom width. 

Additional transitioning of bottom width 

should be included in the earth transition. 

(15) Depth a/Id thickness of’ tramitioll 

clrtojj: -Referring to the appropriate table 

on figure 7-2, for normal depth in the canal 

of 1.25 feet, the transition cutoff depth, e, 

should be 24 inches and the thickness, tw, 

should be 6 inches. 

( 16) Corlcretc trunsitiorl lellgth, L (fig. 

7-2). ~ 

L = 3 pipe dia. = 3 x 2 = 6 feet 

( 17) Trallsition dinwmiolz B (jig. 

7-?I.-The width of the base at the headwall 

is B and is equal to 0.303 x D = 0.303 x 24 

inches = 7.272 inches. Use B = 8 inches. 

(18) Pipe e m b r d rn e II t a I1 d 

bclzds.-Embedment details for the pipe at 

the headwalls and construction requirements 

of the pipe bends are discussed in chapter 

VIII and shown on figures 8-14 and 8-l 0, 

respectively. Since the deflection angles of 

the bends will be less than 45’, only one 

miter is necessary. Also because the pipe 

diameter is less than 42 inches, a banded 

mitered pipe bend may bc used with a 

minimum band thickness of 1 inch. Since 

the hydraulic thrust caused by the bend is 

directed into the pipe foundation, stability 

of the bend is probably sufficient. 
CONVEYANCE STRUCTURES 

Unusually poor foundation conditions in 

addition to high heads, large diameter pipe, 

and large deflection angles may, however, 

require that the thrust be considered when 

determining the foundation reaction. 

(19) Firzul siphon prof’ile (fig. 

2-Y). -Using the elevations, dimensions, and 

earth slopes previously computed or given, 

determine the final structure stationing, pipe 

elevations, and pipe slopes. 

Stations C and F at the transition 

headwalls are controlled by the roadway 

earthwork dimensions and side slopes and 

headwall thickness. From figure 2-9 it can be 

determined that station C must be at least 

34.36 feet upstream from the roadway 

centerline. 

Sta. C = Sta. J - 34.36 ft. 

= Sta. (150+00) - 34.36 ft. 

= Sta. 149+65.64 (or less) 

Use Sta. C = Sta. 149+65 

Sta. B is then 

= Yta. C - 6.00 feet 

= Sta. (149+65) - 6.00 feet 

= Sta. 149+59 

and Sta. A becomes 

= Sta. B ~ 10.00 ft. 

= Sta. (149+59) - 10.00 ft. 

= Sta. 149+49 

The small difference in the given value for 

station A (149+47) and the computed 

station (149+49) is not significant enough to 

require any canal invert profile changes. 

Stations F, G, and H are determined in 

the same manner as stations A, B, and C. 

From figure 2-9 it can be determined that 

station F must be at least 30.38 feet from 

the roadway centerline. 

Sta. F = Sta. J + 30.38 ft. 

= Sta. (150+00) + 30.38 ft. 

= Sta. 150+30.38 (or greater) 

Use Sta. F = Sta. 1 SO+3 1 

Sta. G is then 

= Sta. F + 6.0 ft. 

= Sta. (150+3 1) + 6.0 ft. 

= Sta. 150+37 and 

Sta. H becomes 

= Sta. G + 10.0 ft. 

= Sta. ( 150+37) + 10.0 ft. 

= Sta. 150+47 

35 

Here again the difference between the given 

and computed values for station H is small 

and will not require any canal invert profile 

changes. 

Stations D and E are selected to insure 

that a 2-foot minimum of earth cover on the 

pipe is provided at the roadway ditches. The 

inverts of the V-ditches are located 15.25 

feet from the roadway centerline. Therefore, 

the pipe bend inverts should be located 

about 16 feet from each side of the 

centerline of the roadway. 

Then Sta. D = Sta. J - 16.00 ft. 

= Sta. (150+00) - 16.00 ft. 

= Sta. 149+84 

El. D is determined by subtracting the pipe 

diameter, the shell thickness, and the 

minimum cover from the elevation of the 

ditch invert. 

El. D = (5407.00 - 1.5 ft.) - (2.00 ft. 

+ 0.25 ft. + 2.00 ft.) = 5401.25. 

Determine Sta. E = Sta. J + 16.00 ft. = 

Sta. (150+00) + 16.00 ft. = Sta. 150+16. 

El. E is determined by subtracting the 

product of the distance between stations D 

and E and the pipe slope 0.005 (which is a 

minimum slope) from El. D. 

El. E = El. D - 32 ft. x 0.005 = 

5401.25 - 0.16 ft. = 5401.09. 

Upstream pipe slope (S, ). Slope of the pipe 

between stations C and D is calculated as 

follows: 

Horizontal distance = Sta. D ~ Sta. C 

= (149+84) - ( 149+65) = 19 feet 

Vertical distance = El. C ~ El. D 

= 5405.31 - 5401.25 = 4.06 feet 

s1 = 

vertical distance _ 4.06 ft. 

horizontal distance 19 ft. 

= 0.214 

Angle of the slope is the angle whose 

tangent is 

= 0.214, (Y* = 12OO5’ 
36 

60’lOtS = 3 ‘13 

7 

-25 

91+051= 3 ‘VlS 

3 

c 

F 

I 

IE’SOPS= 3 ‘13 

S9+6W = 3 ‘VlS f 

-0 -- 

d 

zS’90tS = v ‘13 I 

6P+6*1= v ‘VlS 

,SZ’I -‘P 

SMALL CANAL STRUCTURES 
CONVEYANCE STRUCTURES 37 

Downstream pipe slope (S3). Determine 

slope of the pipe between stations E and F. 

Horizontal distance = Sta. F ~ Sta. E 

= Sta. (150+31) - Sta. (150+16)= 15 ft. 

Vertical distance = El. F - El. E 

= 5404.50 - 5401.09 = 3.41 ft. 

s, = 

vertical distance = 3.41 ft. 

horizontal distance 15 ft. 

= 0.228 

Angle of the slope is the angle whose 

tangent is 0.228, 

012 = 12’51’ 

(20) Final siphon head losses. -Total final 

siphon head loss with 10 percent safety 

factor = 1.1 (inlet transition convergence 

loss + pipe friction loss + pipe bend losses + 

outlet transition divergence loss), 

or H, = 1.1 (hi+h,+h,+h,) 

H, = 1. 1 [ 0.4Ah, + pipe length x sf 

+ C h, P 

x 2 + 0.7nh,] 

Determine pipe length: 

From station C to station D 

Length = (Sta. D - Sta. C) 

coscl, 

19 ft. = 

cos 12’05’ 

_ 19 ft. 

0.978 

= 19.4 ft. 

From station D to station E. Since pipe 

slope is relatively flat, use horizontal 

distance = 

Sta. E ~ Sta. D = Sta. (150+16) 

- Sta. (149+84) = 32.0 ft. 

From station E to station F 

Length = (Sta. F - Sta. El = 15 ft. 

cos cl2 cos 12’51’ 

=g&= 15.4 ft. 

Total pipe length = 19.4 + 32.0 + 15.4 = 

66.8 ft. Therefore, the total head loss in the 

siphon is: 

H, = 1.1[0.4(0.35 - 0.07) + 66.8 

x 0.0044 + (0.04 x 0.35) 

x 7 + 0.7 (0.35 - 0.07)] 

= 1.1 (0.11 + 0.29 + 0.02 + 0.20) 

= 0.68 ft. 

Since the head provided (1.02 feet) is 

greater than the head required (0.68 foot), a 

slight water surface drawdown will occur for 

a short distance upstream from the siphon. 

This excess head will cause faster than 

normal velocities. For this design example 

assume that these velocities are still 

noneroding so neither the canal profile nor 

the pipe size need be revised. 

(2 1) Erosion pro tectiow -Refer to figure 

7-8 in chapter VII B. The water depth in the 

canal is less than 2 feet so protection is not 

required at the end of the siphon. 

(22) Pipe collars. -Refer to subchapter 

VIII C. Assume that collars are not needed 

to discourage burrowing animals but collars 

may be necessary to slow the percolation of 

water along the pipe even without their 

burrows. The difference in elevation 

between the canal water surface and the 

roadway ditch is 2.3 feet (AH). The 

weighted creep ratio, percolation factor, 

required to prevent piping is assumed to be 

3.0. Determine the weighted creep length 

(L, ) from the inlet transition to the first 

roadway ditch assuming the seepage water 

flows along the bottom side of the siphon 

from station B to station D; then along the 

outside of the pipe to the top of the pipe; 

and finally through the earth to the ditch 

invert. Weighted creep lengths are derived by 

multiplying the path length by one if the 

path is vertical and between structure and 

earth; by one-third if the path is horizontal 

and between structure and earth; and by two 

if the path is through earth. 

L, = (2 x vertical dimension of cutoff) 

x 1 + (Sta. D - Sta. B) x l/3 

+ (outside diameter of pipe) x 1 

+ (earth cover on pipe) x 2 

= (2 x 2) x 1 + (25) x l/3 + 2.5 x 1 

+2x2 

= 4.0 + 8.3 + 2.5 + 4.0 = 18.8 feet 
3% 

Determine the percolation factor (PF) that 

this weighted creep distance will provide. 

Since the percolation factor provided (8.2) is 

greater than that assumed to be necessary 

(3.0), pipe collars are not needed. 

(24) Blowhack. -Refer to section 8-16. 

This siphon structure is short and not likely 

(23) Blotvojlf: -Refer to subchapter VIII 

C. The structure is short and the pipe may 

be drained by pumping from the ends so 

a blowoff is not required. 

SMALL CANAL STRUCTURES 

to have blowback because the air that might 

be entrained due to a possible freeflow inlet 

and hydraulic jump will probably be carried 

downstream and exhausted at the 

downstream end of the siphon. 

(26) S~jbf~> jeutlrvcs. -Refer to chapter 

IX. 

(25) C1as.s of’ PCP.-The equivalent earth 

load on the pipe will not exceed 10 feet (3 

feet of earth cover + H20 loading is a total 

equivalent earth cover of 9.1 ft.-subchapter 

1 B) and the hydrostatic head measured to 

the centerline of the pipe will not exceed 25 

feet, therefore class B 25 PCP is satisfactory. 

The pipe designation will then be 24 B 25. 

D. BENCH AND ELEVATED FLUMES 

R. B. YOUNG’ 

2- I 4. Purpose and Descriptiorr. -(a) Germ - 

crul.--Flumes are used to convey canal water 

along steep sidehill terrain, or to convey canal 

water over other waterways, or natural 

drainage channels. Flumes are also used at 

locations where there is restricted right-of-way 

or whcrc lack of suitable material makes 

construction of canal banks undesirable or 

impracticable. 

Flumes supported on a bench excavated into 

a hillside are called bench flumes (figs. 2-l 0 

and 2-l 1). Flumes supported above the ground 

with reinforced concrete, structural steel, or 

timber are called elevated flumes (figs. 2-I 2 

and 2- 13). 

(b) BcJtlch fl~r?ze.s.--A bench flume is usually 

rectangular in shape and made of reinforced 

concrete (fig. 2-l 7) with inlet and outlet 

transitions to the adjoining canal. Excavation 

into the hillside to form the bench should be of 

sufficient width to provide for an access road 

along the downhill side unless other provisions 

have been made for a road. 

Some reasons for using a bench flume along 

steep sidehill terrain rather than a canal or 

pipeline, could be economy or practicality of 

construction and maintenance. 

Where there is a possibility of falling rock 

damaging the flume, protective backfill should 

be placed to near the top of the flume wall 

adjacent to the hillside. Where severe rockfall 

problems may be encountered, especially with 

flumes for small discharges, it may be more 

economical and practicable to use precast 

concrete pressure pipe in a trench and provide 

3 feet of earth cover as is shown in figure 2-14. 

If the rockfall is only over a short reach of 

flume it may be preferable to provide a 

reinforced concrete cover for this reach. 

(c) Elevated Flumes. -Elevated steel flumes 

with a semicircular shape were commonly used 

at one time to carry canal water over natural 

drainage channels or depressions. Elevated 

flumes now are seldom used because of 

associated maintenance problems, 

environmental considerations, aesthetics, and 

because of the the availability of precast 

concrete pressure pipe with rubber gasket 

joints that can usually be more economically 

constructed under natural drainage channels or 

depressions. 

Because the elevated flume is so limited in 

its usage it will not be discussed in detail in this 

publication. Overchutes, discussed in 

subchapter IV C (fig. 4-30), are a type of 

elevated flume used to convey cross-drainage 

water over a canal. These overchutes are 

usually steel pipe or rectangular reinforced 

‘Op. cit., p. 19. concrete channels. 
CONVEYANCE STRUCTURES 39

Figure 2.12. Elevated flume crossing natural drainage.

PX.D-4592

Figure 2.10. Concrete bench flume.

Figure 2-13. Early day elevated flume. P42-D-45751

Figure 2-11. Concrete bench flume.

P336-D-48829

1. Hydraulic Considerations

2-1 S .Flume Section. -(a) Ratio ~- The

most hydraulically efficient rectangular bench

flume section is one with atratio equal to 2 [ 6] .

Although this ratio is often used, other

considerations may suggest that the flume

should be narrower or wider. For example, a

narrower section may be more economical

alang a steep hillside where rock excavation is

required. A narrower section may also be

necessary because of limited right-of-way, yet a

wider section reduces the wall heights which

could effect economy.

A study of tratios in regard to hydraulic

efficiency and construction costs ( excluding

excavation and backfill) indicates that an

accePtable-} ratio is in the range between

about 1 and 3. For any *ratio in this range the

respective values of area, velocity, and wetted

perimeter are nearly identical for any slope

between 0.000 1 and 0.100 and for any flow

between 0 and lOO cfs.

(b) Slope and Velocity.-The most

economical flume section will have velocities

greater than those allowed in an earth canal.

Because velocities in a flume are ordinarily

greater than in an earth canal, a steeper slope

will be required.

Flume design velocities are ordinarily

substantially slower than critical velocities, and

therefore, subcritical flow exists. If. however.
SMALL CANAL STRUCTURES 

Compacted backf i 1 I 

Figure 2-14. Concrete pipeline for bench construction. 103-D-1258 

design velocities are faster than critical, 

supercritical flow exists and the bench flume 

performs hydraulically as a chute and an 

energy dissipator is required at the structure 

outlet. See subchapter II F for chute design. 

Studies show that with the i ratio equal to 

1, 2, or 3 and for capacities of 100 cfs or less 

the slope of the flume invert should not be 

steeper than s = 0.002. This criteria applies not 

only to the nume design slope but also to the 

actual flume slope due to construction 

tolerances that could otherwise result in 

supercritical slopes. 

Studies also show that with these ratios and 

capacities a rectangular flume invert slope of 

0.005. for example, is nearly always steeper 

than critical slope resulting in supercri tical 

flow. Flume slopes should be substantially 

flatter than critical slope because flows at or 

near critical depth tend to be rather unstable. 

resulting i n undesirable water surface 

undulations. 

Using an n value of 20 percent less than the 

nominal design ii, a verification should be 

made to see that the depth does not approach 

critical depth where the bottom might be 

raised above design grade due to construction 

tolerances. 

( c) Freehouvu’. --Bench flume freeboard 

should be correlated with the adjacent canal 

freeboard so that overflow from either will 

result in the least amount of damage to canal, 

flume, and facilities downhill from the 

overflow. 

Freeboard for flumes will depend upon a 

number of factors, such as the size of flume, 

velocity of water, curvature of alinement, and 

anticipated method of operation. Figure l-9 

may be used as a guide for determining 

minimum freeboard for flumes. 

2-l 6. Transitions. -(a) Gerzerul. -Wherever a 

bench flume is used with a canal, transitioning 

from the canal section to the flume section is 

usually required to provide a relatively smooth 

water surface and to conserve energy. This is 

usually also true with transitioning from flume 

section to canal section, especially if the canal 

section is unlined. 

As discussed in chapter VII, where concrete 

transitions are required for inline structures 

they are usually broken-back (type 1) 

transitions for the capacity range in this 

publication. Where the flume velocity is not 

much more than the canal velocity, an abrupt 

change in water prism from canal to flume may 

be permitted. The canal base width should, 

however, be uniformly varied to match the 

flume base width and flume wingwalls should 

be provided to retain the canal banks and to 

serve as cutoffs to prevent flow along the 

outside of the flume. 

( b) lizlet. -Usually flume velocities are 

greater than canal velocities, resulting in 

increasing velocities through the inlet transition 

and a drop in the water surface by an amount 

sufficient to produce the necessary increase in 

velocity and to overcome friction and 

transition losses. Neglecting the transition 

friction loss, which is usually small, and 
CONVEYANCE STRUCTURES 41 

assuming 0.3 Ah, for a broken-back inlet 

transition loss, the total drop in water surface 

is 1.3 ah,. 

The transition invert elevation at the cutoff 

is set to match that of the canal, whereas the 

transition invert elevation at the flume is set 

below the flume normal water surface by an 

amount equal to normal depth in the flume. 

The length of the inlet transition is 

determined by using a maximum convergence 

angle of 27-l/2’ between the water surface and 

the transition centerline. 

(c) Outlet. -The outlet transition divergence 

loss for a broken-back outlet transition to a 

rectangular channel is approximately 0.5 Ah,. 

The total rise in the water surface from the 

flume to the canal, neglecting friction, is equal 

to (l-0.5) nh, = 0.5 Ah,. 

The transition invert at the cutoff and at the 

flume is set in the same manner as the invert 

for the inlet transition except 0.5 Ah, is used 

for difference of water surface (LIWS). 

The length of the outlet transition is 

determined by using a maximum divergence 

angle of 22-l/2’ between the water surface and 

the transition centerline. 

(d) Freeboard. -Freeboard at the transition 

cutoff adjacent to concrete canal lining, other 

hard surface, or buried-membrane canal lining 

is usually the same as the lining freeboard. In 

unlined and earth-lined canals the minimum 

freeboard should be 6 inches for water depths 

up to 1.25 feet; 9 inches for depths of 1.26 to 

2.00 feet; and 12 inches for depths of 2.01 to 

5.00 feet. Freeboard at the flume end of the 

transition should be the same as the flume 

freeboard. 

(e) Cutofjk -Transition cutoff walls should, 

in general, be a minimum of 24 inches deep for 

water depths up to 3 feet at the cutoff; 2 feet 6 

inches deep for water depths of 3 to 6 feet; and 

3 feet for water depths greater than 6 feet. The 

minimum concrete thickness should be 6 

inches for 24-inch cutoffs and 8 inches for 

cutoffs deeper than 24 inches. 

2. Structural Considerations of a 

Rectangular Bench Flume 

2-l 7. Flume Section. -(a) Stability. -After 

backfill requirements have been determined, 

resistance to sliding from uphill b&ckfill 

pressure must be provided. If the deadweight 

of the empty flume does not furnish the 

required resistance to backfill pressure on the 

uphill side, the base may be extended to engage 

additional earth weight. The ratio of the 

horizontal forces to the vertical forces should 

not exceed the coefficient of sliding. The 

friction coefficient for sliding of concrete on 

earth is frequently assumed to be 0.35. Then 

$-$ should be equal to or less than 0.35. The 

resultant of all forces considered in the analysis 

for sliding should intersect the base of the 

flume within the middle-third to provide 

bearing pressure over the entire base width. 

(b) Wall Lauds. -Considerations for the 

structural design of a concrete bench flume 

section must include the deadweight of the 

flume and the backfill loads outside the flume 

with and without water in the flume. 

If backfill is not required behind the walls, 

the water surface inside the flume is assumed 

to be at the top of the walls. 

For flume walls which retain backfill, the 

internal water pressure is usually omitted for 

this size structure and only the exterior earth 

load due to the backfill is used. A saturated 

earth load and wheel loads are used where 

appropriate. 

If wintertime operation is required, an ice 

load must also be considered. 

(c) Comvetc Thichwss. -Concrete thickness 

at the base of vertical cantilever flume walls is 

determined by conventional reinforced 

concrete design methods. The floor thickness is 

usually made the same as the wall thickness at 

the junction of the wall and floor, and is 

usually uniform across the width of the flume. 

(d) Druirzage. -Pipe drains are intermittently 

placed under the flume to remove storm runoff 

water or any other water which might 

otherwise collect behind the uphill flume wall 

and cause stability and foundation problems. 

(e) Joilzts.-The flume should be provided 

with rubber water stop joints every 25 feet. 

The joints are usually butt joints without 

elastic filler except that elastic filler joints 

should be used from the PC to the PT of curves 

and adjacent to transitions. Bell joints are not 

recommended. 
42 

(f) Sufety Requirements. -Most flumes with 

capacities of 100 cfs and less do not require 

safety facilities because they are generally in a 

low exposure classification, and in addition a 

combination of the depth and velocity of water 

in the flume is not considered hazardous. 

Flumes in class A, B, or C exposure areas will 

require fencing to prevent persons from 

entering the flume. This is especially necessary 

if the flume is backfilled to the top of the 

hillside wall. Fencing or guardrail may also be 

required to keep animals and vehicles out of 

the flume and to protect operating personnel. 

Flumes with wall heights greater than 3 feet 

will require escape ladders at 500-foot intervals 

to permit a person to climb out. See chapter IX 

for additional safety de tails. 

2-l 8. Design Example. -(a) GiverI. - 

(1) A bench flume is to be used along a 

canal alinement to convey the canal water 

along a steep hillside. Excavation for the 

bench will be in rock. Debris and loose rock 

is not expected to be falling so the uphill 

flume wall will not require backfill. 

(2) Pipe drains will be required under the 

flume to remove hillside runoff water from 

behind the uphill flume wall. Assume that a 

6-inch drain every 100 feet will fulfill this 

requirement. 

(3) An access road adjacent to the flume 

on the downhill side will not be required 

since a natural bench exists a short distance 

downhill from the flume and will be 

improved to provide access. 

(4) The earth canal has the following 

hydraulics properties at each end of the 

flume: Q = 100 cfs, s = 0.00056, n = 0.025, 

d = 3.00 ft., b = 10 ft., S:S = l-1/2:1. A = 

43.5 sq. ft., V = 2.30 f.p.s., R = 2.09, h, = 

0.08, and F, = 1.9 ft. At the upstream end 

of the flume structure the canal station is 

l+OO and the invert elevation of the canal is 

1000.00. At the downstream end of the 

flume structure the canal station is 6+50 and 

the invert elevation of the canal is 998.80. 

The head loss provided for the bench flume 

structure is therefore 1.20 feet. 

(5) Use broken-back inlet and outlet 

transitions from the earth canal to the flume 

set tion. 

SMALL CANAL STRUCTURES 

(6) Flume roughness coefficient n is 

assumed to be 0.014 (see sec. l-16). 

(b) Determine. - 

(1) Bench f’lume section. -Bench 

excavation for construction of the flume will 

be in rock on a fairly steep hillside. For 

economy of construction including 

excavation costs, assume that of the 

acceptable flume sections previously 

mentioned the one with a i ratio equal to 

about 1, for slopes 0.0001 to 0.100 and 

flows 0 to 100 cfs, is also the most 

economical. 

For ideal hydraulic conditions, the drop 

in water surface from the canal to the flume 

using a broken-back transition will be equal 

to 1.3nh,. At the outlet the rise in water 

surface ideally will be O..Mh,. Slight 

deviations from these values are not 

objectionable and will exist if the head loss 

provided by the drop in canal water surface, 

from the inlet to the outlet of the flume, is 

different from the actual flume loss. 

It can be shown for these ideal hydraulic 

conditions and for the same canal hydraulic 

properties at each end of the flume, that the 

drop in rectangular section invert from the 

inlet to the outlet of the rectangular flume 

will be equal to: 

AInv+ = Y - 0.8 Ah, 

where Y is the drop in canal invert provided 

for the structure. Assume that the head 

provided will permit a flume velocity of 

about 5 feet per second and hvf = 0.39 ft. 

Then nInv.f = Y ~ 0.8 Ah, 

= 1.20 -- 0.8 (.39 ~ .08) 

= 1.20 - 0.25 = 0.95 ft. 

Further, assume that preliminary 

computations for transition lengths show 

that the inlet transition will be 

approximately 15 feet long and the outlet 

transition approximately 20 feet long. The 

rectangular flume length, L, will then be 

station 6+50 minus station l+OO minus 15 

feet minus 20 feet = 5 15 feet. 
CONVEYANCE STRUCTURES 43 

The resulting flume invert slope is then 

equal to: 

n1nv.r 0 95 

s, = - L = c5 = 0.00 184, 

rounded to 0.0018 

It has been recommended that the slope 

should not be steeper than S = 0.002 for 

subcritical flow design, so this is probably 

satisfactory. 

For S, = 0.0018 and II = 0.014 determine 

the water depth and velocity for a $ ratio = 

1 then, A = d*, wp = 3d, R =$ = 0.33d and 

R2/” = 0 48d2/3 

Using Manning’s formula [ 61 

v = 1.486 R2/3 Sll2 = 106.1 x 0.48d2 ‘3 

~;0.0018)~‘~ = 2.16d2’3 

also 

“+JB 

d2 

By equating the two expressions for 

velocity, 2. 16d2 I3 = y 

d”13 = 46.29 

d = 4.21 ft. 

Then 

A = d2 = 17.72 ft.2 

and 

100 V= m= 5.64 

and velocity head, 

hvf = 0.49 foot 

This velocity is reasonably close to the 

assumed velocity used in calculating S,. 

Design of flume section may therefore 

proceed. 

Determine critical depth and critical slope 

to see if the flume invert slope is flat enough 

to insure that design flow will be stable. Use 

n = 0.011 in the computations for critical 

slope. 

For 

b dz4.21 ft. and-= 1 d 

b= 4.21 ft. 

Use 

b = 4 ft. 3 in. or 4.25 ft. 

Then 

Q loo-. q = 6 = 4.75 - 23.5 cfs and d, 

= 0.314 q2’3 = 0.314 x 8.204 

= 2.58 ft. 

Then 

A, = b x d, = 4.25 x 2.58 = 10.98 ft.2 

Q 100 v, = xc = m= 9.1 1 f.p.s. 

wpc = 2d, + b = 2 x 2.58 + 4.25 

= 9.41 ft. 

R, =-A, _ 10.98 

-- = 1.17 

wpc 9.4 1 

RC4’” = 1.23 

s, = 3 q;413 (nV)2 =(3.211x 123) L.& . - 

x (0.011 x 9.11)2 = 0.0037 

Design slope is 0.0018 which is much 

flatter than the critical slope of 0.0037 

calculated using an n of 0.0 1 1. 

Assume that the tolerance for 

construction allows the invert to rise 1 inch 

(0.08 foot) at random points above the 

normal invert elevation. Determine what 

effect this will have on the flow using an n 

of 0.01 1. Studies show that with this n value 

and this 0.08 foot irregularity, the depth at 

this irregularity will always be greater than 

critical depth for invert slopes flatter than 

0.005 when the $ ratio is equal to 1, 2, or 3 

and capacities are not greater than 100 cfs. 

Because the value b has been rounded off 

to 4 feet 3 inches or 4.25 feet, normal depth 

for the flume section must be recomputed. 
44 SMALL CANAL STRUCTURES 

Find normal depth for b = 4.25 ft., Sb = 

0.0018, and n = 0.014. 

If the difference in the computed head 

loss and the available head is considered to 

be significant, several alternatives are 

available to the designer to theoretically 

make them equal: (1) revise the flume 

width; (2) revise the flume invert slope; or 

(3) revise the upstream or downstream canal 

invert elevations as required to pi-ovide the 

precise, calculated head loss. 

Q = 1.486 ,,4R2 13 S’ 12 

= &&-f AR213 (0.0018)“2 

= 106.14 x 0.0424AR2’3 = 4.50 AR2’” 

Assume different values for d,, until Q = 

100 cfs (see tabulation below). 

Normal depth, d,,, is therefore 4.15 feet, 

and velocity = x Qua- - - loo - 5.67 f p.s. 17.63 . L 

therefore, h,,. = 0.50 foot. Normal depth 

could also have been determined by using 

table 2-5. 

It is desirable at this stage of the design 

process to compute the total head loss of the 

bench flume structure and compare it with 

the head available. The total head loss (H,) 

is composed of three parts: (1) inlet 

transition convergence loss: (2) bench flume 

friction loss; and (3) outlet divergence loss. 

H, = 0.3 nh, + h, + 0.5 nh, 

= 0.8 ah, + Sf x L 

= 0.8 (0.50 ~- 0.08) + 0.0018 x 515 

= 0.34 -t 0.93 = 1.27 ft. 

There is only 1.20 feet of drop provided 

in canal water surface between the flume 

ends so the available head is deficient by 

0.07 foot. This shortage of head is small and 

insignificant but will cause a very slight rise 

in water surface upstream from the flume. 

Note that in the computation for total 

head loss, the canal velocity head at both the 

upstream and downstream ends of the flume 

structure was based on flow assumed at 

normal depth in the canal. Since the 

computations indicate only a slight water 

surface rise in the canal at the upstream end, 

the comparison of total head loss to head 

available is sufficiently accurate. 

(2) Lerzgth oj‘ trmsitiom (fig. 2-15). - 

0, = 27-l/2’ max. 

tan 0 1 = p = 0.52057 1 

7.38 L, = o.52057 = 14.2 feet 

Use L, = 15 feet 

O2 = 22-1/2O max. 

tan 0 2 = y= 0.41421 

2 

L2 = ~ 7.38 = 17.8 0.4142 1 feet 

Use L2 = 20 feet 

(3) Outkt tvmsition elevatiorls.-As the 

hydraulic control is downstream the outlet 

transition should be dcsigncd first, then 

proceed back through the structure to design 

the inlet transition. There is a theoretical rise 

in water surface in the outlet transition of 

0.5 Ah, or 0.5(0.50 - 0.08) which equals 

0.21 foot. The invert elevation at the 

upstream end of the outlet transition is 

therefore set below the canal normal water 

surface by an amount equal to the water 

surface rise plus normal depth in the flume, 

The upstream invert elevation is then: El. 

1001.80 ~ 0.21 - 4.15 = 997.44. The 

downstream invert elevation is set at the 

canal invert elevation which is El. 998.80 at 

station 6+50. 

Assume A, sq. ft. wp, ft. R. ft. R 213 Q, cfs 

% (4.25d) (2d+4.25) 

4.20 17.85 12.65 

4.15 17.63 12.55 

A 

WP 

(4.50 AR2’3) 

1.41 1.26 101 

1.41 1.26 100 
CONVEYANCE STRUCTURES 45 

Inlet transltton 

Figure 2-1.5. Transition lengths. 103-D-1259 
46 SMALL CANAL STRUCTURES 

C 4) III IL’ t tralzsitio?l elevatiom. -The 

station of the downstream end of the inlet 

transition is station l+OO plus 15 feet which 

equals station 1+15. The station of the 

upstream end of the outlet transition is 

station 6+50 minus 20 feet which equals 

station 6+30. The downstream invert of the 

inlet transition is set at the same elevation as 

the upstream invert of the flume. 

design flow through the flume is determined 

as follows: 

Energy El. required = Energy El. at 

the downstream end of transition + 

transition loss = El. 1003.02 

+ 0.3(11,, ~~ 11,) 

U.S. flume invert El. = D.S. flume invert El. 

+ length x slope 

= 997.44 +(Sta. 6 + 30 

- Sta. 1+ 15) 0.0018 

= 997.44 + 0.93 

= 998.37 

The energy elevation at this station is also = 

canal invert elevation + canal depth + 

velocity head in canal = 1000.00 + d + h,. 

Equate the two above equations: 

The upstream invert is set at the canal invert 

elevation which is El. 1000.00. Figure 2-16 

shows a schematic profile of the flume. 

The energy elevation at the downstream 

end of the inlet transition is determined as 

follows: 

1003.02 + 0.3(h,r - h,) 

= lOOO.OO+dth, 

or 

d + 11, ~~ 0.3(11,r -- 11,) 

= 1003.02 ~ 1000.00 = 3.02 feet 

Energy El. = Flume Inv. El. 

+ flume normal water depth 

+ flume velocity head 

= El. 998.37 + 4.15 + 0.50 

= El. 1003.02 

Assume different canal water depths d, until 

the following energy balance equation is 

satisfied: 

d + 11, ~ 0.3(h,, ~ h,) = 3.02 ft. 

The energy elevation required at the 

upstream end of this transition to discharge 

Assume a canal water depth equal to 3.07 

feet. 

NWS 

n ws 0 Outlet 

\ I r 

NWS 

El 1001.80 

dn= 4.W’ 

n 

sb =0.0018 ’ 

dn = 3.00’) 

Bench Flume ~ 

1 Outlet Itransition 

Canal - 

Figure Z-16. Schematic profile of bench flume. 103-D-1260 
CONVEYANCE STRUCTURES 47 

then : 

A = 44.85 ft. * 

V = 2.23 f.p.s. 

h, = 0.08 foot 

therefore any backwater from the flume will 

not affect the next upstream structure. It 

can also be assumed that the loss of 0.07 

foot of canal freeboard is insignificant. 

Substitute the above appropriate values in 

the energy balance equation to determine if 

a balance exists: 

(5) Flume fkeboavd. -Assume that in the 

design example, damage would be of less 

consequence if the bench flume walls were 

overtopped rather than the canal banks 

being overtopped. The canal freeboard is 1.9 

feet, so determine if about 1 foot of 

freeboard will be sufficient for the flume. 

d + h, - 0.3(h,, - h,) = 3.02 

3.07 + 0.08 - 0.3(0.50 - 0.08) = 3.02 

3.02 = 3.02 

Since a balance does exist the assumed canal 

depth of 3.07 feet is also the actual canal 

water depth. 

From the curves in figure 1-9 it can be 

determined that about 0.75 foot will be 

adequate freeboard, but 0.85 foot will result 

in a wall height of 5 feet 0 inch. Therefore, 

use a 5-foot O-inch wall height and 0.85-foot 

freeboard (fig. 2- 17). 

This means the canal depth is 3.07 feet 

instead of the normal depth of 3.00 feet. 

Assume in the design example that there is a 

long reach of canal between this flume and 

the next upstream structure and the depth in 

the canal will have returned to normal, 

(6) Erosim protection. -Refer to figure 

7-8. Protection is not required in the canal 

upstream from the flume. Downstream from 

the flume the protection requirement is a 

12-inch layer of coarse gravel extending 

about 8 feet beyond the transition and to an 

elevation 12 inches above the normal water 

surface elevation. 

Original ground surface / 

3,’ 

I 

/ 

les 

\ Compacted wshlon of 

selected moterlal 

Figure 2-Z 7. Cross section of bench flume. 103-D-I 261 
48 SMALL CANAL STRUCTURES

E. DROPS

1

R. B. YOUNG

I. General (figs. 2-23, 2-24, and 2-25) are used where the

decrease in elevation is in the range of 3 to 15

feet over a relatively short distance. Economics

dictate if it is more practicable to use a pipe

drop or an R.I. drop. Usually a pipe drop will

be selected for the smaller flows and an R.I.

drop will be selected for the larger flows. If the

drop crosses another waterway or a roadway it

will probably be more economical to use a pipe

drop.

Chutes (fig. 2-34) are usually used where the

drop in elevation is greater than 15 feet and

where the water is conveyed over long

distances and along grades that may be flatter

2-19. Function. -The function of drop

structures is to convey water from a higher to a

lower elevation and to dissipate excess energy

resulting from this drop. A canal along this

same terrain would ordinarily be steep enough

to cause severe erosion in earth canals or

disruptive flow in hard surface lined canals.

The water must therefore be conveyed with a

drop structure designed to safely dissipate the

excess energy. Different kinds of drops that

may be used are vertical, baffled apron,

rectangular inclined, and pipe drops.

Subchapter III C, Check-Drops, discusses

vertical drops without blocks for drops of 3

feet and less. Subchapter IV C, Overchutes,

discusses vertical drops with blocks.

Baffled apron drops (fig. 6-3) may be used

for nearly any decrease in water surface

elevation where the horizontal distance to

accomplish the drops is relatively short. They

are particularly adaptable to the situation

where the downstream water surface elevation

may vary because of such things as degradation

or an uncontrolled water surface. A further

discussion on baffled aprons may be found in

subchapter VI B, Baffled Aprons.

Rectangular inclined (R.I.) drops (figs. 2-18,

2-19, 2-20, 2-21, and 2-22) and pipe drops

Figure 2-19. Rectangular inclined drop with control

notch inlet.

~

Figure 2-18. Series of rectangular inclined drops. P.328-701-7738

Figure 2-20. Rectangular inclined drop. lOp.cit..p.19.
CONVEYANCE STRUCTURES 49

Figure 2-21. Rectangular inclined drop under

construction. p 222-117-36402

Figure 2-22. Rectangular inclined drop in operation.

p 222-116-53590

Figure 2-23. Pipe drop with baffled outlet and pipe

collars. P 328-701-8417
50

Figure 2-24. Pipe drops. PX-D-31406

SMALL CANAL STRUCTURES

closely spaced as to possibly preclude uniform

flow between outlet and inlet of consecutive

structures, particularly where checks or control

notches are not used at the inlets. The danger is

that sufficient tailwater depths may not exist

to produce hydraulic jumps in the pools, and

thus shooting flow may develop through the

series of drops and possibly damage the canal.

Also, with drops too closely spaced on a steep

slope, problems of excavation and backfill may

make such construction undesirable or

prohibitive. Very broadly speaking, about 200

feet of canal should be the minimum between

inlet and outlet cutoffs of consecutive drop

structures. The economic study should

compare costs of a series of drops and a chute,

taking into account advantages and

disadvantages pertinent to the specific

conditions. Since the maintenance costs for a

series of drops is usually considerably more

than for a chute accomplishing the same

function, it is sometimes economically

justifiable to spend considerably more for a

chute than for a series of drops. A more

complete discussion on chutes will be found in

subchapter II F.

2-20. Hydraulic Design. -The hydraulic

design of a drop should be completed before

the structural design with only general

consideration initially being given to the

structural details. Minimum required field data

will be the hydraulic properties and bottom

grade elevations of waterway sections above

and below the drop, and a profile of the

ground line at the drop location with

information about the foundation material.

Further hydraulic design considerations are

included with the discussion of structure

components.

Figure 2-25. Pipe drop with baffled outlet.

P-328- 701-9502

2. Rectangular Inclined Drops

2-21. Purpose and Description.-A

rectangular inclined (R.I.) drop (figs. 2-26 and

2-27) is a rectangular shaped structure with

constant width that conveys water from a

higher elevation to a lower elevation. This drop

in elevation may be any amount between 3 and

about 15 feet. The R.I. drop not only conveys

water, but it also stills the water after it has

reached the lower elevation resulting in excess

than those for drops but yet steep enough to

maintain supercritical velocities. The decision

as to whether to use a chute or a series of drops

should be based upon a hydraulic and

economic study of the two alternatives. From a

hydraulic viewpoint, drops should not be so
CONVEYANCE STRUCTURES 51 

F&we 2-26. Rectangular inclined drop-type 1. 103-D-1262 
52 SMALL CANAL STRUCTURES 

t m 

TYPICAL SLIDE SAT 

ASSEHBLl 

E 

Figure 2-27. Rectangular inclined drop-type 2. 103-D-1263 
CONVEYANCE STRUCTURES 53 

Si 

Table 2-1 .-Carla1 and lateral rectangular inclined drop dimensions and reinfbrccrnent (for lose with with fks. 2-26 and 2-27) 

(Sheet 1 of‘3). 103-D-1264-1 

S INGLE LAYER REINFORCEMENT IN POOL FLOOR 

TYPE I 

H 

HAX. 

30 

50 

70 

90 

II 0 

I3 0 

15 0 

30 

50 

70 

90 

ii 0 

13 0 

15 0 

30 

50 

70 

90 

II 0 

‘3 0 

15 0 

30 

50 

70 

90 

/I 0 

I3 0 

15 0 

30 

5 0 

70 

90 

If 0 

I3 0 

I5 0 

30 

50 

70 

90 

Q 

#AX. 

5 

5 

5 

5 

5 

5 

5 

IO 

IO 

IO 

10 

IO 

IO 

IO 

15 

15 

is 

I5 

I5 

15 

15 

TO 

20 

20 

20 

20 

20 

20 

25 

25 

25 

25 

25 

25 

25 

30 

30 

30 

30 

- 

LF LB LP HP 

3’~ 8 ” 

7’- 8 ” 

3: 8” 

I’~ 0” 

1’. 4 

+‘- 8 ” 

5-O” 

3’. 8 ” 

3’- IO” 

4’~ 3” 

q’- 8” 

5’- 0” 

5’- 5” 

5’-IO” 

4- 0” 

I’- 5” 

4’- IO” 

5’- 4 ” 

r’- g ” 

6;‘~ 2 ” 

6’ 8’, 

5’ 0” 

5 0” 

5-6” 

6 -0” 

6’- 6” 

5’. 0” 

6’- 0” 

6’- 0” 

6’- 6” 

7’-0” 

,‘-0” 

7’~ 6” 

$o’ 

7’-6’ 

8 ~0” 

8’-6- 

9’~ 0’ 

9’-6’ 

Co’ 

860’ 

8’~ 6’ 

946’ 

10’ 0’ 

IO ~6’ 

II’ 0’ 

If’-0 

8’-6’ 

9’- 6 

10’~ 0’ 

,I’~0 

If’-6 

12 ~0’ 

‘$0’ 

Y’-0 

IO’-0 

//CO 

‘/‘-6 

12’~ 0 

l2’-6 

13’-0 

Y’-6 

IO’-6 

If’-0 

/2,-o 

0 

7-6” 

5-2” 

5’ 6” 

6’ 0” 

6’ 7’ 

’ 2 

7-R’ 

8’ 2’ 

56, 

:-Ii:’ 

6’- 5’ 

7’- 0’ 

12” 

14” 

15” 

16” 

/ 7” 

/ 7” 

18” 

16” 

18” 

20” 

PI” 

22” 

23” 

24” 

l9,, 

PI’ 

23’ 

24’ 

z’- ,’ 

2,-z’ 

0’ L 3 

20’ 

?3’ 

24’ 

2’- p’ 

2’ 3’ 

7’ 4’ 

*‘. 5’ 

22 

24 

2s2 

2’.4 

2 -5 

2,-6 

P’-7 

23 

2’. I 

2’- 3 

2’-5 

- 

,‘. 7” 

2’. 9” 

!‘. ,/” 

j ‘- 0 ” 

3’- , ” 

3 ‘- p ” 

3’- 3” 

L/O” 

3’ /” 

3’ 3” 

3 ‘- 4 ” 

3 ‘- 5 ” 

3’. 6” 

3’. 7” 

3’- 4 ” 

3 ‘~ 7 ” 

3’.IO’ 

4’ 0” 

4’ 2” 

4’~ 3’ 

4’~4’ 

j’- 6” 

3’-10’ 

4&l’ 

4’. 4, 

4’~ 6’ 

4’- 8’ 

4’ 9’ 

3’ IO 

4’. 2’ 

4&t’ 

4’- 8’ 

4,-/o 

5,-o’ 

5’- 2 

4’- 0 

4’. 4 

4’ 7 

4,-/o 

dz 

+ 

hvz 

I 28’ 

I 41’ 

54’ 

/ 63’ 

, 71’ 

I 77, 

I 84’ 

I 70’ 

I 8Y 

2 03’ 

2 IS’ 

2 25’ 

2 33’ 

2 42’ 

’ 36’ 

2 18’ 

? 34’ 

2 48’ 

2 58’ 

2 69’ 

2 77’ 

2 15’ 

2 39’ 

2 56 

2 70 

2 83 

2 94 

3 03 

2 29 

2 53 

2 72 

2 87 

3 00 

3 I/ 

3 22 

2 41 

2 66 

2 85 

3 00 

h t t' 

8” 

8” 

8” 

8” 

8” 

8 

8” 

8” 

8” 

8” 

8” 

8” 

8” 

8” 

8” 

8,’ 

8” 

8” 

8” 

8” 

y ” 

8” 

8” 

8” 

8” 

Y’, 

9” 

9’ 

8” 

8” 

8” 

9” 

9” 

IO” 

IO” 

8” 

8’ 

9,, 

9” 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

5 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

5” 

6” 

6” 

5” 

5” 

5” 

5” 

/ " 

65 

5; " 

61 " 2 

64 " 

6; " 

6; " 

6; " 

6; " 

61 " 2 6; " 

6t " 

t;,L " 

7” 

7” 

6; ‘8 

$ If 

2 

6; ” 

6; ” 

7 ” 

7 ” 

7 I’ 

6:; ” 

(jf ” 

6f ” 

7 ” 

7’ 

7’ 

7 ” 

6; 

6i’ 

6;’ 

7’ 

7’ 

7, 

7;’ 

61’ 

6; 

7’ 

7’ 

- 

N 

W 

HC 

3. OF r 

EEP 

ILES 

4 

4 

4 

4 

4 

4 

4 

4 

6 

6 

6 

6 

6 

6 

6 

6 

6 

6 

6 

6 

6 

6 

6 

6 

6 

6 

6 

6 

6 

6 

6 

8 

8 

8 

8 

8 

8 

6 

8 

POOL REINF l- QUANTITIES 

EINF 

TEEL 

LB.5 

470 

560 

630 

7/o 

790 

860 

940 

600 

700 

800 

900 

990 

1090 

1190 

710 

830 

960 

IO80 

I220 

1330 

1440 

830 

980 

/i/O 

1300 

1470 

1630 

1740 

920 

/ 100 

1310 

15oc 

164C 

1780 

i98C 

103c 

1236 

143c 

164G 

l/SC 

ETA1 

LBS.. 

I65 

165 

/ 6 5 

iG5 

I65 

65 

I65 

?05 

105 

?05 

PO5 

PO5 

205 

205 

210 

210 

210 

Pi0 

?f3 

2’0 

210 

250 

? 5 0 

250 

250 

250 

250 

250 

255 

255 

25.: 

255 

255 

2.5 5 

255 

?6C 

76i 

26C 

26C 

-0NGIT REINF 

4ALLS 

‘ONC. 

J YDS 

47 

55 

6 I 

68 

75 

Hi 

88 

59 

69 

78 

96 

94 

IO 3 

II I 

’ / 

8 / 

93 

IO 4 

II 5 

1; 4 

13 2 

83 

9: 

10 7 

12 2 

13 3 

14 4 

15 4 

92 

IO 6 

12 I 

13 4 

14 6 

I6 3 

17 8 

IO 2 

I/ 7 

I! 2 

I4 7 

R I- S 

1 

i 
SMALL CANAL STRUCTURES 

Table 2-I.-Canal and lateral rectangular inclined drop dimensions and reinforcement (.for use with figs. 2-26 and 2-27) 

(Sheet 2 o,f3).-Continued. 103-D-1264-2 

TYPE I 

SINGLE LAYER REINFORCEMENT IN POOL FLOOR 

1 

iTt?UCT H Q dz 

POOL RElNF, 1 QUANTITIES 

NO. MAX MAX ‘F ‘0 LP HP h t t’ 

0 OF 

YEEP 

OLC ; 

I 

N 

H 

H 

-- 

TRANSV 

ZA’: 

FLOORS 

s 

#4@9 

#4@8 

qE7 

#4@6 

+T 

#4@8 

+- 

% I 

-4@71 

#4@ 7 

%jic 

#4@/0 

#4@8 

#4@7i 

#4@ 7 

‘4@6; 

ft4@8 

# 

4@38 

w 

‘4@7 

#4@6 

#4@io 

-8 

qi?T 

*4@ 6 

f4@7$ 

*4@ 8 

*4&s 7 

#4@ 6 

*4&J 7 

#4@8 

#4@7 

“4@6j 

#4@6j 

#4@7j 

#4@6 

“4@5i 

#44@5j 

‘EINF 

TEEL 

L8S.l I M 1 

MlSC 

‘ETAL 

LBSI 

1 

1800 260 

1990 260 

8 

5 

8 

8 

8 

8 

8 

IO 

8 

8 

8 

8 

IO 

8 

8 

8 

IO 

10 

10 

IO 

10 

IO 

IO 

IO 

IO 

IO 

IO 

10 

IO 

10 

-A 

5’-2” 1 3 26’ 1 IO” 1 6” 

2200 

iz30 

1500 

1710 

1970 

260 

295 

295 

295 

IO” 7” 295 

Ii” 7” 

I I” 

2150 

2400 

2600 

/4/o 

1700 

2010 

2240 

2530 

2770 

295 

295 

295 

310 

310 

/ ” 

* 

7, 

6,i ” 

7,’ 

/ /” 

9” 

IO” 

IO” 

/I” 

7 ” 310 

310 

310 

310 

345 

345 

7” 

12” 

12” 

7j ” 

7i ” 

2 

/ I’ 

6, 

7” 

1610 

1950 

2230 

2510 

-. 

2880 

1740 

7 ” 

7 ” 

345 

345 

345 

350 

7; ” 

1 ” 

6, 

7 ‘I 21.50 

7500 

7900 

3060 

1930 

2350 

2730 

3020 

2100 

2530 

3010 

3360 

2270 

2600 

3330 

3710 

350 

350 

350 

7 ” 

7f ” 

7itf 

2 

6f ” 

7 ” 

yixt I #4(as I 24 9 

350 

355 

355 

355 

355 

395 

395 

395 

395 

400 

400 

3 46’ 10” 

3 80’ i2” 

4 06’ 12” 

4 27’ 1.3” 

3 56’ ii” 

6” 

6” 

6” 7 ” 

7; ” 

6; ” 6” tf4@7i #4@8 196 

‘f4@ 7 *4(&v 22 7 

4t4@ 7 #4g7 26 3 

#44@62’ ft4@7 29 3 

#4@7; *44gs 208 

#4@ 7 *44gs 24 0 

7 ” 

400 

400 
CONVEYANCE STRUCTURES 55 

Table 7-I.-Canal and lateral rectanmlar inclined drop dimensions and rcinforcenlent lfor use with fi,s. 2-26 arzd Z-271 

DOUBLE 

LF LE 

,d-5” 3’.3 

IO’- I ” 3’. 4 

/O-IO” 3’.5 

d6” 3’.5 

II’- 3” 3’. 7 

to’- / ” 3’. 7 

IO -10” 3’. 8 

7 

ii -8” 3’.IG 

IO’- 6” 3’. a 

I/‘- 4” 3’.IC 

iP’- I ” 3’.II 

II’-3” 3’.I( 

12’. I ” 4’.0 

13’- 0” 4’.2 

(Sheet 3 of.3)..-Continued. 103-D-1”264-3 ‘” 

TYPE 2 

LAYER REINFORCEMENT IN POOL FLOOR 

REINE MISC. 

STEEL NETIP‘ 

fLBS.I I fL9S.I I 

1*4@5; ‘t4@ *4= 33.6 

i?g ‘4@16 #4@ 7 31 9 

‘4@5 ‘4@6 ‘4@ 7 34 2 

“4@6 *4 ($15 +4@/6 37.8 

,9’.0” f-2’, 4 85’ 15” 7” 8” IO *4@5 +%@I6 ‘4@7 331 

pO’.g 7’-4” 5 02’ 15” 8” 8; /o *%$6 tt4@15 *4@6 374 

20’~6” 7’76’ 5 17’ 16” 8” 8;” IO ‘4@$ 64@t5 *4@6 396 

5 2 4” 

10 24” 

15 24” 

20 24” 

25 24” 

30 24” _I 40 24” 

50 2&X 

60 $6” 

70 3’-0” 

80 3’0” 

90 3’~6” 

100 J’L6” 

5 JANDARO DIMENSIONS 

a b Lo + Ho HS c d 

MIN. M/N 

2 I” 3’.o” 2’. 7” 2’.6” 12” 20” 3 6” 

2’. ,” 3’. 6” 3’. 7” 2’.IO” 16” 24’ 3 9” 

2’. i’ 4’-o”-- 3rm,’ ~~7 ~ ,Y -~~ 

3-2” 20” 2-2” 5 2’ 

T 

CHECK INLET 1 TYPE I ONLY 1 

LT 

GA TE I 

SIZE 

5’. 0” 36”X 12” 

6’. 0” 42”~ 16” 

7’ylj 48’;2oy 

8’. 0” 54,; 22” 

8’. 0” 60’; 24” I_: g’. 0” 66’;27” 

g’- o” 72; 3 0” 

IO’- 0” 78’; 33” 

7 ,, 

IO 0 84’;36” 

,,To” 90,x39,, 

/I’- 0” 90’142” 

P-0” 96;45” 

12’.0” 96’;45” 

‘RAML 

“T 

5’. o” 

j-6” 

5’. 6” 

5’. 6” 

5! 6” 

6’~o” 

6’. 0’ 

6’. 0” 

6’~o” 

6’-6” 

6’.6” 

6’.6’ 

6’.6” 

DESIGN CRITERIA 

Structure No 5-3 rndrcotes Q = 5 c f s H = 3 ft 

The djmensrons of the control notch ot the #n/et of the structure should be determrned for der,gn 

0 and 20% of desrgn 0 wrth control notch graphs OS shown ,n des,gn example 

The base wrdth of the structure LS determjned from the formula b = $$$ 

The m,n,m~m downstream energy grodrent for full desrgn copoc~ty IS determrned by reducrng the 

assumed “n” value for the channel by 20% ond comput!ng the depth 

“H” is the vert~col fall from the normal upstream energy gradlent to the m~n!mum downstream energy 

gradlent 

“d,” IS the height of th downstream end of the hydrouljc tump and may be determrned from the 

formula d, =-$‘+ j* or from figure 2-37 

“d,” moy be determrned by usrng figure Z-37, then from d, , A, and V, con be determrned 

The ,nvert El 

gradlent 

of the strll!ng pool IZ found by subtroctrng d,+hVp from the downstream energy 

The m,n,m~m strllrng pool length IS 4d, 

The m,n,mum freeboard for the strll,ng pool IS obtolned by urrng figure 2-33 os o guide 

The m,n,mum drstonce between chute blocks and floor blocks IS Ed 

Rernforcement steel desrgn IS based on corkrng stresses of 24,006 P s ! with o speclfred 

m,n,mum ylefd strength of 60.000 P s , 

Monol,th,c concrete des,gn based on o compress,ve strength of 4,000 P *.I at 28 days wrth 

o working stress of 1.800 P s , 

When o gate with o speclfled herght IS not ovorlable, o gate w,th next greater ovorloble 

herght should be “red with oppropr~ote frame height 
56 SMALL CANAL STRUCTURES 

Table 2-2.~ Was1ewa.v and drain rectangular inclined drop diwlensions and reinforcement (for use with figs. 2-26 and 2-27) 

/Sheet I of3,!. 103-D-I 265-l 

TYPE I 

SINGLE LAYER REINFORCEMENT IN POOL FLOOR 

I POOL REINF OUANTlTlES _.- -- 

“4@ 12 *4407; 6.7 1 680 ( 205 

12.9 
CONVEYANCE STRUCTURES 

Table 2-2.- Wasteway and drain rectangular inclined drop dinlensions and reinforcement (for use with figs. 2-26 and 2.27) 

(Sheet 2 of.?/.-Continued. 103-D-1 265-2 

TYPE I 

SINGLE LAYER REINFORCEMENT IN POOL FLOOR 

57 
58 SMALL CANAL STRUCTURES 

Table 2-2.- Wastewa)’ and drain rectangular inclined drop dimensions and reinforcement (for use with figs. 2-26 and 2-27) 

(Sheer 3 of3/.-Continued. 103-D-1265-3 

TYPE 2 

DOUBLE LAYER REINFORCEMENT IN POOL FLOOR 

POOL REINF 

de 

QUANTITIES 

NO. OF OUTER LAYER 

h:, 

h t t’ H”,:‘,‘, TRAINS”. 

RElNF 

‘ONSIT REINF. CONC s”;:“E: 1 

FLOOR 1 WALLS (‘” ‘Oy 1LBS.J 

4 44’ 14^ 7” 8” I- . . 

- -L I ~~~ 

4 46’ 14” 7” 8” IO 

~. -.-~ ~. *Gi; llfq;,6 1 

z ‘t4@7 28.2 3360 

4 63’ 14” 7” 8” IO *4@6 ‘4@6 ‘4@7 30.1 3650 

4 77’ 15” 7” 8;” IO Iy 4 (a 5; ‘f4 ($15 t@ 7 32.3 3990 

,__ II 0 ]“@5j ‘4@6 If4@7 30.9 3840 

i 4 75’ 14” -7” 8” IO 

4 90’ 15” 8’ 8;” 10 

310 

345 

345 

350 

350 

355 

355 I 355 

395 

395 

395 

400 

400 

400 

STANDARD DIMENSIONS CHECK INLET 1 TYPE I ONLY 

DESIGN CRITERIA 

Structure No 5-3 rndlcotes Q = 5 cfs H = 3 fl 

The d,mens,ons of the control notch ot the rnlet of the slructure should be delermlned for desrgn 

0 and 20% of desrgn 0 w!th control notch graphs os shown rn desrgn example 

3609% The base w#dlh of the structure 1s delerm,ned from the formula b = h+350 

The m!n#mum downstream energy grodjent for full desrgn copoc~ty 1s determIned by reducrng the 

assumed ” n ” value for the channel by 20% ond computing the depth When the strllrng pool dlscharges Into an uncontrolled channel. o control must be provrded by the ovtlel structure and 

crrt~cal deoth ot the control sectfon should be used to determrne the downstream energy gradrent 

“Ii” 1s the vertrcol foil from the normal upslreom energy grodrent lo the rn~n~nwm downstream energy 

gradrent 

d, I1 IS the herghl of the dowstreom end of the hydroultc jump ond moy be determlned from the formula. 

d2 =--$+ $-+$ or from f,gure 2-37 

“d, ” may be deiermrned by us,ng figure 2-37 then from d, , A, and V, con be delerm#ned. 

The invert El of the strll~ng pool IS found by sublroctrng d,+h,* from the downstream energy 

srodrent 

Th; m,n,mum strlllng pool length IS 3d, 

The m,n,mum freeboard for the strllrng pool ,s obtolned by us!“g figure 2-33 os o gurde 

The m,n,mum drsionce between chute blocks ond floor blocks IS 8d, 

Rernforcement steel design 1s based on working stresses of 24,000 p s ! wllh o speclfred minimum 

yreld strength of 60.000 P s I 

Monolrthrc concrete design based on o compressive strength of 4.000 P s I ot 28 days wrth o worklng 

*ire** of 1.800 p s I 

When o gate wrth o specrf,ed herghi IS not avorloble, o gale with next greater oval fable herght 

should be used with oppropr~oie frame height 
CONVEYANCE STRUCTURES 59 

energy being dissipated. The inlet of the 

structure may also serve as a control to regulate 

the water depth in the channel upstream from 

the drop. 

2-22. Advantages and 

Disadvantages. -Rectangular inclined drops are 

easily designed, built, and operated. The inlets 

and outlets can be easily adapted to either an 

earth or a lined waterway. The inlets can be 

made to incorporate a control notch, a check, 

or a weir. If there is a control or check inlet 

side overflow walls for emergency situations 

should be included. It is important to provide 

adequate gravel or rock protection of outlets 

discharging into unlined waterways. The 

maximum fall in water surface for any one R.1. 

drop is about 1.5 feet. The R.1. drop should 

have adequate percolation path and sufficient 

resistance to sliding. The standard R.I. drop 

structures in figures 2-26 and 2-27 are designed 

to provide this stability; however, if unusual 

foundation conditions are encountered, the 

percolation and sliding resistance should be 

checked, and additional stability may be 

obtained by increasing the length L, 

2-23. Structure Components. -The principal 

hydraulic elements of an R.I. drop are the 

upstream transition, the inlet, the short 

inclined channel, the stilling pool, the outlet, 

and the downstream transition. 

(a) Upstreurn Trumitiorzs. -The upstream 

transition produces a gradual change of 

velocity from waterway to structure. When 

using a control inlet there is not a change in 

invert elevation from waterway to structure. 

When a check inlet is used the transition 

usually must provide for a gradual decrease in 

invert elevation from the waterway to the 

opening in the structure. The invert slope to a 

check inlet should not be steeper than 4 to 1. 

An earth transition may require erosion 

protection. For design of protection see the 

discussion on Erosion Protection, subchapter 

VII B. 

(b) Inlet to Drop.-The inlet to an R.I. drop 

may be any of the following: 

(1) Criticd-depth corztrol sectiolz. -In an 

earth canal requiring no check, the inlet to 

the drop should be designed to provide a 

control section which will prevent racing 

upstream and scouring of the canal. The 

inlet must be designed so that the full 

capacity can be discharged into the drop 

with normal depth in the canal. The inlet 

should be symmetrical about the centerline 

and, whenever possible, of sufficient 

distance from horizontal bends upstream as 

to limit undesirable wave action due to 

unsymmetrical flow. The trapezoidal 

critical-depth control should be 

proportioned in bottom width and side 

slopes for varying discharge from design flow 

to 0.2 design flow. For any flow in this 

range the notch causes the upstream canal 

water depth to be at or very near normal 

depth. It may also be proportioned to 

control 011ly one specific discharge. 

Generally, the notch is designed for the 

varying discharge. For method of notch 

design for control of varying discharge see 

subchapter III G. The top of the notch 

should be at the same elevation or slightly 

higher than the normal upstream water 

surface. The invert of the notch should be 

the same elevation as the canal invert. The 

depth of the notch will be equal to or 

slightly more than the depth in the canal at 

normal flow. A control notch which requires 

slightly more energy than that available from 

normal flow conditions in the canal will 

cause a slight rise in water surface elevation 

in the canal, but this is not considered 

serious. For the critical condition of canal 

flow at or near full design flow, the water 

surface rise is minimized by part of the flow 

being able to overflow the sidewalls. The 

sidewalls, with tops set at the same elevation 

as the top of the notch, also provide for 

emergency overflow into the inlet structure 

if there should be an obstruction of the 

notch or if the flow in the canal is greater 

than design flow. The overflow sidewalls, 

figures 2-26 and 2-27 are of sufficient length 

to permit design flow to go over the 

sidewalls with complete blockage of the 

notch. If canal bank freeboard is based on 

figure 1-9, the resulting freeboard will still 

be about 0.5 foot. 

The invert to the inlet structure (elevation 

B, figs. 2-26 and 2-27) is set low enough so 

that the flow at the beginning of the incline 

will not affect the flow through the control 
60 SMALL CANAL STRUCTURES 

foot, the hgth of the sidewalls should be 

increased until the canal freeboard is about 

0.5 foot for this overilow condition. 

Stoplogs may be used in vertical guides for 

water depths of 5 feet or less. For greater 

depths the guides should be placed on a 

slope of l/4 to 1 to facilitate handling. The 

sidewalls, with their tops set at the same 

elevation as normal water surface in the 

canal. provide for emergency overflow into 

the structure if the gate or stoplogs are not 

appropriately set for a particular flow in the 

canal, if the inlet becomes obstructed, or if 

the inlet is closed. For the extreme 

condition of flow at canal design capacity 

and complete closure of the opening, the 

inlets in figures 2-26 and 2-27 are designed 

so that there will continue to be about 

OS-foot canal bank freeboard if freeboard 

design is based on figure 1-9. The depth of 

flow over the walls and closure is dependent 

on a coefficient of discharge, the length of 

the walls, the width of the structure, and the 

flow in the canal. 

The floor of the inlet structure (elevation 

B) is set a distance H, below normal water 

surface in the canal. The vertical distance H, 

in the table of dimensions, tables 2-1 and 2-2 

(sheet 3) is great enough so that design flow 

into the inclined section will not cause 

backwater in the canal. 

Walk planks provide a platform for 

operating a gate or handling stoplogs. The 

l&inch clearance between the top of 

sidewalls and bottom of walk planks (figures 

2-26 and 2-27) provides clearance for the 

passage of floating debris that might 

otherwise obstruct the flow of water over 

sidewalls. 

The check inlet structure also has 

wingwalls and cutoffs for the purpose of 

retaining the canal earthwork and for 

reducing seepage. 

(3) Weir.-Sometimes a measuring weir is 

required at the inlet to an R.I. drop. See 

subchapter V E for a discussion on water 

measurement structures pertaining to weirs. 

For a lined canal, generally the minimum 

freeboard at the inlet should be the same as 

for the lining. For unlined canals up to a 

capacity of 100 cfs, the minimum freeboard 

should be 6 inches for water depths to 1.25 

notch. Expressed differently, elevation B is 

set low enough to prevent the flow into the 

inclined section from controlling the canal 

water surface. 

The inlet structure also has wingwalls and 

cutoffs for the purpose of retaining canal 

earthwork and for reducing seepage from the 

canal. 

(2) C’llec~li. -Check structures are often 

combined with the inlet to drops. The 

checks in such cases are utilized as a control 

to prevent racing of the water upstream 

from the inlet, in addition to their usual 

function of raising the water surface to 

permit diversion through upstream turnouts 

during periods of partial flow in the canal. 

Checks may also be used to shut off the 

canal flow if there is some provision such as 

an upstream wasteway to allow the canal 

flow to go elsewhere. This inlet closure 

could provide for isolation of a canal reach 

in case of canal embankment failure or for 

maintenance purposes. 

The area of the inlet opening should be 

proportioned to limit the design flow 

velocity to about 3.5 feet per second. This 

velocity is considered as the maximum 

desirable for ease of stoplog handling. The 

width is usually the same as that detcrmincd 

by the width requirement for the stilling 

pool. If the width of the inlet is greater than 

6 feet and stoplogs are used, a center pier 

with stoplog guides should be added so 

shorter stoplogs can be used. Stoplogs longer 

than 6 feet are difficult to handle. Without a 

center pier, the opening has two gate frame 

guides for installation of a gate or for use as 

stoplog guides. The elevation of the inlet 

opening should be the same or lower than 

the invert of the canal, never higher. Slide 

gates may be operated automatically. The 

gate sizes in the table of dimensions (tables 

2-l and 2-2) cause the top elevation of the 

gates, when closed, to be approximately the 

same elevation as the top of the side 

overflow walls. If these gate sizes are not 

available and the next greater available 

height is used, the taller gate may cause the 

canal freeboard to be less than 0.5 foot 

when the gate is closed and all of the normal 

canal flow is spilling over the sidewalls and 

gate. If this freeboard is much less than 0.5 
CONVEYANCE STRUCTURES 61 

feet, 9 inches for depths 1.26 to 2 feet, 12 

inches for depths 2.01 to 5 feet, 15 inches 

for depths 5.1 to 7 feet, and 18 inches for 

depths 7.1 to 9 feet. 

(c) R ectalzgulav hclined Ck~r~nel. -The 

channel is rectangular in shape, and it is usually 

practical to make the base width the same as 

that required for the pool or inlet section. The 

vertical height of the walls may be determined 

by computing the depth in the section with 

theoretical velocity and adding freeboard of 12 

inches for flows up to 100 cfs. The slope of the 

incline may be as steep as l-1/2 to 1 but is 

usually 2 to 1. R.I. drops with flows up to 100 

cfs do not require curved trajectories, therefore 

the incline will intersect the level inlet invert 

and also the level pool invert. 

(d) Stillillg Pool. -Stilling pools for 

hydraulic jumps are installed at the lower ends 

of R.1. drops to obtain the required loss of 

energy between the lower end of the inclined 

channel and the downstream pool. The outlet 

transition further reduces velocity and 

turbulence of the water thereby reducing 

erosion in the channel below. See subchapter I1 

F for design of stilling pools. The necessary 

depth, d, , at the lower end of the pool may be 

computed by the pressure-momentum equation 

or may be determined as demonstrated in the 

design example. The minimum downstream 

energy gradient for the hydraulic jump 

computations is determined by using a reduced 

n value. This reduced n should be 0.8 times the 

assumed design n for the canal. These smaller 

values of n are used as a factor of safety against 

possible lower canal water elevations than 

indicated using the rougher n value. The 

friction loss on the incline of an R.I. drop is 

also neglected which provides an additional 

factor of safety for the stilling pool. If there is 

not downstream water surface control in the 

channel, backwater for the jump may be 

provided by building a control into the outlet 

transition. See subchapter II F. 

For a controlled downstream water surface, 

the elevation of the pool floor may be 

determined by subtracting (dq + hVT) from the 

minimum downstream energy elevation. 

When use of a stilling pool is to be 

intermittent and for short duration of flow, 

such as in most wasteways or structures 

carrying floodwater, the minimum pool length 

should be 3 d, . Where uninterrupted use or 

long duration of flow is expected, the 

minimum pool length should be 4 d, . 

For rectangular pools and discharges up to 

100 cfs, the width of pool may be obtained by 

the empirical formula, 

b= 360a 

Q+350 

where b = width of pool in feet and Q = 

discharge in cubic feet per second. 

(e) Outlet.-The outlet of an R.I. drop 

connects the pool with an earth canal, a 

concrete-lined canal, or a natural channel and 

prevents or lessens downstream erosion. 

Some of the more common types of outlets 

used are: Broken-back transition, straight or 

curved diverging vertical walls extending into 

the earth canal banks on either side, and a 

straight rectangular channel with vertical walls 

tapering from pool wall height to zero. A 

portion of the transitions may be made in earth 

provided the velocity at the downstream cutoff 

is not too great for the soil. Riprap or gravel 

protection is used as required on the earth 

transition section. See subchapter VII B for 

protection. Where broken-back or warped 

transitions are used, the tops of these transition 

walls should be the same elevation as the 

stilling pool walls. 

Cutoffs at the ends of the outlets should be 

a minimum of 24 inches deep and 6 inches 

thick for water depths of 0 to 3 feet over the 

cutoff, and 2 feet 6 inches deep and 8 inches 

thick for warer depths from 3 to 6 feet. 

Where an earth transition is used at the inlet 

or outlet, it should be a minimum of 10 feet 

long. 

2-24. Percolatiorz. -Where water stands at 

different elevations above and below a 

structure, there is a tendency for the water to 

flow along the surfaces of the structure or 

through the surrounding soil from the higher 

elevation to the lower. The velocity that the 

water will attain in passing from the higher to 

the lower elevation will depend on the 

hydraulic head differential, the length of the 

path that the water is required to follow, and 

the permeability of the soil. Obviously, it is 

possible for percolating water to attain a 
62 SMALL CANAL STRUCTURES 

velocity sufficiently great to move the soil 

particles with consequent hazard to the 

foundation of the structure. 

The length of the percolation path along the 

structure, as computed by Lanes’ 

weighted-creep method, should bc such that 

the phreatic line does not intersect the tops of 

the inclined channel or stilling pool walls. The 

type of soil will govern the choice of the 

maximum allowable slope of the assumed 

percolation lint. In general, the slope of the 

percolation line along the backside of the walls 

should be held to a slope not steeper than 3.5 

to 1 (horizontal to vertical) from the canal 

water surface at the cutoff to any point at the 

top of the inclined channel or stilling pool 

walls. A slope of 5 to 1 is common. See 

subchapter VIII C for discussion on Lanes’ 

weighted-creep ratio, sometimes called 

percolation factor. 

The need for cutoff collars and the length of 

the portion of the inlet between the inlet 

cutoff and the incline may be decided by the 

susceptibility to percolation and seepage. It is 

sometimes necessary to lengthen the inlet 

structure or provide cutoff collars to lengthen 

the path of percolation on the standard R.1. 

drops, figures 2-26 and 2-27. 

2-25. Desigu Example of R.I. Drop With 

Control I&et arid Stilling Pool Outlet (see figs. 

2-26 and 2-27 arid tables 2-1 arld 2-2). -The 

topography for the canal alinement is assumed 

to be such that the general ground drops 

abruptly at this point and a drop structure is 

the feasible way to convey the water to the 

lower elevation. 

(a) Give/~. ~ 

(1) Type of waterway = earth canal. 

(2) Hydraulic properties of the canal at 

inlet and outlet of structure: 

Q = 50 cfs b = 5.0 ft. d, = 2.83 ft. 

s = 0.0005 s”~ = 0.02235 s:s = l-1/2: 1 

n = 0.025 v = 1.91 f.p.s. h, = 0.06 ft. 

E = 2.89 ft. 

(3) Type of conveyance structure = R.I. 

drop with stilling pool. 

(4) El. A = 5406.00 (from a profile 

sheet). 

(5) NWS El. at Sta. A = El. A + d, = 

5406.00 + 2.83 = 5408.83. 

(6) Energy El. at Sta. A = NWS El. + h, = 

5408.83 + 0.06 = 5408.89. 

(7) El. top of bank = 5410.4. 

(8) El. D = 5392.00 (from a profile 

sheet). 

(9) NWS El. at Sta. D = El. D + d, = 

5392.00 + 2.83 = 5394.83. 

(10) Energy El. at Sta. D = El. NWS + h, 

= 5394.83 + 0.06 = 5394.89. 

(11) There is no requirement for a check 

upstream from the drop, but a con.trol is 

required to minimize erosion in the canal for 

flows in the range of about 0.2 to full design 

flow. 

(b) Detcrmirlc~ Corltrol lrllct Dinlemiorls. - 

(1) Standard dimensions b, L,, H,, H,, 

and a are read from dimension table 

Structure Q max. of 50 (table 2-1, sheet 3) 

for canals and laterals. 

The value for b = 6 feet 6 inches in the 

table was calculated from the formula: 

The value of L, = 5 feet 7 inches in the 

table was determined by emergency 

side-overflow requirements, and the value of 

H” = 2 feet 9 inches minimum was 

determined by the requirement that El. B is 

set low enough so that hydraulic control of 

the upstream canal water surface is at the 

control notch. 

In the table, H, = 4 feet 3 inches 

minimum, was determined by adding 18 

inches to H,, From the above table, a = 4 

feet 0 inch. 

( 2) The procedure and calculations 

required to select the appropriate control 

notch are explained in detail in subchapter 

III G. The design example in subchapter III 

G is for the same hydraulic conditions and 

therefore only the design values will be 

repeated here: 

P = 20 inches, S = 0.50, and N = 4 ft. 6 in. 

(3) T should be equal to or greater than 

normal depth in the canal, 2.83 feet. Select 

T = 2 feet 10 inches. 

(4) The value used for H, must not be 

less than the value selected for T. Since the 
CONVEYANCE STRUCTURES 

value T = 2 feet 10 inches exceeds the 

tabulated value for H, = 2 feet ? inches 

min., use H,, = 2 feet 10 inches. 

(5) The value for H, must bc H,, + 18 

inches = 4 feet 4 inches. 

(6) Determine minimum jnside width of 

inlet structure with control notch. 

b mill. = N + 3 in. min. each side 

= 4 ft. 6 in. + 6 in. = 5 ft. 0 in. or, 

b ,,,i;,. = 6 ft. 6 in., from dimension S~OWII 

on table 2-1 (sheet 3) thercfor LEX 6 ft. 

6 in. 

(7) Determine El. top of notch and side 

overflow walls. The invert elevation of the 

notch is equal to El. A. 

= El. A + T = 5406.00 + 2.83 = 5408.83. 

(8) Determine El. B 

= El. top of notch and sidewalls - H, 

= 5408.83 - 2.83 = 5406.00 which for 

this example happens to equal El. A. 

(c) Deterrnirle H)~drolllic Settitg for Stilliqq 

Pool hi, Using Tuble 2-1. 

(1) Determine the minimum downstream 

energy at station D for design flow using an 

II value of 0.8 the normal II value. 

Mill. energy at Sta. D = El. D + d + h, 

From Manning’s equation 161 

AR*‘3 zz Qn = 50 x 0.8 x 0.025 

1.486 S’ ‘* 1.486 x 0.02235 

= 30.1 

Assume different water depths, d. in the 

canal and solve for AR2’” until AR2’3 = 

30.1 (see tabulation below). 

The assumed d of 2.53 feet properly 

balances the Manning equation, so normal 

Assumed I-- d, ft. 

- 

2.50 

I--- 

2.53 

63 

depth is 2.53 feet, and A = 22.25 feet*, V = 

22.25 AL= 2.25 fps, 11, 5; 5 06 = = - 64.4 = 0.08 

foot, E = d + h, = 2.53 + 5.08 = 2.61 feet. 

The normal depth could also have been 

determined by using table 2-5. 

So minimum energ)’ at Sta. D = El. D + E 

= 5392.00 + 2.6 1 = 5394.6 1. 

(2) Determine H value 

H = energy El. at Sta. A ~~ minimum 

energy El. at Sta. D. = 5408.89 5394.61 

= 14.28 feet. Use H = 15 feet t’or 

determining structure number. Structure 

number = Q-H or 50-I 5. This structure is 

for a canal so LISC table 2- 1 (shec t 3) for 

standard dimensions. From this table b, = 

2 feet 6 inches, H, = 2 feet 9 inches, c = 7 

spaces, d = 1 1 inches. L, = 10 feet 0 inch, 

L,: = 10 feet 5 inches, L, = 3 feet 3 

inches, L, = 16 feet 0 inch, H, = 6 feet 2 

inches, d, + hvz = 4.02 feet, 11 = 12 

inches, t = 6 inches, and t’ = I: inzhcs. 

Other additional information regarding 

wingwalls, cutoffs. weep holes, concrete 

thicknesses, rcinforcemcnts. a 11 d 

cstimatcd quantities may bc taken from 

figure 2-27 and table 2-1. 

(3) Determine stilling pool invert 

elevation (HI. C) = minimum downstream 

energy elevation (d? + h,2) = 5394.61 - 

4.02 feet = 5390.59, use 5390.50. 

(d) A Iternutiw Mc~thod jijr Detwmiuing 

Stillirlg Pool It~vcrt Elrvation. ---An alternate 

determination of stilling pool invert elevation 

(El. C) would be to USC figure 3-37, subchapter 

II F and make the following computations: 

(1) Determine critical depth in pool 

section from equation d, = 0.3 1433q’ ‘3, 

Q-B- where q = 6 - 6,5 - 7.69 and q 2’3 = 3.896. 

d, = 1.22 ft. 

d2, lSd*, b, db A = db+l.5d2, 

sq. ft. sq. ft. ft. sq. ft. sq. ft. 

3.606d, wp = b+3.606d, R = $ 

ft. ft. ft. 

----.~-~-. 

6.25 9.37 5.0 12.50 21.87 9.01 14.01 1.560 

6.40 9.60 5.0 i2.65 22.25 9.12 14.12 1 s7s 

- ~- 

R2’3 
64 SMALL CANAL STRUCTURES 

H (2) Determine - 

42 

zz yL2$ = ‘1.7 

.I 

(3) Obtain values 2 and 4 by using 

c 1 

above value of F and table in figure 2-37, 

L 

subchapter II F. 

d, 

d, = o.184 

dz d, = 17.43 

(4) Determine d, 

d, = 0.184 x d, = 0.184 x 1.22 

= 0.224 foot 

(5) Determine d, 

d, = 17.43 x d, = 17.43 x 0.224 

= 3.92 feet 

(6) Determine A, V, and 11, for depth, d, 

A, = b d2 = 6.5 x 3.92 = 25.45 ft.’ 

v2+ = 

h Vi 

&= 1.96 f.p.s. 

zr-= 1.96’ 

v2 22 - 64.4 = 0.06 foot 

(7) Determine stilling pool invert 

elevation (El. C). 

= minimum downstream energy El. 

- Cd, + hV2 > 

= 5394.61 - (3.92 + 0.06) 

= 5390.63 use 5390.50 

2-26. Design Example of R.I. Drop With 

Check Inlet aizd Stilling Pool Outlet (see figs. 

2-26 atzd 2-27 and tables 2-1 and 2-2). -The 

topography for the canal alinement is assumed 

to be such that the terrain drops abruptly at 

this point, and a drop structure is the feasible 

way to convey the water to the lower 

elevation. 

(a) Given. - 

( 1) Type of waterway = earth canal. 

(2) Hydraulic properties of the canal: 

Q = 50 cfs b = 5.0 ft. d, = 2.83 ft. 

s = 0.0005 s’ ‘* = 0.02235 s:s = l-l/2: 1 

n = 0.025 v = 1.91 f.p.s. h, = 0.60 ft. 

E = 2.89 ft. 

(3) Type of conveyance structure = R.l. 

drop with stilling pool. 

(4) El. A = 5406.00 (from a profile 

sheet). 

(5) NWS El. at Sta. A = El. A + d, = 

5406.00 + 2.83 = 5408.83. 

(6) Energy El. at Sta. A = NWS El. + h, = 

5408.83 + 0.06 = 5408.89. 

(7) El. top of bank = 54 10.40. 

(8) El. D = 5392.00 (from a profile 

sheet). 

(9) NWS El. at Sta. D = El. D + d, = 

5392.00 + 2.83 = 5394.83. 

(10) Energy El. at Sta. D = El. NWS + h, 

= 5394.83 + 0.06 = 5394.89 

( 1 1) A cheek inlet structure is required at 

the inlet to provide diversion requirements 

to turnouts. The check should be furnished 

with a gate because of the desire to 

automate the check. 

(b) Detcrmirw Check Inlet Dirnetkora- 

( I ) Standard dimensions b, L, and H, arc 

read from dimension table Structure Q max. 

of 50 (table 2-l) (sheet 3). 

The value for b = 6 feet 6 inches in the 

table was calculated from the formula: 

,=36m 

Q + 350 

The value of L, = 5 feet 7 inches in the 

table was determined by emergency 

side-overflow requirements and H, = 2 feet 

9 inches minimum was determined by the 

requirement that El. B is set low enough so 

that hydraulic control of the upstream canal 

water surface is at the check opening. 

(2) El. top of sidewalls = El. NWS in 

canal = 5408.83. 

(3) El. B = El. NWS in canal - H, 

minimum = 5408.83 - 2.75 = 5406.08, but 
CONVEYANCE STRUCTURES 

this is higher than canal invert. El. B should 

not be higher than the canal invert, therefore 

make El. B = El. canal invert = 5406.00, then 

H, = 5408.83 - 5406.00 = 2.83 feet. 

(4) Gate size, frame height, and number 

of walk planks are also read from the 

Standard Dimension tabulation on table 2-1 

(sheet 3): 

Gate size = 78 inches x 33 inches 

Frame Ht. = 6 feet 0 inch 

Number of planks = 11 

(cj Detemiw Hydruz~lica Settirg jhv Stilling 

Pool. -The following dimensions and elevations 

are identical to those for the R.1. drop with 

control inlet, set tion 2-25. 

(1) Minimum downstream energy 

elevation = 5394.6 1. 

(2) H = 1.5 ft. 

(3) d, = 1.22 ft. 

(4) ;= 11.7 

c 

(5) d, = 0.224 ft. 

(6) d, = 3.92 ft. 

(7) A, = 25.45 ft.‘, V, 

0.06 ft. 

z 1.96 fps, hV2 = 

(8) El. C = 5390.50. 

(9) Lp = 16 ft. 0 in. 

(10) L, = 10 ft. 0 in. 

(1 1 j H, = 6 ft. 2 in. 

(12) b, = 2 ft. 6 in. 

(13) L, = 3 ft. 3 in. 

(14) c=7. 

(15) d= 11 in. 

(16) h= 12in. 

Cd) D e t c r m i II e 

Dirlzeil,siotis.-These dimensions are also 

identical to those for the R.1. Drop with 

control inlet discussed in section 2-25. 

3. Pipe Drops 

2-27. Purpose and Description. -A pipe 

drop conveys water from a higher elevation to 

a lower elevation. This drop in elevation may 

be any amount between 3 and about 15 feet. A 

pipe drop not only conveys water but it must 

also dissipate the excess energy and still the 

65 

water after it has reached the lower elevation. 

The two general types of closed conduit drops 

are type 1 and type 2. 

(a> Type I.-The type 1 pipe drop (figs. 

2-28, 2-29, 2-30. and 2-3 1 j is a practical and 

economical drop and is used as an inline canal 

structure where the possibility of clogging is 

minimal. Another type of drop structure 

should be used for cross drainage. The pipe is 

sumped an amount required to create a 

hydraulic jump in the pipe which dissipates the 

excess energy. 

The type 1 pipe drop should have a check 

inlet or a control inlet, but may have only an 

earth outlet transition if the full pipe velocities 

are not greater than 3.5 feet per second. If this 

drop has a reinforced concrete outlet transition 

the full pipe velocities may be as high as 5 feet 

per second. 

(b) Tvpe 2.-The type 2 pipe drop figure 

2-32 is a practical and economical drop and is 

used as an inline canal structure or as a 

cross-drainage structure. It is generally used in 

preference to the type 1 pipe drop if sediment 

and debris is carried in the water. With a type 2 

pipe drop the excess energy dissipation must be 

accomplished at the outlet with either a baffled 

outlet or a stilling pool. However, if there is a 

possibility of having weeds in the water, a 

stilling pool should be used because of the 

difficulty with weeds clogging a baffled outlet. 

The type 2 pipe drop should have a check inlet 

or a control inlet if the drop is an inline canal 

structure. If the type 2 pipe drop is a 

cross-drainage structure it may have a 

reinforced concrete inlet transition. 

2-28. Advarltages and Disadvantages. -Pipe 

drops are easily designed, built, and operated. 

The inlets can be readily adapted to either an 

earth or a lined waterway and the outlets can 

be easily adapted to an earth or a lined canal or 

to a waterway where there is no downstream 

water surface control. The inlets can be made 

to incorporate a control notch, a check, or a 

weir. If there is a control or a check inlet there 

should be side overflow walls for emergency 

flows. A pipe drop can easily be taken under 

another waterway or a roadway. Pipe drops are 

economical, especially for small discharges. 

Pipe drops require very little maintenance, 

provided they are constructed of durable pipe 
66 

having good rubber gasket joints and provided 

the bends are properly made. It is important to 

provide adequate gravel or riprap protection at 

outlets discharging into unlined waterways. 

The maximum fall for any one pipe drop is 

about 15 feet. The type 1 pipe drop (sumped 

drop) should not be used if there is a strong 

possibility of the pipe becoming clogged with 

sediment. There is also the possibility of the 

drop becoming clogged with weeds or debris. 

To prevent this, the drop may have a weed 

screen on the inlet or the pipe may be 

sufficiently sized to discharge this material if it 

should get into the pipe drop. Usually clogging 

is not a problem with a type 2 pipe drop 

because its profile lends itself more readily to 

self-cleaning. 

2- 2 9. Type I Pipe Drop Structure 

Componerzts. -The principle hydraulic 

elements of the type 1 pipe drop arc the 

upstream transition, the inlet structure, the 

pipe, and the outlet transition. 

(a) Upstrrurrz Trurlsitiorz. -The transitions 

may be earth or concrete. With a control inlet 

there is no change in invert elevation from the 

normal waterway to the structure and the 

length of either an earth or concrete lining 

transition is 10 feet. With a check inlet the 

transition provides for a gradual change in 

invert elevation from the waterway to the 

opening in the cheek structure. This transition 

invert slope should not be steeper than 4 to 1, 

and the length of this transition is also 10 feet. 

An earth transition may require erosion 

protection which is discussed in subchapter VII 

B. 

(b) ///ler.-The inlet to a type 1 pipe drop 

may be cithcr of the following: 

( 1) co11 trol urld pip inlet (jig. 

3-_)Y).-When a check structure is not 

required at the inlet to a type 1 pipe drop, 

the inlet to the drop should be designed to 

provide a control notch which will prevent 

upstream racing and scouring of earth canals. 

The inlet must be designed so that the full 

capacity can be discharged into the drop 

with normal depth in the canal. 

A properly designed control notch will 

cause the upstream canal water to be at or 

near normal depth for discharges ranging 

from design flow to 0.2 design flow. It may 

SMALL CANAL STRUCTURES 

also be proportioned to control only one 

specific flow. For a detailed discussion of a 

control and pipe inlet and a method of 

notch design for control of varying flow, see 

subchapter III G. The inlet should be an 

adequate distance from upstream horizontal 

bends as to limit undesirable wave action 

due to unsymmetrical flow. Figure 3-39 has 

standard dimensions for inlet control 

structures with flows up to 100 cfs. 

(2) C’ht~~li utd pipe irdet.-A check and 

pipe inlet structure is often used at the inlet 

to a pipe drop. By adjusting the gate or 

stoplogs, the check serves as a control to 

prevent racing of the water upstream from 

the inlet, in addition to its usual function of 

raising the water surface to permit diversion 

through upstream turnouts during periods of 

partial discharge. The check inlet can also 

serve as a cutoff point in a canal provided 

there is a wasteway or some other structure 

that can take the flow that otherwise would 

continue down the canal. This may be 

desirable when water delivery downstream 

from the drop is not required or when 

maintenance downstream is required for 

reasons such as canal embankment failure. 

For further discussion of check and pipe 

inlet, see subchapter Ill F and figure 3-38. 

(c) Pipe. -The pipe may be precast 

reinforced concrete pressure pipe (PC?‘) or 

asbestos-cement pressure pipe (AC). 

(d) Olltlet Trulzsitiom-Outlet transitions 

can reduce earth canal erosion and can provide 

smooth flow by making the velocity change 

less abrupt. Concrete transitions and 

combinations of concrete and earth transitions 

are used for these purposes. Concrete outlet 

transitions in earth canals are required on those 

drops that cross under railroads and state 

highways, on all drops with 36-inch-diameter 

pipe or larger, and as previously stated, on all 

pipe with velocities between 3.5 and 5 feet per 

second. A type 1 outlet transition (broken 

back) is ordinarily used with a type 1 pipe 

drop. 

For the design of transitions for pipe 

structures and standard pipe transitions see the 

discussion on transitions subchapter VII A. 

2-30. Type I Pipe Drop Desigrl 

Considerations. -The hydraulic design of a type 
CONVEYANCE STRUCTURES 67 

1 pipe drop includes selecting a pipe diameter 

for a given capacity that will result in (1) a 

velocity of 3.5 feet per second or less for a pipe 

with only an earth transition at one or both 

ends or (2) 5 feet per second or less for a pipe 

with a concrete structure at each end. The 

table on figure 2-3 1 may be used to select pipe 

sizes. 

If the type 1 pipe drop has a control and 

pipe inlet or a check and pipe inlet the invert at 

the beginning of the pipe should be low enough 

so the hydraulic control is at the inlet to the 

inlet structure instead of at the pipe inlet. 

Standard dimensions for check and pipe inlet 

structures sllown on figure 3-38 provide for 

this. With a properly designed control notch. 

the standard dimensions shown on figure 3-39 

for control and pipe inlets also provide for this. 

The inclined portion of the pipe should be 

on a slope of 0.500 or flatter. 

To dissipate the excess energy from the 

supcrcritical velocities in the sloped part of the 

pipe profile, stilling is accomplished by 

providing a depressed (sumped) section of pipe 

near the outlet end. The drpth at which the 

bottom of the pipe is to be depressed below 

the downstream water surface can be 

determined from the equation (P, + M, >+ = 

(P, + Mzk. This is the pressure momentum 

equation for a hydraulic jump derived from 

Newton’s second law of motion. See figure 

2-28 and the explanation and procedure 

following this figure for determination of the 

elevation of the pipe invert at the beginning of 

the jump. This elevation can be determined by 

this procedure as is demonstrated in the design 

example or by using information on figures 

2-29 and 2-30. The sumped section of pipe is 

set with the upstream end at this elevation and 

with a minimum slope of 0.005 towards the 

downstream end. The length of the sumped 

section must be at least 4d, ((,-foot min.) for a 

drop with an earth outlet transition. A drop 

with a concrete outlet transition should have at 

least a 5 D length for the sumped section and 

should also have a 4d, (6-foot min.) length of 

pipe between the upstream sloped pipe and the 

transition but part of this distance can be 

sloped pipe as shown in figure 2-28. 

On figures 2-29 and 2-30 type 1 pipe drops 

have been standardized so the entire pipe 

profile can bc designed using these figures and 

accompanying tables 2-3 and 2-4. There are 

standard designs for type 1 pipe drops with a 

concrete downstream transition for capacities 

up to 50 cfs (fig. 3-30) and standard designs for 

type 1 pipe drops with an earth outlet 

transition with capacities up to 22 cfs (fig. 

2-29). Type 1 pipe drops can be designed and 

built for flows greater than 50 cfs but 

ordinarily it will be more economical to use ;I 

rectangular inclined drop for larger capacities. 

(a) BcJ/zds. -Changes in pipe grade and 

alinemcnt (bends) may be made with special 

fittings, by miter cutting pipe, with beveled 

end pipe or by pulling joints where grade and 

alinement can be established on a sufficiently 

large radius. See chapter VII1 for detailed 

information on bends. 

(b) Pip COIVV. --At all railroad and road 

crossings except farm roads a minimum of 3 

feet of earth cover should be provided for pipe. 

Farm roads require 2 feet of earth cover and 

are frequently ramped using 10 to 1 slopes ( 10 

percent grade) when necessary to provide a 

minimum cover requirement. If roadway 

ditches exist and are extended over the pipe, 

the minimum cover from the ditch to the top 

of the pipe should be 2 feet. 

(c) Pwcolutiorz. -Water has a tendency to 

flow through soil or along a structure to reach 

a lower elevation. The velocity the water will 

attain in passing to the lower elevation will 

depend upon the difference in elevation, the 

length of the path, and the soil itself. 

Obviously, it is possible for percolating water 

to attain a velocity sufficiently great to move 

the particles of the material through which it is 

passing, with consequent hazard to the 

foundation of the structure or possibility of 

the water developing an unrestricted channel 

around it. The location of the inlet structure 

may be decided by the susceptibility to 

percolation and seepage. The weighted length 

of the percolation path along the structure or 

through the surrounding material as computed 

by Lane’s weighted-creep method, should be 

great enough to dissipate the difference in 

water surface elevations using an appropriate 

assumed weighted-creep ratio. 

Pipe collars may be required to reduce the 

velocity of the water moving along the outside 
68 SMALL CANAL STRUCTURES 

NWS-, EG-, 

Concrete tronsltlon 

-TheoretIcal El.E 

G Drop wtth earth tronsltlon 

PROCEDURE: Use hydroullc tables b][7] to determine cross section orea A, 

ond Y, of pipe flowing partially full. 

I. Assume values of i 

2. Compute d, and A, from $ andjfound in hydraulic tables @] c73 

3. v, = ; 

4. A,=irea Of full pipe 

5. v,= $ 

6. Comp&e Y, for assumed $ by usmg hydraulic tobles b] D] 

7. Solve for d, 

8. SOIW for F 

9. By trial and error, repeat until computed F =Actual F 

10. Elevotlon of sump =El. downstream E G -h, P 

-I.ld, (10% safety factor) 

Hydraulic head losses such as entronce.frictlon, bend,ond exit are omitted 

because they are small. 

Theoretical Equation for d, 

P,+M,=P*+M* 

NOTE: Wt. of water is omltted from all values. 

A,% + $ = A2E + y 

QhV - 

9 +A,% =A,Y, 

d =m+!i-+& 

2 A2g A, y, 2 

F=d,+hv,-d,-hV P 

K=d2-B 

2 

nv = v, -v, 

VI 

“v, = qFigure 2-28. Determination of sump elevation for type 1 pipe drop. 103-D-1266. 
structure Earth out let 

Earth tran>\t \on lenqth / L2 

Check and p,pe 

control and 

MItered p,pe bends 

LONGITUDINAL SECTION 

NOTES 

Thee itandsrd dwgni are for fla.& 1~~3 than 23 cubic feet Per 

iecond. For flow\ qreater than 22 cubic feet pr second It IS 

probably rare ccon~n~cal to USE a concrete out let transItton 

and J ir~ill ler p,pe Fiqure 2-30. For flows greater than 22 cubic 

,,er second haglnq an earth outlet transition, design of the PIPE 

structure wst be perforw. 

Ordinarily the rrux,mum water surface drop for d pipe drop htructure 

15 15 feet. Ha*wer. itandard dwqn tablei extend il~qhtly 

beyond thii wax ~mum. 

Figure 2-29. Type 1 pipe drop with earth outlet transition-explanation sheet for table 2-3. 103-D-1267. 
“q - ad!d,o ra1aureyJ -- hj - Eq + dAq + zp1.1 = a3uaaauqng 

SE’OZ 

05'9t 

M'E 

8L'O 

‘Of-,ZZ 

00'9 

OS'91 

OO'EP 

6P‘Z 

80'0 

6L'LI 

S8'SI 

ZE'ZI 

os'sz 

$1 E 

IL'0 

‘Of-,zz 

OO'P 

OO'EI 

OYEZ 

99' I 

90'0 

9L.6 

OL'8 

SE'OZ 

OS'9b 

IZ'E 

ZL'O 

.o-$1 

00'9 

OO'EI 

96'20 

99'1 

LO'0 

6L'LI 

EL.91 

ZE'ZI 

os'sz 

9s'z 

8s'O 

.o-,SI 

OO'f 

OS01 

9SEZ 

LO‘1 

SO'0 

9L.6 

I!='6 

L6'61 6S'6b 

OSS* OS'PP 

16'E 88'E 

SL'O ZL'O 

ow9 00.9 

00'91 00'91 

OO'ZP OI'TP 

6p'Z 6t'Z 

80'0 80'0 

IVLI EO'LI 

OS'S1 ST'S1 

P6'11 SST1 

OS'PZ OS&Z 

60'E to'& 

99'0 09'0 

OO'P OO'P 

OS'ZI OSZI 

QYZZ OL'IZ 

99'1 99' I 

90'0 90'0 

8E.6 66'8 

LE.8 PO.8 

OZ.61 28'81 

OS&$ OS'Zb 

es'& OE'E 

L9'0 EYO 

00'9 00'9 

OU91 OS'S1 

OZ'OP G&,6& 

6p'Z 6VZ 

80'0 80'0 

P9'91 9Z.91 

18'Pl Lf'PI 

LI'II 61'01 

oszz OS'IZ 

OOE 56'5 

9S'O IS'0 

OO'P OO'P 

OO'ZI OO'ZI 

OE'OZ 06'61 

99'1 99'1 

90'0 90'0 

19'8 &Z'S 

0L.L 8E'L 

KY osz = n 1aIv 

L6'61 65'61 OZ.61 

OS'SP OSfP OS&P 

81.f SI'& ZI'E 

69'0 SYO 19'0 

00'9 ow9 00'9 

OVEI OWE1 OSZI 

WZf II'IP 6I'OP 

99'1 99‘1 99'1 

LO'0 LO'0 90'0 

Ib'LI EWLI PY91 

8E'91 W91 69'SI 

Ph‘II SST1 LI'II 

OSPZ OS&Z OS’ZZ 

ZS’Z 6p'Z svz 

&SO OS'0 9p'o 

00'9 OO'P 00'9 

00'01 00'01 00'01 

wzz IL‘IZ 6c'OZ 

LO'1 LO‘1 LO'1 

SO'0 50'0 SO'0 

SE'6 66'8 19'8 

80.6 ZL'8 8&'8 

Z8‘81 

oszc 

60'E 

as0 

00'9 

OS'ZI 

92'6E 

99'1 

90.0 

9z.91 

E&‘SI 

6L'OI 

OSIZ 

zvz 

89'0 

OO'E 

00‘01 

9%61 

18'0 

SO‘0 

fZ'8 

IJo.8 

tV81 90'81 

OSIC OS'Of 

LL.& EL'& 

09'0 sso 

00'9 00'9 

OS'S1 OS'S1 

OP'8E OP'LE 

6p'Z 6p'Z 

80.0 80'0 

88'SI OS'S1 

ZI'bI 6L'EI 

OP'OI ZO'OI 

osoz OS'61 

06'2 C8.Z 

sp'o OL'O 

.O&-,zz ‘O-J1 

0o.t 00'S 

OO'ZI OS11 

00'61 00'81 

99'1 PE'I 

90.0 90'0 

P8.L 9VL 

WO'L EL.9 

L9'LI 6Z'LI 

OS‘6f OS'8E 

OL'E 99'E 

IS.0 LP'O 

00'9 00'9 

00‘51 OO‘SI 

OS'9E 09'S& 

6VZ 6VZ 

LO'0 LO'0 

II'S1 EL'PI 

&P-&l 60'EI 

$9‘6 92'6 

OS.81 OSLI 

6L'Z fL'Z 

s9.0 65'0 

00'S 00'S 

OS.11 OS'11 

OTLI OZ.91 

$&'I bE.1 

90‘0 900 

80'1 OL'9 

op'9 80'9 

PP.81 

OSIC 

90'E 

sso 

00'9 

OS'ZI 

b&.8& 

99'1 

90'0 

88'SI 

86'PI 

osoz 

8E‘Z 

PYO 

OO’E 

OS'6 

WY81 

18'0 

so'0 

P8'L 

69'L 

100, L I ‘0 = dnq 

90'81 L9'LI 

osoc 35'6E 

EO'E our 

zso 8p'O 

00'9 00'9 

OSZI 00.21 

ZP'LE OS9E 

99'1 99'1 

90'0 90'0 

OS'S1 II'S1 

PYPI 6Z'PI 

LO'01 P9'6 

OS61 OS81 

SE'Z IE'Z 

09'0 9S'O 

OO'E OO'E 

OS'6 00'6 

ZO'81 6o‘LI 

18'0 18‘0 

SO‘0 50'0 

9P‘L 80'L 

PEL IO L 

lOOJ 60'0 = dAq 

6Z.LI 

OF8E 

L6'Z 

sp'o 

00'9 

OO'ZI 

LS'X 

99'1 

90'0 

EL'@1 

t6'fI 

9Z.6 

OS‘LI 

822 

&SO 

OO'E 

00'6 

L1.91 

18'0 

SO'0 

OL'9 

99'9 

16'91 ES.91 

OS'LE OS'9E 

Z9.E 85-E 

ZP'O 8E.O 

00 9 00'9 

00‘51 OS'PI 

OL'PE OL'EE 

6p'Z 6VZ 

LO'0 LO'0 

SEPI L6'EI 

9L'ZI Zt'Zl 

Le.8 6P8 

OS.91 OS'S1 

89'Z E9'Z 

zso 9P'O 

00'S 00'S 

00'11 00.11 

OZ'SI Of‘tI 

PE'I PE'I 

so.0 SO'0 

If9 &6'S 

SL s Ef'S 

PI'91 9L'SI 

OS SE OS'bf 

PS'E OS& 

SL'O IL'0 

00'S 00.5 

OS'!=1 OS'PI 

08'ZE 06'IE 

LOZ LO'Z 

LO'0 LO'0 

8SE1 OZ'EI 

80'ZI bL'I1 

11‘8 EL'L 

OS'bI OS‘&1 

asz zs z 

IV0 19 0 

00'S OO'P 

OS.01 OS'01 

OP‘EI OS'ZI 

Pf'I LO' I 

50'0 SO'0 

SS'S LT.5 

01 s 6L'P 

W 91~ = do 

16'91 ES.91 PI.91 9L'SI 

OS LE OS9E OS'S& OS'PE 

P6'Z 16.2 88'Z S8'Z 

IP'O OL'O 19'0 P9'0 

00'9 00'S 00'S 00'S 

00'21 OOZI OS11 OS'11 

S9'PE ZL'EE 08‘Zf L8'1E 

99'1 @&'I PE‘I PE' I 

90‘0 90'0 90'0 90'0 

SE'PI L6'EI 8S'EI OZ.&I 

09.&I PZ'EI 68'21 PS'ZI 

L8'8 6f'8 11'8 EL'L 

OS'91 OS'S1 OS'bI OS'&1 

PZ'Z OZ'Z 9l.Z ZI'Z 

8P'O VP.0 OPO EYO 

.o-,SI .O&-,L 

OO'E OO'E OO'E OO'P 

00'6 00'6 00'6 OS.8 

VZ'SI ZE'$I Ot'EI 6p'ZI 

18'0 18'0 18'0 75'0 

SO'0 SO'0 so.0 PO'0 

If.9 &6'S sss LI'S 

ZE'9 86‘S P9.S OE'S 

SE'S1 OO'SI 

OS'EE OSZE 

LPE EVE 

89.0 E9'0 

0o.s 00'S 

OO'PI OO@I 

OO'IE OO~OE 

LO'Z LO'Z 

LO‘0 LO'0 

ZR'ZI PVZI 

6E'II 90'11 

t&'L 96'9 

OS‘ZI OS11 

9vz ovz 

SS'O SF0 

OO't- 00.9 

00'01 00'01 

09'11 09'01 

LO.1 LO'1 

so.0 so.0 

8L'P OP'b 

9P P SI'P 

19'PI ETPI 

OS'IE OSOE 

6&‘& SEE 

65'0 sso 

00'S 00'S 

OO'!JI OS&I 

01'62 OZ'8Z 

LO'Z LO'Z 

LO'0 LO'0 

SO'ZI L9.11 

IL.01 S&.01 

85'9 oz.9 

OS'01 OS.6 

SE'Z 822 

Et,'0 19.0 

OO'P OO'f 

00.01 OS6 

OL'6 08'8 

LO'1 18'0 

so.0 SO‘0 

Z0.P P9'E 

za f ES& 

SR'EI 

OS.6Z 

I&'& 

OS'0 

0o.s 

OS&I 

OE'LZ 

LO z 

LOO 

62 11 

PO.01 

18'S 

OS'8 

ZZ'Z 

PS'O 

OO'E 

OS.6 

06.1 

18'0 

SO'0 

SZ'E 

OZ.& 

saqx! Sl = adld JO ra~aure,a 

8ESI OO‘SI 19'PI EZ'PI S8.&1 

OS&& oszt OSIE OS'OE OS6Z 

Z8'Z 6L'Z 9L'Z ZL'Z 69'2 

09'0 LS'O tso 8p'O se.0 

00'S 00'S 00'S 00‘S 0o.s 

OS'11 OS'11 0071 OS01 OS.01 

S6'OE &O'O& 01'62 81.82: SZ.LZ 

*&'I PE'I PEI PE'I PE'I 

90'0 90'0 90'0 SO'0 so.0 

78'21 ft‘Z1 SO'ZI L9'11 67'11 

61'21 f8.11 6t"II ST.11 08'01 

VE'L 96'9 85'9 oz.9 18'S 

OS'S1 OS'11 OS'01 OS'6 OS'8 

LO'Z EO'Z 86'1 E6'1 88'1 

8S'O ES0 EP'O 890 E9'0 

OO'P OO'P OO'P OO'Z OO'Z 

OS8 OS'8 00'8 00‘8 00'8 

SS'II E9'01 OL'6 6L'8 S8'L 

ZS'O ZS'O zs.0 9Z'O 91'0 

WO'O HI'0 PO0 WI'0 PO'0 

8L'@ OP'P ZO'P P9'E SZ'E 

L6'P P9.P IE'f 86.f S9.E 

-$ PVZ = do saqsm SI = ad!d JO ,a~au,qj 

palo” as+laqlo ssqun pa, “! an! smp w 

~“1 ad!d plre Ior,WJ lapI adrd p" VW) 

uo!~!sue~l WlvlO WJq 

SON38 kl31lW HllM dOlXl 3dld 

LB &I 

OS.8Z 

LZ'E 

9vo 

DO'S 

OS&I 

Of'9Z 

LO'Z 

LO'0 

16'01 

OL'6 

Et s 

OS'L 

SI'Z 

9to 

OO'E 

00'6 

OO'L 

18'0 

PO0 

L8.Z 

06 Z 

LPEI 

0581 

s9 z 

190 

OO'P 

OS'01 

fE'9Z 

LO‘1 

so.0 

16'01 

9VOI 

&P'S 

OS'L 

CB'I 

is.0 

OO'Z 

OS'L 

E6'9 

9Z'O 

W'O 

L8'Z 

EEE 

80.&I OL'ZI 

OS LZ OS‘9Z 

ZZf 8I'E 

6E.O 91'0 

<or-,ZZ 

0o.s OO'P 

00 &I OO'EI 

OP sz OSPZ 

LO'Z 99'1 

90'0 90'0 

ZS'OI *I'01 

LE.6 EO.6 

s0.s 99'P 

OS.9 OS'S 

aoz IO‘Z 

990 BS'O 

$0.,SI 

00 z 00'5 

00 6 OS.8 

00 9 01'S 

&SO &SO 

WO PO.0 

6P'Z OI'Z 

65'5 85'5 

w P = 0 

80.&I OL.ZI 

OS' LZ os.9z 

Z9'Z 6SZ 

i-9.0 19'0 

‘0.,SI 

0o.t OO'P 

OS'01 OS'01 

IP'SZ BP'PZ 

LO.1 LO'1 

SO'0 so-o 

ZS'OI t1.01 

71'01 9L.6 

SO'S 99'P 

OS'9 OS'S 

LL'I ZL'I 

IS‘0 sp'o 

.O&-,L 

0o.z OO'Z 

OSL OS'L 

10'9 80'S 

9z.o 9Z‘O 

WO WI‘0 

6VZ OI'Z 

IO'& 89'2 

SP E =cl 

I.w+ IP 

3 

ZP 

~3"%%Uqllp 

ES 

$1 

El 

Zl 

h 

Eq 

ZV 

1 

I*q+ IP 

3 

ZP 

as”aslaluq”g 

ES 

p-l 

E-l 

Zl 

!=q 

&q 

zq 

?I 

1.q + IP 

5 

ZP 

a3"a%Lmq"g 

ES 

Pl 

El 

Z-I 

*q 

Eq 

Zq 

cl 

.JAq+IP 

1 

ZP 

aa"a%Gnuq"g 

ES 

% 

El 

Zl 

% 

Eq 

zq 

.3 
F 

h2 

h3 

ha 

L2 

L3 

f-4 

S3 

Submergence 

2 

d, + hv; 

F 

b2 

b3 

h4 

f-2 

L3 

l-4 

S3 

Submergence 

dL2 

d, + hr; 

F 

L2 3 

b4 

f-2 

L3 

f-4 

S3 

Submergence 

P 

dl+hv; 

F 

h2 

b3 

b4 

L2 

L3 

L4 

S3 

Submergence 

d2 

LX dl + hv, 

Q = 5 cir hameter of p,pe = 18 Inches 

2.35 2 65 

2.10 2.49 

0.04 0 04 

0.26 0.26 

5.10 6.00 

8.00 8.50 

2.00 2.00 

70.30 

0.53 0.62 

1.99 2.07 

5.50 6.50 

4.66 5.05 

2 96 3.27 3.59 3.92 

2.87 3.25 3.64 4.02 

0.04 0.04 0.04 0 05 

0.52 0.52 0.52 0.52 

7 00 7.90 8.80 9.70 

8.50 9.00 9.00 9.50 

4.00 4.00 4.00 4.00 

0.43 050 0.58 0.63 

2.14 2.20 2.26 2.31 

7.50 8.50 9.50 10.50 

5.43 5.81 6.20 6.58 

9.27 9.60 

10.14 10.52 

0.06 0.06 

1.34 1.34 

24.50 2S.40 

12.00 12.50 

5.00 5.00 

lS0-O 

0.59 0.63 

3.01 3.05 

26.50 27.50 

12.70 13.08 

9.96 10.30 

10.91 11.29 

0.06 0.06 

1 34 1.34 

26.30 27.30 

12.50 12.50 

5.00 5 .oo 

15O-0 

10.64 10.98 

11.67 12.05 

0.06 0.06 

1.66 I .66 

28.20 29.10 

13.00 13.00 

4.00 4.00 

22’.30 

0.43 0.47 

3 15 3.19 

30.50 31.50 

14.23 14.61 

D,m,eter of p,pe = 18 Inches 

0.67 0.71 

3.08 3.12 

28.50 29.50 

13.47 13.85 

Q = 6 cis 

2.07 2.37 2.66 2.97 

2.10 2.49 2.87 3.25 

0 05 0.05 0 05 0.05 

0.52 0.52 0.52 0.81 

5.10 6.00 100 7.90 

9.00 9.00 9.50 10.00 

4.00 4 00 4.00 3 00 

70.30 70.30 150.0 

0.56 0 65 0 73 052 

2.19 2.27 2.35 2.42 

5.50 6.50 7 50 8.50 

4.66 5.05 5.43 5.81 

8 79 9.13 

10.14 10.52 

0.07 0.07 

1.66 1.66 

24.50 25.40 

13.50 14.00 

4.00 4.00 

22’.30’ 

0.76 0.80 

3.39 3.43 

26.50 27.50 

12.70 13.08 

9.47 9.80 10.12 10.46 10.80 11.14 

10.91 11.29 11.67 12.05 12.44 12.82 

0.07 0.07 0 07 0.07 0.07 0.07 

2.07 2 07 2.07 2.07 2.07 2.07 

26.30 27.30 28.20 29.10 30.00 31.00 

14.00 14.OD 14.50 14.50 15.00 IS.00 

5.00 5.00 5.00 5.00 5.00 5.00 

0.44 0.49 0.55 0.59 0.63 0.68 

3.47 3.52 3.57 3.61 3.65 3.69 

28.50 29.50 30.50 31.50 32.50 33.50 

13.47 13.85 14.23 14.61 15.00 15.38 

Table 2.3.-Type I pipe drop with earth outlet tramition (to be used with fig. Z-ZY/. -Continued. 103-D-l 268-2 

PIPE DROP WITH MITER BENDS 

Earth Outlet Transition 

Check and Pipe Inlet Control and Pipe Inlet 

AJI values are in feet unless otherwne noted 

4.24 

4.40 

0 05 

0.52 

10.60 

9.50 

4.00 

70.30 

0.69 

2.36 

11.50 

6.96 

11.33 

12.44 

0.06 

I 66 

30.00 

13.00 

4.00 

0.5 I 

3.23 

32.50 

15.00 

F=(d,+hv,)-(1 ld2+hvp) dl+hvl=R+h2+0.06 

VP = 3.40 ipr hvp = 0.18 foot 

3.29 3.59 3.89 4.21 

3.64 4.02 4.40 4.78 

0.05 0 05 0.05 0.05 

0.81 0.81 1.07 1.07 

8.80 9.70 10.60 11.60 

10.00 10.50 10.50 11.00 

3.00 3.00 4.00 4.00 

4.54 4.85 5.16 

5.17 5.55 5.93 

0.05 0.06 0.06 

1.07 1.07 1.34 

12.50 13.40 14.30 

11.00 11.50 11.50 

4.00 4.00 5 00 

5.49 5.81 

6.31 6.70 

0.06 0.06 

1.34 1.34 

15.20 16.20 

12.00 12.00 

5.00 5.00 

0.59 0.66 049 0 55 0.61 0.68 0.49 0.54 0.61 

2.48 2.55 2.63 2.68 2.74 2.80 2.86 2.91 2.97 

9.50 10.50 11.50 12.50 13so 14.50 15.50 16.50 17.50 

6.20 6.58 6.96 7.34 7.73 8.11 8.49 8.87 9.26 

11.47 11.80 12.14 

13.20 13.58 13.97 

0.07 0.08 0.08 

2.07 2.07 2.49 

31.90 32.80 33.70 

15.00 15.50 15.50 

5.00 5.00 6 00 

0.73 0.79 0.42 

12.47 12.81 

14.35 14.73 

0.08 0.08 

2.49 2.49 

34 70 35.60 

15.50 16.00 

6.00 6.00 

3.74 3.78 3.83 

34.50 35.50 36.50 

15.76 16.14 16.53 

0.47 0.51 

3.87 3.91 

37.50 38.50 

16.91 17.29 

Submergence = l.ld2 + bvp + h3 h4 D,ameter of prpe hv 

VP = 2 83 fps hvp = 0.12 foot 

4.57 

4.78 

0.05 

0.81 

1160 

10.00 

3.00 

150.0 

0.45 

2.41 

12.50 

7.34 

4.90 5.23 5.55 5.88 6.22 6.55 6.89 7.22 7.57 7.90 8.24 

5.17 5.55 5.93 6.31 6.70 7.08 7.46 7.84 8.23 8.61 8.99 

0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.06 0.06 0.06 0.06 

0.81 0.81 0.81 0.81 1.07 1.07 1.07 1.07 1.07 1.07 1.34 

12.50 13.40 14.30 15.20 16.20 17.10 18.00 19.00 19.90 20.80 21.70 

10 00 10.00 10.50 10.50 1100 11.00 11.00 11.50 11.50 11.50 12.00 

3.00 3.00 3.00 3.00 4.00 4.00 4.00 4 .oo 4.00 4 .oo 5 .oo 

0.5 1 0.56 0.6 1 0.67 0.46 0.51 0.55 0.61 0.65 0.70 0.47 

2.46 2.51 2.56 2.61 2.65 2.70 2.74 2.78 2.82 2.86 2.90 

13.50 14.50 15.50 16.50 17.50 18.50 19.50 20.50 21.50 22.50 23.50 

1.73 8.lI 8.49 8.87 9.26 9.64 10.02 10.40 10.79 11.17 11.55 

11.67 12.02 12 36 12.71 13.05 13.40 13.74 14.09 14.44 14.78 15.13 15.48 

12.82 13.20 13.58 13.97 14.35 14.73 15.11 15.50 15.88 16.26 16.64 17.03 

0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 

1.66 1.66 1.66 1.66 1.66 1.66 1.66 1.66 2.07 2.07 2.07 2.07 

31.00 31.90 32.80 33.70 34 70 35.60 36.50 37.40 38.40 39.30 40.20 41.10 

13.50 13.50 13.50 13.50 14.00 14.00 14.00 14.00 14.50 14.50 14.50 14.50 

4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 5.00 5.00 5.00 5.00 

0.56 0.59 0 63 0.67 0.71 0.74 0 78 0.82 

3.26 3.29 3.33 3.36 3.40 3.43 3.46 3.50 

33 50 34.50 35.50 36 50 37.50 38.50 39.50 40 50 

15.38 15 76 16.14 16.53 16.91 11.29 17.67 18.06 

0.44 0.48 

3.53 3.56 

41.50 42.50 

18.44 18.82 

0.5 1 0.55 

3.59 363 

43.50 44.50 

19.20 19.59 

Inlet R = 2.50 feet 

Inlet R = 2.50 feet 

6.14 6.47 

7.08 7.46 

0.06 0.06 

1.34 1.34 

17.10 I8 00 

12.00 12.50 

5.00 5.00 

d-0 

0.66 0.71 

3.02 3 06 

18.50 19.50 

9.64 10.02 

13.14 13.49 

15.11 15.50 

0.08 0.08 

2.49 2.49 

36.50 37.40 

16.00 16.00 

6.00 6.00 

0.55 0.60 

3.95 3.99 

39.50 40.50 

17.67 18.06 

0.64 0.70 

4.03 4.08 

41.50 42.50 

18.44 18.82 

0.74 0.79 

4.12 4.16 

43.50 44.50 

19.20 19.59 

6.80 7.13 

7.84 8.23 

0.06 0.06 

1.66 1.66 

19.00 19.90 

12.50 12.50 

4.00 4.00 

22’.30’ 

0.44 0.50 

3.11 3.16 

20.50 21.50 

10.40 10.79 

7.47 7.81 

8.61 8.99 

0.06 0.06 

1.66 1.66 

20.80 21.70 

13.00 13.00 

4.00 4.00 

0.54 0.58 

3.20 3.24 

22.50 23.50 

II.17 I1 55 

13.83 14.15 14.49 14.83 

15.88 16.26 16.64 17.03 

0.08 0.08 0.08 0.08 

2.49 2.49 2.49 2.49 

38.40 39.30 40.20 41.10 

16.50 16.50 16.50 17.00 

6.00 6.00 6.00 6.00 

8.59 8.92 

9.38 9.76 

0.06 0.06 

1.34 1.34 

22.60 23.60 

12.00 12.00 

5 .oo 5 .oo 

150-O’ 

0.51 0.56 

2.94 2.98 

24.50 25.50 

11.94 12.32 

15.82 16.17 

17.41 17.79 

0.07 0.07 

2.07 2.07 

42.00 43.00 

15.00 15.00 

5.00 5.00 

22’.30’ 

0.59 0.62 

3.66 3.69 

45.50 46.50 

19.97 20.35 

8.13 8.45 

9.38 9.76 

0.07 0.07 

1.66 1.66 

22.60 23.60 

13.50 13.50 

4.00 4.00 

22’.30’ 

0.65 0.70 

3.30 3.35 

24.50 25.50 

11.94 12.32 

15.17 15.49 

17.41 17.79 

0.08 0.08 

2.90 2.90 

42.00 43.00 

17.00 17.00 

7.00 7 .oo 

22’.30 

0.42 0.47 

4.20 4.25 

45.50 46.50 

19.97 20.35 
k 

“2 

h3 

h4 

L2 

L3 

L4 

S3 

Submergence 

d2 

L 

d, + hv, 

2.57 2.89 

2.10 249 

0.05 0.05 

0.26 0.26 

5.10 6.00 

9.00 9.50 

2.00 2.00 

7O-30 

0.57 0.64 

2.24 2.30 

5.50 6.50 

5.16 5.55 

3.20 

2.87 

0.05 

0.52 

7.00 

9.50 

4 00 

0.45 

2.36 

7.50 

5.93 

1. 9.5 I 9.84 10.19 

“2 10.14 10.52 10.91 

h3 (1.06 0.07 0.07 

h4 1.34 1.34 1.34 

L2 24.50 25.40 26.30 

L3 13.00 13.50 13 50 

L4 5.00 5.00 5.00 

S3 15O-0’ lSO~O 

Suhmergencc 0.60 0.64 0.70 

d2 3.24 3.28 3.32 

LX 26.50 27.50 28.50 

d, + hv, 13.20 13.58 13.97 

Q = 8 cfs 

F 

“2 

b3 

h4 

L2 

L3 

L4 

S3 

Suhmergencc 

d2 

LX 

d, + hv, 

2.35 2.61 2.97 3.28 3.59 

2.10 2.49 2.87 3.25 3.64 

0.05 0.05 (I.05 0.05 0.05 

0.52 0.52 0.52 0.81 0.81 

5.10 6 00 7.00 7.90 8.80 

10.00 10.00 10.50 10.50 II.00 

4.00 4.00 4.00 3.00 

70.30 

3.00 

70.30 150.0 

0.53 0.60 0.68 046 0.54 

2.40 2.46 2.54 2.60 2.67 

5.50 6 50 7.50 8.50 9.50 

5.16 5.55 5.93 6.31 6.70 

F 

h2 

hi 

h4 

L2 

L3 

L4 

S3 

Submergence 

d2 

LA 

d, + hv, 

9.14 9.41 

10.14 10.52 

0.07 0.07 

I .66 1.66 

24.50 25.40 

14.50 14.50 

4.00 4.00 

22’.30 

0.66 0.71 

3.54 3 58 

26.50 27.50 

13 20 13.58 

9.82 10.15 10.49 10.82 II.15 11.49 11.81 12.15 12.49 12.83 13.16 13.49 13.83 14.16 

10.91 11.29 11.67 12.05 12.44 12.82 13.20 13.58 13.97 14.35 14.73 15.11 15.50 15.88 

0.07 0.07 0.07 0.07 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 

I .66 1.66 2.07 2.07 2.07 2.07 a.07 2.07 2.07 2.07 2.07 2.49 2.49 2.49 

26 30 27.30 28.20 29 IO 30.00 31.00 31.90 32.80 33.70 14.70 35.60 36.50 37.40 38.30 

14.50 15.00 15.00 15.00 15.50 15.50 16.00 16.00 16.00 16.00 16.50 16.50 17.00 17.00 

4.00 4.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 6.00 6.00 6.00 

0.75 0.80 0.43 0.48 0.55 0.59 0.65 0.69 0.74 0.78 0.82 0.46 0.52 0.56 0.61 0.67 0.71 0.77 

3.62 3.66 3.70 3.75 3.80 3.84 3.89 3.93 3.97 4.01 4.05 4.10 4.15 4.19 4.24 4.28 4.32 4.37 

28.50 29.50 30.50 31.50 32.50 33.50 34.50 35.50 36.50 17.50 38.50 39.50 40.50 41.50 42.50 43.50 44.50 45.50 

13.97 14.35 14.73 15.11 15.50 15.88 16.26 16.64 17.03 17.41 17.79 18.17 18.56 18.94 19.32 19.70 20.09 20.47 

Q = 7 cfs Dlamcter of p,pe = 2, mchcs V,=29lfps 

3.52 3.84 4.16 4.40 

3.25 3.64 4.02 4.40 

0.05 0.05 0.05 0.05 

0.52 0.52 0.52 0.52 

7.90 8.80 9.70 10.60 

10.00 10.00 10.50 10.50 

4.90 4.00 4.00 4.00 

70.30 

0.5 1 0.58 0 64 0.70 

2.42 2.48 2.54 2.59 

8.50 9.50 10.50 11.50 

6.31 6.70 7.08 7.46 

4.81 

4.78 

0.05 

0.81 

11.60 

10.50 

3.00 

l5O-0 

0.46 

2.64 

12.50 

7.84 

5.14 5.48 5.81 6.14 

5 17 5.55 5.93 6.31 

0.05 0 05 0.06 0.06 

0.81 0.81 0.81 0.8 I 

12.50 13.40 14.30 15.20 

II.00 11.00 II.50 11.50 

3.00 3.00 3.00 3.00 

0.50 0.56 0.63 0.67 0.47 0.51 0.57 0.61 0.67 0.44 0.48 0.53 

2.69 2.73 2.78 2.82 2.87 2.91 2.96 3.00 3.05 3.09 3.13 3.17 

13.50 14.50 15.50 16.50 17.50 18.50 19.50 20.50 21.50 22.50 23.50 24.50 

8.23 8.61 8.99 9.37 9.76 10.14 10.52 10.90 11.29 11.67 12.05 12.44 

10.52 IO.86 1120 11.55 

11.29 11.67 12.05 12.44 

0.07 0.07 0.07 0.07 

I .66 1.66 1.66 1.66 

27.30 28.20 29.10 30.00 

13.50 14.00 14.00 14.00 

4.00 4.00 4.00 4.00 

22’.30’ 

0.43 0 47 0.5 I 0.55 

3.36 3.40 3.44 3.47 

29.50 30.50 31.50 32.50 

II.89 12 24 12.57 12.93 13.27 

12.82 13.2C 13.58 13.97 14.35 

0.07 0.07 0.07 0.07 0.07 

1.66 I .66 1.66 1.66 I .66 

31.00 31.90 32.80 33.70 34.70 

14.00 14.50 14.50 14.50 1500 

4.00 4.00 4.00 4.00 4.00 

14.35 14.73 15 II 15.50 

Dnmeter of p,pe = 2, mches 

0.59 0.62 0.67 0.70 0.74 

3.5 1 3.54 3.58 3.61 3.65 

33.50 34.50 35.50 36.50 37.50 

15.88 16.26 16.64 17.03 17.41 

VP = 3.33 fps 

3.91 4.22 4.55 4.87 5.19 5.51 5.83 6.17 6.50 6.83 7.16 

4.02 4.40 4.78 5.17 5.55 5.93 6.31 6.70 7.08 7.46 7.84 

0.05 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 

0.81 0.81 1.07 1.07 1.07 1.07 1.34 1.34 1.34 1.34 1.34 

9.70 10.60 II.60 12.50 13.40 14.30 15.20 16.20 17.10 18.00 19.00 

11.00 11.50 11.50 12.00 12.00 12.00 12.50 12.50 13.00 13.00 13.00 

3.00 3.00 4.00 4.00 4.00 4.00 5.00 5.00 5.00 5.00 5.00 

0.60 0.68 0.47 0.54 0.60 0.66 0.45 0.50 0.55 0.60 0.65 

2.73 2.79 2.84 2.90 2.95 3.01 3.06 3.11 3.15 3.20 3.25 

10.50 11.50 12.50 13.50 14.50 15.50 16.50 17.50 18.50 19.50 20.50 

7.08 7.46 7.84 8.23 8.61 8.99 9.37 9.76 10.14 10.52 10.90 

Table 2-3.--T)~pe I pipe drop with earth orrtlct tramitior? (to hc frscd with .fig. I?-ZY).-Continued. 103-D-1268-3 

PIPE DROP WITH MITER BENDS 

Earth Outlet Transition 

dl+hv,=K+h2+0.06 Submergence = l.ld2 + hvp + h3 - h4 - Diameter of pipe - hr 

h”P = 0.13 foot 

6.47 6.81 7.13 

6.70 7.08 7.46 

0 06 0.06 0.06 

1.07 1.07 I .07 

16.20 17.10 18.00 

11.50 12.00 12.00 

4.00 4.00 4.00 

13.61 13.95 14.30 

14 73 15.11 15.50 

0.07 0.07 0.07 

1.66 1.66 2.07 

35.60 36.50 37.40 

15.00 15.00 15.00 

4.00 4.00 5.ocI 

0.78 0.82 0.44 

3.68 3.72 3.75 

38.50 39.50 40.50 

17.79 18.17 18.56 

hvp = 0.17 foot 

7.47 7.81 8.14 8.48 8.82 

7.84 8.23 8.61 8.99 9.38 

0.06 0.06 0.06 0.06 0.06 

1.07 I .07 I.34 1.34 1.34 

19.00 19.90 20.80 21.70 22.60 

12.00 12.50 12.50 12.50 13.00 

4.00 4.00 5.00 5.00 5.00 

14.64 14.99 15.32 15.68 16.02 

15.88 16.26 16.64 17.03 17.41 

0.08 0.08 0.08 0.08 0.08 

2.07 2.07 2.07 2.07 2.07 

38.30 39.30 40.20 41.10 42.00 

15.50 15.50 15.50 16.00 16.00 

5.00 5.00 5.00 5.00 5.00 

0.50 0.53 0.58 0.61 0.65 

3.79 3.82 3.86 3.89 3.93 

41.50 42.50 43.50 44.50 45.50 

18.94 19.32 19.70 20.09 20.47 

Inlet R = 3.00 feet 

7.50 7 83 8.15 

8.23 8.61 8.99 

0.07 0.07 0.07 

1.34 1.66 I .66 

19.90 20.80 21.70 

13.50 13.50 13.50 

5.00 4.00 4.00 

150.0’ 22’.30 

0.71 0.44 0.50 

3.29 3.34 3.39 

21.50 22.50 23.50 

11.29 11.67 12.05 

8.49 

9.38 

0.07 

1.66 

22.60 

14.00 

4.00 

0.55 

3.44 

24.50 

12.44 

14.49 14.82 15 17 

16.26 16.64 17.03 

0.08 0.09 0.09 

2.49 2.49 2.49 

39.30 40.20 41.10 

17.00 17.50 17.50 

6.00 6.00 6.00 

15.49 

17.41 

0.09 

2.49 

42.00 

17.50 

6.00 

Inlet R = 3.00 feet 

9.16 

9.16 

0.06 

1.34 

23.60 

13.00 

5.00 

150.0’ 

0.57 

3.21 

25.50 

12.82 

16.36 

17.79 

0.08 

2.07 

43.00 

16.00 

5.00 

22’.30 

0.69 

3.96 

46.50 

20.85 

8.81 

9.76 

0.07 

1.66 

23.60 

14.00 

4.00 

22’.30 

0.61 

3.49 

25.50 

12.82 

15.82 

17.79 

0.09 

2.90 

43.00 

18.00 

7.00 

22’.30 

0.41 

4.42 

46.50 

20.85 
Table 2-3.-7)~pe I pipe drop with earth outlet transitiorz (to hc’rls~d with .fig. Z-ZYI. -Continued. 103-D-12684 

F 

h2 

h3 

"4 

L2 

L3 

L4 

s3 

Submergence 

d2 

LX 

d,+hvl 

F 

h2 

h3 

h4 

L2 

L3 

L4 

s3 

Submergence 

d2 

LX 

d, + hvl 

F 

h2 

h3 

h4 

L2 

L3 

L4 

s3 

Submergence 

d2 

LX 

dL+hv, 

F 

h2 

"3 

h4 

L2 

L3 

L4 

s3 

Submergence 

d2 

LX 

dl + hvl 

Q = 9 CfS 

2.72 3.03 3.33 

2.10 2.49 2.81 

0.05 0.05 0.05 

0.26 0.26 0.26 

5.10 6.00 7.00 

9.50 10.00 10.00 

2.00 2.00 2.00 

70-30 

0.42 0.50 0.58 0.65 0.47 

2.33 2.40 2.47 2.54 2.61 

5.50 6.50 7.50 8.50 9.50 

5.41 5.80 6.18 6.56 6.95 

961 9.95 10.29 

10.14 10.52 1091 

0.07 007 0.07 

1.34 1.34 1 34 

24.50 25.40 26.30 

13.50 14.00 14 00 

5.00 5.00 5.00 

ISO-0' 

050 0.55 0.60 

3.37 3.41 3.45 

26.50 27.50 28.50 

13.45 13 83 14.22 

Q= IOcfr 

10.63 10.97 

11.29 11.67 

0.07 0.07 

1.34 1.34 

27 30 28.20 

14.00 14.50 

5 00 5 .oo 

0.64 068 

3.49 3.53 

2950 3050 

14.60 14.98 

lhmeter of pqx = 24 Inches VP = 3.18 fp, hvp= 016faot Met R. 3.25 feet 

2.51 2.81 3.09 

2.10 2.49 2.87 

0.05 0.05 0.05 

052 0.52 0.52 

5.10 6.00 7.00 

10.50 10.50 10.50 

4.00 4.00 4.00 

70.30 

0.37 046 0.56 

249 2.57 2.66 

5.50 6.50 7.50 

5.41 5.80 6.18 

9.34 9.68 1002 

10.14 10.52 10.91 

0.07 0.07 0.07 

1.66 1.66 1.66 

24.50 25.40 26.30 

14.50 14.50 15.00 

4.00 4.00 4.00 

22'.30' 

0.46 0.50 0.55 

3.59 3.63 3.67 

26~50 27.50 28.50 

13.45 13.83 14.22 

hameter of pipe = 24 Inches 

3.64 3.95 

3.25 3.64 

0.05 0.05 

0.26 0.52 

7.90 8.80 

10.50 10.50 

2.00 4.00 

3.42 

3.25 

0.05 

052 

7.90 

11.00 

4 00 

0.61 

271 

850 

6.56 

3.74 4.06 

3.64 4.02 

0.05 0.06 

0.52 0.81 

8.80 970 

11.00 11.50 

4.00 3.00 

7O-30' 150.0 

0.68 0.46 

2.77 2.83 

9.50 10.50 

6 95 7.33 

4.37 470 5.03 5.37 5.69 602 6.35 6.68 7.00 7 33 7.67 8.01 a.33 

4.40 4.78 5.17 5.55 593 6.31 6.70 7 08 7.46 7.84 8.23 8.61 8.99 

0 06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.07 0.07 0.07 0.07 0.07 

0.81 0.81 081 0.81 1.07 1.07 1 07 1.07 1.34 1.34 1 34 1.34 1.34 

10.60 11.60 12.50 13.40 14.30 15 20 16.20 17.10 18.00 19.00 19.90 20.80 21.70 

11.50 12.00 12.00 12.50 12.50 1250 13.00 13.00 13.50 13.50 13.50 14.00 14.00 

3.00 3.00 3 00 3.00 4.00 4 00 4.00 4.00 5.00 5.00 5.00 5.00 5.00 

10.35 10.68 11.01 

11.29 11.67 12.05 

0.07 0.07 0.08 

1.66 1.66 1.66 

27.30 28.20 29.10 

15.00 15 00 15.50 

4.00 4.00 4.00 

0.53 0.58 

2.89 294 

11.50 12.50 

7.71 8 09 

11.36 11.69 

12.44 12.82 

0.08 0 08 

1.66 1.66 

30.00 31.00 

15.50 15.50 

4.00 4.00 

0.60 0.65 0.71 0.15 0 80 

3.12 3.76 3.81 3.85 3.89 

29.50 30.50 31.50 32.50 33.50 

14.60 14.98 15.36 15.75 16.13 

PIPE DROP WITH MITER BENDS 

Earth Outlet Transition 

Check andPipelnlet Control and P~pelnlet 

A" values are m feet unless otherwse noted 

4.27 4.60 4.92 

4.02 4.40 4.78 

0.05 0.05 0.05 

0.52 0.52 0.52 

9.70 10.60 11.60 

11.00 11.00 11.00 

4.00 4.00 4.00 

70.30 

0.53 0.58 0.64 

2.66 271 2.16 

10.50 11.50 12.50 

7.33 7.71 8.09 

11 31 11.66 12.00 

12.05 12.44 12.82 

0 07 0.07 0.07 

1.34 1.66 1.66 

29 10 30.00 31.00 

14.50 1450 15 00 

5 00 4.00 4.00 

15O-0' 22'.30' 

0.72 0.44 0.48 

3.56 360 3.64 

31.50 32.50 33.50 

15.36 15.75 16.13 

5.25 5.58 

5.17 5.55 

0.06 0.06 

0.81 0.81 

12.50 13.40 

11.50 11.50 

3.00 3.00 

15O-0 

0.42 0.47 

2.82 2.86 

13.50 14.50 

8.48 8.86 

12.33 12.67 

13.20 13.58 

0.07 0.07 

1.66 166 

31.90 32.80 

15.00 15.00 

4 00 4.00 

0.53 0.57 

3.68 3 72 

3450 35.50 

16.51 16.89 

VP = 2.86 fps 

0.64 0.68 048 0.53 0.59 

2.99 3.03 3.08 3.13 3.18 

13.50 14.50 15.50 16.50 17.50 

8.48 8.86 9.24 9.62 10.01 

12.03 12 36 

13.20 13.58 

0.08 0.08 

2.07 2.07 

31.90 32.80 

16.00 16.00 

5.00 5.00 

0.43 0.48 

3.93 3 97 

34.50 35.50 

16.51 16.89 

12.71 13.05 13.38 

13.91 14.35 14.73 

0.08 0.08 0.08 

2.07 2.07 2.07 

33.70 34.70 35.60 

16.00 16.50 16.50 

5.00 5.00 5.00 

0.52 0.56 0.61 0.65 0.71 0.74 0.79 0.42 0.46 

4.01 4.05 4.09 4.13 4.17 4.21 4.25 4.29 4.33 

3650 37.50 38.50 39.50 40.50 41.50 42.50 43.50 44.50 

17.28 17.66 18.04 18.42 18.81 19.19 19.57 19.95 20.34 

b”P 

5.91 6.24 6.58 6.92 7.24 7.58 7.92 8.26 a.59 

5.93 6.31 6.70 7.08 7.46 7.84 8.23 8.61 8.99 

0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 

0.81 0.81 081 0.81 1.07 1.07 1.07 1.07 1.07 

14.30 15.20 16.20 17.10 18.00 19.00 19.90 20.80 21.70 

12 00 12.00 12.00 12.50 12.50 12.50 13.00 13.00 13.00 

3.00 3.00 3.00 3.00 4.00 4.00 4.00 4.00 4.00 

0.52 0.57 0.62 0.66 0.46 

2.91 2.95 3.00 3.04 3.09 

15.50 16.50 17.50 18.50 19.50 

9.24 9.62 10.01 10.39 10.77 

0.50 0.55 

3.13 3 17 

20.50 21.50 

11.15 11.54 

14.74 15.08 

15.88 16.26 

0.08 0.08 

1.66 2.07 

38.30 39.30 

16.00 16.00 

4.00 5.00 

0.59 0.63 

3.21 3.25 

22.50 23.50 

11.92 12.30 

13 01 13.35 13.69 14.03 14.39 

13.97 14.35 14.73 15.11 15.50 

0.07 0.08 008 0.08 0.08 

1.66 1.66 1.66 1 66 1.66 

3370 34.70 35.60 36.50 3740 

15.00 15.50 15.50 15.50 16.00 

4 00 4.00 4.00 4.00 4 00 

15.43 15.79 

16.64 17.03 

0.08 008 

2.07 2.07 

40.20 41.10 

16.00 16.00 

5.00 5.00 

0.62 0.67 0.71 0 75 0.78 0.81 0.44 0.47 0.50 

3.76 3.80 3.84 3.87 3.90 3.93 3.96 3.99 4.02 

36.50 37.50 38.50 39.50 40.50 41.50 42.50 43.50 44.50 

17.28 17.66 18.04 18.42 18.81 19.19 19.57 19.95 20.34 

0.13 foot Lnlct R = 3.25 feet 

0.64 0.44 0.49 0.54 

3.23 3.28 3.33 3.37 

18.50 19.50 20.50 21.50 

10.39 10.77 II.15 11.54 

13.72 14.06 14.40 14.73 

15.11 15.50 15.88 16.26 

0.08 0.08 0.08 0.08 

2.07 2.07 2.07 2.07 

36.50 37.40 38.30 39.30 

16.50 17.00 17.00 17.00 

5.00 5.00 5.00 5.00 

0.58 064 

3.41 3.46 

22.50 23.50 

11.92 12.30 

15.07 15.42 

16.64 17.03 

0.09 0.09 

2.49 249 

40.20 41.10 

17.50 17.50 

6.00 6.00 

0 

m 

F=(dl+hvl)-(l.ld2 +hqJ dl+hvl= R+h2+0.06 Submergence = Lld2+ hv,,+ h3 - h4 - Diameter ofpipe hv 
Table 2-3.-Type I pipe drop with earth outlet transition (to be used with fig. 2-2Y). -Continued. 103-D-1268-5 

PIPE DROP WITH MITER BENDS 

Earth Outlet Transition 

Check and Pipe Met Control and pipe Inlet 

Au values are m feet unless otherwise noted 

Q= 11 cfs Diameter of pipe = 24 inches VP = 3.50 fps hvp = 0.19 foot Inlet R = 3.25 feet 

3.56 3.88 4.20 4.5 1 4.84 5.16 5.47 5.80 6.12 

3.64 4.02 4.40 4.78 5.17 5.55 5.93 6.31 6.70 

0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.07 0.07 

0.81 0.81 1.07 1.07 1.07 1.07 1.34 1.34 1.34 

8.80 9.70 10.60 11.60 12.50 13.40 14.30 15.20 16.20 

12.00 12.00 12.50 12.50 12.50 13.00 13.00 13.50 13.50 

3.00 3.00 4.00 4.00 4.00 4.00 5.00 5.00 5.00 

7.74 8.06 

8.6 1 8.99 

0.07 0.07 

1.66 1.66 

20.80 21.70 

14.50 15.00 

4.00 4.00 

0.58 0.63 0.44 0.5 1 0.57 0.63 0.43 0.49 0.56 

2.91 2.96 3.02 3.08 3.14 3.19 3.25 3.30 3.36 

9.50 10.50 11.50 12.50 13.50 14.50 15.50 16.50 17.50 

6.95 7.33 7.71 8.09 8.48 8.86 9.24 9.62 10.01 

6.4s 6.76 7.09 7.41 

7.08 7.46 7.84 8.23 

0.07 0.07 0.07 0.07 

1.34 1.34 1.66 1.66 

17.10 18.00 19.00 19.90 

14.00 14.00 14.00 14.50 

5.00 5.00 4.00 4.00 

15OxI)’ 22’.30 

0.61 0.68 0.41 0.48 

3.41 3.47 3.52 3.58 

18.50 19.50 20.50 21.50 

10.39 10.77 11.15 11.54 

c.53 0.59 

3.63 3.68 

22.50 23.50 

11.92 12.30 

10.40 10.73 11.07 11.40 

11.67 12.05 12.44 12.82 

0.08 0.08 0.08 0.08 

2.07 2.07 2.07 2.07 

28.20 29.10 30.00 31.00 

16.00 16.50 16.50 16.50 

5.00 5.00 5.00 5.00 

11.73 12.06 12.40 

13.20 13.58 13.97 

0.08 0.08 0.08 

2.07 2.49 2.49 

31.90 32.80 33.70 

17.00 17.00 17.00 

5.00 6.00 6.00 

0.73 0.78 0.41 

4.17 4.22 4.26 

34.50 35.50 36.50 

16.51 16.89 17.28 

VP = 2.44 fps 

12.73 13.06 13.39 13.74 14.06 14.40 14.72 15.07 

14.35 14.73 15.11 15.50 15.88 16.26 16.64 17.03 

0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 

2.49 2.49 2.49 2.49 2.49 2.49 2.49 2.91 

34.70 35.60 36.50 37.40 38.30 39.30 40.20 41.10 

17.50 17.50 18.00 18.00 18.00 18.50 18.50 18.50 

6.00 6.00 6.00 6.00 6.00 6.00 6.00 7.00 

0.53 0.58 0.63 0.68 

3.99 4.04 4.08 4.13 

30.50 31.50 32.50 33.50 

14.98 15.36 15.75 16.13 

0.47 0.5 I 0.57 0.61 0.67 0.71 0.77 0.39 

4.31 4.35 4.40 4.44 4.49 4.53 4.58 4.62 

37.50 38.50 39.50 40.50 41.50 42.50 43.50 44.50 

17.66 18.04 18.12 18.81 19.19 19.57 19.95 20.34 

Q= 12cfs Dmmeter of p,pe = 30 Inches Inlet R = 3.7s feet 

3.05 3.38 3.71 4.03 4.37 4.70 

2.10 2.49 2.87 3.25 3.64 4.02 

0.05 0.05 0.05 0.05 0.05 0.05 

hvp = 0.09 foot 

2.38 

2.10 

0.05 

0.52 

5.10 

10.50 

4.00 

7930 

2.68 

2.49 

0.05 

2.96 3.26 

2.87 3.25 

0.05 0.06 

0.81 0.81 

7.00 7.90 

11.00 11.50 

3.00 3.00 

ls”-0 

0.41 0.49 

2.75 2.83 

7.50 8.50 

6.18 6.56 

9.74 10.07 

10.91 11.29 

0.08 0.08 

2.07 2.07 

26.30 27.30 

16.00 16.00 

5.00 5.00 

0.43 0.48 

3.90 3.95 

28.50 29.50 

14.22 14.60 

F 

h2 

h3 

“4 

L2 

L3 

L4 

S3 

Submergence 

d2 

LX dl+hvl 

F 

“2 

4 

“4 

L2 

L3 

L4 

S3 

Submergence 

9 

LX 

dl+hvl 

F 

h2 

“3 

“4 

L2 

L3 

L4 

S3 

Submergence 

d2 

LX 

dl+hvl 

F 

h2 

“3 

“4 

L2 

L3 

L4 

S3 

Submergence 

d2 

LX 

dl+hvl 

5.10 6.00 7.00 7.90 8.80 9.70 

10.50 10.50 10.50 11.00 11.00 11.00 

5.04 5.38 

4.40 4.78 

0.06 0.06 

0 0.26 

10.60 11.60 

11.50 11.50 

2.00 

70.30 

0.67 0.45 

2.80 2.84 

11.50 12.50 

8.21 8.59 

5.72 6.07 6.40 6.74 7.09 7.42 7.76 8.01 8.46 8.80 9.15 

5.17 5.55 5.93 6.31 6.70 7.08 7.46 7.84 8.23 8.61 8.99 

0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 

0.26 0.26 0.26 0.26 0.26 0.52 0.52 0.52 0.52 0.52 0.52 

12.50 13.40 14.30 15.20 16.20 17.10 18.00 19.00 19.90 20.80 21.70 

11.50 12.00 12.00 12.00 12.50 12.50 12.50 12.50 13.00 13.00 13.00 

2.00 2.00 2.00 2.00 2.00 4.00 4.00 4.00 4.00 4.00 4.00 

0.57 0.62 

2.72 2.76 

9.50 10.50 

7.4s 7.83 

0.50 0.53 0.57 0.62 0.66 0.45 0.49 0.52 0.56 0.60 0.63 

2.88 2.91 2.95 2.99 3.03 3.07 3.11 3.14 3.17 3.21 3.24 

13.50 14.50 15.50 16.50 17.50 18.50 19.50 20.50 21.50 22.50 23.50 

8.98 9.36 9.74 10.12 10.51 10.89 11.27 11.65 12.04 12.42 12.80 

11.57 11.92 12.28 12.62 12.97 13.32 13.69 14.04 14.39 

11.67 12.05 12.44 12.82 13.20 13.58 13.97 14.3s 14.73 

0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 

0.81 0.81 0.81 1.07 1.07 1.07 1.07 1.07 1.07 

28.20 29.10 30.00 30.10 31.90 32.80 33.70 34.70 35.60 

14.00 14.00 14.50 14.50 14.50 14.50 15.00 15.00 15.00 

3.00 3.00 3.00 4.00 4.00 4.00 4.00 4.00 4.00 

15.45 15.81 16.16 16.52 

15.88 16.26 16.64 17.03 

0.08 0.08 0.08 0.08 

1.07 1.34 1.34 1.34 

38.30 39.30 40.20 41.10 

15.50 15.50 15.50 15.50 

4.00 5.00 5.00 5.00 

0.61 0.64 0.67 0.45 0.48 0.51 0.53 0.56 0.59 

3.47 3.50 3.53 3.56 3.59 3.62 3.64 3.66 3.69 

30.50 31.50 32.50 33.50 34.50 35.50 36.50 37.50 38.50 

15.48 15.86 16.25 16.63 17.01 17.39 17.78 16.16 18.54 

14.74 15.10 

15.11 15.50 

0.07 0.07 

1.07 1.07 

36.50 37.40 

15.00 15.00 

4.00 4.00 

0.62 0.65 

3.72 3.75 

39.50 40.50 

18.92 19.31 

0.69 0.44 0.47 0.50 

3.77 3.79 3.82 3.85 

41.50 42.50 43.50 44.50 

19.69 20.07 20.45 20.84 

8.4 1 8.73 

9.38 9.76 

0.07 0.08 

1.66 1.66 

22.60 23.60 

0.52 

6.00 

11.00 

4.00 

70.30 

15.00 15.50 

4.00 4.00 

22’.30 

0.63 0.70 

3.72 3.77 

0.54 0.62 

2.62 2.69 

5.50 6.50 

5.41 5.80 

9.07 

10.14 

0.08 

1.66 

24.50 

15.50 

4.00 

22’.30 

0.74 

9.39 

10.52 

0.08 

2.07 

25.40 

15.50 

5.00 

0.39 

3.86 

27.50 

13.83 

24.50 25.50 

12.69 13.07 

15.39 15.73 

17.41 17.79 

0.09 0.09 

2.91 2.91 

42.00 43.00 

19.00 19.00 

7.00 7.00 

22’.30 

0.45 0.49 

4.67 4.71 

45.50 46.50 

20.72 21.10 

3.81 

26.50 

13.45 

9.50 9.84 

9.38 9.76 

0.06 0.07 

0.52 0.81 

22.60 23.60 

13.00 13.50 

4.00 3.00 

70.30 150.0 

0.67 0.43 

3.27 3.31 

24.50 25.50 

13.19 13.57 

16.87 17.22 

0.35 0.4 1 0.46 0.52 

2.52 2.57 2.62 2.67 

5.50 6.50 7.50 8.50 

5.91 6.30 6.68 7.06 

10.19 10.53 10.88 11.23 

10.14 10.52 10.91 11.29 

0.07 0.07 0.07 0.07 

0.81 0.81 0.81 0.81 

24.50 25.40 26.30 27.30 

13.50 13.50 14.00 14.00 

17.41 17.79 

0.08 0.08 

1.34 1.34 

42.00 43.00 

15.50 16.00 

3.00 3.00 3.00 3.00 

150.0 

0.46 0.50 0.54 0.57 

3.34 3.37 3.41 3.44 

26.50 27.50 28.50 29.50 

13.95 14.33 14.72 15.10 

5.00 5.00 

HO-0 

0.53 0.56 

3.87 3.90 

45.50 46.50 

21.22 21.60 

F = (d, + hvl) - (l.ld2+ hvp) d, + hvl = R + h2 + 0.06 Submergence = l.ld2 + hvp + h3 h4 - Diameter of pope hv 
Q= 13 cfs Diameter of pipe = 30 mches VP = 2.65 fps hvp = 0.1 1 foot Inlet R = 3.75 feet 

8.28 8.61 8.95 9.30 

8.23 8.61 8.99 9.38 

0.07 0.07 0.07 0.07 

0.81 0.81 0.81 0.81 

19.90 20.80 21.70 22.60 

13.50 13.50 14.00 14.00 

3.00 3.00 3.00 3.00 

0.46 0.51 0.55 0.59 

3.32 3.36 3.40 3.44 

21.50 22.50 23.50 24.50 

12.04 12.42 12.80 13.19 

9.63 

9.16 

0.07 2 

0.81 

23.60 ? 

14.00 

3.00 

ISO- z 

0.64 

3.48 xl 

25.50 

13.57 

16.30 16.64 16.99 

17.03 17.41 11.79 

0.08 0.08 0.08 

1.34 1.66 1.66 

41.10 42.00 43.00 

lb.50 lb.50 lb.50 

5.00 4.00 4.00 

150.0 22'.30 22'.30 

0.72 0.44 0.47 

4.03 4.06 4.09 

44.50 45.50 46.50 

20.84 21.22 21.60 

Q = 14 cfs Diameter of pope = 30 Inches VP = 2.85 fps hvp = 0.13 foot Inlet R = 3.75 feet 

7.77 8.12 8.45 8.19 9.13 

7.84 8.23 8.61 8.99 9.38 

0.07 0.07 0.07 0.07 0.07 

0.81 0.81 0.81 1.07 1.07 

19.00 19.90 20.80 21.70 22.60 

14.00 14.00 14.00 14.50 14.50 

3 00 3.00 3.00 4.00 4 00 

0.62 0.67 0.45 0.50 

3.45 3.49 3.53 3.57 

21.50 22.50 23.50 24.50 

12.04 12.42 12.80 13.19 

15 34 15.69 16.05 lb.39 

lb 26 16.64 17 03 17.41 

0.08 0.08 0.08 0.09 

1.66 1.66 1.66 1.66 

39.30 40.20 41.10 42.00 

17 00 17.00 17 00 17.50 

4.00 4.00 4.00 400 

9.47 

9.76 

0.07 

1.07 

23.60 

14.50 

4.00 

15O-0 

0.54 

3.61 

25.50 

13.57 

0.55 0.59 0.62 0.65 070 

4 15 4 18 4.21 4.24 4.27 

41.50 42.50 4350 44.50 45.50 

19.69 2007 20.45 20.84 21.22 

lb.74 

17.79 

0.09 

166 

43.00 

17.50 

4.00 

22'.30' 

0.73 

4.30 

46.50 

21.60 

Table 2-3.-Type I pipe drop with earth outlet transition (to be used with .fig. 2.29/.-Continued. 103-D-1268-6 

PIPE DROP WITH MITER BENDS 

Earth Outlet Transition 

Check and Pipe Inlet Control and Pipe inlet 

AU values are m feet unless otherwise nored 

2.93 3.25 

2.10 2.49 

0.05 0.05 

5.10 6.00 

10.50 11.00 

3.58 3.90 

2.87 3.25 

0.05 0.05 

7.00 7.90 

11.00 11.00 

4.91 5.23 5.58 5.91 6.24 6.51 6.91 

4.40 4.78 5.17 5.55 5.93 6.31 6.70 

0.06 0.00 0.06 0.06 0.06 0.06 0.06 

0.26 0.26 0.26 0.52 0.52 0.52 0.52 

10.60 11.60 12.50 13.40 14.30 15.20 16.20 

12.00 12.00 12.00 12.50 12.50 12.50 13.00 

2.00 2.00 2.00 4.00 4.00 4.00 4.00 

0.59 0.65 

2.72 2.71 

7.50 8.50 

6.68 7.06 

4.25 4.59 

3.64 4.02 

0.06 0.06 

0.26 0.26 

8.80 9.70 

11.50 11.50 

2.00 2.00 

70.30' 

0.44 0.49 

2.81 2.85 

9.50 10.50 

7.45 7.83 

0.54 0.60 0.64 0.43 0.48 0.53 0.58 

2.90 2.95 2.99 3.04 3.08 3.13 3.17 

11.50 12.50 13.50 14.50 15.50 16.50 17.50 

8.21 8.59 8.98 9.36 9.74 10.12 10.51 

7.25 7.59 7.93 

7.08 7.46 7.84 

0.06 0.06 0.07 

0.52 0.52 0.81 

17.10 18.00 19.00 

13.00 13 00 13.50 

4.00 4.00 3.00 

70.30 15O-0 

0.62 0.66 0.42 

3.21 3.25 3.28 

18.50 19.50 20.50 

10.89 11.27 11.65 

10.66 11.04 11.36 11.70 12.06 12.41 12.75 13.09 13.47 13.82 14.16 14.51 14.87 15.22 15.57 15.93 

10.91 11.29 11.67 12.05 12.44 12.82 13.20 13.58 13.97 !4.35 14.73 15.11 15.50 15.88 16.26 16.64 

0.07 0.07 0.07 0.07 0.07 0.07 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 

1 .a7 1.07 1.07 1 .a7 1.07 1.07 1.07 1.34 1.34 1.34 1.34 1.34 1.34 1.34 1.34 1.34 

26.30 27.30 28.20 29.10 30.00 31.00 31.90 32.80 33.70 34.70 35.60 36.50 37.40 38.30 39.30 40.20 

14.50 14.50 15.00 15.00 15.00 15.00 15.50 15.50 15.50 15.50 15.50 lb.00 16.00 16.00 lb.00 lb.00 

4.00 4.00 4.00 4.00 4.00 4.00 4.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 

0.50 0.53 0.56 0.60 0.63 0.66 0.71 0.46 0.49 0.52 0.56 0.59 0.62 0.65 0.68 0.70 

3.59 3.62 3.65 3.68 3.71 3.74 3.77 3.79 3.82 3.85 3.88 3.91 3.94 3.96 3.99 4.01 

28.50 29.50 30.50 31.50 32.50 33.50 34.50 35.50 36.50 37.50 38.50 39.50 40.50 41.50 42.50 43.50 

14.72 15.10 15.48 15.86 lb.25 16.63 17.01 17.39 17.78 18.16 18.54 18.92 19.31 19.69 20.07 20.45 

0.58 

3.41 

20.50 

11.65 

15.00 

15.88 

0.08 

166 

38.30 

17.00 

400 

F 

“2 

h3 

"4 

L2 

L3 

L4 

s3 

Submergence 

d2 

LX 

dl+hv, 

0.47 0.54 

2.61 2.67 

5.50 6.50 

5.91 6.30 

F 9.98 10.32 

h2 

h3 

4 

L2 

L3 

L4 

s3 

Submergence 

d2 

LX 

d, + hvl 

10.14 10.52 

0.07 0.07 

0.81 1.07 

24.50 25.40 

14.00 14.50 

3.00 4.00 

15O-0 

0.67 0.46 

3.51 3.55 

26.50 27.50 

13.95 14.33 

2.80 3.12 

2.10 2.49 

0.05 0.05 

0.26 

5.10 6.00 

11.00 11.00 

2.00 

7O-30 

0.60 0.41 

2.71 2.77 

5.50 6.50 

5.91 6.30 

9.81 10.14 

10.14 10.52 

6.42 6.76 7.10 7.43 

6.31 6.70 7.08 7.46 

0.06 0.07 0.07 0.07 

0.52 0.81 0.81 0.81 

3.43 3.75 4.09 4.41 4.75 5.08 5.42 5.75 6.09 

2.87 3.25 3.64 4.02 4.40 4.78 5.17 5.55 5.93 

0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 

0.26 0.26 0.26 0.26 0.52 0.52 0.52 0.52 0.52 

7 00 7.90 8.80 9.70 10.60 11.60 1250 13.40 14.30 

11.50 11.50 12.00 12.00 12.50 12.50 12.50 13.00 13.00 

2.00 2.00 2.00 2.00 4 00 4.00 4.00 4.00 4.00 

0.49 0.55 0.60 0.66 0.44 0.49 0.54 0.59 0.63 

2.84 2.89 2.94 2.99 3.03 3.07 3.12 3.16 3.20 

7.50 8.50 9.50 10.50 11.50 12.50 13.50 14.50 15.50 

6.68 7.06 7.45 7.83 8.21 8.59 8.98 9.36 9.74 

10.49 10.83 11.18 11.53 11 87 12.22 12.56 12.88 13.06 

10.91 11.29 11.67 12.05 1244 12.82 13.20 13.58 13.97 

0.07 0.07 0.08 0 08 0.08 0.08 008 0.08 0.08 

1.07 1.07 1.34 1.34 1.34 1.34 I34 1.34 1.34 

26.30 27.30 28.20 29.10 30.00 31.00 31.90 32.80 33.70 

15.00 15.00 15.50 15.50 15.50 lb.00 16.00 lb.00 16.00 

400 4.00 5.00 5.00 5.00 5 00 5.00 5.00 5.00 

0.67 071 0.48 0.51 0.56 0.59 0.63 0.67 0.70 

3.73 3.76 3.79 3.82 3.86 3.89 3.93 3.96 3.99 

28.50 29.50 30.50 31.50 32.50 33.50 34.50 35.50 36.50 

14.72 15.10 15 48 15.86 lb.25 16.63 17.01 17.39 17.78 

F 

h2 

h3 

"4 

L2 

L3 

L4 

s3 

Submergence 

d2 

LX 

dl + hvl 

15.20 lb.20 17.10 18.00 

13.00 13.50 13.50 13.50 

4.00 3.00 3.00 3.00 

70.30 15O-0 

0.69 0.45 0.49 0.54 

3.25 3.29 3.33 3.37 

lb.50 17.50 18.50 19.50 

10.12 10.51 10.89 11.27 

F 13.61 13.96 14.30 14.66 

14.35 14 73 15.11 15.50 

0.08 008 0.08 0.08 

1 34 166 166 1.66 

34.70 35.60 36.50 37.40 

h2 

“3 

“4 

L2 

L3 

L4 

s3 

Submergence 

0.07 0.07 

1.07 1.01 

24.50 25.40 

15.00 15.00 

4.00 4.00 

lS0-0’ 

0.58 0.63 

3.65 3.69 

16.50 lb 50 lb.50 16.50 

5 00 4.00 4.00 4.00 

150-O' 22'.30' 

0.73 0.45 0.48 0.5 1 

4.02 4.05 4 08 4.11 

26.50 27.50 

13.95 14.33 

37.50 38.50 39.50 40.50 

18.16 18.54 18.92 19.31 

F = (dl + hv,) (l.ld2 + hvp) dl+hvl=R+h2+0.0b Submergence = l.ld2 + hvp + h3 - h4 D~ametcr of pipe hv 
Table 2-3 Type 1 pipe drop with earth outlet transition (to be used with ,fig. Z-29). -Continued. 103-D-1268-7 

F 

“2 

h3 

“4 

L2 

L3 

L4 

S3 

Submergence 

d2 

LX dl+hvl 

F 

h2 

h3 

“4 

L2 

L3 

L4 

S3 

Submergence 

d2 

LX 

dl + hvl 

F 

b2 

“3 

“4 

L2 

L3 

L4 

S3 

Submergence 

d2 

LX 

dl + hv, 

F 

“2 

h3 

“4 

L2 

L3 

L4 

S3 

Submergence 

d2 

LX 

dl+hv, 

Q = 15 cfs 

2.67 3.00 

2.10 2.49 

0.06 0.06 

0.26 0.26 

5.10 6.00 

II.50 11.50 

2.00 2.00 

7O-30 

0.48 0.54 

2.81 2.86 

5.50 6.50 

5.91 6.30 

9.63 9.97 

10.14 10.52 

0.08 0.08 

1.34 1.34 

24.50 25.40 

15.50 15.50 

5.00 5.00 

15O-0 

0.50 0.54 

3.79 3.83 

26.50 27.50 

13.95 14.33 

Q= 16cfs 

2.51 2.90 

2.10 2.49 

0.06 0.06 

0.26 0.26 

5.10 6.00 

11.50 12.00 

2.00 2.00 

70.30 

0.58 0.64 

2.88 2.94 

5.50 6.50 

5.91 6.30 

9.45 9.18 

10.14 10.52 

0.08 0.08 

1.34 1.34 

24.50 25.40 

16.00 16.00 

5.00 5.00 

150.0 ls”-0 

0.68 0.73 

3.94 3.98 

26.50 27.50 

13.95 14.33 

3.33 

2.87 

0.06 

0.26 

7.00 

12.00 

2.00 

3.65 3.98 

3.25 3.64 

0.06 0.06 

0.26 0.52 

7.90 8.80 

12.00 12.00 

2.00 4.00 

0.59 

2.91 

7.50 

6.68 

10.31 

10.91 

0.08 

1.34 

26.30 

15.50 

5.00 

0.65 0.45 

2.96 3.02 

8.50 9.50 

7.06 7.4$ 

10.65 10.98 

11.29 11.67 

0.08 0.08 

1.34 1.34 

27.30 28.20 

16.00 16.00 

5.00 5.00 

0.59 

3.87 

28.50 

14.72 

Dmneter of p,pe = 30 mchci VP = 3.05 fps 

4.29 4.62 4.94 5.27 5.59 

4.02 4.40 4.78 5.17 5 55 

0.06 0.06 0 06 0.06 0.07 

0.52 0.52 0.52 0.52 0.81 

9.70 10.60 11.60 12.50 13.40 

12.50 12.50 13.00 13.00 13.50 

4.00 4.00 4.00 4.00 3 00 

lo-30 150-O’ 

0.52 0.57 0.63 0.69 0.47 

3.08 3.13 3.18 3.24 3.29 

10.50 11.50 12.50 13.50 14.50 

7.83 8.21 8.59 8.98 9.36 

11.33 11.68 12.01 12.35 12.68 

12.05 12.44 12.82 13.20 13.58 

0.08 0.08 0.08 0.08 0.08 

1.34 1.66 1.66 1.66 1.66 

29.10 30.10 31.00 31.90 32.80 

16.00 16.50 16.50 16.50 15.50 

5.00 4.00 4.00 4.00 4.00 

22’.30 

0.71 0.43 0.48 0.52 0.55 

3.98 4.02 4.06 4.10 4.13 

31.50 32.50 33.50 34.50 35.50 

15.86 16.25 16.63 17.01 17.39 

Diameter of pope = 30 inches VP = 3.26 fps 

0.63 0.67 

3.91 3.95 

29.50 30.50 

15.10 15.48 

3.20 3.52 3.86 

2.87 3.25 3.64 

0.06 0.06 0.06 

0.52 0.52 0.52 

7.00 7.90 8.80 

12.00 12.50 12.50 

4.00 4.00 4.00 

4.18 

4.02 

0.06 

0.52 

9.70 

13.00 

4.00 

0.46 0.52 0.57 0.63 

3.01 3.06 3.11 3.16 

7 50 8.50 9.50 10.50 

6.68 7.06 1.45 7.83 

10.12 

10.91 

0.08 

1.66 

26.30 

16.50 

4.00 

22’.30 

0.46 

4.03 

28.50 

14.72 

10.45 10.79 

11.29 11.67 

0.08 0.08 

1.66 1.66 

27.30 28.20 

16.50 16.50 

4.00 4.00 

11.13 

12.05 

0.08 

1.66 

29.10 

17.00 

4.00 

0.5 1 0.55 0.59 

4.07 4.11 4.15 

29.50 30.50 31.50 

15.10 15.48 15.86 

PIPE DROP WITH MITER BENDS 

Earth Outlet Transition 

Check and Pipe Inlet Control and Pipe inlet 

All values are m feet unless otherwise noted 

5.92 

5.93 

0.07 

0.81 

14.30 

13.50 

3.00 

0.52 

3.34 

15.50 

9.74 

13.04 

13.97 

0.08 

1.66 

33.70 

17.00 

4.00 

0.60 

4.17 

36.50 

17.78 

4.51 4.82 5.15 

4.40 4.78 5.17 

0.06 0.06 0.07 

0.52 0.81 0.81 

10.60 11.60 12.50 

13.00 13.00 13.50 

4.00 3.00 3.00 

70.30 15O-0 

0.68 0.46 0.53 

3.21 3.27 3.33 

11.50 12.50 13.50 

8.21 8.59 8.98 

11.47 11.81 12.14 

12.44 12.82 13.20 

0.08 0.08 0.09 

1.66 1.66 1.66 

30.00 31.00 31.90 

17.00 17.00 17.50 

4.00 4.00 4.00 

0.64 0.68 0.74 

4.19 4.23 4.27 

32.50 33.50 34.50 

16.25 16.63 17.01 

5.47 5.79 6.11 6.46 6.78 7.12 7.45 7.79 8.11 8.44 8.79 

5.55 5.93 6.31 6.70 7.08 7.46 7.84 8.23 8.61 8.99 9.38 

0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.08 0.08 

0.81 0.81 1.07 1.07 1.07 I.07 1.07 1.34 1.34 1.34 1.34 

13.40 14.30 15.20 16.20 17.10 18.00 19.00 19.90 20.80 21.70 22.60 

13.50 14.00 14.00 14.50 14.50 14.50 15.00 15.00 15.00 15.50 15.50 

3.00 3.00 4.00 4.00 4.00 4.00 4.00 5.00 5.00 5.00 5.00 

0.59 0.65 

3.38 3.44 

14.50 15.50 

9.36 9.74 

12.46 12.83 

13.58 13.97 

0.09 0.09 

1.66 2.07 

32.80 33.70 

17.50 17.50 

4.00 5.00 

0.45 0.49 0.55 

3.49 3.53 3.58 

16.50 17.50 18.50 

10.12 IO.51 10.89 

0.59 0.64 

3.62 3.66 

19.50 20.50 

11.27 11.65 

14.17 14.50 

15.50 15.88 

0.09 0.09 

2.07 2.07 

37.40 38.30 

18.00 18.50 

5.00 5.00 

0.42 0.48 0.54 0.58 

3.71 3.76 3.81 3.85 

21.50 22.50 23.50 24.50 

12.04 12.42 12.80 13.19 

13.16 13.50 13.82 

14.35 14.73 15.11 

0.09 0.09 0.09 

2.07 2.07 2.07 

34.70 35.60 36.50 

17.50 18.00 18.00 

5.00 5.00 5.00 

14.84 15.17 15.51 15.85 

16.26 16.64 17.03 17.41 

0.09 0.09 0.09 0.09 

2.07 2.07 2.07 2.49 

39.30 40.20 41.10 42.00 

18.50 19.00 19.00 19.00 

5.00 5.00 5.00 6.00 

0.78 0.41 0.46 0.50 0.56 0.60 0.65 0.69 0.74 0.79 0.41 

4.31 4.35 4.39 4 43 4.48 4.52 4.56 4.60 4.65 4.69 4.73 

35.50 36.50 37.50 38.51. 39.50 40.50 41.50 42.50 43.50 44.50 45.50 

17.39 17.78 18.16 18.54 18.92 19.31 19.69 20.07 20.45 20.84 21.22 

6.25 6.60 6.93 7.11 7.59 7.94 8.27 8.59 8.94 

6.31 6.70 7.08 7.46 7 84 8.23 8.61 8.99 9.38 

0 07 0.07 0.07 0.07 0 07 0.07 0.07 0.07 0.07 

0.81 0.81 0.81 1.07 1.07 1.07 1.07 1.07 1.07 

15 20 16.20 17.10 18.00 19.00 19.90 20.80 21.70 22 60 

13.50 14.00 14.00 14 00 14.50 14.50 14.50 15.00 15.00 

3.00 3.00 3.00 4.00 4.00 4.00 4.00 4.00 4.00 

0.57 0.61 0.66 0.45 0.50 0.54 0 59 0.65 0.68 

3.38 3.42 3.46 3.5 1 3.55 3.59 3.64 3.69 3.72 

16.50 17.50 18.50 19.50 20 50 21.50 22.50 23.50 24.50 

10.12 10.51 10.89 11.27 11.65 12.04 12.42 12.80 13.19 

13.38 13.72 14.05 14.40 14.73 15.07 15.40 15.75 16.09 

14.35 14.73 15.li 15.50 15.88 16.26 16.64 17.03 17.41 

0.08 0 08 0.09 0.09 0.09 0.09 0.09 0.09 0.09 

1.66 1 66 1.66 1.66 2.07 2.07 2.07 2.07 2.07 

34.70 35.60 36.50 37.40 38.30 39.30 40.20 41.10 42.00 

17.00 17.00 17.50 17.50 17.50 18.00 18.00 18.00 18.50 

4.00 4.00 4.00 4.00 5.00 5.00 5.00 5.00 5.00 

0.64 0.68 0.74 0.78 0.42 

4.21 4.25 4.29 4.33 4.37 

37.50 38.50 39.50 40.50 41.50 

18 16 18.54 18.92 19.31 19.69 

0.46 0.50 

4.41 4 45 

42.50 43.50 

20.07 20.45 

Met R = 3.75 feet 

0.55 0.59 

4.49 4.53 

44.50 45.50 

20.84 21.22 

hvp = 0.17 foot 

hvp = 0.15 foot Met R = 3.75 feet 

9.29 

9.76 

0.07 

1.34 

23.60 

15.00 

5.00 

150.0 

0.44 

3.75 

25.50 

13.57 

16.42 

17.79 

0.09 

2.07 

43.00 

18.50 

5.00 

22’.30’ 

0.64 

4.57 

46.50 

21.60 

9.12 

9.76 

0.08 

1.34 

23.60 

15.50 

5.00 

150-O‘ 

0.63 

3.89 

25.50 

13.57 

16.18 

17.79 

0.10 

2.49 

43.00 

19.50 

6.00 

22’.30 

0.47 

4.77 

46.50 

21.60 

F = (d, + hvl) - (l.ld2 + hvp) dl+hvl=R+h2+0.06 Submergence = l.ld2 + hvp + h3 h4 - Dnmeter of pipe - hv 
~~~~~ 2-3.-r~pc I pipe drop with cart/z outlet transitio/z (to be used with fig. 2-29). -Continued. 103-D-1268-8 

F 

h2 

h3 

“4 

L2 

L3 

L4 

S3 

Submergence 

d2 

LX 

d,+hvl 

F 

h2 

b3 

4 

L2 

L3 

L4 

S3 

Submergence 

d2 

LX 

dl + hv, 

F 

h2 

h3 

ha 

L2 

L3 

L4 

S3 

Submergence 

d2 

LX 

d,+hv, 

F 

h2 

h3 

“4 

L2 

L3 

L4 

S3 

Submergence 

d2 

LX 

dl+hvl 

Q= 17cfs Dnmeter of pope = 30 inches VP = 3.46 fps hvp = 0.19 foot 

2.47 2.80 

2.10 2.49 

0.06 0.06 

0.52 0.52 

5.10 6.00 

12.00 12.00 

4.00 4.00 

70.30 

0.41 0.48 

2.95 3.01 

5.50 6.50 

5.91 6.30 

3.10 

2.87 

0.06 

0.52 

7.00 

12.50 

4.00 

0.56 

3.08 

7.50 

6.68 

3.41 3.74 4.05 4.43 

3.25 3.64 4.02 4.40 

0.06 0.06 0.06 0.07 

0.52 0.52 0.81 0.81 

7.90 8.80 9.70 10.60 

12.50 13.00 13.00 13.50 

4.00 4.00 3.00 3.00 

70.30 15O-0 

0.62 0.69 0.47 0.54 

4.69 5.02 5.34 5.66 5.98 6.31 8.63 6.96 7.28 

4.78 5.17 5.55 5.93 6.31 6.70 7.08 7.46 7.84 

0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.08 

0.81 0.81 1.07 1.07 1.07 1.07 1.34 1.34 1.34 

11.60 12.50 13.40 14.30 15.20 16.20 17.10 18.00 19.00 

13.50 14.00 14.00 14.50 14.50 15.00 15.00 15.00 15.50 

3.00 3.00 4.00 4.00 4.00 4.00 5.00 5.00 5.00 

3.14 3.20 3.26 3.32 

8.50 9.50 10.50 11.50 

7.06 7.45 7.83 8.21 

0.60 0.66 0.46 0.52 0.58 0.64 0.43 0.48 0.55 

3.37 3.43 3.48 3.54 3.59 3.65 3.70 3.75 3.80 

12.50 13.50 14.50 15.50 16.50 17.50 18.50 19.50 20.50 

8.59 8.98 9.36 9.74 10.12 10.51 10.89 Il.27 11.65 

9.26 9.59 

10.14 10.52 

0.08 0.08 

1.66 1.66 

24.50 25.40 

16.50 16.50 

4.00 4.00 

22’.30 

0.55 0.60 

4.09 4.14 

26.50 27.50 

13.95 14.33 

9 93 10.25 10.59 10.92 11.26 11.60 11.94 12.24 12.61 12.93 13.27 13.59 13.94 14.26 

10.91 11.29 11.67 12.05 12.44 12.82 13.20 13.58 13.97 14.35 14.73 15.11 15.50 15.88 

0.08 0.08 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 

1.66 1.66 1.66 2.07 2.07 2.07 2.07 2.07 2.07 2.07 2.07 2.07 2.49 2.49 

26.30 27.30 28.20 29.10 30.00 31.00 31.90 32.80 33.70 34.70 35.60 36.50 37.40 38.30 

17.00 17.00 17.50 17.50 17.50 18.00 18.00 18.00 18.50 18.50 18.50 19.00 19.00 19.00 

4.00 4.00 4.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 6.00 6.00 

0.65 0.70 0.76 0.40 0.45 0.49 0.53 0.59 0.63 0.69 0.73 0.79 0.41 0.45 

4.18 4.23 4.27 4.32 4.36 4.40 4.44 4.49 4.53 4.58 4.62 4.67 4.71 4.76 

28.50 29.50 30.50 31.50 32.50 33.50 34.50 35.50 36.50 37.50 38.50 39.50 40.50 41.50 

14.72 15.10 15.48 15.86 16.25 16.63 17.01 17.39 17.78 18.16 18.54 18.92 19.31 19.69 

Q = 18 cfs Diameter of pope = 36 mches VP = 2.54 fps hvp = 0.10 foot 

3.14 3.48 3.80 4.13 4.46 4.80 5.13 

2.10 2.49 2.87 3.25 3.64 4.02 4.40 

0.06 0.06 0.06 0.06 0.06 0.06 0.06 

5.47 5.81 

4.78 5.17 

0.06 0.06 

5.10 6.00 7 .oo 7.90 8.80 9.70 10.60 

12.00 12.00 12.00 12.50 12.50 12.50 13.00 

11.60 12.50 

13.00 13.00 

6.81 7.16 7.49 7.83 8.18 

6.31 6.70 7.08 7.46 7.84 

0.07 0.07 0.07 0.07 0.07 

0.26 0.26 0.26 0.52 0.52 

15.20 16.20 17.10 18.00 19.00 

13.50 14.00 14.00 14.00 14.50 

2.00 2.00 2.00 4.00 4.00 

0.27 0.32 0.37 0.42 

2.88 2.93 2.98 3.03 

5.50 6.50 7.50 8.50 

6.41 6.80 7.18 7.56 

0.47 0.53 0.58 

3.08 3.12 3.16 

9.50 10.50 11.50 

7.95 8.33 8.71 

0.62 0.67 

3.20 3.25 

12.50 13.50 

9.09 9.48 

6.14 6.48 

5.55 5.93 

0.07 0.07 

0.26 0.26 

13.40 14.30 

13.50 13.50 

2.00 2.00 

70.30 

0.48 0.52 

3.29 3.33 

14.50 15.50 

9.86 10.24 

0.56 0.60 0.64 0.43 0.46 

3.37 3.41 3.45 3.49 3.52 

16.50 17.50 18.50 19.50 20.50 

10.62 11.01 11.39 11.77 12.15 

10.29 10.64 11.00 

10.14 10.52 10.91 

0.07 0.07 0.07 

0.52 0.52 0.81 

24.50 25.40 26.30 

15.00 15.00 15.00 

4.00 4.00 3.00 

70.30 70.30 15O-0 

0.65 0.68 0.42 

3.69 3.72 3.75 

26.50 27.50 28.50 

14.45 14.83 15.22 

11.34 

11.29 

0.08 

0.81 

27.30 

15.50 

3.00 

11.69 12.04 12.39 

11.67 12.05 12.44 

0.08 0.08 0.08 

0.81 0.81 0.81 

28.20 29.10 30.00 

15.50 15.50 15.50 

3.00 3.00 3.00 

0.50 0.53 0.57 

3.81 3.84 3.87 

30.50 31.50 32.50 

15.98 16.36 16.75 

12.74 13.09 13.43 13.79 14.14 14.49 14.84 15.20 15.55 

12.82 13.20 13.58 13.97 14.35 14.73 15.11 15.50 15.88 

0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.06 0.08 

0.81 0.81 0.81 1.07 1.07 1.07 1.07 1 07 1.07 

31.00 31.90 32.80 33.70 34.70 35.60 36.50 37.40 38.40 

16.00 16.00 16.00 16.00 16.50 16.50 16.50 16.50 16.50 

3.00 3.00 3.00 4.00 4.00 4.00 4.00 4.00 4.00 

0.47 

3.78 

29.50 

15.60 

0.60 0.63 0.67 0.44 0.47 0.50 0.53 0.56 0.59 

3.90 3.93 3.96 3.99 4.02 4.05 4.07 4.10 4.13 

33.50 34.50 35.50 36.50 37.50 38.50 39.50 40.50 41.50 

17.13 17.51 17.89 18.28 18.66 19.04 19.42 19.81 20.19 

PIPE DROP WITH MITER BENDS 

Earth Outlet Transition 

Check and Pipe inlet Control and Pipe inlet 

D = (dl + hvl) (l.ld2 + hvp) dl+hvl=R+h2+0.06 Submergence = l.ld2 + bvp + h3 h4 Dmmeter of pipe hv 

inlet R = 3.75 feet 

7.62 

8.23 

0.08 

1.34 

19.90 

15.50 

5.00 

0.60 

3.85 

21.50 

12.04 

7.94 8.26 

8.6 1 8.99 

0.08 0.08 

1.34 1.66 

20.80 21.70 

16.00 16.00 

5.00 4.00 

150-o 22’.30 

0.66 0.39 

3.90 3.95 

22.50 23.50 

12.42 12.80 

14.60 14.93 15 27 

16.26 16.64 17.03 

0.10 0.10 0.10 

2.49 2.49 2.49 

39.30 40.20 41.10 

19.50 19.50 20.00 

6.00 6.00 6.00 

0.52 0.57 0.62 

4.80 4.85 4.89 

42.50 43.50 44.50 

20.07 20.45 20.84 

Inlet R = 4.25 feet 

8.54 8.88 9.24 

8.23 8.61 8.9’9 

0.07 0.07 0.07 

0.52 0.52 0.52 

19.90 20.80 21.70 

14.50 14.50 14.50 

4.00 4.00 4.00 

0.49 0.53 0.55 

3.55 3.58 3.60 

21.50 22.50 23.50 

12.54 12.92 13.30 

15.91 16.25 16.61 

16.26 16.64 17.03 

0.08 0.08 0.08 

1.07 1.07 1.07 

39.30 40.20 41.10 

17 .oo 17.00 17.00 

4.00 4.00 4.00 

0.61 0.65 0.68 

4.15 4.18 4.21 

42.50 43.50 44.50 

20.57 20.95 21.34 

8.60 8.94 

9.38 9.76 

0.08 0.08 

1.66 1.66 

22.60 23.60 

16.00 16.50 

4.00 4.00 

22’.30 

0.45 0.49 

C 

4.00 4.04 n 

24.50 25.50 

13.19 13.57 

15.60 15.93 

17.41 17.79 

0.10 0.10 

2.49 2.49 

42.00 43.00 

20.00 20.00 

6.00 6.00 

22’.30’ 

0.67 0.72 

4.94 4.98 

45.50 46.50 

21.22 21.60 

9.60 9.94 

9.38 9.76 

0.07 0.07 

0.52 0.52 

22.60 23.60 

14.50 15.00 

4 .oo 4.00 

70.30’ 

0.58 0.62 

3.63 3.66 

24.50 25.50 

13.69 14.07 

16.97 17.31 

17.41 17.79 

0.08 0.08 

1.34 1.34 

42.00 43.00 

17.00 17.00 

5 00 5.00 

15O-0’ 

0.43 0.48 

4.23 4.26 

45.50 46.50 

21.72 22.10 
Table 2-3.-~vpc I pipe drop with earth outlet transition (IO he rrwl with fig. 2-ZY). Xontinued. 103-D-l 268-9 

PIPE DROP WITH MITER BENDS 

Earth Outlet Transition 

o= 19‘1s 

3.05 3 39 373 4 05 

2.10 2.49 2.87 3 2s 

0.06 0 06 0.06 0.06 

7 "0 

12.50 

0.36 0.41 

2.95 3.00 

5.50 6.50 

6.4 I 680 

IO.17 1052 

IO.14 IO.52 

0.08 U.08 

0 81 0.81 

24.50 25.40 

15.50 15.50 

3.00 3 00 

150-O 

0.49 0.52 

3.79 3.X2 

26.50 27 50 

14.45 14.83 

0.45 051 

3.04 3.09 

7.50 8.50 

7 18 7.56 

1088 11.22 

IO.91 II.29 

0 08 0 08 

0.81 0 XI 

26.30 27 30 

16.00 16.00 

3.00 3.00 

0.55 0.59 

3 85 3.88 

28 SO 29.50 

15 22 lS.hO 

0 = 20 ct\ 

2.98 3 31 3 64 3.96 

2.10 2.49 2.87 3 25 

0.06 0 06 0 06 0.06 

5.10 6 00 7 0" 7.9U 

12.00 12.50 1250 13.00 

0.43 0.49 0.54 0 60 

301 3.06 3.1 I 3.16 

5.50 650 7.50 8.50 

6.41 6.80 7.18 7.56 

IO.01 l(1.35 

IO.14 IO.52 

0.08 0.08 

0.81 O.RI 

2450 25.40 

16.00 I6.01, 

3.00 3.00 

150.0 

0.65 0.69 

3.93 3 96 

26.50 27 50 

14.45 14.83 

IO.71 11.06 

10.9 I 11.29 

008 0.08 

1.07 1.07 

26.30 27.30 

16.00 16.50 

4.00 4.00 

0.46 0.49 

3.99 4.02 

28.50 29.50 

15.22 15.60 

,llh!I R = 4.25 ICC, 

4.39 

3.64 

0.06 

0.56 

3.14 

9.50 

7.95 

11.57 

11.67 

0 OX 

0 XI 

28.20 

16.00 

3.00 

0.62 

391 

30.50 

I5 98 

4.71 5 05 

4 02 4.40 

0.06 0 06 

9.70 10.60 

13 00 13 00 

0 62 0.66 

3.19 3.23 

10.50 II so 

8.33 8.71 

11.92 12.27 

12.05 IL.44 

0.08 O.08 

0.81 IO7 

29.10 30.00 

16.00 16 00 

3.00 4 00 

0.65 0.43 

3 94 3.91 

3150 32.50 

16.36 16.75 

6.39 6 73 

5.93 6 31 

0.07 0 07 

0.26 0.26 

14 30 15 20 

14.00 14 00 

2 00 2 00 

0.60 0.64 

3.40 3.44 

15.50 l6.5U 

1024 10.62 

13 66 14 00 

13.97 14 35 

0.08 0 08 

IO7 1.07 

33.70 34.70 

1650 16.50 

4.00 4.m 

0 51 0 61 

4 10 4 I4 

36.50 37.50 

18.28 18.66 

5 72 6.05 

5.17 5.55 

I, 07 0.07 

0.26 0.26 

12.50 13.4U 

I3 5u 13.50 

2.00 2.00 

051 0.56 

3.32 3.36 

13.50 1450 

948 9 X6 

I2 96 13.30 

13.20 1358 

0.08 0 08 

I 07 I 07 

31 90 32 XC, 

16.50 16.50 

4.00 4.00 

0.50 0.54 

4.04 4.07 

34 50 35.50 

17 51 17.89 

7 07 741 

6.70 7.08 

0 "7 0 07 

0.52 0.52 

1620 17 IO 

14.00 14.00 

4 00 4.00 

0.43 0.47 

3.48 3.52 

17.50 18.50 

II 01 11.39 

14.34 14 69 

14.73 15.11 

0.08 0 ox 

I .07 IO7 

35.60 36.50 

17 on 17 00 

4 00 4.00 

0 65 II.68 

4.17 4.20 

38.50 39.50 

19.04 19.42 

I 

L2 3 

"4 

L2 

L3 

L4 

s3 

S"b~llCUXilW 

d2 

LY 

dl + h"] 

I 

h2 

h3 

"4 

L2 

L3 

L4 

s3 

Subnlcrgence 

d2 

L, 

d,+hv, 

r 

1'2 

'13 

"4 

l-2 

L3 

L4 

s3 

sutmcrgcnce 

d2 

L, 

d, +hv, 

I‘ 

62 3 

"4 

L2 

L3 

L4 

s3 

S"binerI!ence 

dL2 

d, + hv; 

5.38 

4.78 

0.07 

0 26 

II.60 

13.50 

2.00 

7D-30 

046 

3 21 

12 SO 

9 (19 

7.74 808 

746 7 84 

0.07 0.07 

0.52 0.52 

18 00 19.00 

14 50 I4 50 

4 00 4.00 

I1 52 0.56 

3.56 3.60 

1950 20.50 

II 71 12 15 

I? 62 

t 2.82 

0.08 

I .07 

3 I 00 

16.00 

4.00 

0.46 

4.00 

33.50 

17.13 

15.05 15.39 

15.50 15.88 

(1.08 (I.08 

I 34 1.34 

37.40 38.40 

17.00 17.00 

5 00 5.00 

0.44 0.48 

4.23 4.26 

40.50 4150 

19.81 20 19 

4.95 5.27 5.60 

4.40 4.78 5.17 

0.07 0.07 0.07 

0.26 0.26 0.26 

10.60 II.60 12.50 

I3 50 13.50 14 0" 

2.w 2.00 2.on 

5 92 6 27 

5.55 5.93 

0 07 0.07 

0.26 0.52 

13.40 14 30 

6.61 6.95 

6.31 6 70 

0.07 0.07 

0.52 0.52 

IS.20 16.20 

14.50 14.50 

4.00 4.00 

7.29 7.62 7.96 

7.08 7.46 7.84 

0 07 0.07 0.07 

0.52 0.52 0.52 

14.00 14.00 

2.00 4.00 

051 0.57 063 0.69 0 46 0.50 0.55 

3 31 3 36 342 3.47 3.50 354 3.58 

II.50 12.50 13.5c 14.50 15.50 16.50 17.50 

871 9 09 948 9.86 10.24 10.62 11.01 

17.10 18.00 19.00 

14.50 15 00 15.00 

4.00 4.00 4 "0 

7O~30' 

0.59 0.64 0.68 

3.62 3.66 3 70 

18.50 1950 20.50 

11.39 il.77 12 15 

12.08 12.42 12.71 

1244 12.x2 13.20 

0.08 0.08 0.08 

107 IO7 1.34 

30 00 31.00 11.90 

17.00 17.00 17 00 

4 00 4 00 5.00 

13 12 13.47 

13.58 1397 

0 OR 0.08 

I34 1.34 

32 80 33.70 

17.00 1700 

5.00 5.00 

13.82 14.17 

14 35 14 73 

0.09 0 09 

1.34 1.34 

34.70 15.60 

17 50 17.50 

5.00 5 00 

14.51 14.87 15.22 

15.11 15 50 15 88 

0.09 II 09 0.09 

1.34 1.34 I34 

36.50 37.40 38 40 

17 50 17.50 I8 00 

5.00 5 .oo 5 00 

0.62 0.66 0.42 0 45 0.49 053 0 56 060 063 0.66 

4.14 4.17 4.20 4.23 4.26 4.29 4 32 4.35 4 38 4.41 

32.50 3350 34.50 35.50 36.50 37.50 38 50 3950 4050 41.50 

16 75 17.13 17.51 17 89 I8 2x 18 66 19 04 19.42 19.81 20.19 

844 8.78 9 13 

X23 8.6, 899 

0 07 0.07 0 07 

052 0.52 0.81 

19.90 20.80 21 70 

14.50 15.00 15.00 

9.49 

9.38 

0.07 

0.81 

9.82 

9 16 

O.08 

0.81 

23.60 

15.50 

3.00 

15".0‘ 

0.45 

3.76 

25.50 

14.07 

I7 15 

17.79 

0 09 

1.34 

43.00 

18.00 

5.00 

15% 

0.64 

4.40 

46.50 

22.10 

966 

9.76 

0.08 

0.81 

23.60 

16.00 

3.00 

15O-0 

0.62 

3.90 

25.50 

14.07 

16.96 

17.79 

0.09 

1.66 

4300 

18.50 

4.00 

22'.30' 

0.51 

4.56 

46.50 

22.10 

22.60 

15.0(1 

4.00 4.00 3.00 3.00 

70.30' 15".0‘ 

0.59 0.63 0.37 

3.63 3 66 369 

2150 22.50 23.50 

1254 12.92 13 30 

0.40 

3.72 

24 50 

13.69 

15 74 16.09 16.45 16.79 

16 26 lb.64 17.03 17.41 

0 09 0.09 0.09 0.09 

I34 1.34 I 34 1.34 

39 30 40.20 41.10 42.00 

17 50 17.50 17.50 17.50 

5 .oo 5.00 5 .oo 5.00 

0 52 0.55 0.58 0.62 

4.29 4.32 4.35 4.38 

42.50 43 50 44.50 45 50 

20.57 20.95 21.34 21.72 

Inlet R = 4.25 rrrt 

4.30 4.62 

364 4.02 

0 06 0.06 

0.26 

R 80 9.70 

I3 00 13.00 

2 00 

7v-30 

0.65 0.45 

3.21 3.26 

9.50 10.50 

7.95 8.33 

11.39 11.73 

II 67 I2 OS 

008 0.08 

1.07 107 

28.20 29 IO 

16.50 16.50 

4.00 400 

0.54 0.58 

4.06 4.10 

30.50 31.50 

15 98 16.36 

8 31 8.64 898 

8 23 X.61 x.99 

0.07 0.08 0.08 

0 81 0.81 081 

9 32 

9.38 

0.08 

0.81 

22.60 

15.50 

3.00 

0.58 

3 X6 

24.50 

13.69 

16.62 

1741 

0.09 

1.66 

4200 

18.50 

4.00 

0.47 

4.53 

45 50 

2172 

19 90 20.x0 21.70 

IS ou 15.50 15.50 

3.00 3 00 3.00 

15O~O‘ 

0.43 049 053 

3.74 378 3.82 

21.50 2250 23.50 

12.54 12.92 13.30 

15.57 15.91 16.27 

16.26 16 64 17.03 

0.09 0.09 0.09 

1.34 166 1.66 

39.30 4020 41.10 

18 00 18.00 18 on 

5 00 4 00 4 00 

150.0' 22".30' 

069 0.41 0.44 

4.44 4.47 4.50 

42.50 43.50 44.50 

20.57 20.95 21.34 

d,+hv,=R+h2+0.06 Submergence = I Id2 +t,v,, + h3 h4 D~mctcr ot ppc hv 
Table 2-3.-Type I pipe drop with eurth outlet transitio!i (to be used with fig. 2-29). -Continued. 103-D-1268-10 

0 

m 

6 50 h 84 7 18 752 

631 h 70 7 08 746 

0.07 0 07 IJ 07 0.07 

0 52 0 52 U 52 0x1 

15 20 16 20 17.10 I8 00 

I4 50 I5 00 15.UO 15 00 

4 00 4 00 4.00 3 00 

7"~30‘ 15o-u 

0 61 0.66 II JO 0.45 

3h2 3 66 3 70 3.74 

,650 17 50 1850 1950 

10.62 I, 01 II 39 I, 17 

136X 14 02 I4 35 14 70 

14.35 14 73 15 I, 15 50 

0 09 0 09 0 09 0 09 

I 34 I34 I66 I66 

34 71, 35 60 36 50 37 411 

I x.uo IX 00 lX.lJO ,850 

5 00 5.01, 4 00 4 uu 

15% 22".30 

Oh7 0 71 0 44 0 48 

4.40 444 448 452 

37 50 38.50 39 50 40 50 

1866 19.04 1942 1981 

llrp = ,,.,5 ,001 

6.41 6 i6 7 08 742 

631 6.71) 7.0x 7.46 

0 07 0 07 0 ,,?I ,I OX 

0 52 0.x1 0 XI 0.x I 

15.20 I6 20 11 IIJ :8 00 

15.00 15.00 15 so 15 51~ 

4.00 3 00 3 00 3 00 

7".30‘ 15".0' 

1J 70 ,I 45 0 52 0 56 

3.69 3 73 3 78 3 x2 

16.50 17 50 IX 50 19 50 

1062 11.01 11.39 ,I 77 

1356 17.89 14 24 14.60 

14.35 1473 15 11 15 5U 

0 09 0 09 0 09 0.09 

1.66 166 I66 I66 

34 70 35.60 36 50 37.40 

IX.00 I8 51) 18 50 18 50 

4 00 4 00 4.00 4 UIJ 

22~~-30 

U47 0.50 0 55 0 58 

4.50 453 457 4 60 

3750 38.50 39.50 40.50 

1866 19 04 1942 1981 

2 RY 3 23 355 387 

2 IO 249 287 3 25 

0 Oh 0 06 0 06 0.06 

0 52 0 57 

3 Ul 3 i2 

5.50 6.50 

64, 6 80 

988 lO2l 

IO.14 10.52 

(I.08 II.08 

I (17 I U7 

24 50 25 40 

16 50 16.50 

4.00 4 uu 

,5"-(I‘ 

0 52 0 57 

403 401 

26 50 27.50 

1445 1483 

0 63 0 69 

3 17 323 

7 50 8 50 

7 18 7 56 

IO 57 1092 

IOYI 11 29 

0 08 008 

1.07 1.07 

26 30 21 30 

16 50 16 50 

4 00 4.00 

U60 0 63 

4 10 4 13 

28.50 2950 

15 22 I5 hU 

0 = 22 it\ 

2.82 3 14 

2.10 249 

I1.M 0 06 

5.lU 6 00 

I2 50 I3 (IO 

0 59 0 66 

3 13 3 19 

5 50 6 50 

6 41 6.80 

9.19 IO.14 

I U.14 IO 52 

11.08 (I.08 

1.07 I 07 

24 50 25.40 

16.50 1650 

4.00 4.00 

15% 

0 6 I 0 64 

4.10 4.13 

26.50 27 50 

14.45 14.83 

347 

287 

0 06 

U.?h 

7 00 

I3 wi 

2 00 

7<'~30 

0 45 

3 24 

7.50 

7 18 

3 79 4 13 445 4 76 5 09 5 42 5.15 b 07 

3 25 3 64 4 02 4.40 418 5 I7 5 55 5 93 

0 07 (I (17 0 07 0.07 0 07 0 07 0 07 0 07 

,I 2h 0 26 0 26 0.26 0.52 0 52 II.52 0 52 

7 90 X.80 Y 70 IO 60 ,160 12.50 1340 14 30 

13 50 13 50 14.w 14 uo 14 00 14.50 14 50 15 00 

2 00 2 ",I 2 00 2.00 4.UC 4 00 4.00 4 00 

0 52 u 57 0 63 0 70 04Y 0 55 0 60 Oh6 

3 29 3 34 339 3 45 3 50 355 3 60 3 h5 

8.50 Y 51, 1050 II 50 12.50 13 51, 14.50 I5 5(1 

7 5h 7.95 8.33 H 71 Y 09 948 Y 86 IO 24 

1048 IO 83 II 17 II.51 II87 1221 12.64 

IO.9 I II 29 II67 1205 12.44 12.x2 13 20 

0.08 0 08 0.08 0.09 0 09 u 09 0.09 

I 07 I .(I7 I 07 1.34 I34 I34 I 34 

26.30 27.311 2x.20 29 10 30.00 3, 00 31 90 

I7 00 1700 17.00 17 50 17.50 17.50 17 50 

4.00 4.00 4 00 5 00 5.00 5.00 5.00 

0.69 0 72 0.76 0.54 057 ".hl 0.66 

4.1, 4.20 4 24 4 21 4 30 4.34 4.38 

28.50 29 50 30.50 31.50 32.50 33 50 34 50 

15 22 15.60 I5 98 16 36 16 75 17 13 17 5, 

X86 

8 YY 

0 08 

0 XI 

?I 71) 

16 U,, 

3 00 

0.65 

3.91 

2350 

13 30 

16.05 

17 03 

Cl.09 

I66 

4 1.10 

19 00 

4 ur, 

0.63 

4 65 

44 5v 

21 34 

4 20 452 4 x4 

364 402 4 40 

5 17 551 

47x 5 17 

007 007 

0 26 0 52 

Ii 60 1250 

14 00 I4 00 

2 00 4 00 

067 0.46 

344 348 

I? 5(, 13.50 

Y 09 948 

I2 30 12.64 

12.82 13 20 

0 OH 0.09 

I34 134 

3 I 00 31.911 

17."" ,750 

5 00 5 00 

5 84 6 17 

555 5 93 

0 07 0 lJ7 

iJ.52 0 52 

1340 I4 3u 

,450 14 5U 

4 00 4 /,I, 

1299 13 33 

1358 13.97 

0 09 II.09 

I34 I34 

32 80 33 7u 

1750 1750 

5 00 5 00 

059 064 

4 33 4.31 

35 50 36 50 

17.89 18.28 

954 

Y 76 

0.08 

I (17 z 

23.60 

,600 

4 00 

15O~O. z 

0 48 ;D 

3 YY 

25 50 

14 07 

8 ?(I 

8 23 

O.08 

URI 

IY 90 

15 50 

3 00 

9 20 

Y 38 

0 08 

,I 8, 

22 611 

16 00 

400 

0 51 

3 78 

20.50 

I? 15 

0 55 

3x2 

21.50 

12 54 

0 6, 

3 x7 

2250 

,292 

,I 71) 

3.95 

24.51) 

13.69 

15 39 

I6.2h 

IJ UY 

1.66 

39.30 

18.50 

4 00 

15 14 

lb64 

o.u9 

I66 

40 20 

1x50 

4 00 

0.52 

4 5S 

41 50 

20 19 

0 55 

458 

42 50 

20.57 

0 5x 

4.61 

43.50 

21195 

0 66 

4.68 

45 5U 

2, 72 

7 85 X.09 842 8 76 9.12 

7.84 8 23 R61 899 Y 3x 

0.0x 0.08 Il.08 0.08 0 08 

//RI 0 81 0 81 0 XI 1.07 

19 00 19 90 20 80 21.70 226O 

15 50 16 00 ih.Ui) ih 00 1650 

3 00 3 00 3 ,,,I 3 00 4.00 

0.6 I 0 66 1x7 I 0 7.1 0 52 

3 X6 3Yl 3 95 3.9') 4 112 

20.50 21 51) 22.50 23 50 24 5U 

12.15 12.54 12 Y? 13.30 I369 

14 94 15 28 15.b? 15.Yh 16.31 

15 88 I6 26 16 64 17 03 17.41 

0 09 u 09 " UY 0.09 0.10 

I66 1.66 I.66 1.66 1.66 

38 40 39 30 40.20 41.111 42.00 

19 00 1Y.00 19.00 19.00 1950 

4 00 4.00 4.0,1 4 00 4.00 

0 62 066 0 70 0 75 0.79 

4.64 467 471 4.75 4.7R 

4, 50 12 50 43 50 44 50 45.5U 

20.19 2057 20 9s ?I 34 21 72 

I 

1'2 

"3 

"4 

L? 

L3 

L4 

Si 

Submrrpcn& 

d, 

L; 

d, + h", 

I 

E2 3 

"4 

L2 

L3 

L4 

% 

Submcrgcncc 

d2 

L, 

d , + In , 

I 

"2 

"3 

114 

L2 

L3 

L4 

s3 

Submergcncr 

"2 

J-L 

d, +'I", 

0.07 II 07 0 07 

026 0.26 i) 26 

8 80 Y 70 1 I, 60 

13.50 13.50 14 00 

2 00 2 00 2 00 

7"~3U 

0 50 056 062 

3 28 3 34 3 39 

Y 50 IO 50 II 50 

7 95 8 33 87, 

16.18 

17 79 

0 09 

1.66 

43 nu 

19.00 

4 00 

22".30' 

0 69 

4 7, 

4650 

22.10 

0 08 0 08 u.ou 

I 07 1 07 1.34 

28.20 29 10 30 0" 

0 67 0 70 047 

4 16 4 19 423 

30 50 31 50 32 50 

I5 98 16 36 I6 75 

IZ.K7 13 22 

13 58 1397 

0 0') 0.09 

1.34 , 34 

32.80 3370 

LB no 18.W 

5 00 5.00 

15% 

0 70 0.75 

442 4.46 

35.50 36511 

17 89 1828 

945 

9.16 

0 08 

107 

23 60 

16.50 

4 00 

15%. 

057 

4 06 

25 50 

14 07 

16.66 

17.79 

II 10 

1.66 

43.w 

19.50 

4 00 

22O~30 

0.82 

4.81 

46.50 

22 IO 

d, ftw, = K + 11~ + 0 Oh 
Check and 

cantro and 

length 

/El .G 

‘-Concrete tranwtion 

LONGITUDINAL SECTION 

NOTES 

The pipe slopes used WIII allow the subitltutlon of 7% preczst 

concrete elbcws for the mltered p!pe bends. 

The max,mum velocity II. the pipe at the outlet equali 5 feet per 

second for p,pe flowlnq full. 

‘lydraul,c head IOSSES due to entrance, frlctlon, bends, and exit 

have beer. neg!ected. 

Precast concrete pressure pope wth mitered pope bends shown. AC 

or RPM ray be substituted. 

These standard designs are for flows less than 50 cubic feet per 

second. For flows greater than 49 cubic feet per second It is 

probably more economical to use a rectangular lncllned drop 

Ftgures 2-26 and 2-27 If It should be desirable to have a 

p,pe drop with a flow greater than 49 cubic feet per second, 

It ~111 be necessary to actually design the pipe drop. 

Ordinari Iy the ~wzx!rnum water surface drop far a pipe drop strucm 

ture IS I5 feet. However, standard design tables extend slightly 

beyond this n~aximun. 

Figure 2-30. Type 1 pipe drop with concrete outlet transition-explanation sheet for table 24. 103-D-1269. 
I 

112 

"3 

"4 

L2 

L3 

L4 

s3 

sutmerpcnce 

d2 

L, 

d , + hV , 

I' 

h2 

h3 

h4 

L2 

L3 

L4 

s3 

Suhmer~rnce 

d2 

L, 

d, tllv, 

0 1 if\ 

2 bH 3 01 

2.10 249 

0 u3 0.03 

0.26 0.26 

5.10 6.UU 

5.uc 6 00 

2.00 2 ou 

7O-30 

0.43 (1.49 

1.72 Ill 

5.50 6.50 

4.66 5 05 

10.46 1080 

IO.91 11.29 

0.04 0.04 

IO7 , 07 

26.30 27.30 

7.00 7 "0 

4 00 4.00 

15" 

0.63 067 

2.65 2.69 

2850 29.50 

13.41 13.85 

0 = 4 CfL 

I 2.28 

h? 2.10 

h3 003 

h4 0.53 

L? 5.10 

L3 5.00 

L4 4.00 

s3 7O-30 

Subrnergcncr 056 

d2 2.01 

L, 5.50 

d, + hv, 4.66 

I 

"2 

h3 

"4 

L2 

L3 

L4 

s3 

Submcrgcnce 

dz 

LX 

dl +llv, 

9 70 

10.91 

0.04 

1.88 

26.30 

7.00 

1.0" 

15C' 

0.58 

3 27 

28.50 

13.47 

2.59 2.90 

2.49 2 87 

0.03 0.03 

0.53 0.53 

6.00 7 00 

5.00 5.00 

4.00 4.00 

0.64 0.72 

2.08 2.15 

6.50 7.50 

5.05 543 

IO.04 ,038 

II 29 11.67 

0.04 0.04 

1.88 1.88 

27.30 28.20 

7.00 7.00 

7 00 7.00 

0.62 067 

331 3.35 

29.50 30.50 

13 85 14.23 

3.33 3.65 

287 125 

1LO3 u.u3 

0 26 0 26 

7 0" 7 90 

6 UU 6.00 

2.00 200 

0 55 0.61 

I83 18X 

7 50 8.50 

5.43 5.81 

11.15 11.49 

II.67 12 05 

0.04 0.04 

1.07 1.34 

28 20 29.10 

7 00 7.00 

4.00 5.00 

0.70 048 

272 2 76 

30.50 31.50 

1423 14.61 

320 3.52 3.82 4.15 4.46 4.79 5.10 5.43 

3.25 3.64 402 4.40 478 5.17 5.55 5.93 

0.03 0.03 003 0.03 003 0.04 u 04 0 04 

0.53 0.66 0.66 066 U 66 1.07 107 1.07 

7.90 8.80 970 10.60 116U 12.50 13.40 14 30 

5 00 5.00 5.00 5.00 5.00 7.00 7.00 7 uu 

4.00 5.00 5.00 5 00 5 00 4.00 4 00 4 00 

70.30' 150 

0.79 0.73 0.81 0.86 0.93 0.56 0.63 068 

2.22 2.28 2 35 2.40 2.46 2.52 258 2.63 

8.50 9.50 10.50 11.50 12.50 13.50 1450 15 50 

5.81 6.20 658 6.96 7.34 7.13 8.11 8.49 

1071 11.06 11.39 I, 74 12.08 1242 12.76 13.09 

12.05 1244 12.82 13.20 1358 13.97 14 35 1413 

0 04 0.04 0.04 0.04 0 05 0.05 11.05 0 05 

I.88 1.88 1.88 I88 2.01 2 07 2.07 2 07 

29.10 30.00 31 00 31.9u 32.80 33 70 34.70 35 6U 

7.00 7.00 7.00 7 00 10.00 lO.UU 10.00 1o.ou 

7.00 7.ou 7.00 7 00 5.00 5.00 5 00 5.00 

15" 22'~3U‘ 

071 0.75 0.80 0 83 0.63 068 0.72 0.77 

3.39 3.43 347 3.50 3.54 3.58 3.62 3 66 

3150 32.50 33.50 34.50 35.50 36.50 37.50 38.50 

14.61 15.00 15.38 15.76 16.14 16.53 1691 17 29 

3.98 

3 64 

0.03 

U 26 

8.80 

b 00 

200 

0 66 

193 

9.50 

6 20 

II.84 

12.44 

0 04 

1.34 

30.00 

7 00 

5 00 

0 5 I 

2.79 

32.50 

15.00 

4.3, 

4 02 

0 u3 

0.26 

9.70 

b UU 

2.00 

0.12 

1.98 

,050 

6.58 

12 19 

12.82 

0.04 

1.34 

3 1.00 

7.00 

5.00 

(1.54 

2.82 

3350 

15.38 

4 64 

4 40 

0.03 

0.39 

1060 

6 00 

3 00 

u.64 

2 03 

I I.50 

b 96 

12.54 

1320 

0.04 

1.34 

31.90 

7.00 

5 00 

0 58 

2.85 

34.50 

15.76 

PIPE DROP WITH MITER BENDS 

Concrete Outlet Transition 

4.97 

4 78 

u 03 

0.39 

11.60 

6.00 

3 00 

Oh9 

2 07 

12.50 

7.34 

12.89 

13.58 

u.04 

1.34 

32 80 

7.00 

5.00 

0.61 

2 88 

35.50 

I6 14 

5 30 5 64 5 YH 

5 17 5.55 5 93 

0.03 u 03 u 03 

0 39 0.39 0.39 

1250 ,340 14.30 

6 UU b.UU 6.00 

3 uu 3.00 3 uu 

0.14 0 79 0.83 

2.12 2 I6 2 20 

1350 14.50 15.5" 

7.73 8.11 849 

13 24 13.60 13.94 

13.97 14.35 14 73 

0 04 u.04 u u4 

1.34 1.34 I 34 

33.70 34 70 35 60 

7 00 7 00 7.00 

5.uu 5 00 5 00 

0 64 0.67 071 

291 2 94 2 97 

36.50 37.50 38.50 

16 53 ,691 17 29 

b 32 

6.31 

0.03 

(1.39 

15.20 

6.00 

3 00 

on7 

2.24 

I6 5U 

8.87 

6 bb 7 0, 

6 7U 7 08 

(1.03 0.04 

0 53 u 80 

16 20 17.10 

6.00 7 00 

4 00 3 00 

7".30, 15') 

0 78 II.52 

2.28 2.31 

17.50 18 50 

9.26 964 

14 29 14.64 

15 II I5 50 

u "4 0 04 

1.34 1.6, 

36.50 37 40 

7 00 7.00 

5 00 6 00 

0 74 

3 uu 

39 50 

1767 

0 5u 0 54 

3 03 3 06 

10.50 1150 

18 06 1844 

5.75 6.08 640 6.73 7 04 

6.3, 6.70 7.08 7.46 7 n4 

0.04 u 04 0.04 0.04 0.04 

107 1.07 1.34 1.34 I 34 

15 20 16 20 17.10 18.00 lY.UU 

7 00 7 00 7.00 7 00 7.00 

4 00 4.00 5.00 5 00 5.00 

0.74 0.80 0.59 064 0.71 

2 68 2.74 2.79 2 84 2 90 

16 50 1750 18.50 19.50 20.50 

8 87 9.26 964 IOU2 10.40 

1343 13.79 14.12 14 47 14.81 

15.11 15 50 15.88 16.26 16.64 

0.05 0 105 0 05 0.05 u 05 

2 07 2 07 248 248 2.48 

36 50 37 40 38.40 39.30 40 20 

lU.00 10.00 1000 I 0.00 10 00 

5 00 5 00 6.00 6.00 6 00 

0.81 0 84 0.48 051 0.55 

370 3 73 3.7, 3.80 3.84 

39.50 10.50 41.50 42.50 43.50 

1167 18.06 18.44 18.82 19.20 

14.98 

I5 88 

UW 

1.61 

38.40 

7 "0 

6 00 

1 34 

7.4b 

0.w 

0.80 

18.00 

J UU 

3.00 

0.57 

2.35 

19.50 

10.02 

15 33 

16.26 

0.04 

I61 

39.30 

7 00 

h.UO 

u 57 

3 UY 

4250 

18.82 

7.69 

7 84 

0 "4 

0.80 

19.00 

7.00 

3 00 

0.60 

2 38 

20.50 

10.40 

I5 69 

16.64 

0 04 

161 

40.20 

7 .uo 

b 00 

U 6O 

3 I2 

43.50 

19.20 

n 04 838 8.12 9.08 9.4, 9.76 10.12 

8.23 861 8.99 9.38 9.76 10 14 10.52 

0 04 0.04 u 04 0.04 0.04 0.04 0.04 

OR,, 0.80 0.80 1.07 1.07 1.07 1.07 

19.90 20 80 21.70 22.60 23.60 24.50 25.40 

7.00 7.00 7.00 7.00 7.00 7.00 7.00 

3 uu 3 00 3.00 4.00 4.00 4 00 4.00 

ISO 

U 64 068 0.72 0.48 0.53 0.56 0.59 

242 245 249 2.52 2.56 2.59 2.62 

21.50 22 50 2350 24.50 25.50 26.5U 27.50 

1079 I, 17 11.55 11.94 12.32 1270 13.08 

16.04 lb.31: 16.73 17.09 1743 17.78 18.13 

17.03 17.41 17 79 18 18 18.56 In.94 19.32 

OW 0.04 0.04 0.04 0.05 0.05 005 

1.6 I I61 1.61 1.61 1.86 1.86 1.86 

41.10 42.0" 4300 43.90 44 80 45.70 4670 

7 00 7 00 7.ou 7.00 9.50 950 9.50 

6.OU 6 00 6.00 6.00 4.50 450 4.50 

15" 22".30' 22'.30' 

064 067 0.70 073 0.47 0.50 0.53 

3 15 3.18 3.21 3 24 3.21 3 30 3.33 

44.50 45 50 46.50 47.50 48 50 49.50 50.50 

19.59 ,997 20 35 2074 21.12 2150 21.88 

lnlct R = 2.50 fret 

7 38 7.70 8.04 8 37 870 9.03 9.37 

8.23 861 8.99 9.38 9 76 10.14 10.52 

0 04 0.04 0.03 0.03 0.03 0.03 0.03 

1.34 L.34 1.74 1.74 1.14 1.14 1.74 

1990 20.80 21.70 22.60 23.60 24.50 25.40 

7 uu 7.00 650 650 6.50 6.50 6.50 

5.00 5.00 650 6.50 6.50 6.50 6.50 

150 

0 77 0 R2 0 45 0.5 I 0.5b 0.61 0.65 

i 95 3.00 3 04 3.09 3.14 3.18 3.22 

21.50 22.50 23.50 24.50 25.50 26.50 27.50 

,019 11.17 II 55 11.94 12.32 12.10 13 cl8 

15 15 15.50 15.85 16.19 16.54 16.89 17 22 

,703 1741 17.79 18.18 18.56 In.94 19.32 

o.u5 005 0.05 0.05 0.05 0.05 0.05 

2.48 2.48 248 2.48 2.69 2.69 2.69 

41.10 42 00 43.00 43.90 44.80 45.70 46.70 

lUO0 IO.OU lO.UO lU.00 10.50 10.50 10.50 

6.UO 600 6 "0 6 00 650 6.50 650 

22'.30' 

060 0 63 0.66 0.7 I 0.53 0.56 0.6 I 

3 88 3.91 3.94 3.98 4 01 4.04 4.08 

44 50 45.50 4650 47.50 48.50 49.50 50.50 

19 59 19.97 20.35 20.74 21.12 21.50 21.88 

I =(d,+hv,j (l.ld2+hv,,, d, + hv, = R + h2 + 0.06 Submeieencc = 1 Id2 + hv,, + h3 h4 d,amefer ofpqe hv 
Table 24.-i’)yx I pipe drop with concrete outlet tratnitiorz (to be ~rscd with /Yg. Z-30). Continued. 103-D-l 270-2 co 

N 

lnlct R = 2.50 tcet 

7.4” 7 72 8.03 

Q = 5 Cf\ 

1.91 2.19 

2.10 2.49 

0.03 0.03 

II 66 1.07 

5.10 6.00 

5.00 h.oo 

5 00 4.00 

70.3” 15” 

0 8” 0.47 

2 26 2.36 

5.50 6 50 

4.66 5 05 

9.01 9 33 

IO.91 I, 29 

0.05 0.05 

2.49 2.49 

26.30 27.3” 

10.0” 1000 

6.0” 6 00 

22O-30’ 

0.61 0 67 

3.82 3.87 

28.50 29.50 

13.47 13 85 

0 = 6 cf, 

1.61 1.88 

2.1” 2 49 

0.03 0 03 

I.21 I 34 

5 IO 6 0” 

5.5” 6 00 

4.50 5.00 

150 

0.52 U.52 

2.44 2 55 

5.50 6 5” 

4.66 5.05 

8.34 8.65 

IO.91 11.29 

0.05 0.05 

3.1, 3 II 

26.30 27 30 

10.50 10.50 

7.5” 7 5” 

22”.3” 

0.66 0 73 

4.33 4 39 

28.5” 29.50 

13.47 13.85 

Lhrrnetcr 01 p&l’ = 15 l”ChCI VP = 4 “7 tp< 

2.11 3 07 3 36 3 65 3 96 4 26 4.56 4 86 5 18 

3.25 3 64 4.02 4 40 4.78 5.17 5.55 5 93 6.31 

(1 “3 0 “3 0.03 0 “3 0 “3 0.03 0.03 0 “3 0 03 

8.36 8.67 

IO.52 

0 U5 

2.49 

25.4” 

,o.oo 

6.00 

22O-3”’ 

0.56 

3.71 

21.50 

13 “8 

16.27 

19.32 

0.06 

3.73 

46.7” 

I I .oo 

9 0” 

72”L3” 

-0.53 

4.86 

50.50 

21.88 

2 48 

2 87 

0 03 

I “7 

7.0” 

6.0” 

4 00 

0 57 

2 45 

7 5” 

5.43 

9 66 

I,.67 

0.05 

2.49 

28 20 

10.0” 

6.00 

0.72 

3.92 

3” 50 

14 23 

2 13 

2.87 

0.03 

I 34 

7 “0 

6.UlJ 

5 “0 

0 b4 

2.66 

7.50 

5.43 

8.95 

II 67 

0.05 

3.11 

28.20 

10.50 

7.50 

0.81 

4.46 

3c1.50 

14.23 

I.21 I.21 1.21 1.47 1.47 147 I47 I 74 1.74 

7.90 R RU 9.7” lo.60 II 6” 12.50 ,340 14.30 15.2” 

6.50 h.50 6.5” 6.50 6 5” 6.50 6 50 6 50 6.5” 

4 50 4.5” 4.50 5 50 5.50 5.5” 5.5” 6 50 6.5” 

3.50 

6.70 

0 03 

1.74 

16.20 

6.50 

6.51) 

05, 0.60 0.69 0.52 0.59 0.68 0.76 0.57 0.63 

2.53 261 2.69 2 17 2 84 2.9? 2.99 3 “6 3 12 

8.5” 9.50 10.5” 11.51) I2 5” 13 5” 14.5” 15 50 16.5” 

5 81 6 20 6.58 6.96 7 34 1.13 8.11 R 49 8.87 

9.97 10.31 10.63 lo96 II 28 II b2 11.94 I? 28 12.60 

0.70 

3 I8 

17 50 

9 26 

12.05 12.44 12.82 13 20 13.58 13.97 14 35 14 73 IS.11 

0 05 0.05 0.05 0 05 0 05 0.05 0 “5 0 “5 0.05 

2 49 2.90 2.90 2 9” 2 9” 2.90 3 II 3 1, 3 II 

29 10 30.00 31.00 31.90 32 8” 33.70 34.70 35 bU 36.50 

10.0" IO.00 10.00 1” oo 10.00 10.00 10.50 10.50 10.50 

6 “0 7.0” 7.00 7 00 7 “0 7 “0 7.5” 7.5” 7.50 

0.79 0.43 0 49 0 54 0.6” O 65 0 5” 0.54 0.6” 

3.98 4 03 4.08 4.13 4.18 4 23 4 28 4.32 4 37 

31.5” 32 5” 33.50 34.50 35.50 36.5” 37 50 38.5” 39.50 

14.61 15 00 15.38 15.70 16.14 16.53 16.91 17 29 17 67 

I2 94 

15 50 

0 “5 

3.1 I 

37.40 

10 50 

150 

0 65 

4.42 

40.50 

18.06 

4 69 5 “0 

6.31 6 70 

0.05 0 05 

2 07 2.49 

15 2” 16.2” 

9 “0 9.00 

5 “0 6.“” 

0 75 11.41 

3 46 3 54 

16.50 17.5” 

8.87 Y 26 

11 82 12.15 

15.1, 15.50 

0.06 0.06 

3 73 4.14 

36 50 37.4” 

I1 00 Il.00 

9 00 10 oo 

o 77 “42 

4 98 5.04 

39 50 40 50 

17 67 18.06 

5.8, 6.12 6 44 

7.08 1.46 7 x4 

0.03 0.05 II 05 

1.74 2 07 2.07 

17 IO 18.0” 19.00 

6.50 9 “0 9 00 

6.50 5.00 5.00 

150 2?“-30 

0.78 0.47 0.53 

3.?5 3.31 3.3b 

18.5” 19.50 20.5” 

9.64 10.02 ,040 

13 26 13.6” 13 92 

15.88 I6.26 16.64 

6.76 7 “8 

8 23 8.61 

0.05 0.05 

2 “7 ? 07 

19.9” 20.80 

9 00 9.00 

5 00 5 00 

8.99 9 38 9 76 

0.05 0 05 0 “5 

2 28 2.28 2.28 

21 70 22.60 23.60 

9.50 9 50 9.50 

5.50 5 50 5.5” 

IO.14 

0.05 

2.28 

24.50 

0.6” 0.66 

3.43 3.48 

21.50 22.5” 

IO.79 11.17 

9.50 

5 50 

05, 0.58 0.65 0.70 

3 54 3.6U 3 66 3.7 I 

23.50 24.50 25.5” 26.50 

I,.55 11.94 12.32 12.70 

0.05 0.06 0 “6 

?.I, 3.31 3 3, 

38.40 39 30 40.20 

IO.50 II 00 11.0” 

14 27 14 6, 

17 “3 174, 

II “6 0 06 

3 31 3.31 

4, 1” 42.00 

I I “0 Il.00 

8 “0 8.“” 

14.94 15.28 15.61 

17.79 18.18 18.56 

0 “6 0.06 0.06 

15 94 

18.94 

0.06 

3 73 

7 50 8 00 x.00 

071 0.56 0.62 

4 47 451 4.56 

I, 50 42 50 43 5” 

1844 18 82 19.2” 

0.66 10.7” 

4 60 4 64 

44.50 45.50 

19.59 1997 

43.“” 43.90 44.80 

1 I .“O I I .oo ,I 00 

8.0” 8.“” 9 00 

0 75 0.8” 0.43 

4.68 4.73 4.77 

46.5” 47 5” 48 50 

20.35 20 74 21.12 

0.4x 

4.82 

49.50 

21 5” 

,nlet It = 2 50 tcrt 

5 29 

7 08 

0 05 

2 49 

17.10 

9 “0 

6 0” 

5 88 

7.84 

0 “5 

2.69 

19.0” 

9.5” 

6.5” 

6 20 

8.23 

0.05 

2 69 

19 90 

9 5” 

6.5” 

6 50 

8.61 

0.05 

2.69 

20.8” 

9.5” 

6.5” 

0 5” 

3 62 

18.5” 

9.64 

0 47 

3.77 

20.5” 

,040 

0.54 

3.84 

21.50 

10.79 

0.62 

3.91 

22.50 

II 17 

5 58 b 80 7 IO ?.42 7 72 8.02 

7 46 8 99 9 38 9.76 10.14 10.52 

0.05 0.05 0.05 0 05 0.05 

2 49 2 69 2 90 2 90 2.90 3.1 I 

IX.“0 2, 70 22.6C 23.60 24 50 25.40 

9.00 9.5” 10.“” 10 “0 IO.“0 10.5” 

6 0” 6.5” 7.“” 7 .oo 7.00 7.50 

22’.30 cn 

0 59 0 7” 0 58 0.64 0.72 0.59 

3 7” 3 98 4.06 4 12 4.19 4.26 zi 

19 511 23 5” 24.50 25.50 26.5” 27 50 D 

10 02 11.55 11.94 12.32 12.7” 13.08 

7 

12 80 14.10 14.42 14 73 15.06 15.38 

16 26 17.79 18.18 18.56 18.94 19.32 

0 “6 0.06 0.06 0.06 0.06 0.06 

4.14 4.35 4.35 4.35 4.56 4.56 

39 30 43 oo 43.9” 44 80 45 70 46 70 

11.00 11.5” I1 50 1150 ,200 12.00 

10.0” 1” 50 1050 10.5” 1100 ,I 00 

22’.30’ 

r 

053 0 56 0 62 0.69 “53 059 

5.14 5 35 5.41 5.47 5.52 5 57 r? 42.5” 46 50 47 50 48.5” 49 50 5050 

I8 82 20 35 20 74 21 I2 21.50 21.88 A r 

Submcrynce = 1 Id2 + hv,, + hi h4 - dumetrr 01 ,vr hv 

? 

,247 

15 88 

0 “6 

4.14 

38 4” 

110” 

IO.00 

li.ll 

16.64 

0.06 

4 14 

4” 2” 

II 0” 

1”“” 

13 44 

17.03 

0.06 

4.14 

41.10 

11.00 

10 00 

13.77 

17.41 

11.06 

4.35 

42 00 

II 50 

IO 50 

O 48 

5 .“9 

415” 

La.44 

0 6” 

5 2” 

43 50 

19 20 

0.66 

5.25 

44 50 

19 59 

0 5” 

5 3” 

45 50 

19.97 

h2 

“3 

“4 

L2 

L3 

L4 

s3 

S”blllUgL%X 

d2 

L, 

d, +tlv, 

1. 

11, 

“5 

“4 

L2 

L3 

2 

S”b”rcrge”c3u 

*2 

LX 

d, +ilv, 

“lametci of p,pe = 15 mch VP = 4 89 tpi 

2.4” 2.68 

3 25 3.64 

0 03 0.03 

Ib, I61 

7.9” 8.80 

6 0” 6.00 

6.00 6.0” 

“48 0.59 

2 76 2.86 

8 50 9.50 

5 81 6 20 

9.27 9.59 

12.05 12.44 

0.05 0.05 

3 52 3.52 

29 10 30.00 

10.50 10.50 

8.50 8.50 

0.46 0 53 

4.52 4 58 

31.50 32.50 

14.61 15.“” 

2 97 3.?5 

4.02 4.40 

0.03 0 03 

1.61 1.74 

9.70 I”60 

6.011 6.50 

6.00 6.50 

0.69 0 65 

2 95 3 04 

10.50 II 50 

6.58 6.96 

9.91 1” 22 

12.82 13.20 

0.05 0.05 

3.52 3.52 

31.00 319” 

10.50 10 5” 

8.50 8.50 

0.59 0.66 

4 64 4.70 

33 5” 34.50 

15 38 15 76 

3.53 3.82 4.1 I 4 40 

4 78 5.17 5 55 5.93 

0 “3 0.03 0.05 0 “5 

1.74 1 74 2 07 2 07 

11.6” 1250 ,340 14 30 

6.50 6.50 9.00 9 “0 

6 5” b 50 5.00 5 0” 

150 22c’-30‘ 

0.75 0 85 0.57 0.66 

3.13 3 22 3.3” 3 38 

12.50 13.50 14 50 15 50 

7 34 7.13 8.1 I 8.49 

10.54 lo.87 II 18 11.51 

13.58 13.97 14 35 14.73 

r 

hz 

“3 

“4 

L2 

L3 

3 

SuhmcrgcnL3e 

*2 

L, d, + hvl 

1: 

h2 

h3 

“4 

L2 

L3 

L4 

s3 Submergence 

0.05 0.06 0.06 0.06 

3.52 3.73 3 73 3.73 

32.80 33 70 34 70 35 60 

10 50 11.00 I I on II “0 

8 50 9 00 9 “0 9 00 

0 72 0.58 0 65 0.7” 

4 75 481 4 87 4 92 

35 5” 36.50 37 50 38 50 

16 14 16.53 16.91 17 29 

*2 

L, 

d, thr, 

I =,d,+hv,, (I Id2+hvpl dl+hv,=K+h2+““6 
Table 2-4.-Type I pipe drop with corwete outlet trmsitiofz (to be used with fig I-30). -Continued. 103-D-1270-3 

PIPE DROP WITH MITER BENDS 

Concrete Outlet Transition 

0=7cs, 

F 182 2 I2 241 

“2 2.10 249 2 81 

h3 003 003 0 04 

h4 0.66 0.66 1 07 

L2 5 10 6 00 7 00 

L3 5 00 5 00 7.00 

L4 5.00 5.00 4 00 

s3 70.30' 70.30 150 

Sulmlergcnce 0.64 0.74 038 

d2 2.36 2.45 2.53 

LX 5.50 650 750 

d,+hv, 4.66 5 05 543 

1‘ 

h2 

h3 

he 

L2 

L3 

L4 

% 

S"blTWg~"C~ 

9 

LX d,+hv, 

8.96 9 28 

1"91 II 29 

0.05 0 05 

2.28 2.20 

26.30 27 30 

10.50 ,050 

5.50 5.51) 

22'.30 

0.60 0.66 

3.88 3 94 

28.50 29 50 

13 47 13 85 

Q=Bds 

960 9.93 10.26 

II 67 1205 1244 

0.05 0.06 006 

2 28 2.49 2.49 

28 20 29.10 3" 00 

10.50 11.00 11.00 

5.50 6 00 6 00 

0 72 "57 0.63 

3 99 4 04 4 09 

30.5n 3150 32.50 

14 23 14.61 15.00 

,n,ct K = 2 5" fCCl 

7 35 7 67 

8.99 9.38 

0 04 0.04 

2 01 201 

2, 7" 22.6" 

7.50 7.50 

7 50 750 

0.62 0.69 

3.6" 3.66 

23 50 24.50 

II 55 II 94 

14 93 15 26 

17 79 18.lB 

0 06 0.06 

3 11 3 31 

43 "0 43.90 

11.50 12.00 

7 50 800 

069 0.55 

411 4.76 

46.5" 47.5" 

20 35 20 74 

,n,et R = 2 50fcet 

6.92 7.23 

8.99 9.38 

0 05 0 05 

2 28 2.28 

21 70 22 6" 

,050 IO.50 

5 50 5.50 

"72 0.8" 

3 92 3 99 

23.50 24 5" 

II.55 11.94 

14.31 14 64 

17.79 18.18 

0 06 0.06 

373 3.73 

43 "0 43 9" 

12.0" 12.0" 

900 900 

0 69 0.75 

5 2" 5.25 

4650 4150 

20.35 20 74 

2 71, 3 00 3 30 36" 39" 4 21 453 483 5 14 5 46 5 77 

325 3.64 402 440 478 5.1-l 5.55 5 93 631 6 70 7 U8 

004 004 004 004 004 0 04 0 04 0 04 0.04 0 04 0 04 

I"7 I07 107 I ."7 I34 I34 147 1.47 I47 1.47 I74 

790 880 9.7" ,060 11.60 ,250 1340 14 30 15 20 16 20 17.10 

1.00 7 00 8 00 8.00 7 00 7.00 7.5" 7.50 7.5" 7.50 7.50 

4 00 4 00 4 00 4.00 5 00 5.00 5.5" 5.50 5.50 5 50 650 

0.47 056 0 64 0 72 053 0.6, "54 062 069 0.76 "56 

2.61 2.69 2.76 2 84 2.91 298 3.04 3.11 3.17 3 24 3 30 

8.50 950 10.5" 11.5" 12 50 13.50 1450 15 50 16.50 17 50 I050 

5.81 6.20 6.58 6.96 7 34 7 73 8 II 8 49 8.87 9 26 9 64 

10.59 LO 91 11.25 II58 II 92 1225 1258 1291 

12 82 13.20 1358 13.97 14.35 14.73 IS.1 I 15 50 

0.06 0.06 0.06 0.06 0.06 006 0 06 0.06 

2.49 249 249 290 2.90 2.9" 2.9" 290 

3100 319" 32 80 3370 34 70 35.60 36 5U 37 40 

II 00 II 00 11.00 II 00 11.00 11.00 II 00 Il.00 

6 00 6 "0 6 "0 7 00 7 0" 7 00 7 on 1 00 

0.68 0 74 0 78 0 43 0.47 "52 0 57 0.63 

4.14 4.19 423 4.28 4.32 4 36 4.41 446 

33 50 34.50 35.50 36 50 37 5U 38.50 39.50 405" 

15.38 15 76 16 14 16.53 16.91 11.29 17.67 18.06 

13.25 

15.88 

0 06 

290 

38.40 

I! 0" 

1 00 

067 

450 

11.50 

1844 

6 4" 

7 84 

0 04 

1 74 

19 00 

7.51) 

65" 

0.69 

342 

20511 

IO.40 

13.92 

1664 

006 

3.11 

40.20 

II 50 

7 5" 

0 55 

4.58 

43.5" 

19 20 

6 "8 

7.46 

0 04 

I74 

18 00 

7 50 

65" 

0.63 

3 36 

19.50 

10 02 

13.58 

16 26 

0 "6 

3.1 I 

39.30 

11.50 

7.50 

052 

455 

425" 

18.82 

l- I58 

h2 2.10 

h3 0.04 

"4 1.07 

L2 5.10 

L3 7 00 

L4 4.00 

s3 15O 

S"blll.Xg~"C~ 044 

d2 2.5 I 

LX 5.50 

dl+hv, 4.66 

F 8.49 

h2 1091 

h3 0.05 

"4 2.69 

L2 26.30 

L3 10.5" 

L4 650 

s3 22O-3" 

Submergence 0.66 

d2 4 24 

LX 28.5" 

d,+hv, 13.47 

6 72 7 "4 

8.23 861 

0 04 0 "4 

I 74 2.01 

19.90 20.80 

750 150 

6.50 75" 

0 76 055 

3.48 3 54 

2150 22.50 

,079 /I 17 

14 26 14.59 

,703 17.4, 

0.06 0 06 

3 I, 3.11 

41 10 4200 

11.50 II 5" 

7.50 7 5" 

060 0.65 

4.63 4.67 

445" 45 50 

1959 19 97 

D,anetcr oiplpr = 18 mchcr v,=453sps 

I.86 2 14 2.42 2 71 2.99 3.28 35x 3.x7 4 16 4.46 4.77 5.08 5 38 

249 2.87 3.25 3.64 4.02 440 4 78 5 17 555 5.93 6.31 6 7" 7 08 

0 04 0.04 0.04 0.04 0.04 0.04 0 04 004 0.04 0 04 0 04 0 04 0.04 

1.07 IO7 I34 1.34 1.34 1.61 I61 1.61 1.88 I88 I88 2 01 2.01 

600 7 00 7.90 8 80 9.10 10.60 I, 60 12.50 13.40 14.30 15.20 16.20 17 IO 

7 00 7 00 7.0" 7 00 7 00 7.00 7."" 7.00 7.00 7 00 7 no 7 50 75" 

4.00 4 00 5 00 5.00 5 00 6.00 6."" 6.00 7 0" 7 00 7 00 7 50 750 

568 5 99 6 29 

7 46 7.84 8.23 

0.04 0.04 0 05 

2 01 20i 2 28 

,800 19.0" 19 90 

750 750 IO50 

7.50 75" 5.5" 

Ii0 22"~3" 

0.76 "83 059 

3 65 3.72 3.80 

19 50 205n 21.50 

10 02 1040 10 79 

6.6" 

8.61 

0 05 

2.28 

2080 

1050 

5.50 

055 0.65 0.48 058 068 0.50 058 068 050 058 0.65 0 60 "68 

2.61 2.70 2.79 2.88 2.97 3.05 3.13 3 22 3.3" 3.37 3.44 351 358 

6.50 7.50 8.50 9.50 LO.50 1150 I250 ,350 14.50 L5.50 16 50 17 50 ,850 

5.05 5.43 5 81 6 20 658 6 96 134 1.13 8.11 849 8.87 9.26 964 

0 66 

3 86 

2250 

II 17 

8.8" 9.11 9.43 9 76 10.09 1040 10.12 I, 04 II.36 II 69 I202 I2 35 1268 13.00 13 32 1366 13 98 

11.29 11.67 12 05 1244 1282 13.20 13.58 13.97 14.35 14 73 15.11 15 5" 15 88 16.26 16.64 17 03 17.41 

006 006 006 0.06 0.06 0.06 0.06 006 0 06 0.06 006 0 "6 0.06 0 of' 0 06 oO6 0.06 

290 2.90 2.90 2.90 3.11 3.11 3 IL 3.11 3.11 3.52 352 3.52 3 52 3.52 3 73 3 13 373 

27.3" 28.20 29.10 30.00 31.00 31.90 3280 33 70 34 70 35 60 36.5" 37 40 38 40 39 3U 40.2" 41 10 42 00 

11.00 II 00 11.00 11 00 11.50 II 50 11.50 11.50 II 50 II 5" ,I 5" II 50 11.5" II 5" 12.0" 12.00 12.0" 

7 00 7.0" 7 00 7.00 7.50 7.50 7.50 7.50 150 8 50 8.50 x so 8 50 85" 9 00 9 00 9.00 

0.53 0.60 066 0.72 0.56 063 0.69 0 76 0.82 0.46 0.52 11.57 0.63 !I 68 0.53 0 58 0.64 

4.30 4 36 4.42 441 4.52 4.58 4.64 4 70 4 75 4.80 4.85 4 9" 4 95 5 00 5 "5 5 10 5.L5 

29.50 30.50 31.50 32.51) 33 50 34.50 35 50 36.50 37 50 38 51) 39.50 40.50 11.50 425" 43.50 44.50 45 5" 

13.85 14.23 14.61 15.00 I5 3n 15.76 16.14 1653 1691 17.29 17.67 18 "6 18.44 18.82 19 20 1959 1997 

7.98 8 3" 863 

9 76 IO.14 1052 

0 04 0 05 0 "5 

2.01 

23.60 

7.50 

2.28 2 28 

24.50 

10.50 

25.40 

105" 

5.50 

22'.30 

"54 

3.83 

27 5" 

13 "8 

750 5.50 

I5V 22O-30' 

0.76 0.49 

3.73 3 78 

25 50 26.50 

1232 12 7" 

15 60 15 94 

1856 18.94 

0.06 0 06 

3.31 3 31 

44.80 45 70 

12.00 !2."" 

8.00 8 no 

(1.59 0.63 

48" 4.84 

48.5" 49.5" 

2, I? 21 50 

16 27 

1932 

0 06 

3.31 

46.7" 

12.00 

8 00 

22'.30' 

068 

4.88 

5050 

2188 

753 

9.76 

0.05 

2.69 

23 61) 

10.5" 

6.50 

11.47 

4.96 

25.50 

1232 

7 85 

1" 14 

0.05 

2.69 

24 50 

I050 

6.50 

8 16 

10.52 

0.05 

269 

25 4" 

105" 

6.5" 

220.3" 

0.6" 

4.18 

2750 

1308 

15.64 

1932 

0.06 

3.93 

0 53 

4.12 

265" 

,?.70 

14.97 15.31 

18.56 18.94 

006 0.06 

3.93 

44.80 

12.50 

950 

45 70 

12.50 

9.50 

46 70 

1250 

9.50 

22O-3"' 

"69 

5.38 

0.60 

5 3" 

48.50 

21 12 

0 64 

5 34 

495" 50.5" 

21 50 ?I 88 

d,+hv,=R+h2+o.06 Submei~ence = I Id, + hvp + h3 h4 d,anietcr<,t p,pc hv 
84 SMALL CANAL STRUCTURES 
Table 2-4.-~~~~~ I pipe drop Wiill couwte outlet trarfsitiott (to he used with fig 17.30). Continued. 103-D-1270-5 2 

1: 

“2 

L3 4 

LZ 

L3 

L4 

s3 

Sutmlergrncc 

d2 

LY 

d,+hv, 

I.81 2.07 

2.10 249 

0.05 0.05 

(I.80 1.07 

5.10 b 00 

9.0" 9.00 

3.0" 4."" 

150 

0.73 058 

2.75 2.86 

5 50 6.50 

5.16 5.55 

2.3b 

2 87 

0.05 

I .(I7 

7.00 

950 

4.00 

0.68 

2.95 

7.50 

593 

1: 

k2 3 

h4 

L2 

L3 

L4 

s3 S"bIll~rge"C~ 

d2 

LA 

d,t hv, 

8.73 9.05 

,091 11.29 

0.07 0.07 

2.90 2.90 

26.30 27.30 

14.00 14.00 

7.00 7 00 

22O-30 

0.46 052 

4.46 4.52 

28.50 295" 

13.91 14.35 

Q= 12cfs 

936 968 

11.67 12.05 

0.07 0 07 

2.90 2.90 

28.20 29 ,U 

14 00 14.50 

7.00 7 on 

0.59 0.66 

4.58 4 64 

3050 31.50 

14.73 15 I, 

F I64 1.90 2.17 

"2 2.10 2.49 2 87 

"3 0.05 0.05 0.05 

h4 1.07 1.07 I24 

L2 5.10 6.00 7.00 

L3 9.00 9.00 10.00 

L4 4.0" 4 00 3.00 

s3 19 15u 22'.30 

S"bTllUp~"C~ 063 0 75 0.62 

d2 2 85 2.96 3.06 

L 5 50 6.50 7.50 

d,+hv, 5.16 5 55 5.93 

F 

h2 

h3 

h4 

L2 

L3 

L4 

s3 

S"bmeigence 

‘3 

4 

dlfhv, 

8 39 

IO.91 

0 07 

2.90 

26.30 

14.00 

7 00 

22"~30 

0.80 

412 

285" 

13 97 

870 902 9.33 965 9 97 I" 28 10.60 1091 1122 1155 II X6 I2 19 ,251 1282 13.15 

11.29 11.67 12.05 12.44 12.82 13.20 13.58 13 97 14.35 14 73 15.11 15.50 15.88 16.26 ,664 

007 0.07 0.07 0.07 0.07 "07 0 ox 008 0.08 0.08 008 "08 " 08 0.08 0.08 

3.3, 3 3, 3.31 3.31 3 3, 3.31 3 73 373 3 73 3 73 3.73 3.73 4 14 4.14 4 14 

27 30 28 20 29.10 3000 31."" 31 90 3280 33.70 34.70 35 60 36 50 37 40 3840 39.30 411 20 

,400 14.00 14 00 14.50 14.50 14.50 15.00 15.00 15 00 15.50 15.50 16 00 16"" ,600 16 00 

8.00 8 00 8.00 8 00 8.00 8 00 9.00 9.00 9.00 900 9.00 9 "0 IO.00 1000 1000 

0.45 052 059 0.65 0.72 0.78 045 052 "59 064 0.7 I 078 042 049 054 Cl.61 0 66 0 12 079 1) 43 048 054 

478 4.84 49u 496 5 02 5.08 5 14 5.21 5.27 5 32 5 38 5 44 549 5 55 5 60 5.66 5 71 5 76 5 82 5.87 592 5.97 

29.50 30.50 3150 32.50 33.50 34.50 35.50 36.50 37.50 3850 39.50 10.50 4, 5" 42.50 43.5" 44.50 45.50 46.50 47 50 4850 49.50 50 50 

14.35 ,4 13 15 ,I 15 50 ,588 1626 16 64 17 03 17.4, 17 79 18 17 18 56 18.94 19 32 197" 20.09 2041 20x5 2, 24 2162 22 uo 22.38 

Q= II‘,, 

2 64 

3.25 

0 05 

1.07 

790 

9.50 

4.00 

150 

078 

3.w 

8.50 

6.3, 

Ilumctrr “1 p,pc = 2, m‘ho vp=457tp\ 

2.92 3.21 3 50 3 79 4 09 4 39 468 4 99 

3 64 4 02 4 40 4 78 5 17 5 55 593 6.3, 

0 05 0.05 0 115 lU.05 0 06 006 0.06 0.06 

I 24 1.24 I66 166 1.66 166 1.66 1.66 

R80 970 IO.60 11.60 12 50 13.40 14.30 I5 20 

10.00 10.00 10.50 10.50 11.00 II.00 ,I "0 I,.50 

3.00 3.00 4.0" 4.00 4.00 4.00 4 00 4 00 

22'.30' 

0.64 073 0.40 0.49 058 0.67 0.76 0.83 

3 14 3.22 330 3 38 3.46 3.54 362 368 

95" 1050 Il.50 12.50 13 50 14.50 15.50 16.50 

6.70 7 08 746 7 84 8.23 8.6 I 8 99 9.37 

5 29 

b 70 

2 07 

16.2" 

II 5" 

5.00 

5.6” 

7 08 

0.06 

207 

17 1" 

12.00 

5.00 

0 50 0.58 

3 76 3.83 

17.50 18.50 

9.76 10.14 

10.01 10.33 10.65 10.96 Il.29 Il.61 11.94 I2 26 

12.44 12.82 13.20 13.58 13.97 14.35 14 73 15 I, 

0.07 0.08 0.08 0.08 0.08 0 08 0.08 0.08 

290 2 90 3.31 331 3.31 3 3, 331 3.3, 

30.00 31.00 31.90 328" 3310 34 7" 35.60 36 50 

14.5" 15.00 15.0" 15 00 15 50 15.50 16 00 I6 00 

7 00 7.00 8.00 800 X.00 8.00 8 00 8.00 

0 7, 0.78 0.42 0.49 0.56 061 067 0 12 

4.69 4.75 4.80 4.86 4 92 4 97 5 "2 5 07 

32.50 3350 34.50 35.50 36 50 37.50 385" 3950 

15.50 15.88 16.26 16.64 17 03 1741 17 79 18 17 

Diameter 0, p,pe = 1, Inche, VP = 4.99 fpps 

2.12 299 3 28 1.57 3.86 4 I5 4.43 4.73 

3.64 4 "2 440 4.78 5 17 5.55 593 631 

0.05 OJS 0 05 006 0.06 006 006 0.06 

I66 166 1.66 I66 1.66 2.07 2.07 2.07 

8.80 970 10.60 11.60 12.50 1340 14.30 15 20 

10.00 10.00 1000 I, 00 II "0 11.00 ,* 50 ,I 5" 

4.00 4 00 4.00 4.00 4.00 5.00 5.00 5 .O" 

1260 12.92 

15.50 15.88 

0 08 0.08 

3.31 3 73 

37.4" 3840 

l6.00 16 00 

8 "" 9 00 

0.78 042 

5.12 5.17 

40.50 4150 

18 56 18.94 

5 90 62, 

746 7 84 

0 06 0.06 

2.07 2 "7 

18 00 19 00 

12.00 12.50 

5.0" 5 00 

0.66 "73 

390 3.96 

1950 20.50 

10.52 1090 

13 24 13.57 

16.26 16 64 

0.08 0.08 

3 73 3 73 

39 30 40.2" 

16.00 16.00 

9.00 9.00 

048 0.53 

5 23 5 27 

4250 43 50 

19.32 19.7" 

hvp = 0.39 foot 

244 

3.25 

0 05 

1.24 

7.90 

1000 

3.00 

5.04 5 32 5 62 5 91 

6.70 7 08 7.46 7.84 

0 06 U.06 0 06 006 

2 "7 2.49 2.49 249 

lb.20 I7 IO 18.00 19 00 

12 00 12.00 1200 12.00 

5.00 6 00 6.00 6.00 

0.73 042 053 063 0.72 0 83 0.5" 0.60 0 68 0 78 0.44 0.52 061 

3 16 3.26 3 36 3.45 3.53 3.62 3 70 3 79 3.86 3 94 4.03 4 1" 4 18 

8.50 950 10.5" ,I 50 12.50 13 50 14 50 15.50 ,650 17 50 I8 5" 19.50 20 5" 

6.31 6.10 7.08 7.46 7.84 8.23 8.61 8 99 9 37 9 76 10.14 ,052 1090 

PIPE DROP WITH MITER BENDS 

Concrete Outlet Transitwn 

hvp = 0 33 ,OOf ,n,ei K = 3 0" feet 

6.53 6.84 7 14 7.47 7.78 R.IlI 8.41 

8 23 861 8.99 9.38 9.16 ,014 10.52 cn 

0.06 0.07 0.07 0.07 0.07 0.07 0.07 -I 

2.07 249 249 2.49 2.49 2.49 1.49 

19 90 20 80 21.70 2260 23.60 24.50 25.40 ,250 13 "0 13 no 13.00 13.50 13.50 14 00 z 

5.00 6.00 6.00 6.00 6.00 6.00 6.00 o 

22'.30‘ --I 

0 80 0.46 0.54 0.60 0.67 0.74 0.81 c 

4 03 4.09 4 16 4.22 4 28 4 34 440 33 

21 50 22.50 23.50 24.50 25.50 26.50 27.50 

11.29 11.67 12.05 ,244 12.82 13.20 13.58 

13.9, 14.23 14.56 14 89 15.22 15 54 15.88 

17.03 17 41 17 79 18.18 18.56 18.94 19.32 

008 0 08 0.08 0.09 0.09 0.09 0.09 

3.73 3.73 3.73 373 373 4.14 4.14 

41 10 42 00 43 00 43.90 44.80 45.70 46.70 

16.50 ,650 16.50 17."" 17 00 17.00 L7.00 

9.00 9.ou 900 9."" 9.00 IO.00 10.00 

22'.30‘ 

059 0.64 0 7" 0 75 0.81 0.45 0.49 

5 32 5.37 5.42 547 5.52 5.57 5.61 

4450 45 53 46 50 47 5" 48.50 49.50 50.50 

20.09 2047 20.85 21.24 21.62 22.00 22.38 

,n,rt R = 3 00 feet 

6.24 6.53 6.83 7 14 7.46 7 lb 8.08 

8.23 8.6, 8.99 9.38 9.76 10.14 LO.52 

0 06 0.06 0.07 "07 0.07 0.07 0.07 

2.49 249 2.90 2.90 2.90 2.90 2.90 

19.90 20.80 21.70 22.6" 23.60 24.50 25.40 

,250 12.50 13.00 13.00 13.00 13.50 13.50 

6.00 6 00 7 .oo 1 uo 7.00 7 0" 7 00 

._ m0.m. -I 

0.67 016 cl44 052 0.58 066 U73 

4 24 4 32 4 39 4.46 452 4.59 4.65 

21.50 22 50 23.50 245" 25.50 2650 2150 

1, 29 II 67 1205 ,244 ,282 13 20 13.58 

1347 13.80 14 12 ,445 1477 15.10 15 42 

1703 ,741 ,779 18 18 18.56 I8 94 19.32 

0 OR "OX "08 009 0.09 0.09 009 

4 14 4.14 4 14 4.14 456 456 4.56 

41.1" 42.0" 43 00 4390 44 80 45 70 4670 

,600 16 50 16 50 17."" 17 00 I7.Ol.I 17 "0 

1000 ,000 IO.00 ,000 II "0 ,100 II 00 

22'.30' 

I: = (d, + hv,, (1 ld2 + hvp) d,+hv,=R+h2t006 Submc~pencc = 1 Id2 + hvp + hi h4 dmnerer ofplpr hv 
SMALL CANAL STRUCTURES 

?43ul- 

--??C 

*vl=N 

-- 
CONVEYANCE STRUCTURES 87 
F 

h2 

“3 

“4 

LZ 

L3 

L4 

S3 

Submergence 

dz 

LX 

dl+hv, 

F 

h2 

“3 

“4 

L-2 

L3 

L4 

S3 

Submergence 

d2 

LX 

dl +hv, 

F 2.5 I 2.83 

h2 2.10 2.49 

h3 0.05 0.05 

h4 0.39 0.39 

L2 5.10 6.00 

L3 9.00 9.00 

L4 3.00 3.00 

S3 7O-30‘ 

Submergence 0.48 0.55 

d2 2.92 2.98 

LX 5.50 6.50 

d,+hvl 5.91 6.30 

F 

"2 

h3 

h4 

L2 

L3 

L4 

S3 Submergence 

d2 

LX 

d,+hv, 

9.95 10.28 

10.91 11.29 

0.07 0.07 

1.45 1.45 

26.30 27.30 

13.50 13.50 

3.50 3.50 

22'.30 

0.62 0.67 

4.16 4.21 

28.50 29.50 

14.72 15.10 

Q = 16 cfr 

1.64 1.91 

2.10 2.49 

0.04 0.04 

1.21 I.21 

5.10 6.00 

8.50 8.50 

4.50 4.50 

150 

0.47 0.59 

3.06 3.17 

5.50 6.50 

5.41 5.80 

8.40 8.70 

10.91 11.29 

0.06 0.06 

3.11 3 II 

26.30 27.30 

1250 12.50 

7.50 150 

22'.30 

0.55 0.63 

4.93 5.00 

28.50 29.50 

14.22 14.60 

Q=,7cfs 

r&k 2-4.-Type 1 pipe drop with concrete outlet transition (to be used with fig 17.30). Continued. 103-D-1 270-S 

2 18 245 

2 81 3.25 

OW 0.04 

1.47 1.47 

7.00 7.90 

8.50 8.50 

5.50 550 

Dumcter ofp,pe = 24 mcho VP = 5 09 fp, 

2.72 3.0, 3.28 3.58 3 Rh 4 I5 443 471 

8.80 

8.50 

5.50 

3.64 4.02 440 4.78 5.17 5.55 593 6 3; 

0.04 0.04 0 04 0 04 0.04 0.04 0 06 0.06 

I47 1.74 I74 1.74 2.01 201 2.07 2.07 

10.60 II.60 12.5" 1340 14.30 15.20 

8.50 8.50 850 85" 12.00 1200 

6.50 6.50 7.50 75" 5 0" 5.00 

9.70 

850 

6.50 

0.44 0.55 0.67 049 

3 27 3 37 3.48 3.56 

7.50 8.50 9.50 10.50 

6.18 6.56 6.95 7.33 

0.60 0.68 0.52 061 0.58 0.66 

3.66 3.74 3.84 3.92 401 4 08 

5.03 5 33 5.62 592 6 22 6.54 6 84 7.14 7.46 7.77 

6.7" 7.08 146 184 8.23 861 8.99 9.38 9 76 ,".,4 

0.06 0 06 U "6 0.06 0.06 0.06 0.06 0.06 0 "6 0.06 

2.07 2 07 249 2 49 249 2 69 2.69 2.69 2.69 3.11 

16.20 I7 1" 18 00 19.00 19.90 20 8U ?I 70 22.61) 23.60 24 5" 

12.00 12.00 12.w I? "0 12.00 12.50 125" ,250 12.50 1250 

5.00 5.0" 6.00 6.0" 6."" 6.50 6.50 6.50 6.5" 7 59 

11.50 I2 50 13.50 14.50 I5 50 16 50 

7.71 8.09 8.48 8.86 9.24 962 

0.75 

4.16 

17.50 

IOU1 

0.83 0.50 ,I 58 067 0.53 0.61 0.70 U 76 

4.24 4 32 4.39 4.47 4.53 4.60 4.68 4.14 

9.01 9.33 9.65 P.97 10.28 1058 1090 II21 11.53 11.85 12.17 

11.67 12.05 12.44 12.82 13.20 13.58 13.97 14.35 I4 73 I5 I, 15.50 

007 0.07 0.07 0.07 007 0.07 0 07 007 0 "7 0.07 0.07 

3.31 3.31 3.31 3 31 3.52 3.52 3.52 3.52 3.93 3.93 3.93 

28.20 29 IO 30.00 31 00 31.90 32.80 33.70 34.70 35.60 36.50 37.40 

13.00 13.00 13.00 13.00 13.50 I3 50 13.50 13.50 13.50 13.50 I3 50 

8.00 8.00 8.00 8.00 8.50 8.50 8.50 8.50 950 9.50 9.50 

I8 50 19.50 20.50 2150 22.50 2350 24 5" 25 50 

IO.39 1" 77 II.15 II.54 11.92 12.30 12.69 :3.07 

12.50 12.81 I3 13 13.45 13 72 14.10 1442 14.75 

0.5 1 0.57 0.64 0.70 0.56 0.64 0.7 I 0.78 0.43 0.49 "56 

5.06 5.12 5 18 5.24 5.30 5.37 5.44 5.50 5.55 5.6, 5.67 

30.50 31.50 32.50 33 50 34.50 35.50 36.50 31.50 38.50 39.50 4050 

14.98 15 36 15.75 16.13 16.51 16.89 17.28 17.66 18.W 18.42 18.81 

15 88 16.26 16.64 17.03 17.41 17 79 18.18 18.56 

0.07 0.07 0.07 0.07 007 0 "7 0.01 u.07 

3 93 4.14 4.14 4 14 4 14 4.14 4.35 4.35 

3840 39.30 40 20 41 10 42 "0 43.00 43.90 44 80 

I3 50 14.00 14.00 14.00 14.00 14.00 14.50 I4 50 

9.50 I" 00 IO 00 10.00 10.00 IO.00 IO.50 1050 

Dmmeter ofp,pe = 30mches Vp = 3.46 fps 

0.61 047 0.53 0.60 0.61 0.71 0.57 0.62 

5.72 5 7s 5.84 5.90 5.96 6.00 6.06 6.11 

41.50 42.50 43.50 44.50 45.50 46.50 47.50 48.50 

19.19 19.57 19.95 20.34 20.72 21.10 21.49 21.87 

hvp = 0.19 foot Inlet R = 3.75 fee, 

3.15 3.46 3.77 

2.87 3.25 3.64 

0.05 0.05 0.05 

0.46 0.46 0.46 

7.00 7.90 8.80 

9.50 950 9.50 

3 50 3.50 3.50 

0.54 0.62 069 

3.M 3.11 3.17 

7.50 8.50 9.50 

6.68 7.06 7.45 

4.08 4.39 4.71 5.03 5.35 5.68 6.00 

4.02 4.40 4.78 5.17 5.55 5 93 6.31 

0.05 0.06 0.06 0.06 0.06 0.06 0.06 

0.46 0.80 0.80 0.80 0.80 0.94 0.94 

9.70 10.60 11.60 12.50 13.40 1430 I5 20 

9.50 il.00 11.00 II 00 II.00 II50 II 50 

3.50 3.00 3.00 3.00 3.00 3.50 3.50 

70.30. 150 

0.75 0.43 0.50 0.56 0.62 0.53 0.59 

3.23 3.30 3.36 3.42 3.41 3.52 3.57 

10.50 II.50 12.50 13.50 14.50 15.50 16.50 

7.83 8.21 8.59 8.98 9.36 9.74 10.12 

6.33 6.65 6.98 7 30 7.63 7.95 

6.70 7.08 1.46 7 84 8 23 8.61 

U "6 0.06 0.06 0.06 0.06 0.06 

0.94 0.94 0 94 1.21 1.21 1.21 

16.20 17.10 18.00 I9 00 19.90 20.80 

II.50 II.50 11.50 11.50 11.50 II.50 

3.50 3 5" 3.50 450 4.50 450 

0.65 0.71 U.76 0 56 0.6, 0.67 

3.63 3.68 3.73 3.79 3.84 3.89 

17.50 18.50 19.50 2050 2150 22 50 

10.51 10.89 II.27 11.65 12.04 12.42 

1062 10.95 11.29 11.62 11.96 12.29 12.63 12.97 13.31 13.65 13.99 I4 33 

11.67 12.05 12.44 12.82 13.20 13.58 13.97 14.35 14.73 15.11 15 50 15.88 

0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.01 0.07 0.07 0 07 

1.45 1.66 1.66 1.66 1.66 1.66 1.86 1.86 1.86 I 86 1.86 1.86 

28.20 29.10 30.00 31.00 31.90 32.80 33.70 34.70 35.60 36.50 37.40 38.40 

13.50 14.00 14.00 14.00 14.00 14.00 14.50 14.50 14.50 14.50 14.50 14.50 

3.50 4.00 4.00 4.00 4.00 4.00 4.50 4.50 4.50 4.50 4.50 4.50 

0.72 0.55 0.60 

4.25 4.29 4.34 

30.50 31.50 32.50 

15.48 15.86 16.25 

0.65 0.69 0.75 0.59 0.64 0.68 0.71 

4.38 4.42 4.41 4.51 4.55 4.59 4.62 

33.50 34.50 35.50 36.50 37.50 38.50 39.50 

16.63 17.01 17.39 17.78 18.16 18.54 18.92 

dl+hvl=R+h2+006 

0.76 0.80 

466 410 

40.50 11.50 

19.31 19.69 

PIPE DROP WITH MITER BENDS 

Concrete Outlet Transition 

lhp = 0 40 IO,,, Inlet R = 3.25 feet 

14.68 15.02 15.37 

16.26 16.64 I7 03 

0.07 0.07 0.07 

1.86 2.28 2.28 

39.30 40 20 41.10 

14.50 I4 50 14.50 

4.50 5.50 5.50 

0.83 0.45 0.48 0.52 0.56 0.63 

15.72 

,741 

0.07 

2.28 

42.00 

14.50 

5.50 

8.28 

8.99 

0.06 

1.21 

21.70 

11.50 

450 

U.72 

3.94 

23.50 

12.80 

16.07 

17.79 

0.07 

2.28 

43.00 

14.50 

5.5" 

8.61 8.94 

9.38 9.76 

0.06 0.07 

1.21 1.45 

22.60 23.60 

11.50 13.50 

4.50 3.50 

l5O 22'.30 

0.78 0.48 

3.99 4.04 

24.50 25.50 

13.19 13 57 

9.27 

10.14 

0.07 

1.45 

24.50 

l3.5U 

3.50 

0.53 

4 08 

26.50 

13.95 

16.42 16.76 17.1" 

18.18 18.56 18.94 

0.07 0.07 0.07 

2.28 2.28 2.28 

43.90 44.80 15.70 

14.50 14.50 14.50 

5.5" 5.50 5.50 

0.4, 

4.80 

26.50 

13.45 

15.07 

18.94 

0.07 

4.35 

15.70 

14.50 

10.50 

0.68 

6.16 

49.50 

22 25 

0.6, 

4.73 4.76 4.19 4.83 4.86 4.89 493 4.96 

42.50 43.50 44 50 45.50 46.50 47.50 48.50 49.50 

2007 20.45 20.84 21.22 21.60 21 99 22.37 22.75 

8.07 

lO.5? 

0 06 

3.11 

25.4" 

12.5" 

7.50 

22"~30 

0.49 

4.87 

27.50 

13.83 

15.39 

19.32 

0.07 

4.35 

46 70 

I4 50 

10.50 

22'.30 

0 74 

6.22 

50.50 

22.63 

9.61 

10.52 

0.07 

1.45 

25.40 

13.50 

3.50 

22'.30 

0.57 

4.12 

27.5" 

14.33 

17.46 

19.32 

0.07 

2.28 

16.70 

14.50 

5.50 

220.30 

0.69 

4.98 

SO.50 

23.13 

F=(d,+hvl)-(I.ld2+hvp) Submergence = I Id2 +hvp + h3 h4 dwneicrofp,pe hv 
Table 2-4..-Type I pipe drop with concrete outlet transition (to be used with fig. 2-30).m-Continued. 103-D-1270-9 

P 

h2 

h3 

"4 

L2 

L3 

L4 

s3 

S"bllKrge"W 

d2 

LX 

d, +hv, 

F 

"2 

h3 

"4 

l-2 

L3 

L4 

s3 

Submergence 

d2 

LX 

dl +hv, 

F 

h2 

h3 

h4 

l-2 

L3 

L4 

s3 

Submergence 

d2 

LX 

d,+hvl 

F 

h2 

h3 

h4 

L2 

L3 

l-4 

s3 

Submergence 

9 

LX 

d,+hvl 

Q= 19cfx lhmetrr of p*pc = 30 Inches VP = 3.87 fp\ 

2.30 2.62 

2.10 2.49 

0.04 0.04 

0.59 0.59 

5.10 6.00 

8.50 8.50 

4.50 4.50 

70.30 

0.48 055 

3.07 3.14 

5.50 6.50 

5 91 6 30 

9.59 9.92 

,091 11.29 

0.07 0.07 

1.66 1.66 

26.30 27 30 

14.00 14.00 

4.00 4.00 

22'.30' 

0.77 0.82 

445 450 

28.50 2950 

14.12 15 10 

Q= 21 cfs 

292 

2 81 

0.04 

0.59 

7 .oo 

850 

4.50 

5.08 5.40 5.7, 6.03 

5.55 5.93 6.31 6 70 

006 0.06 0.06 0 06 

1.07 1.07 1.21 1.21 

13.40 14.30 15.2" 16 20 

,100 11 00 ,150 1150 

4.00 4.00 4.50 4.50 

0.63 

3.21 

7 50 

6.68 

0.62 0.68 0 6, 068 0 74 

3.68 3 74 3.80 3.86 3.92 

1450 15 50 lb.50 1750 ,850 

9.36 9.74 10 12 10.51 10.89 

10.25 

11.67 

0.07 

2.07 

28.20 

14.00 

5.00 

0.47 

4.55 

30.50 

,548 

3 22 3.53 3.84 4 15 4.46 4.77 

3.25 3 64 4.02 4.40 4.78 5.11 

0.04 0.04 0.04 0.04 0.06 0.06 

0.72 0.72 0.72 0.72 1.07 1.07 

7 90 8.80 9 JO 10.60 11.60 12.50 

8.50 8.50 8.50 3.50 11.00 1100 

5.50 5.50 5.50 5.50 4 00 4.00 

7O-30. l5O 

0.58 0.66 073 0 80 0.48 055 

3 28 3.35 342 348 3.55 3.62 

850 9.50 ,050 1150 12.50 1350 

7.06 7 45 7.83 8.21 859 8 98 

10.58 10.92 11.25 II.59 11.92 12.26 

12.05 12.44 12.82 13.20 13.58 13.97 

007 0.07 007 0 07 0.01 0.07 

2.07 2 07 2.07 2.07 2.28 2.28 

29.10 30.00 31.00 31.90 32 80 33.70 

14.00 14.00 14.00 ,400 1450 14.50 

5.00 5 00 5 00 5 00 5.50 5.50 

0.52 0.56 0.61 0 65 0.50 054 

4.60 4 64 468 4.12 4 77 481 

3150 32.50 33.50 3450 35.50 36 50 

15 86 lb.25 lb.63 17.01 17.39 17 78 

Dlametei ofpqx = 30 inches 

12.60 12.92 13.25 13.59 13.92 14.26 

14 35 14 73 15.11 15 50 15 88 1626 

0.07 O.OJ 0.07 0 01 0.08 0.08 

2.28 2.28 2 28 2.28 2.49 249 

34 70 35 60 36.50 3740 38 4" 39 30 

14.50 14.50 1450 14.50 15.00 15 00 

550 5 50 5.50 5.50 6 "0 600 

0.59 0.64 070 0 74 0.58 0.63 

4 85 4 90 4.95 4.99 5.03 5 07 

37.50 38.50 39.50 40.50 41.50 4250 

18.16 18.54 18 92 19 31 19.b9 20 07 

V,, = 4.28 fp< 

2.13 2.42 

2.10 2.49 

0.04 0.04 

0.72 0.72 

5 10 6.00 

7.50 850 

5.50 5.50 

70.30' 

0.52 0.62 

3.18 3.21 

5.50 6.50 

5.9, 6.30 

9.24 9.56 

10.91 II.29 

0.06 0.07 

2.14 2.28 

26.30 27.30 

II 00 14.50 

8.00 5.50 

150 22'.30 

0.75 0.56 

4.13 4.78 

28.50 29.50 

14.72 15.10 

2.7, 

2.87 

0.04 

0.72 

7.00 

8.50 

5 50 

4.79 5 10 5.42 5.74 

5.55 593 63, 670 

0.06 0.06 0 06 006 

I34 I34 1.61 I61 

,340 14.30 15 20 16 20 

1100 11.00 II 00 11.00 

5 00 5 00 6.00 6 00 

0.72 

3 36 

7.50 

6.68 

3 00 3.30 359 3.89 4.19 4.49 

3 25 3.64 4.02 440 4.78 5.17 

0.04 0.06 0.06 0.06 0.06 006 

0.72 1.07 1.07 1.07 107 1.34 

7 90 8.80 9.70 1060 ,160 ,250 

8.50 II 00 Il.00 11.00 1100 11.00 

550 4.00 4.00 4 00 4 00 5 00 

70.30' 150 

080 0.49 058 0.66 0 75 0.55 

3.44 3.52 3.60 3 67 3.75 382 

8.50 9.50 10.50 ,150 1250 13.50 

7.06 7.45 7.83 8.21 8.59 8 98 

10.21 10.54 10.86 11.19 1152 11.85 

12.05 12.44 12.82 13.20 13.58 13 97 

0.07 0.07 0.07 0 07 0.07 0.07 

2.28 2.28 2.28 2 69 2.69 2.69 

29.10 3000 3100 31.90 32 80 33 70 

14 50 14.50 14.50 1450 14.50 14.50 

5.50 5 50 5.50 6.50 650 6.50 

067 073 0.79 0.43 0.48 054 

4.88 4.94 4.99 5.04 5.08 5 14 

3150 32.50 33.50 34.50 35.50 36.50 

15.86 16.25 16.63 17.01 17.39 17 78 

064 071 0 50 0.57 

3 90 3 96 4 IO2 4 08 

14.50 15 50 lb 50 17 50 

9 36 9 74 10 I2 ,051 

9.89 

11.67 

0.07 

2.28 

28 20 

14.50 

550 

12.17 12 50 ,283 13 I6 ,348 13.8, 14 14 14.48 1481 15 15 15 49 I5 82 16 15 

14.35 14 73 15.1, 15 50 15.X8 16 26 lb 64 17 03 17.41 17.79 18.18 18.56 1894 

0.07 0.07 008 0 08 0 08 0 08 0.08 008 0.08 0.08 008 008 0.08 

2 69 2.69 2.90 2.90 290 2.90 2 90 3.11 3 I, 3 I, 3 II 3.11 3.11 

34 70 35.60 36.50 3140 38.40 39.30 40.20 41.10 4200 43.00 43.90 44.80 45.70 

14.50 L4.50 15 00 15.00 15.00 15.00 15.00 15.50 15.50 15 50 15 50 15 50 15.50 

650 650 7 00 7.00 7 00 7.00 7 00 7 50 7.50 7 50 7 50 750 75" 

0.61 

4.83 

30.50 

15.48 

0.60 O.b5 05, 0.56 0.62 11.67 072 055 061 0.65 0 70 0 75 0.8, 

5 19 5 24 5.29 5.34 5.39 5 44 5 48 5.52 5 51 5bl 5 65 5 70 5.75 

37 50 38.50 3Y50 40 50 4150 4250 4350 44 50 45 50 46.50 47.50 4x.50 49.50 

18.16 18.54 18.92 19.31 19 69 20.07 2045 20 84 21.22 21b" 2199 22 37 22 75 

PIPE DROP WITH MITER BENDS 

Concrete Outlet Transition 

hvp = 0 23 Iout ln,ct R = 3 75 feet 

6.35 667 6.98 7.30 7.63 1.96 8 29 8.61 

1 08 7 4b 7 84 8.23 8.61 8.99 9.38 9.16 

006 0.06 0.06 0.06 0.06 0 06 0.06 0.07 

1.21 I.21 147 I .41 1.47 1.47 147 1.66 

17 10 18 00 19.00 19.90 20.80 21.70 22.60 23.60 

Il.50 11.50 ,I 50 1150 ,150 ,150 1150 I4 00 

450 450 5.50 5 50 5.50 5.50 5 50 4 00 

l5" 22'.30 

0.80 

3.97 

1950 

II 27 

061 0 68 0 74 0 19 0.85 

4 04 4 10 4.l5 4 20 4.25 

2050 2150 2250 2350 2450 

II 65 12.04 1242 12.80 13.19 

14 60 14 93 15.26 15.60 15.93 

16.64 17 "3 17.41 17 79 18 18 

0.08 008 0 08 0 08 008 

249 2.49 2.49 249 2 90 

40.20 41 10 42.00 43.00 43.90 

,500 I5 00 15 00 15 00 15 00 

6 00 6.00 6.00 6.00 7.00 

067 073 0 78 083 047 

5 11 5.16 5 21 5.25 5.30 

4350 44 50 45.50 46.50 47.50 

2045 20.84 21.22 21.60 2199 

0.60 0.67 

4.30 4 36 

25.5" 2650 

1357 13.95 

lb.27 lb.60 

18.5b 18.94 

0.08 008 

290 2.90 

44.80 15.70 

15.00 15.00 

7.00 7.00 

0.5 l 

5.34 

48.50 

22.37 

hbp = 0 28 foot lnlei R = 3 15 rcct 

6.06 6 38 6 70 7.02 733 7.64 7.96 8 28 

1.08 7 46 7.84 8 23 8.61 8.99 9.38 9 76 

0.06 0 06 006 0.06 0.06 006 006 0 06 

I61 I61 I61 I.88 I88 1.88 1.88 2 14 

11 10 18.0" 19.00 1990 20.80 21.70 22 60 23.60 

!I 00 Il.00 ,100 Il.00 il.00 11.00 Il.00 I,.00 

6.00 6 00 6 00 7 00 7 00 7 00 7.00 8 00 

0 b3 0 69 0 76 0.55 0.62 0.69 0 76 0.57 

4.14 4.19 4 25 4.31 4.31 4.44 4.5" 456 

,850 19.50 2O50 2, 50 22 50 235" 2450 25.50 

10 89 II 27 ,165 12.04 ,242 12 80 13.19 1357 

893 

10.14 

0.07 

1.66 

24.50 

14.00 

4.00 

056 

5.38 

19.50 

22.15 

8.60 

10 14 

006 

2.14 

24.50 

Il.00 

8.00 

11.62 

4.61 

26.50 

13.95 

9.2b 

,052 

0.07 

I.66 

25.40 

14.00 

4.00 

22'.30 

071 

440 

2750 

14 33 

16.95 

1932 

0 08 

2.90 

16.70 

15 00 

1.00 

22'.30' 

0 60 

5.42 

50.50 

23 13 

8.92 

10.52 

0 Oh 

2.14 

25 40 

1, 00 

8 00 

l5O 

0 69 

4.67 

27.50 

14 33 

,648 

19.32 

0 08 

3.52 

46.7" 

15.50 

850 

22O 30‘ 

045 

5.K 

50.5" 

23 13 

F=(d, +hv,) - (l.ld2+hvp) dl+hv,=R+h2+0."6 Submer&wcr = l Id2 + hvp+ h3 h4 d~"etcr 01 WC hv 
Table 2-4.-Tvpe I pipe drop with cotwrcte outlet tramitioil (to De used with fig. 2-30). -Continued. 103-D-1 270.10 

PIPE DROP WITH MITER BENDS 

Concrete Outlet Transition 

5 75 

7 08 

0 06 

6 "6 

7 46 

006 

1.88 

6 37 

7 84 

0 "6 

I88 

6.69 

8 23 

0.07 

2 07 

19.90 

14.00 

5 00 

22'.30' 

058 

4 55 

21.50 

I2 "4 

7 “I 7.32 

861 8 99 

0 07 0.07 

2 07 2.07 

2” 8" 21.70 

14 0” 14.00 

5 00 5.00 

7.63 7 94 

9 38 Y.76 

0 07 0 07 

2 07 2.49 

22 6” 23.60 

14 00 14.00 

5.00 6."" 

0.78 0.43 

4 74 4.80 

24 50 25.50 

13 19 13.57 

,503 15 36 

18.,X 18.56 

0 08 008 

352 3.73 

43.90 44 80 

4 25 4 54 4.84 

5.17 5.55 5 93 

0 "6 0 06 0 “6 

I 34 161 I61 

12.5" 13 4" 14.30 

I I 00 1100 IL,,” 

5 on 6.0" 6.00 

5.14 5.44 

6 31 6 70 

0.06 O "6 

161 I.88 

15 2" 16.20 

II "0 II 0" 

6 "0 7 00 

0.79 0.60 

4.23 4 30 

16.5U 17 50 

IO.,2 1051 

12.42 12.76 

15 II 15.50 

0 "8 "08 

i.88 

17.10 

I I .oo 

7 on 

18 00 19 0” 

11.00 11.0” 

7 00 7.0” 

150 

8 25 

10 14 

0.07 

2.49 

24 50 

14.00 

6.00 

0 80 0.62 0.7 I 

3 99 4 07 4.15 

1350 14.5" 15 50 

8.98 Y 36 9.74 

0.67 0 13 081 

4.36 44? 4.49 

18 5" 1950 20.50 

lo.89 11.27 II 65 

0.64 072 

4.61 468 

22.50 23.50 

12.42 12.80 

0.5 I 

4.87 

26 50 

1395 

II.42 11.75 12.08 

13.97 14 35 14.73 

0.08 0 08 O 08 

2 9" 3.31 331 

33 70 34 7" 35 60 

15.00 15 "0 15 00 

7 00 8 0" 8.00 

13 08 

15 88 

0 08 

331 3 31 

36 50 37 40 

15 0” 15.0" 

8.00 8 00 

331 

38.4" 

15.00 

8.00 

13.4" 13 72 14 05 14 38 14.71 

16 26 1664 17.03 1741 17 79 

0.08 0.08 0 08 0.08 0 OX 

3.52 352 352 3.52 3 52 

39.3" 4" 20 41 10 42 00 43 0” 

15 50 15.5c 15.50 15.5,) 15.50 

8.50 8.50 850 8.50 850 

15 50 16.00 

8 5" 9.00 

15 70 

1894 

008 

373 

45.70 

16.00 

9.00 

0.77 0.40 0.46 050 0.56 0.61 0.47 (1.52 058 0.62 0.68 0.73 0.58 0.63 

547 551 5.56 5 60 5 65 5.7" 5.16 5.81 5.86 5.90 5.95 6 00 6.05 6.10 

36.50 37.50 38.50 39.50 40.50 41.50 42.50 43.50 4450 45.50 4650 47.50 48.50 49.50 

17 78 18.16 18.54 1892 1931 19.69 20.07 20.45 20 84 21.22 21.60 21.99 22.31 22.15 

1.92 

10.14 

0.07 

2.69 

24.50 

14.50 

6.50 

0.64 

5.12 

26.50 

13.95 

15.24 

18.94 

0.08 

4.14 

45.7" 

16.00 

10.00 

0.68 

6.46 

49.50 

22.15 

8.57 

111.52 

o.o7 

?.49 

25 4U 

14.00 

6 00 

72".30‘ 

-0 51 

4 93 

27.5" 

14.33 

16.03 

19 32 

0.08 

3.73 

46.70 

16.00 

9 00 

22".30' 

0.69 

6.15 

50.50 

23.13 

8.23 

1052 

0.07 

2.69 

25.40 

14.50 

6.50 

22O-30 

0.71 

5.18 

27.50 

14.33 

15.58 

19 32 

0.08 

4.14 

46.70 

16.00 

IO.00 

22'.30' 

0.72 

6.50 

50.50 

23.13 

r 1.94 2.22 2.49 2.77 3.06 3 35 3.65 3 95 

2 IO 2.49 2.87 3.25 3.64 4 02 4.40 478 

0.05 0.05 0 05 0.05 0.05 006 0 06 0.06 

0.94 0.94 0.94 1.21 I.21 134 I34 1.34 

5.10 6.00 7.00 7.90 8.80 9.70 1060 II 60 

10.50 105" 10.50 10.50 1050 11.00 11.00 II 00 

3.50 350 3.50 4.50 450 5.00 5.00 5.00 

150 

0.43 054 0.65 0.49 0.58 055 0.62 0.7 I 

3 3" 340 350 3.60 3.68 3.76 383 3.91 

5.50 6.50 7.50 8.50 950 10.50 II 5" 12.50 

5.91 6.30 6.68 7.06 7.45 7.83 8 :I 859 

8.89 9.21 952 9.84 10.16 10.47 10 79 II 10 

10.91 11 29 1167 12.05 1244 12.82 1320 13.58 

9.07 0 “7 0 07 0.07 0.07 0.08 (1.08 0.08 

2.49 2.69 269 2.69 2 69 290 2 90 290 

26.30 27 30 28.20 29.10 30.00 31.00 31.90 32 80 

14.00 14.50 14.50 14.50 14 50 15.00 15.00 15 00 

6.0" 6.50 6.50 6.50 650 7.00 7.00 7.00 

22'.30 

0.64 0.5 1 0.57 0.64 0.70 0.57 064 071 

4.99 5.05 5.11 5.17 5.23 5.29 5.35 5.42 

28.50 29.50 30.50 31.50 32.50 33.50 34 50 35.50 

14.72 15.10 15 48 15.86 16 25 16.63 17.01 17.39 

Q = 25 cfs hameter of p,pe = 30 Inches 

1.75 2 03 2 30 2.51 2.86 3.14 3.42 3 70 

2.10 2.49 2 87 3.25 3.64 4.02 4.40 4.78 

0.05 0.06 0.06 0 06 0.06 0.06 006 0.07 

1.07 1.07 1.07 1.07 I45 145 1.45 1.66 

5.10 6.00 7.00 7 90 8.80 9.70 1060 11.60 

10.00 11.00 Il.00 11.00 12.50 12.50 12.50 13.00 

4.00 4.00 4.00 4.00 3.50 350 3.50 4 00 

Ii0 150 22'~30' 

VP= 5 09 fps h”* = 0.40 f”Of Ink, R = 3 75 feet 

4 “0 4 29 

5 17 5.55 

0.07 0 07 

1.66 1.66 

12.50 13.40 

13.00 1300 

4.OG 4.00 

0.49 0.61 0.72 083 0.43 053 0.64 0.53 0.62 0.72 

3.42 3.52 3.62 3.12 3.81 3 90 4.00 4.08 4.16 4.25 

5.50 6.50 7.50 8.50 9.50 1050 11.50 12.50 13.50 14.50 

5.91 6.30 668 7 06 1.45 7.83 8.21 8.59 8.98 9.36 

8.55 8.87 9.18 950 9.82 10.14 10.44 10.76 11.09 11.40 

10.91 11.29 11.67 12 II5 12.44 1282 13.20 13.58 13.97 14.35 

0.07 0.08 0.08 0.08 0.08 0.08 0.08 0.08 008 0.08 

2.69 2.90 2.90 2.90 2.90 3.31 3.31 3 31 3 31 3.52 

26.30 27.30 2R.20 29.10 30.00 31.00 31.90 32.80 33 70 34 70 

14.50 15.00 15.00 15 00 15 00 15.00 15.00 15 00 15 00 15.50 

6.50 7.00 i.00 7.00 7.00 800 8.00 8.00 8.00 850 

4.58 4.88 

5.93 6 31 

0.07 0.07 

1.86 1.86 

14.30 15 20 

13.50 13.50 

4.50 4.50 

060 0.68 

433 440 

15.50 16.50 

9.74 10.12 

22'.30 

0.77 0.64 0.71 077 0.84 0.49 0.56 0.63 

5.24 5 30 5.36 542 5.48 5.54 5.60 5 66 

28.50 29.50 3050 31.50 3250 33.50 34.53 35.50 

14.72 15.10 15.48 15.86 16 25 16.63 17.01 17 39 

11.71 12.02 

14.73 15.ll 

0.08 0.08 

352 3.52 

35 60 36.50 

15.50 15.50 

8.50 8.50 

0.69 055 0.61 0.69 

5.12 5.78 5.84 5.91 

36.50 37.50 38.50 39.50 

17.78 18.16 18.54 18.92 

h2 

h3 

“4 

L2 

L3 

L4 

s3 Submergence 

d2 

k 

d, + hv, 

F 

"2 

h3 

"4 

L2 

L3 

L4 

s3 Submergence 

9 

LX d, + hv, 

5 18 5.49 5.19 6.08 6.38 

6.70 7.08 1.46 7.84 8.23 

0.07 0.07 0.07 0.07 0.07 

I86 2.07 2.07 2.07 2.49 

16.20 17.10 18.00 19.00 19.90 

13 50 14.00 14 00 14.00 14.00 

6.68 6.98 7.30 7.61 

8.61 8.99 9.38 9 76 

007 0.07 0.07 0.07 

2.49 2.49 2.49 269 

20.80 21.70 22.60 23.60 

14.00 14.00 14.00 14.50 

6.00 6.00 6.00 6.50 

0 55 0.63 0.70 0.57 

4.85 4 93 4.99 5.05 

22.50 23 50 24.50 25.50 

12.42 ,280 13.19 13.57 

13.95 14 27 14.60 14.92 

1741 17.79 18.18 18.56 

P 

h2 

h3 

he 

L2 

L3 

L4 

s3 

Submergence 

450 5.00 5 00 5.0" 6.00 

0.77 0.62 0.71 0.81 0.47 

4.48 4 54 4.62 4.71 4.78 

17.50 18.50 19.50 20.50 21.50 

10.51 10.89 II 21 11.65 12.04 

d2 

LX 

d,+hv, 

12.34 12.66 12 97 13.28 13.62 

15.5" 15.88 1626 16.64 17.03 

0.08 0.08 0 08 0.08 0.08 

352 3.73 3.73 3.73 3 73 

3740 38.40 39 30 40.20 41.10 

F 

b 

h3 

“4 

L2 

L3 

L4 

s3 S”hElCIge”CX 

9 

LY 

dl+hv, 

0.08 0 "8 0.08 0.08 

3.73 4 14 4.14 4 14 

42.00 43.00 439" 44.80 

15.50 16 "0 16 00 16.00 16.00 16 00 16 00 16.0" 16.00 

8.50 9 00 9 00 9.00 9.00 

0.76 0.61 0.68 0.75 0.80 

9.00 10 00 10.00 1000 

0.86 050 "56 0.62 

5.91 6.03 6 09 6.15 6.20 6.25 630 6.35 641 

40.50 41.50 42.50 43.50 44.50 

19.31 19.69 20.07 20.45 20.84 

P = (d, +hv,j (l.ld2+hvp) dl+hv,=R+h2+0.06 Subrncrgencc = I-Id2 + hvp + h3 h4 

45.50 46.50 47.50 4850 

21.22 21.60 21.99 22 37 

dnmeter of p,pc hv 
I’ 

9 

h3 

“4 

L2 

L3 

L4 

S3 Submergence 

d2 

LX 

dl+hvl 

F 

b2 

h3 

h4 

L2 

J-3 

L4 

S3 

Submergence 

d2 

LX 

Ii, +h”, 

F 

b2 

b3 

h4 

L2 

L3 

L4 

S3 

Submergence 

9 

LX 

d, + bv, 

1: 

h2 

h3 

“4 

L2 

L3 

L4 

S3 

Submergenc? 

9 

L, 

dl+hvl 

Table 2-4.-Type I pipe drop with concrete outlet trarzsition (to be used with fig. 2-30).-Continued. 103-D-1 270-I 1 

PIPE DROP WITH MITER BENDS 

Concrete Outlet Transition 

Q = 26 cfs “nmeter of pope = 36 Inches VP = 3.67 fpn ihVp = 0 21 to”t inlet R = 4.25 ice, 

6.95 7.28 7.61 7 94 8.26 8.60 8 93 9.26 

7.46 7 84 8.23 8.61 8.99 9 38 9 76 10 14 

0.08 Il.08 0.08 0.08 0.08 0.08 0.U8 0.08 

1 07 I .07 1.07 1.24 1.24 1.24 1.24 1.24 

IX.00 19 cl0 19.90 20 80 21.7” 22.60 23.60 2450 

15.00 15.5” 16 00 16.0” 16 00 ,600 16.50 16.50 

4 no 4 00 4 00 3.00 3 00 3.00 3.00 3.00 

15” 22”.30‘ 

0 66 0.7 I 0 77 0.51 0.57 062 0.67 0.72 

4.19 4 24 4.29 4 34 4.39 4.44 4.48 4.53 

19.50 20.50 21.50 22.50 23.50 24 5” 25.50 26.50 

11.77 12.15 12.54 12.92 13.30 13.69 14.07 14.45 

2.53 2.83 3.14 3.44 3.78 4 08 4.41 4.71 

2 10 2.49 2.87 3.25 3.64 4.02 4.40 4.78 

0.06 0.06 0.06 0.06 0.06 0.06 0.06 0 07 

0.40 040 0.40 0.40 0.40 0.40 0.53 0.80 

5.10 6.00 7 00 7.90 8.80 9 70 10.60 11.60 

11.00 11.00 1, 00 12.00 12.00 12.00 12.00 13.00 

3.00 3.00 3.00 3 00 3.00 3.00 4.00 3.00 

70.30 70.30’ 150 

0.45 0.54 0.6 1 0.68 0.74 0.82 0.74 0.48 

3.34 3.42 3.48 3.55 3.60 3.61 3.12 3.79 

5.5” 6.50 7.50 8.50 9.50 10.50 11.50 12.50 

6.41 6.80 7.18 7.56 1.95 8.33 8.71 9.09 

9 _.- 97 I” ...~~ 25 10.5R ~~ ,091 II 25 11.58 11.91 12 25 

10.91 11.29 11.67 ii.05 12.44 12.82 13.20 13.58 

0.09 0.09 0.09 0.09 0.09 0.09 0 09 0.09 

1.66 1.66 L.66 I 66 I .66 1.66 I 66 1.66 

26.30 27.30 28 20 29.10 30.00 31.00 31.90 32.80 

17.00 17.00 17.00 17.00 17.50 1750 17 50 18 00 

4.00 4 00 4 00 4.00 4.00 4.00 4.00 4 00 

22’.30 

0.42 0.47 0.52 0.57 0.62 0.66 072 0 76 

4.63 4.67 4.72 4.16 4.81 4.85 4 90 4.94 

28.50 29.50 30.50 31.50 32.50 33.50 34 50 35.50 

15.22 15.60 15.98 16.36 16.75 17.13 17 51 17.89 

Q = 29 css thmeter of prpe = 36 mches VP = 4 1” tpi hvp = 0.26 foot inlet R = 4.25 feet 

2.31 2.60 

2.10 2.49 

0.06 0.06 

0.40 0.53 

5.10 6.00 

11.00 1200 

3.00 4 00 

70-30 

0.61 0.64 

3.49 3.58 

5.50 6 50 

6.4 1 6.80 

9.55 9.87 

10.91 11.29 

0.09 0.09 

1.66 2.07 

26.30 27.30 

2.90 

2 87 

0.06 

0.53 

7.00 

12.50 

4.00 

3.20 

3.25 

0.07 

0.53 

7.90 

13.00 

4.00 

7v-30 

3.5 1 3 80 

3.64 4.02 

0.07 0.07 

0.80 0 80 

8.80 9.70 

13.00 13 00 

3.00 3.00 

150 

4.10 4.42 4.73 5.05 

4 40 4.78 5.17 5 55 

0.07 0 07 0.07 0 07 

0 80 0.80 1.07 1.07 

10.60 11.60 12.50 1340 

13.50 14 00 14.00 14.50 

3.00 3.00 4.00 4.00 

6 30 6 63 6.95 7 26 7 59 7 9, 8.24 8 57 8.89 

7.08 7.46 7.84 8 23 8.61 8.99 9.38 9.76 10.14 

0.08 0.08 0 08 0.09 0 09 0 09 0 09 0.09 0.09 

1 24 1 24 1.24 I 24 I .66 1.66 1 66 I .66 1.66 

17.10 18.00 19.00 19.90 20.80 21.70 22.60 23.60 24.50 

15 00 16 50 16 5” 17 “0 17.00 17 00 17.00 17.00 17.50 

3.00 3.00 3 00 3 00 4.00 4 .oo 4.00 4.00 4.00 

0.72 

3.65 

7 50 

7.18 

0.81 

3.73 

8.50 

7.56 

0 54 0 63 0.70 0 77 0.58 0.64 

3.80 3.88 3.95 4 01 4.08 4.14 

9.50 10.50 11.50 12.50 13.50 14.50 

7.95 8.33 8.71 9.09 9.48 9.86 

5.36 5.66 

5 93 6.3 1 

0 08 0 08 

1.07 1 07 

14 30 15.20 

15.00 15.00 

4.00 4 00 

I5O 

0.72 0 80 

4.20 4 27 

15 50 16 50 

IO.24 10 62 

12 82 13.14 

14.73 15.11 

0.10 0 IO 

2 48 2 48 

35.60 36.50 

19.00 19 00 

6.00 6.00 

0.53 0.59 

5.42 5.47 

38.50 39.50 

19 04 19.42 

6.00 

6 70 

0.08 

1.24 

16 20 

15.00 

3 0” 

22’.30 

0 54 

4 32 

17 5” 

II “1 

10.51 10.85 11.17 

12.05 12.44 12.82 

0.09 0.09 0.09 

2.07 2.07 2.07 

29.10 30.00 31.00 

18.00 18.00 18.00 

1349 

15.50 

0 10 

2.48 

37.40 

19.00 

6 00 

0 62 067 0 73 

4.39 4.44 4.49 

18.50 19 50 20 50 

11.39 II 77 12 15 

13.81 14.l5 14 49 

15 88 16 26 16.64 

0.1” ,I 10 0.1” 

2.48 2.48 2.48 

38.40 39.30 40.20 

19 5” 19.5” 19.50 

6.00 6.00 6.“” 

0.69 0.73 0.77 

5 56 5 60 5.64 

41.50 4?.50 43 50 

20.19 20 57 20.95 

0 82 0 45 0.5 1 “57 0 62 0.68 

4 56 4.61 4.66 4 72 4.76 4 82 

21.50 22.50 23.50 24.50 25 50 26.50 

12.54 12.92 13.30 13.69 14.07 14.45 

10.19 

II.67 

0.09 

2.07 

28.20 

18.00 

5 00 

il.49 11.82 

13.20 13.58 

0.09 0.09 

2.07 2.07 

31.90 32.80 

18.50 18.50 

5 00 5.00 

0.73 0.79 

5 24 5.28 

34.50 35 50 

17.51 17 89 

12.16 12 54 

13.97 14 35 

0.09 0.10 

2.4X 2.48 

33.70 34.70 

18.50 19.00 

6.00 6.00 

14.83 15 17 15.50 15 84 16.17 16.52 

17 03 17.41 17.79 18.18 18.56 18.94 

0 IO 0.10 0 IO 0.10 0 10 0.10 

2.90 2.90 2.90 2.90 2.90 2.90 

41.10 42 00 43.00 43 90 44.80 45.70 

20.00 20.00 2o.olJ 20 00 20.00 20.00 

7 “0 7 00 7.00 7.00 7 00 7.00 

17.50 18.00 

4.00 5.00 

22’.30 

0.79 0.44 

4.92 4.97 

28.50 29.50 

15.22 15 60 

5.00 

0.50 0 56 

5.03 5.08 

30.50 31.50 

15.98 16.36 

5 00 5.00 

0.61 0.67 

5.13 5.18 

32.50 33.50 

16.75 17.13 

5 03 5.35 5 66 5 99 6.31 6 63 

5 17 5.55 5 93 6.31 6 10 7 08 

0.07 0.07 0 07 0 07 0 07 0 08 

0.80 0 80 0.80 0 80 0.80 1 “7 

12.50 13.40 14.30 15.20 16 2” 17.10 

13.50 13 50 14 00 14 00 14 5” 15.00 

3 00 3 00 3 .oo 3 00 3 00 4.00 

0.54 0.61 0.68 0.73 0.80 0.60 

3.85 3.91 3.97 4 02 4.08 4 14 

13.50 14 50 15.50 16.50 17 50 18.50 

9 46 9 86 LO.24 1062 Il.01 11 39 

12.59 12.93 13.25 13.59 13.93 14 28 

13 97 14.35 14.73 15.1 I I5 50 15.88 

0.09 0 09 0.09 0.09 0.09 u.09 

1.66 2.07 2.07 2 07 2.07 2 0, 

33.70 34.70 35.60 36.50 37 40 38.40 

18.00 18 00 18 00 18.00 I8 00 18.00 

4.00 5 00 5 00 5 00 5 “0 5 0” 

081 0.44 0.50 0.54 U.58 0 62 

4 98 5.02 5.07 5.1 I 5 15 5.18 

36.50 37.50 38.50 39 50 40 50 ?I 50 

18.28 1866 19.04 19.42 19 RI 20 19 

0.42 0 48 

5.33 5.31 

36.50 37.50 

18.28 1866 

0 63 

5.5, 

40.50 

19.81 

14 62 14.95 L5 30 15.65 15.98 16.34 16.68 17.01 

16.26 16 64 17.03 1741 17.79 18.18 1856 18.94 

0.09 0 09 0 09 0 IO 0.10 0.10 0.10 0 10 

2 07 2.07 2 “7 2.07 2 48 2.48 2.48 2.48 

39 30 40 20 4 I. I 0 42 00 43.00 43 90 44.80 45.70 

18.50 18 50 18.50 19 00 19.00 19 00 1900 19.00 

5.00 5.00 5 0” 5.00 6 00 6 00 6.00 6.00 

0.66 “71 0.75 0 79 0.43 0 46 0.50 0 55 

5 22 5 26 5 30 5.33 5 37 5 40 5.44 5 48 

42 50 43.50 44.50 45 50 46.50 47.50 48 50 49.513 

2057 20 95 21.34 21.72 22.10 22 49 22.87 23.25 

0.40 0.44 0 49 0 54 ” 58 0.62 

5 68 5.12 5.76 5x1 5 85 5.88 

44.50 45.50 46.50 47.50 48.50 49.50 

21.34 21.72 22.10 22.49 22.87 23.25 

9.59 

10.52 

0.09 

1.24 

25 40 

17 00 

3.00 

22’.30’ 

0.78 

4.57 

27.50 

14 83 

17.35 

19.32 

0.10 

2.48 

$6 70 

19.00 

6.00 

22O-30‘ 

0.59 

5.52 

50.50 

23.63 

9 21 

10.52 

0.09 

1.66 

25 40 

17.50 

4.00 

22’.30 

0 74 

4.87 

27.50 

14.83 

16.85 

19.32 

0.10 

2.90 

46.70 

20.50 

7.00 

22’.30’ 

0.67 

5.93 

50.50 

23 63 

I.=,d,+bv,,~(l.ld2+hvp) d,+hv,=R+h2+ll.“6 Submcrgencc = i.ld, + hv,+b-. hr - d,ameter ofemc hv 

_ , .I 4 
Table 2-4.-Type I pipe drop with concrete outlet transition (to be used with fig. 2-30). --Continued. 103-D-l 270-l 2 

F 

h2 

“3 

“4 

L2 

L3 

L4 

s3 

S”bmergence 

d2 

LX 

dl + hv, 

F 

h2 

h3 

h4 

L2 

L3 

L4 

s3 

S”bIllEXge”Ce 

d2 

LX 

d, + hv, 

F 

“2 

“3 

h4 

L2 

L3 

L4 

s3 

Submergence 

9 

LX 

d,+hvl 

F 

h2 

“3 

ha 

L2 

L3 

L4 

s3 

S”herge”Ce 

% 

LX d,+hv, 

PIPE DROP WITH MITER BENDS 

Concrete Outlet Transhm 

Q = 32 cf< Lhmctcr of ppr = 36 Inches 

2.10 2.39 2.67 2 95 3.25 3.54 3.85 4.15 4.45 

2.10 2.49 2.81 3.25 3 64 4.02 4.40 4.18 5.17 

0.06 0.06 0.07 0.07 0.07 0 07 0.07 0.08 0.08 

0.53 0.80 0.80 0 80 0.80 1.07 1.07 I 07 1.24 

5.10 6.00 7.00 7.90 8.80 9.70 10.60 11.60 I2 50 

11.00 1200 13.00 13 00 13.50 14 00 14 50 15.00 15.00 

4.00 3.00 3.00 3.00 3.00 4 00 4.00 4.00 3.00 

70.30‘ 150 15u 22’.30 

0.75 0.50 0.61 0.71 0.80 0.62 0 70 0.78 0.56 

3.63 3 72 3.81 3.90 3.98 4 06 4 13 4.20 4.28 

5.50 6.50 7.50 8 50 9.50 10.50 11.50 12.50 13.50 

6.41 6.80 7.18 7.56 7.95 8.33 8.71 9.09 9 48 

9.15 9.47 9.80 10.12 1045 10.76 11.08 11.47 11.74 

10.91 11.29 II 67 12 05 12.44 1282 13.20 13 58 13.97 

0.09 0.09 0.09 0 09 0 09 0 09 0.09 0.09 0 10 

2.07 2.48 2.48 2.48 2 48 2 48 2.48 2 48 2 90 

26.30 27.30 28.20 29.10 30 00 3100 31 90 32 80 33 70 

17.50 18.00 18 00 18 00 1800 18 50 18.50 18 50 1900 

5.00 6.00 6.00 6 00 6 00 6 00 6 00 6 00 7.00 

22’.30‘ 

0 78 0.43 0.48 0.54 0 60 0 67 0.72 0 78 042 

5 23 5.28 5.33 5 38 5 44 5 50 5 55 5.60 5 65 

28.50 29.50 30.50 31.50 32 50 33 50 34.50 35.50 36 50 

15.22 15.60 15.98 16 36 16.75 17.13 17.51 17.89 18.28 

Q = 34 cfr h~rnetcr of p,pe = 36 mcher 

1.96 2.23 2.51 2 80 3.13 3.31 3.66 3.96 4.21 

2.10 2.49 2.87 3.25 3.64 4.02 4.40 4.18 5.17 

0.06 0.07 0.07 0 07 0.07 0.07 0.08 0.08 0.08 

0.80 0.80 0.80 1.07 1.07 1.07 1.24 1 24 I .24 

5.10 6.00 7.00 7 90 8.80 9.70 10.60 11 60 12.50 

12.00 13.00 13.50 1350 14.00 14.50 15.00 15.00 15 50 

3.00 3.00 3.00 4.00 4.00 4.00 3.00 3.00 3 00 

15O 150 22’.30 

0.54 0.67 0.77 0.59 0.69 0.79 0.58 0 66 0 74 

3.72 3.83 3.92 4.00 4.09 4.18 4.26 4.34 441 

5.50 6.50 7 50 8.50 9.50 10.50 11.50 1250 13 50 

6.4 1 6.80 7.18 7.56 7.95 8.33 8.71 9.09 9.48 

8.89 9.21 9.53 9.84 10.17 1049 IO.81 I1 13 11.46 

10.91 11.29 II 61 12.05 12.44 12.82 13.20 13.58 13.97 

0.09 0.09 0.09 0.10 0.10 0.10 0.10 0 10 0.10 

2.48 2.48 2.48 2.48 2.90 2.90 2.90 2 90 2.90 

26.30 27.30 28.20 29.10 30.00 31.00 31.90 32.80 33 70 

18.00 18.50 18.50 19.00 19.00 19.00 19.00 19.50 19.50 

6.00 6.00 6.00 6.00 7.00 7 00 7.00 7 00 7.00 

22’.30’ 

0.63 0.69 0.75 0.83 0.46 0.53 0.59 0.65 071 

5.43 5.48 5.54 5.60 5.65 5 71 5.76 5.82 5.87 

28.50 29.50 30.50 31.50 32.50 33.50 34 50 35.50 36.50 

15.22 15.60 15.98 16.36 16.75 17.13 17.51 17.89 18.28 

VP = 4.52 fps 

4.75 5.06 

5 55 5.93 

0.08 0.08 

1.24 1.24 

1340 14.30 

15 00 15.50 

3.00 3.00 

0 63 0.71 

4.35 4 42 

14 50 15 50 

9.86 10.24 

12.07 I2 39 

14.35 14.73 

0 10 0.10 

2.90 2 90 

34.70 35 60 

19.00 1900 

7 00 7 00 

0 48 0 54 

5.70 5 75 

37 50 38.50 

18.66 1904 

5 37 5.67 5 98 

6 31 6.70 7.08 

0.08 0.08 0 08 

1 24 1.66 I .66 

15.20 16.20 17 10 

16 00 16.00 16 00 

3.00 4 00 4.00 

0.78 0.45 0.52 

4.48 4.56 463 

16.50 17.50 18.50 

10 62 11.01 11.39 

12 72 13 05 13.38 

15 II 15.50 15.88 

0.10 0.10 0 10 

2 90 2 90 2.90 

36.50 37 40 38.40 

19 00 19.00 19 50 

7.00 7 00 7 00 

0.59 0 64 0.70 

5.80 5 85 5.90 

39.50 40 50 41.50 

19.42 19.81 20.19 

VP = 4.81 fps hvp = 0 36 foot 

4 57 4 86 5 16 

5 55 5.93 6 31 

0 08 0.08 0.08 

I 24 1.66 I 66 

13 40 14.30 15 20 

16.00 16.00 16 00 

3.00 4.00 4 00 

0.82 0.49 0.57 

5.47 5 77 6 09 6.38 6 70 

6.70 7 08 7 46 7.84 8 23 

0.08 0 08 0 09 0.09 0 09 

1.66 1 66 1 66 2.07 2.07 

16.20 17 IO 18.00 19.00 1990 

16.50 16.50 17 00 17 00 17 00 

4 00 4 00 4 00 5 00 5 00 

0.65 0 73 0.8” 0.48 0.55 0.62 

4 71 4.78 4 84 4.92 4.98 5 05 

17.50 18.50 19.50 20.50 21.50 22 50 

11.01 1, 39 I1 77 12.15 1254 12.92 

4.48 4.56 4 64 

14.50 15.50 16.50 

9 86 10.24 10 62 

II 78 12.09 1242 

14.35 14.73 15.11 

0.10 0.10 0 IO 

2.90 3.31 3.31 

34.70 35.60 36.50 

19.50 20.00 20.00 

7.00 8.00 8.00 

0.77 0.43 0.48 

5.93 5 99 6.04 

37.50 38.50 39.50 

18.66 19.04 19.42 

6.30 6.60 

7.46 7.84 

0.08 0 08 

I 66 1.66 

18.00 19.00 

16.00 16.00 

4.00 4 00 

0 58 0.66 

4 68 4.75 

19.50 20.50 

11 77 12 15 

13 72 14 04 

16 26 1664 

0 10 0.10 

2.90 2.90 

39 30 40 20 

19.50 19 50 

7.00 7 00 

0.74 0.80 

5.94 5 99 

42 50 43.50 

20.57 20.95 

6 93 7.24 7.56 7 87 8.19 8.5 1 

8 23 8.6 I 8.99 9.3R 9.76 10 14 

0.08 0 09 0.09 0 09 0.09 0 09 

I .66 I .66 2.01 2.07 2.07 2.07 

19.90 20.80 21.70 22.60 23.60 24.50 

16.50 17.00 17.00 17 00 17.00 17.00 

4.00 4.00 5.00 5.00 5.00 5.00 

0.72 0.80 0.45 053 0.58 0.65 

4.81 4 87 4 93 5.00 5.05 5.11 

21.50 22.50 23 50 24.50 25.50 26.50 

1254 12.92 13.30 13.69 14.07 14.45 

14 38 14.70 

17 03 17 41 

0.10 0 10 

3 31 3 31 

41 10 42 00 

20.00 20.00 

8.00 8 00 

0 44 0 50 

6.04 6.09 

44.50 45 50 

21.34 21.72 

7 00 

8.6 I 

0.09 

2.07 

?0.80 

17 00 

5.00 

12 75 13.08 13.41 13.73 14.05 14 37 

15 50 15.88 16 26 16 64 17.03 17.41 

0 10 0.10 0.10 0.10 0 II 0 II 

3 31 3.31 3 31 3 31 3.31 3.73 

37 40 38.40 39.30 40.20 41.10 42 00 

20.00 20.00 20.50 20.50 21.00 21.00 

8.00 8.00 8.00 8.00 8.00 9.00 

0.54 0.59 0.64 0 70 0.78 0 42 

6 09 6.14 6.18 6.24 6 30 6 35 

10.50 $1.50 42.50 43.50 44.50 45.50 

19 81 20.19 20.57 20.95 21.34 21.72 

lhvp = 0 32 Soot lnlct R = 4 25 feet 

15.03 15.36 15.70 

11.79 18 18 18 56 

II.10 il.10 0 IO 

3 31 3 31 3 31 

43.00 43.90 44.80 

20.00 a0 00 2050 

8.00 8 00 8 00 

Cl.55 061 0 65 

6 14 6 19 6 23 

46 50 47 50 48 50 

22.10 22.49 22.87 

inlet R = 4 25 feet 

7 32 7.63 1.95 

8.99 9.38 9 76 

0 09 0.09 0 09 

2 07 2.07 2 48 

21 70 22.60 23 60 

17 50 17.50 18.00 

5.00 5 .oo 6.00 

0 69 0.77 0 42 

5 I! 5.18 5.24 

23.50 24.50 25.50 

13.30 13.69 14 07 

14.70 15.03 15.37 

17.79 18.18 18.56 

0.11 0.11 0.11 

3.73 3.73 3.73 

43.00 43 90 44.80 

21.00 21.00 21 00 

9.00 9.00 9.00 

0.47 0.52 0.57 

6.40 6.45 6.49 

46.50 47.50 48.50 

22.10 22.49 22 87 

1602 

18.94 

0.10 

3.31 

45 70 

20.50 

8.00 

0.7 I 

6 28 

49 50 

23.25 

8.26 

10.14 

0.09 

2.48 

24.50 

18.00 

6 00 

0.49 

5 30 

26.50 

14.45 

15.70 

18.94 

0.1 I 

3.73 

45.70 

21.00 

9.00 

0.62 

6.54 

49.50 

23.25 

X.83 

10.52 

0.09 

2.07 

25.40 

17.50 

5.00 

22’.30‘ 

071 

5.16 

27.50 

14.83 

16 36 

19 32 

0 10 

3 31 

46 70 

2050 

8 00 

22’.30‘ 

0 75 

6.32 

50.50 

23.63 

8 57 

1052 

0.09 

2.48 

25.40 

18.00 

6.00 

22’.30’ 

0.56 

5.36 

27.50 

14.83 

16.01 

19.32 

Oil 

3.73 

46.70 

21.50 

9.00 

22’.30‘ 

0.69 

6.60 

50.50 

23.63 

r 

Y 

A 

c 

F=(d,+hv,)-(l.ld2+hvD) d, + hv, = R + h2 + 0.06 Submrigence = ,.,d2 + hv,, + h3 h4 dmnetcr ofplpe hv 
CONVEYANCE STRUCTURES 93 
Table 2-4.-Type I pipe drop with comrete outlet tratlsition (to be used with fig. J-30/. -Continued. 103-D-1270-14 

"2 

“3 

“4 

L2 

L3 

L4 

s3 Submcrpcnce 

dz 

L, 

d, + hv, 

F 

“2 

h3 

h4 

L2 

L3 

L4 

s3 Submergence 

d2 

LX 

d, + hv, 

h2 

z3 4 

L2 

L3 

L4 

s3 

Submergence 

dz 

L 

d, + hv, 

“2 

k3 4 

L2 

L3 

L4 

s3 

Submcrgcnce 

dz 

L, 

dl+hv, 

0 = 40Cf\ Dwnetcr 01 pqx = 42 mcho 

241 2.7 I 

2.10 2.49 

0.06 0.06 

0.53 0.53 

5.10 6.00 

12.00 12.00 

4.00 4.00 

70.30 

0.45 0.53 

3.85 3.93 

5.50 6.50 

6.91 7.30 

3.00 3.30 

2 87 3.25 

0.06 0.06 

0.66 0.66 

7.“” 7.90 

1200 12.00 

5 00 5.00 

362 3.92 4.22 4.52 

3 64 4.02 4.40 4.78 

0 06 0.06 0.07 0.07 

0.66 0.66 0.94 0.94 

8.80 9.70 10.60 11.60 

12.00 12.00 14.50 14.50 

5.00 5.00 350 3.50 

f-30. 15" 

0.49 0.57 065 0.72 044 0.52 0.59 0.66 062 0.68 0.75 

4.01 4.08 4.15 4.22 4.29 4.36 4.43 4.49 456 462 4.68 

7.50 8.50 9.50 10.50 II.50 12 50 13.50 14.50 15 50 16 50 17.50 

7 68 8.06 8.45 8.83 9.21 9.59 9.98 IO.36 IO 74 11.12 11.51 

9.64 997 

10.91 11.29 

0.09 0.09 

I.86 1.86 

26.30 27 3" 

17.5" 17.50 

4.50 4.50 

22'.30 

0.46 0.51 

5.28 5.33 

28.50 29.50 

15.72 16.10 

10.29 10.62 

11.67 I? 05 

0.09 0.09 

1.86 1.86 

28.20 29.10 

17 50 17.50 

4.50 4.50 

1095 I1 29 11.61 IL.94 

12.44 12.82 13.20 13.58 

0.09 0.09 0.09 0.09 

1.86 2.07 2 07 2 07 

30.00 31.00 31.90 32.80 

17.50 18.00 18 00 18.00 

4.50 5.00 5 0" 5.00 

0.57 0.62 

5.38 5.43 

3050 31.50 

16.48 16.86 

0.68 0.51 0.57 062 

5.48 5.52 557 562 

32.50 33.50 34.50 35.50 

17.25 17.63 18 01 18.39 

Q=43cf, “mnetcr of pqe = 42 mchw 

2.24 2.55 

2.10 2.49 

0.06 0.06 

0.66 0.66 

5.10 6.00 

11.00 12.00 

5.00 5.00 

7O-30 

0.48 0.56 

3.96 4.04 

5.50 6.50 

6.91 7.30 

9.36 9.68 

10.91 1129 

0.09 0.09 

1.86 2.07 

26.30 27.30 

17.50 18.00 

4.50 5.00 

22'.30 

0.74 0.59 

5.50 5.55 

28.50 29.50 

15.72 16.10 

2.84 

2.87 

0.06 

0.66 

7.00 

12.00 

5.00 

3.13 

3.25 

0.06 

0.66 

7 90 

12.00 

5 00 

70.30 

0.74 

4.20 

8.50 

806 

3.43 3.72 4 03 432 

3.64 4.02 440 4.78 

007 0.07 007 0.08 

0.94 094 0.94 1.07 

8.80 9 70 10.60 II.60 

14.50 14 50 14.50 15.00 

3.50 3.50 3.50 

I<0 

4 00 

0.65 

4.12 

7.50 

7.68 

Ii:47 0.56 0.63 060 

4.28 4.36 4.43 4.5 I 

950 10.50 11.50 1250 

8.45 8 83 9.21 9.59 

10.01 1032 

11.67 12.05 

0.09 0.09 

2.07 2.07 

28.20 29.10 

18.00 18.00 

5 “0 5.00 

10.65 10.97 II.30 11 62 

12.44 12.82 13.20 13 58 

009 0.09 0.09 0.09 

2 07 2.49 2.49 2.49 

30.00 31.00 31.90 32.80 

18.00 18.00 18.00 18.00 

5.00 6.00 6.00 6 00 

0.64 0.71 

5.60 5.66 

30.50 31.50 

16.48 16.86 

0.77 0.41 0.46 0.52 

5.72 5 71 5.82 5 87 

32.50 33.50 34.50 35.50 

17.25 17.63 18 01 18.39 

PIPE DROP WITH MITER BENDS 

Concrete Outlet Transition 

4.84 5 I5 545 5.77 6 09 

5.17 5.55 5 93 6.31 6 70 

0.07 0 07 0.08 0.08 0 08 

0.94 0.94 1.07 IO7 1.07 

12.50 13.40 14.30 15 2" 16.20 

14.50 14 50 15.00 I5 00 15.00 

3.50 3.50 4.00 4 00 4 00 

6.41 6 73 7 04 

7.08 1.46 7 84 

0.08 0.08 0 08 

1 07 1.34 1.34 

17.10 18 00 19.00 

15 0” 15.00 15 00 

4.00 5.00 5.00 

0.81 0.60 0.67 

4.74 4.79 4.85 

1850 19.50 20.50 

11.89 12.27 12.65 

7.37 769 

8.23 8.61 

O.08 0.08 

1.34 1.34 

19.90 ?0.80 

15.00 15.00 

5.00 5."" 

8.01 8.33 8.66 

8.99 93x 9.76 

0.08 008 0.08 

1.61 1.61 1.61 

21 70 22.60 2360 

15 00 15.00 15.00 

8.98 

10.14 

0 08 

161 

24.50 

15.00 

6.00 

0.73 0.79 

4.91 4.96 

21.5" 22.50 

13.04 13.42 

6 00 6.00 6 00 

0.58 0.65 0.70 

5.02 5.08 5.13 

23.50 24.50 25.50 

1380 14.19 14.57 

".?6 

5.18 

2650 

14 95 

1227 12.61 12.93 13.27 1362 13.94 14.28 14.60 14.95 15.27 15.61 15.96 16.29 16.62 

13 97 14.35 14 73 15 11 15 50 I5 88 16 26 16.64 17.03 1741 17.79 18.18 ,856 18.94 

0.09 0.09 009 0 09 0 09 0.09 (I 09 11.09 0.09 0.09 0.09 0.09 0.09 0.09 

2.07 2.07 2 28 2.28 2 28 2.28 2 28 2.28 2.69 2.69 2.69 2.69 2.69 2.69 

33.70 34 7" 35 60 36 50 37.40 38 4” 39 30 40.20 41.10 42 “0 43 00 43.90 44.8" 45.70 

18 00 18.00 1850 18.50 18.50 18.50 18.50 18.50 1850 18.50 18.511 18 50 18.50 18.50 

5.00 5 00 5.50 5.50 5.50 5.50 5.5" 5 50 650 6.50 6 50 6.50 6.5” 6.50 

0.68 0.72 0.57 061 065 

5.61 5.71 5 76 5 80 5.84 

36.50 37 50 3850 3950 40.50 

18.78 19 16 19.54 19.92 20.3 I 

0.71 0.75 il8l 

5 89 5.93 5.98 

41 50 42.50 43.50 

20.69 2107 21.45 

hvp = 0.31 foot 

6.18 6.49 6.81 

7.08 7.46 7.84 

0.08 0.08 0.09 

1.34 I 34 I 66 

0.44 0.50 

6.02 6.07 

14.50 45.50 

21 84 22.22 

0.54 0.59 063 

6.11 6.15 6.19 

46.50 47.50 48.50 

22.60 22.99 23.37 

Inlet R = 4.75 seeet 

0.68 

6.24 

495" 

23.75 

VP=447 Ip, 

4.64 4.95 5 25 555 5.88 

5.17 5.55 5.93 6.31 6.70 

0.08 0.08 008 0 08 0.08 

1.07 1.07 1.07 1.34 1.34 

12.50 13.40 14 30 15.20 16.20 

15.00 15.00 15.00 I5 00 15 00 

4.00 4.00 4 00 5.00 5.00 

7.15 7.43 

8.23 8.61 

0.09 0 09 

1.66 1.66 

19 90 20.80 

17 00 17.00 

4.00 4.00 

7.75 8.07 840 

8.99 9.38 9.76 

0.09 0.09 0.09 

1.66 1.86 1.86 

21.70 22.60 23.60 

17 “0 1750 17.50 

4.00 4.50 4.50 

8.71 

10.14 

0.09 

1.86 

24.50 

17.5" 

4.50 

0.67 0.74 082 0.63 069 

4.57 4.64 4 71 4 78 4.84 

13.50 14.50 15 50 16.50 17.50 

9.98 10.36 10.74 II.12 11.51 

II.96 12.28 12.61 I2 93 13 27 

13.97 14.35 14.73 15.11 IS.50 

009 009 009 0.09 009 

249 2.49 2.69 2.69 2.69 

33 70 34.70 35.60 36 50 37.4" 

18.00 18.00 18.50 18 50 18.50 

6.00 6.00 6.50 6.50 6.50 

11.89 12.27 12.65 

13.60 13.93 14.25 

15.88 16 26 16.64 

0.09 0 09 0.10 

0.49 0.57 063 0.50 0.55 0.62 

5.09 5.16 5.22 5.28 5.33 5.39 

21.50 22.50 23.50 24.5" 25.50 26.50 

13 04 13.42 13.80 14 19 14.57 14.95 

14.60 

17.03 

0 IO 

269 269 2.9" 2.90 

38.40 39.30 40.20 41.10 

18.50 1850 19 0” 19.00 

6.50 6.50 7.00 7.00 

0.64 069 0.55 0.59 

6.16 6.21 6.26 630 

14.92 

17.41 

0.10 

290 

42.0" 

19.00 

7.00 

15 26 15.60 15.93 

17.79 18.18 18.56 

0.10 0.10 0.10 

29" 2.90 2.90 

43 00 43.90 44.80 

19 00 19.00 19.00 

16.26 

18.94 

0.10 

3.31 

45.70 

0.57 0.63 048 0.54 059 

5.92 5 97 6.02 6.07 6.12 

16.50 37 50 38.50 39.50 40.50 

18.78 19.16 19.54 19.92 20.31 

7.00 7 “0 7.00 

0.69 0.74 0.79 

6.39 6.44 6.48 

46.50 47.50 48.50 

22.60 22.99 23.37 

8.00 

11.50 42.50 4350 4450 

20.69 21.07 21.45 21.84 

065 

6.35 

45.50 

22.22 

043 

6.53 

49.50 

23.75 

VP=4 Ihfp\ hvp = 0.27 fuot Inlet R = 4.75 feet 

F=(d,+hvI)-(I.ld2+hvp) d, + hv, = R + h2 + 0.06 Submergence = 1 Id2 + hvp + h3 -. h4 - dwnetrr 01 ppe hu 

9.31 

10.52 

0.08 

1.6 I 

25.40 

15.00 

6.00 

15" 

0.81 

5.23 

27.50 

15.33 

16.95 

19.32 

0.10 

2.90 

46.70 

19.00 

7.00 

22'~30 

0.53 

6.28 

50.50 

24 13 

9.04 

10.52 

0.09 

1.86 

25.40 

17.50 

4.50 

22'.30 

0.67 

5.44 

27 50 

15.33 

16.58 

19 32 

u 10 

3 31 

16.70 

19.00 

8.00 

22'.30 

0.49 

6.58 

50.50 

24.13 
CONVEYANCE STRUCTURES 95 
96 SMALL CANAL STRUCTURES 

Figure 2-31. Type 1 pipe drop-plan and sections. 103-D-1271. 

of the pipe or through the surrounding earth, 

thereby preventing removal of soil particles 

(piping) at the point of emergence. Pipe collars 

may also be necessary to discourage rodents 

from burrowing along pipe. Pipe drops should 

be examined to see if collars are required. A 

detailed discussion on pipe collars and 

percolation may be found in subchapter VIII 

C. 

(d) Freeboard. -Type 1 pipe drop structures 

have either a check and pipe inlet or a control 

and pipe inlet. Figures 3-38 and 3-39 are 

standard designs for these structures and have 

adequate freeboard incorporated into their 

design. Freeboard for concrete outlet 

transitions should be in accordance with 

chapter VII. 

2 - 3 1. Type 2 Pipe Drop Structure 

Components and Design Considerations (fig. 

2-32). -The principle hydraulic elements of the 

type 2 pipe drop are the upstream transition, 

the inlet structure, the pipe, and the outlet 

Ttructure. The type 2 pipe drop is similar to the 

type 1 pipe drop except that a reinforced 

concrete transition of the type 1, 2, 3, or 4 

may be used at the inlet if the pipe drop is a 
Figure 2-32. Type 2 pipe drop-plan and sections. 103-D-1272. 
98 SMALL CANAL STRUCTURES 

cross-drainage structure and a baffled outlet or 

a stilling pool is always used at the outlet end. 

(a) Buff7ed Outlets. -Baffled outlets are 

generally used at the outlet end of a type 2 

pipe drop to dissipate excess energy. See 

chapter VI for a discussion on baffled outlets. 

( b) Stilliug Pools. Stilling pools are 

sometimes used at the outlet end of a type 2 

pipe drop to dissipate excess energy. The pool 

reduces velocity and turbulence of the water at 

the outlet end and thereby reduces erosion in 

the channel below. See subchapter II F for 

design of stilling pools. 

When the stilling pool discnarges mto an 

uncontrolled channel, a control such as a weir 

must be provided in the outlet structure. 

Critical depth over this weir control section 

should be used to determine the downstream 

energy gradient. These controls are especially 

suitable for wasteways discharging into natural 

channels. Figure 2-36 of subchapter II F shows 

such a control. The aperture in the weir 

permits the pool to drain. In general, for any 

pool depending on downstream tailwater for 

sufficient d, to cause the hydraulic jump, the 

elevation of the pool floor may be determined 

by subtracting (d2 + h,* ) from minimum 

energy elevation downstream of the pool. 

Where use of the stilling pool is to be 

intermittent and for short duration of flow, 

such as is most wasteways or structures 

carrying flood water, the minimum pool length 

should be 3d,. Where uninterrupted use or 

long duration of the flow is expected, the 

minimum pool length should be 4d,. 

For rectangular pools with discharges up to 

100 cfs, the width of pool may be determined 

by the empirical formula 

,, = 3h%/v 

Q + 350 

where b = width of pool in feet and 

Q = discharge in cubic feet per 

second. 

(c) Outlet Trmsition-The outlet from a 

stilling pool connects the pool with the earth 

or concrete-lined canal downstream and 

prevents or lessens canal erosion. Some of the 

more common types of stilling pool outlets 

used are: broken-back transitions and straight 

or curved diverging vertical walls extending 

into the earth canal banks on each side. A 

portion of a transition may be made in earth 

provided the velocity at the downstream cutoff 

of the concrete transition is not too great for 

erosion. Riprap or gravel protection is generally 

used on the earth transition section. See 

subchapter VII B for protection. Where 

broken-back transitions are used, the top of the 

walls should be the same elevation as the pool 

walls. 

Cutoffs at the ends of the concrete 

transitions should be a minimum of 24 inches 

deep and 6 inches thick for water depths 0 to 3 

feet over the cutoff, and 2 feet 6 inches deep 

and 8 inches thick for water depths from 3 to 6 

feet. 

Where an earth transition is used at the inlet 

or outlet, it should be a minimum of 10 feet 

long. 

(d) Desigrz Layout. -While exact methods of 

design of pipe drop cannot be laid down, it will 

usually be helpful to first plot the profile of 

the natural ground surface on the centerline of 

the drop to natural scale on cross-section 

paper, and lay out a tentative bottom grade 

line. From this same profile a study can be 

made to determine the tentative location of the 

inlet of the structure and the proper location 

of the stilling pool or the baffled outlet. 

(e) Freeboard.-Type 2 pipe drop structures 

have either a check and pipe inlet, a control 

and pipe inlet, or a type 1, 2, 3, or 4 concrete 

transition. Figures 3-38 and 3-39 are standard 

designs for check and pipe inlet and control 

and pipe inlet and have adequate freeboard 

incorporated into their design. Freeboard for 

concrete transitions should be in accordance 

with chapter VII. 

2-32. Design Example of a Type I Pipe 

Drop with a Control and Pipe Inlet (see fig. 

2-3:).-The topography for the canal at this 

station is assumed to have a road crossing the 

canal and an abrupt drop in the general terrain. 

A type 1 pipe drop sumped to dissipate energy 

and to cross under the roadway is assumed to 

be the feasible structure to use. 

Assume that a control and pipe inlet will be 

the feasible type of inlet structure to minimize 

erosion in the earth canal upstream from the 

drop. 
CONVEYANCE STRUCTURES 

Assume that for this drop structure it will be 

more economical to have a concrete 

downstream transition which will permit the 

use of a smaller pipe because the pipe velocity 

can be as much as 5 feet per second. 

(a) Given. - 

(1) Type of waterway = earth canal. 

(2) Hydraulic properties of the canal at 

upstream and downstream ends of structure: 

Q= 49cfs b = 5.0ft. d, = 2.81 ft. 

S:S = l-1/2: 1 A = 25.90 ft.2 wp = 15.15 ft. 

R= 1.71 v = 1.89 f.p.s. h, = 0.06 ft. 

E = 2.87 ft. s = 0.0005 s’ ‘2 = 0.02235 

n = 0.025 

(3) El. A = 5406.00 (from a canal profile 

sheet). 

(4) NWS El. at Sta. A = El. A + d, = 

5406.00+ 2.81 = 5408.81. 

(5) Energy El. at Sta. A = El. NWS + h, = 

5408.81 + 0.06 = 5408.87. 

(6) El. H = 5392.0 (from a canal profile 

sheet). 

(7) NWS at Sta. H = 5392.0 + 2.81 = 

5394.81. 

(8) Energy El. at Sta. H = 5394.81 + 0.06 

= 5394.87. 

(b) Determine. - 

(1) Pipe size (see table on fig. 2-31). -For 

a discharge of 49 cfs and a maximum 

allowable velocity of 5 feet per second the 

table would permit the use of a 

45-inch-diameter pipe. 

However, a 42-inch diameter is considered 

satisfactory since V = 5.09 feet per second 

and does not exceed the maximum velocity 

appreciably. 

(2) Inlet Structure Number. -Figure 3-39 

provides standard dimensions for control 

and pipe inlets. A structure inlet with a 

42-inch-diameter pipe and a maximum 

allowable V, of 5 feet per second is 

numbered 42-l. 

99 

(3) Determine control and pipe inlet 

standard dimensions R and L by entering the 

structure table figure 3-39 for structure no. 

42-l. Read R = 4 ft. 9 in. and L = 4 ft. 6 in. 

(4) Determine the normal depth in the 

canal and its velocity head for a Q of 0.2 the 

design Q. 

= 7.38 

Assume different water depths, d, in the 

canal and solve for AR2 ‘3 until AR2 ‘3 = 

7.38 (see tabulation below). 

CANAL SECTION 

A=db+ 1.5d2 

wp= b+ 2,/m = b+3.606d 

when d = 1.19 ft., AR2’3 = 7.35 which is 

close to the desired value of 7.38. Therefore 

for a normal depth of d = 1.19 ft., A = 8.07 

0.2 x 49 ft.2, v = 8.07 = 1.21 feet per second, h, = 

V2 1.212 

- = __ = 0.02 ft. 

2g 64.4 

E=d+h,= 1.21 ft.andQT9.8cfs 

The normal depth, d, could also have been 

determined by using table 2-5. 

(5) Determine the control notch 

dimensions using the procedure in 

subchapter II1 G, Control and Pipe Inlets. 

Assumed d2, I .5d2, b, db, A = db+l .5d2, 3.606d, 

d, ft. sq. ft. y. ft. ft. 

wp = b+3,6O6d, R x L% 

sq. ft. sq. ft. ft. ft. wp’ R213 AR213 

ft 

- ~- 

1.19 1.415 2.12 5.0 5.95 8.07 4.29 9.29 0.868 0.910 7.35 

1.2 1.44 2.16 5.0 6.0 8.16 4.33 9.33 0.875 0.920 7.51 
I 

100 SMALL CANAL STRUCTURES 

P = 20 inches T = d, = 2.81 feet 

s = 0.50 makeT= 2 ft. loin. 

N = P+2ST 

= 4 ft. 6 in. 

(6) Determine inlet box inside width. 

Minimum width = pipe dia. + 6 inches 

= (3 ft. 6 in.) 

+ 6 inches 

= 4 ft. 0 in. 

or 

Minimum width = N+6 inches 

= (4 ft. 6 in.) 

+ 6 inches 

= 5 ft. 0 in. 

Use width = 5 ft. 0 in. 

(7) Determine El. top of notch and 

sidewalls = El. A + T = 5406.00 + 2.83 ft. = 

5408.83. 

(8) Determine El. D figure 3-39 (invert of 

box) = El. C of figure 2-31 = El. top of 

sidewalls - R = 5408.83 - 4.75 = 5404.08. 

(9) Determine vertical distance F shown 

on figure 2-28 = Energy El. at Sta. A - 

Energy El. at Sta. H = 5408.87 - 5394.87 = 

14 ft. 

(10) Determine El. D - Refer to figure 

2-28. -Use the procedure associated with the 

above figure and hydraulic tables that may 

be found in different handbooks toLompute 

the cross-sectional area (A, ) and Y, for a 

pipe flowing partially full. 

d, 

Assume D = 0.20. Then from hydraulic 

tables [6] or [ 71 for area of pipe flowing 

partially full: 

C = 0.1 118 

A, = CxD2 =0.1118x3.5* 

= 1.37 ft.* 

d, = 0.20 x D = 0.20 x 3.50 = 0.70 ft. 

From hydraulic tables [6] for $ = 0.20, 

compute U, for pipe flowing partially full: 

C = 0.082 

Y1 = C x D = 0.082 x 3.5 = 0.287 ft. 

For full pipe: 

AZ = 9.62 ft.’ 

v, = & = 5.09 f.p.s., 

h “2 = 0.40 ft., also = h, 

P 

Now, following the procedure outlined with 

figure 2-28, 

- d 2 = 49 (35.8 5.09) + 9.62 x 32.2 g 0.287 

. 

+3.5 

2 

= 4.86 + 0.04 + 1.75 = 6.65 ft. 

F = d, + hvl - d2 - h, = 0.7 + 19.9 

- 6.65 - 0.40 = lT.55 ft. 

This is not compatible with the actual drop 

of 14.00 feet. 

d, 

Try D = 0.195. Then from hydraulic 

tables [6] or [ 71 for area of pipe flowing 

partially full. 

c = 0.1079 

A, = C x D2 = 0.1079 x 3.52 = 1.32 ft.2 

d, = 0.195 x 3.5 = 0.68 ft. 

V, = s = 37.2 f.p.s. 

h =k 37 22 = 

“1 64.4 21.52 ft. 

From hydraulic tables [ 61 for $ = 0.195, 

compute Y, for pipe partially full: 

C = 0.08 

P, =CxD 

P, = 0.08 x 3.5 = 0.28 ft. 
CONVEYANCE STRUCTURES 

For full pipe: 

A, = 9.62 ft.’ 

v, = 5.09 f.p.s., 

‘1” 2 = 0.40 ft., also = hv 

P 

+3.5 

2 

= 5.07 + 0.04 + 1.75 = 6.86 ft. 

F=di +h,r -d, -hv =0.68+21.52 

- 6.86 - 0.40 = 14p.94 ft. 

The $ ratio of 0.20 produces a computed F 

value closer to actual (14 ft.) so use this 

ratio and dz = 6.65 ft. to get El. D. 

101 

El. D = Energy El. at Sta. H - (d2 + hv + 

P 

0.1 d2 ) where 0.1 dz is a factor of safety. El. 

D = 5394.87 - 6.65 - 0.40 - 0.67 = 

5387.15 Use El. D = 5387.00. 

The other portions of the pipe drop may 

be designed as explained in the narrative. 

The designer may use figures 3-38 and 3-39 

for design of the inlet structures. 

The entire pipe profile may be extracted 

from table 2-4 which is for use with figure 

2-30. Difference in elevations and distances 

that correspond to a discharge of 49 cfs, a 

pipe diameter of 42 inches, and an F value 

of 14.24 feet are taken from this table. 

There is no tabulation for F = 14 feet, 

therefore use the next greater value which is 

14.24 feet. By using these tables El. D = 

NWS El. in the canal at the upstream end of 

the drop minus R and minus h2 = 5408.81 - 

4.75 - 17.41 = 5386.65 The first solution 

was El. D = 5387.15 which is 0.5 foot 

higher. Either solution is considered 

satisfactory. 

F. CHUTES 

D. L. WINSETT’ 

2-33. Purpose and Description. -Chutes are 

used to convey water from a higher elevation 

to a lower elevation. A chute structure may 

consist of an inlet, a chute section, an energy 

dissipator, and an outlet transition. Figure 2-33 

shows the relationship of the different parts of 

the structure. The chute section may be pipe as 

in a pipe chute or an open section as in an open 

channel chute. Chutes are similar to drops 

except that they carry the water over longer 

distances, over flatter slopes, and through 

greater changes in grade. Figure 2-34 shows an 

open channel chute on a steep slope. Figures 

2-35 and 2-36 show stilling pools and outlets at 

the lower ends of chute structures. 

The inlet portion of the structure transitions 

the flow from the channel upstream of the 

structure to the chute section. The inlet should 

provide a control to prevent racing and 

4Civil Engineer, Hydraulic Structures Branch, Bureau of 

Reclamation. 

scouring in the channel. Control is achieved by 

combining a check, a weir, or a control notch 

with the inlet. The inlet used should be 

symmetrical about the centerline of the chute, 

it should allow the passage of the full capacity 

of the upstream channel into the chute with 

normal water surface upstream and where 

desirable, it should allow the channel upstream 

to be drained when operations are suspended. 

It should have cutoffs, as required, to provide a 

sufficient length of percolation path as 

computed by Lane’s weighted-creep method. 

Head losses through the inlet may be neglected 

provided they are small enough that they do 

not significantly affect the end result. 

Otherwise the losses through the inlet should 

be computed and used in the determination of 

the energy level at the beginning of the chute 

section. If the bottom grade of the inlet is flat, 

it may be assumed that critical flow occurs 

where the flat grade of the inlet portion meets 

the steeper grade of the chute section. If the 
102 SMALL CANAL STRUCTURES 
CONVEYANCE STRUCTURES 103

Figure 2-35. Terminal wasteway with a rectangular

inclined drop into a stilling pool. p 343-529-112 NA

Figure 2-34. Rectangular concrete chute on a steep

slope. p 482-417-908

Figure 2-36. Stilling pool and outlet portions of a

spillway structure. Control built into the stilling pool

maintains tailwater for the hydraulic jump. P-833-128- 70

outlet must be controlled. If a concrete outlet

transition is provided and there is no

downstream control of flow in the channel, the

transition may be used to provide backwater

by raising the floor of the transition at the

cutoff as 5hown on figure 2-33. Tailwater may

also be provided by building a control into the

outlet transition (fig. 2-36). Head loss in the

outlet transition is neglected.

slope of the inlet portion is made steep enough

to support a velocity greater than the critical

velocity, this velocity and its water depth

should be computed and used to determine the

energy gradient at the beginning of the chute

section.

The chute section, either pipe or open

channel, generally follows the original ground

surface and connects to an energy dissipator at

the lower end. Most fluid mechanics textbooks

discuss the behavior of water on steep slopes

and in hydraulic jumps and derive the

equations used to determine the characteristics

of flow under these conditions. Some of the

solutions are obtained through trial and error.

The use of a computer and programs similar to

the one presented in appendix C makes these

solutions less tedious.

Stilling pools or baffled outlets are used as

energy dissipators on chute structures. Baffled

outlets are discussed in chapter VI [ 8] .

An outlet transition is used when it is

necessary to transition the flow between the

energy dissipator and the downstream channel.

If it is necessary to provide tailwater for the

energy dissipator, the water surface at the
104 SMALL CANAL STRUCTURES 

I. Open Channel Chute 

2-34. Design Considerations. -(a) Manning’s 

Coefjicient of’ Roughness (n). -In computing 

characteristics of flow in a chute structure, 

conservative values of n are used. When 

computing wall heights in a concrete chute, an 

n of 0.0 14 is assumed. In computing energy 

values in a concrete chute, n is assumed to be 

0.010. 

(b) Transitions. -Transitions in an open 

channel chute should be designed to prevent 

the formation of waves. An abrupt change in 

section, either a convergence or a divergence 

may set up waves that can be troublesome as 

they travel through the chute section and the 

energy dissipator [9]. To avoid the formation 

of waves, the cotangent of the deflection angle 

of the water surface in developed plan of each 

side of a chute transition should not be less 

than 3.375 times the Froude number(F). This 

restriction on deflection angles should apply to 

any change in section made in the inlet, the 

chute section, or in the stilling pool. If this 

restriction does not control the angle of 

deflection, the maximum deflection angle in 

the water surface in the inlet transition may be 

about 30’. The angle of the water surface with 

the centerline in the outlet transition may be 

about 25’ maximum. 

The maximum angle of deflection is 

computed as follows: 

Cotangent = = 3.375 x F (1) 

where : 

(2) 

The mean of the values of F at the 

beginning and end of the transition 

may be used. 

d = water depth normal to the floor of 

the chute. Using 

d= Area of the section 

Top width of the section 

allows for various shapes of section, 

g = acceleration of gravity, 

g = 32.2 ft./set.’ 

K = an acceleration factor as determined 

below: 

With the floor of the transition in a 

plane : 

K=O 

With the floor of the transition on a 

circular curve: 

K= ‘* 

gR cos 0 (3) 

With the floor of the transition on a 

parabolic curve: 

(tan 8 

K= 

L - tan0.)2h, cos* B0 

LT 

(4) 

The Bureau of Reclamation limits the 

value of K to 0.5 maximum to insure 

positive pressure on the floor. 

In (3) and (4): 

h, = velocity head at the origin of 

the trajectory, 

LT = length of trajectory, 

R = radius of curvature of the 

floor, 

V = velocity at the point 

being considered, 

0 = slope angle of the flocr at 

the point being considered, 

0” = slope angle of the floor at 

the beginning of the trajectory, 

and 

8, = slope angle of the floor at 

the end of the trajectory. 

The flare angle and the widths for several 

points along the transition may be computed 

and plotted. A chord which approximates the 

theoretical curve can be drawn to determine 

the flare to be used. Limiting the angle of flare 

in an inlet transition minimizes the possibility 

of separation and pulsating flow being initiated 

in that part of the structure. Unsymmetrical 
CONVEYANCE STRUCTURES 

inlet transitions and changes in alinement 

immediately upstream of the structure are to 

be avoided because they may set up cross 

waves or transverse flow that will continue in 

the chute section. 

(c) Chute Section. -The usual section for an 

open channel chute is rectangular but the flow 

characteristics of other shapes should be 

considered where wave suppression is an 

important part of the design. Economics and 

ease of construction are always considered in 

choosing a section. When it is necessary to 

increase the resistance of the chute section to 

sliding, cutoffs are used to key the structure 

into the foundation. 

For chutes less than about 30 feet long, 

friction in the chute may be neglected. 

Bernoulli’s equation is used to compute the 

flow variables at the bottom of the chute. The 

equation: 

d, +hV1 +Z=d, +hVz (5) 

is solved by trial. The distance Z is the change 

in elevation in the chute floor. For chutes 

longer than 30 feet, friction losses are included 

and the equation becomes: 

The 

and 

the 

d, + h,, + Z = d2 + hvz + h, (6) 

quantity h, is the friction loss in the reach 

is equal to the average friction slope s, in 

reach times the length of the reach L. 

Manning’s n is assumed to be 0.010. The 

friction slope, sf, at a point in the chute section 

is computed as: 

s = n2 V2 

f 2.2R4’3 

R = hydraulic radius of the section. 

In equations (5) and (6): 

d, = Depth at the upstream end of 

the reach, 

h “1 = Velocity head at the upstream 

end of the reach, 

d2 = Depth at the downstream end of 

the reach, and 

105 

h 

“2 

= Velocity head at the downstream 

end of the reach. 

Using either equation (5) or (6), dz is assumed 

and the energy levels are computed and 

compared. Additional trials are made until the 

two energy levels balance. 

Another form of the equation in which 

friction is considered is: 

L= 

Cd, + hvl > - (6 + hV2 ) 

s, - s (7) 

where: 

s, = average friction slope 

s = slope in channel floor. 

In using equation (7) a stepwise procedure is 

used in which small changes in energy are 

assumed and the corresponding change in 

length is computed. This procedure is repeated 

until the total of the increments of length is 

equal to the length of the reach of chute being 

considered. The smaller the increment of 

length is, the greater the accuracy will be. 

The height of the walls in the open channel 

chute section should be equal to the maximum 

depth computed in the section plus a freeboard 

allowance or to 0.4 times the critical depth in 

the chute section plus freeboard, whichever is 

greater. The recommended minimum freeboard 

for open channel chute sections (capacity 100 

cfs or less) is 12 inches. Depth and freeboard 

are measured normal to the floor of the chute 

set tion. 

At velocities greater than about 30 feet per 

second, water may take on additional bulk due 

to air being entrained by the water. The 

recommended freeboard allowance for chute 

walls will result in a wall of sufficient height to 

contain this additional bulk. 

(d) Trujectory. -When the energy dissipator 

is a stilling pool, a short steep section should 

connect the trajectory with the stilling pool. 

The slope of this steep section should be 

between 1.5 to 1 and 3 to 1 with a slope of 2 

to 1 preferred. Flatter slopes may be used in 

special cases but slopes flatter than 6 to 1 

should not be used. A vertical curve is required 

between the chute section and the steep slope 

section. A parabolic curve will result in a 
106 

constant value of K over the length of the 

curve and is generally used. A parabolic 

trajectory may be determined from the 

following equation: 

SMALL CANAL STRUCTURES 

energy is dissipated in the resulting turbulence. 

The stilling pool is proportioned to contain the 

jump. For a stilling pool to operate properly 

the Froude number 

c 

VI F = ~ 

di& > 

where the 

water enters the stilling pool should be 

between 4.5 and 15. Special studies or model 

testing are required for structures with Froude 

numbers outside this range. If the Froude 

number is less than about 4.5 a stable hydraulic 

jump may not occur. If the Froude number is 

greater than about 10 a stilling pool may not 

be the best choice of energy dissipator. Stilling 

pools require tailwater to force the jump to 

occur where the turbulence can be contained. 

Stilling pools usually have a rectangular cross 

section, parallel walls, and a level floor. The 

following equations to determine pool width 

and water depth after the jump apply to this 

type of pool. Flared pools are sometimes used 

and require special consideration. For 

discharges up to 100 cfs, the equation: 

Y=Xtan0, + 

(tan BL ~ tan 0,) X2 

2LT 

(6) 

where: 

X = Horizontal distance from the 

origin to a point on the 

trajectory, 

Y = Vertical distance from the origin 

to point X on the trajectory, 

LT = Horizontal length from the 

origin to the end of the 

trajectory, 

0, = The angle of inclination of the 

chute channel at the origin of 

the trajectory, and 

Ed = The angle of inclination of the 

chute channel at the end of 

the trajectory. 

A length of trajectory (LT) can be selected 

which, when substituted into equation (4), will 

result in a value of K of 0.5 or less. The 

length L, is then used in the computation of Y 

using equation (8). 

The trajectory should end at or upstream 

from the intersection of the chute section walls 

with the stilling pool walls. A long-radius curve 

slightly flatter than the computed trajectory 

may be used. If practicable the trajectory 

should coincide with any transition required. 

The variables of flow on the trajectory and 

the steep section are computed in the same 

way as those in the chute section. An elevation 

for the floor of the stilling pool is assumed and 

the energy gradient at the junction of the chute 

section and the pool floor is computed. The 

flow variables at this point are used as the 

variables ahead of the hydraulic jump in the 

design of the stilling pool. 

(e) Stilling Pool. -In a stilling pool the water 

flows down the steep slope section at a velocity 

greater than the critical velocity. The abrupt 

change in slope where the flat grade of the 

stilling pool floor meets the steep slope section 

forces the water into a hydraulic jump and 

34a 

b=Q+350 

where: 

b = width of pool in feet, and 

Q = discharge in cfs. 

may be used to determine the width of a pool 

for the initial calculations. The water depth 

after the hydraulic jump may be computed 

from the formula: 

where 

d, = Depth before the jump, 

V, = Velocity before the jump, 

d2 = Depth after the jump, and 

g = Acceleration of gravity 

For structures where the vertical drop is less 

than 15 feet the water depth after the jump 

may be obtained from figure 2-37. The 

elevation of the energy gradient after the 
CONVEYANCE STRUCTURES 107 

16.74 ,189 [ 16.W] .I88 ( 16.941 .187 -- b.04; ,187 [ 17.13 ~ .l86~17,23i - .I85 117.331 --*-- ,185 ~L7~4_117.5Z’ --. 183 117.62 ( ,183 

0.5 I 

yq 

,680 

,425 

351 L 

,308 

278 L 

.257 

,240 

226 

0 

- 

j2/d, d l/d, 

I .o I .c 

T&G 

-- 

6.18 ,356 

7.66’ ,311 

7I5TzY 

-C- 

+%% ---t--m 

9.64’ ,269 

--- 

10.25 ( 259 

11.44’,241 

13.34’ 

14.41 

-i12.57 ,227 

13.66) ,215 

r- 

‘1.72 ,205 

1574: 

8 

9 

lo 

15.44 

16.45’ 

.I78 

,173 

167 

- 

+g+ 

20.25 

,176 

,171 

‘7.Q ,182 

18.67 ’ .I’6 

19.61 ,170 

19 24.06, 149 24.14 / ,149 24.23 ,148 24.31 1 ,148 24.40’ .I48 24.49’ .I47 24.57 ’ .I47 24.66 1 I47 24.74, ,146 24.83 .146 

20 24.91 e 24.99 1 ,145 25.08, ,145 25.16 1 ,145 25.25 ,145 25.33 1 ,144 25.42! 144 25.50, ,144 25.58’ ,143 25.67, ,143 

21 25.75 ,143 25.83) ,142 25.92 ,142 26.001 ,142 26.06 ,141 26.17: ,141 26.251 141 26.33 ,141 26.421 .I40 26.50’ .I40 

22 

23 

26.58 ,140 126.66 ( ,139 [ 2675’ ,139 12683, ,139 26.91 .I39 [ 26.99, ,138 

27.40 ,137 127.481 .I37 127.57 ,136 127.65’ ,136 12T.73 136 127.81 .I36 

24 

-i-T 

- 

26 

27 

28 

- 

,134 

--c L 

.I29 

127 1 

,125 

133 

- 

--- 

28.781 .I33 

29 58 1 ,130 

31.93j 

-- 

+ 

J3J 

,129 

127 L 

,125 

.I30 

,128 

,126 

,124 

,128 

,126 

.I24 

29 32.16 ~ ,123 32.23 ,123 32.31, .I23 32.391 ,123 32.46, ,123 32.54’ ,122 32.62, ,122 32691 ,122 32.77 ,122 32.851 ,122 

30 32.92, ,121 33CC .12’ 33.08 ~. ~~ .I21 33.151 ,121 33.23 ,121 33.31! ,121 33.381 .I20 

--- 

3; 33.68 .lZC 33.76 ,119 33.84 ,119 33.91(.119 33.9919 34061.116 34.14 ,119 

33.461 ,120 33.53 c-----c- ,120 33.61 ,120 

34.21 ,118 34,29,.ll8 3436 II8 

32 34.441.118 34.51 ,118 34.59 ,118 34.66;.117 3474 .ll~7 & 348TLz .~- _~ -~A 3giJ!7 3i&$_117_ c 35.04’.117 --- c-- 35nll6 -~- 

33 35.19, ,,I6 35.26i ,116 35.34 ,116 35.41~.116 35.49 .I16 

3+.115 36.2;L.E 

35.56’ II: 35.63’.115 35.71 ,115 35.78 115 35.86u5 

+--.-- ---- 

34 35.93 .I15 36.08 ,114 36.15 114 36s.4 --+-- 36.37; ,114 36,45’,li4 36.521 ,113 36.59, .ll-? 

37.G 36.8,113 3262 36.89 .I13 ,111 36.96769 ,1121 ~7~.lll 37.03 2 37.1184 1.112 ,111 37.91 37.lQ.112 i ,111 37.98 .I// 12 37.33805 , ,110 .I 12~ 

37 38.13 I.110 38X .I10 38.271 .I10 38.34; .I10 38.42 ,110 38.4<.n0 38.56( .I09 38.63, .I09 38.707,251 ,109 38’81 ,109 

----A---- 

38 3885 1 .I09 38.92 .I09 38.k ,109 39.06! .I09 39.14 I.108 39.21, ,108 39.28, ,108 39.351 .I08 39.42 ,108 39.49 .I08 

39 39.561 ,108 39.64 ,107 39.71 ,107 39.781 ,107 39.851 ,107 39.92’.107 39.99i ,107 40061 ,107 40.14 ,107 40.2 ,106 

40 40.281 .I06 40.35 ,106 40.42 ,106 40.49 .I06 40.56, .I06 40.63 ,106 40.70 ,106 40.77 ,105 40.84 ,105 40.91 ,105 

Relation of erergy Icss, critical depth ord depth before and after lump, for hydraulic ~urrps in rectargular 

channels wth level ilocr 

i 

Energy level ot upstream 

H=Difference in energy levels at upstream 

end of Jump 

El c, ~~- 

and downstreom ends of jump Woter surf=- _ - ---f-/Energy level ot A 

d,=Crttlcol depth for flow consldered. 

based on pool wdth dc=w 

d,=Depth at upst:eom erd of jump 

d,=Deptb at downstream end of lump 

K=d,-d, 

El C,= El C,-[d, + h,,)= El C,-(d, + h, 

2+H, 

p-‘ms 

Figure Z-37. Energy loss in hydraulic jump. 103-D-1274 
108 SMALL CANAL STRUCTURES 

should be set to provide tailwater for the 

hydraulic jump. 

hydraulic jump should be balanced by the 

energy gradient in the channel downstream of 

the structure. If the gradients do not balance, a 

new elevation for the pool floor or a new pool 

width should be assumed and the energy levels 

recomputed. Trials are repeated until a balance 

is obtained. 

The elevations selected should be reviewed 

to insure that the stilling pool will operate 

effectively at partial flow. Designs are normally 

checked at one-third the design flow or curves 

may be drawn as on figure 2-38. If the review 

indicates it to be necessary, the pool floor 

should be lowered or a different pool width 

assumed and the design procedure repeated. 

The minimum pool length (LP on fig. 2-33) 

for structures used on canals is normally 4 

times d,. For structures on wasteways or 

drains where the flow will be intermittent and 

of short duration the minimum length may be 

about 3 times dz . The recommended freeboard 

for stilling pools may be determined from 

figure 2-33. Freeboard is measured above the 

maximum downstream energy gradient. 

When the stilling pool discharges 

intermittently or discharges into a natural or 

other uncontrolled channel, a control should 

be built into the outlet of the stilling pool to 

provide the necessary tailwater. The critical 

depth at the control section should be used to 

determine the downstream energy gradient. 

When the stilling pool discharges into a 

controlled channel, the depth in the channel 

should be computed with the n value of the 

channel reduced by 20 percent and this depth 

used to determine the downstream energy 

gradient. If a flared pool is used, the deflection 

angle of the sidewalls should not exceed the 

angle permitted in the chute walls. Weep holes 

with gravel pockets (fig. 2-39) may be used to 

relieve hydrostatic pressure on the floor and 

walls of the stilling pool and outlet transition. 

Chute and floor blocks are provided to break 

up jet flow and to stabilize the hydraulic jump. 

The location, spacing, and details of the blocks 

are shown on figure 2-33. 

If a concrete outlet transition is not 

provided, a solid end sill is required (fig. 2-40). 

The upstream side of the sill should have a 2 to 

1 slope and the downstream side should be 

vertical. The elevation of the top of the sill 

A stilling pool and outlet transition built to 

the d imensions recommended may not 

completely contain the spray caused by the 

turbulent water but the structure should 

contain enough of the turbulence to prevent 

erosion damage downstream of the structure. 

(f) Wuve Formutiw-Waves in a chute 

structure are objectionable because they may 

overtop the chute walls and they cause surging 

in the energy dissipator. A stilling pool would 

not be an effective energy dissipator with this 

type of flow because a stable hydraulic jump 

could not form (fig. 2-41). An unstable 

pulsating type of flow known as slug flow or 

roll waves may develop in long, steep chute 

structures (figs. 2-42 and 2-43). These waves 

generally form in chute channels that are 

longer than about 200 feet and have bottom 

grade slopes flatter than about 20’ [91. The 

maximum wave height that can be expected is 

twice the normal depth for the slope and the 

maximum momentary slug flow capacity is 

twice the normal capacity. Transverse flow or 

cross waves may also develop in a chute. These 

waves are caused by: 

(1) Abrupt transitions from one channel 

section to another, 

(2) Unsymmetrical structures, and 

(3) Curves or angles in the alinemcnt of 

the chute. 

The probability of these waves being generated 

in the structure may be reduced by following 

the recommendations concerning deflection 

angles and symmetry made in the discussions 

pertaining to transitions and by avoiding 

changes in direction in the structure. 

Some chute sections are more likely to 

sustain waves than others. Shallow dished 

sections appear to be particularly susceptible to 

transverse flow while deep, narrow sections 

resist both transverse and slug flow. Chute 

sections that theoretically should prevent the 

formation of waves have been developed 

[91[111. A theoretically waveless chute 

section is shown on figure 2-44. 
CONVEYANCE STRUCTURES 

L I 

-w-v-- I 

Kub!saa - cI / 

W 

(3 

oz 

a 

I 

0 

v) 

0 
110 SMALL CANAL STRUCTURES 

Provide sultoble onchoroqe 

to secwe pipe to concrete. 

Locate to clear reinforcement 

OutsIde face of wall 

I =-. 1 /’ \ --- unpoct plostlc pipe 

\ 2’fJm rm,d.hmh 

B 

Conical. copped, 

or p/upped 

ends. 

Outstde face of well. 

Pipe coupled here ot 

rod/o/ zone surfaces 

DETAIL OF WEEP PIPE 

iALTERNATIVES) 

12 I 

(PLAN 

oorse oqqreqote 

SECTION A-A 

L7;434- 

SECTION B- B 

GRADATION DF FILTER MATERIALS 

PERCENT tGY “EIGNTI RETAINED ON STANDARD SEIVE 

NOTE 

The confiqurotlon of the falter envelope moy be chonqed to 

wt constructfon, provided thot o minimum rodiol 

thxkness of 6’1s mointolned for each zone 

Figure 2-39. Weep hole with gravel pocket. 103-D-1276 
CONVEYANCE STRUCTURES

Figure 2-40. Stilling pool with end sill. lO3-D-1277

Figures 2-45 and 2-46 have been developed

to predict the possibility of slug flow occurring

in a chu te. The use of the figures requires the

following operations:

( I) Divide the chu te in to a null ber of

reaches as shown on figure 2-47. Point I

should be at the beginning of the chute

section.

(2) Using equation (6) or (7), with Q

equal to 0.2, 0.5, and 1.0 times design Q,

compute the water depth and energy levels

at the points along the chute section that are

'to be checked for slugging. Use Manning's n

= 0.010.

(3) Determine sL for the point to be

checked (fig. 2-47).

(4) At the points to be considered:

a. Compute the Vedernikov number (y)

10]

2 v=-x

-3

b v -xwp ygd cas f}

b. Compute the square of the Montuori

number CM) [ 11] .

y2 (11)

~

b = bottom width of the chute

section

d = average water depth in the chute

section:

Figure 2-41. Surging in a stilling pool caused by

unstable flow in a chute structure. P222-117-36223

M2 -

--gsLcos ()

In equations ( 10) and ( 11 )
SMALL CANAL STRUCTURES 

Figure 2-42. Pulsating flow in steep chute. Flow is 

57 cfs. P222-117-36208D 

g = acceleration of gravity. 

L = length of reach under 

consideration, 

s = average slope of the energy 

gradient. 

s = tan 0. 

V = velocity, 

wp = wetted perimeter of the section. 

and 

0 = angle of inclination of the 

energy gradient. 

(5) Plot the computed values on figure 

3-45. If the plotted points fall within the 

slug flow zone, intermediate points may be 

checked to determine the point at which the 

waves begin to form. 

(6) Compute the shape factor for the 

chute section. 

d 

Figure Z-43. Unstable flow at shallow depth. H-686-55D 

(7) Plot the computed value of Gp 

against the slope of the energy gradient, s, 

on figure 2-46. 

Waves are not likely to be generated in the 

structure, unless the plotted data falls within 

the slugging zone on both figures 2-45 and 

2-46. 

If the charts indicate that slug flow will 

occur, the design may be modified to reduce 

the probability of waves being generated or the 

structure may be adapted to accommodate the 

Normal water surface 

Figure 2-44. Theoretical waveless chute section. Triangular 

wP shape prevents both cross waves and slug flow. 103-D-1 278 

112 SMALL CANAL STRUCTURES
CONVEYANCE STRUCTURES 

surging flow that does occur. Possible design 

changes include: 

(1) Divide the flow in the chute section 

with a wall down the center of the chute. 

(2) Change the shape of the section. The 

theoretical waveless shapes could be 

considered. 

(3) Reduce the length of the chute. A 

series of shorter chutes or drops could be 

considered. 

(4) Steepen the chute. 

(5) Replace the open channel chute 

section with pipe. 

6 

>I 

2 

Zone of slug flow 

J--J-J- I I 

O 0.2 0.4 0.6 0.8 

Montuori number’ (M2) 

113 

If these design changes are impractical, the 

chute section might be adapted to 

accommodate surging flow by: 

(1) Increasing the freeboard of the chute 

walls. 

(2) Providing a cover for the chute 

section to contain the waves, or 

(3) Protecting the backfill around the 

chute section with riprap or paving. 

Adaptations to the stilling pool could 

include : 

(1) Designing the pool to provide for the 

momentary surge discharge. This would 

Zone of no slug flow 

Figure 245. Criteria for slug flow. 103-D-1279 

I. .O 
114 SMALL CANAL STRUCTURES 

provide a longer pool and higher pool walls 

to contain the surge. 

(2) Provide additional riprap to protect 

the channel downstream and the backfill 

around the pool. 

(3) Provide a surge suppressing device in 

the stilling pool. A baffle or weir wall in the 

pool could prevent flow from sweeping 

through the pool and outlet transition (fig. 

2-48). Weir walls could also provide tailwater 

0.2 

Q 

5 0.1 

-0 

OS 

( 

,_ 

:.c 

- 

i 

I 

I 

I 

I 

-I 

I 

I 

-t 

I 

I 

-I 

I 

I 

1 1 

to submerge the surges. Rafts or other 

floating wave dampeners could be used. 

(4) An energy dissipator less sensitive to 

surging could be used. 

The study of wave action in chute structures 

is based largely on empirical data. If a serious 

wave problem in a structure is indicated, 

further studies should be undertaken to verify 

the extent of the problem and the effectiveness 

of the proposed solutions. 

Zone of no slug flow 

I 

i 

Corrugated metal 

chutes 

w- ----------a 

Concrete chutes 

Zone of slug flow 

0.1 0.2 

SLOPE s=TAN 0 

0.3 

Figure 2-46. Shape and slope criteria for slug flow. 103-D-1280 

I 

- 

I 

I 

I 

I 

I 

-7 

I 

I 

I 

I 

-I 

I 

I 

I 

0.4 
CONVEYANCE STRUCTURES

s = Slope of energy gradient = tan -9-

Figure 2-47. Invert, water surface, and energy profiles of a chute structure. IO3-D-1281

2-35. Design Procedure. -

( I) Select and design the type of inlet to be

used.

(2) Determine the energy gradient at the

beginning of the chute section.

(3) Compute the variables of flow down the

chute section.

( 4) Design the trajectory and the steep

portion of the chu te section.

(5) Assume an elevation for the floor of the

stilling pool and compute the characteristics of

flow upstream of the hydraulic jump.

Determine d2 and the energy gradient after

the hydraulic jump.

(6) Determine the energy gradient in the

channel downstream and compare to the

energy gradient after the jump.

(7) It may be necessary to assume a new

pool invert elevation and to recompute the

above values several times before a check in

energy gradients is obtained.

(8) Review for proper operation at partial

capacity.

(9) Determine the length of the pool and

the height of the pool walls.

( 10) Design the chu te and floor blocks and

the end sill or outlet transition as required.

( 11) Check the possibility of waves

developing on the structure.

Figure 2-48. Wave sweeping through the outlet

transition of a stilling pool. Flow is 140 cfs.

P222-117-36227
116 SMALL CANAL STRUCTURES 

(12) Provide protection in the chamlel 

downstream as required. 

2-36. Design Example.-Design an open 

channel chute that will convey 35 cfs over the 

profile shown on figure 2-49. Use a stilling pool 

to dissipate excess energy at the downstream 

end of the chute. The structure is to be used on 

a canal with a section as shown on the drawing. 

Inlet Design: 

The inlet is designed to provide a control for 

the ch;jnnel upstream. Channel properties at 

point @ taken from figure 2-49 are: 

Q = 35 cfs 

b = 6.0 ft. 

d = 2.40 ft. 

n = 0.025 

s = 0.00035 ft./ft., and 

s:s= 1.5 to 1 

If channel properties are not given, tables 2-5 

and 2-6 may be used to compute flow 

properties. 

The elevation of the energy gradient 

at 0 is computed as follows: 

A, = 23.04 ft.’ 

V, = 1.52 f.p.s. 

11” 1 = 0.04 ft. 

E, =dl +h,, = 2.40+ 0.04 = 2.44 ft. 

The elevation of the energy gradient in the 

channel upstream (point 0 ) equals the invert 

elevation + E, or 3703.18 + 2.44 = 3705.62. 

Assume that critical depth will occur 

at @ With a discharge of 35 cfs, a chute 

section width of 3 feet is a reasonable choice. 

The elevation of the invert at 0 will be: 

d, = $= dg= 1.62ft. 

A, = 4.86 ft.2 

V, = 7.20 ft. 

h, . = 0.80 ft. 

I?: = 0.78 ft. 

2 

s, = 

7.20 x 0.010 

1.486 x 0.847 > = o’oo33’ 

E, = d, + h “c = 1.62 + 0.80 = 2.42 ft. 

Losses in the inlet transition are (1) a 

convergence loss which is assumed to be 0.2 

times the change in velocity head between the 

beginning of the transition and the end of the 

transition and (2) a friction loss equal to the 

average friction slope in the inlet times the 

length of the inlet. 

Inlet losses: 

Convergence loss = 0.2 x (0.80 - 0.04) 

= 0.15 ft. 

With a transition 10.0 feet long the 

friction loss will be: 

0.00035 + 0.0033 x I()= 0.02 foot 

2 

To balance the energy in the canal 

upstream, the invert of the inlet at 0 must 

equal: 

3705.62 - E, - Transition losses 

or 

3705.62 ~ 2.42 - 0.15 - 0.02 = 3703.03 

An elevation of 3703.00 at 0 will provide 

a control for flow into the chute channel. 

Determine the maximum angle of deflection 

of the inlet side walls: 

From equation (l), cotangent a = 3.375 x 

F. 

F= V 

[(I-K)gl d case 

K = 3, cos 0 = 0.99984 

F, = 

2.43 

d32.2 x 2.40 x 0.99984 

= 0.276 

F, = 

7.2 

~‘32.2 x 1.62 x 0.99984 

= 1.00 

For n = 0.0 10: 
4 

117 

C.OI\IVEYANCE -- STRUCTURES 

z 

0 
118 SMALL CANAL STRUCTURES 

The normal depth on a slope of 0.105 10 

is 0.48 foot. This depth is reached 

;: 8 and the energy levels 

and 0 balance. Between 

points @ and @ the flow is uniform at a 

depth of 0.48 foot. 

For flow between @ and @ : 

A normal depth of 0.60 foot is reached at 

point 0 and the flow 

between 0 and @ is uniform flow at a 

depth of 0.60 foot. 

For the water depths that will occur on this 

chute section a minimum wall height of 24 

inches will provide the required 12 inches of 

freeboard. 

The mean value of F = 0.64 

Cotangent a = 3.375 x 0.64 = 2.16 

a = about 25’. 

With a transition 10 feet long the deflection 

angle will be about 8.5O which indicates that 

waves will not be initiated in the inlet. 

Determine the flow in the chute section: 

The flow at 0 is critical flow. Flow 

characteristics in the chute section are 

computed using Bernoulli’s equation (6) to 

balance the energy at various points on the 

chute section. Uniform flow is at a depth of 

0.50 feet on a slope of 0.08163. This denth 

will be reached at @ , 170.0 feet from 0. 

Design the trajectory: 

The energy at 0 will be: 

E, =dr +h,r +Z 

z=sxL=o.o8163x 170 

= 13.88 ft. 

E2 = 1.62 + 0.80 + 13.88 

= 16.30 ft. 

The energy at @ will be: 

E, = dz + hV2 + h, 

h, = friction loss in the reach, 

h, = average friction slope 

in the reach times L, 

h, = s, x L. 

d3 = 0.50 ft. 

A3 = 1.50 ft.2 

V3 = 23.33 f.p.s. 

l&3 = 8.45 ft. 

s3 = 0.08163 

s, = 

0.08163 ; 0.0033 = o.0425 

h, = 0.0425 x 170 = 7.23 ft 

E, = 0.50 + 8.45 + 7.23 

= 16.18 feet 

E3 balances E, for practical 

purposes. 

The flow between 0 and @ is uniform 

flow with the loss in elevation Z equal to the 

friction loss, h,, in the reach. 

For flow between @ and @ : 

Flow characteristics on the trajectory and 

the steep slope section are computed in the 

same way as those on the chute section. 

Computed water depths are shown on figure 

2-49. 

Use a transition 25.0 feet long to flare the 

bottom width from 3 to 5 feet. Flow 

characteristics at the beginning of the 

transition (point @ ) are: 

ds = 0.60 ft. 

As = 1.80 ft.* 

v, = 19.44 f.p.s. 

h 

;;“, 

= 5.86 ft. 

= 0.43 ft., and 

S, = 0.05241 ft./ft. 

At the beginning of the trajectory (point @ ) 

flow properties are: 

d, = 0.44 ft. 

As = 1.78 ft.2 

Vg = 19.66 f.p.s. 

h = 6.00 ft. 

ii = 0.36 ft., and 

S, = 0.0683 ft./ft. 

The value of K used to compute the 

trajectory is limited to 0.5. The minimum 

length of trajectory that will provide a 

satisfactory value for K is obtained using 

equation (4): 
CONVEYANCE STRUCTURES 

L 

T 

= (0.5 - 0.0524) x 2 x 6.00 x 0.99863 

0.5 

119 

L, = 10.72 feet 

Make the trajectory 12.0 feet long. Coordinates 

of points on the trajectory are computed using 

equation (8). 

* Y. 

3 0.33 

6 0.99 

9 1.98 

12 3.31 

At the lower end of the transition and the 

trajectory (point @ ) the characteristics of 

flow will be: 

d 10 = 0.30 ft. 

A,, = 1.50 ft.2 

VI0 = 23.33 f.p.s., 

RIO = 0.27 ft., and 

s,, = 0.14107 

The maximum angle of deflection in the 

sidewalls of the transition is determined from 

equation (1): 

Fs at @ with K = 0.0. 

F, = 

19.44 

J32.2 x 0.60 x 0.99863 

= 4.43 

Fro at @ with K determined from equation 

(4): 

K 

10 

= (0.50-0.052) x 2 x 6.0 x 0.9992 

12 

= 0.45 

F,o = 23.33 

d [(l-0.45) x 32.21 x 0.30 x 0.89441 

= 10.70 

F 

a 

= 4.43 + 10.70 = 7 56 

2 

Cotangent a = 3.375 x 7.56 = 25.52 

a = 2015’ k 

The deflection angle with a transition 

25.0 feet long will be: 

tangent a = & = 0.04 

a = 2O1 j' + 

The deflection angle in the transition 

sidewall is satisfactory. 

Design the Stilling Pool: 

An elevation for the invert of the stilling 

pool must be assumed before the flow 

properties at the bottom of the steep slope 

section can be computed. Assume this 

elevation to be 3642.06. Balancing the energies 

between the end of the trajectory 0 10 and the 

bottom of the steep slope section 0 11 gives 

the following flow properties at the bottom of 

the steep slope section or immediately ahead of 

the hydraulic jump: 

d 11 = 0.26 ft., 

A, 1 = 1.30 fL2 ) 

v,, = 26.92 f.p.s., and 

hv~ I = 11.25 ft. 

The Froude number at this point = 

F= 26.92 

432.2 x 0.26 

= 9.30 

The Froude number is within the range in 

which a stilling pool may be expected to 

operate effectively as an energy dissipator. The 

water depth after the jump dz is computed 

from equation (9): 

d, =d=+~ 

2 

2 x 26.92’ x 0.26 I 0.26” 

32.2 4 

= 3.29 feet 

The flow characteristics after the jump are: 

AZ = 16.45 ft.* 

V, = 2.13 f.p.s. 

h 

i: 

= 0.07 ft. 

= 3.29 + 0.07 = 3.36 ft. 

The elevation of the energy gradient after the 

jump = 3642.06 + 3.36 = 3645.42. This energy 

must be balanced by the energy in the channel 

downstream computed with the n for the 

channel reduced by 20 percent. 
120 

Energy downstream of the structure: 

Q = 35 cfs 

n = 0.025 x 0.80 = 0.020 

b = 6.0 ft. 

d = 2.16 ft. 

A = 19.96 ft.2 

v = 1.75 f.p.s. 

11, = 0.05 ft. 

E = 2.16 + 0.05 = 2.21 ft. 

The minimum elevation of the canal invert 

required to balance the energy after the jump 

is: 

3645.42 - 2.21 = 3643.21 

The invert elevation shown on figure 2-49 is 

3643.73. The energies balance, therefore the 

elevation assumed for the floor of the stilling 

pool is satisfactory. Generally several trials 

with different assumed elevations for the pool 

floor or with different pool widths must be 

made before a check in energy levels is 

obtained. 

The length of the stilling pool should be 

about four times d2 or 4 x 3.29 or 13.16 feet. 

Use a length of 14 feet. From figure 2-33 the 

freeboard allowance for the stilling pool should 

be about 2.0 feet. This freeboard should be 

above the maximum downstream energy level. 

Make the chute walls 6 feet 0 inch high. Chute 

and pool blocks are sized and positioned as 

shown on figure 2-33. 

Design the Outlet Transition: 

When required, a concrete outlet transition 

is used to transition the flow from the stilling 

pool to the downstream channel. In this design 

example an outlet transition is not used. An 

end sill is provided at the end of the stilling 

pool and the elevation at the top of the sill is 

set to provide tailwater for the hydraulic jump. 

Critical energy at the end of the stilling pool is: 

d, = 1.23 ft. 

h “c = 0.50 ft. 

E, = 1.73 ft. 

The minimum height of sill required to 

SMALL CANAL STRUCTURES 

provide a control for the downstream flow 

equals the energy after the jump, Ez, minus the 

critical energy at the end of the pool, E,, or 

3.36 - 1.73 = 1.63 feet. A sill height of 1.67 

feet is used in the design example. 

In parts of the structure where the velocity 

of the water is high the minimum concrete 

cover on the top 

may be increased 

follows: 

Velocity, f.p.s. 

10 

20 

30 

Increase in the minimum 

concrete cover, inches 

0 

0.5 

1 .o 

A transition in the downstream channel and 

layer of reinforcement steel 

according to the velocity as 

protection for the channel, where they are 

required, complete the structure. 

Check for slug flow: 

The possibility of waves forming on the 

structure should be checked at 

points @ , @ , and @ . At @ (Sta. 

1842+00) the invert elevation is 3651.05. A 

check at design discharge will indicate that 

waves will not form on the structure. The 

following check at 0.5 times design discharge 

demonstrates the steps required to check for 

slug flow. 

For Q = 17.5 cfs: 

(1) At point 0 (Sta. 1835+78 with an 

invert elevation of 3703.00) 

d, = 

A, = 3.06 ft.2 

V, = 5.72 f.p.s. 

hvc = 0.51 ft. 

The elevation of the energy gradient 

at 0 is: 

3703.00 + 1.02 + 0.51 = 3704.53. 

(2) At point @ with Q = 17.5 cfs. 

Using equation (6) the flow characteristics 
CONVEYANCE STRUCTURES 

between @ and @ are computed. 

At @ : 

d = 0.38 ft. 

A = 1.14 ft.’ 

v = 15.35 f.p.s. 

h, = 3.66 ft. 

wp = 3.76 ft. 

The elevation of the energy gradient 

at @ = 3651.05 + 0.38 + 3.66 = 3655.09. 

(3) Determine SL (fig. 2-47): 

SL = 3704.53 -~ 3655.09 = 49.44ft. 

(4) Determine L and s: 

L= 1842+00- 1835+78 

= 622 ft. 

s = tan 0 = 4*= 622.0 0.07949 

6’ = about 4’ 33’ 

Cost’ = 0.99685 

(5) Using equation ( 10). compute JJ: 

2 3 15.35 

’ = gxmx\/32.2 x 0.38 x 0.99685 

v_= 2.34 

“Control Inlet 

121 

(6) Using equation (1 I) compute M2 : 

M2 = 1 5.352 

32.2 

= 

x 49.44 x 0.99685 

0.148 

(7) Plotted on figure 2-45, the point falls 

near the slugging zone. 

(8) Check shape and slope parameters: 

d - 0.38 = 0.101 

Fp - 3.76 

s=o.o7949 

(9) Plotted on figure 2-46, the point falls 

near the zone of slug flow. 

( 10) Both charts indicate that waves may 

form on this structure at 0.5 times Q. In this 

example problem with the shallow depths 

involved, slug flow may not be a problem if 

it does occur. If slug flow is indicated where 

the waves would be troublesome, the 

remedies listed in the text should be 

considered. 

2. Pipe Chute 

2-37. Pipe Chute. -In a pipe chute the open 

chute section is replaced by pipe (fig. 2-50). 

Pipe chutes may be used to provide a crossing 

,-Orlgrnal ground surface 

Precast concrete pipe,’ 

Stllllng pool-, 

ProtectIon/ 

Baffled pipe outlet--, i 

Precast concrete pipe-’ 

Protection-’ 

Figure 2.50. Pipe chutes. 103-D-1283 
122 SMALL CANAL STRUCTURES 

or to allow farming or grazing over the 

structure. A pipe structure is largely 

underground and may be desirable from an 

esthetic point of view. Baffled outlets or 

stilling pools are used as energy dissipators. 

Figure 2-5 1 shows a stilling pool at the bottom 

of a pipe chute. The procedure for designing a 

pipe chute is similar to that used in designing 

an open channel chute. The inlet transition 

should be designed to prevent the flow at the 

entrance to the pipe from controlling the flow 

through the structure. Concrete transitions 

between open channels and pipe sections are 

discussed in chapter VII. The pipe is sized to 

allow a maximum full pipe velocity of 12 feet 

per second. Air in a closed conduit can cause 

serious problems and care must be exercised in 

choosing the slopes for the pipe section. The 

pipe slopes selected should prevent a hydraulic 

jump from occurring in the pipe. The Bureau 

of Reclamation requires that for pipe slopes 

steeper than critical the minimum slope should 

be two times the critical slope. The pipe slope 

should not be changed from a steeper slope to 

a flatter slope. If a change to a flatter slope 

must be made, the pipe should be transitioned 

to an open chute channel for a short reach and 

the change in grade made in a section open to 

the atmosphere. 

Flow variables for circular sections flowing 

partly full may be computed using table 2-7. 

For concrete pipe use Manning’s n = 0.010. 
CONVEYANCE STRUCTURES 123 
124 SMALL CANAL STRUCTURES 

Table 2-5.-Uniform flow in trapezoidal channels by Manning’s formula. 103-D-1 255-l 

d/b' On 

Values of b8/3 ~ 

s 112 

z=o L= l/4 z= l/2 z = 314 z= I 7. = l-1/4 z= l-1/2 r'= l-3/4 x=2 x=3 

.02 .00213 .00215 .00216 .00217 .00218 .00219 .00220 .00220 .00221 .00223 

.03 .00414 .00419 .00423 .00426 .00429 .00431 .00433 .00434 .00437 .00443 

.04 .00661 .00670 .00679 .00685 .00690 .00696 .00700 .00?04 .00707 .00722 

.05 .00947 .00964 .00980 .00991 .OlOO .OlOl .0102 .0103 .0103 .0106 

.06 .0127 .0130 .0132 .0134 .0136 .0137 .0138 .0140 .0141 .0145 

.07 .0162 .0166 .0170 .0173 .0176 .0177 .0180 .0182 .0183 .0190 

.08 .0200 .0206 .0211 .0215 .0219 .0222 .0225 .0228 .0231 .0240 

.09 .0240 .0249 .0256 .0262 .0267 .0271 .0275 .0279 .0282 .0296 

.lO .0283 .0294 .0305 .0311 .0318 .0324 .0329 .0334 .0339 .0358 

.ll .0329 .0342 .0354 .0364 .0373 .0380 ,038 7 .0394 .0400 .0424 

.12 .0376 .0393 .0408 .0420 .0431 .0441 .0450 .0458 .0466 .0497 

.13 .0425 .0446 .0464 .0480 .0493 .0505 .0516 .0527 .0537 .0575 

.14 .0476 .0501 .0524 .0542 .0559 .0573 .0587 .0599 .0612 .0659 

.15 .0528 .0559 .0585 .0608 .0628 .0645 .0662 .0677 .0692 .0749 

.16 .0582 .0619 .0650 .0676 .0699 .0720 .0740 .0759 .0776 .0845 

.I7 .0638 .0680 .07lJ .0748 .0775 .0800 .0823 .0845 .0867 ,094 7 

.18 .0695 .0744 .0786 .0822 .0854 .0883 .0910 .0936 .0961 ,105 

.19 .0753 .0809 .0857 .0900 .0936 .09 JO ,100 ,103 ,106 ,117 

.20 .0813 .0875 .0932 .09 79 ,102 .106 ,110 ,113 ,116 ,129 

.21 .0873 .0944 ,101 ,106 .lll .115 ,120 .123 ,127 ,142 

.22 .0935 ,101 ,109 ,115 ,120 .125 .130 .134 .I 39 ,155 

.23 .0997 ,109 ,117 ,124 ,130 ,135 ,141 ,146 ,151 ,169 

.24 ,106 ,116 ,125 ,133 ,139 ,146 ,152 ,157 ,163 ,184 

.25 ,113 ,124 .133 ,142 ,150 ,157 ,163 .l JO ,176 ,199 

.26 ,119 .131 ,142 ,152 .160 .168 ,175 ,182 ,189 ,215 

.2J ,126 .139 ,151 .162 ,171 ,180 ,188 ,195 ,203 ,232 

.28 ,133 ,147 .160 ,172 ,182 ,192 ,201 ,209 .217 ,249 

.29 ,139 ,155 ,170 ,182 ,193 .204 ,214 ,223 ,232 ,267 

.30 ,146 .163 ,179 ,193 ,205 .217 ,227 ,238 ,248 ,286 

.31 ,153 ,172 ,189 ,204 .217 .230 ,242 ,253 .264 ,306 

.32 ,160 ,180 ,199 ,215 ,230 ,243 .256 ,269 ,281 .327 

.33 ,167 ,189 .209 ,227 ,243 ,257 .271 .285 ,298 ,348 

.34 .174 .198 .219 ,238 ,256 ,272 ,287 ,301 .315 ,369 

.35 .181 .207 ,230 .251 ,270 .287 .303 .318 ,334 .392 

.36 ,190 ,216 ,241 ,263 ,283 .302 .319 ,336 ,353 .416 

.37 ,196 ,225 ,251 .275 ,297 ,317 ,336 ,354 ,372 ,440 

.38 ,203 .234 .263 ,289 .311 ,333 ,354 .373 ,392 .465 

.39 .210 ,244 .274 ,301 .326 .349 .371 ,392 ,412 ,491 

.40 ,218 ,254 ,286 .314 ,341 ,366 ,389 ,412 ,433 ,518 

.41 .225 ,263 ,297 ,328 .357 ,383 ,408 .432 ,455 ,545 

.42 ,233 ,279 ,310 ,342 .373 ,401 ,427 .453 ,478 ,574 

.43 ,241 ,282 ,321 ,356 .389 ,418 ,447 ,474 ,501 ,604 

.44 ,249 ,292 ,334 ,371 ,405 ,437 ,467 ,496 ,524 ,634 

'For d/blessthan 0.04, use of the assumption R = d IS more convenient and more accurate than interpolation in the table 
CONVEYANCE STRUCTURES 125 

‘ lib 

.45 ,256 ,303 ,346 .385 ,422 ,455 ,487 .519 ,548 .665 

.46 ,263 ,313 ,359 ,401 ,439 .475 ,509 ,541 ,574 ,696 

.47 ,271 ,323 ,371 ,417 ,457 ,494 .530 ,565 .600 ,729 

.48 ,279 .333 ,384 .432 .475 ,514 ,552 ,589 .626 ,763 

.49 .287 ,345 .398 ,448 ,492 .534 ,575 ,614 .652 ,797 

.50 ,295 ,356 ,411 ,463 ,512 ,556 .599 ,639 ,679 ,833 

.52 ,310 ,377 ,438 .496 ,548 ,599 ,646 ,692 ,735 ,906 

.54 ,327 ,398 ,468 .530 ,590 ,644 ,696 ,746 ,795 ,984 

.56 ,343 ,421 ,496 .567 .631 ,690 ,748 ,803 .856 1.07 

.58 .359 ,444 ,526 ,601 .6Jl .739 .802 ,863 .922 1.15 

.60 ,375 ,468 ,556 .640 ,717 ,789 ,858 ,924 ,988 1.24 

.62 ,391 ,492 .590 ,679 ,763 .841 ,917 .989 1.06 1.33 

.64 .408 ,516 .620 .Jl8 ,809 .894 ,976 1.05 1.13 1.43 

.66 ,424 ,541 ,653 ,759 ,858 ,951 1.04 1.13 1.21 1.53 

.68 .44 1 .566 .687 ,801 ,908 1.01 1.10 1.20 1.29 1.64 

.JO ,457 ,591 .722 ,842 ,958 1.07 1.17 1.27 1.37 1.75 

.72 .474 ,617 ,757 ,887 1.01 1.13 1.24 1.35 1.45 1.87 

.74 ,491 ,644 .793 ,932 1 .OJ 1.19 1.31 1.43 1.55 1.98 

.76 ,508 ,670 ,830 ,981 1.12 1.26 1.39 1.51 1.64 2.11 

.78 ,525 ,698 ,868 1.03 1.18 1.32 1.46 1.60 1.73 2.24 

.80 ,542 ,725 ,906 1.08 1.24 1.40 1.54 1.69 1.83 2.37 

.82 .559 ,753 ,945 1.13 1.30 1.47 1.63 1.78 1.93 2.51 

.84 .576 ,782 ,985 1.18 1.36 1.54 1.71 1.87 2.03 2.65 

.86 ,593 .810 1.03 1.23 1.43 1.61 1.79 1.97 2.14 2.80 

.88 .610 .839 1 .OJ 1.29 1.49 1.69 1.88 2.07 2.25 2.95 

.90 ,627 ,871 1.11 1.34 1.56 1.77 1.98 2.17 2.36 3.11 

.92 ,645 ,898 1.15 1.40 1.63 1.86 2.07 2.28 2.48 3.27 

.94 ,662 ,928 1.20 1.46 1.70 1.94 2.16 2.38 2.60 3.43 

.96 ,680 .960 1.25 1.52 1.78 2.03 2.27 2.50 2.73 3.61 

.98 ,697 .991 1.29 1.58 1.85 2.11 2.37 2.61 2.85 3.79 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

.oo ,714 1.02 1.33 1.64 1.93 2.21 2.47 2.73 2.99 3.97 

.05 ,759 1.10 1.46 1.80 2.13 2.44 2.75 3.04 3.33 4.45 

.I0 ,802 1.19 1.58 1.97 2.34 2.69 3.04 3.37 3.70 4.96 

.I5 ,846 1.27 1.71 2.14 2.56 2.96 3.34 3.72 4.09 5.52 

.20 ,891 1.36 1.85 2.33 2.79 3.24 3.68 4.09 4.50 6.11 

I.25 .936 1.45 1.99 2.52 3.04 3.54 4.03 4.49 4.95 6.73 

.30 .980 1.54 2.14 2.73 3.30 3.85 4.39 4.90 5.42 7.39 

.35 1.02 1.64 2.29 2.94 3.57 4.18 4.76 5.34 5.90 8.10 

.40 1 .OJ 1.74 2.45 3.16 3.85 4.52 5.18 5.80 6.43 8.83 

I.45 1.11 1.84 2.61 3.39 4.15 4.88 5.60 6.29 6.98 9.62 

Table 25.-Uniform flow in trapezoidal channels by Manning’s formula. -Continued. 103-D-1 285-2 

7. = 0 z= l/4 z= 112 z = 314 z= I 7. = I-114 I = I-l/Z 7. = l-314 z=3 
126 SMALL CANAL STRUCTURES 

Table 2-S.-Uniform flow in trapezoidal channels by Manning’s formula.-Continued. 103-D-1285-3 

d/b Qn Values of ~ $13 ~112 

1.55 1.20 2.05 

1.60 1.25 2.15 

1.65 1.30 2.27 

1.70 1.34 2.38 

1.75 1.39 2.50 3.73 4.98 6.21 7.41 8.57 9.72 10.9 15.2 

1.80 1.43 2.62 3.93 5.28 6.60 7.89 9.13 10.4 11.6 16.3 

1.85 1.48 2.74 4.15 5.59 7.01 8.40 9.75 11.1 12.4 17.4 

1 .90 1.52 2.86 4.36 5.91 7.43 8.91 10.4 12.4 13.2 18.7 

1.95 1.57 2.99 4.59 6.24 7.87 9.46 11 .o 12.5 14.0 19.9 

2.00 1.61 3.12 4.83 6.58 8.32 10.0 11.7 13.3 14.9 21.1 

2.10 1.71 3.39 5.31 7.30 9.27 11.2 13.1 15.0 16.8 23.9 

2.20 1.79 3.67 5.82 8.06 10.3 12.5 14.6 16.7 18.7 26.8 

2.30 1.89 3.96 6.36 8.86 11.3 13.8 16.2 18.6 20.9 30.0 

2.40 1.98 4.26 6.93 9.72 12.5 15.3 17.9 20.6 23.1 33.4 

2.50 2.07 4.58 7.52 10.6 13.7 16.8 19.8 22.7 25.6 37.0 

2.60 2.16 4.90 8.14 11.6 15.0 18.4 21.7 25.0 28.2 40.8 

2.70 2.26 5.24 8.80 12.6 16.3 20.1 23.8 27.4 31.0 44.8 

2.80 2.35 5.59 9.49 13.6 17.8 21.9 25.9 29.9 33.8 49.1 

2.90 2.44 5.95 10.2 14.7 19.3 23.8 28.2 32.6 36.9 53.7 

3.00 2.53 6.33 11.0 15.9 20.9 25.8 30.6 35.4 40.1 58.4 

3.20 2.72 7.12 12.5 18.3 24.2 30.1 35.8 41.5 47.1 68.9 

3.40 2.90 7.97 14.2 21.0 27.9 34.8 41.5 48.2 54.6 80.2 

3.60 3.09 8.86 16.1 24.0 32.0 39.9 47.8 55.5 63.0 92.8 

3.80 3.28 9.81 18.1 27.1 36.3 45.5 54.6 63.5 72.4 107 

4.00 3.46 10.8 20.2 30.5 41.1 51.6 61.9 72.1 82.2 122 

4.50 3.92 13.5 26.2 40.1 54.5 68.8 82.9 96.9 111 164 

5.00 4.39 16.7 33.1 51.5 70.3 89.2 108 126 145 216 

2.78 3.63 4.46 5.26 6.04 6.81 7.55 10.4 

2.96 3.88 4.78 5.65 6.50 7.33 8.14 11.3 

3.14 4.14 5.12 6.06 6.99 7.89 8.79 12.2 

3.33 4.41 5.47 6.49 7.50 8.47 9.42 13.2 

3.52 4.69 5.83 6.94 8.02 9.08 10.1 14.2 

r=O z= l/4 z= l/2 z = 314 z= 1 L = l-1/4 z = l-1/2 7. = I-314 1=2 2=3 

1.50 1.16 1.94 
CONVEYANCE STRUCTURES 127 

d/b1 

Table 2-6.-Uniform ,j7ow in trapezoidal channels by Mannirzg’sfbrrnula. 103-D-l 286-I 

Qn Values of ___ 

d 813 ~112 

z=o z= l/4 

147.6 

73.4 

48.6 

36.3 

148.3 

74.0 

49.3 

36.9 

148.6 

74.3 

49.5 

31.2 

148.8 

74.5 

49.8 

37.4 

28.9 

23.9 

20.4 

17.73 

15.72 

29.5 

24.6 

21.1 

18.43 

16.39 

29.8 

24.8 

21.3 

18.70 

16.66 

30.0 

25.1 

21.6 

18.95 

16.91 

14.14 

12.76 

11.65 

10.71 

9.91 

14.75 

13.42 

12.31 

11.37 

10.57 

15.02 

13.69 

12.59 

11.65 

10.85 

15.28 

13.94 

12.84 

11.90 

11.10 

9.21 

8.61 

8.08 

7.61 

7.18 

9.88 

9.27 

8.74 

8.27 

7.85 

10.16 

9.55 

9.02 

8.55 

8.13 

10.42 

9.81 

9.28 

8.81 

8.39 

.Ol 146.7 147.2 148.0 148.9 149.2 

.02 72.4 72.9 73.7 74.8 74.9 

.03 47.6 48.2 49.0 50.0 50.2 

.04 35.3 35.8 36.6 37.6 37.8 

.05 27.9 28.4 29.2 30.2 30.5 

.06 23.0 23.5 24.3 25.3 25.5 

.07 19.45 19.97 20.8 21.8 22.0 

.08 16.82 17.34 18.13 19.18 19.40 

.OP 14.78 15.29 16.08 17.14 1.7.36 

.lO 13.16 13.66 14.44 15.51 15.74 

.ll 11.83 12.33 13.11 14.18 14.41 

.I2 10.73 11.23 12.00 13.08 13.31 

.13 9.80 10.29 11.06 12.14 12.38 

.14 9.00 9.49 10.26 11.35 11.58 

.15 8.32 8.80 9.57 10.67 10.89 

.16 7.72 8.20 8.96 10.06 10.29 

.17 7.19 7.67 8.43 9.53 9.77 

.18 6.73 7.20 7.96 9.05 9.30 

.I9 6.31 6.78 1.54 8.64 8.88 

.20 5.94 6.40 7.16 8.26 8.50 

.21 5.60 6.06 6.82 7.92 8.16 

.22 5.30 5.75 6.50 7.61 7.86 

.23 5.02 5.47 6.22 7.33 7.58 

.24 4.77 5.22 5.96 7.07 7.32 

.25 4.54 4.98 5.73 6.84 7.08 

.26 4.32 4.77 5.51 6.62 6.87 

.27 4.13 4.57 5.31 6.42 6.67 

.28 3.95 4.38 5.12 6.23 6.48 

.29 3.78 4.21 4.95 6.06 6.31 

.30 3.62 4.05 4.78 5.90 6.15 

.31 3.48 3.90 4.63 5.75 6.00 

.32 3.34 3.16 4.49 5.61 5.86 

.33 3.21 3.64 4.36 5.48 5.73 

.34 3.09 3.51 4.23 5.35 5.60 

.35 2.98 3.40 4.12 5.23 5.49 

.36 2.88 3.29 4.01 5.12 5.38 

.37 2.78 3.19 3.90 5.02 5.27 

.38 2.68 3.09 3.81 4.92 5.17 

.39 2.59 3.00 3.71 4.83 5.08 

.40 2.51 2.92 3.62 4.74 4.99 

.41 2.43 2.84 3.54 4.66 4.91 

.42 2.36 2.16 3.46 4.58 4.83 

.43 2.29 2.68 3.38 4.50 4.76 

.44 2.22 2.61 3.31 A 4 43 4.68 

- P 

6.81 

6.47 

6.16 

5.87 

5.62 

7.47 

7.13 

6.82 

6.53 

6.27 

7.75 

7.41 

7.10 

6.81 

6.56 

8.01 

7.67 

7.36 

7.08 

6.82 

5.38 

5.16 

4.96 

4.77 

4.60 

6.04 

5.82 

5.62 

5.43 

5.25 

6.32 

6.10 

5.90 

5.71 

5.54 

6.58 

6.37 

6.16 

5.98 

5.81 

4.44 

4.29 

4.15 

4.02 

3.89 

5.09 

4.94 

4.80 

4.67 

4.54 

5.38 

5.23 

5.08 

4.95 

4.83 

5.64 

5.49 

5.35 

5.22 

5.09 

3.78 

3.67 

3.56 

3.47 

3.37 

4.43 

4.32 

4.21 

4.11 

4.02 

4.71 

4.60 

4.49 

4.40 

4.30 

4.98 

4.87 

4.76 

4.67 

4.57 

3.29 

3.20 

3.13 

3.05 

2.98 

3.93 

3.85 

3.77 

3.69 

3.62 

4.21 

4.13 

4.05 

3.97 

3.90 

4.48 

4.40 

4.32 

4.24 

4 17 L 

z= l/2 z = 314 z=l 2 = l-1/4 = l-1/2 = I-314 2=2 

149.9 

75.6 

50.9 

38.6 

31.2 

26.3 

22.8 

20.2 

18.21 

16.60 

15.28 

14.19 

13.26 

12.48 

11.80 

11.20 

10.68 

10.21 

9.80 

9.43 

9.09 

8.79 

8.51 

8.26 

8.03 

7.81 

7.62 

7.43 

7.26 

7.1c 

6.96 

6.82 

6.69 

6.56 

6.45 

6.34 

6.24 

6.14 

6.05 

5.96 

5.88 

5.80 

5.73 

5.66 

For d/b less than 0.04, use of the assumption R =d is more convenient and more. accurate than interpolation in the table. 

z=3 
128 SMALL CANAL STRUCTURES 

Table 2-6..-Uniform flow in trapezoidal channels by Marzningk formzrla. -Continued. 103-D-1 286-2 

d/b 

.45 2.15 2.55 2.91 3.24 3.55 3.83 4.10 4.36 4.61 5.59 

.46 2.09 2.48 2.85 3.18 3.48 3.77 4.04 4.29 4.55 5.52 

.41 2.03 2.42 2.78 3.12 3.42 3.70 3.97 4.23 4.49 5.46 

.48 1.977 2.36 2.72 3.06 3.36 3.64 3.91 4.17 4.43 5.40 

.49 1.923 2.31 2.67 3.00 3.30 3.58 3.85 4.12 4.37 5.34 

.50 1.872 2.26 2.6 I 2.94 3.25 3.53 3.80 4.06 4.3 1 5.29 

.52 1.771 2.16 2.5 1 2.84 3.14 3.43 3.70 3.96 4.21 5.19 

.54 1.689 2.06 2.42 2.14 3.05 3.33 3.60 3.86 4.1 I 5.09 

.56 1.608 1.977 2.33 2.66 2.96 3.24 3.51 3.77 4.02 5.00 

.58 1.533 1.900 2.25 2.57 2.87 3.16 3.43 3.69 3.94 4.92 

.60 1.464 1.827 2.11 2.50 2.80 3.08 3.35 3.61 3.86 4.85 

.62 1.400 1.760 2.11 2.43 2.73 3.01 3.28 3.54 3.79 4.77 

.64 1.340 1.697 2.04 2.36 2.66 2.94 3.21 3.41 3.72 4.71 

.66 1.285 1.638 1.979 2.30 2.60 2.88 3.15 3.41 3.66 4.64 

.68 1.234 1.583 1.922 2.24 2.54 2.82 3.09 3.35 3.60 4.59 

.70 1.184 1.531 1.868 2.18 2.48 2.76 3.03 3.29 3.55 4.53 

.I2 1.139 1.482 1.818 2.13 2.43 2.7 I 2.98 3.24 3.49 4.48 

.I4 I .096 1.437 1.770 2.08 2.38 2.66 2.93 3.19 3.45 4.43 

.76 1.056 1.393 1.725 2.04 2.33 2.61 2.88 3.15 3.40 4.38 

.78 1.018 1.353 I .683 1.998 2.29 2.57 2.84 3.10 3.35 4.34 

.80 .982 1.315 1.642 1.954 2.25 2.53 2.80 3.06 3.3 1 4.30 

.82 .949 1.278 1.604 1.916 2.21 2.49 2.16 3.02 3.27 4.26 

.84 ,917 1.245 1.568 1.886 2.17 2.45 2.72 2.98 3.23 4.22 

.86 .887 1.211 1.534 1.843 2.14 2.41 2.68 2.94 3.20 4.18 

.88 .858 1.180 1.501 1.810 2.10 2.38 2.65 2.91 3.16 4.15 

.90 ,831 1.153 1.470 1.777 2.07 2.35 2.62 2.87 3.13 4.12 

.92 .805 1.122 1.441 1.747 2.04 2.32 2.58 2.84 3.10 4.08 

.94 ,781 1.095 1.413 1.718 2.01 2.29 2.55 2.81 3.07 4.05 

.96 ,758 1.070 1.396 1.690 1.981 2.26 2.53 2.78 3.04 4.03 

.98 .736 1.046 1.360 1.663 1.954 2.23 2.50 2.76 3.01 4.00 

1 .oo .7 14 1.022 1.335 1.638 1.928 2.21 2.47 2.13 2.99 3.97 

1.05 ,666 ,969 1.278 1.579 1.871 2.14 2.4 1 2.67 2.92 3.91 

1.10 .622 ,920 1.226 1.525 1.813 2.09 2.36 2.61 2.87 3.85 

1.15 ,583 ,876 1.178 1.477 1.763 2.04 2.30 2.56 2.82 3.80 

1.20 .548 .836 1.136 1.432 1.717 1.993 2.26 2.51 2.77 3.76 

1.25 ,516 .800 1.098 1.392 I .676 1.950 2.22 2.47 2.73 3.71 

1.30 .487 .767 1.062 1.354 1.638 1.912 2.18 2.43 2.69 3.61 

1.35 .460 .736 1.028 1.320 1.603 1.876 2.14 2.40 2.65 3.64 

1.40 .436 ,708 .998 1.288 1.570 1.843 2.11 2.37 2.62 3.60 

1.45 .414 .682 .970 1.259 1.540 1.812 2.08 2.34 2.59 3.57 

1.50 .393 .658 ,944 1.231 1.512 1.784 2.05 2.31 2.56 3.54 

1.55 ,374 .636 ,920 1.206 1.486 1.157 2.02 2.28 2.53 3.52 

1.60 ,357 .615 .897 1.182 1.461 1.731 1.995 2.25 2.5 1 3.49 

1.65 .341 .596 .876 1.160 1.438 1.708 1.972 2.23 2.48 3.47 

1.70 .325 ._‘7s .856 1.139 1.416 1.686 1.949 2.21 2.46 3.44 

z=o L= 114 z= 112 

Qn Values of ~~ 

d 813 S1/2 

t IAd L u J zl-b-iZ 

7 = 3/4 z=l ! = l-l/4 = l-112 = l-314 2=2 L=3 
CONVEYANCE STRUCTURES 129 

Table 2-6.-Uniform ,flow in trapezoidal channels by Manning’s formula. Xantinued. 103-D-1 286-3 

Value\ ot ~-___ Qn d8/3 s1/2 IW L 73 J 

zh--b-iz 

L = 0 7 = l/4 z= 112 7. = 314 z= I 1= l-l/4 %= l-1/2 %= l-314 2=2 z=3 

1.75 ,312 ,561 .838 1.119 1.396 1.666 1.928 2.19 2.44 3.42 

1.80 ,298 ,546 ,820 1.101 1.377 1.646 1.905 2.17 2.42 3.40 

1 .85 ,286 ,531 ,804 1.083 1.359 1.628 1.890 2.15 2.40 3.38 

1.90 .275 ,517 ,788 1.067 1.342 1.610 1.872 2.13 2.38 3.37 

1 .95 ,264 ,504 ,773 1.051 1.326 1.594 1.856 2.11 2.36 3.35 

2.00 .254 ,491 ,760 1.036 1.310 1.578 1.840 2.10 2.35 3 33 

2.10 ,236 ,469 ,734 1.009 1.282 1.549 1.811 2.07 2.32 3.30 

2.20 ,219 ,448 ,711 ,984 1.256 1.523 1.784 2.04 2.29 3.27 

2.30 .205 ,430 ,690 ,962 1.233 1.499 1.760 2.02 2.27 3.25 

2.40 .1919 ,413 ,671 ,941 1.212 1.477 1.737 1.993 2.24 3.23 

2.50 .I800 ,398 ,653 ,922 1.192 1.457 1 ,717 1.972 2.22 3.21 

2.60 .I693 ,383 ,637 ,905 1.174 1.438 1.698 1.954 2.21 3.19 

2.70 .1597 ,371 ,623 ,889 1.157 1.422 1.681 1.937 2.19 3.17 

2.80 .I508 ,359 ,609 ,874 1.142 1.406 1.665 1.920 2.17 3.15 

2.90 .1427 ,348 ,596 ,861 1.128 1.391 1.650 1.905 2.16 3.14 

3.00 .I354 ,338 ,585 ,848 1.114 1.377 1.636 1.891 2.14 3.12 

3.20 .1223 ,320 ,563 ,825 1.090 1.353 1.611 1.865 2.12 3.10 

3.40 .I111 ,305 ,545 .805 1.069 1.331 1.589 1.843 2.09 3.07 

3.60 .I015 .291 ,529 ,787 1.050 1.312 1.569 1.823 2.07 3.05 

3.80 .0932 .279 ,514 ,771 1.033 1.294 1.552 1.805 2.06 3.04 

4.00 .0859 ,268 ,501 ,757 1.019 1.279 1.536 1.790 2.04 3.02 

4.50 .OJll ,245 ,474 ,727 .987 1.246 1.502 1.755 2.01 2.98 

5.00 .0601 .228 ,453 ,704 ,962 1.220 1.476 1.729 1.979 2.96 
130 SMALL CANAL STRUCTURES 

Table 2.I-Uniform flow in circular sectionsflowing partly fidl. 103-D-1281 

d = depthofflow 

D = diameter of pipe 

A = area of flow 

R = hvdraulic radius 

0 = discharge in cubx feet per second by Manning’s formula 

” = Manning’s coefficient 

S = slope of the channel bottom and of the water surface 

d 

D 

0.01 0.0013 0.0066 0.00007 15.04 0.51 0.4027 0.2531 0.239 1.442 

0.02 0.0037 0.0132 0.00031 10.57 0.52 0.4127 0.2562 0.247 1.415 

0.03 0.0069 0.0197 0.00074 8.56 0.53 0.4227 0.2592 0.255 1.388 

0.04 0.0105 0.0262 0.00138 7.38 0.54 0.4327 0.2621 0.263 1.362 

0.05 0.0147 0.0325 0.00222 6.55 0.55 0.4426 0.2649 0.271 1.336 

0.06 0.0192 0.0389 0.00328 5.95 0.56 0.4526 0.2676 0.279 1.311 

0.07 0.0242 0.0451 0.00455 5.47 0.57 0.4625 0.2703 0.287 1.286 

0.08 0.0294 0.0513 0.00604 5.09 0.58 0.4724 0.2728 0.295 1.262 

0.09 0.0350 0.0575 0.00775 4.76 0.59 0.4822 0.2753 0.303 1.238 

0.10 0.0409 0.0635 0.00967 4.49 0.60 0.4920 0.2776 0.311 1.215 

0.11 0.0470 0.0695 0.01181 4.25 0.61 0.5018 0.2799 0.319 1.192 

0.12 0.0534 0.0755 0.01417 4.04 0.62 0.5115 0.2821 0.327 1.170 

0.13 0.0600 0.0813 0.01674 3.86 0.63 0.5212 0.2842 0.335 1.148 

0.14 0.0668 0.0871 0.01952 3.69 0.64 0.5308 0.2862 0.343 1.126 

0.15 0.0739 0.0929 0.0225 3.54 0.65 0.5404 0.2882 0.350 1.105 

0.16 0.0811 0.0985 0.0257 3.41 0.66 0.5499 0.2900 0.358 1.084 

0.17 0.0885 0.1042 0.0291 3.28 0.67 0.5594 0.2917 0.366 1.064 

0.18 0.0961 0.1097 0.0327 3.17 0.68 0.5687 0.2933 0.373 1.044 

0.19 0.1039 0.1152 0.0365 3.06 0.69 0.5780 0.2948 0.380 1.024 

0.20 0.1118 0.1206 0.0406 2.96 0.70 0.5872 0.2962 0.388 1.004 

0.21 0.1199 0.1259 0.0448 2.87 0.71 0.5964 0.2975 0.395 0.985 

0.22 0.1281 0.1312 0.0492 2.79 0.72 0.6054 0.2987 0.402 0.965 

0.23 0.1365 0.1364 0.0537 2.71 0.73 0.6143 0.2998 0.409 0.947 

0.24 0.1449 0.1416 0.0585 2.63 0.74 0.6231 0.3008 0.416 0.928 

0.25 0.1535 0.1466 0.0634 2.56 0.75 0.6319 0.3017 0.422 0.910 

0.26 0.1623 0.1516 0.0686 2.49 0.76 0.6405 0.3024 0.429 0.891 

0.27 0.1711 0.1566 0.0739 2.42 0.77 0.6489 0.3031 0.435 0.873 

0.28 0.1800 0.1614 0.0793 2.36 0.78 0.6573 0.3036 0.441 0.856 

0.29 0.1890 0.1662 0.0849 2.30 0.79 0.6655 0.3039 0.447 0.838 

0.30 0.1982 0.1709 0.0907 2.25 0.80 0.6736 0.3042 0.453 0.821 

0.31 0.2074 0.1756 0.0966 2.20 0.81 0.6815 0.3043 0.458 0.804 

0.32 0.2167 0.1802 0.1027 2.14 0.82 0.6893 0.3043 0.463 0.787 

0.33 0.2260 0.1847 0.1089 2.09 0.83 0.6969 0.3041 0.468 0.770 

0.34 0.2355 0.1891 0.1153 2.05 0.84 0.7043 0.3038 0.473 0.753 

0.35 0.2450 0.1935 0.1218 2.00 0.85 0.7115 0.3033 0.477 0.736 

0.36 0.2546 0.1978 0.1284 1.958 0.86 0.7186 0.3026 0.481 0.720 

0.37 0.2642 0.2020 0.1351 1.915 0.87 0.7254 0.3018 0.485 0.703 

0.38 0.2739 0.2062 0.1420 1.875 0.88 0.7320 0.3007 0.488 0.687 

0.39 0.2836 0.2102 0.1490 1.835 0.89 0.7384 0.2995 0.491 0.670 

0.40 0.2934 0.2142 0.1561 1.797 0.90 0.7445 0.2980 0.494 0.654 

0.41 0.3032 0.2182 0.1633 1.760 0.91 0.7504 0.2963 0.496 0.637 

0.42 0.3130 0.2220 0.1705 1.724 0.92 0.7560 0.2944 0.497 0.621 

0.43 0.3229 0.2258 0.1779 1.689 0.93 0.7612 0.2921 0.498 0.604 

0.44 0.3328 0.2295 0.1854 1.655 0.94 0.7662 0.2895 0.498 0.588 

0.45 0.3428 0.2331 0.1929 1.622 0.95 0.7707 0.2865 0.498 0.571 

0.46 0.3527 0.2366 0.201 1.590 0.96 0.7749 0.2829 0.496 0.553 

0.47 0.3627 0.2401 0.208 1.559 0.97 0.7785 0.2787 0.494 0.535 

0.48 0.3727 0.2435 0.216 1.530 0.98 0.7817 0.2735 0.489 0.517 

0.49 0.3827 0.2468 0.224 1.500 0.99 0.7841 0.2666 0.483 0.496 

0.50 0.3927 0.2500 0.232 1.471 1 .oo 0.7854 0.2500 0.463 0.463 

R 

- 

D 

Q” Q” d 

D8/3s1 I2 d8/+1/2 0 

- ,“2 cl” Q” 

D8/3s1 I2 d8/3s1 I2 
CONVEYANCE STRUCTURES 

G. BIBLIOGRAPHY 

131 

2-38. Bibliography. 

[ 1 ] Armco Handbook of Drainage and Construction Product, 

C.M.P. 

[2] Cretex Pipe Products Publication-The Cretex Companies 

Inc., Elk River, Minnesota. 

[3] ASTM Designation C 443. 

(41 Standard Specifications for Reinforced Concrete Pressure 

Pipe, February I, 1969, United States Department of 

the Interior, Bureau of Reclamation. 

[S] Standard Specifications for AsbestosCement Pressure 

Pipe, United States Department of the Interior, Bureau 

of Reclamation. 

[6] King, H. W. and Brater, E. F., “Handbook of Hydraulics,” 

Fifth Edition, McGraw-Hill Book Co., New York, 1963. 

[7] Hydraulic and Excavation Tables, Bureau of Reclamation, 

Eleventh Edition, 1957, Reprint, 1974. 

[8] Pete&a, A. J., “Hydraulic Design of Stilling Basins and 

Energy Dissipators,” Engineering Monograph No. 25, 

U.S. Bureau of Reclamation, Denver, 1964. 

[P] Thorsky, G. N., Tilp, P. J., and Haggman, P. C., “Slug 

Flow in Steep Chutes,” Report No. CB-2, U.S. Bureau 

of Reclamation, Denver, February 1967. 

[lo] Mortuori, C., Discussion of “Stability Aspects of Flow in 

Open Channels,” Journal of the Hydraulics Division, 

ASCE, Vol. 89, No. HY4, Proc. Paper 3580, July 1963. 

(111 Arsenishvili, K. I., “Effect of Wave Formation on 

Hydro-Engineering Structures,” NSF Translation No. 

TT65-50094, U.S. Department of the Interior, 1965. 

[12] Brock, R. R., “Development of Roll-Wave Trains in 

Open Channels,” Journal of the Hydraulics Division, 

ASCE, Vol. 95, No. HY4, Proc. Paper 6704, July 1969. 

[13] Thorsky, G. N., and Haggman, P. C., Discussion of 

“Development of Roll-Wave Trains in Open Channels” 

Journal of the Hydraulics Division, ASCE, Vol. 96, No. 

HY4, Proc. Paper 7189, April 1970. 

[14] Posey, C. J., “Fundamentals of Open Channel 

Hydraulics,” Rocky Mountain Hydraulic Laboratory, 

Allenspark, Colorado, 1969. 

«Chapter III

A. GENERAL

may be used. Weirs mayor may not be

adjustable. Slide gates and weirs may be bolted

to the check walls or they may be moun ted in

frames that are inserted in grooves in the

structure. Weirs are discussed later in chapter

V.

Either stoplogs or slide gates, or a

combination of both, are the usual means of

flow regulation. Stoplogs are less expensive

than gates and are more quickly adjusted but

do not control the flow as closely. When

stoplogs are used, flow through the structure

can be determined from the formula for flow

over a rectangular weir:

3-1 .Regulating Structures. -A regula ting

structure in an open irrigation system is used to

regulate the flow passing through the structure,

to control the elevation of the upstream canal

water surface, or to do both. Structures which

perform these functions include: ( I) checks,

(2) check-drops, (3) turnouts, ( 4) division

structures, (5) check inlets, and (6) control

inlets.

Regulation is achieved with weirs, control

inlets, stoplogs, and slide gates. Control inlets

(fig. 3-1) are designed to regulate the canal

water surface within particular limits. Stoplogs

and slide gates are adjusted as required. Where

measurement at the structure is required, weirs

Q = CLH3/2

When gates are used the flow through the

structure can be detennined from the fonnula

for flow through a submerged orifice:

Q=CA~

Figure 3.1. Control notch maintains water surface above a

drop inlet to a pipe structure. Discharge is 10 cfs.

PX-D-72615D

The equations will show that the flow over

stoplogs is more responsive to changes in water

depths in the canal than flow through a gate,

therefore the required adjustment of stoplogs is

less frequent. Similarly where adjustable weirs

are used for control, they require less frequent

adjustment than gates.

Floating trash that can pass over stoplogs

and adjustable weirs can be a problem in a

133
134 SMALL CANAL STRUCTURES

motorized operation. Gates using motor-driven

hoists can be equipped with. control devices

that will automatically maintain constant water

surface elevations regardless of the discharge

[ 1] [2].1

gated structure. Jetting of flow under gates can

pull debris below the water surface and cause

the gate opening to become obstructed.

If the canal must be closely regulated or if

automatic or remote control of the canal is

anticipated, gates must be used. Gates are often

manually operated but automation requires

I Numbers in brackets refer to items in the bibliography,

sec. 3-29.

B. CHECKS

2

D. L. WINSETT

Figure 3-2. Concrete check structure. Metal turnout

structures and outlet for railroad crossing in

background. p 796-701-2630

3-2. Purpose and Description. -Checks are

used to regulate the canal water surface

upstream of the structure and to control the

downstream flow. When a canal is flowing at

partial capacity, checks are operated to

maintain the canal water surface elevation

required for upstream water deliveries. The

water surface that the check must maintain is

the control water surface. It is generally the

same as the normal water surface at the check.

In the event of a break in the canal bank,

checks can be used to limit the volume of

escaping water to that confined between check

structures and prevent the entire canal from

being emptied. The use of checks also allows

reaches of the canal to be isolated and

dewatered for repair or inspection.

Checks have a deck spanning the structure to

provide access to the gates or stoplogs.

Overflow walls or check walls are provided on

both sides of the gates or stoplogs. The tops of

these walls are set at or slightly above the

control water surface. Excess water in the canal

can flow over these walls, the water surface rise

in the canal is limited, and the canal banks are

less likely to be overtopped. The amount of

overflow provided for will depend on the

amount of excess water expected in the canal

and the degree of safety required for the

structure and the canal.

Figure 3-2 shows a typical check structure

with rip rap downstream to protect the channel.

3-3. Combination Structures. -Checks may

be separate structures or they may be

combined with the inlets of other structures.

Check inlets (figs. 3-3 and 3-4) are often used

Figure 3-3. Check inlet to pipe structure.

Adjustable weir installed in the stoplog

groove. p 372-701-765

2Civil Engineer, Hydraulic Structures Branch, Bureau of

Reclamation.
REGULATING STRUCTURES 135

Figure 3-4. Check inlet to pipe structure.

Stoplogs and slide gate installed in

grooves. p 328-701-9494

with such structures as road crossings, inverted

siphons, pipe drops, rectangular inclined drops,

and chu tes.

Checks, when combined with other

structures, can prevent water surface

drawdown and scour upstream of the structure.

Combination structures are generally more

economical than separate structures.

3-4. Spacing. -Checks are spaced along a

canal primarily to maintain the water surface

eleva tions required by upstream water

deliveries. Steeper canal grades usually require

closer spacing between the checks. From an

initially selected check location, a level line at

the control water surface elevation projected

upstream will determine the last upstream

turnout that can be served.

Check spacing in a concrete-lined canal is

often controlled by limiting the drop in normal

water surface between check structures. Then,

if for any reason, operation of the system must

be suddenly suspended the drop in water

surface is controlled as the water surface

profile changes from the normal water surface

to a level checked water surface. Displacement

of the concrete lining by unequal hydrostatic

pressures is consequently prevented or

minimized.

Check spacing may also be influenced by the

following considerations:

( I) Canal storage-Locating checks closer

together increases the amount of storage in the

canal.
136 SMALL CANAL STRUCTURES 

(2) Travel time between checks-Spacing 

may be influenced by the time required for 

operating personnel to travel between 

structures. 

(3) Canal properties-Checks are usually 

located where changes in canal cross section or 

capacity occur. 

surface. A downstream handrail on the deck is 

required when the deck is 3.5 feet or more 

above the floor and both an upstream and a 

downstream handrail are required if the height 

is 5 feet or more. 

3-5. Design Cotzsideratiom-(a) Stubilitv 

und Percolution. -Checks are designed to 

withstand the hydraulic forces imposed by 

water ponded to the top of the check wall on 

the upstream side and no water on the 

downstream side. Adequate check length is 

provided to dampen water turbulence caused 

by: (1) the sheet of water flowing over 

stoplogs, or (2) the jet of water flowing 

through a partially opened gate. The length in 

conjunction with the cutoff walls also provides 

a percolation path with sufficient length to 

prevent the removal of foundation material by 

water moving adjacent to the structure. For a 

discussion of percolation see subchapter VIII 

C. The structure must be stable against sliding 

and overturning. 

(c) Heacl Loss.-The head loss through a 

check structure is computed as 0.5 Ah, (0.5 

times the difference between the velocity head 

at the check opening and the velocity head in 

the canal section upstream of the structure). A 

minimum loss of 0.1 foot should be allowed 

for isolated checks in small canals. Except for 

this head loss, checks normally do not provide 

for a drop in grade across the structure. At 

partial canal capacities, with the water 

upstream checked to the control water surface, 

a drop in water surface elevation will occur 

across the structure. 

(b) Stoplogs. Gates, uncl Deck.-Velocity 

through check structures using stoplogs should 

be limited to about 3.5 feet per second for 

efficient stoplog operation. The velocity 

through checks using gates may be increased to 

about 5 feet per second. The use of stoplogs is 

not recommended if: (1) the flow is greater 

than 50 cfs, (2) the width of the stoplog 

opening is greater than 5 feet, or (3) the water 

depth is greater than 6 feet. Stoplog guides 

may be vertical if the distance from the floor 

of the check to the bottom of the operating 

deck is less than 6 feet. For greater heights, 

sloping the stoplog guides on a 1 to 4 slope 

may make the installation or removal of 

stoplogs less difficult. Where stoplogs are not 

used operating decks are designed for a live 

load of 100 pounds per square foot. Where 

stoplogs are used the live load is increased to 

150 pounds per square foot. 

The Bureau of Reclamation has developed 

standard dimensions for checks with capacities 

of 100 cfs and less. These checks are shown on 

figures 3-5 and 3-6. The selection of a check 

from these standard structures and the 

determination of the required elevations are 

shown by the following design example. 

3-6. Design Example.-Select a check to be 

used in a canal with a capacity of 25 cfs and a 

normal water depth of 1.75 feet. Assume that 

the canal profile shows elevation A (the 

bottom grade elevation upstream of the 

structure) to be 1207.18. 

Figure 3-5 shows a number of check 

structures with standard dimensions. There is 

no structure listed for a maximum capacity of 

25 cfs. From the table on figure 3-5, select 

structure number 4 with the next largest Q 

which is 26 cfs. If more than one structure is 

listed for the required capacity, choose the 

most economical structure that best fits the 

canal section. If gates are to be used, the 

availability of gate sizes may influence the 

choice of structure. 

Determine elevation B: 

For safety, operating decks should be a 

minimum of 2 feet wide where the height of 

the deck above the check floor is less than 3.5 

feet. Where the height above the floor is 3.5 

feet or greater, decks should be a minimum of 

3 feet wide. Concrete deck surfaces should be 

floated or broomed to acquire a skid-resistant 

Upstream bottom grade 

(El. A) 1207.18 

+ Upstream normal water 

depth + 1.75 

Upstream normal water 

surface elevation 1208.93 
REGULATING STRUCTURES 

SECTION A-A 

TYPICAL SLIDE GATE 

ASSEMBLY 

STOPLOG OR GATE FRAME GUIDE DETAILS 

iTWO REQ”lRED, 

PLAN OF PRECAST CONCRETE DECK 

NOTES 

Figure 3-5. Standard check structures. Q less than 70 cfs. 103-D-1208 
138 SMALL CANAL STRUCTURES 

L PLAN 

ia 

SECTION A-A 

,- Prccos+ Concrete 

ec* 

t 

SECTION c-c 

SECTION i-i SiMILAR 

SECTION D-D 

TYPICAL SLIDE GATE 

ASSEMBLY 

PLAN OF PRECAST CONCRETE DECK 

STOPLOG OR GATE FRAME GUIDE FOR PIER 

IONE REWIRED) 

;~~~~“~~~.~~~~

; 

STOPLOG OR GATE FRAME GUIDE FOR CHECK WALL 

t TWO REOUIRED, 

Figure 3-6. Standard check structures. Q greater than 70 and less than 105 cfs. 103-D-1209 
REGULATING STRUCTURES

downstream

equals:

bottom grade elevation

Upstream water surface

elevation

-Head loss

1208.93

0.10

The top of the check wall is set at or slightly

above the elevation of the upstream normal

water surface.

From figure 3-5, dimension C for structure

number 4 = 2.67 feet.

Elevation of the top of

the check wall 1208.93

-Dimension C 2.67

Elevation B r.,-,,--- 1208.83 2o~

Downstream water surface

elevation

-Downstream normal water

depth 75

Elevation C ( downstream

bottom grade ) 207.08

Transitions are provided as required to fit

the structure to the canal section. In unlined

canals the channel should be protected above

and below the structure to prevent erosion.

Checks for capacities between 70 and 100

cfs are shown on figure 3-6.

Elevation B should be equal to or less than

elevation A to avoid a hump in the bottom of

the canal. If elevation B is higher than elevation

A, a structure with a larger dimension C should

be selected.

Determine elevation C:

The head loss through the structure must be

determined in accordance with subsection

3-5(c) of this chapter. For this example,

assume a minimum head loss of 0.1 foot. The

c. CHECK-DROPS

D. Lo WINSETT

Check-drops are designed to meet the same

requirements for percolation, stability,

velocity, and safety as checks. In addition, the

20po cit., po 134

3- 7. Purpose and Description. -Check-drops

are structures that provide a means of making

small changes in canal invert elevations. The

structure com bines the function of a vertical

drop with those of a check. The drop portion

of the structure dissipates excess head in the

canal while the check portion maintains the

required water surface upstream and controls

the flow downstream. Figures 3- 7 through 3-11

show typical che~k-drop structures.

The design and operation of the check

feature of the check-drop is similar to that of

checks and the preceding discussion of checks

applies generally to check-drops. Gates,

stoplogs, and weirs are used for regulation.

3-8. Design Considerations. -The vertical

drop through this type of structure in an

unlined canal is generally limited to 3 feet for

canal capacities of 70 cfs and less and to 1.5

feet for larger capacities. In lined sections these

structures have been used for vertical drops up

to about 8 feet. For the larger drops, economic

and stability considerations may indicate the

use of another type of structure.

Figure 3- 7. Operator removing stop logs from a

check-drop structure. Constant-head orifice

turnouts in background. P-606-600-66A
140 SMALL CANAL STRUCTURES

Figure 3.10. Concrete check-drop. Water upstream

checked to top of check wall. Discharge is

10 cfs.P222-116-53587

Figure 3-8. Drop structure using a weir for

regulation. p 257-500-2967NA

Figure 3-9. Concrete check with slide gate.

Design discharge is 24 cfs. p 222-116-53583

Figure 3-11. Check-drop maintaining an upstream

water surface. p 17-100-285.

structures are shown on figures 3-12,3-13, and

3-14. The design example demonstrates how a

check-drop structure is selected from these

standard structures and how the required

elevations are determined.

3-10. Design Example. -Select a check-drop

structure to be used in a channel with a

capacity of 50 cfs and a water depth of 2.75

feet. Assume that the channel profile shows

elevation A, the bottom grade at the upstream

end of the structure, to be 1207.18 and

structure must be long enough to contain the

falling water and to provide a stilling pool to

control turbulence downstream.

Overflow walls on each side of the check

opening allow excess water in the canal to pass

through the check-drop in the same manner as

through a check.

3-9. Application. -Check-drops are located

in a channel where a small change in grade is

required. The best use of the dual features of

this structure is made when it is placed where a

check would normally be located.

The Bureau has developed standard

dimensions for check-drop structures with

vertical drops of up to 3 feet. These standard
REGULATING STRUCTURES 141 

,l”rtr*nm h”“A?“,i SECTION A-A 

STOPLOG OR GATE FRAME GUIDE DETAILS 

,TWO ‘1EO”IRED) 

+*c- x--- x- -r --x--Id 

PLAN OF PRECAST CONCRETE DECK 

Figwe J-12. Standard checkdrop structures. Q less than 70 cfs. 103-D-1210 
142 SMALL CANAL STRUCTURES 

_ /--t,o”dra~~ not shown ‘+-~ 22’H 7’ 

SECTION D-D 

TYPICAL SLIDE GATE 

ASSEMBLY 

_ -L c Pm nO”drO,l pm+ tonneCt,onl 

PLAN OF PRECAST CONCRETE DECK 

-f-yJ---I ~~~~ 1 f STOPLOG OR GATE FRAME GUIDE FOR PIER 

SECTION A-A 

,, PreCOIf concrete STOPLOG OR GATE FRAME GUIDE FOR CHECK WALL OPCi ,TWO REOUIRED, 

Figure 3.13. Standard checkdrop structures. Q greater than 60 and less than 100 cfs. 103-D-121 1 
REGULATING STRUCTURES 143 

elevation C, the bottom grade at the 

downstream end of the structure, to be 

1205.92. The change in grade then is: 

Elevation A 

- Elevation C 

1207.18 

- 1205.92 

Change in grade 1.26 feet 

Refer to figure 3-12 which shows a number 

of check-drop structures with standard 

dimensions for a drop in grade of up to 1.5 

feet. There is not a structure listed for a canal 

capacity of 50 cfs. Therefore, from the table 

on figure 3-l 2 select structure number 1 1 

which has the next largest capacity, or 52 cfs. 

If more than one structure is listed for the 

required capacity, choose the most economical 

structure that best fits the channel section. If 

gates are to be used, the availability of gate 

sizes may influence the choice of structure. 

Determine elevation B : 

From figure 3-l 2, dimension C for 

structure number 11 is 3.25 feet and the 

drop in the floor is 1.5 feet. 

Elevation A 

+ Upstream normal water 

depth 

Upstream normal water 

surface elevation 

1207.18 

+2.75 

1209.93 

The top of the check wall is set at or slightly 

above the elevation of the upstream normal 

water surface. 

Elevation of the top of 

the check wall 1209.93 

Dimension C 3.25 

1206.68 

Drop in floor - 1.50 

Elevation B 1205.18 

Elevation B should be equal to or lower than 

elevation C. If elevation B is higher than 

elevation C, a structure with a larger dimension 

C should be selected. 

Determine the downstream water surface 

elevation: 

Since there is no change in channel 

properties at the structure, the downstream 

normal water depth equals the upstream 

normal water depth. 

Elevation C 1205.92 

+ Downstream normal water 

depth + 2.75 

Downstream normal water 

surface elevation 1208.67 

Transitions are provided as required to fit 

the structure to the canal cross section and in 

unlined canals the channel should be protected 

above and below the structure to prevent 

erosion. 

Check-drops for capacities between 60 and 

100 cubic feet per second are shown on figure 

3-13. For structures with a drop in the floor of 

3 feet, see figure 3-14. 
144 SMALL CANAL STRUCTURES 

SE CTION A-A 

Figure 3-14. Standard dimensions for a 3-foot checkdrop structure. (Sheet 1 of 2.) 103-D-1212 
REGULATING STRUCTURES 145 

SECTION B-6 

SECTION c-c 

0 

SEC. D-D 

n, 

TYPICAL SLIDE GATE 

ASSEMBLY 

STOPLOG OR GATE FRAME GUIDE FOR CHECK WALL 

t 7wo REQUIREDi 

Figure 3-14. Standard dimensions for a 3-foot check-drop structure. (Sheet 2 of 2.) 103-D-1212 
146 SMALL CANAL STRUCTURES 

D. TURNOUTS 

D. L. WINSETT’ 

3- 1 I . Purpose and Description. -Turnouts 

are used to divert water from a supply channel 

to a smaller channel. The structure will usually 

consist of an inlet, a conduit or a means of 

conveying water through the bank of the 

supply channel and, where required, an outlet 

transition. Gates are generally used in the inlet 

to control the flow. Pipes are generally used to 

carry the water through the bank of the supply 

channel. The conduit and outlet sections of the 

structure may be designed as part of another 

type of structure such as a siphon or a drop or 

they may connect to a water measurement 

structure. 

3 - 1 2. Design Considerations. -(a) Vclocif),.-For structures not having a concrete 

outlet transition and discharging into an 

unlined channel, the maximum velocity in the 

pipe should bc about 3.5 feet per second. If an 

outlet transition is provided, the maximum 

velocity in the pipe may be increased to about 

5 feet per second. A minimum pipe diameter of 

18 inches is generally used. 

(b) Percolution und Stability. -The structure 

must provide a percolation path of sufficient 

length to prevent the removal of foundation 

materials by seepage water. It may be necessary 

to attach collars to the conduit to increase the 

length of the percolation path. For a discussion 

of percolation and the design of collars see 

subchapter VI C. Turnout inlets must be stable 

against flotation and sliding. 

(c) H.vt/r(lLrlics.-The amount of 

submergence on the conduit depends on the 

type of turnout inlet and outlet used. The 

submergence should be in accordance with the 

paragraphs dealing with the particular type of 

structure used. The proper submergence 

promotes smoothness of flow and the accuracy 

of water measurement devices where they are 

incorporated into the turnout structure. The 

design examples demonstrate the computation 

of losses through a turnout structure. When 

there is excessive head across the structure, the 

conduit and outlet portions of the turnout 

must be designed as a drop structure. If the 

20p. cit.. p. 134. 

design delivery water surface elevation is higher 

than the maximum elevation to which the 

turnout can deliver the required flow, some 

means must be found of either reducing the 

losses through the structure or raising the 

control water surface elevation in the supply 

channel. The use of larger pipe will reduce the 

losses a small amount. The control water 

surface may be raised by moving the check that 

maintains the water surface, closer to the 

turnout. If the required head cannot be 

obtained by the above methods, it may be 

necessary to relocate the turnout or to pump 

to the required delivery water surface 

elevation. 

(d) Miscellmeous. -Turnout inlets should be 

set so that they do not protrude into the canal 

prism. The slope of the sidewalls should be 

such that they will not interfere with cleaning 

and maintaining the canal. 

Cast iron slide gates with machined seats are 

used as turnout gates to insure watertightness 

when gates are closed. Steel slide gates are used 

as orifice gates in constant-head orifice 

structures. 

For watertightness, Reclamation requires 

rubber gasketed joints in pipe used as a 

conduit. The air vent shown on figures 3-15, 

3-29, and 3-30 is to prevent the formation of a 

vacuum downstream of the turnout gate and 

may be omitted when the turnout gate is 

submerged by the design delivery water 

surface. 

3-13. Turnouts Without Water 

Measurement. -If water measurement at the 

turnout is not required, the turnout structure 

will require only proper sizing and setting to 

deliver the required flow from the supply 

channel. Figure 3-l 5 shows a straight, throughthe-bank turnout with neither an outlet 

transition nor a provision for measurement. 

The following example shows how this type of 

structure is set into a canal bank to fulfill a 

given set of conditions. 

3-l 4. Design Example. -Design a straight, 

through-the-bank turnout to divert a Q of 25 

cfs from a supply channel to an earth ditch. 

Neither an outlet transition nor water 
REGULATING STRUCTURES 147 

I 

4 

SECTION A-A 

I 

’ 1 

I 

SECTION B-B 

Figure 3-15. Turnout. 103-D-1213 
148 SMALL CANAL STRUCTURES 

The highest elevation to which this turnout can 

deliver 25 cfs is: 

measurement is required. The control water 

surface in the supply channel is at elevation 

1217.58. Determine the size of pipe to be used 

and the maximum elevation to which 25 cfs 

can be delivered. 

Without an outlet transition the velocity in 

the pipe should be limited to about 3.5 feet per 

second. Consider a 36-inch-diameter pipe 

which has an area of 7.07 square feet. Pipe 

properties may be obtained from tables or 

computed as below: 

Q 

Pipe velocity, V = A = 3.5 fps 

V2 

Velocity head in pipe, h, = - = 0.19 ft. 

33 

Wetted perimeter of pipe, wp = 71 x diameter 

= 9.4 ft. 

Hydraulic radius of pipe, R = G= 0.76 ft. 

WP 

2 

Friction slope of pipe, s = 

s = 0.0014 ft./ft. 

Manning’s coefficient of roughness for 

precast concrete pipe, n = 0.0 13 

The head loss through this structure is 

comprised of: 

(1) A loss at the entrance to the pipe. This 

loss is assumed to be 0.78 times h, where 0.78 

is the entrance loss coefficient, or 

0.78 x 0.19 = 0.15 ft. 

(2) Pipe losses.-In this example friction is 

the only pipe loss incurred. The pipe loss 

equals the length of pipe times the friction 

slope of the pipe (s). If 50 feet of pipe are 

required to convey the water through the canal 

bank, the loss will be: 

50 x 0.0014 = 0.07 ft. 

(3) A loss at the exit from the pipe. This 

loss equals 1 times h, (chapter VII) or: 

1 x 0.19 = 0.19 ft. 

The total loss through the structure equals the 

sum of the above losses: 

-0.15 + 0.07 + 0.19 = 0.4 1 ft. 

1217.58 - 0.41 = 1217.17 

Set elevation D (fig. 3-15) so that the 

control water surface in the supply channel 

submerges the top of the pipe at the turnout 

headwall a distance equal to 1.78 times h, 

plus 3 inches minimum: 

1.78 x 0.19 + 0.25 = 0.59 ft. 

To determine elevation D: 

Control water surface 

elevation 

- Submergence on top of pipe 

Elevation of the top of 

pipe 

- Pipe diameter 

Elevation D 

~ 4 inches (fig. 3- 15) 

Elevation of turnout floor 

Determine elevation A: 

1217.58 

0.59 

1216.99 

3.00 

1213.99 

0.33 

1213.66 

The elevation at the cutoff (El. A) should 

be set to prevent this point from controlling 

the flow through the structure. 

The width of the structure at the cutoff is 

equal to the pipe diameter plus 12 inches or 

in this example, 4 feet. 

Assume that the cutoff acts as a 

suppressed rectangular weir. The head (h) 

required on a 4foot weir for a discharge of 

25 cfs is obtained from weir tables, or h = 

1.6 feet. 

Control water surface 

elevation 

-- h 

Maximum elevation A 

1217.58 

1.60 

1215.98 

If additional width at the cutoff is required, 

the sidewalls may be flared 8 to 1. 
REGULATING STRUCTURES 149

Choose an elevation A that satisfies both the

above criteria and the conditions found in the

field. Set elevation J to provide the

submergence at the pipe outlet (0.25 ft.) as

shown on figure 3-15.

one structure. Line meters are similar to

open-flow meters but are installed in pipelines.

Because trash in the water can foul or

damage these meters, racks or screens are

sometimes installed on the turnou t inlet to

protect them. See chapter IV for a discussion

of flow meters. Figure 3-23 shows the brackets

on the outlet headwall that hold the flow

meter and the slots into which stoplogs are

placed to force the conduit to flow full.

1217.17

0.25

Delivery water surface

elevation

-Submergence at pipe outlet -

1216.92

3.00

1213.92

Elevation top of pipe at

outlet

-Pipe diameter

Elevation J

Select a class of pipe that will withstand the

internal and external loads to which it will be

subjected, and provide an earth transition and

protection at the outlet as required.

Figures 3-16 and 3-17 show completed

precast concrete turnout inlets in the casting

yard. Figures 3-18 through 3-21 show typical

turnout installations using both precast and

cast-in-place concrete transitions.

3-15. Turnouts With Measurement.-

(a) Flow Meters.-Open-flow meters can be

used to measure the amount of water diverted.

They are propeller devices that are especially

useful where the head available for

measurement is limited. They may be attached

to the outlet of a structure as shown on figure

3-22. The outlet must be designed to force the

conduit to flow full. The flow meter may be

detachable allowing it to be used on more than

Figure 3-17. Completed turnout inlets in casting yard.

PX 303-602

Figure 3.16. Precast concrete turnout inlets.

PX.D.72616 D Figure 3-18. Lateral turnout gates. PX-D-72619 D
150 SMALL CANAL STRUCTURES

Figure 3-19. Turnout structure in earth channel. P214-D-73783

the flow of water. It may be used as an inline

structure or as a turnout inlet. Figures 3-24

through 3-26 show various details of the

construction and operation of constant-head

orifice turnouts.

At least two gates are required for the

structure to operate. The first gate, the

upstream gate, controls the size of the

rectangular orifice. A second gate, the

(b) Parshall Flumes and Weirs.-Parshall

flumes and weir structures are sometimes

incorporated into turnout designs to measure

flows where the required head is available.

They should be designed in accordance with

the criteria set forth in chapter IV.

(c) Cons/an/-head Orifice S/ruc/ures.- The

constant-head orifice structure was developed

by Reclamation to both regulate and measure
REGULATING STRUCTURES 151

Figure 3-20. Precast turnout inlet in place in canal

bank. Note concrete lining blocked out around

structure. PX 303-429 NA

Figure 3-22. Flow through turnout being measured with an

open-now meter. Discharge is 1.7 cfs. p 499-700-615.

Figure 3-21. Completed turnout structure ready for

backfilling. p 328.701-6580

downstream gate, controls the water depth

below the orifice and is operated to maintain

the head across the orifice at a constant value.

The flow through the structure is varied by

changing the area of the orifice. The

approximate flow through the structure can be

computed from the equation:

structures are normally operated with a head

differential (h) of 0.2 foot but where the head

is available a greater differential may be

used. Staff gages are used to measure the head

across the orifice.

Approximate discharge tables for two orifice

gate sizes, 24 by 18 inches and 30 by 24 inches

operating under a head of 0.2 foot are shown

in tables 3-1 and 3- 2. The tables show

discharges with both one and two gates in

operati'on. For larger flows, more or larger

openings are used.

3-16. Design Considerations.- The following

criteria are for constant-head orifice structures

with capacities of up to 30 cfs (fig. 3-27).

Area of orifice required:

A= Q

c../2gh

Q=CA..['Igh where'

The coefficient of discharge (C) is generally

considered to be 0.7. Constant-head orifice

c = orifice coefficient = 0.7, and

h = differential head = 0.2 ft.
152 SMALL CANAL STRUCTURES

Figure 3-23. Farm turnout outlet. Brackets on headwan

hold open-flow meter. Angles in foreground hold

stop logs to force conduit to flow fun. p 499-700-383.

Figure 3-25. Constant-head orifice turnout inlet.

PX-D-72618 D

This area should be provided in 75 to 80

percent of the gate rise.

The upstream submergence on the orifice

gate (s) should be equal to or greater than the

orifice gate opening (y m ) at maximum

capacity. The submergence on the turnout gate

opening should be 1.78 times the velocity head

of the full pipe plus 3 inches minimum.

A level floor length equal to the height of

the orifice gate opening (y m ) should be

provided in front of the orifice gates. For

structures with capacities up to 10 cfs the

minimum distance between the orifice gate and

the turnout gate (L) should be 2-1/4 times the

orifice gate opening for maximum flow (y m )

or 1-3/4 times the wall opening (y t) whichever

is greater (3-foot 6-inch minimum). For

structures wi th capacities greater than 10 cfs, L

should be 2-3/4 times the height of the orifice

gate opening (y m ). The width of the structure

Figure 3-24. Constant-head orifice turnout with

stilling wells. Discharge is 7 cfs. PX-D-72604 D
REGULATING STRUCTURES 153

Figure 3-26. Operator adjusting orifice gate on a

constant-head orifice turnout. P222-116-52046 A

must accommodate the gates used and the

width at the cutoff must be great enough to

prevent it from becoming a control. The

sidewalls may be flared 8 to 1 if additional

width at the cutoff is needed.

The conduit and outlet section of the

structure should be designed as a siphon or

drop if conditions dictate. An air vent behind

the turnout gate should be provided when the

pipe profile will pennit a vacuum to form

downstream of the turnout gate.

The above criteria are for structures with

capacities up to 30 cfs. For larger flows special

structures with multiple gates and conduits are

designed to suit conditions.

The accuracy of a constant-head orifice
I 

154 

structure is affected by: 

(1) Flow conditions upstream from the 

orifice gate, 

(2) Flow conditions downstream from the 

gate, 

(3) Errors in reading the head differential, 

and 

(4) Obstruction of the orifice by trash in 

the water. 

With the accuracy of the structure 

dependent upon so many variables, field rating 

of the structure should be made when 

accuracies of better than about 10 percent are 

required. 

A constant-head orifice structure built inline 

can perform checking and measuring functions 

in the canal (fig. 3-28). One or more orifices 

with gates are built into a wall that extends 

across the channel. A second wall with gated 

openings is built at the downstream end of the 

structure. These structures also use the 

principle of a submerged orifice under a known 

head and are operated in the same manner as 

smaller constant-head orifice structures. The 

head differential is measured by either 

piezometers or staff gages. Generally discharge 

curves for these larger structures are prepared 

from field rating data. 

The following example demonstrates the 

procedure in designing a constant-head orifice 

turnout. 

3-17. Design Example.-Refer to figure 

3-29. Design a straight, through the bank 

turnout to divert 20 cfs from a supply channel 

to an earth ditch. The diversion is to be 

measured with a constant-head orifice inlet. A 

broken-back outlet transition is to be provided. 

The control water surface in the supply 

channel is at elevation 1217.58. Determine the 

size of pipe to be used. Determine the 

maximum elevation to which 20 cfs can be 

delivered. 

With an outlet transition, the full pipe 

velocity may be about 5 feet per second. 

Consider a 30-inch-diameter pipe with an area 

(A) of 4.9 square feet. Pipe properties may be 

obtained from tables or computed as below: 

Q 20 

Pipe velocity V = A = 4.9 = 4.1 feet per 

second; therefore, a 30-inch-diameter pipe is 

satisfactory. 

SMALL CANAL STRUCTURES 

Pipe velocity head h, = g = 0.26 ft. 

Wetted perimeter of the pipe 

diameter or 71 x 2.5 = 7.9 ft. 

Hydraulic radius of the pipe R 

= 0.62 ft. 

(wp) = 71 x 

area 4.9 =-orwp 7.9 

The coefficient of roughness n for precast 

concrete pipe is assumed to be 0.0 13. 

2 

Friction slope of the pipe s = 

= 0.0024 ft./ft. 

Determine the area of the orifice gate: 

Q Area = - 

Cd23 

Assume C = 0.7, h = 0.2 ft. 

A = 8 square feet 

Consider an orifice gate 42 inches wide by 

36 inches high. The area equals 3.5 x 3.0 = 

10.5 square feet. 

Determine the gate opening to provide an 

area of 8 square feet: 

8 Gate rise = 3.5 = 2.3 ft. 

23 2 = 0.77 or 77 percent 3 

From above, the gate must be 77 percent 

open to provide the required area. This meets 

the requirement that the orifice area must be 

furnished in 75 to 80 percent of the gate rise. 

To accommodate a gate 42 inches wide the 

width of the box must be approximately 5 

feet. A 30-inch-diameter cast iron turnout gate 

will fit both the pipe and the size of box 

selected. 

A level floor length equal to the orifice gate 

opening (2.3 feet minimum) should be 

provided in front of the orifice gate. 

Because the design capacity is greater than 

10 cfs, the length of the measuring well should 

be 2-3/4 times 2.3 or 6.33 feet minimum. The 

orifice gate opening should be submerged a 

distance equal to the orifice gate opening (2.3 

feet minimum). The elevations pertaining to 

the orifice will be: 
REGULATING STRUCTURES 

Table 3-l.-Discharge oj’constant-head orifice turnout in cubic feet per second. Capacity 20 cfs, 

gatesize30~24inches,&=O.ZOfoot. 103-D-1214 

155 

Discharge, 

cfs 

I-- 

II Discharge 

2 gates 

I 

1 gate 

II 

Gate opening in feet Gate opening in feet 

!> 

-11 

. 

cfs 

2 gates 1 gate 

3.00 

0.25 0.02 0.04 10.25 0.8 1 

.50 .04 .08 10.50 .83 

.I5 .06 .12 I0.G .85 

1.00 .08 .16 11.00 .87 

1.25 .I0 .20 11.25 .89 

1.50 I .12 11.50 .91 

1.15 .14 

I .24 II 

.28 11.75 

2.00 .16 

2.25 .18 

I 

I II .93 

.32 12.00 .95 

.36 12.25 

2.50 .20 I .40 II 

.91 

12.50 .99 

2.15 .22 .44 12.75 1.01 

.24 .48 13.00 1.03 

.26 .52 13.25 

.28 .56 13.50 I 1.05 1.07 

.30 .60 13.75 1.085 

.32 .64 14.00 1.10 

.34 358 

.72 II 

14 _ 2s ..-- 1.12 

.36 14.LJ 1.14 

.38 ,755 14.75 1.16 

.40 .I9 15.00 1.18 

.42 .83 15.25 1.20 

-44 

5.15 

I 146 -81 I ._ .91 I I 

15 __.-l 15.75 sn 1.24 12 

1.26 

3.25 

3.50 

3.75 

4.00 

4.25 

4.50 

4.15 

5.00 

5.25 

5.50 

6.00 .48 .95 16.00 

6.25 .50 .99 

6.50 .52 1.03 

6.75 .54 1.065 

7.00 .56 1.10 

7.25 .58 1.14 11.25 

7.50 .60 1.18 i7.50 

7.75 I A2 I 122 II 1775 

16.25 

16.50 

16.75 

17.00 

8.00 .64 

_.-- 

1.26 

8.25 .66 1.30 

8.50 .68 1.34 

8.75 .70 1.375 

9.00 .72 1.41 

9.25 .I4 1.45 

9.50 .76 1.49 

9.75 ,175 1.525 

10.00 .79 1.56 

II 

_ .,._ 

18.00 

18.25 

18.50 

18.75 

19.00 

192s 

1.28 

1.30 

1.32 

1.34 

II 19.50 

1.355 

1.37 

1.39 

~ 

1.41 

1.43 

1.45 

1.47 

1.49 

1.51 

1.53 

1.545 II 19.75 

20.00 I 1.56 I 
156 SMALL CANAL STRUCTURES 

Table 3-2.-Discharge of constant-head orifice turnout in cubic feet per second. Capacity 10 cfs, 

gate size 24 x 18 inches, &I = 0.20 foot. 103-D-1215 

Discharge, 

cfs 

Gate opening in feet 

2 gates 1 gate 

Discharge, 

cfs 

Gate opening in feet 

0.25 

.50 

.I5 

1.00 

1.25 .125 .25 6.25 

1.50 .15 .30 6.50 

1.75 ,175 .35 6.75 

2.00 .20 .40 7.00 

2.25 .225 .45 7.25 

2.50 .25 

2.15 ,275 2 

7.50 

7.75 

3.00 .30 .60 8.00 

3.25 ,325 .65 8.25 

3.50 .35 .70 8.50 

3.15 .375 ,145 8.75 

4.00 .40 .79 9.00 

4.25 ,425 .84 9.25 

4.50 .45 .a9 9.50 

4.75 ,475 .94 9.75 

5.00 .50 .99 10.0 

0.025 0.05 5.25 

.05 .lO 5.50 

,075 .15 5.75 

.lO .20 6.00 

Control water surface in 

the canal 

- Submergence on the 

orifice gate (S) 

1217.58 

wall is limited to about 8 inches (0.67 ft.). 

2.30 

Elevations pertaining to the turnout gate 

are : 

Elevation of the turnout 

floor 1212.98 

+ 4 inches (fig. 3-29) + 0.33 Elevation top of orifice 

gate 1215.28 

- Gate opening (Y, ) 2.30 

Elevation of the turnout 

floor 12 12.98 

+ Gate height (Y,) + 3.00 

Elevation top of orifice 

gate opening 1215.98 

From figure 3-27, X, = 3.00 - 2.30 

= 0.70 ft. 

Elevation D 1213.31 

+ Pipe diameter + 2.50 

Elevation top of pipe at 

headwall 1215.81 

With a 0.2-foot head differential across the 

orifice the submergence on the top of the pipe 

at the headwall equals: 

Control water surface in 

the canal 1217.58 

Head differential 0.20 

The distance X, must be greater than or 

equal to the thickness of the orifice wall (t). 

Then the maximum thickness of the orifice 

Water surface elevation in 

the measuring box 1217.38 
REGULATING STRUCTURES 157 

Orif 

Gate opening for max. Q.?=o.B max. 

Full gate leaf travel. 

Submergence 

Turnout gate 

not shown- 

” Xr;’ must be equal to or greater than “I-” for max. Q. 

” s ” is equal to or greater than ” y,,,” for good accuracy. 

For Q up to to cfs, L must be at least 2$ ym or I+ yt, 

whichever is greater. (3'-6" minimum) 

For Q above Ia cfs, L = 2f y,,, minimum. 

h = 0.2' (Normally) 

Figure 3-27. Dimensions for a constant-head orifice. 103-D-1216 

Water surface elevation in 

the measuring box 1217.38 

- Elevation top of pipe at 

headwall - 1215.81 

Submergence on turnout 

pipe 1.57 ft. 

The required minimum submergence on the 

turnout pipe equals 1.78 times h, plus 3 inches 

minimum = 1.78 x 0.26 + 0.25 = 0.71 ft. The 

elevations selected meet this requirement. 

Determine elevation A: 

The elevation at the cutoff (El. A) should 

be set to prevent this point from controlling 

the flow through the structure. 

The width of the structure at the cutoff in 

this example is 5 feet. Assume that the 

cutoff acts as a suppressed rectangular weir. 

The head (h) required on a 5-foot weir for a 

discharge of 20 cfs is 1.2 ft. (table 5-6). 

Control water surface 

elevation 

-h 

1217.58 

1.20 

Maximum elevation A 1216.38 

Choose an elevation A that satisfies both the 

above criteria and the conditions found in the 
SMALL CANAL STRUCTURES 158

The total loss across the structure is the sum

of the above losses:

0.20 + 0.20 + 0.12 + 0.18 = 0.70 ft

The maximum elevation to which this

structure can deliver 20 cfs is:

1217.58

0.70

Control water surface

elevation

-Head loss in the

structure

Maximum delivery water

surface 1216.88

Submerge the top of the pipe 0.50 foot at

the outlet transition headwall as shown on

figure 3-29.

Figure 3-28. Constant-head orifice structure used as a

check. Structure maintains upstream water surface

and measures flow in the canal. PX-O-7260S

1216.88

Maximum delivery water

surface

-Submergence on the top

of pipe

field. If additional width at the cutoff is

required, the sidewalls may be flared 8 to I.

The losses through the structure will consist 0.50

of: ( 1) Measurement loss (h) = 0.20 ft.

(2) A loss at the entrance to the

turnout pipe equal to 0.78 times hy or:

Elevation top of pipe at

outlet headwall

-Pipe diameter

1216.38

2.50

0.78 x 0.26 = 0.20 ft.

Elevation pipe invert at

outlet headwall (3) Pipe loss. Assuming that the only

pipe loss incurred in a So-foot length of

pipe is the friction, the pipe loss equals

the length of pipe times the friction slope

of the pipe (s):

1213.88

50 x 0.0024 = 0.12 ft.

(4) A loss at the exit from the pipe

equal to 0.7 times 6hy (chapter VII) or:

A class of pipe should be selected that will

withstand the external and internal loads to

which it will be subjected. The concrete pipe

transition provided should fit the structure to

the channel, and the channel should be

protected to prevent erosion.

Figure 3-30 shows a number of

constant-head orifice turnout structures with

0.7 x 0.26 = 0.18 ft. capacities greater than 30 cfs.
REGULATING STRUCTURES 159 

: 1 
160 SMALL CANAL STRUCTURES 

I 

-1 

L 
REGULATING STRUCTURES 161 
SMALL CANAL STRUCTURES

E. DIVISION STRUCTURES

D. L. WINSETT 2

162

3-18. Purpose and Description. -Division

structures are used to divide the flow from a

supply pipe or channel among two or more

channels or pipes. The division structure may

be a separate structure or it may be the outlet

of a siphon, a drop, or a turnout from which

further diversion is required. If measurement is

not required at the point of division, the flow

through the structure may be directed through

the various outlets with gates or stoplogs. If the

flow must be measured and the required head

is available, weirs may be used to proportion

the flow. Weirs that are both movable and

adjustable are often used in division structures.

Adjustable weirs can be adjusted vertically and

provide a means of controlling the flow as well

as a means of measurement. Movable weirs are

mounted in frames that are inserted into

grooves in the division structure and may be

moved from one structure to another. To avoid

reducing the accuracy of the weir

measurement, the structure should be designed

to provide suitable conditions for the weir as

set forth in the discussion of weirs in chapter

V. Weir discharges may be obtained from

discharge tables or from flow formulas. The

head on the weir is generally obtained from

staff gages mounted in the structure.

20p. cit., p. 134.

Figure 3-31. Division structure usin~ 2-foot adjustable

weirs. Design Q 3 cfs over each weir. PX-D-72614 D
REGULATING STRUCTURES 163

Figure 3-33. Division structure with now over IS-inch

weir in foreground. p 33-D-33913

Figure 3-32. Pipe division box. Note 3-foot adjustable

weirs center and left. P222-116-53582

Figures 3-31 and 3-32 show division

structures using adjustable weirs to proportion

the flow. Figure 3-33 shows a structure with a

fixed weir in operation. Figure 3-34 shows the

slots which could accept stoplogs, gates in

frames, or movable weirs.

Various combinations of supply and delivery

are shown on figures 3-35 and 3-36. In practice

any of the possible combinations may be

encountered. The pool shown ahead of the

structures is an attempt to approach standard

conditions to increase the accuracy of any weir

measurement made in the division structures.

Design considerations.-Water must be

delivered to the division structure at an

elevation that will provide enough head on the

weirs to furnish the required flow at the

required delivery water surface elevation.

When delivery to the division structure is

through a pipe, the velocity in the pipe is held

to about 1.5 feet per second to reduce

turbulence ahead of the weirs.

Figure 3-34. Division structure used as outlet to

turnout. p 328-701-7166
164 SMALL CANAL STRUCTURES 

SECTION A-A 

.G -Y SECTION S-E 

2’“DJ IVEIR J’AOJ WEIH 

DETAILS OF OPENING 

FOR ADJUSTASLE WEIR 

,I 1 PLAN 

TYPICAL CONNECTION 

TO CONCRETE LINING 

Figure 3-S. Division structure. 103-D-1219 
REGULATING STRUCTURES 165 

CONCRETE PLANK 
166 SMALL CANAL STRUCTURES

CHECK AND PIPE INLETS

3

R. B. YOUNG

F.

crossings, inverted siphons, pipe drops, and

pipe chutes where the capability of providing a

checked water surface in the canal is required.

Check spacing has been previously discussed in

subchapter III B.

3-21. Design Considerations. -(a) Upstream

Transitions. -The transition from the canal

section produces a smooth change of velocity

from canal to structure and provides for a

gradual change in invert elevation from the

canal to the opening in the structure. The

invert slope should not be steeper than 4 to I.

(b) Pro tection. -Protection is often used

adjacent to structures in earth-Iined canals

where erosion may occur. F or design of

protection see the discussion on Protection in

subchapter VII B.

(c) Inlet Opening. -The area of the inlet

opening should be proportioned to limit the

design flow velocity to about 3.5 feet per

second. This velocity is considered as the

maximum desirable for ease of stoplog

handling. The width of the opening is set to

reasonably approximate a canal base width for

the design flow. The opening has gate frame

guides for installation of a gate or for use as

stoplog guides. If there is a need to operate the

check automatically, a gate should be used.

The elevation of the inlet opening should be

the same or lower than the invert of the canal.

(d) Sidewalls.- The sidewalls should have a

top elevation equal to the elevation of the

normal canal water surface, irrespective of the

control water surface elevation. If the inlet of

the structure is inadvertently closed or

improperly regulated, the flow in the canal will

spill over the sidewalls and inlet closure.

Referring to the structure in figure 3-38,

assuming the extreme condition of flow at

canal design capacity and complete closure of

the inlet opening, there will still remain about

0.5 foot of canal bank freeboard provided the

freeboard design was based on figure 1-9. The

depth of flow over the walls and closure is

dependent on the coefficient of discharge, the

3-19. Description and Purpose. -The check

and pipe inlet is a box-type structure on the

upstream end of a pipe (see fig. 3-37). The inlet

to the box is an opening that provides for

installation of either a gate or stop logs. Walk

planks covering the top of the box provide a

platform for operation of the gate or stop logs.

The purpose of a check and pipe inlet is to

maintain a water surface at a required elevation

for turnout deliveries upstream with partial

flows in the canal. By partially closing the inlet

with the gate or stoplogs, the canal water

surface can be controlled to the desired

elevation. The sidewalls provide for emergency

overflow into the box if the gate or stoplogs

are not appropriately set for a particular flow

in the canal; if the inlet becomes obstructed; or

if the inlet is closed. This structure can also

serve as a shutoff point in the canal. When

water delivery downstream from the inlet is

not required, or if a canal break should occur ,

complete closure of the inlet with diversion to

a wasteway could isolate the appropriate canal

reach.

3-20. Application. -The check and pipe

inlet is combined with and used on the

upstream end of such structures as road

Figure 3-37. Check inlet to 42-inch-diarneter pipe

siphon. p 222-116-48458

3Civil Engineer, Hydraulic Structures Branch, Bureau of

Reclamation.
REGULATING STRUCTURES 167 

: 

---, 

. ..& 

f -- 

PRECAST CONCRETE WALK PLANK 

Figure 3-38. Check and pipe inlet. 103-D-1221 
168 SMALL CANAL STRUCTURES 

(2)‘ 3.5 feet per second for a pipe drop 

having only an earth transition at the outlet, 

(3) 5 feet per second for a pipe drop having 

a concrete outlet transition, 

(4) 10 feet per second for a relatively long 

inverted siphon having a concrete outlet 

transition, or 

(5) 12 feet per second for a pipe drop or 

pipe chute having a baffled outlet or a stilling 

pool outlet. 

After the maximum allowable pipe velocity 

has been determined, the pipe diameter may be 

selected by using the tables on figures 2-2, 2-4, 

or 2-3 1. 

(i) Pipe Vc/ztS.-If a hydraulic jump occurs 

in the pipe and the inlet is sealed there is a 

possibility of blowback. A vent at the headwall 

or immediately upstream from the jump may 

be required to prevent this blowback. See 

figures 3- 15 and 8-2 1 for air vent details. 

3-22. Structure Numbering. -A combination 

of the pipe diameter and maximum allowable 

velocity in the pipe is used to identify a 

check-and-pipe inlet structure. Thus, structure 

number 12-l represents a structure with a 

12-inch-diameter pipe having a maximum 

allowable pipe velocity of 5 feet per second. 

This structure should also be used with a 

12-inch-diameter pipe having a maximum 

allowable pipe velocity of 3.5 feet per second 

(also see notes on fig. 3-38). Structure number 

12-2 represents a structure with a 

12-inch-diameter pipe having a maximum 

allowable pipe velocity of 12 feet per second. 

This structure should also be used with a 

12-inch-diameter pipe having a maximum 

allowable pipe velocity of 10 feet per second. 

The check and pipe inlet structures selected for 

3.5 and 10 feet per second will have 

conservative dimensions, but the difference in 

cost is not considered excessive. The table in 

figure 3-38 provides standard dimensions for 

structures corresponding to structure numbers. 

3-23. Design Example (see fig. 

3-38).-Assume that a pipe drop is required to 

convey the canal water to a lower elevation. In 

addition assume that a check will be required 

at the inlet of the drop to raise the canal water 

surface to a required elevation for delivery to a 

lateral. 

length of walls, the width of structure, and the 

flow in the canal. When a slide gate is selected 

from the table of dimensions (fig. 3-38), the 

top elevation of the gate, when closed, will be 

at approximately the same elevation as the top 

of the sidewalls. If the exact selected gate size 

is not available from the manufacturer and the 

next greater available height is used, the taller 

gate when closed with design flow in the canal 

may cause the canal freeboard to be less than 

0.5 foot as the resultant water elevation will 

have been increased. If the resultant freeboard 

is much less than 0.5 foot, the sidewalls should 

be lengthened until the canal freeboard is 

about 0.5 foot when the gate is closed and 

normal canal flow is spilling into the structure. 

(e) Headwall.-The headwall at the pipe end 

of the box retains earthwork; provides for pipe 

embedment; and by its horizontal extension 

into the canal banks and vertical extension 

below the pipe, serves as a percolation cutoff. 

(f) Floor of Inlet Box and Pipe Invert. -The 

invert elevation of the box floor is set at the 

same elevation as the invert of the pipe. The 

table of dimensions shown on figure 3-38 was 

established to set the pipe invert low enough to 

allow for hydraulic losses through the inlet 

opening and the pipe entrance, thereby 

preventing backwater in the canal for its design 

flow. A minimum loss of 0.5 of the velocity 

head in the pipe is provided. 

(g) W&k Plalrks.-Walk planks are supported 

by the headwall and the walk plank support 

angle. The planks provide a platform for 

operating a gate or handling stoplogs. The 

18-inch clearance between the top of sidewalls 

and bottom of walk planks provides clearance 

for the passage of floating debris that might 

otherwise obstruct the flow of water over 

sidewalls. 

(h) Pipe Diumeter.-The pipe is sized by 

design steps discussed in respective paragraphs 

of road crossings, inverted siphons, pipe drops, 

and pipe chutes. The criteria for determining a 

pipe size for a structure having a check and 

pipe inlet is based on providing a pipe with an 

adequate diameter so that the velocity in the 

pipe will not exceed the following: 

(1) 5 feet per second for a road crossing or a 

similar structure such as a short inverted siphon 

having a concrete outlet transition, 
REGULATING STRUCTURES 

(a > Assume the fi~llowing design 

informa fion is given : 

(1) Type of waterway = earth canal. 

(2) Type of conveyance structure = 

pipe drop sumped for energy dissipation 

with an earth outlet transition. 

(3) The conveyance structure would 

have a maximum allowable pipe velocity 

of 3.5 feet per second. 

(4) Q = 50 cfs. 

(5) El. A = 5407.00 (from a profile 

sheet). 

(6) d, = 2.00 ft. (normal depth at Sta. 

A). 

(7) NWS El. at Sta. A = El. A + d, = 

5407.00 + 2.00 = 5409.00. 

(8) El. top of bank = 5410.6. 

(9) Check and pipe inlet is required. 

(10) Check structure to be automated. 

(b) Determine: 

(1) Need for either gate or stoplog 

control.-Use gate because of need to 

automate the check. 

(2) Pipe size (see table on fig. 2-3 1). 

For a Q of 50 cfs and a maximum 

allowable velocity of 3.5 feet per second 

use a 54-inch-diameter pipe. 

(3) Structure number.-Structure 

number 54-1, although proportioned for a 

maximum allowable pipe velocity of 5 

feet per second, can also be used for a 

maximum allowable pipe velocity of 3.5 

feet per second. 

(4) Determine standard check and pipe 

inlet dimensions R, Y, L, and k. These 

dimensions are read from the standard 

dimension table for structure number 

54-l: 

R = 5 ft. 9 in. 

Y = 18 in. 

L = 6 ft. 6 in. 

k = 6 ft. 

(5) Pipe velocity head.-For 

54-inch-diameter pipe and Q = 50 cfs. 

A, = 0.785 x diaZ = 15.90 ft.z 

169 

2 3.142 h, =$ = - = 0.15 foot 

P 64.4 

where g = gravitational acceleration 

In lieu of performing the above 

calculation, the hydraulic properties may 

also be determined by using table 8- 1. 

(6) Determine elevation D: 

El. D =(NWS El. at Sta. A)- R 

= 5409.00 - 5.75 

= 5403.25 

(7) Drop and slope in earth 

transition.- 

Drop = El. A - (El. D + Y) 

= 5407.00 - (5403.25 + 1.50) 

= 5407.00 - 5404.75 

= 2.25 ft. 

Slope = 10 to 2.25 = 4.6 to 1 (as 

this is flatter than 4 to 1 

it is satisfactory). 

(8) Gate size.-The standard dimension 

table shows a 72- by 51-inch gate for 

structure number 54-l. Assume for this 

example problem that this gate is not 

available and that the next available 

greater gate height is 60 inches for a 

72-inch-wide gate. 

(9) Normal canal freeboard = El. canal 

bank - El. NWS in canal = 5410.60 - 

5409.00 = 1.60 ft. 

(10) Canal freeboard with check gate 

closed and normal flow in the canal.-If 

the 72- by 51-inch gate had been 

available, then the top of gate when 

closed would have been at the same 

elevation as the sidewalls. The head 

required for discharging the design flow 

over the sidewalls and gate closure would 

have been, H=( &) 2’3= (&) 2’3 

= (0.S)2’3 = 0.86 foot. 

The above equation is derived from the 

weir equation: 

I Q 50 

v, = q zm= 3.14 f.p.s. Q=CWH”‘“, 
170 

The acceptable coefficient of discharge C 

is assumed to be 3.3. 

W = length of sidewalls plus the width 

of the structure 

=2(L)+k=2x6.5+6= 19ft. 

The resulting canal freeboard would 

then be the El. canal bank - (El. of 

sidewalls + H) = normal canal freeboard - 

H = 1.60 ~ 0.86 = 0.74 foot. 

However, use of the 60-inch-high gate 

results in the top of gate, when closed, 

being at a higher elevation than the 

sidewalls, which reduces the canal 

freeboard to less than 0.74 foot. A canal 

freeboard of about 0.5 foot is considered 

satisfactory for the extreme condition of 

normal Q overflowing the sidewalls and 

gate closure. 

Assume a 0.5-foot canal freeboard and 

solve for the Q that will overflow into the 

box using the basic weir equation. For the 

flow over the sidewalls Q = C2LH3 ‘2 and 

for flow over the top of the gate Q = 

CkH, 3 ‘2 therefore, combining these flows 

we have: 

Q = (3.3 x 2 x 6.5 x 1.15) + (3.3 x 6 x 0.01) 

= 49.4 + 0.2 = 49.6 cfs. 

SMALL CANAL STRUCTURES 

where 

H = (El. canal bank - 0.5 ft. of 

freeboard) -- El. top of sidewalls 

= (5410.60 - 0.50) - 5409.00 

= 1.1 feet 

H3’2 = 1.15 feet 

and 

H, = (El. canal bank - 0.5 ft. of 

freeboard) - El. top of closed gate 

= (5410.60 - 0.50) ~ 5410.04 

= 0.06 foot 

then 

H, 3’2 = 0.01 foot 

and 

El. top of closed gate 

= El. D + Y + 3-l/2 inches + height of gate 

= 5403.25 + 1.50 + 0.29 + 5.00 

= 5410.04 

The 3- l/2 inches in the above equation 

is the assumed size of the vertical leg of 

the gate-frame bottom angle-iron. 

The calculated overflow of 49.6 cfs is 

slightly less than the design flow of 50 cfs. 

Canal bank freeboard will therefore be 

just slightly less than 0.5 foot. 

G. CONTROL AND PIPE INLETS 

R. B. YOUNG3 

3-24. Description and Purpose. -A control of such structures as pipe drops and pipe 

and pipe inlet is a concrete box structure with chutes where the hydraulic control of the 

a trapezoidal-shaped notch for upstream water upstream canal water surface is at the inlet for 

surface control, overflow sidewalls, and an inlet all flows. Occasionally it is also used at inlets to 

to a pipe at the box headwall (see fig. 3-l). inverted siphons to prevent water surface 

The purpose of the control inlet is to drawdown which may occur for flows less than 

prevent drawdown of the canal water surface design flow. 

for a range of flows between design flow and 

about 0.2 of design flow. In addition, the inlet 

3-26. Design Considerations.-(a) Upstream 

Earth Transition.-The transition is used to 

provides a controlled water surface for 

turnouts. 

effect a gradual change from canal base width 

3-25. Application. -The control and pipe 

inlet is sometimes used on the upstream ends 30p. cit., p. 166. 
REGULATING STRUCTURES 171 

to that of the structure and in so doing 

produce a more uniform velocity change from 

the canal to the structure. The transition invert 

is level since the notch invert is set at the canal 

invert elevation. 

(b) Erosiorl Protectiotl. -Protection is used 

adjacent to control and pipe inlets in earth 

canals to prevent erosion resulting from high 

velocities. For design of protection see the 

discussion on Protection, subchapter VII B. 

(c) Corltrol Notch. -The trapezoidal-shaped 

opening or control notch is designed to control 

upstream canal water depths and velocities for 

all flows between design flow and about 0.2 of 

design flow. For any flow in this range the 

notch causes the upstream canal water depth to 

be at or very near normal depth thereby 

preventing increased velocities which otherwise 

could cause canal erosion. The elevation of the 

notch invert should be equal to the upstream 

canal invert elevation. The depth of the notch 

should be equal to or slightly more than the 

depth in the canal for normal flow. The 

bottom width, top width, and side slopes of 

the notch may be determined by the procedure 

shown in the design example (see sec. 3-28). 

A control notch which requires slightly more 

energy than that available from normal flow 

conditions in the canal will cause a very small 

rise in water surface elevation in the upstream 

canal, but this is an acceptable condition. For 

the critical case of canal flow at or near full 

design Q, the water surface rise is minimized by 

a portion of the flow being able to overflow 

the sidewalls. 

(d) Overflow Sidewulls. -These walls, with 

tops at the same elevation as the top of the 

notch, provide for emergency overflow into the 

box in the event there is an obstruction in the 

notch or the flow in the channel is greater than 

normal. The sidewalls should be of sufficient 

length to permit design flow to overtop the 

sidewalls with complete blockage of the notch. 

Channel banks must have sufficient freeboard 

for the higher water surface required to 

overflow these walls. The length of sidewalls 

(fig. 3-39) are designed to provide about 0.5 

foot of channel bank freeboard based on figure 

l-9. 

(e) Headwall. -The headwall retains channel 

earthwork, embeds the inlet end of the pipe, 

and by its extension into the earth below and 

on each side of the pipe, serves as a cutoff to 

reduce seepage from the channel. 

(f) Width of l/z/et BOY. .-The minimum 

width should be the larger of either 6 inches 

plus notch width or 6 inches plus inside pipe 

diameter. 

(g) Inlet Invert Elevation.-This elevation is 

the same as the pipe opening invert elevation 

and should be low enough so the water surface 

at the pipe opening required to convey the 

flow into the pipe will not cause the upstream 

channel water surface elevation to exceed 

normal. The R values, for commonly used full 

pipe velocities of 3.5, 5, 10, and 12 feet per 

second, in the table of dimensions on figure 

3-39, were established to prevent the pipe 

entrance from controlling the channel water 

surface. A minimum loss of 0.5 pipe velocity 

head is provided. The dimension R is slightly 

more than the pipe diameter plus 1.5 pipe 

velocity head. 

(h) Yipe Diameter.-The pipe is sized by 

procedures discussed in paragraphs of road 

crossings, inverted siphons, drops, and chutes. 

Generally, the criterion for determining a pipe 

size for a structure having a control and pipe 

inlet is to provide a large enough diameter pipe 

so that the pipe velocity will not exceed the 

following : 

(1) 5 feet per second if a concrete outlet 

transition is provided on a road crossing or a 

similar structure such as a short inverted 

siphon, 

(2) 3.5 feet per second for a pipe drop 

having only an earth transition at the outlet, 

(3) 5 feet per second for a pipe drop having 

a concrete outlet transition, 

(4) 10 feet per second for a relatively long 

inverted siphon having a concrete outlet 

transition, or 

(5) 12 feet per second for a pipe drop or a 

pipe chute having a baffled outlet or a stilling 

pool. 

After the maximum allowable pipe velocity 

has been determined, the pipe diameter may be 

selected by using the tables on figures 2-2, 2-4, 

or 2-3 1. 

3-27. Structure Numbering. -The pipe 

diameter and maximum allowable full-pipe 

velocity are used to number the control and 

pipe inlet structures. Structure number 12-l 

represents a structure with a 12-inch-diameter 

pipe and a maximum allowable full-pipe 
172 SMALL CANAL STRUCTURES 

3-45”inamfe~5 L *4 (a 12 

SECTION C-C 

NOTES 

,SOMETR,C PROJECTION 

Figure 3-39. Control and pipe inlet. 103-D-1222 
REGULATING STRUCTURES 

velocity of 5 feet per second. This structure 

should also be used with a 12-inch-diameter 

pipe and a maximum allowable full-pipe 

velocity of 3.5 feet per second. Similarly, 

structure number 12-2 represents a structure 

with a 12-inch-diameter pipe and a maximum 

allowable full-pipe velocity of 12 feet per 

second. This structure should also be used with 

a 12-inch-diameter pipe and a maximum 

allowable full-pipe velocity of 10 feet per 

second. The control and pipe inlet structures 

selected for 3.5 and 10 cfs will have 

conservative dimensions, but the difference in 

cost is not considered excessive. The table on 

figure 3-39 presents standard dimensions for 

each structure number. 

3-28. Design Example (see fig. 

3-39).-Assume that a pipe drop is required to 

convey the canal water to a lower elevation, 

and that a control and pipe inlet will be 

required to control the water surface in the 

canal upstream from the drop. 

(a) Given : 

(1) Type of waterway = earth canal. 

(2) Hydraulic properties of the canal 

173 

Q = 50 cfs 

b = 5.0 ft. 

d, = 2.83 ft. 

s = 0.0005 

s:s = l-1/2: 1 

n = 0.025 

v = 1.91 f.p.s. 

h, = 0.06 ft. 

E (energy) = 2.89 ft. 

(3) Type of conveyance structure = 

pipe drop sumped for energy dissipation 

with an earth outlet transition. 

(4) This drop structure would have a 

maximum allowable velocity of 3.5 feet 

per second. 

(5) El. A = 5406.00 (from a profile 

sheet). 

(6) NWS El. at Sta. A = El. A + d, = 

5406.00 + 2.83 = 5408.83. 

(7) El. top of bank = 5410.4. 

(8) Control structure at inlet is 

required to minimize erosion in the canal 

for flows in the range of about 0.2 design 

flow to full design flow. 

(b) Determine: 

( 1) Pipe size (see table on figure 2-3 1). 

For a Q of 50 cfs and a maximum 

allowable velocity of 3.5 feet per second 

the table permits the use of a 

54-inch-diameter pipe. 

(2) Structure number.-A structure 

with a 54-inch-diameter pipe and a 

maximum allowable pipe velocity of 3.5 

feet per second is numbered 54-l. 

(3) Determine control and pipe inlet 

standard dimensions R and L by entering 

the structure table for structure number 

54-l. Read R = 5 ft. 9 in. and L = 5 ft. 6 

in. 

(4) Determine A,, V, and hvp for a 

54-inch-diameter pipe with a Q = 50 cfs: 

A, = 0.785 x dia’ = 15.90 ft.’ 

v, = A, Q= 15.90 50 = 3.14 f.p.s. 

hv P =2g--- %J’- 3.L42 64.4 - 0 ’ 15 ft ’ 

where g = gravitational acceleration. 

In lieu of performing the above 

calculations, the hydraulic properties may 

also be determined by using table 8- 1. 

(5) Determine the canal hydraulic 

properties for a flow of 0.2 the normal Q, 

so that E (energy) may be calculated for 

use on the control notch graphs (fig. 

3-40). The area, wetted perimeter, and 

hydraulic radius equations and associated 

sketch are as follows: 

CANAL SECTION 
174 SMALL CANAL STRUCTURES 

wp = wetted perimeter 

= b + 2dd2 + (1.5d)’ 

=b+2x/m 

= b + 2( 1.803d) 

= b + 3.606d 

From Manning’s equation [ 31 

2/3 - o.2 Qn AR - 

= 1.486s’ ‘* 

10 x 0.025 

= 1.486 x .02235 

= 7.53 

and Assume various depths, d, in the canal 

and solve for AR2’3 until it equals7.53. 

A = area 

= db+ d(1.5d) 

= db+ 1.5d2 

also 

From the tabulation below, a d value of 

1.2 feet results in AR2’3 = 7.51 which is 

close to the desired 7.53. The area A, 

corresponding to a depth of 1.2 feet is 8.16 

sq. ft. 

R = hydraulic radius = $ 

Then to calculate hydraulic properties 

for flow of 0.2Q 

Knowing d and A, we can now compute 

the remaining hydraulic properties: 

V= y=&= 1.23 f.p.s. 

0.2Q = 0.2 x 50 = 10 cfs h, -y - 1.123~ 

- = 0.02 ft. 

2g 64.4 

and 

s’ ‘* = 0.00051 ‘2 = 0.02235 

E (energy) depth of water + velocity head 

= d+h, = 1.20 + 0.02 = 1.22 ft. 

3.606d, wp= 

b+3.606d, 

ft. 

8.97 

9.33 

R= R2/3 Assume AR2j3 

d, 

ft. 

1.1 

1.2 

d2, 

sq. 

ft. 

1.21 

1.44 

l.Sd*, b, 

w. ft. 

ft. 

1.82 5.0 

2.16 5.0 

db, 

sq. 

ft. 

5.5 

6.0 

A= 

db+lSd’, ft 

sq. ft. 

1.32 3.97 

8.16 4.33 

A/WP 

0.816 

0.875 

0.87 6.36 

0.92 7.51 

An alternative method may be used to 

compute normal depth of water as 

follows: use table 7-l 1, Handbook of 

Hydraulics [ 31 as shown below, to find 

D: 

K, = o’2 Qn 10 x 0.025 

S l/2 b8 13 = 0.02235 x 73.1 

= 0.153 

Enter table with K1 = 0.153 and side 

slopes of 1.5 to 1 and read a: ratio of 

0.24 = 

depth of water 

canal base width 

So D = depth of water = 0.24 x 5 = 

1.20 ft. 

Values of A, V, h,, and E are then 

determined as before. 

(6) Determine control notch 

dimensions using sketch below: 

CONTROL NOTCH 

N = P + 2 (ST) 

P = bottom width of control notch 

Horizontal S = side slopes = Vertical 

T = Height of notch > d 

d = Normal water depth in canal 
REGULATING STRUCTURES 175 

For a given condition, there is usually 

more than one notch that can provide 

approximately the same control for the 

range of flows to be controlled. In this 

example, the control notch is to act as a 

control between the limits of 10 and 50 

cfs. 

From given values and previous 

computations the hydraulic properties for 

the canal with full Q and 0.2Q are: 

FlOW 

Full Q = 50 cfs 

0.2 Q = 10 cfs 

b, ft. 

5.0 

5.0 

d, ft. 

2.83 

1.20 

S 

0.0005 

0.0005 

To begin the process of selecting a 

control notch, select the graph from 

figure 3-40 having the smallest P value 

which furnishes the full range of discharge 

from 10 through 50 cfs. In this example 

the control notch graph with P = 12 

inches is first selected. Enter the graph at 

E (energy) = 2.89 ft.; go vertically to the 

intersection with the horizontal line for Q 

= 50 cfs. Read the value of S for the slope 

curve which lies immediately to the 

RIGHT of the point. This curve is for 

slope of S = 0.75. Check in the same 

manner to see if the same curve will also 

control for 10 cfs (0.2Q). Enter the graph 

at E (energy) = 1.22 ft.; go vertically to 

the intersection with the horizontal line 

for Q = 10 cfs. The curve immediately to 

the RIGHT of this point shows a slope, S 

= 1.00. The slope curve should have been 

the same for both discharges so that the 

notch will act as a control for both Q = 50 

cfs and 10 cfs; however, this did not 

occur. 

P = 20 inches, S = 0.50, T = d, = 2.83 

feet = 2 ft. 10 in. 

N = P + 2 ST = 20 in. + 2 (0.5)(2 ft. 10 

in.) = 4 ft. 6 in. 

By using the same procedure a control 

notch with P = 16 or 12 inches could have 

been used if a lesser range of control (50 

cfs to something greater than 10 cfs) had 

been determined adequate. 

(7) Determine inlet box inside width, 

figure 3-39. 

min. width= pipe dia. + 6 in. = (4 ft. 

6 in.) + 6 in. = 5 ft. 

or 

min. width = N + 6 in. = (4 ft. 6 in.) 

+ 6 in. = 5 ft. 

use width = 5 feet. 

It is necessary then to try the graph 

with the next greater P value = 16 inches. 

Repeating the previous procedure the 

notch slope is determined to be S = 0.50 

for Q = 50 cfs and s = 0.75 for Q = 10 cfs. 

Therefore, try the graph with the next 

greater value of P = 20 inches. Repeat the 

previous procedure from which the notch 

slope is determined to be S = 0.50 for Q = 

50 cfs and S = 0.50 for Q = 10 cfs. This 

control notch is satisfactory as it will act 

as a control for all discharges between 10 

and 50 cfs. 

(8) Determine El. top of notch and 

sidewalls 

= El. A + T = 5406.00 + 2.83 

= 5408.83 

(9) Determine El. D 

= El. top of sidewalls 

- R (from structure table) 

= 5408.83 - 5.75 = 5403.08 
176 SMALL CANAL STRUCTURES 

Figure 3-40. Control notch graphs (Sheet 1 of 2). 103-D-1223 
REGULATING STRUCTURES 177 

Figure 3-40. Control notch graphs (Sheet 2 of 2). 103-D-1223 
178 SMALL CANAL STRUCTURES 

H. BIBLIOGRAPHY 

3-29. Bibliography. 

[ 11 Operation and Maintenance, Equipment and Procedures, 

Release No. 20, April, May, and June 1957, Bureau of 

Reclamation. 

[2] Operation and Maintenance, Equipment and Procedures, 

Release No. 32, April, May, and June 1960, Bureau of 

Reclamation. 

[3] King, H. W. and Brater, E. F., “Handbook of Hydraulics,” 

Fifth Edition, McGraw Hill Book Co., New York, 1963. 
((Chapter IV 

Protective Structures 

R. B. HAYES’ 

A. GENERAL 

4-1. Purpose. -Protective structures protect 

the canal system and adjacent property from 

damage which would result from uncontrolled 

storm runoff or drainage water, or an 

uncontrolled excess of flow within the canal. 

Storm and drainage water must be 

controlled to prevent erosion of the uphill 

canal bank, and accompanying silting of the 

canal prism. Storm or drainage water must have 

either: (1) controlled entrance into the canal 

through a drain inlet; (2) controlled 

conveyance over the canal in an overchute; (3) 

controlled conveyance under the canal through 

a culvert; or (4) the canal must be routed under 

the cross-drainage channel in a siphon. 

‘Civil Engineer, Hydraulic Structures Branch, Bureau of 

Reclamation. 

Excess flows within a canal must be 

controlled to prevent damage from overtopping 

of the bank, or deterioration of the bank 

resulting from operation at an excessive depth. 

Wasteways are provided to remove excess water 

which may result from: (1) entrance of 

crossdrainage flows at drain inlets; (2) 

operational mismatch of water supply and 

demand due to upstream gate operation; or (3) 

shutdown of a pumping plant or powerplant 

downstream from a wasteway. 

Wasteways are also used to empty the canal 

for inspection, maintenance, seasonal 

shutdown, or an emergency such as a canal 

bank failure. A terminal wasteway, located at 

the end of a canal, provides controlled 

discharge of unused water to a channel or 

reservoir. 

B. WASTEWAYS 

4-2. Description. -Basically, a wasteway is 

comprised of an overflow or gate structure, in 

combination with a drop or chute structure 

and a wasteway channel. The overflow and gate 

structures are frequently combined as shown 

on figure 4-1, to provide for the various 

conditions of canal operation. 

(a) Wastewa,~ Inlets. -An overflow 

structure, such as a side channel spillway or a 

siphon spillway, provides automatic release of 

excess canal water. A wasteway turnout gate 

provides the capability of emptying the canal. 

The alinement of most wasteway inlets is 

normal to the canal, but an inline structure is 

more effective in removing trash or floating ice. 

A check and pipe inlet structure provides 

both an overflow for automatic control of 

excess water and a gated or stoplogged section 

for emptying the canal (see fig. 4-2). It is used 

primarily as an inline terminal wasteway 

structure at the end of the canal to dispose of 

the unused canal flow. However, it is also used 

at other locations along the canal, by providing 

a short channel from the canal to the check 

179 
180 SMALL CANAL STRUCTURES

Figure 4-1. Wasteway turnout with side channel

spillway and slide gate. P-271-701-3736

Figure 4.2. Check and pipe inlet in operation.

P-222-116-535790

Wasteway turnout gates may be operated

manually, with or without power hoists, or by

automatic or remote control.

(b) Wasteway Outlets. -The wasteway

outlet usually performs the function of

dissipating excess energy, to protect the

wasteway structure and channel from erosion.

Where the vertical drop from the canal to the

wasteway channel is minimal, a transition will

suffice. For greater drops in elevation, either a

baffled outlet, baffled apron, or stilling pool, in

conjunction with a drop or chute structure is

required.

Baffled outlets are effective energy

dissipators for pipe discharges, but should not

be used where a heavy weed load exists.

Baffled apron drops are best suited for use

with open-flow discharges, but have been used

downstream from closed conduits by providing

a long transition to the baffled apron drop. The

presence of a heavy weed load requires cleaning

of the baffle blocks to insure optimum

<;>peration. Where floating debris such as brush

is probable, baffled apron drops should not be

used. Baffled apron drops do not require a

downstream water surface for satisfactory

operation. They can operate with a wide

variation of downstream water surface

elevations, and are therefore often used as

terminal structures discharging into reservoirs.

Stilling pools are ideally suited for use below

rectangular inclined drops or chutes, but have

been used downstream from closed conduit by

providing a long transition to the pool. They

are not adversely affected by normal weed

loads, but do require a controlled downstream

water surface to insure a hydraulic jump.

Where the natural channel does not provide a

downstream control, a concrete sill, stoplog sill,

or a control notch can be incorporated in the

stilling pool, as described in subchapter II F .

Downstream control can also be provided by

sloping the transition invert, as shown in figure

4-32.

(c) Wasteway Channel and Channel

Structures. -A natural channel is utilized where

practicable (see sec. 4-3), to transport the

wasteway discharge to a disposal point, such as

a river or reservoir .However, it is usually

necessary to construct a channel to connect the

wasteway structure to the natural drainage

and pipe inlet.

A check drop is equally suitable as a

wasteway structure in providing both the

overflow and the gated or stoplogged section

(see fig. 3-10).
PROTECTIVE STRUCTURES 181 

channel. Such connections may be only a few 

feet in length, or may extend thousands of 

feet. The cross section of such connecting 

channels is similar to that for the canal, but 

with a lesser emphasis on protective features. 

Wasteway channel structures are sometimes 

required to control flow and prevent excessive 

erosion of the channel. These structures 

include rectangular inclined (R.I.) drops or 

chutes, baffled apron drops, control and pipe 

inlets, pipe drops or chutes and road crossings. 

(d) Appurtenant Canal Structures. -Check 

structures while not a part of the wasteway 

itself, are usually provided in the canal a short 

distance downstream from the wasteway, so 

that the entire canal flow can be diverted to 

the wasteway. 

4-3. Location and Number. -Many factors 

must be considered in determining the 

optimum number and location of wasteways. 

An evaluation of the following factors serves as 

a guide: 

(a) The cost of the canal system and 

wasteways, 

(b) The presence of natural drainage 

channels of adequate capacity, at locations 

suitable for wasteways, 

(c) The volume and rate of storm or 

drainage water that can enter the canal through 

drainage inlets, 

(d) The volume available for safe storage in 

the canal or in regulating reservoirs, 

(e) The extent of automatic or remote 

control of the canal system, or the estimated 

time required to operate manually, and 

(f) The magnitude of the economic loss that 

could result from a canal bank failure. 

Wasteways may not be required for short 

laterals having fewer than four or five farm 

turnouts. Longer laterals should have a 

terminal wasteway at or near the end, located 

near a natural channel if possible. The number 

of turnouts downstream from the last 

wasteway should be limited to avoid 

overloading that reach of canal in the event 

that it is necessary to close all the turnouts. 

4-4. Wasteway Capacity 

Considerations. -The variety of situations and 

needs for which wasteways are provided 

requires that each wasteway be given individual 

consideration in determining its design 

capacity. 

(a) Spillway. -The required automatic 

overflow capacity is dependent upon inflows 

from drain inlets, additional flows resulting 

from upstream gate operation, and deliveries to 

pumping plants or powerplants, as follows: 

( 1 ) I~z~lows from drain inlets.-The 

spillway design capacity should be adequate 

to permit wasting of the cumulative design 

inflows from drain inlets upstream from the 

wasteway. Generally, this inflow should be 

limited to about 20 percent of the canal 

design capacity. See subsection 4-41 (c) for 

other limitations on inflows from drain 

inlets. 

(2) Upstream gate operation. -Closure of 

upstream turnout gates, without a 

corresponding adjustment of the canal 

hcadgate will result in additional flow in the 

canal. The required spillway capacity is 

sometimes controlled by the capacity of the 

largest upstream turnout. 

(3) Pumpirlg plants and powerplants. -A 

canal that delivers water to a pumping plant 

or powerplant usually requires provision for 

automatic spillway capacity equal to the 

design capacity of the plant. This 

requirement arises when a pumping plant 

experiences a power failure, or when a 

powerplant must shut down suddenly. Since 

plant shutdowns are likely to occur during a 

storm, while the drain inlets are flowing at 

full capacity, it may be desirable to provide 

a spillway capacity equal to the plant 

capacity plus the design capacity of the 

drain inlets. This could be about 120 percent 

of the canal design capacity. 

(11) Wasteway Turnout Gate. -The wasteway 

turnout gate capacity should equal or exceed 

the canal design capacity to divert the entire 

canal flow to the wasteway in the event of a 

canal break, or other downstream emergency. 

To protect the endangered reach of canal, the 

wasteway turnout gate should be opened and 

the adjacent check gate closed. 

Sizing the wasteway turnout gate for the 

canal design capacity provides more than 

adequate capacity for unwatering the canal for 

inspection, maintenance, or end of irrigation 

season shutdown. 

(c) Wasteway Outlet. -The wasteway outlet 

should be capable of discharging the 
182 SMALL CANAL STRUCTURES

simultaneous flows of the wasteway turnout

gate and overflow feature (see fig. 4-4).

(d) Natural Drainage Channels.-The

capacity of the wasteway turnout or spillway

features should not exceed the safe capacity of

the natural channel into which it discharges.

TlIUS, the capacity of the natural channel may

control the design capacity of the wasteway,

unless the channel is improved.

4-5. Limitations. --Operation of the

wasteway turnout gate should be such that the

canal water surface drawdown rate is within

the limits imposed by the structural stability of

the canal bank, lining, and appurtenant

structures. Generally, to avoid excessive

hydrostatic pressures in the bank or behind the

lining, the canal water surface should not be

lowered more than 6 inches in 1 hour, and not

more than 1 foot in 24 hours.

1. Side Channel Spillways

4-6. General. -Side channel spillways are

located along the canal bank with the spillway

crest parallel to the canal alinement (see figure

4-1 ). As the canal water surface rises above the

crest, the excess water is automatically

discharged into a side channel. From the side

cr.annel, the water drops into a pool from

which the flow is directed through a pipe or

open section, into the wasteway channel.

The structure is generally used in

conjunction with a slide gate which provides

for complete drainage of the canal. Such a

combination is shown in figure 4-3. A check

structure is usually provided in the canal a

short distance downstream from the wasteway,

to permit diversion of the entire canal flow

into the wasteway.

Overflow spillways have been used

effectively for removal of weeds, trash, or ice

from the canal. The water surface can be raised

by partial closure of the downstream check,

until weeds or ice overflow the spillway crest.

A floating boom is sometimes placed

diagonally across the canal to divert weeds,

trash, or ice to the wasteway. Baffled outlets

should not be used where such a weed, trash,

or ice load is anticipated.

4- 7. Design Considerations. -The following

design considerations and recommendations are

considered appropriate for side channel

spillways on small canals. The design capacity

should be based upon the requirements of

section 4-4.

(a) Overflow Crest. -The spillway crest

should be level and set about 0.2 foot above

the normal water surface to prevent

unnecessary waste of water from normal wave

action. To provide a reasonable safety factor.

against overtopping, the maximum water

surface encroachment on freeboard is normally

limited to:

50 percent of the canal lining

freeboard, or

25 percent of the canal bank freeboard

in an unlined canal section.

However, during emergency operation of the

spillway flowing at full design capacity, a

maximum encroachment of 50 percent of the

canal bank freeboard may be permitted in the

vicinity of the wasteway.

The crest length should be computed using

the formula [ I] : 2

Q = 3.33 Lc H3/2

Figure 4.3. Side channel spillway in operation in

foreground, and wasteway gate at far end of spillway

crest. Constant head orifice turnout at left side of

side channel spillway. PX-D-72608D

2Numbers in brackets refer to items in the bibliography, sec

4-46,
PROTECTIVE STRUCTURES 183 

SECTION C-C 

PLAN OF WASTEWAY 

SECTION A-A 

SECTION E-8 

Figwe 4-4. Side channel spillway used as a wasteway turnout. 103-D-1294 
184 

(b) Side Channel.-The side channel usually 

has a rectangular cross section. The width, 

depth, and slope should be adequate to provide 

free flow while carrying a weed, trash, or ice 

load, and should provide adequate dimensions 

to facilitate construction. A reasonable width 

should vary uniformly from about 2 feet at the 

upstream end, to about 4 feet at the 

downstream end, except that a downstream 

width of 3 feet is sufficient for discharges of 50 

cubic feet per second (cfs) or less. A constant 

channel width may be more practical under 

some conditions. 

To insure free spillway discharge into the 

side channel, the side channel water surface 

must be below the spillway crest. This is 

accomplished by setting the side channel 

invert, at the downstream end, below the crest 

a distance equal to the specific energy plus 1 

foot, based upon total design flow. Assuming 

critical flow, the specific energy is equal to the 

critical depth plus velocity head (d, + h,c), 

which for a rectangular cross section, is equal 

to 1 Sd,. The minimum downstream wall 

height is thus equal to 1.5d, plus 1 foot. 

The invert slope should be sufficient to 

provide supercritical flow to the pool. 

However, the transverse flow of incoming 

water over the crest impedes the flow in the 

side channel, causing bulking (increased volume 

due to entrained air). Therefore, the invert 

should be set considerably steeper than the 

critical slope. An arbitrary slope of about 0.05 

is a conservative value. 

The upstream wall height, h, , is then equal 

to the downstream wall height, 11, , minus 0.05 

times the crest length. 

(c) Wasteway Turnout Gate. -The wasteway 

turnout gate is ordinarily used when the canal 

must be emptied. To empty the downstream 

reach, the design discharge of the canal must 

flow through the wasteway gate without 

overflowing the downstream check gate or the 

side channel spillway. As the need to pass the 

canal design discharge through the wasteway 

gate will be infrequent, a velocity of 10 cfs is 

used in determining the gate area. With this 

gate area, it is necessary to provide sufficient 

head, as shown by the orifice equation[ 21 : 

Q=CAa 

SMALL CANAL STRUCTURES 

which may be expressed: 

]I = Q’ V2 

2gA2 C2 

,orh =--- 

2gc2 

Using a value of 0.6 for the coefficient C,[3] 

and a velocity of 10 feet per second, the 

required head must be equal to 4.32 feet. The 

centerline of the gate should therefore be set 

4.32 feet below the normal water surface of 

the canal. However, to avoid an unnecessarily 

deep structure, and to minimize the problem of 

silt removal, the gate centerline should not be 

set below the canal invert. The head is thus 

limited to a maximum equal to the normal 

depth of the canal. Where this limitation is 

applied, the required gate area should be 

recomputed for the reduced head (see fig. 

4-6C). If a gate of the size required is not 

available, the next larger standard size should 

be selected, and the head requirement 

recomputed. 

(d) Pool. -To approach free-flow conditions 

through the gate or from the side channel, the 

pool invert should be set low enough that the 

pool water surface is no higher than the 

centerline of the gate [9], and not appreciably 

higher than the side channel invert. 

If the pool discharges into a pipe, the top of 

the pipe requires a minimum submergence of 

1.5 11, 

P ( 

see fig. 4-6B), to provide for an 

entrance loss of 0.5 h 

vP 

and a pipe velocity 

head, h, 

P’ 

(e) Pipe. -Typically, the wasteway includes 

a pipe from the pool, extending under the 

operating road to the outlet structure. A 

diameter of 24 inches is considered to be a 

minimum where the passage of weeds, trash, or 

ice may be required. 

If the outlet structure consists of a concrete 

transition, the pipe diameter may be based 

upon a maximum velocity of 10 feet per 

second flowing full. The invert slope should be 

about 0.001 to facilitate complete drainage, 

without inducing supercritical flow. 

If the pipe terminates in a baffled outlet, the 

pipe diameter should be based upon a 
PROTECTIVE STRUCTURES 185 

maximum velocity of 12 feet per second, 

flowing full. The pipe slope may be as steep as 

l-1/2 to 1, provided other design 

considerations are satisfied. 

(f) Wasteway Outlet Structure. -The type of 

outlet structure is dependent upon the 

topography. Where excess energy is minimal, 

an outlet transition as shown on figure 7-4 

should be used to protect the wasteway 

channel from erosion (see chapter VII). Where 

a considerable drop is required, the excess 

energy should be dissipated by use of a pipe 

drop, baffled outlet, baffled apron drop, or 

stilling pool. For design of these energy 

dissipators, see chapter VI. 

(8) Percolation.-As the canal water surface 

is usually considerably higher than the channel 

invert at the wasteway outlet (see dimension F, 

figure 4-6), there will be a tendency for the 

water to percolate through the soil, or along 

the structure, toward the outlet. If the 

percolation path is too short, the percolation 

rate will be sufficient to remove soil particles 

by piping which may cause failure of the bank 

or structure. To prevent piping, the percolation 

path should be increased by providing collars 

on the pipe (see sec. 4-27). 

(11) Protection. -Figure 7-8 may be used as a 

guide for determining protection requirements 

for unlined or earth-lined canals or wasteway 

channels. It indicates that type 2 or type 3 

protection should be used at the outlet. Type 1 

protection should be used on the canal invert 

adjacent to the wasteway turnout gate inlet, 

extending to the canal centerline and along the 

canal for a length equal to twice the gate width 

(see fig. 4-4). 

(i) Operation. -For limitation on drawdown 

rate, see section 4-5. 

4-8. Design Example. -Utilizing a side 

channel spillway and a slide gate, design a 

wasteway turnout for the canal features shown 

in figure 4-5. 

(a) Assumptions. - 

(1) Assume an earth-lined canal with the 

following properties: 

Figure 45. General plan of typical canal with side 

channel spillway. 103-D-1295 

Q= 100 cfs b = 8.0 ft. R = 2.0 

A = 37.5 sq. ft. d, = 3.0 ft. n = 0.025 

v = 2.67 f.p.s. fb = 2.0 ft. s= 0.0008 

ss= l-1/2:1 h, = 5.0 ft. h, = 3.5 ft. 

(2) The head from the pool to the 

wasteway channel is sufficient to discharge 

the design flow, but not great enough to 

require a structure to dissipate excess 

energy. 

(3) A wasteway channel having 

dimensions approximately equal to those of 

the canal is required to connect the 

wasteway structure to the natural channel. 

(4) The natural channel has sufficient 

capacity to safely discharge the wasteway 

design flow without damage to the wasteway 

or adjacent property. 

(b) Solution: (see fig. 4-6): 

(1) Set spillway crest 0.2 foot above 

NWS. Find maximum head, H, on spillway 

crest, allowing 50 percent encroachment on 

normal canal bank freeboard (see subset. 

4-7(a)): 

H = 0.5 x 2.0 - 0.2 = 0.8 ft. 

(2) Find the required crest length from 

the standard suppressed rectangular weir 

formula, for a discharge equal to the design 

inflow from upstream drain inlets. Assume 

inflow Q= 20 cfs. 

L,= Q =-- 

20 

= 8.4 

3.33H3” 3.33 x 0.83’2 

Use L, = 9 feet 
SMALL CANAL STRUCTURES 

A. CANAL AND SPILLWAY 

6. SIDE CHANNEL AND POOL 

C. WASTEWAY TURNOUT AND OUTLET 

Figure 4-6. Side channel spillway-typical sections. 103-D-1296 

(3) Design side channel. 

Bottom width. 

Upstream end: Use bI = 2 ft. min. 

Downstream end: Use b, = 3 ft., since 

Q < 50 cfs.” 

Wall height. 

q, =r-- Q - 2o = 6 . 67 cfs 

2 3 

d, = 0.314c~~‘~ 

= 1.1 ft. (see table 17, [4] ) 

h2 = 1.5 d, + 1.0 = 1.5 x 1.1 + 1.0 

= 2.65 ft. 

Use 2 ft. 8 in. 

h, = 11, - 0.05 L, = 2.67 - 0.05 x 9 

= 2.22 ft. 

Use 2 ft. 2 in. 

(4) Determine wasteway turnout gate size 

and head for normal canal Q = 100 cfs, 

maximum gate velocity of 10 feet per second, 

and a coefficient of discharge, C = 0.6. 

100 Gate area, A = 10 = 10 sq. ft. Try a 42- by 

36-in. gate with an area of 10.5 sq. ft. 

Required head, 

h=-!?!? = 

(100)” 

- = 3.92 ft. 

2gA2 C2 64.4( 1 0.5)2 (0.6)2 

As this would require setting the gate 

centerline below the canal invert, set the 

centerline of gate at canal invert elevation, 

and recompute gate size for resultant head 

of 3.0 feet: 

A=Q= 100 

Cm 0.6x8.02 m 

= 12.0 sq. ft. required 

Therefore, use 42- by 42-inch gate. (A = 

12.2 sq. ft.). Refer to gate catalog to 

determine adequate structural dimensions 

for mounting gate frame, and find e = 7 

inches. 

(5) For optimum flow, assume pool WS at 

gate centerline, or at the side channel invert 

dc plus --2’, whichever WS is lower. Pool WS at 

gate centerline places pool WS at canal 

d 

invert. Pool WS at side channel invert plus -? 

2 

places pool WS 1.08 feet above canal invert. 

Therefore, pool WS at gate centerline will be 

used. 

(6) Determine pipe diameter and crown 

submergence for the normal canal capacity 

of 100 cfs plus the drain inlet capacity of 20 

cfs, and with a pipe velocity of 10 feet per 

second. 

The pipe area, A = ; = s = 12 sq. ft. min. 

*< = Less than 

> = Greater than 
PROTECTIVE STRUCTURES 

Then the diameter, 

D= $= 

f 

3.91 ft. min. 

Use D = 4 ft.; A = 12.56 sq. ft.; V = 9.55 

f.p.s.; hvp = 1.42 ft. 

Set pipe crown 1.5 hv below the pool 

WS. Submergence, P 

Sm= 1.5 hv 

P 

= 1.5 (1.42)= 2.13 ft. 

Set pipe invert on a slope of 0.00 1. 

(7) Find structure height: 

H ST = 11, + Sm + D = 5.0 + 2.13 + 4.0 

= 11.13 ft. 

(8) Select outlet transition from figure 

7-4: 

D = 4.0 ft., L = 9.0 ft., E = 6.0 ft. 

(9) Determine pipe length, Lp (see fig. 

4-6): 

Lt, = W+ 1.5 (H,, -E)+ 1 

=12+1.5(11.13-6.0)+1 

= 20.70 

Use 21 ft. 

(I 0) Use type 1 protection at the inlet, 

extending to the canal centerline, for a 

length equal to twice the gate width. Use 

type 3 protection at the outlet, in 

accordance with figure 7-8. As the maximum 

velocity from the pipe is less than 15 feet 

per second, the standard protection 

provision is adequate. 

(11) Check the percolation path 

according to the design parameters included 

in chapter VIII, using the appropriate soil 

type and head, F, shown in figure 4-6C, and 

by the criteria given in section 4-27. 

(c) Check of Hydraulics (see fig. 

d-7). -Check pool WS (assumed in design) by 

the Bernoulli Theorem [2], to verify that a 

submergence of 1.5 11, 

P 

is adequate. Assume 

Lp is total length of conduit. 

187 

~~~~~~ 

I 

a em - - - 

A 

-----L p--p--J 

F&ure 4-7. Side channel spillway-outlet hydraulics. 103-D-1297 

(1) Assume wasteway channel as follows: 

Q = 120 cfs b= 8 ft. R= 1.96 

A = 36.65 sq. ft. d, = 2.95 ft. n = 0.025 

V = 3.28 f.p.s. f,, = 2.05 ft. s = 0.00125 

hVq = 0.17 ft. h, = 5.00 ft. ss = l-l/2: 1 

Specific energy in wasteway channel, 

ES4 = d, + hVq = 3.12 ft. 

(2) Compute pipe flow at critical flow 

(minimum energy), using tables 21, 22, 58, 

and 60 [lo]. ForD=4feet, 

D2 = 16; D5’ 2 = 32.0; and Ds’3 = 40.32. 

Q Then, - D5 12 

= 3.75, and i = 0.825, from 

which d, = 3.30 feet, and 

A G = 0.693, giving 

A = 11 .I sq. ft,, V, = $ = 10.82 feet per 

second, and h vc2 

“c = - = 1.82 feet. 

32 

Minimum specific energy, 

Esc = d, + h, = 5.12 feet 

c 

From Qn 

D8 /3 sl 12 

= 0.466, with Q = 120 cfs 

and n = 0.013, s,’ ” = 0.083 and s, = 

0.0069. 

(3) As the pipe slope of 0.001 is flatter 

than that required for critical flow, 0.0069 

(0.0041 if n = O.OlO), subcritical flow in the 

pipe is assured. 

(4) According to the Bernoulli theorem, 

the energy in the downstream channel 

controls the flow in the pipe if a balance of 
188 SMALL CANAL STRUCTURES 

energy exists. That is, if the energy required 

in the pipe, ES3 is equal to the energy 

required in the outlet channel plus outlet 

losses, the outlet channel controls the flow, 

as indicated by the equation: 

Es3 = ES‘$ +ho 

Assume the outlet loss, 11, = 0.8nh,, where 

Ah, is the difference in velocity heads in the 

pipe and in the channel. Thus, the outlet 

channel controls if 

ES3 = 3.12 + 0.8 (1.82 - 0.17) 

= 3.12 + 1.32 = 4.44 ft. 

Since this is less than the minimum energy 

of 5.12 feet required to sustain a flow of 

120 cfs in the pipe, the channel does not 

control the pipe flow. As the excess energy 

of 0.68 foot is small, an energy dissipator is 

not considered necessary; especially since 

the maximum discharge of 120 cfs occurs 

very infrequently. 

(5) It should be noted that a depth of 

flow in the pipe, either greater than or less 

than d,, would require more energy, 

resulting in an even greater imbalance of 

energy. Therefore, critical flow exists at the 

pipe outlet. 

(6) Determine specific energy, ES* , in the 

upstream end of the pipe, using the 

Bernoulli theorem relationship: 

ES2 + s, L, = ES3 + h, 

where 

s2 + s3 hf = friction loss = L, -___- ( 2 ) 

Try d, = 3.73 ft., 

which results in E = 0.933, % = 0.7627, 

and Qn 

D8/3Sl/2 

= 0.498, from which A = 

12.20 sq. ft., V2 = 9.84, and hV2 = 1.51 ft. 

With Q = 120 c.f.s. and n = 0.013, 

s’ ‘2 = 0.0777, and s = 0.0060. 

From the Bernoulli equation, 

ES2 =ESY +h, - s, L,: 

d2 + 11,~ = 5.12 + L, 

0.0060 + 0.0069 

3.73 + 1.51 = 5.12 + 21 2 > 

-0.001 x21 

5.24 = 5.12 + 0.14 ~ 0.02 

5.24 = 5.24 

Therefore, 

d, = 3.73 ft., hv2 = 1.51 ft., and ES2 

= 5.24 feet. 

(7) Determine specific energy, ES1 , in 

pool. Assume a zero velocity in the pool, 

with respect to the direction of flow in the 

pipe. Assume pipe entrance loss, h, = 0.5 

ah,. 

Then h, = 0.5 (1.5 1 ~ 0) = 0.76 ft. 

E 

Sl 

= ES2 + h, = 5.24 + 0.76 = 6.0 ft. 

As 11, 1 = 0, the pool water depth, 

d, = 6.0 ft. 

Required submergence, Sm = d, - D 

= 6.0 - 4.0 

= 2.0 ft. 

(8 ) Conclusion.-The submergence of 

2.13 feet provided in part (6) of the solution 

is ample to sustain a discharge of 120 cfs. 

(9) If the required submergence had been 

greater than the 2.13 feet provided, the 

outlet design would have to be modified by 

lowering the pipe, or increasing the pipe 

diameter, and possibly improving 

downstream channel hydraulics. 
PROTECTIVE STRUCTURES 189

2. Gated Wasteway Turnouts

4-9. General. -(a) Usage. -While wasteway

gates are usually combined with side channel

spillways or siphon spillways to provide both

the automatic control feature and the

capability of emptying the canal, some

wasteway turnouts do not have provision for

overflow. Such wasteways, which depend upon

timely gate operation, are best used in canals

that do not have drain inlets, or are equipped

with automatic or remote control operation, or

in canals that can, for a short time, store or

a c commodate excess flows without

endangering the system .

This type of wasteway turnout provides the

means of removing all or part of the canal

water to safeguard the canal and adjacent

property in the event of a canal bank failure or

threatened failure. To perform this function, it

is usually necessary to provide a check

structure on the canal, immediately

downstream from the wasteway turnout (see

fig. 4-8). The threatened reach of canal may be

isolated by closing the check gate and opening

the wasteway turnout gate to divert the canal

flow to the wasteway.

The wasteway turnout is also used to empty

the canal for inspection or maintenance, or at

the end of the irrigation season. Stoplogs and

stoplog slots are usually provided just upstream

from the gate, to permit maintenance of the

gate without draining the canal. The gates may

be operated manually, remotely, or

automatically.

(b) Wasteway Capacity. -Most wasteway

turnouts should be capable of discharging the

entire canal capacity, including inflows from

drain inlets. The check overflow wall usually

has a freeboard of 0.2 foot maximum above

the normal water surface. Therefore, the

maximum head available for this wasteway

turnout gate without overflowing the check

walls is equal to the normal depth plus 0.2

foot.(c) Types of Gates. -

(1) Slide gates are readily available in

many types to meet the varying head and

operational requirements. A low-head slide

gate with no back-pressure requirement is

usually satisfactory for a wasteway turnout

from a canal. However, to prevent gate

leakage, it should be of cast iron

construction. A11 air vent is sometimes

required behind the gate ir the gate is

attached to a closed conduit (see chapter

VIII).

As design considerations for slide gates are

discussed in subsections 4-7(c) and 4-10(b),

the following discussion places an emphasis

on radial gate wasteway turnouts. Slide gate

wasteway turnouts do not differ essentially

from the standard turnouts discussed in

chapter III.

(2) Radial gates (see fig. 4-9).-Radial

gates are not often used for small discharges.

However, they have an advantage over slide

gates in that they can be lifted clear of the

water surface, allowing floating debris and

ice to be flushed into the wasteway channel.

This, combined with excellent flow

characteristics give the radial gate wasteway

turnout a definite advantage in some

locations. With a gate freeboard of about 0.2

foot, to prevent waste of water from minor

wave action, the gate can accommodate

some overflow before it is opened.

Radial gates used for wasteway turnouts

are equipped with rubber seals which bear

against metal wall and floor plates for better

watertightness. The floor and wall plates

may be equipped with heating cables or

tapes, to insure free movement of the gate

during the winter, when ice might otherwise

Figure 4-8. Wasteway turnout at left, and radial gate

check structure at right side of photograph. Backfill

not completed. PX-D-72606D
190 SMALL CANAL STRUCTURES

foot

d2 +hV2 = dl + 0 +0. -0.5 hV2

d2 =dl +0.1 .5 hV2

d2 = dl + 0. -2.34

d2 = dl -2.24 ft.

(b) Slide Gates. -The slide gate installation

is usually designed for an upstream water

surface above the top of the gate opening.

U n d er this condition, the discharge is

determined by the orifice equation [2] ,

Figure 4.9. Radial gate used in combination with

overflow spillway. P24S-700-140SD

Q = CA ..f2gh

where

render the gate inoperable.

4-10. Hydraulics.-(a) Inlet.-The wasteway

turnout structure usually includes an inlet

transition which converges the flow to the gate

bay. The invert at the gate is usually slightly

lower than the canal invert to facilitate

complete drainage of the canal.

The entrance loss is a function of the

differential velocity heads, /:"hy, and is usually

assumed to be O.S/:"hy (see chapter VII). The

differential velocity head at an in line transition

is equal to hy 2 -hy 1 .However, a transition

oriented in a position normal to the canal

alinement, as shown in figure 4-11, will have a

differential velocity head equal to hy2 ' as the

canal velocity is equal to zero in the direction

of the turnout flow. Thus, assuming a

transi tion loss of 0. S hy 2 ' the specific energy

available in the gate bay,

Es = Es + ~El. -0.5 hy

2 1 1

d2 +hV2 = dl +hVl +f:.EI 0.5 hV2

Having assumed a zero velocity in the canal in

the direction of the wasteway flow, the

velocity head, hy 1 = 0. If the velocity in the

gate bay, V 2 = 10 feet per second, the velocity

head,

Q is the discharge in cubic feet per second,

C is the discharge coefficient,

A is the area of the gate opening in square

feet,

h is head available at the gate in feet, and

9 is the acceleration of gravity in feet per

second per second

If free flow exists downstream from the

gate, as shown in figure 4-12, the head, h, is

measured from the upstream water surface

elevation to the centerline of the gate opening.

If, however, the bottom of the ga te is

submerged on the downstream side also, the

head, h, is a measure of the difference in water

surface elevations, upstream and downstream

from the gate. A conservative value of the

coefficient of discharge, C, for the slide gate

[3] is equal to about 0.60.

As the wasteway is not often operated at the

maximum design discharge, the gate size is

determined on the basis of a maximum velocity

of 10 feet per second through the fully opened

gate. However, if sufficient head is not

available to attain this velocity, a larger gate

may be required to obtain the desired

discharge.

(c) Radial Gates.-When the radial gate is
PROTECTIVE STRUCTURES 191 

operated partially open, the discharge is 

determined by the orifice equation [ 21 , 

Q = CA&@ 

Where free flow exists downstream from the 

gate, as shown in figure 4-12, the head, 11, is 

measured from the upstream water surface 

elevation to the centerline of the gate opening. 

If the downstream water depth submerges the 

bottom of the gate, as shown in figure 4-lOA, 

the head is a measure of the difference in water 

surface elevations, upstream and downstream 

from the gate. The coefficient of discharge, C, 

for the radial gate [3] is equal to about 0.72. 

The radial gate, when operated for 

maximum discharge, is fully open. with the 

bottom of the gate above the upstream water 

surface, as shown in figure 4-IOB. Under this 

condition, the discharge is determined from the 

weir equation [ 21 , 

Q = CLH3 ‘2 

where H is the upstream water depth. A 

discharge coefficient [ 21 , C, of 3.09, is often 

A. Submerged orifice flow 

0: CAV%$ 

B. Submerged flow over broad crested weir 

O=CL(nH13" 

Figure 4-10. Radial gate wasteway turnout-submerged 

flow (for free flow at outlet see fig. 4-12). 103-D-1298 

used for the broad crested weir with free flow. 

Where the weir flow is partially submerged 

by the downstream depth, a correction factor, 

n, is used: 

Q= CL (nH)3’z 

Values of n may be taken from table 37 [4J . 

As the wasteway is not often operated at the 

maximum design discharge, the size of the 

radial gate is determined on the basis of a 

maximum velocity of 10 feet per second 

through the gate bay (with the gate fully 

opened). The minimum gate width, equal to 

$, is then equal to LL 10d . An excessively wide 

2 2 

radial gate would be uneconomical, and may 

also present binding problems in opening and 

closing. The gate width should not be greater 

than 3h,, where 11, is the gate height (equal to 

d, plus e plus a freeboard of 0.2 foot 

minimum, as shown in figure 4-l 2). 

(d) Trajectory. -When the gate is open 

slightly, a jet of water will flow under the gate 

at a high velocity. Where a drop or chute is 

situated downstream from the gate, the flow 

should be transitioned to the steeper slope. 

Without such a transition, the high velocity 

flow may spring free from the invert at the 

beginning of the steeper slope, resulting in 

negative pressure, and unstable flow 

conditions. 

To avert such a condition, a trajectory could 

be used to transition the flow to the steeper 

slope. The length of the trajectory should be 

determined from the equation [5 J , 

X2 = 4HY 

where 

is the horizontal distance from the 

beginning of the curve to a point on the 

curve. 

is the vertical distance from the beginning 

of the curve to a point on the curve, and 

is the head measured from the maximum 

upstream water surface to the gate bay 

invert, assuming no inlet head loss. 

The required length and profile of the 
I 

192 SMALL CANAL STRUCTURES 

trajectory may be determined by plotting 

points on the curve, ending where the slope of 

the curve is equal to the slope of the chute or 

drop. The length may also be determined by 

solving the above equation by differential 

calculus, for the distance, X, at which point the 

slope of the curve is equal to the slope of the 

downstream drop. 

Where both the upstream and downstream 

inverts are on a slope, a better solution is 

described in chapter II. 

(e) Outlet.-For a discussion of 

considerations for wasteway outlets, see 

subsection 4-7(f). 

4-l 1. Lifts and Hoists.-(a) Manually 

Operated Lifts. -Lifts, consisting of a hand 

crank or wheel and gears are required to open 

and close the gates. The gear ratio should be 

consistent with the gate weight and the 

frictional force imparted by the hydrostatic 

load on the slide gate, or by the rubber seals of 

the radial gate. An unnecessarily high gear ratio 

should be avoided, as it would retard the rate 

of opening, which may be critical. 

(b) Power-operated Lifts or Hoists. -Slide 

gates and radial gates may be controlled 

automatically, remotely, or by a local on-off 

switch, where electrical power is available or 

where a motor-generator is used. The water 

level is monitored by floats or probes, which 

actuate the hoist controls. One such device for 

providing automatic control of the water 

surface level is the “Little Man” [ 61 , designed 

and used by the Bureau of Reclamation. 

(c) Hydraulically Controlled. --Automatic 

radial gates have been used without an external 

power source, by utilizing the increased 

hydrostatic head which accompanies increased 

depth. To provide upstream water level 

control, the gate leaf includes a horizontal 

projection, upon which the uplift pressure 

imparts a force to open the gate. With an 

adjustable counterweight to provide sensitivity, 

any rise in the upstream water level causes an 

equivalent rise in gate position. 

This type of automatic gate, if the 

installation provides enough clearance to move 

freely, has a tendency to leak, and should be 

used only where some leakage is acceptable. It 

is also susceptible to erratic behavior if weeds 

or trash lodge under the gate, preventing 

complete closure. 

4-l 2. Miscellaneous Considerations.- 

(a) Protection.-Erosion protection for the 

canal at the inlet, and for the outlet channel 

should be in accordance with the requirements 

of figure 7-8. 

(b) Percolation. -Excessive percolation of 

water from the canal to the outlet channel 

should be avoided. See section 4-27 and 

subchapter VIII C for design considerations for 

alleviation of percolation. 

(c) Operation. -For limitations on 

drawdown rate, see section 4-5. 

4-l 3. Design Example. --Utilizing a radial 

gate, design a wasteway for the canal features 

shown in figure 4-l 1. (A design example using 

a slide gate is included in section 4-8.) 

C Wastesay Channel 

E Wastewoy Turnout 

Goted Check Inlet 

Figure 4-1 I. General plan of typical canal with 

wasteway turnout. 103-D-1299 

(a) Assumptions. ~ 

(1) Assume an earth-lined canal with the 

following properties: 

Q= 1OOcfs 1lL = 5.0 ft. n = 0.025 

b = 8.0 ft. h, = 6.3 ft. s = 0.0002 

d, = 4.3 ft. fb = 2.0 ft. ss = l-1/2: 1 

V = 1.61 f.p.s. 

(2) Assume that the entire canal flow 

must be diverted to the wasteway to prevent 

failure of the canal bank downstream. As 

there are no drain inlets upstream, the 

maximum wasteway discharge will be equal 

to the normal canal capacity of 100 cfs. 

(3) Assume that a check structure is 

located immediately downstream from the 

wasteway, as shown in figure 4-l 1, and that 

an overflow wall is provided with a 

freeboard of 0.2 foot above the normal 

water surface. 
PROTECTIVE STRUCTURES 

(4) Assume that the drop in the 

wasteway profile provides free flow 

downstream from the wasteway gate, and 

enough fall (see dimension F, fig. 4-12) to 

require energy dissipation. 

(5) Assume an invert drop, e = 0.5 foot, 

is desired in the inlet transition. 

(6) Assume that a natural channel is 

available, having sufficient capacity to take 

the maximum canal flow without damage to 

adjacent property. 

(b) SolutioPl (set fig 4-12). - 

(1 ) Inlet dimensions: 

Length, L, : Assuming the top of the 

structure at about the elevation of the 

top of the bank, 

L1 = 1.5 11, 

= 1.5 x 6.3 = 9.45 feet 

Use 

L, = 9 ft. 6 in. 

PLAN 

PROFILE 

TRAJECTORY 

Figure 4.12. Radial gate wasteway turnout-typical 

sections. 103-D-1 300 

193 

Wall heigh t, 11, : 

11, = !I! 

ss 

+e 

9 50 =--+0.5 1.5 

= 6.33 + 0.5 = 6.83 feet 

Use h2 = 6 ft. 10 in. 

(2) Determine required gate height for 

normal depth. Assume gate freeboard, f, = l? 

0.20 foot 

Gate height, 

h, =d, +e+f, E? 

= 4.3 + 0.5 + 0.20 = 5.00 feet 

Use 5 ft. 0 in. 

(3) Determine maximum canal depth, d, , 

witllout overflowing the check overflow 

wall. 

d, = d, + 0.2 

= 4.3 + 0.2 = 4.5 feet 

(4) Determine depth, d,, in gate bay, 

assuming a velocity, V, = 10 feet per second 

in the gate bay, and a velocity, V, = 0 in the 

canal (in the direction of the turnout flow). 

The specific energy. 

Es,, = ES1 + e - 0.5 Oh, 

d2 + h,z = d, +hvI + e - 0.5 (h,* - hvl) 

d2 + 1.56 = 4.5 + 0 + 0.50 - 0.5 (1.56) 

and 

dz = 5.00 - 1.5 (1.56) = 2.66 ft. 

(5) Determine the required gate bay 
194 SMALL CANAL STRUCTURES 

width, B, using a maximum velocity of 10 

feet per second. 

*++= 1 0 sq . ft. minimum 

A 10 

B = ci, = 2.66 ~ = 3.76 feet minimum 

(6) Determine the required gate bay 

width, B, using the available head, (d, + hV2 

= 2.66 + 1.56 = 4.22 feet) in the weir 

equation [ 21 (assuming the radial gate is 

fully opened), 

Q = CB H3” 

B=--Q = 

100 

CH3’2 3.09(4.22)” 

= 3.73 feet 

< 3.76 feet 

Use 

B = 4 ft. 0 in. 

(7) Design a trajectory to transition the 

flow from the level invert at the gate to the 

2 to 1 invert slope (tan $ = 0.5) which 

precedes the stilling pool. The minimum 

length of the trajectory is determined from 

the equation, 

X2 = 4HY 

where H = d, = 4.5 feet 

Then X2’ 18Y 

and Y = X2/18 

The slope of the tangent to the curve at 

any point is represented by the first 

derivative. 

d x2 2x x ----z-zdX 18 18 9 

Setting this slope equal to the downstream 

slope of 0.5, 

$= 0.5 

X = 0.5 x 9 = 4.5 feet 

Solving for the vertical distance, Y, at l-foot 

intervals of X, using the relationship, 

y=f$ 

The following tabulation in feet can be 

made: 

X Y 

- - 

0 0 

1 0.06 

2 0.22 

3 0.50 

4 0.89 

4.5 1.12 

(8) Check of turnout capacity.-To insure 

the capability of discharging the design flow 

without exceeding the maximum canal water 

surface, the hydraulics should be checked by 

the Bernoulli equation [ 21. 

Assume that the gate is fully open, and 

that critical depth occurs at the beginning of 

the trajectory, as the downstream slope is 

obviously steeper than critical (see fig. 4-l 2). 

Use an entrance loss of 0.5 nh,, and 

disregard the minimal effect of friction. 

In the rectangular section, critical depth 

d, =g = 0.3 14 q2/3 

= 0.314 ; 

0 

213 

100 2’3 

= o.314 ( 4 > 

= 0.314 (8.55) = 2.68 feet 

d and h = C 2.68 

“C 

= - = 1.34 feet 

2 2 
195 PROTECTIVE STRUCTURES

From the Bernoulli equation,

dl =dc +hvc + 0.5 f:johy -e

= 2.68 + 1.34 + 0.5 (1.34) -0.5

4.19 feet

spillway eliminates the need for frequent

manual manipulation of control structures

along the canal. A distinct advantage is its

ability to discharge a large volume of water

with a small rise in water surface.

(b) Description. -The siphon spillway

consists of a closed conduit, having an upper

leg extending into the upstream pool, and a

lower leg extending down from the crest into

the lower pool (see fig. 4-17). A siphon

breaker, consisting of an air vent pipe, extends

upward from the siphon crown, and down into

the upstream pool (see fig. 4-13). The

downstream pool provides dissipation of excess

energy.

(c) Function.-Small excesses of flow from

the inflow of storm water at drain inlets will

result in a slowly rising water surface in the

canal, initially causing the siphon to act as a

weir. If the canal water surface continues to

rise, the discharge through the siphon will

attain a velocity sufficient to prime the siphon.

As the maximum canal water depth is

4.50 feet, the structure, as designed, has

sufficient capacity.

(9) Design the stilling pool and outlet

protection in conformance with the design

requirements discussed in chapters II and

VII.

( 10) Protection.- Inlet protection should

consist of 6 inches of coarse gravel, and

should extend to the canal centerline for a

canal length equal to twice the gate width,

or 8 feet minimum.

(II) Percolation.-Percolation should be

checked by the Lane weighted-creep

method, as discussed in subchapter VIII C.

3. Siphon Spillways

Figure 4-13. Siphon spillway with siphon breaker pan.

Gate hoist in foreground. P17-D-6210S

4 -14. Ge neral. -(a) Usage. -Siphon

spillways, as discussed in this text, are limited

to hydrostatic heads no greater than the

atmospheric pressure equivalent at the site. For

this reason, they are sometimes referred to as

"low-head siphon spillways."

As distinguished from the inverted siphon

(discussed in chapter II), which operates under

positive pressure, the siphon spillway, which

operates under negative pressure, is sometimes

called a true siphon. Once primed, the siphon

spillway has the capability of lifting the water

over the crest, and discharging it at a lower

elevation (see fig. 4-17).

Siphon spillways are very effective in rapidly

removing a large volume of water from a canal,

but may be more expensive to construct than

other wasteway turnouts, because of the

formwork required to construct the structure.

However, the narrow crest width required for

the siphon spillway favors its use where space is

inadequate for structures utilizing free-t1ow

crests.

The automatic operation of the siphon
196 SMALL CANAL STRUCTURES

Figure 4.14. Siphon spillway hood at left, radial gate

for wasteway turnout in center, and hoist for radial

gate check at right side of photograph. PX-D.72609

(2) Reduction in priming time,

(3) Attaining a prime with a smaller crest

head, and

( 4) Simplicity of construction resulting in

greater economy.

(b) Capacity. -The siphon spillway utilizes a

large differential head to discharge large flows

through a siphon barrel of small cross-sectional

area, as computed from the following orifice

and vortex flow equations [8] :

Rs

q = c Dy1"2gH

~ Rcv'O.7h (2g) loge

Rc

where

The resulting siphonic flow will quickly lower

the canal water surface and break the siphonic

action.

It is necessary that the siphon be fully

primed, to discharge its full design capacity.

That is, all the air must have been removed

from the rectangular siphon barrel. Only then

is the full area of the barrel effective for flow.

Priming is initiated as the water flowing over

the crest and into the downstream leg attains a

velocity sufficient to carry an air-water mixture

out of the barrel. To facilitate the air-water

mixing process, a deflector is included on the

sloping invert, positioned to cause the

trajectory of water to leave the invert and

intercept the top side of the barrel. A full

prime occurs when evacuation of air from the

barrel is complete, and pressure over the crest

becomes subatmospheric.

Once fully primed, siphonic action continues

until the canal water surface drops below the

inlet elevation of the siphon breaker pipe,

allowing an inflow of air to restore atmospheric

pressure at the crest, ending the flow abruptly.

One disadvantage to the use of a siphon

spillway in a small canal is the abrupt

drawdown and the attendant surges or bore

waves which may accompany the sudden

action of priming and breaking. See Design

Considerations, section 4-15 (11). This may

disturb briefly the fine adjustment of turnout

gates, and may also cause erosion in the

downstream channel.

(d) Appurtenances. -Slide gates or radial

gates are generally used in conjunction with

siphon spillways to provide complete drainage

of the canal. Such a combination is shown in

figure 4-14. A check structure is usually

provided in the canal, a short distance

downstream from the wasteway, to permit

diversion of the entire canal flow into the

wasteway.

4-15. Design Considerations. -

(a) General. -While many types of siphon

spillways have been used in the past, this

discussion will be limited to the configuration

shown in figure 4-17, which features a straight

leg on the downstream side of the crest. The

advantages [7] of this type over the S-curve

type structure are as follows:

( 1) Greater consistency of discharge

capacity,

q is the discharge per foot of width;

D, H, Rc, and Rs are dimensions shown in

figure 4-17 ;

C is the coefficient of discharge in the orifice

equation (a conservative value being 0.6

for the design illustrated);

h, in the vortex flow equation is the

atmospheric pressure at the site, in feet

of water; and the constant, 0.7 provides

a conservative limitation on the

sub a tmospheric pressure allowed [ 8] .

(c) Head. -The atmospheric pressure head,

h, is based upon the elevation at the site. The
PROTECTIVE STRUCTURES 

operating head, H, should not exceed the 

atmospheric pressure head. 

The concrete structure should be capable of 

withstanding a negative internal pressure equal 

to the head, H, plus any other loads imposed 

upon the structure. 

(d) Entrance. -The inlet orifice should 

provide an area equal to at least twice the 

throat area. The normal canal water surface 

should submerge the top of the inlet orifice at 

least 1.5 hVO plus 6 inches, or at least 1 foot, 

whichever is greater (where hVo is the velocity 

head through the orifice). 

(e) Crest.-The siphon crest should be set 

about 0.2 foot above the normal water surface. 

An adjustable crest is sometimes used, but an 

adverse effect upon priming may result. To 

provide a satisfactory discharge coefficient, a 

RQ ratio, D = 2.0 is recommended (see fig. 4-l 7). 

(f) Throat. -To facilitate construction, and 

to allow passage of some debris, the throat 

opening, D, as shown in figure 4-l 7, should be 

at least 2 feet, and the crest width, b, should be 

at least 3 feet. It is often desirable to use two 

or more adjacent siphons in lieu of one having 

a wide throat, to avoid long spans subjected to 

heavy loads. 

(g) Downstream Leg. -The straight leg 

design has several advantages over the S-curve 

design as itemized above (see subsection (a) 

above). A deflector is positioned on the sloping 

invert, as shown on figure 4-17, at a location 

designed to deflect the flow to a trajectory 

extending across the tube to the top side. 

Impact with the top side, and turbulence in the 

pool serve to mix air and water. The turbulence 

thus created and the forward component of 

velocity combine to produce immediate air 

evacuation to initiate the prime. 

The top side of the downstream leg 

terminates in the pool. The terminal end 

should be pointed as shown in figure 4-l 7, to 

facilitate an exodus of air bubbles from the 

siphon tube. 

(11) Siphon Breaker.-The location of the 

siphon breaker should be determined precisely. 

It opens into the crown area at a point 15O 

downstream from the vertical axis through the 

crest, as shown in figure 4-l 7. It has been 

197 

found that maximum negative pressures occur 

at or near this point. The cross-sectional area of 

the siphon breaker pipe should be about one 

twenty-fourth of the throat area. 

The upstream end of the siphon breaker pipe 

should be set at the normal water surface 

elevation in the canal. An adjustable sleeve 

permits a fine adjustment to compensate for 

operational changes. It should be airtight to 

insure negative pressure in the siphon barrel. 

To prevent the siphon from lowering the 

canal water surface below the normal water 

surface elevation, a shallow pan is mounted a 

short distance below the siphon breaker pipe to 

break the prime (see fig. 4-17, detail A). 

Without the pan, some siphon breaker pipes act 

as siphons themselves, lifting a free column of 

water, allowing the siphon spillway to continue 

to operate while the canal water surface is 

drawn down well below the siphon crest, 

before siphonic action is broken [9] . With the 

pan in place, as shown in figure 4-15, the 

magnitude of water surface fluctuations in the 

canal should be very slight. 

(i) Pool. -The downstream pool submerges 

the siphon tube outlet to prevent re-entry of 

air. The top of the sloping sill should be at the 

same elevation as the crown of the siphon tube 

outlet. 

The roof of the pool section should be of 

sufficient distance above the pool water surface 

to permit free escape of air from the pool. 

Assuming that the outlet channel does not 

materially submerge the flow over the sill, a 

wall height above the sill should be equal to the 

critical depth plus velocity head, plus 1 foot of 

freeboard, as shown in figure 4-17. 

The width of the pool should be equal to the 

throat width. A minimum width of 3 feet is 

recommended for capacities of 100 cfs and 

less. 

Cj) Outlet Transition. -The outlet transition, 

usually in a well defined channel, should be 

designed on the same basis as broken-back 

transitions for stilling pools (see subchapter II 

F). An angle of divergence of 25’ on each side 

may be used. 

(k) Protection. -Erosion protection should 

conform to the requirements of figure 7-8 for 

cross drainage. Inlet protection in an unlined 

canal, should extend to the canal centerline for 

a canal length equal to twice the siphon throat 
SMALL CANAL STRUCTURES 198

(a) Assumption,\,:

(1) Canal properties are as follows:

Qn = 100 cfs

dn = 3.7 feet

b = 8 feet

hB = 5.7 feet

fb = 2.0 feet

ss= 1-1/2:1

(2) The canal flows to a pumping plant

downstream from the wasteway. A power

failure occurs at the plant while the canal is

flowing at design capacity plus drain inlet

capacity, resulting in a total discharge of 120

cfs.

(3) The available head, H, as shown in

figure 4-17, is equal to 6 feet.

(4) A wasteway channel, having

dimensions approximately equal to those of

the canal, is required to connect the

wasteway structure to the natural channel.

(5) The natural channel has sufficient

capacity to safely discharge the wasteway

design flow without damage to the wasteway

or adjacent property.

(6) The wasteway structure is located at

an elevation of 6,000 feet, with an

atmospheric pressure, h, equal to 11.8

pounds per square inch, or 27.3 feet of

water.

Figure 4-15. Siphon spillway with siphon breaker (b) Solution ( see fig. 4-17). -

pan in place. P-17-D-62107

(1) Given

Q = 120 cfs

H = 6 ft.

h=27ft.

(2) Use:

width, or 8 feet minimum.

(I) Percolation. -To control percolation of

water from the canal to the outlet channel, a

percolation study should be made in

accordance with chapter VIII, and cutoff walls

provided where necessary. A cutoff wall is

often located in line with the bottom of the

pool sill as shown in figure 4-17.

4-16. Design Example. -Design a siphon

spillway to be used for discharging excess canal

flows into a wasteway channel, as shown in

figure 4-16. A slide gate, designed separately,

provides for emptying the canal.

c= 0.6

R~ D =2.0

(3) Try:

D = 2 ft .

Natural Cha"/ -

...

~ IQ"OO onol heodgote cfsi

~ Cono~

~~

Wasteway chan",1

~~~~I plant

¥

= 3 ft.

/ S,phon ~

Spli Iwoy ::--c-

~IQ,,2.0CfSJ

-(0== eOCh)~-

Figure 4.16. General plan of typical canal with

siphon spillway. IOJ-D-IJOl

= 5 ft

( 4) Crest dimensions :

R~ = 20 = 2 x 2 = 4 ft

0

Rc=R'i.-2=4-1

0

R =Rr:+-=4+1 s 'L 2=
PROTECTIVE STRUCTURES 

199 
200 

(5) Determine discharge by the orifice 

equation: 

q=CDm 

= 0.6 x 2 q’- 

= 0.6 x 2 x 8.02 x/% 

= 23.6 cfs per foot of width 

(6) Determine discharge by the vortex 

equation: 

qmax. =R, mLQgcR\ 

RC 

= 3 do.7 x 27 x 64.4Log, 5 

-- 

= 3016Log, 1.667 

= 3 x 34.9 x 0.5 1 1 

= 53.5 cfs per foot of width 

(7) As q does not exceed qmax, the 

design of the siphon for q = 23.6 cfs per foot 

of width is valid. If q had been greater than 

q max., the head, H, should be decreased; or, 

had the dimensions D or R, been greater 

than the minimum permitted, they could be 

reduced to provide a discharge q < q max. 

(8) Determine the throat width,b. 

,,=_a- 120 

9 - 23.6 = 5.08 ft. 

Use b = 5 feet 

Had the width, b, resulted in an 

excessively wide span, a greater dimension, 

D, should be used to reduce the span. 

(9) Determine siphon breaker pipe 

diameter, D, , to provide a pipe area, A,, 

equal to or greater than one twenty-fourth 

the throat area, A,. 

Thus. 

At A, =~4 = % = 0.41 

Then, the pipe diameter, 

D, = 0.73 ft. 

.7 sq. ft. 

SMALL CANAL STRUCTURES 

Use 

D, = 9 inches 

(10) Pool sill height, 

11, = 1.5D 

= 1.5 x 2 = 3 ft. 

(1 1) Pool box height (see fig. 4-l 7), 

11, = 1.5D+d, +hVc + 1 

where the pool width, W, = 5.0 feet, 

q = y= 24.0 cfs 

d, = 2.62, and 

h 

"C 

= Li’ = 1.31 (in rectangular section) 

Then, 

11, = 1.5 x 2 + 2.62 + 1.31 + 1 

= 7.93 feet 

Use 

h2 = 8 ft. 0 in. 

(12) Outlet Transition. -Assuming a well 

defined outlet channel with a bottom width 

of 8 feet and a water depth, d = 4 feet (for Q 

= 120 cfs), use a broken-back transition with 

a uniform invert width equal to the pool 

width, W, = 5.0 feet. 

The water surface width at the cutoff, 

T, = 5.0 + 2 x 1.5 d 

=5.0+3x4= 17.0feet 

The water surface divergence is equal to 

T,-W,=17-5=12.0 

with 6 feet of divergence on each side. 
PROTECTIVE STRUCTURES 201

The transition length,

Use

and should extend to the canal centerline ,

for a canal length equal to twice the throat

width. Outlet protection should consist of

12 inches of riprap on 6 inches of sand and

gravel bedding, extending 16 feet

downstream from the structure.

( 16) Percolation. -Percolation should be

checked in accordance with the

requirements of subsection 4-15(1).

LT = 13 feet

4. Check Inlet Wasteway Turnouts

The remaining divergence to the channel

having a bottom width of 8 feet, should be

accomplished in an earth transition.

( 13) Determine entrance hydraulics,

using an orifice slope length of 2D (see fig.

4-17).

v=Q=@

A 2Db

4-17. General.- The check and pipe inlet,

and the rectangular inclined (R.I.) drop with a

check inlet are ideally suited as turnouts to

small terminal wasteways. They include an

overflow (see fig. 4-18) to spill (automatically)

the unused water resulting from operational

mismatch of water supply and demand, or

excess water from storm or drainage inflows.

Complete drainage of the canal can be

accomplished by removal of stoplogs or

opening of the gate.

As the need to empty the canal is

infrequent, stoplogs are usually satisfactory for

use with the check and pipe inlet. However ,

they should be sealed with a waterproofing

material if leakage is objectionable. Slide gates

should be used where remote control or

frequent adjustment is desired. To minimize

( 1 4) Check

(minimum of

submergence,

entrance submergence

foot) for NWS, to insure a

Sn1 = 1.5 hy + 0.5 n1in.

= 1.5 x 0.56 + 0.5 = 1.34 ft. n1inin1un1

Sn1 = dn -y

where

y = 2D sin ~

and <1> is the angle of the canal side slope.

Assume the bottom of the orifice at the

canal invert.

Then,

Sm = dn -2 D sin 33041'

= 3.7 -4 x 0.5546

= 3.7- 2.22 = 1.48 feet

> 1.34 feet minimum

( 15) Protection. -As indicated in figure

7-8 for cross-drainage flows, inlet protection

should consist of 6 inches of coarse gravel,

Figure 4.18. Check and pipe inlet spilling over crest.

P222-116-53588
202 SMALL CANAL STRUCTURES 

leakage, the gate should be of cast iron. Where 

the gate frame is mounted in stoplog guides, it 

should be sealed in the guides. See section 4-l 1 

for lift requirements. 

The check and pipe inlet provides a 

connection to a pipe drop, as shown in figure 

2-31, or to a pipe chute. A check inlet with 

R.I. drop is shown in figure 2-26. The check 

inlet can also be used with a baffled apron 

drop, making an excellent combination for a 

terminal wasteway to a reservoir having a 

variable tailwater elevation. 

4-l 8. Design Considerations. -A check and 

pipe inlet, or a check inlet for an R.I. drop 

should be designed for an overflow capacity 

(with stoplogs or gates closed) equal to the 

design capacity of the canal. When used as a 

wasteway turnout, the overflow crest should be 

sufficient to accommodate the design 

discharge, encroaching no more than 50 

percent on the normal canal bank freeboard. 

For other design considerations and a design 

example, see subchapters II E and III F. 

C. CROSS-DRAINAGE STRUCTURES 

4-19. General. -The need for cross-drainage 

structures results from the flow of drainage or 

storm runoff water from the high side of the 

canal to the low side. To protect the canal 

from such flows, cross-drainage structures are 

provided at locations best suited for handling 

them. 

While the alinement of a canal usually 

follows the natural ground contours, in the 

interest of economy it is often necessary to 

take shortcuts across natural drainages or 

through ridges. In crossing natural drainage 

channels, the canal flows may go under the 

channel in a siphon, or the channel flows may 

go under the canal in a culvert. Where natural 

channels are not available, or where economy 

dictates, the cross-drainage flows may be 

carried over the canal in an overchute, or small 

flows may be taken into the canal through a 

drain inlet. 

Cross-drainage flows are sometimes collected 

in open drain channels which parallel the canal 

on the uphill side. These drain channels may 

carry the water to a natural channel, where it is 

conducted under the canal in a culvert, or to a 

collection point where the water can be carried 

over the canal in an overchute, or into the 

canal through a drain inlet, or over a siphon 

crossing. 

(a) Siphon Crossings. -(See subchapter II 

C.) Where a small canal crosses a large drainage 

channel, it is usually more economical to carry 

the canal water under the channel in an 

inverted siphon than to carry the drainage 

water under the canal through a culvert. 

Siphons provide excellent reliability, as the 

accuracy of the cross-drainage flow prediction 

is less critical where siphons are used. However, 

the use of a siphon is contingent upon 

availability of head for siphon losses. Other 

factors which will affect the results of a cost 

comparison are the width and depth of the 

drainage channel. 

(b) Cross-drainage Alternatives. -Where the 

capacity of the canal is large in comparison to 

the channel capacity, it is usually more 

economical to carry the drainage water under 

or over the canal prism, or into the canal. In 

addition to the original cost of a structure, the 

maintenance cost should be included in the 

cost comparison. Another factor, sometimes 

difficult to evaluate, is the degree of reliability 

offered by the various types of cross-drainage 

structures. Overchutes are better able than 

culverts to handle flows where sand, gravel, or 

debris are present. Neither culverts nor 

overchutes impose an additional head 

requirement on the canal. 

Other factors affecting the best choice of 

cross-drainage structures are as follows: 

(1) Culverts. -Where the canal section is 

primarily in fill as it crosses a drainage 

channel, a culvert is the logical structure to 

carry the drainage water under the canal. 

Small culverts may become plugged with 

trash, particularly if the drainage area has a 

cover of brush. Weed screens have been used, 

but sometimes increase the susceptibility to 

plugging. 

(2) Overchutes. -Where the drainage 
PROTECTIVE STRUCTURES 203

channel invert, on the uphill side of the

canal, is higher than the normal water

surface of the canal, an overchute may be

the logical choice of structure, carrying the

drainage water over the canal. The

rectangular concrete overchute is able to

pass a considerable amount of debris,

whereas the pipe overchute, like the culvert,

is subject to plugging.

(3) Drain inlets. -If the design flow for a

drainage area is so small that the canal can

accommodate the additional flow, it may be

desirable to take the drainage water into the

canal through a drain inlet. If an economic

study is made, it should include the cost of

additional sediment removal from the canal,

and the added cost for greater wasteway

capacity, if required.

(c) Cross-drainage Capacity.-For the determination of the required design capacity for

cross-drainage structures, based upon expected

storm runoff, see Design of Small Dams [8] .

Generally, for small irrigation systems,

cross-drainage structures are sized on the basis

of storm runoff for a 25-year flood frequency.

Figure 4-19. Culvert, constructed prior to

construction of canal. PS14-417-366

1. Culverts

However, where natural channels are not

available, such flows should be diverted across

the canal at locations based upon economic

culvert size and spacing.

4-22. Profile. -The profile of the culvert is

usually determined by the invert profile of the

natural channel and the cross section of the

canal. The inlet invert should be located near

the existing ground surface, or at the bottom

grade of the inlet channel, if provided, to

prevent upstream degradation. Hydraulic

requirements are discussed in section 4-26.

Where the conduit is on a uniform grade, it

should be steep enough to prevent

sedimentation in the conduit but not steep

enough to require an energy dissipator. In

practice, it has been found satisfactory to use a

minimum slope of 0.005, and a maximum

slope slightly steeper than the critical slope, Sc .

For determination of critical slope, see

subsection 4-26(e ).

Where a uniform slope would greatly exceed

the critical slope, requiring an energy

dissipator, it is usually preferable to include a

vertical bend and two invert slopes, SI and S2 ,

as shown in figure 4-28. The upstream slope,

SI, should be much steeper than critical,

4-20. General. -Culverts, as discussed in this

text, carry storm runoff or drainage water

under the canal (see fig. 4-19). Thorough

consideration should be given to the culvert

alinement, profile, conduit, inlet, and outlet,

with special attention given to the hydraulic

design.

4-21. Alinement. -A primary rule in

locating a culvert is to utilize the natural

channel with as little disturbance as possible to

the natural runoff pattern. Thus, if a canal

crosses a natural channel on a skew, it is

usually better to locate the culvert on a skew

with the canal, rather than to realine the inlet

or outlet channel. If the natural channel

changes direction between the inlet and outlet

of the culvert, a horizontal bend may be

required in the culvert conduit.

Open drains paralleling the canal on the

uphill side to intercept runoff water, should

flow, if possible, to a natural channel, where

conditions are best for locating a culvert.
204 SMALL CANAL STRUCTURES

prevent leakage and to provide flexibility.

Determination of the required diameter of

pipe, based upon hydraulic considerations, is

included in subsection 4-26(c). To avoid

Figure 4-20. Double-barreled pipe culvert with

concrete percolation collars. P-328- 701-2021

resulting in free flow at the inlet, and inlet

control. The downstream slope, S2, is usually

set on the flat slope .of 0.005 to facilitate

dissipation of excess energy by a hydraulic

jump in the pipe, without being flat enough to

permit sedimentation in the pipe. To obtain a

downstream leg of sufficient length to insure a

hydraulic jump in the pipe, or to reduce the

velocity in the pipe, it may be necessary to

steepen the upstream slope, SI.

Two slopes, SI and S2 , are also required

where the culvert inlet is relatively high with

respect to the canal invert elevation. The pipe

should cross under the canal prism with at least

2 feet of clearance below the invert of an earth

section canal, and at least 0.50 foot below the

lining of a concrete-lined canal.

To minimize the "daylighting" length of the

outlet channel, the culvert outlet should be no

lower than necessary to extend beyond the

canal bank and provide adequate protection to

the canal.

4-23. Conduit. -Culverts may be single or

multibarreled as shown in figure 4-20, and may

consist of any of the following types of

conduit:

(a) Precast reinforced concrete pressure

pipe (PCP),

(b) Precast reinforced concrete culvert

pipe (RCCP),

(c) Asbestos-cement pressure pipe (AC),

(d) Reinforced plastic mortar pressure

pipe (RPM), or

( e ) Rectangular concrete box section.

Subsequent references to pipe, pipe velocity,

etc., are not intended to exclude the concrete

box section. The type of conduit selected for a

particular site is dependent upon the project

life, the life expectancy of the pipe, the loading

conditions to be imposed upon the pipe, the

relative cost of each type, and its availability at

the site. For a detailed discussion of the various

types of pipe, see subchapter VIII B. Generally,

the concrete box section, as shown in figure

4-21, is used for flows larger than those

considered applicable to this text.

Considering the above factors, precast

concrete pipe is the usual choice for culverts

under canals, providing excellent strength,

durability, watertightness, and flow

characteristics. Rubber gasket joints are used to

Figure 4-21. Concrete box culvert with concrete

percolation collars. P328-701-3743
PROTECTIVE STRUCTURES 205

plugging with debris, the minimum diameter

usually considered for culverts is 24 inches.

However, this should not be considered

inflexible, as the nature and quantity of debris

in the drainage area, together with the extent

of damage that could result from plugging,

should be evaluated in establishing a minimum

diameter .

4-24. Inlet. -Several types of transitions are

used as culvert inlets. The best choice for any

particular situation is dependent upon the

hydraulics, the topographic character of the

site, and the relative elevations of the canal and

drainage channel. Suitability of each of the

basic types of transitions to use under various

conditions is given as follows:

(a) Type 1. --The broken-back transition, as

shown in figures 4-21 and 7-2, is best suited to

a well defined inlet channel, where the channel

banks can be shaped to conform to the sides of

the transition.

(b) Type 2. -The type 2 transition is well

suited to use in a wide, poorly defined channel,

and combines the economy of simple lines with

good flow characteristics (see figs. 4-19 and 7-4).

(c) Type 3. -The type 3 transition (see figs.

4-22 and 7-5), like type 2, is suitable to use in a

poorly defined channel. By extending the pool

beyond the end of the sloping sidewalls, a

longer crest results. By lowering the invert, the

headwall opening is lowered, permitting a

lower water surface elevation for the inlet pool

(provided the control is upstream).

(d) Type 4.-Except for its sloping floor,

and the omission of the headwall cutoff, the

type 4 transition, as shown in figure 7-6, is

similar to the type 3. The sloping floor permits

a lower pipe invert at the inlet headwall with

the type 4 transition.

For a more detailed discussion of these

transitions, see subchapter VII A.

(e) Precast Concrete Transitions. -Precast

concrete transitions, as shown in figure 4-23

are usually quite satisfactory, and may be more

economical in some areas, particuarly if a large

number of transitions of the same size are

required.

(0 Earth Transitions. -The designer may

find that a particular culvert does not require a

concrete transition due to the character of the

earth or rock material in which it is

constructed. An earth transition is permitted if

the design flow can be carried with a maximum

full pipe velocity of 5 feet per second with no

encroachment on the freeboard requirement.

In such a case, a concrete headwall may be

used to shorten the length of pipe required, or

the pipe may be extended completely through

the canal bank.

Concrete transitions provide the following

benefits:

( I) A greater capacity is provided by

good transitioning.

(2) The required length of pipe may be

shortened by the length of the concrete

transitions.

~

Figure 4-22. Precast concrete pipe culvert with type 3

inlet transition. P482-417-824

Figure 4-23. Precast concrete pipe culvert with precast

concrete inlet transition. P-328-701.6507
SMALL CANAL STRUCTURES 206

Figure 4.24. Baffled outlet at end of a culvert.

P328.701-8219

construct a channel with its invert

considerably below the original ground

surface.

(2) Type 2 concrete transition. -The type

2 transition as shown in figure 4-19 is well

suited to use in a poorly defined channel.

For this reason, it is the best choice where

the outlet elevation is not appreciably lower

than the original ground surface.

(b) Outlet Energy Dissipators. -The need

for energy dissipation structures at culvert

outlets should be avoided if possible, by

dissipating excess energy in the pipe. In

addition to a higher construction cost for

energy dissipators, their maintenance cost is

also greater. The pipe velocity may be reduced

by diminishing the slope, S2 but to not less

than a slope of 0.005.

Excess energy at culvert outlets may be

dissipated by the following structures:

( I) Baffled outlets. -Baffled outlets, as

shown in figure 4-24 perform well in

dissipating excess energy, provided clogging

by weeds or other debris can be avoided.

(3) The potential reduction in erosion

reduces the threat to the canal bank.

( 4) The cutoff walls used with concrete

transitions augment the function of the pipe

collars, and reduce the threat of piping by

percolation.

To prevent erosion, concrete inlet transitions

should be set with the inlet sill or lip at or near

the elevation of the channel invert. The sill

may be lowered slightly to permit complete

drainage of the inlet area.

Freeboard from the inlet water surface to

the top of the bank should be at least 2 feet.

Freeboard to the top of the concrete headwall

varies with the type of transition. Where the

normal bank height does not provide the

required inlet freeboard, the bank should be

raised for such a distance that the top will

intersect the natural ground surface at the

required elevation.

4-25. Outlet. -The culvert outlet performs

the basic function of releasing water to the

outlet channel without excessive erosion.

Depending upon the amount of excess energy

to be dissipated, this function may be

performed by a concrete transition, baffled

outlet (as shown in fig. 4-24), baffled apron

drop (as shown in fig. 4-25), or some other

form of energy dissipator (see chapter VI). The

concrete transition should be used where

possible in preference to most other types of

outlets which are more susceptible to problems

with weeds, trash, and sediment.

( a) Concrete Transitions. -Concrete

transitions may be used at culvert outlets

provided: the conduit is sized on the basis of a

maximum full pipe velocity of 10 feet per

second; standard outlet protection is used if

the pipe velocity at the outlet is equal to, or

less than 15 feet per second; and the next

higher class of protection is required if the pipe

velocity at the outlet is greater than 15 feet per

second.

Two basic types of concrete outlet

transitions are used as follows:

(1) Type 1 concrete transition.-The type

I transition as shown in figure 4-26A, is best

suited to a well defined outlet channel,

where the banks can be shaped to conform

to the sides of the transition. Thus, it is

generally used where it is necessary to
PROTECTIVE STRUCTURES 207

Figure 4-25. Concrete box culvert with baffled apron

drop at outlet. P-707-729-1947

When using a baffled outlet, the culvert pipe

should be sized on the basis of a full pipe

velocity of 12 feet per second. The

theoretical velocity, V t = V2gh, should not

exceed 50 feet per second. For a detailed

discussion of baffled outlet design, see

subchapter VI C.

The potential damage from plugging of

the culvert cannot be overemphasized, as

failure of the canal banks and the culvert

could occur .

( 2) Other types of energy

dissipators. -Drops and chutes with stilling

pools have been used at culvert outlets, as

have baffled apron drops (see fig. 4-25). The

stilling pool requires sufficient tailwater to

produce a hydraulic jump whereas the

effectiveness of the baffled apron drop is

independent of tailwater. See chapter VI for

design requirements of these structures.

4-26. Hydraulics.-(a) Design

Capacity.-For determination of the required

design capacity, see comments in subsection

4-19(c).

(b) Pipe Velocity.- The culvert should be

designed for a maximum full pipe velocity of

10 feet per second if a concrete transition is

used at the outlet, and for a maximum full pipe

velocity of 12 feet per second if an energy

dissipator is used. In the rare cases that

concrete inlets and outlets are not considered

necessary, the pipe should be designed for a

maximum full pipe velocity of 5 feet per

second.

The actual full pipe velocity will usually be

less than the maximum design velocity, due to

the availability of pipe in 3-inch increments of

diameter, only. However, the pipe will not

necessarily flow full, and the actual velocity

may be considerably faster than the full pipe

velocity. If the exit velocity in the pipe exceeds

20 feet per second, an energy dissipator should

be provided.

(c) Pipe Diameter.-The diameter of the

pipe is determined from the basic equation,

Q = A V when related to a pipe flowing full.

This reduces to: D = 1.13 4 The minimum

diameter usually permitted for culvert pipe is

24 inches. Precast concrete pipe is widely

supplied in increments of 3 inches of diameter .

(d) Hydraulic Control. -The upstream water

surface will be controlled by the head that is

required to satisfy: inlet conditions or outlet

conditions (such as a high tailwater, or pipe

losses). To insure the validity of other

hydraulic computations, it must be determined

whether the hydraulic control is located at the

inlet or outlet.

( I) Inlet control. -If the upstream water

surface is not influenced by flow conditions

downstream from the inlet, it is said to have

inlet control. Inlet control results from the

following conditions:

A downstream water surface that is low

enough with respect to the inlet, that it

does not influence the upstream water

surface, combined with an upstream pipe

slope that is steeper than the critical

slope.
208 SMALL CANAL STRUCTURES 

I r-- 

A. TYPICAL PLAN WITH TYPE I OUTLEl 

PROFILE 

8. TYPICAL PLAN WITH BAFFLED OUTLET 

PROFILE 

Figure 4.26. Plan and profile of typical culverts. 103-D-1303 
PROTECTIVE STRUCTURES 209 

(2) Outlet control. --lf the upstream 

water surface is influenced by downstream 

conditions, it is said to have outlet control. 

Outlet control results from the following 

conditions: 

downstream point), plus intermediate 

hydraulic losses, 

or Es2 + AH. = I;,,? + losses 

A downstream water surface that is 

high enough with respect to the inlet, that 

it influences the upstream water surface; 

or pipe losses that cause pipe flow at a 

depth greater than the critical depth. 

(e) Detcrmimtiou o.f’ Idet or Outlet 

co I1 tro 1. ~ 

Beginning with the water surface and energy 

established for the outlet, a balance of 

energy, if obtainable, should be verified 

between pairs of points proceeding 

upstream. 

( 1 ) Lkarnirzutiolz c?f‘ po~ile. -The type of 

control can sometimes be determined by 

examination of the culvert profile. For 

example. illlet corltrol is suggested if the 

downstream channel is wide, poorly defined, 

and considerably lower than the inlet. Ozrtlct 

corltvol is suggested if a high tailwatcr 

(relative to the inlet invert) is assured by a 

well defined channel with a flat slope. Such 

conclusions sllould be supported by 

performing minimal hydraulic computations. 

The critical slope for the design discharge, 

pipe diameter, and roughness coefficient can 

be determined from tables 21, 22, 58, and 

60 of bibliography reference 141. using the 

equation: 

If a balance of energy results between 

each pair of points, outlet control is assured. 

If a balance cannot be achieved between any 

two points, this indicates that a hydraulic 

jump occurs between the two points, 

resulting in additional head loss. This 

inability to achieve a balance of cncrgy 

confirms iiilet cotitrol of the upstream water 

surface, except that such an imbalance 

occurring between the outlet channel and a 

point just inside the pipe indicates outlet 

control if pipe friction and bend losses 

produce subcritical flow in the pipe, but a 

low tailwater in the channel allows the flow 

to pass through critical depth as it emerges 

from the pipe. 

,,8 13 sl 12 

(f) I~ilct Colitrol II)~dml~lics. ~-Where inlet 

control exists. the head required at the culvert 

inlet is computed from the orifice equation 

121, Q= CAJ2,i- (7 I, where C is the coefficient of 

discharge, A is the area of the pipe, and h is the 

head of water. Under inlet control, the head, 11, 

is measured from the upstream water surface to 

the centerline of the pipe at the headwall. To 

determine the required head, the orifice 

equation may be written 

01 

where k is the tabulated value in table 21, n 

is the coefficient of roughness of the pipe, D 

is the pipe diameter in feet, and Q is the 

design discharge in cubic feet per second. 

Among other requirements, inlet control 

cannot bc assured unless the upstream pipe 

slope is greater than the critical slope. 

(2) Bcmodli Theorem. -Where the 

location of the hydraulic control cannot be 

definitely established by examination of the 

profile, the Bernoulli theorem [2] should be 

used. By the Bernoulli process, it should bc 

determined if an energy balance exists 

throughout the length of the culvert as 

shown in figure 4-29. That is, the specific 

energy, Es* at one point, plus the drop in 

%vert elevation to a downstream point is 

t:lual to the specific energy, E,- (at the 

Q” 

h= ___ 

2g C2 A2 

Q’ 

With C = 0.6, and substituting V2 for 2 

11 = 0.0433 v2 

where V is the velocity with the pipe flowing 

full (see subchapter VII A). 

(g ) 011 t le t Control l[~~tIraulics. -Where 

outlet control exists, the head required to 

produce the design discharge is a function of 
I 

210 SMALL CANAL STRUCTURES 

the losses in the system as follows: 

(1) Inlet losses. -The inlet loss, 

hi = Kinh, 

(2) Pipe losses. -The pipe losses consist of 

friction and bend losses. The friction loss 

should be computed from the Manning 

equation [ 21 , 

Q = 1.486 AR* ‘3 s’ ‘* 

n 

where s is the friction slope of the pipe, and 

n is the roughness coefficient, equal to 0.013 

for precast concrete pipe. Pipe bend losses 

may be determined as shown in subchapter 

VIII A. 

(3) Outlet losses-The outlet loss, 

h, = K,nh,. 

See subchapter VII for explanation of inlet 

and outlet losses. 

4-27. Pipe Collars. -Percolation of water 

from the canal to the drainage channel could 

result in piping, or the gradual removal of 

material along the percolation path, allowing a 

gradually increasing flow. Failure of the canal 

bank could result unless proper precautions are 

taken in the design and construction of the 

culvert. 

Pipe collars, as shown in figure 4-23, are 

effective in reducing the percolation along 

culverts. Unless the percolation study indicates 

otherwise, it is customary to locate collars on 

the pipe as follows: 

One collar below the centerline of the 

uphill canal bank; two collars under the 

downhill bank, with one under the inside 

edge, and one located 2 feet downstream 

from the outside edge (see fig. 4-28). 

A “short path” between collars will occur if 

the resistance to percolation through the soil is 

less than the resistance to percolation along the 

concrete surface of the pipe and collars. To 

evaluate these resistances, Lane’s 

weighted-creep method [8] uses the following 

weighted resistance values: 

K, = 1.0 - For flow along a vertical 

concrete surface, such 

as that of the collar. 

Kz = 0.33 - For flow along a horizontal 

or nearly horizontal 

concrete surface, such 

as that of the culvert 

pipe (primarily along 

the under side). 

K3 = 2.0 - For flow through the soil. 

By this method, where X is the distance 

between collars, and Y is the vertical projection 

of the collar from the pipe (see fig. 4-27), it 

can be shown that a short path occurs if the 

distance, X, is less than the following: 

or 

K3X=KzX+2K1 Y, 

2X=0.33 X+2(1 xY> 

Solving for X in terms of Y, 

or 

and 

2x - 0.33x = 2Y 

1.67 X = 2Y 

X (min.) = 1.2Y 

n 

K,=I K2 = 0.33 

I- X4 

Figure 4-27. Weighted-creep method. 103-D-l 304 

To determine the adequacy of the 

customary three collars, in providing sufficient 

path to prevent piping, use Lane’s 

weighted-creep method as discussed in 

subchapter VIII C. To assure the stability of 

the culvert and adjacent earth material, a high 

quality of construction must be achieved. 

4-28. Protection. -Protection for the culvert 

should meet the requirements of figure 7-8, 

chapter VII. If the outlet velocity in the pipe 

exceeds 15 feet per second, the outlet 

protection should be based upon the next 

higher discharge class. 

4-29. Design Example.-Assume that a 

precast concrete pipe culvert is needed to 
PROTECTIVE STRUCTURES 

convey storm runoff water under a canal at its 

intersection with a natural channel. 

(a) Assumptiotzs. ~ 

( 1) Properties of the canal section are as 

follows: 

b = 8 ft., h, = 6 ft., ss = l-112: 1, d, = 4 ft., 

W, = 6 ft., and W, = 12 ft. to accommodate 

an operating road. 

(2) The outside bank heights, measured 

at the toe of the outside bank slopes, are: 

‘lb 1 = 4 ft., and h, 

2 

= 9 ft., as shown in 

figure 4-28. 

(3) The cross-drainage channel is wide, 

shallow, and poorly defined, both at the 

inlet and outlet. It is estimated that the 

outlet channel will support a depth of 1 foot 

and a velocity of 1 foot per second for the 

design flow. 

(4) It has been determined that the 

25-year flood could yield a discharge of 45 

cfs. 

(13) Solution. ~ 

(1) Pipe velocity. -To use a standard 

outlet transition, the pipe diameter is 

determined on the basis of a maximum full 

pipe velocity of 10 feet per second. 

(2) Pipe diameter and c&s.-The 

required pipe diameter (see section 4-26(c)), 

D= 1.13G 

= 1.136 

= 2.38 ft. (min.) 

/ 

Ortglnal ground surface 

(Channel Invert) 

211 

Use a 30-inch diameter, which provides an 

area of 4.91 square feet, resulting in a full 

pipe velocity of 9.17 feet per second. 

For pipe class, see subchapter VlII B. 

( 3) Hydraulic control. -From a 

preliminary profile, using, tentatively, a type 

3 inlet transition and a type 2 outlet 

transition in the poorly defined channel (see 

section 4-24), it is seen that the culvert can 

clear the canal invert by the required 2 feet, 

and emerge beyond the lower canal bank 

with an outlet channel of minimal depth, 

requiring only minor excavation to daylight. 

As the depth of cut in the poorly defined 

outlet channel is minimal, the tailwater will 

spread as permitted by the natural 

topography, and will probably not influence 

the upstream water surface. Further, to 

provide 2 feet of clearance beneath the canal 

invert, the pipe must descend on a slope 

which is presumed to be steeper than the 

critical slope, resulting in free flow at the 

pipe inlet, assuring inlet control. This will be 

verified. 

(4) Inlet type. -As the drainage channel is 

not well defined, a type 1 transition is not 

suitable. With the upper canal bank only 4 

feet higher than the channel invert, a type 3 

or 4 inlet transition would probably be 

better than a type 2, as they require less 

water depth at the inlet. The type 3 inlet 

will be used, provided the head is adequate 

to discharge the design flow without 

encroaching on the required bank freeboard. 

(5) Pipe friction slope (for pipe flowing 

f’u 111. -Where inlet control is certain, 

determination of the friction slope is not 

necessary. However, a better understanding 

of the culvert hydraulics is gained by an 

Figure 4-28, Culvert-typical profile. 103-D-1 305 
212 SMALL CANAL STRUCTURES 

awareness of the relative slopes. From the 

Manning equation [ 21 , the pipe velocity is: 

v= 1.486 R2l3 sl/2 

n 

Using a coefficient of roughness, n = 0.013, 

and a hydraulic radius, 

R = f = y= 0.625 

R 2’3 = 0.731 

the friction slope, 

2 

1.486 x 0.731 1 

= 0.0120 

This friction slope can also be determined 

from table S-1, sheet 2 of 9, chapter VIII: 

H 

s = --=u&z ()0]2() 

f 1000 

(6) Critical slope. -Determine the critical 

slope (for comparison with the invert slope, 

sl) for Q = 45 cfs and D = 2.5 feet, using 

tables 21, 22, 58, and 60 [4]. 

Find D”’ = 9.882 from table 58 

and D8’j = 11.51 from table 60 

and 

Then &$ = F4&= 4.55 

4 . 3 = 0.89 from table 22 

Also Qn 

D8 I3 S 1 ,2 = 0.491 from table 21 

Then s,“’ = 0.49%/3 

SC l/2 45 x 0.013 = 

0.491 x 11.51 

s c 1’2 =0.1034 

and s, = (o.lo34)2 = 0.0107 

(7) Invert slope, sl .-From figure 4-28, 

determine the required pipe invert slope to 

provide a minimum of 2 feet of clearance 

between the canal invert and the concrete 

pipe. Assume class B-25 pipe (see subchapter 

11 C) will be used, with a wall thickness, t = 

3- l/2 inches. 

yl =D+t+2+h, -h, PB 

= 2.5 + 0.3 + 2 + 6 - ; - 3 = 3.8 ft. 

L, =1.5h,+w, +l.5(h,l +BBH)+t, -0.5 

= 1.5 x 6 + 6 + 1.5 (4 + 3 - 6) + 0.5 - 0.5 

= 9 + 6 + 1.5 = 16.5 ft. 

Sl = yl /L, = 3.8/16.5 = 0.23 

(= tan (Ye in figure 4-28) 

Therefore sl > s,, permitting free flow at 

the pipe inlet, with inlet control; providing 

the downstream water surface does not 

control (see subsection 4-29(c)). 

(8) Invert slope, s2. -Since sl is too steep 

to be extended to the outlet, without an 

outlet channel of excessive depth and length, 

a bend and a second slope, s2 are required. 

Let s2 = 0.005, as indicated in section 4-22. 

(9) Length, L,. -The length, L, must be 

sufficient to locate the outlet headwall 

beyond the canal bank at its intersection 

with the top elevation of the headwall, 

which should be consistent with an invert 

elevation providing an outlet of minimal 

daylighting length and depth (see fig. 4-28). 

Determine L, by scaling the preliminary 

profile (see step 3). L, = 41 feet. 

(10) Outlet type. -As the outlet channel 

is poorly defined, the type 1 transition 

would not be suitable. Therefore, the type 2 

transition is selected. From figure 7-4, 

chapter VII, with D = 30 inches, dimensions 

L and E are found to be 6 feet 9 inches and 

4 feet 6 inches, respectively. 

(11) Inlet hydraulics. -Proceeding with 

the assumption that inlet control exists, the 

ability to discharge the design flow is a 

function of the inlet hydraulics, without 

regard to the culvert pipe and outlet 

conditions. The type 3 inlet transition 

dimensions provide hydraulic control at the 

headwall opening. Therefore the head 
PROTECTIVE STRUCTURES 213 

required to discharge 45 cfs can be 

determined from the orifice equation [ 21 , 

Q=CAm 

which, with the coefficient, C = 0.6, can be 

written (see subchapter VI1 A): 

or 

h = 0.0433 V2 

h = 0.0433 (9.17)* = 3.64 ft. 

(12) Inlet Jreeboarcl. -Referring to figure 

7-5, the type 3 transition would require 

ponding the channel water surface to a 

depth, 

where D’ = & (see fig. 4-28) 

= & = 2.56 ft. 

Then, di = 3.64 - [3 ~ 1.281 = 1.9 ft. 

The bank freeboard, fb, is equal to the 

bank height above the channel invert minus 

the required ponding depth, or 

ft, =h,l -dl 

1 

fb I 

=4- 1.9 

= 2.1 ft., which exceeds 

the required freeboard of 2 feet minimum. 

(13) Collars. -Unless percolation studies 

show that more concrete collars are 

required, one collar should be located under 

the upper bank of the canal, and two under 

the lower bank, as shown in figure 4-28. For 

a detailed treatment of percolation, see 

subchapter VIII C. 

(14) Pipe belzd. -For pipe bend 

requirements, see chapter VIII. 

(1 5) Protection. -From figure 7-8, 

chapter VII, it is determined that erosion 

protection is not required at the culvert 

inlet. Type 2 protection is indicated for the 

outlet. However, if the pipe velocity at the 

outlet should exceed 15 feet per second, as 

determined by the following Bernoulli 

solution of hydraulics, the outlet protection 

should be increased to that required for the 

next greater discharge, resulting in type 3 in 

lieu of type 2 protection. 

(c) Verification of lyd~aulics hy the 

Bernoulli Method (see fig. 4-29). - 

(1) Energy balance at outlet. -The 

specific energy in the outlet channel is 

determined as follows: 

= 1.o+2x32,2- (l)’- 1 . 02 ft. 

The specific energy in the outlet end of the 

pipe can not be less than ESc, as minimum 

energy accompanies critical flow. From step 

(b)(6), above, 

d 

c = 0.89 D 

Then 

d, = 0.89 (2.5) = 2.22 ft. 

From table 2 1 [ 41, 

AC 

-g = 0.7384 

and 

A, = 0.7384 (2.5)* = 4.62 sq. ft. 

giving 

Q 45 v, = A, = 4.62 = 9.74 f.p.s. 

and 

V2 hvc =2g = 1.48 ft. 

Finally, 

ESc = d, + h, 

c 

= 2.22 + 1.48 = 3.70 ft. 
214 SMALL CANAL STRUCTURES 

AZ = 0.3727 (2.5)* = 2.33 sq. ft. 

Figure 4-29. Culvert hydraulics. 103-D-l 306 

As EsC > ESq, and Es 

c 

represents 

minimum energy, a balance of energy is 

unobtainable at the outlet. Therefore, the 

tailwater cannot provide outlet control. 

(2) Specific energy at point I (just inside 

the pipe at the inlet).-As s, is steeper than 

S c, and the tailwater does not control, 

supercritical flow will occur from point 1 to 

point 2, and critical flow (flow at minimum 

energy) will occur at point 1. From step 1 

above, the specific energy for critical flow, 

EsC = 3.70 ft. 

(3) Specific energy at point 2.-Find d2 

and hV2 yielding a specific energy, ES2 such 

that 

Es2 = E, +yl - hfl C 

where hf , is the pipe friction loss from point 

1 to point 2. 

Try 

dz = 1.2Oft.;; = 0.48 

Then, from table 21 [43, 

v, 2= 45 

- = 19.3 f.p.s. 

A2 2.33 

h 

“2 

= 5.8 ft. 

Es2 = 4 + h,r2 = 1.2 + 5.8 = 7.0 ft. 

Qn 

= 0.216 

DE 13 

( > 

sf2 

1 12 

( ) 

, ,* _ Qn/D’ ‘3 

Sf, - 0.216 

( Sf, > 1,2 _ - 45(0.013)/11.51 0.216 -- _0.2160508 

= 0.235 

sf2 = (o.235>2 = 0.0554 

Friction loss in the length, L1 , is 

SC + Sf hfl = + L, [ 1 

1 16.5 = 0.54 ft. 

Finally, the assumption that d, = 1.20 feet 

is correct if 

Es2 =Esc +yl -hfl 

7.0 = 3.7 + 3.8 - 0.5 

7.0 = 7.5 - 0.5 

7.0 = 7.0 (check) 

Therefore, Es2 = 7.0 ft. 

(4) Specific energy and velocity at point 

3 (just inside the pipe). -Find d, and hV3 

yielding a specific energy, ES3 such that 

Es3 = Es2 + ~2 - hf2 

where 

Yz = s2 L2 

A2 

- = 0.3727 

D* y2 = 0.005 x 41 = 0.2 ft. 
PROTECTIVE STRUCTURES 215

Try d3 = 1.40ft.;d3/D=O.56. Finally, the assumption that d3

is correct if

= 1.40 feet

Then from table 21 [ 4] ,

A3

= 0.4526:

E $3 = E $2 + Y2 -h f 2

5.3 = 7.0 + 0.2- 1.8

5.3 * 5.4; close enough for design

D2

A3 = 0.4526 (2.5)2 = 2.83 sq. ft.

V3 = !}; = ~ = 15.9 f.p.s.;

hV3 = 3.94 ft.

ES3 =d3 +hV3 = 1.4+3.9= 5.3 ft.

On

Therefore,

ES3 = 5.3 ft., and V3 = 15.9 f.p.s.

(5) Outlet protection. -Since the velocity

in the outlet end of the pipe is 15.9 feet per

second, exceeding the velocity of 15 feet per

second pennitted with normal protection,

type 3 protection should be used in lieu of

type 2, as indicated in step (b)15, above.

os !3 Si !2 = 0.279

Qn/D8/3

= .= 0.182

2. Overchutes

4-30. General. -Overchutes are structures

used to carry storm runoff or drainage water

over a canal. They may consist of a rectangular

concrete flume section, supported on piers as

shown in figure 4-30, or a closed conduit such

as the steel pipe shown in figure 4-31. The

concrete flume section is used primarily for

large cross-drainage flows, or in areas where a

0.279

8[3 = (0.182f = 0.033

Friction loss,

hf? =

=

Figure 4-30. Rectangular concrete overchute. SO-2217-R2.

45 x 0.013/11.51

~JL2
216 SMALL CANAL STRUCTURES

Figure 4-31. Steel pipe overchute on the Colorado-Big

Thompson Project. P-245-713-300

pipe would be susceptible to plugging with

trash.

The inlet can be any of the standard types of

concrete transitions described in chapter VII.

The outlet may be a standard transition, but

sometimes consists of an energy dissipator ,

such as a stilling pool, a baffled apron drop, or

a baffled outlet. The outlet may also include a

rectangular concrete box section through the

downhill canal bank, to accommodate traffic

on the operating road. A similar provision may

be made for the uphill bank if required, as

shown in figure 4-32.

4-31. Alinement.-The alinement of

overchutes usually follows natural drainage

channels. While an alinement normal to the

canal is shorter and more economical, a skewed

alinement is sometimes used, as the natural

channel should be disturbed as little as

possible. An overchute may also be located at

the end of a drain which parallels the canal, to

provide a crossing over the canal. If a natural

channel is not available at such a location, a

downstream channel should be constructed.

4-32. Profile. -To permit complete drainage

of the inlet channel and the structure,

overchutes should slope enough to compensate

for a slight amount of unequal settlement of

the piers. Overchutes are best suited to use

where the canal is in thorough cut, or where

the ground surface on the uphill side is well

above the canal water surface. A minimum

clearance of 1 foot should be maintained

between the canal water surface and the

overchute section, which should also clear the

top of the concrete lining in a lined canal

section. If the uphill ground surface is not

sufficiently above the canal water surface to

provide the required clearance, a culvert should

'be used under the canal in lieu of the

overchute.

A flat slope of the cross-drainage channel

profile is usually accompanied by a flat slope

and slow velocity in the overchute, permitting

the use of a standard outlet transition.

A steep slope of the cross-drainage channel

profile may be accompanied by a steep slope

and fast velocity in the overchute. If the

overchute has an exit velocity exceeding 20

feet per second, an energy dissipator is required

at the outlet to dissipate the excess head.

Where weeds or trash are not prevalent, a

baffled outlet may be used in conjunction with

a pipe overchute.

A concrete overchute, having an energy

dissipator such as a stilling pool, may be set on

a supercritical slope to minimize the required

cross section. After crossing the canal water

prism, the overchute often drops on a 2 to 1

slope to the pool, or vertically to a pool as

shown in figure 4-35.

Where a baffled apron drop is used with a

concrete overchute, the slope should be less

than critical (see chapter VI).

4-33. Capacity. -For determination of the

required design capacity, refer to subsection

4-l9(c).

4-34. Conduit. -An overchute should have a

rectangular concrete section, or a circular pipe

section, based upon a cost comparison for the

particular span and drainage capacity required,

or upon inlet conditions. Generally, the

rectangular concrete section is used for larger

capacities, and the pipe section for smaller

capacities.

Concrete piers are usually required, and

should preferably be located just outside the

canal water prism to allow unobstructed flow

in the canal.

(a) Rectangular Conduit. -The conduit for

the rectangular concrete overchute will be

referred to, hereinafter, as a flume or chute. It

may span from one bank of the canal to the

other, but it is often jointed over the piers to

accommodate differential settlement of the
PROTECTIVE STRUCTURES 

217 

,N 

7 

T 

/ 

1 

;I 
218 

piers without resulting in undue stress in the 

overchute. The size of the flume section can 

sometimes be minimized by setting the flume 

invert on a supercritical slope (see sec. 4-38). 

(b) Pipe Conduit. -Pipe overchutes usually 

consist of steel pipe supported on two piers, as 

shown in figure 4-33. The steel pipe is usually 

terminated within the canal prism, and 

extension of the pipe through the canal banks 

is made with precast concrete pipe, coupled to 

the steel pipe. 

The required gage of the steel pipe for beam 

strength depends on the span and pipe 

diameter. As shown in table 61 [ 101, a pipe of 

a given gage and diameter can span a much 

greater distance if reinforced with stiffeners at 

the supports. 

4-35. Met Types. -With slight modification, 

the standard types of concrete transitions, as 

discussed in chapter VII, may be used for 

transitioning to a rectangular section. For 

recommended usage of the various types, see 

section 4-24. 

The concrete transition invert should be set 

at or slightly below the elevation of the 

channel invert, to permit complete drainage of 

the upstream pool without excessive upstream 

erosion. The canal bank height should be 

sufficient to provide a freeboard of 2 feet 

above the inlet water surface. An inlet dike 

may be required where the normal bank height 

is insufficient. 

4-36. Outlet Types. -The overchute outlet, 

like the culvert outlet, should release water to 

the outlet channel without excessive erosion. 

The energy to be dissipated in a rectangular 

concrete overchute is often sufficient to 

require an energy dissipator such as a stilling 

pool or a baffled apron drop. As pipe 

overchutes are usually designed for a smaller 

capacity, a concrete outlet transition is often 

satisfactory. However, an energy dissipator 

such as a baffled outlet may be required if the 

drop in elevation is considerable. The concrete 

transition should be used where possible in 

preference to other types of outlets which are 

susceptible to problems with weeds, trash, and 

sediment. The standard outlet transitions may 

be used for exit velocities of 20 feet per second 

or less, provided outlet protection conforms to 

the requirements discussed in section 4-25. 

SMALL CANAL STRUCTURES 

Overchute outlets should preferably be free 

draining, to eliminate ponding of water. 

However, if this is impracticable, ponding is 

sometimes permitted. 

(a) Concrete Transitions. -The comments 

concerning concrete transitions as culvert 

outlets (see subset. 42-5(a)) apply equally to 

their use as overchute outlets. 

Generally, a concrete outlet transition can 

be used with pipe overchutes if the pipe is sized 

on the basis of a full-pipe velocity of 10 feet 

per second or less and the slope of the 

downstream leg of the pipe is not greater than 

the critical slope, s,. For proper use of the type 

1 and type 2 transitions, see section 4-24. 

(b) Outlet Energy Dissipators. -Rectangular 

concrete overchutes often require an energy 

dissipator such as a stilling pool or baffled 

apron drop. Pipe overchutes require an energy 

dissipator, such as a baffled outlet, only if the 

exit velocity from the pipe exceeds 20 feet per 

second. 

The various types of energy dissipators are 

used as follows: 

(1) Stilling pool. -Stilling pools are often 

used to dissipate the excess energy at the 

outlet of concrete overchutes. They are 

dependent upon a sufficient tailwater depth 

in the outlet channel to insure a hydraulic 

jump. See chapter Vl for design of the 

standard stilling pool. 

Stilling pools usually follow a chute or 

drop on a 2 to 1 slope, but may follow a 

vertical drop, as shown in figure 4-35. This 

arrangement is particularly useful if an 

operating road must cross over the stilling 

pool structure. 

(2) BaffZed apron drops. -Baffled apron 

drops may be used for concrete overchute 

outlets without dependence upon tailwater. 

See chapter VI for design of baffled aprons. 

(3) Baffled outlets.-Where weeds and 

trash are not prevalent, and where excess 

energy cannot be satisfactorily dissipated in 

the pipe, baffled outlets may be considered 

for pipe overchutes. They have been adapted 

to use at the end of an open chute section, 

as well as with pipe. See chapter VI for 

design of the standard baffled outlet. 

4-37. Pipe Overchute Hydraulics. -(a) Inlet 

Transition. -The elevation of the overchute 
PROTECTIVE STRUCTURES 

P R 0 F I L E 

WELDED STEEL PIPE AND PRECAST CONCRETE PIPE 

Ye? we 

e 13 

u p,:, 

. ~*/a -,r,.s2 - SECTION 8-B SECTlcJN n-n 

WELDED STEEL PIPE AND CORRUGATED METAL PIPE 

Figure 4-33. Overchutes-typical plan and sections. 103-D-1 308 
220 

Inlet is limited by three factors as follows: 

(1) Canal ~vater surjtice. -The inlet must 

be high enough to provide flow across the 

canal above the canal water surface, as 

discussed in section 4-32. 

(2) Pipe submergence. -To fully utilize 

the capacity of the pipe, the water surface in 

the inlet channel should submerge the top of 

the pipe opening by at least 1.5 h, . This P 

provides for an inlet loss of 0.5 h, and for a P 

velocity head of 1 .O h, 

P 

in the pipe. 

( 3 ) Ban k freeboard. -The maximum 

water surface for the design flow in the inlet 

channel should be at least 2 feet lower than 

the top of the uphill canal bank, or inlet 

dike as shown in figure 4-44. 

In a well-defined cross-drainage channel, a 

type 1 inlet transition is ordinarily used, and 

the above limitations can usually be met 

without inundation of an excessively large area. 

However, where there is no channel, or 

where the channel is poorly defined, a large 

area may be inundated. To minimize this area, 

the pipe inlet may be lowered by using a type 3 

or type 4 inlet transition (in lieu of the type 2 

transition), provided that it does not infringe 

on the required pipe clearance above the canal 

water surface. This capability can be 

facilitated, if necessary, by using an oversized 

pipe, with little or no submergence of the inlet 

end. 

A complete hydraulic analysis should be 

made to determine the location of the 

hydraulic control (see subset. 4-26(d)), and the 

elevation of the inlet water surface. Where the 

channel is well defined, the flow to and from 

the overchute should coincide, as much as 

possible, with the natural channel flow. 

With inlet control, the upstream water 

surface is controlled by the head required for 

entrance into the pipe. Thus, the water surface 

will rise to a height above the inlet centerline, 

SMALL CANAL STRUCTURES 

Q” 11 = ~ 

2gC2 A2 

(see subset. 4-26(f)) 

where the coefficient of discharge, C = 0.6. 

Where outlet control exists, the head 

required to produce the design discharge is a 

function of the losses in the system as follows: 

( 1) Inlet losses. -The inlet loss, 

hi = Ki nh, 

(2) Pipe losses. -The pipe losses consist of 

friction and bend losses. The friction loss 

should be computed from the Manning 

equation [ 21 , 

Q = 1.486 AR213 s’ I2 

n 

where s is the friction slope of the pipe, and 

n is the roughness coefficient, equal to 0.013 

for precast concrete pipe. Pipe bend losses 

may be determined as shown in subchapter 

VIII A. 

(3) Outlet losses. -The outlet loss, 

h, = K,nh V’ 

See subchapter VII for explanation of inlet 

and outlet losses. 

(b) Pipe Velocity. -Pipe overchutes should 

be sized for a maximum full pipe velocity of 10 

feet per second if a concrete transition is used 

at the outlet, and for a maximum full pipe 

velocity of 12 feet per second if a baffled 

outlet is used. 

(c) Pipe Diameter.-The diameter of the 

pipe is determined from the basic equation, 

Q = AV, when related to a pipe flowing full. 

This equation reduces to: 

II= 1.13 J-$ 

The minimum diameter usually permitted 

for pipe overchutes is 24 inches for 

cross-drainage water which could carry weeds 

or trash. A minimum diameter of 12 inches 

may be permitted if the overchute carries canal 

irrigation flows that are relatively clean. In this 

case the overchute is sometimes called an 

irrigation crossing. 

The pipe diameter may be increased from 

the value determined by the above equation to 

reduce the area of inundation in the upstream 

channel, or to provide a greater area for passage 

of weeds. 

(d) Pipe Outlet.-Hydraulics in the outlet 

end of the pipe should be determined by the 

Bernoulli process, as illustrated in the design 
PROTECTIVE STRUCTURES 221 

example for side channel spillway, subsection 

4-8(c). 

4-38. Concrete Overchute 

Hydraulics. -(a) Rectangular Section. -As 

overchutes are fairly short, the most 

economical section is not necessarily the most 

desirable. A wider and shallower section will 

permit a shallower inlet pool depth, resulting in 

less inundation of the channel. Thus, the 

freeboard requirement can more easily be 

satisfied without excessively raising the uphill 

bank of the canal. The wide, shallow overchute 

section is particularly applicable to a shallow or 

poorly defined natural channel. 

Where a stilling pool is used as an outlet 

energy dissipator, the width and depth of the 

flume section may be minimized by setting the 

chute on a supercritical slope, provided such a 

slope can be used within the limits imposed by 

the ground surface and the required clearance 

above the canal water surface. Critical flow 

may then be assumed to occur at the beginning 

of the chute section. Caution should be used to 

avoid a slope at or near the critical slope, as 

critical flow is rather unstable. A small change 

in energy will cause a relatively large change in 

water depth. To avoid excessive water surface 

undulations from unstable flow, a supercritical 

slope should be used, exceeding the critical 

slope by about 20 percent, with computations 

based upon a “rough” n (e.g., 0.015 in lieu of 

0.013 in the concrete section). 

If a baffled apron drop is used as an outlet 

energy dissipator, the chute velocity should be 

less than critical, as required for entrance to a 

baffled apron drop (see chapter VI). 

The wall height in the chute section should 

provide a freeboard of at least 1 foot at the 

inlet, and for the full length of the chute 

section, based upon a “rough” n in the chute. 

(b) Critical Flow. -Where the chute is set on 

a supercritical slope, critical depth at the 

beginning of the chute should be determined 

from table 17 [4] , or the equation: 

2 13 

d, L%-- 

1 I3 = 0.3 14q2/3 

g 

Then, the area, A, = bd,, where b is the width 

of the chute section. The velocity, 

v, =$ 

c 

and the velocity head, 

h v =- 

“C 2g 

Specific energy, 

ESc = d, + h, 

c 

Finally, the critical slope, s,, should be 

determined from the Manning equation [ 21 : 

Q= 1.486 AR213 s”~ 

n 

or 

‘C = [,/&‘i] 2 

where n is the roughness coefficient and R is 

the hydraulic radius, which is equal to the area 

divided by the wetted perimeter, wp. 

(c) Inlet Transition. -An inlet transition is 

required to provide entrance from this channel 

to the chute. The upstream water surface 

elevation must be equal to the energy gradient 

in the chute, plus inlet losses. That is, it should 

be equal to the invert elevation at the 

beginning of the chute, 

plus d, + hvc + 0.3 Oh, 

As the velocity in the inlet pool is near zero, 

and the velocity at the beginning of the chute 

is V,, the inlet loss, hi = 0.3 h, . 

(d) Chute Hydraulics. -AfFer determining 

critical flow conditions at the upstream end of 

the chute section, the hydraulics can be 

determined at the downstream end by using 

the Bernoulli process [ 2 ] : 

ES2 + h, = E, 1 + s, L (see fig. 4-36) 

where 

E,, is the known specific energy; 
I 

222 SMALL CANAL STRUCTURES 

pool. Thus, the invert of the pool must be 

set far enough below the downstream 

channel water surface to insure a pool depth, 

dz, that is sufficient to cause a hydraulic 

jump as shown in figure 4-35. As the 

required depth, d,, is dependent upon the 

depth, dI , which is dependent upon the 

vertical drop, D, and it is dependent upon 

the available tailwater surface, a 

trial-and-error solution is necessary to 

determine the optimum dimension, D. After 

assuming a drop, D, the depths d, and d, 

are determined as shown in the following 

paragraphs. 

The tailwater elevation is established using 

a conservative (smoother than expected) 

roughness coefficient for the downstream 

channel, to insure a hydraulic jump under 

extreme conditions. A reduction of 

approximately 20 percent in the normal 

value of n is generally used to give a 

conservative value for the earth section. 

The downstream water surface should not 

submerge the crest of the drop by more than 

0.6d,, as shown in figure 4-34, as greater 

submergence would prevent a hydraulic 

jump and excessive waves would continue 

into the downstream channel. 

ES* is the specific energy to be determined; 

h, is the friction loss between points 1 and 

2; and 

s, L is the drop in invert elevation between 

points 1 and 2. 

Various values of d2 are assumed until the 

associated velocity head and friction loss (from 

the Manning equation) provide an energy 

balance in the foregoing equation. 

The chute walls usually have a uniform 

height, except that a greater height is often 

used through the upper bank of the canal (see 

fig. 4-35). The wall height through the bank, 

h, , should include a minimum freeboard of 1 

foot above the upstream water surface. The 

remaining portion of the chute should have a 

wall height, hz, which includes a minimum 

freeboard of 1 foot above the maximum water 

depth in the chute. With the chute set on a 

supercritical slope, the maximum depth in the 

chute would be d,, occurring at the inlet end. 

(e) Stilling Pool. -Two types of stilling 

pools are used to dissipate the excess energy of 

cross-drainage flows in an overchute. With 

either type, a well-defined outlet channel is 

required to provide a reliable tailwater which is 

an essential factor in forming a hydraulic jump 

in the pool. Where the natural channel does not 

provide adequate tailwater, stoplogs, or a 

concrete curb have been used in the 

downstream end of the pool to assure the jump 

(see fig. 2-36). The standard stilling pool 

should be designed in accordance with the 

requirements shown in chapter II. 

The vertical drop and pool requires less 

length than does the standard drop and pool, 

giving it an advantage where right-of-way is a 

consideration. However, in the interest of 

economy, its use should be limited to a vertical 

drop, D, that does not extend much below the 

canal invert. Where greater drops are required, 

other types of energy dissipators, or a culvert 

should be considered. 

The design procedure for the vertical drop 

and pool is as follows: 

(1) Vertical drop. -The magnitude of the 

vertical drop, D, should permit a 

free-draining pool to discharge into an outlet 

channel that can provide a reliable tailwater, 

capable of insuring a hydraulic jump in the 

Rectangular 

Overchute 

-iFigure 4-34. Overchute-vertical drop hydraulics. 

103-D-1 309. 

(2) Depth, dI .-The depth, dr , can be 

obtained from the equation [ 111 

d1 =l.06~& 

Even though the rectangular chute is set 

on a supercritical slope, the water depth,d,, 

at the crest of the drop, will not be 
PROTECTIVE STRUCTURES 

appreciably less than d,, as the relatively 

short length required to span the canal is not 

sufficient to attain normal depth for a steep 

slope. Therefore, the substitution of critical 

depth for the actual depth can be made 

without a significant error. 

(3) Deptl1. cl, . -The depth, d,, can be 

obtained from the standard equation for 

depth in stilling pools (see chapter II), 

223 

intersection of the upper nappe surface with 

the pool floor. The flow trajectory can be 

determined from the equations [ 21: 

Y = (1/2k tZ 

and 

x=vt 

d2 =-dl+ J 

d, 2 2V, 2 d, 

-+- 

2 4 g 

(4) Pool freeboard. -The required pool 

freeboard is normally determined from the 

curve in figure 2-33, chapter II. Entering 

along the ordinate with the value of 

QV, dL 

-, or V,‘d, 

A 

the freeboard can be read along the abscissa. 

If the pool has a concrete top (for a road 

crossing, e.g.) a freeboard of 1 foot is 

sufficient. 

(5) Pool leugtli (see fig 4-35). -Length 

L, : The mirCmztm length for L3 should be 

great enough to provide clearance between 

the headwall and the upper nappe of the 

flow trajectory. The profile of the upper 

nappe can be determined as shown for Lq, 

following. The maximum length should 

preferably not exceed the horizontal 

component of: the bank height above the 

canal lining height; or of the bank height 

above the water surface of an unlined canal. 

However, the stilling pool is sometimes 

permitted to encroach slightly upon the edge 

of the water prism in an unlined canal. 

Further, the headwall at the downstream 

end of L, is often permitted to encroach 

slightly upon the alinement of the normal 

canal bank. This is essential where the bank 

is raised to permit the operating road to 

cross the pool. Between the minimum and 

maximum values, the length, L3, may be 

rounded as desired. 

Length L, : The length, L, , is designed to 

locate the first row of pool blocks 

immediately downstream from the 

where 

y is the vertical drop in water surface in t 

seconds, 

x is the horizontal distance traveled in t 

seconds, 

v is the velocity of flow at the beginning of 

the trajectory, and 

g is the acceleration of gravity, equal to 32.2 

feet per second per second. 

Thus, 

L, =x=vt 

where t is the time required to drop a distance 

y, with 

Y=d, +D 

Length L, : From the standard 

dimensions for stilling pools (see chapter 

vu, 

L = (3/4) d, 

Length L6: 

L, = 3 d, minimum 

The total length, L, + L6 - L, must also 

be sufficient to accommodate a crossing for 

the operating road, if required (see fig. 

4-35). 

(6) Pool blocks. -From the standard 

dimensions for pool blocks (see chapter II), 

the block height should be equal to +, and 

the block length should be equal to 1.25 $ 

The block width (8 inches minimum) should 

conform to the requirement for equal block 

and space widths. Two rows of blocks 

should be located as shown in figure 4-35, 
224 SMALL CANAL STRUCTURES 

with blocks in each row staggered with those 

in the other. One row will then consist of 

one block less than the other row, but will 

include a half block at each end, in contact 

with the sidewall. These half blocks are 

sometimes omitted. In either row, the block 

width, 

W 

b 

= pool width 

2N 

where N is the number of whole blocks 

plus one-half for each half block. 

In the standard stilling pool, the first row 

of blocks are referred to as chute blocks, and 

are smaller than the floor blocks (see fig. 

2-33). However, in the pool with a vertical 

drop, the blocks in each row should have the 

same dimensions. 

Where other considerations require a 

length, L6, equal to or greater than 5d,, the 

blocks may be omitted. 

(7) Outlet transition. -The outlet 

transition should be of the broken-back 

type, as a well-defined outlet channel is 

required below stilling pools. A level invert is 

desirable to provide a free-draining pool. 

However, it is sometimes necessary to slope 

the invert up to the outlet channel, to 

provide an adequate tailwater depth, dz, 

thereby insuring a hydraulic jump in the 

pool. See chapter VII for general 

requirements for transitions. 

4-39. Other Considerations.-(a) Bank 

Heiglz ts. - 

(1) Upper canal bank. -The upper bank 

of the canal should provide at least 2 feet of 

freeboard above the inlet pool water surface. 

Where this would increase the normal bank 

height, the bank should be raised for such a 

distance that the top will intersect the 

natural ground surface at the required 

elevation. An inlet dike, as shown in figure 

4-44, may be preferable to raising a long 

reach of the canal bank. 

(2) Lower canal bank. -The normal 

height of the lower bank may not be great 

enough to permit the operating road (if 

required) to cross the stilling pool on its 

normal grade. Where such a crossing is 

required, the road should be ramped up as 

necessary, to provide adequate pool 

freeboard and concrete thickness, plus 2 feet 

of earth cover to reduce vehicular impact 

loads (see fig. 4-35). The grade of the ramp 

should not exceed 10 percent, and any 

change in alinement should be gradual to 

avoid introducing a roadway hazard. Where 

an earth cover over the box structure is not 

desired, the box should be designed to 

withstand the impact load. 

(b) Protection. -The outlet channel should 

be protected from erosion by providing riprap 

or gravel protection in accordance with figure 

7-8. 

(c) Percolation. -Excessive percolation of 

water from the canal to the outlet channel, or 

from the inlet pool to the canal, should be 

avoided. See subchapter VIII C for design 

consideration for percolation. 

4-40. Design Example.-Assume a canal, 

crossing a natural drainage channel, has 

insufficient head to accommodate a siphon 

under the channel. Therefore a cross-drainage 

structure is required to carry drainage water 

across the canal. As the profile of the channel 

invert is above the canal water surface, a 

culvert would require the construction of a 

long, deep outlet channel. An overchute is 

selected, as it can carry the drainage flows over 

the canal with little channelization required. 

Note that an overchute may have been selected 

on the basis of economics even if the canal had 

sufficient head for a siphon. 

(a) Assumptions. - 

(1) Properties of the canal section are as 

follows: 

d, = 3.6 feet 

hL = 4.3 feet 

h, = 5.6 feet 

b = 6 feet 

ss = l-1/2: 1 

W1 = 6 feet 

W, = 12 feet 

(2) The drainage channel has a 

well-defined section at the inlet, having 

properties approximately as follows: 

b = 8 feet, 11, = 6 feet, ss = l-l /2: 1, and 

a downstream slope s = 0.0002, with n = 

0.030. 

The alinement of the natural channel is 

approximately normal to the canal 

alinement, permitting a normal crossing for 
PROTECTIVE STRUCTURES 

the overchute. The invert elevation of the 

natural channel drops about 4 feet as it 

crosses the canal, and then becomes rather 

level beyond the canal, as shown in figure 

4-35. 

(3) Weeds and other debris can be 

expected to accompany the storm runoff. 

(4) It has been determined that the 

25-year flood yields a discharge of 200 cfs in 

the channel. 

(5) A 12-foot-wide operating road is 

located along the lower bank of the canal, 

and should be ramped up, if necessary, to 

cross over the overchute pool. 

(b) Solution. - 

(1) Type of overchute. ~-Assume that a 

cost comparison has indicated that a 

rectangular concrete overchute is 

competitive with a pipe overchute. As it is 

better able to carry the trash load, the 

rectangular concrete overchute should be 

used. 

(2) Overcliute width. -An economic 

study indicates that a 6-foot width gives the 

most economical cross section. However, a 

wider, shallower section, 8 feet wide, is 

selected to minimize the required depth of 

the inlet pool, and to increase the 

trash-carrying capability of the structure. 

(3) Critic& flow hydraulics. -By setting 

the chute invert on a supercritical slope, 

critical depth, d,, will occur at the upstream 

end of the chute, as shown in figure 4-35. 

The discharge per foot of width, 

,=A= zoo- 

-- 25 cfs b 8 

d, = 2.69 feet from table 17 [ 41 

hVC = 0.5d, = 1.35 feet 

225 

Then 

ESC = 1.5d, = 4.04 feet 

A, = b d, = 8 x 2.69 = 21.5 sq. ft. 

v, = a_ - --- 200 A, 21.5 - 9.3 f.p.s. 

Wetted perimeter, wp, = b + 2d, = 8 + 5.38 

= 13.38 ft. 

AC 21.5 Hydraulic radius, R = wpC = 13.38 = 1.61 

From the Manning formula [ 21, with a 

roughness coefficient, n = 0.014, 

(4) Imert slope. -To insure supercritical 

flow in the flume, the invert is set on a slope 

of 0.005, which is steeper than the critical 

slope of 0.0041 by about 20 percent. 

(5) Inlet depth.-The required inlet 

depth, d, (see fig. 4-35), is equal to the 

specific energy at the beginning of the 

chute, plus transition losses. 

Thus, 

d, = ESC + 0.3nh, 

= d, + hVC + 0.3 (1.35-O) 

= 2.69 + 1.35 + 0.41 

= 4.45 feet 

/Top of natural 

Figure 4-35. Overchute-typical profile. 103-D-1310 
226 SMALL CANAL STRUCTURES 

the elevation of the channel thalweg. 

(8) Chute wull height, h, (at inlet). -The 

wall height, h, , should include a minimum 

freeboard of 1 foot above the upstream 

water surface. As the invert of the inlet 

transition is level, the wall height, 

(6) Idet bank height. -To provide 2 feet 

of freeboard above the inlet pool water 

surface, the upper bank of the canal should 

be raised to an elevation equal to 

El. A + d, + 2 

Then 

hb = 4.45 + 2 

= 6.45 feet 

(7) fnler transition. -To transition the 

flow from the well-defined natural channel 

to the g-foot-wide rectangular flume section, 

a broken-back transition, similar to the type 

1 transition described in chapter VII, is best 

suited. As the length of the transition is 

dependent upon the convergence required, a 

part of the convergence will be accomplished 

in a lo-foot (minimum) earth transition, 

reducing the convergence and length 

required for the concrete transition. The 

length of the earth transition should be 

extended, as required, to the length of the 

inlet protection. 

An invert width (b,) of 4 feet will be used 

at the cutoff to reduce the width of the 

concrete transition. This will result in a 

water surface width at the cutoff, 

T, = b, + 2(1.5 d,) 

= 4 + 3 x 4.45 = 17.35 ft. 

If the trash problem is sufficiently severe, 

the bottom width should not be reduced. 

The concrete transition must accomplish 

the remaining required convergence to the 

g-foot-wide flume (T, = 8 feet). Conforming 

to the maximum angle of convergence 

(27.5O on each side), the concrete transition 

must have a length, 

Tc - Tf 17.35 - 8 

Lt1 = 

= = 9 ft. 

2 tan 27.5’ 2 x 0.52 

The profile indicates that it is unnecessary 

to slope the invert of the concrete transition, 

and a level, free-draining inlet will be used, 

with the invert elevation at the cutoff set at 

h, = d, + 1.0 minimum 

= 4.45 + 1 minimum 

= 5.45 ft. minimum 

Use h, = 5 ft. 6 in. 

(9) Chute wall height, h2 .-The height of 

the chute wall should be equal to the 

maximum water depth in the chute plus a 

freeboard of 1 foot minimum. As the invert 

slope is steeper than critical, the maximum 

depth in the chute is d,, which occurs at the 

inlet end. Then, the minimum wall height in 

the chute 

11, = d,,,, + 1 .O 

= 2.69 + 1.0 = 3.69 

Use h, = 3 ft. 9 in. 

( 10) Chute length. -Determine lengths L, 

and L, to clear the canal prism. 

Use L, = 28 ft. 7 in. 

Lz = 11 ft. 1 in. 

and L = 39 ft. 8 in. 

(11) Depth, d,. -Determine the depth, 

dL ) at distance L from the inlet transition 

(see fig. 4-36), using the Bernoulli method 

and a “slick” n. 

Es1 +h,=E 

SC 

+s,L 

Figure 4-36. Overchute-chute hydraulics. 103-D-1 311 
PROTECTIVE STRUCTURES 

Using a “slick” n = 0.01 1 , 

SC = [l .486;*. j * =[l:j?8: :33;;171 

= (O.OSO)* = 0.0025 

Try 

I 

2 

d, = 2.4ft., A= 19.2sq. ft.,V= 10.41 f.p.s. 

11, = 1.69ft., wp= 12.8 ft., R= 1.5 

E sL = 4.09 ft., R2 ” = 1.3 1 

Then 

Vn 0.011 x 10.41 

St I/2 = 

1.486R2’3 = 1.486x 1.31 

= 0.059 

Sf = 0.0035 

h( = 2 

* L,loo35 ~0.0025)x 39.67 

= 0.12 

and, from 

ESL +h,=E, +s,L 

c 

4.09 + 0.12 = 4.04 + 0.20 

4.2 1 # 4.24 (close enough for design) 

Therefore, d, = 2.4 ft. 

(12) Vertical Drop, D. -From the profile 

of the natural channel, it is seen that a 

downstream channel requiring a minimum of 

excavation; can probably support the 

required tailwater to insure a hydraulic jump 

in the pool if the invert is set about the same 

elevation as the canal invert. Thus, in the 

trial-and-error solution for the optimum 

drop, D (see fig. 4-35) try a value 

D = d, + 1.0 + t, 

= 3.6 + 1.0 + 0.67 = 5.27 ft. 

say 5.25 ft. 

Proceed with the trial-and-error 

227 

computations by using D = 5.25 feet to 

determine d, and d2 in the pool. 

( 13) ,Ytilling pool depths, dl and 

u’* .-From the equation in bibliography 

reference [ 111 

d, = lE+J+-.-= (See fig. 4-35) 

j- +1.5 

L 

1.414 (2.4) 3.393 

= 1.06 +dm = 1.06 + 1.92 

= 1.14 feet 

Q Q and V, = A = bd = 

200 

= 22 f.p.s. 1 1 8 x 1.14 

From the design of the standard stilling pool 

(chapter II) it is seen that 

d, _ -“II +,,/ y + 2(v, 1’ d, 

g 

(1.14)2 + 2 (22)* x 1.14 

4 32.2 

= -0.57 + do.324 + 34.3 

= 5.31 feet 

Then, A2 = 8 x 5.31 = 42.48 sq. ft., 

v ,a, ___- 200 -471 

* A 42.48 ’ ’ 

h 

y* 

_ v2 - (4.71)* - 0 . 

2g 64.4 

35 ’ 

and ES2 =d2 +hvz 

= 5.3 1 + 0.35 = 5.66 feet 

(14) Tailwater depth, d,. -The depth, d, , 

in the downstream channel, should be 

determined on the basis of a “slick” n, equal 

to about 80 percent of the estimated 

roughness coefficient in the earth section: 

11, = 0.80 x 0.030 = 0.024 

As the dimensions of the channel are only 

approximate, an additional safety factor is 

used by rounding to the next lower standard 

value, 
228 SMALL CANAL STRUCTURES 

1’s = 0.0225. 

The tailwater depti1, d3, is determined by 

the trial-and-error method as follows, for the 

channel with dimensions as shown in 

assumption, subsection (a)(2) above: 

Try d3 = 5.8 feet 

Then A = bd + 1.5d2 

= (8 x 5.8) + 1.5 (5.8)* 

= 97.0 sq. ft. 

wp = b + 2d csc @ (see table 16 [4] ) 

= b + 3.606d 

= 8 + 20.90 = 28.9 ft. 

and R =$=g= 3.355 

~2’3 = 2.24 

Finally, v = 1.486 R* ‘3 s’ ‘* 

slick 11 

= 1.486 x 2.24 (0.0002)’ ‘2 

0.0225 

and 

= 2.09 f.p.s. 

Q = AV = 97.0 x 2.09 = 202.7 cfs 

>200 cfs 

Therefore, d, is approximately 5.8 feet. 

(1 5) Outlet e~zevg~ bulurrce. -To support 

the pool deptl1, d, , which is required to 

produce a hydraulic jump in the pool, the 

tailwater depth, d3, must be sufficient to 

provide a downstream specific energy, E,, 

that is equal to or greater than the specific 

energy in the pool, minus the outlet 

transiti loss. Neglecting the friction loss, a 

Bernoulli balance is checked as follows: 

E ZE: 

s3 s2 

- 0.5n11, 

5.87 2 5.66 ~ 0.5 (hv2 ~ 11”$ 

> 5.66 ~ 0.5 (0.35 ~ 0.07) 

2 5.66 -~ 0.14 

5.87 > 5.52 

The tailwater is more than adequate to 

support the jump in the pool. The vertical 

drop, D. could tllerefore be reduced slightly, 

to attain optimum economy at the expense 

of the safety factor provided by the excess 

downstream energy. However, as the 

permissible reduction in D is small, the pool 

design will be continued using a drop of 5.25 

feet as assumed above. 

If the net energy in tl1e tailwater channel 

had not been equal to or greater than the 

energy in tlie stilling pool, ES2, the vertical 

drop, D, should be increased, to lower the 

energy gradient in the pool. The resulting 

energy balance should again be checked to 

insure adequate tailwater energy to insure a 

hydraulic jump in the pool. 

( 16) Backwutcl- depth in r)ool.-The 

stilling pool depth, d,, as computed from 

d, , is valid only if an exact energy balance 

exists from d, to d,. As the Bernoulli 

equation indicated an excess of energy, ES3, 

tile resulting backwater depth in the pool, 

d; > d, 

The depth, d;, sl1ould be determined by a 

Bernoulli balance as follows: 

Ncglccting friction losses, 

Es2 = ES3 + 0.5Ul” 

= d3 + hV3 + 0.5nh, 

= 5.8 + 0.07 + 0.5hb2 -- 0.5 h,3 

Thend; + Ilk2 ~ 0.5hk2 = 5.87 ~ 0.03 

and d; + 0.511b2 = 5.84. 

Try d; = 5.69 

Then, A; = b di = 8 x 5.69 = 45.50 sq. ft. 

Q 200 v; = A; = 45.50 - = 4.4 f.p.s. 

cc I2 (4.412 = o 3. ft, and hb2 = - = - 

2g 64.4 ’ 

Check: d; + 0.511b2 = 5.84 (from above) 

5.69 + (0.5 x 0.30) = 5.84 

5.84 = 5.84 

Therefore, cl; = 5.69 feet as assumed. 

(17) Crest .suDruzevgerzce. -The backwater 

depth in the pool should not be permitted to 

submerge the chute crest more than O.Gd, 

(see fig. 4-34). T!lercfore, the submergence, 
PROTECTIVE STRUCTURES 

Smz 0.6 d, 

d; - Dz 0.6 x 2.4 

5.69 - 5.255 1.44 

Sm = 0.44< 1.44 ft. 

229 

(18) Pool wall height.-The pool wall 

height, h,, should be equal to the depth, di , 

plus a freeboard (or clearance below the top 

slab of the box) of 1 foot. Thus, 

hp = 5.69 + 1 = 6.69 ft. 

Use h, = 6 ft. 9 in. 

(19) Bank height, h B *. -The lower bank 

must be raised, locally, to a height suitable 

for crossing over the pool. As the pool invert 

was set at the same elevation as the canal 

invert, the height of the lower bank, 

hB* = h, + t, + C 

= 6.75 +0.75 + 2 

= 9.5 ft. 

assuming the slab thickness, t, = 9 inches, 

and minimum earth cover, C = 2.0 feet. As 

the normal bank height, 11, is only 5.6 feet, 

the ramp should provide the additional 

height, 9.5 - 5.6 = 3.9 feet. 

The ramp height may be reduced by 

eliminating the earth cover, provided that 

the concrete box is designed to withstand 

the full vehicular impact load. The minimum 

bank height, hB,, is then equal to 9.5 - 2.0, 

or 7.5 feet. 

(20) Pool length (see fig. 4-3.5). -Length 

L3 : The minimum permissible length, L, 

minimum, should provide clearance between 

the headwall and the upper nappe of the 

flow trajectory. 

From the relationship, 

with 

u=(1/2)gt2, 

y = (dL + D) - h, 

= 7.65 - 6.75 

= 0.90 ft. 

the time, 

= 0.24 sec., 

and from L3 min. = vt + t, 

L3 min. = 2.5 +0.67 = 3.17 ft. 

The maximum length, 

L 3 max. =1.5(hBz -hL)-tw -+-cl. L 

=1.5(9.5--4.3)-0.67-0.25-0.25 

= 7.8 - 1.17 = 6.63 Et 

where 

h, 2 is the raised bank height, 

h, is the canal lining height, 

t, is the wall thickness, 

f L 

1 

is half the lining flange width, and 

cl. is the minimum clearance. 

Let L3 = 5.0 feet, resulting in a 

clearance of 1.88 feet. 

Length Lq : From the relationship, 

Y = (1 /2M2 

withy=dL +D 

= 2.4 + 5.25 

= 7.65 ft. 

the time, t=e=JT 

= 0.69 sec. 

and L, =vt 

= 10.41 x 0.69 = 7.18 ft. 

Use L4 = 7 ft. 2 in. 

Length L, : 

L5 = (3/4) d2 = (3/4) x 5.31 = 3.98 ft. 

Use L5 = 4 ft. 0 in. 

Length L,: 

L6 = 3d2 (min.) = 3 x 5.31 

= 15.93 ft. (min.) 

Use L6 = 16 ft. 
230 SMALL CANAL STRUCTURES 

Length L, : The pool length, 

L, = L, + Lb 

= 7 ft. 2 in. + 16 ft. 0 in. 

= 23 ft. 2 in. 

This would accommodate a maximum 

roadway width, 

w; = L, -- Lj - t w = 23.17 ~ 5 -- 0.75 

= 17.42 ft. 

(Required roadway width, W, = 12.0 feet.) 

(2 1) Pool blocks 

d2 5.31 

Block height = 4 = - 4 = 1.33 ft. Use 16 

inches 

Block length = 1.25 ; = 1.67 ft. Use 20 

inches. 

Block width, W, = 8 in. minimum. 

Try N = 4 blocks in second row. 

Then wb = ’ 001 width 2N =&= l.Oft. 

Use three 12-inch blocks in first row, 

staggered with the second row 

blocks. 

(22) Outlet transition.-A broken-back 

transition is the best type to use between 

the 8-foot-wide rectangular stilling pool and 

the well-defined trapezoidal channel (see 

chapter VII). 

As the length of the transition is 

dependent upon the divergence required, a 

part of the divergence will be accomplished 

in a l(rfoot (minimum) earth transition, 

reducing the divergence and length required 

for the concrete transition. The length of the 

earth transition should be extended, as 

required, to the length of the outlet 

protection. An invert width b, of 4 feet will 

be used at the cutoff to reduce the width of 

the concrete transition. This will result in a 

water surface width at the cutoff, 

T, = b, + 2(1.5d3) 

= 4 +3 x 5.8 = 21.4 ft. 

The concrete transition must accomplish 

the remaining divergence from the 

8-foot-wide pool (T,, = 8 feet). As 

conservation of head is not a consideration, 

a water surface divergence, @ = 25’ (on each 

side) will be used in lieu of the usual 22.5’. 

The concrete transition will then have a 

length, 

- 

T, T, 

21.4 8 

L = _ - 

t2 2 tan @ 2 x 0.47 

= 14.26 ft. 

Use Lt2 = 15 ft. 

(23) Protection. - From figure 7-8, inlet 

protection should be type 1, extending 1 

foot above the design water surface and 2.5 

d, upstream from the cutoff. Thus, the 

length of the upstream protection, 

L, = 2.5 d, = 2.5 x 4.45 

= 11.10 ft. 

Use L, = 12 ft. 

Type 3 outlet protection is indicated, 

extending 16 feet downstream from the 

cutoff. The protection should extend to an 

elevation 1 foot above the design water 

surface in the channel. 

(24) Percolation. -Percolation should be 

checked by the Lane method, as discussed in 

subchapter VIII C. 

3. Drain Inlets 

4-41. General.-Drain inlets are structures 

used to carry relatively small amounts of storm 

runoff or drainage water into the canal. For 

larger flows, it is usually preferable to take the 

cross-drainage water over or under the canal in 

an overchute or culvert to be discharged 

beyond the canal. This is particularly true for 

flows that are expected to carry an appreciable 

amount of silt, sand, or debris. However, it is 

sometimes possible to bring relatively clean 

water into the canal more economically than 

diverting it to the other side of the canal. 

(a) Location. -The drain inlet may be 
PROTECTIVE STRUCTURES 231

energy is dissipated as the inflow mixes with

the canal flow.

The gravel blanket drain inlet should be

used only at locations which provide a

suitable subgrade, as erosion or excessive

percolation through the bank could cause

bank failure.

(c) Design Capacity. -Drain inlets should be

designed to accommodate the storm runoff

Figure 4-37. Drain inlet on far bank of earth section

canal, and motor-operated gate hoist for turnout gate

in foreground. P-222-116-50929

located in a natural drainage channel, or at the

terminal end of an interceptor drain which

parallels the canal. As the inlet end must be

above the canal water surface, the drain inlet is

best suited where the canal prism is below the

original ground surface. In a fill section

(requiring embankment of earth material),

ponding of undrained water may result unless

the inlet channel is filled with earth material to

the invert elevation of the conduit.

(b) Types. -Drain inlets are of three basic

types as follows:

( 1) Pipe section. -A pipe section (see fig.

4-37) is generally used where the design flow

is small, and it is therefore the type most

commonly used for the range of discharges

covered by this text. Use of the pipe section

is desirable if an operating road crosses the

drain inlet. Corrugated-metal pipe is often

used, as it usually provides a moderately

long life at a relatively low cost.

Replacement of the pipe does not require

shutdown of the canal.

The outlet of the pipe discharges above

the canal water surface, with dissipation of

energy being accomplished as this inflow

mixes with the canal flow.

(2) Rectangular concrete section. -The

rectangular concrete section is used

primarily where the flow is relatively large,

and it is therefore used infrequently with

small canals. However, it is particularly well

suited where the drainage channel is wide,

shallow, or where a pipe inlet would be

subject to clogging with weeds.

A box section should be provided, as

shown in figure 4-38, where roadway traffic

is required over the drain inlet. In an earth

section, the concrete chute terminates in a

rectangular concrete pool extending below

the canal invert, and the excess energy is

dissipated in the pool. In a concrete-lined

canal, the concrete chute may extend only

to the concrete lining, as shown in figure

4-39.

(3) Gravel blanket. -Where the inflow is

very small, a coarse gravel blanket may be

used to cover the top and sides of the upper

canal bank, as shown in figure 4-42. The

entrance is shaped to confine the flow to a

relatively narrow section. Again, excess

Figure 4.38. Rectangular inclined drain inlet to earth

section. Erosion protection incomplete. P.707-729-1550
232 SMALL CANAL STRUCTURES

from the drainage area, based upon the design

storm frequency (usually 25 years).

Where overflow wasteway facilities are not

provided for a reach of canal, the total design

capacity of all drain inlets within that reach

should be limited to 10 percent of the normal

design capacity of the canal.

Where an overflow wasteway facility is

provided, the design capacity of an individual

drain inlet should not exceed 10 percent of the

normal design capacity of the canal, and the

cumulative inflows from all drain inlets within

that reach should not exceed 20 percent of the

normal design capacity of the canal.

Further, inflows from drain inlets should not

cause the canal water surface to rise above its

normal depth by more than one-half the

normal lining freeboard, or by more than

one-fourth the normal bank freeboard.

Exceptions may be made to the foregoing

limitations for the short duration of the

maximum design flow provided an automatic

wasteway feature, such as a side channel

spillway, is located within a short distance of

the drain inlet. However, the resulting canal

bank freeboard should never be less than 1

foot. Where drain inlets cannot accommodate

the design discharge of the drainage area within

the foregoing limitations, culverts, overchutes,

or canal siphons should be used.

(d) Canal Bank. -The upper canal bank

adjacent to the drain inlet should be raised if

necessary, to provide adequate freeboard above

the inlet water surface, or to provide adequate

cover over a pipe drain inlet. When the

requirement for pipe cover is the controlling

criterion, this increase in bank height should

extend for a minimum distance of 3 pipe

diameters. Where an operating road crosses the

drain inlet, the roadway should be ramped up

as required on a slope not exceeding 10

percent.

If inlet freeboard is the controlling criterion,

the raised bank should be extended as required.

Where the upper bank of the canal is in cut

(excavation), the drain inlet dike should be

extended to intersect the natural ground

surface at the top elevation of the dike (see fig.

4-44).

4-42. Pipe Drain Inlets (see fig.

4.41 ). -(a) Inlet. -Earth inlet transitions are

usually satisfactory for drain inlets. If a

particular situation requires a concrete

transition, its type should be determined on

the basis of the conditions discussed in section

4-24.

To prevent degradation of the inlet channel

and to provide complete drainage of the

channel, the pipe invert (assuming an earth

transition) should be set at or slightly below

the original ground surface of the channel

invert. The pipe inlet should be high enough

above the canal water surface to prevent

reverse flow. Reverse flow, or failure to effect

complete drainage of the inlet channel, could

result in hydrostatic pressure in the canal bank,

causing bank failure; or behind the canal lining,

causing lining failure. A flap gate, as shown in

figure 4-40, is sometimes included to prevent

reverse flow.

The inlet water surface should provide pipe

submergence as follows:

( 1) Subcritical pipe slope. -Where the

slope of the pipe is less than the critical

slope (see sec. 4-26), the top of the pipe

inlet should be submerged at least 1.5 hv ,

p

where hv is the velocity head in the pipe at

p

the inlet. See chapter VII for a detailed

discussion of inlet losses.

Figure 4-39. Rectangular concrete drain inlet to a

concrete-Iined canal section. P-430-500-383
PROTECTIVE STRUCTURES 233

Figure 4-40. Drain inlet with flap gate to prevent

reverse flow. PX-D-73101

(2) Supercritical pipe slope. -Where the

slope of the pipe is equal to or greater than

the critical slope, the invert of the pipe inlet

should be submerged at least 1.5 hy + dc,

c

where dc is the critical depth in the pipe.

Freeboard from the inlet water surface to

the top of the canal bank, or drain inlet dike,

should be at least 2 feet.

(b) Conduit. -Pipe drain inlets usually

consist of corrugated-metal pipe (CMP). Other

types of pipe could be used, but probably not

as economically. The pipe should be designed

as follows :

( I) Diameter. -The pipe diameter should

be determined on the basis of a maximum

full pipe velocity of 10 feet per second if a

concrete inlet is used, and 5 feet per second

if an earth transition is used. However, a

minimum diameter of 18 inches should be

used where weeds or debris can be expected,

and 12 inches where relatively clean water is

assured.

The pipe diameter is determined from the

basic equation, Q = A V, which reduces to

D = 1.128 .f!lj

(2) Slope. -The slope of the pipe should

be at least 0.005 to permit complete

drainage. No maximum slope is established;

however, it is sometimes desirable to include

a pipe bend and two slopes, SI and S2 , as

shown in figure 4-28, to reduce the slope of

th e outlet pipe. This is particularly

appropriate where a considerable drop in

grade occurs, or where an intermediate berm

is used.

(3) Gage or shell thickness. -For the

required gage of corrugated-metal pipe, or

the shell thickness of other types of pipe for

various loading conditions, see the pipe

manufacturer's recommendations (see

bibliography references [ 4] and [ 5] in

chapter VIII).

(4) Pipe cover.-The drain inlet pipe

should have a minimum cover that provides

6 inches of earth over the percolation collar ,

as shown in figure 4-41. Where a collar is not

provided, the pipe should have a cover of at

least 1 foot. However, the inlet freeboard

requirement of 2 feet will often control the

bank height, resulting in a pipe cover of at

least 2 feet.

(c) Outlet. -The drain inlet pipe discharges

directly into the canal prism, having its invert

preferably 6 inches, but at least 4 inches, above

the normal water surface in an earth canal; or 1

inch above the maximum water surface,

whichever results in the higher elevation. Where

the canal section has concrete lining, the pipe

invert should be above the top of the lining.

The end of the pipe usually extends about 1

pipe diameter (24 inches minimum) into the

canal prism, as shown in figure 4-41. However,

they are sometimes cut flush with the canal

bank. The relative advantages of each type are

as follows:

( 1) Uncut projection. -The pipe discharge

enters the canal water prism far enough from

the bank to minimize erosion at the bank.

(2) Flush cut. -A flush end facilitates

weed cutting along the bank, and may

present a better appearance. While a saving

in pipe length results, it may be offset by

additional labor cost and poorer energy

dissipation.

(d) Percolation. -To reduce percolation
234 SMALL CANAL STRUCTURES 

‘Corruqated metal PIP? 

P L A N 

l,, iI 

of embankment. OS drected 

LONGITUDINAL SECTION 

r Urwnforced concrete 

CONCRETE LINED CANAL SECTION SECTION A-A 

Figure 4-41. Drain inlet-plan and sections. 103-D-1312 

from the inlet channel to the canal, a collar 

should be placed around the pipe as shown in 

figure 4-4 1. Some drain inlet pipes may require 

two or more collars. The requirement for 

collars should be determined by an analysis of 

percolation as discussed in section 4-27 and in 

chapter VIII. The standard collar for 

corrugated-metal-pipe drain inlets extends 

radially two-thirds D (18 inches minimum) 

from the periphery of the pipe. 

(e) Protection. -Inlet protection should 

consist of 6 inches of coarse gravel, extending 

at least 12 inches above the normal or ponded 

water surface. The length of protection should 

be at least 3 pipe diameters (5 feet minimum) 

if an earth transition is used, and at least 2.5 

pipe diameters (5 feet minimum) if a concrete 

transition is used. Where the inlet channel 

alinement is perpendicular to that of the pipe, 

or if the inlet channel is poorly defined, the 

protection should extend at least 2-l/2 pipe 

diameters each side of the pipe centerline. 

Outlet protection, except in a concrete-lined 

canal section, should consist of a minimum of 

12 inches of coarse gravel, extending 12 inches 

above the normal water surface of the canal, 

and at least 2-l /2 diameters upstream and 

downstream from the pipe centerline. 

4-43. Rectangular Concrete Drain Inlet to 

Earth Section (see figure 

4-42). -(a) Inlet. -The rectangular concrete 

flume usually requires no transitioning other 

than connecting the earth channel to the 

rectangular opening. Wingwalls are provided to 
PROTECTIVE STRUCTURES 235 

TOP of ChO”rm bO”k PLAN 

=?. 

SECTION 6-B SECTION C-C 

SECTION A-A 

A. RECTANGULAR INCLINED DRAIN INLET 

“12” coarse grovel 

SECTION A-A 

PLAN 

LONGITUDINAL SECTION 

B. GRAVEL BLANKET DRAIN INLET 

Figure 4-42. Drain inlets-plan and sections. 103-D-131 3 
236 SMALL CANAL STRUCTURES 

2 /Flume 

F, 

FT 

j: 5 IO IS 20 

b, FT: 2’-0” 3’-0’ 3’- 6’s 4’-0” 

Figure 4-43. Concrete drain inlet dimensions. 

103-D-l 314 

retain the bank or dike slope, and a cutoff to 

reduce percolation. The concrete invert should 

be set at or slightly below the channel invert, 

to permit complete drainage of the channel, 

and at least 6 inches above the canal water 

surface to prevent reverse flow. 

The canal bank should have 2 feet of 

freeboard above the water surface in the 

channel. 

(b) Flume. -The rectangular concrete flume 

extends through the canal bank on a subcritical 

slope (usually 0.005) assuring a velocity less 

than critical, until the flow reaches the steep 

slope of the chute section, at which point 

critical depth occurs (see fig. 4-43). Critical 

depth, d,, can be determined from table 17 

[4], or from the equation: 

d, =< = 0.3143 q2/3 

g 

where q is the discharge per foot of width and 

g is the acceleration of gravity, equal to 32.2 

feet per second per second. 

The flume width, b, is selected so that the 

specific energy (d + 11,) in the flume does not 

exceed the specific energy in the inlet channel. 

As the flume section is short, friction losses 

may be disregarded, and it can be assumed that 

d, is equal to d,. Then, assuming an inlet loss 

of 0.5 Ah, and using the Bernoulli theorem 

[21: 

E so = Es + 0.5 nh, 

c 

or 

do + h” 0 = d, + h, + 0.5 Ah, c 

Assuming a zero velocity head in the inlet 

channel. 

do = d, + h, + 0.5 11, c c 

In a rectangular section, hVc = $ 

Then 

do = d, + 0.5 d, + 0.5 (0.5 d,) 

or 

do = 1.75 d, 

If the required depth, do, in the inlet 

channel is not attainable without excessive 

ponding, or without use of excessively high 

banks or dikes, the drain inlet width, b, should 

be increased. The height of the flume walls 

should provide a freeboard of at least 1 foot 

above the inlet channel water surface. The 

invert at the downstream end of the flume 

should be at least 6 inches above the normal 

water surface in the canal. 

(c) Chute. -The chute descends to the pool 

on an invert slope equal to the side slope of the 

canal, with the top of the chute walls 

coinciding with the canal bank. The wall 

height, measured normal to the chute slope, 

should be : 

h, = d, + 1 foot minimum 

(d) Outlet PooZ.~The pool dimensions are 

determined for the condition of full flow in the 

drain inlet when the canal is empty. For the 

more common inlet conditions, these 
PROTECTIVE STRUCTURES 

dimensions are tabulated in figure 4-43. Pool 

dimensions for other inlet conditions should be 

determined from the basic equations for pools 

as discussed in chapter 11. 

The dimensions tabulated in figure 4-43 are 

based upon the assumption that critical depth, 

d,, occurs at the beginning of the chute, and 

that F/d, is equal to H/d, in figure 2-37, 

chapter II, where the pool depth, d, associated 

with the hydraulic jump, is tabulated in terms 

of critical depth, and d, in terms of d, . 

Friction loss in the chute is neglected. 

The pool wall height, K, should be equal to 

or greater than d2, and the pool length should 

be equal to 3K. The vertical wall at the end of 

the pool provides a positive tailwater to insure 

the hydraulic jump; therefore, pool and chute 

blocks, which would interfere with sediment 

removal, are not considered necessary. If the 

pool length, L, exceeds the bottom width of 

the canal, the drain inlet should be set back 

into the canal bank as required. 

(e) Percolation. --Percolation of water from 

the inlet to an empty canal should be checked 

by Lane’s weighted-creep analysis discussed in 

chapter VIII. Additional cutoff walls should be 

used if necessary. 

(f) Protection. -Inlet protection should 

consist of 6 inches of coarse gravel, extending 

upstream a distance equal to 2.5 d, (5 feet 

minimum), and to an elevation 1 foot above 

the water surface in the inlet channel (see fig. 

4-43). 

Outlet protection in the canal should consist 

of a minimum of 12 inches of coarse gravel, 

extending 5 feet upstream and downstream 

from the structure, and up the sloping canal 

banks to an elevation 1 foot above the normal 

water surface. 

4-44. Other Types of Drain 

Inlets. -(a) Rectangular Concrete Drain Inlets 

to a Concrete-lined Canal. -The rectangular 

concrete drain inlet to a concrete-lined canal 

section should be similar to the concrete drain 

inlet to an earth section, except that the chute 

section is terminated at the top of the concrete 

lining (see fig. 4-39). A thicker lining with 

reinforcement should be considered for the 

section adjacent to the drain inlet. 

(b) Gruvel Blanket Drain Inlet. -The gravel 

blanket drain inlet, as shown in figure 4-42, 

channels the flow from the drainage channel 

237 

into an earth section canal, utilizing a wide 

earth transition with a layer of gravel 

protection. Dimensions are as follows: 

(I) Inlet transition. -The inlet transition 

should converge to a throat width equal to 

at least 1 foot for each cubic foot per second 

of design flow. Thus, a design flow of 3 cfs 

would require a throat width of 3 feet. The 

transition length should be sufficient to 

divert the flow, but at least twice the throat 

width, and not less than the normal canal 

bank width. The invert of the transition 

should slope toward the canal on a slope of 

0.01 minimum, and 0.10 maximum. 

The berms should provide a freeboard of 

1 foot above the drain inlet water surface, 

assuming critical depth at the beginning of 

the canal bank slope. The angle of 

convergence should not exceed 30’ on each 

side. 

(2) Gravel blanket. -The gravel blanket 

should consist of 12 inches of coarse gravel. 

The inlet protection should extend the full 

length and width of the inlet transition, to 

an elevation 1 foot above the inlet water 

surface for the design flow from the inlet 

channel. 

Canal protection should extend down the 

upper canal bank and across the invert. It 

should extend longitudinally along the canal 

for a length equal to at least twice the inlet 

throat width. 

4-45. Design Example. -A canal intercepts a 

drainage channel that has an invert above the 

normal canal water surface. The flow from the 

drainage area is expected to be about 6 cfs of 

clean water (relatively free of weeds or debris). 

The canal, having a normal flow of 75 cfs and a 

wasteway overflow not far downstream, can 

probably accommodate the addition of the 6 

cfs from the drainage channel without 

excessive infringement upon canal freeboard. If 

this proves to be true, a drain inlet shall be 

designed to handle this flow, as shown in figure 

4-44. 

(a) Assumptions. - 

(1) Properties of the earth section canal 

are as follows: 

Q = 75 cfs n = 0.025 s = 0.0005 

b=8ft Wl = 6 ft. ss= l-1/2:1 

d, = 2.9 ft h, = 4.7 ft. 
238 SMALL CANAL STRUCTURES 

Top of drown 

Inlet dike --_ 

~ ,,l r;“p of conol bank , , , , 

Top of dralnage channel bank 

PLAN 

Top of drain Inlet dike 

Top of normal conol bank 

Invert of drainage channel 

PROFILE 

Figure 4-44. Pipe drain inlet-plan, profile, and nomenclature. 103-D-1315 

(2) The drainage channel is well defined 

and has an invert elevation 1.5 feet above 

the normal water surface of the canal. 

(3) Properties of the natural channel are 

approximately as follows: 

Q= 6 cfs d, = 1.5 ft. 

b = 6 ft. h, = 3 ft. 

Find normal depth in canal for 81 cfs: 

Try d = 3.05 ft. and determine the resultant 

hydraulic properties, 

A=bd+ 1.5 d2 

= 8 x 3.05 + 1.5(3.05)2 

= 24.40 + 13.94 = 38.34 sq. ft. 

WP = b + 3.606 d (see bibliography 

ref. 141) 

(b) Solutiotz (see fig. 4-44). ~ 

(1) Cam1 freeboard. -Determine the 

reduced freeboard in the canal resulting 

from the inflow of 6 cfs, which increases the 

canal flow from 75 to 81 cfs. 

Freeboard for 75 cfs = 11, ~ d, 

= 4.7 - 2.9 

= 1.8 ft. 

= 8 + 3.606 x 3.05 

=8+ 11 = 19.0ft. 

R = A - 38.34 _ 

wP 19 * 0 2*02 

R 2 ‘3 = 1.598 (see table 63 [4] ) 

Then 

Q= 1.486 AR2 I3 s’ ‘2 

n 

= 1.486 x 38.34 x 1.598 x 0.02236 

0.025 

= 8 1.4 > 8 1 cfs (close enough) 
PROTECTIVE STRUCTURES 

Therefore, d = 3.05 ft. for Q = 81 cfs 

Remaining freeboard = h, - d(,, cfsI 

= 4.7 - 3.1 = 1.6 ft. 

Infringement on normal freeboard = 1.8 ~- 1.6 

= 0.2 ft. 

‘b 

Permissible infringement,? = y= 0.45 ft. 

> 0.2 ft. 

Therefore, the canal can accommodate the 

additional flow of 6 cfs without excessive 

infringement upon canal freeboard. 

(2) Drain inlet type. -The well-defined 

inlet channel and the relatively small 

discharge indicate that a pipe drain inlet 

would be suitable. 

(3) Pipe diameter.-It is determined that 

an earth inlet transition will be satisfactory, 

and the pipe diameter should be based upon 

a pipe velocity of 5 feet per second flowing 

full. 

D= 1.128 4 

= 1.128 J- $ 

= 1.128 (1.095) 

= 1.24 ft. 

Use D = 15 inches. (Note that the minimum pipe diameter permitted for 

relatively clean water is 12 inches.) 

Then, A = 1.227, and for a full pipe, V = 

4.89, and 11, = 0.37 (from table 8-1, 

chapter VIII). 

(4) Invert slope, s,.-The invert of the 

pipe inlet will be set at the invert of the 

drainage channel, 1.5 feet above the normal 

water surface (NWS) of the canal. The outlet 

end of the pipe will be set 6 inches above the 

NWS, leaving a drop of 1.0 foot in the pipe. 

By scaling, the pipe length is found to be 

1.0 about 18 feet. The pipe slope is then - = 18 

0.056, which is greater than the minimum 

required slope of 0.005. 

(5) Critical slope. s,. -Determine the 

critical slope for Q = 6 cfs, D = 1.25 feet, 

239 

and n = 0.024, using tables 21, 22, 58, and 

60 141. 

Find D5” = 1.747 from table 58. 

Q 6 Then, b= = 1 .747 = 3.435, 

and 

- = 0.79 from table 22. D 

Also, Qn 

= 0.447 from table 21. 

D8/3 s1 1’2 

Then, 

SC 

l/2 - Qn --0~~8/3 (where D8’3 = 1.813 

from table 60) 

6 x 0.024 

= 0.447 x 1.813 

= 0.178 

and 

s, = (0.178)2 = 0.032 < 0.056 

(6) Locatiorz of Ii~dradic control. -As 

the actual invert slope, s,, is steeper than the 

critical slope, s,, the hydraulic control is 

located at the inlet, just inside the pipe. 

Critical ‘flow conditions at the inlet end of 

the pipe are then: 

d, = 0.79 D 

= 0.79 x 1.25 

= 0.99 ft. 

A, = 0.666 DZ (from table 21) 

= 0.666 x ( 1.25)2 

= 1.04 sq. ft. 

Q-C v, = A, = 1 .04 = 5.77 f.p.s. 

and h = vz= 0.52 ft “I.? 2g 
240 SMALL CANAL STRUCTURES 

Check to see if this dike height will 

provide the required minimum cover, C, over 

the 15-inch-diameter pipe: 

Had the actual slope of the pipe been 

flatter than the critical slope, the hydraulic 

control would be located at the outlet. Then 

the hydraulics in the inlet end would be 

determined by the Bernoulli method. 

balancing energies from the outlet end to the 

inlet end, as shown in subsection 4-8(c). 

(7) Zlzlef water surface.-The water 

surface in the inlet channel must rise to a 

depth sufficient to provide a specific energy 

equal to the specific energy in the pipe, plus 

inlet losses, hi. Thus, 

E sg = E, + hi 

4, + ‘lv,, = d, ‘+ h, . + h. 

c 1 

Assume that the velocity head in the inlet 

channel is negligible and that the inlet loss, 

h, = 0.5 Ah,, where Ah, is the difference in 

velocity heads, hvc for critical flow in the 

pipe and 11,” for flow in the inlet channel. 

Then 

d, + 0 = d, + 11, + 0.5 h 

d, = d, + 1.: h 

“C 

= 0.99 + 1.5yo.52) 

= 1.77 ft. 

Thus, the water surface in the inlet 

channel will be 1.77 feet above the invert of 

the pipe inlet, to produce a discharge of 6 

cfs in the 15-inch pipe. The normal depth of 

1.5 feet will be increased by 0.27 feet at the 

inlet. 

(8) Irdet dike height and pipe cover. -The 

inlet dike must provide the required 

freeboard above the inlet water surface. 

Thus, the height of the dike, as shown in 

figure 4-44, is: 

h, = f,, + d 

= 2.0 + Y.77 

= 3.77 ft. 

C = 3 D (18 in. min.) + 6 in. min. 

As?jD= 5 x 15 = lOinches,and 10+6 0 

= 16 inches, the 18-inch minimum 

controls, and 

C=l8+6 

= 24 in. minimum 

(2.0 ft. minimum) 

Pipe cover, C, resulting from the required 

freeboard: 

c = hd -- D 

= 3.77 ~ 1.25 

= 2.52 > 2.0 ft. 

Therefore, the height of the dike is 

controlled by the freeboard requirement. 

(9) Pevcolution. -Percolation from the 

inlet pool to the canal should be checked by 

the Lane method as discussed in 

subsection VIII C. 

(10) Protection. -Inlet protection should 

consist of 6 inches of coarse gravel, 

extending at least 12 inches above the 

maximum inlet water surface, for a length of 

3D (5 feet minimum). Use 5-foot length 

(since 3 x 1.25 is only 3.75 feet). 

Outlet protection should consist of 12 

inches of coarse gravel, extending 12 inches 

above the normal water surface of the canal, 

as shown in figure 4-44, and 2-l/2 D, or 

3.13 feet (use 3.5 feet) upstream and 

downstream from the pipe centerline. 
PROTECTIVE STRUCTURES 

D. BIBLIOGRAPHY 

241 

4-46. Bibliography. 

[I ] “Water Measurement Manual,” Bureau of Reclamation, 

Second Edition, 1967, Revised Reprint, 1974. 

[2] King, H. W. and Brater, E. F., “Handbook of Hydraulics,” 

Fifth Edition. McGraw-Hill Book Co.. New York. 1963. 

[3] “Handbook of Water Control,” Armco Drainage and 

Metal Products, Inc., 1949. 

141 “Hydraulic and Excavation Tables,” Bureau of 

Reclamation, Eleventh Edition, 1957, Reprint, 1974. 

[5] “Design Standards No. 3, for Canals and Related 

Structures,” Bureau of Reclamation, 1967. 

[6] “Operation and Maintenance Equipment and Procedures, 

Release No. 20,” Bureau of Reclamation, 1957. 

[7] McBirney, W. B., “Some Experiments with Emergency 

Siphon Spillways,” ASCE Proceedings 1807, Hydraulics 

Division, October 1958. 

[8] “Design of Small Dams,” Bureau of Reclamation, Second 

Edition, 1973, Revised Reprint 1974. 

191 “Operation and Maintenance Bulletin No. 66,” Bureau of 

L _ 

Reclamation, 1968. 

1101 “Handbook of Welded Steel Pipe,” Armco Drainage and 

L 1 

Metal Products, Inc., 19.50. - 

(111 Rouse, H., “Engineering Hydraulics,” Second Printing, 

1958. 

«Chapter V

H. J. W ARREN

A. GENERAL

5-1. Types of Measuring Structures. -There

are many different types of water measurement

structures used in irrigation systems. The types

most commonly used in Reclamation systems

are Parshall flumes, figures s-I and 5- 2; weirs,

figure 5-3; open-flow meters, figures 5-4 and

3-22; and constant-head orifices (CHO).

Constant-head orifices are mainly used in

turnou ts and have been previously discussed in

chapter III. Acoustic velocity meters and

magnetic flow meters are expected to offer a

reliable method of flow measurement in

irrigation systems but they are not included

herein. Parshall flumes, weirs, weir boxes and

open-flow meters are discussed in this chapter.

A general description of each type of structure

is given, along with its advantages and

disadvantages. Design examples show how a

particular size of water measurement structure

is determined. Standard design drawings of

Reclamation measuring structures are also

included.

In a typical irrigation system, water is

usually measured at the storage reservoir

ou tlet, the canal headworks, and at lateral and

farm turnouts. The type of measuring structure

selected for these locations depends on

availability of head, adaptability to site,

economy of installation, and ease of operation.

1 General Engineer, Engineering Reference Branch, Bureau

of Reclamation.

Figure 5-1. Flow through a 9-inch Parshall flume.

P 20-D-29299-S20

Figure 5.2. Recently constructed Parshall flume.

PX-D-72610

243
244 SMALL CANAL STRUCTURES

Figure 5.3. Concrete weir structure with standard

contracted Cipolletti weir. PX-D-72611

Figure 5-4. Open-flow meter attached to a

concrete pipe. 222-0-33586

B. PARsHALL FLUMES

tailwater depths. The tailwater elevation may

be appreciably higher than the flume crest

without affecting the free-flow discharge

through the flume. However, if the

5-2. Description.-Parshall flumes are

s p e c i a II y designed inline open channel

measuring structures in which canal water

flows over a broad, flat-converging section

through a narrow downward sloping throat

section and then diverges on an upward sloping

floor (fig. 5-5).

The floor of the converging section is the

crest of the flume. It is level both

longitudinally and laterally and is usually set

above the upstream canal invert.

The flume geometry forces the water at

free-flow conditions to pass through critical

depth on the crest, thereby providing a means

of determining the rate of flow from a single

water depth measurement. Free-flow

conditions occur when the downstream canal

water surface (tailwater) is low enough to have

no effect on the depth of water on the crest.

These conditions prevail over a wide range of Figure 5-5. Artist sketch showing Parshall flume

ina canal. CTPX-D-31408.
WATER MEASUREMENT STRUCTURES 

downstream water surface exceeds specified 

limits, submerged-flow conditions occur and 

two water depth measurements are required to 

determine the rate of flow. 

Parshall flumes can be designed to measure 

flow from 0.01 cubic foot per second (cfs) to 

3,000 cfs. This discussion will be limited to 

small Parshall flumes having free-flow 

capacities of 0.05 to 139.5 cfs. These 

discharges correspond to throat widths of 6 

inches through 8 feet. For 6- and 9-inch 

flumes, the maximum degree of submergence 

Hb (H ratio, see fig. 5-6) for free-flow discharge is 

‘3 

60 percent, whereas, for flumes 1 through 8 

feet in width, the maximum degree 

of submergence for free flow is 70 percent 

[ !I.* Gage zeros for both H, and H, are set at 

the flume crest elevation so that water depth 

measurements are depths above the crest. 

Correct zeroing and reading of the gages is 

necessary for accurate results which is usually 

within about 2 percent for free flows and 

about 5 percent for submerged flows [ 21. 

Parshall flumes can be constructed of 

concrete, wood, galvanized metal or any other 

construction material that can be built to the 

given dimensions in the field or prefabricated 

in a shop. Care should be taken in construction 

so that the structure is built as closely as 

possible to the standard dimensions given in 

figure 5-7 with one exception; the wingwalls 

may be lengthened as required. Also, it is 

important to have the floor of the converging 

section level so that the same amount of water 

is passing over each increment of throat width. 

An angle iron is usually embedded flush with 

the floor and perpendicular to the flow at the 

downstream end of the crest to prevent crest 

erosion and to provide a smooth surface for 

setting gage zeros. Sidewalls of the throat must 

be parallel and vertical. 

Parshall flumes should be located only in 

straight sections of channels where the flow is 

relatively smooth and uniform. They should 

never be located on a curve or at right angles to 

the canal flow, as in a turnout, unless the flow 

*Numbers in brackets refer to items in the bibliography, see 

S-29. 

245 

has been straightened and uniformly 

redistributed. Parshall flumes should be located 

as close as possible to canal discharge regulating 

gates for convenience of operation, but far 

enough away from the gates so that the flow is 

uniform and free from eddies, turbulence, and 

waves. 

S-3. Advantages. -Parshall flumes are 

recognized as accurate and reliable flow 

measuring structures and have the following 

advantages: (1) capable of measuring rate of 

flow with relatively small head loss, (2) 

capable of measuring a wide range of free-flow 

discharges with relatively high tailwater depths 

using a single water depth measurement, (3) 

capable of measuring submerged flow using 

two water depth measurements when the 

degree of submergence impedes the free-flow 

discharge, (4) virtually a self-cleaning structure 

because of flume geometry and the throat 

velocity, (5) can not be easily altered to obtain 

unallocated water, and (6) unaffected by 

velocity of approach, which is automatically 

controlled, when the flume is built to the given 

standard dimensions and used where the 

incoming flow is uniform, evenly distributed, 

and free of turbulence. 

5-4. Disadvantages. -Parshall flumes: (1) are 

usually more expensive to construct than weirs, 

(2) cannot be used in close combination 

with turnouts because the inflow must be 

uniform and the water surface relatively 

smooth, and (3) must be constructed carefully 

and accurately for satisfactory performance. 

5-5. Size Selection. -Parshall flume sizes are 

designated by their throat widths. Before a 

Parshall flume can be selected, the channel 

cross section, the range of discharges to be 

measured, allowable head loss through the 

flume, and the normal depth of the flow in the 

channel must be known. Minimizing 

construction costs is an important factor. 

A particular discharge or discharge range can 

be measured by any one of several different 

size flumes. Final selection is based on the 

flume width which best fits the canal 

dimensions and hydraulic properties. As a 

general rule, the width of the Parshall flume 

should be about one-third to one-half the 

width of the upstream canal water surface at 

design discharge and normal depth. With these 
246 SMALL CANAL STRUCTURES 

conditions known, the selection and setting of 

a Parshall flume for free flow and submerged 

flow can be described best by design examples. 

5-6. Design Example with Free-flow 

Discharge.-In this example, assume that a 

Parshall flume is to be selected for use in a 

canal to measure flows from 4 to 40 cfs with 

free-flow discharge. The design capacity of the 

canal is 40 cfs, bottom width 6.0 feet, side 

slopes l-1/2 to 1, normal depth of water in the 

canal 2.0 feet, width of water surface 12.0 feet 

and the canal bank freeboard 1.5 feet. Further 

assume that 0.65 foot of head is available if 

required for losses through the flume. From 

figure 5-7 “Standard Parshall Flume 

Dimensions,” the Parshall flumes that have 

free-flow measuring capabilities within the 

desired discharge range are those with throat 

widths from 3.0 to 8.0 feet. 

Using the general rule to determine the 

throat width, the size range would be 4.0 to 

6.0 feet. Since the crest of the Parshall flume is 

set above the upstream canal invert a distance 

M of - a flume that is too narrow would cause 4 

the headwater to rise and encroach on the 

upstream canal freeboard. Consider for now 

only the size range where the depth at H, for 

free-flow discharge is less than or equal to the 

upstream water depth. 

Table 5-3 gives the following values of H, 

for a discharge of 40 cfs for different flume 

widths that meet the criteria set forth in the 

preceding paragraph. 

Flume size 

throat width, feet 

5 

6 

7 

8 

Upper head 

H,. feet 

1.55 

1.38 

1.25 

1.15 

Allowable head loss through the Par-shall 

flumes must also be considered. For flume sizes 

in this example, free-flow discharge exists until 

the degree of submergence exceeds 70 percent. 

The following head losses for a discharge of 40 

cfs and a 70 percent degree of submergence are 

obtained from figure 5-S (see subsection 5-8(c) 

for explanation on reading this chart). 

Flume size 

throat width, feet 

5 

6 

7 

8 

Head loss 

HL, feet 

0.58 

0.49 

0.42 

0.37 

The head loss, H,, is the difference in water 

surface elevation of the headwater and 

tailwater as shown in figure 5-6. 

The 5.0- through 8.0-foot flumes meet the 

depth and loss requirements; however, further 

investigation is required and the final selection 

of the flume is made on a trial and error basis. 

First try a 5-foot flume as it is the smallest and 

least expensive to build. The head loss for a 

5-foot flume is 0.58 foot, therefore the 

tailwater elevation is set 0.58 foot lower than 

the headwater elevation. As noted from the 

dimensions in figure 5-7 the crest elevation is 

set + above the upstream canal invert or 0.38 

foot. Assume the upstream canal invert 

elevation is 100.00, and as previously indicated 

the normal depth of water in the canal is 2.0 

feet, then the headwater elevation is 102.00. 

The depth at H, for a free-flow discharge of 40 

cfs is 1.55 feet. From the continuity equation, 

Q = VA where A is the cross-sectional area at 

H,, the velocity at H, is 3.85 feet per second 

(fps) and the velocity head,$, is 0.23 foot. 

The energy at H, is the crest elevation + H, + 

g or (100.0 + 0.38) + 1.55 + 0.23 = 102.16 

feet. If this flume were used, the headwater 

would rise about 0.16 foot and encroach on 

the upstream canal freeboard which is 

undesirable. Next check to see if this is a 

free-flow flume. Since the water surface at H, 

is the same elevation as the tailwater, the 

Hb degree of submergence is the ratio of --H. Then 

H, is the difference in elevation %f the 

tailwater and the crest of the flume, or 1.04 

Hb feet. The ratio of K = 1.04 

- = 67 percent, 1.55 

a 

which meets the free-flow criteria. The 6-foot 

flume is the next smallest, so using the same 

procedure try a 6-foot Parshall flume. Since the 
WATER MEASUREMENT STRUCTURES 247 

head loss through the flume is 0.49 foot, set 

the downstream water surface 0.49 foot below 

the upstream water surface. The crest elevation 

is the same as for the 5-foot flume, as 

dimension M is the same for both the 5- and 

6-foot flumes. The depth at H, for a discharge 

of 40 cfs is 1.38 feet. From the continuity 

equation the velocity at H, is 3.70 feet per 

be designed for fret-flow discharge, however 

they will measure submerged flows up to 95 

percent submergence. If a flume is set for this 

high submergence and hydraulic conditions in 

the downstream channel change to cause 

greater submergence, the flume becomes 

useless. 

V2 second and velocity head, z, 0.21 foot. The 

energy at H, is 100.38 + 1.38 + 0.21 = 101.97 

which is slightly less than the upstream water 

surface elevation. When checking this flume for 

Hb free flow, the degree of submergence is K = 

1.:; Ls: = 82 percent (should be 70 percen;? or 

less as previously determined), which does not 

meet the criteria for free-flow discharge. 

Recalling that 0.65 foot of head was initially 

available, the downstream water surface should 

be set at elevation 101.35 and the new Hb = 

Hb 

In the preceding example of the 6-foot 

Parshall flume assume that the flume is set for 

90 percent submergence. Recall that the 

headwater elevation is 102.00, crest elevation is 

100.38 and Ha for free-flow discharge is 1.38 

feet. Then the ratio 3 = 0.90 and Hb = 

Ha 

0.97 foot. The ratio of K now equals 0.97 foot 

1.38 feet 

a 

0.9 ( 1.38) = 1.24 feet. The tailwater surface is 

then tentatively set at elevation 10 1.62 or 1.24 

feet above the crest. From figure 5-8 determine 

the head loss for 90 percent submergence, 

40-cfs discharge and a 6-foot flume. Read a 

head loss of 0.17 foot. Submergence in excess 

of 70 percent, however, will influence the 

water surface at the H, measuring well and an 

erroneous discharge would be read or 

computed using only this reading. Hence a new 

Ha and H, for 90 percent submerged flow 

must be determined. Using a trial and error 

procedure, select values of H, from table 5-3 

and read the free-flow discharge for a 6-foot 

flume. Then from figure 5-I 1 read the 

correction for 90 percent submergence and 

subtract it from the free-flow discharge until an 

Ha is found that will give a correct reading for 

measuring 40 cfs through a 6-foot flume at 90 

percent submergence. 

or 70 percent which meets the criteria for 

free-flow conditions. The 6-foot flume should 

be selected because it is the least expensive to 

construct, can be set for free-flow conditions, 

and does not cause an encroachment on the 

upstream freeboard. 

If a Parshall flume is always going to be 

operated at 70 percent or less submergence, 

that portion of the flume downstream from the 

throat section is not needed. If, however, the 

downstream channel should become silted up 

or clogged with vegetation, the submergence 

would increase to greater than 70 percent and 

the downstream portion of the flume with an 

Hb measuring well would be needed to 

determine the discharge for submerged flow. 

5-7. Design Example with Submerged-f10 w 

Discharge. -If possible Parshall flumes should 

An Ha of 1.58 feet is then determined to be 

satisfactory. Then the new H, reading is 

0.90 (1.58) = 1.42 feet. The new tailwater 

surface is set 1.42 feet above the crest elevation 

or 100.38 + 1.42 = 101.80. The flume is now 

set for 90 percent submergence and will 

measure 40 cfs with an Ha reading of 1.58 feet 

and an H,, reading of 1.42 feet. The actual 

Ha, 

feet 

Throat width, 

feet 

Free-flow discharge, 

cf.? 

Submerged-flow 

correction (correction* 

times multiplying 

factor M) 

Submcrgcd-flow 

discharec ~ 3 

cfs 

1.62 6.0 51.81 

1.58 6.0 49.78 

1.57 6.0 49.28 

*This value is only an approximation determined from figure 5-l 1. 

2.24 x 4.3 = 9.63 42.18 

2.23 x 4.3 = 9.58 40.20 

2.22 x 4.3 = 9.54 39.74 
248 SMALL CANAL STRUCTURES 

The corrections for submerged-flow 

discharge in I- through 8-foot flumes are 

determined from figure 5-l 1 [ 1 ] . These 

discharge corrections are then subtracted from 

the free-flow values in table 5-3. For instance, 

the flow through a 6-foot flume with an H, 

gage reading 1.58 feet and H, gage reading 

1.42 feet would be computed as follows: (I) 

Hb compute submergence ratio, __ = 1.42= 90 

Ha 1.58 

percent. Submerged flow conditions exist 

because the submergence ratio is greater than 

70 percent, (2) from table 5-3 the free-flow 

discharge for H, = 1.58 would be 49.78 cfs. On 

figure 5-l 1 project a line horizontally to the 

right from 1.58 feet to the 90 percent sloping 

submergence line. From this point drop 

vertically downward to the base of the figure 

and read a correction of about 2.23 cfs. This 

correction should then be multiplied by the 

size or multiplying factor, M, for a 6-foot 

flume which is in the insert table on figure 

5-l 1. In this case M = 4.3. The corrected 

discharge for the 90 percent submerged 6-foot 

flume is the free-flow discharge minus the 

correction times the size factor, or 49.78 cfs 

minus 2.23 (4.3) = 40.2 cfs. 

(c) Head Losses.-Head losses for I- through 

8-foot Parshall flumes can be obtained from 

figure 5-8 by the following procedure: (1) for 

the free-flow design example find 70 percent 

submergence at the bottom of the chart. 

Follow the 70 percent submergence line 

vertically upward until it intersects the sloping 

discharge line where Q = 40 cfs, (2) from this 

intersection project a horizontal line to the 

6-foot throat width, W, and (3) from this 

point go vertically downward and read the 

head loss of 0.49 foot. 

calculated difference between the headwater 

and tailwater elevation (102.00 -- 101.80) is 

0.20 foot, which is slightly greater than the 

0.17-foot head loss taken from figure 5-8. 

Engineers at Utah State University have 

developed submerged-flow calibration curves 

for a number of Parshall flumes. The discharge, 

Q, in cubic feet per second is plotted as the 

ordinate; (H, - Hb), in feet as the abscissa; and 

H 

the submergence ratio $- in percent as the 

a 

varying parameter [ 31. These curves eliminate 

the need for trial and error procedure as given 

in the example problem for submerged flow. 

Knowing the design discharge and the desired 

degree of submergence, the value of (H, - H, ) 

can be read directly. The desired submergence 

ratio gives the relationship of H, to H,. The 

two simultaneous equations may be solved for 

H, and H, for a specified flow and a specified 

submergence. The downstream canal water 

surface is set above the crest an amount equal 

t0 H,. 

5-8. Use of Tables and Figures for Discharge 

and Free-flow Determinations. -(a) Free-jlo w 

Discharge. -Free-flow discharge for 6-inch, 

9-inch, and l- through 8-foot Parshall flumes 

can be read directly from tables 5-1, 5-2, and 

5-3, respectively [I] . When the flow is 

submerged, a correction must be applied to the 

free-flow discharges. 

(b) Submerged-jlow Discharge. -Figures 5-9 

and S-10 give the submerged-flow discharge 

directly for 6- and 9-inch flumes respectively 

[Il. 

For example, assume flow through a 6-inch 

flume with an H, gage reading = 1.25 feet and 

Hb H, = 1.05 feet. The submergence ratio, H. = 

1.05= 

1.25 84 percent. Find 84 per&t 

submergence on the left side of figure 5-9. 

Proceed horizontally along the 84 percent 

submergence line to half way between the 1.2 

and 1.3 sloping H, lines. From this point 

proceed vertically downward and read a 

discharge of 2.25 cfs on the bottom line of the 

figure. 

Figure 5-6. Relationship of flow depths to the 

flume crest elevation. 103-D-1224 
WATER MEASUREMENT STRUCTURES 249 

Extend wingwall into 

canal bonk OS required 

--h 

I 

i, t 

Converging Throat , Diverging 

Section (Section ( Section 

I i I 

\ 

I i ; 

LA ‘f? wingwol I 

PLAN 

PROFILE 

Figure 5-7. Standard Parshall flume dimensions. 103-D-1225 
250 SMALL CANAL STRUCTURES 

9Y-- 90 a5 80 70 60 50 015 02 025 03 04 05 06 07 08 09 /I 10 15 20 I 25 30 35 40 50 60 70909010 

PERCENT OF SUBMERGENCE HEAD LOSS, FEET 

Figure 5-8. Head loss through Parshall flumes, 1 through 8 feet wide. 103-D-1226 

UPSTREAM HEAD Ha, FEET 

-cur)tu? (0 r- m 0) ;” z 2 2 ” P 

94 

96 

0 0.e 0.4 0.6 0.8 I .o 1.2 1.4 

DISCHARGE. CFS 

W=6 INCk 

Figure 5-9. Diagram for determining rate of submerged flow in a 6-inch Parshall flume. 103-D-1227 
WATER MEASUREMENT STRUCTURES 251 

UPSTREAM HEAD Ha, FEET 

DISCHARGE, SECOND-FEET 

Figure 5-10. Diagram for determining rate of submerged flow in a 9-inch Parshall flume. 103-D-1228 

NOTE: Correction is used directly for 

I/ ,/I,/ 

I-foot flumes. For lor~er sizes the 

9% PJb 96 

correction equals the value from the 

/I/ //I chart multiplied by size factor, M. 

.30 35 4045.50 60 .70 80.90 I.0 12 I4 1.6 I.8 2.0 2.5 3 3.5 4 4.5 5 6 7 89 

CORRECTION, SECOND-FEET 

Figure 5-II. Diagram for determining correction to be substracted from free-flow discharge to obtain rate of submerged-flow 

discharge through Parshall flumes, 1 through 8 feet wide. 103-D-1229 
252 SMALL CANAL STRUCTURES 

Table 5-l .-Fret-jlow discharge through h-inch Parshall measurinx flume in cubic ,feet per second. 

Computedfi-om the formula Q= 2.06 Ha”s8. 103-D-1230 

Head 

H 

feea; 

0.10 0.05 0.61 0.94 1.11 2.43 

.ll .06 .62 .97 1.12 2.46 

.12 .07 .63 .99 1.13 2.50 

.13 .08 .64 1.02 1.14 2.53 

.14 .09 .65 1.04 1.15 2.57 

.15 .lO .66 1.07 1.16 2.60 

.16 

.17 

.18 

.ll .67 1.10 1.17 

.12 .68 1.12 1.18 

.14 .69 1.15 1.19 

.15 .70 1.17 1.20 

.16 .71 1.20 1.21 

2.64 

2.68 

2.71 

2.75 

2.78 

.19 

.20 

.21 

.22 

.23 

.24 

.25 

.26 

.27 

.28 

.29 

.30 

.25 .71 1.36 

.26 .78 1.39 

.28 .79 1.42 

.29 .80 1.45 

.31 .81 1.48 

.31 .32 .82 1.50 

.32 .34 .83 1.53 

.33 .36 .84 1.56 

.34 .38 .85 1.59’ 

.35 .39 .86 1.62 

.36 .41 .87 1.65 

.37 .43 .88 1.68 

.38 .45 .89 1.71 

.39 .47 .90 1.74 

.40 .48 .91 1.17 

.41 .50 .92 1.81 

.42 .52 .93 1.84 

.43 .54 .94 1.87 

.44 .56 .95 1.90 

.45 .58 .96 1.93 

.46 .61 .97 1.97 

.47 .63 .98 2.00 

.48 .65 .99 2.03 

.49 .67 1.00 2.06 

.50 .69 1.01 2.09 

Sl .71 1.02 2.12 

.52 .73 1.03 2.16 

.53 .76 1.04 2.19 

.54 .78 1.05 2.22 

.55 .80 1.06 2.26 

.56 .82 

.57 .85 

.58 .87 

.59 .89 

.60 .92 

1.07 2.29 

1.08 2.32 

1.09 2.36 

1.10 2.40 

Discharge, 

cfs 

Head 

H 

feea; 

Discharge, 

cfs 

Head 

H 

fee”; 

Discharge, 

cfs 

.18 .72 1.23 1.22 2.82 

.19 .73 1.26 1.23 2.86 

.20 .74 1.28 1.24 2.89 

.22 .I5 1.31 1.25 2.93 

.23 .I6 1.34 1.26 2.91 

1.21 3.01 

1.28 3.04 

1.29 3.08 
WATER MEASUREMENT STRUCTURES 253 

Table 5-2.~Free-flow discharge through 9-inch Parshall measuring flume in cubic feet per second. 

ComputedfromtheformulaQ=3.07Ha’~53. 103-D-1231 

Head 

H 

fe$ 

Discharge, 

cfs 

Head 

H 

feti 

Discharge, 

cfs 

Head 

H 

feea; 

Discharge, 

cfs 

0.10 0.09 0.61 1.44 1.11 3.60 

.ll .lO .62 1.48 1.12 3.65 

.12 .12 .63 1.51 1.13 3.10 

.13 .14 .64 1.55 1.14 3.15 

.14 .15 .65 1.59 1.15 3.80 

.15 .17 .66 1.63 1.16 3.85 

.16 .lY .61 1.66 1.17 3.90 

.17 .20 .68 1.70 1.18 3.95 

.18 .22 .69 1.74 1.19 4.01 

.lY .24 .70 1.78 1.20 4.06 

.20 .26 .71 1.82 1.21 4.11 

.21 .28 .I2 1.86 1.22 4.16 

.22 .30 .I3 1.90 1.23 4.22 

.23 .32 .74 1.94 1.24 4.27 

.24 .35 .75 1.98 1.25 4.32 

.25 .37 .I6 2.02 1.26 4.37 

.26 .39 .77 2.06 1.21 4.43 

.27 .41 .78 2.10 1.28 4.48 

.28 .44 .79 2.14 1.29 4.53 

.29 .46 .80 2.18 1.30 4.59 

.30 .49 .81 2.22 1.31 4.64 

.31 .51 .82 2.27 1.32 4.69 

.32 .54 .83 2.31 1.33 4.75 

.33 .56 .84 2.35 1.34 4.80 

.34 .59 .85 2.39 1.35 486 

.35 .62 .86 2.44 1.36 4.92 

.36 .64 .87 2.48 1.37 4.91 

.31 .67 .88 2.52 1.38 5.03 

.38 .70 .89 2.57 1.39 5.08 

.39 .73 .YO 2.61 1.40 5.14 

.40 .76 .Yl 2.66 1.41 5.19 

.41 .78 .92 2.70 1.42 5.25 

.42 .81 .93 2.75 1.43 5.31 

.43 .84 .94 2.79 1.44 5.37 

.44 .87 .95 2.84 1.45 5.42 

.45 .YO .96 2.88 1.46 5.48 

.46 .94 .Yl 2.93 1.47 5.54 

.47 .Yl .98 2.98 1.48 5.59 

.48 1.00 .YY 3.02 1.49 5.65 

.49 1.03 1.00 3.07 1.50 5.11 

.50 1.06 1.01 3.12 1.51 5.11 

.51 1.10 1.02 3.17 1.52 5.83 

.52 1.13 1.03 3.21 1.53 5.89 

.53 1.16 1.04 3.26 1.54 5.94 

.54 1.20 1.05 3.31 1.55 6.00 

.55 1.23 1.06 3.36 1.56 6.06 ’ 

.56 1.26 1.07 3.40 1.57 6.12 

.57 1.30 1.08 3.45 1.58 6.18 

28 1.33 1 .OY 3.50 1.59 6.24 

.59 1.37 1.10 3.55 

.60 1.40 
254 

Head 

H 

feS 

0.20 0.35 0.66 0.97 1.26 

.21 .31 .71 1.04 1.36 

.22 .40 .I1 1.12 1.47 

.23 .43 .82 1.20 1.58 

.24 .46 .88 1.28 1.69 

.25 .49 .93 1.37 1.80 2.22 2.63 

.26 .51 .99 1.46 1.91 2.36 2.80 

.21 .54 1.05 1.55 2.03 2.50 2.97 

.28 .58 1.11 1.64 2.15 2.65 3.15 

.29 .61 1.18 1.73 2.27 2.80 3.33 

.30 .64 1.24 1.82 2.39 2.96 3.52 4.08 4.62 

.31 .68 1.30 1.92 2.52 3.12 3.71 4.30 4.88 

.32 .71 1.37 2.02 2.65 3.28 3.90 4.52 5.13 

.33 .I4 1.44 2.12 2.18 3.44 4.10 4.15 5.39 

.34 .I1 1.50 2.22 2.92 3.61 4.30 4.98 5.66 

.35 .80 1.57 2.32 3.06 3.78 4.50 5.22 5.93 

.36 .84 1.64 2.42 3.20 3.95 4.71 5.46 6.20 

.31 .88 1.72 2.53 3.34 4.13 4.92 5.70 6.48 

.38 .92 1.79 2.64 3.48 4.31 5.13 5.95 6.74 

.39 .95 1.86 2.75 3.62 4.49 5.35 6.20 7.05 

.40 .99 1.93 2.86 3.17 4.68 5.57 6.46 7.34 

.41 1.03 2.01 2.91 3.92 4.86 5.80 6.12 7.64 

.42 1.07 2.09 3.08 4.07 5.05 6.02 6.98 7.94 

.43 1.11 2.16 3.20 4.22 5.24 6.25 1.25 8.24 

.44 1.15 2.24 3.32 4.38 5.43 6.48 1.52 8.55 

.45 1.19 2.32 3.44 4.54 5.63 6.12 7.80 8.87 

.46 1.23 2.40 3.56 4.70 5.83 6.96 8.08 9.19 

.41 1.21 2.48 3.68 4.86 6.03 7.20 8.36 9.51 

.48 1.31 2.51 3.80 5.03 6.24 1.44 8.65 9.84 

.49 1.35 2.65 3.92 5.20 6.45 1.69 8.94 10.17 

.50 1.39 2.73 4.05 5.36 6.66 7.94 9.23 10.51 

.51 1.44 2.82 4.18 5.53 6.87 8.20 9.53 10.85 

.52 1.48 2.90 4.31 5.70 7.09 8.46 9.83 11.19 

.53 1.52 2.99 4.44 5.88 7.30 8.72 10.14 11.54 

.54 1.57 3.08 4.51 6.05 1.52 8.98 10.45 11.89 

.55 1.62 3.17 4.10 6.23 1.74 9.25 10.76 12.24 

.56 1.66 3.26 4.84 6.41 7.97 9.52 11.07 12.60 

.57 1.70 3.35 4.98 6.59 8.20 9.19 11.39 12.96 

.58 1.75 3.44 5.11 6.71 8.43 10.07 11.71 13.33 

.59 1.80 3.53 5.25 6.96 8.66 10.35 12.03 13.70 

.60 1.84 3.62 5.39 7.15 8.89 10.63 12.36 14.08 

.61 1.88 3.12 5.53 7.34 9.13 10.92 12.69 14.46 

.62 1.93 3.81 5.68 7.53 9.37 11.20 13.02 14.84 

.63 1.98 3.91 5.82 7.72 9.61 11.49 13.36 15.23 

.64 2.03 4.01 5.97 7.91 9.85 11.78 13.70 15.62 

.65 2.08 4.11 6.12 8.11 10.10 12.08 14.05 16.01 

.66 2.13 4.20 6.26 8.31 10.34 12.38 14.40 16.41 

.67 2.18 4.30 6.41 8.51 10.59 12.68 14.75 16.81 

.68 2.23 4.40 6.56 8.71 10.85 12.98 15.10 17.22 

.69 2.28 4.50 6.71 8.91 11.10 13.28 15.46 17.63 

.70 2.33 4.60 6.86 9.11 11.36 13.59 15.82 18.04 

Table 5-3.-Free-flow discharge through Parshall measuring flumes, I- through 

X-foot size, in cubic feet per second. Computed from the formula 

Q = 4 Wf la *.SZZW0.026 . 103-D-1232-1 

1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 

Width of thrc lat. W, feet 

SMALL CANAL STRUCTURES 

1 
WATER MEASUREMENT STRUCTURES 

Head 

H 

fee? 

l0.71 2.38 4.70 7.02 9.32 11.62 13.90 16.18 18.45 

.72 2.43 4.81 7.17 9.53 11.88 14.22 16.55 18.87 

.73 2.48 4.91 7.33 9.74 12.14 14.53 16.92 19.29 

.74 2.53 5.02 7.49 9.95 12.40 14.85 17.29 19.71 

.75 2.58 5.12 7.65 10.16 12.67 15.17 17.66 20.14 

.76 2.63 5.23 7.81 10.38 12.94 15.49 18.04 20.57 

.77 2.68 5.34 7.97 10.60 13.21 15.82 18.42 21.01 

.78 2.74 5.44 8.13 10.81 13.48 16.15 18.81 21.46 

.I9 2.80 5.55 8.30 11.03 13.76 16.48 19.20 21.91 

.80 2.85 5.66 8.46 11.25 14.04 16.81 19.59 22.36 

.81 2.90 5.77 8.63 11.48 14.32 17.15 19.99 22.81 

.82 2.96 5.88 8.79 11.70 14.60 17.49 20.39 23.26 

.83 3.02 6.00 8.96 11.92 14.88 17.83 20.79 23.72 

.84 3.07 6.11 9.13 12.15 15.17 18.17 21.18 24.18 

.85 3.12 6.22 9.30 12.38 15.46 18.52 21.58 24.64 

.86 3.18 6.33 9.48 12.61 15.75 18.87 21.99 25.11 

.87 3.24 6.44 9.65 12.84 16.04 19.22 22.40 25.58 

.88 3.29 6.56 9.82 13.07 16.33 19.57 22.82 26.06 

.89 3.35 6.68 10.00 13.31 16.62 19.93 23.24 26.54 

.90 3.41 6.80 10.17 13.55 16.92 20.29 23.66 27.02 

.91 3.46 6.92 10.35 13.79 17.22 20.65 24.08 27.50 

.92 3.52 7.03 10.53 14.03 17.52 21.01 24.50 27.99 

.93 3.58 7.15 10.71 14.27 17.82 21.38 24.93 28.48 

.94 3.64 7.27 10.89 14.51 18.13 21.75 25.36 28.97 

.95 3.70 7.39 11.07 14.76 18.44 22.12 25.79 29.47 

.96 3.76 7.51 11.26 15.00 18.75 22.49 26.22 29.97 

.97 3.82 7.63 11.44 15.25 19.06 22.86 26.66 30.48 

.98 3.88 7.75 11.63 15.50 19.37 23.24 27.10 30.98 

.99 3.94 7.88 11.82 15.75 19.68 23.62 27.55 31.49 

1.00 4.00 8.00 12.00 16.00 20.00 24.00 28.00 32.00 

1.01 4.06 8.12 12.19 16.25 20.32 24.38 28.45 32.52 

1.02 4.12 8.25 12.38 16.51 20.64 24.77 28.90 33.04 

1.03 4.18 8.38 12.57 16.76 20.96 25.16 29.36 33.56 

1.04 4.25 8.50 12.76 17.02 21.28 25.55 29.82 34.08 

1.05 4.31 8.63 12.96 17.28 21.61 25.94 30.28 34.61 

1.06 4.37 8.76 13.15 17.54 21.94 26.34 30.74 35.14 

1.07 4.43 8.88 13.34 17.80 22.27 26.74 31.20 35.68 

1.08 4.50 9.01 13.54 18.07 22.60 27.13 31.67 36.22 

1.09 4.56 9.14 13.74 18.34 22.93 27.53 32.14 36.76 

1.10 4.62 9.27 13.93 18.60 23.26 27.94 32.62 37.30 

1.11 4.68 9.40 14.13 18.86 23.60 28.35 33.10 37.84 

1.12 4.75 9.54 14.33 19.13 23.94 28.76 33.58 38.39 

1.13 4.82 9.67 14.53 19.40 24.28 29.17 34.06 38.94 

1.14 4.88 9.80 14.73 19.67 24.62 29.58 34.54 39.50 

1.15 4.94 9.94 14.94 19.94 24.96 30.00 35.02 40.06 

1.16 5.01 10.07 15.14 20.22 25.31 30.41 35.51 40.62 

1.17 5.08 10.20 15.34 20.50 25.66 30.83 36.00 41.18 

1.18 5.15 10.34 15.55 20.78 26.01 31.25 36.50 41.75 

1.19 5.21 10.48 15.76 21.05 26.36 31.68 37.00 42.32 

1.20 5.28 10.61 15.96 21.33 26.71 32.10 37.50 42.89 

1.21 5.34 10.75 16.17 21.61 27.06 32.53 38.00 43.47 

Table 5.3.-Free-jlow discharge through Parshall measuring flumes, I- through 

tl-foot size, in cubic feet per second. Computed from the jbrnzl/la 

-Continued. 103-D-1232-2 

255 

1.0 2.0 3.0 

dth of thrc 

4.0 

W, feet 

5.0 6.0 7.0 8.0 

1 
256 SMALL CANAL STRUCTURES 

Table 5-3.-Free-Jlow discharge through Parshall measuring ,flumes, I- through 

&foot size, in cubic .feet per secorld. Computed from the formula 

Q=4WHa 1.S2*W0.026 -Continued. 103-D-1232-3 

Head 

H 

feea; 1.0 2.0 3.0 

Width of throat, W, feet 

4.0 5.0 6.0 7.0 8.0 

1.22 5.41 10.89 16.38 21.90 27.42 32.96 38.50 44.05 

1.23 5.48 11.03 16.60 22.18 27.18 33.39 39.00 44.64 

1.24 5.55 11.17 16.81 22.41 28.14 33.82 39.51 45.22 

1.25 5.62 11.31 17.02 22.15 28.50 34.26 40.02 45.80 

1.26 5.69 11.45 11.23 23.04 28.86 34.70 40.54 46.38 

1.27 5.76 11.59 17.44 23.33 29.22 35.14 41.05 46.97 

1.28 5.82 11.73 17.66 23.62 29.59 35.58 41.57 47.51 

1.29 5.89 11.87 17.88 23.92 29.96 36.02 42.09 48.17 

1.30 5.96 12.01 18.10 24.21 30.33 36.47 42.62 48.78 

1.31 6.03 12.16 18.32 24.50 30.70 36.92 43.14 49.38 

1.32 6.10 12.30 18.54 24.80 31.07 37.31 43.67 49.99 

1.33 6.18 12.44 18.76 25.10 31.44 37.82 44.20 50.60 

1.34 6.25 12.59 18.98 25.39 31.82 38.28 44.13 51.22 

1.35 6.32 12.74 19.20 25.69 32.20 38.74 45.26 51.84 

1.36 6.39 12.89 19.42 25.99 32.58 39.20 45.80 52.46 

1.37 6.46 13.03 19.64 26.30 32.96 39.66 46.35 53.08 

1.38 6.53 13.18 19.87 26.60 33.34 40.12 46.89 53.70 

1.39 6.60 13.33 20.10 26.90 33.12 40.58 47.44 54.33 

1.40 6.68 13.48 20.32 27.21 34.11 41.05 41.99 54.95 

1.41 6.75 13.63 20.55 27.52 34.50 41.52 48.54 55.58 

1.42 6.82 13.78 20.78 27.82 34.89 41.99 49.09 56.22 

1.43 6.89 13.93 21.01 28.14 35.28 42.46 49.64 56.86 

1.44 6.91 14.08 21.24 28.45 35.67 42.94 50.20 57.50 

1.45 7.04 14.23 21.47 28.76 36.06 43.42 50.76 58.14 

1.46 7.12 14.38 21.70 29.07 36.46 43.89 51.32 58.78 

1.47 7.19 14.54 21.94 29.38 36.86 44.37 51.88 59.43 

1.48 1.26 14.69 22.17 29.70 37.26 44.85 52.45 60.08 

1.49 7.34 14.85 22.41 30.02 37.66 45.34 53.02 60.74 

1.50 7.41 15.00 22.64 30.34 38.06 45.82 53.59 61.40 

1.51 7.49 15.16 22.88 30.66 38.46 46.31 54.16 62.06 

1.52 7.57 15.31 23.12 30.98 38.87 46.80 54.74 62.72 

1.53 1.64 15.47 23.36 31.30 39.28 47.30 55.32 63.38 

1.54 7.72 15.62 23.60 31.63 39.68 47.19 55.90 64.04 

1.55 7.80 15.78 23.84 31.95 40.09 48.28 56.48 64.71 

1.56 7.87 15.94 24.08 32.27 40.51 48.78 57.06 65.38 

1.57 7.95 16.10 24.32 32.60 40.92 49.28 51.65 66.06 

i.58 8.02 16.26 24.56 32.93 41.33 49.78 58.24 66.14 

1.59 8.10 16.42 24.80 33.26 41.75 50.28 58.83 67.42 

1.60 8.18 16.58 25.05 33.59 42.17 50.79 59.42 68.10 

1.61 8.26 16.74 25.30 33.92 42.59 51.30 60.02 68.79 

1.62 8.34 16.90 25.54 34.26 43.01 51.81 60.62 69.48 

1.63 8.42 17.06 25.19 34.60 43.43 52.32 61.22 70.17 

1.64 8.49 17.22 26.04 34.93 43.86 52.83 61.82 70.86 

1.65 8.57 17.38 26.29 35.26 44.28 53.34 62.42 71.56 

1.66 8.65 17.55 26.54 35.60 44.10 53.86 63.03 72.26 

1.67 8.73 17.72 26.79 35.94 45.13 54.38 63.64 72.96 

1.68 8.81 17.88 27.04 36.28 45.56 54.90 64.25 13.66 

1.69 8.89 18.04 27.30 36.62 46.00 55.42 64.86 74.37 

1.70 8.97 18.21 27.55 36.96 46.43 55.95 65.48 75.08 

1.71 9.05 18.38 27.80 37.30 46.86 56.48 66.10 15.79 

1.72 9.13 18.54 28.06 37.65 47.30 57.00 66.72 76.50 
WATER MEASUREMENT STRUCTURES 257 

Table 5-3.-Free-flow discharge through Parshall measuring flumes, I- through 

X-foot size, irz cubic feet y;;cond. Computed from the formula 

Q4wH,l.522w . -Continued. 103-D-12324 

Head 

H 

fee? 1.0 2.0 3.0 

Width of throat, W, feet 

4.0 5.0 6.0 7.0 8.0 

1.73 9.21 18.71 28.32 38.00 47.74 57.53 67.34 77.22 

1.74 9.29 18.88 28.57 38.34 48.17 58.06 67.96 77.94 

1.75 9.38 19.04 28.82 38.69 48.61 58.60 68.59 78.66 

1.76 9.46 19.21 29.08 39.04 49.05 59.13 69.22 79.38 

1.77 9.54 19.38 29.34 39.39 49.50 59.67 69.85 80.10 

1.78 9.62 19.55 29.60 39.74 49.94 60.20 70.48 80.83 

1.79 9.70 19.72 29.87 40.10 50.38 60.74 71.11 81.56 

1.80 9.79 19.90 30.13 40.45 50.83 61.29 71.75 82.29 

1.81 9.87 20.07 30.39 40.80 51.28 61.83 72.39 83.03 

1.82 9.95 20.24 30.65 41.16 51.73 62.38 73.03 83.77 

1.83 10.04 20.42 30.92 41.52 52.18 62.92 73.68 84.51 

1.84 10.12 20.59 31.18 41.88 52.64 63.46 74.33 85.25 

1.85 10.20 20.76 31.45 42.24 53.09 64.01 74.98 86.00 

1.86 10.29 20.93 31.71 42.60 53.55 75.63 

1.87 

64.57 86.75 

10.38 21.10 31.98 42.96 54.00 65.13 76.28 87.50 

1.88 10.46 21.28 32.25 43.32 54.46 65.69 76.93 88.25 

1.89 10.54 21.46 32.52 43.69 54.92 66.25 77.58 89.00 

1 .PO 10.62 21.63 32.79 44.05 55.39 66.81 78.24 89.76 

1.91 10.71 21.81 33.06 44.42 55.85 67.37 78.90 PO.52 

1.92 10.80 21.99 33.33 44.79 56.32 67.93 79.56 91.29 

1.93 10.88 22.17 33.50 45.16 56.78 68.50 80.23 92.05 

1.94 10.97 22.35 33.87 45.53 57.25 69.06 80.90 92.82 

1.95 11.06 22.53 34.14 45.90 57.72 

1.96 

69.63 81.57 93.59 

11.14 22.70 34.42 46.27 58.19 

1.97 

70.20 82.24 94.36 

11.23 22.88 34.70 46.64 58.67 

1.98 

70.78 82.91 95.14 

11.31 23.06 34.97 47.02 59.14 71.35 83.58 95.92 

1.99 11.40 23.24 35.25 47.40 59.61 84.26 96.70 

2.00 

71.92 

11.49 23.43 35.53 41.77 60.08 84.94 97.48 

2.01 

72.50 

11.58 23.61 35.81 48.14 60.56 73.08 85.62 98.26 

2.02 11.66 23.79 36.09 48.52 61.04 73.66 86.30 99.05 

2.03 11.75 23.98 36.37 48.90 61.52 74.24 86.99 99.84 

2.04 11.84 24.16 36.65 49.29 62.00 74.83 87.68 100.6 

2.05 11.93 24.34 36.94 49.67 62.48 75.42 88.37 101.4 

2.06 12.02 24.52 37.22 50.05 62.97 76.00 89.06 102.2 

2.07 12.10 24.70 37.50 50.44 63.46 76.59 89.75 103.0 

2.08 12.19 24.89 37.78 50.82 63.94 77.19 90.44 103.8 

2.09 12.28 25.08 38.06 51.21 64.43 77.78 91.14 104.6 

2.10 12.37 25.27 38.35 51.59 64.92 78.37 91.84 105.4 

2.11 12.46 25.46 38.64 51.98 65.41 78.97 92.54 106.2 

2.12 12.55 25.64 38.93 52.37 65.91 79.56 93.25 107.0 

2.13 12.64 25.83 39.22 52.76 66.40 80.15 93.95 107.9 

2.14 12.73 26.01 39.50 53.15 66.89 80.75 94.66 108.7 

2.15 12.82 26.20 39.79 53.54 67.39 81.36 95.37 109.5 

2.16 12.92 26.39 40.08 53.94 67.89 81.97 96.08 110.3 

2.17 13.01 26.58 40.37 54.34 68.39 82.58 96.79 111.1 

2.18 13.10 26.77 40.66 54.73 68.89 83.19 97.5 1 111.9 

2.19 13.19 26.96 40.96 55.12 69.39 83.80 98.23 112.8 

2.20 13.28 27.15 41.25 55.52 69.90 84.41 98.94 113.6 

2.21 13.37 27.34 41.54 55.92 70.40 85.02 PP.66 114.4 

2.22 13.46 27.54 41.84 56.32 70.90 85.63 100.4 115.3 

2.23 13.56 27.73 42.13 56.72 71.41 86.25 101.1 116.1 
25% SMALL CANAL STRUCTURES 

Table 5-3.-Free-flow discharge through Parshall measuring flumes, I- through 

a-foot size, in cubic .fect y:,;~ond. Computed from the formula 

Q=4wH,l.s22w . -Continued. 103-D-1232-5 

Head 

H 

fee? 

2.24 

2.25 

2.26 

2.27 

2.28 

2.29 

2.30 

2.31 

2.32 

2.33 

2.34 

2.35 

2.36 

2.37 

2.38 

2.39 

2.40 

2.41 

2.42 

2.43 

2.44 

2.45 

2.46 

2.47 

2.48 

2.49 

2.50 

1.0 2.0 

13.65 27.92 

13.74 28.12 

13.84 28.31 

13.93 28.50 

14.02 28.70 

14.12 28.90 

14.21 29.09 

14.30 29.29 

14.40 29.49 

14.49 29.69 

14.59 29.89 

14.68 30.08 

14.78 30.28 

14.87 30.48 

14.97 30.69 

15.07 30.89 

15.16 31.09 

15.26 31.29 

15.35 31.49 

15.45 31.69 

15.55 31.89 

15.64 32.10 

15.74 32.30 

15.89 32.50 

15.94 32.10 

16.03 32.90 

16.13 33.11 

Width of throat, W,feet 

3.0 4.0 5.0 6.0 7.0 8.0 

42.43 57.12 71.92 86.87 101.8 116.9 

42.73 51.52 72.43 87.49 102.6 117.8 

43.02 57.93 72.94 88.11 103.3 118.6 

43.32 58.34 73.46 88.73 104.0 119.5 

43.62 58.74 73.97 89.35 104.8 120.3 

43.92 59.15 14.49 89.98 105.5 121.2 

44.22 59.56 75.01 90.61 106.2 122.0 

44.52 59.96 75.53 91.24 107.0 122.9 

44.83 60.37 76.05 91.87 107.7 123:7 

45.13 60.79 76.57 92.50 108.5 124.6 

45.43 61.20 77.09 93.14 109.2 125.4 

45.74 61.61 77.61 93.77 110.0 126.3 

46.04 62.03 78.13 94.41 110.7 127.2 

46.35 62.44 78.66 95.05 111.5 128.0 

46:66 62.86 79.19 95.69 112.2 128.9 

46.96 63.27 79.72 96.33 113.0 129.8 

47.27 63.69 80.25 96.97 113.7 130.7 

47.58 64.11 80.78 97.62 114.5 131.5 

47.89 64.53 81.31 98.21 115.3 132.4 

48.20 64.95 81.84 98.91 116.0 133.3 

48.51 65.38 82.38 99.56 116.8 134.2 

48.82 65.80 82.92 100.2 117.6 135.1 

49.13 66.23 83.45 100.9 118.3 135.9 

49.45 66.65 83.99 101.5 119.1 136.8 

49.76 67.07 84.53 102.2 119.9 137.7 

50.08 67.50 85.07 102.8 120.6 138.6 

50.39 67.93 85.62 103.5 121.4 139.5 
WATER MEASUREMENT STRUCTURES 259 

C. MODIFIED PARSHALL FLUMES 

5-9. Description. -Some of the Parshall 

flume dimensions shown in figure 5-7 are 

modified so that the flume fits the canal 

profile. 

Generally, only the flumes operating at 

free-flow conditions are modified, and the 

major modifications are made downstream of 

the throat section. All critical factors which 

can significantly affect accurate measurement 

such as dimensions for the crest, throat, and 

location of the H, pressure tap are constructed 

to the standard dimensions given in figure 5-7 

[ I] . For instance, a Parshall flume, chute, and 

stilling basin may be combined into one 

structure as shown in figure 5- 12. As previously 

stated, for free-flow measurement, that portion 

of the flume downstream of the throat is not 

required. Therefore, the downward sloping 

floor of the throat section can be extended as a 

rectangular chute into a stilling pool without 

affecting the flow measurement accuracy and 

the standard free-flow discharge tables may be 

used. 

If modifications are made for submerged 

l-4, Measuring 

t-low (greater than 60 percent submergence for 

6- and 9-inch flumes, and 70 percent for lthrough 8-foot flumes), then the flow should 

be calibrated with a current meter or some 

other suitable device to determine the effects 

of the modifications. 

S-10. Determination of Upstream Canal 

Water Surface. -The upstream canal water 

surface required for a modified, free-flow 

Parshall flume should be determined as 

follows: (1) from the given discharge and 

selected width of flume, read the H, value 

from the appropriate Parshall flume tables 5- 1, 

5-2 or 5-3, (2) determine the width of the 

converging section at the H, measuring point. 

Using this width and the depth, H,, compute 

the velocity and velocity head in the flume. 

The energy is then the depth, H,, plus the 

velocity head, hva, (3) neglecting losses, the 

energy elevation of the upstream canal water 

will be the same elevation as the energy at H,. 

The canal water surface is obtained by 

subtracting the velocity head in the canal from 

the energy elevation. 

Figure 5-12. Modified Parshall flume. 103-D-1233 
260 SMALL CANAL STRUCTURES 

D. STILLING WELLS 

S-11. Description. -Stilling wells are used in 

combination with Parshall flumes, figure 5-2; 

weirs, figure 5-3; and constant head orifices, 

figure 3-24, to permit more accurate reading of 

gages. They provide a water surface essentially 

free from surface fluctuations. 

Stilling wells are connected to the measuring 

structures by small pipes and provide a place 

for the installation of staff gages, hook gages, 

float gage recorders or any other type of device 

suitable for measuring water surface levels. The 

water surface in the stilling well is essentially 

the same elevation as in the measuring 

structure at the pressure taps. 

5-l 2. Design Criteria. -Gages for Parshall 

flumes and weirs should be set so they show 

the depth of the water above the crest and not 

above the pressure openings. 

By restricting the area of inlet port to 

1 approximately 1000 [ l] of the inside 

horizontal cross-sectional area of the well, 

water surface in the measuring structure is 

effectively dampened. The inlet area of the 

conduit should be increased if the stilling well 

is offset from the channel by more than 20 to 

30 feet. 

Some dimensions [ 11 for stilling wells and 

their inlet pipe diameters are given in the 

following tabulation: 

Diameter of inlet 

Diameter of conduit, 20 to 

Float well dimensions inlet port, 30 feet long, 

inches inches 

12-inch diameter 112 112 

16-inch diameter 112 314 

20-inch diameter 518 314 

24-inch diameter 314 1 

30-inch diameter 1 l-1/2 

36-inch diameter l-114 2 

3 feet by 3 feet 

square l-1/4 2 

3 feet by 4 feet 

rectangular l-112 3 

4 feet by 5 feet 

rectangular 2 4 

Stilling wells can be constructed 

monolithically with a measuring structure or 

placed adjacent to it. In either case, since the 

primary purpose of the stilling well is to 

provide a smooth water surface, the structure 

must be well anchored to prevent movements 

that would otherwise cause undesirable water 

surface fluctuations. 

Intake pipes to stilling wells should be 

cleaned occasionally either by hand or by some 

type of flushing system. Sediment or other 

foreign material lodged in the pipe could cause 

improper water levels to be transmitted to the 

stilling well. However, permanent flushing 

systems usually are not warranted except 

where the water normally carries a significant 

suspended sediment load. 

E. WEIRS 

5-l 3. Purpose and Description. -Weirs are 

overflow structures built across open channels 

to measure the rate of flow of water. They 

have been used for many years and offer a 

simple, reliable method for water measurement 

if they are built correctly and maintained 

properly. Weirs discussed herein are those that 

will measure flows from about 1 to 100 cfs. 

5-14. Types of Weirs.-Weirs are identified 

by the shape of their openings. These openings 

can be either sharp-crested or broad-crested. 

Those most frequently used for water 

measurement and discussed herein are 

sharp-crested rectangular, trapezoidal or 

Cipolletti, and triangular or 90’ V-notch weirs 

shown in figure 5- 13. 

Weirs also may be designated as suppressed 

or contracted. depending on whether or not the 

sides of the weir are coincident with the sides 

of the approach channel. If the sides of a 

rectangular weir are coincident with the sides 

of the approach channel and extend 

downstream from the weir, the sheet of water 

(nappe) leaving the weir crest does not contract 

laterally, thus the end contractions are 

suppressed and weir is called a suppressed weir 

(fig. 5-14). However, if the sides and crest of a 

rectangular, trapezoidal, or V-notch weir are 

far enough away from the sides and bottom of 

the approach channel, the nappe will fully 
WATER MEASUREMENT STRUCTURES 261 

RECTANGULAR WEIR CIPOLLETTI WEIR 90°V- NOTCH WEIR 

STANDARD CONTRACTED WEIRS 

\ Q.., (UPSTREAM FACE) 

Flow 

-=. War blade 

SECTION A-A 

V-Notch 

mstalled. 

Weirs 

Figure 5-13. Standard contracted weir discharging at free flow. 103-D-1234 

contract laterally at the ends and vertically at 

the crest of the weir. When these conditions 

occur, the weir is called a contracted weir. In 

this case water flows slowly and uniformly in 

its lateral approach to the weir ends. As the 

water nears the weir it accelerates and turns to 

pass through the opening. When the water 

turns, the streamlines contract and the water 

springs free (fig. 5-l 5) from the weir ends to 

form a jet narrower than the weir opening [ 11. 

Similarly, streamlines from the bottom spring 

free from the crest. A contracted Cipolletti 

weir is shown in figure 5-16. 

If the weirs and weir pools are built to 

specified shapes and definite dimensions as 

shown in figures 5-17 and 5-18, standard 

conditions exist and the weirs are classified as 

standard weirs. Standard type weirs used by 

Reclamation are standard contracted and 

standard suppressed rectangular weirs, standard 

Cipolletti weirs, and 90’ V-notch weirs. 

5-15. Types of Flow.-All weirs may be 

classified as free flow or submerged flow. 

Free-flow conditions exist when the water 

surface downstream of the weir is low enough 

to allow air to circulate between the weir and 

the underside of the nappe. In a suppressed 

weir the sides of the structure prevent the air 

from circulating under the nappe so the 

underside of the nappe has to be vented. 

Submerged-flow conditions exist when the 

water surface downstream of the weir rises 

above the heir crest. Weirs should be designed 

to discharge freely rather than submerged 

because of greater measurement accuracy, 

although a slight submergence does not 

appreciably affect the discharge as much as the 

lack of ventilation under the nappe. The 

underside of the nappe on a free-flow weir 

should be properly vented so the nappe springs 

free from the weir crest and full contraction 

occurs. 

5-16. Application.-Weirs can be used, 

where adequate head is available, as inline 

measuring structures as shown in figures 5-l 7 

and 5-18, or in combination with division 

structures and turnouts as shown in figures 

5-I 9 and 5-26, respectively. 
262 SMALL CANAL STRUCTURES 

Air vent -l 

Figure 5-14. Typical suppressed weir in a flume drop. 103-D-1235 

5- 17. Adjustable Weirs. -Weirs used in 

division structures are usually adjustable (fig. 

5-20). Adjustable weirs can be rectangular, 

trapezoidal, or V-shaped. They are mounted in 

a frame and can be raised or lowered by a 

threaded stem and handwheel (fig. 5-21). Some 

adjustable weirs are attached permanently to 

the division structures while others are 

constructed so the weir and frame may be 

removed from one structure and used on 

another (figs. 5-22 and 5-23). Adjustable weirs 

installed in division structures serve as 

measuring devices but their primary purpose is 

to control or divide the flow. When two or 

more adjustable weirs are used in one division 

box (fig. 3-3 l), the proximity of the weirs and 

the small pool could have a detrimental effect 

on the head-discharge relationship of each weir. 

Consequently, the accuracy of the flow 

measurement is less than that expected from a 

weir operating under standard conditions. The 

division structures shown in figures 3-35 and 

3-36 in chapter III do not include staff 

gages for measuring heads on the weirs. Instead 

a portable staff or weir gage (fig. 5-25) is 

placed on the crest of the weir to measure the 

head as shown in figure 5-l 9. Some of these 

gages or weir sticks contain both a piezometer 

and manometer to show the total head (depth 

over the weir and velocity head) causing the 

flow. After measuring the head, the flow can 

be determined from the standard weir tables. If 

a permanent-type weir gage installation is 

preferred over the portable gage, the weir gage 

may be installed as shown in figure 5-24. If 

greater accuracy is required for either the 

portable or permanent gage installation the 

weir should be calibrated to determine the 

head-discharge relationship. 

5-l 8. Advantages and Disadvantages. -Weirs 

have the following advantages: 

( 1) Capable of accurately measuring a wide 

range of flow. 

(2) Easy to construct. 
WATER MEASUREMENT STRUCTURES 263

Figure 5-15. Water flowing over a standard Cipolletti weir. P20-0-34861

r--\

~w

A

<1 Cresj

~

~Weir ga-ge

(... ,,\,."

" " ---"

>,. r ./.'c.,,\,

?1"~ .:c' .

.;t:- -1

~

-1

~~ ,~

~ ~~,~

CIPOLLETTI WEIR DETAIL

UPSTREAM SiDE

.," : ~ "::!,.:,.

.~ ""...

,4,.,. ,."-

-~ .' "

," ,.1.,

,. -,\, -

r / ;

" ' ' " I'~' ' '~,

~/,,: ' "II" !"

V/ -..,"'

~~'c

~""'--;:,;.,

Flow

->-

/' Weir blade ~ ,!".1"":;,,

-"' ,

- ."" -

4'". "1.

~

+"

e

.""J\",,~-,i

~~ ..~I,,~,1 ,1\, , -!,"1!',.,..,.:.,..,~..

,. -

'",;..!..,,~"/

SECTION A-A Nappe

Figure 5-16. CipoUetti weir in a permanent bulkhead-free-flow conditions. lO3-D-1236

::":".": 0:

:Li ~ :.,;.
264 SMALL CANAL STRUCTURES 

Figure 5-17. Cipolletti weir structures-12 inches to 4 feet. 103-D-1237 
WATER MEASUREMENT STRUCTURES 265 

-- :-~ ; 

SECTlON C-C 

J -zc 

WEIR DETAILS 

WElR STRUCTURES 

Figure 5-18. Cipolletti weir structures-5 feet to 16 feet. 103-D-1238 
266 SMALL CANAL STRUCTURES

Figure 5.19. Division structure with adjustable

weirs. Operator is measuring depth of water on

weir crest. P222-116-52034

(3) Can be used in combination with

turnouts.

( 4) Can be used in division structures.

(5) Can be both movable (portable) and

adjustable.

Some disadvantages of weirs are:

( 1) Impose a greater head loss in the canal

system than other water measurement

structures.

(2) Weir pools must be cleaned of sediment

periodically and kept free of weeds and trash-

( 3) Can be easily altered to obtain

unallocated water.

( 4) Some leakage occurs around movable

weirs.

5 -19. Requirements for Accurate

Measurement. -To obtain the highest degree of

measurement accuracy, standard weir

structures must be accurately constructed and

properly maintained. The necessary

requirements for weir blade, nappe, approach

channel-weir relationship and gage location are:

(a) Weir Blade. -The weir blade should be

designed and installed as follows:

( 1) The upstream face of the bulkhead

and weir blade must be vertical.

(2) The crest of the weir blade should be

level and have a sharp right angle corner on

the upstream side.

(3) The sides of a rectangular contracted

weir blade should be vertical, have a sharp

right angle corner on the upstream side and

form a right angle at the junction with the

crest.

( 4) The sides of a Cipolletti weir blade

should be on 1 to 4 slope, and have sharp

right angle corners on the upstream side.

(5) The sides of a 900 V-notch weir blade

should have a sharp right angle corner on the

upstream side.

( 6) The downstream edge of the crest and

sides of a movable weir blade should be

chamfered at a 45° angle or more (crest

should be about one-eighth inch thick);

however, knife edges on all weirs should :he

avoided because they are difficult to

maintain.

(7) Weir blades must be kept free of rust

and nicks. Any form of roughness will cause

the weir to discharge more water than

indicated in the standard tables.

(b) Nappe.-The nappe requirements are:

( I) Air should circulate freely under the

nappe. In suppressed weirs the underside of

the nappe should be vented from both sides.

An increase in discharge as much as 25

percent may occur if the nappe is not

properly vented [2] .

(2) The nappe should only touch the

upstream side of the crest and sides of the

weir blade.

(c) Approach Channel-to-weir

Relationship.-The following design criteria

have been developed from extensive tests and

prolonged use of standard weirs:

( 1) The approach channel or weir pool

should be designed so that the velocity of

approach in the weir pool is about 0.5 foot

per second. I t should extend upstream from

the weir a distance of 15 to 20 times the

head on the weir. If for some reason the

weir pool cannot be designed to meet this

velocity requirement, then a discharge

correction coefficient must be applied. The

second edition of the Bureau of Reclamation

"Water Measurement Manual" [ 1] contains

a table for determining the discharge

correction for various heads and approach

velocities.

(2) The distance between the weir crest

and the invert of the approach channel or
WATER MEASUREMENT STRUCTURES 267 

WEIR ASSEYBL Y CL t 

-IA 

Y 

SECTION C-C 

SECT/ON S-B 

Figure 5-20. Adjustable weirs-2 and 3 feet wide. 103-D-1239 
268 SMALL CANAL STRUCTURES 

COk? 

/$'I? 

Smooth costfng 

Rough bronze nut cost ,n 

bondwheel, threaded 8 

overs,ze for /:-’ stern 

w,+h s,“g,e AC”%? fi7OS 

4 per inch 

HAND WHEEL 

t*si ,RON 

Some COVER PLlTt 

used for i8”ond 21’ 

die handwheels 

COVER PLATE 

CAST ,RON 

For ia’ond 21” dto handwheels 

Copooty 550 Lbs 

Rough bronze nu cos ,n 

hondwheel, threaded f 

OWPS~ZP for /i’stern wth 

smgle Acme threads 4 

per inch 

HAND WHEEL 

‘ 1ST 

ASSEMBLY 

Cowctty 495 Lbs 

Capacity .G’S Lbs 

Hub cast smooth 

Rough bronze nut cost in 

hoodwheel. threaded $” 

OYtTSllP for !;‘stem 

wlfn sl”g,e Acme threads 

4 per mc h 

HAND WHEEL 

CAST iRON 

Smooth costi 

COVER PLATE 

CAST ,RON 

For 14” die handwheel 

core f 

i’RSmooth costmg 

COVER PLATE 

Rough bronze nut Cost 

CAST ,RDN 

For 12’ die hondwheei 

4 per &h 

HAND WHEEL 

CAST iRON 

NOTE 

Capacity based on o handwheel 

,wll of 20 pounds 

Figure 5-21. Handwheels-12, 14, 18, and 21 inches. 103-D-1240 
WATER MEASUREMENT STRUCTURES 269 

FILLER 

STEEL 

TWO REO”iRE.9 

SEC B-8 

SECTION A -A 

Figure 5-22. Two-foot movable weir. 103-D-1241 
270 SMALL CANAL STRUCTURES 

SEC. S-8 

=nnn 

SECrlON c-c SEC D-D 

LEGEND 

Figure 5-23. Three-foot movable weir. 103-D-1242 
WATER MEASUREMENT STRUCTURES 

t I 

/ 

Operotmg rood A II 

’ I 

I I 

If’ Pipe cop 

/Bottom of wer goge 

4 ~8"DlO 

SECTION A-A 

2” U-Bolt Round bend 

Golvonved 2- Requwed 

Bar IX; Golvonrzed. 

tier nuts - golvanrzed 

SECTION D-8 

Not to scale 

above 

BAR DE TAIL 

Not to scale 

NOTES 

With wer m fully lowered pos!t,on set zero of we/r goge 

below crest of wwr o dlstonce equal to A 

h For ony pwtmn of wer crest equals wer goge reodrng 

nunus stem protection above handwheel hub 

271 

Figme 5-24. Staff or weir gage installation. 103-D-1243 
272 SMALL CANAL STRUCTURES 

- - 

8 e 

b'iocki' - 

- 

6 - - 

NOTES 

Gqges to be mode of No Mgoge (US stondordlmtid steelplote 

and to be covered with utreo~s eoomel with 0 mmniwm 

+hickneSS ofi2 miis on numeroi side and3 ml/s On the 

reverse side and on edges where Plate has been Cut. 

,,unched or drilled 

Ail cutting. drilling and punching of the Plates shall be 

completed before the vitreous enamel is applied 

The face of the gage Shoii be white ond ailnumeroIs and 

oroduotions shoii be black 

Griduotions shall be sharp and occuroie to the dimensmns 

shown 

in COSP o greater ,eng+h than +&On,5 required the deta!ls 

who,, be s,m,,w to deto,,~ ~hovm for shorter lengths 

Figure 5-Z. Staff OI weir gage. 103-D-1244 
WATER MEASUREMENT STRUCTURES 

weir pool should be at least twice the head 

on the weir and never less than 1 foot for all 

weirs. The distance between the corners of 

the weir crest and the sides of the approach 

channel should also be at least twice the 

head on the weir and never less than 1 foot 

for all standard contracted weirs. 

(d) Heud on Weir. -The head on the weir is 

the difference in elevation between the weir 

crest and the water surface upstream. The head 

is measured by: 

(1) Either a staff gage in the weir pool or 

a gage in a measuring well located upstream 

of the weir a distance of four times the 

maximum head on the weir. 

5-20. Head-discharge 

Relationship. -(a) Rectangular and Cipolletti 

Weirs.-The discharge in cubic feet per second 

of these standard weirs depends on the crest 

length and the head on the weir. Knowing the 

weir length and head on the weir, the free-flow 

discharge can be read directly from tables 5-4, 

5-5, and 5-6. 

The minimum head on standard rectangular 

and Cipolletti weirs is 0.2 foot. At heads less 

than 0.2 foot the nappe does not spring free of 

the crest and measurement error results. 

The maximum head on standard rectangular 

and Cipolletti weirs is one-third of the crest 

length. For the weir structure shown in figure 

5-18, the maximum head (h max.) on the weir 

should not exceed the values given in the table 

because in unlined canals excessive channel 

erosion may occur immediately downstream of 

the structure. If this structure is used in a hard 

surface lined canal where erosion is not a 

problem, the head on the weir can be one-third 

the crest length and the discharge computed 

from the appropriate weir formula. 

(b) V-notch W&s-The discharge in cubic 

feet per second of a standard 90’ V-notch weir 

is determined only by the head on the bottom 

of the V-notch. Table 5-7 gives the discharges 

for various heads. The V-notch weirs are 

usually limited to flows of 10 cfs or less. More 

head is required in V-notch weirs to pass a 

given discharge than in rectangular and 

Cipolletti weirs but for flows up to 1 cfs they 

are generally more accurate. The reason for this 

is that the nappe springs free from the V-shaped 

section even for small heads, whereas the nappe 

273 

clings to the crest of other weirs. The minimum 

head on a V-notch weir should be 0.2 foot. 

S-21. Design Example of Selecting and 

Setting a Weir. -(a) Requirements. -Select and 

set a Cipolletti weir structure to measure a 

maximum flow of 40 cfs. The weir structure is 

to be constructed in a trapezoidal earth canal 

which has the following hydraulic properties: 

Q = 40 cfs; bottom width = 6.0 feet; side slopes 

l-1/2 to 1; normal water depth upstream (dl ) 

and downstream (d,) of weir = 2.0 feet; 

velocity = 2.22 feet per second; and canal bank 

freeboard = 1.5 feet. Assume a 3-foot drop (F) 

between upstream and downstream normal 

water surfaces has been provided in the canal 

profile. 

(b) Weir Selection.-The table of weir 

structures in figure 5-l 8 gives some standard 

weir lengths with their corresponding 

maximum discharges, Q max., and minimum 

and maximum drops, F, between upstream and 

downstream water surfaces. Select the 

structure having the least weir length for a 

design discharge of 40 cfs and F = 3.0 feet. 

Structure No. 6A (from table on fig. 5-18), has 

a crest length, W, of 6 feet which meets this 

criteria. The maximum design capacity of this 

structure is 57 cfs and a maximum allowable F 

= 3 feet. Table 5-5 shows that for a 6-foot weir 

and a discharge of 40.1 cfs, the head, h, equals 

1.58 feet. 

(c) Weir Setting. -Set the weir pool invert so 

that elevation B shown in figure 5-18 is 3h 

below the upstream normal water surface 

(NWS) elevation. Assume the upstream canal 

invert elevation is 100.00 feet. Then 

El. B = Canal invert elevation + d1 - 3h 

El. B = 100.00 + 2.00 - 3( 1.58) 

= 97.26 feet 

Since 2h = 3.16 feet is greater than the 12-inch 

minimum, El. B is satisfactory. The elevation 

of the top of weir wall (El. T) is given by the 

following equation: 

2.50 El. T = El. B + 2h - x+ G 

El. T = 97.26 + 3.16 - 2.50 l2 + 3.21 

El. T = 103.42 feet 

In the above calculation, 12 2.50 is the weir blade 
274 SMALL CANAL STRUCTURES 

projection in feet above the concrete sill and G 

is the concrete depth of the weir notch given in 

the Anchor Bolt and Weir Blade Data table 

shown in figure 5-l 8. 

Next calculate the elevation of the weir floor 

(El. K). 

El. K = NWS El. (upstm.) - F - d, - 0.5 (min.) 

El. K = 102.00 - 3.00 - 2.00 - 0.50 

El. K = 96.50 feet 

In all cases El. K should be at or below El. B. 

The height of the weir wall, H, is: 

H = El. T - El. K 

H = 103.42 - 96.50 

H = 6.92 feet 

The height of the sloping sidewall, H’, is: 

H’ = 0.5 (minimum) + dz 

+ structure freeboard 

As the weir structure freeboard is 1 foot, then 

H’ = 0.50 + 2.00 + 1.00 = 3.50 feet 

The length, L, of the weir structure should be 

long enough to contain the plunging nappe and 

to provide a pool for stilling the water before it 

passes downstream into the canal. The length is 

computed by the following empirical formula: 

L= 3h+ 2F 

L = 3( 1.58) + 2(3.0) = 10.74 feet 

Therefore, the structure can be made 11 feet 

long. 

Cutoff walls are added to provide additional 

percolation path to prevent piping of 

foundation materials from under the structure, 

to protect the structure from being 

undermined if channel erosion occurs, and to 

provide structure stability to resist overturning 

and sliding. As a general rule cutoff walls 

should extend below the canal invert as shown 

for the following water depths at the cutoff: 

Water depth, 

feet 

Cutoff depth, 

feet 

Cutoff thickness, 

inches 

o-3 2.0 6 

3-6 2.5 8 

>6 3.0 8 

The upstream water depth (3h) adjacent to 

the upstream face of the structure for this 

example is 4.74 feet. Using the general rule, the 

cutoff should extend 2.5 feet below the invert. 

Then Gin. shown in figure 5-l 8 is: 

K,,,in. = 2.5 - (E1.B - E1.K) 

Kmin, = 2.5 - (96.26 - 96.50) 

Qin, = 2.5 - 0.76 

Kmin, = 1.74 feet 

Water depth at the downstream cutoff is 2.5 

feet and using the general rule, emin. is 24 

inches. Use 24 inches for both Kmin. and 

emin. . Additional cutoff lengths may be 

required depending on the percolation factor as 

discussed in detail in section 8-10. Lane’s 

weighted creep length in this example is: 

Weighted creep length 

+ cemin. - 

protection thickness) 

= (97.26 - 96.50) + 2.00+ 9 + (2 - ;) 

6 + (2 - 12) + (2 - 1) 

= 10.43 feet 

Next determine the maximum difference in 

water surface @WS) between the upstream 

and downstream ends of the structure: 

(1) For design discharge. AWS = 3.0 

feet 

(2) For upstream water ponded to weir 

crest and downstream water at canal 

invert 

AWS = Crest elevationDownstream canal 

invert elevation 

= (El. B+2h) ~ (El. K+0.50) 

= 100.42 - 97.00 = 3.42 feet 

Compute weighted creep ratio (percolation 

factor) for AWS = 3.42 feet, 

10.43 Percolation factor = 342= 3.1 

Assume the required percolation factor for the 

foundation material for this structure is 2.5. 

The percolation factor calculated is greater 

than 2.5 and therefore the cutoffs are adequate 

in length. 
I 

WATER MEASUREMENT STRUCTURES 275 

Head 

h, 

feet 

Len of weir, L, f 

4.0 5.0 6.0 7.0 

0.20 0.29 0.58 0.88 1.18 1.48 1.78 2.07 

.21 .31 .63 .95 1.27 1.59 1.91 

.22 .33 .67 1.02 1.36 1.70 2.05 

.23 .3s .72 1.08 1.45 1.82 2.19 

.24 .37 36 1.16 1.55 1.94 2.33 

.25 .40 .81 1.23 1.64 2.06 2.48 

2.23 

2.39 

2.55 

2.72 

2.89 

‘26 .42 .86 1.30 

.21 .44 .91 1.38 

.28 .47 .96 1.45 

.29 .49 1.01 1.53 

.30 .51 1.06 1.61 

1.74 2.18 2.63 3.07 

1.84 2.31 2.78 3.24 

1.95 2.44 2.93 3.43 

2.05 2.57 3.09 3.61 

2.16 2.70 3.25 3.80 

.31 

.32 

.33 

.34 

.35 

.s4 

.56 

.59 

-+ 

1.11 1.69 2.26 2.84 3.41 3.99 

1.17 1.77 2.37 2.98 3.58 4.18 

1.22 1.85 2.48 3.12 3.75 4.38 

1.28 1.94 2.60 3.26 3.92 4.58 

1.33 2.02 2.71 3.40 4.09 4.78 

.36 .69 1.39 2.11 

.3? .71 1.44 2.19 

.38 .74 1.50 2.28 

.39 .I7 1.56 2.37 

.40 .80 1.62 2.46 

2.82 3.54 4.26 4.98 

2.94 3.69 4.44 5.19 

3.06 3.84 4.62 5.40 

3.18 3.99 4.80 5.61 

3.30 4.14 4.99 5.83 

.41 .83 1.68 2.55 

.42 .86 1.74 2.64 

.43 .89 1.80 2.74 

.44 .92 1.86 2.83 

.45 .95 1.92 2.92 

3.42 4.30 5.17 6.05 

3.55 4.46 5.36 6.27 

3.68 4.61 5.55 6.49 

3.80 4.77 5.75 6.72 

3.93 4.94 5.94 6.95 

.46 .98 

.47 1.01 

.48 1.04 

.49 1.08 

SO 1.11 

1.98 3.02 4.06 5.10 6.14 7.18 

2.04 3.12 4.19 5.26 6.34 7.41 

2.11 3.22 4.32 5.43 6.54 7.64 

2.11 3.32 4.46 5.60 6.74 7.88 

2.24 3.4 1 4.59 5.71 6.95 8.12 

.Sl 

.52 

.53 

.54 

.55 

2.30 3.52 4.73 5.94 7.15 8.37 

2.37 3.62 4.86 6.11 7.36 8.61 

2.43 3.72 5.00 6.29 7.57 8.86 

2.50 3.82 5.14 6.46 7.79 9.11 

2.57 3.92 5.28 6.64 8.00 9.36 

.56 2.64 4.03 5.43 6.82 a.22 9.61 

Sl 2.70 4.14 5.57 7.00 8.44 9.87 

.58 2.71 4.24 5.71 7.18 8.66 10.1 

.59 2.84 4.35 5.86 7.37 8.88 10.4 

.60 2.91 4.46 6.00 7.55 9.10 10.6 

.61 2.98 4.57 6.15 7.74 9.32 10.9 

.62 3.05 4.68 6.30 7.93 9.55 11.2 

.63 3.12 4.79 6.45 8.12 9.78 11.4 

.64 3.19 4.90 6.60 8.31 10.0 11.7 

.65 3.26 5.01 6.75 8.50 10.2 12.0 

.66 3.34 5.12 6.91 

.67 3.4 1 5.23 7.06 

.68 3.58 5.35 7.22 

.69 3.66 5.46 7.37 

.7Q 3.74 5.58 7.53 

8.69 10.5 12.3 

8.89 10.7 12.5 

9.08 11.0 12.8 

9.28 11.2 13.1 

9.48 11.4 13.4 

Table 54.-Discharge of standard contracted rectaangular weirs in cubic feet per second. Values below 

and to the left of heav,v line determined esperinxntoily; others computed 

from the formula Q = 3.33 (L-0.Jk]h3”. 103-D-1245-1 

7 
276 SMALL CANAL STRUCTURES 

Table 54.-Discharge of standard contracted rectangular weirs in cubic feet per second. Values below 

and to the left of heavy line determined experimentally: others computed from the formula Q = 3.33 (L-0.2h)h3’2.-CQntinued. 

103-D-1245-2 

Head Length of weir, L, feet 

h, 

feet 2.0 3.0 4.0 5.0 6.0 7.0 

I 

0.71 3.82 5.69 7.69 9.68 11.7 13.7 

.72 3.90 5.81 7.84 9.88 11.9 13.9 

.73 3.98 5.93 8.00 10.1 12.2 14.2 

.74 4.06 6.05 8.16 10.3 12.4 14.5 

.75 4.14 6.16 8.33 10.5 12.7 14.8 

.76 4.22 6.28 8.49 10.7 12.9 15.1 

.77 4.30 6.40 8.65 10.9 13.2 15.4 

.78 4.38 6.52 8.82 11.1 13.4 15.7 

.79 4.46 6.64 8.98 11.3 13.7 16.0 

.80 4.54 6.77 9.15 11.5 13.9 16.3 

.81 4.62 6.89 9.32 11.7 14.2 16.6 

.82 4.70 7.01 9.48 12.0 14.4 16.9 

.83 4.78 7.14 9.65 12.2 14.7 17.2 

.84 4.87 7.26 9.82 12.4 15.0 17.5 

.85 4.96 7.38 10.0 12.6 15.2 17.8 

.86 5.05 7.5 1 10.2 12.8 15.5 18.1 

.87 5.14 7.64 10.3 13.0 15.7 18.4 

.88 5.23 7.76 10.5 13.3 16.9 18.8 

.89 5.32 7.89 10.7 13.5 16.3 19.1 

.90 5.41 8.02 10.9 13.7 16.5 19.4 

.91 5.50 8.15 11.0 13.9 16.8 19.7 

.92 5.59 8.28 11.2 14.2 17.1 20.0 

.93 5.68 8.40 11.4 14.4 17.4 20.4 

.94 5.77 8.53 11.6 14.6 17.6 20.7 

.95 5.86 8.66 11.7 14.8 17.9 21.0 

.96 5.95 8.80 11.9 15.1 18.2 21.3 

.97 6.04 8.93 12.1 15.3 18.5 21.7 

.98 6.13 9.06 12.3 15.5 18.8 22.0 

.99 6.22 9.19 12.5 15.8 19.0 22.3 

1.00 6.31 9.32 12.7 16.0 19.3 22.6 

1.01 12.8 

1.02 

16.2 19.6 23.0 

13.0 

1.03 

16.5 19.9 23.3 

13.2 

1.04 

16.7 20.2 23.6 

13.4 

1.05 

16.9 20.5 24.0 

13.6 17.2 20.1 24.3 

1.06 13.8 

1.07 

17.4 21.0 24.7 

14.0 

1.08 

17.6 21.3 25.0 

14.1 

1.09 

17.9 21.6 25.4 

14.3 

1.10 

18.1 21.9 25.7 

14.5 18.4 22.2 26.0 

1.11 14.7 

1.12 

18.6 22.5 26.4 

14.9 

1.13 

18.9 22.8 26.7 

15.1 

1.14 

19.1 23.1 27.1 

15.3 19.3 

1.15 

23.4 21.4 

15.5 19.6 23.1 21.8 

1.16 15.7 19.8 

1.17 

24.0 28.2 

15.9 20.1 

1.18 

24.3 28.5 

16.1 20.3 

1.19 

24.6 28.9 

16.3 20.6 

1.20 

24.9 29.2 

16.5 20.8 25.2 29.6 
WATER MEASUREMENT STRUCTURES 277 

Table S-4.-Discharge of standard contracted rectangular weirs in cubic feet per second. 

Computed from the formula Q = 3.33 (L-0.2~~)/23’2.-Continued. 103-D-1245-3 

‘ead 

h, 

bet 

Length of weir, L, feet l4.0 5.0 6.0 7.0 

Head 

h, 

feet 

Length of weir, L, feet 

-- 

6.0 7.0 

-- 

1.21 16.7 21.1 25.5 30.0 1.71 42.1 49.6 

1.22 16.9 21.3 25.8 30.3 1.72 42.5 50.0 

1.23 17.1 21.6 26.1 30.7 1.73 42.8 50.4 

1.24 17.3 21.8 26.4 31.0 1.74 43.2 50.8 

1.25 17.5 22.1 26.8 31.4 1.75 43.6 51.3 

1.26 17.7 22.4 27.1 31.8 1.76 43.9 51.7 

1.27 17.9 22.6 27.4 32.2 1.77 44.3 52.1 

1.28 18.1 22.9 21.7 32.5 1.78 44.6 52.5 

1.29 18.3 23.1 28.0 32.9 1.79 45.0 53.0 

1.30 18.5 23.4 28.3 33.3 1.80 45.4 53.4 

1.31 

1.32 

1.33 

1.34 

1.35 

18.7 

18.9 

19.1 

23.7 28.6 33.6 1.81 45.7 53.8 

23.9 29.0 34.0 1.82 46.1 54.3 

24.2 29.3 34.4 1.83 46.4 54.7 

24.4 29.6 34.8 1.84 46.8 55.1 

24.7 29.9 35.2 1.85 47.2 55.6 

1.36 25.0 30.3 35.5 1.86 47.5 56.0 

1.37 25.2 30.6 35.9 1.87 47.9 56.4 

1.38 25.5 30.9 36.3 1.88 48.3 56.9 

1.39 25.8 31.2 36.7 1.89 48.6 57.3 

1.40 26.0 31.6 37.1 1.90 49.0 57.7 

1.41 26.3 31.9 37.5 1.91 49.4 58.2 

1.42 26.6 32.2 37.8 1.92 ,49.8 58.6 

1.43 26.8 32.5 38.2 1.93 50.1 59.0 

1.44 27.1 32.9 38.6 1.94 50.5 59.5 

1.45 27.4 33.2 39.0 1.95 50.9 59.9 

1.46 27.7 33.5 39.4 1.96 51.2 60.4 

1.47 27.9 33.9 39.8 1.97 51.6 60.8 

1.48 28.2 34.2 40.2 1.98 52.0 61.3 

1.49 28.5 34.5 40.6 1.99 52.4 61.7 

1.50 28.8 34.9 41.0 2.00 52.7 62.2 

1.51 29.0 35.2 41.4 2.01 62.6 

1.52 29.3 35.5 41.8 2.02 63.1 

1.53 29.6 35.9 42.2 2.03 63.5 

1.54 29.9 36.2 42.6 2.04 64.0 

1.55 30.1 36.6 43.0 2.05 64.4 

1.56 30.4 36.9 43.4 2.06 64.9 

1.57 30.7 37.2 43.8 2.07 65.3 

1.58 31.0 37.6 44.2 2.08 65.8 

1.59 31.3 37.9 44.6 2.09 66.2 

1.60 31.5 38.3 45.0 2.10 66.7 

1.61 31.8 38.6 45.4 2.11 67.1 

1.62 32.1 39.0 45.8 2.12 67.6 

1.63 32.4 39.3 46.2 2.13 68.1 

1.64 32.7 39.7 46.7 2.14 68.5 

1.65 33.0 40.0 47.1 2.15 69.0 

1.66 

1.67 

1.68 

1.69 

1.70 

33.2 40.4 41.5 

40.7 47.9 

41.1 48.3 

41.4 48.7 

41.8 49.2 

2.16 69.4 

2.17 69.9 
SMALL CANAL STRUCTURES 

Head 

h, 

feet 

Length of weir, L, ff :et 

8.0 9.0 10.0 12.0 15.0 18.0 20.0 

0.20 2.37 2.67 2.91 3.56 4.45 5.35 5.94 

.21 2.55 2.87 3.19 3.83 4.79 5.15 6.39 

.22 2.13 3.08 3.42 4.11 5.14 6.17 6.83 

.23 2.92 3.29 3.66 4.39 5.49 6.59 1.33 

.24 3.11 3.50 3.90 4.68 5.86 7.03 7.81 

.25 3.31 3.72 4.14 4.91 6.22 1.41 8.30 

.26 3.51 3.95 4.39 5.28 6.60 7.93 8.81 

.27 3.11 4.18 4.65 5.58 6.98 8.38 9.32 

.28 3.92 4.41 4.91 5.89 1.31 8.86 9.84 

.29 4.13 4.65 5.17 6.21 1.11 9.33 10.4 

.30 4.34 4.89 5.44 6.53 8.17 9.82 10.9 

.31 4.56 5.14 5.71 6.86 8.59 10.3 11.5 

.32 4.18 5.39 5.99 7.19 9.00 10.8 12.0 

.33 5.01 5.64 6.27 7.53 9.43 11.3 12.6 

.34 5.24 5.90 6.56 7.88 9.86 11.8 13.2 

.35 5.47 6.16 6.85 8.23 10.3 12.4 13.7 

.36 5.70 6.42 7.14 8.58 10.7 12.9 14.3 

.37 5.94 6.69 7.44 8.94 11.2 13.4 14.9 

.38 6.18 6.96 1.14 9.30 11.6 14.0 15.5 

.39 6.42 7.24 8.05 9.67 12.1 14.5 16.2 

.40 6.67 7.51 8.36 10.0 12.6 15.1 16.8 

.41 6.92 7.80 8.61 10.4 13.0 15.7 17.4 

.42 7.18 8.08 8.99 10.8 13.5 16.2 18.1 

.43 1.43 8.37 9.31 11.2 14.0 16.8 18.7 

.44 7.69 8.66 9.63 11.6 14.5 17.4 19.4 

.45 7.95 8.96 9.96 12.0 15.0 18.0 20.0 

.46 8.22 9.26 10.3 12.4 15.5 18.6 20.7 

.41 8.48 9.56 10.6 

.48 

12.8 16.0 19.2 21.4 

8.75 9.86 11.0 13.2 16.5 19.8 22.0 

.49 9.03 10.2 11.3 13.6 17.0 20.4 22.7 

.50 9.30 10.5 11.7 14.0 17.5 21.1 23.4 

Sl 9.58 10.8 12.0 14.4 18.1 21.1 24.1 

.52 9.86 11.1 12.4 14.9 18.6 22.3 24.8 

.53 10.1 11.4 12.7 15.3 19.1 23.0 25.6 

.54 10.4 11.8 13.1 15.7 19.7 23.6 26.3 

.55 10.7 12.1 13.4 16.2 20.2 24.3 27.0 

.56 11.0 12.4 13.8 16.6 20.8 25.0 27.8 

.57 11.3 12.7 14.2 17.0 21.3 25.6 28.5 

.58 11.6 13.1 14.5 17.5 21.9 26.3 29.2 

.59 11.9 13.4 14.9 17.9 22.5 21.0 30.0 

.60 12.2 13.7 15.3 18.4 23.0 27.7 30.8 

.61 12.5 14.1 15.7 18.8 23.6 28.4 31.5 

.62 12.8 14.4 16.1 19.3 24.2 29.1 32.3 

.63 13.1 14.8 16.4 19.8 24.8 29.8 33.1 

.64 13.4 15.1 16.8 20.2 25.4 30.5 33.9 

.65 13.7 15.5 17.2 20.1 25.9 31.2 34.1 

.66 14.0 15.8 17.6 21.2 26.5 31.9 35.5 

.61 14.4 16.2 18.0 21.7 27.1 32.6 36.3 

.68 14.7 16.6 18.4 22.2 21.8 33.4 37.1 

.69 15.0 16.9 18.8 22.6 28.4 34.1 37.9 

.I0 15.3 17.3 19.2 23.1 29.0 34.8 38.7 

Table 5-4.-Discharge of standard contracted rectangular weirs in cubic feet per second 

Computed from the formula Q = 3.33 (IA2h)h3’2.-Continued. 103-D-12454 
WATER MEASUREMENT STRUCTURES 

Table S-4.-Discharge of standard contracted rectangular weirs in cubic feet per second 

Computed from the formula Q = 3.33 (L-O. 2h)h3’*.-Continued. 103-D-1245-5 

279 

0.71 

.72 

.I3 

.I4 

.75 

.I6 

.77 

.78 

.I9 

.80 

.81 19.0 21.5 23.9 28.7 36.0 43.3 48.2 

.82 19.4 21.8 24.3 29.3 36.7 44.1 49.0 

.83 19.7 22.2 24.8 29.8 37.4 44.9 49.9 

.84 20.1 22.6 25.2 30.3 38.0 45.7 50.8 

.85 20.4 23.0 25.7 30.9 38.7 46.5 51.8 

.86 20.8 23.4 26.1 31.4 39.4 47.3 52.7 

.a7 21.1 23.8 26.6 32.0 40.1 48.2 53.6 

.a 21.5 24.3 27.0 32.5 40.7 es.0 54.5 

.89 21.9 24.7 21.5 33.1 41.4 49.8 55.4 

.90 22.2 25.1 27.9 33.6 42.1 50.7 56.4 

.91 22.6 25.5 28.4 34.2 42.8 51.5 57.3 

.92 23.0 25.9 28.8 34.7 43.5 52.4 58.2 

.93 23.3 26.3 29.3 35.3 44.2 53.2 59.2 

.94 23.7 26.7 29.9 36.0 45.1 54.2 60.3 

.95 24.1 27.2 30.2 36.4 45.7 54.9 61.1 

.96 24.5 27.6 30.7 37.0 46.4 55.8 62.0 

.91 24.8 28.0 31.2 37.6 47.1 56.6 63.0 

.98 25.2 28.4 31.7 38.1 47.8 57.5 64.0 

.99 25.6 28.9 32.2 38.7 48.6 58.4 65.0 

1.00 26.0 29.3 32.6 39.3 49.3 59.3 65.9 

1.01 26.4 29.8 33.1 39.9 50.0 60.2 66.9 

1.02 26.7 30.2 33.6 40.5 50.7 61.0 67.9 

1.03 27.1 30.6 34.1 41.0 51.5 61.9 68.9 

1.04 27.5 31.1 34.6 41.7 52.3 62.9 69.9 

1.05 27.9 31.5 35.1 42.2 53.0 63.7 70.9 

1.06 28.3 31.9 35.6 42.8 53.7 64.6 71.9 

1.07 28.7 32.4 36.1 43.4 54.5 65.6 72.9 

1.08 29.1 32.8 36.6 44.0 55.2 66.4 74.3 

1.09 29.5 33.3 37.1 44.6 56.0 67.4 75.0 

1.10 29.9 33.7 37.6 45.3 56.8 68.3 76.0 

1.11 30.3 34.2 38.1 45.9 57.6 69.3 17.1 

1.12 30.7 34.6 38.6 46.5 58.3 70.1 78.0 

1.13 31.1 35.1 39.1 47.1 59.1 71.1 79.1 

1.14 31.5 35.6 39.6 47.7 59.9 72.0 80.1 

1.15 31.9 36.0 40.1 48.3 60.6 73.0 81.2 

1.16 32.3 36.5 40.6 48.9 61.4 73.9 

1.17 32.7 36.9 41.2 49.6 62.3 74.9 

1.18 33.1 37.4 41.7 50.2 63.0 75.8 

1.19 33.6 37.9 42.2 50.8 63.8 76.8 

1.20 34.0 38.3 42.7 51.5 64.6 77.7 

15.7 17.6 19.6 

16.0 18.0 20.1 

16.3 18.4 20.5 

16.6 18.8 20.9 

17.0 19.1 21.3 

17.3 19.5 21.7 

17.7 19.9 22.2 

18.0 20.3 22.6 

18.3 20.7 23.0 

18.7 21.1 23.4 

Head Length of weir, L, feet 

h, . 

I I 

I I I 1 

feet 8.0 9.0 IO.0 : 12.0 15.0 18.0 

23.6 29.6 35.6 39.6 

24.1 30.2 36.3 40.4 

24.6 30.9 37.1 41.2 

25.1 31.5 37.8 42.1 

25.6 32.1 38.6 42.9 

26.1 32.8 39.4 43.8 

26.7 33.4 40.2 44.7 

27.2 34.1 40.9 45.5 

27.7 34.7 41.7 46.4 

28.2 35.4 42.5 47.3 

20.0 

82.2 

I 83.3 

84.4 

I 85.4 

I 86.5 
280 SMALL CANAL STRUCTURES 

Table 5-4.-Discharge of standard contracted rectangular weirs in cubic feet per second 

Computed from the formula Q = 3.33 (L-0.2h)h3’*.-Continued. 103-D-1245-6 

H;d 1 , , Length Of WieI,L, feet 

I 

feet 8.0 ! 9.0 ! 10.0 

1.21 I 34.4 I 38.8 I 43.2 

1.22 34.8 39.3 43.8 

44.3 

52.1 

52.8 

53.4 

65.4 

66.2 

67.0 

18.0 1 20.0 

78.7 I 87.6 

79.7 88.7 

1.23 35.2 39.8 80.6 89.7 

1.24 35.6 40.2 44.8 54.0 67.8 81.6 90.8 

1.25 36.1 40.7 45.4 54.7 68.7 82.6 91.9 

1.26 36.5 41.2 45.9 55.3 69.4 83.6 93.0 

12.0 15.0 

1.27 36.9 41.7 46.4 56.0 70.3 84.6 94.1 

1.28 37.3 42.2 47.0 56.6 71.1 85.6 95.2 

1.29 37.8 42.7 47.5 57.3 71.9 86.6 96.3 

1.30 38.2 43.1 48.1 57.9 72.7 87.5 97.4 

1.31 38.6 43.6 48.6 58.6 73.6 

1.32 39.1 44.1 49.2 59.3 74.4 

1.33 39.5 44.6 49.7 59.9 75.3 

1.34 39.9 45.1 50.3 60.6 76.1 

1.35 40.4 

I 

45.6 50.8 61.3 77.0 

1.36 40.8 46.1 51.4 61.9 77.8 

1.37 41.3 46.6 51.9 62.6 78.7 

1.38 41.7 47.1 52.5 63.3 79.5 

1.39 42.1 47.6 53.1 64.0 80.4 

1.40 42.6 48.1 53.6 64.7 81.2 

1.41 43.0 48.6 54.2 

1.42 43.5 

1.43 43.9 

I 

65.3 82.0 

49.1 54.7 66.0 82.9 

49.6 55.3 66.7 83.8 

1.44 44.4 50.1 55.9 67.4 84.7 

1.45 44.8 

I 

50.6 56.5 68.1 85.5 

88.5 

89.6 

90.6 

91.6 

92.6 

98.5 

99.7 

100.8 

93.6 

94.7 

95.7 

96.7 

97.8 

98.8 

99.8 

100.9 

1.46 45.3 51.2 57.0 68.8 86.4 

1.47 45.7 51.7 57.6 69.5 87.3 

1.48 46.2 52.2 58.2 70.2 88.2 

1.49 46.6 52.7 58.8 70.9 89.1 

1.50 47.1 53.2 59.3 71.6 89.9 

1.51 47.6 i 53.7 59.9 

1.52 48.0 54.3 60.5 

1.53 48.5 54.8 61.1 

1.54 49.0 55.3 61.7 

1.55 49.4 55.8 62.3 

1.56 1 49.9 I 56.4 62.8 I I I I 

1.57 50.3 56.9 63.4 

1.58 50.8 57.4 64.0 

1.59 51.3 58.0 64.6 

1.60 51.8 58.5 65.2 

1.61 52.2 59.0 65.8 

1.62 52.7 59.6 66.4 

1.63 53.2 60.1 67.0 

1.64 53.7 60.6 67.6 

1.65 54.1 61.2 68.3 

1.66 54.6 61.7 

1.67 55.1 62.3 

1.68 55.6 62.8 

1.69 56.1 63.4 

1.70 56.5 63.9 

68.9 

69.5 
I 

WATER MEASUREMENT 281 STRUCTURES 

~~~~~ 5-5,-Discharge of stm&wd Cipolletti weirs in cubic feet Per second. Values below and to 

the left of heavy lines determined experimentally; others computed from 

tile formula Q = 3.367 Lh312. 103-D-1246-1 

7 

:ad 

h, 

:et 

I.20 

.21 

.22 

.23 

‘24 

.25 

.26 

.21 

.28 

.2¶ 

.30 

.31 

.32 

.33 

.34 

.35 

.36 

.37 

.38 

.39 

.40 

.41 

.42 

.43 

.44 

.4.5 

.46 

.47 

.48 

.49 

.50 

.51 

.52 

.53 

.54 

.55 

.56 

.57 

.sa 

.59 

60 

.61 

.62 

.63 

.64 

.65 

.66 

.67 

.68 

.69 

.7O 

1.0 

0.30 

.32 

.35 

.37 

A0 

.42 

.45 

.47 

SO 

.53 

.55 

.58 

.61 

.64 

+- 

.I3 

.76 

.79 

.82 

.85 

.88 

.92 

.95 

.98 

1.02 

1.05 

1.08 

1.12 

1.16 

1.20 

Length 

2.0 3.0 

0.60 0.90 1.20 

.65 .9? 

.70 1.04 

.74 1.11 

.79 1.19 

.84 1.26 

1.30 

1.39 

1.48 

1.58 

1.68 

.89 1.34 

.94 1.42 

1.00 1.50 

1 .os 1.58 

1.11 1.66 

1.78 2.23 

1.89 2.36 

2.00 2.49 

2.10 2.63 

2.21 2.77 

1.16 1.74 

1.22 1.83 

1.28 1.92 

1.34 2.00 

1.39 2.09 

2.32 2.90 

2.44 3.05 

2.55 3.19 

2.67 3.34 

2.79 3.49 

1.45 2.18 

1.52 2.27 

1.58 2.37 

1.64 2.46 

1.70 2.56 

2.91 

3.03 

3.16 

3.28 

3.41 

1.77 2.65 3.54 

1.83 2.75 3.66 

1.90 2.85 3.80 

1.96 2.95 3.93 

2.03 3.05 4.06 

2.10 3.15 

2.17 3.25 

2.24 3.36 

2.31 3.46 

2.38 3.57 

4.20 5.25 

4.34 5.42 

4.48 5.60 

4.62 5.77 

4.76 5.95 

2.45 3.68 

2.52 3.79 

2.60 3.90 

2.67 4.01 

2.75 4.12 

4.90 6.13 

5.05 6.31 

5.20 6.50 

5.34 6.68 

5.49 6.87 

2.82 4.23 

2.90 4.35 

2.97 4.46 

3.05 4.58 

3.13 4.69 

5.64 7.05 

5.80 7.24 

5.95 7.44 

6.10 7.63 

6.26 7.82 

3.21 

3.29 

3.37 

3.45 

3.53 

4.81 6.42 

4.93 6.57 

5.05 6.73 

5.17 6.90 

5.29 7.06 

3.61 

--He 

3.90 

3.98 

5.42 

5.54 

5.66 

5.19 

5.92 

7.22 

7.38 

7.55 

7.72 

1.89 

5.0 

1.51 1.81 2.11 

1.62 1.94 

1.74 2.08 

1.86 2.23 

1.98 2.38 

2.10 2.53 

2.68 3.12 

2.83 3.31 

2.99 3.49 

3.15 3.68 

3.32 3.87 

3.49 4.07 

3.66 4.27 

3.83 4.47 

4.00 4.67 

4.18 4.88 

3.64 

3.79 

3.94 

4.10 

4.26 

4.36 5.09 

4.55 5.30 

4.73 5.52 

4.92 5.74 

5.11 5.96 

4.42 

4.58 

4.15 

4.91 

5.08 

5.30 6.19 

5.50 6.41 

5.70 6.65 

5.90 6.88 

6.10 7.11 

6.30 7.35 

6.51 7.59 

6.72 7.84 

6.93 8.08 

7.14 8.33 

7.36 

7.57 

7.79 

8.02 

8.24 

8.47 9.88 

8.69 10.1 

8.92 10.4 

9.15 10.7 

9.39 11.0 

8.02 9.62 

8.22 9.86 

8.42 10.1 

8.62 10.3 

8.82 10.6 

9.03 

9.23 

9.44 

9.65 

9.86 

10.8 

11.1 

11.3 

11.6 

11.8 

6.0 7.0 

2.27 

2.43 

2.60 

2.77 

2.95 

- 

8.58 

8.84 

9.09 

9.35 

9.61 

11.2 

11.5 

11.8 

12.1 

12.4 

12.6 

12.9 

13.2 

13.5 

13.8 
282 SMALL CANAL STRUCTURES 

Table 5-5.-Discharge of standard Cipolletti weirs in cubic feet per second. Values below and to 

the kft of heavy lines determined experimentally; others computed from the 

formula 0 = 3.367 Lh3”.-Continued. 103-D-1246-2 

Head 

h, 

feet 2.0 3.0 

Length of weir, L, feet 

4.0 5.0 6.0 7.0 

0.71 4.06 6.04 8.06 10.1 12.1 14.1 

.72 4.15 6.17 8.23 10.3 12.3 14.4 

.73 4.24 6.30 8.40 10.5 12.6 14.7 

.74 4.33 6.43 8.57 10.7 12.9 15.0 

.75 4.42 6.56 8.75 10.9 13.1 15.3 

.-'6 4.51 6.69 8.92 11.2 13.4 15.6 

.77 4.60 6.82 9.10 11.4 13.7 15.9 

.78 4.69 6.96 9.24 11.6 13.9 16.2 

.79 4.78 7.09 9.46 11.8 14.2 16.6 

.80 4.87 7.23 9.64 12.0 14.5 16.9 

.81 4.96 7.36 9.82 12.3 14.7 17.2 

.82 5 .os 7.50 10.0 i2.5 15.0 17.5 

.83 5.14 7.64 10.2 12.7 15.3 17.8 

.84 5.24 7.78 10.4 13.0 15.6 18.1 

.85 5.34 7.92 10.6 13.2 15.8 18.5 

.86 5.44 8.06 10.7 13.4 16.1 18.8 

.87 5.54 8.20 10.9 13.7 16.4 19.1 

.88 5.64 8.34 11.1 13.9 16.7 19.5 

.89 5.74 8.48 11.3 14.1 17.0 19.8 

.90 5.84 8.62 11.5 14.4 17.3 20.1 

.91 5.94 8.77 11.7 14.6 17.5 20.5 

.92 6.04 8.91 11.9 14.9 17.8 20.8 

.93 6.14 9.06 12.1 15.1 18.1 21.1 

.94 6.25 9.20 12.3 15.3 18.4 21.5 

.95 6.36 9.35 12.5 15.6 18.7 21.8 

.96 6.47 9.50 12.7 15.8 19.0 22.2 

.97 6.58 9.65 12.9 16.1 19.3 22.5 

.98 6.69 9.80 13.1 16.3 19.6 22.9 

.99 6.80 9.95 13.3 16.6 19.9 23.2 

1.00 6.91 10.1 13.5 16.8 20.2 23.6 

1.01 10.5 13.7 17.1 20.5 23.9 

1.02 10.6 13.9 17.3 20.8 24.3 

1.03 10.8 14.1 17.6 21.1 24.6 

1.04 10.9 14.3 17.9 21.4 25.0 

1.05 11.1 14.5 18.1 21.7 25.4 

1.06 11.3 14.7 18.4 22.1 25.7 

1.07 11.4 14.9 18.6 22.4 26.1 

1.08 11.6 15.1 18.9 22.7 26.5 

1.09 11.7 15.3 19.2 23.0 26.8 

1.10 11.9 15.5 19.4 23.3 27.2 

1.11 12.1 15.8 19.7 23.6 27.6 

1.12 12.2 16.0 20.0 23.9 27.9 

1.13 12.4 16.2 20.2 24.3 28.3 

1.14 12.5 16.4 20.5 24.6 28.7 

1.15 12.7 16.6 20.8 24.9 29.! 

1.16 12.9 16.8 21.0 25.2 29.4 

1.17 13.0 17.0 21.3 25.6 29.8 

1.18 13.2 17.3 21.6 25.9 30.2 

1.19 13.4 17.5 21.9 26.2 30.6 

1.20 13.6 17.7 22.1 26.6 31.0 
WATER MEASUREMENT STRUCTURES 

Table 5-5.-Discharge of standard Cipolletti weirs in cubic feet per second. Values computed 

from the formula Q = 3.367 Lh3’*.-Continued. 103-D-1246-3 

283 

Head 

k ’ 

feet 

1.21 

1.22 

1.23 

1.24 

1.25 

1.26 

1.27 

1.28 

1.29 

1.30 

1.31 

1.32 

1.33 

1.34 

1.35 

1.36 

1.37 

1.38 

1.39 

1.40 

1.41 

1.42 

1.43 

1.44 

1.45 

4.0 

17.9 

18.1 

18.4 

18.6 

18.8 

19.0 

19.3 

19.5 

19.7 

20.0 

20.2 

20.4 

20.7 

Length of weir, L, feet 

5.0 6.0 

22.4 26.9 

22.7 27.2 

23.0 27.6 

23.2 27.9 

23.5 28.2 

23.8 28.6 

24.1 28.9 

24.4 29.3 

24.7 29.6 

25.0 29.9 

25.2 30.3 

25.5 30.6 

25.8 31.0 

26.1 31.3 

26.4 31.7 

26.7 32.0 

27.0 32.4 

27.3 32.8 

27.6 33.1 

27.9 33.5 

28.2 33.8 

28.5 34.2 

28.8 34.5 

29.1 34.9 

29.4 35.3 

7.0 

31.4 

31.8 

32.2 

32.5 

32.9 

33.3 

33.7 

34.1 

34.5 

34.9 

35.3 

35.7 

36.2 

36.6 

37.0 

37.4 

37.8 

38.2 

38.6 

39.0 

39.5 

39.9 

40.3 

40.7 

41.2 

Head 

. h, - 

feet 

1.71 

1:72 

1.73 

1.74 

1.75 

1.76 

1.77 

1.78 

1.79 

1.80 

1.81 

1.82 

1.83 

1.84 

1.85 

1.86 

1.87 

1.88 

1.89 

1.90 

1.91 

1.92 

1.93 

1.94 

1.95 

Length of weir, L, feet 

6.0 7.0 

45.2 52.7 

45.6 53.2 

46.0 53.6 

46.4 54.1 

46.8 54.6 

47.2 55.0 

47.6 55.5 

48.0 56.0 

48.4 56.4 

48.8 56.9 

49.2 57.4 

49.6 57.9 

50.0 58.3 

50.4 58.8 

SO.8 59.3 

5 1.2 59.8 

51.7 60.3 

52.1 60.8 

52.5 61.2 

52.9 61.7 

53.3 62.2 

53.7 62.7 

54.2 63.2 

54.6 63.7 

55.0 64.2 

1.46 29.7 35.6 41.6 1.96 55.4 64.7 

1.47 30.0 36.0 42.0 1.97 55.9 65.2 

1.48 30.3 36.4 42.4 1.98 56.3 65.7 

1.49 30.6 36.7 42.9 1.99 56.7 66.2 

1.50 30.9 37.1 43.3 2.00 57.1 66.7 

1.51 31.2 37.5 43.7 2.01 67.2 

1.52 31.5 37.9 44.2 2.02 67.7 

1.53 31.8 38.2 44.6 2.03 68.2 

1.54 32.2 38.6 45.0 2.04 68.7 

1.55 32.5 39.0 45.5 2.05 69.2 

1.56 32.8 39.4 45.9 2.06 69.7 

1.57 33.1 39.7 46.4 2.07 70.2 

1.58 33.4 40.1 46.8 

1.59 33.8 40.5 47.3 

1.60 34.1 40.9 47.7 

1.61 34.4 41.3 48.1 

1.62 34.7 41.7 48.6 

1.63 35.0 42.0 49.0 

1.64 35.4 42.4 49.5 

1.65 35.7 42.8 50.0 

1.66 36.0 43.2 so.4 

1.67 43.6 so.9 

1.68 44.0 51.3 

1.69 44.4 51.8 

1.70 44.8 52.2 
284 SMALL CANAL STRUCTURES 

Head 

h, 

feet 

0.20 2.41 2.71 3.01 3.31 3.6J 3.91 4.22 

.21 2.59 2.92 3.24 3.56 3.89 4.21 4.54 

.22 2.78 3.13 3.47 3.82 4.17 4.52 4.86 

.23 2.97 3.34 3.71 4.09 4.46 4.83 5.20 

.24 3.17 3.56 3.96 4.35 4.75 5.15 5.54 

.25 3.37 3.79 4.21 4.63 5.05 5.47 5.89 

.26 3.51 4.02 4.46 4.91 5.36 5.80 6.25 

.21 3.18 4.25 4.72 5.20 5.67 6.14 6.61 

.28 3.99 4.49 4.99 5.49 5.99 6.49 6.98 

.29 4.21 4.13 5.26 5.78 6.31 6.84 7.36 

.30 4.43 4.98 5.53 6.09 6.64 7.19 7.75 

.31 4.65 5.23 5.81 6.39 6.97 7.55 8.14 

.32 4.88 5.48 6.09 6.70 7.31 7.92 8.53 

.33 5.11 5.14 6.38 7.02 1.66 8.30 8.94 

.34 5.34 6.01 6.68 1.34 8.01 8.68 9.35 

.35 5.58 6.27 6.97 7.61 8.37 9.06 9.76 

.36 5.82 6.54 7.21 8.00 8.73 9.45 10.2 

.37 6.06 6.82 7.58 8.34 9.09 9.85 10.6 

.38 6.31 7.10 7.89 8.68 9.46 10.3 11.0 

.39 6.56 7.38 8.20 9.02 9.84 10.7 11.5 

.40 6.81 1.61 8.52 9.31 10.2 11.1 11.9 

.41 1.01 7.95 8.84 9.12 10.6 11.5 12.4 

.42 7.33 8.25 9.16 10.1 11.0 11.9 12.8 

.43 1.59 8.54 9.49 10.4 11.4 12.3 13.3 

.44 1.86 8.84 9.83 10.8 11.8 12.8 13.8 

.45 8.13 9.15 10.2 11.2 12.2 13.2 14.2 

.46 8.40 9.45 10.5 11.6 12.6 13.7 14.7 

.41 8.68 9.76 10.9 11.9 13.0 14.1 15.2 

.48 8.96 10.1 11.2 12.3 13.4 14.6 15.7 

.49 9.24 10.4 11.6 12.7 13.9 15.0 16.2 

.50 9.52 10.7 11.9 13.1 14.3 15.6 16.7 

.51 9.81 11.0 12.3 13.5 14.7 15.9 17.2 

.52 10.1 11.4 12.6 13.9 15.2 16.4 17.7 

.53 10.4 11.7 13.0 14.3 15.6 16.9 18.2 

.54 10.7 12.0 13.4 14.7 16.0 17.4 18.7 

.55 11.0 12.4 13.7 15.1 16.5 17.9 19.2 

.56 11.3 12.7 14.1 15.5 16.9 18.3 19.8 

.51 11.6 13.0 14.5 15.9 17.4 18.8 20.3 

.58 11.9 13.4 14.9 16.4 17.9 19.3 20.8 

.59 12.2 13.7 15.3 16.8 18.3 19.8 21.4 

.60 12.5 14.1 15.7 17.2 18.8 20.3 21.9 

.61 12.8 14.4 16.0 17.7 19.3 20.9 22.5 

.62 13.2 14.8 16.4 18.1 19.7 21.4 23.0 

.63 13.5 15.2 16.8 18.5 20.2 21.9 23.6 

.64 13.8 15.5 17.2 19.0 20.7 22.4 24.1 

.65 14.1 15.9 17.6 19.4 21.2 22.9 24.1 

.66 14.4 16.3 18.1 19.9 21.7 23.5 25.3 

.61 14.8 16.6 18.5 20.3 22.2 24.0 25.9 

.68 15.1 17.0 18.9 20.8 22.7 24.5 26.4 

.69 15.4 17.4 19.3 21.2 23.2 25.1 27.0 

.I0 15.8 17.8 19.7 21.7 23.7 25.6 21.6 

Table 5-5.-Discharge of standard Cipolletti weirs in cubic feet per second. Values computed 

from the formula Q = 3.367 Lh312.-Continued. 103-D-1246-4 

Leneth of weir. L. feet 

8.0 

-- 

9.0 10.0 

-- 

11.0 12.0 13.0 14.0 
WATER MEASUREMENT STRUCTURES 285 

Head 

h, 

feet 

0.7 I 16.1 18.1 20.1 22.2 24.2 26.2 28.2 

.72 16.5 18.5 20.6 22.6 24.7 26.7 28.8 

.73 16.8 18.9 21.0 23.1 25.2 27.3 29.4 

.74 17.2 19.3 21.4 23.6 25.7 27.9 30.0 

.75 17.5 19.7 21.9 24.1 26.2 28.4 30.6 

.76 17.8 20.1 22.3 24.5 26.8 29.0 31.2 

.77 18.2 20.5 22.8 25.0 27.3 29.6 31.9 

.78 18.6 20.9 23.2 25.5 27.8 30.2 32.5 

.79 18.9 21.3 23.6 26.0 28.4 30.7 33.1 

.80 19.3 21.7 24.1 26.5 28.9 31.3 33.7 

.81 19.6 22.1 24.6 27.0 29.5 31.9 34.4 

.a2 20.0 22.5 25.0 27.5 30.0 32.5 35.0 

.83 20.4 22.9 25.5 28.0 30.6 33.1 35.6 

.a4 20.7 23.3 25.9 28.5 31.1 33.7 36.3 

.85 21.1 23.7 26.4 29.0 31.7 34.3 36.9 

.86 21.5 24.2 26.9 29.5 32.2 34.9 37.6 

.a7 21.9 24.6 27.3 30.1 32.8 35.5 38.3 

.88 22.2 25.0 27.8 30.6 33.4 36.1 38.9 

.a9 22.6 25.4 28.3 31.1 33.9 36.8 39.6 

.90 23.0 .25.9 28.8 31.6 34.5 37.4 40.3 

.91 23.4 26.3 29.2 32.2 35.1 38.0 40.9 

.92 23.8 26.7 29.7 32.7 35.7 38.6 41.6 

.93 24.2 27.2 30.2 33.2 36.2 39.3 42.3 

.94 24.6 27.6 30.7 33.8 36.8 39.9 43.0 

.95 24.9 28.1 31.2 34.3 37.4 40.5 43.7 

.96 25.3 28.5 31.7 34.8 38.0 41.2 44.3 

.97 25.7 29.0 32.2 35.4 38.6 41.8 45.0 

.98 26.1 29.4 32.7 35.9 39.2 42.5 45.7 

.99 26.5 29.9 33.2 36.5 39.8 43.1 46.4 

1.00 26.9 30.3 33:7 37.0 40.4 43.8 47.1 

1.01 27.3 30.8 34.2 37.6 41.0 44.4 47.9 

1.02 27.8 31.2 34.7 38.2 41.6 45.1 48.6 

1.03 28.2 31.7 35.2 38.7 42.2 45.8 49.3 

1.04 28.6 32.1 35.7 39.3 42.9 46.4 50.0 

1.05 29.0 32.6 36.2 39.9 43.5 47.1 50.7 

1.06 29.4 33.1 36.8 40.4 44.1 47.8 51.4 

1.07 29.8 33.5 37.3 41.0 44.7 48.5 52.2 

1.08 30.2 34.0 37.8 41.6 45.4 49.1 52.9 

1.09 30.6 34.5 38.3 42.2 46.0 49.8 53.6 

1.10 31.1 35.0 38.8 42.7 46.6 50.5 54.4 

1.11 31.5 35.4 39.4 43.3 47.3 51.2 55.1 

1.12 31.9 35.9 39.9 43.9 47.9 51.9 55.9 

1.13 32.4 36.4 40.4 44.5 48.5 52.6 56.6 

1.14 32.8 36.9 41.0 45.1 49.2 53.3 57.4 

1.15 33.2 37.4 41.5 45.7 49.8 54.0 58.1 

1.16 33.7 37.9 42.1 46.3 50.5 54.7 58.9 

1.17 34.1 38.4 42.6 46.9 51.1 55.4 59.7 

1.18 34.5 38.8 43.2 47.5 51.8 56.1 60.4 

1.19 35.0 39.3 43.7 48.1 52.5 56.8 61.2 

1.20 35.4 39.8 44.3 48.7 53.1 57.5 62.0 

Table 5-5.-Discharge of standard Cipolletti weirs in cubic feet per second. Values computed 

from the formula Q = 3.367 Lh312.-Continued. 103-D-1246-5 

r Length of weir, L, feet 

8.0 9.0 10.0 11.0 12.0 13.0 

-? 

14.0 
286 SMALL CANAL STRUCTURES 

Table S-5.-Discharge of standard Cipolletti weirs in cubic feet per second. Values computed 

from the formula Q = 3.367 Lh3’2.pContinued. 103-D-1246-6 

Head 

h, 

feet 

1.21 

1.22 

1.23 

1.24 

1.25 

35.9 40.3 44.8 49.3 53.8 

36.3 40.8 45.4 49.9 54.5 

36.7 41.3 45.9 50.5 55.1 

37.2 41.8 46.5 51.1 55.8 

37.6 42.4 47.1 51.8 56.5 

1.26 38.1 42.9 47.6 52.4 57.2 

1.27 38.6 43.4 48.2 53.0 57.8 

1.28 39.0 43.9 48.8 53.6 58.5 

1.29 39.5 44.4 49.3 54.3 59.2 

1.30 39.9 44.9 49.9 54.9 59.9 

1.31 40.4 45.4 

1.32 40.9 46.0 

1.33 41.3 46.5 

1.34 41.8 47.0 

1.35 42.2 47.5 

50.5 

51.1 

51.6 

52.2 

52.8 

55.5 60.6 

56.2 61.3 

56.8 62.0 

57.5 62.7 

58.1 63.4 

1.36 42.7 48.1 53.4 58.7 64.1 

1.37 43.2 48.6 54.0 59.4 64.8 

1.38 43.7 49.1 54.6 60.0 65.5 

1.39 44.1 49.7 55.2 60.7 66.2 

1.40 44.6 50.2 55.8 61.4 66.9 

1.41 45.1 50.7 56.4 62.0 67.7 

1.42 45.6 51.3 57.0 62.1 68.4 

1.43 46.1 51.8 57.6 63.3 69.1 

1.44 46.5 52.4 58.2 64.0 69.8 

1.45 47.0 52.9 58.8 64.7 70.6 

1.46 47.5 53.5 59.4 65.3 71.3 

1.47 48.0 54.0 60.0 66.0 72.0 

1.48 48.5 54.6 60.6 66.7 72.8 

1.49 49.0 55.1 61.2 61.4 73.5 

1.50 49.5 55.7 61.9 68.0 74.2 

1.51 50.0 56.2 62.5 

1.52 50.5 56.8 63.1 

1.53 51.0 57.3 63.7 

1.54 51.5 57.9 64.4 

1.55 52.0 58.5 65.0 

68.7 

69.4 

70.1 

1.56 52.5 59.0 65.6 

1.57 53.0 59.6 66.2 

1.58 53.5 60.2 66.9 

1.59 54.0 60.8 67.5 

1.60 54.5 61.3 68.1 

1.61 55.0 61.9 

1.62 55.5 62.5 

1.63 56.1 63.1 

1.64 56.6 63.6 

1.65 57.1 64.2 

1.66 57.6 64.8 

1.67 58.1 65.4 

1.68 58.7 66.0 

1.69 59.2 66.6 

1.70 59.7 67.2 

8.0 9.0 10.0 

68.8 

69.4 

70.1 

1 of weir. L. feet 

11.0 I 12.0 14.0 

62.7 

63.5 

64.3 

65.1 

65.9 

66.7 

61.5 

68.3 

69.1 

69.9 

70.7 

71.5 

72.3 

73.1 

73.9 

74.8 

15.6 

76.4 

77.3 

78.1 

78.9 

79.8 

80.6 

81.5 

82.3 

83.2 

84.0 

84.9 

85.7 

86.6 
VVA I tK IVltHSUKtlVltl’J I S I KUL I UKtS 

Table 5-5.-Discharge of standard Cipolletti weirs in cubic feet per second. Values computed 

from the formula Q = 3.367 Lh3”.-Continued. 103-D-1246-7 

Head 

h, 

feet 

Length of weir, L, feet 

15.0 16.0 

Head 

h, . 

feet 

Length of weir, L, feet 

15.0 16.0 

Head 

h, 

feet 

Length of weir, L, feet 

15.0 16.0 

0.20 4.52 4.82 0.71 30.2 32.2 1.21 67.2 71.7 

.72 30.9 32.9 1.22 68.1 7 2.6 

.21 4.86 5.18 .73 31.5 33.6 1.23 68.9 73.5 

.22 5.21 5.56 .74 32.2 34.3 1.24 69.7 74.4 

.23 5.57 5.94 .75 32.8 35.0 1.25 70.6 75.3 

.24 5.94 6.33 

.25 6.31 6.73 .76 33.5 35.7 1.26 71.4 76.2 

.77 34.1 36.4 1.27 72.3 77.1 

.26 6.70 7.14 .78 34.8 37.1 1.28 73.1 78.0 

.27 7.09 7.56 .79 35.5 37.8 1.29 74.0 78.9 

.28 7.48 7.98 .80 36.1 38.6 1.30 74.9 79.9 

.29 7.89 8.41 

.30 8.30 8.85 .81 36.8 39.3 1.31 75.7 80.8 

.82 37.5 40.0 1.32 76.6 81.7 

.31 8.72 9.30 .83 38.2 40.7 1.33 77.5 82.6 

.32 9.14 9.75 .84 38.9 41.5 1.34 78.3 83.6 

.33 9.57 10.2 .85 39.6 42.2 1.35 79.2 84.5 

.34 10.0 10.7 

.35 10.5 11.2 .86 40.3 43.0 1.36 80.1 85.4 

.87 41.0 43.7 1.37 81.0 86.4 

.36 10.9 11.6 .88 41.7 44.5 1.38 81.9 87.3 

.37 11.4 12.1 .89 42.4 45.2 1.39 82.8 88.3 

.38 11.8 12.6 .90 43.1 46.0 1.40 83.7 89.2 

.39 12.3 13.1 

.40 12.8 13.6 .91 43.8 46.8 1.41 84.6 90.2 

.92 44.6 47.5 1.42 85.5 91.2 

.41 13.3 14.1 .93 45.3 48.3 1.43 86.4 92.1 

.42 13.8 14.7 .94 46.0 49.1 1.44 87.3 93.1 

.43 14.2 15.2 .95 46.8 49.9 1.45 88.2 94.1 

.44 14.7 15.7 

.45 15.3 16.3 .96 47.5 50.7 1.46 89.1 95.0 

.97 48.3 51.5 1.47 90.0 96.0 

.46 15.8 16.8 .98 49.0 52.3 1.48 90.9 97.0 

.47 16.3 17.4 .99 49.8 53.1 1.49 91.9 98.0 

.48 16.8 17.9 1 .oo 50.5 5 3.9 1.50 92.8 99.0 

.49 17.3 18.5 

.50 17.9 19.1 1.01 51.3 54.7 

1.02 52.0 55.5 

.51 18.4 19.6 1.03 52.8 56.3 

.52 18.9 20.2 1.04 53.6 57.1 

.53 19.5 20.8 1.05 54.3 58.0 

.54 20.0 21.4 

.55 20.6 22.0 1.06 55.1 58.8 

1.07 55.9 59.6 

.56 21.2 22.6 1.08 56.7 60.5 

.57 21.7 23.2 1.09 57.5 61.3 

.58 22.3 23.8 1.10 58.3 62.2 

.59 22.9 24.4 

.60 23.5 25.0 1.11 59.1 63.0 

1.12 59.9 63.9 

.61 24.1 25.7 1.13 60.7 64.7 

.62 24.7 26.3 1.14 61.5 65.6 

.63 25.3 26.9 1.15 62.3 66.4 

.64 25.9 27.6 

.65 26.5 28.2 1.16 63.1 67.3 

1.17 63.9 68.2 

.66 27.1 28.9 1.18 64.7 69.1 

.67 27.7 29.5 1.19 65.6 69.9 

.68 28.3 30.2 1.20 66.4 70.8 

.69 29.0 30.9 

.70 29.6 31.6 
288 SMALL CANAL STRUCTURES 

Table M-Discharge of standard suppressed rectangular weirs in cubic feet per second. 

Computed from the formula Q = 3.33 I,h312. 103-D-1 241-l 

Head I Length of weir, L, in feet 

fezG 1.0 1.5 2.0 3.0 4.0 5.0 

I I I I I I 

0.20 0.30 0.45 0.60 0.89 1.19 1.49 

.21 .32 .48 .64 .96 

.22 .34 .52 .69 1.03 

.23 .31 .55 .74 1.10 

.24 .39 .59 .I8 1.18 

.25 .42 .62 .83 1.25 

1.28 1.60 

1.37 1.72 

1.41 1.84 

1.51 1.96 

1.67 2.08 

.26 .44 .66 .88 1.33 1.77 2.21 

.41 .I0 .93 1.40 1.87 2.34 

.49 .I4 .99 1.48 1.91 2.41 

.52 .I8 1.04 1.56 2.08 2.60 

.55 .82 1.09 1.64 2.19 2.14 

.21 

.28 

.29 

.30 

.31 

.32 

.33 

.34 

.35 

.58 

.60 

.63 

.66 

.86 1.15 1.12 

.90 1.21 1.81 

.95 1.26 1.89 

.99 1.32 1.98 

1.03 1.38 2.07 

2.30 

2.41 

2.53 

2.64 

2.16 

2.87 

3.01 

3.16 

3.30 

3.45 

.36 1.08 1.44 2.16 2.88 3.60 

.31 1.12 1.50 2.25 3.00 3.15 

.38 1.11 1.56 2.34 3.12 3.90 

.39 1.22 1.62 2.43 3.24 4.06 

.40 1.26 1.68 2.53 3.31 4.21 

.41 1.31 1.75 

.42 1.36 1.81 

.43 1.41 1.88 

.44 1.46 1.94 

.45 1.51 2.01 

2.62 

2.12 

2.82 

2.92 

3.02 

3.50 4.31 

3.63 4.53 

3.16 4.10 

3.89 4.86 

4.02 5.03 

.46 1.56 2.08 3.12 4.16 5.19 

.41 1.61 2.15 3.22 4.29 5.31 

.48 1.66 2.22 3.32 4.43 5.54 

.49 1.11 2.28 3.43 4.5 I 5.11 

SO 1.17 2.35 3.53 4.11 5.89 

.5 1 2.43 3.64 4.85 6.06 

.52 2.50 3.15 5.00 6.24 

.53 2.51 3.85 5.14 6.43 

.54 2.64 3.96 5.29 6.61 

.55 2.12 4.08 5.43 6.19 

.56 2.79 4.19 5.58 6.98 

.57 2.81 4.30 5.13 1.11 

.58 2.94 4.4 1 5.88 1.35 

.59 3.02 4.53 6.04 1.55 

.60 3.10 4.64 6.19 1.14 

.61 3.17 4.16 6.35 1.93 

.62 3.25 4.88 6.50 8.13 

.63 3.33 5.00 6.66 8.33 

.64 3.41 5.12 6.82 8.53 

.65 3.49 5.24 6.98 8.73 

.66 

.61 

.68 

.69 

.I0 

3.57 

3.65 

5.36 1.14 8.93 

5.48 1.31 9.13 

5.60 7.41 9.34 

5.73 7.63 9.54 

5.85 7.80 9.15 
WATER MEASUREMENT STRUCTURES 289 

h, 

feet 

0.71 5.98 

.72 6.10 

.73 6.23 

.74 6.36 

.75 6.49 

.76 6.62 

.77 6.75 

.78 6.88 

.79 7.02 

.80 7.15 

.81 7.28 

.82 7.42 

.83 7.55 

.a4 7.69 

.a5 7.83 

.86 7.97 10.6 13.3 1.36 26.4 

.a7 8.11 10.8 13.5 1.37 26.7 

.aa 8.25 11.0 13.8 1.38 27.0 

.a9 8.39 11.2 14.0 1.39 27.3 

.90 8.53 11.4 14.2 1.40 27.6 

.91 8.67 11.6 14.5 1.41 

.92 8.82 11.8 14.7 1.42 

.93 8.96 11.9 14.9 1.43 

.94 9.10 12.1 15.2 1.44 

.95 9.25 12.3 15.4 1.45 

.96 9.40 12.5 15.7 1.46 

.97 9.54 12.7 15.9 1.47 

.98 9.69 12.9 16.2 1.48 

.99 9.84 13.1 16.4 1.49 

1.00 9.99 13.3 16.7 1.50 

1.01 

1.02 

1.03 

1.04 

1.05 

13.5 16.9 

13.7 17.2 

13.9 17.4 

14.1 17.7 

14.3 17.9 

14.5 18.2 

14.7 18.4 

14.9 18.7 

15.2 19.0 

15.4 19.2 

1.51 

1.52 

1.53 

1.54 

1.55 

1.06 

1.07 

1.08 

1.09 

1.10 

1.11 

1.12 

1.13 

1.14 

1.15 

1.16 

1.17 

1.18 

1.19 

1.20 

Table M-Discharge of standard suppressed rectangular weirs in cubic feet per second 

Computed from the formula Q = 3.33 Lh3’2.-Continued. 103-D-1247-2 

Length of weir, L, in feet 

3.0 4.0 5.0 

7.91 9.96 

8.14 10.2 

8.31 10.4 

8.48 10.6 

8.65 10.8 

8.83 11.0 

9.00 11.3 

9.18 11.5 

9.35 11.7 

9.53 11.9 

9.71 12.1 

9.89 12.4 

10.1 12.6 

10.3 12.8 

10.4 13.1 

15.6 19.5 

15.8 19.7 

16.0 20.0 

16.2 20.3 

16.4 20.5 

16.6 20.8 

16.9 21.1 

17.1 21.3 

17.3 21.6 

17.5 21.9 

Head 

h, 

feet 

1.21 

1.22 

1.23 

1.24 

1.25 

1.26 

1.27 

1.28 

1.29 

1.30 

1.31 

1.32 

1.33 

1.34 

1.35 

1.56 

1.57 

1.5’8 

1.59 

1.60 

1.61 

1.62 

1.63 

1.64 

1.65 

1.66 

Length of weir, I,, in feel 

18.8 

I 

23.6 

19.1 23.8 

19.3 24.1 

19.5 24.4 

19.7 24.7 

20.0 25.0 

20.2 25.3 

20.4 25.5 

25.8 

26.1 
290 SMALL CANAL STRUCTURES 

Table 5-7.-Discharge of 90° V-notch weirs in cubic feet per second. 

Computed from the formula Q = 2.49h2’48. 103-D-1248 

Head 

h, 

feet 

Discharge, 

cfs 

Head 

h, 

feet 

Discharge, 

cfs 

Head 

h, 

feet 

Discharge, 

cfs 

0.20 0.04 0.55 0.56 0.90 1.92 

.21 .05 .56 .59 .91 1.97 

.22 .06 .57 .62 .92 2.02 

.23 .06 .58 .64 .93 2.08 

.24 .07 .59 .67 .94 2.13 

.25 .08 .60 .70 .95 2.19 

.26 .09 .61 .73 .96 2.25 

.27 .lO .62 .76 .97 2.31 

.28 .ll .63 .79 .98 2.37 

.29 .12 .64 .82 .99 2.43 

.30 .13 .65 .85 1 .oo 2.49 

.31 .14 .66 .89 1.01 2.55 

.32 .15 .67 .92 1.02 2.61 

.33 .16 .68 .96 1.03 2.68 

.34 .17 .69 .99 1.04 2.14 

.35 .18 .70 1.03 1.05 2.81 

.36 .20 .71 1.06 1.06 2.87 

.37 .21 .72 1.10 1.07 2.94 

.38 .23 .73 1.14 1.08 3.01 

.39 .24 .74 1.18 1.09 1.08 

.40 .26 .75 1.22 1.10 3.15 

.41 .27 .76 1.26 1.11 3.22 

.42 .29 .77 1.30 1.12 3.30 

.43 .31 .I8 1.34 1.13 3.37 

.44 .32 .79 1.39 1.14 3.44 

.45 .34 .80 1.43 1.15 3.52 

.46 .36 .81 1.48 1.16 3.59 

.47 .38 .82 1.52 1.17 3.67 

.48 .40 .83 1.57 1.18 3.75 

.49 .42 .84 1.61 1.19 3.83 

.50 .45 .85 1.66 1.20 3.91 

.51 .47 .86 1.71 1.21 3.99 

.52 .49 .81 1.76 1.22 4.07 

.53 .52 .88 1.81 1.23 4.16 

.54 .54 .89 1.86 1.24 4.24 

1.25 4.33 
WATER MEASUREMENT STRUCTURES 291

F. WEIR BOXES

5-22. Purpose and Description. -Weir boxes

are small structures used in combination with

pipe turnouts (fig. 5-26) to dissipate excess

energy and measure rate of flow of water to

laterals or farm turnouts. Three-foot weir

boxes developed by Reclamation have been

successfully used for a number of years. They

are equipped with 3-foot suppressed

rectangular weirs and are capable of measuring

flows up to 5 cfs with effective heads up to 6

feet on the control gate. These structures are

economical to build, easy to operate and have

proven to be an accurate and reliable method

of measuring small flows. Recently a 4-foot

weir box was developed and calibrated by

Reclamation. The box is capable of measuring

flows up to about 12 cfs with effective heads

of 6 feet on the control gate. In both of these

structures, the water passes from the canal

through a gated turnout, into a short length of

pipe, and through a system of baffles into the

weir box. Although the baffle arrangement in

the 3-foot weir box is different from that in

the 4-foot weir box, both baffle assemblies

dissipate excess energy and distribute the

inflow from the pipe so that the water surface

in the weir pool is smooth and free from

turbulence as it passes over the weir.

5- 23. Design Considerations. -(a) Head

Discharge Relationship. -Figures 5-27 and 5-28

are design drawings for 3- and 4-foot weir

boxes respectively. Examination of these

drawings show that the weir pool dimensions

and the placement of the weir gage do not

conform to the standard conditions given in

subchapter E for sta.ndard weirs. Therefore, the

Figure 5-26. Longitudinal section turnout and weir

box. PX-D-31417

standard discharge equation for rectangular

weirs is not applicable to weir boxes. The

discharges for various heads are given on the

design drawings. These discharges were

determined from full-scale model studies

conducted in Reclamation's Hydraulic

Laboratory in Denver, CO. [ 4] [ 5] .

(b) Head Losses. -The inlet loss to the pipe

is 0.5 of the velocity head in the pipe with the

slide gate fully opened. The pipe loss is

controlled by the pipe diameter, length of pipe,

and discharge. Normally the pipe should be

sized so that the water velocity in the full pipe

at the entrance to the box does not exceed

about 4 feet per second. The loss through the

pipe outlet, baffle assembly, and into the

stilling well vary with the discharge. In the

4-foot weir box, the loss varies uniformly as

shown in figure 5-29 from 0.045 foot for a

discharge of 3 cfs to 0.33 foot for a discharge

of 12.4 cfs. No figures are available on the

losses through the 3-foot weir box baffle

assembly, however, experience indicates that

for a flow of 5 cfs the head loss through the

baffle assembly and stilling pool is about 0.15

foot.

The following example problem gives a

procedure for selecting and setting a weir box.

5-24. Design Example. -For this example,

assume that water is to be turned out from a

canal to a lateral through a turnout with a weir

box as shown in figure 5-28. The control water

surface in the canal is assumed to be at

elevation 103.00. The delivery water surface

elevation required in the lateral is elevation

101.35. The normal water depth in the lateral

is 1.0 foot. Assume the length of pipe between

the turnout gate and the weir box is 50 feet.

Further assume that there is one 5° mitered

bend in the pipe. Then, select and set a weir

box at th~ downstream end of the turnout to

measure a flow of 9 cfs.

(a) Solution. -From the con tinuity

equation, Q = V 1 Al = V 2 A2 , find the area of

pipe to satisfy the allowable velocity of 4 feet

per second in the pipe.

Q=VA

A = 9/4

A = 2.25 square feet
SMALL CANAL STRUCTURES 

PreCo5f CDnCrPfP 

PreliUrP pipe 

O”d f,OLv 

LONG,T”O,NAL SECTION i”o,ome,er hoie 

APLAN OF BAFFLE ASSEMBLY 

AN0 ST,LLING WELL 

-, SECTlON A-d SECTlON 8-B 

DETAIL B 

ESTlMATCO C)UANTIT,ES 

/Weir bar, 

Figure 5-27, Three-foot weir box. 103-D-1249 
WATER MEASUREMENT STRUCTURES 293 

iier,--. 

\ 

i_’ 

Figure 5-28. Four-foot weir box. 103-D-1250 
294 

Then from table 8-l select a 

2 l-inch-diameter pipe which has more than 

adequate pipe area. The mean velocity of water 

in the pipe, V, velocity head, h,, and the 

friction loss per 1,000 feet of pipe, H, can also 

be read from table 8-1 after the pipe diameter 

has been determined as shown above. 

Pipe inlet loss = 0.5 h, = 0.5 (0.22) 

= 0.11 foot 

and the pipe loss = loo0 H(L)= S(50) 

= 0.16 foot 

From figure 8-1, Loss Coefficients for Pipe 

Bends, the loss coefficient (<) for a single angle 

miter bend of 5’ is 0.013. The bend loss is 

then: 

Bend loss = 0.013 h, = 0.013 (0.22) 

= about 0.003 foot 

Since the bend loss is so small, it can be 

neglected for this problem. 

The pipe outlet loss and the baffle assembly 

loss are determined from figure 5-29. With a 

discharge of 9 cfs, the pipe outlet loss and 

baffle assembly loss is 0.15 foot. From the 

discharge table on the weir box drawing, figure 

5-28, a 4foot weir box will measure a flow of 

9 cfs with 0.74 foot of head on the weir. The 

total head loss from the canal to the weir is the 

sum of the pipe inlet loss, pipe loss, baffle 

assembly loss, bend loss if any, and the head on 

the weir. Therefore 

H, =0.11+0.16+0.15+0.74 

H, = 1.16 feet 

The maximum elevation of the weir crest is: 

El. weir crest = 103.00 - 1.16 

= 101.84 feet 

then: 

El. K (fig. 5-28) 

= El. weir crest - weir height 

El. K = 101.84 - 2.58 = 99.26 feet 

SMALL CANAL STRUCTURES 

i 

a Fbintsbemge) 

ii?’ 14 

Sid~skwerbge) 

Water surface 

differential 

0.01 - I//” I 

0 2 4 6 6 IO 12 14 

DISCHARGE, cfs 

Figure 5-29. Water surface drop and total head loss 

across baffles and weir gage stilling well of 4-foot 

weir box. 103-D-1251 

Since the delivery water surface (DWS) 

elevation required in the lateral was 101.35, 

and the normal depth in the lateral was 1.0 

foot, set the invert of the lateral at elevation 

100.35. In this problem the DWS could have 

been as high as 101.59 without submerging the 

weir. 

Always set the crest of the weir at least 0.25 

foot above the downstream water surface to 

prevent submergence and to assure air 

circulation under the nappe of the weir. 

If the differential head between the control 

water surface in the canal and the water surface 

in the weir box exceeds the head loss through 

the structure, the turnout gate can be partially 

closed to obtain the appropriate water surface 

elevation in the weir box for the desired 

discharge. 
WATER MEASUREMENT STRUCTURES

G. OPEN-FlOW METERS

295

velocity of the water is less than abou t 1.5 feet

per second. For velocities exceeding 8 feet per

second, standard meter bearings require

excessive maintenance. Heavy-duty meters are

usually used for velocities greater than 8 feet

per second.

(b) Requirements for Accurate Flow

Measurement.-When used properly, the

propeller should always be submerged and the

conduit should be flowing full. To provide for

this requirement, stoplog guides are included in

the outlet transition as shown on figure 5-31 to

accommodate placing stoplogs when required

to force the conduit to flow full.

The propeller should be suspended so that

the propeller hub is in the center of the

conduit which can be either rectangular or

round. A slight eccentricity or misalinement of

the propeller will affect measurement accuracy.

Therefore, anchor bolts for the mounting

bracket must be located very accurately (fig.

3-23).

Propeller meters are very sensitive to spiral

flow, and large measurement errors result from

this condition. Flow straightening vanes,

several pipe diameters in length, installed a

short distance upstream of the propeller will

reduce the measurement errors caused by spiral

flow. Straightening vanes are not required if a

straight level section of pipe, as recommended

by the meter manufacturer, is used

immediately upstream from the meter location.

(c) Size Determination. -The selection of

the size of the meter is a very important design

consideration. Many meters have been taken

out of service because they were too large to

accurately measure the average day-to-day

flows. If possible, a meter that measures flow

in the midrange of its capability should be

selected. Meter propeller diameters generally

range f;:om 0.5 to 0.8 of the pipe diameter.

Laboratory tests show that the best accuracy is

obtained when the propeller diameter is 75

percent or more of the pipe diameter .

( d) Head Loss. -The head loss across a

propeller-type meter is usually considered to be

negligible; however, some allowance for loss

should be included in the design, particularly if

head is a critical consideration. The meter

5-25. Purpose and Description. -Open-flow

meters are propeller-type meters which may be

installed at the ends of gravity pipe turnouts as

shown in figures 5-30 and 5-31, to measure and

record the rate of flow of water. The

multibladed, conical propeller is rotated by the

energy of the moving water. The rotation of

the propeller actuates a register which totals

the flow and gives a direct volumetric reading

in gallons, cubic feet, acre-feet, or in any other

desired units common to water measurement.

Some meters not only totalize the flow but

give an instantaneous discharge reading in

desired units on a dial, similar to a speedometer

in an automobile.

Open-flow meters are commercially available

for pipe diameters ranging from 4 to 72 inches.

The meter size is designated according to the

diameter of the conduit where it will be used.

Thus, a 24-inch meter would be used in a

24-inch-diameter pipe.

Open-flow meters have a reasonably accurate

measurement range of about 1 to 10, that is,

the meter can measure and total flows up to 10

times the minimum flow. They are generally

accurate to plus or minus 2 to 5 percent of the

actual discharge. Some manufacturers

guarantee accuracy to 2 percent of the true

flow for all flows above the minimum specified

rate.

5-26 Design Considerations.-(a) Velocity. -Open-flow meters provide accurate

measurement for flow velocities of 0.5 to 17

feet per second; however, measurement

accuracy is likely to be affected when the

Figure 5-30. Artist sketch of turnout with open-flow

meter attached. PX-D-31428
296 SMALL CANAL STRUCTURES 

Anchor bolts and brackets 

,nsta,,olm” for open flow 

PLAN 

‘No protect!on for Form Tur 

SECTION A-A 

f’l0 Xb’Plpe 

DETAIL A 

SECTION B-B 

Figure 5-31. Outlet transition for open-flow meter. 

103-D-1252 

manufacturer can usually provide meter head 

loss information. 

5-27. Advantages. -Portability of a meter 

permits the user to measure flows at several 

turnouts which have the same pipe diameters 

or turnouts having different pipe diameters if 

the meter is specially equipped with a 

removable register and change gears. Flow rate 

and volume can be read directly thus 

eliminating computations. As previously 

mentioned, these meters have a flow range in 

excess of 10 to 1 above the minimum flow and 

the head loss is very small. 

S-28. Disadvantages. -Initial cost of an 

open-flow meter is usually relatively high. 

Maintenance costs may also be high, 

particularly if the meter is used in water that 

contains appreciable sediment. The sediment 

causes the bearings to wear and this becomes a 

problem unless a well-planned maintenance 

program is followed. Meters should be 

inspected and serviced at regular intervals as 

corrosion and wear may affect the calibration. 

Although the propellers are designed to pass 

some weeds and debris, there is a limit to the 

amount that can pass without clogging or 

affecting the water measurement. 

Spiral flow, air in the line, or any other 

factor that affects the rate of propeller rotation 

affects the measurement. Practically all 
WATER MEASUREMENT STRUCTURES 297 

conditions which affect the propeller rotation and result in underregistration. 

rate reduce the number of propeller revolutions 

H. BIBLIOGRAPHY 

S-29. Bibliography. Structures”-Part 2 Parshall Flumes, Utah State 

[1] Water Measurement Manual, Bureau of Reclamation, 

University, Logan, Utah, 1967. 

Second Edition, 1967, Revised Reprint, 1974. 

[4] Simmons, W. P., Case, W. C., “Hydraulic Model Studies of 

Small Weir Box Turnout Structures for General 

[2] Water Measurement Procedures, Report No. Hyd-577, Irrigation Use” Hyd-396, Bureau of Reclamation, 1954. 

Bureau of Re clamation, 1967. 

[3] Skogerboe, V. B., Hyatt, M. L., “Design and Calibration 

[5] Palde, U. J., “Hydraulic Laboratory Studies of a 4-foot 

of Submerged Open Channel Flow Measurement 

Weir Box Turnout Structure for Irrigation 

Use”-REC-ERC-72-31, Bureau of Reclamation, 1972. 

<<Chapter VI 

Energy Dissipators 

A. GENERAL 

6-l. Energy Dissipators. -Energy dissipators 

are used to dissipate excess kinetic energy 

possessed by flowing water. This energy or 

velocity head is acquired by the water where 

the velocity is high, such as in a chute or drop 

and energy dissipators are incorporated into 

the design of these structures. An effective 

energy dissipator must be able to retard the 

flow of fast moving water without damage to 

the structure or to the channel below the 

strut ture. 

Impact-type energy dissipators direct the 

water into an obstruction that diverts the flow 

in all directions and in this manner dissipates 

the energy in the flow. In some structures the 

flow plunges into a pool of water where the 

energy is diffused. Check drops and vertical 

drops (chapter III C), baffled outlets, baffled 

aprons, and vertical stilling wells are all 

impact-type energy dissipators. The use of a 

vertical drop in combination with an overchute 

is shown in chapter IV C. 

Other energy dissipators use the hydraulic 

jump to dissipate excess head. In this type of 

structure water flowing at a higher than critical 

velocity is forced into a hydraulic jump and 

energy is dissipated in the resulting turbulence. 

Stilling pools (chapter II F) contain the 

turbulent water until it can be discharged into 

the downstream channel without damage to 

the channel. The sumped pipe drop (chapter II 

E) is a closed conduit drop in which the 

hydraulic jump occurs within the pipe. 

The impact-type of energy dissipator is 

considered to be more efficient than the 

hydraulic jump type. Generally, the use of an 

impact-type energy dissipator results in smaller 

and more economical structures. 

The design of energy dissipators has been the 

subject of many model studies and the designs 

recommended for this type of structure are 

based primarily on empirical data resulting 

from these studies. The studies continue in an 

attempt to develop more effective and more 

economical energy dissipators. 

6. BAFFLED APRON DROPS 

R. B. HAYES’ 

6-2. General. -(a) Usage. -Baffled apron in grade. Energy dissipation occurs as the water 

drops are used in canals or wasteway channels flows over the concrete baffle blocks, which 

to provide dissipation of excess energy at drops are located along the floor of the chute. The 

ability of the baffled apron drop to 

‘Civil Engineer, Hydraulic Structures Branch, Bureau of accommodate a widely fluctuating tailwater 

Reclamation. elevation makes it especially suitable as an 

299 
300 SMALL CANAL STRUCTURES

deliveries, and where the upstream channel is

sufficiently stable to withstand (without

erosion) the higher velocities associated with

water surface drawdown. To minimize

splashing as the flow strikes the first row of

baffle blocks, an invert curve may be

provided to allow the flow to strike the

blocks in a direction normal to their

upstream face. Where flows are infrequent,

and some splashing is permissible, the curve

is sometimes omitted, as shown in figure

6-2B.

(c) Miscellaneous Features. -

( 1) Bridge deck. -Where a crossing is

required, a bridge deck may be incorporated

in the inlet design.

( 2) Cutoff walls and wingwalls. -In

addition to the inlet cutoff walls, wingwalls

are provided at, or near the downstream end

of the structure, to decrease percolation and

to retain the backfill along the slope. Where

the downstream channel is subject to

degradation, a cutoff wall is extended down

energy dissipator at the end of a canal or

wasteway that discharges into a reseIVoir. The

length of the baffled apron does not affect the

efficacy of the structure. It is effective in

dissipating excess energy for drops of any

magnitude (see fig. 6-1), but it becomes

uneconomical for large flows with great drops,

due to the wide section and numerous blocks

required. Where an excess of trash, trees, or

tumbleweeds accompanies the flow, they may

become lodged in the baffle blocks, restricting

the flow. Removal of this material is sometimes

difficult.

(b) Inlet Control Features.-Various types

of inlet control features are utilized to

maintain an upstream water surface as required

for turnouts; or to provide a velocity of

approach consistent with the scouring

tolerance of the upstream section; or to avoid

the excessive splashing that would result from

supercritical flow at the inlet. The more

common types of inlet control features are as

follows:

( 1) Sill control. -A sill may be provided

at the inlet, as shown in figure 6-2A, to

reduce the velocity of approach, and

minimize scour in the upstream section. The

sill also provides a controlled water surface

for upstream turnouts. To permit complete

drainage of the upstream pool, a slot is

provided through the crest, as shown in

figure 6-5. The inlet should be kept free of

sediment deposits, as the extensive

accumulation of sediment would allow the

flow to sweep over the sill at a velocity too

fast for effective dissipation of energy.

(2) Control notch.-A control notch may

be provided at the inlet, as shown in figures

6-28 and 6-3, to control the upstream water

depth. While the control notch is designed to

maintain normal depth and velocity in the

upstream section, it produces a fast velocity

in the inlet itself, causing splashing as the

fast velocity flow strikes the first row of

baffle blocks. Excessive splashing may

require frequent maintenance of the erosion

protection. The control notch should be

kept free of trash.

(3) Inlet without control. -The simplest

type of inlet (shown in fig. 6-2C) is used

where there is not a requirement to control

the upstream water surface for turnout

Figure 6-1. Baffled apron drop before backfilling.

P-328-701-9501
ENERGY DISSIPATORS 301

Figure 6-4. Baffled apron drop with wingwalls located

upstream from the outlet end. P-492-701-IIO2A

-0-

(Curve

optionol }

C. NO UPSTREAM CONTROL

Figure 6-2. Typical inlet types. IO3-D-1334

which should be located above the tailwater

elevation to minimize erosion.

(3) Protective drains. -Protective drains

are sometimes provided under the invert of

the baffled apron drop to relieve the uplift

pressure following the termination of flow.

6-3. Design Considerations. -(a) General. -

For consideration of the baffled apron drop to

provide dissipation of the excess energy at a

wasteway turnout, see subsection 4-2(b)

Wasteway Outlets. For the application of

baffled apron drops to cross-drainage

structures, see subchapter IV C.

(b) Capacity. -The capacity of the baffled

apron drop is a function of the allowable

discharge, q, per foot of width, as shown in

table 6-1. They have been operated for short

periods at about twice the design capacity

without excessive erosion.

Table 6-1.-Recommended discharge

Figure 6-3. Baffled apron drop with inlet control

notches. PX-D-72607

from the invert, as shown in figure 6-5. The

wingwalls may be located at the end of the

structure to coincide with the cutoff, but

they are often located a few feet upstream

from the end as shown in figure 6-4. This

provides a better stilling action at the outlet,

and raises the top elevation of the wingwall,

*Discharge per foot of width, q should be interpolated

within the range indicated.

(c) Inlet.- The inlet should be the same

width as the baffled apron, and should provide
302 

a velocity of approach slower than the critical 

velocity, V,. Where splashing must be 

minimized [ 1 ] ,* the entrance velocity should 

V 

not exceed about >, where 

2 

SMALL CANAL STRUCTURES 

[ I]. This is assured by limiting the radius of 

curvature to a maximum of 9 feet. A 6-foot 

radius is frequently used. The sill has a 

6-inch-wide slot to provide drainage of the 

upstream pool. 

(2) Control notch.-A control notch, 

where used, should conform to the design 

requirements of subchapter III G. The 

rectangular inlet section should begin 5 feet 

upstream from the control notch, and the 

length between the notch and the sill should 

be equal to three times the upstream water 

depth, as shown in figure 6-2B, to permit the 

flow to spread to the full width of the 

section. 

(d) Baffled Apron Dimensions (see fig. 

h-5).-The following steps are suggested as a 

guide to be used in setting the dimensions [2] : 

(1) Set the longitudinal slope of the 

chute floor and sidewalls at 2 to 1 (tan @ = 

0.5). 

(2) Approximate width of structure 

should be set by the relation, 

v, = 4% 

in the rectangular inlet section. Other design 

considerations are as follows: 

(1) Sill control.-The inlet length should 

be at least 2d, , as shown in figure 6-2A. The 

required height of the sill above the inlet 

floor may be determined from the energy 

balance between the inlet and the upstream 

channel. 

Thus. 

Es1 =E, 

c +hi+h, 

or 

k = Es, - Esc - hi 

where 

h, is the sill height, 

E,, = d, + hvl in the upstream channel, 

EsC = d, + hvC in the control section 

at the sill, 

and 

hi = 0.5nh, 

= 0.5 (h”, - h,i ) 

vc2 VI2 =“.5 [ -.-2g 22 1

The curvature of the sill crest should 

terminate at its point of tangency with the 

slope of the downstream apron (see subset. 

6-4(b)(7)). This point should not be more 

than 12 inches in elevation below the crest 

*Numbers in brackets refer to references in bibliography, 

see sec. 6-14. 

B=Q 

9 

where 

B = width, 

Q = maximum total discharge, and 

q = allowable discharge per foot of 

width (see table 6-l). 

For the permissible entrance velocity, see 

subsection 6-3(c). 

(3) Set the first row of baffles so that the 

base of the upstream face is at the 

downstream end of the invert curve and no 

more than 12 inches in elevation below the 

crest. 

(4) Baffle block height, h,, should be 

about 0.9 times critical depth, d,, to nearest 

inch. 

(5) Baffle block widths and spaces should 

be equal, and not less than h,,, but not more 

than l-1/2 h,. Partial blocks, having a width 

not less than l/3 h, and not more than 2/3 

h, should be placed against the sidewalls in 

rows 1, 3, 5, 7, etc. Alternate rows of baffle 

blocks should be staggered so that each 

block is downstream from a space in the 
ENERGY DISSIPATORS 303 

adjacent row. The structure width, B, 

determined above, should be adjusted so 

convenient baffle block widths can be used. 

(6) The slope distance, s, between rows 

of baffle blocks, as shown in figure 6-5, 

should be at least 2 h, , but no greater than 6 

feet. A spacing of 6 feet may be used for all 

blocks equal to or less than 3 feet in height. 

(7) A minimum of four rows of baffle 

blocks should be used. The baffled apron 

should be extended so that the top of at 

least one row of baffle blocks will be below 

the bottom grade of the outlet channel as 

discussed in subsection 6-3(g). The apron 

should be extended beyond the last row of 

blocks a distance equal to the clear space 

between block rows. 

(8) Baffle blocks are constructed with 

their upstream faces normal to the chute 

floor. The longitudinal thickness, T, of the 

baffle blocks at the top should be at least 8 

inches, but not more than 10 inches. See 

block detail, figure 6-5. 

(9) Suggested height of the walls to 

provide adequate freeboard is three times 

the baffle block height measured normal to 

the chute floor. It is generally not feasible to 

set the freeboard for these structures to 

contain all of the spray and splash. 

(e) U,ulift Stubility.-The net force causing 

flotation of the structure should be considered, 

assuming a sudden cessation of flow in the 

channel. The net flotation force is equal to the 

weight of the empty structure minus the 

hydrostatic force remaining in the soil around 

the structure. The magnitude of the maximum 

hydrostatic force, or uplift pressure varies with 

the theoretical height of the percolation 

gradient as determined by Lane’s 

weighted-creep method [ 31, assuming an 

upstream gradient at the normal water surface 

elevation. 

(f) Slidirag Stability. - 

(1) Long baj~led apron drops. -The slope 

stability or tendency of long baffled aprons 

to slide down the 2 to 1 slope should be 

checked. This is particularly important in 

channels where erosion may remove the 

earth material at the downstream toe of the 

apron. In model studies performed on 

baffled aprons, piezometer readings on the 

b&l, Hocks have indicated an average net 

water pressure on the blocks in the 

downstream direction of between 4 and 5 

feet of water. This is equivalent to a force of 

between 250 and 310 pounds per square 

foot of block area. 

(2) Short baffled apron drops.-Short 

baffled apron drops also should be checked 

for sliding. Complete removal by erosion of 

the earth material downstream from the 

downstream cutoff walls should be assumed, 

unless the stability of the downstream 

channel is assured. A horizontal sliding plane 

should be assumed rather than the sloping 

plane assumed for long baffled apron drops. 

Major forces, F,, tending to induce sliding 

along the horizontal plane, during maximum 

flow in the channel are as follows: 

F, = F, + F, + F, + F,, 

where 

F, is the hydrostatic force on the 

upstream face of the upstream cutoff 

walls, 

F, is the hydrostatic force on the vertical 

face of the sill, 

F, is the horizontal component of the 

hydrostatic force on the upstream face 

of the baffle blocks, and 

F, is the force of the saturated earth load 

on the upstream face of the 

downstream cutoff walls (see 

bibliography, reference [ 51 , in chapter 

I). 

Major forces F,, resisting sliding during 

maximum flow in the channel are frictional 

resistance and passive earth pressure. 

Frictional resistance is considered for the 

inlet portion only (length L, + Lz ). as the 

sloping portion can move horizontally with 

no frictional resistance. The frictional 

resistance is a function of the structure 

weight reduced by uplift, and the passive 

earth pressure is a function of the angle of 

internal friction of the earth material. The 

hydrostatic load on the downstream side of 

the cutoff walls is omitted as a safety factor, 

and a safety factor is also included in the 

coefficient of sliding. 
I 

304 SMALL CANAL STRUCTURES 

Thus, 

FR = p (W, + w, - U) + passive earth 

force, 

where 

I-( is the coefficient of sliding friction, 

generally assumed to be equal to 0.35 

(see chapter I), 

W, is the weight of concrete in the inlet 

portion of the structure, 

W, is the weight of water in the inlet 

portion of the structure, 

U is the vertical uplift force as determined 

by Lane’s weighted-creep method. An 

approximate method of determining 

the hydrostatic uplift pressure may be 

used by assuming a pressure gradient 

extending from the maximum upstream 

water surface to the downstream water 

surface. 

Passive earth force is the total force 

resulting from passive earth pressure on the 

downstream side of the cutoff walls (see 

bibliography reference [ 51 in chapter I). 

If the forces tending to induce sliding are 

greater than the forces resisting sliding (using 

suitable safety factors), additional cutoff 

walls should be included. 

(g) Miscellu~2eous Considerutions. ~ 

(1) Gravel or riprap should be provided 

on each side of the structure from the top of 

the slope to the downstream wingwall, 

extending laterally a distance equal to the 

wall height. This protection above the 

maximum downstream water surface is to 

prevent erosion from splashing. Below this 

water surface the protection is required to 

prevent erosion by eddy currents. Wingwalls 

(see fig. 6-4) hold the slope protection in 

place. Channel protection downstream from 

the structure should be in accordance with 

subchapter VII B. Rockfill at the bottom of 

the apron may be unnecessary. 

(2) The channel grade may be controlled 

by a downstream structure, by geologic 

formation, or by being on a stable slope for 

the design capacity. A slope of 0.0018 will 

usually be stable for storm waterflows, but 

for normal canal flows the assumed slope 

should be no steeper than that of a canal in 

the same material. 

The bottom row of blocks should be set 

below the computed channel invert 

elevation. When scour has occurred, to 

provide for future storms, the apron and 

walls should be extended by exposing the 

reinforcement in the end of the structure 

and bonding a new extension to the original 

installation. 

(3) Greater economy may be achieved by 

precasting the concrete baffle blocks. 

6-4. Design Example. -A wastcway channel 

descends a slope that requires energy 

dissipation to prevent excessive erosion. As a 

dependable tailwater cannot be assured, it is 

decided that a baffled apron drop would best 

meet the need. 

(a) Asswnptiom- 

(1) On the basis of soil type and 

operating conditions, it is decided that little 

splashing should be permitted, and a sill-type 

control is preferable (see fig. 6-2 A). 

(2) Hydraulic properties of the wasteway 

channel are as follows: 

Q= 120cfs 

b = 8 ft. 

d, = 4.10 ft. 

A, = 58.02 sq. ft. 

Vl = 2.08 f.p.s. 

h 

“1 

= 0.07 ft. 

r = 2.55 

n = 0.025 

s = 0.00035 

ss = l-1/2: 1 

f, = 2.0 ft. 

h, = 6.1 ft. 

(3) A drop of 6 feet in invert elevation is 

required. 

(b) Solution (SW fig. 6-S for dimension 

rwmenclutwe).p 

(1) From table 6-1, find the 

recommended discharge per foot, q, for a 

total capacity of 120 cfs, and determine a 

preliminary chute width. 

For 

Q = 120 cfs, 

find by interpolation 

q = 16 cfs (approximately). 
ENERGY DISSIPATORS 

Then 

305 

Then, use alternate rows as follows: 

B = % F= 7.5 ft. 

9 

(2) Determine the limits of baffle block 

dimensions, based upon critical depth, d, 

For d, = 2.0 ft. (from table 17 in 

bibliography reference [ 4]), 

Block height, h, = 0.9 d, = 1.8. 

Say 1 ft. 10 in., or 1.83 ft. 

Block width and space, w: 

Min. w = h, = 1.83 ft. 

Max. w = 1.5 h, = 1.5 x 1.83 

= 2.75 ft. 

(3) Determine exact dimensions of baffle 

blocks and chute width. As the partial block 

width, 

wP = khb min. = 0.6 1 min.. 

and 2 h max. = 1.22 max., 3 b 

Try wP = + hb , for simplicity. i 

BLOCK DETAIL 

Figure 6-5. Baffled apron drop design. 103-D-1 335 

Rows 1 and 3: 

1 full block = 1 w 

2 full spaces = 2w 

2 half blocks = Iw 

B = 4w 

Rows 2 and 4: 

2 full blocks = 2w 

1 full space = lw 

2 half spaces = Iw 

B = 4w 

Thus, the total width, B, of any row is 

B=4w 

Using the minimum block width of 

1.83 ft. 

B = 4 x 1.83 = 7.32 ft. 

To simplify dimensions, 

Use 

w = 2.0 ft. (> 1.83<2.75), 

and 

wP = 1 .o ft. (>0.61< 1.22). 

Then, 

B=4w=4x2=8ft., 

q = y= 15 cfs, 

d, = 1.91 ft., 

hb = 1.72 ft. 

Use 

hb = 1 ft. 9 in. 

Select T = 9 inches (see block detail, 

fig. 6-5) 

> 8 inches 

< 10 inches 

(4) Determine inlet length, L1 : 

L1 = 2d, = 2 x 4.1 = 8.2 ft. 

Use L, = 8 ft. 3 in. 
306 SMALL CANAL STRUCTURES 

(5) Determine inlet sill height, h,. 

-Although the baffle blocks just 

downstream from the crest may have some 

effect on the water depth over the sill, the 

assumption that critical depth occurs at the 

sill is adequate for determining the sill 

height.) 

Using B = 8 ft., q = 15 cfs, d, = 1.9 1, 

h vc = 0.96, and V, = 7.86 f.p.s. 

Then 

h, =EsI - Esc - hi (where hi = inlet 10s~) 

=(d, +hvl)-(d,+h, -0.5(h, 

=(4.10+0.07) -(l.91C+o.96) 

C 

-hvI) 

- 0.5(0.96 - 0.07) 

= 0.85 ft. 

Use 

h, = 10 inches = 0.83 foot 

(6) Check inlet velocity to minimize 

splashing: 

Determine depth, d, , at inlet cutoff: 

d, = h, + d, + h, 

C 

=h,+d, +d” 

2 

= 0.83 + 1.9 1 + 0.96 

= 3.70 feet 

The entrance velocity is then 

v, =Q= Q 

A1 d, 

= 120 

- = 4.0 f.p.s. 

3.7 x 8 

Determine critical velocity, V, over crest: 

v =Q = 120 

’ A d,B 

= 120 

1.91 x 8 

= 7.85 f.p.s. 

Thus, the inlet velocity is approximately 

equal to half the critical velocity, and 

splashing will be minimized. 

(7) Determine sill length, L, , and 

dimension e, as shown in figure 6-6. 

Figure 6-6. Sill curve dimensions. 103-D-1336 

Using a radius, R = 6 ft., and an invert 

slope of 2 to 1) 

@ = 26’34’ 

sin @ = 0.4472 = y/z 

tan # = 0.5 = y/x 

G/2 = 13O17’ 

tan @/2 = 0.2361 = z/R 

Substituting, 

z = 0.2361R = 1.42 ft. 

y = 0.4472~ = 0.63 ft. 

x = &= 1.26 ft. 

Then, 

L, = x + z = 1.26+1.42 = 2.68 feet, 

and 

e = h, ~ y = 0.83 - 0.63 = 0.20 foot. 

(8) Determine the slope distance, S, 

between rows of baffle blocks, as shown in 

figure 6-5. 

S = 2 h, min. 

= 2 (1.75) = 3.5 ft. 

use 

S = 6 feet (see subset. 6-3(d)(6)). 
ENERGY DISSIPATORS 

(9) Determine minimum depth of cover, 

j, at outlet to insure that the last row of 

baffle blocks will be covered by the backfill, 

placed in the structure to the elevation of 

the downstream grade. 

307 

S, = S sin $J = 6(0.4472) = 2.68 ft. 

h; 12 +“; @ = 1.75(0.8944) = 1.57 ft. 

Y Y = 4.25 ft. 

(10) Determine apron lengths, L3 and L,, 

for a drop, F = 6 feet. 

Minimum distance, 

L, =e+F+j 

= 0.20 + 6 + 4.25 = 10.45 ft. 

Minimum rows of blocks: 

Kows+~ @$=3.9 

Y . 

Use 4 rows. 

Where the ratio, 2 indicates that fewer 

Y 

rows would be adequate, the minimum 

number of four rows should be used by 

extending two or more rows below the 

downstream grade. 

Finally, 

L,=4S 

= 4 (6) = 24 ft. 

L, = 4 s, 

= 4 (2.68) = 10.72 ft. 

L, = 4 s, 

= 4(6 cos @) 

= 24 x 0.8944 = 2 1.47 ft. 

(1 1) Determine overall length of 

structure. 

L = L, + Lz + L3 

= 8.25 + 2.68 + 21.47 

= 32.40 ft. 

(12) Determine the following wall heights 

(see fig. 6-S): 

h, = d, + 1 ft. = 4.10+ 1 = 5.1 ft. 

Use h, = 5 ft. 2 in. 

With a level invert, and with the top of 

the walls level from h, to h2 , 

h2 = h, -h, 

= 5 ft. 2 in. minus 10 in. 

= 4 ft. 4 in. 

The height of the chute walls, 

h, = 3h, = 3( 1.75) = 5.25 ft. 

= 5 ft. 3 in. 

(13) Determine length, M, , of the 

upstream wingwalls, as shown in figure 6-7. 

M, = 1.5hl + c, , 

where the cutoff depth, C, = 2.5 feet for a 

water depth, 

d, = 4.1 ft. (see fig. 7-2). 

Then, 

M, = 1.5 (5.17) + 2.5 

= 10.25 ft. 

= 10 ft. 3 in. 

Figure 6- 7. Upstream wingwalls. 103-D-1337 

( 14) Determine length, MS, of 

downstream wingwalls, as shown in figure 

6-8. 

M3 = 1.5h; +C,, 

where the cutoff depth, C, = 2.5 feet for an 

assumed channel water depth of 4.1 feet (see 

fig. 7-2), and 
308 SMALL CANAL STRUCTURES 

(15) Check flotation of the structure 

(due to uplift forces) according to the 

requirements of subsection 6-3(e). 

( 16) Check sliding stability of the 

structure according to the requirements of 

subsection 6-3(f). 

(17) Determine protection requirements. 

Select type of protection from figure 7-8, 

chapter VII, for inclined drops with a water 

depth of 4.1 feet. 

Figure 6-8. Downstream wingwalls. 103-D-l 338 

h; = c$ (with @ = 26’34’) 

- 5.25 

0.8944 

Inlet Protection: Type 1, extending a 

distance d, upstream, and up the sloping 

sides to an elevation 1 foot above the 

normal water surface. 

Slope Protection: Type 1, as described 

in subsection 6-3(g). 

= 5.87 ft. 

Then 

M, = 1.5(5.87) + 2.5 

= 8.81 + 2.5 

= 11.31 

Use 

M3 = 11 ft. 4 in. 

Outlet Protection: Type 3, extending 

downstream a distance 4d, , and up the 

sloping sides to an elevation 1 foot above 

the assumed water surface, or to top of 

constructed bank, whichever is greater. 

Note that the backfill, placed over the last 

row of blocks, covers the riprap to the 

elevation of the natural grade (see fig. 

6-5). 

( 18) Check percolation by the 

requirements of chapter VIII, and provide 

cutoff walls if needed. 

C. BAFFLED OUTLETS 

R. B. YOUNG3 

6-5. Purpose and Description. -Excess 

energy forces in flowing or falling water must 

be effectively dissipated to prevent erosion 

damage to downstream channels. Pipe drops. 

pipe chutes, and pipe cross-drainage culverts 

are examples of structures that require some 

form of energy dissipator. Usually the energy is 

dissipated in a sumped pipe, a stilling pool, or a 

baffled outlet. A hydraulic jump is involved 

with the energy dissipation in a sumped pipe 

and a stilling pool whereas the baffled outlet is 

an impact-type energy dissipator. 

The baffled outlet is a boxlike structure 

having a vertical hanging baffle and an end sill 

(figs. 6-9, 6-10, 2-23, 2-25, and 4-24). Excess 

3Civil Engineer, Hydraulic Structures Branch, Bureau of 

Reclamation. 

energy of the incoming water jet is dissipated 

primarily by striking the baffle and to a lesser 

degree by eddies that are formed after the jet 

strikes the baffle. A tailwater depth is not 

required for satisfactory hydraulic performance 

as is the case for a hydraulic jump basin; 

although a smoother outlet water surface will 

sometimes result if there is tailwater. For the 

best operation, the tailwater should be about 

(t + f) above the invert of the baffled outlet. 

The height of tailwater above the baffled outlet 

invert should never exceed b + f because then 

some of the flow will not strike the baffle. If 

the tailwater depth is uncontrolled, the baffled 

outlet invert is usually a distance f below the 

downstream channel invert. Because the 

baffled outlet does not require tailwater, this 
ENERGY DISSIPATORS 309

Figure 6.9. Large baffled outlet. P455-520-408

outlet is therefore particularly useful where

tailwater depth is uncontrolled or where the

rate of discharge increase is sudden and the

tail water buildup is slow. The baffled outlet, if

properly designed, is a more effective energy

dissipator than the hydraulic jump [ 5] .

6-6. Hydrau/ic Considerations. -The baffled

outlet was developed using hydraulic model

studies [5] from which detailed dimensions for

the baffled outlet were determined for various

Froude numbers. To standardize the method of

computing Froude numbers, the shape of the

jet is assumed to be square; thus, the depth of

the incoming flow, d, is considered to be the

square root of its cross-sectional area using the

equation A = SJ. In this equation V is the

theoretical velocity and is equal to ~ [6] .

The head, h, is the head to be dissipated and it

is usually sufficiently accurate to use the

difference in the channel invert elevations at

the inlet and outlet ends of the structure for

this value. However, friction loss in long chutes

may be significant and therefore it should be

considered in the determination of h.

Water surface roughness and downstream

channel erosion together with the ability of the

basin to contain the flow were used as

guidelines in evaluating the hydraulic

performance of the test flows. Each of the test

flows was judged to be satisfactory or

unsatisfactory and plotted in dimensionless

terms using Froude number, F, of the incoming

flow and the ratio of basin width to the

incoming depth of flow, ~. From this data a

recommended design curve for determining

proper basin widths could be drawn and is

shown on figure 6-10. Because the size of the

jet was becoming very small in relationship to

the width of the basin, the curve was not

extended beyond a width-to-depth ratio of 10,

which corresponded to flow having a Froude

number of about 9. For a ~ ratio of about 3,

tests showed that the corresponding Froude

number of the incoming flow was about I. For

this Froude num ber excess energy is minimal.

Therefore the use of this basin for excess

energy dissipation appeared to be impractical

for ~ ratios smaller than 3.

The curve on figure 6-10 indicates the

minimum width of basin that should be used

for a given Froude number. However, if the

basin is too wide the energy will not be

effectively dissipated because the incoming jet

will spread and pass under the baffle rather

than strike the baffle. Also the depth of the

baffle should not be less than the diameter of

the incoming pipe to prevent the jet from

passing over the baffle. For partial discharge as

well as design discharge, best overall dissipation

is achieved only if the basin design wid th is

equal to or slightly greater than the width

determined from the curve for design

discharge. Other basin dimensions are ratios of

the width as shown on figure 6-10.

To prevent cavitation or impact damage to

the basin, the theoretical pipe velocity (~)

should be limited to 50 feet per second.

The diameter of the pipe outletting into the

baffled outlet structure, should be determined

using a velocity of 12 feet per second assuming

the pipe is flowing full.

If the entrance pipe slopes downward, the

outlet end of the pipe should be turned

horizontal for a length of at least 3 pipe

diameters so as to direct the jet into the baffle.

If there is a possibility of both the upstream

and downstream ends of the pipe being sealed,

an air vent near the upstream end may be

necessary to prevent pressure fluctuations and

associated surging of flow in the system.

Figures 6-11 through 6-20 show complete

(continued page 321)
I 

310 SMALL CAN AL STRUCTURES 

Protectioc.as required, 

b=?&(W) 

c=1/2 (W) 

5 

4 

m 

23 

2 

I 

SECTION Rock diameter for protection= I/,,(W) 

I 

2 3 4 5 

FROUDE NUMBER 43 

-t 

, 

4 

6 7 8 9 IO 

W,ft., Is the inside width of the basin 

V,fps, Is the theoretical velocity of the incomlng flow and is \12gh 

h,ft.,Isthe head to be dissipated 

A,ft.TIsthe area of flow entering the basin and is Q/V 

d,ft., Represents the depth of flow entering the basin and isfi 

Figure 6-10. Design width of basin. 103-D-1339 
ENERGY DISSIPATORS 311 

PLAN 

s=O for o dlstonce 

of (It ieo5t 3 

May beconstructed 

with 8" heodwoll I" 

he" of 6'heodwall 

and 3"collor shown 

SECTION A-A 

"4 Hoops 

SECTION B-B 

“4@12 

"4 Hoop 

L-IN 

m 

SECTION C-C 

Edge bol 

across c OptlOnOl 

SECTION D-D 

ELEVATION E-E 

NOTE 

Speclol design IS required where ~ncormng pope diameter 

IS greater than the Inside depth of baffle 

Figure 6-11. Type 1 baffled outlet. 103-D-1340 
312 SMALL CANAL STRUCTURES 

E optlonol 

SECTION C-C 

PLAN 

z’- 3” 16’y 3’. 3” 1’ 6’1 5-o” / 

f-0” * 

SECTION A-A 

m 

Edge bar 

ELEVATION E-E 

ESTIMATED QUANTITIES concrete 2 8 Cu Yds 

Reinforcement steel 230 Lbs 

NOTE 

Special desq" 1s reqwred where mcomng p,pe d,ome+er 

15 greater than the ~ns,de depth of baffle 

SECTION B-B 

Figure 6-12. Type 2 baffled outlet. 103-D-1341 
ENERGY DISSIPATORS 313 

E 

1, 

Splice ocioss c optlonol 

For face, 1 -4 Edge bar 

SECTION C-C 

PLAN 

coarse 

‘4Hoops - 6”- ; 

Maybe constructed 

wifh 8”headwoii 

in lieu of6’heodwoll 

and 3”collor shown 

SECTION A-A -Splice o’cio*s 

E optional 

ELEVATION E-E 

ESTIMATED QUANTITIES 

SECTION El-8 

Figure 6-13. Type 3 baffled outlet. 103-D-1342 
SMALL CANAL STRUCTURES 

‘Splfceacross C optmnol 

SECTION C-C 

PLAN 

SECTION D-D 

2"Riprop on 6"sond 

ond gro vel bedding 

,^ - 3 -- 

Splm ocr**s 

E optmal 

NOTE’ 

May be constructed SECTION A-A 

wth 8”headuali 

in lieu of6"heodroll 

ond J'collar shown 

ELEVATION E-E 

ESTIMATED QUANTITlES 

r.. . ..L. 

SECTION B-B 

Figure 6-14. Type 4 baffled outlet. 103-D-1343 
315 

ENERGY DISSIPATORS 

,- ^^ ^,.mrC 6 nn,,nna/ 

SECTION A-A 

SECTION C-C 

_ -i 

SECT/ON D-D 

6” sand 

bedding 

ELEVATION E-E 

SEC T/ON 5-B 

Figure 6.15. Type 5 baffled outlet. 103-D-1344 
316 SMALL CANAL STRUCTURES 

34 Edge 

bars 

SECTION C-C 

PLAN 

Splice *cr*ss E optional’ i-e 

SECTION D-D 

Q 9”Bond into side walk 

9ravel bedding 

r 1 

,I - 

*4(a/z 

'4@9 

SECTION A-A 

ELEVATION E-E 

ESTIMATED QUANTITIES 

Concrete il.3 Cu Yds 

Rei?forceme,+ Steel 860 Lbs 

SECTION B-B 

Figure 6-16. Type 6 baffled outlet. 103-D-1345 
ENERGY DISSIPATORS 

r 

-L 

-15 L4’, 

PLAN 

-r 

SECTION A-A 

IT4 

S4@/2,' splice across P 

- p6” - 0pt,0M7/ 

SECTION C-C 

if4 Edge bar 

each face 

%@I2 *4@/2 

ELEVATION E-E 

SECTION B-8 

Figure 6-17. Type 7 baffled outlet. 103-D-1346 
318 SMALL CANAL STRUCTURES 

* 8” 

i 1 

Y r’ Yplrce across 

- po” I c optionoi 

SECTION c-c 

PLAN 

,/’ 

(I=0 

cf 

PIP 

-2-c --i 

SECTION A-A 

SECTION B-8 

,-i-*4 Edge bar 

/ each face \ 

Figure 6-18. Type 8 baffled outlet. 103-D-1347 
ENERGY DISSIPATORS 

PLAN 

E 

I #4 Edqe hors 

1: Lm3.6,, J

L Splice *cross EoptiOnol 

SECTION D-D 

~z”R,prop on 6” sand 

and qrovel bedding 

SECTION A-A 

ELEVATlON E-E 

SEC T/ON B-8 

Figure 6-I 9. Type 9 baffled outlet. 103-D-1348 
320 SMALL CANAL STRUCTURES 

PLAN 

SECT/ON C-C 

I 

E 2-c Edge bars 

Splice across c 0ptKJnoi' -3'.6 ‘I J 

SECTION D-D 

SECT/ON A-A 

SECTION B-B 

Figure 6-20. Type 10 baffled outlet. 103-D-1349 
ENERGY DISSIPATORS 321 

design dimensions and details for baffled 

outlets ranging in widths from 3 feet 6 inches 

to 14 feet 3 inches with flow entering the 

baffled outlet from pipes. Although 

uncommon, flow may also enter the basin from 

a rectangular open channel. In this case the 

channel walls should be as high as the basin 

walls and the invert should be horizontal for a 

minimum of three channel widths upstream 

from the basin. 

6-7. Sediment and Debris. -During periods 

of very low flow or nonoperation, sediment 

may accumulate in the basin. Notches in the 

baffle permit concentrated jets to form which 

will normally start erosion of the sediment and 

eventually wash the sediment from the basin 

with an increase in flow. However, as an added 

safety precaution, the basin is capable of 

satisfactorily discharging the entire design flow 

over the top of the baffle. 

There is no practical method of making the 

basin self-cleaning of debris, such as Russian 

thistle. This is a serious deficiency of this 

structure in many locations. Where debris is a 

problem, other types of energy dissipators 

should be used; or if practical, screening devices 

are recommended at the entrance to the 

incoming pipe and at some locations it may be 

advantageous to screen the top of the baffled 

outlet structure itself. If thistles are allowed to 

enter the basin, they will not wash out. 

6-8. Protection, -Protection with a 

well-graded mixture of rocks, most having 

diameters equal to one-twentieth of the basin 

width, should be placed to a depth equal to the 

height of the end sill for a distance equal to 

one basin width downstream from the end sill. 

See figure 7-8. This protection will generally 

consist either of 12-inch coarse gravel or 

12-inch riprap on a 6-inch sand and gravel 

bedding. 

6-9. Basin Width Design Procedure.-For a 

given design Q and head, h, the width of the 

baffled outlet basin is determined as follows: 

(1) Compute the theoretical velocity in feet 

per second, V = &!gh 

(2) Then compute the cross-sectional area 

of the incoming flow in square feet, A = $ 

(3) Next compute the depth of flow, d in 

feet, d = fi (This assumes the shape of the jet 

is square.) 

V 

(4) Compute the Froude number, F = - 

VQ 

(5) For this Froude number read T ratio 

from the curve on figure 6- 10. 

(6) Then W in feet = d(!). This is the 

minimum width which should be used. 

6-l 0. Design Example. -(a) Given : 

(1) Hydvuulic data. -Cross-drainage pipe 

structure with a design Q of 150 cfs, and a 

head, h, of 30 feet. 

(2) Select pipe diamc ter. -Selection of 

the pipe diameter is based on a maximum 

pipe velocity of 12 feet per second assuming 

the pipe is flowing full. Minimum pipe area 

Q - 150 required = v - 12 = 12.5 ft.‘. Select 

4%inch-diameter pipe (A = 12.57 ft.* >. 

(3) Air vent requirement.-The water 

surface required at the inlet will submerge 

the top of the pipe and the outlet of the 

pipe is assumed to be sealed for this 

example. An air vent into the pipe near the 

inlet is therefore required. The vent diameter 

1 should be about - of the pipe diameter 

no 6 

or -2 = 8 inches. 

(b) Determination o.f’ the basin dimensions: 

( 1) Theore tical velocity 

V = &!gh = d/z x 32.2 x 30 = 43.93 f.p.s. 

The maximum allowable theoretical velocity 

is 50 feet per second for a baffled outlet. 

Therefore a baffled outlet may be used. 

(2) Area of flow 

A=% -- 15’ -3.42ft* 

v 43.93 ’ 

(3) Depth of flow 

d=fi=m2= 1.85 ft. 

(4) Froude number 

F=?= 43.93 

&d d32.2 x 1.85 = 5’7 

(5) !Ratio 
322 

For 

W F = 5.7, read - = 7.7 from curve on d 

figure 6- IO. 

(6) Minimum width of basin 

W = d x ; = 1.85 x 7.7 = 14.25 ft. 

(7) Baffled outlet design width 

Use 

W = 14 feet 3 inches 

(8) Basin invert.-Set the basin invert a 

distance f below the natural ground surface. 

(9) Other dimensions, including the 

notch dimensions are related to the design 

width and may be computed using 

relationships to W as shown on figure 6-l 0. 

For this particular example, figure 6-20 

would be selected to construct the basin. 

(c) Determination o,f erosion protection 

reqrlirements: 

W 1425 (1) Required rock diameter = 20 = 20 

= 0.71 foot. The volume of a rock 0.71 foot 

SMALL CANAL STRUCTURES 

71 dia3 in diameter is - 6 = 0.19 cubic foot. From 

subchapter VII B, Erosion Protection, it can 

be seen that coarse gravel protection has a 

maximum size of $ or 0.13 cubic foot which 

is less than required. Therefore, coarse gravel 

is too small and should not be used. The 

next size protection is 12-inch riprap on 

6-inch sand and gravel bedding and is 

adequate, since the average volume of the 

largest and smallest permissible rock for 

12-inch riprap = 0.5 cubic foot. 

(2) Length of protection required W = 

14.25 feet. Use 15 feet. 

(3) Depth of protection required = T = 

14.25 _ 

6 2.38 feet. Twelve-inch riprap on 

6-inch sand and gravel bedding has a total 

thickness of only 18 inches (1.5 feet), but 

the size of rock is much larger than required 

so this thickness will be considered 

adequate. 

For this particular example, if the baffled 

outlet in figure 6-20 had been selected the 

protection would agree with the above 

protection. 

D. VERTICAL SLEEVE VALVE STILLING WELLS 

R. B. HAYES’ 

6-l 1. General. -(a) Descriptiotz.-The 

vertical sleeve valve stilling well is capable of 

dissipating an excess head as great as 800 feet, 

discharging a tranquil flow to the downstream 

canal. The sleeve valve can also be used to 

regulate the flow. A gate valve is usually 

required upstream from the sleeve valve to 

permit closing down the installation for 

maintenance or for the end of the seasonal 

operation. 

Field usage and laboratory studies have 

contributed to the development of design 

criteria for optimum dissipation of energy in 

sleeve valve stilling wells. The general 

arrangement is of two types: 

‘Op. cit., p. 299. 

( 1) Basic arrangement (descending 

flow).-This is the usual arrangement, with 

the inflow entering near the top of the well, 

where an elbow directs it vertically 

downward through the sleeve valve. 

Dissipation of energy occurs as the vertical 

jet strikes the floor and floor cone and as the 

subsequent radial flow strikes the sidewalls 

of the well (see fig. 6-2 1 A). 

Other losses occur through pipeline 

friction, bend losses, and valve losses. This 

arrangement represents the configuration for 

which design parameters are presented in 

detail in subsequent paragraphs. 

( 2 ) Alternate arrangement (ascending 

flow).-To conform to the ground surface 

and pipeline profile another configuration is 
ENERGY DISSIPATORS 323 

(4) Other features. -To assist in obtaining 

optimum dissipation of energy two 

innovations have been used in the corners of 

the stilling well: 

The cOr?ZeY fillet design [ 73 has resulted 

in a very smooth water surface at the 

outlet. The corlzer angle design, as tested 

in the USBR Hydraulics Laboratory, also 

yields a very smooth outlet water surface 

and is more economical. As the corner 

angle design has not yet been proven in 

the field, the corner fillet design is 

illustrated in the following paragraphs. 

To improve the energy dissipation 

characteristics of the well for the basic 

arrangement, the earlier designs used a 

pedestal on the floor of the well. The 

pedestal also provided a convenient means of 

seating and anchoring the valve. Recent 

experience has indicated that the pedestal 

may be causing concrete erosion in the well 

and that a more effective arrangement is 

offered by omitting the pedestal and lining 

the floor and sides with steel, as indicated in 

subsection 6-12(e). 

The standard sleeve valve, as described in 

the following paragraph, has in the past been 

supported by legs extending from the 

bottom of the valve to the floor or pedestal, 

as shown in figure 6-22. As this location is 

in the zone of high velocity and concrete 

erosion has been experienced on the 

sidewalls opposite these legs, it is suspected 

that the legs may be creating the erosion 

problem on the sidewalls [7]. Subsequent 

designs may locate the supports higher on 

the vertical pipe, extending to the sidewalls, 

provided mounting and alinement 

difficulties can be overcome. 

(b) Types of Vertical Sleeve ValvespTwo 

basic types of vertical sleeve valves are used: 

(1) The standard sleeve valve includes 

two basic designs, each using a plain sleeve 

(without ports). The sleeve may be inside or 

outside the valve housing. Most of the earlier 

sleeve valves incorporated an internal sleeve 

fastened to an internal valve stem which 

extended through the vertical pipe and 90’ 

elbow to the handwheel. 

Turbulence, vibration, noise, and 

cavitation resulted from the location of the 

A. BASIC ARRANGEMENT 

Valve stem 

B. ALTERNATE ARRANGEMENT 

Figure 6-21. Sleeve valve stilling well arrangements. 

103-D-1350. 

sometimes used, with the pipe entering the 

well near the bottom and discharging 

upward through the sleeve valve (see fig. 

6-21B). Dissipation of energy occurs in a 

manner similar to that described for the 

basic arrangement, except that the initial jet 

strikes a baffle instead of the floor. This 

arrangement has the advantage that the 

sleeve valve control stem is not subjected to 

the high velocity flow encountered in the 

basic arrangement, giving it the capability of 

withstanding higher velocities without 

excessive vibration. 

(3) Horizontal arrangernest.-A third 

arrangement, currently being developed in 

the Bureau of Reclamation Hydraulics 

Laboratory, consists of a horizontal sleeve 

valve discharging into a horizontal chamber. 
324 SMALL CANAL STRUCTURES 

PLAN 

SECTION C-C 

SECTION A-A SECTION B-B 

VALVE DETAIL 

Figure 6-22. Typical sleeve valve installation for pipe turnout. 103-D-135 1. 
ENERGY DISSIPATORS 325 

or slots of carefully determined sizes and 

configurations. Flow from the small jets 

mixes with the water in the well, dissipating 

the energy with very little vibration, noise, 

or cavitation. 

(c) Usuge of Verticul Slmve Valve Stilling 

We&.-The ability of the vertical sleeve valve 

stilling well to dissipate high heads is utilized in 

the following design conditions: 

(1) Cum1 headworks.-Excess energy may 

exist at the outlet of a pipe extending from a 

reservoir to a canal. 

(2) Pipe drop. ~ A canal may have a need 

for a drop on a slope that is too deep for 

other types of energy dissipators. 

(3) Tur/?out.-A turnout for water 

delivery may be required from a siphon, 

pump discharge line, or pipeline at a location 

where a considerable excess of head exists 

(see fig. 6-22). 

(4) Powerplant bypass. -A powerplant 

bypass, carrying the discharge that would 

otherwise flow through the penstocks and 

the powerplant, must dissipate a head 

approximately equal to the operating head 

on the plant. 

(d) Limitations.-In the design of the 

vertical sleeve valve stilling well, a few major 

aspects warrant careful consideration: 

(1) Head und velocity. -Standard sleeve 

valves have been used by the Bureau of 

Reclamation for heads in excess of 400 feet. 

However, experience indicates that damage 

from severe vibration of the internal valve 

control stem may result where they are used 

with velocities greater than 30 feet per 

second in the vertical pipe. 

With proper design of the valve, head in 

itself need not be a limiting factor. 

However, to allow for widely varying 

conditions of operation. the failure to 

suggest some head limitation may constitute 

an irresponsible omission. Therefore the 

following recommendations are offered as 

flexible limitations on the maximum 

permissible pressure head and velocity at the 

valve while discharging the design flow: 

stem in the high velocity flow. A 

modification [8, 101 to the internal sleeve 

design alleviated this problem by increasing 

the diameter of the pipe used for the 90’ 

bend, providing a gross cross-sectional area 

of about twice the area of the vertical pipe. 

Further, the stem connections to the 

internal sleeve were streamlined to reduce 

turbulence. 

Subsequent designs have incorporated an 

external sleeve, with stem connections 

outside the valve and therefore outside the 

high velocity flow (see fig. 6-23A). This 

design greatly reduces the possibility of 

cavitation and vibration in the valve and 

obviates the need for an enlarged bend. 

(2) The ported sleeve vuZve (multijet), as 

shown in figure 6-23B, is being used to 

dissipate heads considerably greater than 

those permitted for the standard sleeve 

valve. The ported sleeve valve incorporates a 

perforated housing with many tapered holes 

Vertical 

PIP? 

WV? 

(INTERNAL SLEEVE 1 (EXTERNAL SLEEVE) 

A. STANDARD SLEEVE VALVES 

8. PORTED SLEEVE VALVES 

Figure 6-23. Typical vertical sleeve valves. 103-D-1352. 

150 feet ~ Standard sleeve valve with 

internal sleeve and enlarged pipe 

for bend (30 fps), 
326 SMALL CANAL STRUCTURES 

400 feet ~ Standard sleeve valve with 

external sleeve (38 fps), 

600 feet - Ported sleeve valve with enlarged 

pipe for bend (38 fps). 

Current investigations arouse confidence 

that improvement to the ported sleeve valve 

will soon permit satisfactory performance 

for heads to 800 feet. 

(2) Water quality. -The standard sleeve 

valve can tolerate a small amount of the 

weed or trash load which usually 

accompanies the flow in an open irrigation 

system. The ported sleeve valve, however, 

should be used only where clean water is 

assured by screening. Inlet trashracks should 

be submerged to facilitate the intake of 

clean water. Where a pipe turnout branches 

off from a pipeline, the centerline of the 

turnout pipe should be set at the centerline 

of the pipeline. 

(3) Opcratiolzal limitations-To avoid air 

problems in the pipe upstream from the 

stilling well, the sleeve valve should be 

operated in such a way that the pipe will 

flow full. As the canal discharge varies, the 

sleeve valve opening should be adjusted to 

conform to the change in discharge. This 

adjustment can be simplified by the use of 

automatic or remote control to synchronize 

the pipe flow with the upstream discharge. 

Rapid closure of the sleeve valve should 

be avoided, as the resulting water-hammer 

pressures [ 91 could destroy the installation. 

6 - I 2. Design Considerations (Standard 

Sleeve Valve with Corner Fillets in 

Well). -(a) Itllet Conditions.-To minimize 

noise, vibration, and cavitation, the standard 

sleeve valve with an internal sleeve and stem 

should have an inlet bend which provides a 

gross cross-sectional area equal to about twice 

the area of the vertical pipe, thus reducing the 

velocity in the bend [ lo]. A reducer is 

required to comrect the bend to the vertical 

pipe. It should have a convergence no greater 

than 1 in 2 on each side [8]. The minimum 

length of the reducer is then equal to AD, the 

difference in diameters. 

A thrust force on the pipe bend results from 

the change in direction of flow and should be 

balanced by an opposing force supplied by 

suitable anchorage as shown in figure 6-22. To 

provide adequate anchorage of the sleeve valve, 

the total thrust force, F,, should be resolved 

into two forces, F, and F, (see fig. 6-24), 

representing the horizontal and vertical 

components of the thrust force. 

The thrust force is a function of two forces 

as follows: 

(1) Hydrostatic force. -The horizontal 

and vertical components of the hydrostatic 

force on the 90’ bend are: 

F,x = Fhy = wAH 

= 62.4 ‘F H 

= 50D2H 

where 

w is the weight of water per cubic foot, 

A is the cross-sectional area of the pipe, 

D is the inside diameter of the pipe, and 

H is the hydrostatic head at the centerline 

of the pipe. 

(2) Acceleration force. -The horizontal 

and vertical components of the acceleration 

force on the 90’ bend are as follows: 

F 

ax 

=-Qp (V,coscu-V,) 

and F. ay = Qp (V, sin cy - 0) 

where 

Q is the discharge in cubic feet per 

second, 

p = w/g = 62.4132.2 = 1.94, 

V is the velocity in feet per second, and 

cr is the change in direction of flow in 

degrees. 

When 

V, = V, , and 01 = 90°, 

F,x = FaY = QpV 

The horizontal and vertical components 

of the total thrust force are shown to be 

equal where a 90’ pipe bend has a uniform 

diameter of pipe Thus, 

FTx = FTy = 50D2H+QpV 
ENERGY DISSIPATORS 

Figure 6-24. Thrust forces on bend. 103-D-1353. 

The horizontal thrust force, F, should x 

be resisted by adequate horizontal bracing, 

as shown in figure 6-22, and the vertical 

thrust force, F, should be resisted by the 

legs placed at or%ear the base of the vertical 

pipe. 

(b) Sleeve Valve Design. -The sleeve valve is 

often designed for manual operation with 

adaptability to power operation. A handwheel 

attached to the valve stem is operated to adjust 

the valve opening as follows: 

( 1) Standard sleeve valve. -The standard 

sleeve valve usually has a sleeve travel equal 

to one-half the sleeve diameter. The sleeve 

diameter should be large enough to permit 

discharge of the design flow when fully 

open. Complete closure of the standard 

sleeve valve would shut off all flow. A steel 

truncated cone is located under and 

concentric to the valve. It provides a seat for 

the beveled edge of the sleeve and seals off 

the flow when the valve is fully closed. The 

cone also improves the sensitivity of the 

valve to small adjustments. 

The sleeve diameter, travel, and cone 

angle can be varied to meet specific 

conditions. For control of flow velocities at 

higher heads, it may be desirable to oversize 

the sleeve and increase the cone angle. 

(2) Ported sleeve valve. -The ported 

sleeve valve has a sleeve similar to the 

internal sleeve of the standard sleeve valve. 

The sleeve is raised by the handwheel, 

exposing the ported (or perforated) housing. 

Valves have been tested with various port 

327 

sizes and shapes. The smaller the individual 

port, the more rapid is the diffusion of its jet 

and the greater the energy dissipation. 

However, the smaller the port, the smaller 

the discharge and the greater its 

susceptibility to plugging. The bottom row 

of ports should be about 24 port diameters 

above the base to eliminate cavitation 

damage [7]. Further testing is necessary 

before optimum port size, shape, and 

distance from the well surfaces can be 

established. 

(c) Hydraulic Requirements. - 

(1) Head. -The head, AH, to be dissipated 

by the sleeve valve is the differential pressure 

head across the valve equal to H, - H, as 

shown in figure 6-28. The head, H, , is 

measured from the centerline of the pipe to 

the hydraulic gradient immediately upstream 

from the valve elbow. The head, H,, is 

measured from the same pipe centerline 

elevation to the water surface in the well. As 

the head, H, , varies with the upstream water 

surface and also with the discharge, the 

worst condition is not always apparent 

without a hydraulic analysis (see comments 

in (3) below, and in section 6-l l(d)(3). 

(2) Velocity.-To reduce the threat of 

cavitation in the valve, a conservative 

velocity limitation should not exceed 30 feet 

per second when using an internal sleeve and 

38 feet per second when using an external 

sleeve. 

(3) Sleeve valve diameter.-The diameter 

of the vertical pipe and sleeve valve should 

be determined for maximum design 

discharge when minimum head exists. This 

diameter may not be the same as the 

diameter of the pipeline or of the pipe bend. 

(4) Orifice area (standard sleeve 

valve). -The standard sleeve valve usually has 

D 

a maximum sleeve travel equal to 2. When 

2 

fully open, the orifice area of the sleeve 

valve is greater than the cross-sectional area 

of the valve. The orifice of a valve with a 

45’ cone, as shown in figure 6-25, has a 

flow area, A,, equal to the cross-sectional 

area of the valve, A,, when the vertical 

opening, a = 0.46 D,, and the diagonal 

opening, a, = 0.707a. Therefore, the valve 
328 SMALL CANAL STRUCTURES 

Figure 6-2.5. Orifice of the standard sleeve valve. 

103-D-1354. 

can be considered 100 percent open when 

a = 0.46 D, 

The orifice area, 

A, = 0.707a (nD,,>. 

Substituting 

D, = D, - t( see fig. 6-25), 

A, = 0.707an (D, ~ ;). 

(5) Dischurge coejficim t for stmdurd 

s 1 e e v e valve.-Laboratory studies [ 71 

indicate a head loss coefficient, 

K = v= 1.84 (see fig. 6-26), 

when the valve is fully open (a = 0.46D,), 

where AH is the differential head across 

the valve, and V is the velocity in the 

vertical pipe. 

The valve discharge coefficient. C, is related 

to the head loss coefficient, K, as follows: 

K=-L 

c ‘2 

Figure 6-26. Head loss coefficient for the standard 

sleeve valve. 103-D-1355. 

or 

When the valve is fully open, 

c=&= 0.735 

Use C = 0.73 for the fully open valve. 

(d) Well Dimctzsiotls (set jig. (i-28 Jar 

/zornctzcluture). -Well dimensions are 

determined from figure 6-27 as follows: 

Enter along the abscissa with Q’ “’ [ g 1 

Follow vertically to the curve representing 

h’ 

D, 

and then horizontally to the ordinate, 

b and read the ratio - 

D” 

where 

Q is the design discharge in cubic 

feet per second, 
ENERGY DISSIPATORS 329 

A. Based on a ratio, d,=l.sb 

B. Based on a ratio, d,=Zb 

Figure 6-2 7. Vertical sleeve valve stilling well 

dimensions. 103-D-1 356. 

g is the acceleration of gravity 

(32.2 feet per second per second), 

D” is the valve diameter in feet, 

h’= z h (see fig. 6-28) 

ELEVATION 

SECTION A-A 

w 

SEC C-C 

Figure 6-28. Typical sleeve valve and stilling well. 

103-D-1357. 

d W 

-= 1.5 

b 

dW 

and b = 2.0 

Figures 6-27A and 6-27B are provided to 

utilize both ratios. 

The foregoing well dimensions are valid for a 

tailwater depth to well width ratio, 

d 

-L= 0.5 

or h’ = 1.8h for l- l/2 to 1 side slope 

‘ 

and h’ = 2.23h for 2 to 1 side slope, After determining the well width and depth 

b is the width of the well in feet from figure 6-27, 

(3 ft minimum required for 

access), and where d, >i, 

dW is the depth of the well in feet as 

shown in figure 6-28. the dimension d, could be reduced by the 

amount, 

From the Bureau of Reclamation Hydraulics 

Laboratory Studies [ 71 , it has been established and 

d, - $ 

that satisfactory performance is achieved using 

well depth to width ratios. where d, < b 2’ 
330 SMALL CANAL STRUCTURES 

velocity heads in the well and in the 

downstream section. The velocity head in the 

well is considered to be zero (in the direction 

of the downstream flow). Therefore, the total 

water surface differential is equal to 1.3 times 

the downstream velocity head. 

The design of the outlet transition should be 

similar to that discussed for bench flumes 

(subchapter II D). Where the tailwater elevation 

may vary considerably, as between the 

maximum and minimum water surfaces in a 

reservoir, a baffled apron drop is sometimes used 

in conjunction with, or downstream from, the 

sleeve valve stilling well. 

(g) Outlet Protection. -To prevent erosion 

damage in the outlet channel, protection 

should be provided in accordance with figure 

7-8, as indicated for a closed conduit drop with 

baffled pipe outlet. 

6-13. Design Example. -A canal profile 

requires a drop of 150 feet on a steep slope. It 

is decided to accomplish the drop with a pipe 

and vertical sleeve valve stilling well. 

(a) Assumptions. - 

(1) Canal properties are as follows: 

the dimension d, should be increased by the 

amount 

g- dll 

Corner fillet dimensions are determined 

from the following relationships: 

C = O.lOOb 

J = 0.210b 

F = 0.417b 

and Z = 0.715 

See figure 6-28 for nomenclature. 

Establishing a permissible tailwater wave 

height is a judgment factor based upon the 

depth, freeboard, and erosion resistance of the 

tailwater channel or canal. For the range of 

discharges treated in this text, a permissible 

wave height, h, of about 0.02 to 0.05 times the 

normal depth is recommended (see fig. 6-28). 

(e) Armor Plating.-To prevent cavitation or 

abrasion damage to the floor and walls of the 

stilling well, they should be covered with a 

steel cover as follows: 

l/2-inch-thick stainless steel on the floor and 

on the sidewalls to a height of 1.5 D,. 

The steel plating should be welded at 

junctions and should be anchored to the 

concrete with stainless steel anchors to prevent 

loosening. To avoid damage from galvanic 

action, care should be taken to prevent contact 

between the stainless steel and the 

reinforcement steel. 

(f) Outlet Transition.-The flow from the 

well is discharged through a rectangular 

opening, through a transition to the outlet 

channel or canal. The transition is usually the 

broken-back type, which is suitable for a 

well-defined channel or canal section. 

The water surface in the well must be higher 

than the tailwater elevation by an amount 

equal to the velocity head, h,, in the 

downstream section, plus transition losses. 

Allowing a loss of 0.3nh, for the broken-back 

transition, the total water surface differential is 

equal to 1.3Ah,, where Ah, is the difference in 

Maximum Q = 70 c.f.s. d, = 3.2 ft. 

b= 8 ft. v = 1.69 f.p.s. 

ss = l-1/2: 1 h, = 0.04 ft. 

n = 0.025 s = 0.0003 

(2) The maximum differential head, AH, 

across the closed valve is 150 feet, measured 

from the upstream canal water surface to the 

dcwnstream canal water surface. 

(3) At the design flow of 70 cfs, friction 

and bend losses plus pipe velocity head are 

equal to a total of 50 feet, leaving a 

differential head: 

AH= 150- 50= lOOfeet 

(4) The basic arrangement (downward 

flow) best fits the profile. 

(5) Trashracks at the inlet to the pipe 

drop assure fairly clean water through the 

valve, removing all but small debris. 

(6) A tailwater wave height, h, equal to 

0.10 foot (0.031 d,), measured vertically 

from trough to crest (see fig. 6-28), is 

considered to be permissible. 
ENERGY DISSIPATORS 331 

(b) Solution. - 

(1) Sleeve vulve type.-A standard sleeve 

valve with an internal sleeve is adequate for 

dissipating the maximum head of 150 feet, 

or the minimum head of 100 feet during 

maximum discharge, and it is better able 

than the ported valve to pass the small debris 

that may pass through the trashracks. 

(2) Diameter.-To minimize cavitation, 

the diameter of the vertical pipe and sleeve 

valve is determined on the basis of a 

maximum velocity of 30 feet per second. 

Thus 

Q 70 A= v= 30= 2.33 sq. ft. 

Then, the diameter of the valve (and vertical 

pipe), 

D, fig?= 1.725 feet. 

Use 

D, = 1.75 feet, 

A, = 2.41 sq. ft. 

and 

V, = 29.1 f.p.s. 

(3) 90’ elbow and taper.-The 

long-radius bend should have a pipe diameter 

providing a gross area equal to twice the area 

of the vertical pipe, 

or 

2 x 2.41 = 4.82 sq. ft. 

Then, the pipe diameter for the bend, 

D, = 2.48 ft. minimum 

Use 

D, = 2.50 ft. 

The length of the taper should be at least: 

LID = (2.5 - 1.75) = 0.75 ft. 

Use 1 foot. 

Anchorage of the bend should be designed 

to resist the thrust forces discussed in 

subsection 6-12(a). 

(4) Discharge.-Check the adequacy of 

the 21-inch-diameter sleeve valve, when fully 

open (A, = A,), to discharge the design 

flow, using a coefficient of discharge, 

c = 0.73, 

A, = A,= 2.41 sq. ft., 

and AH = 100 ft. 

From the orifice equation, 

Q = CA&m 

= 0.73 (2.41)~/64.4~100 

= 141>70 cfs 

Therefore, the diameter of 21 inches 

(determined to prevent cavitation) is more 

than adequate to discharge the design flow. 

(5) Required vulva ope?lirzg. -Using a 

trial-and-error method, determine the 

required valve opening, a, for a discharge of 

70 cfs, with a differential head, AH = 100 ft. 

Try an area ratio, A,/A,, equal to 72 

percent. 

Thus, 

A, = 0.72A, 

= 0.72 x 2.41 = 1.74 sq. ft. 

From figure 6-26, with A,/A, equal to 72 

percent, 

K = 4.0 

giving 

1 

c=== 0.50 

From the orifice equation, the required 

orifice area, 

A,= --% 

C&!gER 

70 

= 

0.5oJi?ixam 

= 1.75 > 1.74 sq. ft. (close enough) 
332 SMALL CANAL STRUCTURES 

Therefore, an orifice area equal to 72 

percent of the valve area is sufficient for the 

design discharge at the design head. 

Actually 

d, = 3.2 feet 

From the equation for area of the sleeve 

valve orifice (see subsection 6-l 2(c)(4)), 

and 

b 717 -= &= 3.58 feet 2 2 

A, = 0.707 arr(D, - 4) 

1.75 = 2.22 a (1.75 - g) 

1.75 = 3.88 a ~ 1.1 la* 

Then, by trial, or from the quadratic 

equation, the required sleeve travel, 

a = 0.55 ft. 

(6) Determine well dimensions, b and d, , 

4v using figure 6-27A, with a ratio T = 1.5 

On the abscissa, 

Q’ 

c I 

1 /z 

g(D, >” 

(70)* 

= [ 1 1 /2 

g(16.41) 

= (9.27)“’ = 3.05 

Using the curve, 

h’= lD8” - 1.8 ; ;510 = o.lo, 

D, v . 

find 

b 

D,= 4.1. 

Then, 

b = 4.1 x 1.75 = 7.18 ft. 

(say b = 7 ft. 2 in.), 

and d, = 1.5 b 

= 1.5 x 7.17= 10.76 feet 

These values for b and d, are valid, as 

indicated in subsection 6-l 2(d), only if: 

Therefore, the well depth, d, , should be 

increased to compensate for the relative 

deficiency, 6, in tailwater depth, 

where 

6=+-d 

n 

= 3.58 - 3.2 = 0.38 feet 

Thus, d, should be increased, resulting in a 

depth 

d, = 10.76 + 0.38 = 11.14 feet 

Say d, = 11 ft. 2 in. 

(7) For an economic comparison, the 

dimensions, b and d, , should be determined 

again, using figure 6-27B, with a ratio, 

dw 

- = 2.0 

b 

On the abscissa, 

l/2 

= 3.05 

as before, and using the same curve, 

where 

h’ 

D,= 0.10, 

find 

b 

D, = 3.45 

Then 

d, =$ b = 3.45 x 1.75 = 6.04 feet 

(use b = 6 ft.) 
ENERGY DISSIPATORS 

and 

d, =2b= 12ft. 

These dimensions are valid only if 

d,=; 

Actually 

d, = 3.2 feet 

and b 6 T= 7 = 3.0 feet 

Therefore, the well depth, d, could be 

reduced to compensate for the relative 

excess of tailwater depth, 

s=d,-$ 

L 1.5D, = 1.5x1.75 = 2.63 ft. 

= 3.2 - 3.0 = 0.2 ft. Use 2 ft. 8 in. 

Thus, d, could be reduced, resulting in a 

depth of 

12.0 - 0.2 = 11.8 ft. 

Say 11 ft. loin. 

Assuming the more economical well is 

obtained by using the dimensions resulting 

in the smaller concrete area, the structure 

designed with a ratio, 

dw 

- = 1.5, 

b 

is slightly more economical. 

333 

(8) Determine the following dimensions 

from the established ratios: 

C= 0.100 b 

= 0.100 x 7.17 

= 0.72 ft. (use 9 in.) 

J = 0.210 b 

= 0.210 x 7.17 

= 1.51 ft. (use 18 in.) 

F = 0.417 b 

= 0.417 x 7.17 

= 2.99 ft. (use 3 ft.) 

(9) Steel plating should be provided in 

accordance with subsection 6-l 2(e), 

extending up the sidewalls to a minimum 

height: 

(10) Outlet trmsition and losses.-As the 

canal section is well defined, a broken-back 

transition should be used, and the water 

surface differential from the well to the 

canal is equal to: 

1.3nhv = 1.3 x 0.04 = 0.05 ft. 

(1 1) Outlet protection.-The earth 

section of the canal downstream from the 

vertical sleeve valve stilling well should be 

protected from erosion by providing type 2 

protection, extending 14 feet beyond the 

concrete transition, in accordance with 

figure 7-8. 

E. BIBLIOGRAPHY 

6- 14. Bibliography. 

(11 Peterka, A. J. “Hydraulic Design of Stilling Basins and 

Energy Dissipators,” Bureau of Reclamation, 1964. 

(21 “Design Standards No. 3, for Canals and Related 

Structures, Bureau of Reclamation, 1967. 

[3] “Design of Small Dams,” Bureau of Reclamation, Second 

Edition, 1973, Revised Reprint, 1974. 

[41 “Hydraulic and Excavation Tables,” Bureau of 

Reclamation, Eleventh Edition, 1957, Reprint, 1974. 

[5] “Hydraulic Design of Stilling Basin or Channel Outlets,” 

Research Report No. 24-1971 United States 

Department of the Interior-Bureau of Reclamation. 

[6] King, H. W. and Brater, E. F., “Handbook of Hydraulics,” 

Fifth Edition. McGraw-Hill Book Co., New York, 1963. 

[7] Burgi, P. H., “Hydraulic Model Studies of Vertical Stilling 

Wells,” Bureau of Reclamation, 1973. 

[8] Johnson, D. E., “Sleeve Valves” from “Institute on 

Control of Flow in Closed Conduits,” Colorado State 

University, 1970. 

[9] Parmakian, John, “Waterhammer Analysis,” 1955. 

[lo] Miller, E., “Some Recent Developments in Flow 

Regulating Valves,” Water Power, September 1969. 

« Chapter VII

R. B. YOUNG

A. TRANSITIONS

I. General structure or concrete transition to that of the

waterway section.

7-2. Types.-(a) Inline Canal Structure

Transitions. -The most common concrete

transi tions for in line canal structures are: ( I )

streamlined warp, (2) straight warp, and (3)

broken-back. Broken-back refers to the

intersection of the vertical and sloping plane

surfaces on the sides of the transition as shown

on figures 1-12, 2-6, 7-1, and 7-2 and is

sometimes also referred to as dogleg.

Broken-back transitions used with structures

other than pipe structures (fig. 2-19) are

discussed in other chapters. However, criteria

in this chapter for water surface angles, cutoff

dimensions, and freeboard at the cutoff are

applicable. The streamlined and straight warp

transitions will not be discussed because their

refinement is usually not justified for the

capacity range in this publication.

7 -I. Purpose and Description. -Transitions

usually produce gradual changes in water prism

cross sections and are used at structure inlets

and outlets and at changes in canal sections to:

(I) provide smoother water flow, (2) reduce

energy loss, (3) minimize canal erosion, (4)

reduce ponded water surface elevations at

cross-drainage structures, (5) provide additional

stability to adjacent structures because of the

added resistance to percolation, and (6) to

retain earthfill at the ends of structures.

Transi tions usually produce gradually

accelerating velocities in inlet transitions and

gradually decelerating velocities in outlet

transitions. Because of the improved flow

conditions at the ends of a pipe structure, the

allowable pipe velocity may be increased and

the size of pipe may be decreased if sufficien t

head is available.

Transitions are either open (no top) or

closed. Closed transitions are used to further

reduce energy losses for pipe structures by

providing an additional gradual change of water

prism cross section from rectangular to round.

The refinement of rectangular to round

transitions is usually not justified for capacities

discussed in this publication. Open transitions

may be either concrete or earth. Earth

transitions are used to transition base width,

invert elevation, and side slopes from a canal

1 Civil Engineer, Hydraulic Structures Branch, Bureau of

Reclamation. Figure 7-1. Type 1 concrete transition. P33-D-25693

335
336 SMALL CANAL STRUCTURES 

A type 5 transition (fig. 7-3) is sometimes 

used to transition from a concrete-lined canal 

to a pipe structure. The transition energy head 

loss will be greater with this transition than 

with a more streamlined transition. 

(b) Cross-drainage Pipe Structure 

Trunsitiom-The most common concrete 

transitions used with cross-drainage structures 

are type 1 (broken-back), figure 7-2; type 2, 

figures 7-4 and 4-19; type 3, figures 7-5 and 

4-22: and type 4, figures 7-6 and 7-7. Addition 

of an inlet transition to a cross-drainage pipe 

structure permits the pipe inlet to be lowered 

which results in lowering of the required 

upstream water surface (provided the control is 

upstream). Lower upstream water surface 

minimizes inundation of farmland and 

increases the canal embankment freeboard. 

A type 1 transition is used if the natural 

drainage channel has a well-defined cross 

section with dimensions that can reasonably be 

transitioned to the broken-back cross section. 

Where the uphill canal bank obstructs storm 

runoff from a relatively wide or lesser defined 

drainage channel, a type 2, 3, or 4 transition is 

usually more suitable. See chapter IV for 

further discussion of cross-drainage structures. 

2. Desigrr Considerations for Pipe 

Structure Transitions 

7-3. Hydraulic Design. -(a) Pipe 

S24bmergencc. -Inlet transitions to pipe 

structures where the hydraulic control is at the 

downstream end of the structure should have a 

seal of 1.5 times the difference of velocity 

heads in the pipe and canal ( 1.5 Ah,) or 3 

inches minimum. The seal is measured between 

the upstream water surface of the inlet 

transition and the top of the opening in the 

transition headwall. This inlet submergence 

allows for a pipe entrance loss and a conversion 

of static head in the canal to full-pipe velocity 

head. For minimum head loss, the top of the 

opening at the outlet transition headwall 

should have little or no submergence. If the 

submergence exceeds one-sixth of the depth of 

the opening at the outlet, the head loss should 

be computed on the basis of a sudden 

enlargement rather than as an outlet transition. 

Theoretical differences in water surface in the 

canal and immediately inside the conduit at the 

headwalls are: AWS = (l+K, ) Ah, at the inlet, 

and AWS = ( l-K2 ) Ah, at the outlet. These 

values omit the small transition friction losses, 

and K, and Kz are transition head loss 

coefficients described in the following 

paragraphs. 

Where an inlet transition connects to a 

free-flow closed conduit in such a way that the 

conduit inlet is sealed, the head required to 

discharge the design flow can be determined by 

the orifice equation [ 11 ,’ Q = CA- = 

discharge coefficient x pipe area x 

4 2 x g x head. The head is measured from the 

center of the headwall opening to the inlet 

water surface, and a discharge coefficient of 

C = 0.6 should be used. 

(b) Head Losses. -The energy head loss in a 

concrete transition will depend primarily on 

the difference between the velocity heads 

(Ah,) at the cutoff end of the transition 

(usually taken to be the canal velocity head) 

and at the normal to centerline section of the 

closed conduit at the headwall. Friction losses 

for short transitions associated with capacities 

up to 100 cfs will be small and are usually 

omitted. Coefficients used with Ah, which are 

considered adequate for determining energy 

losses in broken-back transitions are K, = 0.4 

for the inlet and K, = 0.7 for the outlet or 

inlet loss = 0.4 Ah,, and outlet loss = 0.7 ah,. 

Dimensions for broken-back transitions are 

usually such that additional transitioning to the 

canal section must be made with an earth 

transition where the canal is earth and a lined 

transition where the canal is lined. However, 

energy losses attributed to these transitions are 

small, and it is usually considered adequate in 

the hydraulic design to use only the concrete 

transition losses with the assumption that the 

velocity at the transition cutoff is the same as 

the velocity in the canal. 

Coefficients of Ah, considered adequate for 

determining energy losses for earth transitions 

connecting a canal section to a pipe are K, = 

0.5 for the inlet and Kz = 1.0 for the outlet. 

2Numbers in brackets refer to items in the bibliography, ee 

set 7-16 
TRANSITIONS AND EROSION PROTECTION 337 

ON 8-E 

PLAN 

- , 

LONGlTUDlNAL SECTION 

DIMENSIONS d AN0 tw 

SECTION A-A 

ISECT!ON c-c SW!‘““, 

Figure 7-2. Concrete transitions-type 1. 103-D-1288 
338 SMALL CANAL STRUCTURES 

Figure 7-3. Concrete transitions-type 5. 103-D-1289 
TRANSITIONS AND 

B> r 

t t--- F 

Space horirontolly on Structure E’ 

INLET OUTLET 

TYPICAL PLANS 

Pppe emoedment. 

LONGITUDINAL SECTlONS 

c 

*4 @)12 Bend i 

mto w/i / SECT/ON A-A 

ISECTION 8-B SIMILAR, 

339 

Figure 7-4. Concrete transitions-type 2. 103-D-1290 
340 SMALL CANAL STRUCTURES 

PLAN 

SECTION A-A 

embedment 

f concrete pioe 

STR. MAX. DlMENSlONS EST QUANTITIES 

Tabulated d/mensions and ml w/mum Ok, proude freeboard at the heodwoll, 

1.90 

200 

0’1 6’ 26 2 6 210 

615’ 24” 2 8 220 

.,24’ 30 240 

‘-0-l 3:6 1 6’ 24’ 3.2 260 

0’1 8’ $6” 4 3 290 

320 

340 

wth full-p!pe velocfties ronglng up to IO fps 

Figure 7-5. Concrete inlet transitions-type 

24 Q /z Bend mto 

heodwoll 

24 @ 12 In center 

of heodwoll 

’ (?4 @ 12 /n center of heodwoll 

SECTION B-B 

3. 103-D-1291 
TRANSITIONS AND EROSION PROTECTION 341 

/ Symm about tPLAN 

Ape embedmenf 

SECTION A -A 

SEC T/ON B-E 

TABLE OF DIMENSIONS AND QUANTITIES 

Figure 7-6. Concrete inlet transitions-type 4. 103-D-1292 
342 SMALL CANAL STRUCTURES

Figure 7-7. Type 4 inlet concrete transition. P-328-70t-9300

(c) Water Surface Angle.- To obtain the

most desirable hydraulic conditions, the angle

between the water surface and the transition

centerline should not exceed 27-1/2° for inlet

transitions and 22-1/2° for outlet transitions.

For some structure designs it may be

economical to use an angle of 25° to allow the

same concrete transition to be used for both

inlet and outlet. For this angle the loss

coefficients remain 0.5 for the inlet and 1.0 for

the outlet.

(d) Channel Erosion.-To prevent undue

channel erosion downstream from a structure

outlet, the following criteria for pipe velocity

should be observed. If the pipe velocity is equal

to or less than 3.5 feet per second, an earth

outlet transition is usually sufficient. If the

pipe velocity is greater than 3.5 feet per second

a concrete outlet transition or other outlet

structure is required. If the pipe velocity is

greater than 10 feet per second a baffled outlet

or a stilling pool should be used.

7-4. Cutoffs.-Cutoffs are provided to

reduce percolation around transitions and to

add stability and structural strength to

transitions. Cutoffs are required at the ends of

transitions in concrete-lined canals as well as in

other lined or earth canals.

Cutoff walls should, in general, be a

minimum of 24 inches deep for water depths

up to 3 feet at the cutoff; 2 feet 6 inches deep

for water depths of 3 to 6 feet; and 3 feet for

water depths greater than 6 feet. For some

small structures, 18-inch cutoffs may be

satisfactory .The minimum concrete thickness

ShoUld be 6 inches for 18- and 24-inch cutoffs

and 8 inches for cutoffs deeper than 24 inches.

Excavation for the structure may disclose soils

that are unusually susceptible to piping, in

which case the cutoff ShoUld be extended

vertically or horizontally, or both, beyond

these minimums to provide adequate

protection against percolation. Nonreinforced

Concrete may be used for the extension.

7-5. Standardization. -Concrete transitions

may be standardized as a means of reducing

CoSt by designing them to fit a range of

conditions thereby rendering them applicable

for a number of transition installations. If

Concrete transitions are standardized for inline

canal structures it will probably be necessary to

supplement the Concrete transitions with earth

or Concrete lining transitions to complete the

transitioning to the canal section. Transition

losses for these supplemental transitions are

usually neglected.

7-6. Type 1 Transitions

(Broken-back). -Figure 7-2 ShoWS a typical

type I transition. The type I transition is

generally used with inline structures because of

its applicability to a well-defined channel croSS

section.

A transition length L equal to three times

the pipe diameter has given satisfactory

performance in providing the necessary

distance for smoothly changing the water

velocity.

Dimension B is chosen So that the I-I/2 to I

sloping walls are approximately tangent to

the opening at the headwall, and may be

determined using the relationship, B = 0.303

times the pipe diameter. The computed value is

rounded to the nearest greater inch.

The base width C at the cutoff walls is

dependent on the design refinement of the

water surface angle. If y -6 inches is assumed

to be approximately the same as the depth d in

the canal at the cutoff, an acceptable C value

can be determined by using the following water

surface angles, equations, and relationships for

pipe diameter D to depth d:

For a water surface angle of 22-1/20:

C = 0.5D when D = d,

C = I.ID when D = 1.25d,

C = 1.5D when D = 1.5d, and

C = 2D when D = 2d
TRANSITIONS AND EROSION PROTECTION 343 

For a water surface angle of 25’: 

C = 0.8D when D = d, 

C = 1.4D when D = 1.25d, 

C = 1.8D when D = l.Sd, and 

C = 2.3D when D = 2d 

For a water surface angle of 27-l/2’: 

C= l.lDwhenD=d, 

C = 1.7D when D = 1.25d, 

C = 2.1D when D = l.Sd, and 

C = 2.6D when D = 2d 

Additional transitioning to the canal base 

width, if required, can be accomplished with an 

earth or concrete-lined transition. 

Dimension y should not be less than the 

sum of the water depth at the cutoff and 

design freeboard at the cutoff. To avoid 

unnecessary erosion in an earth canal, it is 

desirable to set the invert of the transition 

cutoff at the canal invert. Freeboard at the 

transition cutoff adjacent to concrete canal 

lining or other hard surface or 

buried-membrane canal lining is usually the 

same as that of the lining. For capacities up to 

50 cfs this freeboard will usually be 6 inches, 

and for capacities between 50 and 100 cfs the 

freeboard will generally range between 6 and 9 

inches. In unlined and earth-lined canals the 

minimum freeboard at broken-back transition 

cutoffs should be as follows: 

Water depth at cutoff, Minimum freeboard, 

feer inches 

0 to 1.25 6 

1.26 to 2.00 9 

2.01 to 5.00 12 

The value for p is the difference in elevations 

of the inverts at the transition cutoff and at the 

headwall opening. The invert at the headwall 

opening is established by the required 

submergence of the top of the opening as 

previously discussed, and the invert at the 

transition cutoff is assumed to be the same as 

the canal invert. The p value should not exceed 

:D for an inlet transition or ;D for an outlet 

transition. These dimensions provide maximum 

floor slopes of 4 to 1 for inlet transitions and 6 

to 1 for outlet transitions. If additional 

transitioning to the canal invert is required, it 

should be accomplished in the adjacent earth 

transitions, or with concrete lining for a 

concrete-lined canal. 

Dimension “a” is dependent on the design 

headwall freeboard and the invert of the 

opening established by required submergence 

as previously discussed. The freeboard at the 

broken-back transition headwall should be as 

great as or greater than the freeboard shown in 

the preceding tabulation for freeboard at the 

cutoff. Headwall freeboard for transitions 

connected to 24-inch-diameter pipe and smaller 

may be the same as the freeboard at the cutoff, 

therefore the tops of broken-back transition 

walls are level for this pipe diameter range. For 

larger diameters, the transition headwall 

freeboard should increase as the size of the 

structure increases; frequently, freeboard at the 

headwall will be twice that at the cutoff. 

Cutoff dimensions have previously been 

discussed in section 7-4, and required pipe 

embedment at the headwall is discussed in 

chapter VIII. 

7-7. Type 2 Transition.-Figure 7-4 shows a 

typical type 2 transition. Dimensions in the 

table are for pipe diameters sized for a full-pipe 

flow velocity of 10 feet per second, and a 

free-flow pipe with hydraulic control at the 

inlet transition headwall. A free-flow pipe is 

common for cross-drainage culvert structures 

where the water surface at the outlet is usually 

considerably below the invert of the opening at 

the inlet headwall. A maximum full-pipe flow 

velocity of 10 feet per second is permitted for 

cross-drainage culvert structures having 

concrete outlet transitions. 

To prevent degradation at the inlet, the 

invert at the transition cutoff is located at or 

near existing ground surface. Sloping the 

transition floor lowers the headwall opening, 

and because the hydraulic control for the 

design flow is at the inlet headwall, the water 

surface required to discharge the flow is also 

lowered. 

Inlet sidewalls are flared for three reasons: 

(1) to produce a more hydraulically efficient 

entrance condition for the opening (orifice) at 

the headwall, (2) to provide a width at the 

cutoff sufficient to insure that the hydraulic 

control of the water surface is at the pipe 

entrance, and (3) to provide a greater width at 
344 

the cutoff which reduces the likelihood of 

erosion by reducing the depth and velocity for 

flows less than design flow. Flaring the outlet 

sidewalls also allows the water to be released at 

the cutoff with less likelihood of erosion for 

partial flows. 

The tabulated dimensions (fig. 7-4) provide 

for freeboard at the inlet headwall which 

increases as the size of the structure increases. 

If submergence of the top of the headwall for 

design flow is not objectionable, the listed 

transition dimensions may also be used for the 

design flow for a full-pipe velocity of 12 feet 

per second. This velocity is allowed if a baffled 

outlet is used. 

To provide adequate freeboard for the canal, 

the inlet water surface for design flow 

should be at least 2 feet below the top of the 

canal bank. The orifice equation, [ I] Q = 

CA&?$ may be used to calculate the inlet 

water surface required to discharge the design 

flow. For a type 2 inlet transition, a discharge 

coefficient, C = 0.6 may be used. The head, h, 

measured from the centerline of the opening to 

the water surface for free flow may be 

conveniently determined by rearranging the 

orifice equation and making appropriate 

substitutions: 

SMALL CANAL STRUCTURES 

h = 0.0433V2 

where V is the design velocity for the pipe. 

7-8. Type 3 Transitions.-Figure 7-5 shows a 

typical type 3 transition. Dimensions provided 

in the table are for capacities from 16 to 70 cfs 

and pipe diameters of 24 through 36 inches. 

Full-pipe velocities range from about 5 feet per 

second for 24-inch-diameter pipe to about 10 

feet per second for all pipe diameters listed. 

The dimensions provide control at the inlet 

headwall and also freeboard at the headwall for 

the design capacity and free-flow pipe. A 

maximum full-pipe flow velocity of 10 feet per 

second is permitted for cross-drainage culverts 

having concrete outlet transitions. 

To prevent degradation at the inlet, the top 

of the inlet wall is placed at or near existing 

ground surface. Lowering the transition floor 

by an amount equal to B lowers the headwall 

opening and, because the hydraulic control is 

at the inlet headwall, the water surface 

required to discharge the design flow is also 

lowered. 

Structures numbered 24-4, 27-2, 30-2, 33-2, 

and 36-l may also be used for capacities 

greater than those tabulated with resulting 

full-pipe velocities up to 12 feet per second, 

provided there is a baffled outlet or a stilling 

pool for these higher capacities and provided 

freeboard at the headwall is not required. 

To provide adequate canal bank freeboard, 

the inlet water surface for design flow should 

be at least 2 feet below the top of the canal 

bank. The orifice equation [ 11, Q = CA&!& 

may be used to calculate the inlet water surface 

required to discharge the design flow. For type 

3 inlet transitions, a discharge coefficient, C = 

0.6 may be used. The head, h, measured from 

the centerline of the opening to the water 

surface for free flow may be conveniently 

determined by rearranging the orifice equation 

and making appropriate substitutions: 

h = 0.0433V’ 

where V is the design velocity for the pipe. 

7-9. Type 4 Transitions.-Figure 7-6 shows a 

typical type 4 transition. Dimensions in the 

table are for pipe diameters sized for a full-pipe 

flow velocity of 12 feet per second with a 

free-flow pipe inlet. The dimensions provide 

control at the inlet headwalls for design 

capacity and free-flow pipe. A maximum 

full-pipe flow velocity of 12 feet per second is 

permitted for cross-drainage culvert structures 

having baffled outlets or stilling pools. 

To prevent degradation at the inlet, the top 

of the inlet wall is placed at or near existing 

ground surface. Dropping the transition floor 

by an amount equal to e, and sloping the 

transition floor lowers the headwall opening. 

Because of this and as the hydraulic control is 

at the inlet, the water surface required to 

discharge the design flow is also lowered. 

Inlet sidewalls are flared to provide a width 

at the cutoff sufficient to insure that the 

hydraulic control of the water surface is at the 

headwall and to provide a greater width at the 

cutoff which reduces the likelihood of erosion 
TRANSITIONS AND EROSION PROTECTION 345 

by reducing the depth and velocity for flows 

less than design flow. 

To provide adequate canal bank freeboard, 

the inlet water surface for design flow should 

be at least 2 feet below the top of the canal 

bank. The orifice equation [ 11, Q = CA&!& 

may be used to calculate the inlet water surface 

required to discharge the design flow. For a 

type 4 inlet transition, a discharge coefficient, 

C = 0.6 may be used. The head, h, measured 

from the centerline of the opening to the water 

surface for free flow may be conveniently 

determined by rearranging the orifice equation 

and making appropriate substitutions: 

2. Transition length equal to 3 pipe 

diameters or 5 feet minimum. 

3. Maximum invert slope of 4 to 1. 

4. Inlet pipe submergence of at least 1.5 

pipe velocity heads when full-pipe velocity 

equals 5 feet per second. 

5. Pipe submergence at outlet sufficient to 

cause pipe to flow full. 

6. lnlet and outlet freeboard varying from 

the lining freeboard to about 1.5 feet at the 

headwall. 

h = 0.0433V2 

where V is the design velocity of the pipe. 

7-10. Type 5 Transitions.-Figure 7-3 shows 

a typical type 5 transition. These transitions 

are simply an extension of the concrete canal 

lining which matches the normal concrete-lined 

section at one end and has a headwall on the 

pipe end. These transitions may be used where 

minimum head loss is not a factor. Figure 7-3 

has a table of dimensions for pipes up to 36 

inches in diameter. Because of headwall 

stability considerations, the maximum pipe 

diameter used with type 5 transitions is 36 

inches. 

The table of dimensions provide for the 

following: 

1. Full-pipe velocity of 5 feet per second. 

7-1 1. Earth Transitions. -Earth transitions 

may be used for transitioning from a canal 

section to a canal structure where structure 

velocities do not exceed 3.5 feet per second. 

Lengths of earth transitions are usually related 

to the size of the structure. For pipe structures, 

inlet and outlet earth transition lengths are 

both usually equal to 3 pipe diameters or a 

minimum of 5 feet. For other structures, earth 

transition lengths are usually 5 feet for 

relatively small capacity structures and 10 feet 

for other structures. Invert slopes should not 

be steeper than 4 to 1 for both inlet and outlet 

transitions. 

Lengths used for earth transitions in 

conjunction with concrete transitions should 

be 10 feet long or as otherwise required so that 

invert slopes are not steeper than the maximum 

allowable for the type 1 concrete transitions, 4 

to 1 for inlets and 6 to 1 for outlets. 

B. EROSION I I PROTECTION 

7-12. Purpose and Description. -Riprap and 

gravel protection (fig. 7-8) is often used 

adjacent to structures and at other locations in 

earth-surfaced canals where erosion may occur. 

Local conditions must be considered in 

determining the type and the amount of 

protection to be provided. These conditions 

include the cost of riprap; cost of gravel; 

danger to structures and crops or to human life 

should scour occur; rodent damage; type of 

soil; and velocity of water. The following 

protection requirements should be used as a 

guide only. The types shown represent 

minimum thicknesses and sizes of material to 

be used, and adjustments should be made to 

meet the local conditions mentioned above. 

Type l -6-inch coarse gravel 

Type 2- 12-inch coarse gravel 

Type 3-12-inch riprap on 6-inch sand and 

gravel bedding 

Type 4-18-inch riprap on 6-inch sand and 

gravel bedding 

Except for cross-drainage structures, type 3 

minimum protection should be used where 

velocities exceed 5 feet per second, regardless 

of water depth. 

7 - 13. Inverted Siphons. -The following 

protection is considered minimum for inverted 

siphons, 
346 SMALL CANAL STRUCTURES 

Figure 7-8. Erosion protection. 103-D-1293 
TRANSITIONS AND EROSION PROTECTION 347 

I I I 

Water depth, feet 

0 to 2.00 

2.01 to 3.50 

3.51 to 7.00 

7 ypc of protection Length of inlet 

Inlet Outlet protection 

None None __ 

None Type 1 __ 

Type 1 TYPO 2 1 depth (3 ft. min.) 

Length of outlet 

protection 

2.5 depths (5 ft. min.) 

2.5 depths (5 ft. min.) 

I I , I 

7-14. Cross-drainage Structures.-The 

following protection is considered minimum 

for cross-drainage structures with concrete 

transitions. 

Where the velocity in the conduit is greater 

than 15 feet per second at the outlet, use the 

protection type for the next higher discharge 

(type 3 minimum). Where baffled outlets are 

provided at the outlet of a structure the 

protection should be a thickness of F with the 

minimum diameter of rock equal to $$ and 

extending a distance W (5 feet minimum) 

beyond the baffled outlet. W is the inside 

width of the baffled outlet box. 

7 - 15. Other structures. -The following 

protection is considered minimum for Parshall 

flumes, checks, check-drops, inclined drops, 

chutes, turnouts, road crossings and pipe drops 

with the hydraulic control section on concrete, 

that is, where critical depth does not occur 

beyond the concrete structure. Where critical 

depth may occur beyond the concrete, the 

next higher type of protection should be used 

at the inlet. 

Length of protection for outlets should 

normally be 2.5 depths (5.0 feet minimum), 

but where turbulent water may occur at the 

outlet, the length of protection should be 

increased to 4 depths. Gates or stoplogs near 

the outlet increase turbulence. 

The rock for riprap and gravel protection 

should be hard, dense, durable, and should 

be reasonably well graded. The size range of 

rock used for 18-inch riprap should have a 

maximum size of l/S cubic yard and a 

minimum size of l/l0 cubic foot. The size 

range used for 12-inch riprap should have a 

maximum size of 1 cubic foot and a minimum 

size of l-1/2 inches. The size range used in 

coarse gravel protection should have a 

maximum size of l/8 cubic foot and a 

minimum size of 3/ 16 inches. 

The 6-inch sand and gravel bedding for 

riprap should be a continuous layer of sand and 

gravel or sand and crushed rock, reasonably 

well graded to a maximum of l-1/2 inches in 

size. 

C. BIBLIOGRAPHY 

7- 16. Bibliography. 

[l] King, H. W. and Brater, E. F., “Handbook of Hydraulics,” 

Fifth Edition, McGraw-Hill Book Co., New York, 1963. 

((Chapter VIII 

Pipe and Pipe Appurtenances 

R. B. YOUNG’ 

A. GENERAL 

8-l. Pipe and Pipe Appurtenances. -In this 

publication, pipe is considered to be any 

circular conduit used for conveying water and 

may be manufactured from many different 

materials such as reinforced concrete, 

corrugated metal, asbestos cement, reinforced 

plastic mortar, and welded steel. 

Appurtenances to a pipe are those structural 

elements necessary to provide efficient 

hydraulics, structural integrity, effective 

watertightness, adequate percolation path, easy 

access for inspection and maintenance, and 

effective safety. 

A minimum pipe diameter of 12 inches 

should be used for structures in an open 

irrigation system to reduce the possibility of 

clogging by sediment or debris. It may be 

desirable to use a larger minimum diameter if 

clogging by indigenous weeds is a major 

consideration. A pipe diameter range of 12 

through 72 inches for this publication was 

established by the above 12-inch minimum 

diameter and by what was considered to be a 

large enough pipe for cross-drainage structures 

that will be encountered in this publication. 

8-2. Hydraulic Head Losses.-The main 

energy losses (hydraulic head losses) associated 

with water flowing through a pipe include 

friction losses, entrance and exit losses, and 

bend losses. 

Friction losses can be determined by using 

‘Civil Engineer, Hydraulic Structures Branch, Bureau of 

Reclamation. 

Manning’s formula [ 1 ] * : 

v = 1.486 r* I3 s’ I2 

1-l 

r = hydraulic radius (water area divided 

by wetted perimeter) 

For a pipe flowing full 

A l-2 

wP 

= nR* __ =-=- R D 

2rR 2 4 

then 

v = 0.59 D2’3~“2 or s = 

n 

where 

V= 

r= 

S= 

A, = 

wp = 

R= 

D= 

n= 

velocity of water in feet per second, 

hydraulic radius 

slope of energy gradient in feet per 

foot, 

cross-sectional area of full pipe in 

square feet , 

wetted perimeter, in feet 

radius of pipe in feet, 

diameter of pipe in feet, and 

coefficient of roughness (see sec. 

I- 16). The assumed roughness 

(continued on page 359) 

2 Numbers in brackets refer to items in the bibliography, see 

sec. S-19. 

349 
350 SMALL CANAL STRUCTURES 

Table 8-l.-Friction losses for circular conduits. 103-D-1 316-l 
PIPE AND PIPE APPURTENANCES 

Table 8-l.-mFriction losses/or circular conduits.-Continued. 103-D-1316-2 

A :?42 

3.5C .19 

3.82 .*3 

ii.13 .27 

4.45 .31 

4.77 .35 

5.09 .40 

5.41 .‘+b 

5.73 .51 

6.04 .57 

6.36 .63 

6.68 .69 

7.00 .76 

7.32 .83 

1.63 .04 .38 

1.67 .04 .39 

1.71 ;os .a, 

1.75 ,05 .43 1.79 .05 .45 1.83 ,05 4, 

1.87 r05 .50 1.91 .06 .52 1.95 .06 .54 

1,5 . *z 

1.38 .03 .2* 

I.41 .03 .25 

1.‘*5 .03 .Lb 

1.48 .03 ..?7 

.52 o’i 29 

1.55 .o* .30 

1.58 .o* .31 

1.65 .o+ .3* 

l.bb 04 

0 

CfS 

3.00 

3.20 

3.40 

3.60 

3.80 

*oo . 

4.20 

4.40 

L.60 

A 

X0 

5.20 

5.1.0 

5.66 

+g 

6.10 

6.40 

6.60 

6.80 

7. 0 

7.20 

7.40 

7.60 

'. 

8.00 

8.20 

8.40 

8.60 

8.80 

9.0" 

9.20 

9.40 

9.60 

18.00 

19.00 

LO.00 

21.00 

22.03 

13.00 

FRICTION LOSSES FOR CIRCULAR CONDUITS 

MANNING’S FORMULA n=.013 

24”, 27”, 30”, AND 33”. DIAMETERS 

Sheet 2 Of 9 

351 
352 SMALL CANAL STRUCTURES 

Table 8-l.-Fricfion losses.for circular conduits.-Continued. 103-D-1316-3 

0 A El68 e-296 4 2” n 4.9621 n i I?045 0 

cfs v h” H ” h” H Y h” H- ” h” H CfS 

8.00 1.13 .02 .1c 8.00 

8.ZO 1.16 .OZ .15 8.20 8.40 1.19 .02 .15 8.W 

8.60 1.*2 .02 .16 8.60 

8.80 ’ 1.25 .02 .17 8.80 

9.00 1.27 .02 .18 9.00 

9.20 1.30 .03 .I8 9.20 

XI . :*:: . :I: ::% 9.406 

9.80 1.39 .03 .21 9.80 10.00 i.ll *OS .22 10.00 11.00 1.56 .04 .27 11.00 12.00 1.70 .04 .3* 12.00 13.00 1.84 .05 .38 13.00 

14.00 1.98 .06 .44 14.00 

15.00 2.12 .07 .50 15.00 

16.00 2.26 .08 .57 16.00 17.30 2.40 .09 .64 17.00 

18.00 2.54 .10 .72 18.00 

19.00 2.68 .I1 .80 ’ 19.00 

20.00 2.82 .12 .89 21.00 / 20.00 2.97 .I4 .99 2i.00 

22.00 3.11 .15 1.08 22.00 

23.00 ; 3.25 .16 I.18 23.00 

24.00 1 3.39 .I8 1.29 24.00 

25.00 I 3.53 .19 1.39 25.00 

26.00 3.67 .21 1.51 3.13 .15 .98 2.70 .li .66 2.35 .09 .Gb 26.00 27.00 3.82 .23 1.63 3.25 .16 I.06 2.81 .12 .72 2.45 .09 .50 27.00 

28.00 3.96 .24 1.76 3.37 .18 I.14 2.91 .13 .77 2.53 .10 .53 28.00 

29.00 0.10 .Zb 1.88 3.49 .19 1.22 3.01 .14 .82 2.63 .il .57 

30.00 .28 Z.01 2m k.24 3.61 .ZO 1.31 3.12 .I5 .89 2.71 .II .61 30.00 

31.00 r.38 .30 2.15 3.7* .2* 1.41 3.22 .16 .94 2.81 .I2 .65 31.0’2 

32.00 6.52 .32 2.29 3.86 .*3 1.50 3.32 .17 1.00 2.89 .13 .69 32.00 33.00 4.66 .34 2.*3 3.98 .25 1.59 3,43 .18 I.07 2.99 .li* .7’* 33.00 

34.00 4.81 .36 2.59 6.10 *26 1.69 3.53 .19 1.13 3.07 .15 .78 34.00 

35.50 4.95 .38 2.75 4.22 .28 1.79 3.6” .*1 1.21 3.17 .I6 .83 35.00 

36.00 5.09 .*o 2.90 *.3rr .ZS 1.90 3.74 .ZL 1.27 3.26 .ib .88 36.00 

37.00 5.23 .43 3.07 4.46 .31 2.00 3.85 .23 1.35 P.35 .17 .93 37.00 

3.3.00 5.37 .45 3.23 4.58 .33 2.11 3.95 .2* 1.42 3.44 .I8 .98 38.00 

39.00 5.51 .47 3.40 4.70 .34 2.22 4.05 .Lb 1.49 ?.53 .19 1.03 ! 39.00 

w.00 

41.00 ~ 

5.65 .50 3.58 4.82 .36 2.34 4.15 .27 1.57 / 3.62 .20 1.09 40.00 

42.30 5.9480 .55* 3.9677 1 4.95 5.06 .*o38 2.5847 L.36 42.29ZB 

‘3.00 6.08 .58 4.15 5.19 .ZZ 2.71 4.47 .31 

Iii,: 1 iif 2; ;:g 

. 

ia:;: 

44.00 6.22 .60 4.34 5.30 .r* 2.83 4.X .32 1.90 3.9d .25 1.32 r4.00 45.00 6.37 .63 4.55 5.43 .46 2.97 ‘.68 .3* *.to 11.07 .26 1.38 45.00 

4 46.009 47.008 501.006.506579 6.93:% .669725 .8814.74 0.96 53917.61 5856.0315 554.677 591.5n648c .5293.092638 3.526781 4.78 la.89 4.99 50:-:z . .357v40 .II*Z 2.081 z277.36 2454.16 ii.2r.34 4.4452 k6.293i37 .28311.51644’l !.57 1.708 19.00 ‘16.00 r7.00 48.00 .0*00 51.00 

52.00 7.35 .84 6.06 6.27 .61 3.96 5.40 .*5 2.66 4.71 .34 1.85 52.00 

53.00 7.50 .87 6131 6.39 .64 4.12 5.51 .47 2.77 4.80 .36 1.92 53.00 

54.00 7.63 .90 6.53 6.51 .66 4.27 5.61 .&9 2.87 4.89 .37 1.39 54.00 

55.00 7.78 .94 6.79 6.63 .68 4.43 5.72 .51 2.99 4.98 .39 2.06 55.00 56.30 7.92 .97 7.04 6.75 .71 4.59 5.82 .52 3.09 5.07 .4O Z.l’i 16.00 

57.00 8.06 1.01 7.29 6.88 -73 4.7, 5.92 .55 3.20 2.22 57.00 58.CO 8.20 1.04 7.55 6.99 *76 il.93 6.03 .56 3.32 i Z:E .‘*1 .43 2.29 18.00 

59.00 8.35 1.08 1.83 7.12 .79 5.11 6.13 .58 3.43 / 5.34 .&4 2.37 59.00 

60.00 8.&B I.11 8.07 7.23 .81 5.27 6.23 .60 3.54 ! VT I.&5 60.00 

62.00 8.77 1.19 8.63 7.47 .87 5.63 6.44 .64 3.79 1.61 .49 2.62 bZ.OC 64.03 9.05 1.27 9.19 7.72 .92 6.01 0.65 .69 6.04 5.79 .52 2.79 64.00 

66.00 9.33 1.35 9.77 7.96 .9B 6.39 6.86 .73 4.30 5.97 .55 2.91 66.00 

68.00 9.62 1.43 10.39 8.2‘ 1.C4 6.78 7.06 077 4.55 6.15 .55 3.15 be.00 

70.00 9.90 1.52 11.00 R.G,4 1.10 7.19 1.27 .8L 4.83 6.33 .bZ 3.lr. 70.00 

72.00 10.19 1.61 ii.66 8.68 1.17 7.00 7.48 .R7 5.11 6.52 .bb 3.14 72.00 7L.00 10.47 1.70 12.31 8.92 1.13 8.03 7.69 .9* 5.40 6.10 .70 3.74 7c.00 

76.01 1u.75 1.79 12.97 9.16 1.30 t3.46 7.90 .97 1.70 5.88 .73 3.94 76.00 

J8.00 9.40 1.37 8.91 8.10 1.02 5.99 1.06 .17 4.15 78.00 

80.30 9.65 1.44 9.40 8.31 1.07 6.31 7.22 .81 4.‘7 80.00 82.00 9.88 1.51 9.85 8.52 1.12 6.63 7.42 .85 4.5 82.00 

84.00 , 10.13 1.59 10.35 8.73 1.18 6.96 7.60 .93 a.81 19.30 

86.00 8.94 1.24 7.30 7.78 .94 5.04 86.02 

88.10 9.14 1.30 7.63 I.96 .98 5.26 88.00 

90.00 9.35 1.36 7.99 8.15 1.03 5.54 90.00 

92.00 9.56 1.42 8.35 

, 

a.33 I.08 5.78 92.00 

94.00 9.77 1.98 8.72 8.>1 I.12 6.04 94.00 96.00 9.98 1.5’1 9.10 8.69 1.17 6.29 96.03 

98.00 10.18 1.61 9.47 8.87 I.22 6.56 98.00 00.00 10.39 1.67 9.87 9.05 1.21 6.83 100.00 OZ.00 9.24 1.33 7.12 102.00 

04.00 9.42 1.38 7.60 10’1.03 06.00 9.60 1.43 7.68 106.00 

08.00 9.78 1.49 7.97 108.00 

10.00 9.95 1.5” 8.25 110.00 

12.00 NOTES 10.14 I.60 8.57 112.00 14.00 Rosed on form”,0 v: * .f s+ 10.32 1.66 8.88 114.00 

4.Are0 of Pipe in SQUOW feet 

v: Velocity In feet per second 

h”=“PlOCl+y he& In feet 

n = Coefficient of ra”gh”ess 

r= Hydro”ilc rod,“5 I” tee+ 

FRICTION LOSSES FOR CI!?CULAR CONDUITS 5’ Frlctlon loss I” feet per foot 

MANNING’S FORMULA n:.013 

H=Frictlon loss in feet per thouwnd feet 

36”, 39”. 42”, AND 45”. DIAMETERS 

Sheet 3 Of 9 
PIPE AND PIPE APPURTENANCES 

Table 8-l.-Frict~on (ones for circular conduits. -Continued. 103-D-1316-4 

FRICTION LOSSES FOR CIRCULAR CONDUITS 

MANNING’S FORMULA n=.013 

48”, 51”, 54”, AND 57”. DIAMETERS 

ibee, 4 n* 9 
354 SMALL CANAL STRUCTURES 

Table 8-l .-Frlriction losses for circular conduits. -Continued. 103-D-l 3 16-5 

, 
PIPE AND PIPE APPURTENANCES 

Table 8-l .-Friction lossesfor circular conduits. -Continued. 103-D-l 316-6 

355 

.zz .bZ .23 .65 .24 .67 .2* .69 .25 .72 .26 .74 

- ::z :,‘,’ .29 .8i .SC .“5 .31 .88 .3* .91 .3? .94 .3+ .97 

9.34 1.3’ 3.-c, 

FRICTION LOSSES FOR CIRCULAR CDND”,TS 

MANNING’S FORMULA n: 013 

72”, 75”. 78”. AND El”, DIAMETERS 
356 SMALL CANAL STRUCTURES 

Table 8-1.pFriction Iosses,for circular conduits.-Continued. 103-D-l 316-7 

3.6” .*1 .4-s 

3.77 .** .51 

3.39 .I8 .39 

3.52 .I9 .‘rZ 

3.06 .15 .30 

3.17 .16 .33 

7.28 .I7 .,5 

k.117 .37 .78 4.98 .3R .RZ 

5.39 .40 .R5 5.21 .i.L .,9 5.32 .44 .91 

4.56 .32 .SC 4.66 .34 .bd 

5.3; .45 .5* 

5.19 .4Z .P5 

8.?D I.01 *.c: 

“.L, l.Cb L.16 

FA,CTION LOSSES FOR CIRCULAR CONDUITS 

MANNING’S FORMULA n=.013 

84’O. 87”, go”, AND 93”, DIAMETERS 
PIPE AND PIPE APPURTENANCES 

Table S-I.-Friction lossesfor circular conduits.-Continued. 103-D-l 316-S 

357 
358 SMALL CANAL STRUCTURES 

Table 8-1 .-Friction losses for circular conduits. -Continued. 103-D-l 316-9 

t 
PIPE AND PIPE APPURTENANCES 359 

coefficient for pipe as related to this transitions, entrance and exit losses for a 

publication is n = 0.013, except for submerged condition are assumed to be 0.5hv 

corrugated-metal pipe where n = 

P 

0.024 is assumed. Except for and l.Ohv P 

, respectively, where h, 

P 

is the pipe 

corrugated-metal pipe, the friction velocity head for pipe flowing full. 

loss for all pipe flowing full can also Bend losses can be determined by using the 

be determined by multiplying the formula: 

friction loss per 1,000 feet (table 

S-1) by 0.001 times the number of 

feet of pipe. V2 

Entrance and exit losses for pipe structures 

h, =$ 

having concrete inlet and outlet transitions are 

discussed in section 7-3. The value of Hind’s c (zeta) can be obtained 

For pipe structures without concrete from figure 8-1. 

B. PIPE 

8-3. Precast Reinforced Concrete Pressure 

Pipe (figs. 2-5, 2-6, 8-2, and 8-3).-Precast 

reinforced concrete pressure pipe (PCP) is used 

for conveying canal water or storm runoff 

water under roadways, railroads, other canals, 

natural drains, channels, depressions, down 

steep terrain to a lower elevation, and for 

turnouts through canal banks. All precast 

concrete pipe which must operate under 

hydrostatic pressure or pipes used for turnouts, 

chutes, and cross drain culverts under canals 

should be PCP which has watertight rubber 

gasket joints to prevent leakage. 

Pipe structures using PCP are limited to 

combination loadings of hydrostatic heads 

measured to the centerline of the pipe not 

exceeding 150 feet with earth cover over the 

top of the pipe (fill) not exceeding 20 feet. 

Table 1 in the Standard Specifications [2] 

shows designs for pipe, 12 through 108 inches 

in diameter, that will meet requirements for 

various loading combinations of head and fill. 

A special design is required for fills exceeding 

20 feet. The use of PCP is limited to a 

maximum head of 150 feet. 

8-4. Precast Reinforced Concrete Culvert 

Pipe.-Precast reinforced concrete culvert pipe 

(RCCP) is used for conveying canal water or 

storm runoff water under roadways and 

railroads. The pipe design may be determined 

from tables provided by a pipe manufacturer. 

A typical set of tables is provided in 

bibliography reference [ 31. 

8-S. Corrugated-metal Pipe (figs. 8-4 and 

8-5).--Corrugated-metal pipe (CMP) fabricated 

from either galvanized steel or aluminum alloy 

is used for conveying canal water or storm 

runoff water under roadways and railroads, and 

also for conveying storm runoff water through 

canal banks into canals. In use this pipe should 

have little or no internal hydrostatic pressure. 

The required gage of CMP for a combination of 

given height of fill and surcharge load from 

vehicles may be determined from tables 

provided by a pipe manufacturer. A typical set 

of tables is provided in bibliography references 

[4] and [5]. 

8-6. Asbestos-cement Pressure 

Pipe.-Asbestos-cement pressure pipe (AC) may 

be used as an alternative to PCP pipe for 

conveying canal water or storm runoff water. 

This pipe has a connecting collar with rubber 

gaskets and may be used for hydrostatic heads 

up to 675 feet in combination with fills up to 

20 feet. The selection table for pipe, 4 through 

42 inches in diameter, in the Standard 

Specifications [6] shows the class of pipe 

required to withstand the loadings imposed for 

various combinations of head and fill. 

8-7. Reinforced Plastic Mortar Pressure 

Pipe.-Reinforced plastic mortar pressure pipe 

(RPM) may be used as an alternative to PCP 

pipe for conveying canal water or storm runoff 

water. This pipe is composed of resin, sand, 
360 SMALL CANAL STRUCTURES 

i’\ i / 

,L++-.+ 

i i 

I i i I rr I I\I I I I I \ I h I 0 

I I G- I I I I I II-I I I I I I\I\I 0 - 
PIPE AND PIPE APPURTENANCES 361

Figure 8-2. Precast reinforced concrete pressure pipe

in trench prior to backfilling. P-271-701-3819

Figure 8-4. Corrugated-metal pipe used for road

crossing. P-796-701-1548

Figure 8-5. Installation of corrugated-metal-pipe road

crossing. P-328- 701-8759

paragraphs for specifications [ 7] shows the

class of pipe required to withstand various

combinations of head and fill.

8-8. We/ded Stee/ Pipe (figs. 8-6 and

8-7).-Welded steel pipe (WSP) is used for

carrying canal or storm runoff water over other

structures or natural features. Steel pipe is

usually used for this purpose because lengths of

pipe may be welded together to form a

continuous length of pipe with sufficient

strength and watertightness for spanning

between supports. Stiffeners mayor may not

be required to obtain the required beam

strength.

Figure 8-3. Precast reinforced concrete pressure pipe

used for inverted siphon. P-328-701-8498

and fiberglass reinforcement and may be used

for heads up to 450 feet in combination with

fills not exceeding 15 feet.

The selection table for pipe, 8 through 48

inches in diameter, included with the standard
SMALL CANAL STRUCTURES 362

Figure 8- 7. Overhead welded steel pipe crossing.

P-31-D-22581

Figure 8.6. Welded steel pipe flume. P-211-101-38SS

8-9. Other Pipe.-Generally reinforced

monolithic concrete pipe, pre tensioned

concrete pipe, or prestressed concrete pipe are

not economical when used for structures

discussed in this publication, therefore their

design has been omitted.

The required gage of WSP for a given span

length and internal water pressure may be

conveniently determined from tables and other

information provided by the pipe

manufacturer. A typical set of tables is

provided in bibliography reference [ 8] .

c. PIPE APPURTENANCES

(percolation factors) vary with the type of soil

due to the soils resistance to percolating water.

Lane's weighted-creep ratio is the

weighted-creep length divided by the effective

head. Effective head is the difference in water

surface elevations at the beginning of path and

point of relief, and weighted-creep length is the

sum of: ( I) vertical path distance along the

structure (steeper than 450), (2) one-third of

the horizontal path distance along the structure

(flatter than 450), and (3) two times any

percolation path distance that short-cuts

through the soil.

weighted-creep ratio -weighted-creep length

(percolation factor) -difference in water

surface elevations

8-10. Pipe Collars and Percolation. -Pipe

collars are transverse fins (figs. 2-23, 4-19,

4-22, and 8-8) that extend from the pipe into

the surrounding earth and function as barriers

to percolating water and burrowing rodents.

Collars are often needed to reduce the

velocity of water moving along the outside of

pipe or through surrounding earth thereby

preventing removal of soil particles (piping) at

the point of emergence. For any pipe structure

where the inlet water surface is significantly

higher than a potential point of relief for the

percolating water (percolation gradient through

earth of 5 to lor steeper), the structure should

be examined to determine the need for pipe

collars.

Lane's weighted creep method [9] is

commonly used for percolation path studies

related to canal structures. Using this method,

the length of weighted creep (weighted path)

necessary to prevent piping is directly related

to the head of water and the type of soil.

Recommended weighted-creep ratios

The weighted-creep ratio should be at least

2.5 to 1 as computed by Lane's weighted-creep

method. Larger ratios may be required where

warranted by the type of soil or importance

and the type of structure.
PIPE AND PIPE APPURTENANCES 363 

I Pipe to be centered ,n collar I 

t-L_ 

AZ- L 

ELEVATION 

(Pope collar for precast concrete pope. asbestos-cement 

pipe and reinforced plostlc mortar pIpei 

5 D (/B”Min ) 

LEVEL PIPE SLOPED PIPE 

SECTION A-A 

;FSymm about (1 

DIMENSIONS AND 

ESTIMATED QUANTITIES 

iPIpe collar for precast concrete pipe, asbestos-cement 

pipe and reinforced plastic mortar plpel 

/ , , 

ELEVATION 

(Pipe collar for corrugated metal plpel 

~16 Gage with 

vert corrugotlon 

SECTION B-B 

Figure 8-8. Pipe collars. 103-D-1318 
364 SMALL CANAL STRUCTURES

Lane's recommended weighted-creep ratios

are:

Material Ratio

8.5:1

7.0:1

6.0:1

5.0:1

4.0:1

3.5: I

3.0: I

2.5:1

3.0: I

2.0:1

1.8:1

1.6:1

Very fine sand or silt

Fine sand

Medium sand

Coarse sand

Fine gravel

Medium gravel

Coarse gravel including cobbles

Boulders with some cobbles and gravel

Soft clay

Medium clay

Hard clay

Very hard clay or hardpan

Figure 8-9. Forms for thrust block on 54-inch-<liameter

precast concrete pipe. P-499- 700-5 19

sliding coefficient of 0.35 is frequently used.

For vertical bends which are convex (~),

thrust forces tend to push the pipe out of the

ground. Resisting these forces are the weight of

the full pipe and the earth cover. Earth cover is

usually omitted in the stability computations

as such cover may be removed or washed away.

The total static thrust (T) on a bend can be

computed by

If the computed weighted-creep ratio is less

than that recommended, collars should be

added to the pipe structure.

Cross-drainage structure pipe under a canal

requires at least one collar around the pipe in

the uphill bank and two collars around the pipe

in the downhill bank. Two collars are required

around the pipe in the upper bank if the invert

elevation at the inlet cutoff is below the

bottom grade of the canal. See figures 4-26 and

4-28 and chapter IV for locating collars on

cross-drainage structures.

8-11. Pipe Bends (fig. 8-9 ).-(a) Purpose

and Design Considerations.-Pipe bends are

used both for horizontal changes in pipe

alinement and for vertical changes in grade.

Bends in pipe cause directional changes in

the flow of water which results in dynamic and

static thrusts at the bends.

Dynamic thrust for most pipe structures can

be omitted because of the relatively slow

design velocities. Static thrust for low heads is

also usually insignificant. However, for

relatively high heads, the static thrust is

significant and stability of the bend should be

investigated. Thrust on horizontal bends and

on vertical bends which are con~ave (~) is

resisted by soil pressure. If allowable

soil-bearing capacity for these vertical bends or

allowable passive pressure for these horizontal

bends is exceeded, thrust blocks are provided

usually by encasing the bend in concrete. The

thrust is thereby spread over a greater surface

area resulting in reduced soil pressures. For

horizontal bends, resistance to sliding

developed by friction is also sometimes

included in the bend stability computations. A

where:

T = thrust, in pounds

H = hydrostatic head to centerline of

pipe

A = area of pipe opening in square feet

6 = deflection angle of bend in degrees

62.4 = weight in pounds of a cubic foot of

water .

For a vertical convex upward bend, the

thrust is resisted by the dead weight of the full
PIPE AND PIPE APPURTENANCES 

pipe for a length extending between joints at 

each end of the bend. If additional weight is 

required for equilibrium, the pipe bend is 

usually encased in a concrete thrust block. 

Pipe bend energy losses can be determined 

by using the equation: 11, = 5‘ ? as was 

(1) Banded mitered pipe. -Bends formed 

with mitered pipe are commonly used for 

pipe structures in small canals. These bends 

are fabricated by cutting straight pipe units 

to one-half the required deflection angle and 

mortaring the two pipe units together as 

shown on figures 8- 10 and 8- 11. The class of 

pipe used in fabricating the bends should not 

be less than the class of pipe in the adjacent 

pipe units. 

It is often necessary to provide additional 

weight when using miter bends because of 

static thrust as previously discussed. If 

concrete encasement is used with pipe 

having rubber gasket joints, the distance 

from the face of the encasement to the pipe 

joint should be limited to 18 inches for pipe 

up to 36 inches in diameter and one-half the 

diameter for pipe larger than 36-inch 

diameter. 

(2) Bevel-end pipe.-Bends may also be 

formed using beveled-end pipe. The 

deflection of each bevel should not exceed 

5’. This limitation permits the use of 

circular joint-forming rings at the slightly 

elliptical (beveled) end of the pipe. 

(3) Precast elbows. -Precast elbows are 

sometimes used for fabricating pipe bends as 

shown on figure 8-l 1. The units may either 

be curved or contain an angle such that the 

ends of the elbow units are normal to the 

longitudinal axis. Elbows should be the same 

class of pipe with the same type of joint as 

the adjacent pipe. 

(4) Pulled ioilzts.-Bends of long-radius 

may be produced by deflecting (pulling) a 

sufficient number of pipe units at their 

joints, provided that the alinement or profile 

will permit this procedure. A full-laying 

length of pipe should be used on both sides 

365 

of each joint. 

Where tongue-and-groove mortar joint 

pipe is laid on a long-radius curve, the joint 

opening at any point on the inside 

circumference should not be more than 

one-half inch wider than a normal joint. 

Where pipe with type R-l joints is laid on 

a long-radius curve, the distance A (fig. 1 in 

bibliography reference [2] ) should not be 

less than one-fourth inch. 

Pipe with type R-2 joints may be 

deflected an amount such that distance A 

(fig. 2 in bibliography reference [2] ) is not 

less than one-eighth inch; however, the grout 

space on the outside of the pipe should not 

be less than one-half inch wide and the 

mortar space on the inside of the pipe 

should not be less than one-fourth inch 

wide. 

Type R-3 and R-4 joints may be pulled on 

one side of the pipe so that the joint opening 

on that side of the pipe is not more than 

one-half inch wider than the joint opening 

on the opposite side of the pipe provided 

that the distance A (fig. 3, 4, 5, and 6 in 

bibliography reference [2] ) is not less than 

one-fourth inch at any point on the 

circumference of the joint. 

(c) Bends for Asbestos-cement 

Pipe.-Methods used for changes in alinement 

or grade of asbestos-cement pipe include the 

following: 

(1) Mitered pipe.-Bends may be 

fabricated by joining mitered 

asbestos-cement pipe with an approved type 

of cement and encasing the bend in concrete 

as shown on figure 8-12. The stability of the 

bend for static thrust may require additional 

concrete encasement. The pipe extension 

beyond the concrete encasement should be 

limited to 18 inches for pipe up to 36 inches 

in diameter and one-half the diameter for 

pipe larger than 36-inch diameter. 

The miter bend shown on figure 8-13 may 

also be used as shown or with cast-iron 

fittings substituted for the mortar-lined steel 

pipe. 

(2) Pulled joints. -Long-radius bends 

formed by deflecting (pulling) joints may be 

used where pipe alinement or profile will 

permit this procedure. The deflection angle 

between adjacent pipe units should not 

(continued on page 371) 
366 SMALL CANAL STRUCTURES 

Reinf 2"" 2"'/2**/2 weided 

wrre fabric Weld or lap 4- 

Drovide transverse reinforcement not Pipe jorntless fhon tl,ot required for o,i equal 

ienqth of odjacent pipe Transverse 

reinforcement to be welded or lopped 

24 bar diomefers of splice, ---mmBANDED MITERED PIPE BEND 

ENCASED MITERED PIPE BEND 

#ret of tro~sverse reinforcement 

shall be equivalent to that required 

in pipe whose rnslde dro is equal to 

outside die of encased pipe oud of 

the s"me p!pe cioss Lop bars 24 bar O/J 

Encasement symm. 

'z about C pipe 

l6' i 

SECTJON A -A 

NOTES 

Compoci bockfiii to top of encasement of o/i bends 

Eievotion of compacted backfill for banded mitered 

pipe bends shall be the some OS the elevation of 

compacted bockfrll specified for the odlacent pipe 

P!pe extension shall be i8"mox when D 4 36"ondj 0 

mox when 0'36: 

TIISS flqure shoas ivv~ occeptobie woj‘ n wh cn p,pe bends 

r,:j be fobrtcoted The stability of the bend in ic ';',rq 

hydrosfat!c thrust must be checked if the thrust IS 

great enough to make these bends ‘nsiub'e, rhe 

rncocemcn- omensions of +he encased bend may be 

wcreoied for c+obrlity 

Figure &IO. Precast concrete pressure pipe bends. 103-D-1319 
PIPE AND PIPE APPURTENANCES 367 

Pipe reinforcement not shown, 

Reinf may becut 

offorextended 

’ 3”Min / I A .-A 

Omit encasement if ‘i, 

3 is iess thon 22”m30’ , 

Provide transwrre rein?orcement not less thaq 

that required for a” equal length of 

adjacent pope Transverse reinforcement 

to be welded or lapped 24 bar d/a’s at 

ENCASED MITERED PIPE BEND 

ENCASED PRECAST ELBOW WENDS 

Provice transverse reinforcement not 

less than that required for on equal 

lenqth of CdjaCeat pipe Transverse 

reinforcement to be welded or lopped 

24 bar diameters ot spices 

Remf 2’; 2”. it/2x “12 welded __ 

we fobrrc 

Longitudinal bars shall /;‘“M,“. 

be loppedamin~mumof e2,, M 0 x 

,, 

(iI,-ro 0’ +ronsverse re~niorcrmenl 

‘5 shall be equlvolent to that required 

\ in pipe whose inside die is equal to 

die of encased pipe and of 

same pipe class Lop bars 24 bnr die 

Symm about E 

onqit @ /z J 

BANDED MITERED PIPE BEND SECTION A-A 

WAND THICKNESS DATA 

NOTES 

Clevutior of compacted backfiii for unencosed elbow bends 

and bonded pipe bends shall be the same as the elevalmn 

of compacted backftll specified for the odlacent p,pe 

Compnct backfill to top of concrete ot all encased bends 

This ftgure shows three occeptoble WOJS in which p!pe 

bends may be fabricated 

Figure 8-11. Precast concrete culvert pipe bends. 103-D-1320 
368 SMALL CANAL STRUCTURES 

E Asbestos-cement 

Pipe extenslo”, see notes 

TYPICAL BEND (SO” MAX.) 

E Asbestos-cement 

Jomt to be fobr,coted 

&-~~~~--P,pe extens9 

see notes 

Ak 

TYPICAL BEND (460 MA x.1 

HORIZONTAL OR VERTICAL SENDS 

Complete hoops lone or two p~ecesl wrth total steei 

oreo computed for bursting stress of II.oDOp s I 

w,th hydrostotx heod ct E pipe ,g#plled on outsIde 

drometer of p!pe for encasement length, 

acted bockffll 

Excovot,on Ime 

d-*4 Longrt hors 

SECTION A-A 

PfPC 

P’P’ 

NOTES 

Comport bockhll to top of encasement at oil bends. 

Pipe extensfon shall be I6’mox when 0s 36”ond i D mox when 

D > 36” Min extensfon shall be a* 

For olternot!ve bend fobrlcotton. see Figure 6-13 

Detolls show” o,-P muwnum bend fobr,cot!on requwements. 

The stabfifty of the bends I” resisting hydrostatic thrust must 

be checked if the thrust IS great enough to make these bends 

unstable, the encasement d,mens,ons moy be /“creased forstobd!iy 

Figure 8-12. Asbestos-cement pressure pipe bends (maximum head 17.5 feet). 103-D-1321 
PIPE AND PIPE APPURTENANCES 369 

See Je’ad A\ 

shown on the pion ondprofiie of the 

specific structure 

Steei pipe For thickness of stee, 

cylinder ond mortar iioing see Tobie , 

Mortar c-oofmgondrod wroptobe omr'teo 

'%/I At 

and 

E to be computed usmg "R" voices in Table 

“A’ angles Minimum *C’ to be / 0' 

TABLE I 

For hand applied or p"e"mot~‘0li;apDII?d iinings uIP 

"G"for IhlchnPss ofmortor iinlng 

Hand applied or pnwmotrcoliy oppiied linrn~s shoii b? 

reInforced wrth 2x,x,3 gogp welded w,rc fobrrc 

for SIIPS greater than 42:' 

TABLE 2 

NOTE 

for optional asbestos-cement pr'essur~p~pt- bmds,see 

flqure 8-12. 

Figure 8-13. Asbestos-cement pressure pipe and reinforced plastic mortar pressure pipe bends 

(maximum head 4.50 feet). 103-D-1322 
SMALL CANAL STRUCTURES 

,P” THROUGH 7e” DIA 

SECTlON A-A 

PARTIAL PLAN OF 

CHECK AN0 PlPE INLET OR 

CONTROL AN0 PPE lNLET 

w,r/1 I”’ .rri ,: o’-r,ll 

12” THROUGH 72” Did 

SECTION A-A 

A‘TERNATIYE DE5,‘N FOP 

12” THROUGH 27” DIA 

SECTION A-A 

PARTIAL PLAN OF OWlSlON BOX ELEVATlON B-8 

PIPE DlWSlON BOX, BAFFLED OUTLET 

OR WE,,? BOX 

~w,-l.,~, <.A71 a- iianw. 

J u X8 

PARTIAL PLAN OF PlPE TURNOUT IP” rHRoUGH 72” o,n 

OR C.H.0. TURNOUT SECTION E-E 

WIT” CLTF 47 b#l^PL”*L_ m 

IN 

ELEVATION D-D 

,Z” THROUGH 72” D,A 

SECT/ON E-E A‘TERNATIVE DESIGN FOR 

is?” THROUGH p,- DIA 

SECTION E-E 

Figure 8-14. Precast concrete pipe embedment (asbestos-cement pressure and reinforced 

plastic pressure pipe similar). 103-D-1323 
PIPE AND PIPE APPURTENANCES 

exceed 5’ for 18-inch-diameter pipe and 

smaller, 4’ for 2 l-inch-diameter pipe, and 

3’ for 24-inch-diameter pipe and larger. A 

full-laying length of pipe should be used on 

both sides of each joint to insure stability 

against static thrust. 

(d) Bends for Rcirzforced Plastic Mortur 

Pipe.-Changes in alinement or grade may be 

made by one of the following methods: 

(1) Mitered [‘@-Miter bends may be 

fabricated and encased in concrete as shown 

on figure 8- 13. 

(2) Pulled joints. -Long-radius bends may 

be formed where alinement or profile will 

permit by deflecting (pulling) joints a small 

amount. The joints may be pulled on one 

side of the pipe so that the joint opening on 

that side will not be more than one-half inch 

wider than the joint opening on the other 

side; however, the distance A (fig. 1 in 

bibliography reference [71) should not be 

less than one-fourth inch at any point in the 

circumference of the joint. A full-laying 

length of pipe should be used on each side of 

the joint to provide stability for static 

thrust. 

(e) Bends for Corruguted-metul 

Pipe. -Changes in alinement or grade of 

corrugated-metal pipe may be made with 

standard prefabricated elbow fittings of the 

same gage as the adjacent pipe. Encasement in 

concrete may be required to provide bend 

stability for static thrust. 

8-l 2. Pipe Embedment. -Figure 8- 14 shows 

connections between precast concrete pipe and 

adjoining structures. To insure good bond 

between the concrete structure and the precast 

concrete pipe, the end of the pipe to be 

embedded should be wire-brushed to remove 

all laitance and foreign matter and then wetted 

prior to placing concrete. 

The alternative embedment for sloping pipe 

as shown on the figure is restricted to 

diameters 27 inches and less. The alternative 

allows pipe of this size range to be miter-cut 

and is restricted, by usual practice, to a 

maximum diameter of 27 inches. This diameter 

restriction is not applicable if other than 

precast concrete pipe is used. 

When pipe having a rubber gasket joint is 

used, the pipe joint should be placed within 18 

371 

inches from the face of the embedment for 

36-inch pipe and smaller and within one-half 

the pipe diameter for pipe larger than 36 

inches. This provision allows small movements, 

due to unequal settlement of the structure and 

the pipe, to be absorbed in the joint and 

minimizes the possibility of cracking the pipe 

or the pipe embedment. 

Embedment of corrugated-metal and welded 

steel pipe may be similar to that shown on the 

figure, or the pipe may extend through the 

headwall with the pipe end flush with the face 

of the headwall. Steel pipe laid on a steep slope 

will usually have a steel ring welded to the pipe 

near the end that will be embedded in the 

concrete and will provide pipe anchorage with 

the concre tc. 

Embedment for a gated structure requires a 

vertical step in the floor at the headwall as 

shown on the figure to accommodate 

installation of the gate frame. 

8-l 3. Pipe Joints. -(a) Purpose mu’ Design 

Corzsideratiom. -Pipe joints are used to 

connect individual pipe units to form a 

continuous pipeline for a pipe structure. 

Careful consideration must be given to the type 

of joint permitted so that the pipe structure 

will function as intended without unnecessary 

maintenance. Considerations should include 

joint leakage from hydrostatic pressure; joint 

flexibility, especially where some uneven 

foundations settlement may reasonably be 

expected; relative importance for the safety of 

a structure under which the pipe may be 

placed; exposure of the joint to cold water in 

the spring months which may cause 

contraction cracking; and exposure to 

atmospheric temperature changes which cause 

contraction-expansion movement. 

(b) Joints for Precast Reinforced Concrete 

Pressure PiPe.-These joints use solid rubber 

gaskets, circular in cross section, and are the 

only element in the joint to provide 

watertightness. These joints also provide for 

slight movements in each pipe unit of the pipe 

structure which may be caused by foundation 

settlement, expansion, contraction, or lateral 

displacement. The joint assemblies should form 

a continuous watertight conduit having a 

smooth and uniform interior surface. 

Rubber gasket joints for precast reinforced 
372 

concrete pressure pipe may be type R-l, type 

R-2, type R-3, or type R-4 (figures 1, 2, 3, 4, 5, 

and 6, in bibliography reference [ 21). 

Type R-2 is used for installations where the 

pipe is to be jacked. Some cushioning between 

the joints will reduce the likelihood of 

breakage due to concentrated pressure. This 

cushioning can be provided by a piece of 

l/2-inch manila rope stuck to the pipe with 

asphaltic cement, strips of asphalt roofing 

paper, metal strips, or cement grout inserted 

around the circumference, in the joints, as each 

piece of pipe is placed ahead of the jacking 

SMALL CANAL STRUCTURES 

form. After the pipe is in final position, the 

joint may be pointed from the inside with 

mortar or joint compound. 

Requirements for all materials used in type 

R joints and other detailed requirements of 

these joints are given in bibliography reference 

[2], see sec. 8-19. 

(c) Joints for Culvert Pipe, -Reinforced 

mortar-banded joints of type B or type B-l 

(fig. 8-15) are perhaps the most commonly 

used joints for culvert pipe installations. 

The ends of culvert pipe sections are formed 

to permit effective jointing which reduces 

Reinforcement 2”x 2”- #I2 x#l2 

Welded wire fabric 

.,. . 

:. .‘.....‘..‘, Reinforcement 

Inside cement mortar joint, hand __/ L Cement mortar joint u Inside face 

pocked for 24”dio. ond lorgel: for 2l”dio. and smaller. 

TONGUE AND GROOVE JOINT 

TYPE 6 

Reinforcement 2”x 2”-*l2x#l2 

Welded wire fabric 

Reinforcement 

SELF-CENTERING JOINT 

TYPE B-I 

DIA OF PIPE 12”TO 20’ PfTO 24=27.TO 33” 36*TO 45’ 48’TO 51’ 54=TO 60’ 63=TO 96’ 

MINIMUM I, 

THICKNESS (t 1 if 

$9 ‘I I If” If” I;= 2” 

Figure 8-1.5. Precast concrete pipe joints-types B and B-l. 103-D-1324 
PIPE AND PIPE APPURTENANCES 373 

leakage and infiltration to a satisfactory 

minimum, and produces a continuous and 

uniform line of pipe. 

Type F joints may be substituted for type B 

or type B-l joints. The type F joint design and 

rubber gaskets for this joint should be in 

accordance with the American Society for 

Testing amd Materials [ 103 except that the 

taper on the tongue and groove should not be 

more than 3-1/2O measured from a longitudinal 

trace on the inside surface of the pipe. 

overlapped l-l /4 inches and soldered or brazed 

together along the edges of the lap. Copper for 

seals should be in accordance with Federal 

Specifications [ 111. At the opposite end of 

each pipe unit, wire fabric is embedded in the 

concrete pipe and protrudes into the annular 

joint space. 

(d) Joints fkr Corruguted-metul Pipe. -These 

joints are made with corrugated coupling 

(connecting) bands [4] [5] which are 

furnished by the pipe manufacturer. 

Type D joints (fig. 8-16) are used if a 

copper-seal-type joint is specified where culvert 

pipe is to be jacked under a railroad or 

highway. The tongue and groove dimensions 

should provide an inside or outside annular 

joint space for filling with grout as shown on 

the figure. A copper expansion strip is 

embedded in the tongue or groove end of each 

pipe unit and protrudes into the annular joint 

space. The ends of the copper strip are 

(e) Joints for Asbestos-ccmetzt Pressure 

Pipe.-These joints are made with coupling 

sleeves having rubber gaskets circular in cross 

section. With these couplings, units of pipe 

may be joined to form a continuous watertight 

conduit with a smooth and uniform interior 

surface. The joint assemblies provide for slight 

movements which may be caused by 

expansion, contraction, settlement, or lateral 

displacement. Detailed requirements of these 

joints are given in bibliography reference [6], 

see sec. 8-l 9. 

(f) Joints for Reirzjkwccd Plustic Mortar 

Pip-These joints also use solid, circular 

rubber gaskets to serve as the only element of 

the joint to provide watertightness. The joint 

assemblies form and provide a continuous 

watertight conduit with smooth and uniform 

in t erior surface and provide for slight 

movements due to expansion, contraction, 

settlement, or lateral displacement. Detailed 

requirements of these joints are given in 

bibliography reference [ 71, see sec. 8- 19. 

(g) Joints for Welded Steel Pipe.-These 

joints are made by welding or by using 

sleeve-type couplings [ 121 without pipe stops. 

These couplings provide for 

expansion-contraction and other slight pipe 

movement. Resilient gaskets in the couplings 

effect a flexible, watertight joint assembly. 

8- 14. Pipe Safety Barrier. -Pipe safety 

barriers made of barbed wire strung on a frame 

are placed on pipes crossing over waterways to 

discourage the use of the pipe as a pedestrian 

walkway. Figure 8-17 shows details of the 

barrier and a means of fastening it to steel or 

corrugated-metal pipe. 

The need for a barrier is dependent on the 

accessibility of the site to the general public. 

Past experiences indicate that regardless of the 

Paint surface af/arnt 

wth seolfng compound 

Ffeld cement 

grout aofsrde 

/- W!re fabrx 

<Capper expansion strip No 2688s 

Gage) 4” w/de , lap Ii-” 

PIPE DIA.- 2i”OR SMALLER 

Pipe re/nfarcement 

not shown 

Ohae face -\ 

Copper elpO”*lD” 

s trq Nosl 268 0 5 

Gage, 4 rrae, 

lap If” 

Ffeld cement 

i 

LPa,nt surface 

grout Ins/de 

afJa/nt with 

sealing compound 

PIPE DIA.-24”OR LARGER 

Figure 8-16. Precast concrete pipe joint-copper 

seal-type D. 103-D-1325 
SMALL CANAL STRUCTURES 

PLAN OF PIPE SAFETY BARRIER 

N WS 

SECTION A- A 

kid u 

DETAIL A 

Go/v barbed w,re space 

welded to angles 

SECTION B-B 

STEEL PlPE 

DE TAIL 

C.M.P 

B 

SECTION C -C 

Figure 8-l 7. Pipe safety barrier. 103-D-1326 
PIPE AND PIPE APPURTENANCES 

proximity of other pedestrian access over the 

waterway, a pipe barrier should be used on all 

pipe crossings except those in remote areas and 

for those crossing over fenced waterways. 

8- I5 Blowoff Structures (figs. 8-I 8 and 

8-Z9).-Blowoff structures are provided at or 

near the low point of relatively long inverted 

siphons to permit draining the pipe for 

inspection and maintenance or wintertime 

shutdown. These structures consist essentially 

of a valved steel pipe tapped into the siphon 

barrel. Blowoffs may also be used in an 

emergency in conjunction with wasteways for 

evacuating water from canals. Short siphons 

may be dewatered by pumping from either end 

of the siphon, and therefore, a blowoff is not 

required. 

Details of blowoff installations vary with the 

size of the siphon pipe and the topography 

near the siphon low point. The drain 

arrangement associated with the blowoff 

installation is also determined by the 

topography. Where feasible, blowoff structures 

should be located to permit the water to flow 

directly into the natural drainage channel. A 

6-inch blowoff is commonly used with siphon 

pipe to accommodate a reasonable time for 

draining. If annual wintertime draining is not 

required, breaking into pipe smaller than 

24-inch diameter for emergency draining is an 

alternative to providing a blowoff. 

A blowoff can be tapped into the siphon at 

or near the top of the pipe which will permit 

the draining of water from the pipe by gravity 

to the invert elevation of the blowoff discharge 

pipe. Draining can then be completed by 

pumping. A pipe drain may be tapped into the 

siphon near the bottom of the pipe which will 

permit draining the entire pipe by gravity. 

TO drain the entire pipe by gravity, the 

topography should permit the discharge pipe to 

be relatively short and laid on a steep slope 

without bends. This is essential to prevent 

clogging of the pipe. 

Draining by the combination gravity and 

pump method is usually required. After the 

siphon has been drained by gravity down to the 

discharge pipe elevation, the blind flange is 

then removed from the vertical pipe and a 

pump suction line is inserted into the siphon, 

and the remaining water can then bc drained 

by pumping. 

375 

The blowoff appurtenances should 

ordinarily be enclosed in a covered well 

extending above the adjacent original ground 

surface and protected by earthwork to near the 

top. Figure 8- 18 shows a typical 6-inch blowoff 

installation tapped into the top of precast 

concrete pipe. 

A manhole should be included with a 

blowoff on siphons one-half mile in length and 

longer and 36 inches and larger in diameter, to 

provide an intermediate access point for 

inspection and maintenance. A typical manhole 

and blowoff combination structure is shown on 

figure 8- 19. 

The hydraulic head on the blowoff will 

determine the class of fittings such as valves, 

tees, flanges, rings, and also the size of required 

welds. 

Blowoff and manhole assemblies for 

asbestos-cement and reinforced plastic mortar 

pipe require steel pipe fittings, concrete 

encasement, and covered wells similar to those 

shown for precast concrete pressure pipe. An 

inline section of mortar-lined steel pipe is used 

to provide connections for the blowoff and 

manhole nozzles. Joints at connections of the 

mortar-lined steel pipe and AC or RPM pipe 

should be as shown on figure 8-13. 

8-16. Air Vents.-Air vents should be 

provided at all locations along a pipe structure 

where air may accumulate or where a partial 

vacuum may occur. 

One of the more common uses of an air vent 

as related to structures for an open irrigation 

system is to prevent formation of 

subatmospheric pressures immediately 

downstream from a gate. High water velocity 

issuing through a partial gate opening can 

entrain air immediately downstream of the gate 

and cause a partial vacuum. This condition can 

create very undesirable water surface surging 

resulting in unsteady flow; can cause 

blowbacks of air and water of sufficient force 

to damage the structure; and can cause 

detrimental unequal air pressure loads on the 

gate leaf. An air vent having a diameter of 

one-sixth the pipe diameter (or 4 inches 

minimum) and located as shown on figure 3-l 5 

has given satisfactory performance in 

preventing these adverse conditions. 

The probability of an air and water 

blowback occurring in a long, inverted siphon 
376 SMALL CANAL STRUCTURES 

ul@i? 

SECTION O-O 

Figure 8-18. Blowoff for precast concrete pipe. 103-D-1327 
PIPE AND PIPE APPURTENANCES 377 

Figure 8-f 9. Manhole and blowoff for concrete pressure pipe. 103-D-1 328 
37% SMALL CANAL STRUCTURES 

LADDER 

iON. PitCEl 

TOP SECTION 

MO”NT,!vGS TURNED IN NO”NTINGS TURNED OUT 

TYPICAL WALL MOUNTING DETAIL 

INTERMEDIATE SECTION BOTTOM SECTION 

a 

FLOOR MouNTiNG DETAIL 

RUNG DETAIL 

i T”P,Chi , 

SPLICE DETAIL 

Figure 8-20. 16-inch steel ladder. 103-D-1329 
PIPE AND PIPE APPURTENANCES 379 

with a free-flow inlet may be determined by 

the procedure shown on figure 2-7. Siphon 

design should be adjusted if necessary to 

reduce this probability. These blowbacks are 

caused by air being entrained in the water at 

different locations such as the hydraulic jump 

then accumulating in the downstream portion 

of the jump until the pressure and volume of 

the resulting bubble is sufficient to cause it to 

rise and explode into the atmosphere. The 

process is repetitive and may produce sufficient 

violent force to damage the structure; 

therefore, design effort should be made to 

avoid this condition. Air vents are discussed 

here only as a corrective measure in the event a 

blowback condition develops. 

Air vents are also commonly located at high 

points along a pipe profile to allow 

accumulated air to escape and also to permit 

entry of air when the pipe is being drained. Air 

release is essential to avoid trapping air bubbles 

which can reduce or completely stop the flow 

of water. Air entry into a pipe while being 

drained is essential to equalize air pressures 

inside and outside of the pipe which otherwise 

might collapse the pipe. Figure 8-21 shows the 

installation requirements of a concrete pipe air 

vent used for the above purposes. 

Six-inch-diameter air vents are commonly used 

with inline pipe diameters as large as 21 inches 

while la-inch air vents are installed in larger 

diameter pipe. The pipe vent should extend at 

least 24 inches above the hydraulic gradient. 

Air valves are sometimes used in place of pipe 

vents. 

Installation of air vents in asbestos-cement, 

and reinforced plastic mortar pipe may be 

similar to figure 8-21 except tee fittings may be 

used. 

8 - 17. Step-type Pipe Tapers (fig. 

8-22).-These tapers may be used to transition 

from one pipe size to another, provided the 

hydraulic head is 50 feet or less and provided 

the head loss in the taper is permissible. If the 

head is greater than 50 feet or if the head loss 

associated with this taper is too great it may be 

necessary to use a gradual pipe taper instead of 

the step type. 

Head losses for step-type pipe tapers may be 

assumed to be 0.25 times the change in 

velocity head through the taper for an 

increasing diameter and 0.10 times that change 

for a reducing diameter. If taper is gradual the 

above losses may be reduced by one-half. 

8-18. Pipe Earthwork. -Excavation required 

for pipe installation in an open irrigation 

system is generally such that the use of a 

motorized trenching machine would seldom be 

advantageous. For example, steep topography 

at chutes, drops, and inverted siphon sites, or 

generally shallow cuts at road crossings and 

turnouts, which are usually relatively short, are 

not particularly conducive to machine 

trenching. Also, pipe installation in an open 

irrigation system is generally a minor part of 

the total work. As a result, side slope 

excavation pay lines used are 1 to 1 for earth 

and l/4 to 1 for rock. These temporary 

excavation slopes will generally be stable 

during the time required for construction. 

Unusual soil conditions may, however, make it 

desirable or necessary to use flatter slopes. 

Figure 8-23 shows the excavation, backfill, 

and bedding for precast concrete and 

asbestos-cement pipe. To be assured that the 

distribution of foundation pressures 

approximates the distribution assumed in the 

design of concrete pressure pipe and 

approximate field strength requirements of 

concrete culvert pipe and asbestos-cement pipe, 

special attention must be given to the bedding 

during field installation. Backfill should be 

compacted to a vertical distance of 

three-eighths the outside diameter of the pipe 

above the bottom of the pipe to achieve these 

conditions. If the backfill is consolidated by 

surface compaction, an earth cradle to fit the 

bcttom of the pipe is needed. The depth of the 

cradle should be 0.05 D, (outside diameter). 

The cradle can be omitted if free-draining, 

noncohesive backfill material is used and 

compaction of the backfill is accomplished by 

saturation and internal vibration. Experience 

has shown that this method will fill the small 

spaces around the bottom of the pipe for pipe 

laid on unshaped bedding and on pipe slopes 

not exceeding 30 percent (0.30). In rock or 

other unsuitable foundation material, the 

trench should be overexcavated to provide a 

compacted cushion of selected material to 

furnish a uniform bedding for the pipe. 

Figure 8-24 shows the excavation, backfill, 

and bedding for reinforced plastic mortar pipe 

(RPM). Because RPM pipe is relatively flexible, 
380 SMALL CANAL STRUCTURES 

Hardware cloth screen No P i~go 

cut to frt bell and grout," p/m,\ 

1 4A 

PLAN t 

SECTION A-A 

LONGITUDINAL SECTION 

Figure 8-21. Concrete pipe air vent. 103-D-1330 

the backfill should be compacted to a vertical 

distance of 0.7 Do above the bottom of the 

pipe. With this earth support on the sides of 

the pipe, earth pressures around the pipe will 

adjust and approach the more favorable 

condition of uniform pressure around the pipe 

as the pipe deflects from external loading. 

Excavation and bedding requirements are 

otherwise the same as previously discussed for 

precast concrete and asbestos-cement pipe. 

For corrugated-metal pipe, excavation 

should carefully follow the alinement and 

grade to provide a firm and uniform bearing for 

the entire length of the pipe. In rock or other 

unsuitable material, the foundation should be 

overexcavated to the same requirements used 

for the other types of pipe as previously 

discussed. In open irrigation systems, 

corrugated-metal pipe is often used for such 

structures as drain inlets into canals and drain 
PIPE AND PIPE APPURTENANCES 381 

t 

One or more umts of p!pe (IS requlredtoabtun change in dlometer speclfled 

Joint type R reqwed between 

steooed woe tooer 1 

cone P4P.c 

reaulred I 

required Locate at 

center of pipe sectloll 

CONCRETE STEP TYPE TAPERS 

,PIPE RElNFORCEMENT NOT SHOWN, 

where 

.ocote ot 

pipe SeCtIon 

For precast bond details. see detm 

Monollthlc bond moy be 

wbstltuted for precast bond 

Remf not shown 

CASE I CASE 2 

TYPICAL JOINT AT CHANGE OF PIPE SIZE 

The amount of clrcumferentlol reinforcement 

("the bond shall not be less than that requred 

for on equivalent length of the odjocent pfpe - 

PRECAST BAND DETAIL MONOLITHIC BAND 

TABLE FOR PRECAST BAND DIMENSIONS NOTES 

7 

DIA. OF PIPE 6" TO IS" 18" 21" 24" TO 45" 48" TO 63' 66" TO 72" 7E' 84" 90" 96" 

Mln thickness It] I$ I;' 2; 2; 2f' 4' 5; 6" .q 7' 

Mm lenqth ELI 6" 6' 7; 9" 

Mn colkmq space I" : 

Step typetopers shall be used I" p,pe where head IS 

50' or less except that step type tapers moy be 

replaced by precast or Steel tapers otthe 

Contractors OptIOn 

All ftttlnq to be the some class of pipe osthe odjocent 

line OS shown on proflle 

Clean and roughen surface of pipe in contact wtth mortar 

and concrete 

Figure 8-22. Step-type pipe taper. 103-D-1 33 1 
382 

culverts under roadway approaches to bridges 

over the canal. For pipe which is to be placed 

within canal or roadway embankment, it is 

commonly required that the embankment 

material be placed to an elevation 

approximately one-fourth the diameter of the 

pipe above the prescribed pipe invert and then 

excavated carefully to provide a firm and 

uniform bedding for the pipe. The backfill 

should be compacted to a vertical distance of 

0.7 D, above the bottom of the pipe as is 

shown for RPM pipe on figure 8-24. 

Backfill over the top of the pipe and above 

the compacted backfill required for properly 

bedding the pipe is usually uncompacted 

Jy~ml orlqmol qround surface 

Provrde cushron of 

compacted bockfrll 

of se/e&d materrol 

oy or eXCO”O ran wherever rock 

found&on IS 

encountered 

EARTH ROCK 

NOTES 

Backfill over p,pe she,, be to the onqmoi qround surfoce 

em-p+ the m~n,m”m shall be 3 feet 

Bockf!li sholi be compacted OS shown unless otherwiSe 

sptvfed 

Figure 8-23. Pipe earthwork details-precast concrete 

or asbestos-cement pipe-earth or rock excavation. 

103-D-1332 

SMALL CANAL STRUCTURES 

Typrcol oriqmoi ground surface- 

\ 

earth 

Cradle required ,f 

bockhii for beddmq 

is compacted by 

tompmq. or surface 

vfbro tlon methods 

Provrde cushion of compacted backfill 

of selected moterrol wherever 

rock foundotmn ,s encountered 1 

EARTH ROCK 

NOTES 

Backfill over- pipe shall be to the onqmol ground surface 

except the mmmwm shall be 3 feet, 

Bockfdl shall be compacted OS shown unless 

othcrwse soecifrcd 

Figure 8-24. Pipe earthwork details-reinforced plastic 

mortar pipe-earth and rock excavation. 103-D-1333 

except at roadway crossings and where pipe 

extends through or under canal sections. For 

roadway crossings all backfill to the top of the 

roadway should be compacted. For structures 

such as turnouts, drain inlets, cross drain 

culverts, or any other pipe structure which 

extends through or under canal sections, the 

backfill should be compacted to the highest of: 

(I) 1 foot minimum over the top of the pipe 

and the collars, (2) original ground surface, or 

(3) to top of compacted embankment if canal 

embankment has been compacted prior to 

construction of the pipe structure. Pipe damage 

from construction equipment travel is thereby 

avoided, and seepage along the pipe is reduced. 

D. BIBLIOGRAPHY 

8- 19. Bibliography. 

(11 King, H. W. and Brater, E. F., “Handbook of Hydraulics,” 

Fifth Edition, McGraw-Hill Book Co., New York, 1963. 

[2] Standard Specifications for Reinforced Concrete Pressure 

Pipe-United States Department of the Interior, Bureau 

of Reclamation. 

[3] Cretex Pipe Products Publication-The Cretex Co.‘s Inc., 

Elk River, Minnesota. 

[4] Armco Handbook of Drainage and Construction Product, 

C.M.P. 

[5] Culvert Pipe made of Reynolds Aluminum Culvert Sheet, 

C.M.P. 

161 Standard Specifications for Asbestos-cement Pressure 

Pipe, United States Department of the Interior, Bureau 

of Reclamation. 

(71 Standard Specifications for Reinforced Plastic Mortar 

Pipe-United States Department of the Interior, Bureau 

of Reclamation. 

[S] Armco Handbook of Welded Steel Pipe., W.S.P. 

[9] Lane, E. W., “Security from Under-Seepage,” Trans. 

ASCE Vol. 100 1935, pg. 1235. 

[lo] ASTM Designation C443. 

[ 1 l] Federal Specification QQ-C-576b. 

(121 Sleeve Type Coupling Welded Steel Pipe Handbook, 

Armco. 
<<Chapter IX 

Safety 

H. J. WARREN’ 

9-l. General. -The Bureau of Reclamation is 

acutely aware of the safety hazards associated 

with open waterways, and incorporates 

protective features [ l] ’ into the design of new 

facilities and modifies existing irrigation 

features for the protection of the public. 

Similar preventive measures have been 

undertaken for animals but on a smaller scale. 

This chapter presents the design and 

selection of some waterway safety devices, and 

their classification and use. 

9-2. Hazard Exposure Classification. -The 

type of safety features included on an 

irrigation structure depends on many factors, 

so it is impractical to standardize designs. 

However, some general rules on safety are 

useful to the designer in determining if safety 

devices are needed. One of the most important 

considerations is the number of people which 

will be exposed to the hazard through 

‘General Engineer, Engineering Reference Branch, Bureau 

of Reclamation. 

‘Numbers in brackets refer to items in the bibliography, 

sec. 9-4. 

operation, recreation, or living nearby. This 

consideration has prompted Reclamation to 

classify hazard exposures as follows [ 21 : 

Class A.-Those canals adjacent to schools 

and recreational areas, such as 

playgrounds, subject to frequent visits by 

children 

Class B.-Those canals nearby or adjacent to 

urban areas or highways and subject to 

frequent visits by the public 

Class C.-Those canals nearby or adjacent to 

farms or highways which could be subject 

to visits by children seeking recreation, 

such as swimming 

Class D.-Those canals far removed from any 

dwelling subject to infrequent visits by 

operating personnel and an occasional 

sportsman 

Class E.-Those canals that would be a 

hazard to domestic animals 

Class F.-Those canals that would be an 

extreme hazard to big game animals 

The type of protection used on or around 

canal structures is dependent on the class of 

exposure. 

A. SAFETY DEVICES 

9-3. Types.-Many types of safety devices (2) Those which are escape devices in the 

are used on canal structures. These safety event a person enters the canal either 

devices can be separated into two groups: deliberately or by accident 

(1) Those which limit access or deter people Fencing, guardrails, warning signs, and pipe 

and animals from getting into the canal safety barriers are safety devices which limit or 

383 
384 

deter people and animals from entering a canal 

system. Of these, fencing is probably the most 

effective deterrent; however, warning signs are 

heeded by some people and guardrails are used 

to keep people and vehicles from accidentally 

falling or driving into canals. Pipe safety 

barriers present enough of an obstacle to 

reduce the temptation for people to use the 

pipe crossings over a canal as a walkway. 

Safety nets, safety cables, safety racks, and 

safety ladders are devices which aid people to 

escape from a canal. A combination of these 

devices and those which deter access are 

usually constructed at the upstream ends of 

hazardous structures where a fatality would 

surely occur if a person entered the structure. 

(a) Fencing.-A fence is the most common 

and effective safety device to deter people and 

animals from entering a canal. Reclamation 

uses six types of safety fences. Selection of the 

appropriate type fence is dependent on the 

hazard exposure classification. Requirements 

of these fences, constructed on or near the 

canal right-of-way, are described in table 9-l. 

SMALL CANAL STRUCTURES 

Standard design drawings for different types 

of fences are given in figures 9-1 through 9-5. 

Fences are used in conjunction with safety 

nets or safety cables around inlets to siphons 

30 inches in diameter and larger for Class A, B, 

or C exposures. The fence should meet the 

requirements of the pertinent exposure 

classification. It should be constructed across 

the transition headwall and extend along the 

sides of the transition to the anchor posts of 

the safety net or cable as shown in figure 9-6. 

Sometimes a short length of the fence is 

constructed to the water’s edge as shown in 

figure 9-7 [3] . 

Fences or guardrails should bc constructed 

along each side of chutes (fig. 9-8), rectangular 

inclined drops and stilling pools (fig. 9-9) 

having a 4-foot depth or more in Class A, B, or 

C exposure. Fence or guardrail might also be 

used on each side of a bench flume to prevent 

people from stumbling into the flume when the 

flume is set into the ground flush with the top 

of the wall. 

(b) Gzluru’vails.-There are two types of 

Table 9-1 .-Safety Fence Classification. 103-D-l 196 
SAFETY 385 

PLAN 

2m Stvod Wia12; 9oye 9clv barbed IVLT~ 

w'h4-poi"+borbs not more than 5'oporf 

IPIC't qote Itop : 

ddoptoble to qote -~- 

3tch used 

GATE AND ADJOINING PANELS 

Z- Stropd NO al 9o9e qalv barbed wire with 

epoint bores ootmore than 5'oport, 

Combinotron cop and barb 

CORNER AND PLAIN PANELS 

/Gate post 

,-Combrnotion cop ord 

i,PP or coroer post 

Attachment on *ewe side 

pa/v *ire strffeoer 

post 

3- ~'DIo. P'pftch spiroled loops 

of No 4 goqe wre 

Undisturbed Wuroi qround 

or compacted bockfrli 

TYPICAL SECTION 

z-Strand NO 12; qoge 90/v borbcd yire 

with 4 point barbs "ot more than 5 apart 

\ 

Cho," ii"k obrrc 

/ II 

k-- IO-0 

II 

m----- JCL-- ~- 4 

PANELS ADJOINING PULL POST 

\I l90i” pIpI?- -; 

GATE AND 

AAlOlNlNG PANELS 

NOTES 

A p,pe dia!rPterS xhown ore fro" prpe sizes, standard 

we,9ht 

Morimum inteiroi betwren ou:lpos+s 2~x7 feet 

bolbed wrc guard t0 be mounted vert~coiiy onall 

9ote posts 

Barbed wre supporting arms shoii conform with monufocturerj 

stondords or shall be fobrlcoted from 1; inch p,pe 

They shoii be welded in place or otherwe secured 

to prevent rotot,on 

School safety fence 7?0" high 

Urban safety fence 5'-0"hiqh 

Figure 9-I. School and urban fence. 103-D-1197 
386 SMALL CANAL STRUCTURES 

Figure 9-2. Rural fence. 103-D-l 198 
Figure 9-3. Stock fence with wood posts. 103-D-l 199 
388 SMALL CANAL STRUCTURES 
SAFETY 389 

n 

Figure 9-5. Deer fence. 103-D-1201 
390 SMALL CANAL STRUCTURES

Figure 9-6. Warning sign, safety cable, and safety

fence at siphon inlet. 805-236-14106

Figure 9-8. Safety fence along a chute.

Figure 9-7. Safety fence, handrail, and safety rack at

siphon inlet. P328-700-103 NA

Figure 9.9. Typical pipe handrail installation along

sides of inclined drop and stilling pool.

guardrails: ( 1) Those used to keep vehicles

from entering the canal along the canal bank at

dangerous turns; and (2) Those used to prevent

pedestrians from falling into the canal at

structures. Only the latter type, which is

identified as pipe handrail, will be discussed

here.

Handrails are usually constructed of

1-1 /2-inch-diameter metal pipes in combination

with metal posts set in concrete or attached to

a wall mounting. They are 42 inches high and

have two or three horizontal pipe rails

depending on the exposure classification.

Two-rail handrail (fig. 9-10) will suffice for

most canal structures having a Class C or D

exposure. For Class A or B exposure, a

three-rail handrail (fig. 9-11) is recommended.

Sometimes chain link fence is used in

conjunction with three-rail handrail to prevent
SAFETY 391 

INTERMEDIATE CORNER POST END POST 

POST 

GUARD CHAIN 

POST 

4 Std block D,DF 

STEEL POST SOCKET 

WALL MOUNTING 

w*.r*;. 

GUARD CHAIN 

WALL ANCHOR 

SPLICE NO. 3 
SMALL CANAL STRUCTURES 

GUARD CHAIN 

POST WALL ANCHOR 

Figure 9-U. Three-rail handrail-42 inches high. 103-D-1203 
SAFETY 393

Figure 9-12. Check inlet with safety fence, safety

net, and having handrails on both sides of walkway.

P328-701-7147

children from crawling or slipping between the

rails and falling into a structure.

Pipe handrails are used in conjunction with

safety racks around the inlet transitions of all

siphons 30 inches and larger in diameter for

Class A, B, or C exposure unless safety fence

and safety nets or cables are used as previously

described. Pipe handrails are also required

around the outlet transition of all siphons 30

inches in diameter and larger for Class A, B, or

C exposure as well as around the inlet

transition for Class D exposure. These handrails

are constructed across the transition headwall

and extend the length of the transition on both

sides of the canal. Pipe handrails are also used

along operating platforms and walkways of

many irrigation structures. Generally, handrails

are required where the top of the walkway or

operating platform is more than 3-1/2 feet

above the downstream floor of the structure.

Only a downstream handrail is required when

the operating deck is 3-1/2 to 5 feet above the

downstream floor (fig. 3-10). Handrails are

required on both sides of the walkway if the

walkway is 5 feet or more above the floor (fig.

9-12).

If a check structure is constructed

monolithically with or immediately upstream

from a siphon inlet whose diameter is 36 inches

or larger, or a steep chute of similar size,

handrails should be built on both the upstream

and downstream side of the operating platform

(fig. 9-12).

Oftentimes the handrails on structures

interfere with handling stop planks or cleaning

trash from trashracks. In these cases removable

pipe rails or guard chains as shown in figures

9-10 and 9-11 are used in place of permanent

type rails.

(c) Warning Signs.-Oftentimes the public is

not aware of the dangers associated with

structures in a canal system. To alert them of

these dangers, well-worded warning signs

advising of specific dangers, should be installed

near the structure in a conspicuous place as

shown in figure 9-6. No trespassing signs serve

a useful purpose, but signs pointing to a

specific danger are more effective. In areas

where a large number of people speak a

language different from the native language,

warning signs should be written in dual

languages. For instance, in southwestern

United States warning signs are written in both

English and Spanish.

(d) Pipe Safety Barrier.-Pipe safety barriers

which have been previously shown in figure

8-17, are safety devices installed on pipes

crossing over canals. Their purpose is to

discourage people from trying to walk on the

pipe and then accidentally falling into the

canal.

Pipe safety barriers should be used on all

pipe crossings except those in remote areas and

those within fenced waterways.

(e) Safety Nets.-Safety nets are escape

devices suspended across the canal immediately

upstream of siphons, checks, and similar

structures. They provide an opportunity for

the person in the canal to save his life by

grabbing the net and pulling himself along the

net to the safety ladder where he can escape

from the canal.

Many different types of safety nets have

been used. Some have been made of rope

netting (fig. 9-13) ; others have been made from

galvanized wire mesh enclosed in a wood frame

and suspended from a cable (fig. 9-14) ; and

some were simply wire rope suspended across

the canal with rope or chain drop lines hanging

from it.

Figure 9-15 shows the design of a typical

safety net and cable currently preferred on
394 SMALL CANAL STRUCTURES

Figure 9-13. Rope safety net upstream of checked

siphon inlet. Note handrails on both sides of walkway.

P328-701-7223

Figure 9-14. Wire mesh safety net at siphon inlet.

P328.701-4241

Reclamation projects. This device is used in

canals (fig. 9-16) where water depth is greater

than 3 feet. If the water depth is less than 3

feet, the chain tie, suspenders, and rungs can be

omitted.

(0 Safety Cables. -Another type of safety

device used to aid people in escaping from the

canal is safety cables. Safety cables consist of a

number of floats attached to a cable that is

placed across the canal immediately upstream

of siphons, checks, or similar structures (fig.

9-17). Safety cables serve the same purpose as

safety nets but are simpler to build and less

expensive. They are usually used on large

canals where excessive spans might limit the

use of safety nets or safety racks. Figure 9-18

shows a safety cable currently used on

Reclamation canals. The components of this

safety cable are commercially available. The

cable assembly includes a 5/8-inch-diameter

yellow polypropylene rope with a minimum

tensile strength of 5,800 pounds. The floats are

high-density polyethylene shells filled with

2-pound-density polyurethane foam. The shells

should be at least 0.1 inch thick and contain an

ultraviolet inhibitor and orange color pigment

incorporated into the polyethylene during

manufacture. The polyurethane foam should

have a minimum of 95 percent closed cells and

should not absorb more than 10 percent water

by weight when subjected to a 6-inch head of

water for 24 hours. The ends of the float

should have a counter bore molded at least

1-1/2 inches into the float to provide a wearing

surface for the rope. Short pieces of rope are

braided into the cable at each end of the floats

to hold them in place.

(g) Safety Racks. -Safety racks are barriers

placed across inlets to inverted siphons, pipe

chutes, and pipe drops to prevent people from

being drawn into the structure. They also

provide a means for a person to climb out of

the canal. Safety racks and guardrails in

combination can be used in lieu of fencing and

safety nets or cables at the inlet transitions to

siphons 30-inch diameter and larger in Class A,

B, or C exposure areas. They are generally used

in small canals where the canal is relatively free

from weeds and de bris.

Since safety racks are designed in a num ber

of ways to fit the various types and sizes of

inlet transitions, the Bureau of Reclamation

does not have standard design drawings for

safety racks. Figure 9-19 is a design drawing of

a safety rack placed on an inlet transition with

a check. Figure 9-20 shows a safety rack on a

warped transition. In comparing the two safety

racks there are obvious differences, but both

types accomplish the same purpose.

Generally, safety racks are made from

standard steel galvanized pipe, bolted and

welded together to form a grille that is

attached to the headwall of an inlet transition.

The sloping steel pipes are usually 1-1/2 inches

in diameter with 9 inches of clear spacing

between pipes. The welded frame, on which

the sloping pipes are bolted, may be 2-inch
SAFETY 395

.'

.'? i"x12' Turnbuckle

with one eye --

6' Min threod length

Typlcol conolor

Loterol bonk ~

1-.;.

".

"' "'

~ Tie ."'

~~

Suspender L.

Wire spiral

reinf ~

",

2'-6" -12-..

-c-NWS "'

i

'0

-.;,

1

,~(

;"Oio anchor bar ~

{Standard brace bands

---+t ~End past 2" standard pipe

,,/i"x4" Eye bait with I cut washer and nut

~ i"xI2" Turnbuckle eye and eye I

~ i" Wire rape thimble f--Symm abaut { canal

" ar lateral ;-J-i Wire rape clips

, i' Wire rape safety cable

~Attach suspenders ta cable with repair links

rAt tach ties firmly ta suspenders

-1

'10

!

:-Pipe rungs see Detail A.

Far spacing see chart .10 -2'-6" 12

!4@7 T

"

:i

.0

-.;,

~~

I 14" I

r-ota:--1

,

Typic

late

Nate All t,es and suspenders tabe 1. ' cail chain

,.

'I:

'Concrete deodmon

24"squore

~

DETAIL A

NOTES

All concrete sholl be placed In undisturbed earth or campacted

fll{

All foundation for end posts to be reinfarced with Na 4 gage

x 5'-0' wire spiral reinf, 2' pitch, 6" dia

All parts of safety net and cable assembly ta be galvanIzed

Figure 9.15. Safety net and cable. IO3.D.1204

Figure 9-16. Safety net and cable at siphon inlet.

PX-D-72613

Figure 9-17. Safety cable with floats upstream of a

siphon inlet. P214-D-37162
SMALL CANAL STRUCTURES 

F&u-e 9-18. Safety cable with floats. 103-D-1205 

pipe or larger depending on the span of the 

safety rack. 

The horizontal pipes give the rack rigidity 

and provide steps for aiding a person to escape; 

however, these pipes do catch weeds and make 

cleaning the rack difficult. Safety racks should 

be placed on a 3 to 1 slope or flatter so a 

person may pull himself from the canal. 

(h) S’ujc’tJ Ladders-Ladders are the most 

commonly used escape devices in a 

concrete-lined canal. Their effectiveness, 

however, depends on the ability of the person 

in the canal to get to them. An accelerating 

velocity usually occurs where canal water 

enters a canal structure. For this reason safety 

nets or safety cables should be installed in 
SAFETY 397 

“4‘F PL4N - TRANSITION WlTH CHECK 

SECTION A-4 

SECTION B-S 

HALF PLAN-S4FETY RACK 

DET4lL 4 

DETAIL 13 

/ 6 I .‘I 1”. 6 ‘0”s 

SECTION C-C 

Figure 9-19. Safety rack. 103-D-1206 
398 SMALL CANAL STRUCTURES

Figure 9.21. Safety ladder and safety cable with

floats upstream of a siphon inlet. PX-D-49120

or cable and pull himself to the ladder where

he can usually escape from the canal.

In concrete-lined canals where the vertical

lining height is 30 inches or greater, ladders are

required immediately upstream of all siphons,

checks, check drops, pipe drops, and chu tes.

Safety ladders are also required to be installed

at 500-foot intervals in bench flumes where

walls are 36 inches and higher. Figure 9-22 is a

design drawing of a ladder used in a

con crete-lined canal or in a bench flume.

Generally, safety ladders are used only in

hard-surface-lined canals.

Figure 9.20. Safety rack on inlet transition.

P328-701-9467

combination with ladders and located a short

distance upstream of the canal structure (fig.

9-21 ). This allows the person to grasp the net

B. BIBLIOGRAPHY

[3) Latham, H. S., and Verzuh,

People and Animals

REC-ERC- 71-36, Bureau of

9-4. Bibliography.

[ 1] Reclamation Instructions, Part 131, Bureau of

Reclamation.

[2] Design Standards No.1, Chapter 3-Revised Safety

Standards. Bureau of Reclamation.

J. M., .'Reducing Hazards to

on Reclamation Canals,"

Reclamation, Sep. 1971.
SAFETY 

Use two or more /odder sect/ens when 

the requfred length exceeds 13'.3" 

Mm operot/ng water surface, 

5.O'Mln for water depth equal 

to or greater than 8.0'-- F *?a 1 - 

Concrete conoi Iming 

~Polnt area 16"~ lB"0n concrete with 

two coots of trofflc yellow pain% 

not shown 

LATION DETAIL 

Anchors not shown 

Limng th/ckness f2f' M/n) i ' 

SECTION A-A 

I*1OOER RUNG OETdll 

C Anchors, =_ 

Anchor of center of/adder 

for sect/ens longer than 6!3" 

[for ladders w/th 5or 7 

rungs, offset anchors 5" 

from center of ladder) J 

C Anchors 

(See notes.) 

NOTES 

Lauders Lauders to oetobricatea oetobricated trom steel or 6061.T6 6061~T6 alum,num. alum,num. 

Ladders Ladders shallbe shallbe anchored anchored to the conoll~n~ng conoll~n~ng wfth staInless staInless 

steei exponslan exponslan type orlmpoct orlmpoct type anchors, anchors, subject subject 

to the approval approval of the contracting contracting officer. officer. 

Lodders Lodders to be paInted paInted yellow after fabrlcatton fabrlcatton 

Lodders ta be used on sides of canal where the vertical 

Ilnlng hefght IS 2; feet or more. 

Ladders to be located opposite eachotherot750-footmtervolsoneoch 

s/deofthecan~l,andupstreomofstructures as d/rected. 

.,, _ 

LADDER SECTION 

Figure 9-22. Safety ladder. 103-D-1207 

<<Appendix A 

Glossary of Terms 

A-l. List of Symbols and Abbreviations. -The following is a list of symbols and abbreviations 

used in this publication. Commonly used mathematical symbols and abbreviations are not listed. 

Symbol or 

abbreviation 

A 

Definition - 

Area; cross-sectional area of flow in an open 

channel or pipe; cross-sectional area of a 

pipe or an orifice 

AASHO American Association of State Highway Officials 

AC Asbestos-cement pipe 

Adj Adjustable 

Approx Approximate 

ASCE American Society of Civil Engineers 

ASTM American Society for Testing and Materials 

Avg Average 

b Bottom width of a channel 

C Coefficient of discharge 

Centerline 

cc Center to center 

CF Cold finish 

cfs Cubic feet per second 

CHO Constant-head orifice 

401 
402 

Symbol or 

abbreviation 

CI 

CMP 

cone 

crs 

csk Countersink 

cu 

CWS 

D 

Cubic 

Control water surface 

Diameter of a pipe; height of a siphon throat 

opening; vertical drop of invert 

d 

dc 

d” 

D” 

Dia, 4 

Dim 

DOC 

Dw 

DWS 

E 

EC 

Es 

EG 

El 

.AEl 

SMALL CANAL STRUCTURES 

Definition 

Cast iron 

Corrugated-metal pipe 

Concrete 

Centers 

Depth of flow in an open channel or pipe flowing 

part full 

Critical depth 

Normal depth 

Outside diameter of a pipe 

Diameter; diameter of a bar 

Dimension 

Designers’ operating criteria 

Drawing 

Delivery water surface 

Energy 

Critical energy 

Specific energy 

Energy gradient 

Elevation 

Difference in elevations 
GLOSSARY OF TERMS 

Symbol or 

abbreviation 

F 

403 

f c 

f 5 

fY 

Fb, fb 

fig 

fps 

Frm 

ft 

ft2 

i! 

Ga 

galv 

H.h 

AH 

CH 

hb 

11 f 

Definition 

Froude number; difference in energy elevations; 

difference in water surface elevations; 

difference in invert elevations 

Allowable extreme fiber compressive stress in 

concrete 

Specified compressive strength of concrete 

Allowable tensile stress in reinforcement steel 

Specified yield strength of reinforcement steel 

Freeboard 

Figure 

Feet per second 

Frame 

foot or feet 

Square feet 

Gravitational acceleration 

Gage 

Galvanized 

Hydrostatic head; head on the centerline of a 

free-flow orifice or head across a submerged 

orifice; head across a structure; head on a 

weir crest; head at the centerline of a pipe; 

head on a siphon spillway; atmospheric 

pressure head 

Difference in water surface elevations; 

differential pressure head 

Summation of lateral forces acting parallel to 

assumed sliding plane 

Head loss in a pipe bend 

Head loss due to friction 
404 SMALL CANAL STRUCTURES 

Symbol or 

abbreviation 

k Velocity head 

Definition ____- ~~ 

Difference in velocity heads 

h “c 

w 

hd 

Velocity head for flow at critical flow 

Head 

hex 

Ht 

ID 

In 

IllV 

Alnv 

K 

L 

Lv 

Lbs 

LF 

Longit 

M 

math 

max 

min 

Mist 

n 

ZN 

Hexagon, hexagonal 

Height 

Inside diameter of a pipe 

Inch or inches 

Invert 

Difference in invert elevations 

Head loss coefficient; acceleration factor for 

trajectory of flowing water 

Length; length of a weir crest; length of a pipe; 

length of a structure: length of a transition 

Length of weighted creep for percolating water 

Pounds 

Load factor 

Longitudinal 

Montuori number 

Machine (machine bolt) 

Maximum 

Minimum 

Miscellaneous 

Manning’s roughness coefficient 

Summation of forces acting normal to assumed 

sliding plane 
GLOSSARY OF TERMS 

Symbol or 

abbreviation 

No, N, # 

Nws 

O&M 

OD 

OGS 

PC 

PCP 

PF 

PI 

Pl 

pr0.i 

PSf 

psi 

PT 

Q 

9 

R 

r 

RCCP 

Reinf 

req ‘d 

RI 

ROW 

RPM 

405 

Definition ~-___- 

Number 

Normal water surface 

Operation and maintenance 

Outside diameter of pipe 

Original ground surface 

Point of curvature 

Precast reinforced concrete pressure pipe 

Percolation factor 

Point of intersection 

Plate 

Projection; project 

Pounds per square foot 

Pounds per square inch 

Point of tangency 

Discharge; rate of flow in cubic feet per second 

Discharge per foot of width in cubic feet per 

seconu 

Hydraulic radius; radius of a circular curve; 

radius of a pipe bend; radius of a pipe 

Hydraulic radius 

Precast reinforced concrete culvert pipe 

Reinforcement 

Required 

Rectangular inclined (rectangular inclined drop) 

Right-of-way 

Reinforced plastic mortar pressure pipe 
406 

Symbol or 

abbreviation 

sq 

s: s, ss 

s4s 

SPC 

Sta 

Stnd 

Str, Struct 

Symm 

T 

t 

TO 

Transv 

v 

V 

- 

vc 

vt 

LIV 

SMALL CANAL STRUCTURES 

Definition 

Slope of energy gradient in the Manning equation 

(friction loss in feet per foot); invert slope 

of channel or pipe 

Average slope of energy gradient between two 

points 

Slope of profile of channel bottom 

Critical slope 

Friction slope; head loss due to friction in feet 

per foot 

Square 

Side slope of channel, horizontal to vertical 

ratio 

Dressed lumber, surfaced on four sides 

Spaces 

Station 

Standard 

Structure 

Symmetrical 

Thrust acting on a pipe bend; top width of water 

surface in an open channel 

Time in seconds; concrete thickness 

Turnout 

Transverse 

Velocity 

Vedernikov number 

Critical velocity 

Theoretical velocity 

Difference in velocities 
GLOSSARY OF TERMS 407 

Symbol or 

abbreviation 

CV 

vert 

W 

Definition 

Summation of vertical forces 

Vertical 

Throat width of Parshall flume; length of weir 

crest; baffled outlet basin width; roadway 

width 

W Unit weight 

WP 

ws 

Wetted perimeter 

Water surface 

nws Difference in water surface elevations 

WSP Welded steel pipe 

X A coordinate for defining a trajectory profile 

Y A coordinate for defining a trajectory profile 

Depth from water surface or hydraulic gradient to 

center of gravity of a water prism cross 

section 

YdS Yards 

Z Difference in invert elevations between two 

points 

GREEK LETTERS 

Greek letter 

a 

Greek name 

Alpha 

Greek letter 

IJ 

Greek name 

Mu 

P Beta 7-r Pi 

Delta P Rho 

Zeta c Sigma 

e Theta Phi 

<<Appendix B 

Conversion Factors 

B-l. Internet/one/ System (SI metric)/U.S. Customary ConversIon Factors 

To convert from To Multiply by To convert from To Mulbply by 

angstrom units nanometers (nm) 0.1 

micrometers urn) 1 x 10’ 

millimeters (mm) 1 x IO’ 

meters (m) 1 x 10-10 

mils 3.937 01 x 10~6 

inches (ln) 3937 01 x 10-9 

micrometers mlllwneters 1 x 10~3 

meters 1 x 10-s 

angstrom umts (A) 1 x 10’ 

mils 0 039 370 

Inches 3.937 01 x 10-s 

mtllimeters micrometers 1 x 103 

centimeters (cm) 0.1 

meters 1 x 103 

mils 39.3701 

inches 0 039 370 

feet (ft) 3.260 a4 x 103 

centimeters milhmeters IO 

meters 0 01 

mils 393 701 

inches 0.393 701 

feet 0.032 808 

Inches mllhmeters 25.4 

meters 0 0254 

mils 1 x 103 

feet 0.063 333 

feet mrlluneters 304.6 

meters 0.3046 

inches 12 

yards (yd) 0.333 333 

yards meters 0.9144 

Inches 36 

feet 3 

meters mlllwneters 1 x 103 

kllometers (km) 1 x 103 

Inches 39.3701 

yards 1 093 61 

miles (ml) 6.213 71 x 10~’ 

kilometers meters 1 x 103 

feet 3 260 64 x 103 

miles 0.621 371 

miles meters 1.609 34 x 103 

kilometers 1609 34 

feet 526 x 103 

yards 1.76 x 103 

nautical miles kilometers 1.653 24 

(nmi) miles 1151 55 

LENGTH 

AREA 

square milli- square centimeters (cmz) 0.01 

meters 

square cemmeters 

square inches 

square feet 

square yards 

square Inches (II+) 

square millmwters (mmZ) 

square meters (m2) 

square inches 

square feet (fP) 

square millimeters 

square centimeters 

square meters 

square feet 

square meters 

hectares (ha) 

square inches 

acres 

square meters 

hectares 

square feet 

.9cres 

1.55 x 103 

100 

1 * 10-4 

0.155 

1.076 39 x 10~3 

645 16 

64516 

6.4516 x 10~’ 

6.944 44 x 10~3 

0.092 903 

0.092 903 x 10-e 

144 

2.295 68 x 10~5 

0.636 127 

6.361 27 x IO-5 

9 

2.066 12 x 10’ 

square meters 

acres 

hectares 

square kilometers 

square miles 

hectares 

square feet 

WWS 

square yards (ydz) 

square meters 

hectares 

square feet 

square meters 

acres 

square meters 

hectares 

square feet 

acres 

square miles (ml?) 

square meters 

hectares 

square kllometers (km?) 

square feet 

acres 

1 x 10.’ 

10.7639 

2.471 05 x 10-J 

1.195 99 

4046 66 x 103 

0 404 686 

4.356 x IW 

1 x 10’ 

2.471 05 

1 x 108 

100 

1076 39 x IO’ 

247.105 

0.366 102 

2.569 99 x 108 

256.996 

2.589 99 

2.767 84 x 10’ 

640 

409 
410 SMALL CANAL STRUCTURES 

To convert from To Multiply by TO convert from To Multiply by 

VOLUME-CAPACITY 

cubic millimeters 

cubic centimeters 

milliliters 

cubic inches 

11ters 

gallons 

cubic feet 

cubic centimeters (cmJ) 1 x 10~3 

liters (I) 1 x 10-e 

cubic inches (ins) 6102 37 x 10-S 

liters 1 x 10-a 

milliliters (ml) 1 

cubic inches 0.061 023 

fluid ounces (11 OL) 0.033 614 

liters 1 x 10-S 

cubic centimeters 1 

milliliters 16.3671 

cubic feet (113) 5 767 04 x 10-4 

cubic meters 1 x 10~3 

cubic feet 0 035 315 

gdlO”S 0.264 172 

fluid ounces 33.6140 

liters 3.705 41 

cubic meters 3.765 41 x 103 

fluid ounces 126 

cubic feet 0.133 661 

liters 26.3169 

cubic meters (m3) 0 026 317 

cubic dekameters (darns) 2.631 69 x 10-S 

cubic inches 1.729 x 103 

cubic yards (ydJ) 0 037 037 

gallons (gal) 7.460 52 

acre-feet (acre-ft) 2.295 66 x 10-S 

cubic miles 

cubic yards 

cubic meters 

acre-feet 

cubic dekameters 

cubic kilometers 

cubic dekameters 4.166 16 x 10s 

cubic kilometers (km3) 4.166 16 

acre-feet 3.3792 x 10s 

cubic meters 0.764 555 

cubic feet 27 

liters 1 x 103 

cubic dekameters 1 x 10-S 

gallons 264172 

cubic feet 35.3147 

cubic yards 1.307 95 

acre-teat 6.107 13 x 10-a 

cubic meters 1.233 46 x 103 

cubic dekameters 1.233 46 

cubic kilometers 1.233 46 x 10-0 

cubic feet 4.356 x l(r 

gallons 3.256 51 x 105 

cubic meters 1 x 103 

cubic feet 3.531 47 x 104 

acre-feet 0.610 713 

gallons 2.641 72 x 1W 

cubic dekameters 1 x 1w 

acre-feet 6.107 13 x 105 

cubic miles (mia) 0.239 913 

ACCELERATION 

feet per second 

squared 

meters per 

second 

squared 

meters per second 

squared (m/sz) 

G’S 

1-t per second 

squared (ltw) 

G’s 

0.3046 

0.031 061 

3.260 64 

0.101 972 

G’s (standard meters per second 

gravitational squared 

acceleration) feet per second squared 

9.606 65 

32.1741 

VELOCITY 

feet per second 

meters per 

second 

pounds 

kilograms 

(force) 

meters per second (m/s) 

kilometers per hour 

(km/h) 

miles per hour (milh) 

kilometers per hour 

feet per second (ft/s) 

miles per hour 

newtons (N) 

newtons 

pounds (lb) 

0.3046 kilometers per tneten per second 0.277 776 

1.097 26 hour 1-t per second 0.911 345 

miles per hour 0.621 371 

0.661 62 miles per hour kilometers per hour 1.609 34 

3.6 meters per second 0.447 04 

3.260 64 feet per second 1.466 67 

2.236 94 feet per year millimeters per 9.665 14 x 10-e 

WY0 second (mm/s) 

FORCE 

4.446 22 newtons pounds 0.224 609 

9.606 65 dynes newtons 1 x 10-S 

2.204 62 

grams 

O”“CBS (evdp) 

pounds (evdp) 

kilograms 

slugs 

kilograms (kg) 

0”“~~s (avdp) 

grams (9) 

kilograms 

pounds (avdp) 

kilograms 

O”“CBS (avdp) 

kilograms (force)-second 

squared per meter 

(kg1 . S/m) 

pounds (avdp) 

slugs 

kilograms 

MASS 

1 x 10-S 

0.035 274 

26.3495 

0.026 350 

0.0625 

0.453 592 

16 

0.101 972 

2.204 62 

0.066 522 

14.5939 

short tons 

metric tons 

(tonne or 

megagram) 

long tons 

kilograms 907.165 

metric tons (1) 0.907 165 

pounds (evdp) 2 x 103 

kikagrams 1 x 103 

pounds (avdp) 2.204 62 x 101 

short tons 1.102 31 

kilograms 1.016 05 x 1W 

metric tons 1.016 05 

pounds (avdp) 2.24 x 103 

short tons 1.12 
CONVERSION FACTORS 

To convert from To Multiplv bv 

411 

To convert from TO Multiplv by 

TEMPERATURE 

degrees Celsius 

degrees 

Fahrenheit 

degrees 

Fahrenheit 

kelvin (K) fK4OC + 273.15 

degrees Celsius foe = (‘oF - 32)/1.6 

kelvin fK = (fOF + 459.67)/l .6 

degrees 

Rankine 

kelvin fK = f.,R/l 6 

VOLUME PER UNIT TIME 

FLOW 

cubic feet per 

second 

gallons per 

minute 

liters per second (I/s) 

cubic meters per second 

(mVs) 

cubic dekameters per day 

(dams/d) 

gallons per minute 

(gallmin) 

acre-feet per day 

(ecreft/d) 

cuboc feet per mmute 

(Wmin) 

cubic meters per second 

liters per second 

liters per minute 

cubic dekameters per day 

cubic feet per second 

(ftv.3) 

acre-feet per day 

26.3169 acre-feet per 

0026 317 d=Y 

2.446 57 

448.631 

1.963 47 

60 

6309 02 x 10~5 

0.063 090 

3.785 41 

5.450 98 x 10-Z 

2.226 01 x 10-S 

4419 19 x 103 

cubic dekameters per day 

cubic meters 

per second 

million gallons 

per W 

(msd) 

cubic meters per second 

cubic dekameters per day 

cubic feet per second 

cubic meters per second 

cubic feet per second 

acre-feet per day 

acre-feet per day 

cubic feet per second 

gallons per minute 

liters per second 

million gallons per day 

cubic meters 

per second 

0.014 276 

1.233 46 

0.504 167 

0.011 574 

0.406 735 

0.610 713 

70.0456 

35.3147 

1.565 03 x 1w 

1 x 103 

22.6245 

0.043 613 

FORCE PER UNIT AREA 

PRESSURE-STRESS 

pounds per 

square inch 

pounds per 

sauare foot 

short tons per 

square foot 

‘feet Of water 

kilopascals (kPa) 

‘meten-head 

zmm of fig 

‘fee1 Of water 

pounds per square 

foot (IblfV) 

std. atmospheres 

kilopascals 

lmeters-head 

zmm of Hg 

‘feet Of water 

pounds per square Inch 

std. atmospheres 

kilopascals 

pounds per square 

inch (lb/W) 

kilopascals 

+nrn of tip 

‘feet Of water 

pounds per square Inch 

pounds per square foot 

ktlopascals 

Imeters-head 

2mm of Hg 

*inches of Hg 

pounds per square Inch 

pounds per square foot 

6.894 76 

0.703 091 

51.7007 

2.306 73 

144 

0.068 046 

0047 880 

4.662 60 x 10~3 

0.359 033 

0.016 019 

6.944 44 x 10-a 

4.7254 x 10-4 

95.7605 

13.6669 

9.806 36 

73.5334 

3.260 84 

1.422 29 

204.610 

2.988 90 

0.3048 

22.4130 

0 662 401 

0.433 514 

62.4259 

‘Column of H,O (water) measured at 4 ‘C. 

2Column of Hg (mercury) measured at 0 “C 

kilopascals 

kilograms (1) 

per square 

meter 

millibars (mbar) 

bars 

std. atmospheres 

newtons per square 

meter (N/m*) 

zmm of Hg 

‘meters-head 

Mches of Hg 

pounds per square foot 

pounds per square inch 

std atmospheres 

kilopascals 

%m of Hg 

pounds per square 

inch 

kilopascals 

kilopascals 

kilopascals 

Vnm of Hg 

pounds per square mch 

‘feet of water 

1 x 103 

7.496 55 

0.101 975 

0.295 216 

20.6655 

0.145 039 

9.869 26 x 10-a 

9.806 65 x 10-a 

0.073 556 

1 422 73 x 10-x 

0.1 

100 

101.325 

760 

14.70 

33.90 
412 SMALL CANAL STRUCTURES 

To convert from To Multiply by To convert from TO Multiply by 

MASS PER UNIT VOLUME 

DENSITY AND MASS CAPACITY 

pounds per 

cubic foot 

pounds per 

gallon 

pounds per 

cubic yard 

grams per cubic 

centimeter 

ounces per 

gallon 

(mml) 

kllograms per cubic meter 

WOW 

slugs per cubic foot 

(slug/ft3) 

pounds per gallon 

(lb/gal) 

kllograms per cubic meter 

CW”W 

slugs per cubic foot 

kilograms per cubic meter 

pounds per cubic foot 

(Ib/fF) 

kilograms per cubic meter 

pounds per cubic yard 

grams per liter (g/l) 

kilograms per cub!c meter 

16.0165 

0.031 061 

0 133 661 

119626 

0.232 502 

0.593 277 

0.037 037 

1 x 103 

1 665 55 x 

7.469 15 

7409 15 

103 

kllograms per 

cubic meter 

long tons per 

cubic yard 

ounces per 

cubic inch 

(oz/irG) 

slugs per cubic 

foot 

grams per cubic centimeter (g/cmr) 

metric tons per cubic 

meter (t/m,) 

pounds per cubic foot 

Wft?) 

pounds per gallon 

pounds per cubic yard 

kilograms per cubic meter 

kilograms per cubic meter 

kilograms per cubic meter 515.379 

1 x 103 

1 x IO-3 

0.062 430 

6.345 40 x 10-S 

1.665 56 

1.326 94 

1.729 99 x 103 

VISCOSITY 

centipoise 

pascal-second 

pounds per 

foot-hour 

pascal-second (Pa. s) 

poise 

pounds per foot-hour 

(Ib/ft . h) 

pounds per foot-second 

(Ib/ft . s) 

slug per foot-second 

(slug/ft . S) 

centipoise 

pounds per foot-hour 

pounds per foot-second 

slug per foot-second 

pascal-second 

pounds per foot-second 

centipoise 

1 x 103 

0.01 

2.419 09 

6719 69 x 10~’ 

2.066 54 x IO-5 

1 x 103 

2.419 09 x 103 

0.671 969 

0020 685 

4133 79 x lo-’ 

2771 70 x IO’ 

0413 36 

pounds per 

foot-second 

Centistokes 

square feet 

per second 

stokes 

rhe 

pascal-second 

slug per foot-second 

centlpolse 

square meters per second 

(mVs) 

square feat per second 

(W/S) 

stokes 

square meters per second 

centistokes 

square meters per second 

1 per pascal-second 

(l/Pa. S) 

1.466 16 

0.031 061 

1.466 16 x 103 

1 x IO-8 

1.076 39 x 10~5 

0.01 

0.092 903 

9.290 30 x 10’ 

1 x 10-d 

10 
<<Appendix C 

Computer Program 

C- 1. Program 223X3 WSP. - 

A COMPUTER PROGRAM TITLED 223-E3WSP HAS BEEN DEVELOPED BY THE 

6UREAlJ OF RECLAMATION TO DETERMINE WATER SURFACE PkOFILEs IN 

RECTANGULAR, TRAPEZOIDAL, CIRCULAR AND “MODIFIED HORSESHOE" 

SHAPED CHANNELS. THE PROGRAM WILL COMPUTE BACKWATER CURVES IN 

RECTANGULAR OR TRAPEZOIDAL CHANNELS AND WILL COMPUTE THE 

CONJUGATE DEPTH IN TRAPEZOIDAL AND RECTANGULAR STILLING bASIrJS. 

A b*M~D~F~ED HORSESHOE" SHAPED CHANNEL Is DEFINED AS A SHAPE WITH 

A SEMI-CIRCULAR TOP, VERTICAL SIGES (ANY HEIGHT) AND A BOTTOM 

WHICH MAY BE FLAT OR HAVE THE SHAPE OF AN INVERTED ft v (I . THE 

HEIGHT OF THE "v" CANNOT EXCEED THE HEIGHT OF THE SIDES. THE 

PROGRAM COMPUTES THE VELOCITY, THE WATER DEPTHI AND THE ENLRGY 

GRADE ELEVATION AT EACH SECTION. 

WHEN COMPUTING THE WATER S~JRFACE PROFILE, THE DEPTH OF WATER IS 

ASSUMED TO BE NORMAL TO THE SLOPE OF THE FLOOR AND THE DISTANCE 

E!ETWEEN SECTIONS IS EQUAL TO THE SLOPE DISTANCE. 'WHEN COMPUTING 

u BACKWATkR CURVE, THE DEPTH OF WATER IS ASSUME: TO BE VERTICAL 

RNU THE IJISTANCE BETWEEN SECTIONS IS EQUAL TO THE HORIZONTAL 

LlISTANCE. THE PROGPAY PROVIDES FOR CHANGES IN SHAPE AT ANY 

413 
414 SMALL CANAL STRUCTURES 

SLCTION PUT DOES NOT INCLUDE A LOSS CAUSED BY A CHANGE IN SHAPE. 

A TRIAL AND ERROR METHOD IS USEUI THEREFORE THE INPUT DATA 

SHOULD BE REASONABLE. IF THE DEPTH IS EXTREMELY SHALLOW kITH A 

HIGH VELOCITY, THE NUMBER OF TRIALS BECOMES EXCESSIVE. A 

SIMILIAR SITUATION M4Y OCCUR IF THE DISTANCE BETWEEN SECTIONS IS 

UNREASONABLY LONG. IF IT IS ANTICIPATED THAT THE RATE OF CHANGE 

IN DEPTH OR VELOCITY Is GREAT, THE SECTIONS SHOULD BE CLOSER 

THAN THEY WOULD BE NORMALLY. 

THE PROGRAM IS LIMITED TO DEPTHS LESS THAN CRITICAL DEPTH WHEN 

COMPUTING A WATER SURFACE PROFILE AND TO DEPThS GREATER THAN 

CRITICAL DEPTH WHEN COMPUTING BACKwATER CURVES. 

IT IS ASSUMED THAT IF THE DEPTH OF WATER EXCEEDS 0.9 TIMES THE 

HEIGHT OF A CIRCULAR OR *8M~~IF~ED HORSESHOEfl SECTION, THE FLOW 

WILL BECOME UNSTABLE. wHEN THIS CONDITION OCCURS, A MESSAGE IS 

PRINTED STATING ' THE DEPTH IS GREATER THAN 0.9 TIMES THE HEIGHT 

OF THE STRUCTURE." EXECUTION OF THE PROGRAM WILL THEN CONTINUE 

PROVIDED THAT THE DEPTH OF EATER IS LESS THAN CRITICAL DEPTH. 

wHtN COMPUTING THE wATEH SURFACE PROFILE A CHECK IS MADE TO 

DETERMINE IF A SOLUTION Is POSSIBLE. IF THE HEPD AVAILABLE Is 

INSUFFICIENT TO OVERCOME THE LOSSES THAT WILL BE INCURRED9 AN 

h,-PROPRIATE MESSAGE iILL BE PBINTED OUT AND THE EXtCUTION WILL 

BE TERMINATED. 

INPUT 

e--wTHE INPUT REQUIRtD IS : 

(1) ChANYEL SHAPE OF THE INITIAL SECTION. Eb!TEP EITHEP: 

(A) RECTANGULAR, 
COMPUTER PROGRAM 415 

(2) 

(3) 

(4) 

(5) 

(6) 

(7) 

(8) 

(8) TRAPEZOICAL, 

(Cl CIRCULAR9 OR 

(D) "MODIFIED HORSESHOE" (MUST BE ENCLOSED IN 

QUOTES). 

ASSUMED DISCHARGE IN C. F. S. 

MANNING'S "N" VALUE. 

INITIAL DEPTH (IF A BACKWATER CURVE IS BEING COMPUTEDI 

THE INITIAL DEPTH MUST bE AdOVE CRITICAL DEPTH. IF A 

WATER SURFACE PROFILE IS BEING COMPUTED THE INITIAL 

DEPTH MUST Bt; BELOW CRITICAL.) 

INITIAL STATION (IF A BACKWATER CURVE IS BEING COMPUTED, 

Tti1.S STATION MUST BE THE DOWNSTREAM STATION). 

INITIAL INVERT ELEVATIOi4. 

INITIAL SLOPE OF THE INVERT (VERTICAL OVER HORIZONTAL). 

ADDITIONAL DATA REQUIRED TO DESCRIBE THE INITIAL 

SECTION: 

(F\) 

(RI 

(Cl 

(D) 

FOR RECTANCULAR SECTIONS, ENTER: 

INITIAL wIDTH 

FOR TRhPEZCIDAL SLCTIONS, EYTLR: 

INITIAL WIDTH, AND 

INITIAL SLOPE OF SIDES (HGRIZONTAL OVER 

VERTICAL). 

FOR CIRCULAR SECTIONS, ENTER: 

INITIAL CIAMETER 

FOR 'tMODIFIED HORSLSHOE~~ SECTIOF'SI ENTER: 

INITIAL wIDTH, 

INITIAL HEIGHT TO SPRINGLINE, AND 
416 SMALL CANAL STRUCTURES 

INITIAL HEIGHT OF "V" BOTTOM (IF BOTTOM 

IS FLAT ENTER 0). 

(9) DIMENSIONS OF EACH SECTION USED MUST BE ENTERED. THE 

DATA MUST BE IN THE SAME SEQUENCE AS THE DIRECTION OF 

FLOW (REVERSE OF THE DIRECTION OF FLOW WHEN COMPUTING A 

BACKWATER CURVE). THE FIRST ITEM IN THE FOLLOWING LISTS 

(f?,T,C, OR MH) DEsIGNATLS THE SHAPE OF THE SECTION. 

(A) FOR RECTANGULAR SECTIONS ENTER: 

PT 

STATION, 

INVERT ELEVATION9 

WIDTH, ANU 

SLOPE OF 1NVEpT (VERTICAL OVER HORIZONTAL) 

(6) FOR TRAPEZOIDAL SECTIONS ENTER: 

T1 

STATION9 

INVEPT ELEvATIONI 

hIIJTH, 

SLOPE OF THE SIDES (HORIZCNTAL OVER 

VERTICAL), AND 

SLOPE OF THE INVERTrf VERTICAL OVER THE 

HORIZONTAL) 

(Cl FOR CIRCULAR SECTIONS ENTER: 

L, 

STATION9 

INVERT ELEVATION9 
COMPUTER PROGRAM 417 

DIAMETER, AND 

SLOPE OF THE INVERT (VERTICAL OVER HORIZONTAL). 

(D) FOR “MODIFIED HORSESHOE” SECTIONS ENTER: 

MH, 

STATION, 

INVERT ELEVATION? 

WIDTH? 

HEIGHT TO THE SPRINGLINE, 

HEIGHT OF THE “V” BOTTOM, AND 

SLOPE OF THE INVERT (VERTICAL OVER HORIZONTAL) 

110) THE LAST DATA ENTRY SHOULD BE THE WORD “END”. 

OUTPUT 

m-w--- 

THE OUTPUT NILL CONSIST OF: 

(1) INITIAL LIATAq 

(A) DISCHARGE 

(@I MANNING’S N 

(C) INITIAL DEPTH 

(3) INITIAL WIETH 

(2) STATION, 

(3) INVERT ELEVATION, 

( 4 1 VELOCITY? 

(5) ENERGY GRADIENT, 

(6) DEPTH9 
418 SMALL CANAL STRUCTURES 

(7) CCNJUGATE WATER IJEPTH AND VELOCITY IF REQUESTED, AND 

(8) INPUT CATA IF REQUESTED. 

A LISTING OF THE PROGRAM AND SAMPLE RESULTS ARE SHOWN IN THIS 

APPENDIX. INPUT DATA WA: TAKEN FROM THE CHUTE STRUCIURE USED AS 

A ENSIGN FXAMPLE IN CHAFTER II. STATIONS USED Ik THE EXAMPLE 

H4vk BEEN TRUNCATED TO MEtT REQUIREMENTS OF THE PROGRAM. 

DISCLAIMER STATEMENT 

CBMPUTER PRBGRAMS DEVEL0PED BY THE BUREAU 0F RECLAMATIJN 

ARE SUBJECT T0 THE FBLL0WiNG CBdDITLBNS. C0NSULTING 

SERViCE AND ASSlSTANCE WITH CBNVERSIBNS TO 0ThER CB@UTER 

SYSTEMS CANNOT BE PRldVIDED* N0 WARRANTY AS T0 THE ACCURACY, 

USEFULNESSI 0R CBMPLETENESS OF THE PRBGRAMS IS EXPRESSED dR 

IMPLIED. 

10 

100 

110 

120 

130 

140 

150 

170 

160 

190 

200 

210 

220 

230 

240 

250 

280 

290 

300 

310 

320 

330 

350 

360 

370 

380 

390 

400 

410 

420 

430 

PRBGRAM 223-E3WSP 

REM WATER SURFACE PRQFlLE PRBGRAM <223-E3WSP) SYSTEM-BASIC 

PRINT “WHAT IS THE NAME 0F THE DATA FILE”I 

INPUT fS 

FiLE# I =FS 

PRINT “IS THIS A W4TER SURFACE PR0fILE CQMPUTATI0N--YES BR i\JB”I 

INPUT GS 

PRINT 

F0R I=1 T0 10 

INPUT# 1 rAS 

1F A$=“RECTANGULAR” THEN 250 

IF A$=“TRAPELBiDAL” THEN 250 

1F AS=“CIRCULAR” THEi’J 250 

IF AG=“MBDlflED hJRSESH0E” THEN 250 

PRINT TAB<lO))AS 

,\IEXT I 

PRINT 

IF GS=“,YB” THEi’d 3 10 

PRINT “WATER SURF4CE PR0FILE - “JAS:” SECTIBN” 

G0 T0 320 

PRINT “BACKWATER CURVE -“IABJ” SECTIQd” 

INPUT#~~O~NID~~L~~E~.T~ 

H=Q?2/32*16 

PRINT 

PRINT”DISCHARGE=“:Qi”C.F.S~” 

PRINT “MANNIINGS N=“I,V 

PRINT “INITIAL DEPTH=“JDl 3”FT.” 

1F AS=“RECTANGULAR” THEN 2000 

if AS=:“TRAPEL01DAL” THEN 4000 

If AS=“C IRCULAd" THE,\1 6000 

IF AS="t'lVIBDIFIED H0RSESHdE” THEN 8000 

GO T0 2370 
COMPUTER PROGRAM 419 

440 

450 

460 

470 

480 

490 

500 

510 

520 

530 

540 

550 

560 

570 

580 

590 

600 

2000 

2010 

2020 

2030 

2040 

2050 

2060 

2070 

2080 

2090 

2100 

2110 

2120 

2130 

2140 

2150 

2160 

2170 

2180 

2190 

2200 

2210 

2220 

2230 

2240 

2250 

2260 

2270 

2280 

2290 

2300 

2310 

2320 

2330 

2340 

2350 

2360 

2370 

2380 

2390 

2400 

2410 

2420 

2430 

2440 

2450 

:#I+*# .R# ###RI .+r ###*##iv #YY#*.##I #I# .#I 

L3=1NT<21/100) 

Z4=Ll -Z3*100 

IF Z4~10 THEN 500 

PRINT USiNG 440rL3rZ4>ElrVlsEaDl 

Gd Td 560 

IF L4<1 THEN 540 

:##+O#.#u ####A.## W##.U#R ####A .#A# (I##.## 

PRINT USING 510,Z3~Z4rElrVl rEsD1 

G0 T0 560 

:#A+oo.## I####.## I##.### URQ#X.##Y ##I .A# 

PRINT USING 540rZ3sZ4rElrVlaEsDl 

RETURN 

PRINT 

PRINT “STATI~N”~“ELEVA‘TI~IY”.“VEL~CJTY”.”E. G. &LEV.“r”DEPTH” 

PRINT 

RETURN 

REM THIS BL0CK (2000-3499) IS USED FBR C0MPUTATIQN OF 

HElY RECTANGULAR SECT IONS 

INPUT#l l Wl 

PRINT “FIRST WiDTH=“lkl j*‘FT.” 

D3 =<<Q/Wl)t2/32.16)t.3333 

IF GS=“YES” THEN 2080 

IF D3<Dl THEN 2100 

G0 Ti4 2350 

IF D3>Dl THEN 2100 

G0 T0 2320 

GBSUB 570 

Rl=ATN<ABS(Tl)) 

Al = Dl*Wl 

Vl = Q/CDl*Wl) 

Hl = Vlt2164.32 

E = El + Dl*CldS(Bl) + Hl 

Rl = A1/(2*Dl+Wl> 

Sl = Vlf2*Nf2/<1.486t2*Rlt<4/3)) 

GBSIJB 440 

INPUTtlrBS 

1F BS=“MH” THEN 8980 

IF BS = “T” THEN 4840 

IF BS = “END” ThEN 12020 

IF BS= “C” THEN 7010 

INPUT# 1 s L2rE2r W2rT2 

M1=01=02=03=04=0 

P=Z2-Zl 

IF P=O THEN 2370 

L9=SQR<<E2-E1)*2+Pt2) 

IF P<O THEN 2970 

IF GS=“YES” THEN 2410 

G0 T0 2370 

PRINT “INITIAL DEPTH IS GREATER THAN CRITICAL DEPTH” 

PRINT “CRITICAL DEPTH =‘*iD3 

STBP 

PRINT “INITIAL DEPTH IS LESS THAN CRITICAL DEPTH” 

GQ TO 2330 

PRINT “ERROR IN DATA” 

STBP 

T2=0 

L9=P 

D3 =(<Q/W2)t2/32.16)t.3333 

B2=ATN(ABS<TB)) 

X = E-E2 

D2 = D3 

A2 = D2*W2 
420 SMALL CANAL STRUCTURES 

2460 

2470 

2480 

2490 

2500 

2510 

2520 

2530 

2540 

2550 

2560 

2570 

2580 

2590 

2600 

2610 

2620 

2630 

2640 

2650 

2660 

2670 

2680 

2690 

2700 

2710 

2720 

2730 

2740 

2750 

2760 

2770 

2780 

2790 

2800 

2810 

2820 

2830 

2840 

2850 

2660 

2870 

2880 

2890 

2900 

2910 

2920 

2930 

2940 

2950 

2960 

2970 

2980 

2990 

3500 

3510 

3520 

3530 

3540 

3550 

3560 

3570 

3580 

v2 = Q/A2 

G0 T0 2520 

V2 = SQR(64=32*M) 

D2 = (Q/V2)/W2 

A2 = D2 * w2 

V2=B/A2 

R2 = A2/(2*D2+W2) 

s2 = V2t2*Nt2/<1.486t2*R2t<4/3)) 

H3=L9*<Sl+S2)/2 

H2 = V2t2164.32 

H4=D2*CdS(B2)+H2+H3 

IF Ml>0 ThEiJ 2670 

Ml=1 

H=H8=H2 

1F t=<O THEd 2900 

IF H4cX ThEN 2680 

IF D2*CdS<B2)+H2<X ThEN 6500 

PRli'JT 

PKi,VT ",\10 S~LIJTIBIV t='@SSlBLE-" 

l'RI+JT "CBdTROL IS DBWdSTREAM dF AR0VE STATI0N" 

G13 Td 2.730 

1F Ii4 >= X+.OOS THEN 2690 

iF H4 ' X-.005 THEN 2790 

Ga SUB 3520 

IF Pa0 THEI\I 2760 

IF i-lxD.3 THEN 2740 

D2=h 

Gd T0 2450 

D2=D3 

GG3 TO 2450 

IF Hah8 THEN 2480 

h=HtS 

GQ T;d 2480 

Dl = D2 

Ll = L2 

El = E2 

w 1 = w2 

s1=s2 

v1=v2 

E=E-H3 

Gd Td 2180 

PR~~VT TAB<~)~**cHANGE OF s~criad ~0 RECTANGULAR** 

Y=LY=o 

Gd Ta 2240 

IF X-H3<D2+H2 ThEN 2930 

IF B$="T" THEN 4640 

G0 Td 2670 

L3=idT(Ll/loo) 

L4=L1-100*43 

PRINT "CdNTfildL 1.5 UPSTREAM 0F STATI~i\l":~31"+"iL4 

STQP 

IF G$="YES" THEi'd 2370 

iF B16="R" THEd 2390 

1F R%="T" THEd 5030 

REM THlS BLdCK (3500-3999) IS USED FJR II'JCREME~JTII'JG 

REM EITHER THE VEL0CITY HEAD 0R DEr'TH 

IF ?<O THEN 3550 

IF B$="R" THE?J 3590 

IF B$="T" THEI\I 3590 

H=D2 

IF P<O THEN 3590 

IF H4<X THE.'J 3630 

GB T0 3600 
COMPUTER PROGRAM 421 

3590 IF H4+X THEN 3630 

3600 IF 01>0 TrlEd 3680 

3610 H=h+l 

3620 RETURd 

3630 IF 04>0 THEN 3780 

3640 IF 02>0 THEN 3720 

3650 H=H-.l 

3660 01=01+1 

3670 RETURN 

3680 IF 03~0 THEN 3750 

3690 H=H+.Ol 

3700 02=02+1 

3710 RETURN 

3720 H=H-.OOl 

3730 03=03+1 

3740 RETURN 

3750 H=H+.OOOl 

3760 04=04+1 

3770 RETURN 

3780 IF B$="R" THEN 2790 

3790 IF B$="T" THEN 4760 

3800 iF BS="C" THEN 6460 

3810 IF B$="MH" THEN 8900 

4000 REM THIS BL0CK(4000-5999) iS USED FOR CBMPUTATIBN OF 

4010 REM TRAPELdlDAL SECTI~IJS 

4020 INPIJTI~D WlrL 

4030 PRINT "FIRST SIDE SL~PE="~L~"T~ 1" 

4040 PRINT "FIRST WIDTH="iWlI"FT." 

4050 IF G$="YES" THE&V 4070 

4060 Tl=O 

4070 w3=w1 

4080 Tl=ABS<Tl) 

4090 Bl=ATt'I<Tl) 

4100 Y=SQR((L+L*Tlf2)f2+Tlt2) 

4110 G0SUB 4860 

4120 IF G$="YES" THEN 4150 

4130 IF D3<Dl THEI'J 4170 

4140 G0 T0 2350 

4150 IF D3>Dl THEN 4170 

4160 G'd T0 2320 

4170 GBSUB 570 

4180 Vl=Q/<Dl*Wl+Dlt2*Y) 

4190 Hl = Vlt2164.32 

4200 E=El+Dl*C0S<Bl)+Hl 

4210 Rl=<Dl*Wl+Dlt2*Y)/<Wl+2*SQR(Dlt2+(Y*Dl)~2~~ 

4220 Sl = Vl~2*Nf2/(1.486t2+RlrO) 

4230 GOSUB 440 

4240 lNPUT#lr 88 

4250 IF B$ = '*R" THEN 2870 

4260 IF BB='*C" THEN 7010 

4270 1F BS="MH" THEN 8980 

4280 IF B$="END" THEN 12020 

4290 INPUTIla L2rE2aW2rL9rT2 

4300 X=E-E2 

4310 P=Z2-Zl 

4320 IF P=O THEN 2370 

4330 IF PC0 THEN 2970 

4340 IF GG='*YES" THEN 4360 

4350 GQ T0 2370 

4360 T2=ABS<T2) 

4370 L9=SQR<(E2-El)t2+Pt2> 

4380 M1=01=02=03=04=0 

4390 k;3=ki2 
422 SMALL CANAL STRUCTURES 

44OO D3=0 

4410 Y2=9T1J<'l'2) 

4420 Y'=SQR((LY+LY*T2t2)tZ+TZt2) 

4430 GaSUH 4860 

4440 V2=a/A3 

4450 D2=D3 

4460 G0 I.0 4530 

4470 A2=D2*b2+DZtP*Y 

4480 v2=(3/42 

4490 G3 TJ 4530 

4500 V8 = SQR(64.32*h) 

4510 D2 = (-~~+S~K(~~T~+~*Y*Q/V~))/(~~Y) 

4520 Gd TO 4470 

4530 R2=(D2*~!2+D2tRxY)/(b2+2~S~~(D2T2+(Y~O2)T2)) 

4540 S2 = VZt2*1~?2/(1.486?2*~2t<4/3)) 

4550 H3=L9*(Sl+S2)/2 

4560 HZ = V2t2164.32 

4570 Mi=D2*CZIS<B2)+H2+H3 

458Ll IF Prl>O THF.V 4640 

45YO Ml=1 

4600 H=H8=h2 

4610 1F t'<O ThEiq 2900 

4620 IF H4<X THEN 4650 

4630 GJ T0 2620 

4640 IF H4>=X+.005 TtiEi'I 4660 

4650 IF n4 z= X- .005 THEN 4760 

4660 GO SUS 3520 

4670 1F P>O ThEt'J 4730 

4680 IF H<D3 THE&\) 4710 

4690 DZ=ti 

4700 G0 T0 4470 

4710 02=D3 

4720 G0 TO 4470 

4730 IF H>HB THEN 4500 

4740 h=h8 

4750 Gd T0 4500 

4760 Dl = D2 

4770 Ll = L2 

4780 El = E2 

4790 Wl = w2 

4800 v1=v2 

4810 E=E-H3 

4820 s1=s2 

4830 G0 T0 4230 

4840 PHIdT TAB(6);"CHAc'JGE c?F SECTIdr'J TO TKAPEL~IDAL" 

4350 Gd Td 4290 

4860 D3=D3+1.0 

4870 GQSUR 4990 

4880 IF r(l<r; TnEt'J 4860 

4890 D3=D3-.I 

4900 GZlSU5 4990 

4910 IF Kl>K TtlEi'J 4890 

4920 D3=03+.01 

4930 GldSUB 4990 

4940 IF Kl<ri THEI\I 4920 

4950 D3=D3-.OOl 

4960 GdSUB 4990 

4970 IF Kl>K THEN 4950 

4980 RETURN 

4990 T3=W3+2*D3*Y 

5000 A3=W3*D3+D3?2*Y 

5010 Kl=A3?3/T3 

5020 RETURI'J 
COMPUTER PROGRAM 423 

5030 T2=B2=0 

5040 L9=P 

5050 G0 TO 4380 

6000 REM THIS BLBCK (6000-7999) IS USED F0R CBMPUTATI0N OF 

6010 REM CIRCULAR SECTIQNS 

6020 IF Gf="NB" THEN 6980 

6030 INPUTRlr D8 

6040 PRINT "DIAMETER IS"3D81"FT~" 

6050 PRINT 

6060 Bl=ATN<ABS<Tl)) 

6070 82 = Bl 

6080 R8 = D8/2 

6090 G0SUB 6530 

6100 D3=D2 

6110 IF Dl>D3 THEN 2320 

6120 GBSUB 570 

6130 D2 =Dl 

6140 GBSUB 6790 

6150 E = El + D2*CBS(B2) + H2 

6160 Dl = D2 

6170 Vl = v2 

6180 Sl = s2 

6190 GBSUB 440 

6200 IF Dl<.9*D8 THEN 6230 

6210 PRINT "DEPTH IS GREATER THAN 09 TIMES" 

6220 PRINT "THE HEIGHT 0F THE STRUCTURE*' 

6230 INPUTRlr B6 

6240 IF BB="Mh" THEN 8980 

6250 IF BS="R" THEN 2870 

6260 IF B%="T" THEN 4840 

6270 IF BS = “END” THEN 13000 

6280 lNPUT#l, L2aE2rDSrT2 

6290 P=Z2-Ll 

6300 82=ATN(ABS(T2)) 

6310 IF P=O THEN 2370 

6320 IF PC0 THEN 6960 

6330 X = E-E2 

6340 R8 = D8/2 

6350 G0 SUB 6530 

6360 D3=D2 

6370 IF H4>X THEN 2620 

6380 H=HS=DB 

6390 01=02=03=04=0 

6400 GBSUB 3520 

6410 D2=H 

6420 G0 SUB 6790 

6430 IF H4>X+.005 THEN 6400 

6440 IF H4>X- .005 THEN 6460 

6450 G0 T0 6400 

6460 Zl = L2 

6470 El = E2 

6480 E=E-H3 

6490 G0 T0 6160 

6500 PRINT 

6510 PRINT "SECTIBNS T00 FAR APART" 

6520 STBP 

6530 H5 = 1.7014lE38 

6540 D2 = 001 

6550 GBSUB 6790 

6560 IF D2 + H2 > HS THEN 6640 

6570 H5 = D2+H2 

6580 D2 = D2 + .l*DS 

6590 IF D2<D8 THEN 6630 
424 SMALL CANAL STRUCTURES 

6600 D2=.9999*D8 

6610 GBSUB 6790 

6620 GO T0 6640 

6630 G0 T0 6550 

6640 I-IS = H2 + D2 

6650 D2 = D2 - l Ol*D8 

6660 GBSUB 6790 

6670 IF D2 + H2 > H5 THEN 6690 

6680 G0 T0 6640 

6690 H5 = D2 + H2 

6700 D2 = D2 + l OOl*D8 

6710 GBSUB 6790 

6720 IF D2 + H2 ’ X5 THEN 6740 

6730 G0 T0 6690 

6740 H5 = D2 + H2 

6750 D2 = D2 - .OOOl*D8 

6760 G0SUB 6790 

6770 IF D2 + H2 < HS THEN 6740 

6780 RETURN 

6790 IF D2 > R8 THEN 6830 

6800 IF D2 < R8 THEN 6850 

6810 86 = 90/57.29577774 

6820 G0 T0 6860 

6830 B6=180/57.29577774-ATN(SQR(R8)t2)/(D2-R8)) 

6840 G0 T0 6860 

6850 B6 = ATN(SQR<R8*2-<R8-D2)t2)/<Hg-D2>> 

6860 88 = 2*B6 

6870 A2 = R8*2*(86-.5*SIN(B8)) 

6880 P2 = R8*B8 

6890 v2 = Q/A2 

6900 R2 = A2/P2 

6910 S2=V2t2*Nt2/<1*486t2*R2?<4/3>) 

6920 H2 = V2t2164.32 

6930 H3=SQR<~E2-El)~2+<22-Z1)12)*(S1+S2)/2 

6940 H4 = D2*C0S<B2) + H2 + H3 

6950 RETURN 

6960 PRINT 

6970 IF GS=“YES” THEN 2370 

6980 PRINT “BACKWATER CURVES CANNBT BE” 

6990 PRINT “CBMPUTED IN CIRCULAR SECTIBNS” 

7000 STBP 

7010 PRINT TAB(6)I”CHANGE 0F SECTIBN T0 CIRCULAR” 

7020 G0 T0 6280 

8000 REM THIS BL0CK <8000-9999) IS USFD F0R CBMPUTATIBN 0F 

8010 REM HBRSESHBE SECTIBNS 

8020 IF GS=“NB” THEN 8470 

8030 INPUTRl s WlrD7aXl 

8040 PRINT “FIRST WIDTH=“, Wl ;“FT.” 

8050 PRINT “FIRST HEIGHT OF SIDE=“ID73”FT*” 

8060 R4=W1/2 

8070 D8EWl 

8080 GOSUB 10000 

8090 IF D3*Dl THEN 2320 

8100 GBSUB 570 

8110 81 =ATN(ABS<Tl)) 

8120 IF Dl > D7 THEN 8210 

8130 IF Dl ’ Xl THEN 8180 

8140 Ll = Dl*R4/Xl 

8150 Al = Dl*Ll 

8160 Rl = A1/<2*<Dl+SQR<Llf2+Dlt2))) 

8170 G0 T0 8300 

8180 Al = Wl+Dl-Wl*X1/2 

8190 RI = A1/(2*Dl+SQR<Xlf2+R412)*2)*2) 
COMPUTER PROGRAM 425 

8200 G0 T0 8300 

8210 IF Dl-D7 <’ 0 THEN 8240 

8220 86 = 90157.29577774 

8230 G0 T0 8250 

8240 86 = ATN<SQR(R4?2 - (Dl-D7)*2)/<Dl-D7>) 

8250 88 = 2*B6 

8260 Al=kl*D7+3.141593+DSt2/8- .S*R4t2*<BS-SIN(BS))-R4*Xl 

8270 Pl =2*D7+SQR(Xlf2+R4t2)*2+1.570796*DS-R4*BS 

8280 RI = Al/P1 

8290 Sl=Vlt2*Nt2/(1.486t2*Rlt(4/3)) 

8300 Vl = Q/Al 

8310 HI = Vlt2164.32 

8320 E = El + Dl*CBS<Bl) + Hl 

8330 GBSUB 440 

8340 IF D1<.9*(D7+R4) THEN 8370 

8350 PRINT “DEPTH IS GREATER THAN 09 TIMES ” 

8360 PRINT “THE HEIGHT 0F THE STRUCTURE” 

8370 INPUTll a Bb 

8380 IF BS = “R” THEN 2870 

8390 IF BS=“T” THEN 4840 

8400 IF BS=“C” THEN 7010 

8410 IF BS=“END” THEN 13000 

8420 INPUTb 1s L2rE2rW2rD7rXlrT2 

8430 P=L2-Zl 

8440 IF P=O THEN 2370 

8450 IF Pa0 THEN 8500 

8460 IF GS=“YES’* THEN 2370 

8470 PRINT “BACKWATER CURVES CANNQT BE” 

8480 PRINT “CBMPUTED IN MBDIFIED HBRSESHBE SECTI0NS” 

8490 STBP 

8500 D8 = w2 

8510 X=E-E2 

8520 R4 = D8/2 

8530 GSSUB 10000 

8540 B2=ATN<ABS<T2>) 

8550 D2=D3 

8560 M1=01=02=03=04=0 

8570 G0 T0 8580 

8580 IF D2 * D7 THEN 8670 

8590 IF D2 ’ Xl THEN 8640 

8600 L2 = D2*R4/Xl 

8610 A2 = D2*L2 

8620 R2 = A2/(2*(D2+SQR(L2*2+D2r2)>) 

8630 GB T0 8750 

8640 A2 = D2*W2-b;2*X1/2 

8650 R2 = A2/<2*D2+SQR<Xlt2+R4t2)*2) 

8660 GB T0 8750 

$670 IF <D2-D7) <> 0 THE,\) 8700 

8680 96 = 90157.29577774 

B690 Gd Td 8710 

8700 B6 = ATN(SQR<R4*2-(D2-D7)*2)/(D2-D7)) 

8710 US = 2*B6 

B720 A2=W2*D7+3.141593*D812/8- .S*H4t2*<BS-Sli~<B~))-Xl*~~2/2 

8730 P2=2*D7+1.570796*DS-R4*BB+SQR(Xlf2+R4*2)*2 

f3740 R2 = A2/P2 

8750 v2 = Q/A2 

8760 s2 = V2*2*Nt2/(1.486t2*R2t<4/3)) 

8770 H3=SOR(<E2-El)t2+(L2-L1)12)*(S1+S2)/2 

8780 H2 = V2t2164.32 

8790 H~=D~*IZ~S(B~)+H~+H~ 

8800 IF Ml>0 THEN BBS0 

8810 PI 1 = 1 

8820 ti=H8=D3 
426 SMALL CANAL STRUCTURES 

8830 IF H4<X THEiV 8860 

8840 GQ TEI 2620 

8850 IF H4>= X+.01 THEI’J 8870 

8860 IF H4 >= X - 001 THEIV 8900 

8870 GBSUB 3520 

8880 D2=H 

8890 GB TO 8580 

8900 v1=v2 

8910 Dl =D2 

8920 s1=s2 

8330 21 = Z.2 

8940 Hl =H2 

8950 El = E2 

8960 E=E-Ii3 

8970 GQ T0 8330 

8980 PRINT TAB(6);“CHANGE 0F SECTl;/N Td M0DIFIED HdRSESH0E” 

8990 Ga T0 8420 

10000 REM THIS BL0CK (10000-11999) IS USED F0R COMPUTATi0d 0F 

10010 REM CRITICAL DEPTH 1N A MJDIFIED HdRSESHQE SECTIdh’ 

10020 K=Qt2/32.16 

10030 1F X1=0 THEN 10180 

10040 r<2= <.5*Q)f2/32.16 

10050 D3=Xl 

10060 A3=D3*R4/2 

10070 Kl=A3r3/R4 

10080 IF Kl<r<2 THEN 10160 

10090 D3=D3-*01*X1 

10100 T3=D3*R4/Xl 

10110 A3=T3*D3/2 

10120 Kl=A3?3/T3 

10130 IF r(l>K2 THEN 10090 

10140 R3=A3/<D3+SQR<T3*2+D3t2)> 

10150 V3=Q/(2*A3) 

10160 S2=V3t2*‘tt2/(1.486t2*R3t(4/3)) 

10170 RETURN 

10180 D3=D7 

10190 G0SUB 10420 

10200 IF r:l<K THEN 10310 

10210 D3=D3-•l*D7 

10220 G;JSUB 10420 

10230 IF Kl>r( THEiJ 10210 

10240 D3=D3+*0l*D7 

10250 GBSUB 10420 

10260 TF Al<& THEN 10241) 

10270 D3=D3-•OOl*D7 

10280 GdSUB 10420 

10290 IF t(l>K ‘THEA 10270 

10300 GdSlJB 10450 

10310 D3=.YYY*(R4+D7) 

10320 D3=D3-.l*K4 

10330 G0SUB 10480 

10340 IF K1 >K THEiJ 10320 

10350 D3=D3+aOl*K4 

10360 G0SUB 10480 

10370 IF Kl <r( THEiq 10350 

10380 D3=D3-.OOl*R4 

10390 G0SUE 10480 

10400 IF Kl>K THEN 10360 

10410 G&SUB 10540 

10420 43=D3*D8-Xl *K4 

10430 u(l=A3t3/D8 

10440 RETUHL’J 

10450 R3=A3/(2*(D3+SQK(XltB+R4t2)))~ 
COMPUTER PROGRAM 427 

10460 V3=O/A3 

10470 GO l-3 10160 

10480 ~~=ATI~<SOR<R~~Z-(D~-D~)~~)/(D~-D~)) 

10490 B8=2*B6 

10500 A3=D8*D7+3.141593*D8t2/8-. S~R~T~*(R~-S~I\~(R~))-X~~D~:/,~ 

!OSlO T3=2%i?4*SI8(56) 

10520 u;l=A3?3/T3 

1 OS30 RETUR.\J 

10540 P3=2+D7+1 .570796*D8-!?4*Bt(+SOJ?~Xlt2+R4~2~~2 

10550 R3=A3/P3 

10560 GJSIJR 10460 

1 OS70 RETURN 

12000 REi.r THIS BL3CK (12000-12999) IS USED FOR THE C0i4PUTATI0N 0F 

12010 REM THE C0NJUGATE DEPTH(hYDRAULlC JIJMl”) 

12020 IF P<O ThEN 13000 

1203O PRidT 

12040 PRINT “DO YOU WAi\IT THE C’cl,\lJUGATE DEPTH C;3MPJJTED--YES ij;i \\lrd”; 

12050 It\JPUT C5 

12060 PRINT 

12070 IF CS = “igO” THEN 13000 

12080 G = 32.16 

12090 Y5=Y 

12100 IF Z9=0 THEN 12230 

12110 FBR D2=D3+1 T0 100 

12120 GBSUB 12280 

12130 IF X>Y THEhN 12150 

12140 ,JEXT D2 

12150 D2 = 02-01 

12160 GOSUB 12280 

12170 IF X<Y THEN 12190 

12180 GO TkJ 12150 

12190 D2 = D2+*01 

12200 GBSUB 12260 

12210 IF X>Y THEN 12250 

12220 G0 T5 12190 

12230 D2=-Dl/2+SQR(Dlr2/4+2*Vlt2*D1/G) 

12240 V2=Q/(D2*Wl) 

12250 PRINT TAB<6)3”D2 = “iD2;” FT” 

12260 PRINT TAB(6)i”V2 = “iV23” FPS” 

12270 G0 T0 13000 

12280 Y=Q*Vl/G+Wl*Dlt2/2+Y9*Dlt3/3 

12250 V~=O/<W~*D~+L~*D~T~) 

12300 X=Q*V2/G+Wl*D2?2/2+L9*D2?3/3 

12310 RETURN 

13000 REM THlS BLBCK(l3000-13959) IS USED T0 

13010 REM LIST DATA FRBM THE DATA FILE 

13020 PRINT 

13030 PRINT “D0 Y0U WANT THE INPUT DATA PRINTED BUT--YES QR INO*‘; 

13040 INPUT C$ 

13050 1F C$=“N0” THEI’I 14000 

13060 RESTBRE Rl 

13080 PRINT 

13090 INPUT #lrA$ 

13 100 1 F A$=“RECTANGULAR” THEN 13160 

13110 IF A$=“TRAPEZBIDAL” THEN 13190 

13120 IF A$=“CIRCULAR” THEN 13220 

13130 IF A$=“hBDIFIED HBRSESHdE” THEN13250 

13140 PRINT AS 

13150 G0 T0 13090 

13160 INPUT 4lrQ,N1Dl~Ll,El,TlrWl 

13170 PRItiVT A$iQjNjDliLljEljTliUl 

13180 G3 T0 13270 

13190 INPUT #lr9r~~tDl,ilrElrTlrWI,i 
428 SMALL CANAL STRUCTURES 

13200 PRINT A$iQ~NZDlILl~El~Tl~Wlii 

13210 GO TO 13270 

13220 IdPUT #l~Q1~~1DlrLl,ElrTl,D8 

13230 PHI!VT A$IQj,~;Dli~ljEliTljD8 

13240 G0 TO 13270 

13250 INPUT ~~~QIN~D~~L~JE~~T~,W~~D~~X~ 

13260 PRINT A$iQ~N3Dl~Ll3El3’~13k;l3D73Xl 

13270 INPUT AlrB$ 

13280 IF 61F=‘*R” ThEN 13330 

13290 IF BS=“T” THEiJ 13360 

13300 IF BS=“C” THEtJ13390 

13310 IF B$=“MH” THEN 13420 

13320 IF B$=“END” THEN 13450 

13330 INPUT #lsZ2rE2*b!2rT2 

13343 PRINT BSiZ2JE2Jb121T2 

13350 GO T0 13270 

13360 li\IPUT #lsL2,E2rk2,Z9,T2 

13370 PRINT BSjL2iE2iW2iL9iT2 

13380 G0 T0 13270 

13390 INPUT YlsL2~E2rDtSrT2 

13400 PRIIVT BBiL2iEZJD8iT2 

13410 G0 T0 13270 

13420 INPUT #lsL2rE2rW2>D7rXlrT2 

13430 PRINT B!Ti3~23E23W2307~XliT2 

13440 G0 T0 13270 

13450 PRINT B$ 

14000 END 

EXAMPLE OUTPUT FRBM PRBGRAM 223-E3WSP 

DESIGN EXAMPLE CHUTE FRBM CHAPTER II 

WATER SURFACE PRBFILE - RECTANGULAR SECTIBN 

INITIAL DATA: 

DISCHARGE 3s C.F.S. 

MANNING ‘S N 0.010 

INITIAL DEPTH 1.615 FT. 

FIRST WIDTH 3 FT. 

STATIBN ELEVATIBN VEL0C LTY E. G. ELEV. DEPTH 

35+78.00 3703 000 7.224 3705.426 1.615 

37+4f3.00 3689.12 22.906 3697.786 *so9 

38+05 900 3684.47 22.626 3692.942 0516 

39+40.00 3670.28 24.531 3680.106 .476 

40+46.42 3659.10 24.417 3668.845 .478 

41+68.00 3652.73 19.495 3659 0233 .598 

42+00 .OO 3651.05 19.466 3657.528 l 600 

42+13*00 3650.37 19.527 3656.777 9479 

42+16.00 3650.04 19.788 3656 0581 .452 

42+19.00 3649.38 20.538 3656.357 0417 

42+23.82 3647.06 23.305 3655.810 .339 

42+35=00 3642.06 27.024 3653.641 0259 

D0 Y0U WANT THE C0NJUGATE DEPTH CBMPUTED--YES OR NB?YES 

D2 = 3.30285 FT. 

v2 = 2.11938 FPS. 
COMPUTER PROGRAM 

D0 Y0U WANT THE INPUT DATA PRINTED OUT--YES OR NB?YES 

INPUT DATA 

DESIGN EXAMPLE CHUTE FRBM CHAPTER II 

RECTANGULAR 35 -01 1=615 3578 3703 0 3 

R 3748 

R 3805 

R 3940 

R 4046.42 

R 4168 

R 4200 

R 4213 

R 4216 

R 4219 

R 4223.82 

R 4235 

3689.12 

3684.47 

3670.28 

3659.10 

3652-73 

3651.05 

3650.37 

3650*04 

3649.38 

3647.06 

3642=06 

END 

3 .08163 

3 .08163 

3 .lOSl 

3 .lOSl 

3 .05241 

3 .05241 

3.74 .05241 

3.91 .05241 

4.09 .OS241 

4.43 .soooo 

5 .soooo 

429 

Index 

Adjustable weirs, 162, 163, 262 

Air vents, 375 

for inverted siphons, 29 

for siphon spillways, 195 

for structures with baffled outlets, 309, 321 

for turnouts, 146 

Appurtenances for pipe (see Pipe appurtenances) 

Baffled apron drops 

design considerations, 301 

design example, 304 

general, 299 

used with 

culverts, 207 

overchu tes, 2 18 

Baffled outlets 

design example, 321 

design procedure, 321 

figures for standard outlets, 31 l-320 

hydraulic considerations, 309 

protection, 321 

purpose and description, 308 

sediment and debris, 321 

used with 

chutes, 103 

culverts, 206 

overchu tes, 2 18 

type 2 pipe drops, 98 

Barrier, safety for pipe, 373, 393 

Bench flumes 

design example, 42 

hydraulic considerations, 39 

purpose and description, 38 

structural considerations, 4 1 

Bends (see Pipe bends) 

Bernoulli theorem, 10, 105, 187,209, 220, 236 

Blowoff structures, 375 

Cables, safety, 394 

Canal 

freeboard, 14, 28 

general, 4 

profile sheet, 14 

winter operation, 14 

Check and pipe inlet 

application, 166 

description and purpose, 166 

design considerations, 166 

design example, 168 

figure and table for standard design, 167 

used with 

pipe drops, 66 

wasteway turnouts, 201 

Check-drop structures 

application, 140 

design considerations, 139 

design example, 140 

figures and tables for standard design, 141, 142, 144,145 

purpose and description, 139 

Check inlet, 64, 201 

Check structures 

combination structures, 134 

design considerations, 136 

design example, 136 

figures and tables for standard design, 137, 138 

purpose and description, 134 

spacing, 135 

used with drops, 60 

Chutes 

open channel chute, 104 

design considerations, 104 

design example, 116 

design procedure, 115 

pipe chute, 121 

purpose and description, 101 

Coefficient of (see specific coefficient) 

Collars, pipe 

figure and table for standard collars, 363 

general, 362 

minimum distance between, 210 

Components and appurtenances for structures, 4 

Constant-head orifice, 150 

discharge coefficient, 15 1 

discharge tables for, 155,156 

Control and pipe inlets 

application, 170 

description and purpose, 170 

design considerations, 170 

design example, 173 

figure and table for standard design, 172 

used with pipe drop, 66 

Control inlet, 62 

Control notch (see Control and pipe inlets) 

Control section, 59 

Conversion factors, 409 

Conveyance structures 

general, 1, 19 

Cover (see Earth cover on conduits) 

Critical-flow hydraulics 

in pipe, 187,209,212,213,239 

in rectangular channels, 40,43,63,116, 184,194,221,225, 

236 

Cross-drainage structures, 202 

Cross-waves (see Waves) 

431 
432 INDEX 

Culverts 

alinemcnt, 203 

conduit, 204 

design example, 2 10 

hydraulics, 207 

inlet, 205 

outlet, 206 

pipe collars, 2 10 

profile, 203 

Cutoffs (see also specific structure) 

for transitions, 342 

general, 14 

Dead loads, 7 

Design considerations 

general, 6 

Design examples 

baffled apron drop, 304 

baffled outlet. 321 

bench flume, 42 

check and pipe inlet, 168 

check-drop structure, 140 

check structure, 136 

Cipolletti weir structure, 273 

control and pipe inlet, 173 

culvert, 2 10 

drain inlet, 237 

gated wasteway, 192 

inverted siphon, 29 

open channel chute, 116 

overchute, 224 

Parshall flume 

with free-flow discharge, 246 

with submerged-flow discharge, 247 

pipe drop, Type 1,98 

rectangular inclined drop 

with control inlet, 62 

with check inlet, 64 

road crossing, 23 

side channel spillway, 185 

siphon spillway, 198 

turnout 

without water measurement, 146 

with water measurement (CHO), 154 

vertical sleeve valve stilling wells, 330 

weir box, 291 

Discharge coefficients 

orifice, 10, 15 1 

weir, 10,191 

standard sleeve valve, 328 

Division structures 

design considerations, 163 

figures for standard design, 164, I65 

purpose and description, 162 

Drain inlets 

capacity, 231 

design example, 237 

figure and table for standard rectangular, 236 

location, 230 

types 

gravel blanket, 231, 237 

pipe, 231, 232 

rectangular, 231, 234,237 

Drops 

baffled apron, 299 

check-drops, 139 

general, 48 

pipe, 65 

rectangular inclined, 50 

vertical, 222 

Earth cover on conduits 

minimum requirements for 

cross drainage channels, 27 

drain inlets, 233 

earth canals, 27 

farm roads, 22,27,67 

lined canals, 27 

railroads, 8,22,27, 67 

road crossings, 22,27, 67 

road ditches, 22, 27, 67 

total equivalent for highway wheel loads, 8 

special provisions, 8 

Earth loads, 7 

Earthwork for pipe, 379 

Elevated flumes, 38 

Embedment for pipe, 37 1 

Energy dissipators 

baffled apron drops, 299 

baffled outlets, 308 

check-drops, 139 

chutes with stilling pools, 101 

general, 4, 299 

pipe drops, 65 

rectangular inclined drops with stilling pools, 50 

vertical drops with stilling pools, 222 

vertical sleeve valve stilling wells, 322 

Entrance loss coefficient 

orifice, 10 

Erosion protection 

figure and table for minimum requirements, 346 (see also 

design considerations and design examples for specific 

structures) 

purpose and description, 345 

Fencing, 384 

Flumes (see Bench flumes, Elevated flumes, or Parshall flumes) 

Freeboard 

bench flume, 40,41 

canal, 14, 28, 166, 171, 232,233 

culverts, 206 

drain inlets, 232, 233, 237 

open channel chute, 105 

overchutes, 222, 223 

transitions for pipe structures, 343, 344, 345 

stilling pools, 108 

Friction 

sliding (see Sliding coefficient) 

head loss (see Losses) 

Froude number, 104,106 

Gatcd wasteways 

automatic radial gates, 192 

design example, 192 

general, 189 

hydraulics, 190 

lifts and hoists, 192 

slide gates, 190 

radial gates, 190 

Handrail, 390 

Head loss (see Losses) 

Hydraulic control 

location of, 9, 207, 220 

Hydraulic jump 

in culverts, 204 

in inverted siphons, 29 

figure to determine blowback, 30 

in stiIIing pools, 61, 106, 222, 237 

table to determine stilling pool invert, 107 

in sumped pipe, 67 

figure to determine sump invert, 68 

Hydrology, 6 

Inverted siphons 
INDEX 433 

advantages and diradvantapcs, 26 

application, 24 

design example, 29 

design procedure, 29 

hydraulic desipn consideration, 28 

purpose and description, 24 

structure components, 26 

Joints for pipe, 371 

Jump (FCC Hydraulic jump) 

Ladders, safct),. 396 

Lane, E. W., wcightcd creep theory (see Percolation) 

Live loads. 7 

Loads 

dead loads, 7 

earth, 7 

hydraulic transients. 8 

ice. 7 

live loads. 7 

seismic. 8 

uplift, 8 

water, 7 

wheel. 7. 8 

wind. 8 

Losses 

check structure. I36 

friction 

pipe, IO, 349 

structures, 10 

tables for pipe, 350-358 

orifice entrance, IO 

Parshall flume, 248, 250 

pipe bends, IO. 359 

figure for coefficient, 360 

pipe entrance. 336. 359 

pipe exit, 359 

pipe taper. 379 

standard sleeve valve, 328 

transitions (xc Transition losses) 

weir boxes. 29 I 

Manhole, 375 

Manning formula, 10. 105, 210, 220, 221, 349 

Measurement of water (see Water measurement structure?) 

Meters, open-tlow, 149. 295 

Modrfied Parshall flumes 

description, 259 

hydraulics, 259 

Nets, safety. 393 

Open-flow meters 

advantages and disadvantages, 296 

design considerations, 295 

figure for standard outlet transition, 296 

purpose and description, 295 

Open irrigation system 

general requirements. I 

Operation and maintenance, 6 

Orifice 

constant-head I50 

discharge tables for, 155, 156 

drscharge coefficients, IO. I5 I 

equation. IO 

Overchutes 

alinemcnt, 2 16 

conduit, 216 

design example, 224 

hydraulics 

pipe, 218 

rectangular section, 22 I 

inlet, 2 18 

outlet, 218 

profile, 21 6 

Parshall flumes 

advantagzs, 245 

description, 244 

design example 

free-flow discharge, 246 

submerged-flow discharge, 247 

disadvantages. 245 

figure and table for standard Parshall flumes, 249 

modified, 259 

sire selection, 245 

used with turnouts. 150 

USC of tables and fi$urcs, 248 

Percolation 

criteria to prevent pipiny, 362 (see also specific structures) 

minimum distance between pipe collars, 210 

standard structure provisions. 9 

Percolation factor 

design example computattons. 274 

for standard structures. 9 

recommended ratios, 364 

Pipe 

asbc5tos-cement pressure pipe, 359 

corrugated-metal pipe, 359 

gcncral, 4, 349 

precast rcinforccd concrete culvert pipe, 359 

precast reinforced concrete pressure pipe, 359 

prcstresscd concrete pipe, 362 

pretensioncd concrete pipe, 362 

reinforced monolithic concrete pipe, 362 

reinforced plastic mortar pressure pipe. 359 

welded steel pipe, 361 

Pipe appurtenances 

air valves. 379 

air vents. 375 

blowoff, 375 

collars, 362 

general, 4. 349 

manhole, 375 

sat‘cty barrier. 373 

Pope bends 

losses. 10. 359 

sliding coefficient. 364 

thrust, 326, 364 

types. 365 

Pipe chutes. I2 I 

Pipe drop\ 

advantages and disadvantages. 65 

figure\ and tables for design, 68-95 

purpocc and description, 65 

type I 

dc\rgn constderations. 66 

dcstgn c~mplc. 98 

structure components. 66 

type 2 

design considerations, 96 

structure components, 96 

Pipe earthwork, 379 

Pipe embedment. 37 I 

Pipe handrail. 390 

Pipe joints, 37 I 

Pipe tapers, 379 

Precast concrete, 16 

Protection (see Erosion protection) 

Protective structures 

gcncral. 2. 179 

Racks, safety, 394 

Rectangular inclined drops 

advantages and disadvantages, 59 
434 INDEX 

Trajectory. 105, 191, 223 

Transitions (see also Transition losses and Transitions for specific 

structures) 

design considerations for pipe structure transitions, 336 

earth, 345 

figure and table for standard Type 1, 337 

figure and table for standard Type 2, 339 

figure and table for standard Type 3, 340 

figure and table for standard Type 4, 341 

figure and table for standard Type 5, 338 

gcncral, 4 

purpose and description, 335 

standardization, 342 

types, 33s 

Transitions for specific structures 

bench flumes, 40 

checks, 139 

check-drops, 143 

culverts, 205, 206 

drain inlets, 232, 237 

gated wasteway turnout, 190 

inverted siphons, 27 

open channel chutes, 104 

open-flow meters, 295 

overchutes, 218, 221,224 

pipe drops, 66,98 

rectangular inclined drops, 59, 61 

road crossings, 22 

side channel spillway wastcway outlet, 185 

siphon spillways, 197 

turnouts, 146 

vertical sleeve valve stilling well, 330 

Transition losses 

broken-back to pipe, 28, 336 

with excess seal at outlet, 29 

broken-back to rectangular, 41 

converging rectangular, 116 

earth to pipe, 29, 336 

Transverse flow (see Waves) 

Turnouts 

design consideration, 146 

figure for standard turnout, 147 

purpose and description, 146 

without water measurement 

design example, 146 

with water measurement 

constant-head orifice, 150 

design considerations, 15 1 

design example, 154 

figure and table for standard double-barrel CHO, 160, 161 

figure for standard single-barrel CHO, 159 

flowmeters, 149 

Parshall flumes, 150 

weirs, 150 

Valves 

air, 379 

vertical sleeve, 322 

Vents, air (see Air vents) 

Vertical drop, 139,222 

Vertical sleeve valve stilling wells 

descriptton, 322 

design considerations, 326 

design example, 330 

limitations, 325 

ported&eve valves, 325, 327 

standard sleeve valves, 323, 327 

usage, 325 

Wastcways 

capacity consideration, 18 1 

design csample 

with check inlet, 64 

with control inlet, 62 

figures and tables for standard design, 51-58 

purpose and dcscriptton, 50 

structure components, 59 

used with wasteway turnouts, 201 

Regulating structures 

general, 1, 133 

Reinforced concrete 

allowable stresses, 10 

fillets, 14 

minimum reinforcement, 1 I 

minimum wall thickness, 11 

Road crossings 

advantages, 21 

application, 19 

design considerations. 21 

design example, 23 

purpose and description, 19 

Roll waves (see Waves) 

Roughness coefficient, 10, 104, 349 

Safety 

devices (see Safety devices) 

fcaturcs, 4 

general. 383 

hazard cxposurc classification, 383 

Safety devices 

fencing, 384 

handrail, 390 

p~pc safety barrier, 373, 393 

safety cab&, 394 

safety ladders, 396 

safety nets, 393 

safety racks, 394 

types, 383 

warning signs. 393 

Seal 

at inverted siphon headwalls, 29 

Sedimentation, 6 

Side channel spillways 

design considerations, 182 

design example, 185 

general, 182 

Signs, warning, 393 

Siphon breaker, 195, 197 

Siphon spillways 

design considerations, 196 

design example, 198 

general, 195 

Sleeve valves (see Vertical sleeve valve stilling wells) 

Sliding coefficient, 9, 41, 364 

Slug flow (see Waves) 

Soils exploration, 5 

Spillways (see Side channel spillways and Siphon spillways) 

Stability of structures 

foundation bearing capacity, 9 

overturning, 9 

percolatton, 9 

sliding, 9 

Staff gage. 262 

Stilhngpool, 61,98, 103, 106, 207,218,222, 236 

table for computing required invert. 107 

Stilling wells - - 1 

for energy dissipation, 322 

for water surface measurement, 260 

Structural steel. 14 

Structure components and appurtenances, 4 

Tapers, pipe, 379 
INDEX 435 

rectangular suppressed, 288-289 

90’ V-notch, 290 

equations for, 10 

figure and table for standard adjustable weirs, 267 

figures and tables for standard Cipolletti weir structures, 264, 

265 

figures for staff or weir gage, 27 1, 272 

figure for standard 2-foot movable weir, 269 

figure for standard 3-foot movable weir, 270 

head-discharge relationship, 273 

purpose and description, 260 

requirements for accurate measurement, 266 

types, 260 

types of flow, 26 1 

used with turnouts, 150 

Weir boxes 

design considerations, 291 

design example. 291 

figure and table for standard 3-foot weir box, 292 

figure and table for standard 4-foot weir box, 293 

purpose and description, 29 1 

Weir gage, 262 

Welding, 14 

Wells, stilling 

for energy dissipation, 322 

for water surface measurement, 260 

Wheel loads 

equivalent earth cover tabulation for highways, 8 

equivalent lateral earth load, 7 

impact factors, 8 

railroads. 8 

description, 179 

gated (see Gated wasteways) 

limitations, 182 

location and number, 18 1 

Wasteway turnouts with check inlet 

design considerations, 202 

general, 201 

Water loads, 7 

Water measurement structures 

constant-head orifice, 150 

general, 2, 243 

modified Parshall flumes, 259 

open-flow mctcrs, 295 

Parshall flumes, 244 

weirs, 260 

weir boxes, 291 

Waves 

action of, 114 

cross, 108 

formation of, 108 

roll, 108 

Weighted-creep (see also Percolation factor) 

method, 362 

ratios, 364 

Weirs 

adjustable, 162, 163,262 

advantages and disadvantages, 262 

application, 261 

design example, 273 

discharge tables for 

Cipolletti, 281-287 

rectangular contracted, 275-280