Erosion, Sediment Discharge,

and Channel Morpholoy

in the Upper Chattahoochee

iver Basin, Georgia
Erosion, Sediment Discharge, 

and Channel Morphology 

in the Upper Chattahoochee 

River Basin, Georgia

With a discussion of the Contribution

of Suspended Sediment to Stream Quality

By R. E. FAYE, W. P. CAREY, J. K. STAMER, and R. L. KLECKNER 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1107

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1980
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY

H. William Menard, Director

Library of Congress Cataloging in Publication Data

Main entry under title:

Erosion, sediment discharge, and channel morphology in the Upper Chattahoochee River Basin, Georgia, with

a discussion of the contribution of suspended sediment to stream quality.

(Geological Survey professional paper ; 1107)

"Open-file report 78-576."

Bibliography: p.

Supt. of Docs, no.: I 19.16:1107

1. Erosion Chattahoochee River watershed. 2. Sediment transport Chattahoochee River watershed. 3. 

Chattahoochee River Channel. I. Faye, R. E. II. Series: United States. Geological Survey. Professional paper ; 1107.

QE571.E783 551.3 78-27110

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402

Stock Number 024-001-3305-4
CONTENTS

Metric conversion table _______ — ___

Definition of terms ____________ — _

Abstract ____________ — ______ — __

Introduction ___________ — ____ — ___

Acknowledgments ___ — ________

Description of the problem ____

Units of measurement _________

Description of study area _________

Physiography and topography _ 

Climate _____________________

Land use and vegetation ______

Dahlonega Plateau ________

Atlanta Plateau ________

Geology and soils _____________

Network description __________

Collection and analysis of water data 

Water-data stations ___________

Water-quality data ____________

Streamflow data __ ________

The stream system ________________

Channel characteristics ________

Flow characteristics ___________

Streamflow hydrographs ___ 

Flow durations ___________

Watershed and channel morphology 

Stream-order analysis _________

Page 

V

vi

1

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1

1

2

2

2

4

6

6

8

9

10

10

10

11

12

12

12

13

13

13

18

18

Watershed and channel morphology—Continued

Overland flow length ____ —— —— -- ——— -- — --

Erosion and sediment discharge __ ————————————— 

Description of environmental factors _____ — ----

Land use _______ — _- — - — ----- ———-

Soils and topography _____ —— ____-___—_ —

Erosion _________-____-_---------------—-----

Sediment discharge ___-__-__--_-------——-—

Suspended sediment ___ — - —— — — ___ — 

Average annual suspended-sediment discharge _____---__--____------—-—--

Mechanics of suspended-sediment transport _____-_--_--_------—-—--——

Unmeasured and bed sediment _ — ___ — ____

Description and source ____ — _ — __-_ —

Computation ___________-__--- — — -- —

Transport curves ___________—__—__—

Average annual discharge ___________ —

Delivery ratios ___ — ___________ — __________ — _____

Management implications of erosion and sediment discharge data ____________------_----—-_---_—-__

Contribution of suspended sediment to stream quality 

Turbidity _____________________ — — — ——

Chemical quality _____________________ — — — --

Management implications of chemical-quality data __ 

Summary _____________-__---_-----_-____------ — -

Selected references _____________________ — _____ —

Page

26

28

28

28

30

37

50

51

52

55

58

58

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63

66

68

72

72

75

80

82

84

ILLUSTRATIONS

FIGURE 1.

2.

3.

4.

5.

6.

7.

Map showing area and location of water-data stations ___________

Map showing long-term average annual precipitation _____________

Map showing long-term average annual air temperature ________

Generalized geology of study area _________________________

Channel characteristics at:

A. Chestatee River near Dahlonega _______ ______________

B. Big Creek near Alpharetta ___________ ____________

C. Chattahoochee River at Atlanta ________ _____________

D. Peachtree Creek at Atlanta _________ ______________

E. Chattahoochee River near Fairburn ______ _____________

Graphs showing mean daily streamflow and daily precipitation at: 

A. Chestatee River near Dahlonega _______ ______________

B. Big Creek near Alpharetta _________________________

C. Chattahoochee River at Atlanta _______ ____________

D. Peachtree Creek at Atlanta _________ _________.

Flow duration curves at:

A. Chestatee River near Dahlonega _______________________

B. Big Creek near Alpharetta __________________________

C. Chattahoochee River at Atlanta ______________________

D. Peachtree Creek at Atlanta _________ ______________

Page 

3

6

7

9

14

14

14

15

15

16

16

17

17

20

20

21

21

in
IV CONTENTS

Page

8-15. Graphs showing:

8. Relation of number of channels to stream order _________ — -___ ——— _ — — — ———— 23

9. Relation of average drainage area to stream order _______ — ___ —— _____ —— —— — — 23

10. Relation of average channel length to stream order ____ ———— - ———— ——————————— - 23

11. Relation of cumulative average channel length to stream order ——————_—————————— 23

12. Relation of average channel drop to stream order _________ —— ———— ____———————— 23

13. Relation of cumulative average channel drop to stream order —————————————————— 24

14. Relation of average channel slope to stream order ————————————————————————— 24

15. Relation of average drainage area to cumulative average channel length ——— ——— —— __ 25

16. Relation of cumulative average channel length to true stream order —___ — — _ — ___ — ______ 26

17. Relation of number of channels to true stream order_____ — __________________ — _________________ 27

18-23. Maps showing land use in watersheds draining to:

18. Chattahoochee River near Leaf ___ —— _________ — —— — ________ — ___________ — _— 31

19. Soque River near Clarkesville _________ — ______________ — ____ —— __ — _-_ ———— — 32

20. Chestatee River near Dahlonega ___- ——— ____________________ —— — __ — ______ — —— 33

21. Big Creek near Alpharetta _______ — ____——________________________---------_ — _____ 34

22. Peachtree Creek at Atlanta, Nancy Creek at Atlanta, and Woodall Creek at Atlanta —— 35

23. Snake Creek near Whitesburg ______——_____________-____---_-_-_- — _ —— —— — - 36

24. Photographs showing typical basin land uses ____ — _______-_____--___---_-__-_-_--- 37,38,39,40,41,42

25-30. Maps showing soil associations in watersheds draining to:

25. Chattahoochee River near Leaf ___________—-__-____-_ — _____________________________ 43

26. Soque River near Clarkesville ____ — _______--_-----_----__----__ — ____ — ______ — _____ 44

27. Chestatee River near Dahlonega _______—-- — ----- ————— _____________ ————— ____ 45

28. Big Creek near Alpharetta _______———————— ————— -- —— --———————————— 46

29. Peachtree Creek at Atlanta, Nancy Creek at Atlanta, and Woodall Creek at Atlanta —— 47

30. Snake Creek near Whitesburg ____________---------- — -------- — ______________ —— _ 48

31-35. Graphs showing relation of suspended-sediment concentrations to stream discharge at:

31. Chestatee River near Dahlonega _______— — __________________ ——— _ — _________—— 51

32. Big Creek near Alpharetta _____________ — _---------------_-------------_---_-_ — _ — _ 52

33. Chattahoochee River at Atlanta ___________----------- — ------_- — _--___-_____———— 53

34. Peachtree Creek at Atlanta ___________--_- — -------------_-----------------___ — _____ 54

35. Chattahoochee River near Whitesburg ___—------______ — ______________ — _____________ 54

3/6-40. Graphs showing lateral distributions of suspended-sediment concentration, flow velocity, flow depth, 

and size of bed material at:

36. Chestatee River near Dahlonega __-___-__-------------- — ___--___-__-________ — _—— 56

37. Big Creek near Alpharetta _________———___-_-____ — ___ — _ —— _______ — — ___— 57

38. North Fork of Peachtree Creek near Atlanta ————————— ————————— __ ———— ————— 58

39. Peachtree Creek at Atlanta _______--——————————————————————————————— 60,61

40. Snake Creek near Whitesburg ___________-- — ------__--_--________-_________________ 62

41. Graphs showing storm loading of suspended sediment at:

A. Chestatee River near Dahlonega ____________----_-------_ — - — _______________ — _______ 64

B. Big Creek near Alpharetta __________________ — --____-______ — _____________ — _______— 64

C. Snake Creek near Whitesburg _____________-- — -__-______ — _____________ — _ — _ — _ — ___ 65

D. Chattahoochee River near Whitesburg ____ — -- — _____________ — _______ — _ — _ — ____ — _— 65

42. Photographs of typical streambeds and stream channels on the Dahlonega and Atlanta

Plateaus _______________________________„_ — — — — — __ — — — — __ — _ — — 66,67,68,69

43. Graphs showing relation of unmeasured- and bed-sediment discharge to stream discharge at:

A. Chattahoochee River near Leaf __________ — _-_-----_-______________________ — _ — _ — ___ 70

B. Chestatee River near Dahlonega ____________ — _______________ ———— ___________ — ___ 70

C. Big Creek near Alpharetta ________________------------_-- — _____________ — ____ — ____— 71

D. Chattahoochee River at Atlanta _______ — - —— -- — ------ —— _ —— — _________ — ___ 71

E. Peachtree Creek at Atlanta _________-- ———————— — —————— — --- ———— ———— 71

F. Chattahoochee River near Whitesburg _____-- — --_____ — ____________________________— 71

44. Graphs showing relation of turbidity to suspended silt plus clay concentrations at:

A. Chestatee River near Dahlonega ___________--- — -_-__-____ — _____________ — ____________ 73

B. Big Creek near Alpharetta _______________-- — — -- — — ________________ — __ — — 73

C. Chattahoochee River at Atlanta ___________-_------_-__-_—_____________ — ____ — _—___ 73

D. Peachtree Creek at Atlanta _________- ————————————————— --—————————— 73 

45-46. Graphs showing relation of suspended-constituent concentrations to concentrations of suspended silt 

plus clay at:

45. Chestatee River near Dahlonega ______ — ___ — _____ — ____ — _____ ———— ___ — ___— 74,75

46. Peachtree Creek at Atlanta ___________——————————————————————————————— 76,77
TABLE

CONTENTS

TABLES

	Page

1. Summary of precipitation and air temperature data for Dahlonega, 1928-1957 _________________ 5

2. Summary of precipitation and air temperature data for Cornelia, 1941-1970 _________--_-------_- 5

3. Summary of precipitation and air temperature data for Atlanta, 1941-1970 __________ — __________ 5

4. Summary of precipitation and air temperature data for West Point, 1941-1970 ________ ——— — ___ 8

5. Station number, name, and watershed area of principal and miscellaneous water-data stations ----- 11

6. Summary of regression data relating daily discharge at urban partial-record stations to daily discharge at Peachtree Creek at Atlanta _____ — __________________--_--------__------------- 14

7. Summary of flow duration data ___________________________________— __________ — _ — _________ 18,19

8. Summary of geomorphic characteristics _________________-___--___--- — ____ — _____-___- — ______ 24

9. Summary of overland-flow length computation using Strahler stream-order data _________________ 27

10. Summary of land-use data by category ____________._-------__ — ______________--_-------_------ 28,29

11-19. Summary of soil and topographic data for watersheds draining to:

11. Chattahoochee River near Leaf _______________----__—________-________-_-_-_-_---__ 30

12. Soque River near Clarkesville _______________—________-_____-_______-____-__---__---_ 30

13. Chestatee River near Dahlonega _____________ — _________________________ — ___________ 37

14. Big Creek near Alpharetta ________________________________ — __________________ 37

15. North Fork of Peachtree Creek near Atlanta----------- — ____________________ — ________ 38

16. South Fork of Peachtree Creek at Atlanta __________________ — __-___-___ 38

17. Peachtree Creek at Atlanta ____________________ — ___________________________________ 39

18. Nancy Creek at Atlanta ___________-_________________ — _______ 39

19. Snake Creek near Whitesburg ___________________________________________ — ___________ 40

20. Sheet erosion and erosion yields computed by the Universal Soil Loss Equation ____________ 49

21. Summary of regression data relating suspended-sediment concentrations to stream discharge _____ 50

22. Average annual suspended-sediment discharge and yield ________________________________________ 55

23. Summary of unmeasured- and bed-sediment discharge computations _____________________________ 63

24. Summary of regression data relating unmeasured- and bed-sediment discharges to stream discharge 66

25. Average annual total-, unmeasured-, and bed-sediment discharges __________________________ 67

26. Summary of regression data relating turbidity to concentrations of suspended silt plus clay ______ 72

27. Summary of regression data relating suspended-constituent concentrations to concentrations of suspended silt plus clay __________________ — -_---__-________________________ 78, 79

28. Mean concentrations of dissolved constituents used to compute average annual dissolved-constituent

discharges ________________________________________________________________ 80, 81

29. Summary of regression data relating dissolved-constituent concentrations to stream discharge ____ 82

30. Annual yields of suspended constituents from representative land-use watersheds ______________ 83,84

31. Summary of average annual suspended- and total-constituent discharges _____________ 84

CONVERSION FACTORS

Factors for converting inch-pound units to metric units are shown to four significant figures. However, in the text the metric equivalents are shown

only to the number of significant figures consistent with the values for the inch-pound.

Inch-pound

ft (foot)

ft (foot)

ft/s (foot per second)

ftVs (cubic foot per second)

in. (inch)

in. (inch)

mi (mile)

mi2 (square mile)

tons (tons, short)

tons/d (tons per day)

tons/ft3 (tons per cubic foot)

tons/yr (tons per year)

°F=9/5(°C)-f32

Multiply by

3.

3.048x10"

3.048 XlO-1

2.832x10--

2.540x10^

2.540X101

1.609

2.590

9.072 xlO'1

9.072 XlO-1

3.204X101

9.

Metric

m (meter)

mm (millimeter)

m/s (meter per second)

nr/s (cubic meter per second)

m (meter)

mm (millimeter)

km (kilometer)

knr (square kilometer)

t (metric tons)

t/d (metric tons per day)

t/m3 (metric tons per cubic meter)

t/yr (metric tons per year)

°C=5/9(°F-32)
VI CONTENTS 

DEFINITION OF TERMS

Terms used in this text to describe hydrology, 

sediment, the erosion and transport of sediment, and 

the collection and analysis of water-quality data are 

defined below.

ALLUVIUM: A general term for all detrital deposits resulting directly or indirectly from the sediment transport of 

(modern) streams, thus including the sediments laid down 

in river beds, floodplains, lakes, fans, and estuaries.

BED LOAD: Material moving on or near the streambed by 

rolling, sliding, and sometimes making brief excursions 

into the flow a few diameters above the bed. It is not 

synonymous with discharge of bed material.

BEDLOAD DISCHARGE: The quantity of bedload passing a 

transect in a unit of time.

BED MATERIAL: The sediment mixture of which the bed 

is composed. Bed material particles may or may not be 

moved momentarily or during some future flow condition.

CHANNEL EROSION: Includes the processes of streambank erosion, streambed scour, and degradation.

COLLUVIUM: A general term applied to loose and incoherent deposits at the foot of a slope or cliff and brought 

there chiefly by gravity.

DRAINAGE AREA OF STREAM AT SPECIFIED LOCATION: That area, projected to and measured on a horizontal plane, enclosed by a topographic divide from which 

direct surface runoff from precipitation normally drains by 

gravity upstream from a specified point; synonymous with 

watershed.

EROSION: The detachment and movement of soil and rock 

fragments by water and other geological agents which results in the wearing away of the land. When water is the 

eroding agent, erosional processes include sheet and rill 

erosion, gully erosion, and channel erosion.

EROSION YIELD: The rate of erosion per unit area; generally expressed in units of tons per year per square mile

(t/yr/mi2 ).

GEOMORPHOLOGY: The observation and description of 

land forms and the changes that occur during land form 

evolution.

GROSS EROSION : The total of all sheet, gully, and channel 

erosion in a catchment, usually expressed in mass (tonnes), 

but sometimes expressed volumetrically.

GULLY EROSION: The formation of relatively deep channels that cannot be readily crossed during normal cultivation.

OVERLAND FLOW: Thin sheetlike, lateral flow across the 

land surface. Occurs subsequent to the beginning of surface runoff and prior to the entrance of flow into well-defined stream channels. The distance of overland flow is the 

true slope length of the local landscape.

PARTICLE-SIZE CLASSIFICATION OF SEDIMENT:

Class Name Size (mm)

>256

64-256

2.0-64

0.062-2.0

0.004-0.062

0.00024-0.004

Boulders _____--______---—________

Cobbles ____________—____________

Gravel __________________—___—_.

Sand _____________________- 

Silt -_________-_-____- — — -—-_.

Clay ____________________________

RILL EROSION: Land erosion forming small but well-defined incisions in the land surface, generally less than 30 

cm in width and depth.

RUNOFF (Surface): The flow of water across the land surface and in stream channels. Occurs only after the local 

storage capacity of the landscape has been exceeded and 

includes both overland flow and streamflow.

RECURRENCE INTERVAL: The average number of years 

within which a given event will be equaled or exceeded.

SEDIMENT: (1) Particles derived from rocks or biological 

materials that have been transported by a fluid, (2) solid 

material (sludges) suspended in or settled from water.

SEDIMENT DISCHARGE: The average quantity of sediments, mass or volume, but usually mass passing a section in a unit of time. The term may be qualified as, for 

example, suspended-sediment discharge, bedload discharge, 

or total-sediment discharge; expressed in units of tons per 

day or tons per year (t/d or t/yr).

SEDIMENT LOAD: The sediment that is in transport. (Load 

is a general term that refers to material in suspension and 

(or) in transport. It is not synonymous with discharge.)

SEDIMENT TRANSPORT CURVE: A graph relating water 

discharge and sediment discharge.

SEDIMENT YIELD: The rate of sediment outflow per unit 

of catchment (watershed) area; expressed in tons per year 

per square mile [t/yr/)mi2 ].

SHEET EROSION : The more or less uniform removal of soil 

from an area without the development of water channels. 

Included with sheet erosion, however, are the numerous but 

conspicuous small rills that are caused by minor concentrations of runoff.

SLOUGHING OR SLUMPING: The downward slipping and 

displacement of masses of bank material.

SUSPENDED SEDIMENT: Sediment that is carried in suspension by the turbulent components of the fluid or by 

Brownian movement.

UNMEASURED LOAD: The sum of bedload and unmeasured 

suspended-sediment load.

UNMEASURED SEDIMENT DISCHARGE: The difference 

between total-sediment discharge and measured suspendedsediment discharge.

WATERSHED: All land enclosed by a continuous hydrologic 

drainage divide and lying upslope from a specified point 

on a stream; synonymous with drainage area.
EROSION, SEDIMENT DISCHARGE, AND CHANNEL MORPHOLOGY 

IN THE UPPER CHATTAHOOCHEE RIVER BASIN, GEORGIA

By R. E. FAYE, W. P. CAREY, J. K. STAMER, and R. L. KLECKNER

ABSTRACT

The 3,550 square miles of the Upper Chattahoochee River 

basin is an area of diverse physiographic and land-use characteristics. The headwater areas are mountainous with steep, 

relatively narrow channels. Land in the headwater areas is 

heavily forested, but small towns and farms are common in 

the valleys of large streams. Downstream, the basin is characterized by low hills and wider stream channels. Land in 

this part of the basin is also predominantly forested; however, large agricultural and urban areas are common. Urban 

land use is particularly intensive within the Atlanta Metropolitan Area.

Rates of sheet erosion were computed in nine watersheds 

using the Universal Soil Loss Equation. The dominant land 

use in each watershed ranged from forested to mostly urban. 

Computed average annual erosion yields ranged from 900 

to 6,000 [(t/yr)/mr]. Erosion yields were greatest in 

watersheds with the largest percentages of agricultural and 

transitional land uses. The lowest yields occurred in highly 

urbanized watersheds. The sensitivity of average annual 

sheet erosion to timber harvesting was also evaluated with 

the Universal Soil Loss Equation. In general, post-harvest 

erosion yields were several orders of magnitude greater than 

computed pre-harvest yields in the same areas.

Average annual suspended-sediment yields were calculated 

from measurements of sediment discharge from the same 

mine watersheds and ranged from about 300 to 800 [(t/ 

yr)/mi2 ]. Seodiment-discharges were greatest in urban water 

sheds and least in forested watersheds. A large part of the 

sediment discharged in urban streams was considered to be 

derived from stream-channel erosion. Unmeasured sediment 

discharge computed for four watersheds ranged from about 

6 to 30 percent of the total annual sediment discharge.

The impact of suspended sediment on the quality of streamflows was evaluated for 14 watersheds. In general, 60 percent or more of the total annual discharge of trace metals 

and phosphorus was contributed by suspended sediment. 

Corresponding discharges of suspended nitrogen and organic 

carbon ranged from about 10 to 70 percent of total. Yields 

of suspended trace metals and nutrients from urban watersheds were consistently greater than corresponding yields 

from forested watersheds. Turbidity in basin streams increased with increasing concentrations of suspended sediment. Such increases, in turn, decreased the aesthetic quality 

of the watercourse and the depth of light penetration into 

the water column.

INTRODUCTION

This investigation is one part of the U.S. Geological Survey's intensive river quality assessment of 

the Upper Chattahoocheee River basin in Georgia 

(Cherry and others, 1976). In contrast to similiar 

studies in the Southeastern United States, this investigation examines erosion and sediment transport in large watersheds. Relations are developed, 

albeit imperfectly, between rates of erosion and 

sediment discharge and characteristic land-use, 

soil, topographic, and climatic parameters. Such relations, in turn, can be used by resource managers, 

hydrologists, and other earth scientists to better 

understand and accommodate the processes of erosion and sediment discharge in the study area.

ACKNOWLEDGMENTS

Much of the collection and analysis of data for 

this study was accomplished by field observers and 

hydrologic field assistants employed by the U.S. 

Geological Survey. The field observers were particularly dedicated and helpful, and our thanks and 

acknowledgements are herein extended to Charles T. 

Satterfield of Dahlonega, Ga., and the Steven Wells 

family of Whitesburg, Ga. Equally notable were the 

efforts of our hydrologic field assistants; especially 

the contributions of Douglas F. duMas, Reid C. 

Webb, Michael D. Holcomb, David G. Pinholster, 

and Ronald Boyd. The help of these personnel and 

others is gratefully acknowledged.

DESCRIPTION OF THE PROBLEM

The periodic occurrence of large quantities of 

sediment in the Chattahoochee River and its tributaries confronts the water-resource manager with a 

complex set of problems. Large-scale sedimentation 

aggrades stream channels, causing inundation of 

valuable bottom lands and increasing peak elevations of floods. Sediment deposition in reservoirs 

reduces their efficiency and useful life, and in some
EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

situations destroys the aesthetic and recreation 

potential of the impoundment. The sorbing capacity 

of sediments, especially clays and silts, provides a 

mechanism whereby nutrients, trace metals, and 

other chemical compounds are carried with the sediment into streams and reservoirs. High concentrations of suspended sediment in a water supply increase treatment costs and often restrict use of the 

water in certain industrial processes.

Faced with these and a host of related problems 

the resource manager must decide on reasonable 

methods to control or accommodate erosion and the 

discharge of sediment to basin streams. Decisions to 

implement control methods should be based on information of sufficient quality and quantity to permit such methods to be successful as well as economically and environmentally feasible. Unfortunately, comprehensive data relative to the processes 

of erosion and sediment discharge in the Upper 

Chattahoochee River basin have never been collected. To collect and interpret such data and to 

detevmine causal relationships between sediment 

discharge and the source environment are the overall objectives of this study. To accomplish these objectives, data-collection sites were established on 

the Chattahoochee River and on selected tributary 

streams. Selection of each site was based, for the 

most part, on physiographic location, dominant 

watershed land use, and availability of streamflow 

record. Specific study objectives at each data-collection site included:

(1) A description of sediment and sediment transport characteristics in the stream channel.

(2) A determination of average annual sediment 

discharge.

(3) A determination of the chemical nature of 

suspended sediment and its contribution to 

stream quality.

Study objectives relative to watersheds draining 

to selected data-collection sites included:

(1) An evaluation of channel and watershed 

morphology using Strahler (1957) streamorder analyses.

(2) A determination of average annual sheet erosion using the Universal Soil Loss Equation.

(3) The development of causal relations between 

stream quality, sediment discharge, land use, 

and other environmental factors.

UNITS OF MEASUREMENT

Data describing streamflow, lengths, and areas 

are defined or dimensioned in inch-pound units. Concentrations of suspended and dissolved constituents 

are defined in metric units and given in milligrams 

per liter (mg/L). Suspended- and dissolved-constituent discharges are expressed in terms of tons 

per year (t/yr). A list of inch-pound to metric conversions follows the "Contents" section of the report.

Symbols used in this report are defined where they 

first appear in the text.

DESCRIPTION OF THE STUDY AREA

The Upper Chattahoochee River basin comprises 

the area drained by the Chattahoochee River from 

its headwaters to West Point Dam (fig. 1)—a total 

of 3,550 square miles. The basin extends from the 

southern periphery of the Blue Ridge Mountains 

southwestward to the Alabama border, a distance 

of about 230 river miles. The basin is narrow compared with its length, with widths ranging from 2 

to 30 miles. The width of the flood plain, in general, 

parallels that of the basin but seldom extends to 

more than 1 mile. The stream channel is well-incised 

within the flood plain and is characterized by steep 

banks and generally uniform sections. At several 

points in the basin, most notably downstream of 

Morgan Falls Dam (fig. 1), the flood plain is virtually nonexistent and channel incisement is relatively extreme. Two similar sites are occupied 

presently by West Point Dam and Buford Dam 

which impound, respectively, West Point Lake and 

Lake Sidney Lanier (fig. 1).

Since 1955, flow in the Chattahoochee River between Lake Lanier and West Point Lake has been 

regulated and, to a large extent, dominated by hydropower releases from Buford Dam. Waves generated by such releases can be observed at gaging stations along the entire reach of the river between the 

reservoirs.

As described by Fenneman (1938), the Upper 

Chattahoochee River basin is entirely contained 

within the Southern Piedmont physiographic province. Within this general province, the basin occupies parts of two smaller physiographic entities— 

the Dahlonega and Atlanta Plateaus (fig. 1). The 

Dahlonega Plateau includes most of the basin upstream from Lake Sidney Lanier and contains the 

headwaters of the Chattahoochee River and two 

of its larger tributaries, the Chestatee and Soque 

Rivers. The area is characterized by mountains 

separated by deep, generally narrow valleys. Moun-
35° 85°

DESCRIPTION OF STUDY AREA

84°

3

83°

34°

33C

——---——.TENNESSEE /NORTH CARQ^- 

N ALABAMA ! " ^cJ^Tr———"^

t 1

UPPER 1 jmf C| ' 

CHATTAHOOCHEE^CfW [-., 

RIVER BASIN mV$i ) \

^ 

River-jNACOOCHEE 3 ^& * ,

7 VALLEY *? \ J 

1 xMOUNTYONAH 

I - 

Clevelando Chattahoochee River

_ALABAMA^ I 1- 

FLORIDA" •

INDEX MAP

r

^Gainsuille

Lafce Sidney Lanier

L^/OflD O4M

Alphar.etta^- ^ 

KENNESAW ^ 

MOUNTAIN^ Vn /-J °Pulut — \ ^~^ " ^-r /

-MORGAN FALLS DAM

Chamblee

., ^fPeachtree Creek Nancy Cr"

' J

*S Fork Peachtree Creek

EXPLANATION

11A Water-data station

— ••— Hydrologic boundary

— • —•— Physiographic boundary

-IVX 

WEST POINT DAM Base from U.S. Geological Survey, 

Greater Atlanta Region 1:100,000,1974; 

Phenix City, 1963; Greenville, 1964; 

Rome, 1972,1:250,000

0 10 20 30 40 50 60 70 80 KILOMETERS I I I I I I I

I

) 10

I 

20

I 

30

I 

40 50 5 MILES 

FIGURE 1.—Study area and location of water-data stations.

tain peaks in this part of the basin generally exceed 

2,000 feet in altitude and at least three exceed 2,500 

feet. The highest of these is Mount Yonah with a 

summit altitude of 3,166 feet.

The stream channel network draining the Dahlonega Plateau is generally rectangular and, for the 

most part, is structurally controlled. Flood plains 

for most streams are narrow or nonexistent. Small
EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

alluvial valleys have been formed by larger streams, 

however, most notably by the Chattahoochee River, 

south of Helen, and by the Soque River, in the 

vicinity of Clarkesville (fig. 1). Land and channel 

slopes are steep in this part of the basin. The Chattahoocheee River, in flowing across the Dahlonega 

Plateau, falls from altitude 2,980 feet to altitude 

1,220 feet in approximately 28 river miles.

Aerial definition of the Dahlonega Plateau by 

Fenneman (1938) is less than precise; he places the 

plateau at the "high inner edge of the Piedmont in 

Georgia." McCallie and others (1925) provide a 

brief, verbal description of the plateau's boundaries 

and list several cities and towns located on the 

plateau. A small scale map delimiting the physiographic divisions of north Georgia also is provided 

by McCallie, but includes virtually no topographic 

control. By combining information from both 

sources, the authors have approximately defined that 

part of the Dahlonega Plateau drained by the Chattahoochee River and its tributaries (fig. 1). The 

area drained equals about 450 square miles or about 

13 percent of the upper basin.

The Atlanta Plateau is discussed only briefly by 

Fenneman (1938) and is described as a southwestward extension of the Dahlonega Plateau. McCallie 

and others (1925) discuss the area in more detail 

and describe its major river systems. Within the 

Atlanta Plateau, the Chattahoochee River basin is 

characterized by low hills separated by narrow valleys. Alluvial bottomlands are prominant along the 

Chattahoochee River and its major tributaries, but 

generally are less than 1 mile in width. Small mountains do occur, most notably along the northern 

divide, and include Sawnee Mountain, northwest of 

Cummings, and Kennesaw Mountain, northwest of 

Marietta. Summit altitudes of these mountains are 

1,920 feet and 1,800 feet, respectively. The stream 

channel network that drains the Atlanta Plateau to 

the Chattahoochee River is slightly more dendritic 

than its counterpart on the Dahlonega Plateau. The 

channel of the Chattahoochee River is severely controlled by structure in this part of the basin and 

occupies or directly parallels the trend of the Brevard Fault along most of its reach (Higgins, 1968). 

Major tributary streams on the Atlanta Plateau 

include Big, Peachtree, and Sweetwater Creeks in 

the vicinity of Atlanta and Snake Creek near 

Whitesburg (fig. 1).

Land and channel slopes on the Atlanta Plateau 

are generally not as steep as those on the Dahlonega 

Plateau. The Chattahoochee River, in flowing across 

the Atlanta Plateau, falls from altitude 1,220 feet

to altitude 635 feet in approximately 200 river miles. 

The Chattahoochee River drains about 3,100 square 

miles of the Atlanta Plateau, which accounts for 87 

percent of the study area.

CLIMATE

Climate in the study area is influenced, for the 

most part, by the mountainous terrain and the 

basin's proximity to the Gulf of Mexico (fig. 1). The 

higher mountains, most notably those along the 

northern perimeter of the basin, affect the climate 

most directly by serving as partial barriers to the 

flow of air masses. During the winter, these mountains inhibit the southerly flow of polar air into the 

basin, resulting in moderate winter temperatures 

with relatively few periods of excessively cold 

weather. During the summer, these same mountains 

serve as a barrier to north-flowing, moisture-laden 

winds from the Gulf. Consequently, summer convective storms are common and summertime rainfall 

is relatively high.

Summers on the Dahlonega Plateau are generally 

mild. Daytime temperatures from June through 

August are highest, but rarely exceed 100°F. Summer nights are cool but are seldom less than 60°F. 

Winters are moderately cold. Daytime temperatures 

are lowest from December through February and 

rarely exceed 55 °F. Subfreezing temperatures 

(<32°F) occur frequently, but subzero temperatures (<0.0°F) are rare.

Average annual precipitation in this part of the 

basin is in excess of 60 inches. Most rainfall occurs 

in the winter and early spring months, but rainfall 

in excess of 10 inches has occurred in every month. 

Frozen precipitation in the form of sleet and snow 

is common during the winter; however, accumulations on the ground remain only a short time. During the summer, convective storms having short 

periods of intense rainfall are common.

A summary of precipitation and air temperature 

data for the city of Dahlonega is shown in table 1. 

Maps showing lines of equal average annual precipitation and temperature for the period 1941-70 are 

shown for the entire study area in figures 2 and 3, 

respectively.

Climatic conditions on the Atlanta Plateau are 

similar in most respects to those described for the 

Dahlonega Plateau. By comparison, the effects of 

altitude on rainfall and temperature are less pronounced, whereas the closer proximity to the Gulf 

of Mexico provides for a warmer, more humid climate. Temperature and precipitation are generally
DESCRIPTION OF STUDY AREA 

TABLE 1.—Summary of precipitation and air temperature data for Dahlonega, 1928-1957

Temperature <°F)

Month

January

February

June _ _ _ _

July _ —— — _ —— __

September _ _ _

October __ _ _ _

November _ _

December _ _

Year _ __ __

Means

Daily 

jnaximum

52.5 

55.3 

62.3

72.1 

79.9 

86.2 

87.9 

86.6 

81.5 

71.8 

60.4 

52.7 

70.8

Daily 

jftinimum

33.9 

34.4 

39.4 

47.4 

54.6 

62.3 

65.6 

64.8 

59.9 

49.0 

38.9 

33.6 

48.7

Extremes

Record 

Jligh

76

76 

87 

92 

96 

100 

103 

100 

100 

92 

83 

74 

103

Record 

.low

-1

5 

9 

24 

34 

43 

50 

49 

36 

23 

3 

5 

1

Precipitation Totals 

(in.)

Mean

6.8 

6.03 

6.71 

5.00 

4.38 

3.91 

5.78 

5.00 

3.89 

3.15 

4.37 

6.18 

60.48

Greatest 

daily

4.30 

3.90 

4.50 

4.10 

2.67 

2.98 

4.18 

4.73 

5.44 

4.12 

3.51 

3.89 

5.44

a function of location. Rainfall generally decreases 

from the northeast to the southwest as the temperature increases (figs. 2 and 3).

Summaries of precipitation and air temperature 

data for the cities of Cornelia, Atlanta, and West 

Point are shown in tables 2 through 4, respectively.

TABLE 2.—Summary of precipitation and air temperature data for Cornelia, 19^1-1970

Temperature (°F)

Month

January

April

IVTa TT

June _

July ______________

August

October

December

Year

Means

Daily 

maximum

51.6 

54.3 

61.2 

71.9 

78.8 

84.3 

86.4 

86.1 

80.0 

71.6 

60.9 

52.2 

69.9

Daily 

minimum

31.2 

32.3 

37.8 

46.9 

54.1 

61.3 

64.3 

63.9 

58.4 

47.7 

37.7 

31.5 

47.3

Precipitation Totals 

(in.)

Extremes

Record 

high

80 

78 

83 

90 

96 

100 

102 

99 

98 

92 

82 

76 

102

Record •low

-6

4

7 

24 

30 

40 

50 

46 

30 

24 

7 

1 

c

Mean

5.57

5.50 

6.44 

5.26 

3.85 

4.85 

5.71 

4.58 

4.02 

3.37 

4.01 

5.18 

58.34

Greatest 

daily

4.85 

3.99 

4.70 

3.42 

2.65 

4.45 

3.64 

3.98 

4.55 

4.28 

4.54 

2.95 

4.85

TABLE 3.—Summary of precipitation and air temperature data for Atlanta, 194.1-1970

Temperature (°F)

Month

May __ _

July ______________

September

November

December

Year

Means

Daily 

maximum

51.4 

54.5 

61.1 

71.4 

79.0 

84.6 

86.5 

86.4 

81.2 

72.5 

61.9 

52.7 

70.3

Daily 

minimum

33.4 

35.5 

41.1 

50.7 

59.2 

66.6 

69.4 

68.6 

63.4 

52.3 

40.8 

34.3 

51.3

Precipitation Totals 

(in.)

Extremes

Record 

high

72 

85 

85 

88 

93 

98 

98 

98 

93 

88 

84 

77 

98

Recprd

lovf

3

8 

21 

26 

37 

48 

53 

56 

36 

29 

14 

1 

-3

Mean

4.34 

4.41 

5.84 

4.61 

3.71 

3.67 

4.90 

3.54 

3.15 

2.50 

3.43 

4.25 

48.34

Greatest 

daily

3.91 

5.67 

5.08 

4.26 

5.13 

3.41 

5.44 

5.05 

5.46 

3.27 

4.11 

3.85 

5.67
6 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

35C

85° 84° 83 C

34C

33°

EXPLANATION

—50— Line of equal average annual precipitation. 

Contour interval, 5 inches

— ••— Hydrologic boundary

Base from U.S. Geological Survey, 

Greater Atlanta Region 1:100,000,1974; 

Phenix City, 1963; Greenville, 1964; 

Rome, 1972,1:250,000

0 10 20 30 40 50 60 70 80 KILOMETERS

0 10 20 30 40 50 MILES 

FIGURE 2.—Long-term average annual precipitation.

LAND USE AND VEGETATION

DAHLONEGA PLATEAU

The basin area within the Dahlonega Plateau is 

not densely populated nor is the land actively used 

on a large scale. In 1970, the population of the area

was estimated to be about 16,000 persons (U.S. 

Bureau of Census, 1971), or a population density of 

one person per 16 acres. Ownership of land in this 

part of the basin is about equally divided between 

the Federal Government and private individuals.
35C

85°

DESCRIPTION OF STUDY AREA

84°

7 

83°

34C

33°

EXPLANATION

58— Line of equal average annual air temperature. 

Contour interval, 2 degrees Fahrenheit

•••— Hydrologic boundary

Base from U.S. Geological Survey, 

Greater Atlanta Region 1:100,000,1974; 

Phenix City, 1963; Greenville, 1964; 

Rome, 1972,1:250.000

0 10 20 30 40 50 60 70 80 KILOMETERS

I I I I 

0 10 20 30 40 50 MILES

FIGURE 3.—Long-term average annual air temperature.

About 200 square miles of the basin south of the 

northern divide is administered by the Federal Government as part of the Chattahoochee National 

Forest. Except for several small State parks and 

some county and municipal properties, all lands

south of the National Forest are held in private 

ownership.

At the present time (1976), active use of basin 

land within the Dahlonega Plateau is confined to the 

valleys of larger streams and is principally agricul-
EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN 

TABLE 4.—Summary of precipitation and air temperature data for West Point, 194.1-1970

Month

Temperature

Means Extremes

Daily 

maximum

Daily 

minimum

Record 

high

Record 

low

Precipitation Totals 

(in.)

Mean Greatest 

daily

January

May __ ———— —

July _ — ———

August __ _ —

September __ _

October _ _

November

December _

Year _ __

58.2

61.2

67.9

77.6

84.4

89.5

90.6

90.3

85.4

77.3

66.9

58.9

75.7

34.1

QC 1

41.6

Cft 1

57.7

CC C

68.6

67.8

62.1

50.1

39.8

04 o

50.6

Oft

84

00

94

no

104

iftc

1 O9

101

Q7

87

79

105

1

11

27

35

43

CO

52

35

9A.

8

1

1

4.47

5.16

6.34

4.89

3.82

3.81

5.76

4.08

3.60

2.47

3.51

5.08

52.99

2.98

7.18

5.71

4.75

3.76

4.69

3.87

5.02

6.00

3.00

7.26

4.60

7.26

tural in nature. Grazing, row cropping, and poultry 

feeding account for most agricultural activities and 

occupy about 9 percent of the total land area. Urban 

and residential land use is minor and is confined to 

the immediate vicinities of such small towns as 

Helen, Cleveland, and Clarkesville.

Most basin land (90 percent) within the Dahlonega Plateau is occupied by forests and woodlands. 

Forested areas are characterized by mixed stands of 

conifer and deciduous trees dominated by pine and 

oak, respectively. Dominant pines include the Virginia and shortleaf varieties; common deciduous 

trees include white oak, red oak, and black oak. 

Forest undergrowth is dominated by dogwood, 

greenbriar, and blackberry briars. Abandoned fields 

are naturally seeded with broom sedge and other 

grasses, but are gradually overgrown by small pines, 

sassafras, and hardwoods. Yellow poplar is common 

in most areas and white pine is found at higher elevations.

Commercial logging was an important industry in 

this area at one time, and most forested areas have 

been logged at least twice. Timber is not presently 

logged on a large scale. Commercial stands of timber 

are available, however, and the potential for extensive future logging is great.

ATLANTA PLATEAU

Population density in that part of the Atlanta 

Plateau drained by the Chattahoochee River is much 

higher than in corresponding areas on the Dahlonega Plateau and active use of the land is more widespread and varied. In 1970, the population of the 

area was estimated to be about 1,500,000 persons 

(U.S. Bureau of Census, 1971), or a population density of one person per 1.3 acres. Active use of the

land is characterized, for the most part, by the 

urbanization of forests and agricultural areas. At 

the present time (1976), about 12 percent of basin 

land on the Atlanta Plateau is urban or suburban. 

Corresponding percentages for agricultural lands 

and forests are 17 percent and 67 percent, respectively. The remaining area (4 percent) is mostly 

wetlands and reservoirs.

Major urban centers in this part of the basin include Atlanta, Gainesville, Marietta, Cornelia, and 

Alpharetta (fig. 1). Urban areas are characterized 

by extensive residential communities separated by 

commercial, industrial, and transportation centers.

Agricultural lands are located generally within 

the flood plains of the Chattahoochee River and its 

major tributaries. Grazing, row cropping, poultry 

feeding, and orchards constitute most of the agricultural land use. Row crops are mostly corn and hay. 

Apples and peaches are the most common orchard 

crops. Pasture lands generally are of poor quality 

and contain grasses such as broom sedge, crabgrass, 

lespedeza, and bermuda grass.

Forests in this part of the basin consist mostly of 

oak, pine, and hickory. Common varieties of pine 

are the shortleaf and loblolly. Dominant oak species 

are the red, black, blackjack, and white oaks. Common plants in the forest undergrowth include dogwood, greenbriar, sassafras, and blackberry briars.

Basin land on the Atlanta Plateau is nearly all 

privately owned. Lands administered by the Federal 

Government constitute the bulk of public properties 

and include several military reservations as well as 

lands adjacent to West Point Lake and Lake Lanier. 

The total area of public lands does not exceed 200 

square miles.
DESCRIPTION OF STUDY AREA

Other land uses within the Atlanta Plateau include recreation, commercial logging, and sand 

dredging. Such activities are not areally extensive, 

and their impact on water quality at the present 

time (1977) is considered minor.

GEOLOGY AND SOILS

Metamorphic and intrusive igneous rocks underlie most of the Dahlonega and Atlanta Plateaus. A 

generalized geologic map designating major rock 

groups and formations is shown in figure 4. For

35° 85° 84° 83°

34°

EXPLANATION

Undifferentiated metamorphic rocks

Granites

Mafic an

Brevard zone of cataclasis

Geological contact

Shear zone

Fault

—.. — Hydrologic boundary

33°

Base from U.S. Geological Survey, 

Greater Atlanta Region 1:100,000,1974; 

Phenix City, 1963; Greenville, 1964; 

Rome, 1972,1:250,000

0 10 20 30 40 50 60 70 80 KILOMETERS I I I I I I I

I 

) 10

I 

20

I 

30

F 

40 50 MILES 

FIGURE 4.—Generalized geology of study area. Geology modified from Georgia Department of Natural Resources (1976),
10 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

the most part, the metamorphic rocks include slate, 

mica schist, gneiss, and quartzite. Intrusive igneous 

rocks include granites and ultramafics. The age of 

both the metamorphic and intrusive rocks is uncertain; however, Precambrian is most often cited in 

the literature (Crickmay, 1952; Hatcher, 1971).

Structural features of the basin include the 

Brevard Fault Zone and several minor faults and 

shear zones (fig. 4). The structure and orientation 

of the Brevard Fault dominate the physiographic 

character of the Atlanta Plateau including much of 

the southern half of the Upper Chattahoochee River 

basin.

Soils in the basin are derived from the disintegration of underlying rocks and range in texture from 

gravelly sandy loam to clay loam. Similar soil types 

occur on both the Dahlonega and Atlanta Plateaus.

NETWORK DESCRIPTION

The total drainage of the Chattahoochee River 

basin is about 8,650 square miles; the most upstream part of which is the 3,550 square miles of 

study area. The Chattahoochee River is joined by 

the Flint River near the Georgia-Florida State line, 

where the combined rivers form the Appalachicola 

River, which, in turn, flows to the Gulf of Mexico

(fig. I)-

On occasion in this section, points on the Chattahoochee River will be designated by river mile 

(RM). Zero river mile (RM 000.00) is defined as 

the confluence of the Flint and Chattahoochee 

Rivers.

The Chattahoochee River rises in the upland 

areas of the Dahlonega Plateau and flows, initially, 

in a southeasterly direction. About 10 miles downstream of the headwaters, the river flows through 

the small urban center of Helen and enters the 

Nacoochee Valley. Here the Chattahoochee is joined 

by two large tributaries, Sautee Creek at river mile 

415.95 and Dukes Creek at river mile 418.08. The 

Chattahoochee river enters the Atlanta Plateau 

at about river mile 405.50 and continues on a southeasterly course to its confluence with the Soque 

River (RM 402.50) ; here the channel abruptly 

turns to the southwest. Several miles downstream 

of the Soque confluence the Chattahoochee enters 

the headwaters of Lake Sidney Lanier—a multipurpose reservoir impounded behind Buford Dam 

(RM 348.32). The Chestatee River joins the Chattahoochee within Lake Lanier at river mile 362.98.

Between Buford Dam (RM 348.32) and Morgan 

Falls Dam (RM 312.62), the Chattahoochee river 

is joined by many tributaries, most notably Suwanee Creek (RM 338.12) and Big Creek (RM 

317.37).

Downstream of Morgan Falls Dam the Chattahoochee River enters the Atlanta metropolitan area 

and continues to flow through mostly urban areas 

to its confluence with Camp Creek (RM 281.79). 

Major tributaries in this reach include Peachtree 

Creek (RM 300.54), Proctor Creek (RM 297.50), 

Nickajack Creek (RM 295.13), Sweetwater Creek 

(RM 288.56), and Camp Creek (RM 283.53).

Downstream of the Atlanta metropolitan area, 

the Chattahoochee River continues to flow in a 

southwesterly direction toward West Point Lake. 

Major tributaries along this reach include Dog 

River (RM 273.50), Snake Creek (RM 261.72), 

Cedar Creek (RM 261.25), and Centralhatchee 

Creek (RM 236.52). In the vicinity of Franklin, 

Ga. (RM 235.46), the Chattahoochee River flows 

into West Point Lake and continues as West Point 

Lake to the terminal point of the study area at West 

Point Dam (RM 201.40).

COLLECTION AND ANALYSIS OF WATER 

DATA

WATER-DATA STATIONS

Study objectives and the paucity of relevant data 

required that a comprehensive water-data collection 

effort be established and maintained during the first 

year of study (Sept. 1975 to Sept. 1976). To this 

end, 12 locations in the basin were chosen as principal stations for periodic water-data collection and 

three locations were selected for miscellaneous or 

less-intense data collection. Primary criteria used 

to locate each station were land use, physiography, 

and length of at-site or correlative streamflow 

record. Continuity of data and data interpretation 

relative to downstream stations were also considered. Figure 1 shows the location of all waterdata stations referenced in this report. Table 5 lists 

the stations in downstream order and keys their 

location to figure 1.

Principal data-collection sites on the Atlanta 

Plateau were located at Big Creek near Alpharetta, 

Peachtree Creek at Atlanta, and Snake Creek near 

Whitesburg. Land use within these watersheds was 

classified as rural, urban, and forest, respectively. 

In order to provide more data relative to an urban 

environment, several other principal data-collection 

sites were located within the Peachtree Creek 

watershed. These stations include Nancy Creek at 

Randall Mill Road at Atlanta, North Fork of Peachtree Creek at Buford Highway near Atlanta, and
COLLECTION AND ANALYSIS OF WATER DATA 11

TABLE 5.—Station number, name,

[C,

and watershed area of principal and miscellaneous water-data stations

Continuous Stage Record; P, Partial Stage Record]

Key U.S. Geological 

No. Survey 

(fig. 1) station number

1 _ — 02331000

2 __ _ 02331250

3 _ __ __ 02331500

4 _____ _ 02333500

5_ _ _ __ __ 02334430

6 _ _ _ _ 02334500

7_ _ __ 02334590

8 _ _ _ 02335700

9 _ __ 02336000

10 _____ _ 02336120

11_ __ __ _ 02336250

12 __ _ 02336300

13- __ __ 02336313

14 _ ___ ___ 02336339

15 __ ____ 02336380

16 _ __ 02336526

17_ ______ 02337170

18 _ _ __ _ 02337500

19__ __ _ _ 02338000

Drainage 

area

(mi-)

150

96.0

156

153

1040

72.0

1450

34.1

29.6

86.8

3.1

3.2

34.8

15.5

2060

37.0

2430

Stage 

record

p

C

C

P

P

C

P

P

P

P

C

C

C

P'eriod 

of 

record

1Q40 71

1906 09

1931,

1941-45

IQQfl 71

1Q71 7fi

1942 71

1961 76

1930-76

1Q7fi

197G

1959-76

1976

1976

1976

1976

1965 76

1955-76

1939 53,

1965-76

Station name

Chattahoo hee Riv r near Leaf

Soque River near Demorest.

Chestatee River near Dahlonega.

Chattahoochee River at Buford

Dam near Buford. 

Chattahoochee River near

Buford. 

Chattahoochee River at State

Route 120 near Duluth. 

Big Creek near Alpharetta.

Chattahoochee River at Atlanta.

North Fork Peachtree Creek at

Buford Highway near Atlanta. 

South Fork Peachtree Creek at

Atlanta. 

Peachtree Creek at Atlanta.

Woodall Creek at DeFoors Ferry

Road at Atlanta. 

Nancy Creek tributary near

Chamblee. 

Nancy Creek at Randall Mill

Road at Atlanta. 

Proctor Creek at State Route

280 at Atlanta. 

Chattahoochee River near

Fairburn. 

Snake Creek near Whitesburg.

Chattahoochee River near

Whitesburg.

South Fork of Peachtree Creek at Atlanta. The 

location of three principal data-collection stations 

on the Chattahoochee River at Atlanta, near Fairburn, and near Whitesburg provided an opportunity 

to compare tributary and main stream data.

Miscellaneous stations on the Atlanta Plateau 

were located on Proctor Creek at State Route 280 

at Atlanta, on Woodall Creek at DeFoors Ferry 

Road at Atlanta, and on a tributary to Nancy Creek 

near Chamblee.

Principal data-collection stations on the Dahlonega Plateau were located on the Chattahoochee 

River near Leaf, on the Chestatee River near Dahlonega, and on the Soque River near Clarksville. 

The total flow passing these three stations includes 

most of the runoff from the Dahlonega Plateau. 

Site selection criteria in this part of the basin emphasized physiographic location and available 

streamflow record rather than land use.

In addition to the data-collection sites listed 

above, water data from several other stations were 

used in this study. These stations are listed in table 

5 as the Soque River near Demorest, the Chattahoochee River at Buford Dam near Buford, the

Chattahoochee River near Buford, and the Chattahoochee River at State Route 120 near Duluth.

For the most part, subsequent illustrations in this 

text refer to only a few selected water-data stations. 

These stations were chosen to illustrate unusual 

sediment-transport conditions and the range of 

transport and related conditions observed in the 

basin.

WATER-QUALITY DATA

Collection of sediment and water-quality data relative to seasonal low flows and storm runoff began 

in September 1975 and continued for a period of 

1 year. Sampling frequency was mostly determined 

by the occurrence and duration of runoff events. 

Water data collected at each sampling site included 

measurements of streamflow or stage, water temperature, and water samples for chemical and suspended-sediment analyses. In addition, data used 

to compute bedload transport were collected at 

selected sites. All water samples were collected 

using depth-integrating techniques, as described by 

Guy and Norman (1970). Concentrations of suspended sand and suspended silt plus clay were 

determined for each water sample. Chemical analy-
12 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

ses of each sample determined concentrations of 

nutrients and trace metals in both the dissolved and 

total phases as well as fecal contamination, pH, and 

specific conductance. All water-quality data collected during this study will be published by the 

Georgia District of the Water Resources Division, 

U.S. Geological Survey.

Suspended-constituent concentrations within a 

stream cross section commonly exhibit a high degree of spatial variation. To account for this variation, depth-integrated water samples were collected 

at several verticals at each cross section and composited. The suspended-constituent concentrations 

used in this study were derived from the composited 

samples. Suspended-constituent concentrations also 

vary with discharge and should be considered as instantaneous values and representative only of the 

discharge at the given time and location.

Data were collected for this study over the relatively short period of one year. Therefore, the data 

and interpretations presented in this report are influenced, to some degree, by prevailing climatic and 

land-use conditions and may not represent the true, 

long-term water quality of basin streams.

STREAMFLOW DATA

Direct measurement of streamflow and stage over 

a wide range of values defines a generally unique 

relation between stage (water-surface altitude) and 

discharge. This relation (rating) can be used to estimate instantaneous discharges when only stage 

values are known. Such discharges, in turn, can 

be used, in conjunction with other data, to compute 

instantaneous sediment or other water-quality constituent discharges. In addition, stage-discharge ratings permit the computation of daily mean discharge 

from continuous stage records. A plot of daily mean 

discharge against time provides the typical streamflow hydrograph. The tabulation and statistical analysis of long-term records of daily mean discharge 

provides standard streamflow characteristics such 

as flood frequency and flow duration.

During the period of data collection for this study, 

water-data stations described in table 5 as continuous-recording (C) and partial-record (P) were 

located proximate to automatic stage recorders that 

were routinely operated and maintained by the U.S. 

Geological Survey. Information such as current 

stage-discharge ratings and long-term daily discharge records were available for most continuousrecord stations. Streamflow data for the partialrecord stations consisted of a few flood-peak measurements and little or no historical record. Consequently, project efforts to collect streamflow data 

were concentrated at the partial-record stations and 

were sufficient to define valid stage-discharge relations at each site. These ratings, in turn, were used 

with recorded stage data to compute daily mean discharges at each partial-record station for the period 

January to September 1976.

THE STREAM SYSTEM

In general, a stream system is defined in terms of 

channel and streamflow characteristics. Channel 

characteristics include size and shape as well as 

hydraulic descriptors such as slope and channel 

roughness. Streamflow characteristics describe the 

quantity, occurrence, and temporal distribution of 

discharge and commonly include hydrographs, flood 

and drought recurrence intervals, and flow durations.

Stream system characteristics pertinent to this 

study include channel slope, stream-bed characteristics, streamflow hydrographs, and flow durations. 

Channel characteristics are presented to demonstrate the variety of channel slope, channel geometry, and streambed conditions occurring at the 

water-data stations. Streamflow hydrographs are 

presented to demonstrate the sensitivity of streamflow to rainfall and the variety of streamflow conditions that occurred during the period of data 

collection. Flow duration data are required to compute average annual discharges of sediment and 

other suspended water-quality constituents.

CHANNEL CHARACTERISTICS

Channel characteristics are described for selected 

water-data stations in figure 5. Each illustration 

shows a profile of the channel section at the station 

and lists the channel slope and a description of the 

streambed. Slope data in the vicinity of the stations 

were obtained by measuring the length and fall of 

the stream surface as depicted on 1:24,000 scale 

topographic maps.

Stream channel cross sections in the basin tend to 

be mostly rectangular to trapezoidal in shape (fig. 

5). Streambeds on the Dahlonega Plateau consist of 

boulders, cobbles, gravel, and sand that frequently 

lie directly on bedrock. Streambeds on the Atlanta 

Plateau are similar but generally contain thicker, 

more extensive deposits of sand and gravel. Streambed scour and fill may be common on the Atlanta 

Plateau, especially where bridges or other local controls constrict the streamflow. Streambed altitudes 

at various discharges are shown for Big Creek near 

Alpharetta and Peachtree Creek at Atlanta (figs.
THE STREAM SYSTEM 13

5B and 5z>) and indicate the magnitude of scour occurring at these stations.

FLOW CHARACTERISTICS

STREAMFLOW HYDROGRAPHS

Streamflow hydrographs at selected water-data 

stations are shown in figure 6 for the period January through September 1976. Vertical lines at the 

top of each graph indicate total daily rainfall measured at a nearby rain gage. The sensitivity of 

streamflow to rainfall is apparent at most stations. 

Those streamflows showing the least sensitivity to 

rainfall occur at the Chattahoochee River at Atlanta. 

Discharge at this station and at the stations near 

Fairburn and Whitesburg is regulated by Buford 

and Morgan Falls Dams, which dampen the normal 

response of streamflow to all but the largest, most 

areally extensive rainfall events.

The recurrence of peak discharges during water 

year 1976 varied according to station location and 

rainfall distribution. For example, the three largest 

peaks on the Chestatee River near Dahlonega had 

recurrence intervals of about 5 years, 2 years, and 

1.5 years, respectively. Corresponding values for 

Snake Creek near Whitesburg were 4 years, 3 years, 

and 1.3 years. Flood peaks of 4 and 5 years recurrence are not particularly rare events. Their occurrence, however, did permit the collection of sediment 

and other water-quality data over a greater than 

average range of discharges.

FLOW DURATIONS

Flow-duration data are computed from long-term 

streamflow records by arranging daily discharge 

values in order of magnitude and noting the number 

of days of occurrance of each value. The cumulative 

frequency of occurrence of each discharge defines its 

duration, or the percentage of time the discharge 

is equaled or exceeded. Duration data are generally 

presented in the form of a curve. Such curves represent the flow characteristics of a stream throughout 

a given period of record without regard to the sequence of flow events. The area defined by the duration curve equals the average daily stream discharge 

at the station for the given period >of record.

As suggested above, flow durations can be directly 

computed only at stations where long-term, continuous discharge records are available. Duration data 

for stations where streamflow records are shortterm or nonexistent can be extended to longer periods or estimated entirely from long-term records at 

nearby stations. Such extrapolations are generally 

based on the correlation of concurrent daily discharge records or the adjustment of computed durations by ratios of drainage areas.

Duration data at all principal and miscellaneous 

water-data stations were required for this study and 

were computed directly for stations with periods of 

record of 10 years or more (table 5). Duration data 

for stations with less than 10 years of record were 

obtained by extrapolation. Flow durations for partial-record stations in the Atlanta urban area were 

based on the extrapolation of durations computed 

from the long-term record at Peachtree Creek at 

Atlanta. Daily discharge values at each partialrecord station were paired with concurrent values ait 

Peachtree Creek at Atlanta and correlated by linear 

regression. In general, several months of these data 

pairs for the period January to September 1976 were 

used for each regression. The class discharge relative to each directly computed percentage duration 

at Peachtree Creek at Atlanta was then combined 

with the regression equations to compute corresponding discharges at the same percentage duration 

for the partial-record stations.

Because of the large differences in drainage area 

between the smaller urban watersheds and Peachtree 

Creek at Atlanta, the extrapolated duration data 

for Woodall Creek and a tributary to Nancy Creek 

are less representative of long-term flow conditions 

than are corresponding data from the larger drainages. Consequently, average daily discharges and 

other information based on duration data at these 

stations are also less representative of long-term 

conditions and should be treated accordingly.

The regression equations used to correlate the 

concurrent discharge data have the general form

Q, = & (l + &,Qp 

where

Q,=the daily discharge at the partial-record 

station in cubic feet per second,

Q,, = the daily discharge at Peachtree Creek at 

Atlanta in cubic feet per second, and

b0 and &, = regression constants.

A summary of regression data along with computed 

average daily discharge values at each station is 

listed in table 6. Use of the regression data in 

table 6 should be limited to the range of daily flows 

observed at Peachtree Creek at Atlanta during 

water year 1976 (16 to 8,660 cubic feet per second). 

Duration data for the station on the Soque River 

near Clarkesville were determined by the extrapolation of durations computed from the long-term 

record at the Soque River near Demorest. Adjustment of the computed durations was based on the
14 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

1150

1145

1140

Q

p 1135

1130

1125

STREAM BED: Cobbles, gravel and sand on bedrock 

CHANNEL SLOPE: =0.00109 feet/foot

974

972

970

- 968

50 100 150

CHANNEL WIDTH, IN FEET

A

200

775

STREAM BED: Sand and gravel on bedrock

966

964

962

960

958

STREAM BED:Sand and gravel 

CHANNEL SLOPE: =0.00128 feet/foot

• March 16, 1976, discharge=2785 ftVs

A Jan. 27,1976, discharge= 1548 ft 3/s

March 19, 1976 discharge=224 ftVs

10 20 30 40 50 

CHANNEL WIDTH, IN FEET

60 70

745

100 200 300 

CHANNEL WIDTH, IN FEET

400 500

FIGURE 5.—Channel characteristics at (A) Chestatee River near Dahlonega, (B) Big Creek near Alpharetta, and (C)

Chattahoochee River at Atlanta.

TABLE 6.—Summary of regression data relating daily discharge at urban partial-record stations to daily discharge 

at Peachtree Creek at Atlanta

Station name

N. Fork Peachtree 

Creek near

S. Fork Peachtree 

Creek at Atlanta. 

Woodall Creek

Nancy Creek 

Tributary near

Nancy Creek

Proctor Creek 

at Atlanta _

60

-1.36

-3.12 

6.18

1.83

13.7

10.6

61

0.37

.40 

.092

.021

.377

.023

Number 

of 

data 

pairs

119

122 

52

95

122

104

Average 

- daily 

discharge (ft:! /s)

50

53 

19

4.7

67

14

ratio of watershed areas drained by the two 

stations.

The durations of both regulated flows and intervening runoff were required for those stations on 

the Chattahoochee River at Atlanta, near Fairburn, 

and near Whitesburg. Both sets of duration data 

were computed using streamflow records for the 

period 1965-76, the longest common period of 

record (table 5). The occurrence of regulated flow 

in the reach of interest (Atlanta to near Whitesburg) is the result of hydropower production at 

Buford and Morgan Falls Dams. Morgan Falls Dam 

is a "run of the river" facility and provides only 

minimal regulation. Consequently, the computed 

streamflow durations at Buford Dam are considered 

equal to the durations of regulated flow at the three 

downstream stations. The computation of regulated 

flow durations used the combined streamflow
ALTITUDE, IN FEET

O

o

tr

50 o 

o§• fern n to CO S s-

< TO

Q P 

I to

88 

c+-

> 

C+;

P

3

8t

(71

O

X

ALTITUDE, IN FEET

<=!
3

o

3 ^

w g!

MEAN DAILY STEAMFLOW, IN THOUSANDS 

OF CUBIC FEET PER SECOND

a.

DAILY

PRECIPITATION, 

IN INCHES

<ji .1^ co ro -» 

o 'o o 'o o o

MEAN DAILY STEAMFLOW, IN THOUSAND

OF CUBIC FEET PER SECOND
o

§c-t- 5'

CJ

p

> 3 

£ o-

(0 (13

3 r:

oa.

MEAN DAILY STEAMFLOW, IN THOUSANDS 

OF CUBIC FEET PER SECOND

<*" c*

^ & sr ET.

O

sr

DAILY

PRECIPITATION, 

IN INCHES

en ^ co ro -> 

o o o o o o

MEAN DAILY STEAMFLOW, IN THOUSAN

OF CUBIC FEET PER SECOND
18 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

TABLE 7.—Summary of flow duration data: discharge that is equaled or exceeded during percentage of time indicated

[Superscript a indicates extrapolated data]

Percentage 

of time

0.1

.5

1.0

2

4

6

8

10

14

18

22

26

30

35

40

45

50

55

60

65

70

75

80

85

90

95

98

99

99.5

99.9

Station number

1000

5990

2630

1780

1320

970

830

750

630

600

550

530

460

440

400

380

340

310

290

270

250

230

200

190

170

150

130

110

96

85

60

"1250

3000

1720

1200

860

600

490

400

360

310

290

270

250

230

210

200

190

170

160

150

130

120

110

100

95

80

75

60

50

45

32

1500

5100

2800

2090

1320

900

710

620

590

500

460

420

390

370

350

300

280

250

230

220

215

190

180

170

160

140

120

90

75

70

52

3500

5700

2500

1700

1250

900

800

650

610

550

500

450

400

390

360

330

300

280

270

250

220

200

190

160

140

125

105

92

79

70

60

4430 

4500

8400

7400

6700

6200

5700

5500

5400

5100

4600

4100

3700

3300

3000

2600

2300

2000

1700

1500

1300

1200

1100

850

800

630

590

540

530

520

500

450

5700

2100

1300

880

550

380

300

260

240

190

160

140

120

110

100

90

85

75

70

65

55

50

45

40

35

30

26

21

18

16

14

records of stations on the Chattahoochee River at 

Buford Dam and near Buford. A combination of 

records was necessary because of the termination 

of one station after 1971 and the subsequent beginning of the other (table 5). Average daily flow at 

the two stations is nearly equivalent, however.

The durations of intervening runoff at the Chattahoochee River at Atlanta, near Fairburn, and 

near Whitesburg could not be computed directly 

from streamflow records because both runoff and 

regulated flows had been recorded. Division of each 

station's record into regulated flow and runoff was 

accomplished by subtracting the regulated flow recorded for a particular day at Buford Dam from 

the corresponding recorded daily flow at the downstream station. Adjustments for celerity were made 

on a whole-day basis. The difference between the 

daily discharge at each station and the concurrent 

discharge at Buford Dam was attributed to the 

daily runoff entering the river between the dam 

and the station. The sets of these differences for 

the period of record were used to compute the duration of intervening runoff.

A summary of flow durations for each waterdata station, whether extrapolated or computed, is

listed in table 7. Flow duration curves for selected 

water-data stations are shown in figure 7. The lowdischarge parts of the runoff duration curves for 

the Chattahoochee River at Atlanta, near Fairburn, 

and near Whitesburg are poorly defined and are reported only to the limits of accuracy permitted by 

the data and the computation procedure discussed 

previously.

With the exception of stations on the Chattahoochee River downstream from Buford Dam, computed duration data were based on the entire period 

of record available at the station. Thus, no attempt 

was made to select or adjust station records relative to a common period of time. Such use of records 

is consistent with the treatment of daily discharge 

values as random-sample data and provides a better 

description of long-term flow expectancy in the 

basin.

WATERSHED AND CHANNEL MORPHOLOGY

STREAM-ORDER ANALYSIS

The existing network of stream channels in the

study area is the end product of all processes of

erosion and sediment transport that have occurred

in the basin throughout its geomorphic history. A
WATERSHED AND CHANNEL MORPHOLOGY 19

TABLE 7.—Summary of flow duration data: discharge that is equaled or exceeded during percentage of time-indicated

—Continued

of time

0.1

.5

1.0

2

4

6

8

10

14

18

22

26

30

35

40

45

50

55

60

65

70

75

80

85

90

95

98

99

99.5

99.9

0.1

.5

1.0

2

4

6

8

10

14

18

22

26

30

35

40

45

50

55

60

65

70

75

80

85

90

95

98

99

99.5

99.9

Station number

6000 

(total flow)

13200

9200

8100

7100

6500

6200

5800

5600

5000

4600

4200

3800

3400

3100

2700

2500

2300

2100

1900

1800

1600

1500

1400

1300

1250

1100

980

960

940

920

"6380

1200

750

540

375

238

176

145

120

89

72

62

57

52

49

46

43

40

38

35

33

30

29

28

26

24

22

20

19

18

17

6000 

(runoff)

12000

5700

4600

3300

2300

1900

1700

1500

1200

1000

900

800

700

625

590

450

400

350

300

300

300

300

300

300

300

300

300

300

300

300

"6526

83

54

42

32

23

20

18

17

15

14

13

13

13

13

13

13

13

12

12

12

12

12

12

12

11

11

11

11

11

11

"6120

1200

700

500

360

210

150

120

100

70

55

50

41

37

32

29

26

24

22

19

15

14

13

11

10

8.6

6.9

5.0

4.3

3.4

2.2

7170 

(total flow)

27000

18500

12000

11000

9200

8200

7600

7100

6400

5700

5300

4900

4500

4100

3700

3500

3200

2800

2600

2500

2300

2100

1900

1700

1600

1500

1400

1300

1200

1000

« 6250

1300

770

550

380

230

170

125

106

75

58

48

43

39

33

29

26

23

21

19

17

15

14

11

9.6

7.6

5.6

3.8

2.9

1.9

.77

7170 

(runoff)

24000

15000

12000

8900

6200

5000

4100

3900

3000

2500

2300

2000

1800

1400

1300

1200

1100

1000

800

750

600

500

300

300

300

300

300

300

300

300

6300

3200

1950

1400

970

600

430

340

280

200

155

130

115

105

90

82

74

68

64

57

52

46

41

37

32

27

22

18

15

13

9.8

7500

1300

610

420

250

150

130

110

100

84

79

72

67

62

59

54

49

45

42

40

38

33

30

28

25

23

20

16

13

11

11

"6313

300

210

135

95

61

46

36

31

25

20

18

16

15

14

13

13

12

12

12

11

11

10.0

9.6

9.0

8.6

8.0

7.9

7.7

7.4

7.1

8000 

(total flow)

32500

23000

19000

14000

10500

9100

8500

7700

6900

6200

5800

5400

5000

4500

4100

3700

3500

3200

3000

2700

2500

2400

2200

2000

1900

1700

1400

1200

1100

1050

« 6339

68

42

31

22

14

11

8.9

7.5

6.2

5.0

4.6

4.3

3.8

3.7

3.5

3.4

3.3

3.1

3.0

2.9

2.7

2.6

2.5

2.4

2.4

2.3

2.2

2.1

2.1

2.0

8000 

( runoff )

32500

20000

16000

11000

7500

6200

5000

4400

3600

3200

2700

2500

2300

2000

1800

1600

1400

1300

1150

1000

750

600

450

300

300

300

300

300

300

300
20 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

0.01 5 20 50 90 

PERCENT OF TIME DISCHARGE EQUALED OR EXCEEDED

99 99.99

0.01 0.1 1 5 20 50 90 99 99.99 

PERCENT OF TIME DISCHARGE EQUALED OR EXCEEDED

B

FIGURE 7.—Flow durations at (A) Chestatee River near Dahlonega and (B) Big Creek near Alpharetta.
WATERSHED AND CHANNEL MORPHOLOGY 21

0.2 1 5 20 50 90 98 99 

PERCENT OF TIME DISCHARGE EQUALED OR EXCEEDED

c

99.99

Q 4 

Z 

O 

o

LLJ

D 

O

I

CD

CC

I 

o

Q 0

0.01 0.1 1 5 30 50 90 99 99.99 

PERCENT OF TIME DISCHARGE EQUALED OR EXCEEDED 

D

FIGURE 7.—Continued. Flow durations at (C) Chattahoochee River at Atlanta and (D) Peachtree Creek at Atlanta.
22 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

comprehensive treatment of erosion and sediment 

transport should, therefore, include a description of 

the channel network and its relation to basin morphology. To provide this description, stream-order 

analyses of the Soque River and Big Creek watersheds are presented below. Stream-order data developed for the Soque River watershed are considered representative of the channel network and 

channel morphology on the Dahlonega Plateau; corresponding data for the Big Creek watershed are 

considered typical of channels on the Atlanta 

Plateau.

Once compiled, basic stream-order data are used 

to compute morphometric parameters such as drainage density and overland-flow lengths for each 

watershed. Drainage density is a measure of the 

watershed's ability to deliver the products of upland erosion to the channel network. Overland-flow 

length is a function of drainage density and is used 

later in the report in conjunction with the Universal Soil Loss Equation.

Stream-order data were computed using techniques described by Strahler (1957). A Strahler 

analysis considers streams with no tributaries as 

first-order streams. The confluence of two firstorder streams marks the beginning of a secondorder stream. Likewise the confluence of two 

second-order streams initiates a third-order stream. 

This process of stream order numbering continues 

to the most downstream point of the watershed. 

A Strahler analysis thus provides geomorphic data 

relative to channel segments of a given stream 

order. As shown below, the Stabler analysis differs 

slightly from the classical Horton (1945) analysis

in which each successively higher order stream is 

considered to extend headward to the tip of its 

longest tributary.

All measured stream-order data were developed 

from 1:24,000-scale topographic maps (Emmett, 

1975) and are summarized for both watersheds in 

table 8. Data for stream orders one through four 

represent stream-channel characteristics upstream 

from water-data stations 2 and 8 (table 5, fig. 1). 

Data for the main (order five) stream of both 

watersheds pertain to the entire watershed down 

to the main streams' confluence with the Chattahoochee River.

The exponential relations of stream order to the 

number of channels, drainage area, average channel 

length, cumulative average channel length, average 

channel drop, cumulative average channel drop, and 

average channel slope are shown in figures 8 

through 14. Average channel length is defined as 

the sum of the individual channel lengths of a given 

(stream) order divided by the total number of 

channels of that order. Average channel drop and 

average channel slope are similarly defined. Cumulative average channel length and cumulative average channel drop are computed by summing the 

respective quantities of each succeeding stream 

order. This cumulative process numerically duplicates the Horton methodology of extending the 

highest order stream to the head of its longest 

tributary.

The ratio of average channel drop to average 

channel length for each stream order defines average channel slope (fig. 14). A progressive decrease 

in channel slope occurs in both watersheds as

HORTON STRAHLER
WATERSHED AND CHANNEL MORPHOLOGY 23

g 3 

O

1 2

Soque watershed 

I Big Creek watershed

0.1 1 10 

NUMBER OF CHANNELS

100

FIGURE 8.—Relation of number of channels to stream order.

Soque watershed 

Big Creek watershed

0.1 1 10 100 

AVERAGE DRAINAGE AREA, IN SQUARE MILES

FIGURE 9.—Relation of average drainage area to stream

order.

g 3 

O

• Soque watershed

• Big Creek watershed

0.1 1 10

AVERAGE CHANNEL LENGTH, IN MILES

100

FIGURE 10.—Relation of average channel length to stream

order.

g 3 

O

Soque watershed 

Big Creek watershed

0.1 1 10 100 

CUMULATIVE AVERAGE CHANNEL LENGTH, IN MILES

FIGURE 11.—Relation of cumulative average channel length 

to stream order.

S 3

en

O

Soque watershed 

Big Creek 

watershed

10 100 

AVERAGE CHANNEL DROP, IN FEET

1000

FIGURE 12.—Relation of average channel drop to stream

order.

stream order increases. The rate of slope decrease 

for Big Creek channels is constant for the first four 

orders but decreases abruptly for the fifth-order 

stream. A similar break in the slope line for the 

Soque watershed occurs at the second-order level 

and indicates significant topographic differences between those parts of the watershed containing firstand second-order streams and those parts containing longer and flatter higher order streams.
24 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

Soque watershed 

Big Creek watershed

10 100

CUMULATIVE AVERAGE CHANNEL DROP, IN FEET

1000

FIGURE 13.—Relation of cumulative average channel drop to 

stream order.

Topographic distinctions between the plateaus 

are graphically pointed out by the plots of cumulative average channel drop against stream order 

(fig. 13). These graphs show that the rate of change 

of cumulative channel drop in both the Big Creek

TABLE 8.—Summary of geomorphic characteristics

Station name

Big Creek near

Alpharetta ___

Soque River near

Clarkesville __

Big Creek near

Alpharetta _ _

Soque River near

Clarkesville __

Stream 

order

1

2

3

4

5

1

2

3

4

5

Stream

order

1

2

3

4

5

1

2

3

4

5

Number of 

streams

173

38

12

2

1

122

27

7

3

1

Cumulative

average

channel

length

(mi)

0.61

1.46

2.74

6.24

26.4

.93

2.11

4.77

12.5

24.7

Average

drainage 

area

(mi^)

0.24

1.14

3.51

11.4

103

.46

1.86

6.42

29.8

157

CumulaAver- tive

age averchan- age

nel chandro-p nel

(ft) drop

(ft)

68 68

50 118

34 152

52 204

70 274

224 224

120 344

197 541

136 677

180 857

Average

channel 

length

(mi)

0.61

.85

1.28

3.50

20.2

.93

1.18

2.66

7.71

12.2

Average

channel

slope

(ft/ft)

0.021

.0110

.0050

.0028

.00066

.046

.019

.014

.0033

.0028

<r o i 11 O

Q 

CC 

O

to

Soque watershed 

Big Creek watershed

0.0001 0.001 0.01

AVERAGE CHANNEL SLOPE, IN FEET PER FOOT 

FIGURE 14.—Relation of average channel slope to stream order.

0.1
WATERSHED AND CHANNEL MORPHOLOGY 25

100

10

0.1

Soque watershed 

Big Creek watershed

_= 1.45 DA058

0.1 10 100 1000

AVERAGE DRAINAGE AREA, IN SQUARE MILES 

FIGURE 15.—Relation of average drainage area to cumulative average channel length.

and Soque watersheds changes abruptly from low 

to higher order streams. This point of change is a 

reflection of watershed relief and concavity and 

occurs at third-order streams in the Soque watershed and at second-order streams in the Big Creek 

watershed. The higher the order of the point of 

change, the greater is the watershed relief. Thus, 

stream-order analyses indicate greater relief and 

concavity for watersheds on the Dahlonega Plateau. 

The relation between average drainage area and 

cumulative average channel length for each stream 

order for both the Soque and Big Creek watersheds 

is shown in figure 15. Geometric regression of these 

data resulted in the following function

= IA5DA°

where

DA = drainage area in square miles, and

L = cumulative average channel length in miles.

The exponent in this equation is indicative of the 

geometric development of the watershed. An exponent of 0.50 indicates that the length of the 

watershed has developed in the same proportion to 

its width. The computed exponent of 0.58 indicates 

that both the Big Creek and Soque River watersheds 

are increasing in length faster than they are increasing in width. Examination of figures 19 and 21 

shows that both watersheds are indeed elongate. 

Studies similar to this one in different regions of 

the United States have yielded exponent values 

ranging from 0.6 to 0.7 (Leopold and others, 1964).

The coefficient of the regression equation (1.45) 

indicates the average length of principal stream 

channel supported by one square mile of watershed 

area. Thus, 1 square mile of land surface in either 

the Soque or Big Creek watersheds will support, on 

the average, 1.45 miles of principal channel. Leo-
26 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

pold and others (1964) state that the coefficient of 

similar equations for watersheds in the Northeastern United States averages about 1.40. A similar 

analysis of watersheds in the Upper Salmon River 

basin of Idaho (Emmett, 1975) produced a coefficient of 1.50.

Drainage density is denned as the total channel 

length in the watershed divided by the total drainage area and indicates the average total channel 

length supported by each square mile of watershed. 

Computed drainage densities for the Soque and Big 

Creek watersheds are 2.07 and 2.38, respectively. 

These values should not be confused with the coefficient of the regression equation described previously. This coefficient refers solely to the length of 

the principal channel and cannot be compared to 

drainage density. Emmett (1975) considers drainage density to be the most useful parameter for 

comparing stream-channel networks of different 

watersheds. Horton (1945) reported that the Hiwassee River basin above Hiwassee, Ga., has a 

drainage density of 2.06. The Hiwassee basin is 

located just north of the Soque basin, which implies 

that there is regional consistency to drainage 

densities.

OVERLAND FLOW LENGTH

Representative values of overland flow lengths 

for both the Dahlonega and Atlanta Plateaus were 

required for the computation of sheet erosion using 

the Universal Soil Loss Equation. A method to compute such values using Strahler stream-order data 

is described below for those parts of the Soque and

Big Creek watersheds draining to the water-data 

stations near Clarkesville and Alpharetta, respectively.

The length of overland flow is defined as the 

average distance traveled by surface runoff to the 

point where it enters a well-defined channel. Thus, 

by definition, overland-flow lengths pertain mostly 

to stream channels occurring on the local or microtopography and are synonomous with true field 

slope lengths. Stream channels relative to the microtopography are mostly true first-order streams that 

are rigorously defined as the shortest, unbranched 

channels occurring on the landscape. True firstorder and other low-order streams are too small to 

be shown on 1:24,000-scale maps and (generally) 

are ignored. True-order streams are quantitatively 

related to overland flow length, however, through 

drainage density, which is defined by Leopold and 

others (1964) as one-half the reciprocal of the 

length of overland flow. Thus, data required to compute overland-flow length for a particular watershed include total drainage area along with the 

total number of streams and the average stream 

length for each stream order beginning with true 

order one streams.

Field observations in the Soque and Big Creek 

watersheds indicate that first-order streams on 

1:24,000-scale maps are true fifth-order streams. 

Consequently, data from the Strahler analyses of 

stream number and cumulative average channel 

length (figs. 8 and 11) were replotted with adjusted 

ordinates beginning at the fifth-order level. The relations were then linearly extended to predict values

CC 7

111 /

Q 

DC 

O 6

CO 4

LU

I 3 

2 

1

0.01

Soque watershed 

Big Creek watershed

0.1 1.0 10 

CUMULATIVE AVERAGE CHANNEL LENGTH, IN MILES

4

S 

3 g

CM

2 £

DC 1 S

CC

O

LU 

DC

CO

TOO

FIGURE 16.—Relation of cumulative average channel length to true stream order.
WATERSHED AND CHANNEL MORPHOLOGY 27

9

8

cr 7 

m

O 

i 5

UJ o

D 3 

cc

H 2

1

3 I 

o

1 DC

HI 

Q 

DC 

O

• Soque watershed

• Big Creek watershed

10 100 1000 

NUMBER OF CHANNELS

10,000 100,000

FIGURE 17.—Relation of number of channels to true stream order.

for true first- through fourth-order streams (figs. 

16 and 17). Average channel length for the lowerorder streams were computed from the extended 

cumulative average channel-length curve. A summary of stream number and average channel-length 

data as a function of true stream order is listed in 

table 9. Note that predicted lengths of true fifthorder streams are shorter than those listed for 

first-order streams in table 8. This decreased length 

indicates that unbranched channels shown on 

1:24,000-scale maps are actually branching out into 

numerous unmapped tributaries of lower order. By 

extending the cumulative average channel-length

curve, the headwater parts of mapped unbranched 

streams have been effectively assigned to lowerorder streams. Thus, the actual length of true fifthorder streams is shorter than indicated on 1:24,000- 

scale maps and is more accurately defined by the 

data in table 9.

Computation of average overland-flow lengths 

for the Soque and Big Creek watersheds requires 

the products of average channel length and number 

of channels for each true stream order. The sum 

of these products provides a true total channel 

length in each watershed. True drainage densities 

can then be computed and inverted to obtain the

TABLE 9.—Summary of overland-flow length computation using Strahler stream-order data

Stream 

Station name order 

(1:24,000)

Big Creek near Alpharetta

1

2

3

4

5

Soque River near Clarkesville

1

2

3

4

5

True 

stream 

order

1

2

3

4

5

6

7

8

9

Total

1

2

3

4

5

6

7

8

9

Total

(i)

Average 

channel 

length 

(mi)

0.031

.037

.074

.158

.310

.850

1.28

3.50

11.0

stream lengthr=3

0.033

.043

.099

.230

.525

1.18

2.66

7.71

4.0

stream length=3

(2) 

Number 

of 

streams

65,000

15,000

3,350

760

173

38

12

2

1

,067 miles

60,000

13,000

2,800

615

122

27

7

3

1

,099 miles

(1) X (2)

2,015

555

248

120

54

32

15

7

11

1,980

559

277

141

64

32

19

23

4

Overland- Overlandflow flow 

length length 

(mi) (ft)

0.012 62

.015 79
28 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

average overland flow or field-slope lengths (table 

9) which, for the Soque and Big Creek watersheds, 

are 79 feet and 62 feet, respectively.

EROSION AND SEDIMENT DISCHARGE

The erosion and transport of sediment by water 

in the Upper Chattahoochee River basin is affected, 

in part, by four major environmental factors; land 

use, soils, topography, and climate. These factors 

are interrelated and each contributes significantly 

to total soil loss. The impact of land use relates 

directly to man's activities and is most apparent in 

the types and distribution of land cover; whether 

vegetation, roads, buildings, or other facilities. In 

general, greater densities of land cover relate to 

lower rates of erosion and erosion yield. The erodibility of a soil is controlled, for the most part, by 

its composition and structure. For example, less 

cohesive soils, such as sands, are more susceptible 

to erosion than silts or clays, provided all other 

environmental factors remain the same. Silts and 

clays, on the other hand, are more susceptible to 

water transport. The topographic and climatic factors that affect erosion and the stream transport of 

sediment most directly include, respectively, land 

slope length and gradient and rainfall and rainfall 

intensity.

DESCRIPTION OF ENVIRONMENTAL FACTORS

Maps and tables that describe land use, soils, and 

topography within watersheds that drain to selected 

water-data stations are presented below. The impact of these factors on erosion and sediment discharge in the basin is described in succeeding sections of this report.

LAND USE

Land-use data were collected, assembled, and interpreted by the Land Information and Analysis 

Branch of the U.S. Geological Survey. Original data 

were collected as high-altitude, remote-sensor imagery during the period 1971-75. Classification of 

the imagery into land-use categories was accomplished according to criteria developed by Anderson 

and others (1976). These land-use categories are 

listed on p. 30 along with respective imagery widths 

and areas. Image data whose width or area configTABLE 10.—Summary of land-use data by category

Residential

Station name

Big Greek near Alpharetta

N. Fork Peachtree Creek near Atlanta __ 

S. Fork Peachtree Creek at Atlanta _

Peachtree Creek at Atlanta

Woodall Creek at Atlanta

Nancy Creek tributary near Chamblee ___ 

Nancy Creek at Atlanta

Snake Creek near Whitesburg

Area 

(mi'J )

0.58 

.39 

.04 

2.98 

14.84 

16.45 

44.02 

.50 

.86 

18.17 

.32

Percent 

of total 

area

0.39 

.41 

.03 

4.14 

43.54 

55.57 

50.71 

16.08 

26.46 

57.59 

.86

Transportation, 

communication, and utilities

N. Fork Peachtree Creek near Atlanta __ 

S. Fork Peachtree Creek at Atlanta

Peachtree Creek at Atlanta

Nancy Creek tributary near Chamblee _ _ 

Nancy Creek at Atlanta

Snake Creek near Whitesburg

Area (mi-1 )

0.11

1.60 

1.84 

.72 

3.22 

.42 

.33 

.49

Percent 

of total 

area

0.11

2.22 

5.40 

2.43 

3.71 

13.50 

10.15 

1.55

Commercial and services

Area

(mi-1 )

0.003 

.03 

.005 

.31 

2.88 

2.47 

9.65 

.12 

.32 

2.22

Percent 

of total 

area

0.002 

.03 

.003 

.43 

8.45 

8.34 

11.12 

3.86 

9.85 

7.04

Industrial and 

commercial complexes

Area 

(mi 2 )

3.37 

1.46 

6.82 

1.62

1.79

Percent 

of total 

area

9.89 

4.93 

7.86 

52.09

5.67

Area 

(mi-)

0.61 

.41

1.37

.31

Industrial

Percent 

of total 

area

1.79

1.39 

1.58

.98

Other urban or 

built-up land

Area 

(mi-)

0.69 

.57 

.96 

2.64 

.19

1.06

Percent 

of total 

area

0.96 

1.67 

3.24 

3.04 

6.11

3.36
EROSION AND SEDIMENT DISCHARGE 29

TABLE 10.—Summary of land-use data by category—Continued

Ci'opland and pasture Orchards

Area (mi-1 )

Percent

of total

area

Area 

(mi-')

Percent

of total

area

Chattachoochee River ____________ 8.03 5.51

Soque River near Clarkesville ______ 10.36 10.79

Chestatee River near Dahlonega _______ 15.71 10.27

Big Creek near Alpharetta _________ 25.18 34.97

N. Fork Peachtree Creek near Atlanta ___ 0.04 .12

S. Fork Peachtree Creek at Atlanta ___ .05 .17

Peachtree Creek at Atlanta _______ .09 .10 

Woodall Creek at Atlanta ______

Nancy Creek tributary near Chamblee _ .031 .95

Nancy Creek at Atlanta _________ .25 .79

Snake Creek near Whitesburg ____ 5.73 15.49

	Confined feeding operations 

	Area Percent

Chattahoochee River near Leaf ______ 0.26 0.17 0.38

Soque River near Clarkesville __________ .26 .27

Chestatee River near Dahlonega ________ .025

Big Creek near Alpharetta ________ .86 1.19 8.29

N. Fork Peachtree Creek near Atlanta _ 1.02

S. Fork Peachtree Creek at Atlanta ___ 1.57

Peachtree Creek at Atlanta ______ 3.31

Woodall Creek at Atlanta __________ .18

Nancy Creek tributary near Chamblee ___ .01

Nancy Creek at Atlanta __________ 1.43

Snake Creek near Whitesburg _______ .02 .05 8.96

	Mixed forest 

	A . Percent

Chattahoochee River near Leaf ______ 139.25 92.67 0.06

Soque River near Clarkesville _______ 83.77 87.26 .22

Chestatee River near Dahlonega ______ 132.31 86.48 .21

Big Creek near Alpharetta ________ 22.88 31.78 .06

N. Fork Peachtree Creek near Atlanta __ 5.90 17.31 .18

S. Fork Peachtree Creek at Atlanta ___ 3.90 13.18 .04

Peachtree Creek at Atlanta ________ 11.0 12.67 .23

Woodall Creek at Atlanta __________ .08 2.57

Nancy Creek tributary near Chamblee __ 1.42 43.60

Nancy Creek at Atlanta __________ 3.81 12.08 .32

Snake Creek near Whitesburg _____ 13.92 37.62 .13

0.13 

.05

0.14 

.07

Deciduous forest

Area (mi-')

Percent

of total

area

Conifer forest

Area Percent

of total

area

0.25

.02

11.51

2.99

5.30

3.81

5.79

.31

4.53

24.22

1.44

.73

4.65

8.74

1.66

1.20

2.91

.76

1.22

7.84

0.96

.76

3.04

12.14

4.87

4.05

3.35

2.34

3.87

21.19

Reservoirs

Area 

(mi")

Percent

of total

area

Quarries and gravel pits

Area Percent

of total

area

0.04 

.23

.14 

.08 

.53 

.14

.27

1.01 

.35

0.12

.01 

.01

0.17

.03 

.01

Transitional areas

Station name

Anea 

(mi-')

Percent

of total

area

Ratio of cropland

area to pasture

area

(percent)

Chattahoochee River near Leaf _______

Soque River near Clarkesville _________

Chestatee River near Dahlonega ______

Big Creek near Alpharetta ___________

N. Fork Peachtree Creek near Atlanta 

S. Fork Peachtree Creek at Atlanta __. 

Peachtree Creek at Atlanta __________

Woodall Creek at Atlanta __________

Nancy Creek tributary near Chamblee . 

Nancy Creek at Atlanta ______________

Snake Creek near Whitesburg ________

0.24

1.16

.38

1.54

.21 

.48 

.08

0.33

3.40

1.28

1.77

6.34

1.52

.22

26

24

43

11

30
30 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

uration was less than the minimum were not 

mapped.

Land-use conditions in 1976, when most waterquality data were collected, are considered equivalent to those mapped for the period 1971-75.

Land use in watersheds draining- to 11 water-data 

stations is shown in figures 18 through 23. Included 

in figure 22 is land use in watersheds draining to 

North Fork of Peachtree Creek near Atlanta, South 

Fork of Peachtree Creek at Atlanta, Nancy Creek 

at Atlanta, Nancy Creek tributary near Chamblee, 

and Woodall Creek at Atlanta. Land-use data are 

listed, by station and category, in table 10. Cropland-area to pasture-area ratios obtained from the 

U.S. Department of Agriculture (1970) are also 

listed where appropriate. Forested lands account, 

respectively, for about 94, 88, and 90 percent of 

the areas draining to the Chattahoochee River near 

Leaf, the Soque River near Clarksville, and the 

Chestatee River near Dahlonega. The drainage of 

the Soque River is the most heavily urbanized and 

the most intensely farmed of the watersheds on 

the Dahlonega Plateau.

A greater land-use diversity is shown for drainages on the Atlanta Plateau. For example, the watersheds, of Big Creek near Alpharetta, Peachtree 

Creek at Atlanta, and Snake Creek near Whitesburg 

contain, respectively, about 55, 20, and 83 percent 

forest lands. Conversely, the same drainages contain about 8, 78, and 1 percent urban areas, respectively. Photographs of typical basin landscapes 

are shown in figure 24.

SOILS AND TOPOGRAPHY

Soil associations in those watersheds for which 

land-use maps have been previously discussed are 

shown in figures 25 through 30. Included in figure 

29 are soil associations in watersheds draining to 

North Fork of Peachtree Creek near Atlanta, South 

Fork of Peachtree Creek at Atlanta, Nancy Creek 

at Atlanta, Nancy Creek tributary near Chamblee, 

and Woodall Creek at Atlanta. Descriptions of individual soil associations are also listed on each figure. 

Summaries of pertinent soil and topographic data 

are listed in tables 11 to 19. Individual county soils 

reports (see Selected References) provided the general soils maps from, which the various delineations 

of soil associations were made. Also provided in 

these reports were soil descriptions and area and 

slope data relative to each of the soil types that comprise a soil association. Soil erodibility values for 

each soil type were obtained from the Georgia State 

Soil and Water Conservation Committee (1977).

Land use category

Minimum Minimum

width area

(ft) (acres)

Residential ___________________ 660 10

Commercial and services _____________ 660 10

Industrial ________________ 660 10

Transportation, communications,

and utilities ____________— 660 10

Industrial and commercial complexes-__ 660 10 

Mixed urban or built-up land ______ 660 10

Other urban or built-up land _________ 660 10

Cropland and pasture _______________ 1,320 40

Orchards, groves, vineyards,

nurseries, and ornamental

horticultural areas _______________ 1,320 40

Confined feeding operations __________ 660 10

Deciduous forest land ________________ 1,320 40

Conifer forest land ______________ 1,320 40

Mixed forest land _________ 1,320 40

Streams and canals ___________________ 660 10

Lakes ______________________ 660 10 

Reservoirs _____________________ 660 10

Forested wetlands _____________.. 1,320 40 

Nonforested wetlands __________ 1,320 40

Strip mines, quarries, and

gravel pits _________________ 660 10 

Transitional areas _-_____________ 1,320 40

TABLE 11.—Summary of soil and topographic data for the 

watershed draining to the Chattahoochee River near Leaf

Soil 

Association

Mean

slope

(percent)

Soil 

erodibility 

factor

Slope 

length

and

gradient 

factor

Cartecay-ToccoaCongaree _______

Hayesville-FaninWickham _____. 

Hayesville-RabunHiwassee _______

Haysville-FaninEdneyville ______

TallapoosaMusella ________

Edneyville-PortersAshe ________.

Rabun-HayesvilleHiwassee ____. 

Weighted mean

(watershed) ___.

1.0 

.2

37.8

46.2

54.0

2.0

1.0

13

17

17

26

30

14

23

0.18 

.28 

.24 

.23 

.29 

.24 

.25 

.25

0.12

1.74

2.77

2.84

5.52

6.91

2.13

4.95

TABLE 12.—Summary of soil and topographic data for the 

watershed draining to the Soque River near Clarkesville

Soil 

Association

Area 

(mi-)

Mean

slope

(percent)

Soil 

erodibility 

factor

Slope 

length

and

gradient 

factor

Porters-Ashe ____ 14.4 47 0.24 14.30 

Madison-Halewood _ 20.1 23 .32 4.46 

Cecil-Madison ___ 47.8 22 .32 4.11 

Clifton-Davidson __ 4.3 40 .30 11.3 

Congaree^ChewaclaBuncomb ____ 9.1 1.8 .32 .18 

Louisa-Chandler _ .3 41 .27 11.5 

Weighted mean

(watershed) __ _ 25 .30 5.68
EROSION AND SEDIMENT DISCHARGE 31

83°50' 45' 40' 83°37'30"

4 MILES

KILOMETERS

34°47'30"

45'

40'

35'

34°32'30"

Confined feeding 

operations

Water-data station

Reservoirs

FIGURE 18.—Land use in the watershed draining to the Chattahoochee River near Leaf.
32 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

83°40' 35' 30' 83°25'

34°50

45

40

35'

34°32'30"

4 MILES 

J

6 KILOMETERS

Residential

Clarkesville

EXPLANATION

Commercial and services Transportation,

cQmmunications, and

utilities

Cropland and pasture

Mixed forest land Orchards, nurseries,

and ornamental

horticultural areas

A Water-data station

Confined feeding 

operations

FIGURE 19.—Land use in the watershed draining to the Soque River near Clarkesville.
84'

34°45'

'00'

EROSION AND SEDIMENT DISCHARGE

55' 50'

33

83°45'

40'

35'

30'

34°27'30"

4 MILES

6 KILOMETERS

Residential

EXPLANATI O N

Commercial and services Cropland and pasture Mixed forest land

Confined feeding 

operations

Water-data station

FIGURE 20.—Land use in the watershed draining to the Chestatee River near Dahlonega.
34 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

84°22'30" 

34°15'

20' 15' 10' 84°07'30"

10

EXPLANATION

Confined feeding 

operations

Mixed forest land Reservoirs Strip mines, quarries, 

and gravel pits

4 MILES 

J

KILOMETERS

Transitional areas

34°00'

Water-data station 

_____I_____

FIGURE 21.—Land use in the watershed draining to Big Creek near Alpharetta.
EROSION AND SEDIMENT DISCHARGE 35

84° 2730" 25' 20' 15' 84°12'30" 

——I——

33° 57'30'

0 1

55

50'

45'

EXPLANATION

Residential Commercial and services Industrial

34°40'

Industrial and 

commercial complexes

Reservoirs

Other urban or 

built-up land

Cropland and pasture

11.

Transitional areas Unmapped

Transportation,

communications, and

utilities

Mixed forest land

Water-data 

station

FIGURE 22.—Land use in the watersheds draining to Peachtree Creek at Atlanta, Nancy Creek at Atlanta, and Woodall

Creek at Atlanta.
36 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

85C

33°40 05' 85°00' 55' 84°52'30"

1 1 1 1 1

01234 MILES 

il 1 1 1

35'

30'

33°25'

Residential

r T \ T i

23456 KILOMETERS

V..

EXPLANATION

Cropland and pasture Orchards, nurseries, 

and ornamental 

horticultural areas

Mixed forest land

Reservoirs Transitional areas

A18 

Water-data station

FIGURE 23.—Land use in the watershed draining to Snake Creek near Whitesburg.
EROSION AND SEDIMENT DISCHARGE 37

FIGURE 24.—Typical basin land use. (A) Farmstead on the Dahlonega Plateau. (Continued on p. 38.)

TABLE 13. — Summary of soil and topographic data for the 

watershed draining to the Chestatee River near Dahlonega

Slope 

goi] Mean Soil length

association Area slope erodn and (percent) bility gradient 

factor

Cartecay-ToccoaCongaree 8.1 1.0 0.18 0.12

Hayesville-FaninWickham 7.1 13 .28 1.74

Hiwa<5spp 1 17 94 9 77

Hayesville-FaninEdneyville _ 50.4 17 .23 2.84

TallapoosaMusella 45.0 26 .29 5.52

E dney ville-PortersAshe _ 37.3 30 .24 6.91

Rabun-HayesvilleHiwassee _ 5.0 14 .25 2.13

Weighted mean 

(watershed) __ _ 22 .25 4.40

The values of slope and soil erodibility for each association listed in tables 11 to 19 are area-weighted 

means based on the component soil-type data. 

As might be expected, land slopes on the Dahlonega Plateau are about twice as steep as slopes

TABLE 14. — Summary of soil and topographic data for the 

watershed draining to Big Creek near Alpharetta

„ .. Slope

„ ., . Mean ftoi- length Soil Area , erodi- a^d

association (mi*) (perceilt ) bflity gradient 

factor

Cecil-Habersham __ 7.8 7.8 0.32 0.75 

Cecil-Madison 64.2 9.8 .32 1.05

Weighted mean 

(watershed) 9.6 .32 1.02

on the Atlanta Plateau. Soil erodibility factors, on

the other hand, range from only 0.25 to 0.32 for all

of the watersheds studied.

EROSION

Erosion by water in the Upper Chattahoochee

River basin occurs as sheet and rill erosion, gully 

erosion, and channel erosion. Riil erosion is considered a minor form of sheet erosion and subsequent reference in this text to sheet erosion is understood to include both processes. With the exception 

of intensely urbanized areas, sheet erosion occurs
38 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

FIGURE 24.—Continued. Typical basin land use. (B) Cultivated field in the floodplain of the Soque River near Clarkesville.

TABLE 15. — Summary of soil and topographic data for the 

watershed draining to North fork of Peachtree Creek near 

Atlanta

Soil 

Association

ChewaclaWehadkee

Madison-PacoletGwinnett (flood 

plains)

Madison-PacoletGwinnett (hills

LouisburgWeedoweePacolet

Pacolet-GwinnettAppling-PacoletMade land

Weighted mean 

(watershed) __

Area 

(mi a)

5.24

10.56 

.14

2.59 

11.50

2.23 

1.82

Mean 

slope 

(percent)

1.0 

6.4 

16

18 

18

6.4 

18

11

Soil 

credibility 

factor

0.28 

.32 

.32

.29 

.31

.32 

.30

.31

Slope 

length 

and 

gradient 

factor

0.11 

.58 

2.21

2.73 

2.73

.55 

2.73

1.52

TABLE 16. — Summary 

watershed draining 

Atlanta

Soil 

Association

ChewaclaMadison-PacoletGwinnett (flood

Madison- PacoletGwinnett (hills

Pacolet-GwinnettMade land

Weighted mean 

(watershed) _ _ _

of soil and topographic data for the 

to South fork of Peachtree Creek at

Area 

(mi 2 )

4.57 

11.29

9.87

.35 

3.37 

.15

Mean 

slope 

(percent)

1.0

6.4

16

18 

10 

10

9.3

Soil 

credibility 

factor

0.28 

.32

.32

.31 

.31 

.31

.31

Slope 

length 

an,d 

gradient 

factor

0.11

.58

2.21

2.73 

1.14 

1.14

1.14
EROSION AND SEDIMENT DISCHARGE 39

FIGURE 24.—Continued. Typical basin land use. (C) Confined feeding operation in the floodplain of the Chattahoochee River

near Duluth. (Continued on p. 40.)

TABLE 17. — Summary of soil and topographic 

watershed draining to Peachtree Creek at

Soil 

Association

ChewaclaMadison-Pacolet> 

Gwinnett (flood

Madison-PacoletGwinnett (hills 

and ridges)

Pacolet- GwinnettLouisberg

Appling-PacoletLouisbergWeedoweePacolet

Unclassified

Made land

Weighted mean 

(watershed)

Area 

(mi 2 )

10.99 

25.44

10.43 

14.20 

2.23

2.59 

18.92 

1.97

Mean 

slope 

(percent

1.0

6.4

16 

18 

6.4

18 

11 

18

10

Soil

0.28 

.32

.32 

.31 

.32

.29 

.31 

.30

.31

data for the 

Atlanta

Slope 

length 

and 

gradient 

factor

0.11 

.58

2.21 

2.73 

.58

2.73 

1.26 

2.73

1.32

TABLE 18. — Summary of soil 

watershed draining to

Soil 

Association

Chewacla- 

\Vehadkee

Madison-LouisaMadison- PacoletGwinnett (flood

Madison-PacoletGwinnett (hills

Q T"l f\ 1*1 f\ D"O C ^

Gwinnett-PacoletGwinnett-DavisonLouisbergWeedoweePacolet

Appling-LouiisbergPacolet

Pacolet- G winnettAppling-PacoletGwinnett

Made Land

Unclassified _

Weighted mean 

(watershed) _ _

Area

4.40 

.91

13.30

2.59 

.27 

1.55

.33 

.23 

9.08

.09 

.81 

1.22

and topographic data for the 

Nancy Creek at Atlanta

Mean 

slope 

( percent)

1.0 

23

6.4

16 

18 

6.2

18 

6.6 

18

6.4 

12 

12

11

Soil 

credibility 

factor

0.28 

.31

.32

.32 

.31 

.31

.29 

.30 

.31

.32 

.31 

.31

.31

Slope 

length 

and 

gradient 

factor

0.11 

4.16

.58

2.21 

2.73

.55

2.73 

.60 

2.73

.58 

1.42 

1.42

1.38
40 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

FIGURE 24.—Continued. Typical basin land use. (D) High density housing along the Chattahoochee River near Atlanta.

TABLE 19.—Summary of soil and topographic data for the 

watershed draining to Snake Creek near Whitesburg

Soil 

Association

CongareeBuncomb

MadisonTallapoosa

Madilson-LouisaWeighted mean

(watershed) _ _ _

Area 

(mi a)

1.4

16.1

19.5

——

Mean 

slope 

(percent)

1.2

3.8

18

11

Soil

credibility 

factor

0.34

.31

.31

.31

Slope

length 

and 

gradient

0.12

.31

2.73

1.58

throughout the basin and is, by far, the predominant 

erosional process. Gully erosion occurs mostly in 

transitional areas where vegetation has been recently stripped from the land surface. Land-use data 

(table 10) indicate that transitional lands occupy 

only about 1 percent of the basin area. Thus, the 

contribution of gully erosion to total erosion in the 

basin is considered small. Channel erosion occurs

mostly in the form of streambank erosion and was 

qualitatively evaluated through field reconnaissances 

during the period 1975-77. The relative stability of 

channel dimensions was assessed by noting the occurrence of bank sloughing and channel debris and 

the abundance and type of bank vegetation. These 

assessments indicated that relatively severe bank 

erosion had occurred in the headwaters of Nancy 

Creek and South Fork of Peachtree Creek, in downstream parts of Peachtree Creek, and along the 

Chattahoochee River downstream of Buford Dam. 

Local erosion of stream banks was also noted in 

reaches where the landscape had been recently disturbed or where flow velocities were unusually high. 

Bank erosion in the remainder of the stream system 

was observed to be relatively minor.

Average annual sheet erosion within each of the 

watersheds shown in figures 18 through 23 was 

quantitatively evaluated using the Universal Soil 

Loss Equation. As developed by Wischmeier and
EROSION AND SEDIMENT DISCHARGE 41

FIGURE 24.—Continued. Typical basin land use. (E) Residential park in the Peachtree Creek watershed.

(Continued on p. 42.)

Smith (1965), the Universal Soil Loss Equation has 

the general form

E=RxKxLSxCxP

where

E = average annual sheet erosion in tons per

acre,

R = rainfall factor, 

K = soil credibility, 

LS = slope length and gradient factor, 

C = crop management factor, and 

P= conservation practice factor.

The rainfall factor (R) expresses the erosion potential of long-term, average annual rainfall. Bainstorm characteristics used to derive the factor are 

the total kinetic energy of the storm and its maximum 30-minute rainfall intensity. Values of rainfall factor for watersheds discussed in this report 

were derived from Wischmeier and Smith (1965) 

and are listed below by water-data station.

Station name

Rainfall 

factor

Chattahoochee River near Leaf ____. 

Soque River near Clarkesville ______.

Chestatee River near Dahlonega _____.

Big Creek near Alpharetta _________

North Fork Peachtree Creek at Atlanta 

South Fork Peachtree Creek at Atlanta - 

Peachtree Creek at Atlanta _______-

Nancy Creek at Atlanta __________-

Snake Creek near Whitesburg _____.

280

340

300

270

300

300

300

300

325

The soil erodibility factor (K) represents the 

average annual sheet erosion for a particular soil 

in tons per acre per unit of rainfall factor (R). 

Values of K for this study were obtained from literature sources but were originally determined from 

field measurements where erosion of various soil 

types was observed under standard topographic, 

cropping, and conservation conditions.

Wischmeier and Smith (1965) define slope length 

as the distance from the point of origin of overland
42 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

FIGURE 24.—Continued. Typical basin land use. (F) Fossil fuel powerplant adjacent to the Chattahoochee River at Atlanta.

flow to (1) the point where the slope decreases to 

the extent that deposition begins or (2) the point 

where runoff enters a well-defined channel. For this 

study the slope lengths of 79 feet and 62 feet computed from the extrapolation of stream-order data 

were used, respectively, for all areas on the Dahlonega and Atlanta Plateaus. The slope length and 

gradient factor (LS) is used to adjust the estimate 

of sheet erosion to specific landscapes. Each factor 

represents a function of slope steepness and length 

relative to sheet erosion measured on a standard soil 

plot constructed with a slope length of 72.6 feet and 

a land slope of 9 percent. The factor value for a 

specific slope length and land slope is computed by 

the formula

(A) 0- 5 

72.6

• xwhere

A = true slope length (79 or 62 feet), and

a; = the sine function of the angle of land slope 

in degrees.

LS factors for the various soil associations in the 

basin were computed using this function and the 

given slope lengths and area-weighted land slopes 

discussed previously (tables 11 to 19). The computed 

LS factors are listed, according to soil association, 

in tables 11 to 19.

The cropping management factor (C) was originially defined by Wischmeier and Smith (1965) 

as the ratio of (1) sheet erosion measured from 

standard soil plots with specified cropping conditions to (2) the erosion measured from identical 

plots under conditions of clean-tilled, continuous 

fallow. Other C factors have been recently developed 

for various uses such as row crops, forest, pasture, 

and cropped woodland and are listed in publications of the Georgia Soil and Water Conservation 

Committee (1977) and the U.S. Department of 

Agriculture (1977). Cropping management factors
EROSION AND SEDIMENT DISCHARGE 43

83°50' 45' 40' 83° 37'30"

34°47'30"

45'

40'

35'

Cartecay-Toccoa-Congaree 

Loam, fine sandy loam, 

loamy sand, or gravelly 

loamy sand. Alluvium

Hayesville-Fannin-Wickham

Sandy loam, sandy clay loam,or

clay loam derived from schist,

granite, gneiss, quartzite, and

some basic rocks

Hayesville-Rabun-Hiwassee 

Sandy loam, sandy clay loam derived from schist and gneiss and 

their micaceous equivalents, 

granite, and some basic rocks

34°32'30"

Hayesville-Fannin Edneyville 

Sandy loam, sandy clay loam, 

or clay loam derived from 

schist, granite, gneiss, 

quartzite, and some basic 

rocks

Tallapoosa-Musella Edneyville-Porters-Ashe 

Fine sandy loam to cobbly Fine sandy to clay loam 

sandy loam derived from derived from biotite 

mica schist, quartzite, gneiss, schist, and 

mica gneiss, and some granite 

basic rocks

Rabun-Hayesville-Hiwassee 

Clay to sandy loam derived 

from hornblende gneiss, 

diorite, hornblende schist, 

gneiss, and granite

FIGURE 25.—Soil associations in the watershed draining to the Chattahoochee River near Leaf.
44 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

83°40' 35' 30' 83°25' 34°50'

2 3 4 MILES 

I____I____I I \ II I i

1 23456 KILOMETERS

45'

40'

35'-

Clarkesville

EXPLANATION

A Water-data station

Porters-Ashe

Clay to sand loam in stony 

matrix derived from 

granite gneiss

Madison-Halewood 

Fine sandy loam derived 

from quartz and mica 

schist

Cecil-Madison 

Fine sandy to sandy loam 

derived from gneiss and 

micaceous schist

Cliffton-Davidson 

C/ay or c/ay loam in stony 

matrix derived from basic 

rocks, mostly diorite

34°32'30'" -

Congaree-Chewacla-Buncombe Louisa-Chandler

Silt, fine sandy loam Loam and sandy loam derived 

and sand. Alluvium from micaschist, schist and 

micaceous gneiss.

FIGURE 26.—Soil associations in the watershed draining to the Soque River near Clarkesville.
EROSION AND SEDIMENT DISCHARGE 45

84°00' 

34°45'|——

55' 

T"

50'

T~

83°45' 

——I—

40'

34°27'30" -

0 1 2 34 MILES

III I , I I

I'll I I I T

0 1 2 3 4 5 6 \- ILOMETERS

Dahlonega

EXPLANATION

4A Water-data station

Cartecay-Toccoa-Congaree 

Loam, fine sandy loam, 

loamy sand, or gravelly 

loamy sand. Alluvium

Hayesville-Fannin-Wickham 

Sandy loam, sandy clay loam, 

or clay loam derived from 

schist, granite, gneiss, 

guartzite, and some basi 

rocks

Hayesville-Rabum- Hiwassee 

Sandy foam to sandy clay loam 

derived from schist and gneiss 

and their micaceous equiua/ents, 

granite, and some basic rocks

Hayesville-Fannin

Edneyville

Sandy loam, sandy clay loam 

or clay loam derived from 

schist, granite, gneiss, 

quartzite, and some basic 

-. rocks

Tallapoosa-Musella 

Fine sandy loam to cobb/y 

sandy loam derived from 

mica schist, quartzite, 

mica gneiss, and some basic 

rocks

Edneyville-Porters-Ashe 

Fine sandy to c/ay loam 

derived from biotite 

gneiss, schist, and granite

Rabun-Hayesville-Hiwassee 

Clay to sandy loam derived 

from hornblende gneiss, 

diorfte, hornblende schist, 

gneiss, and granite

FIGURE 27.—Soil associations in the watershed draining to the Chestatee River near Dahlonega.
46 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

34°15'

84°20' 15' 84°10'

EXPLANATION

10'

Cecil-Madison 

Clay loam to fine sandy 

loam derived from gneiss, 

schist, granite and 

micaceous equivalents of 

gneiss and schist

Water-data station

34°00'

FIGURE 28.—Soil associations in the watershed draining to Big Creek near Alpharetta.
EROSION AND SEDIMENT DISCHARGE 47

°27'30" 25' 15'

33°57'30

EXPLANATION

^

Water-data station

33°40'-

Chewacla-Wehadkee

Sift loom to sifty clay

loam. Alluvium

Louisburg-Weedowee-Pacolet

Sandy loam to cobb/y sandy

loam derived from diorite,

micaceous quartz, granite,

gneiss, and mica schist

Madison-Louisa-Pacolet 

Gravelly sandy to clay 

loam derived from granite, 

schist, gneiss, and their 

micaceous equivalents

Madison- Pacolet-Gwinnett

(flood plains) 

Sandy clay to gravelly

sandy loam derived from

gneiss and schist

Appling-Louisburg-Pacolet 

Clay to sandy clay loam to 

sandy loam derived from 

granite, diorite. gniess, 

and mica schist

Appling-Pacolet-Gwinnett 

Clay loam, sandy loam,or 

loam derived from gneiss, 

granite schist, and some 

basic rocks

Gwinnett -Pacolet-Musella 

Loam, clay loam, sandy loam, 

or cobb/y sandy loam 

derived from basic rocks, 

granite, and gneiss

Madison-Pacolet-Gwinnett

(hills and ridges) 

Sandy clay to gravelly 

sandy loam derived from 

gneiss and schist

Made Land 

Cuts and fills, soil 

profile disturbed or 

removed

Gwinnett-Davidson-Musella

Sandy loam or clay loam

derived from diorite,

and other basic rocks

Pacolet-Gwinnett-Louisburg 

Clay loam, sandy loam, stony 

loamy sand, or loamy sand 

derived from basic rocks, 

granite, and gneiss

Unclassified 

Heavily built-up land, 

soil profile disturbed 

and covered

FIGURE 29.—Soil associations in the watersheds draining to Peachtree Creek at Atlanta, Nancy Creek at Atlanta,

and Woodall Creek at Atlanta.
48 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

85°05' 

33°40'

85°00' 55' 84°52'30"

35

30'

33°25'

t

Congaree-Buncombe 

Silt loam to fine sandy 

loam to loamy fine sand. 

Alluvium

EXPLANATION

Madison-Tallapoosa 

Fine sandy loam derived 

from mica schist, mica 

gneiss, and quartz mica 

schist

A18 

Water-data station

Madison-Louisa-Tallapoosa 

Gravelly fine sandy loam 

derived from mica schist, 

mica gneiss, and guartz 

mica schist

MILES

KILOMETERS

FIGURE 30.—Soil associations in the watershed draining to Snake Creek near Whitesburg.
EROSION AND SEDIMENT DISCHARGE 49

used in this study were obtained mostly from these 

sources and are listed below by land-use activity.

C factor Land use

0.52 _. 

.07 _. 

.0005 

.30 _. 

.01 - 

.01 _. 

.00 .. 

.05 _. 

.50 _. 

.34 _.

Row crop

Pasture

Undisturbed forest

Orchards

Confined feeding operations

Residential

Industrial and transportation

Other urban

Transitional areas

Cropped woodland

The assignment of a C factor to a particular land 

use was based, in part, on a concept of the general 

character of that use throughout the basin. The C 

factor for croplands (0.52), for example, was based 

on the planting and harvesting of corn, the annual 

reseeding of cornfields, and the turn plowing of 

crop residues into the field after harvest. The C 

factor assigned to pasture lands (0.07) is representative of cleared land with no appreciable canopy 

and a 60-percent cover of weeds and grasses. Forested areas were considered managed with a tree 

canopy of about 80 percent and a 90-percent cover 

of forest litter on the soil surface (C factor = 

0.0005). The C factors assigned to transitional 

areas and cropped woodlands (0.50 and 0.34) are 

typical of land that has undergone a recent and 

large-scale disturbance.

Cropping management factors for residential, 

confined feeding, and other land uses such as parks 

and golf courses were not available from literature 

sources. Cropping management factors were developed for these categories by treating them as 

pasture land with varying degrees of canopy and 

ground cover.

Structures and other impervious areas associated 

with commercial, industrial, and transportation 

land uses cover the land surface so extensively that 

soil erosion is effectively inhibited. A C factor of 

zero was assigned to these areas.

The conservation practice factor (P) accounts 

for control practices such as contour plowing or 

terracing that reduce the erosion potential of runoff 

by influencing drainage patterns, runoff concentration, and runoff velocity. The P factor applies only 

to cultivated areas and relates a particular practice 

to land slope. Contour plowing is widely practiced 

in the basin and was the only conservation practice 

considered in this study. Listed below are the pertinent P factors for various ranges of land slope.

The P factor for land uses other than cropland 

equals 1.0.

Land slope (percent) P factor

1.1 to 2

2.1 to 7

7.1 to 12

12.1 to 18

18.1 to 24

0.4

.5 

.6 

.8 

.9

To compute sheet erosion (E) using the Universal Soil Loss Equation the land use and soil maps 

for each watershed (figs. 18-23 and 25-30) were 

divided into 14-square mile areas or nodes. The 

various equation factors listed above were applied 

to each node according to the location of the area, 

the land use, the soil association, and the land slope 

pertinent to the node. Because cropland and pasture 

were mapped as a single unit (figs. 18-23), the 

designation of cropland or pasture at particular 

nodes was random and based on the ratio of cropland to pasture area listed in table 10. Average 

annual sheet erosion at each node was computed as 

the product of the assigned factors. Total sheet 

erosion in each watershed was computed as the sum 

of all nodal values for that watershed. Table 20 

lists the computed average annual sheet erosion and 

erosion yields.

The impact of future timber harvesting on sheet 

erosion was also estimated using the Universal Soil 

Loss Equation. Cropping management factors were 

converted from 0.0005 to 0.34 for a 2-square mile 

area in the Chattahoochee near Leaf watershed

TABLE 20.—Sheet erosion and erosion yields computed by 

the Universal Soil Loss Equation

Station name

Chattahoochee River

Soque River 

near Clarkesville ____ 

Chestatee River 

near Dahlonega

Big Creek

N. Fork Peachtree 

near Atlanta

S. Fork Peachtree 

at Atlanta

Peachtree Creek

Nancy Creek 

at Atlanta

Snake Creek 

near Whitesburg ____

Drainage 

area 

(mi-)

150

96.0 

153

72.0

34.1

29.6

86.8

34.8

37.0

Average 

annual 

sheet 

erosion 

(tons/yr)

305,000

613,000 

482,000

199,000

41,800

25,600

80,500

30,500

70.300

Erosion 

yield 

(tons/yr/mi-)

2,030

6,390 

3,150

2,760

1,230

860

930

880

1.900
50 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN 

TABLE 21.—Summary of regression data relating suspended-sediment concentrations to stream discharge

Station name

Suspended sediment

Correlation 

coefficient

Number

of 

samples

Chattahoochee River near Leaf ______

Soque River near Clarkesville _______

Chestatee River near Dahlonega ______

1 Big Creek near Alpharetta _________

2 Big Creek near Alpharetta _______.

3 Chattahoochee River at Atlanta ____

4 Chattahoochee River at Atlanta ____

N. Fork Peachtree Creek near Atlanta _ 

S. Fork Peachtree Creek at Atlanta ____

Peachtree Creek at Atlanta _______.

Woodal Creek at Atlanta ___________

Nancy Creek tributary near Chamblee _. 

Nancy Creek at Atlanta ______________

Proctor Creek at Atlanta ____________.

4 Chattahoochee River near Fairburn __. 

Snake Creek near Whitesburg _________

4 Chattahoochee River near Whitesburg .

Chattahoochee River near Leaf ____ 

Soque River near Clarkesville ________

Chestatee River near Dahlonega ______.

1 Big Creek near Alpharetta _______.

- Big Creek near Alpharetta ___________

3 Chattahoochee River at Atlanta _____

4 Chattahoochee River at Atlanta ______

N. Fork Peachtree Creek near Atlanta _. 

S. Fork Peachtree Creek at Atlanta ___. 

Peachtree Creek at Atlanta ___________

Woodall Creek at Atlanta __________.

Nancy Creek tributary near Chamblee _. 

Nancy Creek at Atlanta _____________

Proctor Creek at Atlanta _________.

4 Chattahoochee River near Fairburn __. 

Snake Creek near Whitesburg _________

4 Chattahoochee River near Whitesburg

0.00129

.568

.00119

.0145

5.61

.000820

.000598

.155

.202

.573

14.0

1.85

.384

12.6

.105

.569

.00492

1.61

.950

1.66

1.74

.457

1.27

1.61

1.33

1.34

1.03

.399

1.32

1.20

.787

.884

1.12

1.21

0.94 

.95 

.93 

.99 

.84 

.81 

.93 

.94 

.99 

.89 

.96 

.99 

.97 

.98 

.86 

.81 

.91

14

16

36

5

15

31

9

15

15

39

7

7

9

6

9

37

15

Suspended silt -)- clay

Correlation 

coefficient

Number

of 

samples

0.00780

1.20

.00135

.0249

9.99

.00964

.00110

.279

.350

.517

12.3

1.61

.396

6.76

.0780

.517

.00594

1.27

.701

1.55

1.61

.302

.923

1.49

1.15

1.14

.945

.400

1.30

1.16

.867

.878

1.09

1.16

0.89 

.80 

.93 

.97 

.85 

.68 

.87 

.93 

.97 

.89 

.97 

.98 

.96 

.96 

.90 

.74 

.94

14

19

36

5

16

31

10

16

16

15

7

7

12

8

7

33

15

1 rise

- peak and recession

3 regulated flow

4 intervening runoff

(fig. 18) and a 1-square mile area in the Snake 

Creek drainage near Whitesburg (fig. 23). As a 

result, computed average annual sheet erosion increased from 305,000 tons per year to 536,000 tons 

per year in the Chattahoochee River drainage and 

from 70,300 tons per year to 111,000 tons per year 

in the Snake Creek drainage. Thus, in both watersheds the hypothetical disturbance of a relatively 

small area greatly increased the total computed 

sheet erosion.

Comparison of erosion yields in table 20 with the 

environmental factors discussed previously provides

some insight into the relations between environmental factors and erosion. Erosion yields were 

greater in watersheds with relatively large LS and 

rainfall factors. Relatively large yields also occurred in those watersheds containing large percentages of agricultural and transitional land uses.

SEDIMENT DISCHARGE

Sediment discharge is defined as the rate at which 

sediment passes a section of a stream and is generally reported in tons per day or tons per year. 

When expressed in tons per day, the instantaneous
EROSION AND SEDIMENT DISCHARGE 51

suspended-sediment discharge is calculated as the 

product of stream discharge in cubic feet per 

second (ftVs), suspended-sediment concentration in 

milligrams per liter (mg/L), and the conversion 

factor 0.0027.

For this study, both instantaneous and average 

annual discharges of total-, suspended-, bed-, and 

unmeasured-sediment discharges are considered. 

Total-sediment discharge is defined as the sum of 

the suspended-sediment and unmeasured-sediment 

discharges. Unmeasured-sediment discharge is denned as the sum of the bed- and the suspendedsediment discharges transported in the water 

column below a distance of about 0.3 foot above 

the stream bed. Sediments suspended in this part 

of the water column cannot be measured by depthintegrating samplers, hence the term unmeasured 

discharge. Unmeasured- and bed-sediment discharges listed in this report were computed using 

techniques developed by Colby and Hembree (1955) 

and Einstein (1950).

SUSPENDED SEDIMENT

Regression relations describing suspended-sediment and suspended silt plus clay concentrations as

a function of instantaneous stream discharge were 

developed for each water-data station. At most stations these transport relations were satisfactorily 

explained by the general geometric function

where

C = suspended-sediment concentration in miligrams per liter, 

Qt; = instantaneous stream discharge in cubic

feet per second, and 

a and b = regression constants.

A summary of the regression analyses for each 

water-data station is listed in table 21. Correlation 

coefficients for all regressions ranged from 0.68 to 

0.99 and were 0.85 or greater for 28 relations. The 

minimum data base for any relation wa,s 5 samples; 

17 relations were developed using 14 samples or 

more.

Concentration versus discharge curves for selected 

water-data stations are shown in figures 31 to 35. 

The specific data points from which the curves were 

plotted are also shown and indicate whether the 

water sample was collected on the rise, peak, or recession of a flow event. With the exception of one

10,000

<DC 

K CC

zjg

LU 2

5 <

— DC Q in LU — 

C/5 -j

Q^

1000

100

10

100 1000 10,000

DISCHARGE, IN CUBIC FEET 

PER SECOND

EXPLANATION

• Rise 

A Peak

• Recession

1000

LU DC

ou.

100

10

100 1000 10,000

DISCHARGE, IN CUBIC FEET 

PER SECOND

B

FIGURE 31.—Relation of suspended-sediment concentrations to stream discharge at the Chestatee

River near Dahlonega.
52 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

1000 i——————————i——————ST——i 1000

CO 2 CO

Q H 5 100

10

§1S

fl. H OC tiMK 5i

Q O <

yj z 2

100

10

10 100 500 1000 10 100 500 1000

DISCHARGE, IN CUBIC FEET 

PER SECOND

O QC CJLU

5 $

5 g LU W

DISCHARGE, IN CUBIC FEET 

PER SECOND

B

1000

100

o

1000

CO Z ^

3gB

5PS 

w g <

Q O g

LU Z i2 Q O -J 

2 O —

100

10 100 1000 10,000 10 100 1000 10,000

DISCHARGE, IN CUBIC FEET 

PER SECOND

DISCHARGE, IN CUBIC FEET 

PER SECOND

D

i Rise

EXPLANATION 

A Peak •Recession

FIGURE 32.—Relation of suspended-sediment concentrations to stream discharge at Big Creek near Alpharetta.

station, the relations were not sensitive to riverstage direction. At the excepted station, Big Creek 

near Alpharetta, the concentrations of suspended 

sediment transported during periods of rising stage 

were significantly higher than corresponding concentration transported at the same discharge during periods of peak stage or recession.

At the Chiattahoochee River at Atlanta, the concentration of suspended sediment was observed to 

be sensitive to the source of water in the channel. 

The concentrations of suspended sediment trans^ 

ported by regulated flows were significantly lower 

than sediment concentrations related to intervening 

runoff at the same discharge (fig. 33). The concentration versus discharge relations pertaining to regulated flows were developed from data collected during the late spring and summer of 1976 when tributary contributions to the Chattahoochee River 

between Buford Dam and Atlanta were minimal. 

Sediment data relative to runoff were collected during basin-wide rainfall events when river flows at 

Atlanta were comprised mostly of surface runoff.

Similar, though less pronounced, concentration 

differences were observed at the Chattahoochee 

River near Fairburn and near Whitesburg. Suspended-sediment data listed for these two stations, 

however, were collected mostly during runoff events 

and are not representative of regulated flows 

(fig. 35).

AVERAGE ANNUAL SUSPENDED SEDIMENT DISCHARGE

Average annual suspended-sediment discharges 

were computed by a modified version of the sediment-transport, flow-duration curve method described by Colby (1956) and Miller (1951). For each 

water-data station this method combines discharges 

and corresponding percentages of time from the 

flow-duration curve with corresponding suspendedsediment concentrations from the concentrationdischarge curve. Instantaneous suspended-sediment 

discharges for each river discharge at each flow 

duration are computed and weighted by the corresponding percentage of time. The sum of the
S USPENDED-SEDIMENT CONCENTRATION, 

IN MILLIGRAMS PER LITER

8-

Cb

O

-a 33 m CD

is

O o

SUSPENDED SILT PLUS CLAY CONCENTRATION, 

IN MILLIGRAMS PER LITER

O ^m 

CO _

is

o 3 

o

SUSPENDED-SEDIMENT 

IN MILLIGRAMS 

m /->

"I

-03J 

m CD 

3J m

SUSPENDED SILT PLUS C

IN MILLIGRAMS 

-a 33 

m CD 

33 m

en - 

m ^ 

O ^
54 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

10,000

g

H

oc

t- en

2 LU

^ <

^ oc Q (^

1000

100

10

• Rise 

A Peak

• Recession

1000

10 100 1000 10,000 

DISCHARGE, IN CUBIC FEET PER SECOND

A

1000

LU <T

l8§

a. . -!

100

10

• Rise 

A Peak

• Recession

10 100 1000 10,000

DISCHARGE, IN CUBIC FEET PER SECOND

B

FIGURE 34.—Relation of suspended-sediment concentrations 

to stream discharge at Peach tree Creek at Atlanta.

weighted values is the average annual suspendedsediment discharge at the station. The flow duration 

and concentration-discharge relations used in these 

computations are considered representative of longterm conditions in the basin. Average annual discharges of suspended sediment and suspended silt 

plus clay were computed at each water-data station 

and are listed in table 22.

by 2 i:

5 F LU

LU < Q.

CO OC

A H CO 100

LU ^ Q. O 

CO O 

D 

CO

10

• Rise

• Recession

1000 10,000 100,000 

DISCHARGE, IN CUBIC FEET 

PER SECOND 

A

1000

CO

100

CO O =! 

CO ^

10

• Rise

• Recession

1000 10,000 100,000

DISCHARGE, IN CUBIC FEET 

PER SECOND

B

FIGURE 35.—Relation of suspended-sediment concentrations to stream discharge at the Chattahoochee River near Whitesburg.

Suspended-sediment discharges for Big Creek 

near Alpharetta were computed using the concentration-discharge curves for both rising stage and 

peak and receding stages. These discharges were 

then weighted according to the amount of time the 

daily streamflow at the station was reported to be 

rising (25 percent) and receding (75 percent) during the period of record. The sums of the weighted 

discharges are the values listed in table 22.

Annual suspendedjsediment discharge at the Chattahoochee River at Atlanta was computed for both 

regulated flows and intervening runoff. Computed 

annual suspended-sediment discharges at the Chat-
EROSION AND SEDIMENT DISCHARGE 55

TABLE 22.—Average annual suspended-sediment discharge and yield

Station name

Soque River near Clarkesville _ _ _

Chestatee River near Dahlonega

Big Creek near Alpharetta _ _ _ .

1 Chattahoochee River at Atlanta

N. Fork Peachtree Creek near Atlanta _

S. Fork Peachtree Creek at Atlanta

Peachtree Creek at Atlanta

Woodall Creek at Atlanta _ _

Nancy Creek tributary near Chamblee

Nancy Creek at Atlanta _ _

Proctor Creek at Atlanta

Chattahoochee River near Fairburn

3 Chattahoochee River near Fairburn

Snake Creek near Whitesburg _

Chattahoochee River near Whitesburg _ __

Suspendedsediment 

discharge 

(tons/yr)

_ — _ 43,000

___ _ 43,200

. _ _ 52,300

. ___ 24,000

_ _ _ 108,000

. _ _ 62,300

._ _ 15,100

. — _ 25,400

. _ 65,500

_ __ _ 1,230

275

19,800

______ 1,540

311,000

. _ 62,300

. _ _ 13,300

. _ 449,000

. _ 62,300

Suspendedsediment 

yield 

(tons/yr/mi 2 )

287

450

342

333

415

443

858

755

397

86

569

99

366

359

368

Suspended 

silt plus clay 

discharge 

(tons/yr)

18,800

17,900

24,700

17,800

75,300

41,000

8,820

12,200

32,500

960

224

16,000

1,040

220,000

41,000

10,000

340,000

41,000

Suspended 

silt plus clay 

yield

(tons/yr/mi a )

125

186

161

247

283

259

412

374

310

70

460

67

256

270

274

1 Discharge attributed to regulated flow.

2 Discharge attributed to regulated flow. Equals computed discharge at the Chattahoochee River at Atlanta.

taihoochee River near Fairburn and near Whitesburg pertain only to intervening runoff. The sus^ 

pended-sediment discharges contributed by regulated 

flow to the stations near Fairburn and Whitesburg 

were considered equal to the annual discharge computed for the upstream station at Atlanta. Yields 

of suspended sediment for stations on the Chattahioochee River downstream of Buford Dam were 

computed for intervening runoff only using the 

drainage area between the dam and the particular 

station rather than the total drainage area at the 

station. Sediment transported by regulated flows 

was considered to be derived entirely from the river 

channel.

MECHANICS OF SUSPENDED SEDIMENT TRANSPORT

Although stream discharge has been shown to be 

the primary determinant of suspended-sediment concentrations at the various water-data stations, other 

factors such as channel and streambed characteristics, stream velocity, and depth of flow also influence 

the quantity and distribution of sediment carried in 

suspension, especially with respect to the sand-size 

particles.

Typical channel and streambed characteristics in 

the basin have been summarized previously in figure 

5. In general, suspended-sediment concentrations 

are most sensitive to those channel characteristics 

that tend to produce or increase turbulence. Conse^ 

quently, streamflow along rock beds or beds containing large rocks and boulders tends to transport 

larger quantities of suspended sediment per unit

volume of water than streamflow across a sand and 

gravel bed. Similarly, channel constrictions such as 

debris or bridge piers also tend to increase suspended-sediment concentrations. A major constriction of the channel can cause scour of the streambed as noted at Big Creek near Alpharetta and 

Peachtree Creek at Atlanta (figs. SB and 5z>) .

Lateral distributions of suspended-sediment concentration, mean velocity, and depth of flow are 

shown for several water-data stations in figures 36 

to 40. Also shown are sediment sizes indicating the 

size (D5 o) which was larger than 50 percent, by 

weight, of the sampled bed material. The date and 

discharge relative to the measurements are also 

listed. These data represent measurements made at 

a limited number of discrete, vertical lines and 

should not be construed as a complete description 

of lateral parameter distribution across the various 

sections.

The sensitivity of suspended-sediment concentration to flow parameters is shown to vary not only 

with the station but with different flow conditions 

at the same station. For example, lateral distribution 

of suspended sediment at the North Fork of Peachtree Creek and at Snake Creek near Whitesburg 

were, respectively, directly and inversely related to 

corresponding distributions of flow velocity and 

depth (figs, 38 and 40). At the Chestatee River near 

Dahlonega (fig. 36), the lateral distribution of suspended sediment varied directly with velocity and 

depth at a discharge of 3,200 cubic feet per second 

and varied inversely with velocity at a discharge of 

7,280 cubic feet per second.
56 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

3000

o LLJ -j-1

z cc O LU

o °-

2500

2000

1500

LLJ -j

o i

1- 

LU 

Q_ 

V)

V)

1000

500 -

March 16, 1976 discharge =3200 ftVs 

May 15, 1976 discharge =7280 ft3/s

100 125 150 175

HORIZONTAL DISTANCE, IN FEET

A

200

0 8.0

March 16, 1976 

May 15, 1976

125 150 175

HORIZONTAL DISTANCE, IN FEET

B

200

14.0

12.0

- 10.0 

nf

Q. 

LLJ 

Q

8.0 -

March 16, 1976 discharge =3200 ftVs 

May 15, 1976 discharge =7280 ft3/s

6.0

100 125 150 175 

HORIZONTAL DISTANCE, IN FEET

c

200

2.0

1.5

3 1.0

.5

March 16, 1976 

May 15, 1976

discharge =3200 ft3/s 

discharge =7280 ft3 /s

100 125 150 175 200

HORIZONTAL DISTANCE, IN FEET 

D

FIGURE 36.—Lateral distributions of suspended-sediment concentration, flow velocity, flow depth, and size of bed material

at the Chestatee River near Dahlonega.

The effect of suspended-sediment concentration 

and flow parameters on bed-sediment size can be 

illustrated with data from Big Creek near Alpharetta (fig. 37). At a discharge of 576 cubic feet per 

second the size of bed material across the channel 

varied directly with suspended-sediment concentration, velocity, and depth. An inverse relation between the same parameters occurred at a discharge 

of 1,330 cubic feet per second. Such examples illustrate the uncertainty experienced in relating flow 

parameters to sediment transport. In general, however, the data presented (figs. 36-40) indicate that 

concentrations of suspended sediment in basin 

streams are proportional to stream velocities. Sedi-
o 

a

O

»O Q £D 

£ ^ 3

3 §:

P CD fD

5 5 P" o- g_ S;

CD" CD 3

0- -

c ~

CD

B/ to 

I ?

^ CD

O ^

OTQ CD 

CD o

2 c

rS S

^ O

O O

Hj fO,

5' 3

sP CL

o g

M u

CD O 

P (T>

»1 3

>3£-. P 

*d £T. P^§

a"tt

Fl

tb 1

ffl 3

CL

8*

Q.

g2.

DEPTH, IN FEET

o b

O

33 

N O

O § g

co -»_»_.

•>J co co co

O5 Vj -xj -xj

9". Q. Q- QM -» CJ1

M CO ->J

-sj CO 05

D5n , IN MILLIMETERS

N O

oi

• •

_, co co '

•^ I ~^

CO CO

•xl -xl

cn cn

Qo o cn

CD ^

§g g • "' o

3 » ^

N O

SUSPENDED-SEDIMENT 

IN MILLIGRAMS 

1 w O2

N O

H M 

> o

MEAN VELOCITY, IN FEET 

o o
58 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

Z* 2000 

O

(-

QC

uj *= 1500 o -1

O uj

U Qi- (n

SI ^ 5

Q <2

UJ _l

°? —

Q 2

UJ

Q Z

o0o

500

• March 12, 1976 discharged 300 ftVs

10 20 30 40 50 60 

HORIZONTAL DISTANCE, IN FEET

A

70

8.0

6.0

4.0k

2.0 -

• March 12, 1976 discharge=1300 ftVs

0 10 20 30 40 50 60 

HORIZONTAL DISTANCE, IN FEET

70

5.0

4.0

3.0

2.0

1.0

• March 12, 1976 discharge=1300 ftVs

10 20 30 40 50 60 

HORIZONTAL DISTANCE, IN FEET 

B

0.5 -

$

Q

• March 12, 1976 discharged300 ftVs

0 10 20 30 40 50 60 

HORIZONTAL DISTANCE, IN FEET

D

FIGURE 38.—Lateral distributions of suspended-sediment concentration, flow velocity, flow depth, and size of bed material

at North Fork of Peachtree Creek near Atlanta.

storm was developed by interpolating between the 

instantaneous discharge measurements. At most 

stations, the sediment-discharge and stream hydrograph were in phase or nearly in phase and peaked 

at approximately the same time. At Big Creek near 

Alpharetta, however, most of the sediment load 

significantly preceded the water load from the 

storm. Integration of the sediment-discharge hydrographs provided the storm discharge of suspended 

sediment. The computed storm load is listed on 

each figure and, in most cases, amounts to a significant part of the average annual suspended-sediment discharge (table 22).

UNMEASURED AND BED SEDIMENT 

DESCRIPTION AND SOURCE

Streams in the Upper Chattahoochee River basin 

transport a variety of sediment from several 

sources. Silts and clays are supplied mostly by overland flows; sand and gravel are generally available 

from the streambed and bank storage. During 

transport, the coarser materials (sand and gravel) 

are transported along or just above the bed and 

constitute most of the unmeasured load. Sediment 

concentrations and particle-size distributions in the 

unmeasured zone, therefore, are governed by the
EROSION AND SEDIMENT DISCHARGE 59

amount and size of material available for transport 

and by the capacity of the stream to transport this 

material.

Streambeds on the Dahlonega Plateau consist of 

discontinuous deposits of sand, gravel, and boulders 

on a bedrock base. Sand deposits occur in isolated 

patches or in stringers of varying thickness and 

area. Coarse gravels and cobbles occur sporadically 

and do not form a continuous gradation with the 

finer sediments. Bed material samples collected on 

the Dahlonega Plateau indicate that coarser materials (large gravel and cobbles) are transported 

only when flow velocities are extremely high and 

that sand and fine gravel constitute the vast majority of unmeasured loads. In addition, a considerable quantity of sand is stored on the sides and 

banks of stream channels during low-flow periods 

and becomes available for transport as stream stage 

increases.

Streambeds on the Atlanta Plateau consist mostly 

of sand and fine gravel; however, bedrock sections 

are not uncommon. Channel deposits are generally 

a foot thick or more and are continuous throughout 

the bed. Such channels are by definition alluvial because their beds consist of material that is readily 

available for transport (Einstein, 1950, p. 6; 

Vanoni ed., 1975, p. 114). Deposits of sand on 

channel banks in the Atlanta Plateau are common 

and frequently large and may contribute to unmeasured loads at high flows. Other sources of material that could be transported as unmeasured load 

are derived from channel or gully erosion and, as 

such, may be of local importance.

Photographs of typical streambed and streamchannel conditions on the Dahlonega (A and B) and 

Atlanta (C and D) Plateaus are shown in figure 42.

COMPUTATION

Instantaneous unmeasured and bed-sediment discharges were computed using the modified Einstein 

method developed by Colby and Hembree (1955). 

The computation of sediment discharge using the 

modified Einstein method requires data describing 

the particle-size distribution of both suspended 

sediments in transport and bed sediments assumed 

to be available for transport at the time of sampling. Other data required include instantaneous 

suspended-sediment concentrations, stream discharge, stream top width, water temperature, and 

average flow depth. Results of the modified Einstein computations are listed in table 23. Computation of unmeasured discharge using the modified 

Einstein procedure is terminated when computed

bed discharge is zero. Such occurrences are noted 

by a dash in the unmeasured discharge column of 

table 23 and indicate that the discharge of course 

sediments in the unmeasured zone is considered nil. 

Unmeasured- and bed-sediment discharges listed for 

the Chattahoochee River stations at Atlanta and 

near Whitesburg relate, for the most part, to regulated flow.

TRANSPORT CURVES

Instantaneous sediment-discharge data in table 

23 were sufficiently complete at several water-data 

stations to permit the development of transport 

curves (fig. 43). Regression relations based on 

these curves were computed using the general geometric equations

Q««or Qa6 =

where

Q.,H and Q,,?, = unmeasured- and bed-sediment

discharge, respectively, 

Qir = instantaneous stream discharge in cubic

feet per second, and 

a and b = regression constants.

A summary of the regression analyses is listed in 

table 24.

The sensitivity of unmeasured- and bed-sediment 

discharges to stream discharge points out some interesting aspects of sediment transport in the study 

area. Examination of the unmeasured-sediment discharge data for the Chestatee River near Dahlonega 

(table 23 and fig. 43£) indicates that the quantity 

of unmeasured and bed loads in the river is limited 

by the supply of coarse sediments. Notice in table 

23 that unmeasured- and bed-sediment discharges 

always occurred on the receding limb of the hydrograph. If the occurrence of such discharges is governed solely by the stream's transporting ability, 

then computations based on sample data collected 

on the rising limb should also indicate the presence 

of unmeasured and bed sediments in transport. Instead, computed total-sediment discharge equaled 

measured suspended-sediment discharge. Such an 

occurrence does not indicate an absence of sediment 

in the unmeasured zone. It does indicate, however, 

that bed-sediment discharge was minimal during 

the initial part of the runoff event and that the 

river's capacity to transport course material equaled 

or exceeded its supply. Typically, then, as the 

stream continues to rise, more and more course 

sediment is supplied to it, particularly from bank 

storage. Eventually the supply exceeds the trans-
60 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

1500

September 12, 1975 

January 27, 1976 

March 16, 1976

discharge=76 ft3 /s 

discharge=580 ft3 /s 

discharge=8590 ftVs

1000

Ow 

CJQh-W

P^CC

5S2

LU _l 500

90 100

HORIZONTAL DISTANCE, IN FEET

A

6.0

• September 12, 1975

• January 27, 1976 

A March 16, 1976

discharge=76 ft3/s 

discharge=580 ft3 /s 

discharge=8590 ftVs

1.0

HORIZONTAL DISTANCE, IN FEET 

B

FIGURE 39.—Lateral distributions of suspended-sediment concentration, flow velocity, flow depth, and size of bed material

at Peachtree Creek at Atlanta.
EROSION AND SEDIMENT DISCHARGE 61

25

20

15

• September 12, 1975

• January 27, 1976

A March 16, 1976

discharge=76 ft3 /s 

discharge=580 ft3/s 

discharge=8590 ft3/s

10

100

HORIZONTAL DISTANCE, IN FEET

c

1.5

CO<r

LU

• September 12, 1975

• January 27, 1976 

A March 16, 1976

discharge=76 ft3/s 

discharge=580 ft3 /s 

discharge=8590 ftVs

1.0

s

Q

.5

30 40 50 60 70 80 90 100

HORIZONTAL DISTANCE, IN FEET 

D

FIGURE 39.—Continued.
62 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

o

IDC

LU L:

0

150-

o

100

5; <

^ DC

Q (D

50

T I I I I

September 4, 1975 discharge =37 ftVs

May 14, 1976 discharge =131 ft3 /s

0

10 20 30 40 50 60 

HORIZONTAL DISTANCE, IN FEET

70

2.0

O 

o

LU

w

o: 1-5

LU 

0.

1.0

.5

September 4, 1975 

May 14, 1976

discharge =37 ftVs 

discharge =131 ftVs

10 20 30 40 50 60 

HORIZONTAL DISTANCE, IN FEET

B

70

2.5

2.0

1.0 -

.5

September 4, 1975 

May 14, 1976

discharge =37 ftVs 

discharge =131 ftVs

10 20 30 40 50 60 

HORIZONTAL DISTANCE, IN FEET

c

70

2.5

2.0

DC 

LU

LU 1.5

~ 1.0

S 

Q

.5

• September 4, 1975

• May 14, 1976

discharge =37 ft3/s 

discharge =131 fWs

10 20 30 40 50 60 

HORIZONTAL DISTANCE, IN FEET 

D

FIGURE 40.—Lateral distributions of suspended-sediment concentration, flow velocity, flow depth, and size of bed material

at Snake Creek near Whitesburg.

port capacity of the stream and course sediments 

begin to settle to the bottom and move as bedload. 

During recession, supplies of course sediment from 

outside the channel are progressively reduced and 

sediment deposition on the channel banks takes

place. Material previously deposited on the bed now 

serves as the major supply of bedload and suspendable sands. The stream always attempts to transport as much suspended sediment as it can. Consequently, the bed-sediment transport rate declines
EROSION AND SEDIMENT DISCHARGE 63

TABLE 23.—Summary of unmeasured- and bed-sediment discharge computations

Station name Date

Chattahoochee River near Leaf __ 9-23-75 

3-16-76 

5_28-76 

Soque River near Clarkesville __ 9-22-75 

3-16-76 

5-15-76 

Chestatee River near Dahlonega _ 9-24-75 

3-16-76 

3-16-76 

5-15-76 

5-28-76 

Chattahoochee River near Buford _ 7-22-76 

7-22-76 

7-22-76 

7-22-76 

Chattahoochee River near Duluth _ 7-22-76 

7-22-76 

7-22-76 

7-22-76 

Big Creek near Alpharetta _ 9-22-75

12-31-75 

1-26-76 

1-26-76 

1-27-76 

1-29-76 

3-16-76 

3-18-76 

Chattahoochee River at Atlanta __ 5-27-76 

4-14-77 

4-25-77 

5-28-77 

N. Fork Peachtree Creek near 

Atlanta _ _ __ 3-12-76

5-11-76 

S. Fork Peachtree Creek at 

Atlanta _ _ _ _ 5-11-76

3- 9-76 

3-13-76 

Peachtree Creek at Atlanta 9-12-75

1-27-76 

3-16-76 

Nancy Creek tributary near 

Chamblee 5-27-76

Nancy Creek at Atlanta _ 5-12-76

Chattahoochee River near 

Fairburn 4—14—77

Snake Creek near Whitesburg __ 9- 4-75 

4-14-76 

Chattahoochee River near 

Whitesburg _ __ ___ _ 5-14-76

4-14-77 

6- 2-77

Time

1355 

1335 

1405 

1620 

1015 

1650 

0910 

1610 

2300 

1230 

1105 

1400 

1505 

1640 

2000 

1650 

1809 

1859 

2151 

1030 

1400 

0920 

1405 

1440 

1420 

1915 

1445 

0850 

1400 

1200 

1030

2245 

1000

1100 

1048 

0035 

1130 

1000 

1145

2125 

1130

1255 

1120 

1850

1530 

1125 

1300

rapidly as the bed-sediment supply goes into suspension. Such a decline is manifest in the slope of 

the bed-sediment transport curve shown in figure 

43#. Streambed deposits continue to supply sediment to bedload and suspension until they are depleted. Field observations indicate that similar 

bed-transport processes occur at the other waterdata stations on the Dahlonega Plateau. 

Unmeasured- and bed-sediment transport curves 

for Big Creek near Alpharetta are shown in figure 

43c. Notice that these curves are not as divergent at 

the lower discharges as those developed for the

0 . Bed nlrLi " Ratio of Stream ,. urea ^j t 

dig- .fis- dis. unmlLured -Stag-e 

charge ^tonf/ charge discharge direction

(fWs) day) ( *?ns/ (percent) •" day)

880 0.17 65.5 0.26 Falling 

2800 460 1810 5 Falling 

4440 614 5690 11 Rising 

163 0.0 — — Rising 

2380 221 1280 17 Rising 

3180 158 428 7 Falling 

825 3.84 154 2.5 Falling 

3200 101 1250 8.1 Falling 

1700 27.8 415 6.7 Falling 

8180 1290 5280 24 Falling 

970 0.0 — — Rising 

530 0.0 — — Rising 

8900 248 984 25 Rising 

11700 114 474 24 Peak 

4300 22.6 156 14 Falling 

700 0.0 — — Rising 

1800 0.0 — — Rising 

5400 131.0 716 18 Rising 

7300 191 872 22 Rising 

42 0.0 — — Falling 

672 5.1 43.3 12 Peak 

498 1.31 139 .94 Rising 

764 6.11 76.5 8.0 Rising 

1320 43.4 253 17 Peak 

227 0.45 6.40 7.0 Falling 

2180 80.8 494 16 Rising 

393 0.0 — — Falling 

8120 123 635 19 Falling 

7970 126 766 16 Peak 

6060 41 226 18 Falling 

1200 3.7 3.7 — 100 Falling

1410 395 1580 25 Falling 

30 0.0 — — Steady

25 0.0 — — Steady 

212 3.18 43.2 7.4 Falling 

1200 75.7 768 9.9 Rising 

69 0.67 6.9 9.7 Falling 

580 1.86 46.3 4.0 Falling 

8510 375 2280 16 Peak

89 148 352 42 Rising 

30 0.0 Steady

9900 96.0 703 14 Rising 

37 0.0 — — Steady 

145 .53 .53 -100

4080 59.9 59.9 —100 Falling 

9605 113 368 31 Peak 

1880 18.3 18.3 -100 Steady

Chestatee River near Dahlonega. Big Creek is 

largely an alluvial-channel stream, and it is expected that sufficient bed material is available most 

of the time to satisfy the stream's transport capacity. Thus, the nature of the unmeasured- and bedsediment transport curves should be governed more 

by the stream's ability to transport sediment than 

by the amount of sediment in supply.

AVERAGE ANNUAL DISCHARGE

The average annual discharge of bed and unmeasured sediments was computed using each trans-
64 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

1600 1146

• Suspended-sediment discharge

• Water-surface altitude

Storm suspended-sediment load= 12,300 tons 

May 14-18, 1976

TIME, IN DAYS

1130

- 970

- 969

— 968

• Suspended-sediment discharge

• Water-surface altitude

Storm suspended-sediment load=3380 tons 

Jan. 26-30, 1976

963

TIME, IN DAYS 

B

FIGURE 41.—Storm loading of suspended sediment at (A) Chestatee River near Dahlonega and (B) Big

Creek near Alpharetta.
EROSION AND SEDIMENT DISCHARGE 65

cc

D 

O

X

30

25

• Suspended-sediment discharge

• Water-surface altitude

Storm suspended-sediment load=234 tons 

May 14-15, 1976

3.2

TIME, IN DAYS

c

cc

D 

O

X

cc

LU 

D_

C/D

Z

o

CJ 

C/D

1400

1200

1000

81

600

400

200

Suspended-sediment discharge 

Water-surface altitude

Storm suspended-sediment load=39,400 tons 

March 13-15, 1976

812

808

804 z

LL?

Q

D

800 t

796 <

LL.

cc

D

792

788

784

13 14 15 16

TIME, IN DAYS 

D

FIGURE 41.—Continued. Storm loading of suspended sediment at (C) Snake Creek near Whitesburg and

(D) Chattahoochee River near Whitesburg.
66 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

FIGURE 42.—Typical streambeds and stream channels on the Dahlonega and Atlanta Plateaus—(A) Chattahoochee River

upstream of Helen.

TABLE 24.—Summary of regression data relating unmeasuredand bed-sediment discharges to stream discharge

Station name

Chattahoochee River 

near Leaf

Chestatee River near

Big Creek near 

Alpharetta

Chattahoochee River

Peachtree Creek at 

Atlanta

Chattahoochee River 

near Whitesburg _

Discharge

Unmeasured

bed 

unmeasured

bed 

Bed

bed 

Bed

a

4.42 XlO-7

4.29 XlO-3

.02 Xl0~7 

1.25 XlO-4

4.54 XlO-7 

1 llxlO"5

3.14 XlO-2

1.18 XlO~3 

4.89 XlO-3

b

2.78

1.56

2.50 

1.99

2.49 

1.78

1.22

1.34 

1.11

port relation listed in table 24 and the basic discharge computation techniques described previously 

for suspended sediment. Computed annual discharges are listed in table 25. Average annual totalsediment discharge was computed as the sum of the

average annual unmeasured-sediment and suspended-sediment discharges.

DELIVERY RATIOS

The quantity of sediment transported at a stream 

station depends on the rate of gross erosion in the 

watershed and on the various factors that affect the 

routing, deposition, and transport of sediment. Only 

a part of the material eroded from upland areas is 

transported to streams and out of the watershed. 

The remaining material is deposited wherever the 

entraining characteristics of runoff waters are no 

longer sufficient to maintain transport. Consequently, the magnitude of sediment discharge is 

highly variable with respect to location. A measure 

of this variability is the delivery ratio, which is defined as the ratio of the quantity of sediment delivered to a stream station to the total amount of 

material in transport in the watershed (gross erosion). This relation is presented below as
DELIVERY RATIOS 67

FIGURE 42.—Continued. Typical streambeds and stream channels on Dahlonega and Atlanta Plateaus—(B) Soque River

upstream of Clarkesville. (Continued on p. 68.)

TABLE 25.—Average annual total-, unmeasured- and bed-sediment discharge

Station name

Chattahoochee River near Leaf

Chestatee River near Dahlonega

Peachtree Creek at Atlanta _

Chattahoochee River near Whitesburg

Average 

annual 

total 

discharge

(tons/yr)

64,200

73,600

25,600

71,400

Average 

annual 

unmeasured 

discharge

(tons/yr)

21,200

21,300

1,630

5,890

Average 

annual 

bed 

discharge 

(tons/yr)

945

160

5,630

464

9,960

Ratio of 

unmeasured 

to total 

discharge 

(percent)

33

29

6.4

8.2

Ratio of 

bed 

to total 

discharge 

(percent)

1.3

.62

.62

Z>=-

where

D = delivery ratio,

St = total average annual sediment discharge at 

a stream station, and

EG = average annual gross erosion in the watershed draining to the station.

For this study, total-sediment discharge at a station 

is the sum of the average annual suspended- and 

unmeasured-sediment discharges (table 25). Gross 

erosion in the watershed is considered equivalent to 

the sheet erosion computed by the Universal Soil 

Loss Equation. Delivery ratios at four water-data 

stations can be computed and are listed below.
68 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

FIGURE 42.—Continued. Typical streambeds and stream channels on the Dahlonega and Atlanta Plateaus—(C) Tributary

to the Chattahoochee River downstream of Buford Dam.

Station name Delivery 

ratio

Chattahoochee River near Leaf 

Chestatee River near Dahlonega 

Big Creek near Alpharetta 

Peachtree Creek at Atlanta

0.21 

.15 

.13 

.89

The high delivery ratio for the Peachtree Creek 

station may indicate that a large part of the sediment delivered to that station originated within the 

channel. With the exception of the high ratio noted 

above, the delivery ratios computed for this study 

compare favorably with ratios developed by Roehl 

(1962) from field investigations of reservoir sedimentation in the southeastern Piedmont. Roehl's 

ratio data range from 0.037 to 0.594 and were collected from watersheds ranging in area from 0.61 

to 166 square miles.

The reader should note that both the erosion and 

unmeasured-sediment discharge data used to compute the delivery ratios are somewhat subjective 

and should use the ratios accordingly.

MANAGEMENT IMPLICATIONS OF EROSION 

AND SEDIMENT DISCHARGE DATA

Information of importance to water resource managers includes the definition of background or natural sediment and erosion yields and changes in 

these yields caused by land use. Data from watersheds where land cover has been totally unaffected 

by man were not available from this study. Of the 

drainages studied, however, those contributing to 

the Chattahoochee River near Leaf and Snake Creek 

near Whitesburg were the least affected by man's 

activities. Sediment-yield data from these watersheds indicate a background rate of sediment yield 

in the basin in excess of 200 tons per year per 

square mile. Computed sheet erosion data indicate 

background erosion yields are about 2,000 tons per 

year per square mile.
MANAGEMENT IMPLICATIONS OF EROSION AND SEDIMENT DISCHARGE DATA 69

FIGURE 42.—Continued. Typical streambeds and channels on the Dahlonega and Atlanta Plateaus—(D) Snake Creek near

Whitesburg.

The effect of land use on erosion and sediment 

yield is most apparent for watersheds on the Dahlonega Plateau. Man's influence, though small, is 

most pronounced in the drainage of the Soque River 

near Clarkesville and decreases progressively in 

the watersheds of the Chestatee and Chattahoochee 

Rivers (figs. 18-20). Computed erosion and sediment yields follow this trend exactly, being greatest 

in the Soque drainage and least in the watershed of 

the Chattahoochee River near Leaf.

On the Dahlonega Plateau, the effect of changes 

in land use on erosion is best demonstrated by use 

of the Universal Soil Loss Equation. As discussed 

previously, computed average annual sheet erosion 

in the watershed of the Chattahoochee River near 

Leaf increased from 305,000 tons per year to 536,000 

tons per year after a hypothetical timber harvest 

covering 2 square miles. Thus, a disturbance of the 

land cover over 1.3 percent of the total drainage 

area caused a 76-percent increase in computed annual sheet erosion for the entire watershed.

The effect of large-scale urbanization on erosion 

and sediment yields is not clearly defined by the 

data presented in this report. On the one hand, computed sheet-erosion yields for those areas draining 

to Peachtree Creek and its tributaries are the lowest 

in the basin (table 20). Conversely, the greatest 

yields of stream sediment are recorded for several 

of the same watersheds (table 22). One explanation 

for this apparent dichotomy lies in the nature of 

urban land cover. Typical use of land in the Atlanta 

urban area includes large tracts covered with buildings, homes, streets, roads, parking lots, and runways. Even open areas such as yards, parks, and 

golf courses are generally landscaped and planted 

with grass. The net effect of such land cover is to 

reduce both the opportunity and occurrence of sheet 

erosion. At the same time, however, rates of storm 

runoff to urban streams have increased in proportion to increases in impervious areas. Such increases 

frequently overload the channel capacity of Peachtree Creek and its tributaries causing channel ero-
70 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

100,000

10,000

<

Q

DC 

LLJ 

CL

o

cc

<

O

CO

Q

CO

1000

100

10

A Unmeasured-sediment discharge 

• Bed-sediment discharge

10,000

co

O

DC

CJ 

CO 

Q

1000

100

10

.Unmeasured-sediment discharge 

Bed-sediment discharge

100 1000 10,000 

STREAM DISCHARGE, IN CUBIC FEET 

PER SECOND 

B

100 1000 10,000 

STREAM DISCHARGE, IN CUBIC FEET PER SECOND 

A

FIGURE 43.—Relation of unmeasured- and bed-sediment discharge to stream discharge at (A) Chattahoochee River near

Leaf and (B) Chestatee River near Dahlonega.

sion which, in turn, is measured as sediment 

discharge. Thus, sheet erosion in the Peachtree 

Creek drainage can be relatively low, while, at the 

same time, the sediment yield from Peachtree Creek 

and its tributaries, supplemented by channel erosion, is high.

When urbanization in a particular watershed is 

complete, the dimensions of channels draining the 

watershed will eventually enlarge to accomodate 

the greater runoff rates. After this adjustment, 

erosion of the channels will diminish and sediment 

yields from the channels will reflect the lower rates
MANAGEMENT IMPLICATIONS OF EROSION AND SEDIMENT DISCHARGE DATA 71

10,000

1000

100

10

0.1

A Unmeasured-sediment discharge 

• Bed-sediment discharge

1000

100

10

10 100 1000

STREAM DISCHARGE, IN CUBIC 

FEET PER SECOND

10,000

A Unmeasured-sediment 

discharge .

• Bed-sediment discharge

100 1000 10,000 100,000

STREAM DISCHARGE, IN CUBIC 

FEET PER SECOND

D

10,000

1000

100

10

0.1

A Unmeasured-sediment discharge 

• Bed-sediment discharge

o

1000

100

10

A Unmeasured-sediment discharge 

• Bed-sediment discharge

1000 10,000 100,000

STREAM DISCHARGE, IN CUBIC 

FEET PER SECOND

10 100 1000

STREAM DISCHARGE, IN CUBIC 

FEET PER SECOND

10,000

FIGURE 43.—Continued. Relation of unmeasured- and bed-sediment discharge to stream discharge at 

(C) Big Creek near Alpharetta, (D) Chattahoochee River at Atlanta, (E) Peachtree Creek at Atlanta, and (F) Chattahoochee River near Whitesburg.
72 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

of sheet erosion caused by urbanization. The areas 

draining to Proctor Creek and tributary to Nancy 

Creek are probably indicative of urban watersheds 

in which urbanization is nearly complete and channel dimensions have adjusted to increased runoff. 

The annual sediment yields from these watersheds 

were the lowest recorded of any watershed in this 

study (table 22).

CONTRIBUTION OF SUSPENDED SEDIMENT 

TO STREAM QUALITY

The impact of suspended sediment on stream quality is both aesthetic and chemical. For this study, 

the aesthetic consequences are measured in terms 

of turbidity; chemical consequences are evaluated 

by comparing average annual suspended and total 

discharges of chemical constituents and by noting 

the relation of suspended-constituent concentrations 

to corresponding concentrations of suspended 

sediment.

TURBIDITY

Turbidity is generally denned as a reduction in 

the transparency of water caused by suspended particulate matter. The particulate matter may consist 

of sediment particles as well as organic matter or 

microscopic organisms. In general, an increase in 

stream turbidity reduces the visual appeal of the 

water, the aesthetic value of the water course, 

and decreases the depth to which light can penetrate 

the water column. The unit of turbidity measurement used in this report is defined by Brown and 

others (1970) as the Jackson Turbidity Unit 

(JTU).

Curves of sample turbidity plotted against corresponding concentrations of suspended silt plus

clay are shown for selected water-data stations in 

figure 44. Regression relations based on these curves 

were computed using the general geometric equation

= aSb

where

r = turbidity in JTU's,

S,P = suspended silt plus clay concentration in 

milligrams per liter, and

a and b = regression constants.

A summary of regression data relating suspended 

silt plus clay concentration to turbidity at most 

water-data stations is listed in table 26. Correlation 

coefficients for the 14 stations ranged from 0.80 to 

0.99 with coefficients for 12 stations at 0.90 or 

higher. Note that two regression equations are 

listed for the station at Big Creek near Alpharetta. 

The silt plus clay concentration versus turbidity 

relation is distinctly different at this station depending on the stage direction at the time of sampling (fig. 44J5). The turbidity - suspended-sediment 

relation for the Chattahoochee River at Atlanta includes data from samples collected during regulated 

flow and intervening runoff. The turbidity data 

plotted along the lower part of the curve are relative to regulated flow and are not as sensitive to 

silt plus clay concentrations as the higher turbidity 

values that relate to samples collected during storm 

runoff. The regressions listed for the Chattahoochee 

River near Fairburn and near Whitesburg relate 

only to intervening runoff.

At each water-data station, increases in suspended-sediment concentration resulted in corresponding increases in turbidity. Such increases, in 

turn, decreased the aesthetic appeal of the waterTABLE 26.—Summary of regression data relating turbidity to concentrations of suspended silt plus c.lay

Station name

1 Recession samples.

3 Rise and peak samples.

Correlation 

coefficient

Number 

of samples

Chattahoochee River near Leaf _ _ _

Soque River near Clarkesville

Chestatee River near Dahlonega

1 Big Creek near Alpharetta

2 Big Creek near Alpharetta

Chattahoochee River at Atlanta

N. Fork Peachtree Creek near Atlanta

S. Fork Peachtree Creek at Atlanta

Peachtree Creek at Atlanta

Woodall Creek at Atlanta

Nancy Creek Tributary near Chamblee

Nancy Creek at Atlanta

Chattahoochee River near Fairburn _ _

Snake Creek near Whitesburg

Chattahoochee River near Whitesburg

_ ._ _ 0.783

.217

.686

.029

.882

1.41

2.50

.933

_ __ .825

1.87

2.60

.990

_ ___ 1.34

__ _ 1.42

3.19

0.907

1.14

.915

1.80

.902

.746

.714

.868

.906

.739

.739

.849

.830

.835

.699

0.96

.93

.95

.95

.89

.84

.90

.96

.99

.95

.96

.95

.93

.94

.80

14

18

42

10

11

40

17

17

29

14

15

21

21

36

19
CONTRIBUTION OF SUSPENDED SEDIMENT TO STREAM QUALITY 73

1000

100

10

1000

OQ 

Q [E

m =J

DC \-

100-

10 100 1000

SUSPENDED SILT PLUS CLAY CONCENTRATION,

IN MILLIGRAMS PER LITER

A

100 1000

SUSPENDED SILT

PLUS CLAY CONCENTRATION,

IN MILLIGRAMS PER LITER

B

1000

m 100

-. 10

10 100

1000

- 10

1000

SUSPENDED SILT PLUS CLAY CONCENTRATION, 

IN MILLGRAMS PER LITER

c

10 100

SUSPENDED SILT PLUS CLAY CONCENTRATION, 

IN MILLIGRAMS PER LITER

D

1000

FIGURE 44.—Relation of turbidity to suspended silt plus clay concentration at (A) Chestatee River near Dahlonega, (B) 

Big Creek near Alpharetta, (C) Chattahoochee River at Atlanta, and (D) Peachtree Creek at Atlanta.
74 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

Z CC

LU LU

<-> t

Z _l 8* <~> LU 

rn Cu.

g

0.1

.01

• Rise 

A Peak

• Recession

10 100 1000

SUSPENDED SILT PLUS CLAY CONCENTRATION, 

IN MILLIGRAMS PER LITER

A

100

LU

c_> cc

Z [IJ 

0 ~

~z. cc 1«

CC Cfl

cc g ^

10 -

0.1

• Rise 

A Peak

• Recession

h —

0.1

Z DC 

LU LU 

C_> QQ CC 

< 0

.01

10 100 1000 .001

SUSPENDED SILT PLUS CLAY CONCENTRATION, 

IN MILLIGRAMS PER LITER

10

O

I- cc 

< ^ 

cc t

O -j CC d

Q ^ 

LU

Q

0.1

.01

• Rise 

A Peak

• Recession

10 100 1000

SUSPENDED SILT PLUS CLAY CONCENTRATION, 

IN MILLIGRAMS PER LITER

B

m Rise 

A Peak 

• Recession

10 100 1000

SUSPENDED SILT PLUS CLAY CONCENTRATION, 

IN MILLIGRAMS PER LITER

D

FIGURE 45.—Relation of suspended-constituent concentrations to concentrations of suspended silt plus clay at the Chestatee

River near Dahlonega.
CONTRIBUTION OF SUSPENDED SEDIMENT TO STREAM QUALITY 75

o to

.01

Rise 

Peak 

Recession

10 100 1000

SUSPENDED SILT PLUS CLAY CONCENTRATION, 

IN MILLIGRAMS PER LITER

.001

10 100 

SUSPENDED SILT PLUS CLAY CONCENTRATION, 

IN MILLIGRAMS PER LITER

1000

.01

o

<-> 3j 0.1

«^ _l DC

O - DC

DC V LLJ

.05

.01

• Rise 

A Peak

• Recession

.001

10 100 1000

SUSPENDED SILT PLUS CLAY CONCENTRATION, 

IN MILLIGRAMS PER LITER

G

.0001

10 100 1000

SUSPENDED SILT PLUS CLAY CONCENTRATION,

IN MILLIGRAMS PER LITER

H

FIGURE 45.—Continued.

course and the depth of light-penetration into the 

water.

The reader should note that the measurement of 

turbidity is, by definition, somewhat subjective. 

Consequently, turbidity values should not be used to 

quantitatively determine suspended-sediment concentrations.

CHEMICAL QUALITY

The effect of suspended sediment on the chemical 

quality of a stream is mostly a function of (1) the 

water-quality constituents of interest, (2) the relation of the concentration of these constituents to the 

concentrations of suspended sediment, and (3) the 

constituent loads transported by the stream. The
76 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

z cc m tu o iZ 13

O _

to

0.1

.01

• Rise 

A Peak

• Recession

10 100 1000

SUSPENDED SIllT PLUS CLAY CONCENTRATION, 

IN MILLIGRAMS PER LITER

A

10

z

o

I- cc

< LU

UJ CC

CJ LU

Z 0-

Z <

LU CC

O O

O 13

CC _l

Q

LU 

Q 

Z

LU 

Q. 

CO

D 

CO

0.1

• Rise

A Peak

• Recession

10 100 1000

SUSPENDED SILT PLUS CLAY CONCENTRATION, 

IN MILLIGRAMS PER LITER 

B

100

O 0- 

CQ

10

Rise 

Peak 

Recession

10 100 1000

SUSPENDED SILT PLUS CLAY CONCENTRATION, 

IN MILLIGRAMS PER LITER

10 100

SUSPENDED SILT PLUS CLAY CONCENTRATION, 

IN MILLIGRAMS PER LITER

D

1000

FIGURE 46.—Relation of suspended-constitutent concentrations to concentrations of suspended silt plus clay at Peachtree

Creek at Atlanta.

chemical constituents of interest to this study were 

phosphorus, nitrogen, organic carbon, lead, zinc, 

copper, chromium, and arsenic. Curves relating the 

concentrations of these constituents in the suspended phase to the corresponding concentrations of 

suspended silt plus clay have been established at 

most water-data stations. Curves for selected stations are shown in figures 45 and 46, and represent, 

respectively, relations at the Chestatee River near 

Dahlonega and at Peachtree Creek at Atlanta. Such 

curves indicate that the various constituent-sediment concentrations are generally related by the 

geometric function

where

C., = chemical constituent concentration in the

suspended phase in milligrams per liter,

Sxe = concentration of suspended silt plus clay 

in milligrams per liter, and

a and b = regression constants.
CONTRIBUTION OF SUSPENDED SEDIMENT TO STREAM QUALITY 77

Q. <

Q. CC

O O

9 =i 

Q =!

S S

0.1

.01

0.001

• Rise

A Peak

• Recession

g 

Sffi m Rise 

A Peak 

• Recession

0.1 -

0.01

1000

SUSPENDED SILT PLUS CLAY CONCENTRATION, 

IN MILLIGRAMS PER LITER

10 100 1000

SUSPENDED SILT PLUS CLAY CONCENTRATION, 

IN MILLIGRAMS PER LITER

0.1

.01

°

0.001

AA

• Rise

A Peak

• Recession

10

OC -7

Q P (/5

10 100 1000

0.1

• Rise 

A Peak

• Recession

10 100 1000

SUSPENDED SILT PLUS CLAY CONCENTRATION, 

IN MILLIGRAMS PER LITER

SUSPENDED SILT PLUS CLAY CONCENTRATION, 

IN MILLIGRAMS PER LITER

H

FIGURE 46.—Continued.

A summary of the regression equations relating suspended-constituent concentrations to silt plus clay 

concentrations at most water-data stations is listed 

in table 27. Also listed are correlation coefficients 

and the number of data pairs used in each regression. The omission of regression information for a 

particular constituent indicates that a functional relation could not be established.

In general, suspended concentrations of the constituents of interest correlate well with concentrations of suspended silt plus clay (table 27). Of the 

nutrients studied, the degree of correlation was 

highest for phosphorus and lowest for organic 

carbon.

Average annual suspended-constituent discharges 

were computed using the regression data in table 27 

and the flow-duration data in table 7. For each 

water-data station, the flow duration of a suspendedconstituent concentration was determined by relating the corresponding concentration of suspended
78 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

TABLE 27.—Summary of regression data relating suspended-constituent concentrations to concentrations of suspended silt

plus clay

Suspended phosphorus as P Suspended nitrogen as N

Station name Correlation 

coefficient

Number 

of samples

Correlation 

coefficient

Number 

of samples

Chattahoochee River near Leaf- 0.00274 0.746 0.97 8

Soque River near Clarkesville _ .00248 .834 1.0 9

Chestatee River near Dahlonega .00132 .942 .99 11

Big Creek near Alpharetta __ .00681 .639 .96 12

Chattahoochee River at Atlanta .0103 .500 .91 15

N. Fork Peachtree Creek

near Atlanta __________ .00161 .504 .96 12 

S. Fork Peachtree Creek at

Atlanta _____________ .00330 .781 .99 12 

Peachtree Creek at Atlanta __ .00703 .646 .98 12 

Woodall Creek at Atlanta __ .0665 .372 .91 7 

Nancy Creek tributary near

Chamblee _____ _______ .0185 .391 .90 7

Nancy Creek at Atlanta ____ .00116 .909 .99 13 

Chattahoochee River near

Fairbum _____________ .0413 .379 .61 16 

Snake Creek near Whitesburg _ .000911 .920 .99 7 

Chattahoochee River near

.0198 .484 .85 11

0.0137

.000493

.00167

.0290

.00116

.000600

.00203

.000454

.0163

0.714

1.27

.988

.528

1.06

1.21

.983

1.23

.641

.0000691 1.49

____ __

.00530 .827

0.98 

.91 

.87 

.93

.87

.66

.90 

.93 

.96

.89 

.96

7

8

10

7

9

11

12

6

11

6

Suspended organic carbon

Chattahoochee River near LeafSoque River near Clarkesville _ 

Chestatee River near Dahlonega 

Big Creek near Alpharetta ____ 

Chattahoochee River at Atlanta

N. Fork Peachtree Creek

S. Fork Peachtree Creek at 

Atlanta _ _

Peachtree Creek at Atlanta

Woodall Creek at Atlanta ____

Nancy Creek tributary near 

Chamblee

Chattahoochee River near 

Fairbum

Snake Creek near Whitesburg _ 

Chattahoochee River near 

Whitesburg ___ _ _ ___

a

0.0359 

.818 

.00255 

.0157

.155

.00247 

.201

.00377 

.0446

.00324

b

0.944 

.441 

1.51 

1.09

.705

1.24 

.585

1.37 

.755

1.34

Correlation 

coefficient

0.92 

.99 

.93 

.69

~93

.94

.83

.82 

.90

.95

Number 

of samples

9 

5 

10 

10

~9

7 

9

12

5

13

a

0.00200 

.000964 

.00205

.00217

.00586 

.00349 

.00134

.000346 

.000836

.00208

.00260

Suspended lead

b

0.539 

.639 

.550

.638

.591 

.655 

.463

.890

.789

.625

.610

Correlation 

coefficient

0~82 

.82

.67

.94

.94 

.93 

.95

.87 

.89

.77 

.90

Number 

of samples

12 

9 

11

7

9

12 

7

4 

8

9

7

silt plus clay to a stream discharge (tables 27 to 21 

to 7). The average annual discharge of the chemical 

constituent was then computed using the technique 

described previously for the computation of suspended-sediment discharges. Computed suspendedconstituent discharges are listed by water-data 

station in table 30. Computed suspended-constituent 

discharges contributed by regulated flow to the 

Chattahoochee River at Atlanta are considered 

transported, without loss, to the stations near Fairburn and near Whitesburg.

Average annual dissolved constituent discharges 

were computed on the basis of the relation of the 

constituent concentration to stream discharge. At

those stations where the dissolved constituent concentrations did not significantly change with stream 

discharge, the average annual constituent discharge 

was computed using the relation

Yd = 0.0027 x Qa x Cdm x 365 

where

Y(, = the average annual dissolved-constituent 

discharge in tons per year,

Q0 = the mean daily stream discharge in cubic 

feet per second, and

Cdw =the mean dissolved-constituent concentration in milligrams per liter for all samples at a 

station.
CONTRIBUTION OF SUSPENDED SEDIMENT TO STREAM QUALITY 79

TABLE 27.—Summary of regression data relating suspended-constituent concentrations to concentrations of suspended silt

plus clay—Continued

Suspended zinc

Station name

Chattahoochee River near Leaf_ 

Soque River near Clarkesville _ 

Chestatee River near Dahlonega 

Big Creek near Alpharetta

Chattahoochee River at Atlanta 

N. Fork Peachtree Creek

S. Fork Peachtree Creek at 

Atlanta

Peachtree Creek at Atlanta ___ 

Woodall Creek at Atlanta __

Nancy Creek tributary near 

Chamblee

Nancy Creek at Atlanta

Chattahoochee River near 

Fairburn _ _ _ __

Snake Creek near Whitesburg _ 

Chattahoochee River near 

Whitesburg _ _

a

0.00387 

.00285 

.00112

.00389

.00224

.00115 

.00546 

.0461

.00319 

.000122

.00519

.00140

b

0.477 

.525 

.701

.443

.608

.767 

.544 

.290

.545 

1.07

.488

.728

Correlation 

coefficient

0.91 

.93

.87

~95

.80

.97 

.91

.88

.87 

.92

.70 

.90

Number 

of samples

8 

6

8

~8

8

8 

13

7

4 

10

10 

10

a

0.000306 

.000447

.000253

.00639 

.000594 

.000953

.000103

.00665 

.000313

.00106

Suspended chromium

Chattahoochee River near Leaf_ 

Soque River near Clarkesville _ 

Chestatee River near Dahlonega 

Big Creek near Alpharetta

Chattahoochee River at Atlanta

N. Fork Peachtree Creek 

near Atlanta

S. Fork Peachtree Creek at 

Atlanta _ _

Peachtree Creek at Atlanta ___ 

Woodall Creek at Atlanta ____

Nancy Creek tributary near 

Chamblee

Nancy Creek at Atlanta

Chattahoochee River near 

Fairburn _ __

Snake Creek near Whitesburg _ 

Chattahoochee River near 

Whitesburg _ __ __ _

a

0.00330 2.9x10-° 

.00579

.000654

.00242 

.000198 

.000475

.00137 

3.57X10^

6

0.388 

1.57 

.295

.705

.403 

.796 

.643

.352 

1.37

Correlation 

coefficient

0.88 

.97 

.96

~88

.93

.85 

.93

.78 

.96

Number 

of samples

5 

6 

5

~5

8 

11 

6

5

4

a

7.24xlO-T 

6.85 xlO~7 

6.58x10-'

3.02x10-"'

2.10x10-* 

4.81x10-" 

0.000145

5.40X10-U

4.48x10-' 

3.53 XlO-3

6.19 xlO-5

Suspended copper

i Correlation 

coefficient

0.802 

.900

.872

.343 

.761 

.699

.911

.300 

.366

.622

Suspended

6

1.34 

1.39

.654

.775

1.22 

1.12 

.666

1.10

.747 

.728

.679

0~96 

.96

~92

.85 

.82 

.95

~97

.66 

.91

.81

arsenic

Correlation 

coefficient

0~97 

.85 

.99

.92

.94 

.86 

.93

.98

.89 

.98

.84

Number 

of samples

~7 

9

12

8 

15

7

10

10 

5

10

Number 

of samples

~5 

4

7

5

5 

10 

6

10

10 

4

11

The mean concentrations used for these computations are listed in table 28 along with the average 

daily stream discharge. Mean concentrations are 

listed only for those parameters for which average 

annual suspended-constituent discharges were calculated (table 27).

At those stations where dissolved-constituent concentrations changed significantly with stream discharge, the concentration-discharge relation was 

best described by the geometric function

where

= the instantaneous dissolved-constituent concentration in milligrams per liter,

Q, = the instantaneous stream discharge in cubic 

feet per second, and

a and b = regression constants.

A summary of regression equations relating dissolved-constituent concentrations to stream discharge is listed in table 29. Of particular interest 

are the positive relations between dissolved-nutrient 

concentrations and stream discharge noted at waterdata stations on the Dahlonega Plateau and at Snake 

Creek near Whitesburg. Such relations indicate that 

dissolved nutrient concentrations increase with increases in stream discharge and that substantial
80 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

TABLE 28.—Mean concentrations of dissolved constituents used to compute average annual dissolved-constituent discharges

[a, regression relation (see table 29) ]

Station name

Chattahoochee River near Leaf _ _ _

Soque River near Clarkesville _ _ _

Chestatee River near Dahlonega _ _ _ _.

Big Creek near Alpharetta _ _ _ _ _ .

Chattahoochee River at Atlanta _ _ .

N. Fork Peachtree Creek near Atlanta _ _.

S. Fork Peachtree Creek at Atlanta _ _ _ .

Peachtree Creek at Atlanta _ _ _ _ _.

Woodall Creek at Atlanta __ _ _ _

Nancy Creek tributary near Chamblee _ _ _ .

Nancy Creek at Atlanta _ _ _ ______

Chattahoochee River near Fairburn

Snake Creek near Whitesburg _ _

Chattahoochee River near Whitesburg __

Soque River near Clarkesville _ _ _ _ . Chestatee River near Dahlonega _ _ .

Big Creek near Alpharetta _ _ _ ____.

Chattahoochee River at Atlanta ____

N. Fork Peachtree Creek near Atlanta _

S. Fork Peachtree Creek at Atlanta _ _ _.

Peachtree Creek at Atlanta _ _ _ _ _

Woodall Creek at Atlanta __ _ _.

Nancy Creek tributary near Chamblee __ _

Nancy Creek at Atlanta _ _ _ _ .

Chattahoochee River near Fairburn

Snake Creek near Whitesburg _ _ _.

Chattahoochee River near Whitesburg

discharge

(ftVs)

._ _ 402

219

._ _ 370

119

2890

. __ 50.1

52.6

. _ _ 137

._ _ 19.1

4 74

. __ 66.7

3930

._ _ 58.2

._ _ 4419

Dissolved orgs

Mean 

concentration 

(mg/L)

1 Q

3.5

a

6.4

10

6.2

3.9

a

a

Dissolved phosphorus aa P

Mean 

concentration 

(mg/L)

0.0044

.019 

.0086 

.0090 

.011 

.023 

a 

.025 

.83 

.030 

.022 

a 

.0053 

a

mic carbon

Number 

of 

samples

9 

10

12

--

10

14

24

Number 

of 

samples

9

10 

21 

21 

24 

12

23 

10

7 

14

19

Dissolved nitrogen ag N

Mean 

concentration 

(mg/L)

a 

a 

0.45 

.97 

.54 

1.1 

.94 

1.0 

2.3

.74

a

Dissolved lea

Mean 

concentration

(mg/L)

0.0023 

trace 

.0034 

.0090 

.0057 

.011 

.016 

.014 

.014 

.0095

.0072

Number 

of 

samples

19 

21 

21 

13 

13 

23 

10

14

.d

Number 

of 

samples

~9 

9 

12 

9 

9 

18 

9 

5 

11 

13

11

quantities of dissolved nutrients are contributed to 

basin streams by runoff from forested areas. The 

average annual discharge of dissolved constituents 

whose concentrations varied with stream discharge 

was computed using the procedure described previously for computing the annual discharge of suspended sediment.

The sum of the suspended- and dissolved-constituent discharges is considered the total average annual constituent discharge at the station. The total 

and suspended discharges computed for the constituents of interest at each station are listed in 

table 30 along with the percentage of total constituent discharge contributed by suspended sediment. Of the nutrients studied, the contribution of 

suspended phosphorus at all stations ranged from 

about 31 to 95 percent of total annual phosphorus

discharge and averaged about 76 percent. Corresponding ranges for suspended nitrogen and organic 

carbon were 7 to 53 percent and 18 to 71 percent, 

respectively. The average contribution of suspended 

nitrogen and organic carbon to total annual constituent discharge at all stations was 29 and 43 percent, respectively. Trace metal discharges contributed by suspended sediment constitute a large 

percentage of the total annual metal discharge at 

every station. Suspended lead, for example, contributed about 38 to 100 percent of total lead discharge and averaged 84 percent for all stations.

MANAGEMENT IMPLICATIONS OF CHEMICAL 

QUALITY DATA

With respect to the impact of sediment on stream 

quality, water resource managers are concerned
MANAGEMENT IMPLICATIONS OF CHEMICAL-QUALITY DATA 81

TABLE 28.—Mean concentrations of dissolved constituents used to compute average annual dissolved-constituent discharges

—Continued

Station name

Chattahoochee River near Leaf _ __ ___ __

Soque River near Clarkesville

Chestatee River near Dahlonega __ _ _ _ _

Chattahoochee River at Atlanta

S. Fork Peachtree Creek at Atlanta __ _

Peachtree Creek at Atlanta _ _ _ _

Woodall Creek at Atlanta

Nancy Creek at Atlanta _ _

Chattahoochee River near Fairburn _

Snake Creek near Whitesburg

Chattahoochee River near Whitesburg

Dissolved

Mean 

concentration

(mg/L)

trace

0.0050

.0054

trace

.0089

.014

.021

.037

.0060

.0073

.012

.0075

zine

Number 

of 

samples

9 

8 

11

12 

9 

9 

18 

9 

5 

11 

13

12

Dissolved chromium

Soque River near Clarkesville

Chattahoochee River at Atlanta

N. Fork Peachtree Creek near Atlanta __ . S. Fork Peachtree Creek at Atlanta

Peachtree Creek at Atlanta

Woodall Creek at Atlanta _ _ .

Nancy Creek at Atlanta _ , Chattahoochee River near Fairburn

Snake Creek near Whitesburg

Chattahoochee River near Whitesburg

Mean 

concentration

(mg/L)

trace

0.004

trace

0.0002

.00083

.0015

trace

trace

Number 

of 

samples

9

8 

11

11

~9 

18 

8 

5 

11

--

Dissolved

Mean 

concentration

(mg/L)

0.0023 

.0032

.0021

a 

.0039 

.0050

.0034 

.0041 

.0030 

.0035

Dissolved

Mean 

concentration 

(mg/L)

trace 

trace 

trace 

trace 

trace 

0.00061 

.040

.00054 

.00031 

none 

.00025

copper

Number 

of 

samples

"§

11

12

14 

9

11 

13 

10 

12

arsenic

Number 

of 

samples

11

9 

12 

9 

9 

18 

9

11 

13 

10 

12

with the response of stream quality to increasing 

concentrations of sediment. The relative contribution of sediment to nonpoint pollution and the effect 

of land use on suspended-constituent discharges are 

also cause for concern.

The effects of sediment concentration on the 

chemical quality of basin streams has been demonstrated (figs. 45 and 46, table 27). At every station, 

the suspended concentration of nutrients and trace 

metals increased with increasing concentrations of 

suspended silt plus clay. Similar relations between 

turbidity and suspended sediment (fig. 44, table 26) 

indicate a progressive decrease in the aesthetic and 

light-transmitting quality of streams with increasing concentrations of suspended sediment.

Sediment is commonly considered a nonpoint pollutant. As such, computed suspended-constituent

discharges indicate the minimum nonpoint contribution to stream quality at stream stations receiving 

loads from both point and non-point sources. Five 

large municipal wastewater-treatment facilities discharge treated effluents to the Chattahoochee River 

between the stations at Atlanta and near Fairburn. 

Comparison of suspended and total nutrient discharges at the Fairburn station (table 28) indicates 

that at least 32 percent of the phosphorus transported in the Chattahoochee River downstream of 

the wastewater-treatment facilities is non-point in 

origin.

The effect of land use on suspended-constituent 

discharges can be determined by comparing suspended-constituent yields from watersheds with different land-use characteristics. Table 30 lists the 

yields of suspended constituents from watersheds

TABLE 30.—Annual yields of suspended constituents from representative land use watersheds

Suspended-constituent yield, in tons/yr/mi3

Forest _ _ .

Urban

Rural _ _ _ _

Phosphorus

0.15

.33

.19

Nitrogen

0.36 

.71 

.43

Organic 

carbon

7.4 

8.1 

6.9

Lead

0.033 

.16 

.028

Zinc

0.048

.13

Copper

0.034 

.050

Chromium

0.027 

.023

Arsenic

0.0011 

.0038 

.0028
82 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN

TABLE 29.—Summary of regression data relating dissolved-constituent concentrations to stream discharge

Station name

Chattahoochee River near Leaf

Soque River near Clarkesville

Chestatee River near Dahlonega

S. Fork Peachtree Creek at 

Atlanta

Peachtree Creek at Atlanta _

Nancy Creek tributary near 

Chamblee

Chattahoochee River near 

Fairburn

Snake Creek near Whitesburg

Chattahoochee River near 

Whitesburg

Chattahoochee River near Leaf

Soque River near Clarkesville

Chestatee River near Dahlonega

S. Fork Peachtree Creek at 

Atlanta

Peachtree Creek at Atlanta _

Nancy Creek tributary near 

Chamblee _ _ _

Chattahoochee River near 

Fairburn

Snake Creek near Whitesburg

Chattahoochee River near 

Whitesburg

Dissolved phosphorous as P

, Correlation 

coefficient

0.00350 0.361 0.92

253 0.923 .89

389 0.972 .91

Dissolved organic carbon

, Con-elation 

coefficient

0.192 0.333 0.94

.0853 .704 .77

.140 .410 .74

Number 

of samples

q

90

00

Number 

of samples

9

8

19

Dissolved nitrogen as N

, Correlation Number 

a coefficient of samples

0.00428 0.551 0.92 15

.0336 .385 .83 10

.0458 .427 .74 16

Dissolved copper

, Correlation Number 

coefficient of samples

0.0368 -0.466 0.76 8

where land use is predominantly forest, urban, or 

rural. Yield data were computed as the sum of average annual suspended-constituent discharges from 

representative watersheds divided by the sum of the 

watershed drainage areas. Representative forested 

watersheds were selected as areas draining to the 

Chattahoochee River near Leaf, the Chestatee River 

near Dahlonega, the Soque River near Clarkesville, 

and Snake Creek near Whitesburg. Corresponding 

urban watersheds included the areas draining to 

Peachtree Creek at Atlanta, North Fork of Peachtree Creek near Atlanta, South Fork of Peachtree 

Creek at Atlanta, Woodall Creek at Atlanta, tributary to Nancy Creek near Chamblee, and Nancy 

Creek at Atlanta. The area draining to Big Creek 

near Alpharetta was considered most representative 

of a rural watershed. Note that annual suspendedconstituent discharges were not available for every 

constituent of interest at every watershed listed 

above (table 31). Thus average yield data were 

computed, for the most part, with different numbers 

of watersheds.

The impact of urban land use on average annual 

suspended-constituent yields is clearly indicated. 

The yields of suspended phosphorus and nitrogen

from urban watersheds, for example, are greater 

by a factor of two than corresponding yields from 

forested watersheds. Similarly, the average yields 

of suspended lead and zinc from urban areas exceed 

corresponding yields from forested areas by an order of magnitude. These differences in yield between 

urban and forested areas indicate that sediments in 

urban watersheds contact nutrients and most trace 

metals with greater frequency than sediments found 

in mostly forested watersheds. These data further 

indicate that sediments act as sinks for nutrients 

and some trace metals, thus reducing the dissolved 

concentrations of these constituents in urban 

streams.

Suspended-constituent yields from the designated 

rural watershed were slightly greater or about equal 

to corresponding yields from the forested 

watersheds.

SUMMARY

Land-use, soils and other environmental data 

were used in conjunction with the Universal Soil 

Loss Equation to compute sheet erosion in nine large 

watersheds of the Upper Chattahoochee River basin.
SUMMARY 83

TABLE 31.—Summary of average annual suspended- and total-constituent discharges

Station name

Chattahoochee River near Leaf

Soque River near Clarkesville _ _

Chestatee River near Dahlonega

Big Creek near Alpharetta

Chattahoochee River at Atlanta

1 Chattahoochee River at Atlanta _ _

N. Fork Peachtree Creek near Atlanta __ 

S. Fork Peachtree Creek at Atlanta .. _

Peachtree Creek at Atlanta

Woodall Creek at Atlanta

Nancy Creek tributary near Chamblee

Nancy Creek at Atlanta

Chattahoochee River near Fairburn

2 Chattahoochee River near Fairburn __

Snake Creek near Whitesburg

Chattahoochee River near Whitesburg

2 Chattahoochee River near Whitesburg

Chattahoochee River near Leaf

Soque River near Clarkesville

Chestatee River near Dahlonega

Big Creek near Alpharetta

Chattahoochee River at Atlanta

L Chattahoochee River at Atlanta

N. Fork Peachtree Creek near Atlanta

S. Fork Peachtree Creek at Atlanta

Peachtree Creek at Atlanta

Woodall Creek at Atlanta

Nancy Creek tributary near Chamblee

Nancy Creek at Atlanta

Chattahoochee River near Fairburn _ _ _

3 Chattahoochee River near Fairburn _

Snake Creek near Whitesburg

Chattahoochee River near Whitesburg

2 Chattahoochee River near Whitesburg

Total 

discharge 

(tons/yr)

18

25

27

15

180

11 

11

32

16

.44

11

1,300

6.0

1.300

Total 

discharge

(tons/yr)

960

1,700

2,000

1,300

250

38

670

28,000

290

36,000

Phosphorus as P

Suspended 

discharge

(tons/yr)

16

21

24

14

56

8.6 

10

29

5.3

.30

10

410

5.7

410

Organic carbon

Suspended 

discharge 

(tons/yr)

510

1,200

1,400

500

46

1.9

260

5,800

2,500

110

8,000

2,500

Ratio of 

suspended 

to total 

discharge 

(percent)

88.9

84.0

88.8

93.3

31.1

53.3

78.2 

90.9

90.6

33.1

68.2

90.9

31.5

7.4

95.0

31.5

7.4

Ratio of 

suspended 

to total 

discharge 

(percent)

53.1

70.6

70.0

38.5

18.4

4.8

38.8 ?n 7

8.9

37.9

22.2

6.9

Total 

discharge

(tons/yr)

130

100

200

140

1,700

75 

71

200

46

77

41

Total 

discharge 

(tons/yr)

4.6

.74

5.6

21

.9

2.0

.14

.64

Nitrogen as N

Suspended 

discharge

(tons/yr)

69

32

39

31

120

56

19 

22

62

3.7

28

19

Chromium

Suspended 

discharge 

(tons/yr)

4.6

.65

5.6

10

11

.9

1.9

.11

.64

Ratio of 

suspended 

to total 

discharge 

(percent)

53.1

32.0

19.5

22.1

7.1

3.3

25.3 

30.9

31

8.0

36.4

46.3

Ratio of 

suspended 

to total 

discharge 

(percent)

100

88

100

47.6

52.4

100

95

78.6

100

See footnotes at end of table.

Average annual erosion yields ranged from about 

900 to 6,000 tons per square mile per year. Erosion 

yields were large in those watersheds with relatively 

high percentages of agricultural and transitional 

land uses and were lowest in predominantly urban 

watersheds. The Universal Soil Loss Equation was 

also used to determine the sensitivity of annual 

sheet erosion to timber harvesting. Computed postharvest erosion yields were several orders of magnitude greater than pre-harvest yields in the same 

areas.

Average yields of suspended sediment from the 

same nine watersheds ranged from about 300 to 800 

tons per square mile per year. Yields of sediment 

were greatest from predominantly urban watersheds 

and least from mostly forested watersheds. A large

part of the sediment discharged from urban streams 

was considered to be derived from channel erosion. 

Average annual unmeasured-sediment discharge 

computed at four stations ranged from about 6 to 30 

percent of the total annual sediment discharge.

The contribution of suspended sediment to stream 

quality was evaluated by comparing annual suspended and total constituent discharges at 14 stations. In general, 60 percent or more of the annual 

discharge of phosphorus and trace metals was contributed by suspended sediment. Suspended discharges of nitrogen and organic carbon ranged from 

about 10 to 70 percent of total, respectively. Yields 

of nutrients and trace metals in suspension were 

greater from urban watersheds than from forested 

drainages.
84 EROSION, SEDIMENT DISCHARGE, CHANNEL MORPHOLOGY, CHATTAHOOCHEE RIVER BASIN 

TABLE 31.—Summary of average annual suspended- and total-constituent discharges—Continued

Station name

Chattahoochee River near Leaf _

Soque River near Clarkesville _ _ _____

Chestatee River near Dahlonega _ _ _

Big Creek near Alpharetta _ _____

Chattahoochee River at Atlanta _ _______

Chattahoochee River at Atlanta __

N. Fork Peachtree Creek near Atlanta _ ___

S. Fork Peachtree Creek at Atlanta ____

Peachtree Creek at Atlanta _ _____

Woodall Creek at Atlanta _ __ _____

Nancy Creek tributary near Chamblee _ _ _

Nancy Creek at Atlanta _ _ _ _

Chattahoochee River near Fairburn _

2 Chattahoochee River near Fairburn

Snake Creek near Whitesburg

Chattahoochee River near Whitesburg _ _ _

2 Chattahoochee River near Whitesburg _

Chattahoochee River near Leaf

Soque River near Clarkesville

Chestatee River near Dahlonega

Big Creek near Alpharetta

Chattahoochee River at Atlanta

1 Chattahoochee River at Atlanta

N. Fork Peachtree Creek near Atlanta _ _

S. Fork Peachtree Creek at Atlanta _ _

Peachtree Creek at Atlanta _ _ _ _ Woodall Creek at Atlanta

Nancy Creek tributary near Chamblee

Nancy Creek at Atlanta

Chattahoochee River near Fairburn

2 Chattahoochee River near Fairburn

Snake Creek near Whitesburg

Chattahoochee River near Whitesburg ____

s Chattahoochee River near Whitesburg _

Total

discharge

(tons/yr)

7.5

7.0

7.8

47

2.5

4.2

16

3.4

.12

3.6

200

220

Total

(tons/yr)

0.14

.20

1.70

.071

.10

.33

.79

.20

4.1

.074

5.0

Zinc

Suspended

discharge

(tons/yr)

7.5

5.9

5.8

16

31

2.1

3.4

13

2.7

.096

3.1

86

31

110

31

Arsenic

Suspended

discharge

(tons/yr)

0.14

.20

.77

.96

.071

.10

.33

.037

.16

2.7

.96

.074

3.6

.96

Ratio of

suspended

to total

discharge

(percent)

100

84.3

74.4

34.0

66.0

84.0

81.0

81.3

79.4

80.0

86.1

43.0

15.5

____

50.0

8.3

suspended

to total

discharge

(percent)

100

100

44.5

55.5

100

100

100

4.7

80.0

65.9

23.4

100

72.0

19.2

Total

discharge

(tons/yr)

2.7

7.6

22

2.0

5.1

.36

1.1

73

1.2

78

Total

discharge

(tons/yr)

5.8

2

36

4.9

6.4

16

1.8

.11

4.5

140

170

Copper

Suspended

discharge

(tons/yr)

2.2

6.4

9.3

7.0

1.7

4.6

.27

.94

45

7.0

1.0

46

7.0

Lead

Suspended

discharge

(tons/yr)

5.0

2

14

22

4.5

6.1

15

1.5

.046

3.6

68

22

100

22

Ratio of

suspended

to total

discharge

(percent)

~81.5

84.2

____

42.3

31.8

_ _

85.0

90.2

75.0

85.5

61.6

9.6

83.3

59.0

9.0

Ratio of

suspended

to total

discharge

____

86.2

100

38.9

61.1

91.8

95.3

93.7

83

38.3

80.0

48.6

15.7

58.8

12.9

1 Discharge attributed to regulated flow.

" Discharge attributed to regulated flow. Equals computed discharge at the Chattahoochee River at Atlanta.

SELECTED REFERENCES

Anderson, J. R., Hardy, E. E., Roach, J. T., and Witmer, 

R. E., 1976, A land use and land cover classification system for use with remote sensor data: U.S. Geological 

Survey Professional Paper 964, 28 p.

Atlanta Region Metropolitan Planning Commission, 1967, 

Soils interpretation for regional planning in metropolitan

Atlanta: U.S. Dept. of Agriculture Soil Conservation 

Service, Appendix C, p. 37-64.

Brooks, J. F., 1971, Soil survey of Carroll and Haralson 

Counties, Georgia: U.S. Dept. of Agriculture Soil Conservation Service, 60 p.

Brown, E., Skougstad, M. W., and Fishman, M. J., 1970, 

Methods for collection and analysis of water samples for 

dissolved minerals and gases: Techniques of Water-Re-
SELECTED REFERENCES 85

sources Investigations of the U.S. Geological Survey, 

chapter Al, book 5, 160 p.

Cherry, R. N., Faye, R. E., Stamer, J. K., McGinty, H. K., 

1976, Plan for river quality assessment, Upper Chattahoochee River basin, Georgia: Proceedings, AWWA 

River Water Quality Assessment Seminar, No. 20133.

Colby, B. R., 1956, Relationship of sediment discharge to 

streamflow: U.S. Geological Survey Open-File Report, 

170 p.

Colby, B. R., and Hembree, C. H., 1955, Computations of 

total sediment discharge, Niobrara, River near Cody, 

Nebraska: U.S. Geological Survey Water-Supply Paper 

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•& U.S. GOVERNMENT PRINTING OFFICE: 1980 O— 311-344/65