U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2009–5186

In cooperation with the Illinois Department of Natural Resources–Office of Water Resources

Control-Structure Ratings on the Fox River 

at McHenry and Algonquin, Illinois
Cover photograph:

Downstream side of sluice gates, fish ladder, hinged-crest gate, and broad-crested weir on the Fox River at McHenry, Illinois.
Control-Structure Ratings on the Fox River 

at McHenry and Algonquin, Illinois

By Timothy D. Straub, Gary P. Johnson, Jon E. Hortness, and Joseph R. Parker

In cooperation with the Illinois Department of Natural Resources–Office of Water Resources 

Scientific Investigations Report 2009–5186

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2009

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Straub, T.D., Johnson, G.P., Hortness, J.E., and Parker, J.R., 2009, Control-structure ratings on the Fox River at 

McHenry and Algonquin, Illinois: U.S. Geological Survey Scientific Investigations Report 2009–5186, 61. p
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................1

Streamflow During Study Period........................................................................................................1

Approach................................................................................................................................................1

Previous Studies ...................................................................................................................................3

McHenry Control-Structure Ratings...........................................................................................................3

Broad-Crested Weir .............................................................................................................................8

Hinged-Crest Gate ..............................................................................................................................10

Sluice Gates.........................................................................................................................................14

Example Calculations.........................................................................................................................20

Algonquin Control-Structure Ratings .......................................................................................................22

Ogee Spillway with Hinged-Crest Gate Closed (with and without flow over gate).................26

Ogee Spillway and Hinged-Crest Gate Open ................................................................................31

Example Calculations.........................................................................................................................36

Summary........................................................................................................................................................37

Acknowledgments.......................................................................................................................................37

References Cited..........................................................................................................................................38

Appendixes ...................................................................................................................................................39

A. Fox River Near McHenry, Illinois, Headwater and Tailwater Stages 

for Broad-Crested Weir and Hinged-Crest Gate Measurements.......................................40

B. Fox River Near McHenry, Illinois, Headwater and Tailwater Stages 

for Sluice Gate Measurements ................................................................................................41

C. Fox River at Algonquin, Illinois, Headwater and Tailwater Stages for 

Ogee Spillway and Hinged-Crest Gate Measurements with the 

Hinged-Crest Gate Closed.........................................................................................................43

D. Fox River at Algonquin, Illinois, Headwater and Tailwater Stages 

for Ogee Spillway and Hinged-Crest Gate Measurements with the 

Hinged-Crest Gate Open............................................................................................................44

E. Photographs of Various Flow Conditions, Fox River near McHenry, Illinois.....................45

F. Photographs of Various Flow Conditions, Fox River at Algonquin, Illinois........................49

Figures

1. Location of Fox River control structures at McHenry and Algonquin, Illinois ...................2

2. Layout of control structures on the Fox River at McHenry, Illinois......................................4

3. Downstream side of hinged-crest gate, broad-crested weir, and fish ladder 

on the Fox River at McHenry, Illinois.........................................................................................5

4. Fish ladder with respect to the hinged-crest gate and broad-crested weir 

on the Fox River at McHenry, Illinois.........................................................................................6

5. Downstream side of sluice gates on the Fox River near McHenry, Illinois ........................7

6. Schematic (side view) of hinged-crest gate and broad-crested weir 

on the Fox River at McHenry, Illinois.........................................................................................9
iv

7. Discharge coefficient for free-weir flow and headwater depth for the 

broad-crested weir (fish ladder included) on the Fox River at 

McHenry, Illinois ...........................................................................................................................9

8. Discharge coefficient for free-weir flow and the ratio of headwater 

depth and gate height for the hinged-crest gate on the Fox River at 

McHenry, Illinois .........................................................................................................................12

9. Discharge coefficient for submerged-weir flow and the ratio of headwater 

and tailwater depth for the hinged-crest gate on the Fox River at 

McHenry, Illinois .........................................................................................................................12

10. Measured and computed flows for the broad-crested weir and 

hinged-crest gate near McHenry, Illinois...............................................................................13

11. Schematic (side view) of sluice gates on the Fox River at McHenry, Illinois...................14

12. Discharge coefficient for free-weir flow and headwater depth for sluice 

gates on the Fox River at McHenry, Illinois............................................................................18

13. Discharge coefficient for submerged-weir flow and ratio of tailwater and 

headwater depth for sluice gates on the Fox River at McHenry, Illinois ..........................18

14. Discharge coefficient for submerged-orifice flow and submergence ratio 

for sluice gates on the Fox River at McHenry, Illinois..........................................................19

15. Measured and computed flows for the sluice gates near McHenry, Illinois. .................19

16. Location of control structures on the Fox River at Algonquin, Illinois...............................23

17. Downstream side of hinged-crest gate and ogee spillway on the Fox River

 at Algonquin, Illinois..................................................................................................................24

18. Close-up of downstream side of hinged-crest gate on the Fox River 

at Algonquin, Illinois...................................................................................................................25

19. Vertically averaged velocity vectors for a typical Acoustic Doppler 

Current Profiler streamflow measurement upstream of the control structure 

at Algonquin, Illinois...................................................................................................................26

20. Velocity contour plot for the Acoustic Doppler Current Profiler 

streamflow measurement shown in figure 19 upstream of the control 

structure at Algonquin, Illinois .................................................................................................26

21. Schematic (side view) of hinged-crest gate and ogee spillway on the 

Fox River at Algonquin, Illinois .................................................................................................27

22. Discharge coefficient for free-weir flow and headwater depth for 

ogee spillway and hinged-crest gate (closed or at elevation of 

ogee spillway) on the Fox River at Algonquin, Illinois ..........................................................27

23. Measured and computed flows for the structure with the hinged-crest 

gate completely closed or with the crest set at the elevation of the 

ogee spillway at Algonquin, Illinois. ........................................................................................27

24. Discharge coefficient for affected-weir flow and ogee spillway submergence 

ratio on the Fox River at Algonquin, Illinois................................................................................31

25. Discharge coefficient for free-weir flow, and the ratio of headwater 

depth and gate height for the hinged-crest gate on the Fox River 

at Algonquin, Illinois...................................................................................................................34

26. Discharge coefficient for submerged-weir flow, and the ratio of 

headwater and tailwater depth for the hinged-crest gate on the Fox River 

at Algonquin, Illinois...................................................................................................................34

27. Measured and computed flows for the ogee spillway and hinged-crest 

gate on the Fox River at Algonquin, Illinois ............................................................................35
v

Tables

1. Statistical summary of streamflow on the Fox River at Algonquin, Illinois, 

at USGS streamflow-gaging station 0555000 ...........................................................................3

2. Elevation of structures and streamflow-gaging station datums on the 

Fox River at McHenry, Illinois .....................................................................................................6

3. Broad-crested weir flow characteristics and coefficients on the Fox River 

control structure near McHenry, Illinois...................................................................................8

4. Hydraulic conditions, parameters, and equations for different flow 

regimes for the broad-crested weir and hinged-crest gate on the Fox River 

at McHenry, Illinois.....................................................................................................................10

5. Hinged-crest gate flow characteristics and coefficients near McHenry, Illinois. ..........11

6. Measured and computed flows for the broad-crested weir and 

hinged-crest gate near McHenry, Illinois...............................................................................13

7. Sluice gate measured and computed flow characteristics and coefficients 

near McHenry, Illinois................................................................................................................15

8. Hydraulic conditions, parameters, and equations for different flow regimes 

for the sluice gates on the Fox River at McHenry, Illinois ...................................................17

9. Elevation of structure and streamflow-gaging station datums on the 

Fox River at Algonquin, Illinois .................................................................................................22

10. Ogee spillway and hinged-crest gate (closed or crest at elevation of 

ogee-spillway crest) measured and computed flow characteristics and 

coefficients at Algonquin, Illinois.............................................................................................28

11. Hydraulic conditions, parameters, and equations for different flow regimes 

for the ogee spillway and hinged-crest gate on the Fox River 

at Algonquin, Illinois...................................................................................................................29

12. Hydraulic conditions, parameters, and equations for different flow regimes 

for the hinged-crest gate on the Fox River at Algonquin, Illinois .......................................30

13. Ogee spillway weir-flow characteristics and coefficients at Algonquin, Illinois ............32

14. Hinged-crest gate weir-flow characteristics and coefficients 

at Algonquin, Illinois...................................................................................................................33

15. Measured and computed flows for the ogee spillway and hinged-crest gate 

on the Fox River at Algonquin, Illinois .....................................................................................35
vi

Conversion Factors and Vertical Datum

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Velocity

foot per second (ft/s) .3048 meter per second (m-/s) 

Flow rate

cubic foot per second (ft3/s) .02832 cubic meter per second (m3/s)

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD 29).

Abbreviations, Acronyms, and Symbols

ADCP Acoustic Doppler Current Profiler

AFF affected flow

B length of weir, spillway, or gate 

BCW broad-crested weir 

C computed flow

C/M ratio of computed and measured flow

Comp. computed

CBCW free-weir coefficient for the broad-crested weir

CHCG free-weir coefficient for the hinged-crest gate

CHCG-S submerged-weir coefficient for the hinged-crest gate 

COS free-weir coefficient for the ogee spillway

COS-A affected-weir coefficient for the ogee spillway

CS free-weir coefficient for the spillway, which includes flow over the hinged-crest gate 

set at the elevation of the ogee spillway 

CSLO free-orifice coefficient for the sluice gate 

CSLO-S submerged-orifice coefficient for the sluice gate 

CSLW free-weir coefficient for the sluice gate

CSLW-S submerged-weir coefficient for the sluice gate

FO free-orifice flow

FW free-weir flow 
vii

FW-FL free-weir flow with flow over the hinged-crest gate (crest at elevation of ogee 

spillway)

FW-NF free-weir flow with no flow over the hinged-crest gate

h1BCWheadwater depth above the broad-crested weir crest

h1HCGheadwater depth above the hinged-crest gate crest 

h1OSheadwater depth above the ogee spillway crest 

h1SLheadwater depth above the sluice-gate sill

h3BCWtailwater depth above the broad-crested weir crest

h3HCGtailwater depth above the hinged-crest gate crest 

h3OStailwater depth above the ogee spillway crest

h3SLtailwater depth above the sluice-gate sill

hgHCGhinged-crest gate opening referenced to the broad-crested-weir crest or 

ogee spillway crest

hgSLsluice gate opening referenced to the concrete sill

HCG hinged-crest gate

HW headwater stage

IDNR–OWR Illinois Department of Natural Resources–Office of Water Resources

M measured flow

Meas. measured

NF no flow

pHCG height of hinged-crest gate crest above approach invert

R2 coefficient of determination

OS ogee spillway

SL sluice gate

SO submerged-orifice flow

SW submerged-weir flow 

TW tailwater stage

USGS U.S. Geological Survey 

WY water year

Abstract

The Illinois Department of Natural Resources–Office 

of Water Resources operates control structures on a reach of 

the Fox River in northeastern Illinois between McHenry and 

Algonquin. The structures maintain water levels in the river 

for flood-control and recreational purposes. This report documents flow ratings for hinged-crest gates, a broad-crested weir, 

sluice gates, and an ogee spillway on the control structures 

at McHenry and Algonquin. The ratings were determined by 

measuring headwater and tailwater stage along with streamflow at a wide range of flows at different gate openings. 

Standard control-structure rating techniques were used to rate 

each control structure. 

The control structures at McHenry consist of a 

221-feet(ft)-long broad-crested weir, a 4-ft-wide fish ladder, a 

50-ft-wide hinged-crest gate, five 13.75-ft-wide sluice gates, 

and a navigational lock. Sixty measurements were used to 

rate the McHenry structures. The control structures at Algonquin consist of a 242-ft-long ogee spillway and a 50-ft-wide 

hinged-crest gate. Forty-one measurements were used to rate 

the Algonquin control structures. 

Introduction

The Illinois Department of Natural Resources–Office of 

Water Resources (IDNR–OWR) operates control structures 

on a reach of the Fox River in northeastern Illinois between 

McHenry and Algonquin (fig. 1). The McHenry control 

structure is at river mile 97.8 and has a drainage area of 1,250 

mi2. The Algonquin control structure is at river mile 81.6 

and has a drainage area of 1,403 mi2 (fig. 1). Hinged-crest 

gates were installed at both structures in 2002, to allow more 

streamflow through the structures than was previously possible. This enhanced capability has had appreciable effects 

on the protocols for operating the control structures. To better 

understand these effects, a study was done during 2002–2008 

by the U.S. Geological Survey (USGS), in cooperation with 

the IDNR–OWR.

Purpose and Scope

This report documents development of flow ratings for 

hinged-crest gates, a broad-crested weir, sluice gates, and an 

ogee spillway on the Fox River control structures at McHenry 

and Algonquin, Illinois. Streamflow data collected during 

water years 2003–2008 are summarized and used in the analysis. Also, historic streamflow data at McHenry were used to 

aid in documenting the effects of the broad-crested weir and 

sluice gates.

Streamflow During Study Period

Statistical streamflow summaries at USGS streamflow 

gaging station (05550000) on the Fox River at Algonquin, 

Illinois, during the study for water years (WY) 2003–2008 

are presented in table 1 and compared to statistics for the full 

period of record (WY 1916–2008) at this station. A water year 

(WY) is the 12-month period from October 1 through September 30 and is designated by the calendar year in which it 

ends and includes 9 of 12 months. For example, WY 2004 is 

from October 1, 2003, to September 30, 2004. The summary 

shows that both low and high streamflows occurred during the 

data-collection period, including the highest daily mean and 

peak flows.

Approach

The Fox River control-structure ratings were determined 

by measuring headwater (HW) and tailwater (TW) stage 

along with streamflow at a wide range of flows at different 

gate openings. The HW and TW streamflow gaging stations used on the Fox River near McHenry were 05549500 

and 05549501, respectively. The HW and TW stations were 

installed in 1941 and 1987, respectively. The stations were 

operated as stage-only with miscellaneous streamflow measurements during 1985, 1986, 1991, 1993, and 2002–2008. 

The 1985 and 1986 streamflow measurements also included 

TW measurements consistent with the datum for the TW 

station. The HW and TW stations used on the Fox River at 

Control-Structure Ratings on the Fox River at McHenry 

and Algonquin, Illinois

By Timothy D. Straub, Gary P. Johnson, Jon E. Hortness, and Joseph R. Parker
2 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Lily

Lake

Thunderbird

Lake

Fox River

Fox River

Fox River

Control

structure

Control

structure

05549500

05549501

MC HENRY CO MC HENRY CO

LAKE CO LAKE CO

KANE CO COOK CO

05550000

05550001

05550000

Pistakee Highlands

McCullom Lake

McHenry

Lakemoor

Holiday Hills

Prairie

Grove Island Lake

Oakwood Hills

Cary

Fox River Grove

Lake in the Hills

Algonquin

Carpentersville

88°15'

42°20'

42°15'

42°10'

88°17'30" 88°12'30"

42°22'30"

42°17'30"

42°12'30"

88°10'

ILLINOIS

Study Area

EXPLANATION

U.S. Geological Survey streamflow-gaging station

and identifier

Control structure

Direction of flow

0

0

5 MILE

5 KILOMETER

1

1

2

2

3

3

4

4

Base from U.S. Geological Survey, 1:100,000-scale

Albers Equal-Area Conic Projection

Standard parallels 45 and 33 , central meridian -89 .

digital data

o o o

Figure 1. Location of Fox River control structures at McHenry and Algonquin, Illinois.
McHenry Control-Structure Ratings 3

Algonquin, were 05550000 and 05550001, respectively. The 

HW and TW gaging stations were installed in 1916 and 2002, 

respectively. Streamflow has been measured at the HW station 

since 1916.

To minimize the drawdown effect on the HW stage, the 

HW stations at the McHenry and Algonquin control structures 

are approximately 275 and 140 ft upstream of the structures, 

respectively. For the 50-ft-wide hinged-crest gates at both 

control structures, the upstream distances are greater than two 

times the contraction width recommended for a completely 

eccentric contraction with all flow on one bank (Matthai, 

1967). The TW stage gages at both control structures are 

located beyond the influence of the hinged-crest gate and 

beyond the influence of the sluice gates at McHenry. Streamflow measurements were made for a wide range of streamflows and gate openings. Standard control-structure-rating 

techniques described in Chow (1959), Collins (1977), and 

Roberson and others (1998) were used to rate each structure. 

Previous Studies

To optimize the operational procedures of the gate structures for recreational and flood-control purposes, a hydraulic 

model (Franz and Melching, 1997a and 1997b) was applied 

to simulate flood-event scenarios on this reach of the Fox 

River (Knapp and Ortel, 1992). Dam-break analyses also were 

completed by the IDNR–OWR (Illinois Department of Natural 

Resources, 1999). Inputs to the hydraulic model throughout 

the studied reach included surveyed cross sections, slope, 

roughness, and stage-discharge ratings at control structures 

and were collected and documented by IDNR–OWR and the 

USGS (Illinois Department of Transportation, 1992; Fisk, 

1988). The application of the hydraulic model through this 

reach has been calibrated and verified (Illinois Department of 

Natural Resources, 1999; Ishii and Turner, 1996; and Knapp 

and Ortel, 1992).

McHenry Control-Structure Ratings

The McHenry control structure is at river mile 97.8 on 

the Fox River in northeastern Illinois (fig. 1). The drainage 

area at the headwater gage is 1,250 mi2. The 8,900 acre reservoir created by the dam is part of the Fox Chain of Lakes and 

is used primarily for recreation and flood control. The control 

structures at McHenry consist of a 221-ft broad-crested weir, 

a 4-ft-wide fish ladder, a 50-ft-wide hinged-crest gate, five 

13.75-ft wide sluice gates, and a navigational lock (figs. 2, 3, 

4, and 5). The elevations of structure components and headwater and tailwater gage datums are presented in table 2. 

Table 1. Statistical summary of streamflow on the Fox River at Algonquin, Illinois, at USGS streamflow-gaging station 0555000.

[ft3/s, cubic foot per second; WY, water year] 

Water 

year

Annual

mean

flow

(ft3/s)

Daily mean flow Maximum 

Highest Lowest peak flow

Streamflow

(ft3/s) Date

Streamflow

(ft3/s) Date

Streamflow

(ft3/s) Date

WY2003 516 2,000 May 13,14 90 Sep. 6 2,040 May 10,12–14

WY2004 1,118 6,020 May 31 110 Oct. 3 6,720 May 22

WY2005 665 *2,500 Feb. 19–21 89 Jul. 18 2,600 Feb. 18

WY2006 877 3,200 Mar. 17 140 Oct. 30 3,710 Mar. 14

WY2007 1,673 6,690 Aug. 26 423 Jul. 25 6,720 Aug. 25

WY2008 2,045 6,030 Jun. 19 449 Sept. 2 6,080 Jun. 19

WY1916–2008 910 6,690 Aug. 26, 2007 12 A 6,720 B

*

estimated

 A–Apr.6, 1960; Apr. 2, 1979

 B–May 22, 2004; Aug. 25, 2007
4 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

88°15'10" 88°15'05" 88°15'

42°18'30"

42°18'35"

42°18'40"

Lock

Lockmaster's

house

Sluice

Gates

Weir

(221 feet wide)

Headwater gage

(05549500)

Tailwater gage

(05549501)

Fish

ladder

(4 feet wide)

Hinged-crest

gate

(50 feet wide)

F O X R I V E R

flow

0 100 200 FEET

0 50 100 METERS

Base from U.S. Geological Survey High Resolution Orthoimage, Chicago, IL-IN, 2003.

Universal Transverse Mercator projection, NAD 83, zone 16.

Wall

(11 feet wide total)

Island

Figure 2. Layout of control structures on the Fox River at McHenry, Illinois.
McHenry Control-Structure Ratings 5

Sluice

Gates

Headwater gage

(05549500)

Headwater gage

(05549500)

Hinged-crest

gate

(50 feet wide)

Hinged-crest

gate

Broad-crested weir

Broad-crested weir

Figure 3. Downstream side of hinged-crest gate, broad-crested weir, and fish ladder on the Fox River at McHenry, Illinois.
Sluice

Gates

Tailwater gage

(05549501)

Hinged-crest

gate

(50 feet wide)

Broad-crested weir

Fish

ladder

6 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Figure 4. Fish ladder with respect to the hinged-crest gate and broadcrested weir on the Fox River at McHenry, Illinois. (Top photo looking 

upstream, and bottom photo looking downstream.)

Table 2. Elevation of structures and streamflow-gaging station datums 

on the Fox River at McHenry, Illinois.

[NGVD 1929, National Geodetic Vertical Datum of 1929] 

Structure or gage

Elevation, 

in feet

(NGVD 1929)

McHenry Dam broad-crested weir minimum crest elevation 736.68

McHenry Dam broad-crested weir average crest elevation 736.76

McHenry Dam hinged-crest gate floor elevation 730.08

McHenry Dam sluice gate concrete sill 731.15

Headwater station datum, Fox River at McHenry, Illinois 733.00

Tailwater station datum, Fox River at McHenry, Illinois 730.15
McHenry Control-Structure Ratings 7

Sluice

Gates

Sluice

Gates

Tailwater gage Broad-crested weir

(05549501)

Hinged-crest

gate

(50 feet wide)

Figure 5. Downstream side of sluice gates on the Fox River near McHenry, Illinois.
8 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Broad-Crested Weir

A side-view schematic of the broad-crested weir and 

parameters used in the control-structure rating are shown in 

figure 6. The broad-crested weir was rated by the USGS and 

the results were published in Fisk (1988). Streamflow measurements 5, 13, 15, and 20 listed in table 3 were used by Fisk 

to develop a free-weir-flow coefficient equation (fig. 7 and 

appendix A). A standard weir equation (equation 1 in table 4) 

described in Chow (1959), Collins (1977), and Roberson and 

others (1998) is used. Fisk used a total weir length of 288 ft, 

which included the fish ladder. The measured CBCW in table 3 

is obtained by using the measured BCW flow and measured 

headwater depth, and calculating for CBCW from equation 1. 

The computed CBCW in table 3 is obtained by using regression 

equation 2 (fig. 7 and table 4).

For the purposes of the current study, the free-weir coefficient equation is assumed valid and only the length of the weir 

is adjusted (221 ft for the new weir length after construction 

Table 3. Broad-crested weir flow characteristics and coefficients on the Fox River control structure near McHenry, Illinois. 

[USGS, U.S. Geological Survey; BCW, broad-crested weir; HCG, hinged-crest gate; ft3/s, cubic foot per second; h1BCW , headwater depth above the 

broad-crested weir crest; ft, foot; h3BCW , tailwater depth above the broad-crested weir crest; CBCW, free-weir coefficient for the broad-crested weir; 

FW, free-weir flow; NF, no flow; ---, not determined]

USGS

measurement

number Date

Measured

BCW and 

(or)

 HCG flow

 (ft3/s)

Broad-Crested Weir

h1BCW

(ft)

h3BCW

(ft) h3BCW/h1BCW

Flow

regime

Measured

CBCW

Computed

CBCW

Computed

flow using 

modified 

Fisk1 (ft3/s)

5 05/16/1985 169 0.37 -5.18 -14.0 FW 2.61 2.70 ---

13 08/28/1986 342 .55 -5.48 -9.96 FW 2.91 2.79 ---

15 09/27/1986 1,880 1.66 -.41 -.25 FW 3.05 3.07 ---

20 09/30/1986 2,990 2.22 .45 .20 FW 3.14 3.15 ---

44 11/18/2002 565 .48 -5.60 -11.7 FW --- 2.76 206

45 11/19/2002 1,012 .30 -4.92 -16.4 FW --- 2.65 98

46 11/19/2002 1,345 -.06 -4.93 --- NF --- --- 0

47 11/20/2002 1,775 -.47 -4.41 --- NF --- --- 0

A48 04/04/2003 145 .43 -5.23 -12.2 FW 2.29 2.73 173

49 05/17/2004 803 .62 -3.03 -4.89 FW --- 2.82 310

50 05/17/2004 1,240 .38 -2.75 -7.24 FW --- 2.70 142

51 05/17/2004 2,040 .12 -2.54 -21.2 FW --- 2.44 23

52 05/24/2004 1,820 .36 -.68 -1.89 FW --- 2.69 131

53 03/17/2006 1,077 -1.04 -2.76 --- NF --- --- 0

54 03/17/2006 401 -.31 -3.22 --- NF --- --- 0

55 03/16/2007 1,132 -1.04 -2.21 --- NF --- --- 0

56 08/22/2007 1,710 -.01 -.95 --- NF --- --- 0

57 08/27/2007 2,550 1.15 .50 .43 FW --- 2.98 826

58 03/26/2008 1,440 -1.20 -2.15 --- NF --- --- 0

59 04/16/2008 1,930 .48 -.49 -1.02 FW --- 2.76 206

60 06/20/2008 2,450 1.08 .25 .23 FW --- 2.96 747

ANo flow over hinged-crest gate. All other measurements from 2002–2008 had flow over the hinged-crest gate.

1

Fisk (1988)

of the HCG, plus 4 ft for the fish ladder, equals 225 ft) to compute broad-crested weir flow (tables 3 and 4). The hinged-crest 

gate was closed with no flow over it during measurement 48. 

The calculated flow (173 ft3/s) (using the modified Fisk equation (equation 3) with only the length of weir reduced) was 28 

ft3/s greater than the measured flow (145 ft3/s) (table 3) with 

an average velocity of 0.102 ft/s.

As the tailwater depth increases, the submergence ratio 

(h3BCW/h1BCW) approaches unity, and the flow potentially can be 

overestimated using the free-weir flow equation; therefore, a 

submerged-flow coefficient equation may need to be developed. The greatest h3BCW/h1BCW of 0.43 during a measurement 

occurred on August 27, 2007. Submerged flow, according to 

Collins (1977), occurs when the submergence ratio is equal to 

or greater than 0.60. Given that h3BCW/h1BCW did not exceed 0.60 

during the study by Fisk (1988) or during this study, the submergence ratio suggested by Collins (1977) is assumed to be 

applicable and no submerged-flow coefficient equation could 

be developed.
1

10

0.1 1.0 10.0

HEADWATER DEPTH ( ) h1BCW , IN FEET

FREE-WEIR COEFFICIENT ( ) CBCW

McHenry Control-Structure Ratings 9

Figure 6. Schematic (side view) of hinged-crest gate and broad-crested weir on the Fox 

River at McHenry, Illinois (ft, foot; h1HCG , headwater depth above the hinged-crest gate crest; 

h3HCG , tailwater depth above the hinged-crest gate crest; hgHCG , hinged-crest gate opening 

referenced to the broad-crested-weir crest; pHCG, height of hinged-crest gate crest above 

approach invert; h1BCW , headwater depth above the broad-crested weir crest; h3BCW , tailwater 

depth above the broad-crested weir crest).

Figure 7. Discharge coefficient for free-weir flow and headwater depth for the broad-crested 

weir (fish ladder included) on the Fox River at McHenry, Illinois (from Fisk, 1988), (R2, coefficient 

of determination).

h3HCG

hgHCG

h1HCG

pHCG

h1BCW

h3BCW

Top of broad-crested weir,

elevation 736.68 ft

Top of concrete slab,

elevation 730.08 ft

flow

Air bladder

Hinged-crest gate

NOT TO SCALE

CBCW = 2.94h1BCW

R2

= 0.85

0.087
10 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Hinged-Crest Gate

A side-view schematic of the hinged-crest gate and 

parameters used in control structure rating are shown in figure 

6. Sixteen measurements, ranging from 359 to 2,017 ft3/s, 

were used to describe free and submerged flow through the 

hinged-crest gate. Characteristics of the flow and the measured 

and computed discharge coefficients are listed in table 5 and 

appendix A. A standard weir equation (equation 4 in table 4) 

described in Chow (1959), Collins (1977), and Roberson and 

others (1998) is used to describe flow over the hinged-crest 

gate. Free- and submerged-weir coefficient equations are 

presented in table 4, and in figures 8 and 9. The data indicate 

submerged flow occurs when h3HCG /h1HCG is greater than 0.75. 

The measured and computed broad-crested weir and 

hinged-crest gate flows for the control structures at McHenry 

are presented in table 6 and figure 10 for comparison. 

Thirteen of the 14 computed hinged-crest gate flows are within 

10 percent of measured flows, and the remaining measurement 

is within 16 percent. The combined BCW and HCG flows 

show similar results, and all eight combined measured flows 

above 1,400 ft3/s were computed within 6 percent. 

Table 4. Hydraulic conditions, parameters, and equations for different flow regimes for the broad-crested weir and hinged-crest 

gate on the Fox River at McHenry, Illinois.

[ h3BCW , tailwater depth above the broad-crested weir crest, in feet; h1BCW , headwater depth above the broad-crested weir crest, in feet; QBCW, flow 

over the broad-crested weir, in ft3/s; CBCW, free-weir coefficient for the broad-crested weir; B, length of weir or gate, in feet; h3HCG , tailwater depth 

above the hinged-crest gate crest, in feet; h1HCG , headwater depth above the hinged-crest gate crest, in feet; QHCG, flow through the hinged-crest gate, 

in ft3/s; CHCG, free-weir coefficient for the hinged-crest gate; pHCG, height of hinged-crest gate crest above approach invert; CHCG-S, submerged-weir 

coefficient for the hinged-crest gate]

Structure Flow regime

Hydraulic

conditions Parameters and equations

Equation

number

Broad-crested weir Free weir (FW) 1

2

3

Hinged-crest gate Free weir (FW) 4

5

6

Hinged-crest gate Submerged weir (SW) 7

8

9

h

h

BCW

BCW

3

1

 0 6. 0 Q C Bh BCW BCW BCW  1

1 5.

C h BCW BCW  2 94 1

0 087 . .

B f  225 t

Q h BCW BCW  661 5 1

1 587 . .

h

h

HCG

HCG

3

1

≤ 0 7. 5 Q C Bh HCG HCG HCG  1

1 5.

C

h

p HCG

HCG

HCG



−

3 8 1

0 135

.

.

7





 





B f  50 t

Q h p HCG HCG HCG  193 5 1

1 365 0 135 . . .

h

h

HCG

HCG

3

1

 0 7. 5 Q C C Bh HCG HCG HCG S HCG  − 1

1 5.

C

h

h HCG S

HCG

HCG

−

−

 0 471 3

1

2 94

.

.





 





Q h h p HCG HCG HCG HCG  − 91 14 1

4 305

3

2 94 0 135 . . . .
McHenry Control-Structure Ratings 11

Table 5. Hinged-crest gate flow characteristics and coefficients near McHenry, Illinois.[USGS, U.S. Geological Survey; ft3/s, cubic foot per second; hgHCG , hinged-crest gate opening referenced to the broad-crested-weir crest; h1HCG , headwater depth above the hinged-crest gate crest; ft, foot; h3HCG , tailwater depth above the hinged-crest gate crest; pHCG, height of hinged-crest gate crest above approach invert; CHCG, free-weir coefficient for the hinged-crest gate; CHCG-S, 

submerged-weir coefficient for the hinged-crest gate; FW, free-weir flow; SW, submerged-weir flow; HCG, hinged-crest gate; BCW, broad-crested weir; SL, sluice gate; ---, not determined]

USGS

measurement

number Date

Hinged-Crest Gate

Measured 

flow1

(ft3/s)

Gate

opening

hgHCG (ft)

h1HCG

(ft)

h3HCG

(ft)

pHCG

(ft) h1HCG/pHCG h3HCG/h1HCG

Flow 

regime

Measured

CHCG

Computed

CHCG

Measured2

CHCG-S

Computed

CHCG-S

44 11/18/2002 359 1.0 1.48 -4.60 5.60 0.3 -3.11 FW 3.98 4.63 --- ---45 11/19/2002 914 2.2 2.50 -2.72 4.40 .6 -1.09 FW 4.63 4.18 --- ---46 11/19/2002 1,345 4.1 4.04 -.83 2.50 1.6 -.21 FW 3.31 3.63 --- ---47 11/20/2002 1,775 6.0 5.53 1.59 .60 9.2 .29 FW 2.73 2.87 --- ---49 05/17/2004 493 1.0 1.62 -2.03 5.60 .3 -1.25 FW 4.78 4.58 --- ---

A50 05/17/2004 1,098 2.0 2.38 -.75 4.60 .5 -.32 FW --- --- --- ---

51 05/17/2004 2,017 5.0 5.12 2.46 1.60 3.2 .48 FW 3.48 3.31 --- ---52 05/24/2004 1,689 6.0 6.36 5.32 .60 10.6 .84 SW 2.11 2.81 0.75 0.8053 03/17/2006 1,077 4.0 2.96 1.24 2.60 1.1 .42 FW 4.23 3.80 --- ---

B54 03/17/2006 401 2.0 1.69 -1.22 4.60 .4 -.72 FW --- --- --- ---C55 03/16/2007 1,132 4.5 3.46 2.29 2.10 1.6 .66 FW 3.52 3.62 --- ---

56 08/22/2007 1,710 6.0 5.99 5.05 .60 10.0 .84 SW 2.33 2.84 .82 .7857 08/27/2007 1,724 6.0 7.15 6.50 .60 11.9 .91 SW 1.80 2.77 .65 .6258 03/26/2008 1,440 5.5 4.30 3.35 1.10 3.9 .78 SW 3.23 3.22 1.00 .9859 04/16/2008 1,724 6.0 6.48 5.51 .60 10.8 .85 SW 2.09 2.81 .74 .7660 06/20/2008 1,703 6.0 7.08 6.25 .60 11.8 .88 SW 1.81 2.77 .65 .68

1Determined by subtracting the computed BCW flow from the measured total BCW and HCG flow.2Ratio of measured and computed CHCG.AHinged-crest gate opening changed 30 minutes before measurement, measurement not used in equation development.BOutlier, measurement not used in equation development.CTotal flow (BCW, HCG, and SL) measured without a separate measurement of sluice gate flow. The SL flow is calculated and subtracted from total flow.Bold text rows indicate submerged HCG conditions.
12 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

1

10

0.1 1.0 10.0

RATIO OF HEADWATER DEPTH AND GATE HEIGTH (h 1 ) HCG /pHCG

FREE-WEIR COEFFICIENT ( ) CHCG

( )

Figure 8. Discharge coefficient for free-weir flow and the ratio of headwater depth and 

gate height for the hinged-crest gate on the Fox River at McHenry, Illinois, (R2, coefficient of 

determination). 

Figure 9. Discharge coefficient for submerged-weir flow and the ratio of headwater and 

tailwater depth for the hinged-crest gate on the Fox River at McHenry, Illinois, (R2, coefficient 

of determination). 

R2

= 0.77

CHCG= 3.87

h1HCG

p

HCG

-0.135

0.1

1.0

0.1 1.0

RATIO OF TAILWATER AND HEADWATER DEPTH ( ) h 3HCG /h1HCG

SUBMERGED-WEIR COEFFICIENT ( ) CHCG S-

( )

R2

= 0.91

CHCG-S = 0.471

h3HCG

-2.94

h1HCG
McHenry Control-Structure Ratings 13

0

500

1,000

1,500

2,000

2,500

0 500 1,000 1,500 2,000 2,500

MEASURED HCG FLOW,

IN CUBIC FEET PER SECOND

COMPUTED HCG FLOW, IN CUBIC FEET PER SECOND

Line of perfect agreement Line of perfect agreement

0

500

1,000

1,500

2,000

2,500

0 500 1,000 1,500 2,000 2,500

MEASURED BCW AND HCG COMBINED FLOW,

IN CUBIC FEET PER SECOND

COMPUTED BCW AND HCG COMBINED FLOW,

IN CUBIC FEET PER SECOND

Figure 10. Measured and computed flows for the broad-crested weir and hinged-crest gate near McHenry, Illinois, 

(BCW, broad-crested weir; HCG, hinged-crest gate).

Table 6. Measured and computed flows for the broad-crested weir and hinged-crest gate near McHenry, Illinois. 

[USGS, U.S. Geological Survey; BCW, broad-crested weir; ft3/s, cubic foot per second; HCG, hinged-crest gate; C/M, ratio of computed and measured flow]

USGS

measurement 

number Date

BCW

computed

flow

(ft3/s)

HCG BCW and HCG

Measured

flow1 (M)

 (ft3/s)

Computed

flow (C)

 (ft3/s) C/M

Measured

flow (M)

 (ft3/s)

Computed

flow (C)

 (ft3/s) C/M

44 11/18/2002 206 359 417 1.16 565 623 1.10

45 11/19/2002 98 914 826 .90 1,012 924 .91

46 11/19/2002 0 1,345 1,473 1.09 1,345 1,473 1.09

47 11/20/2002 0 1,775 1,864 1.05 1,775 1,864 1.05

49 05/17/2004 310 493 472 .96 803 782 .97

51 05/17/2004 23 2,017 1,916 .95 2,040 1,939 .95

52 05/24/2004 131 1,689 1,797 1.06 1,820 1,927 1.06

53 03/17/2006 0 1,077 968 .90 1,077 968 .90

55 03/16/2007 0 1,132 1,164 1.03 1,132 1,164 1.03

56 08/22/2007 0 1,710 1,618 .95 1,710 1,618 .95

57 08/27/2007 826 1,724 1,650 .96 2,550 2,476 .97

58 03/26/2008 0 1,440 1,408 .98 1,440 1,408 .98

59 04/16/2008 206 1,724 1,756 1.02 1,930 1,962 1.02

60 06/20/2008 747 1,703 1,775 1.04 2,450 2,522 1.03

1

Determined by subtracting the computed BCW flow from the measured total BCW and HCG flow.
14 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Sluice Gates

A side-view schematic of the sluice gates and parameters 

used in the control-structure rating are shown in figure 11. 

Fifty measurements, ranging from 64 to 4,054 ft3/s, were used 

to describe free- and submerged-weir and orifice flow through 

the sluice gates. Characteristics of the flow and the measured 

and computed discharge coefficients are listed in table 7 and 

appendix B. Standard weir and orifice equations (table 8) 

described in Chow (1959), Collins (1977), and Roberson and 

others (1998) are used to describe flow through the sluice 

gates. Chow (1959) stated the following regarding the orifice 

equation presented in table 8: 

“For the purpose of experimental studies, ... The 

form of this equation is the same for both free and 

submerged flows.” 

For this reason, a submergence coefficient is simply 

added to equation 16 (table 8) to develop the submerged-orifice equation (equation 19); Roberson and others (1998) show 

the same orifice equation. For the purpose of this study, the 

submerged-orifice equation presented by Collins (1977) and 

Fisk (1988) is not used. 

Utilizing the measurement data, the resulting free- and 

submerged-weir and orifice-coefficient equations are presented 

in table 8, figures 12, 13, and 14. There is no figure for the 

free-orifice coefficient. Multiple-linear regression instead was 

used to develop the free-orifice coefficient equation in table 8. 

The coefficient of determination (R2) for this equation (0.80) 

regressing hgSL and h1SL was 0.15 higher compared to using the 

ratio hgSL and h1SL. 

The data indicate the following flow-regime criteria 

conditions. Weir flow occurs when hgSL /h1SL is greater than or 

equal to 0.73. Submerged-weir flow occurs when h3SL /h1SL is 

greater than 0.80. Orifice flow occurs when hgSL /h1SL is less than 

0.73 and either h3SL/hgSL is less than 1.0 or h3SL /h1SL is less than or 

equal to 0.70. Submerged-orifice flow occurs when h3SL/hgSL is 

greater than or equal to 1.0 and h3SL /h1SL is greater than 0.70. 

The measured and computed sluice gate flows for 

McHenry are presented in table 7 and figure 15 for comparison. All 50 computed sluice gate flows are within 11 percent 

of measured flows. All 17 measured flows above 2,000 ft3/s 

were computed within 6 percent. 

Concrete pier

Concrete walkway Motor, for adjusting gates

Headwater pool stage

Sluice gate

Tailwater pool stage

Datum 733.00 ft

Datum

730.15 ft

h1SL

h1SL

h3SL

h3SL

NOT TO SCALE

flow

Concrete sill

Elevation 731.15 ft

EXPLANATION

HEADWATER DEPTH

GATE OPENING

TAILWATER DEPTH

hgSL

hgSL

Figure 11. Schematic (side view) of sluice gates on the Fox River at McHenry, Illinois, (ft, foot).
McHenry Control-Structure Ratings 15

Table 7. Sluice gate measured and computed flow characteristics and coefficients near McHenry, Illinois.—Continued [USGS, U.S. Geological Survey; ft3/s, cubic foot per second; hgSL, sluice gate opening referenced to the concrete sill; ft, foot; h1SL , headwater depth above the sluice-gate sill; h3SL , tailwater depth above the sluice-gate sill; CSLW, free-weir coefficient for the sluice gate; CSLO, free-orifice coefficient for the sluice gate; CSLW-S, submerged-weir coefficient for the sluice gate; CSLO-S, submergedorifice coefficient for the sluice gate; C/M, ratio of computed and measured flow; FW, free-weir flow; FO, free-orifice flow; SO, submerged-orifice flow; ---, not determined]

USGS 

measurement 

number Date

Measured

flow (M)

 (ft3/s)

Gate 

opening

hgSL (ft)

h1SL

(ft)

h3SL

(ft) h3SL/h1SL h3SL/hgSL hgSL/h1SL

Flow

Regime

Measured

CSLW or 

CSLO

Computed

CSLW or 

CSLO

Measured

CSLW-S or 

CSLO-S

Computed

CSLW-S or 

CSLO-S

Computed

flow (C)

(ft3/s) C/M

1 03/22/1985 2,790 4.0 5.36 2.90 0.54 0.72 0.75 FW 3.27 3.17 --- --- 2,700 0.972 03/22/1985 1,990 3.0 5.53 2.70 .49 .90 .54 FO .51 .53 --- --- 2,052 1.033 03/26/1985 2,100 3.8 4.49 2.45 .55 .64 .85 FW 3.21 3.22 --- --- 2,108 1.004 03/26/1985 1,850 3.3 4.56 2.42 .53 .73 .72 FO .48 .48 --- --- 1,876 1.016 05/16/1985 448 .6 5.88 .35 .06 .58 .10 FO .56 .60 --- --- 480 1.07

X7 10/04/1985 1,460 2.5 5.90 1.75 .30 .70 .42 FO .54 .55 --- --- 1,469 1.01X8 11/04/1985 1,830 3.15 5.83 1.82 .31 .58 .54 FO .55 .54 --- --- 1,805 .99

9 03/17/1986 3,230 6.5 6.16 4.03 .65 .62 1.06 FW 3.07 3.12 --- --- 3,280 1.02

10 04/22/1986 833 1.2 5.08 .71 .14 .59 .24 FO .56 .54 --- --- 803 .96

Y11 04/22/1986 1,047 2.0 4.98 .85 .17 .43 .40 FO .53 .52 --- --- 1,018 .97Y11 04/22/1986 133 1.0 4.98 .85 .17 .85 .20 FO --- --- --- --- --- ---

12 05/23/1986 967 1.2 6.01 1.25 .21 1.04 .20 FO .60 .58 --- --- 939 .9714 08/28/1986 180 .2 6.07 .05 .01 .25 .03 FO .66 .65 --- --- 176 .9816 09/27/1986 3,045 4.0 7.20 5.15 .72 1.29 .56 SO .51 .58 0.89 0.94 3,229 1.0617 09/27/1986 4,054 7.0 7.05 5.25 .74 .75 .99 FW 3.15 3.08 --- --- 3,962 .9818 09/27/1986 3,600 4.9 7.07 5.25 .74 1.07 .69 SO .50 .57 .88 .83 3,411 .9519 09/27/1986 3,320 4.5 7.11 5.30 .75 1.18 .63 SO .50 .57 .88 .82 3,127 .9421 09/30/1986 2,600 4.0 7.75 5.98 .77 1.50 .52 SO .42 .60 .71 .74 2,719 1.0522 09/30/1986 2,920 4.5 7.71 5.98 .78 1.33 .58 SO .42 .59 .71 .73 2,973 1.0223 10/15/1986 3,270 7.0 6.10 4.10 .67 .59 1.15 FW 3.16 3.12 --- --- 3,236 .9924 11/01/1990 636 1.0 4.44 .32 .07 .32 .23 FO .55 .51 --- --- 597 .9425 11/01/1990 63.9 .1 4.52 .11 .02 1.10 .02 FO .54 .60 --- --- 70 1.1026 11/01/1990 74.4 .1 4.48 .05 .01 .50 .02 FO .64 .59 --- --- 69 .9327 11/02/1990 73.9 .1 4.53 -.42 -.09 -4.20 .02 FO .63 .60 --- --- 70 .9528 11/03/1990 74.1 .1 4.76 -.55 -.12 -5.50 .02 FO .62 .61 --- --- 73 .9929 11/04/1990 75 .1 5.02 -.65 -.13 -6.50 .02 FO .61 .62 --- --- 77 1.0330 11/04/1990 75.9 .1 5.02 -.65 -.13 -6.50 .02 FO .61 .62 --- --- 77 1.0231 11/05/1990 82.6 .1 5.41 -.60 -.11 -6.00 .02 FO .64 .64 --- --- 83 1.0032 11/05/1990 1,340 2.5 4.69 .74 .16 .30 .53 FO .45 .50 --- --- 1,484 1.1133 11/05/1990 1,310 2.5 4.61 .89 .19 .36 .54 FO .44 .49 --- --- 1,461 1.11
16 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois Table 7. Sluice gate measured and computed flow characteristics and coefficients near McHenry, Illinois.—Continued [USGS, U.S. Geological Survey; ft3/s, cubic foot per second; hgSL, sluice gate opening referenced to the concrete sill; ft, foot; h1SL , headwater depth above the sluice-gate sill; h3SL , tailwater depth above the sluice-gate sill; CSLW, free-weir coefficient for the sluice gate; CSLO, free-orifice coefficient for the sluice gate; CSLW-S, submerged-weir coefficient for the sluice gate; CSLO-S, submerged- orifice coefficient for the sluice gate; C/M, ratio of computed and measured flow; FW, free-weir flow; FO, free-orifice flow; SO, submerged-orifice flow; ---, not determined] USGS measure- ment number Date Measured flow (M) (ft3/s) Gate opening

hgSL (ft)

h1SL

(ft)

h3SL

(ft) h3SL/h1SL h3SL/hgSL hgSL/h1SL

Flow

Regime

Measured

CSLW or 

CSLO

Computed

CSLW or 

CSLO

Measured

CSLW-S or 

CSLO-S

Computed

CSLW-S or 

CSLO-S

Computed

flow (C)

(ft3/s) C/M

34 11/06/1990 1,370 2.5 4.51 1.19 0.26 0.48 0.55 FO 0.47 0.49 --- --- 1,431 1.0435 11/06/1990 1,500 2.5 4.45 1.38 .31 .55 .56 FO .52 .49 --- --- 1,413 .9436 11/07/1990 1,360 2.5 4.54 1.52 .33 .61 .55 FO .46 .49 --- --- 1,440 1.0637 11/07/1990 1,510 2.5 4.54 1.52 .33 .61 .55 FO .51 .49 --- --- 1,440 .9538 11/07/1990 1,480 2.5 4.54 1.56 .34 .62 .55 FO .50 .49 --- --- 1,440 .9739 11/08/1990 1,480 2.5 4.56 1.60 .35 .64 .55 FO .50 .49 --- --- 1,446 .9840 11/08/1990 1,580 2.5 4.56 1.60 .35 .64 .55 FO .54 .49 --- --- 1,446 .9241 11/09/1990 1,460 2.5 4.54 1.58 .35 .63 .55 FO .50 .49 --- --- 1,440 .9942 04/24/1993 3,920 6.0 7.02 2.24 .32 .37 .85 FW 3.07 3.08 --- --- 3,938 1.0043 04/28/1993 3,664 6.0 6.83 1.78 .26 .30 .88 FW 2.99 3.09 --- --- 3,790 1.0349 05/17/2004 1,760 2.2 6.14 2.50 .41 1.14 .36 FO .59 .56 --- --- 1,691 .9650 05/17/2004 1,690 2.2 5.95 2.74 .46 1.25 .37 FO .57 .55 --- --- 1,642 .97

X51 05/17/2004 1,250 2.2 5.62 3.00 .53 1.36 .39 FO .54 .54 --- --- 1,246 1.00

52 05/24/2004 3,020 5.7 5.89 4.85 .82 .85 .97 SW 3.07 3.14 0.98 0.97 2,992 .9953 03/17/2006 1,664 3.0 4.49 2.77 .62 .92 .67 FO .47 .48 --- --- 1,691 1.0254 03/17/2006 1,890 3.0 5.22 2.31 .44 .77 .57 FO .50 .51 --- --- 1,945 1.03

Z55 03/16/2007 --- 4.0 4.49 3.32 .74 .83 .89 FW --- 3.22 --- --- 2,108 ---

56A 08/22/2007 2,760 5.0 5.58 4.59 .82 .92 .90 SW 3.05 3.15 .97 .97 2,778 1.0157A 08/27/2007 3,140 6.2 6.68 6.03 .90 .97 .93 SW 2.65 3.10 .85 .86 3,158 1.01

58A 03/26/2008 1,970 4.5 4.32 3.36 .78 .75 1.04 FW 3.19 3.23 --- --- 1,997 1.01

59A 04/16/2008 2,960 5.3 5.99 5.02 .84 .95 .88 SW 2.94 3.13 .94 .95 2,992 1.0160A 06/20/2008 3,280 6.0 6.60 5.76 .87 .96 .91 SW 2.81 3.10 .91 .90 3,247 .99

xFour gates open, one gate closed. All other measurements had five gates open, unless otherwise noted.YFour gates were set to 2.0 ft, and one gate was set to 1.0 ft. Equations developed in this study were used to subtract flow from the gate open to 1.0 ft; a coefficient for a 2.0 ft opening was determined from the measurement.ZSluice gate flow was not measured directly. The sluice gate flow is calculated to help determine the broad-crested weir and hinged-crest gate flow.Black plain text indicates free-orifice measurements.Red bold text indicates submerged-orifice measurements.Blue italic text indicates free-weir measurements.Green bold italic text indicates submerged-weir measurements.
McHenry Control-Structure Ratings 17

Table 8. Hydraulic conditions, parameters, and equations for different flow regimes for the sluice gates on the Fox River at 

McHenry, Illinois.

[hgSL, sluice gate opening referenced to the concrete sill, in feet; h1SL, headwater depth above the sluice-gate sill, in feet; h3SL, tailwater depth above 

the sluice-gate sill, in feet; QSL, flow through the sluice gates, ft3/s; CSLW , free-weir coefficient for the sluice gate; B, length of gates, in feet; 

CSLW-S, submerged-weir coefficient for the sluice gate; CSLO , free-orifice coefficient for the sluice gate; CSLO-S, submerged-orifice coefficient for the 

sluice gate]

Structure Flow regime Hydraulic conditions Parameters and equations

Equation 

number

Sluice gate weir Free weir

(FW) 10

11

12

Sluice gate weir Submerged 

weir 13

14

15

Sluice gate 

orifice

Free orifice

16

17

18

Sluice gate 

orifice

Submerged 

orifice 19

20

21

h

h

gSL

SL 1

≥0 7. 3 Q C Bh SL SLW SL  1

1 5.

h

h

SL

SL

3

1

≤ 0 8. 0 CSLW h SL  − 3 75 1

0 101 . .

B  5 1 gates × 3 7. . 5 6 ft  8 75 ft

QSL SL  257.8h1

1 4. 01

h

h

gSL

SL 1

≥ 0 7. 3 Q C C Bh SL SLW SLW S SL  − 1

1 5.

and

and

h

h

SL

SL

3

1

 0 8. 0 C

h

h SLW S

SL

SL

−

−

 0 750 3

1

1 33

.

.













Q h h SL SL SL  − 193.4 1

2 731

3

. .1 33

h

h

gSL

SL 1

 0 7. 3 Q C Bh gh SL SL SL SL    2 1

0 5.

O g

h

h

SL

SL g

3  1

and

or C h h SLO SL SL  − 0 271 1

0 429 0 062 . . . g

and

and

Q C SL SLO S C B LO S h gh SL  − 2 1

0 5.

g

SL

  h

h

gSL

SL 1

 0 7. 3

h

h

3SL

SL

≥1 g

C

h

h SLO S

SL

SL

−

−

 0 325 3

1

3 17

.

.













h

h

SL

SL

3

1

 0 7. 0 h h SL g SL SL SL  − 48 6 1

4 0 99 0 938

3

3 17 . . Q h . .

h

h

SL

SL

3

1

≤ 0 7. 0 B  5 1 gates × 3 7. . 5 6 ft  8 75 ft

g  32 2ft s2 . /

Q h h SL g SL SL 149.5 1

0. . 929 0 938
18 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Figure 12. Discharge coefficient for free-weir flow and headwater depth for sluice gates on the 

Fox River at McHenry, Illinois, (R2, coefficient of determination).

Figure 13. Discharge coefficient for submerged-weir flow and ratio of tailwater and headwater 

depth for sluice gates on the Fox River at McHenry, Illinois, (R2, coefficient of determination).

1

10

0.1 1.0 10.0

HEADWATER DEPTH ( ) h1SL , IN FEET

FREE-WEIR COEFFICIENT ( ) CSLW

CSLW = 3.75h1SL

R2= 0.85

-0.101

0.1

1.0

0.1 1.0

WEIR SUBMERGENCE RATIO ( ) h 3SL /h1SL

SUBMERGED-WEIR COEFFICIENT ( ) CSLW S-

( ) R2 = 0.97

CSLW-S = 0.750 h3SL

h1SL

-1.33
McHenry Control-Structure Ratings 19

0

500

1,000

1,500

2,000

2,500

0 500 1,000 1,500 2,000 2,500

MEASURED SLUICE GATE FLOW,

IN CUBIC FEET PER SECOND

COMPUTED SLUICE GATE FLOW,

IN CUBIC FEET PER SECOND

Line of perfect agreement

Figure 15. Measured and computed flows for the sluice 

gates near McHenry, Illinois. 

Figure 14. Discharge coefficient for submerged-orifice flow and submergence ratio for sluice 

gates on the Fox River at McHenry, Illinois, (R2, coefficient of determination).

0.1

1.0

0.1 1.0

ORIFICE SUBMERGENCE RATIO ( ) h 3SL /h1SL

SUBMERGED-ORIFICE COEFFICIENT ( ) CSLO S-

( ) R2 = 0.78

CSLO-S = 0.325

h3SL

h1SL

-3.17
20 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Example Calculations

The following are examples of how streamflow was calculated using equations in table 8 and table 4. Note that total 

flow on the Fox River at McHenry is the summation of flow 

through the sluice gates, broad-crested weir, and hinged-crest 

gate. Thus, flow must be calculated at each of those structures 

separately. At times, the broad-crested weir may experience no 

flow over it, as shown in example 2.

Example 1: The following conditions exist:

Headwater pool stage is 5.15 ft, tailwater pool stage is 

6.20 ft, all gates are opened to 7.0 ft (hgSL ), and the hingedcrest gate opening is 1.0 ft (hgHCG ). See figures 6 and 11 for 

schematic of hinged-crest gate, broad crested weir, sluice gate, 

and variables.

Flow over the broad-crested weir (which includes the fish 

ladder) is determined by first converting the headwater stage 

to depth above the weir crest. This is done by subtracting the 

difference between headwater gage datum (733.00 ft) and the 

elevation of the spillway crest (736.68) from the headwater 

stage reading,

h1BCW 

= 5.15 - (736.68 - 733.00) = 1.47 ft,

and using equation 3 from table 4.

Q h BCW BCW  661 5 1

1 587 . .

= 661.5(1.47)1.587

= 1219 ft3

 / s .

Flow over the hinged-crest gate is determined by first 

converting the stages to depths above the crest of the gate. 

This is done by subtracting the difference between headwater gage datum (733.00 ft) and the elevation of the gate crest 

(736.68 ft - hgHCG ) from the headwater stage and then 

subtracting the difference between the tailwater gage datum 

(730.15 ft) and the elevation of gate crest from the tailwater 

stage.

h1HCG = 5.15 - [(736.68 - 1.00) - 733.00] = 2.47 ft

h3HCG = 6.20 - [(736.68 - 1.00) - 730.15] = .67 ft

Because h3HCG / h1HCG (0.67/2.47=0.27) is less than 0.75, FW 

flow exists. Before calculating flow, the depth from the 

concrete slab to the crest of the gate must be determined by 

calculating the difference between the gate crest elevation 

(736.68 ft - hgHCG) and the elevation of the top of the concrete 

slab (730.08).

pHCG = (736.68 - 1.00) - 730.08 = 5.6 ft.

Using equation 6 from table 4, flow is

Q h p HCG HCG HCG  193 5 1

1 365 0 135 . . .

=193.5(2.47)1.365(5.6)0.135

=838.9 ft3 / s

Flow through the sluice gates is determined by first converting the stages to depths above the sluice-gate sill. This is 

done by adding the difference between headwater gage datum 

and the elevation of the sill (1.85) to the headwater stage and 

then subtracting the difference between the tailwater gage 

datum and the elevation of the sill (1.00) from the tailwater 

stage.

h1SL= 5.15 + 1.85 = 7.00 ft

h3SL= 6.20 - 1.00 = 5.20 ft

Because hgSL /h1SL (7.0/7.0=1.0)is greater than 0.73 and 

h3SL / h1SL (0.74) is less than 0.80 (table 8), free-weir flow exists.

Using equation 12 from table 8, flow is,

Q h SL SL 257.8 1

1 4. 01

= 257.8(7.00)1.401

= 3938 ft3 / s

Therefore, total flow, QTOTAL , is

QTOTAL = 838.9 + 1219 + 3938 = 5996 ft3 / s

Example 2: The following conditions exist:

Headwater pool stage is 2.57 ft, tailwater pool stage is 

3.70 ft, all sluice gates are set to 3.0 ft (hgSL ), and the hingedcrest gate opening is 5.0 ft (hgHCG ).

To find flow over the broad-crested weir, first, convert 

pool stages to depths above weir crest as in example 1.

h1BCW = 2.57 - (736.68 - 733.00) < 0 ft

Because h1BCW is a negative number, the weir experiences zero 

flow.

Flow over the hinged-crest gate is determined using the 

same method as in example 1.

h1HCG = 2.57 - [(736.68 - 5.00) - 733.00] = 3.89 ft

 h3HCG = 3.70 - [(736.68 - 5.00) - 730.15] = 2.17 ft
McHenry Control-Structure Ratings 21

Because h3HCG /h1HCG (2.17/3.89 = 0.56) is less than 0.75, 

FW flow exists.

pHCG = (736.68 - 5.00) - 730.08 = 1.6 ft.

Using equation 6 from table 4:

QHCG = 193.5(3.89)1.365(1.6)0.135

QHCG = 1317 ft3 / s

To find flow through the sluice gates, pool stages must be 

converted to depths above the sluice-gate sill

h1SL = 2.57 + 1.85 = 4.42 ft

h3SL = 3.70 - 1.00 = 2.70 ft

Because hgSL / h1SL (3.0/4.42=0.68) is less than 0.73, orifice flow 

exists. Since h3SL / hgSL (2.70/3.0=0.90) is less than 1.0, freeorifice flow exists. Alternatively, free-orifice flow also exists 

because h3SL / h1SL (2.70/4.42=0.61) is less than 0.70.

Using equation 18 from table 8, the flow is.

Q h h SL g SL SL 149.5 1

0. . 929 0 938

= 149.5(4.42)0.929(3.0)0.938

= 1666 ft3 / s

Therefore, total flow, QTOTAL, is

QTOTAL= 1317 + 1666 = 2983 ft3 / s

Example 3: The following conditions exist:

Headwater pool stage is 4.14 ft, tailwater pool stage is 

5.95 ft, all gates are set to 5.7 ft (hgSL ), and the hinged-crest 

gate opening is 6.0 ft (hgHCG ).

Flow over the broad-crested weir is calculated in the 

same manner as in example 1.

h1BCW = 4.14 - (736.68 - 733.00) = 0.46 ft 

Using Equation 3 from table :

Q h BCW BCW  661 5 1

1 587 . .

= 661.5(0.46)1.587

QBCW = 192.9 ft3 / s 

Flow over the hinged-crest gate is determined by first 

converting the pool stages to depths above the gate and 

determining the value of pHCG.

h1HCG = 4.14 - [(736.68 - 6.0) - 733.00] = 6.46 ft 

h3HCG = 5.95 - [(736.68 - 6.0) - 730.15] = 5.42 ft 

pHCG = (736.68 - 6.0) - 730.08 = 0.6 ft.

Because h3HCG / h1HCG (5.42/6.46=0.84) is greater than 0.75, 

submerged-weir flow exists.

Using equation 9 from table 4,

Q h h p HCG HCG HCG HCG  − 91 14 1

4 305

3

2 94 0 135 . . . .

= 91.14(6.46)4.305(5.42)-2.94(0.6)0.135

= 1819 ft3 / s

To find flow through the sluice gates, pool stages must be 

converted to depths above the sluice-gate sill

h1SL = 4.14 + 1.85 = 5.99 ft 

h3SL = 5.95 - 1.00 = 4.95 ft 

Because hgSL / h1SL (5.7/5.99 = 0.95) is greater than 0.73 and 

h3SL / h1SL (4.95/5.99 = 0.83) is greater than 0.80, submergedweir flow exists.

Using equation 15 from table 8,

Q h h SL SL SL  − 193.4 1

2 73

3

. . 1 33

= 193.4(5.99)2.73(4.95)-1.33

= 3060 ft3 / s

Therefore, total flow, QTOTAL , is 

QTOTAL = 192.9 + 1819 + 3060 = 5072 ft3 / s

Example 4: The following conditions exist:

Headwater pool stage is 5.30 ft, tailwater pool stage is 

6.10 ft, all sluice gates are set to 4.0 ft (hgSL), and the hingedcrest gate opening is 5.5 ft (hgHCG).

Flow over the broad-crested weir is calculated in the 

same manner as in example 1.

h1BCW = 5.30 - (736.68 - 733.00)= 1.62 ft

Q h BCW BCW  661 5 1

1 587 . .

= 661.5(1.62)1.587

= 1422 ft3 / s
22 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Flow over the hinged-crest gate is characterized as 

free-weir flow, so the flow can be found in the same manner 

as in example 1.

h1HCG = 5.30 - [(736.68 - 5.50) - 733.00] = 7.12 ft 

h3HCG = 6.10 - [(736.68 - 5.5) - 730.15] = 5.07 ft 

Because h3HCG / h1HCG (5.07/7.12=0.71) is less than 0.75, FW 

flow exists.

pHCG = (736.68 - 5.50) - 730.08 = 1.10 ft. 

Using equation 6 from table 4, flow is

Q h p HCG HCG HCG  193 5 1

1 365 0 135 . . .

= 193.5(7.12)1.365(1.10)0.135

= 2857 ft3 / s 

To calculate flow through the sluice gates, headwater 

and tailwater pool stages must be converted to depths above 

the sluice gate sill.

h1SL = 5.30 + 1.85 = 7.15 ft 

h3SL = 6.10 - 1.00 = 5.10 ft

Because hgSL / h1SL (4.0/7.15 = 0.56) is less than 0.73, 

h3SL / hgSL (5.10/4.0 = 1.28) is greater than 1, and h3SL /h1SL 

(5.10/7.15 = 0.71) is greater than 0.70, submerged-orifice 

flow exists.

Using equation 21 from table 8,

Q h h h SL g SL SL SL  − 48 6 1

4099 0938

3

3 17 . . . .

QSL = 48.6(7.15) 4.099(4.0)0.938 (5.10)-3.17 

= 3237 ft3 / s

Therefore, total flow, QTOTAL , is 

QTOTAL= 1422 + 2857 + 3237 = 7516 ft3 / s

Algonquin Control-Structure Ratings

The Algonquin control structure is at river mile 81.6 

on the Fox River in northeastern Illinois (fig. 1), 16.2 miles 

downstream of McHenry control structure. The drainage area 

at the headwater gage is 1,403 mi2. The 894-acre reservoir 

created by the dam is primarily for recreation. The control 

structures at Algonquin consist of a 242-ft ogee spillway and a 

50-ft-wide hinged-crest gate (figs. 16, 17, and 18). The elevation of structure components and headwater and tailwater gage 

datums are presented in table 9.

At the Algonquin control structure, streamflow measurements collected by the USGS at high flows during this study 

were made with a tethered ADCP boat off the downstream end 

of the Route 62 Bridge (fig. 16). Given the ability to measure flows within a close proximity to the structure, the total 

flow could be separated into flow through the hinged-crest 

gate and flow over the ogee spillway for the majority of the 

measurements.

The flow separation was completed by analyzing the 

velocity data obtained by the ADCP during each measurement 

and determining the approximate location where the flow 

“splits” between the hinged-crest gate and the ogee spillway. 

The vertically averaged velocity vectors (fig. 19) show a clear 

separation in the area where the flow splits between the gate 

and the spillway. A similar separation can be seen in the velocity contour plot (fig. 20) where the velocities decrease appreciably in the area of the flow split.

The flow separations are more obvious under certain flow 

conditions and gate settings than others. Typically, the actual 

separation point was chosen to be at the center of the break in 

velocity vectors (fig. 19) or at the center of the slower velocity section (fig. 20). A sensitivity analysis was performed to 

determine the potential accuracy of this method. In general, 

selecting separation points at either end of the slower velocity 

section affected the estimated flow through the gate by about 

5 to 8 percent.

Table 9. Elevation of structure and streamflow-gaging station datums on the Fox River at Algonquin, Illinois.

[NGVD 1929, National Geodetic Vertical Datum of 1929] 

Structure or gage

Elevation, in feet

(NGVD 1929)

Algonquin Dam ogee spillway crest elevation 730.10

Algonquin Dam hinged-crest gate floor elevation 723.58

Headwater station datum, Fox River at Algonquin, Illinois 729.48

Tailwater station datum, Fox River at Algonquin, Illinois 719.48
McHenry Control-Structure Ratings 23

88°17'28" 88°17'26" 88°17'24" 88°17'22" 88°17'20"

42°9'54"

42°9'56"

42°9'58"

42°10'

Spillway

Ogee

(242 feet wide)

Hinged-crest

gate

(50 feet wide)

F O X R I V E R

flow

Base from U.S. Geological Survey High Resolution Orthoimage, Chicago, IL-IN, 2003.

Universal Transverse Mercator projection, NAD 83, zone 16.

Wall

(8 feet wide total)

0 50 100 150 200 FEET

0 25 50 METERS

State Route 62

Headwater

gage

(05549500)

Tailwater

gage

(05549501)

Figure 16. Location of control structures on the Fox River at Algonquin, Illinois. 
24 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Hinged-crest

gate

(50 feet wide)

Ogee spillway

Figure 17. Downstream side of hinged-crest gate and ogee spillway on the Fox River at Algonquin, Illinois. 
McHenry Control-Structure Ratings 25

Figure 18. Close-up of downstream side of hinged-crest gate on the Fox River at Algonquin, Illinois. 
26 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Ogee Spillway with Hinged-Crest Gate Closed 

(with and without flow over gate)

A side-view schematic of the ogee spillway, hinged-crest 

gate, and parameters used in the control-structure rating are 

shown in figure 21. Twelve measurements, ranging from 77 to 

3,260 ft3/s, were used to describe free-weir flow over the ogee 

spillway with the hinged-crest gate completely closed and no 

flow over the gate. Nine measurements, ranging from 406 to 

1,960 ft3/s, were used to describe free-weir flow over the ogee 

spillway and the crest of the hinged-crest gate set at the elevation of the ogee spillway with flow over the gate. Characteristics of the flow and the measured and computed discharge 

coefficients are listed in table 10 and appendix C. A standard 

weir equation (table 11) described in Chow (1959), Collins 

(1977), and Roberson and others (1998) is used to describe 

flow over the ogee spillway. The resulting free-weir equations 

are presented in table 11 and figure 22 for the conditions of 

Figure 19. Vertically averaged velocity vectors for a typical Acoustic 

Doppler Current Profiler streamflow measurement upstream of the 

control structure at Algonquin, Illinois, (ft, foot; ft/s, foot per second; 

BT, bottom tracking).

Figure 20. Velocity contour plot for the Acoustic Doppler Current Profiler streamflow measurement shown in figure 19 upstream of the 

control structure at Algonquin, Illinois, (ft, foot; ft/s, foot per second; BT, bottom tracking; Q, streamflow).

flow over only the ogee spillway (QOS) and for flow over both 

the ogee spillway and the hinged-crest gate (denoted as QS for 

flow over the combined 292-ft “spillway”). Equations for conditions when the hinged-crest gate is open also are presented 

in tables 11 and 12 and are discussed in the next section. With 

the hinged-crest gate closed, the submergence ratios(h3OS / h1OS) 

were negative for all of the flow measurements, so submergence ratios could not be evaluated. 

The measured and computed flows for the structure with 

the hinged-crest gate completely closed or with the crest set at 

the elevation of the ogee spillway at Algonquin are presented 

in table 10 and figure 23 for comparison. All 12 computed 

ogee spillway flows with the hinged-crest gate completely 

closed (no flow over the gate) are within 5 percent of measured flows. All nine computed ogee spillway flows with the 

crest of the hinged-crest gate set at the elevation of the ogee 

spillway with flow over the gate are within 11 percent of 

measured.
Algonquin Control-Structure Ratings 27

Top of concrete slab,

elevation 723.58 ft

Top of concrete slab,

elevation 719.00 ft

Crest of Ogee spillway,

elevation 730.10 ft h1OS h1HCG

h3HCG h3OS

flow

Hinged-crest gate

Air bladder

hgHCG

pHCG

NOT TO SCALE

Figure 21. Schematic (side view) of 

hinged-crest gate and ogee spillway on 

the Fox River at Algonquin, Illinois,

(ft, foot; h1HCG , headwater depth above 

the hinged-crest gate crest; h3HCG , 

tailwater depth above the hingedcrest gate crest; hgHCG , hinged-crest 

gate opening referenced to the ogee 

spillway crest; pHCG, height of hingedcrest gate crest above approach invert; 

h1OS , headwater depth above the ogee 

spillway crest; h3OS , tailwater depth 

above the ogee spillway crest).

Figure 22. Discharge 

coefficient for free-weir flow 

and headwater depth for ogee 

spillway and hinged-crest 

gate (closed or at elevation 

of ogee spillway) on the Fox 

River at Algonquin, Illinois (R2, 

coefficient of determination). 

Line of perfect agreement

0

1,000

2,000

3,000

4,000

0 1,000 2,000 3,000 4,000

MEASURED SPILLWAY FLOW, IN CUBIC FEET PER SECOND

COMPUTED SPILLWAY FLOW, IN CUBIC FEET PER SECOND

Figure 23. Measured and computed flows for the structure with the 

hinged-crest gate completely closed or with the crest set at the elevation 

of the ogee spillway at Algonquin, Illinois.

1

10

0.1 1.0 10.0

HEADWATER DEPTH ( ) h 1OS ABOVE OGEE SPILLWAY, IN FEET

FREE-WEIR COEFFICIENT ( OR

COS

CS)

Ogee spillway (no flow over hinged-crest gate)

Ogee spillway and hinged-crest gate (crest of HCG set at elevation of OS)

Ogee spillway

Ogee spillway and hinged-crest gate

COS = 2.67h1OS

0.363

R2 = 0.98

CS = 2.34h1OS

0.546

R2 = 0.87
28 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Table 10. Ogee spillway and hinged-crest gate (closed or crest at elevation of ogee-spillway crest) measured and computed flow 

characteristics and coefficients at Algonquin, Illinois. 

[USGS, U.S. Geological Survey; ft3/s, cubic foot per second; h1OS , headwater depth above the ogee spillway crest; ft, foot; h3OS , tailwater depth 

above the ogee spillway crest; COS, free-weir coefficient for the ogee spillway; CS, free-weir coefficient for the spillway which includes flow over the 

hinged-crest gate set at the elevation of the ogee spillway; C/M, ratio of computed and measured flow; FW-NF, free-weir flow with no flow over the 

hinged-crest gate; FW-FL, free-weir flow with flow over the hinged-crest gate (crest at elevation of ogee spillway); ---, not determined]

 USGS

measurement

number Date

Measured 

 flow (M)

(ft3/s)

h1OS

(ft)

h3OS

(ft) h3OS/h1OS

Flow

regime

Measured

COS or CS

Computed

COS or CS

Computed

flow (C)

(ft3/s) C/M

A505 03/26/2002 1,180 1.38 --- --- FW-NF 3.01 3.00 1,177 1.00

A506 04/11/2002 2,600 2.14 --- --- FW-NF 3.43 3.52 2,666 1.03

A507 06/11/2002 3,260 2.37 --- --- FW-NF 3.69 3.65 3,225 .99

A508 07/23/2002 280 .62 --- --- FW-NF 2.37 2.24 265 .95

509 09/24/2002 577 .96 -3.64 -3.79 FW-NF 2.53 2.63 599 1.04

510 11/07/2002 381 .75 -3.98 -5.31 FW-NF 2.42 2.41 378 0.99

511 01/09/2003 406 .76 -3.52 -4.63 FW-FL 2.10 2.01 390 0.96

B512 03/12/2003 267 .55 -4.15 -7.55 --- --- --- --- ---

513 05/05/2003 1,060 1.24 -2.66 -2.15 FW-FL 2.63 2.63 1,061 1.00

514 05/07/2003 1,960 1.64 -1.81 -1.10 FW-FL 3.20 3.07 1,880 .96

515 06/18/2003 473 .81 -3.74 -4.62 FW-FL 2.22 2.09 444 .94

516 09/03/2003 76.5 .32 -4.57 -14.28 FW-NF 1.75 1.77 77 1.01

517 10/15/2003 203 .55 -3.85 -7.00 FW-NF 2.06 2.15 212 1.05

518 12/02/2003 605 .92 -3.49 -3.79 FW-FL 2.35 2.24 576 .95

B519 02/02/2004 382 .72 -4.00 -5.56 --- --- --- --- ---

520 03/23/2004 989 1.20 -2.85 -2.37 FW-FL 2.58 2.58 992 1.00

C525 07/08/2004 1,240 1.14 -2.74 -2.40 --- --- --- --- ---

526 09/14/2004 301 .67 -4.23 -6.31 FW-NF 2.27 2.31 306 1.02

527 11/08/2004 800 1.12 -3.46 -3.09 FW-FL 2.31 2.49 862 1.08

528 03/10/2005 1,540 1.49 -2.52 -1.69 FW-FL 2.90 2.91 1,545 1.00

529 06/28/2005 121 .41 -4.45 -10.85 FW-NF 1.90 1.93 123 1.01

530 10/04/2005 294 .65 -4.17 -6.42 FW-NF 2.32 2.28 290 .99

535 07/28/2006 368 .72 -4.07 -5.65 FW-NF 2.49 2.37 350 .95

536 10/02/2006 429 .84 -4.03 -4.80 FW-FL 1.91 2.13 478 1.11

D538 06/28/2007 801 1.03 -3.56 -3.46 --- --- --- --- ---

E541 11/09/2007 703 .91 -3.53 -3.88 --- --- --- --- ---

E542 12/17/2007 1,140 1.12 -3.03 -2.71 --- --- --- --- ---

ATailwater gage was not yet installed. Flow regime conditions are considered free weir for computations.

BIce-affected measurement, not used in equation development.

COutlier, measurement not used in equation development.

DHinged-crest gate opening changed 20 minutes before measurement, not used in equation development.

EHinged-crest gate repairs, measurement not used in equation development. 

Measurements in bold indicate that the hinged-crest gate was closed, and no flow was overtopping it.
Algonquin Control-Structure Ratings 29

Table 11. Hydraulic conditions, parameters, and equations for different flow regimes for the ogee spillway and hinged-crest gate on 

the Fox River at Algonquin, Illinois. 

[ h1OS , headwater depth above the ogee spillway crest, in feet; h3OS , tailwater depth above the ogee spillway crest, in feet; QOS, flow through the ogee 

spillway, in ft3/s; COS, free-weir coefficient for the ogee spillway; COS-A, affected-weir coefficient for the ogee spillway; CS, free-weir coefficient for the 

spillway which includes flow over the hinged-crest gate set at the elevation of the ogee spillway; FW-NF, free-weir flow with no flow over the hingedcrest gate; FW-FL, free-weir flow with flow over the hinged-crest gate (crest at elevation of ogee spillway)]

Structure Flow regime Hydraulic conditions Parameters and equations

Eq.

No.

Ogee spillway

(hinged-crest 

gate closed)

Free weir–no 

flow over HCG

(FW-NF)

h

h

OS

OS

3

1

 0 6. 0 22

Ogee spillway

(hinged-crest 

gate open)

Free weir (FW)

h

h

OS

OS

3

1

< −5 0. 23

24

Ogee spillway

and hingedcrest gate 

(crest of the 

hinged-crest 

gate set at 

elevation of 

ogee spillway)

Free weir withflow over HCG

(FW-FL)

h

h

OS

OS

3

1

 0 6. 0 25

26

 

27

Ogee spillway

(hinged-crest 

gate open)

Affected

− < 5 0 < 1 3

1

. h

h

OS

OS

28

29

 30

Q C C Bh OS OS OS A OS  − 1

1 5.

Q C Bh OS OS OS  1

1 5.

Q h OS OS  646 1 1

1 863 . .

C h OS OS  2 67 1

0 363 . .

B f  242 t

Q C Bh S S OS  1

1 5.

C h S OS  2 34 1

0 546 . .

B f  292 t

Q h S OS  683 3 1

2 046 . .

C p

h h

h

h h

h OS A HCG

OS OS

OS

HCG HCG

−  − − 0 442 0 149 1 3

1

0 930

1 3 . .

.

1

0 905

HCG

− .

























Q h p h h

h h

h OS OS HCG OS OS

HCG HCG

HC

=   − − 285 5 1

0 933 0 149

1 3

0 930 1 3

1

. . . .

G

−0.905












30 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Table 12. Hydraulic conditions, parameters, and equations for different flow regimes for the hinged-crest gate on 

the Fox River at Algonquin, Illinois. 

[ h3HCG , tailwater depth above the hinged-crest gate crest, in feet; h1HCG , headwater depth above the hinged-crest gate crest, in feet; 

QHCG, flow through the hinged-crest gate; CHCG, free-weir coefficient for the hinged-crest gate; B, length of gate, in feet; pHCG, 

height of hinged-crest gate crest above approach invert, in feet; CHCG-S, submerged-weir coefficient for the hinged-crest gate]

Structure

Flow 

regime Hydraulic conditions Parameters and equations Eq. No.

Hinged-crest 

gate Free

h

h

HCG

HCG

3

1

≤ 0 7. 7 4

31

32

Hinged-crest 

gate Submerged

h

h

HCG

HCG

3

1

 0 7. 7 7

33

Q h h p HCG HCG HCG HCG  − 146 9 1

1 820

3

0 472 0 152 . . . . 34

Q C Bh HCG HCG HCG  1

1 5.

C

h

p HCG

HCG

HCG



−

3 33 1

0 152

.

.













B f  50 t

Q h p HCG HCG HCG  166 5 1

1 348 0 152 . . .

Q C C Bh HCG HCG HCG S HCG  − 1

1 5.

C

h

h HCG S

HCG

HCG

−

−

 0 882 3

1

0 472

.

.












Algonquin Control-Structure Ratings 31

Ogee Spillway and Hinged-Crest Gate Open 

A side-view schematic of the ogee spillway, hinged-crest 

gate, and parameters used in the control-structure rating are 

shown in figure 21. Twenty-one measurements, ranging from 

868 to 6,600 ft3/s, were used to describe free, affected, and 

submerged flow over the ogee spillway and hinged-crest gate. 

Characteristics of the flow and the measured and computed 

discharge coefficients are listed in table 13 and 14, and appendix D. A standard-weir equation (table 11 and 12) described in 

Chow (1959), Collins (1977), and Roberson and others (1998) 

is used to describe flow over the ogee spillway and hingedcrest gate. 

The ogee spillway free-weir coefficients in table 13 were 

computed with equation 23 in table 11. Determination of a 

submerged-weir coefficient was attempted, but 14 out of 17 

coefficient values were greater than one, indicating more flow 

than expected going over the ogee spillway for the majority of 

the measurements. The resulting coefficients are labeled COS-A

for “affected”-weir coefficient (table 13 and fig. 24). When the 

data are subdivided into three submergence ratio ranges, equations for COS-A are developed with R2

 values of 0.69, 0.49, and 

0.74. With the majority of the coefficient values above one, 

the relation of the three submergence ranges show that there is 

more affecting the flow than submergence when the hingedcrest gate is open (for example: hinged-crest gate height, 

upstream and downstream flow paths, proximity and height 

of streambank downstream of HCG, and (or) narrow channel 

downstream of the structure (fig. 16)). Multiple-linear regression analysis using gate height and hinged-crest gate and ogee 

spillway submergence ratios yields an affected-weir coefficient 

equation for the ogee spillway with an R2 of 0.97 (equation 29, 

table 11). From the range of measurements used, the resulting affected ogee spillway flow equation with the HCG open 

(table 11) is applicable for h3OS / h1OS less than 1.0 and greater 

than -5.0. Split-flow values (OS and HCG separate) for the 

measurements in November 2002 could not be determined. 

Using the available OS equations presented in table 11 and the 

HCG equations described below and presented in table 12, it 

appears that the ogee spillway flow with the HCG open and 

with h3OS / h1OS less than -5.0 are best described by equation 24 

(table 11). Note that there are only two measurements in this 

range with computed ogee spillway flow values of 21 and 158 

ft3/s.

Hinged-crest gate free- and submerged-weir coefficient 

equations are presented in table 12, figures 25 and 26. The 

free-weir coefficient equation at Algonquin is similar to the 

one at McHenry for the hinged-crest gate. Also similarly, the 

data at Algonquin indicate submerged flow occurs when 

h3HCG / h1HCG is greater than 0.77. The submerged-weir coefficient equation deviates from the McHenry equation, and this 

difference could be attributed to the complexities mentioned in 

the above paragraph.

The measured and computed ogee spillway and hingedcrest gate flows for Algonquin are presented in table 15 and 

figure 27 for comparison. Twelve of the 17 computed ogee 

spillway flows are within 5 percent of measured and the 

remaining 5 are within 11 percent. Eight of the 17 computed 

hinged-crest gate flows are within 5 percent of measured, 6 are 

within 10 percent, 2 are within 15 percent, and the remaining measurement is within 24 percent. The combined OS and 

HCG flows show similar results, and all 11 combined measured flows above 3,300 ft3

/s were computed within 7 percent.

Figure 24. Discharge coefficient for affected-weir flow and ogee spillway submergence ratio 

on the Fox River at Algonquin, Illinois, (R2, coefficient of determination). 

OGEE SPILLWAY SUBMERGENCE RATIO ( – h1 )/ OS h h 3 1 OS OS

AFFECTED-WEIR COEFFICIENT ( ) COS-A

0.1

1.0

10.0

0.001 0.010 0.100 1.000 10.000

y = 1.743x0.110

R2 = 0.69

y = 1.460x0.026

R2 = 0.49

y = 0.8833x0.472

R2 = 0.74

-3.0 < h3OS /h1OS<-0.5

-0.5 >= h3OS /h1OS<=0.65

h3OS /h1OS>0.65
32 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois Table 13. Ogee spillway weir-flow characteristics and coefficients at Algonquin, Illinois. [USGS, U.S. Geological Survey; OS, ogee spillway; HCG, hinged-crest gate; ft3/s, cubic foot per second; h1OS , headwater depth above the ogee spillway crest; ft, foot; h3OS , tailwater depth above the ogee spillway crest; COS, free-weir coefficient for the ogee spillway; COS-A, affected-weir coefficient for the ogee spillway; C/M, ratio of computed and measured flow; FW, free-weir flow; NF, no flow; AFF, affected flow; IDNR, Illinois Department of Natural Resources–Office of Water Resources; ---, not determined] USGS measure- ment number Date Measured OS and (or) HCG flow (ft3/s) Ogee Spillway Measured flow (M) (ft3/s) h1OS (ft) h3OS (ft) h3OS / h1OS Flow regime (h1OS-h3OS)/

h1OS

Measured

COS

Computed

COS

Measured1

COS-A

Computed

COS-A

Computed

flow (C)

(ft3/s) C/M

--- 11/19/2002 868 --- 0.47 -2.85 -6.06 FW 7.06 --- 2.03 --- --- 158 ------ 11/19/2002 1,410 --- .16 -1.85 -11.56 FW 12.56 --- 1.37 --- --- 21 ------ 11/20/2002 1,800 --- -.02 -1.43 --- NF --- --- --- --- --- 0 ---

523 05/18/2004 3,570 2,470 2.24 .04 .02 AFF .98 3.04 3.57 0.85 0.80 2,306 0.93522 05/18/2004 3,730 2,330 2.04 .44 .22 AFF .78 3.30 3.45 .96 .97 2,369 1.02521 05/18/2004 3,890 2,340 1.94 .67 .35 AFF .65 3.58 3.39 1.06 1.12 2,481 1.06524 05/24/2004 5,580 3,340 2.04 1.99 .98 AFF .02 4.74 3.45 1.37 1.26 3,078 .92531 02/02/2006 1,580 830 .86 -2.39 -2.78 AFF 3.78 4.30 2.53 1.70 1.70 827 1.00533 03/17/2006 3,160 1,550 1.07 -.49 -.46 AFF 1.46 5.79 2.73 2.12 2.09 1,532 .99532 03/17/2006 3,320 1,410 .93 -.20 -.22 AFF 1.22 6.50 2.60 2.50 2.53 1,425 1.01534 05/31/2006 2,000 1,060 1.04 -2.59 -2.49 AFF 3.49 4.13 2.71 1.53 1.51 1,046 .99537 03/14/2007 3,220 1,660 1.26 -.25 -.20 AFF 1.20 4.85 2.90 1.67 1.86 1,843 1.11539 08/22/2007 5,000 2,910 1.85 1.62 .88 AFF .12 4.78 3.33 1.43 1.41 2,856 .98540 08/27/2007 6,600 4,220 2.83 2.81 .99 AFF .01 3.66 3.89 .94 .99 4,443 1.05543 01/11/2008 3,010 1,570 1.14 -.49 -.43 AFF 1.43 5.33 2.80 1.91 1.87 1,542 .98544 02/22/2008 1,980 920 .98 -1.87 -1.91 AFF 2.91 3.92 2.65 1.48 1.55 966 1.05545 03/26/2008 3,850 2,050 1.25 .06 .05 AFF .95 6.06 2.89 2.10 1.86 1,815 .89546 04/16/2008 5,510 3,140 2.00 1.81 .90 AFF .10 4.59 3.43 1.34 1.32 3,110 .99547 06/11/2008 4,560 2,540 1.66 1.12 .67 AFF .33 4.91 3.21 1.53 1.55 2,580 1.02548 06/20/2008 6,030 3,550 2.33 2.18 .94 AFF .06 4.12 3.62 1.14 1.19 3,698 1.04

IDNR 09/16/2008 2,936 --- 1.60 -.54 -.34 AFF 1.34 --- 3.16 --- 1.16 1,798 ---

1Ratio of measured and computed COS.Black plain text indicates free-weir or no flow conditions.Green bold text indicates “Affected” conditions with h3OS/h1OS ranging from -0.5 to 0.65.Black bold italic text indicates “Affected” conditions with h3OS/h1OS greater than 0.65.Blue italic text indicates “Affected” conditions with h3OS/h1OS less than -0.5 and greater than -5.0.
Algonquin Control-Structure Ratings 33

Table 14. Hinged-crest gate weir-flow characteristics and coefficients at Algonquin, Illinois. [USGS, U.S. Geological Survey; Meas., Measured; ft3/s, cubic foot per second; hgHCG , hinged-crest gate opening referenced to the broad-crested-weir crest; ft, foot; h1HCG , headwater depth above the hinged-crest gate crest; h3HCG , tailwater depth above the hinged-crest gate crest; pHCG, height of hinged-crest gate crest above approach invert; CHCG, free-weir coefficient for the hinged-crest gate; Comp., computed; CHCG-S, submerged-weir coefficient for the hinged-crest gate; C/M, ratio of computed and measured flow; FW, free-weir flow; SW, submerged-weir flow; IDNR, Illinois Department of Natural Resources–Office of Water Resources; OS, ogee spillway; HCG, hinged-crest gate; ---, not determined]

USGS

measurement

number Date

Hinged-crest gate

Meas.

flow1 (M)

 (ft3/s)

 Gate 

opening 

hgHCG (ft) h1HCG (ft) h3HCG (ft) (h3HCG-h1HCG)

Flow 

regime

(h1HCG-h3HCG)

/ h1HCG pHCG (ft) (h1HCG-pHCG)

Meas.

CHCG

Comp.

CHCG

Meas.2

CHCG-S

Comp.

CHCG-S

Comp.

flow (C)

(ft3/s) C/M

--- 11/19/2002 710 2.0 2.47 -0.85 -0.344 FW 1.34 4.52 0.55 3.66 3.65 --- --- 709 ------ 11/19/2002 1,389 4.0 4.16 2.15 .517 FW .48 2.52 1.65 3.27 3.09 --- --- 1,309 ------ 11/20/2002 1,800 6.0 5.98 4.57 .764 FW .24 .52 11.50 2.46 2.30 --- --- 1,680 ---

523 05/18/2004 1,100 1.0 3.24 1.04 .321 FW .68 5.52 .59 3.77 3.61 --- --- 1,053 0.96522 05/18/2004 1,400 1.8 3.80 2.20 .579 FW .42 4.76 .80 3.78 3.45 --- --- 1,276 .91521 05/18/2004 1,550 2.4 4.34 3.07 .707 FW .29 4.12 1.05 3.43 3.30 --- --- 1,494 .96524 05/24/2004 2,240 6.0 8.04 7.99 .994 SW .01 .52 15.46 1.97 2.20 0.89 0.88 2,215 .99531 02/02/2006 750 2.0 2.86 -.39 -.136 FW 1.14 4.52 .63 3.10 3.57 --- --- 863 1.15533 03/17/2006 1,610 4.0 5.07 3.51 .692 FW .31 2.52 2.01 2.82 2.99 --- --- 1,709 1.06532 03/17/2006 1,910 5.0 5.93 4.80 .809 SW .19 1.52 3.90 2.65 2.71 .98 .97 1,905 1.00534 05/31/2006 940 2.0 3.04 -.59 -.194 FW 1.19 4.52 .67 3.55 3.54 --- --- 937 1.00537 03/14/2007 1,560 4.0 5.26 3.75 .713 FW .29 2.52 2.09 2.59 2.98 --- --- 1,796 1.15539 08/22/2007 2,090 6.0 7.85 7.62 .971 SW .03 .52 15.10 1.90 2.20 .86 .89 2,168 1.04540 08/27/2007 2,380 6.0 8.83 8.81 .998 SW .002 .52 16.98 1.81 2.17 .84 .88 2,508 1.05543 01/11/2008 1,440 3.5 4.64 3.01 .649 FW .35 3.02 1.54 2.88 3.12 --- --- 1,559 1.08544 02/22/2008 1,060 2.0 2.98 .13 .044 FW .96 4.52 .66 4.12 3.55 --- --- 913 .86545 03/26/2008 1,800 4.0 5.25 4.06 .773 SW .23 2.52 2.08 2.99 2.98 1.00 1.00 1,784 .99546 04/16/2008 2,370 6.0 8.00 7.81 .976 SW .02 .52 15.38 2.09 2.20 .95 .89 2,218 .94547 06/11/2008 2,020 6.0 7.66 7.12 .930 SW .07 .52 14.73 1.91 2.21 .86 .91 2,141 1.06548 06/20/2008 2,480 6.0 8.33 8.18 .982 SW .02 .52 16.02 2.06 2.18 .94 .89 2,336 .94

IDNR 09/16/2008 1,138 2.0 3.60 1.46 .406 FW .59 4.52 .80 3.33 3.45 --- --- 1,177 ---

1November 2002 and September 16, 2008, “measured” values determined by subtracting the computed OS flow from the measured total OS and HCG flow.2Ratio of measured and computed CHCGBlack plain text indicates free-weir conditions.Red bold text indicates submerged conditions.
34 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Figure 25. Discharge coefficient for free-weir flow, and the ratio of headwater depth and 

gate height for the hinged-crest gate on the Fox River at Algonquin, Illinois, (R2, coefficient of 

determination).

Figure 26. Discharge coefficient for submerged-weir flow, and the ratio of headwater and 

tailwater depth for the hinged-crest gate on the Fox River at Algonquin, Illinois, (R2, coefficient 

of determination).

1

10

0.1 1.0 10.0 100.0

RATIO OF HEADWATER DEPTH AND GATE HEIGHT ( ) h 1HCG /pHCG

FREE-WEIR COEFFICIENT ( ) CHCG

R2 = 0.69

CHCG = 3.33( ( h1HCG

pHCG

-0.152

0.1 1.0

RATIO OF TAILWATER AND HEADWATER DEPTH ( ) h 3HCG /h1HCG

SUBMERGED-WEIR COEFFICIENT ( ) CHCG S0.1

1.0

10.0

R2 = 0.69

CHCG-S = 0.882( ( h3HCG

h1HCG

-0.472
Algonquin Control-Structure Ratings 35

Table 15. Measured and computed flows for the ogee spillway and hinged-crest gate on the Fox River at Algonquin, Illinois. 

[USGS, U.S. Geological Survey; OS, ogee spillway; ft3/s, cubic foot per second; C/M, ratio of computed and measured flow; HCG, hinged-crest 

gate; IDNR, Illinois Department of Natural Resources–Office of Water Resources; ---, not determined]

USGS 

measurement 

number Date

OS HCG Total OS and HCG flow

Measured 

flow (M) 

(ft3/s)

Computed 

flow (C) 

(ft3/s) C/M

Measured 

flow1 (M) 

(ft3/s)

Computed 

flow (C) 

(ft3/s) C/M

Measured 

flow (M) 

(ft3/s)

Computed 

flow (C) 

(ft3/s) C/M

--- 11/19/2002 --- 158 --- 710 709 --- 868 867 1.00

--- 11/19/2002 --- 21 --- 1,389 1,309 --- 1,410 1,330 .94

--- 11/20/2002 --- 0 --- 1,800 1,680 --- 1,800 1,680 .93

523 05/18/2004 2,470 2,306 0.93 1,100 1,053 0.96 3,570 3,359 .94

522 05/18/2004 2,330 2,369 1.02 1,400 1,276 .91 3,730 3,646 .98

521 05/18/2004 2,340 2,481 1.06 1,550 1,494 .96 3,890 3,974 1.02

524 05/24/2004 3,340 3,078 .92 2,240 2,215 .99 5,580 5,292 .95

531 02/02/2006 830 827 1.00 750 863 1.15 1,580 1,690 1.07

533 03/17/2006 1,550 1,532 .99 1,610 1,709 1.06 3,160 3,241 1.03

532 03/17/2006 1,410 1,425 1.01 1,910 1,905 1.00 3,320 3,330 1.00

534 05/31/2006 1,060 1,046 .99 940 937 1.00 2,000 1,984 .99

537 03/14/2007 1,660 1,843 1.11 1,560 1,796 1.15 3,220 3,639 1.13

539 08/22/2007 2,910 2,856 .98 2,090 2,168 1.04 5,000 5,025 1.00

540 08/27/2007 4,220 4,443 1.05 2,380 2,508 1.05 6,600 6,951 1.05

543 01/11/2008 1,570 1,542 .98 1,440 1,559 1.08 3,010 3,101 1.03

544 02/22/2008 920 966 1.05 1,060 913 .86 1,980 1,879 .95

545 03/26/2008 2,050 1,815 .89 1,800 1,784 .99 3,850 3,599 .93

546 04/16/2008 3,140 3,110 .99 2,370 2,218 .94 5,510 5,328 .97

547 06/11/2008 2,540 2,580 1.02 2,020 2,141 1.06 4,560 4,721 1.04

548 06/20/2008 3,550 3,698 1.04 2,480 2,336 .94 6,030 6,034 1.00

IDNR 09/16/2008 --- 1,798 --- 1,138 1,177 --- 2,936 2,975 1.01

1

November 2002 and September 16, 2008, “measured” values determined by subtracting the computed OS flow from the measured total OS and HCG 

flow.

Figure 27. Measured and computed flows for the ogee spillway and hinged-crest gate on the Fox River at Algonquin, Illinois, 

(OS, ogee spillway; HCG, hinged-crest gate).

Line of perfect agreement Line of perfect agreement Line of perfect agreement

0

2,000

4,000

6,000

8,000

0 2,000 4,000 6,000 8,000

OS and HCG MEASURED STREAMFLOW ,

IN CUBIC FEET PER SECOND

OS and HCG COMPUTED STREAMFLOW ,

IN CUBIC FEET PER SECOND

0

1,000

2,000

3,000

4,000

5,000

0 1,000 2,000 3,000 4,000 5,000

OS MEASURED STREAMFLOW, IN CUBIC FEET PER SECOND

OS COMPUTED STREAMFLOW, IN CUBIC FEET PER SECOND

0

1,000

2,000

3,000

0 1,000 2,000 3,000

HCG MEASURED STREAMFLOW, IN CUBIC FEET PER SECOND

HCG COMPUTED STREAMFLOW, IN CUBIC FEET PER SECOND
36 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Example Calculations

The following are examples of how flow was calculated 

using equations in table 11 and table 12.

Example 1: The following conditions exist:

Headwater pool stage is 1.37 ft, tailwater pool stage is 

6.64 ft, and the flow over the hinged-crest gate is zero because 

the crest is closed to an elevation above the ogee spillway and 

(or) the bulkheads are closed. See figure 21 for a schematic.

Flow is determined by first converting the stages to 

depths above the crest of the ogee spillway. This is done by 

subtracting the difference between the crest of the spillway 

(730.10 ft) and headwater gage datum (729.48 ft) from the 

headwater stage and then subtracting the difference between 

the spillway crest and tailwater gage datum (719.48 ft) from 

the tailwater stage.

h1OS = 1.37 - (730.10 - 729.48) = 0.75 ft 

h3OS = 6.64 - (730.10 - 719.48) = -3.98 ft 

Because h3OS / h1OS (-3.98/0.75=-5.31) is less than 0.60 and the 

hinged-crest gate is closed, free-weir flow exists for the spillway and there is zero flow over the gate.

Using equation 24 from table 11,

Q h OS OS  646 1 1

1 863 . .

= 646.1(0.75)1.863

= 378.0 ft3 / s .

Therefore the total flow is 

QTOTAL = QOS = 378.0 ft3 / s 

Example 2: The following conditions exist:

Headwater pool stage is 1.86 ft, tailwater pool stage is 

7.96 ft, there is flow over the hinged-crest gate because the 

crest is at the same elevation as the crest of the ogee spillway.

Flow is determined by first converting the pool stages to 

depths above the crest of the spillway, as in example 1.

h1OS = 1.86 - 0.62 = 1.24 ft 

h3OS = 7.96 - 10.62 = -2.66 ft 

Because h3OS / h1OS (-2.66/1.24=-2.15) is less than 0.60 and the 

crest of the hinged-crest gate is the same elevation as the crest 

of the spillway, free-weir flow exists for the spillway and there 

is flow over the gate.

Using equation 27 from table 11,

Q h S OS  683 3 1

2 046 . .

= 683.3(1.24)2.046

= 1061 ft3 / s .

Therefore the total flow is 

QTOTAL = QS = 1061 ft3 / s 

Example 3: The following conditions exist:

Headwater pool stage is 0.78 ft, tailwater pool stage is 

8.77 ft, and the hinged-crest gate opening is 4.0 ft.

Flow over the spillway is determined by first converting 

the stages to depths above the crest of the spillway.

h1OS = 0.78 - 0.62 = 0.16 ft 

h3OS = 8.77 - 10.62 = -1.85 ft 

Because h3OS / h1OS (-1.85/0.16=-11.56) is less than -5.0 and the 

hinged-crest gate is open, free-weir flow exists.

Using equation 24 from table 11,

Q h OS OS  646 1 1

1 863 . .

= 646.1(0.16)1.863

= 21.26 ft3 / s .

Flow over the gate is determined by first converting the 

stages to depths above the crest of the gate. This is done by 

subtracting the difference between headwater gage datum 

(729.48 ft) and the elevation of the gate crest (730.10 ft - hgHCG ) 

from the headwater stage and then subtracting the difference 

between the tailwater gage datum (719.48 ft) and the elevation 

of gate crest from the tailwater stage.

h1HCG = 0.78 - [(730.10 - 4.00) - 729.48] = 4.16 ft 

h3HCG = 8.77 - [(730.10 - 4.00) - 719.48] = 2.15 ft 

Because h3HCG / h1HCG (2.15/4.16=0.52) is less than 0.77, freeweir flow exists. Before calculating flow, the depth from the 

concrete slab to the crest of the gate must be determined by 

calculating the difference between the gate crest elevation 

(730.10 ft - hgHCG ) and the elevation of the top of the concrete 

slab (723.58).

pHCG = (730.10 - 4.00) - 723.58 = 2.52 ft. 

Using equation 32 from table 12,

Q h p HCG HCG HCG  166 5 1

1 348 0 152 . . .

= 166.5(4.16)1.348(2.52)0.152

= 1309 ft3 / s ,

Therefore the total flow is 

QTOTAL = 21.26 + 1309 = 1330 ft3 / s 
Acknowledgments 37

Example 4: The following conditions exist:

Headwater pool stage is 2.45 ft, tailwater pool stage is 

12.22 ft, and the hinged-crest gate opening is 6.0 ft.

Flow over the spillway is determined by first converting 

the stages to depths above the crest of the spillway.

h1OS = 2.45 - 0.62 = 1.83 ft 

h3OS = 12.22 - 10.62 = 1.60 ft 

Because h3OS / h1OS (1.60/1.83=0.87) is between -5.0 and 1 and 

the hinged-crest gate is open, affected flow exists. For affected 

flow, the values of h1HCG , h3HCG , and pHCG must be determined.

h1HCG = 2.45 - [(730.10 - 6.0) - 729.48] = 7.83 ft 

h3HCG = 12.22 - [(730.10 - 6.0) - 719.48] = 7.60 ft 

pHCG = (730.10 - 6.0) - 723.58 = 0.52 ft. 

Using equation 30 from table 11,

Q h p h h

h h

h OS OS HCG OS OS

HCG HCG

HC

=   − − 285 5 1

0 933 0 149

1 3

0 930 1 3

1

. . . .

G

−0.905 











  









 (7.83)

= 285.5(1.83)0.933 (0.52)0.149 (1.83)−(1.60) 0.930 (7.83)−(7.60)

−0.905

= 2825 ft3 / s .

Because h3HCG / h1HCG (7.60/7.83 = 0.97) is greater than 0.77, 

submerged-weir flow exists. *Note: there are instances when 

free-weir flow, rather than submerged-weir flow, exists over 

the gate while the spillway experiences affected flow. 

Refer to example 3 for calculations of free-weir flow over 

the hinged-crest gate.

Using equation 34 from table 12,

Q h h p HCG HCG HCG HCG  − 146 9 1

1 820

3

0 472 0 152 . . . .

= 146.9(7.83) 1.820(7.60)-0.472 (0.52)0.152 

= 2162 ft3 / s ,

Therefore the total flow is 

QTOTAL = 2825 + 2162 = 4987 ft3 / s 

Summary

The Illinois Department of Natural Resources–Office 

of Water Resources operates control structures on a reach 

of the Fox River in northeastern Illinois between McHenry 

and Algonquin. These structures are used to maintain water 

levels in the river for flood-control and recreational purposes. 

The McHenry control structure is at river mile 97.8 and has 

a drainage area of 1,250 square miles (mi2). The Algonquin 

control structure is at river mile 81.6 and has a drainage 

area of 1,403 mi2. This report documents the effects of the 

hinged-crest gates, a broad-crested weir, sluice gates, and an 

ogee spillway on the Fox River control-structure ratings at 

McHenry and Algonquin.

The Fox River control-structure ratings were determined by measuring headwater and tailwater stage along with 

streamflow at a wide range of flows at different gate openings. 

Standard control-structure rating techniques were used to rate 

each structure. 

The control structures at McHenry consist of a 

221-feet (ft) broad-crested weir, a 4-ft-wide fish ladder, 

a 50-ft wide hinged-crest gate, five 13.75-ft-wide sluice gates, 

and a navigational lock. Sixty measurements were used to 

rate the McHenry control structures. The flow regime for the 

broad-crested weir included free weir, and the hinged-crest 

gate included both free and submerged weir. The flow regimes 

for the sluice gate included free and submerged weir and free 

and submerged orifice. 

The control structures at Algonquin, consist of a 242-ft 

ogee spillway and a 50-ft-wide hinged-crest gate. Forty-one 

measurements were used to rate the Algonquin control structures. The flow regimes for the ogee spillway included both 

free and affected weir. The flow regimes for the hinged-crest 

gate included free and submerged weir. 

Acknowledgments

Arlan Juhl, Rick Gosch, Rita Lee, and Bill Milner 

(IDNR–OWR) supported use of advanced methodologies on 

this study. Rita Lee—along with former and current McHenry 

Lockmasters, Frank Novak, Jr. and John Palmieri, respectively—helped with gate openings to provide various flow 

regimes. Technical assistance also was provided by the following USGS employees: Jennifer Sharpe (report illustration 

development); and Jay Angel, David Schrader, Shawn 

Cutshaw, Perry Draper, Kevin Johnson, Ryan Beaulin, and 

James Duncker (streamflow measurements). Technical reviews 

of the report were provided by Rita Lee, IDNR-OWR, and 

Gregory Fisk, USGS Arizona Water Science Center.
38 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

References Cited

Chow, V.T., 1959, Open channel hydraulics: New York, 

McGraw-Hill, 680 p.

Collins, D.L., 1977, Computation of records of streamflow at 

control structures: U.S. Geological Survey Water-Resources 

Investigation Report 77–8, 57 p.

Fisk, G.G., 1988, Discharge ratings for control structures at 

McHenry Dam on the Fox River, Illinois: U.S. Geological 

Survey Water-Resources Investigations Report 87–4226, 24 p.

Franz, D.D., and Melching, C.S., 1997a, Full Equations (FEQ) 

model for the solution of the full, dynamic equations of motion 

for one-dimensional unsteady flow in open channels and 

through control structures: U.S. Geological Survey 

Water-Resources Investigations Report 96–4240, 258 p.

Franz, D.D., and Melching, C.S., 1997b, Full equations utilities (FEQUTL) model for the approximation of hydraulic 

characteristics of open channels and control structures during 

unsteady flow: U.S. Geological Survey Water-Resources 

Investigations Report 97-4037, 205 p.

Illinois Department of Natural Resources–Office of Water 

Resources, 1999, Fox River Project FEQ Model—Lake, 

McHenry, and Kane Counties [variously paged].

Illinois Department of Transportation–Division of Water 

Resources,1992, Fox River Project FEQ Model: Lake, 

McHenry, and Kane Counties, 114 p.

Ishii, A.L., and Turner, M.J., 1996, Verification of a one-dimensional, unsteady-flow model for the Fox River in Illinois: 

U.S. Geological Survey Water-Supply Paper 2477, 65 p.

Knapp, H.V., and Ortel, T.W., 1992, Effect of Stratton Dam 

operation on flood control along the Fox River and Fox Chain 

of Lakes: Illinois State Water Survey Contract Report 533, 

79 p.

Matthai, H.F., 1967, Measurement of peak discharge at width 

contractions by indirect methods: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 3, 

chap. A4, 44 p.

Roberson, J.A., Cassidy, J.J., and Chaudhry, M.H., 1998, 

Hydraulic engineering (2d ed.): New York, Wiley, 653 p.
Appendixes 39

Appendixes A–F
40 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Appendix A: Fox River near McHenry, Illinois, Headwater and Tailwater 

Stages for Broad-Crested Weir and Hinged-Crest Gate Measurements.

[USGS, U.S. Geological Survey; ft, foot; BCW, Broad-Crested Weir; HCG, Hinged-Crest Gate; ft3/s, cubic foot per second;

 hg

HCG , hinged-crest gate opening referenced to the broad-crested-weir crest; ---, not applicable]

USGS

measurement

mumber Date

Central

Standard

Time

Water surface Measured

BCW and (or) 

HCG Flow

 (ft3/s)

 Gate 

opening 

hgHCG (ft)

Headwater Tailwater

Stage (ft) Elevation (ft) Stage (ft) Elevation (ft)

5 05/16/1985 1350 4.05 737.05 1.35 731.50 169 ---

13 08/28/1986 1500 4.23 737.23 1.05 731.20 342 ---

15 09/27/1986 1345 5.34 738.34 6.12 736.27 1,880 ---

20 09/30/1986 1120 5.90 738.90 6.98 737.13 2,990 ---

44 11/18/2002 1436–1521 4.16 737.16 .93 731.08 565 1.0

45 11/19/2002 0830–0915 3.98 736.98 1.61 731.76 1,012 2.2

46 11/19/2002 1339–1440 3.62 736.62 1.60 731.75 1,345 4.1

47 11/20/2002 0922–1004 3.21 736.21 2.12 732.27 1,775 6.0

A48 04/04/2003 1127–1217 4.11 737.11 1.30 731.45 145 0.0

49 05/17/2004 1134–1155 4.30 737.30 3.50 733.65 803 1.0

B50 05/17/2004 1509–1537 4.06 737.06 3.78 733.93 1,240 2.0

51 05/17/2004 1703–1728 3.80 736.80 3.99 734.14 2,040 5.0

52 05/24/2004 0800–0838 4.04 737.04 5.85 736.00 1,820 6.0

53 03/17/2006 1033–1048 2.64 735.64 3.77 733.92 1,077 4.0

C54 03/17/2006 1551–1628 3.37 736.37 3.31 733.46 401 2.0

D55 03/16/2007 1055–1113 2.64 735.64 4.32 734.47 1,132 4.5

56 08/22/2007 1010–1024 3.67 736.67 5.58 735.73 1,710 6.0

57 08/27/2007 1012–1026 4.83 737.83 7.03 737.18 2,550 6.0

58 03/26/2008 1113–1129 2.48 735.48 4.38 734.53 1,440 5.5

59 04/16/2008 1201–1220 4.16 737.16 6.04 736.19 1,930 6.0

60 06/20/2008 0728–0740 4.76 737.76 6.78 736.93 2,450 6.0

ANo flow over hinged-crest gate. All other measurements from 2002–2008 had flow over the hinged-crest gate.

BHinged-crest gate opening changed 30 minutes before measurement; measurement not used in equation development.

COutlier, measurement not used in equation development.

DTotal flow (BCW, HCG, and SL) measured without a separate measurement of sluice gate flow. The sluice gate flow is calculated and subtracted from 

total flow.
Appendix B 41

Appendix B: Fox River near McHenry, Illinois, Headwater and Tailwater 

Stages for Sluice Gate Measurements.—Continued

[USGS, U.S. Geological Survey; hgSL , sluice gate opening; ft, foot; ft3/s, cubic foot per second]

USGS 

measurement 

number Date

Central

Standard

Time

Gate 

opening

hgSL (ft)

Gates 

open

Headwater Tailwater

Measured

Flow

(ft3 Stage (ft) /s)

Elevation 

(ft) Stage (ft)

Elevation 

(ft)

1 03/22/1985 1250 4.0 5 3.51 736.51 3.90 734.05 2,790

2 03/22/1985 1400 3.0 5 3.68 736.68 3.70 733.85 1,990

3 03/26/1985 1230 3.8 5 2.64 735.64 3.45 733.60 2,100

4 03/26/1985 1430 3.3 5 2.71 735.71 3.42 733.57 1,850

6 05/16/1985 1350 .6 5 4.03 737.03 1.35 731.50 448

7 10/04/1985 1205 2.5 4 4.05 737.05 2.75 732.90 1,460

8 11/04/1985 1026 3.15 4 3.98 736.98 2.82 732.97 1,830

9 03/17/1986 1350 6.5 5 4.31 737.31 5.03 735.18 3,230

10 04/22/1986 1105 1.2 5 3.23 736.23 1.71 731.86 833

B11 04/22/1986 1340 2.0 4 3.13 736.13 1.85 732.00 1,180

B11 04/22/1986 1340 1.0 1 3.13 736.13 1.85 732.00 0

12 05/23/1986 115 1.2 5 4.16 737.16 2.25 732.40 967

14 08/28/1986 1500 .2 5 4.22 737.22 1.05 731.20 180

16 09/27/1986 1530 4.0 5 5.35 738.35 6.15 736.30 3,045

17 09/27/1986 1710 7.0 5 5.20 738.20 6.25 736.40 4,054

18 09/27/1986 1805 4.9 5 5.22 738.22 6.25 736.40 3,600

19 09/27/1986 1850 4.5 5 5.26 738.26 6.30 736.45 3,320

21 09/30/1986 1345 4.0 5 5.90 738.90 6.98 737.13 2,600

22 09/30/1986 1505 4.5 5 5.86 738.86 6.98 737.13 2,920

23 10/15/1986 1040 7.0 5 4.25 737.25 5.10 735.25 3,270

24 11/01/1990 936 1.0 5 2.59 735.59 1.32 731.47 636

25 11/01/1990 1137 .1 5 2.67 735.67 1.11 731.26 63.9

26 11/01/1990 1350 .1 5 2.63 735.63 1.05 731.20 74.4

27 11/02/1990 1243 .1 5 2.68 735.68 .58 730.73 73.9

28 11/03/1990 825 .1 5 2.91 735.91 .45 730.60 74.1

29 11/04/1990 815 .1 5 3.17 736.17 .35 730.50 75.0

30 11/04/1990 1355 .1 5 3.17 736.17 .35 730.50 75.9

31 11/05/1990 1024 .1 5 3.56 736.56 .40 730.55 82.6

32 11/05/1990 1812 2.5 5 2.84 735.84 1.74 731.89 1,340

33 11/05/1990 2035 2.5 5 2.76 735.76 1.89 732.04 1,310

34 11/06/1990 230 2.5 5 2.66 735.66 2.19 732.34 1,370

35 11/06/1990 1300 2.5 5 2.60 735.60 2.38 732.53 1,500

36 11/07/1990 1049 2.5 5 2.69 735.69 2.52 732.67 1,360

37 11/07/1990 1430 2.5 5 2.69 735.69 2.52 732.67 1,510

BFour gates were set to 2.0 ft, and one gate was set to 1.0 ft. Equations developed in this study were used to subtract flow from the gate open to 

1.0 ft; a coefficient for a 2.0 ft opening was determined from the measurement.
42 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Appendix B: Fox River near McHenry, Illinois, Headwater and Tailwater 

Stages for Sluice Gate Measurements.—Continued

[USGS, U.S. Geological Survey; hgSL , sluice gate opening; ft, foot; ft3/s, cubic foot per second]

USGS 

measurement 

number Date

Central

Standard

Time

Gate 

opening

hgSL (ft)

Gates 

open

Headwater Tailwater

Measured

Flow

(ft3 Stage (ft) /s)

Elevation 

(ft) Stage (ft)

Elevation 

(ft)

38 11/07/1990 1640 2.5 5 2.69 735.69 2.56 732.71 1,480

39 11/08/1990 1202 2.5 5 2.71 735.71 2.60 732.75 1,480

40 11/08/1990 1200 2.5 5 2.71 735.71 2.60 732.75 1,580

41 11/09/1990 947 2.5 5 2.69 735.69 2.58 732.73 1,460

42 04/24/1993 1100 6.0 5 5.17 738.17 3.24 733.39 3,920

43 04/28/1993 845 6.0 5 4.98 737.98 2.78 732.93 3,664

49 05/17/2004 1244–1257 2.2 5 4.29 737.29 3.50 733.65 1,760

50 05/17/2004 1434–1447 2.2 5 4.10 737.10 3.74 733.89 1,690

51 05/17/2004 1759–1811 2.2 4 3.77 736.77 4.00 734.15 1,250

52 05/24/2004 0902–0919 5.7 5 4.04 737.04 5.85 736.00 3,020

53 03/17/2006 1033–1048 3.0 5 2.64 735.64 3.77 733.92 1,664

54 03/17/2006 1536–1546 3.0 5 3.37 736.37 3.31 733.46 1,890

56A 08/22/2007 1122–1130 5.0 5 3.73 736.73 5.59 735.74 2,760

57A 08/27/2007 1107–1116 6.2 5 4.83 737.83 7.03 737.18 3,140

58A 03/26/2008 1248–1258 4.5 5 2.47 735.47 4.36 734.51 1,970

59A 04/16/2008 1306–1319 5.3 5 4.14 737.14 6.02 736.17 2,960

60A 06/20/2008 0848–0854 6.0 5 4.75 737.75 6.76 736.91 3,280

BFour gates were set to 2.0 ft, and one gate was set to 1.0 ft. Equations developed in this study were used to subtract flow from the gate open to 

1.0 ft; a coefficient for a 2.0 ft opening was determined from the measurement.
Appendix C 43

Appendix C. Fox River at Algonquin, Illinois, Headwater and Tailwater 

Stages for Ogee Spillway and Hinged-Crest Gate Measurements with the 

Hinged-Crest Gate Closed.

[USGS, U.S. Geological Survey; ft, foot; ft3/s, cubic foot per second; measurements in bold indicate that the hinged-crest gate was closed, and 

no flow was overtopping it; ---, not determined] 

USGS

measurement

number Date Time

Water-surface elevation

Measured 

flow (M)

(ft3/s)

Flow over

hingedcrest gate

Headwater (HW) Tailwater (TW)

Stage (ft) Elevation (ft) Stage (ft) Elevation (ft)

A505 03/26/2002 0803–1020 2.00 731.48 --- --- 1,180 No

A506 04/11/2002 0845–1015 2.76 732.24 --- --- 2,600 No

A507 06/11/2002 0915–1100 2.99 732.47 --- --- 3,260 No

A508 07/23/2002 1250–1350 1.24 730.72 --- --- 280 No

509 09/24/2002 1330–1440 1.58 731.06 6.98 726.46 577 No

510 11/07/2002 1405–1510 1.37 730.85 6.64 726.12 381 No

511 01/09/2003 1125–1235 1.38 730.86 7.10 726.58 406 Yes

B512 03/12/2003 1145–1230 1.17 730.65 6.47 725.95 267 Yes

513 05/05/2003 1040–1140 1.86 731.34 7.96 727.44 1,060 Yes

514 05/07/2003 0950–1140 2.26 731.74 8.81 728.29 1,960 Yes

515 06/18/2003 0800–0900 1.43 730.91 6.88 726.36 473 Yes

516 09/03/2003 1255–1355 .94 730.42 6.05 725.53 76.5 No

517 10/15/2003 0815–0920 1.17 730.65 6.77 726.25 203 No

518 12/02/2003 1130–1240 1.54 731.02 7.13 726.61 605 Yes

B519 02/02/2004 1525–1615 1.34 730.82 6.62 726.10 382 Yes

520 03/23/2004 1300–1450 1.82 731.30 7.77 727.25 989 Yes

C525 07/08/2004 1145–1420 1.76 731.24 7.88 727.36 1,240 Yes

526 09/14/2004 1010–1135 1.29 730.77 6.39 725.87 301 No

527 11/08/2004 1120–1320 1.74 731.22 7.16 726.64 800 Yes

528 03/10/2005 1200–1400 2.11 731.59 8.10 727.58 1540 Yes

529 06/28/2005 1035–1200 1.03 730.51 6.17 725.65 121 No

530 10/04/2005 0850–1005 1.27 730.75 6.45 725.93 294 No

535 07/28/2006 0830–0930 1.34 730.82 6.55 726.03 368 No

536 10/02/2006 1010–1140 1.46 730.94 6.59 726.07 429 Yes

D538 06/28/2007 1009–1023 1.65 731.13 7.06 726.54 801 ---

E541 11/09/2007 1043–1056 1.53 731.01 7.09 726.57 703 ---

E542 12/17/2007 1354–1409 1.74 731.22 7.59 727.07 1,140 ---

ATailwater gage was not yet installed. Flow-regime conditions are considered free weir for computations.

BIce-affected measurement, not used in equation development.

COutlier, measurement not used in equation development.

DHinged-crest gate opening changed 20 minutes before measurement, not used in equation development.

EHinged-crest gate repairs, measurement not used in equation development.
44 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Appendix D. Fox River at Algonquin, Illinois, Headwater and Tailwater 

Stages for Ogee Spillway and Hinged-Crest Gate Measurements with the 

Hinged-Crest Gate Open.

[USGS, U.S. Geological Survey; ft,foot; ft3/s, cubic foot per second; hgHCG , hinged-crest gate opening referenced to the broad-crested-weir crest; 

IDNR, Illinois Department of Natural Resources–Office of Water Resources; ---, not determined] 

USGS

measurement

number Date

Central

Standard

Time

Water-surface elevation Measured

OS and (or) 

HCG flow

(ft3/s)

Gate 

opening 

hgHCG (ft)

Headwater (HW) Tailwater (TW)

Stage (ft) Elevation (ft) Stage (ft) Elevation (ft)

--- 11/19/2002 1118–1200 1.09 730.57 7.77 727.25 868 2.0

--- 11/19/2002 1649–1735 .78 730.26 8.77 728.25 1,410 4.0

--- 11/20/2002 1220–1310 .60 730.08 9.19 728.67 1,800 6.0

523 05/18/2004 1313–1328 2.86 732.34 10.66 730.14 3,570 1.0

522 05/18/2004 0821–0841 2.66 732.14 11.06 730.54 3,730 1.8

521 05/18/2004 0659–0722 2.56 732.04 11.29 730.77 3,890 2.4

524 05/24/2004 1234–1253 2.66 732.14 12.61 732.09 5,580 6.0

531 02/02/2006 0959–1011 1.48 730.96 8.23 727.71 1,580 2.0

533 03/17/2006 1402–1435 1.69 731.17 10.13 729.61 3,160 4.0

532 03/17/2006 1210–1247 1.55 731.03 10.42 729.90 3,320 5.0

534 05/31/2006 1156–1216 1.66 731.14 8.03 727.51 2,000 2.0

537 03/14/2007 1332–1350 1.88 731.36 10.37 729.85 3,220 4.0

539 08/22/2007 1327–1341 2.47 731.95 12.24 731.72 5,000 6.0

540 08/27/2007 1311–1328 3.45 732.93 13.43 732.91 6,600 6.0

543 01/11/2008 1033–1047 1.76 731.24 10.13 729.61 3,010 3.5

544 02/22/2008 1232–1243 1.60 731.08 8.75 728.23 1,980 2.0

545 03/26/2008 0912–0941 1.87 731.35 10.68 730.16 3,850 4.0

546 04/16/2008 1038–1053 2.62 732.10 12.43 731.91 5,510 6.0

547 06/11/2008 0948–1005 2.28 731.76 11.74 731.22 4,560 6.0

548 06/20/2008 0954–1007 2.95 732.43 12.80 732.28 6,030 6.0

IDNR 09/16/2008 1130 2.22 731.70 10.08 729.56 2,936 2.0
Appendix E 45

Appendix E: Photographs of Various Flow Conditions, 

Fox River near McHenry, Illinois

Acronyms

BCW – broad-crested weir

FW – free-weir flow 

HCG – hinged-crest gate

NF – no flow

SW – submerged-weir flow

Figure E1. Looking from left to 

right at tailwater conditions for 

sluice gates, December 1, 2003.
46 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Figure E2. Looking at the 

upstream face of open hingedcrest gate, measurement 58, 

March 26, 2008. 

HCG flow regime=SW.

Figure E3. Looking at 

tailwater conditions of 

open hinged-crest gate, 

measurement 58, March 26, 

2008. HCG flow regime=SW. 

BCW flow regime=NF.
Appendix E 47

Figure E4. Looking from 

right to left at headwater 

conditions for open hingedcrest gate and weir, 

measurement 58, March 26, 

2008. HCG flow regime=SW. 

BCW flow regime=NF.

Figure E5. Looking from left 

to right at tailwater conditions 

for sluice gates, measurement 

58A, March 26, 2008. 

Sluice gate flow regime=FW.
48 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Figure E6. Looking from 

right to left at headwater 

conditions for sluice gates, 

measurement 59A, 

April 16, 2008. 

Sluice gate flow regime=SW.

Figure E7. Looking from 

right to left at hinged-crest 

gate and weir, showing both 

headwater and tailwater 

conditions, measurement 59, 

April 16, 2008. 

HCG flow regime=SW. 

BCW flow regime=FW
Appendix F 49

Appendix F: Photographs of Various Flow Conditions, 

Fox River at Algonquin, Illinois

Acronyms

AFF – affected flow 

FW – free-weir flow 

FW-FL – free-weir flow with flow over the hinged-crest gate (crest at elevation of ogee spillway)

FW-NF – free-weir flow with no flow over the hinged-crest gate

HCG – hinged-crest gate

NF – no flow

OS – ogee spillway

SW – submerged-weir flow

Figure F1. Looking at the downstream face of the 

hinged-crest gate, measurement 506, April 11, 2002. 

Flow regime=FW-NF.

Figure F2. Looking from right to left at both 

headwater and tailwater conditions, measurement 

506, April 11, 2002. Flow regime=FW-NF.
50 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Figure F3. Looking from right to left at tailwater 

conditions, measurement 506, April 11, 2002. 

Flow regime=FW-NF.

Figure F4. Looking downstream at hinged-crest 

gate and spillway from bridge, measurement 506, 

April 11, 2002. 

Flow regime=FW-NF.
Appendix F 51

Figure F5. Looking from right to left at headwater and tailwater 

conditons while gate is fully open, November 20, 2002. 

HCG flow regime=FW. 

OS flow regime=NF.

Figure F6. Looking downstream at headwater 

and tailwater conditions when gate is fully open, 

November 20, 2002. 

HCG flow regime=FW. 

OS flow regime=NF.

Figure F7. Looking downstream of gate at 

tailwater conditions, November 20, 2002. 

HCG flow regime=FW. 

OS flow regime=NF.
52 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Figure F9. Looking downstream at headwater 

conditions from upstream side of bridge, 

November 20, 2002. 

HCG flow regime=FW. 

OS flow regime=NF.

Figure F8. Looking upstream from riprap at 

tailwater conditions, November 20, 2002. 

HCG flow regime=FW. 

OS flow regime=NF.
Appendix F 53

Figure F10. Looking upstream 

at spillway, measurement 511, 

January 9, 2003. 

Flow regime=FW-FL.

Figure F11. Looking 

downstream along new rock 

deposition, measurement 511, 

January 9, 2003. 

Flow regime=FW-FL.
54 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Figure F13. Looking 

downstream of gate and 

spillway, measurement 511, 

January 9, 2003. 

Flow regime=FW-FL.

Figure F12. Looking 

upstream at gate and 

spillway, measurement 511, 

January 9, 2003. 

Flow regime=FW-FL.
Appendix F 55

Figure F14. Looking at conditions of hinged-crest 

gate, measurement 515, June 18, 2003. 

Flow regime=FW-FL.

Figure F15. Looking downstream from gate, 

measurement 516, September 3, 2003. 

Flow regime=FW-NF.

Figure F16. Looking from right to left at tailwater 

conditions, measurement 518, December 2, 2003. 

Flow regime=FW-FL.
56 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Figure F17. Looking at upstream side of hinged-crest gate 

as well as tailwater conditions during flood, measurement 521 

May 18, 2004. 

HCG flow regime=SW. 

OS flow regime=AFF.

Figure F18. Looking right to left at tailwater 

conditions, measurement 525, July 8, 2004. 

Flow regime=FW-FL.

Figure F19. Looking at downstream face 

of gate, measurement 527, November 8, 2004. 

Flow regime=FW-FL.
Appendix F 57

Figure F21. Looking right to left at dam crest with ice, 

February 15, 2007.

Figure F22. Looking right to left at headwater 

conditions, February 15, 2007.

Figure F20. Looking downstream of gate and 

spillway at tailwater conditions, 

February 15, 2007. 
58 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Figure F23. Looking downstream of gate and 

spillway at tailwater conditions, measurement 

537, March 14, 2007. HCG flow regime=FW. 

OS flow regime=AFF.

Figure F24. Looking right to left at headwater 

conditions, measurement 537, March 14, 2007. 

HCG flow regime=FW. 

OS flow regime=AFF.
Appendix F 59

Figure F25. Looking right to 

left at tailwater conditions, 

measurement 543, 

January 11, 2008.

HCG flow regime=FW. 

OS flow regime=AFF. 

Figure F26. Looking 

downstream, measurement 

543, January 11, 2008. 

HCG flow regime=FW. 

OS flow regime=AFF.
60 Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois

Figure F27. Looking right to 

left at tailwater conditions, 

measurement 545, 

March 26, 2008. 

HCG flow regime=SW. 

OS flow regime=AFF.

Figure F28. Looking 

downstream of gate at 

tailwater conditions, 

measurement 545, 

March 26, 2008. 

HCG flow regime=SW. 

OS flow regime=AFF.
Appendix F 61

Figure F29. Looking 

downstream of gate at 

tailwater conditions, 

measurement 546, 

April 16, 2008. 

HCG flow regime=SW. 

OS flow regime=AFF.

Figure F30. Looking right to 

left at headwater and 

tailwater conditions, 

measurement 546, 

April 16, 2008. 

HCG flow regime=SW. 

OS flow regime=AFF.


Straub, Johnson, Hortness, and Parker—Control-Structure Ratings on the Fox River at McHenry and Algonquin, Illinois—Scientific Investigations Report 2009–5186