Effects of Urbanization on Streamflow 

and Sediment Transport in the 

Rock Creek and Anacostia River Basins, 

Montgomery County, Mary I nd, 1962-7 4 

GEOLOGICAL SURVEY PROFESSIO AL PAPER 1003 

Work done in cooperation with the Maryland-National 

Capital Park and Planning Commission (Montgomery 

County and Prince Georges County Planning Boards), 

the Washington Suburban Sanitary Commission, the 

District of Columbia Department of Environmental 

Services, the Montgomery County Department of 

Environmental Protection, and the Maryland 

Department of Natural Resources 

Effects of Urbanization on Streamflow 

and Sediment Transport in the 

Rock Creek and Anacostia River Basins, 

Montgomery County, Maryland, 1962-74 

By THOMAS H. YORKE and WILLIAM J. HERB 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1003 

Work done in cooperation with the Maryland-National 

Capital Park and Planning Commission (Montgomery 

County and Prince Georges County Planning Boards), 

the Washington Suburban Sanitary Commission, the 

District of Columbia Department of Environmental 

Services, the Montgomery County Department of 

Environmental Protection, and theM aryland 

Department of Natural Resources 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1978 
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary 

GEOLOGICAL SURVEY 

V. E. McKelvey, Director 

Library of Congress Cataloging in Publication Data 

Yorke, Thomas H 

Effects of urbanization on streamflow and sediment transport in the Rock Creek and Anacostia River basins, 

Montgomery County, Maryland, 1962-74. 

(Geological Survey professional paper ; 1003) 

Bibliography: p. 

Supt. of Docs. no.: I 19.16:1003 

1. Stream measurements-Maryland-Montgomery Co. 2. Sediment transport-Maryland-Montgomery Co. 

3. Urbanization-Maryland-Montgomery Co. 4. Urban hydrology. I. Herb, William J., joint author. II. 

Maryland. Maryland-National Capital Park and Planning Commission. III. Title: Effects of urbanization 

on streamflow ... IV. Series: United States. Geological Survey. Professional paper ; 1003. 

GB1225.M3Y67 551.3'03 76-608222 

For sale by the Branch of Distribution, U.S. Geological Survey, 

1200 South Eads Street, Arlington, VA 22202 

Stock Number 024-001-03036-5 
CONTENTS 

Page Page 

Abstract 1 Sediment discharge-Continued 

Introduction ------------------------------------- 1 

2 

2 

5 

5 

5 

6 

Size distribution of suspended sediment --------

Bedload contribution -------------------------

Storm variability ----------------------------

16 

17 

19 

20 

21 

41 

41 

51 

56 

63 

64 

66 

67 

69 

70 

Acknowledgments _______________________________ _ 

Factors affecting streamflow and sediment transport_ Correlation matrix -----------------------

Regression equations --------------------- Physiography _______________________________ _ 

Geology and soils ---------------------------- Effects of land use/land cover ----------------

Average annual sediment yields ----------

Construction-site sediment yields ---------

Climate ____________________________________ _ 

Land use/land cover -------------------------

Streamflow -------------------------------------- 8 

8 

9 

Stream-channel erosion ______________ -----

Annual and monthly runoff ------------------- Sediment control --------------------------------- Duration and low flow ----------------------- Field applications ___________________________ _ Storm runoff and flood-peak discharges _______ _ 10 Effects of sediment-control measures ----------

Cost of sediment controls ---------------------- Sediment discharge _____________________________ _ 12 

Annual and monthly suspended-sediment Summary ---------------------------------------- discharge ______________ -------- ______ ---- __ 12 Selected references -------------------------------

PLATE 1. 

2. 

3. 

FIGURE 1. 

2. 

3-15. 

ILLUSTRATIONS 

Map of average slope in North Branch Rock Creek and Northwest Branch Anacostia River basins, 

Montgomery County, Md. _____________________________________________________________ In pocket 

Land use/land cover in North Branch Rock Creek and Northwest Branch Anacostia basins, Montgometry County, Md., 1966 ------------------------------------------------------------In pocket 

Land use/land cover in North Branch Rock Creek and Northwest Branch Anacostia River basins, 

Montgomery County, Md., 197 4 ________________________________________________________ In pocket 

Page 

Location map of Northwest Branch Anacostia River and North Branch Rock Creek basins ----- 3 

Graph showing mean monthly rainfall at locations in and near the study area, October 1962-September 1974 --------------------------------------------------------------------------- 6 

Graphs showing: 

3. Variation in mean monthly precipitation and runoff, Northwest Branch Anacostia River 

near Colesville, Md., October 1962-September 1974 ------------------------------- 9 

4. Flow-duration curves for the Northwest Branch Anacostia River, 1923-39, 1961-74 (A); 

1963-74 (B); and 1967-74 (C) -------------------------------------------------- 9 

5. Flow-duration curves for five small streams draining areas of different land use/land 

cover, 1967-74 ----------------------------------------------------------------- 10 

6. Relation between storm runoff and precipitation for selected subbasins, 1971-74 --------- 11 

7. Annual flood-frequency curves for selected subbasins, 1967-74 -------------------------- 12 

8. Annual variation of precipitation, water discharge, and suspended-sediment discharge, 

Northwest Branch Anacostia River near Colesville, 1963-74 --------------------- 14 

9. Duration of water discharge and suspended-sediment discharge, Northwest Branch Anacostia River near Colesville, 1963-74 __ ------------------------------------------- 15 

10. Mean monthly suspended-sediment discharge, Northwest Branch Anacostia River near 

Colesvill~ 1963-74 -------------------------------------------------------------- 16 

11. Relation of sand, silt, and clay content of suspended sediment to water discharge, Northwest Branch Anacostia River near Colesville, 1960-73 --------------------------- 17 

12. Particle-size distribution of suspended sediment transported during medium and high flows 

in the small study basins, 1967-74 ----------------------------------------------- 18 

13. Daily suspended-sediment and instantaneous bedload transport curves for the Northwest 

Branch Anacostia River near Colesville, 1963-74 -------------------------------- 19 

14. Example of flow-duration (A) and suspended-sediment transport (B) curves used for computing average annual sediment loads __ ------------------------------------------- 48 

15. Relation of suspended-sediment yield to percentage of drainage basin under construction --- 50 

III 
IV CONTENTS 

Page 

FIGURE 16. Map showing construction sites and average slope conditions, Bel Pre Creek and Manor Run 

basins, June 1967 ---------------------------------------------------------------------- 54 

17-19. Photographs showing: 

17. Extensive erosion in the Manor Run basin, 1967 ------------------------------------- 55 

18. Construction activities without (1966) and with (1974) sediment controls, Bel Pre Creek 

basin -------------------------------------------------------------------------- 56 

19. Large sediment-stormwater management basin used to trap sediment before it can leave 

construction sites, Bel Pre Creek basin, 1974 ----------------------------------- 57 

20. Graph showing relation between construction-site sediment yields computed from observed data 

and those estimated by equation 3 ------------------------------------------------------- 58 

21-23. Photographs showing: 

21. Grading for street right-of-way within the Manor Run stream channel, 1967 -------------- 59 

22. Construction site in the Lutes Run basin, 1964 (A), 1968 (B), and 1974 (C) ----------- 60 

23. Stream channel-geometry reaches, 1974: Manor Run (A), Northwest Branch Anacostia 

River at Norwood (B), and Batchellors Run (C) -------------------------------- 61 

24. Graphs showing typical cross-section changes between 1967 and 1974 in straight (sections 9, 8, 

and 4A) and curved (sections 5, 11, and 9) reaches of three typical stream channels in the 

study area ----------------------------------------------------------------------------- 62 

25-27. Photographs showing: 

25. Typical sediment basin used in 1966 ______ ------------------------------------------- 64 

26. Sediment basin before (A) and after (B and C) it was breached for installation of a 

sewer line --------------------------------------------------------------------- 65 

27. Small sediment basin requiring maintenance ----------------------------------------- 66 

28. Graph showing relation between suspended sediment and storm runoff for dormant season (A) and 

growing season (B) storms, Northwest Branch Anacostia River near Colesville, 1963-74 --- 67 

TABLES 

Page 

TABLE 1. Summary of streamflow, suspended-sediment, and recording precipitation stations in the Rock 

Creek and Anacostia River basins ------------------------------------------------------- 4 

2. Land use/land cover, in acres, in the Rock Creek and Anacostia River basins, 1963-74 --------- 7 

3. Monthly and annual water and suspended-sediment discharge, Northwest Branch Anacostia River 

near Colesville, Md., 1963-74 ------------------------------------------------------------ 13 

4. Particle-size distribution of suspended sediment, Northwest Branch Anacostia River near Colesville, 

Md., 1960-73 --------------------------------------------------------------------------- 16 

5. Hydrologic characteristics and related factors for storms in the Rock Creek and Anacostia River 

basins, 1962-74 ------------------------------------------------------------------------ 22 

6. Simple correlation coefficients of storm-related variables -------------------------------------- 42 

7. Regression coefficients, multiple correlation coefficient, and standard error of best equations explaining the variation of storm suspended-sediment discharge ---------------------------------- 46 

8. Example of computation of average annual suspended-sediment discharge ---------------------- 47 

9. Average annual suspended-sediment yields and selected land-use/land-cover factors ------------- 48 

10. Construction-site sediment yields and related factors ___________________ ----------_------------- 53 

11. Summary of stream-channel surveys --------------------------------------------------------- 63 

CONVERSION FACTORS 

The following factors may be used to convert the English units published in this report to metric units. 

Mu.ltiply English unit 

acres 

cubic feet per second (ft3 /s) 

cubic feet per second-day ( f~ Is-d) 

cubic feet per second per square mile 

[ (f~/s) /mF] 

feet (ft) 

inches (in) 

miles (mi) 

pounds per cubic foot (lbs/f~) 

square miles (mi2 ) 

short ton 

tons per acre 

tons per square mile ( tons/mi2 ) 

By 

0.4047 

0.02832 

2447 

0.002447 

0.01093 

0.3048 

25.4 

1.609 

16.05 

2.590 

0.9072 

2.242 

0.3503 

To obtain metric unit 

square hectometers (hm2

) 

cubic meters per second (m3/s) 

cubic meters (m3

) 

cubic hectometers (hm3 ) 

cubic meters per second per square 

kilometer [ (m3/s) /km2

] 

meters (m) 

millimeters (mm) 

kilometers (km) 

kilograms per cubic meter (kg/m3 ) 

square kilometers (km2

) 

metric tons or tonnes ( t) 

tonmis per square hectometer ( t/hm2

) 

tonnes per square kilometer (t/km2

) 
EFFECTS OF URBANIZATION ON STREAMFLOW 

AND SEDIMENT TRANPORT IN THE 

ROCK CREEK AND ANACOSTIA RIVER BASINS, 

MONTGOMERY COUNTY, MARYLAND, 1962-74 

By THoMAS H. YoRKE and WILLIAM J. HERB 

ABSTRACT 

Land use/land cover, precipitation, streamflow, and sediment data were collected from nine drainage subbasins in a 

32-square-mile (83-square-kilometer) area north of Washington, D.C., in Montgomery County, Md. This study was 

begun in 1962 to define urban runoff and sediment problems 

and was expanded in 1966 to evaluate response to sedimentcontrol practices in areas undergoing urban development. 

Land use/land cover varied considerably in the study subbasins, which ranged in size from 0.35 to 21.1 square miles 

(0.91 to 54.6 square kilometers). Three subbasins remained 

virtually rural, while the others underwent urban development. In 1974, urban land represented from 0 to 60 percent 

of the land use in the nine subbasins. Urbanization did not 

affect median and low flows, but did increase storm runoff 

and peak discharges. 

Suspended sediment transported from one of the basins 

that underwent urban development, the 21.1 square mile 

(54.6 square kilometer) Anacostia River basin, averaged 

14,800 tons (13,400 tonnes) per year between 1962 and 1974, 

while urban construction averaged about 3 percent of the 

drainage area during this period of time. Bedload was estimated to be 6 to 13 percent of the total sediment load. Most 

of the suspended load was transported during storms, and 

varied from storm to storm and seasonally. High loads 

were generally associated with high runoff in the spring 

and intense thunderstorms in the summer. Cropland, urban 

land, and construction sites were the major sources of sediment. Annual suspended-sediment yields from land under 

cultivation ranged from 0.65 to 4.3 tons per acre (1.5 to 

9.6 tonnes per square hectometer), compared to estimated 

yields from forest and grasslands ranging from 0.03 to 0.2 

ton per acre (0.07 to 0.45 tonne per square hectometer). 

Yields from urban land were about 3.7 tons per acre (8.3 

tonnes per square hectometer) , most of which came from 

stream-channel erosion. 

Average annual suspended-sediment yields computed for 

urban construction sites ranged from 7 to 100 tons per acre 

(16 to 224 tonnes per square hectometer). The magnitude 

of the yield from construction sites was significantly affected 

by (1) the average slope of the sites, (2) the proximity to 

stream channels, (3) the existence of buffer zones of natural 

vegetation, and ( 4) the use of sediment-control measures. 

Sediment controls, particularly those enforced under a 1971 

sediment-control ordinance, decreased construction-site suspended-sediment yields by 60 to 80 percent. It was estimated 

that the suspended-sediment load in the Anacostia River 

basin between 1962 and 1974 would have been reduced by 

50 percent if strictly enforced sediment controls had been 

used throughout the period. Based on a reported cost of 

$1,030 per acre ( 0.4 square hectometer) , the cost of sediment controls on the 1,900 acres (769 square hectometers) 

developed during the period would have been $19 per ton 

( $21 per tonne). 

INTRODUCTION 

Each year thousands of acres of pastures, cultivated fields, and woodlots are replaced by housing 

subdivisions, apartment complexes, and shopping 

centers. Urbanization is particularly evident in the 

Washington, D.C., metropolitan area. Guy and 

others (1963) estimated that 500 mi2 (1,300 km2 ) 

of rural land would be urbanized between the mid1960's and 1980 to accommodate a population increase of 2 million. Urban construction activities 

and the resulting increase in impervious area place 

a tremendous stress on the local streams. Erosion 

and sediment transport increase manyfold during 

construction, and increased runoff from impervious 

surfaces causes stream-channel erosion and flooding after construction. Studies by Guy and Ferguson (1962), Wolman (1964), Guy (1965), and 

Vice, Guy, and Ferguson (1969) indicate that annual sediment yields for urban construction sites 

range from 25,000 to 120,000 tons/miZ (8,800 to 

42,000 t/km2 ) as compared with rural sediment 

yields of 150 to 500 tons/mi2 (53 to 175 t/km2 ) 

(Wark and Keller, 1963). Anderson (1970) reported that urbanization increased flood peaks in 

northern Virginia by a factor of 2 to 8, depending 

on relative impervious area and the density of the 

storm-sewer system. 

This report presents the results of a study begun 

in 1962 to define urban sediment problems and 

which was expanded in 1966 to evaluate response to 

1 
2 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

a program designed to control runoff and sedimentation from urbanizing areas. Facts about land use/ 

land cover, streamflow, and sedimentation representative of urbanizing areas in the Washington, D.C., 

area are presented. The effects of different land 

uses, construction practices, and sediment-control 

methods on runoff and sediment are evaluated and 

summarized. This information should provide the 

basis for land-use planning that would minimize 

the damaging effects of urban development on 

streams in the Maryland Piedmont and other areas 

of the country with similar climatic and physiographic characteristics. 

The study was made in a 32 mP (83 km2 ) area 

drained by the North Branch Rock Creek and the 

Northwest Branch Anacostia River. Both streams 

enter the Potomac River in the District of Columbia 

(fig. 1). Data from 9 streamflow-sediment monitoring stations, 9 recording rain gages, a varying number of nonrecording rain gages, and 14 sets of aerial 

photographs taken between 1963 and 1974 were 

used in the study. The locations of the gages are 

shown in figure 1. The type of recording and sampling equipment and the type and length of record 

available for ·each site are sum.marized in table 1. 

Streamflow and suspended-sediment discharge 

were measured using the standard procedures described by Carter and Davidian (1968) and Guy and 

Norman (1970). Stage was recorded with digital 

water-stage recorders at a frequency of 48 to 288 

readings per day, depending on the size of the 

drainage area and land use of the basin. Direct 

measurements of water discharge and indirect determinations of one or two peak discharges were 

used to establish the stage-discharge rating for each 

site. Suspended-sediment concentration was sampled 

with a '.:ombination of manual and automatic samplers. Each site was equipped with a single-stage 

sampler, which automatically collected samples at 

preselected levels during storms. Some sites were also 

equipped with pumping samplers. Hand samples 

were collected during most storms to provide a check 

on the automatic samplers and to monitor suspended-sediment concentration during recession 

flow,s. 

Precipitation was measured with a network of 

recording and nonrecording ·rain gages. Recording 

gages were located to provide rainfall duration and 

intensity data for each subbasin within the study 

area. Eight sites were equipped with digital recorders having 5- or 15-minute recording intervals. 

One site was equipped with a weighing-type gage 

with a 24-hour continuous chart. Nonrecording 

gages were located throughout the basins to mea.-

sure the areal distribution of precipitation. 

Land use/land cover data were obtained from 

aerial photographs using grids with a dot density 

of 64 or 100 dots/in2 • The scale of photographs 

available prior to 1966 ranged from 1:23,000 to 

1:37,000, and each dot represented 0.87 to 3.4 acres 

(0.35 to 1.4 hm2 ), depending on the scale of the 

photographs and the dot-grid used. After 1966, 

1: 12,000-scale photographs were obtained at least 

annually. Each dot represented 0.36 acre (0.15 hm2 ) 

on these photographs. Land use~/land cover was 

summarized in five major categories: farmland and 

parks, rural residential, urban residential, commercial, and construction. The amount of cropland, 

grass, forest land, water, and impervious area was 

summarized for farmland and parks. The amount of 

grass, forest land, and impervious area was summarized for the residential or commercial categories. 

ACKNOWLEDGMENTS 

This report was prepared by the U.S. Geologica~ 

Survey in cooperation with the Maryland-National 

Capital Park and Planning Commission (Mont~ 

gomery County and Prince Georges County Planning Boards), the Washington Suburban Sanita.ry 

Commission, the District of Columbia Department 

of Environmental Services, the Montgomery County 

Department of Environmental Protection, and the 

Maryland Department of Natural Resources, Water 

Resources Administration. The authors wish to express their gratitude to the following: J. S. Hewins, 

Inter-Governmental Coordinator, Maryland-National Capital Park and Planning Commission, and E. 

R. Keil, former State Conservationist, U.S. Soil Conservation Service, for their encouragement and their 

strong support during the project; J. D. Large, 

Montgomery County Department of Public Works, 

for providing information on grading and paving 

permits issued to developers in the study area; R. 

M. Seely, Montgomery County Department of Environmental Protection, for providing records of 

sediment control inspections; and L. H. Williams, 

formerly of the U.S. Soil Conservation Service, for 

providing information on sediment-control standards and field applications. in the study area. 

FACTORS AFFECTING STREAI\'IFLOW AND 

SEDIMENT TRANSPORT 

The streamflow and sediment characteristics of 

streams in the study area are affected by numerous 

factors including physiography, soils, climate, and 
39" 

10' 

39" 

05' 

FACTORS AFFECTING STREAMFLOW AND SEDIMENT TRANSPORT 

EXPLANATION 

Continuous-record 

gaging station 

6 Partial-record 

gaging station 

77°05' 

~ Sediment-measurement site 

<t> Recording rain gage 

· - Drainage basin boundary 

- · ·- Sub-basin boundary 

77°05' 

Base from US. Geolog1cal Survey 

Beltsville, Clarksville. Kensington and Sandy Spr1ng 1 24.000, 1971 

3 

7rOO' 

2 MILES 

3 KILOMETERS 

77°00' 

F'IGURE 1.-Location map of Northwest Branch Anacostia River and North Branch Rock Creek basins. 
TABLE 1.-Summary of streamflow, suspended-sediment, and recording precipitation stations in the Rock Creek and Anacostia River basins 

STREAMFLOW AND SUSPENDED-SEDIMENT STATIONS 

Station Drainage 

Station No. area 

(mi2 ) 

Williamsburg Run 01647685 2.25 near ():ney. 

North Branch Rock 01647720 9.73 

Creek near Nor beck. Manor Run near 01647725 1.01 

Norbeck. Northwes·~ Branch 01650050 2.45 

Anacostia River at Norwood. 

Nursery Run at 01650085 .35 Cloverly. Batchellors Run at 01650190 .47 Oakdale. Bel Pre Creek at 01650450 1.69 

Lay hill. 

Lutes Run at Lutes ---- 01650470 .47 

Northwest Branch 01650500 21.1 Anacostia River near Colesville. 

Station 

Olney West -------------------------------------- Oakdale __________________________ ----- _____ ----- __ 

Norbeck Northwest -------------------------------- Sandy Spring South -------------------------------

Cloverly ------------------------------------------- Norwood South ------------------------------------ Layhill East --------------------------------~----- Nor beck ______ ---- _ -~- ------ _____ ------------------

Glenmont _ ----- -----------------------------~----- _ 

Streamflow Suspended sediment 

Period of record Type of record Period of record Type of record 

Automatic 

sampling 

equipm~nt 

Oct. 1966-Sept. 1974 

Oct. 1966-Sept. 1974 

Oct. 1966-Sept. 1974 

Oct. 1966-Sept. 1974 

Oct. 1966-Sept. 1974 

Nov. 1966-Sept. 1974 

Mar. 1963-Sept. 1966 Oct. 1966- Sept. 197 4 Feb. 1963-Apr. 1970; 

July 1971-Sept. 1974 Oct. 1923-Sept. 1974 

Daily 

Daily 

Daily 

Daily 

Daily 

Flood hydrograph 

Flood hydrograph ------

Daily -------------- Flood hydrograph 

Daily 

Oct. 1966-Sept. 1968 Oct. 1968-Sept. 1974 Nov. 1966-Sept. 1974 

Nov. 1966-Aug. 1974 

Mar. 1967-Aug. 1974 

Oct. 1966-Sept. 1968 Oct. 1968-Aug. 1974 

Aug. 1967-Aug. 1974 

Mar. 1963-Aug. 1974 

Feb. 1963-Apr. 1970; June 1973-Sept. 1974 

Sept. 196o-Sept. 1962 Oct. 19&2-Sept. 1974 

Daily ------------------ Storm only ------------ Storm only 

Storm only 

Storm only 

Daily ------------------ Storm only ------------ Storm only 

Storm only 

Storm only 

Storm only ------------ Daily ------------------

Pumping and single stage. 

Pumping and single stage. 

Single stage. 

Single stage. 

Single stage. 

Single stage. 

Single stage. 

Single stage. 

Pumping. 

Pumping and single stage. 

RECORDING PRECIPITATION STATIONS 

Station No. 

01647679 

01647689 

01647719 

01650029 

01650079 

01650119 

01650319 

01600419 

01650469 

Period of record 

Nov. 1966-Sept. 1974 Mar. 1967-Sept. 1974 Dec. 1966-Sept. 1974 Nov. 1966-Sept. 1974 Mar. 1967-Sept. 1974 

May 1963-Sept. 1974 Mar. 1967-Sept. 1974 Nov. 1966-Sept. 1974 Mar. 1967-Sept. 1974 

Recording frequency 

5-min. punch interval prior to Oct. 1968, 15-min. thereafter. 

5-min. punch interval prior to Oct. 1968, 15-min. thereafter. 

15-min. punch interval. 

5-min. punch interval prior to Oct. 1968, 15-min. thereafter. 

5-min. punch interval prior to Oct. 1968, 15-min. thereafter. 

Continuous chart. 

15-min. punch interval. 

5-min. punch interval. 

5-min. punch interval, Mar. 1967-Sept. 1968; Aug. 1972-Sept. 1974; 

15-min. punch interval, Oct. 1968-July 1972. 

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FACTORS AFFECTING STREAMFLOW AND SEDIMENT TRANSPORT 5 

land use/land cover. A summary of each of these 

factors as it relates to the study area and the relative influence of each on streamflow and sediment 

transport are discussed in the following sections. 

PHYSIOGRAPHY 

The nine study basins lie in the eastern division 

of the Piedmont physiographic province. A rolling 

topography, with low knobs and ridges rising above 

the general level, is typical of the area. Altitudes in 

the Anacostia River basin range from 270ft (82 m) 

at the Colesville gaging station to 57 0 ft ( 17 4 m) 

near Olney. Altitudes in the North Branch Rock 

Creek basin range from about 280 ft to 570 ft (85 

to 17 4 m) . The stream valleys are deep and narrow. Slopes on ·the va.Iley floors are generally 0-3 

percent. Areas adjacent to the stream valleys have 

slopes that are typically greater than 8 percent, and 

commonly the range is between 15 and 25 percent. 

Farther from the stream valleys, the slopes tend to 

flatten and generally range between 0 and 8 p·ercent 

along the drainage divides (pl. 1). 

Slopes of construction sites for residential and 

commercial development may significantly affect 

sediment transport and runoff. Steep sites generally 

will require more earthmoving, resulting in more 

cut and fill areas and an increase in the erosion 

potential. Also, runoff from steep sites can cause 

extensive rill and gully erosion. After stabilization, 

water will run off rapidly from steep sites creating 

the potential for flooding immediately downstream 

or adding to flooding problems farther downstream. 

The same volume of water will probably run off 

impervious areas with mild slopes as from those 

with steep slopes, but not as rapidly, resulting in 

lower peak discharges. 

GEOLOGY AND SOILS 

Upland soils of the eastern division of the Piedmont plateau are common to the study area. These 

soils are developed in material weathered from 

igneous and metamorphic rocks. A large percentage 

of the bedrock is a soft micaceous schist, the principal parent material for the predominant ManorChester-Glenelg soil association. Most of the upland 

soils are silt loams in the Manor, Glenelg, Chester, 

Glenville, and Elioak series. There are a few channery silt loams and silty clay loams mixed with the 

silt loams. The surface soils of the silt loams and 

silty clay loams are compos.ed of about 30 percent 

sand or larger particles and 70 percent silt and clay. 

Channery silt loams are composed of about 40 

percent sand or larger particles and 60 percent silt 

and clay. Most of the .soils in the stream valleys are 

Worsham and W ehadkee silt loams. The surface 

horizons of these soils are generally composed of 

the fine materials weathered from upland soils. 

(U.S. Department of Agriculture, 1961). 

The soils generally are uniform with one major 

exception ; the subsoils of the Manor and Glenville 

series are poorly developed, whereas the subsoils of 

the other series are well developed with moderate 

to strong blocky structures. The weak structure of 

the Manor and Glenville subsoils make them highly 

erodible. They are particularly susceptible during 

construction when surface soils are removed during 

rough grading for rights-of-way, parking lots, and 

foundations. The erodibility factor ( k), which is 

used in the universal soil loss equation for predicting erosion (Wischmeir and Smith, 1965), ranges 

from 0.28 to 0.43 for the Glenelg and Elioak subsoils and from 0.43 to 0.64 for the Manor and Glenville subsoils (U.S. Department of Agriculture, 

1970). The higher erodibility factors repres·ent a 

greater susce,ptibility to erosion. 

CLIMATE 

The study area has a temperate and rather humid 

climate. The mean annual temperature is about 

13° C. The length of the growing season is approximately 175 days; the last killing frost usually occurs 

in late April, and the first killing frost usually occurs in mid-October. Calculations based on the Environmental Data Service record of precipitation, 

1926-74, at College Park, Md., show the annual precipitation averaged 42.27 in (1,074 mm). The average monthly precipitation ranged from 2.79 in (71 

mm) in February, to 4.89 in (124 mm) in August. 

Summer precipitation is generally characterized by 

brief, high-intensity rains of convective storms. 

Winter precipitation, which is mostly rainfall, usually results from frontal storms and is. characterized 

by low-intensity, long-duration rainfall. 

The climate and the distribution of precipitation 

during the year significantly affect the streamflow 

and sediment-discharge characteristics in the study 

area. Because of higher evaporation and transpiration losses by vegetation during the growing season, the amount of rainfall that enters the streams 

as surface runoff and baseflow is less than in the 

dormant season. However, the high-intensity summer storms generally produce higher peak discharges than winter storms, particularly on the 

smaller streams. The erosion potential also is greater in the summer than in the winter. Intense rains 
6 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

have a high amount of energy to cause sheet erosion. 

Also, the rapid concentration of runoff caused by 

intense rains has high peak energy to erode the soil 

and transport it in the stream channels. 

Figure 2 illustrates the monthly variation of precipitation in and near the study area between October 1962 and September 197 4. The consistency between the four precipitation stations indicates a 

uniform distribution of precipitation throughout 

the study area. The illustration also indicates that 

the mean monthly precipitation between 1963 and 

197 4 is comparable with the mean monthly precipitation between 1926 and 197 4 at College Park, Md. 

Mean annual precipitation for the 12-year period 

(1963-74) ranged from 38.50 in (978 mm) at the 

Rockville 3NE station to 42.59 in (1,082 mm) at 

College Park. 

LAND USE/LAND COVER 

While each of the factors discussed above influences the runoff and erosional processes, land use/ 

land cover probably has the most dramatic effect. Increased storm runoff and sediment discharge resulting from forest clearing, cultivation, overgrazing, mining, and urbanization have been reported by 

many investigators. Annual sediment yields in 

Maryland range from about 20 tons/mF (7 t/km2 ) 

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J::-

r·::: 1- ·> 

f ::: 

/ 

1- <·I 

/ H 

-

OCT 

~~r--

-

I/ 

/ 

NOV 

[] 

r:-::1 

l:_-J 

D 

I 

~ 

~ 

EXPLANATION 

Wheaton Regional Park 

College Park 

Brighton Dam 

Rockville 3 NE 

College Park (1926-74 mean) 

-;-'"; 

::r---

.. p;~C" ~ 

-:::r---

~:t -

~:::1 

~~~I ~ . / 

/ 

/ 

DEC JAN FEB MAR 

for forest land and 300 to 500 tons/mi2 ( 105 to 175 

t/km:!) for agricultural areas (Wark and Keller, 

1963), to greater than 100,000 tons/mP (35,000 

t/km2 ) for urban construction sites (Guy, 1965; 

Wolman, 1964). Degradation of the stream environJnent related to increased sedimentation from urban 

developments is magnified because the streams affected are in or near population centers, where the 

use of water resources for water supply, waste 

assimilation, flood conveyance, and recreation is 

most intense. 

Land use/land cover in the study area has 

changed considerably between 1963 and 197 4. Suburban land, which includes all land in the rural and 

urban residential and the public-commercial categories in table 2, increased from 6 percent to 23 

percent of the total drainage area of the Northwest 

Branch Anacostia River basin near Colesville between 1963 and 1974. In 1974, suburban land ranged 

from 13 percent in the Northwest Branch Anacostia River basin at Norwood to 73 percent in the 

Lutes Run basin. Urban land, which includes land 

in only the public-commercial and the urban residential categories of table 2, is probably more in-

.dicative of changes that have occurred in the study 

basins. Urban residential represents residential 

housing with lots one-half acre (0.2 hm2 ) or less, 

r.;o,--

- - -

- ~F - ,.-

~ / / 

/ 

~ 

'/ 

/ 

t~ t~ 

/ 

t; 

APR MAY 

~0r--

~75 -

~ 

/ 

r-7: 

<· r--

/ 

/ 

: ... 

/ 

JUNE JULY 

-m-- "':::-

~ ::: ~ ::: 

AUG SEPT 

(/) 

a: 

w 

1-

w 

:::!: 

:J 

...J 

~ 

-- 150 ~ 

z' 

0 

-- i= 

<t: 

1-

ii: 

u -- 100 w 

a: 

0.. 

>- ...J -- I 

1-

z 

0 

--50 :::!: 

z 

<t: 

w 

-- ~ 

0 

FIGURE 2.-Mean monthly rainfall at locations in and near the study area, October 1962-September 1974. 
FACTORS AFFECTING STREAMFLOW AND SEDIMENT TRANSPORT 7 

TABLE 2.-Land use/land cover, in acres, in the Rock Creek and Anacostia River basins, 1963-74 

Farmland and parks Rural Urban Public and 

residential residential commercial Con- Date strucCrops Grass Forest Water lmper- Grass Forest lmper- Grass Imper- Grass lmper- tion 

vious vious vious vious 

Williamsburg Run near Olney ( 1,440 acres) 

1966 __ 615 426 214 2 32 65 13 16 0 1 8 4 44 1967 __ 603 371 211 2 27 74 12 18 0 1 8 4 109 1968 __ 597 355 202 2 27 67 14 17 58 19 8 6 68 1969 __ 597 330 202 2 27 67 14 17 76 30 21 14 43 1970 __ 562 334 212 3 26 62 11 16 89 36 26 16 47 

197L_ 409 414 211 4 22 65 8 18 121 52 26 16 74 1972 __ 409 362 206 4 21 6fi 8 18 139 60 26 16 106 1973 __ 408 331 198 4 21 66 8 19 183 80 27 22 73 1974 __ 400 333 192 4 18 68 9 19 230 105 27 21 14 

North Branch Rock Creek near Norbeck (6,228 acres) 

1966 __ 1809 2137 1574 10 106 264 116 51 7 4 9 6 135 1967 __ 1795 2074 1569 10 101 273 116 53 15 5 9 12 196 1968 __ 1789 2063 1560 10 101 281 118 56 72 23 14 15 126 1969 __ 1789 2037 1556 10 102 281 118 56 98 37 27 23 94 1970 __ 1698 2065 1582 11 101 256 113 50 128 49 33 26 116 

197L_ 1543 2105 1588 12 97 264 114 52 184 73 33 26 137 1972 __ 1543 2035 1572 12 98 264 114 52 227 95 33 26 157 1973 __ 1542 1998 1552 12 98 265 114 53 281 120 34 32 127 1974 __ 1534 1992 1545 12 95 275 115 55 352 159 34 31 29 

Manor Run near Norbeck (646 acres) 

1966 __ 12 267 206 0 14 58 30 15 0 2 0 5 37 1967 __ 12 231 203 0 13 58 30 15 6 3 0 5 70 1968 __ 12 205 200 0 13 58 30 15 19 5 6 7 76 1969 __ 22 152 182 0 9 50 55 23 39 22 18 12 62 1970 __ 22 134 171 0 9 57 53 25 67 29 19 12 48 

197L_ 22 122 171 0 9 58 53 25 89 31 19 12 35 1972 __ 22 115 171 0 9 58 53 25 102 35 19 12 25 1973 __ 22 119 171 0 9 58 53 25 113 40 19 12 5 1974 __ 22 115 171 0 9 58 53 25 115 41 19 12 6 

Northwest Branch Anacostia near Norwood ( 1569 acres) 

1966 __ 321 483 575 3 23 48 49 16 0 0 33 15 3 1967 __ 367 42.2 575 3 23 48 49 16 0 1 33 15 17 1968 __ 367 407 575 3 23 59 50 18 0 1 43 20 3 1969 __ 367 403 574 4 23 60 50 18 0 1 43 21 5 1970 __ 367 397 574 4 23 61 50 18 0 1 44 23 7 

197L_ 367 397 574 4 23 61 50 18 0 1 48 23 3 1972 __ 367 397 574 4 23 61 50 18 0 1 49 23 2 1973 __ 367 391 570 4 23 61 50 18 0 1 47 23 14 1974 __ 367 389 539 4 23 61 50 18 0 2 51 26 39 

Nursery Run at Cloverly ( 224 acres) 

1966 __ 19 110 55 0 4 21 1 8 0 0 2 3 1 1967 __ 19 110 55 0 4 21 1 8 0 0 3 3 0 1968 __ 19 110 55 0 4 21 1 8 0 0 3 3 0 1969 __ 19 109 55 0 4 21 1 8 0 0 3 4 0 1970 __ 19 109 55 0 4 21 1 8 0 0 3 4 0 

197L_ 19 109 55 0 4 21 1 8 0 0 3 4 0 1972 __ 19 109 55 0 4 21 1 8 0 0 3 4 0 1973 __ 19 108 55 0 4 21 1 8 0 0 3 4 1 1974 __ 19 108 55 0 4 21 1 8 0 0 4 4 0 

Batchellors Run at Oakdale (301 acres) 

1966 __ 57 153 41 0 5 36 3 6 0 0 0 0 0 1967 __ 52 153 41 0 5 36 3 6 0 0 0 0 5 1968 __ 55 153 41 0 5 36 3 6 0 0 0 0 2 1969 __ 55 153 41 0 5 36 3 6 0 0 0 0 2 1970 __ 55 153 41 0 5 36 3 6 0 0 0 0 2 

1971__ 56 152 41 0 6 36 3 6 0 0 0 0 1 1972 __ 56 152 41 0 6 36 3 6 0 0 0 0 1 1973 __ 56 152 41 0 6 36 3 6 0 0 0 0 1 1974 __ 56 140 39 3 6 36 3 6 0 0 0 0 12 

Bel Pre Creek at Lay hill ( 1,082 acres) 

1963 __ 55 334 595 0 37 22 14 6 11 6 1 1 0 1964 __ --- --- 0 
8 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

TABLE 2.-Land use/land cover, in acres, in the Rock Creek and Anacostia River basins, 1963-74-Continued 

Farmland and parks Rural Urban Public and 

residential residential commercial Con- Date strucCrops Grass Forest Water lmper- Grass Forest Imper- Grass Imper- Grass ~!:~- tion 

vious vious vious 

Bel Pre Creek at Lay hill ( 1,082 acres) -Continued 

1965 __ 195 

1966 __ 10 360 371 4 14 70 46 20 13 19 1 3 151 

1967__ 9 349 348 4 14 70 46 20 25 43 0 4 150 

1968 __ 9 377 345 6 15 71 46 20 34 49 0 4 106 

1969 __ 9 351 341 6 15 71 46 20 41 58 0 4 120 1970 __ 9 349 341 6 15 71 46 20 44 62 0 14 105 

1971__ 0 342 340 6 15 71 46 20 64 68 0 14 96 

1972 __ 0 313 306 6 15 71 46 20 63 80 0 14 148 

1973 __ 0 267 275 6 18 77 48 21 87 104 0 14 165 

1974 __ 0 278 257 9 18 77 37 14 101 158 0 14 119 

Lutes Run at Lutes (301 acres) 

1963 __ 0 88 95 0 0 12 16 3 16 10 0 0 61 1964 __ 38 1965 __ 20 1966 __ 1 29 62 0 0 15 21 4 79 48 1 1 40 1967 __ 0 25 48 0 0 18 19 3 90 64 3 3 28 1968 __ 0 24 53 0 0 18 19 3 93 69 4 5 13 1969 __ 0 20 53 0 0 18 19 3 93 69 4 9 13 1970 __ 0 20 52 0 0 18 19 3 91 72 4 9 13 

1971__ 0 21 56 0 0 18 19 3 91 72 5 11 5 1972 __ 0 21 56 0 0 18 19 3 91 72 5 11 5 1973 __ 0 21 56 0 0 18 19 3 91 72 5 11 5 1974 __ 0 22 57 0 1 18 19 3 91 72 5 11 2 

Northwest Branch Anacostia River near Colesville ( 13,504 acres) 

1963 __ 3194 4987 3709 15 281 377 183 107 130 87 31 12 391 1964 __ 297 1965 __ 365 1966 __ 1968 4900 4056 19 248 870 389 251 147 102 74 28 452 1967 __ 1970 4774 3957 19 245 921 399 270 176 149 73 33 518 1968 __ 1932 4744 3932 21 246 953 412 278 253 189 84 40 420 

1969 __ 1841 4635 3921 23 245 958 403 288 311 235 99 52 493 1970 __ 1760 4655 3943 24 246 960 402 279 363 269 93 70 440 

1971__ 1784 4516 3916 25 247 955 419 285 477 348 116 70 346 1972 __ 1792 4450 3841 25 248 955 419 285 511 372 122 74 410 1973 __ 1806 4349 3779 25 249 959 421 285 615 438 121 80 377 1974 __ 1827 4301 3725 31 258 961 410 278 697 526 127 84 279 

and it is generally characteristic of the construe- was also concentrated near Norbeck and Olney. The 

tion in the study area, particularly between 1966 runoff and sediment transport characteristics of 

and 197 4. Urban land increased from 3 to 11 percent Williamsburg Run, Manor Run, Lutes Run, and Bel 

of the Northwest Branch Anacostia River basin Pre Creek reflect these land-use/land-cover changes. 

near Colesville between 1966 and 1974. Increases in 

urban land in the other study basins ranged from STREAMFLOW 

0 percent of the Batchellors Run basin to 28 percent of the Manor Run basin. ANNUAL AND MONTHLY RUNOFF 

The distribution of land use/land cover within Annual runoff in the Northwest Branch Anathe study basins is illustrated in plates 2 and 3. In costia River basin averaged 14.03 in (356 mm) be1966, construction for residential housing was con- tween 1963 and 1974. Runoff was fairly consistent 

centrated near the business centers at Glenmont from year to· year except for the exceptionally wet 

and Colesville. As the suburban area continued to years in 1971 and 1972. It rang·ed from 8.51 in (216 

expand, construction radiated from these points and mm) in 1969 to 29.50 in (7 49 mm) in 1972. Mean 

became scattered throughout the basins except for monthly runoff ranged from 0.56 in (14 mm) or 

the northern half of the Anacostia River basin, 17 percent of mean monthly precipitation in Septemwhich remained essetially rural. The heaviest con- ber, to 1.72 in (44 mm) or 52 percent of mean 

centration of housing, other than in the two sites monthly precipitation in March (fig. 3). Higher 

above, was at Norbeck, Olney, and Layhill. Con- runoff rates in the late fall and winter and lower 

struction in the North Branch Rock Creek basin rates in the summer and early fall are generally 
STREAMFLOW 9 

EXPLANATION en 

en D a: Precipitation w w 1- ::I: w u u ~ ~ Runoff :::i / ::::! ~ [EJ ~ 

u: Percent precipitation u.. as runoff ~ 0 

z 5 u..' 

::J 125 u.. 

a: 0 

z 0 4 ::J z 100 a: <( 0 

z z 0 3 75 <( 

i= z <( 0 1-

a: 2 i= 

u <( 

1- w a: a: 

c.. 1 u 

w 

a: 

c.. 

0 0 

0 N D J F M A M J J A s 

FIGURE 3.-Variation in mean monthly precipitation and 

runoff, Northwest Branch Anacostia River near Colesville, Md., October 1962-September 1974. 

representative of the runoff regime of all the study 

basins and all streams in the Middle Atlantic States. 

Runoff is directly related to the amount of rainfall, soil moisture, and ground-water levels. Snowmelt has no appreciable effect on the runoff regime 

in this area. The decline of streamflow in late spring 

and summer reflects the increase in evaporation and 

transpiration by plants. During the growing season, 

vegetation is constantly depleting soil moisture, 

which in turn reduces the amount of soil water 

available to percolate down to the water table. As 

ground-water levels decline, base flows in the 

streams decline. Direct runoff from thunderstorms 

in the summer is not an appreciable percentage of 

the total yearly runoff because most of the rain is 

absorbed by dry surface soils and only a small percentage of the precipitation becomes streamflow. 

Base flow and total streamflow begin to increase in 

the fall when the vegetation is dormant and evaporation is low. Base flow generally reaches maximum 

levels between January and March depending on the 

amount of fall and winter precipitation. 

DURATION AND LOW FLOW 

Another method of showing the distribution of 

runoff is the flow-duration curve. It is a cumulative 

frequency curve that shows the percentage of time 

that specific dis.charges were exceeded during a 

given period and shows the integrated effect of 

climatic, topographic, and geologic factors influencing the runoff characteristics of a stream (Searcy, 

1959). 

The three curves in figure 4 graphically illustrate 

flow duration of the Northwest Branch Anacostia 

River near Colesville for three periods: (A) 1923-

39, 1961-74; (B) 1963-74; and (C) 1967-74. Curve 

A is for the period of record, except the years 1940 

to 1960 when the flow in the Northwest Branch Anacostia River was augmented by pumpage for water 

supply from the Patuxent River basin. Curve B 

covers the period of daily sediment records in the 

Anacostia River basin, and curve C covers the period 

of intensive sampling at all sites in the study area. 

The curves are similar for the range of discharge during the three periods. The 50-percent 

duration discharge, or the discharge that was exceeded 50 percent of the time, ranged from 11 fV/s 

(0.31 m3 /s) for 1963-74, to 13 ft3 /s (0.37 m3 /s) 

during 1967-74. The discharge that was exceeded 

80 percent of the time for the three periods ranged 

from 6 to 7 ft 3 /s (0.17 to 0.20 m3 /s). Similarly, the 

curves are virtually equal at the 1-percent duration. 

The only significant differences between the discharges for the three periods occur below 0.5 percent and above 80 percent. The departure below 0.5 

percent reflects the magnitude of runoff during 

~ <( 

0 

EXPLANATION 

A 1923--39, 61-74 

8 1963--74 100 

c 1967-74 

1000 

10 

100 

10 

0.1 

"· 

0.01 

0.1 L___L___L_j _ _L__L_.L__L____._ _ _.L_____j__~~ 

0.01 0.1 0.5 1 5 10 20 50 80 95 99 99.8 99.99 

PERCENTAGE OF TIME AN INDICATED DISCHARGE WAS EXCEEDED 

0 

z 

0 

~ (/) 

a: 

LLJ 

a... 

(/) 

E5 

f-

~ 

(_) 

iii 

::::J 

(_) 

~ 

ui 

(!J 

a: 

<( 

I 

(_) 

(/) 

0 

z 

~ 

::;::;; 

FIGURE 4.-Flow-duration curves for the Northwest 

Branch Anacostia River. 
10 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

Hurricane Agnes (June 21-22, 1972) and differences in the length of record used for each curve. 

The departure of the curves above 80 percent illustrates the effect of severe droughts in the early 

1930's and mid-1960's, which are reflected in curves 

A and B, but not curve C. The similarity of the 

curves in the medium and high discharge range, the 

discharges at which most of the sediment is transported, suggests there has been no change in the 

flow regime that would affect the sediment-transport characteristics of the stream. 

Flow duration curves for the five small study basins with continuous streamflow records are shown in 

figure 5. Discharge was plotted as a unit value of 

(ft3/s) /mP [ (m3 /s) /km2 ] to facilitate a comparison 

of the runoff characteristics of these basins. The 

wide variation of the curves illustrates the complex 

distribution of runoff from different drainage 

basins, even those in proximity. For example, the 

discharge that was exceeded 50 percent of the time 

variedfrom0.3 (ft3/s)/mi 2 [(0.003m3 /s)/km2 ] for 

Bel Pre Creek, to 1 (ft3/s) /mP [ (0.011 m3 /s) /km2 ] 

for Nursery Run. The variation at medium and high 

discharges probably reflects individual differences 

l.U 

a:: 

<( 

:::> 

Cl 

(/) 

ffi 

a.. 

D 

z 

0 

f:rl 

(/) 

ffi 

a.. 

m 

u 

CD 

:::> 

u 

~ 

100 

80 

60 

40 

20 

10 

8 

6 

4 

1 

0.8 

0.6 

u.i 0.4 (.!J 

a:: 

<( 

:I: 

V5 0.2 

0 

z 

<( 0.1 

~ 0.08 

~ 0.06 

<( 

D Q.Q4 

0.02 

EXPLANATION 

-------Manor Run (urban) 

--- NW. Branch Anacostia River (rural) 

~ . - ·· ·- Nursery Run (rural) 

\ ·~ - · ·-· · Bel Pre Creek (urban) 

\'~.. ---- Williamsburg Run (urban) 

\\ ~. ·. ,. \ ~~- · ..,,\ 

·~\,·. 

· .. '\~. .,~, 

·-:~ 

001 L___.J...____(_...L.____J_..-.....J... _ __J_____.L___j____L _ _j 

0.5 

0.1 

0 05 

001 

0.005 

0.001 

0.0005 

0.01 0.1 1 5 20 50 80 95 99 99.8 99.99 

PERCENTAGE OF TIME AN INDICATED DISCHARGE WAS EXCEEDED 

ffi 

tu 

~ 

g 

Q 

LLJ 

a:: 

<( 

:::> 

Cl 

(/) 

~ 

D 

z 

0 

f:rl 

(/) 

ffi 

a.. 

(/) 

ffi 

f-

~ 

u 

CD 

:::> 

u 

~ 

LLJ-

(.!J 

a:: 

<( 

I 

u 

(/) 

o 

z 

~ 

~ 

~ <( 

D 

FIGURE 5.-Flow-duration curves for five small streams 

draining areas of different land use/land cover, 1967-74. 

in basin response to precipitation that result from 

different soil, slope, and land-cover conditions. At 

low discharges, the divergence exhibited by the 

curves probably reflects the variability of the bedrock material and differences between the surfacewater and ground-water basin divides in the individual drainage basins. 

There is no consistent trend between land use and 

runoff characteristics evident from the curves except that the high discharges for the partly urban 

basins (Manor Run, Bel Pre Creek, and Williamsburg Run) tend to be slightly greater than for the 

rural basins (Nursery Run, North Branch Rock 

Creek, and Northwest Branch Anacostia River at 

Norwood). This difference would be expected since 

surface runoff from storms in urban areas will be 

higher because of the increase in impervious surfaces. Conversely, the median and low flow of 

streams draining urban areas would be expected to 

be lower because of reduced infiltration of precipitation to recharge soil moisture and ground-water 

levels. This assumption is not supported by the 

base-flow or low-flow part of the curves in figure 5. 

The curves scatter at the low discharge rates with 

no apparent relation to land use. Apparently, the 

type of bedrock and the distribution of ground water 

in the basins exhibit a stronger influence than land 

use on the low flow of the streams. 

STORM RUNOFF AND FLOOD-PEAK DISCHARGES 

Urbanization probably has the greatest impact on 

storm runoff and flood peaks. An increase in the 

amount of impervious area results in a greater percentage of the precipitation becoming surface runoff. Peak discharges are often increased because 

improvements in the drainage systems cause the 

surface runoff to concentrate faster. Differences 

between the storm runoff regimes of the rural and 

urban basins were evident in the study area. 

The relations between storm runoff and precipitation for individual basins are shown in figure 6. 

Suspended-sediment samples from storms that occurred between 1971 and 1974 were used for determining the relations. This period was chosen in 

order to have sufficient storms representative of 

urban conditions. Storm runoff was determined as 

the total measured runoff minus the estimated base 

flow, which was defined as the discharge represented 

by the area below a straight line· drawn from the 

point of initial rise to the point where the stage 

hydrograph approached a straight line. There are 

several more refined methods for hydrograph separation, but this simple procedure is probably suf-
STREAMFLOW 11 

1.0 

0.8 

tf3 0.6 I 

u 

~ 

~ 0.4 

:±:" 

0 

z 

::::J 

a:: 

~ 

a:: 

§; 0.2 

0.1 

0.08 

STORM PRECIPITATION, IN MILLIMETERS 

8 10 20 40 60 80 100 

---Williamsburg Run !urban) 

----Manor Run (urban) 

-·-·-·-·- NW. Branch Anacostia R. (rural) •• / /' 

--------Nursery Run (rural) /~ "/ 

----Batchellors Run (rural) _.f}../1 / 

·······----··--·Bel Pre Creek (urban) #/ I / 

----Lutes Run (urban)./}./ 1

1 / v. .. ,· / /;./II // 

~/ I / 

/// I // _/_/~/ I / 

'l/ I / //.···. I / 

_/..·· I / 

/. I / 

/ I / 

/ 

/ 

/ 

I / 

I // 

/ 

/ 

/ 

/ 

0.4 0.6 0.8 1.0 

STORM PRECIPITATION. IN INCHES 

20 (/J 

ffi 

I-

~ 

::l 

~ 

10 ~ 

8 ti 

0 

z 

6 E2 

~ 0 

1- 4 (/J 

FIGURE 6.-Relation between storm runoff and precipitation for selected subbasins, 1971-74. 

ficient for comparing differences in storm runoff 

between the basins. 

The curves indicate that storm runoff was greater 

in the urban basins than in the rural basins. Runoff was highest in the Manor Run, Bel Pre Creek, 

and Lutes Run basins, which have the highest percentage of urban land. Runoff from the other urban 

basin, Williamsburg Run, wa.s less than the runoff 

from the Northwest Branch Anacostia River, but 

considerably greater than the runoff from Nursery 

Run and Batchellors Run. The relatively high runoff from the Anacostia River basin may reflect the 

greater amount of cropland in the basin as compared 

with the other two rural basins. The general trend 

of greater storm runoff from urban basins is substantiated by an earlier study that compared storm 

runoff from the Bel Pre Creek basin before and 

after urban development (Yorke and Davis, 1972). 

In that study, it was found that storm runoff increased 30 percent as a result of urban construction 

in 15 percent of the basin. 

Figure 6 also shows a tendency for the runoff of 

rural and urban basins to converge as storm size 

increases, reflecting a change in surface conditions 

during large storms. Much of the rain falling on 

pervious surfaces during small storms infiltrates 

into the soil or fills small depressions in the land 

surface; but as the storm size increases, the soils 

become saturated, and more and more of the rainfall becomes surface runoff. Virtually all the rain 

falling on impervious surfaces becomes runoff 

during both small and large storms; however, the 

relative contribution from impervious surfaces is 

greatest during the small storms when there is little 

runoff from pervious surfaces within the basins. 

The impact of runoff from impervious surfaces 

is illustrated by the flood-frequency curves for five 

of the study basins (fig. 7) . These curves are based 

on eight annual peak discharges, 1967-74, and 

should not be considered representative of constant 

land use or long-term climatic conditions; however, 

they do illustrate the effect of urban development in 

the basins. Normally, it would be expected that 

these curves would be parallel to each other, with 

the curves for the smaller streams plotting higher 

than those for the larger strearns. The curves appear 

to be approaching a parallel condition for the higher 

recurrence interval peaks, but they diverge markedly for the more frequent floods. Each of the 

curves for the urban basins, Manor Run, Williamsburg Run, and Bel Pre Creek, has a flatter slope, 

indicating larger flood peaks than the rural basins 

for the more frequently occurring floods. 

Although there are insufficient data, with respect 

to time and spatial variation, to permit a detailed 

quantitative analysis, trends detected are comparable with those determined during other studies of 

urbanization in the Piedmont. Anderson ( 1970) 

found significant increases in peak water discharges 

as a result of urbanization. He indicated that an 

increase in imperviousness alone could result in a 

doubling of the mean annual flood. If a small, steep 

basin were 100 percent impervious and completely 

sewered or channelized, the mean annual flood could 

be increased by a factor of 8 over that expected 

from a similar basin in its natural state. He further explained that the effect of these factors decreased as the recurrence interval of the peaks increased. For example, in the same basin the 50-year 

flood would be increased by a factor of 3.5 and the 

100-year flood would be increased by a factor of 3. 

Putnam (1972) obtained similar results in the Piedmont streams in North Carolina. He found that 

flood-peak discharges increased by a factor up to 5, 

depending on the drainage-basin characteristics and 

the recurrence interval of the flood. 
12 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

EXPLANATION 

50 ffi 

~ 

UJ 

~ 

0 

.....J 

UJ ~ 

a: 

<l: 

::J 

0 

en 

D ----

e 

Williamsburg Run (urban) 

Manor Run (urban) 

UJ 

a: 

< 

::J A ------------

6------------------------

NW. Branch Anacostia R. (rural) 0 

en a: 

UJ 

a.. 0----

Nursery Run (rural) 

Bel Pre Creek (urban) a: 

UJ 

a.. Cl 

z 1000 

0 

u 

UJ 

en 

a: 

UJ 

a.. 

~ 

UJ 

UJ 

LL. 

~ 

aJ 

::J 

u 

z 

w' 

(!:) 

a: 

<l: 

I 

u 

en 

0 

Cl 

0 

0 

.....J 

LL. 

.....J 

500 

100 

~ 50 

z 

z 

<l: 

1.01 

D 

1.1 1.5 2 3 4 5 6 7 8 9 10 20 

Cl 

10 z 

0 

u 

UJ 

en 

5 

a: 

w 

a.. 

en 

a: 

UJ 

~ 

UJ 

~ 

~ 

aJ 

::J 

u 

z 

uJ 

(!:) 

a: 

< :r. 

u 

en 

0 

Cl 

0 

0 

.....J 

0.5 LL. 

.....J 

< 

::J 

z 

z 

<l: 

RECURRENCE INTERVAL, IN YEARS 

FIGURE 7.-Annual flood-frequency curves for selected subbasins, 1967-74. 

SEDIMENT DISCHARGE 

The total sediment discharge of a stream can be 

divided into two principal components: (1) the discharge transported through the stream system suspended in the runoff waters, called the wash or 

suspended load, and (2) the discharge transported 

by rolling, sliding, or skipping along the bottom of 

the stream, called the bedload. The suspended load 

consists of fine sediment particles and the discharge 

is dependent on the amount of material available 

for transport from sediment-source areas. The bedload generally consists of coarse sediment particles 

in the streambed that are moved at transport rates 

dependent on the competence of the stream. 

ANNUAL AND MONTHLY SUSPENDED-SEDIMENT 

DISCHARGE 

Suspended sediment transported from the Anacostia River basin averaged 14,800 tons (13,400 t) 

per year between 1963 and 197 4. The annual discharge ranged from 5,500 tons (5,000 t) in 1974, to 

31,000 tons (28,100 t) in 1972 (table 3). The exceptionally high sediment discharge in 1972 resulted 

from the high runoff and flooding during Hurricane 

Agnes in June. The suspended-sediment discharge 

transported during June 21-22 was 12,800 tons 

(11,600 t), which was greater than several previous 

annual discharges. Generally, wet years had high 

annual discharges and dry years had low annual 
TABLE 3.-Monthly and annual water and suspended-sediment discharge, Northwest Branch Anacostia River near Colesville, Md., 1963-74 

Water 

year Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Annual 

Water discharge, in cubic feet per second-days 

1963 ------------ 149.8 521.7 304.5 565.8 553.9 1,276.8 361.3 267.2 771.5 121.7 317.4 176.2 5,387.8 

1964 ------------ 117.0 807.3 448 1,531 871 998 976 485.3 263.1 151.9 116.6 79.4 6,844.6 

1965 ------------ 134.8 193.9 513.4 609.6 619.7 1,297 527 328.4 204.7 148.3 349.0 143.0 5,068.8 

1966 ------------ 526.9 160.4 158.4 226.2 1,153.7 505.4 650.9 530.3 548.3 401.8 1,724.9 627.1 10,757.3 

1967 ------------ 576.0 305.0 451.6 595 514.5 1,266 467 669 302.1 309.4 1,122 161.1 6,738.7 

1968 ------------ 227.1 267.5 1,114.7 947 370.6 989.6 440 633.1 680.0 298.5 105.1 123.9 6,188.1 

1969 ------------ 177.8 445.2 403.8 362.2 453.9 457.7 337.8 283.4 338.3 280.2 919.8 365.3 4,825.4 

1970 ------------ 215.9 309.9 1,024 665.8 784 673 1,559 759 693.9 882.0 321.5 167.8 8,055.8 

1971 ------------ 225.6 877.3 718.5 717 2,149.8 867 716 1,184 548.3 401.8 1,724.9 627.1 10,757.3 

1972 ------------ 1,132.0 1,149.0 789.0 884 2,027 1,340 1,556 1,382 4,244 1,403 530.6 296.3 16,732.9 

1973 ------------ 421.1 1,434.0 1,768 1,064 1,189 1,049 2,091 1,076 862 799.2 401.1 325.9 12,480.3 

1974 ------------ 314.7 261.1 1,260.8 1,016 509 1,088 867 557.8 475.1 172.2 284.1 425.7 7,231.5 

Mean _____ 351.55 561.02 746.22 765.3 933.01 983.96 879.08 679.62 797.32 419.37 518.61 319.0 7,954.1 

Suspended-sediment discharge, in tons 

1963 ------------ 38.1 655.6 14.2 317.8 1,038.9 2,967.2 6.5 24.3 6,331.6 24.5 4,573.1 818.8 16,811.4 

1964 ------------ 3.0 2,994.9 326.6 5,141.5 835.6 700.7 885.0 68.3 62.2 153.7 309.9 114.9 11,596.3 

1965 ------------ 23.0 511.4 1,702.3 665.9 2,444.7 5,446.9 21.7 47.3 68.9 669.1 4,113.0 175.1 15,889.1 

1966 ------------ 3,042.2 0.6 2.3 45.1 4,354.2 192.6 1,091.2 978.4 51.0 105.2 68.0 4,471.2 14,402.0 

1967 ------------ 2,102.6 173.0 60.2 609.8 207.4 3,148.1 26.0 1,152.5 706.7 1,268.0 5,543.1 11.9 15,009.3 

1968 ------------ 344.33 135.29 2,255.50 812.82 62.62 1,561.52 45.62 1,550.84 2,758.80 600.97 5.44 364.71 10,498.46 

1969 ------------ 123.64 330.37 193.01 200.18 233.95 34.79 8.68 797.29 2,593.77 570.88 3,668.42 703.60 9,458.58 

1970 ------------ 84.80 100.49 1,925.36 88.37 684.68 121.61 3,823.02 2,753.00 3,652.57 3,253.04 560.71 222.58 17,270.23 

1971 ------------ 124.62 1,248.46 512.86 133.38 6,405.08 243.81 146.90 1,963.48 224.27 966.43 3,847.01 737.62 16,553.92 

1972 ------------ 2,209.38 1,179.91 191.90 95.72 4,325.41 1,380.66 1,936.92 1,538.62 14,529.45 2,955.40 635.75 10.15 30,989.27 

1973 ------------ 320.92 1,752.89 904.69 487.74 852.71 482.22 4,109.69 379.65 1,549.86 1,894.77 216.83 188.71 13,140.68 

1974 ------------ 66.80 7.29 1,614.01 406.37 36.79 1,744.16 278.05 458.55 158.49 60.48 445.64 225.42 5,502.05 

Mean _____ 706.95 757.52 808.58 750.39 1,790.17 1,502.02 1,031.61 976.02 2,723.97 1,043.54 1,998.91 670.39 14,760.11 

U2 

t_:tj 

t:! 

~ 

a:: 

t_:tj 

z 

t-3 

t:! 

~ 

U2 

0 

ti:: 

> 

~ 

C) 

t_:tj 

1-L 

C/o:) 
14 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

40,000 .-------------------------------, 

1-

z 

w 

~(/) Oz 

wo 

<?1-

Cl 

wz 

oz w· W(.!) 

a.. a: (/)< 

::>I (/)u 

30,000 

20,000 

~ 

~ Suspended-sediment 

discharge 

.. :::::::::.::.::::::::.::::::.:::.::::::::;:::;:: 

30,000 

20,000 

1-

z 

w 

~(/) 

-w @z 

(J)Z 

'0 

@1-

Clz 

zw - a_W 

(/)(.!) 

::>0: 

(/)<( 

..... ~ <t:Cl 

::J 

z 

z 

<( 

0 

lllllillll:lllllllllilllliliiill:lllllllll!lll!l!!:!l!llllillllillliJI!I!IIII!lll!l!llil!lllill!lilllillillllllllllllllllllllllllllllllllll:::::::m=: 

10,000 

0 

I ...JU 

<((/) 

::JZCl 

z 

<( 

a: 

w 

1-

~ 

offi 

ZI 

<t:U 

z 

zOz 

i= -- <Cw 

!:::(.!) 

a.. a: u<C 

WI 

a:u 

Q..(/) 

..... cs 

<( 

::J 

z 

z 

<( 

60 ,--------------------------~ 

Precipitation 

50 

Water discharge 

40 

30 

20 

10 

~ ~ ' 

Q ~.~·~~·~'~'~··~~c~~c~~~~~~~~~~~~~~~~~~~ 

1963 64 65 66 67 68 69 70 71 72 73 1974 

1200 

800 

400 

0 

a: 

w 

1-<(/) 

~a: 

ow 

z~ 

<~ 

z::i 

o:=! 

i=~ 

<Cz I-_ 

a: - -W 

U(.!) 

Wa: 

0:-=:t: 

a.. I 

...JU 

<{(/) 

::JQ 

z 

z 

< 

FIGURE 8.-Annual variation of precipitation, water discharge, and suspended-sediment discharge, 

Northwest Branch Anacostia River near Colesville, 1963-74. 

discharges (fig. 8) ; however, a decreasing trend in 

suspended-sediment discharge with time was also 

apparent. This decrease in sediment discharge, as 

it relates to land use and sediment control, will be 

discussed in detail in later sections of this report. 

Most suspended sediment was transported during 

large storms, as. indicated by the duration curve of 

suspended-sediment discharge (fig. 9). Daily sediment discharge was greater than 100 tons/d (91 

t/d) 5.7 percent of the time or 252 days for the 12 

years of record shown on figure 9. The sediment discharge for those 252 days represents 94 percent of 

the sediment discharged during the 12-year period. 

Sediment discharges of 500 ~:tnd 1,000 tons/ d ( 454 

and 907 t/d) were exceeded 2.2 and 1.0 percent of 

the time and represented 73 and 54 percent of the 

total. The ·quantity of sediment carried during 

storms, particularly large storms, is a significant 

factor that must be considered in any program d~ 

signed to control erosion and sediment transport. If 

controls. such as diversion berms and sediment 

basins are underdesigned, a large part of the total 

sediment eroded from construction sites will still 

reach the streams. 

The seasonal variation of suspended-sediment discharge is another factor affecting sediment control. 

Sediment discharge is generally higher between. 

February and August than it is between September 

and January. The average monthly load for the 

period 1963-74 ranged from. 670 tons (609 t) in 

September, to 2,700 tons (2,400 t) in June (fig. 10). 

A comparison of the 1963-74 and the· long-term precipitation in figure 2, indicates that lower monthly 

loads would be expected in November, December, 
SEDIMENT DISCHARGE 15 

10,000 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

' \ 100 \ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ Sediment discharge 

1000 \/ 1000 \ 

\ 

\ Q 6 \ 

\ z z \ 

OCJ) \ 0 \ u uz \ 

\ w CJ) wo \ 10 CJ)I- \ CJ) w \ z a:z \ a: \ w z w- \ a.. 0 a.. ' \ 

w \ II-(!) \ CJ) \ a: z wa: \ w w<( \ 

I I- LLI I w 100 w 

uu 100 I :E (!) I _CJ) I a: co- I 

~ <( ::)Q I 

I I CD Ul- I ::) u 

z~ I CJ) u Ci -,~ I 

I z w- I I- (!)0 I w' z a:W I w <(CJ) I (!) I ~ I' I a: 

u@ I <( Ci I I w ~Q I 

I u CJ) 

QZ I CJ) w I 6 Ci 10 a: a.. 10 I w I WCJ) I 

a: Q I-:) I z <(CJ) I 

I w w I- ~>- I a.. I <( CJ) 

z::! I 

~ ::) I <(<( I CJ) \ wO 0.1 z I 

~Q \ <( >- \ w ...J \ 

>-z <{ I ~ ...J<( \ Q \ <( \ >- \ ...J Q \ 

\ <{ \ Q \ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

0.01 \ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

' ' ' ' ' ' ' ' 0.1 0.1 

0.01 0.1 0.5 1 5 20 50 80 99 99.99 

PERCENTAGE OF TIME AN INDICATED DISCHARGE WAS EXCEEDED 

FIGURE 9.-Duration of water discharge and suspended-sediment discharge, Northwest Branch Anacostia River near 

Colesville, 1963-74. 

and June, and higher loads would be expected in 

January, July, and August. With the slight adjustments to figure 10 considered, the distribution of 

sediment discharge compares favorably to the distribution of erosion index values for the Atlantic coast 

area (Guy, 1964). The erosion index is highest in 
16 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

(/) 

z 

0 

f-

~ 3000 - w· 

CJ 

c:: 

<( 

:I: 

u 

(/) 

iS 2000 -

fz 

w 

~ 

i5 

w 

(/) 

6 

w 

0 

z 

w 

a.. 

(/) 

:::> 

(/) 

I 

- 3000 

-

r- 2000 

r- 1000 -

0 18Siill :.!iii iii.! · .. i·:l ~·::ll : ... :j i:=ii: li.:!f TI 

ONDJ FMAMJ JAS O 

(/) 

w 

z 

z 

~ 

~ 

w· 

CJ 

c:: 

<( 

:I: 

u 

(/) 

iS 

fz 

w 

~ 

i5 

w 

(/) 

6 

w 

0 

z 

w 

a.. 

(/) 

:::> 

(/) 

FIGURE 10.-Mean monthly suspended-sediment discharge, 

Northwest Branch Anacostia River near Colesville, 1963-74. 

June, July, and August and decreases to lowest in 

December and January. 

The variation of erosion potential and sediment 

discharge during the year creates an opportunity for 

an effective method of sediment control. Scheduling 

construction activities to coincide with the period 

of low erosion potential should result in a significantly lower sediment discharge. It is not possible 

or practical to restrict all grading and heavy earthmoving to the period between September through 

January, but it may be possible to schedule a major 

part of the grading on critical areas of construction sites during this period of low erosion potential. If major grading work were completed in the 

fall and protective measures were installed by midwinter, there would be protection during the high 

runoff in early spring and during the intense storms 

in the summer. Also, if construction activities were 

completed and critical sites were stabilized before 

the high-erosion periods, less intensive control measures would be required on the remainder of the 

construction area, resulting in an overall reduction 

in costs. 

SIZE DISTRIBUTION OF SUSPENDED SEDIMENT 

The size distribution of suspended sediment transported by a stream is an indicator of the sedimentsource material and the competence of the stream. 

In the Northwest Branch Anacostia River near 

Colesville, suspended sediment transported during 

medium and high flows averaged 20 percent sand, 

45 percent silt, and 35 percent clay (table 4) . This 

approximates the distribution of particles in the 

predominant silt-loam and silty clay-loam soils 

found in the basin. The general relationship between 

water discharge and its capability to transport particles of various sizes in suspension is illustrated by 

the curves in figure 11. At low discharges, the suspended sediment is composed mostly of silt and 

clay. As the discharge increases, the percentage of 

the total suspended-sediment load consisting of silt 

and clay generally decreases, while the percentage 

consisting of sand increases. 

The large scatter of points about the generalized 

relationships in figure 11 probably represents differences in the type and amount of sediment eroded 

from various sediment-source areas and the distance 

between the source areas and the sampling sites. The 

TABLE 4.-Particle-size distribution of suspended sediment, Northwest Branch Anacostia River near Colesville, Md. 1960-73 

Suspended- Suspended- Percent suspended-sediment WateT sediment sediment in size class Date discharge concen- discharge ( ft'l/s) tration (tons/day) Sand Silt Clay (mg/1) 

Sept. 12, 1960 --------------------- 628 895 1,520 27 62 11 

Feb. 26, 1962 ---------------------- 247 1,480 987 38 41 21 

Mar. 12, 1962 --------------------- 788 1,080 2,300 30 51 19 

June 3, 1963 ---------------------- 141 4,700 1,790 17 52 31 

Aug. 13, 1963 --------------------- 73 15,100 2,980 7 53 40 

Oct. 7, 1965 ----------------------- 662 8,590 15,400 20 44 36 

Feb. 13, 1966 --------------------- 662 5,070 9,060 36 38 26 

May 19, 1966 --------------------- 50 9,830 1,330 3 44 53 

June 22, 1967 --------------------- 213 9,460 5,440 6 46 48 

July 22, 1969 ---------------------- 895 3,520 8,510 8 43 49 

Apr. 2, 1970 ---------------------- 71 198 38 6 21 73 

Apr. 14, 1970 --------------------- 338 2,000 1,820 35 34 31 

Oct. 21, 1970 ---------------------- 169 2,070 945 17 55 28 

July 29, 1971 --------------------- 197 3,700 1,970 14 45 41 

Aug. 27, 1971 --------------------- 790 2,610 5,570 27 47 26 

Nov. 29, 1971 --------------------- 213 836 423 24 44 32 

Feb. 3, 1972 ---------------------- 626 2,360 4,000 21 50 29 

Feb. 2, 1973 ---------------------- 376 1,660 1,690 24 45 31 

Dec. 26, 1973 ---------------------- 405 1,140 1,250 36 33 31 

Sediment discharge-weighted 

average ------------------ 20 45 35 
SEDIMENT DISCHARGE 17 

01000 0 

z 

z 0 

0 800 • u u 

w 20 ~ • • • (/) 600 • • c:r:: c:r:: w w a.. a.. 400 • • (/) 

1-

w 10 ffi w • • I- LL. 8 w 

u • • • ~ 

iii • • 6 ~ ::J 200- • CD u • • ::J 

~ u • 4 

w' ~ 

(.9 w' c:r:: 100 (.9 <( a: I 80 <( u • • • 2 I (/) u 25 60 (/) 

c:r:: 0 w c:r:: 1-

<( 40 w 

1- ~ 1 <( 

I I I I I I I ~ 0 30 40 50 60 70 10 20 30 40 50 60 70 

PERCENT SILT PERCENT CLAY 

(0.004-0.062 MILLIMETERS) (<0.004 MILLIMETERS) 

FIGURE 11.-Relation of sand, silt, and clay content of suspended sediment to water discharge, Northwest Branch 

Anacostia River near Colesville, 1960-73. 

first storms after cropland or construction sites have 

been opened will generally erode and transport large 

quantities of fine (silt and clay) particles completely 

through the stream system. During these first few 

storms, the larger sand particles, eroded by the 

impact of rain on the bared soils or by runoff from 

the land surface, are generally deposited at some 

place on the site or in the stream channel near the 

point of erosion. Subsequent storms will continue 

to erode fine soil particles and also lift the heavier 

sand particles and redeposit them at some point 

farther downstream. If the surface soils are not 

reworked to expose new sources of fine sediments, 

the surface soils will gradually become armored 

with the remaining large particles. Thus, fewer fine 

particles will be available for transport, and sand 

particles will represent a greater percentage of the 

suspended load. 

An increase in the sand percentage of suspended 

sediment can also be expected after construction 

areas have been stabilized with vegetation. A dramatic reduction in the total load occurs when a,ctive 

source areas are stabilized; however, large quantities 

of sand previously eroded from construction sites 

and deposited in stream channels are still available 

for transport. This is illustrated by the distribution 

of sand, silt, and clay transported during medium 

and high flows in the small study basins (fig. 12). 

Generally, the urban streams transported a higher 

percentage of sand than the rural basins. The suspended load ranged from 7 percent sand for Batchellors Run to 28 percent sand for Lutes Run. The 

higher levels of sand in the suspended load of urban 

streams can be expected to continue until a new 

equilibrium is established between the runoff regime, 

channel size, and bed material. 

BEDLOAD CONTRIBUTION 

Bedload was not measured directly during this 

study; however, the approximate range of its magnitude was computed for the Northwest Branch Anacostia River near Colesville, using the Schoklitsch and 

Meyer-Peter and Muller bedload formulas. Composite bed-material samples from several cross sections and discharge measurements ranging from 20 

to 800 ft 3 /s (0.57 to 22.7 m3 /s) were used for the 

computations. 

The Meyer-Peter and Muller formula converted to 

English units by the U.S. Bureau of Reclamation 

(Sheppard, 1960) is 

G~ ~ 1.606 B [3.306 ( ~, ) ( D:,'

16 

) 'I' dS 

- 0.627 Dm] 3 /"2 

where 

Gs = total bedload discharge, in tons per day; 

B = bottom width of stream channel, in feet; 
18 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

STATION NUMBER OF 

ANALYSES 

PERCENT 

0 20 40 60 80 100 

Williamsburg Run (urban) 

Manor Run (urban) 

NW. Branch Anacostia River 

at Norwood (rural) 

Nursery Run (rural) 

Batchellors Run (rural) 

Bel Pre Creek (urban) 

Lutes Run (urban) 

I I I I I I I I I I I 

5 

7 

4 

4 ~·.·.·.·.·.·.·.·.·.·.·.·.·.·.·.·~ ·::::::::::::::::::::::::::::::: 

3 

11 

5 

I I I I I I I I I I I 

Sand 

(0.062-2.0 mm) 

Silt 

(0.004--Q.062 mm) 

Clay 

(<0.004 mm) 

~ 1: ~: ~: ~: ~: ~: ~: ~: ~: ~: ~:~:~:~:~I I I 

FIGURE 12.-Particle-size distribution of suspended sediment transported during medium and high flows in the small study 

basins, 1967-74. Values are sediment-discharge weighted averages. 

Qs =the water discharge determining the bedload, in cubic feet per second; 

Q =total water discharge, in cubic feet per 

second; 

D9o =particle size at which 90 percent of the 

bed material is finer, in millimeters; 

ns =Manning's roughness coefficient for the 

streambed; 

d= depth of flow, in feet; 

S = slope, in feet per foot, and 

Dm =effective size of bed material, in millimeters. 

Dm . 'SD~p 

100 

where D is the geometric mean diameter of particles in a given size fraction and p is the percent by weight in 

that size fraction. 

The nomographs and standard computation forms 

prepared by the U.S. Bureau of Reclamation were 

used for the computations. 

The Schoklitsch bedload formula for bed material 

of uniform grain size, adapted from the English 

conversion by Shulits ( 1935), is 

3745 3

1

2 ( 

Un - D:.ol/2 S Q 

where 

0.00532wD5o ) 

84/3 

Un =bedload discharge of particles in given 

size fraction, in tons per day; 

D:.o=median diameter of bed material particles, 

in inches; 

S =slope of the energy gradeline, in feet per 

foot; 

w =width of the stream, in feet, and 

Q =total water discharge, in cubic feet per 

second. 

The bed material was divided into uniform size 

fractions and the bedload was · computed for each 

fraction. The total bedload discharge was computed 

by the formula 
SEDIMENT DISCHARGE 19 

where 

G a1g1 + azuz + ***anUn 

100 

G =total bedload discharge, in tons per day, 

and 

an= percent of bed material in size fraction. 

Bedload transport curves computed by the two 

formulas and the average suspended-sediment transport curve for the period of record are shown in 

figure 13. The average annual bedload discharges 

computed for the 1963-7 4 period were 990 and 

2,290 tons/yr (900 and 2,080 tjyr) for the MeyerPeter and Muller and the Schoklitsch methods, repectively. Computed bedloads were 6 and 13 percent 

of the total sediment discharge for the same period. 

Bedload discharges for other streams in the study 

area were not computed; however, since the bed 

material and channel characteristics of the other 

streams in the study area were similar to those 

of the Northwest Branch Anacostia River, the bedloads probably represent about the .same percentage 

of the total load. With other conditions affecting 

bedload being equal, the bedload probably would be· 

slightly less in streams draining rural areas and 

slightly higher in urban streams because of the 

WATER DISCHARGE, IN CUBIC METERS PER SECOND 

10 

~ 0 

ffi 1000 a.. 

(/) 

z 

0 

1-

~ 

w' 

(!) 

a: 

<( 

J: 

u 

~ 100 

1-

z 

w 

:2: 

0 

w 

(/) 

10 

I 

EXPLANATION 

Suspended sediment 

Schoklitsch 

Meyer-Peter, 

Muller 

: , 0" ./ 

< /• ,' .: , : I • 

I : 

I • 

I : 

I : 

I : I • 

I ; 

I : 

I • I : 

I : 

I : 

I : I 0 

I : I • 

I : 

I : I 0 

I : 

100 

I : 10 

10 100 1000 

WATER DISCHARGE, IN CUBIC FEET PER SECOND 

>- <( 

0 

a: 

w 

a.. 

(/) 

w 

z 

z 

0 

1-

~ 

w' 

(!) 

a: 

<( 

J: 

u 

(/) 

0 

1-

z 

w 

:2: 

0 

w 

(/) 

FIGURE 13.-Daily suspended-sediment and instantaneous 

bedload transport curves for the Northwest Branch Anacostia River near Colesville, 1963-74. 

greater availability of sand-size particles in the 

urban strea.ms. 

STORM VARIABILITY 

The sediment discharge of a stream is highly 

variable from year to year, season to season, and 

storm to storm. Many factors affect the erosion of 

soil particles and transport of sediment to the 

stream system. Guy ( 1964) analyzed variables affecting storm-sediment loads for seven Atlantic 

coast streams with drainage areas ranging from 

98.4 to 4,571 mi 2 (255 to 11,840 km2 ). The variables 

that significantly affected sediment discharge included storm runoff, long-term mean air temperature as a measure of season, rainfall intensity, and 

a peakedness index. 

The number of small drainage basins and the 

varying land use/land cover within the basins in 

this project provided an opportunity to expand on 

Guy's study to determine if the sediment-water discharge characteristics of urbanizing basins respond 

differently to various storm variables than the characteristics of rural basins. A total of 16 hydrologic 

variables or related factors was determined for each 

subbasin studied in the Rock Creek and Anacostia 

River basins. These variables are: 

Storm suspended- total suspended-sediment dissediment charge transported during 

discharge ( Q8 ) the runoff period, in tons. 

Total runoff ( Q ) total runoff during days of surt face runoff, in cubic feet per 

second-day. 

Storm runoff ( Qr) total runoff minus estimated 

base flow, in cubic feet per 

second-day. 

Peak discharge (Qp) 

Antecedent discharge (Qa) 

Antecedent 

days (Ad) 

Total precipitation (Rt) 

(Base flow was estimated as 

the runoff below a straight 

line drawn from the point 

of initial rise to the point 

where the recession limb of 

the hydrograph approached 

a straight line.) 

instantaneous peak discharge, 

in cubic feet per second. 

mean daily discharge the day 

before the initial rise, in 

cubic feet per second. 

the number of days between 

storms. 

Average precipitation on the 

drainage basin, in inches, as 
20 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

determined by isohyetal 

maps for each storm, excep~ 

as noted. 

Rainfall intensity maximum rainfall during a 

given interval, as dete·rmined from the closest available recording-rain gage: 

Ro5-maximum 5-min rainfall, in inches per hour. 

R15-maximum 15-min rainfall, in inches per hour. 

R3o-maximum 30-min rainfall, in inches per hour. 

R111-maximum 1-hr rainfall, in inches per hour. 

R311-maximum 3-hr rainfall, in inches per hour. 

NOTE.-The 5-min, 15-min, 30-min, and 1-hr 

rainfall intensities were determined for the Lutes 

Run basin. The 3-hr rainfall was substituted for 

the 5-min rainfall for the other seven basins. 

Number of number of peaks during storm. 

peaks (Np) 

Time (T.m) number of months between the 

beginning of the record and 

the storm. 

Construction ( C P) percentage of basin area under 

active construction at the 

time of the storm. 

Sediment concen- discharge-weighted mean seditration (C) ment concentration. 

Peak ratio (Pr) 

C 370.37 (Q8 ) 

Q,. 

approximated as: 

P,.= Qp-Qa 

Qr 

The basic data compiled for each station are 

listed in table 5. The storms, which range in number 

from 26 for Batchellors Run to 93 for Williamsburg 

Run, represent all storms for which sediment sampling was adequate to define the sediment concentration for the period of storm runoff. 

A stepwise multiple-regression model was selected 

to evaluate the effects of the different storm variables on sediment discharges. The output consists 

of a simple correlation matrix of all selected variables and a series of multiple-regression equations. 

In the first step of the regression program, all the 

variables are included in the computations. In subsequent steps, the variable with the least significant 

partial-regression coefficient in the preceding equation is eliminated from further computations. The 

elimination and recomputation continues until one 

independent variable remains. 

In order to meet the assun1ptions of a linear regression model, hydrologic data generally have to be 

transformed to logarithms. A review of the study 

by Guy (1964) and a partial graphical analysis of 

data used in this study indicated that the following 

transformations were required: log Q.~, log Qn log 

Qp, log (10XQa), log (10XRt), log (10XRor.), log 

(10XR15), log (10XRao), log (10XR1h), log 

(10XR3 h), log C, and log P, .. Antecedent runoff and 

the rainfall factors were multiplied by 10 before 

conversion to simplify the logarithmic expression 

of the origina1 values. 

CORRELATION MATRIX 

Simple correlation matrices of all selected variables for each station are summarized in table 6. 

These matrices were examined with three objectives: to investigate any bias caused by changes in 

sampling procedures or climatic conditions, to determine the degree of relation betwe·en the dependent 

variables (sediment discharge. and sediment concentration) and the independent variables, and to determine the intercorrelation of the independent variables. The relation between time in months (hereafter referred to as the chronology factor) and the 

other independent variables was used as an indicator of a climatic or sampling bias during the study 

period. 

An examination of the correlation between chronology and total storm rainfall indicated that there 

had been no significant change in the magnitude or 

intensity of the sampled rainfall events during the 

study period. Lutes Run was the only exception, exhibiting a highly significant ( 99 percent confidence 

level) negative correlation between chronology and 

total precipitation. Apparently, more smaller storms 

were sampled toward the end of the study pe·riod as 

a result of an improvement in equipment and techniques at the Lutes Run automatic pumping sampler. 

In spite of the nonsignificant correlation between 

chronology and total storm precipitation for individual storms, there was a generally positive correlation between chronology and net storm discharge. Correlations were significant at the 95-percent confidence level for Williamsburg Run, Manor 

Run, and Northwest Branch Anacostia River. The 

positive correlations were probably related to the 

significant positive correlations between chronology 

and antecedent discharge, which reflected a trend 

toward wetter years at the end of the study. This 

interpretation was supported by the precipitation 

records for stations near the project area, which 
SEDIMENT DISCHARGE 21 

indicated an increase in average annual precipitation of about 10 inches (250 mm) during the second 

half of the sample period. Apparently, there were 

more storms and a shorter time between storms 

near the end of the project, resulting in higher soil 

moisture levels and higher base flows at the beginning of each storm. 

Lutes Run and Bel Pre Creek, draining the two 

most extensively urbanized basins in the study area, 

were the only streams exhibiting significant positive 

correlation between chronology and peak ratio. This 

relationship indicated that the ratio of peak discharge to storm discharge had been increasing, 

probably as a result of the effects of increased impervious area and storm sewers in these basins. In 

the Lutes Run basin, the smaller storm size and 

disproportionate number of summer storms in 1973 

and 197 4 also contributed to the significant positive 

correlation betweenchronologyand peak ratio. Summer storms with low runoff volumes generally have 

a single peak of relatively short duration, resulting 

in a high peak ratio. 

The effect of each independent variable on suspended-sediment discharge and sediment concentration was evaluated in subsets to facilitate compari"-

son between basins. Basins were cons,idered as urban 

or rural and small or large. Basins with less than 

10 percent of the area in urban residential or public-commercial were considered rural and the others 

were considered urban. The urban basins generally 

had active construction sites throughout the study 

period. Basins were classified as small or large depending on whether their drainage areas were less 

than or greater than 1.5 mP (3.9 km2 ). 

The relation between each independent variable 

and both suspended-sediment discharge and sediment concentration was generally consistent. If the 

variable had a significant pos,itive correlation with 

sediment discharge, it also had the same relation 

with sediment concentration. The only exception 

was storm runoff. There was no consistent trend 

between sediment concentration and storm runoff 

for the basins; however, there was a highly significant positive relation between suspended-sediment 

discharge and storm runoff. This was expected as 

runoff transports suspended sediment. 

Other variables with a significant positive relation 

with suspended-sediment discharge were peak water 

discharge, total precipitation, and intensity parameters. These were significant for both small or 

large and rural or urban basins. The chronolgy 

factor and percentage construction were only significant for the urban basins. That there was nosignificant correlation between chronolgy and sediment discharge in the rural basins was further 

evidence that the sediment data were not biased 

by changes in sampling or climatic conditions. 

Antecedent discharge, antecedent days, and peak 

ratio affected suspended-sediment discharges differently in the large and small basins. Sediment discharge had a significant positive correlation with 

antecedent water discharge and a significant negative correlation with antecedent days on the large 

basins. The relations were insignificant at the 95 

percent confidence level on the small basins. This 

difference between the large and small basins was 

probably the result of a higher correlation between 

runoff volume and sediment discharges for the large 

basins. The sediment discharge from small basins 

was less affected by runoff volume and more dependent on the intensity or concentration of runoff. 

This was illustrated by the significant correlation 

between peak ratio and suspended-sediment discharge for the small basins. 

A number of independent variables were found 

to be significantly correlated with each other. In 

particular, the correlations between the rainfall 

intensity parameters were highly significant. Correlat,ions between rainfall parameters, peak discharge, and peak ratio were also high. A generally 

negative correlation existed between antecedent discharge and rainfall intensity. This correlation was 

apparently a reflection of the seasonal variation of 

storms, that is, of the occurrence of intense convective storms du~ing the growing season when the 

base flow is, generally lower than during the dormant 

season. Because of the intercorrelation of these 

variables, the regression model was set up so that 

these variables would not be considered simultaneously. As many as 10 runs of the model were made 

for each basin so that the effect of each of these 

variables could be evaluated without the influence 

of the other highly correlated independent variables. 

REGRESSION EQUATIONS 

The computer analyses of various combinations of 

independent variables produced regression models 

of the form 

where 

Q8 ="suspended-sediment discharge; 

bo =regression constant; 

b1 =regression coefficient for the 

corresponding variables ( x") . 
22 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

TABLE 5.-Hydrologic characteristics and related factors for 

Total Storm Mean sedi- Suspended- Peak Antecedent 

Period of runoff runoff ment con- sediment discharge discharge 

storm runoff (Qt) (Qr) centration discharge (Qp) (Qa) 

(ft3/s-d) (ft3/s-d) (C) (Qs) ( ft;3fs) (ft3/s) (mg/1) (tons) 

Williamsburg Run near 

1966 

Nov. 28-29 _________________ 7.40 5.00 644.44 8.70 20.0 1.00 

1967 

Jan. 7- 9 _________________ 14.00 6.20 436.08 7.30 17.0 1.70 

Jan. 27-28 _________________ 15.00 11.00 6,632.98 197.00 71.0 1.40 

Mar. 6- 8 _________________ 70.00 62.00 2,514.93 421.00 242.0 2.40 

May 7- 8 _________________ 19.00 15.00 1,604.94 65.00 51.0 1.30 

Aug. 3- 5 _________________ 22.00 20.00 7,296.28 394.00 127.0 .59 

Aug. 24-25 _________________ 60.00 58.00 1,749.68 274.00 424.0 .68 

Oct. 10-11 _________________ 2.10 .83 267.74 .60 6.7 .57 

Oct. 25-26 _________________ 4.50 2.70 1,248.28 9.10 26.0 .65 

Nov. 2- 3 _________________ 5.80 4.20 1,146.38 13.00 19.0 .69 

Dec. 10-12 _________________ 30.00 23.00 1,127.21 70.00 48.0 1.40 

Dec. 28-29 _________________ 25.00 20.00 425.93 23.00 64.0 1.70 

1968 

Jan. 14-15 _________________ 51.00 46.00 418.68 52.00 118.0 .98 

Mar. 17-18 _________________ 25.00 18.00 2,386.83 116.00 46.0 3.20 

Apr. 24-25 _________________ 5.30 2.10 617.28 3.50 11.0 1.10 

May 27-29 _________________ 38.00 33.00 1,010.10 90.00 84.0 .90 

June 19-20 _________________ 12.00 8.50 3,485.83 80.00 69.0 1.40 

June 26-28 _________________ 20.00 16.00 2,824.07 122.00 70.0 .98 

Aug. 19-20 _________________ 2.20 1.40 3,174.60 12.00 15.0 .34 

Sept. 6 _________________ 1.40 1.20 864.20 2.80 9.6 .17 

Sept. 10-11 _________________ 6.80 6.20 3,166.06 53.00 46.0 .18 

Nov. 18-19 _________________ 12.00 9.10 651.20 16.00 34.0 1.10 

1969 

Jan. 21 _________________ 6.20 5.00 585.18 7.90 15.0 .98 

Feb. 24 _________________ 8.20 4.20 520.28 5.90 20.0 6.20 

May 20-21 _________________ 3.30 1.30 1,054.13 3.70 9.1 .77 

June 2- 3 _________________ 13.00 12.00 1,141.97 37.00 96.0 .47 

June 18-19 ----------------- 11.00 9.80 1,700.68 45.00 90.0 .40 

July 20-21 _________________ 8.20 7.60 1,023.39 21.00 75.0 .17 

July 22-23 _________________ 23.00 21.00 1,005.29 57.00 246.0 .66 

Aug. 1- 4 _________________ 49.00 45.00 1,045.27 127.00 606.0 .47 

Aug. 9-10 _________________ 33.00 31.00 800.48 67.00 259.0 .69 

Aug. 18 _________________ 22.00 21.00 1,022.93 58.00 118.0 .69 

Sept. 3- 4 _________________ 44.00 42.00 740.74 84.00 331.0 .78 

Oct. 2 _________________ 4.30 3.60 1,337.45 13.00 36.0 .60 

Nov. 19-20 _________________ 7.30 5.50 875.42 13.00 62.0 .61 

Dec. 7- 8 _________________ 5.50 3.60 627.57 6.10 45.0 .61 

Dec. 10-11 _________________ 24.00 21.00 776.01 44.00 105.0 1.00 

Dec. 22-23 _________________ 14.00 11.00 606.06 18.00 43.0 .90 

1970 

Apr. 14-15 _________________ 63.00 57.00 1,098.11 169.00 210.0 1.40 

May 13-14 _________________ 18.00 14.00 1,693.12 64.00 103.0 1.90 

May 24-25 _________________ 23.00 19.00 1,423.00 73.00 134.0 1.20 

June 16-17 _________________ 7.10 4.80 2,083.33 27.00 61.0 .85 

June 21-22 _________________ 17.00 15.00 3,012.34 122.00 112.0 .93 

July 9-10 _________________ 31.00 29.00 1,123.88 88.00 194.0 .68 

July 20-21 _________________ 44.00 41.00 1,056.91 117.00 427.0 .70 

Sept. 10-11 _________________ 6.00 4.60 3,462.15 43.00 67.0 .59 

Nov. 3 _________________ 4.20 3.40 871.46 8.00 26.0 .67 

Nov. 4- 5 _________________ 40.00 37.00 950.95 95.00 155.0 4.20 

Nov. 14-15 _________________ 22.00 18.00 1,008.23 49.00 90.0 1.50 

Dec. 16-17 _________________ 14.00 11.00 1,144.78 34.00 57.0 1.00 

Dec. 22 _________________ 18.00 15.00 691.36 28.00 69.0 1.20 

1971 

Feb. 7- 9 _________________ 80.00 72.00 1,347.73 262.00 271.0 3.80 

Feb. 22-23 _________________ 43.00 35.00 1,576.72 149.00 98.0 2.40 

May 13-14 _________________ 34.00 30.00 2,432.09 197.00 218.0 1.10 

May 30-31 _________________ 39.00 34.00 577.34 53.00 109.0 1.40 

June 2- 4 _________________ 38.00 28.00 3,558.19 269.00 345.0 2.30 

July 29-30 _________________ 8.80 7.30 3,754.43 74.00 63.0 .55 

Aug. 1- 2 _________________ 24.00 22.00 2,171.71 129.00 122.0 1.90 

Aug. 3- 4 _________________ 80.00 76.00 2,573.10 528.00 1,140.0 17.00 

See footnotes at end of table. 
SEDIMENT DISCHARGE 23 

storms in the Rock Creek and Anacostia River ba,sins, 1962-74 

ConstrueTotal pre- Maximum Maximum Maximum Maximum tion area 

Antecedent cipitation 15-minute 30-minute 1-hour 3-hour Peak Number of Time (Cp) 

days (Rt) rainfall rainfall rainfall rainfali 1 ratio peaks (Tm) (percent 

(Ad) (inches) (R1:;) (R-:o) (Rih) (Rah) (Pr) (Np) (months) of 

(in/hr) (in/hr) (in/hr) (in/hr) basin 

area) 

Olney, Md. 

39 1.16 0.32 0.30 0.24 0.14 3.80 1 1 6.4 

1 .26 .08 .08 .07 .03 2.47 1 3 6.4 

2 1.02 2.20 1.40 .94 .37 6.33 1 3 6.4 

10 2.68 .72 .68 .55 .41 3.86 1 5 7.0 

9 1.92 .76 .70 .50 .40 3.31 1 7 7.6 

13 2.61 4.24 2.52 1.38 .47 6.32 2 10 7.6 

3 3.20 2.00 1.56 1.03 .59 7.30 1 10 7.6 

43 2 .84 .40 .30 .22 .18 7.39 1 12 6.6 

14 .90 2.16 1.30 .75 .33 9.39 1 12 6.2 

7 1.00 .52 .42 .34 .24 4.36 1 13 6.2 

2 2 1.65 .44 .40 .38 .27 2.03 1 14 6.2 

1 2 1.50 .88 .68 .45 .30 3.11 1 14 6.2 

9 1.50 .52 .48 .46 .37 2.54 1 15 6.2 

3 1.25 .40 .38 .33 .19 2.38 1 17 5.7 

18 2 .97 .76 .60 .40 .15 4.71 2 18 5.2 

2 3.00 .80 .62 .50 .33 2.52 1 19 4.7 

1 .96 2.84 2.28 1.16 .37 7.95 1 20 4.7 

5 1.84 2.76 1.98 1.09 .62 4.31 2 20 4.7 

1 2 .70 3.00 1.66 .86 .29 10.47 1 22 4.3 

17 2 .83 1.12 .98 .79 .42 7.86 1 23 3.8 

3 1.57 3.56 2.62 1.58 .65 7.39 1 23 3.8 

3 2 1.35 .32 .30 .27 .19 3.62 2 25 3.8 

1 .70 .20 .20 .16 .10 2.80 1 27 3.8 

0 2 1.09 .16 .16 .15 .13 3.29 2 28 3.8 

10 1.46 1.44 .76 .43 .18 6.41 2 31 3.0 

11 2.42 2.12 1.84 1.53 .74 7.96 1 32 3.0 

14 1.96 4.40 3.12 2.13 .76 9.14 1 32 3.0 

30 2 1.81 5.36 3.16 1.78 .60 9.85 1 33 3.0 

1 2 1.49 5.88 2.96 1.48 .49 11.68 1 33 3.0 

2 3.20 5.60 4.04 2.54 .88 13.46 3 34 3.0 

3 2.43 2.72 1.46 .80 .63 8.33 1 34 3.1 

6 2 2.08 3.52 2.06 1.07 .36 5.59 2 34 3.1 

11 3.51 2.28 2.06 1.22 .60 7.86 2 35 3.1 

23 1.20 1.68 1.12 .61 .25 9.83 1 36 3.1 

10 1.22 1.16 .72 .47 .22 11.16 1 37 3.1 

16 2 .90 .40 .36 .26 .19 12.33 1 38 3.2 

1 1.46 .52 .44 .40 .28 4.95 1 38 3.2 

10 1.10 .24 .24 .20 .15 3.83 1 38 3.2 

11 3.06 .40 .38 .37 .27 3.66 1 42 3.2 

18 1.41 2.48 1.26 .63 .38 7.22 1 43 3.3 

6 1.57 2.56 1.48 .80 .32 6.99 2 43 3.3 

21 1.81 2.40 1.54 .77 .26 12.53 1 44 3.3 

2 1.51 1.96 1.86 .93 .39 7.40 1 44 3.3 

16 2.71 2.00 1.52 1.04 .50 6.67 2 45 3.9 

9 2.60 3.28 2.32 1.36 .50 10.40 1 45 3.9 

17 1.26 2.44 1.68 .90 .30 14.44 1 47 3.9 

2 2 .57 .68 .48 .33 .15 7.45 1 49 3.9 

0 2.04 .60 .52 .45 .36 4.08 1 49 3.9 

2 1.05 .44 .44 .37 .21 4.92 1 49 3.9 

3 1.04 .24 .24 .20 .16 5.09 1 50 3.9 

4 1.01 .36 .34 .28 .18 4.52 1 50 3.9 

0 1.86 .60 .42 .30 .25 3.71 2 52 4.5 

7 1.69 .52 .30 .29 .17 2.73 2 52 4.5 

4 2.09 1.32 1.06 .78 .48 7.23 1 55 5.1 

3 1.62 .52 .36 .26 .20 3.16 2 55 5.1 

1 1.70 .28 .28 .25 .20 12.24 2 56 5.1 

27 1.84 2.16 1.58 1.10 .42 8.55 2 57 5.1 

2 2 1.99 1.96 1.80 .96 .35 5.46 1 58 5.1 

0 2 2.25 4.80 3.66 1.99 .77 14.78 1 58 5.1 
24 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

TABLE 5.-Hydrologic characteristics and related factors for storms 

Total Storm Mean sedi- Suspended- Peak Antecedent Period of runoff runoff ment con- sediment discharge discharge storm runoff (Qt) (Qr) centration discharge (Qp) (Qa) 

(ft3/s-d) (ft3/s-d) (C) (Q,) (ft3/s) (ft3/s) (mg/l) (tons) 

Williamsburg Run near 

1971-Continued 

Aug. 27-28 _________________ 61.00 56.00 800.26 121.00 305.0 0.89 

Oct. 10 _________________ 33.00 30.00 1,333.33 108.00 160.0 1.30 

Nov. 24-25 _________________ 67.00 61.00 340.01 56.00 258.0 1.60 

Nov. 29-30 _________________ 21.00 15.00 345.68 14.00 84.0 2.40 

Dec. 7 _________________ 16.00 12.00 586.42 19.00 55.0 2.60 

1972 

Feb. 3- 4 _________________ 31.00 25.00 1,200.00 81.00 132.0 1.90 

Feb. 13-14 _________________ 42.00 34.00 1,546.84 142.00 139.0 1.80 

Feb. 18-19 _________________ 37.00 30.00 1,160,49 94.00 147.0 2.50 

Mar. 16-17 _________________ 39.00 33.00 751.96 67.00 121.0 2.90 

Apr. 13 _________________ 22.00 18.00 1,748.97 85.00 59.0 2.10 

Apr. 16-17 _________________ 54.00 46.00 2,922.70 363.00 368.0 5.60 

May 3- 4 _________________ 41.00 29.00 1,468.71 115.00 198.0 2.60 

May 19-20 _________________ 16.00 9.90 635.99 17.00 44.0 2.50 

May 22-23 _________________ 10.00 3.20 729.17 6.30 36.0 3.40 

June 4- 5----------------- 13.00 7.30 3,044.14 60.00 85.0 2.20 

June 29-30 _________________ 60.00 50.00 1,066.67 144.00 411.0 2.60 

July 2- 3 _________________ 87.00 73.00 1,557.58 307.00 982.0 4.60 

Oct. 28 _________________ 14.00 13.00 911.68 32.00 51.0 .69 

Nov. 8 _________________ 21.00 19.00 604.29 31.00 82.0 .88 

Nov. 14 _________________ 39.00 34.00 675.38 62.00 184.0 1.00 

Dec. 8- 9 _________________ 52.00 42.00 793.65 90.00 266.0 2.70 

1973 

Feb. 2 _________________ 31.00 24.00 1,157.41 75.00 86.0 2.40 

Apr. 4 _________________ 20.00 15.00 888.89 36.00 112.0 4.10 

Apr. 27 _________________ 27.00 20.00 740.74 40.00 138.0 16.00 

May 28 _________________ 22.00 17.00 1,089.32 50.00 134.0 3.60 

July 3- 4 _________________ 35.00 32.00 2,754.63 238.00 567.0 2.70 

July 20-21 _________________ 41.00 37.00 2,072.07 207.00 320.0 .90 

Sept. 14 _________________ 16.00 15.00 839.50 34.00 57.0 .45 

Oct. 2 _________________ 6.30 5.40 1,028.80 15.00 30.0 .63 

1974 

Mar. 30 _________________ 67.00 60.00 802.47 130.00 365.0 2.00 

Aug. 19 _________________ 11.00 11.00 673.40 20.00 82.0 .49 

Sept. 3- 4 _________________ 10.00 8.30 397.14 8.90 38.0 .43 

Sept. 6 -7 _________________ 14.00 12.00 148.15 4.80 48.0 .68 

Sept. 28 _________________ 13.00 12.00 305.55 9.90 98.0 .49 

North Branch Rock Creek 

1966 

Nov. 28-29 _________________ 33.00 20.00 500.00 27.00 63.0 5.20 

1967 

Jan. 27-28 _________________ 55.00 38.00 3,118.90 320.00 164.0 6.70 

Mar. 6- 8 _________________ 308.00 266.00 2,826.51 2,030.00 800.0 10.00 

Mar. 15-16 _________________ 65.00 38.00 506.82 52.00 98.0 11.00 

May 7- 8 _________________ 90.00 66.00 1,352.41 241.00 187.0 7.10 

June 22-23 _________________ 14.00 7.50 938.27 19.00 33.0 2.10 

Aug. 3- 5 _________________ 92.00 78.00 5,935.41 1,250.00 317.0 1.70 

Aug. 24-25 _________________ 218.00 203.00 3,995.62 2,190.00 823.0 2.50 

Aug. 27-28 _________________ 54.00 36.00 6,224.27 605.00 132.0 9.10 

Nov. 2- 3 _________________ 22.00 14.00 396.82 15.00 50.0 3.20 

Dec. 3- 4 _________________ 68.00 50.00 496.30 67.00 104.0 4.70 

Dec. 10-11 _________________ 82.00 62.00 388.29 65.00 163.0 7.20 

1968 

Jan. 14-15 _________________ 204.00 182.00 830.28 408.00 413.0 5.50 

Mar. 12-13 _________________ 82.00 53.00 663.87 95.00 99.0 6.60 

Mar. 17-18 _________________ 113.00 66.00 1,032.55 184.00 139.0 16.00 

May 27-29 _________________ 138.00 118.00 1,117.39 356.00 233.0 4.20 

June 16 _________________ 17.00 12.00 4,228.39 137.00 123.0 4.00 

June 19-20 _________________ 48.00 37.00 3.533.53 353.00 196.0 7.60 

June 26-28 _________________ 88.00 74.00 2,007.00 401.00 255.0 4.10 

Sept. 10-11 _________________ 30.00 27.00 4,581.61 334.00 126.0 .71 

Oct. 19-20 _________________ 12.00 6.20 77.66 1.30 16.0 1.90 See footnotes at end of table. 
SEDIMENT DISCHARGE 25 

in the Rock Creek and Anacostia River basins, 1962-74-Continued 

ConstrueTotal pre- Maximum Maximum Maximum Maximum tion area 

Antecedent 15-minute 30-minute 1-hour 3-hour Peak Number of Time (Cp) 

days cipitation rainfall rainfall rainfall rainfali 1 ratio peakJ; (Tm) (percent 

(Ali) (Rt) (Rto) (Rao) (Ru) (Rah) (Pr) (Np) (months) of (inches) (in/hr) (in/hr) (in/hr) (in/hr) basin 

area) 

Olney, Md.-Continued 

7 3.16 1.04 1.04 0.79 0.52 5.43 1 58 5.8 

7 1.88 .68 .68 .55 .35 5.29 1 60 5.8 

20 2.72 .52 .46 .39 .35 4.20 1 61 5.8 

3 2 .78 .44 .34 .25 .20 5.44 1 61 5.8 

6 2 .91 .40 .28 .22 .12 4.37 1 62 5.8 

9 1.23 .40 .34 .29 .17 5.20 1 64 5.8 

8 1.57 .28 .28 .26 .19 4.04 1 64 5.8 

3 1.80 .28 .26 .24 .20 4.82 1 64 5.8 

12 1.52 .84 .48 .27 .20 3.58 1 65 5.8 

4 1.19 .44 .30 .23 .21 3.16 3 66 6.5 

0 1.48 2.60 1.54 .91 .44 7.88 1 66 6.5 

8 1.88 .84 .76 .55 .34 6.74 1 67 7.0 

9 2 1.06 .32 .28 .23 .19 4.19 1 67 7.4 

1 2.42 .84 .64 .39 .13 10.19 1 67 7.4 

2 .76 2.68 2.52 1.31 .44 11.34 1 68 7.4 

2 2.25 1.96 1.40 .73 .27 8.17 2 68 7.4 

0 2.06 2.60 2.26 1.54 .66 13.39 2 69 7.4 

8 1.54 1.84 1.20 .73 .31 3.87 2 72 6.5 

10 1.52 .60 .52 .45 .30 4.27 1 73 6.5 

5 2.00 .72 .52 .39 .34 5.38 1 73 6.5 

1 1.94 .40 .38 .33 .30 6.27 1 74 6.5 

3 1.21 .40 .32 .26 .18 3.48 2 76 6.5 

1 .87 .44 .42 .38 .23 7.19 1 78 6.0 

0 2 1.22 .48 .40 .35 .24 6.10 1 78 5.5 

2 1.39 .68 .66 .49 .23 7.67 1 79 5.1 

0 1.73 3.32 2.86 1.66 .57 17.63 1 81 5.1 

15 2.49 2.60 2.48 1.43 .67 8.62 1 81 5.1 

10 2.08 .80 .56 .50 .36 3.77 1 83 4.8 

17 1.18 .28 .28 .23 .19 5.44 1 84 3.0 

8 2.80 .72 .58 .47 .37 6.05 1 89 2.0 

1 1.46 1.80 1.34 1.09 .45 7.41 1 94 1.0 

4 1.57 .36 .24 .17 .11 4.53 2 95 1.0 

1 1.46 .20 .18 .18 .17 3.94 1 95 1.0 

20 1.85 1.08 .62 .48 .30 8.13 1 95 1.0 

near Norbeck, Md. 

23 1.14 0.32 0.30 0.24 0.14 2.89 1 1 2.8 

16 .97 2.20 1.40 .94 .37 4.14 1 3 2.8 

10 2.67 .72 .68 .55 .41 2.97 1 5 2.8 

5 1.02 1.04 .78 .49 .30 2.29 1 5 2.8 

9 1.94 .76 .70 .50 .41 2.73 1 7 3.1 

43 1.17 1.48 1.28 .93 .35 4.12 1 8 3.1 

12 2.42 4.24 2.30 1.15 .47 4.04 2 10 3.1 

2 3.06 2.00 1.56 1.03 .59 4.04 1 10 3.1 

1 2 .76 .52 .46 .27 .09 3.41 2 10 3.1 

7 .97 .52 .42 .34 .24 3.34 1 13 2.5 

29 2 1.34 .64 .56 .49 .32 1.99 1 14 2.5 

5 2 1.48 .44 .40 .38 .27 2.51 1 14 2.5 

9 1.49 .52 .48 .46 .37 2.24 1 15 2.5 

37 1.95 .52 .34 .32 .19 1.74 1 17 2.5 

3 1.20 .40 .38 .33 .19 1.86 2 17 2.5 

2 2.96 .80 .62 .50 .33 1.94 1 19 2.0 

2 2 1.39 1.96 1.18 .63 .14 9.92 ] 20 2.0 

1 .93 2.84 2.28 1.16 .39 5.09 1 20 2.0 

5 1.82 2.76 1.98 1.09 .62 3.39 2 20 2.0 

3 1.80 3.56 2.62 1.58 .65 4.64 1 23 2.0 

11 2 1.44 .72 .42 .35 .25 2.27 1 24 1.7 
26 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

TABLE 5.-Hydrologic characteristics and 'related factors for storms 

Total Storm Mean sedi- Suspended- Peak Antecedent Period of runoff runoff ment con- sediment discharge discharge storm runoff (Qt) (Qr) centmtion discharge (Qp) (Qa) (C) (Qs) (ft3/s-d) (ft3/s-d) (mg/1) (tons) (ft3/s) ( ft3/s) 

North Branch Rock Creek near 

1969 

Jan. 21-22 _________________ 32.00 17.00 261.44 12.00 42.0 5.20 June 2- 3 _________________ 39.00 35.00 2,677.24 253.00 158.0 1.50 June 18-19 _________________ 37.00 33.00 3,209.87 286.00 167.0 1.40 July 20-21 _________________ 17.00 16.00 1,921.29 83.00 117.0 .42 July 22-23 _________________ 67.00 64.00 2,777.77 480.00 332.0 3.10 Aug. 2- 3 _________________ 142.00 132.00 1,083.05 386.00 676.0 3.80 Aug. 9-10 _________________ 123.00 117.00 2,602.09 822.00 498.0 2.50 Aug. 18-20 _________________ 102.00 88.00 1,094.27 260.00 207.0 2.50 

Sept. 3- 5 _________________ 193.00 176.00 2,735.69 1,300.00 706.0 2.40 

Nov. 19-20 _________________ 27.00 16.00 671.30 29.00 64.0 3.50 

Dec. 10-11 _________________ 86.00 68.00 1,612.20 296.00 255.0 8.20 

Dec. 22 _________________ 37.00 31.00 657.11 55.00 106.0 5.60 

1970 

Apr. 1- 3 _________________ 82.00 46.00 1,167.47 145.00 144.0 12.00 

Apr. 14-15 _________________ 237.00 208.00 1,572.29 883.00 455.0 9.00 

May 13-14 _________________ 69.00 52.00 3,262.10 458.00 255.0 8.10 

May 24-25 _________________ 99.00 82.00 4,042.45 895.00 455.0 6.50 

June 16-18 _________________ 47.00 31.00 812.42 68.00 98.0 3.50 

June 21-22 _________________ 63.00 51.00 2,316.63 319.00 287.0 4.70 

July 9-10 _________________ 156.00 145.00 2,998.72 1,174.00 438.0 2.50 

Sept. 10 _________________ 16.00 13.00 797.72 28.00 79.0 2.10 

Nov. 4- 5 _________________ 111.00 95.00 1,255.36 322.00 327.0 11.00 

Dec. 16-17 _________________ 50.00 31.00 585.42 49.00 130.0 4.70 

Dec. 22-23 _________________ 78.00 54.00 576.13 84.00 165.0 6.50 

1971 

Feb. 7-10 _________________ 317.00 285.00 1,806.36 1,390.00 606.0 19.00 

Feb. 13-14 _________________ 341.00 314.00 1,415.43 1,200.00 1,030.0 8.90 

Feb 22-23 _________________ 175.00 147.00 1,345.43 534.00 335.0 14.00 

Apr. 6- 7 _________________ 69.00 50.00 377.78 51.00 85.0 7.50 

May 13-14 _________________ 148.00 130.00 1,735.04 609.00 498.0 5.40 

May 16-17 _________________ 118.00 93.00 637.20 160.00 333.0 9.70 

May 30-June 1 ______________ 176.00 138.00 791.73 295.00 415.0 8.00 

June 2- 4 _________________ 109.00 70.00 3,910.05 739.00 382.0 15.00 

July 1- 2 _________________ 40.00 29.00 2,094.51 164.00 186.0 4.30 

July 29-30 _________________ 27.00 19.00 1,754.38 90.00 122.0 2.00 

Aug. 1- 4 _________________ 323.00 293.00 1,222.35 967.00 998.0 7.00 

Aug. 19 _________________ 22.00 17.00 849.67 39.00 112.0 3.40 

Aug. 27-28 _________________ 184.00 171.00 1,407.84 650.00 642.0 3.00 

Sept. 17-18 _________________ 25.00 11.00 841.75 25.00 59.0 5.60 

Nov. 24-26 _________________ 286.00 239.00 692.70 447.00 657.0 7.10 

Nov. 29-30 _________________ 85.00 57.00 487.33 75.00 237.0 14.00 

Dec. 7- 8 _________________ 75.00 44.00 404.04 48.00 159.0 10.00 

1972 

Feb. 3- 4 _________________ 110.00 81.00 2,016.46 441.00 308.0 10.00 

Mar. 16-17 _________________ 138.00 108.00 1,080.25 315.00 347.0 14.00 

Mar. 22 _________________ 30.00 15.00 740.74 30.00 85.0 13.00 

Apr. 13 _________________ 71.00 58.00 1,245.21 195.00 163.0 9.70 

Apr. 16-17 _________________ 175.00 136.00 3,867.10 1,420.00 642.0 24.00 

May 3- 4 _________________ 161.00 120.00 1,691.36 548.00 460.0 11.00 

May 19-20 _________________ 58.00 33.00 549.94 49.00 112.0 9.90 

May 30-31 _________________ 213.00 187.00 4,436.52 2,240.00 986.0 8.10 

June 4- 5 _________________ 38.00 18.00 2,818.93 137.00 123.Q.. 9.70 

Oct. 28 _________________ 46.00 39.00 1,291.55 136.00 128.0 4.30 

Nov. 8 _________________ 75.00 65.00 695.16 122.00 268.0 5.50 

Nov. 14-15 _________________ 151.00 128.00 801.50 277.00 398.0 5.10 

1973 

Feb. 2- 3 _________________ 168.00 126.00 1,055.26 359.00 335.0 13.00 

Apr. 1- 2 _________________ 281.00 228.00 2,404.16 1,480.00 612.0 15.00 

Apr. 4 _________________ 97.00 78.00 1,158.59 244.00 362.0 23.00 

Apr. 27 _________________ 158.00 138.00 939.34 350.00 490.0 97.00 

May 28-29 _________________ 144.00 110.00 1,040.40 309.00 415.0 15.00 

July 3- 4 _________________ 146.00 127.00 1,971.42 676.00 660.0 31.00 

July 20-21 _________________ 223.00 207.00 2,343.89 1,310.00 978.0 4.50 

Sept. 14-15 _________________ 77.00 65.00 1,111.11 195.00 242.0 2.70 

See footnotes at end of table. 
SEDIMENT DISCHARGE 27 

in the Rock Creek and Anacostia River basins, 1962-74-Continued 

ConstrueTotal pre- Maximum Maximum Maximum Maximum tion area Antecedent 15-minute 30-minute 1-hour 3-hour Peak Number of Time (Cv) days cipitation rainfall rainfall rainfall rainfall 1 ratio pealQ; (Tm) (percent (Att) (Rt) 

(inches) (R15) (R~o) (Rlh) (Rah) (Pr) (Np) (months) of (in/hr) (in/hr) (in/hr) (in/hr) basin 

area) 

Norbeck, Md.-Continued 

1 0.70 0.20 0.20 0.16 0.10 2.16 1 27 1.7 11 2.57 2.12 1.84 1.53 .74 4.47 1 32 1.5 14 2.14 4.40 3.12 2.13 .76 5.02 1 32 1.5 6 2 1.44 5.36 3.16 1.78 .60 7.29 1 33 1.5 1 2 1.24 5.88 2.96 1.48 .49 5.14 1 33 1.5 3 2 3.12 5.60 4.04 2.54 .88 5.09 1 34 1.5 3 2.36 2.72 1.46 .80 .63 4.24 1 34 1.5 6 2.79 3.52 2.06 1.07 .36 2.32 4 34 1.5 13 3.39 2.28 2.06 1.22 .60 4.00 1 35 1.5 9 1.10 1.16 .72 .47 .22 3.78 1 37 1.5 1 1.49 .52 .44 .40 .28 3.63 1 38 1.5 10 1.09 .24 .24 .20 .15 3.24 1 38 1.5 

2 .87 .24 .22 .21 .13 2.87 2 42 1.5 8 2.98 .40 .38 .37 .27 2.14 1 42 1.9 18 1.10 2.48 1.26 .63 .38 4.75 1 43 1.9 5 1.49 2.56 1.48 .80 .32 5.47 1 43 1.9 20 1.74 2.40 1.54 .77 .26 3.05 2 44 1.9 2 1.50 1.96 1.86 .93 .39 5.54 1 44 1.9 16 2.84 2.00 1.52 1.04 .50 3.00 1 45 1.9 17 1.41 2.44 1.68 .90 .30 5.92 1 47 1.9 0 1.92 .60 .52 .45 .36 3.33 1 49 1.9 24 1.00 .24 .24 .20 .16 4.04 1 50 1.9 3 1.06 .36 .34 .28 .18 2.94 1 50 1.9 

0 1.70 .60 .42 .30 .25 2.06 2 52 1.9 2 1.97 1.24 .80 .62 .36 3.25 1 52 1.9 7 1.65 .52 .30 .29 .20 2.18 1 52 1.9 16 2 1.53 .20 .16 .13 .10 1.55 1 54 2.2 3 2.14 1.32 1.06 .78 .48 3.79 1 55 2.2 1 1.32 .32 .30 .25 .22 3.48 1 55 2.2 3 1.41 .52 .36 .26 .20 2.95 2 55 2.2 0 1.21 .28 .28 .25 .20 5.24 2 56 2.2 22 1.09 1.12 .94 .84 .40 6.27 1 57 2.2 26 1.85 2.16 1.58 1.10 .42 6.32 1 57 2.2 1 4.70 4.80 3.66 1.99 .77 3.38 4 58 2.2 13 2 1.06 1.24 .98 .71 .31 6.39 1 58 2.2 7 3.06 1.04 1.04 .79 .52 3.74 1 58 2.2 3 2 .58 1.28 .92 .61 .21 4.85 1 59 2.2 20 2.78 .52 .46 .39 .35 2.72 1 61 2.2 2 2 .78 .44 .34 .25 .20 3.91 1 61 2.2 6 2.88 .40 .28 .22 .12 3.39 1 62 2.2 

9 1.13 .40 .34 .29 .17 3.68 1 64 2.5 12 1.47 .84 .48 .27 .20 3.08 1 65 2.5 4 2.49 .36 .28 .24 .09 4.80 1 65 2.5 4 1.10 .44 .30 .23 .21 2.64 1 66 2.5 2 1.42 2.60 1.54 .91 .44 4.54 1 66 2.5 8 1.90 .84 .76 .55 .34 3.74 2 67 2.5 8 2 1.02 .32 .28 .23 .19 3.09 1 67 2.5 6 2 2.40 3.44 3.38 2.24 .84 5.23 1 67 2.5 2 .65 2.68 2.52 1.31 .44 6.29 1 68 2.5 8 1.60 1.84 1.20 .73 .31 3.17 1 72 2.5 10 1.48 .60 .52 .45 .30 4.04 1 73 2.5 5 2.07 .72 .52 .39 .34 3.07 1 73 2.5 

3 1.25 .40 .32 .26 .18 2.56 1 76 2.0 5 1.89 1.48 1.16 .62 .28 2.62 1 78 2.0 

1 .83 .44 .42 .38 .23 4.35 1 78 2.0 

0 2 1.30 .48 .40 .35 .24 2.85 1 78 2.0 

2 1.35 .68 .66 .49 .23 3.64 1 79 2.0 0 2.04 3.32 2.86 1.66 .57 4.95 1 81 2.0 

15 2.72 2.60 2.48 1.43 .67 4.70 2 81 2.0 

9 2.20 .80 .56 .50 .36 3.68 1 83 2.0 
28 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

TABLE 5.-Hydrologic characteristics and related factors for storms 

Total Storm Mean sedi- Su.spended- Peak Antecedent Period of runoff runoff ment con- sediment discharge discharge storm runoff (Qt) (Qr) centration discharge (Qp) (Qa) 

(ft3/s-d) (ft3/s-d) (C) (Q.) (ft3/s) (ft3/s) (mg/1) (tons) 

North Branch Rock Creek near 

1973-Continued 

Dec. 9 _________________ 58.00 47.00 606.78 77.00 180.0 4.30 

Dec. 20-22 _________________ 259.00 230.00 790.66 491.00 460.0 5.50 

1974 

Jan. 21 _________________ 84.00 76.00 1,769.00 363.00 322.0 9.30 

Mar. 21 _________________ 35.00 27.00 1,536.35 112.00 204.0 7.10 

Mar. 30-31 _________________ 363.00 327.00 1,449.77 1,280.00 850.0 8.30 

May 12-13 _________________ 76.00 55.00 1,245.79 185.00 240.0 6.90 

June 2 _________________ 51.00 40.00 509.26 55.00 172.0 8.30 

Aug. 19-20 _________________ 64.00 59.00 1,494.03 238.00 465.0 2.20 

Sept. 3- 4 _________________ 27.00 20.00 259.26 14.00 55.0 1.40 

Sept. 6- 7 _________________ 41.00 33.00 258.14 23.00 114.0 2.10 

Sept. 28 _________________ 46.00 43.00 938.84 109.00 235.0 1.70 

Manor Run near 

1966 

Nov. 28 _________________ 4.40 4.00 1,203.70 13.00 23.0 0.40 

1967 

Jan. 27-28 _________________ 8.60 5.90 13,370.97 213.00 57.0 .65 

Mar. 6- 8 _________________ 47.00 44.00 3,779.46 449.00 182.0 1.00 

Mar. 15-16 _________________ 8.40 6.10 1,578.63 26.00 26.0 1.10 

Apr. 17-18 _________________ 2.60 1.30 997.15 3.50 5.0 .63 

May 7- 8 _________________ 16.00 14.00 7,037.02 266.00 66.0 .78 

June 22-23 _________________ 4.60 4.10 11,020.76 122.00 110.0 .21 

Aug. 3- 5 _________________ 8.70 7.80 20,750.21 437.00 77.0 .19 

Aug. 24-25 _________________ 37.00 36.00 14,197.51 1,380.00 364.0 .27 

Oct. 25 _____________ .. --- 2.50 2.20 20,033.64 119.00 42.0 .26 

Nov. 2 _________________ 2.60 2.20 4,208.75 25.00 13.0 .31 

1968 

Jan. 14-15 _________________ 29.00 26.00 1,695.15 119.00 97.0 .50 

Mar. 12-13 _________________ 8.40 5.90 2,385.43 38.00 21.0 .74 

Mar. 17-18 _________________ 13.00 9.50 7,914.21 203.00 56.0 1.80 

May 27-29 _________________ 19.00 17.00 7,647.05 351.00 81.0 .43 

June 12-13 _________________ 3.20 2.20 9,764.29 58.00 19.0 .48 

June 16 _________________ 10.00 9.30 20,430.07 513.00 161.0 .43 

June 19-20 _________________ 11.00 9.30 19,633.58 493.00 194.0 1.10 

June 26-28 _________________ 10.00 8.00 12,962.95 280.00 114.0 .67 

July 2- 3 _________________ 6.50 5.20 16,452.97 231.00 95.0 .67 

Sept. 10-11 _________________ 9.50 8.90 24,219.69 582.00 196.0 .25 

1969 

Jan. 21-22 _________________ 5.60 2.60 3,133.90 22.00 10.0 .60 

May 20-21 _________________ 9.50 8.40 14,814.79 336.00 210.0 .48 

June 2- g _________________ 19.00 17.00 13,137.23 603.00 252.0 .28 

June 8 _________________ 2.30 1.90 4,288.49 22.00 64.0 .34 

June 18-19 _________________ 5.00 3.90 10,826.20 114.00 136.0 .34 

July 22-23 _________________ 2.40 1.70 13,943.34 64.00 76.0 .34 

July 28 _________________ 3.40 3.00 11,111.09 90.00 105.0 .28 

Aug. 9-10 _________________ 26.00 25.00 11,703.69 790.00 335.0 .31 

Aug. 18 _________________ 11.00 10.00 8,222.20 222.00 203.0 .31 

Sept. 3- 4 _________________ 11.00 10.00 8,999.98 243.00 151.0 .60 

Oct. 2 _________________ 3.40 3.10 8,960.56 75.00 89.0 .25 

Dec. 10-11 _________________ 16.00 14.00 6,296.29 238.00 100.0 .40 

1970 

Apr. 1- 2 _________________ 8.00 5.30 10,062.88 144.00 54.0 1.30 

Apr. 14-15 _________________ 32.00 29.00 4,699.86 368.00 126.0 .79 

May 24-25 _________________ 14.00 12.00 11,141.96 361.00 277.0 .52 

June 16 _________________ 8.90 8.50 8,932.45 205.00 262.0 .36 

June 21-22 _________________ 11.00 9.60 8,449.06 219.00 198.0 .39 

July 20 _________________ 18.00 18.00 3,703.70 180.00 448.0 .26 

Aug. 14 _________________ 11.00 11.00 4,814.80 143.00 214.0 .27 

Sept. 10 _________________ 8.40 8.10 7,956.09 174.00 246.0 .65 

Nov. 3 _________________ 2.40 2.00 1,851.85 10.00 30.0 .29 

Nov. 4- 5 _________________ 24.00 23.00 1,465.38 91.00 116.0 2.40 

Nov. 14-15 _________________ 12.00 11.00 2,491.58 74.00 102.0 1.00 

Dec. 22 _________________ 11.00 8.80 2,020.20 48.00 81.0 .74 

See footnotes at end of table. 
SEDIMENT DISCHARGE 29 

in the Rock Creek and Anacostia River basins, 1962-7 4-Continued 

ConstrueTotal pre- Maximum Maximum Maximum Maximum tion area 

Antecedent 15-minute 30-minute 1-hour 3-hour Peak Number of Time (Cp) 

days cipitation rainfall rainfall rainfall rainfaLl 1 ratio peaks (Tm) (percent 

(Ad) (Rt) (R15) (R:w) (Ru) (Rah) (P,.) (Np) (months) of (inches) (in/hr) (in/hr) (in/hr) (in/hr) basin 

area) 

Norbeck, Md.-Continued 

3 1.29 0.40 0.36 0.28 0.19 3.74 1 86 1.2 

10 2 1.90 .40 .40 .26 .17 1.98 1 86 1.2 

7 1.02 .56 .40 .36 .28 4.11 1 87 1.2 

33 .85 .56 .44 .30 .22 7.29 1 89 1.2 

7 2.78 .72 .58 .47 .37 2.57 1 89 1.2 

28 1.38 1.16 .72 .51 .30 4.24 1 91 .5 

19 1.64 .44 .32 .28 .22 4.09 1 92 .5 

19 1.63 1.80 1.34 1.09 .45 7.84 1 94 .5 

4 1.53 1.44 1.14 .74 .31 2.68 2 95 .5 

1 1.45 .20 .18 .18 .17 3.39 1 95 .5 

19 1.78 1.08 .62 .48 .30 5.43 1 95 .5 

Norbeck, Md. 

38 1.29 0.92 0.76 0.50 0.25 5.65 1 1 5.2 

11 .82 1.20 .68 .37 .18 9.55 1 3 5.2 

9 2.61 .96 .86 .67 .47 4.11 1 5 5.2 

7 .95 1.32 .90 .74 .35 4.08 2 5 5.2 

3 2 .66 1.24 1.00 .59 .26 3.36 1 6 10.8 

3 1.98 .68 .52 .46 .37 4.66 1 7 10.8 

37 1.50 3.76 2.42 1.33 .50 26.78 1 8 10.8 

13 2.18 2.88 1.76 .91 .32 9.85 1 10 10.8 

4 3.28 1.64 1.22 .88 .59 10.10 1 10 10.8 

14 .97 2.12 1.32 .77 .34 18.97 1 12 11.8 

7 .98 .48 .40 .33 .24 5.77 1 13 11.8 

8 1.49 .32 .30 .29 .24 3.71 1 15 11.8 

10 1.73 .60 .42 .39 .20 3.43 1 17 11.8 

3 1.29 .60 .50 .41 .24 5.71 2 17 11.8 

2 2.83 .52 .44 .37 .23 4.74 2 19 11.8 

13 2.94 .64 .48 .38 .19 8.42 2 20 11.8 

2 1.49 3.48 2.14 1.21 .40 17.27 1 20 11.8 

1 .88 3.40 1.78 .89 .30 20.74 1 20 11.8 

5 1.61 1.76 1.48 .81 .32 14.17 2 20 11.8 

3 1.31 1.88 1.34 .91 .32 18.14 2 21 11.8 

3 1.99 2.16 1.86 1.28 .53 21.99 1 23 11.8 

1 .55 .12 .10 .08 .07 3.62 1 27 9.6 

10 1.58 2.72 1.92 .99 .33 24.94 1 31 9.6 

11 2.10 3.00 2.02 1.54 .74 14.81 1 32 9.6 

4 .53 1.84 1.18 .60 .20 33.51 1 32 9.6 

9 1.50 2.64 1.58 .84 .29 34.78 1 32 9.6 

1 21.11 4.00 2.20 1.15 .42 44.51 1 33 9.6 

5 2 1.12 2.28 1.24 .64 .24 34.91 1 33 9.6 

5 2.83 2.84 1.50 .77 .75 13.39 2 34 9.6 

7 2.50 3.60 2.18 1.15 .39 20.27 2 34 9.6 

13 2.59 1.12 1.20 .66 .23 15.04 2 35 9.6 

23 1.05 1.64 .98 .51 .22 28.63 1 36 9.6 

1 1.45 .56 .46 .39 .27 7.11 1 38 9.6 

2 .86 .88 .58 .33 .14 9.94 1 42 7.4 

6 2.85 .52 .40 .36 .28 4.32 1 42 7.4 

6 1.43 1.96 1.48 .75 .26 23.04 2 43 7.4 

9 2.01 4.00 2.52 1.39 .46 30.78 2 44 7.4 

3 1.45 2.48 1.28 .67 .37 20.58 3 44 7.4 

9 2.38 3.08 2.34 1.39 .49 24.87 2 45 7.4 

14 1.57 1.24 1.18 1.00 .45 19.43 1 46 7.4 

17 1.76 3.08 2.40 1.35 .45 30.29 1 47 7.4 

12 2 .53 .64 .38 .24 .12 14.85 1 49 7.4 

1 1.90 .56 .54 .41 .34 4.94 1 49 7.4 

2 1.02 .44 .38 .34 .21 9.18 1 49 7.4 

4 1.15 .40 .34 .30 .18 9.12 1 50 7.4 
30 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

1971 

Period of storm runoff 

Feb. 7- 8 ________________ _ May 13 ________________ _ 

July 29 ________________ _ 

Aug. 1- 2 ________________ _ 

Aug. 3- 5 ________________ _ Aug. 27 ________________ _ 

Nov. 24-25 ________________ _ 

1972 

Feb. 3- 4 ________________ _ Feb. 13 ________________ _ 

Mar. 16-17----------------- Apr. 13 ________________ _ May 4 ________________ _ June 29-30 ________________ _ Aug. 27-28 ________________ _ Oct. 28 ________________ _ Nov. 14 ________________ _ Dec. 8- 9 ________________ _ 

1973 

Apr. 

Apr. 

July 

Sept. 

Oct. 

1974 

Jan. 

May 

Aug. 

Aug. 

1967 

1 ________________ _ 

4 ________________ _ 2 ________________ _ 14 ________________ _ 2 ________________ _ 

21 ________________ _ 12 ________________ _ 9 ________________ _ 

19 ________________ _ 

Mar. 15 ________________ _ May 7- 8 ________________ _ June 22-23 ________________ _ Aug. 4- 5 ____ .:._ ___________ _ Nov. 2- 3 ________________ _ 

1968 

Jan. 14-15 ________________ _ 

Mar. 12-13 ________________ _ Mar. 17-18 ________________ _ May 27-29 ________________ _ June 19-20 ________________ _ 

June 27-28 ________________ _ 

1969 

June 2- 3 ________________ _ June 18-19 ________________ _ July 20-21 ________________ _ Aug. 2- 3 ________________ _ Aug. 9-10 ________________ _ Aug. 18 ________________ _ 

Dec. 10-11 ________________ _ 

1970 

Apr. 2- 3 ________________ _ Apr. 14-15 ________________ _ May 24-25 ________________ _ June 16-17 ________________ _ July 9-10 ________________ _ 

July 20-21 ________________ _ Nov. 4- 5 ________________ _ Dec. 22 ________________ _ 

See footnotes at end of table. 

Total 

runoff 

(Qt) 

(ft3/s-d) 

36.00 

18.00 

8.40 

9.60 

37.00 

30.00 

39.00 

17.00 

17.00 

18.00 

8.30 

12.00 

36.00 

11.00 

9.30 

17.00 

25.00 

19.00 

15.00 

13.00 

11.00 

2.80 

10.00 

12.00 

7.90 

16.00 

14.00 

23.00 

3.70 

14.00 

3.80 

46.00 

18.00 

30.00 

39.00 

14.00 

12.00 

11.00 

6.30 

5.20 

30.00 

43.00 

14.00 

32.00 

26.00 

83.00 

40.00 

9.00 

42.00 

34.00 

25.00 

16.00 

TABLE 5.-Hydrologic characte'dstics and related factors for storms 

Storm 

runoff 

(Qr) 

(ft3 /s-d) 

33.00 

16.00 

8.00 

8.10 

34.00 

29.00 

37.00 

15.00 

16.00 

15.00 

6.70 

9.80 

32.00 

9.80 

8.70 

15.00 

20.00 

14.00 

13.00 

13.00 

10.00 

2.30 

8.80 

11.00 

7.40 

16.00 

11.00 

16.00 

2.60 

12.00 

2.30 

42.00 

14.00 

21.00 

33.00 

10.00 

7.80 

9.60 

4.90 

4.70 

28.00 

41.00 

13.00 

28.00 

20.00 

76.00 

36.00 

5.90 

40.00 

32.00 

22.00 

13.00 

Mean sedi- ment con- centration (C) 

(mg/1) 

2,368.12 

8,842.58 

6,851.84 

3,475.07 

2,766.88 

2,848.01 

1,301.30 

1,925.92 

1,342.59 

1,283.95 

829.19 

2,380.95 

1,828.70 

1,625.09 

1,830.56 

567.90 

648.15 

3,518.51 

968.66 

2,222.22 

296.30 

111.11 

925.92 

942.76 

750.75 

1,412.03 

437.71 

4,351.84 

3,133.90 

5,925.91 

338.16 

379.19 

714.28 

1,040.56 

819.30 

2,925.92 

4,083.56 

3,549.38 

3,023.43 

2,836.88 

2,407.40 

2,511.29 

968.66 

1,124.34 

1,962.96 

1,793.37 

1,882.71 

1,067.17 

1,750.00 

1,493.05 

471.38 

284.90 

Suspendedsediment 

discharge 

(Qs) 

(tons) 

211.00 

382.00 

148.00 

76.00 

254.00 

223.00 

130.00 

78.00 

58.00 

52.00 

15.00 

63.00 

158.00 

43.00 

43.00 

23.00 

35.00 

133.00 

34.00 

78.00 

8.00 

0.69 

22.00 

28.00 

15.00 

61.00 

13.00 

188.00 

22.00 

192.00 

2.10 

43.00 

27.00 

59.00 

73.00 

79.00 

86.00 

92.00 

40.00 

36.00 

182.00 

2'78.00 

34.00 

85.00 

106.00 

368.00 

183.00 

17.00 

189.00 

129.00 

28.00 

10.00 

Peak discharge 

(Qp) 

(ft3/s) 

161.0 

210.0 

182.0 

185.0 

510.0 

313.0 

152.0 

105.0 

74.0 

69.0 

46.0 

134.0 

370.0 

169.0 

73.0 

106.0 

141.0 

196.0 

113.0 

240.0 

67.0 

17.0 

107.0 

124.0 

124.0 

295.0 

Antecedent 

discharge 

(Qa) 

(ft3/s) 

Manor Run near 

2.00 

.52 

.35 

.81 

1.00 

.39 

.53 

.68 

.57 

1.10 

.93 

1.00 

.89 

.39 

.32 

.44 

1.10 

2.20 

2.00 

.85 

.37 

.37 

.76 

.53 

.34 

.28 

Northwest Branch Anacostia 

44.0 

75.0 

38.0 

205.0 

13.0 

139.0 

45.0 

89.0 

121.0 

159.0 

102.0 

109.0 

107.0 

109.0 

496.0 

441.0 

155.0 

162.0 

110.0 

322.0 

282.0 

91.0 

382.0 

362.0 

124.0 

69.0 

2.00 

1.40 

.52 

1.90 

.57 

2.20 

1.00 

2.60 

.86 

1.10 

.79 

.45 

.42 

.05 

.49 

.54 

.58 

1.50 

2.90 

1.80 

1.30 

1.00 

.86 

.86 

1.00 

1.50 
SEDIMENT DISCHARGE 31 

in the Rock Creek and Anacostia River ba,sins, 1962-74-Continued 

ConstrueTotal pre- Maximum Maximum Maximum Maximum tion area 

Antecedent 15-minute 30-minute 1-hour 3-hour Peak Number of Time (Cp) 

days cipitation rainfall rainfall rainfall rainfall 1 ratio peaks (Trn) (percent 

(A<i) (Rt) (R1r.) (Rao) (Rlh) (Rah) (Pr) (Np) (months) of (inches) (in/hr) (in/hr) (in/hr) (in/hr) basin 

area) 

Norbeck, Md.-Continued 

1 1.99 0.88 0.62 0.41 0.32 4.82 2 52 5.4 

4 2.15 1.92 1.30 .76 .49 13.09 1 55 5.4 

51 2.19 2.16 1.74 1.48 .56 22.71 1 57 5.4 

1 2 1.63 1.72 1.48 .81 .36 22.74 2 58 5.4 

1 2 3.30 4.80 3.66 2.00 .77 14.97 2 58 5.4 

7 3.18 1.24 1.00 .95 .56 10.78 1 58 5.4 

16 2.70 .52 .46 .37 .34 4.09 1 61 5.4 

5 1.14 .44 .38 .32 .19 6.95 1 64 3.9 

8 1.62 .36 .30 .28 .21 4.59 1 64 3.9 

1 1.53 .68 .42 .32 .21 4.53 1 65 3.9 

2 1.05 .40 .34 .27 .22 6.73 1 66 3.9 

1 2 .64 .60 .58 .37 .16 13.57 1 67 3.9 

3 1.74 1.36 .92 .60 .24 11.53 2 68 3.9 

19 2 1.73 1.28 1.00 .85 .51 17.21 1 70 3.9 

8 1.66 1.80 1.02 .60 .25 8.25 2 72 2.4 

5 2.25 .60 .60 .45 .41 7.04 1 73 2.4 

1 1.89 .56 .52 .41 .31 6.99 1 74 2.4 

1 1.58 .36 .34 .32 .20 13.84 1 78 .8 

1 .94 .20 .16 .15 .13 8.54 1 78 .8 

1 2 1.12 1.16 1.02 .64 .34 18.40 2 81 .8 

7 2.02 .72 .52 .39 .27 6.66 2 83 .8 

17 1.00 .36 .26 .24 .20 7.23 1 84 .8 

8 .98 .80 .50 .47 .26 12.07 1 87 .9 

2 1.40 1.72 1.24 .78 .38 11.22 1 91 .9 

10 2.14 2.96 2.30 1.38 .59 16.71 2 94 .9 

9 2.13 3.28 2.84 1.76 .60 18.42 1 94 .9 

River at Norwood, Md. 

7 0.95 4.24 2.14 1.12 0.50 3.82 2 5 1.1 

52 2.03 .76 .74 .57 .40 4.60 1 7 1.1 

45 1.30 3.16 2.14 1.16 .44 14.42 1 8 1.1 

14 2.54 2.92 1.94 1.09 .38 16.92 1 10 1.1 

7 1.06 .44 .42 .32 .23 5.40 1 13 .2 

16 1.54 .44 .40 .35 .25 3.26 1 15 .2 

57 1.90 .68 .46 .43 .20 3.14 1 17 .2 

3 1.56 .68 .56 .46 .25 4.11 2 17 .2 

69 2.92 .56 .54 .41 .23 3.64 3 19 .2 

20 1.04 4.12 2.44 1.23 .41 15.79 1 20 .2 

6 1.75 1.92 1.10 .60 .25 12.98 1 20 .2 

69 2.10 2.88 1.68 1.13 .61 11.31 1 32 .3 

14 1.30 3.08 1.80 .97 .34 21.75 1 32 .3 

30 2 1.35 3.40 2.54 1.31 .44 23.18 1 33 .3 

3 1.79 1.88 1.48 1.00 .36 17.70 1 34 .3 

6 2.35 3.12 1.64 1.12 .74 10.74 1 34 .3 

7 2 1.66 4.16 2.24 1.17 .39 11.88 2 34 .3 

2 1.46 .56 .42 .38 .27 5.73 1 38 .3 

3 1.02 .58 .46 .29 .12 5.35 1 42 .4 

11 3.16 .68 .60 .56 .39 4.21 1 42 .4 

6 1.92 1.88 1.52 .94 .39 7.80 2 43 .4 

21 1.64 1.68 1.62 .85 .29 15.25 1 44 .4 

17 2.70 1.64 1.38 .97 .53 9.53 2 45 .4 

9 2.37 3.20 2.26 1.49 .53 11.29 1 45 .4 

12 2.02 .56 .48 .44 .34 5.59 1 49 .4 

4 1.00 .36 .36 .30 .18 5.19 1 50 .4 
32 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

TABLE 5.-Hydrologic characteristics and ?'elated factors for storms 

Total Storm Mean sedi- Suspended- Peak Antecedent Period of runoff runoff ment con- sediment discharge discharge storm runoff (Qt) (Qr) centration discharge (Qp) (Qa) 

(ft3/s-d) (ft3/s-d) (C) (Qs) (f1Ns) (ft=1/s) (mg/1) (tons) 

Northwest Branch Anacostia River 

1971 

Feb. 7- 9 _________________ 94.00 84.00 1,009.70 229.00 280.0 5.40 

May 13 _________________ 38.00 33.00 2,065.09 184.00 240.0 1.50 

July 1- 2 _________________ 12.00 9.20 1,409.02 35.00 122.0 1.00 

Aug. 1- 2 _________________ 31.00 28.00 1,058.20 80.00 214.0 2.60 

Aug. 3- 4 _________________ 110.00 104.00 1,324.78 372.00 1,500.0 17.00 

Aug. 27-28 _________________ 67.00 64.00 729.17 126.00 374.0 .77 

Nov. 24-25 _________________ 74.00 65.00 837.61 147.00 253.0 1.60 

Nov. 29-30 _________________ 23.00 16.00 324.07 14.00 84.0 2.90 

Dec. 7 _________________ 18.00 15.00 271.60 11.00 70.0 2.10 

1972 

Feb. 3- 4 _________________ 39.00 31.00 1,851.85 155.00 200.0 2.10 

Feb. 13 _________________ 42.00 39.00 1,082.62 114.00 155.0 1.80 

Feb. 18-19 _________________ 57.00 42.00 1, 772.48 201.00 218.0 6.00 

Mar. 16-17 _________________ 50.00 41.00 1,056.91 117.00 141.0 3.20 

Apr. 16-17 _________________ 40.00 30.00 1,024.69 83.00 143.0 7.40 

May 3- 4 _________________ 55.00 41.00 2,005.42 222.00 280.0 2.80 

June 29-30 _________________ 66.00 54.00 1,021.95 149.00 582.0 2.70 

July 2- 3 _________________ 57.00 46.00 998.39 124.00 338.0 4.70 

July 16 _________________ 70.00 67.00 989.50 179.00 980.0 2.30 

Oct. 28 _________________ 7.00 5.80 178.80 2.80 31.0 .86 

Nov. 8 _________________ 15.00 13.00 267.81 9.40 67.0 1.10 

Nov. 14 _________________ 35.00 30.00 555.55 45.00 209.0 1.30 

Dec. 8- 9 _________________ 58.00 48.00 632.72 82.00 308.0 3.10 

1973 

Apr. 1- 2 _________________ 58.00 39.00 2,174.74 229.00 313.0 4.30 

Apr. 4 _________________ 30.00 25.00 874.07 59.00 215.0 4.70 

Apr. 27 _________________ 33.00 24.00 586.42 38.00 191.0 9.50 July 3 _________________ 16.00 14.00 1,931.21 73.00 210.0 2.10 

July 20-21 _________________ 29.00 25.00 1,244.44 84.00 225.0 1.20 

Dec. 20-21 _________________ 78.00 73.00 826.99 163.00 168.0 1.30 

1974 

Jan. 21 _________________ 16.00 13.00 826.21 29.00 96.0 2.10 

Mar. 30 _________________ 76.00 69.00 1,175.52 219.00 330.0 2.40 

June 2 _________________ 16.00 12.00 740.74 24.00 81.0 1.90 

Aug. 19 _________________ 7.70 6.90 2,039.72 38.00 116.0 .77 

Nursery Run at 

1967 

May 7- 8 _________________ 3.50 2.40 154.32 1.00 9.6 0.41 

July 29-30 _________________ 1.90 1.40 2,566.13 9.70 31.0 .14 

Aug. 3- 5 _________________ 5.10 3.90 1,519.47 16.00 42.0 .16 

Aug. 24-25 _________________ 13.00 12.00 1,450.62 47.00 120.0 .25 

Oct. 25-26 _________________ 1.10 .54 411.52 .60 8.7 .16 

Nov. 2 _________________ .83 .60 61.73 .10 3.7 .17 

1968 

Jan. 14-15 _________________ 7.10 6.40 567.13 9.80 27.0 .18 

Mar. 12-13 _________________ 2.00 1.00 148.15 .40 4.6 .26 

Mar. 17-18 _________________ 3.60 2.40 92.59 .60 6.8 .49 

May 27-28 _________________ 3.30 2.30 209.34 1.30 8.7 .21 

June 19 _________________ 2.40 2.10 3,350.96 19.00 61.0 .36 

June 26-28 _________________ 1.40 .61 60.72 .10 2.9 .24 

Sept. 10-11 _________________ .82 .54 137.17 .20 6.4 .10 

1969 

Jan. 21 _________________ .94 .69 118.09 .22 1.8 .22 

June 2- 3 _________________ .91 .64 144.68 .25 6.0 .12 

June 18-19 _________________ 1.90 1.50 5,185.18 21.00 35.0 .12 

July 22-23 _________________ 1.30 .95 779.73 2.00 14.0 .19 

Aug. 2- 4 _________________ 5.40 4.20 3,350.97 38.00 72.0 .19 

Aug. 18-------~--------- 2.10 1.70 784.31 3.60 25.0 .17 

Sept. 2- 3 _________________ 1.40 .79 797.00 1.70 9.0 .15 

Sept. 4 _________________ 2.50 2.10 1,164.02 6.60 32.0 .64 

Oct. 2- 3 _________________ 1.00 .63 199.88 .34 4.6 .16 

Dec. 10-11 _________________ 3.90 2.90 447.00 3.50 18.0 .31 

Dec. 22 _________________ 2.00 1.50 246.91 1.00 8.0 .25 See footnotes at end of table. 
SEDIMENT DISCHARGE 33 

in the Rock Creek and Anacostia River basins, 1962-74-Continued 

ConstrueTotal pre- Maximum Maximum Maximum Maximum tion area Antecedent 15-minute 30-minute 1-hour 3-hour Peak Number of Time (C,) 

days cipitation rainfall rainfall rainfall rainfall 1 ratio peaks (Tm) (percent 

(Ad) (Rt) (Rt5) (Rao) (Rlh) (Rah) (Pr) (Nv) (months) of (inches) (in/hr) (in/hr) (in/hr) (in/hr) basin 

area) 

at Norwood, Md.-Continued 

11 1.79 0.44 0.40 0.32 0.25 3.27 2 52 .2 

4 2.26 1.52 1.12 .74 .50 7.23 1 55 .2 

27 1.74 2.40 1.90 1.28 .49 13.15 1 57 .2 

2 2 1.99 3.88 2.20 1.22 .49 7.55 2 58 .2 

1 2 3.51 4.92 4.40 2.48 .90 14.26 1 58 .2 

21 3.69 .96 .84 .76 .62 5.83 1 58 .2 

20 3.09 .48 .46 .44 .37 3.87 1 61 .2 

3 2 .84 .44 .36 .27 .19 5.07 1 61 .2 

7 2 .91 .24 .18 .16 .12 4.53 1 62 .2 

23 1.27 .48 .46 .39 .21 6.38 1 64 .1 

9 1.69 .24 .22 .22 .20 3.93 1 64 .1 

5 2.20 .48 .48 .47 .38 5.05 1 64 .1 

12 1.60 .24 .24 .21 .09 3.36 1 65 .1 

2 1.18 .64 .48 .36 .22 4.52 3 66 .1 

10 2.22 1.40 .88 .63 .35 6.76 1 67 .1 

5 1.74 3.24 2.06 1.13 .40 10.73 1 68 .1 

1 1.73 2.20 1.98 1.37 .60 7.25 1 69 .1 

7 1.87 3.16 2.16 1.27 .54 14.59 2 69 .1 

8 1.55 .68 .68 .46 .26 5.20 2 72 .1 

10 1.55 .64 .52 .46 .32 5.07 2 73 .1 

5 1.90 .68 .50 .41 .31 6.92 1 73 .1 

1 2 1.72 .68 .54 .44 .34 6.35 1 74 .1 

5 1.65 1.36 .94 .52 .27 7.92 2 78 .9 

1 .96 .60 .50 .47 .27 8.41 1 78 .9 

15 2 1.03 .56 .46 .32 .20 7.56 1 78 .9 

2 1.14 2.64 1.96 1.20 .40 14.85 1 81 .9 

16 3.08 3.32 2.38 1.34 .77 8.95 2 81 .9 

10 2 2.08 .48 .40 .31 .20 2.28 2 86 .9 

9 .88 .48 .38 .36 .24 7.22 1 87 2.5 

8 3.01 .84 .68 .56 .46 4.75 1 89 2.5 

20 1.81 .48 .42 .32 .25 6.59 1 92 2.5 

8 1.32 2.56 1.82 1.25 .46 16.70 1 94 2.5 

Cloverly, Md. 

3 2.00 0.88 0.80 0.65 0.59 3.83 1 7 0.0 

7 2 1.47 3.20 2.56 1.44 .49 22.04 1 9 .0 

3 2.98 3.12 2.12 1.32 .47 10.73 2 10 .0 

3 3.67 2.52 1.56 1.10 .61 9.98 1 10 .0 

5 .95 1.88 1.28 .73 .31 15.81 1 12 .0 

7 1.03 .40 .34 .28 .21 5.88 1 13 .0 

15 1.61 .56 .46 .40 .17 4.19 1 15 .0 

56 1.76 .72 .50 .42 .19 4.34 2 17 .0 

3 1.68 .52 .44 .35 .23 2.63 2 17 .0 

33 3.15 .48 .42 .38 .24 3.69 2 19 .0 

1 1.24 3.80 2.30 1.15 .39 28.88 1 20 .0 

5 1.26 1.48 .94 .51 .18 4.36 2 20 .0 

3 1.41 .84 .64 .58 .33 11.67 1 23 .0 

1 .70 .12 .12 .10 .07 2.29 1 27 .0 

11 1.54 1.20 .76 .50 .33 9.19 1 32 .0 

14 1.70 5.16 2.94 1.54 .52 23.25 1 32 .0 

1 2 1.48 3.48 2.06 1.18 .44 14.54 1 33 .0 

4 3.40 3.88 2.86 1.86 .88 17.10 2 34 .0 

7 2 1.82 2.88 1.94 1.12 .38 14.61 2 34 .0 

12 1.90 1.84 1.76 .91 .33 11.20 1 35 .0 

1 1.05 1.52 1.32 .80 .29 14.93 1 35 .0 

23 1.15 .68 .54 .31 .20 7.05 1 36 .0 

1 1.93 .60 .52 .46 .34 6.10 1 38 .0 

9 1.20 .52 .44 .39 .30 5.17 1 38 .0 
34 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

TABLE 5.-Hydrologic characteristics and related factors for storms 

Total Storm Mean sedi- Suspended- Peak Antecedent 

Period of runoff runoff ment con- sediment discharge discharge storm runoff (Qt) (Qr) centration discharge (Qp) (Qa) 

( ft3/s-d) (f1Ns-d) (C) (Qs) (ftP/s) (ft3/s) (mg/1) (tons) 

Nursery Run at 

1970 

Apr. 2----------------- 2.40 1.20 1,728.39 5.60 12.0 0.64 

Apr. 14 _________________ 6.00 5.20 619.66 8.70 28.0 .48 

Apr. 24 _________________ 1.00 .26 128.20 .09 1.8 .77 

June 3----------------- 4.20 3.90 3,893.63 41.00 113.0 .28 

June 16-17 _________________ 2.30 1.30 1,111.11 3.90 26.0 .31 

July 9-10 _________________ 3.60 2.60 897.43 6.30 27.0 .22 

July 20-21 _________________ 3.90 3.00 2,716.05 22.00 74.0 .22 

Nov. 4- 5 _________________ 3.60 2.70 589.85 4.30 15.0 .35 

Dec. 22 _________________ 1.60 .96 246.91 .64 7.1 .35 

1971 

Feb. 7- 9----------------- 9.30 7.50 938.27 19.00 28.0 .58 

May 13 _________________ 2.00 1.50 839.50 3.40 13.0 .31 

July 1- 2----------------- 2.70 2.10 4,938.26 28.00 72.0 .22 

July 29-30 _________________ 1.20 .68 816.99 1.50 9.8 .15 

Aug. 3- 4----------------- 7.30 6.20 4,599.75 77.00 260.0 1.90 

Aug. 27 _________________ 6.00 5.50 1,010.10 15.00 44.0 .19 

Nov. 29 _________________ 1.60 .91 227.92 .56 6.4 .57 

Dec. 7----------------- 1.80 1.00 259.26 .70 5.4 .48 

1972 

Feb. 3- 4 _________________ 4.00 2.60 1,709.40 12.00 20.0 .45 

Feb. 18-19 _________________ 5.90 3.90 769.23 8.10 22.0 .61 

June 21-22 _________________ 69.00 66.00 1,402.92 250.00 695.0 .38 

Nov. 14 _________________ 3.20 2.60 470.08 3.30 16.0 .32 

Dec. 8- 9 _________________ 4.40 3.00 259.26 2.10 19.0 .50 

1973 

Apr. 1- 2 _________________ 5.10 3.10 1,911.59 16.00 25.0 .68 

Apr. 4 _________________ 2.60 1.80 493.83 2.40 17.0 .78 

July 3 _________________ .80 .34 1,633.98 1.50 8.2 .46 

July 20 _________________ 2.20 1.90 2,729.04 14.00 25.0 .26 

Sept. 14 _________________ 1.40 1.10 175.08 .52 4.3 .18 

1974 

Aug. 19 _________________ .69 .51 1,016.70 1.40 9.4 .16 

Batchellors Run 

1967 

Aug. 4- 5----------------- 2.40 1.80 555.55 2.70 19.0 0.20 

1968 

Jan. 14 _________________ 12.00 10.00 185.18 5.00 41.0 .30 

May 28 _________________ 4.30 2.60 455.84 3.20 17.0 1.70 

June 19-20 _________________ 6.30 5.40 1,303.15 19.00 133.0 .30 

June 27-28 _________________ 1.90 .70 227.51 .43 7.0 .40 

1969 

June 2- 3 _________________ 2.50 1.90 1.364.52 7.00 20.0 .20 

June 18-19 _________________ 1.50 1.00 3,148.14 8.50 21.0 .10 

Dec. 10-11 _________________ 6.00 5.10 798.84 11.00 32.0 .20 

1970 

Apr. 14 _________________ 12.00 10.00 1,407.41 38.00 67.0 .40 

July 20-21 _________________ 5.40 4.90 400.60 5.30 102.0 .10 

Nov. 4- 5----------------- 4.20 3.60 226.34 2.20 14.0 .20 

Dec. 22 _________________ 3.20 2.80 145.50 1.10 19.0 .20 

1972 

Feb. 3- 4 _________________ 7.10 5.70 1,039.63 16.00 39.0 .40 

May 4 _________________ 4.20 3.50 1,269.84 12.00 54.0 .60 

Aug. 27-28 _________________ 2.50 1.80 308.64 1.50 18.0 .20 

Oct. 28 _________________ 1.90 1.40 203.70 .77 5.7 .30 

Nov. g _________________ 2.50 2.20 144.78 .86 >10.0 .20 

Nov. 14 _________________ 6.60 5.90 238.54 3.80 39.0 .30 

Dec. 8- 9 _________________ 11.00 8.30 446.23 10.00 76.0 .60 

1973 

Feb. 2----------------- 4.80 3.30 426.49 3.80 14.0 .50 

Apr. 1- 2----------------- 8.20 5.20 1,282.05 18.00 70.0 1.00 

See footnotes at end of table. 
SEDIMENT DISCHARGE 35 

in the Rock Creek and Anacostia River basins, 1.962-74-Continued 

ConstrueTotal pre- Maximum Maximum Maximum Maximum tion area Antecedent 15-minute 30-minutJe 1-hour 3-hour Peak Number of Time (Cp) 

da.ys cipitation rainfall rainfall rainfall rainfall 1 ratio peaks (Tm) (percent) 

(A a) (Rt) (Rt5) (R:m) (Rlh) (R~11) (P,) (Np) (months) of (inches) (in/hr) (in/hr) (in/hr) (in/hr) basin 

area) 

Cloverly, Md.-Continued 

3 1.11 1.04 0.64 0.37 0.18 9.47 1 42 0.0 

10 4.32 .72 .68 .55 .43 5.29 1 42 .0 

3 .38 .48 .36 .19 .06 3.96 1 42 .0 

8 1.97 3.56 3.22 2.37 .80 28.90 1 44 .0 

8 1.57 4.05 2.70 1.36 .45 19.76 1 44 .0 

6 2.79 1.92 1.40 1.05 .45 10.30 2 45 .0 

8 2.42 2.72 2.48 1.54 .54 24.59 2 45 .0 

12 2.33 .68 .60 .51 .36 5.43 1 49 .0 

4 1.15 .36 .36 .31 .19 7.03 1 50 .0 

11 1.75 .56 .42 .33 .25 3.66 2 52 .0 

4 2.02 1.20 .84 .66 .42 8.46 1 55 .0 

15 2.30 4.60 3.70 1.90 .66 34.18 1 57 .0 

26 1.88 2.48 1.58 1.16 .43 14.19 2 57 .0 

1 2 2.64 4.52 3.16 1.64 .63 41.63 1 58 .0 

7 3.58 .84 .80 .62 .48 7.97 3 58 .0 

3 2 .83 .36 .36 .32 .21 6.41 1 61 .0 

6 2 1.05 .24 .20 .16 .13 4.92 1 62 .0 

9 1.39 .36 .34 .32 .22 7.52 1 64 .0 

3 2.10 .20 .18 .18 .17 5.48 1 64 .0 

2 2 8.23 2.64 2.50 2.17 1.28 10.52 4 68 .0 

5 1.77 .68 .60 .49 .41 6.03 1 73 .0 

1 1.92 .56 .52 .40 .32 6.17 1 74 .0 

1 1.86 2.48 1.40 .77 .38 7.85 2 78 .4 

1 1.08 .76 .62 .62 .34 9.01 1 78 .4 

2 .87 2.64 1.50 .87 .29 22.76 1 81 .4 

8 2 2.32 2.60 2.40 1.34 .72 13.02 2 81 .4 

7 2.29 .56 .56 .44 .34 3.75 1 83 .4 

2 1.23 1.76 1.58 .99 .38 18.12 1 94 .0 

at Oakdale, Md. 

1 2.18 2.92 1.86 1.04 0.36 10.44 2 10 1.7 

9 1.55 .44 .42 .37 .28 4.07 1 15 .7 

3 2.94 .60 .48 .38 .24 5.88 1 19 .7 

1 1.23 2.84 2.28 1.16 .39 24.57 1 20 .7 

1 2 .58 1.92 1.28 .68 .19 9.43 1 20 .7 

11 2.10 2.72 1.82 1.45 .61 10.42 1 32 .7 

14 1.50 3.60 2.50 1.35 .46 20.90 1 32 .7 

1 1.43 .44 .42 .35 .25 6.24 1 38 .7 

6 3.05 .52 .42 .38 .34 6.66 1 42 .7 

9 2.51 1.44 .96 .50 .23 20.80 1 45 .7 

1 2.08 .60 .54 .44 .36 3.83 1 49 .7 

4 1.06 .40 .36 .30 .18 6.71 1 50 .7 

9 1.17 .48 .38 .33 .19 6.77 1 64 .3 

1 2 1.55 .60 .50 .35 .23 15.26 1 67 .3 

17 2 1.62 1.64 1.10 .88 .50 9.89 1 70 .3 

8 1.64 1.56 1.04 .61 .26 3.86 1 72 .3 

10 1.57 .72 .66 .57 .36 4.45 1 73 .3 

5 1.91 .80 .54 .40 .33 6.56 2 73 .3 

1 1.88 1.64 1.04 1.01 .57 9.08 1 74 .3 

1 1.05 .40 .32 .26 .18 4.09 2 76 .3 

5 1.70 2.20 2.04 1.30 .58 13.27 1 78 .3 
36 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

TABLE 5.-Hydrologic characte'ristics and related factors for storms 

Total Storm Mean sedi- Suspended- Peak Antecedent Period of runoff runoff ment con- sediment discharge discharge storm runoff (Qt) (Qr) centration discharge (Qp) (Qa) 

(ftil/s-d) (ft:Jjs-d) (C) (Qs) (ftil/s) (fti1/s) (mg/1) (tons) 

Batchellors Run at 

197 3-Continued 

July 3- 4 _________________ 6.70 5.40 672.15 9.80 122.0 0.80 

July 20-21 _________________ 7.60 7.10 573.81 11.00 130.0 .20 

Sept. 14 _________________ 1.20 .80 189.81 .41 3.6 .20 

1974 

Jan. 21-22 _________________ 3.80 1.90 467.84 2.40 25.0 .60 

Aug. 19-20 _________________ 4.00 2.70 1,508.91 11.00 39.0 .50 

Bel Pre Creek at 

1963 

June 2- 3 _________________ 23.00 22.00 286.19 17.00 61.0 0.20 

Aug. 20-21 _________________ 20.00 20.00 203.70 11.00 102.0 .30 

Sept. 29 _________________ 4.50 4.20 114.64 1.30 18.0 .10 

Nov. 6- 7 _________________ 40.00 38.00 136.45 14.00 80.0 2.00 

1961, 

Jan. 9-10 _________________ 27.00 26.00 170.94 12.00 117.0 .40 

Aug. 3- 4 _________________ 1.30 1.20 277.78 .90 14.0 .10 

Dec. 27-28 _________________ 11.00 10.00 137.04 3.70 31.0 .20 

1965 

Mar. 5- 6 _________________ 75.00 71.00 944.18 181.00 260.0 .20 

Aug. 26-27 _________________ 71.00 70.00 4,851.84 917.00 410.0 .10 

1966 

Jan. 6 _________________ 6.30 4.50 1,646.09 20.00 22.0 1.20 

Feb. 13 _________________ 65.00 63.00 2,316.28 394.00 180.0 1.50 

Apr. 12-13 _________________ 23.00 19.00 2,358.67 121.00 62.0 .50 

Sept. 14 _________________ 59.00 55.00 2,249.15 334.00 370.0 .30 

Oct. 18-19 _________________ 35.00 34.00 1,361.65 125.00 84.0 .30 

Nov. 28-29 _________________ 13.00 12.00 1,666.66 54.00 63.0 .28 

1967 

Jan. 27-28 _________________ 9.50 8.30 4,283.79 96.00 56.0 .58 

Mar. 6- 8 _________________ 59.00 55.00 2,545.45 378.00 193.0 .98 

Mar. 15-16 _________________ 18.00 15.00 1,407.41 57.00 52.0 .98 

Apr. 17-18 _________________ 3.80 2.50 1,629.63 11.00 11.0 .58 

May 7- 8 _________________ 34.00 30.00 2,037.03 165.00 96.0 1.10 

June 22-23 _________________ 10.00 9.00 4,485.59 109.00 130.0 .39 

July 20-21 _________________ 7.30 6.60 3,198.65 57.00 85.0 .17 

Aug. 3- 5 _________________ 26.00 24.00 8,009.25 519.00 158.0 .24 

Aug. 24-25 _________________ 67.00 64.00 2,575.23 445.00 338.0 .57 

Oct. 25-26 _________________ 12.00 11.00 4,377.10 130.00 135.0 .25 

Nov. 2- 3 _________________ 9.30 8.30 1,383.31 31.00 58.0 .29 

Dec. 3- 4 _________________ 31.00 28.00 396.82 30.00 68.0 .41 

Dec. 28-29 _________________ 29.00 27.00 644.72 47.00 81.0 .49 

1968 

Jan. 14-15 _________________ 48.00 45.00 510.29 62.00 159.0 .30 

Mar. 12-13 _________________ 25.00 22.00 993.26 59.00 63.0 .46 

Mar. 17-18 _________________ 35.00 28.00 1,574.07 119.00 95.0 1.90 

May 27-29 _________________ 44.00 40.00 1,074.07 116.00 106.0 .32 

June 16-17 _________________ 17.00 15.00 1,567.90 104.00 137.0 .37 

June 19-20 _________________ 16.00 14.00 2,804.23 106.00 178.0 1.50 

June 27-28 _________________ 20.00 18.00 5,020.56 244.00 134.0 .40 

July 2- 3 _________________ 16.00 15.00 4,395.05 178.00 114.0 .27 

Sept. 6- 7 _________________ 2.70 2.50 962.96 6.50 29.0 .15 

Sept. 10-11 _________________ 9.70 9.20 2,173.91 54.00 104.0 .11 

Oct. 6- 7 _________________ 4.70 4.40 690.23 8.20 34.0 .17 

1969 

Jan. 21-22 _________________ 12.00 11.00 505.05 15.00 23.0 .47 

May 20-21 _________________ 15.00 14.00 3,412.69 129.00 192.0 .53 

June 2- 3 _________________ 29.00 29.00 1,915.71 150.00 206.0 .10 

June 18-19 _________________ 7.20 6.50 3,646.72 64.00 113.0 .21 

July 20-21 _________________ 14.00 14.00 10,952.36 414.00 214.0 .09 

July 22-23 _________________ 6.00 5.10 5,010.88 69.00 57.0 1.20 

Aug. 9-10 _________________ 58.00 57.00 1,858.35 286.00 307.0 .19 

Sept. 2- 4 _________________ 12.00 11.00 2,794.61 83.00 164.0 .23 

Nov. 19-20 _________________ 11.00 10.00 888.89 24.00 66.0 .21 

Dec. 10-11 _________________ 34.00 33.00 808.08 72.00 153.0 .67 

See footnotes at end of table. 
SEDIMENT DISCHARGE 37 

in the Rock Creek and A nacostia River basins, 1962-7 4-Continued 

ConstrueTotal pre- Maximum Maximum Maximum Maximum tion area 

Antecedent 15-minute 30-minute 1-hour 3-hour Peak Number of Time (C,) 

days cipitation rainfaJll rainfall rainfall rainfall 1 ratio peaks (Tm) (percent) 

(A a) (Rt) (R15) (Rao) (Rlh) (Ral.) (Pr) (N,) (months) of (inches) (in/hr) (in/hr) (in/hr) (in/hr) basin 

area) 

Oakdale, Md.-Continued 

3 0.99 2.36 1.92 1.21 0.40 22.44 1 81 0.3 

15 2 2.21 2.60 2.48 1.43 .67 18.28 1 81 .3 

11 1.87 .72 .54 .41 .31 4.25 1 83 .3 

8 1.08 .60 .50 .45 .30 12.84 1 87 4.0 

1 2.23 2.40 2.16 2.01 .82 14.26 1 94 4.0 

Layhill, Md. 

2 2 2 95 0.44 0.36 0.33 0.22 2.76 1 3 0.0 

5 2 2.75 1.94 1.72 1.00 .52 5.08 2 5 .0 

12 2 2.10 .56 .40 .39 .26 4.26 1 6 .0 

3 2 3.30 .40 .36 .35 .30 2.05 1 8 .0 

1 2 1.16 .36 .32 .25 .22 4.48 1 10 .0 

20 2 1.95 .84 .52 .40 .20 11.58 1 17 .0 

13 2 .72 .60 .40 .25 .13 3.08 1 21 3.1 

7 2 2.95 2.64 1.34 .67 .22 3.66 1 24 18.0 

3 2 2.81 3.32 2.24 1.40 .49 5.86 2 29 18.0 

88 2 .89 .16 .14 .12 .07 4.62 1 34 14.0 

1 2 1.73 1.48 .80 .43 .17 2.83 2 35 14.0 

17 2 2.20 .20 .18 .15 .13 3.24 1 37 14.0 

19 2 5.48 1.12 1.10 .95 .72 6.72 2 42 14.0 

14 2 2.45 .44 .30 .25 .22 2.46 1 43 13.8 

35 1.29 .92 .76 .50 .25 5.23 1 44 13.8 

18 .75 1.20 .68 .37 .18 6.68 1 46 13.8 

12 2.55 .96 .86 .67 .47 3.49 1 48 13.8 

7 .85 1.32 .90 .74 .35 3.40 2 48 13.8 

9 2 .66 1.24 1.00 .59 .26 4.17 1 49 13.9 

3 2.01 .68 .52 .46 .37 3.16 1 50 13.9 

33 1.49 3.76 2.42 1.33 .50 14.40 1 51 13.9 

16 .96 1.28 .80 .47 .23 12.85 1 52 13.9 

3 2.28 2.88 1.76 .91 .32 6.57 2 53 13.9 

3 3.69 1.64 1.22 .88 .59 5.27 3 53 13.9 

6 1.14 2.12 1.32 .77 .34 12.25 1 55 10.0 

7 1.02 .48 .40 .33 .24 6.95 1 56 10.0 

30 21.42 .40 .34 .30 .21 2.41 1 57 10.0 

4 21.48 .48 .36 .22 .17 2.98 1 57 10.0 

15 1.36 .32 .30 .29 .24 3.53 1 58 10.0 

37 1.79 .60 .42 .39 .20 2.84 1 60 10.0 

3 1.49 .60 .50 .41 .24 3.32 2 60 10.0 

2 2.76 .52 .44 .37 .23 2.64 1 62 9.8 

2 21.21 3.48 2.14 1.21 .40 9.11 1 63 9.8 

1 1.04 3.40 1.78 .89 .30 12.61 1 63 9.8 

6 1.70 1.76 1.48 .81 .32 7.42 2 63 9.8 

3 2 1.36 1.88 1.34 .91 .32 7.58 2 64 9.8 

19 2 .76 .64 .48 .37 .19 11.54 1 66 9.8 

3 1.50 2.16 1.86 1.28 .53 11.29 2 66 9.8 

26 2 1.18 .36 .34 .32 .27 7.69 2 67 9.8 

28 .56 .12 .10 .08 .07 2.05 1 70 9.8 

10 1.47 2.72 1.92 .99 .33 13.68 1 74 11.1 

11 1.92 3.00 2.02 1.54 .74 7.10 1 75 11.1 

9 1.34 2.64 1.58 .84 .29 17.35 2 75 11.1 

30 2 1.13 3.60 2.14 1.11 .38 15.28 1 76 11.1 

1 21.11 4.00 2.20 1.15 .42 10.94 1 76 11.1 

4 3.16 2.84 1.50 .77 .75 5.38 2 77 11.1 

12 1.48 1.12 1.20 .66 .23 14.89 6 78 11.1 

10 1.15 1.04 .70 .48 .27 6.58 1 80 11.1 

1 1.45 .56 .46 .39 .27 4.62 1 81 9.7 
38 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

1970 

Period of storm runoff 

Apr. 1- 2 ________________ _ Apr. 14-15 ________________ _ July 9-10 ________________ _ July 20-21 ________________ _ 

Aug. 14-15 ________________ _ Sept. 10 ________________ _ Oc~ 21 ________________ _ No~ 3 ________________ _ 

Nov. 4- 5 ________________ _ 

1971 

Feb. 22-23 ________________ _ July 29 ________________ _ 

Aug. 1- 2 ________________ _ Aug. 3- 4 ________________ _ Aug. 27-28 ________________ _ Sept. 11-12 ________________ _ 

Nov. 24-25 ________________ _ Nov. 29-30 ________________ _ Dec. 7 ________________ _ 

1972 

Mar. 16-17-----------------

Apr. 16-17----------------- June 21-22 ________________ _ July 2- 3 ________________ _ Oct. 28 ________________ _ Nov. 8 ________________ _ Nov. 14 ________________ _ 

Dec. 8- 9 ________________ _ 

2 ________________ _ 1973 

Feb. 

Apr. 

Apr. 

Apr. 

Apr. 

June 

July 

Sept. 

Oct. 

Dec. 

1- 2 ________________ _ 4 ________________ _ 25-26 ________________ _ 27 ________________ _ 29 ________________ _ 3- 4 ________________ _ 14 ________________ _ 2- 3 ________________ _ 5 ________________ _ 

1974 

Jan. 

Mar. 

May 

June 

July 

Aug. 

Aug. 

21 ________________ _ 30-31 ________________ _ 12-13 ________________ _ 2 ________________ _ 

29-30 ________________ _ 9 ________________ _ 19-20 ________________ _ 

1963 

June 2- 3 ________________ _ Nov. 6- 7 ________________ _ 

1964 

Jan. 

Aug. 

1965 

9 ________________ _ 

3 ________________ _ 

Feb. 7- 8 ________________ _ Mar. 26 ________________ _ 

Oct. 7- 8 ________________ _ 

1966 

Feb. 13 ________________ _ Nov. 28 ________________ _ 

See foo•.notes at end of table. 

Total 

runoff 

(Qt) 

(fW/s-d) 

23.00 

79.00 

44.00 

32.00 

12.00 

7.80 

7.20 

2.90 

37.00 

39.00 

13.00 

34.00 

91.00 

63.00 

27.00 

68.00 

17.00 

19.00 

50.00 

33.00 

381.00 

56.00 

20.00 

22.00 

36.00 

52.00 

34.00 

50.00 

26.00 

31.00 

31.00 

8.20 

24.00 

19.00 

7.90 

5.90 

19.00 

71.00 

27.00 

9.70 

6.30 

11.00 

13.00 

9.10 

9.70 

7.70 

3.40 

7.60 

4.80 

37.00 

18.00 

3.40 

TABLE 5.-Hydt·ologic charactet·istics and related factors for stm·ms 

Storm 

runoff 

(Q,.) 

( ft3/s-d) 

21.00 

76.00 

43.00 

31.00 

11.00 

7.50 

6.70 

2.40 

35.00 

34.00 

13.00 

32.00 

87.00 

60.00 

24.00 

63.00 

13.00 

16.00 

45.00 

27.00 

368.00 

49.00 

19.00 

21.00 

35.00 

50.00 

29.00 

40.00 

23.00 

26.00 

27.00 

7.20 

22.00 

18.00 

6.90 

4.70 

16.00 

63.00 

22.00 

7.70 

5.00 

9.60 

11.00 

8.10 

8.80 

7.10 

2.80 

5.80 

3.60 

34.00 

12.00 

3.20 

Mean sedi- ment con- centration (C) 

(mg/1) 

1,975.31 

1,310.91 

956.07 

1,051.37 

1,212.12 

1,629.63 

939.74 

324.07 

529.10 

1,209.15 

5,527.05 

5,925.92 

2,303.10 

2,641.97 

5,679.00 

1,475.60 

1,111.11 

1,018.52 

2,230.45 

2,414.26 

3,713.76 

2,494.33 

6,354.77 

1,181.66 

761.90 

1,022.22 

1,583.65 

2,527.77 

1,433.17 

740.74 

1,001.37 

2,006.17 

2,912.45 

1,481.48 

1,610.30 

1,260.83 

2,500.00 

1,064.08 

1,060.60 

577.20 

2,444.44 

4,089.50 

2,424.24 

9,785.07 

9,301.32 

11,632.73 

10,846.54 

6,066.40 

3,909.46 

3,834.42 

8,950.60 

1,851.85 

Suspendedsediment 

discharge 

(Qs) 

(tons) 

112.00 

269.00 

111.00 

88.00 

36.00 

33.00 

17.00 

2.10 

50.00 

111.00 

194.00 

512.00 

541.00 

428.00 

368.00 

251.00 

39.00 

44.00 

271.00 

176.00 

3,690.00 

330.00 

326.00 

67.00 

72.00 

138.00 

124.00 

273.00 

89.00 

52.00 

73.00 

39.00 

173.00 

72.00 

30.00 

16.00 

108.00 

181.00 

63.00 

12.00 

33.00 

106.00 

72.00 

214.00 

221.00 

223.00 

82.00 

95.00 

38.00 

352.00 

290.00 

16.00 

Peak discharge 

(Qp) 

(ftll/s) 

117.0 

234.0 

265.0 

313.0 

116.0 

141.0 

61.0 

19.0 

138.0 

105.0 

180.0 

255.0 

1,030.0 

262.0 

173.0 

198.0 

59.0 

65.0 

160.0 

134.0 

1,930.0 

264.0 

106.0 

90.0 

142.0 

154.0 

90.0 

198.0 

150.0 

105.0 

135.0 

107.0 

276.0 

79.0 

44.0 

43.0 

131.0 

244.0 

198.0 

50.0 

120.0 

109.0 

128.0 

50.0 

37.0 

42.0 

48.0 

36.0 

46.0 

350.0 

170.0 

23.0 

Antecedent 

discharge 

(Qa) 

(ft3 /s) 

Bel Pre Creek at 

2.00 

.78 

.23 

.22 

.15 

1.10 

.15 

.29 

2.90 

1.50 

.12 

3.10 

15.00 

.33 

.33 

.38 

1.10 

.86 

1.50 

6.80 

1.80 

2.60 

.46 

.45 

.43 

1.50 

1.00 

3.40 

2.10 

1.10 

21.00 

.65 

3.20 

.29 

.31 

.24 

1.00 

1.30 

.63 

.81 

.11 

1.00 

.40 

Lutes Run at 

0.30 

.40 

.10 

.50 

.80 

1.00 

.70 

7.00 

.10 
SEDIMENT DISCHARGE 39 

in the Rock Creek and A nacostia River basins, 1962-7 4-Continued 

ConstrueTotal pre- Maximum Maximum Maximum Maximum tion area Antecedent cipitation 15-minute 30•minute 1-hour 3-hour Peak Number of Time (Cp) d83'S (Rt) rainfaJ!l rainfall rainfall rainfall 1 !·atio peaks (Tm) (percent) (At.t) (inches) (Rl5) (R:w) (Rlh) (R3h) (P,.) (Np) (months) of (in/hr) (in/hr) (in/hr) (in/hr) basin 

area) 

Layhill, Md.-Continued 

2 1.06 0.88 0.58 0.33 0.14 5.48 2 85 9.7 

6 2.92 .52 .40 .36 .28 3.07 1 85 9.7 16 3.18 2.24 1.80 1.23 .52 6.16 2 88 9.7 

9 2.46 3.08 2.34 1.39 .49 10.09 2 88 9.7 

6 1.40 1.24 1.18 1.00 .45 10.53 1 89 9.7 

17 1.48 3.08 2.40 1.35 .45 18.65 1 90 9.7 

4 2 1.35 .72 .50 .39 .24 9.08 1 91 9.7 

2 2 .53 .64 .38 .24 .12 7.80 1 92 9.7 

0 1.94 .56 .54 .41 .34 3.86 1 92 9.7 

8 1.65 .40 .34 .30 .18 3.04 2 95 8.9 

3 2.21 2.16 1.74 1.48 .56 13.84 1 100 8.9 

2 2 1.63 1.72 1.48 .81 .36 7.87 2 101 8.9 

0 2 3.30 4.80 3.66 2.00 .77 11.67 1 101 8.9 

7 3.37 1.24 1.00 .95 .56 4.36 1 101 8.9 

11 3.20 1.72 1.20 .84 .47 7.19 5 102 8.9 

16 2.50 .52 .46 .37 .34 3.14 1 104 8.9 

3 2 .67 .40 .32 .24 .17 4.45 1 104 8.9 

5 2 .97 .32 .24 .18 .12 4.01 1 105 8.9 

1 1.55 .68 .42 .32 .21 3.52 1 108 13.7 

2 1.03 .72 .50 .28 .16 4.71 3 109 13.7 

6 2 8.23 2.40 2.30 1.85 1.48 5.24 2 111 13.7 

1 1.72 2.60 2.54 1.57 .65 5.33 2 112 13.7 

8 1.65 1.80 1.02 .60 .25 5.55 2 115 13.7 

10 1.50 .64 .52 .45 .29 4.26 2 116 13.7 

5 2.00 .60 .60 .45 .41 4.04 1 116 13.7 

1 1.85 .56 .52 .41 .31 3.05 1 117 13.7 

3 1.09 .24 .20 .18 .13 3.07 2 119 15.2 

5 1.55 .36 .34 .32 .20 4.86 2 121 15.2 

1 .95 .20 .16 .15 .13 6.43 1 121 15.0 

14 2 1.94 .68 .56 .38 .22 4.00 2 121 15.2 

0 21.37 .60 .50 .42 .26 4.22 1 121 15.2 

3 .78 1.00 .84 .57 .20 14.77 1 123 15.2 

3 2.03 3.24 2.38 1.23 .41 12.40 1 124 15.2 

7 1.87 .72 .52 .39 .27 4.37 3 126 15.2 

17 1.05 .36 .26 .24 .20 6.33 1 127 15.2 

36 .92 .52 .38 .25 .14 9.10 2 129 13.1 

8 .93 .80 .50 .47 .26 8.13 1 130 13.1 

8 2.63 .64 .52 .45 .36 3.85 1 132 13.1 

27 1.50 1.72 1.24 .78 .38 8.97 2 134 11.0 

19 1.45 .44 .34 .28 .23 6.39 1 135 11.0 

35 1.03 2.68 1.61 .87 .34 23.98 1 136 11.0 

9 2.23 2.96 2.30 1.38 .59 11.25 2 137 11.0 

9 1.50 3.28 2.84 1.76 .60 11.60 1 137 11.0 

Lutes, Md. 

2 2 2.93 0.44 0.36 0.33 0.60 6.14 4 5 20.3 

3 2 2.80 .40 .36 .35 .72 4.16 2 10 14.3 

1 2 1.16 .36 .30 .25 .48 5.90 1 12 14.3 

20 2 1.95 .84 .52 .40 1.20 16.96 1 19 11.3 

12 2 1.38 .24 .22 .20 .48 6.07 1 25 8.3 

6 2 1.26 .40 .34 .30 .84 12.50 1 26 8.3 

12 2 3.45 1.44 1.30 1.02 2.52 10.27 3 33 6.7 

1 21.71 1.48 .82 .42 3.60 13.58 3 37 13.3 

24 1.17 .92 .76 .50 .96 7.16 1 46 10.3 
40 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

TABLE 5.-Hyd?·ologic charactwristics and related factm·s for storms 

Total Storm Mean sedi- Suspended- Peak Antecedent 

Period of runoff runoff ment con- sediment discharge discharge 

storm runoff (Qt) (Qr) centration discharge (Qp) (Qa) 

(ft3 /s-d) (ft3/s-d) (C) (Qs) (f1jl/s) (f1jl/s) (mg/1) (tons) 

Lutes Run at Lutes, 

1967 

Jan. 27 _________________ 2.90 2.70 11,659.79 85.00 44.0 0.10 

May 7 _________________ 9.10 8.30 2,989.73 67.00 43.0 1.30 

June 22 _________________ 5.00 4.80 4,629.62 60.00 189.0 .10 

July 20 _________________ 5.90 5.80 4,661.55 73.00 194.0 .10 

July 29-30 _________________ 3.70 3.50 2,539.68 24.00 153.0 .10 

Aug. 3- 5 _________________ 13.00 13.00 2,849.00 100.00 221.0 .10 

Aug. 19 _________________ 2.70 2.60 4,843.30 34.00 88.0 .10 

Oct. 25-26 _________________ 3.80 3.60 3,292.18 32.00 101.0 .10 

Nov. 2 _________________ 3.00 2.90 753.51 5.90 26.0 .10 

1968 

Jan. 14-15 _________________ 12.00 11.00 673.40 20.00 65.0 .20 

Mar. 17-18 _________________ 8.60 7.30 1,522.07 30.00 51.0 .50 

May 27-29 _________________ 10.00 9.10 1,221.00 30.00 75.0 .20 

June 19-20 _________________ 6.70 6.20 3,643.96 61.00 270.0 .20 

July 2- 3 ----------------- 8.90 8.20 2,393.85 53.00 218.0 .20 

Sept. 2. ________________ .88 .84 2,425.04 5.50 48.0 .02 

1970 

Apr. 2 _________________ 3.90 3.50 5,396.82 51.00 83.0 .20 

1973 

June 29 _________________ 4.10 3.90 2,943.97 31.00 137.0 .20 

July 3 _________________ 4.50 4.10 3,703.70 41.00 170.0 .40 

Sept. 14 _________________ 5.20 5.10 275.96 3.80 43.0 .10 

Oct. 2 _________________ 3.30 3.20 231.48 2.00 26.0 .10 

1974 

May 12 _________________ .64 .45 987.65 1.20 176.0 .20 

June 16 _________________ 2.80 2.70 905.35 6.60 112.0 .10 

June 26 _________________ .45 .30 197.53 .16 9.3 .20 

July 5 _________________ .33 .22 538.72 .32 15.0 .10 

July 29 _________________ 2.70 2.60 2,136.75 15.00 176.0 .10 

Aug. 4 _________________ .26 .21 194.00 .11 12.0 .05 

Aug. 9 _________________ 2.90 2.80 1,230.16 9.30 153.0 .10 

Aug. 28 _________________ .31 .25 400.00 .27 12.0 .06 

Aug. 30 _________________ 1.40 1.30 769.23 2.70 90.0 .06 

Sept. 3 _________________ 3.30 3.20 578.70 5.00 95.0 .06 

Sept. 6- 7 _________________ 7.30 7.10 156.49 3.00 44.0 .10 

1 Maximum 5-minute rainfall for Lutes Run, maximum 3-hour rainfall for all other stations. 2 From single rai,n gage in or near the basin. 

Each model for each station was analyzed, and the 

best models with one, two, three, and four independent variables were selected on the basis of the 

multiple correlation coefficient and the standard 

error of estimate. The regression equations summarized in table 7 were generally consistent with! 

the results of the correlation analyses. Storm runoff 

was the most significant parameter affecting suspended-sediment discharge. It explained 52 to 72 

percent of the variation of sediment discharge for 

the five sites when it was the most significant independent variable. Peak discharge was the most significant independent variable at three sites: North 

Branch Rock Creek, Manor Run, and Nursery Run. 

It explained 40, 83, and 86 percent of the variation 

of suspended-sediment discharge, respectively. 

There was no apparent relation between the size 

of the basin or degree of urban development and the 

significance of peak discharge in the regression 

equations. The addition of a second independent 

variable to the regression model for each basin 

generally resulted in a marked improvement in the 

multiple correlation coefficient and standard error 

of estimate. This was particularly true in the basins 

where storm runoff was the most significant independent variable. The addition of the third and 

fourth independent variables improved the relations to a lesser extent. The standard error tended 

to increase with the addition of a fourth independent variable at stations having a small number of 

storms available for analysis. 

The second and third most significant independent variables in the regression models were generally related to storm intensity. Peak ratio, 15-min 

rainfall, or 30-min rainfall was selected at all sites 

except Nursery Run. Percentage of construction or 
SEDIMENT DISCHARGE 41 

in the Rock Creek and A nacostia River basins, 1962-7 4-Continued 

Total pre- Maximum Maxi·mum Maximum Antecedent cipitation 15-minute 30-minute 1-hour days rainfaJI rainfall rainfall (At~) (Rt) (R15) (R~o) (Rlh) (inches) (in/hr) (in/hr) (in/hr) 

Md.-Continued 

17 0.74 1.24 0.68 0.39 

9 2.06 .64 .54 .46 

5 1.39 3.32 2.22 1.23 

4 1.42 2.84 2.10 1.22 

7 .70 3.60 2.16 1.15 

3 2.67 2.88 1.76 .91 

13 2 1.29 2.52 1.30 .75 

5 1.32 2.80 1.80 1.07 

6 .97 .44 .38 .31 

14 1.45 .44 .38 .33 

3 1.84 .60 .50 .49 

2 3.13 .56 .48 .43 

1 .70 3.40 1.78 .89 

3 1.98 2.88 1.98 1.20 

11 2 .56 1.68 1.10 .56 

3 2 .65 1.24 .74 .44 

2 .98 1.96 1.32 .88 

2 2 .78 3.24 2.38 1.23 

6 1.85 .64 .46 .36 

1 1.10 .32 .30 .25 

8 2 .17 1.20 .92 .61 

13 2 1.04 .56 .36 .25 

2 2 .20 .28 .24 .18 

6 2 .20 .44 .22 .13 

23 .95 2.08 1.34 .74 

4 2 .17 .52 .26 .15 

4 2 .68 1.76 1.26 .67 

1 2 .25 .44 .40 .20 

1 .53 1.48 .82 .47 

3 1.40 1.00 .62 .46 

1 1.50 .28 .26 .25 

the chronology factor was also selected as the second 

or third independent variable for most stations. In 

fact, these were the only factors that showed any 

difference between the urban and rural streams. 

Each basin with active construction showed a significant relation between suspended-sediment discharge and percentage of construction or the closely 

related chronology factor. 

These analyses indicate the complex relation between sediment discharge and the factors affecting 

erosion and sediment transport. As in the study of 

large Atlantic coast streams (Guy, 1964), storm 

runoff, rainfall intensity, and storm peak ratio significantly affect the sediment discharge. However, 

even though a relatively dense network of rain gages 

was used to determine rainfall amount and intensity, the relationships developed for these small 

basins are no better, and in some cases worse, than 

ConstrueMaximum tion area 

3-hour Peak Number of Time (Cp) 

rainfall 1 ratio peaks (Tm) (percent) 

(R311) (Pr) (Np) (months) of 

(in/hr) basin 

area) 

3.60 16.26 1 48 10.3 

.96 5.02 2 52 9.3 

4.20 39.35 1 53 9.3 

3.12 33.43 1 54 9.3 

3.60 43.69 1 54 9.3 

4.20 16.99 3 55 9.3 

4.44 33.81 2 55 9.3 

3.48 28.03 1 57 9.3 

.48 8.93 2 58 9.3 

.44 5.89 2 60 9.3 

.84 6.92 2 62 4.3 

.72 8.22 1 64 4.3 

4.44 43.52 1 65 4.3 

3.96 26.56 3 66 4.3 

2.04 57.12 2 68 4.3 

1.24 23.66 1 87 4.3 

1.96 35.08 1 125 1.7 

3.96 41.37 1 126 1.7 

.84 8.41 4 128 1.7 

.36 8.09 4 129 .7 

1.20 390.67 1 136 .7 

.56 41.44 3 137 .7 

.36 30.33 1 137 .7 

.60 67.73 1 138 .7 

3.00 67.65 1 138 .7 

.84 56.90 1 139 .7 

2.52 54.61 1 139 .7 

1.08 47.76 1 139 .7 

2.40 69.18 1 139 .7 

1.92 29.67 2 140 .7 

.36 6.18 1 140 .7 

the relationships developed for the large basins. The 

lowest standard error of estimate for the equations 

in table 7 is 0.221 log units, or about 52 percent. 

Part of the error is attributable to the inaccuracies 

inherent in suspended-sediment sampling; however, 

much of the error is probably attributable to factors 

not analyzed by the regression model. Factors such 

as the location of sediment source areas and differing soil and cover conditions, with respect to the 

areal distribution of rainfall, must be analyzed 

before individual storm sediment discharges can be 

defined by regression or other modeling techniques. 

EFFECTS OF LAND USE/LAND COVER 

AVERAGE ANNUAL SEDIMENT YlELDS 

Average annual suspended-sediment yields were 

computed for periods of equal land use/land cover 

in the study basins using flow duration and sedi-
42 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

TABLE 6.-Simple correlation coefficients 

Suspended- Mean sediment Storm Peak Antecedent Antecedent sediment concen- runoff discharge discharge day:s discharge (log Qs) tration (log Qr) (log Qp) (log 10 Qa) (Ad) (log C) 

Suspended -sediment 

Williamsburg Run -------------- 1.00 10.84 10.84 10.38 1 -0.37 

Manor Run -------------------- 1.00 1. .50 1 .63 -.07 -.08 

N. Br. Rock Creek -------------- 1.00 1. .84 1 .91 2 .26 2 -.26 

N.W. Br. Anacostia River _______ 1.00 1. .74 1.83 2 .29 -.05 

Nursery Run ------------------- 1.00 1 .81 1.95 .20 -.16 

Batchellors Run 1.00 1 .72 1 .84 

Bel Pre Creek --================ 1.00 1 .76 1 .84 1 .31 2 -.26 

Lutes Run --------------------- 1.00 1 .85 1 .57 

Mean sediment 

Williamsburg Run -------------- 1.00 0.11 10.27 0.05 -0.12 

Manor Run 1.00 -.21 .17 1 -.33 .10 

N. Br. Rock c"i."~~k-============== 1.00 1 .32 1 .53 -.01 -.13 

N.W. Br. Anacostia River _______ 1.00 -.04 2 .33 -.21 .23 

Nursery Run ------------------- 1.00 1,44 1 .79 .10 -.15 

Bel Pre Creek ------------------ 1.00 .12 1 .45 .08 -.03 

Storm runoff, 

Williamsburg Run -------------- 1 0.84 0.11 1.00 10.89 1 0.44 1 -0.39 

Manor Run 1 .50 -.21 1.00 1 .70 1 .32 -.23 

N. Br. Rock c"i-~~k-============== 1 .84 1 .32 1.00 1.92 1 .40 1 -.29 

N.W. Br. Anacostia River 1 .74 -.04 1.00 1.79 1 .56 2 -.27 

Nursery Run ------------======= 

1.81 1.44 1.00 1 .82 1 .26 -.11 

Batchellors Run 1 .72 1.00 1 .80 ---------------- Bel Pre Creek 1 .76 .12 1.00 1.80 1 .38 1 -.35 ------------------ Lutes Run --------------------- 1 .85 1.00 1 .56 

Peak discharge, 

Williamsburg Run -------------- 1

0.84 0.27 10.89 1.00 10.37 1-0.32 

Manor Run -------------------- 1 .63 .17 1 .70 1.00 -.03 -.08 

N. Br. Rock Creek -------------- 1 .91 1 .53 1.92 1.00 1 .33 1 -.29 

N.W. Br. Anacostia River _______ 1 .83 2 .33 1 .79 1.00 1 .35 2 -.30 

Nursery Run ------------------- 1 .95 1 .79 1 .82 1.00 .17 -.19 

Batchellors Run 1 .84 1 .80 1.00 

Bel Pre Creek --================ 

1 .84 2.45 1 .80 1.00 :1.27 1 -.34 

Lutes Run --------------------- 1 .57 1 .56 1.00 

Antecedent discharge. 

Williamsburg Run 10.38 0.05 10.44 10.37 1.00 1 -0.43 -------------- Manor Run -.07 1 -.33 1 .32 -.03 1.00 1 -.44 -------------------- N. Br. Rock Creek -------------- 2 .26 -.01 1 .40 1 .33 1.00 1-.29 

N.W. Br. Anacostia River _______ 2 .29 -.21 1 .56 1 .35 1.00 1 -.40 

Nursery Run ------------------- .20 .10 .26 .17 1.00 2 -.30 

Bel Pre Creek ------------------ :._ .31 .08 1 .38 1 .27 1.00 2 -.25 

Antecedent 

Williamsburg Run 1 -0.37 -0.12 1 -0.39 1 -0.32 1 -0.43 1.00 -------------- Manor Run -------------------- -.07 .10 -.23 -.08 1-.44 1.00 

N. Br. Rock Creek -------------- 2 -.26 -.13 1 -.29 1 -.29 1 -.29 1.00 

N.W. Br. Anacostia River -.05 .23 2 -.27 ~-.30 1-.40 1.00 

Nursery Run ------------------- -.16 -.15 -.11 -.19 2 -.30 1.00 

Bel Pre Creek 2 -.26 -.03 1 -.35 1 -.34 2 -.25 1.00 ------------------

Total precepitation, 

Williamsburg Run -------------- 1 0.64 0.18 10.69 10.69 0.06 0.05 

Manor Run 1 .54 .04 1 .73 1 .63 -.14 .09 -------------------- N. Br. Rock Creek -------------- 1 .56 2 .25 1 .63 1.58 1 -.28 .03 

N.W. Br. Anacostia River 1 .59 2 .27 1.54 1 .54 -.04 .21 

Nursery Run ------------------- 1 .67 1.38 1 .79 L .70 -.12 .12 

Batchellors Run ---------------- .29 .29 .18 

Bel Pre Creek ------------------ 1 .51 .07 1 .69 1 .65 .02 -.20 

Lutes Run --------------------- 1 .78 1.92 2 .38 

Maximum 5-minute 

Lutes Run --------------------- 2 0.36 0.17 10.72 

Maximum 15-minute 

Williamsburg Run 1 0.36 1 0.54 0.08 1 0.37 1 -0.29 0.08 -------------- Manor Run 1 .39 1 .48 -.06 1 .49 1 -.47 .20 -------------------- See footnotes at end of table. 
SEDIMENT DISCHARGE 43 

of storm-related variables 

Total Maximum Maximum Maximum Maximum Maximum Number Chronology Percent Peak preeipi- 5-minute 15-minute 30-minute 1-hour 3-hour of factor construe- ratio tation rainfall rainfall rainfall rainfall rainfall peaks (Tm) tion (log Pr) (log 10 Rt) (log 10 Ros) (log 10 R1s) (log 10 Rso) (log 10 R1h) (log 10 Rsh) (Np) (Cp) 

discharge, log Q. 

0.64 10.36 10.41 10.45 10.55 0.13 0.12 10.27 0.08 1.54 1.39 1.39 1.41 1.43 .14 1 -.33 1 .42 2 .25 1.56 1.35 1.38 1.38 1.49 .16 .05 .14 .05 1.59 .21 .22 2 .28 1.34 -.01 .09 -.05 .07 1 .67 1.55 1.59 1 .65 1.70 2 .33 .16 .01 1.52 

.29 .14 .20 -.02 2.49 

1.51 1 .41 1.43 1.45 1 .49 2 .26 2.26 1.51 -.02 1 .78 2 0.36 2 .33 2 .39 1 -.80 1 .70 1 -.47 

concentration, log c 

0.18 10.54 10.57 10.56 10.44 0.09 -0.20 2 0.23 10.36 

.04 1.48 1.43 1 .37 .18 .05 1 -.59 1.69 1.48 2 .25 1.57 1.59 1.57 1.49 .08 -.14 .19 1.47 2 .27 1.53 1.52 1 .51 1 .37 -.19 2 -.28 .12 1.56 

1.38 1.71 1.73 1.73 1.63 .10 .25 .10 1.78 

.07 1.55 1.53 1.50 1.34 2 .25 1.31 1 .58 1.46 

log Q. 

1 0.69 0.08 0.13 0.19 10.39 0.10 10.29 0.18 -0.14 

1.73 -.06 .01 .11 1 .40 .14 2 .27 2 -.28 2 -.26 

1.63 .03 .06 .08 1.32 .18 .19 .04 1 -.33 

1.54 -.18 -.16 -.09 .12 .15 1.36 -.18 1 -.39 

1.79 .17 .22 2 .33 1.54 1.49 .01 -.11 .04 

.29 -.24 -.18 .05 .08 1 .69 .06 .11 .18 1.39 .15 .08 .20 1 -.48 

1.92 0.17 .18 .27 1 -.59 1.51 1 -.64 

log Qp 

10.69 1 0.37 10.42 10.46 10.59 0.08 10.35 0.10 10.31 

1.63 1.49 1.55 1.58 1 .62 1.22 1 .31 -.18 1.51 1 .58 1.23 2 .26 1 .29 1.46 .12 1 .28 -.02 .07 1 .54 2 .32 1.35 1.40 1 .47 -.01 2 .33 -.12 .25 

1.70 1.61 1.66 1.73 1.78 1.37 .08 -.07 1.59 

.18 .24 1.66 

1.65 1.50 1.56 1.59 1.67 2 .22 1.27 2 .24 .14 2 .38 1 0.72 1.78 1.81 -.13 .05 .27 

log 10 Qa 

-0.06 1 -0.29 2 -0.26 1 -0.27 2 -0.21 0.01 10.27 10.44 -0.16 

-.14 1 -.47 1 -.44 1 -.43 1 -.34 .04 .17 2 -.27 1 -.43 1 -.28 1 -.44 1 -.42 1 -.43 1 -.38 -.01 2 .23 2 .25 1 -.28 

-.04 2 -.29 2 -.28 2 -.27 -.19 .09 1.40 .40 1 -.38 

-.12 -.21 ___;.21 -.22 -.17 -.08 2 .30 .19 -.12 

.02 -.13 -.10 -.11 -.06 0 1.34 2 .21 2 -.25 

days, Ad 

0.05 0.08 0.05 0.04 0.02 -0.08 -0.19 -0.07 0.13 

.09 .20 .21 2 .25 .19 -.17 -.14 .02 .18 

.03 .01 -.01 .02 .01 -.15 -.06 -.02 .06 

.21 .03 .05 .06 .06 .04 1 -.41 .03 -.03 

.12 -.06 -.08 -.06 -.11 .17 -.19 -.14 -.14 

-.20 2 -.21 2 -.21 2 -.23 1 -.28 -.11 -.11 .05 .08 

log 10 Rt 

1.00 10.40 10.43 10.49 1 0.69 0.20 0.12 -0.12 0.08 

1.00 2 .30 1.37 1.47 1 .70 2 .24 .10 -.05 -.02 

1.00 1.41 1.43 1.48 1.65 2 .25 -.03 -.09 -.16 

1.00 .20 .26 1 .34 1.54 .10 .01 -.09 -.03 

1.00 2 .35 1.40 1.52 1.74 1.57 .06 -.06 .14 

1.00 .06 .06 -.04 -.06 

1.00 .28 1 .34 1 .44 1.65 2 .21 -.10 -.05 -.18 

1.00 .06 .15 -.71 

rainfall, log 10 Ros 

1.00 -0.09 0.05 

rainfall, log 10 R1s 

1 0.40 1.00 1 0.98 10.95 1 0.81 0.11 -0.11 -0.11 1

0.66 2 .no 1.00 1 .98 1.93 1.71 2 .27 -.16 2 .22 1 .73 
44 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

N. Br. Rock Creek -------------- N.W. Br. Anacostia River -------

Nursery Run ------------------- Batchellors Run ---------------- Bel Pre Creek ------------------

Lutes Run ---------------------

Williamsburg Run -------------- Manor Run -------------------- N. Br. Rock Creek -------------- N.W. Br. Anacostia River ______ _ 

Nursery Run ------------------- Batchellors Run ---------------- Bel Pre Creek ------------------

Williamsburg Run --------------

Manor Run -------------------- N. Br. Rock Creek -------------- N.W. Br. Anacostia River 

Nursery Run ------------------- Bel Pre Creek ------------------

Williamsburg Run --------------

Manor Run -------------------- N. Br. Rock Creek -------------- N.W. Br. Anacostia River ______ _ 

Nursery Run ------------------- Bel Pre Creek ------------------

Williamsburg Run -------------- Manor Run -------------------- N. Br. Rock Creek -------------- N.W. Br. Anacostia River -------

Nursery Run ------------------- Bel Pre Creek ------------------

Williamsburg Run --------------

Manor Run -------------------- N. Br. Rock Creek -------------- N.W. Br. Anacostia River ______ _ 

Nursery Run ------------------- Batchellors Run ---------------- Bel Pre Creek ------------------

Lutes Run ---------------------

Williamsburg Run -------------- Manor Run -------------------- N. Br. Rock Creek -------------- N.W. Br. Anacostia River -------

Nursery Run -------------------

Bel Pre Creek ------------------ Lutes Run ---------------------

Williamsburg Run --------------

Manor Run -------------------- N. Br. Rock Creek -------------- N.W. Br. Anacostia River -------

Nursery Run ------------------- Batchellors Run ----------------

Bel Pre Creek ------------------ Lutes Run ---------------------

1 Significant at 99 percent confidence level. 2 Significant at 95 percent confidence level. 

Suspendedsediment 

discharge 

(log Q,) 

1 0.35 

.21 

1 .55 

.14 

1 .41 

2 .33 

1

0.41 

1 .39 

1 .38 

.22 

'.59 

.20 

1 .43 

1 0.45 

1.41 

1 .38 

2 .28 

'.65 

1 .45 

1 0.55 

1.43 

1 .49 

1 .34 

1 .70 

1.49 

0.13 

.14 

.16 

-.01 

2 .33 2 .26 

0.12 1 -.33 

.05 

.09 

.16 

-.02 

2 .26 

1 .80 

1 0.27 

1.42 

.14 

-.05 

.01 

1 .51 

1 .72 

0.08 

2 .25 

.05 

.07 

1 .52 

2.49 

-.02 

1-.46 

Mean 

sediment 

concentration 

(log C) 

1 0.57 

1 .53 

1.71 

1 0.56 

1 .37 

1 .57 

1 .51 

1 .73 

1 .50 

1 0.44 

.18 

1.49 

1 .37 1 .63 

1 .34 

0.09 

.05 

.08 

-.19 

.10 

:z.25 

-0.20 

1 -.59 

-.14 

2 -.28 

.25 

2 0.23 

1 .69 

.19 

.12 

.10 

1 .58 

1 0.36 

1.48 

1.47 

.56 

l. .78 

Storm 

runoff 

(log Qr) 

0.03 

-.18 

.17 

-.24 

.06 

.18 

0.13 

.01 

.06 

-.16 

.22 

-.18 

.11 

0.19 

.11 

.08 

-.09 

2 .33 

.18 

1 0.39 

1.40 

1 .32 

.12 1 .54 

1 .39 

0.10 

.14 

.18 

.15 

1.49 

.15 

1 0.29 

2 .27 

.19 

1 .36 

.01 

.05 

.08 1 -.59 

0.18 2 -.28 

-.04 

-.18 

-.11 

.20 

1 .51 

-0.14 

2 -.26 

1 -.33 

1 -.39 

.04 

.08 

1-.48 

1 -.64 

TABLE 6.-Simple correlation coefficients 

Peak discharge 

(log Qp) 

2 0.23 

2 .32 

1 .61 

.24 

1 .50 

l .78 

1

0.42 

1 .55 

2 .26 

1 .35 1 .66 

1 0.46 

1 .58 1 .29 

.40 

1 .73 

'.59 

1 0.59 

1 .62 

1.46 

1 .47 

1 .78 

1 .67 

0.08 

.22 

.12 

-.01 

1 .37 

2 .22 

1 0.35 

1 .31 

1 .28 

2 .33 

.08 

1 .27 

-.13 

0.10 

-.18 

-.02 

-.12 

-.07 

2 .24 

.05 

0.31 

1 .51 

.07 

.25 

1 .59 

\66 

.14 

.27 

Antect!dent 

discharge 

(log 10 Qa) 

Antecedent days 

(Ad) 

Maximum 5-minute rainfall, 

1 -0.44 

2 -.29 

-.21 

-.13 

0.01 

.03 

-.06 

2 -.21 

Maximum 30-minute 

2 -0.26 

1-.44 

1 -.42 

2 -.28 

-.21 

-.10 

1 -0.27 

1 -.43 

1 -.43 

2 -.27 

-.22 

-.11 

2 -0.21 

1 -.34 

1 -.38 

-.19 

-.17 

-.06 

0.01 

.04 

-.01 

.09 

-.08 

0 

1 0.27 

.17 

2 .23 

1 .40 

2 .30 

1 0.44 2 -.27 

2 .25 

.02 

.19 

2 .21 

-0.16 

1-.43 

1 -.28 

1 -.38 

-.12 

2 -.25 

0.05 

.21 

-.01 

.05 

-.08 

2 -.21 

Maximum 1-hour 

0.04 

2 0.25 

.02 

.06 

-.06 

2 -.23 

Maximum 3-hour 

0.02 

.19 

.01 

.06 

-.11 

1 -.28 

Number of 

-0.08 

-.17 

-.15 

.04 

.17 

-.11 

Chronology 

-0.19 

-.14 

-.06 

1-.41 

-.19 

-.11 

Percent 

-0.07 

.02 

-.02 

.03 

-.14 

.03 

Peak ratio, 

0.13 

.18 

.06 

-.03 

-.15 

.08 
SEDIMENT DISCHARGE 45 

of storm-related variables-Continued 

Total Maximum Maximum Maximum Maximum Maximum Number Chronology Percent Peak precipi- 5-minute 15-minute 30-minute 1-hour 3-hour of construe- tation rai.nfall rainfall rainfall rainfall rainfall peaks factor tion ratio 

(log 10Rt) (log 10 R05) (log 10 R15) (log 10 Rao) (log 10 R1~t) (log 10 Rah) (Np) (Tm) (Cp) (log Pr) 

log 10 R1s-Continued 

.10.41 1.00 1 0.98 1 0.95 1 0.81 0.19 -0.16 -0.07 1 0.51 

.20 1.00 1 .99 1.96 1 .77 .05 -.23 .03 1 .77 2 .35 1.00 1 .99 1 .95 1 .75 .20 -.02 .09 1 .84 

.06 1.00 -.06 1 .68 1 .28 1.00 1 .98 1.94 1 .74 .14 .04 .07 1 .64 

.06 1.00 1.51 

rainfall, log 10 R1o 

1 0.43 1 0.98 1.00 10.98 1 0.85 0.07 -0.11 -0.08 10.67 1.37 1 .98 1.00 1 .97 1.77 2 .27 -.13 .20 1 .72 

1.43 1 .98 1.00 1.98 1 .84 .19 -.16 .02 1.51 2 .26 1.99 1.00 1 .98 1 .80 .04 -.20 .02 1.78 

1.40 1 .99 1.00 1 .98 1.80 .22 .03 .08 1.85 

.06 1.00 -.02 1.71 1.34 1 .98 1.00 1 .98 1.80 .18 .07 .06 1 .63 

rainfall, log 10 R1h 

2 0.49 10.95 10.98 1.00 1 0.90 0.05 -0.09 -0.08 1 0.64 

1.47 1.93 1.97 1.00 1 .86 .22 -.09 .15 1 .65 1 .48 1 .95 1.98 1.00 1 .89 .15 -.16 0 1 .51 1 .34 1.96 1.98 1.00 1.87 0 -.17 .03 1.74 1.52 1.95 1 .98 1.00 1 .89 2 .28 .04 .08 1 .82 

1.44 1 .94 1 .98 1.00 1 .89 .16 .08 .04 1 .58 

rainfall, log 10 Rah 

10.69 10.81 1 0.85 10.90 1.00 0.02 -0.02 -0.05 2 0.49 1.70 1.71 1.77 1 .86 1.00 .17 .02 .02 1 .36 

1..65 1 .81 1 .84 1 ·.89 1.00 .08 -.10 -.03 1.34 1.54 1 .77 1.80 1 .87 1.00 -.01 -.05 .07 1 .51 1 .74 1 .75 1 .80 1.89 1.00 2 .33 .12 .10 1 .62 1 .65 1 .74 1 .80 1 .89 1.00 .13 .11 .01 1 .34 

peaks, NP 

0.20 0.11 0.07 0.05 0.02 1.00 0.01 -0.03 -0.06 2 .24 2 .27 2 .27 .22 .17 1.00 .04 0 .13 2 .25 .19 .19 .15 .08 1.00 -.06 .02 -.16 

.10 .05 .04 0 -.01 1.00 0 -.12 -.25 1.57 .20 .22 2 .28 2 .33 1.00 .03 .03 -.06 2 .21 .14 .18 .16 .13 1.00 .13 .08 .08 

factor, Tm 

0.12 -0.11 -0.11 -0.09 -0.02 0.01 1.00 -0.15 0.16 

.10 -.16 -.13 -.09 .02 .04 1.00 1 -.85 .09 

-.03 -.16 -.16 -.16 -.10 -.06 1.00 1 -.54 .19 

.01 -.23 -.20 -.17 -.05 0 1.00 2 .31 -.07 

.06 -.02 .03 .04 .12 .03 1.00 1.49 .13 

-.04 -.06 -.02 1.00 .01 

-.10 .04 .07 .08 .11 .13 1.00 .37 ~ .25 

1 -.61 -0.09 -.08 1.00 1 -.91 1 .57 

construction, cp 

-0.12 -0.11 -0.08 -0.08 -0.05 -0.03 -0.15 1.00 -0.19 

-.05 .22 .19 .15 .02 0 1 -.85 1.00 .10 

-.09 -.01 .02 0 -.03 .02 1 -.54 1.00 -.17 

-.09 .03 .02 .03 .07 -.12 2 .31 1.00 .09 

-.06 .09 .08 .08 .10 .03 1.49 1.00 .02 

-.05 .07 .06 .04 -.01 .08 1 .37 1.00 .02 

0.05 1 -.91 1.00 

log Pr 

0.08 1 0.66 1 0.67 1 0.64 1 0.49 -0.06 0.16 -0.19 1.00 

-.12 J .73 1 .72 1 .65 1 .36 .13 .09 .10 1.00 

-.16 1 .51 1 .51 1 .51 1 .34 -.16 .19 -.17 1.00 

-.03 1 .77 1 .78 1 .74 1 .51 -.25 -.07 .09 1.00 

.14 1 .84 1 .85 1.82 1 .62 -.06 .13 .02 1.00 

-.06 1 .68 1.71 .01 1.00 

-.18 1 .64 1 ,63 1.58 1 .34 .08 2 .25 .02 1.00 1 -.71 1 .51 1.00 
46 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

TABLE 7.-Regression coefficients, multiple correlation coefficient, and standard erTor of best equations explaining the va1·iatio-n of stornt suspended-sediment discharge 

Maxi- Maxi- Stand- Ant~ Mul- ard Number Peak Total Percent mum mum Chro- cedent tiple error Reg res- Storm 30- 15- Peak of ind~ runoff dis- precipi- construe- miniute minute nology ratio dis- oorrela- of sion pendent (log Qr) charge tat'..on tion rainfall rainfall factor (log Pr) charge tion esti- con- variables (log Qp) (log Rt) (Cp) (Tm) (log coeffi- mate stant (log (log 10 Qa) cie.nt (log 10 Rao) 10 R15) units) 

Williamsburg Run near Olney 

1 ------------ 2 

3 

4 

1 1.08 

1 1.03 

1 .99 1 .94 

1 0.05 

2 .04 1 0.13 

0.84 0.304 0.387 

.90 .253 .051 

.91 .240 -.166 

.91 .238 -.241 

North Branch Rock Creek near Norbeck 

1 ------------

2 ------------

3 ------------

4 ------------

1 1.50 

0.30 

1 1.49 

1 1.44 

1 1.13 

1 0.15 

1 .15 

1 .14 

1 0.23 

1 .29 

0.91 0.255 -1.22 

.92 .239 -1.53 

.93 .223 -1.63 

.93 .221 -1.46 

Manor Run near Nor beck 

1 ------------ 2 

3 

4 0.09 

1 0.83 

1 1.07 

1 1.24 

1 1.16 

2 -0.32 

-.01 

1 -0.01 

1 -.01 

1 .03 

0.63 0.410 0.334 

.84 .288 .371 

.85 .278 .385 

.86 .280 .411 

Northwest Branch Anacostia at Norwood 

1 ------------

2 ------------

3 ------------

4 ------------

1 0.97 

'1.19 

1 1.31 

'1.20 0.35 --- 1 -0.004 

--- 2 -.004 

1 0.88 

1 .92 1 .86 

0.74 0.336 0.530 

.84 .274 -.522 

.87 .252 -.470 

.87 .250 -.743 

Batchellors Run at Oakdale 

1 ------------

2 ------------

3 ------------

4 ------------

1 1.18 

1 1.13 

1 1.07 

1 1.07 

0.44 

.43 -0.001 

1 0.88 

1 .90 

1 .90 

0.72 

.84 

.85 

.85 

0.372 0.049 

.297 -.757 

.295 -1.283 

.300 -1.211 

Nursery Run at Cloverly 

1 ------------

2 ------------

3 ------------

4 ------------

0.21 

.29 

1 1.49 

'1.47 

1 1.33 

1 1.34 -0.22 

2 0.003 

2 .003 

2 .003 

0.95 

.95 

.96 

.96 

0.253 -1.33 

.245 -1.45 

.242 -1.34 

.243 -1.10 

Bel Pre Creek at Layhill 

1 ------------

2 ------------

3 ------------

4 ------------

1 1.12 

'1.44 

1 1.31 

'1.18 

1 0.051 

1 .052 2 0.28 

1 1.09 

1 .97 

1 .60 

0.76 

.85 

.91 

.92 

0.402 0.458 

.324 -.791 

.256 -1.088 

.248 -.934 

Lutes Run at Lutes 

1 ------------ 2 

3 

4 

1 1.52 

'1.05 

1 1.32 

1 1.24 

1 Signicant at 99 percent confidence level. 2 Significant at 95 percent confidence level. 

ment-transport curves as described by Miller 

(1951). The number of yields estimated for each 

basin varied depending on land-use/land-cover 

changes in the basins. For example, six average, 

annual yields were estimated for the Williamsburg 

Run basin because of changes in the amount and 

location of construction within the basin. In the 

rural basins, only one average annual yield was 

estimated since the land use/land cover was essen-

--- 1 -0.008 

1 -.010 

0.14 1 -.010 

1 0.66 

.52 

0.85 

.93 

.96 

.96 

0.473 0.438 

.345 1.37 

.274 .520 

.277 .582 

tially constant during the study period. A total of 

27 yields was determined for the eight basins. 

The initial selection of periods for which average 

annual sediment yields were to be estimated was 

based on the variation of land use/land cover between 1967 and 1974. Periods of equal land use/ 

land cover were· determined by examining aerial 

photographs, field notes, and grading and paving 

permits furnished by the Montgomery County D&-
SEDIMENT DISCHARGE 47 

partment of Public Works. Because of constantly 

changing conditions on construction sites, it was not 

possible to define exact periods of equal land use/ 

land cover, but the beginning and ending of each 

period were selected so that the land use/land cover 

on aerial photographs would be representative of 

average conditions during the period. An effort was 

made to delineate periods by the amount of construction and the location of construction within the 

basins so that a range of physical conditions on con"' 

struction sites (slope, proximity to stream, and so 

forth) could be evaluated. 

Once the periods were selected, sediment-transport curves were prepared for the periods having 

adequate storm data. The curves were developed 

from logarithmic plots of daily suspended-sediment 

discharges and the corresponding daily water discharges. Particular attention was given to the medium and high ranges of water and sediment discharge since most of the annual sediment load was 

transported during large storms. Curves for severa] 

periods were not used because the high ends of the 

curves were poorly defined or because a disproportionate number of storms were sampled during 

either the growing or dormant season. 

The sediment-transport curves were used in conjunction with duration curves of water discharge 

for the corresponding streams to compute the average annual sediment yields. Flow-duration curves 

for the period 1967-74 were available for all stations except Lutes Run and Batchellors Run. Since 

only data for days with storm runoff and selected 

base-flow days were available at these two stations, 

curves were estimated using graphical-regression 

methods and the duration curves of the other sites. 

An example of the computation of the average 

annual sediment yield is illustrated by figure 14 and 

table 8. Average water discharges for selected time 

intervals were determined from the flow-duration 

curves (fig. 14A). Suspended-sediment discharges 

corresponding to the water discharges. were determined from sediment-transport curves and multiplied by the duration intervals of water discharge 

to calculate the average annual sediment discharge. 

In the example, the average water discharge for 

2.5 to 4.5 percent of the time is 14 fV/s or 0.40 

m3/s for Williamsburg Run (fig. 14A). The corresponding suspended-sediment discharge is 29 tons 

or 26 t (fig. 14B). Multiplying the suspended-sediment discharge by the time interval for each interval in table 8 and dividing the sum of column 5 

(table 8) by 100 yields the mean daily sediment discharge. The mean daily discharge times 365 days 

TABLE B.-Example of compu,tation of average annual sus- pended-sediment discharge 

[Data from 1967-74 duration curve and January 1972 to December 1973 sediment-transport curve of Williamsburg Run near Olney] 

Sus-: 

Water Sus- pendedCumu- Time Mid- dis- pended- seklilative in ordi- charge sedi- ment 

time inter- nate (cubic ment dis-

(per- val (pe~ feet dis- charge 

(per- per for cent) c$t) cent) sec- charge inter- on d) (tons) val (tons) 1 

(1) (~) (3) (4) (5) (6) 

0.25 0.25 0.125 68 260 65 

.75 .50 .50 42 163 81 

1.5 .75 1.125 32 119 89 

2.5 1.0 2.0 20 61 61 

4.5 2 3.5 14 29 58 

8.5 4 6.5 6.5 5.2 21 

15 6.5 11.75 3.5 .9 5.8 

25 10 20 2.5 .3 3.0 

35 10 30 1.9 .1 1.0 

45 10 40 1.6 0 0 

55 10 50 1.4 

75 20 65 1.0 

95 20 85 .65 

100 5 97.5 .32 Total __ 384.8 

Mean daily suspended-sediment discharge=384.8-T100=3.85 tons. Average annual suspended-sediment discharge= 3.85 X 365 = 1,400 tons. 1 Column 6 =column 2 X column 5. 

equals the average annual suspended-sediment discharge. 

The average annual suspended-sediment yields. 

calculated by this method represent the average 

annual yields that would have been expected between 1967 and 197 4 if land-use/land-cover conditions at each site had remained the same as the 

average during the selected periods. The use of the 

1967-74 flow-duration curves assures that the water 

discharge component of the computations was equal 

for each period at each site. The one questionable 

component of computations is whether the sediment 

data used for developing the individual sedimenttransport curves were significantly affected by different climatic conditions during the selected 

periods. A change in the statistical distribution of 

total precipitation for the sample storms or a change 

in the intensity or time of concentration of sto·rm 

runoff could result in a substantial bias in the computed sediment yields. However, the regression 

models discussed previously indicate no substantial 

change in storm magnitude or intensity during the 

period of record. 

Another factor that could affect the computed 

yields is the total precipitation during the selected 

periods. Miller (1951) found that the flow-duration 

sediment-transport curve method generally overestimated the long-term load when sediment data 

were collected during dry years and underestimated 

it when data were collected during wet years. The 

estimate may be incorrect because the greater number of storms during wet years exhausts the supply 

of sediment readily available for transport. AI-
48 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

though the total load for the year is higher, the 

average load per storm is less than during dry 

years. This explanation may not be valid for urban 

construction sites where the land surface is reworked frequently for right-of-way grading, installation of utilities, lot grading, and final grading 

prior to stabilization. 

The calculated suspended-sediment yields and 

land-use/land-cover conditions corresponding to the 

sample periods are listed in table 9. The basin sediment yields range from 0.27 to 11.3 tons/acre (0.61 

to 25.3 t/hm2 ). Land under construction ranges from 

0 to 13.9 percent of drainage area. Cropland ranges 

from 0 to 43.8 percent, and urban land ranges from 

0 to 54.2 percent of drainage area. 

Regression equations were computed to determine the effect of the land-use factors on suspendedsediment yield. Equation 1, which is the simple 

TABLE 9.-Average annual suspended-sediment yields 

and selected land-use/land-cover factors 

Basin 

sediment 

yield 

(tons/ 

Percentage of basin area 

Period 

acre) 

Cropland Urban 

Williamsburg Run near Olney, Md. 

Oct. 1966-Mar. 1968 ------- Apr. 1968-Mar. 1969 ______ _ 

Apr. 1969-Mar. 1971 ------- Apr. 1971-Dec. 1971 ------- Jan. 1972-Sept. 1973 ------- Jan. 1974-Sept. 1974 -------

1.98 

1.61 

1.18 

1.16 

.98 

.57 

43.8 

43.3 

42.1 

29.9 

29.8 

29.0 

0.1 

5.3 

8.1 

12.0 

16.0 

24.7 

North Branch Rock Creek near Norbeck, Md. 1 

Oct. 1966-Mar. 1968 ------- Apr. 1969-Mar. 1971 ------- Apr. 1971-Dec. 1971 ------- Jan. 1972-Dec. 1973 ------- Jan. 1974-Sept. 1974 -------

2.07 

2.01 

1.39 

1.43 

1.33 

26.4 

25.9 

25.3 

25.3 

25.3 

Manor Run near Norbeck, Md. 

Mar. 1967-Sept. 1968 ------- 11.26 Jan. 1969-Dec. 1969 ------- 10.34 Apr. 197Q-Dec. 1970 ------- 4.92 Feb. 1971-Dec. 1972 _______ 2.05 

Apr. 1973-Aug. 1974 ------- 1.32 

3.9 

4.8 

4.8 

4.8 

4.8 

0.4 

,8 

1.8 

2.7 

3.7 

2.5 

9.4 

14.9 

19.8 

23.8 

Northwest Branch Anacostia River at Norwood, Md. 

Jan. 1968-Mar. 1974 ------- 0.96 24.9 

Nursery Run at Cloverly, Md. 

May 1967-Aug. 1974 ------- 0.62 10.3 

Batchellors Run at Oakdale, Md. 

Aug. 1967-Sept. 1973 ------- 0.32 20.3 

Bel Pre Creek at Layhill, Md. 

Mar. 1963-Dec. 1964 ------- Jan. 1966-Dec. 1967 ------- Jan. 1968-Dec. 1969 ------- Jan. 197o-Dec. 1971 ------- Jan. 1973-Sept. 1974 -------

0.27 

3.31 

3.27 

2.13 

1.90 

6.5 

2.2 

2.2 

1.8 

1.7 

Lutes Run at Lutes, Md. 

Oct. 1966-Jan. 1968 ------- Mar. 1968-Apr. 1970 ------- June 1973-Sept. 1974 -------

5.08 

2.79 

2.21 

0 

0 

0 

0 

0 

0 

0 

4.6 

8.4 

11.0 

20.8 

51.2 

54.2 

54.2 

Construetion 

7.6 

4.7 

3.1 

5.1 

6.2 

1.0 

1.8 

1.3 

1.3 

1.1 

.3 

11.3 

9.6 

7.4 

4.6 

.9 

0.3 

0.7 

0 

13.9 

10.4 

9.2 

13.1 

9.8 

4.3 

1.2 

, Sediment yield and land-use/land-cover percentages equal total for 

North Branch Rock Creek near Norbeck minus the contribution of the Williamsburg Run tributary. 

linear relation between the logarithm of the sediment yield and percentage of the basin under construction, was the best equation for explaining the 

variability of sediment yield. 

Log Y.-=0.059 C-0.047 (1) 

where 

Ys =suspended-sediment yield, in tons per 

acre; 

C =percentage of land under construction. 

Forty-seven percent of the variation of the sediment 

yield is explained by this equation. The standard 

error of estimate is 0.28 log units, or about 62 percent. The use of percentage of urban and percent-1 

age of cropland as additional variables did not significantly improve the explained variation of sediment 

yield. The addition of the percentage of urban land 

increased the explained variation to 50 percent, and 

the addition of the percentage of cropland as a third 

independent variable increased the explained variation of sediment yield to 51 percent. The standard 

errors of estimate for both equations are 0.28 log 

units, the same as the simple relation between sediment yield and percentage of construction. 

The relatively low percentage of variation explained by the regression equations is illustrated by 

the s.catter of data points in figure 15. This large' 

scatter indicates that factors other than the vari10 0 

z 0 0 z 

0 ~ (/) 

~ 100 ~ (/) 

~ (/) 

~ 1.0 ffj 

tu 

~ (.) S::' co CD :::J :::J (.) 

10 (.) 

~ ~ L.U. L.U. (.!J (.!J a:: 0.1 a:: <( <( I I (.) (.) (/) (/) 0 0 z 

<( z 

::g 1.0 ~ 

~ 

::::; ::::; <i:' 0.01 <i:' 0 0 

0.1 L___L_LL._:c...L.._-,L----::1:-----::1:::------=---;;:::;--;~~ 

0.01 0.1 0.5 1 5 

PERCENTAGE OF DAYS INDICATED DISCHARGE WAS EXCEEDED 

FIGURE 14.-Example of flow-duration (A) and suspendedsediment transport (B) curves used for computing average annual sediment loads. A, William!\burg Run flowduration curve, 1967-74. B, Williamsburg Run sedimenttransport curve, January 1972 to December 1973. 
SEDIMENT DISCHARGE 49 

DAILY WATER DISCHARGE, IN CUBIC METERS PER SECOND 

0.1 1.0 

• 

EXPLANATION • 

• Daily value 

0 Average of 

discharge ciass 

100 100 

• 

• 

en en • w z z 

0 -------------------------------------------------------------·---------------- z 1- 0 

z I 

1-

w~ I • z 

(!) w~ 

a: • (!) <( • a: I <( u 10 I en 10 u iS en 

1- iS 

z 1- w z ::E w 

iS ::E w • iS en • w 6 en w 6 Q • w z Q w z (L w en (L 

:::::> • en 

en :::::> 

>- 1.0 en .....J • • 1.0 >- ~ .....J 

Q ~ 

• Q 

~ • 

t • 

• 

I 

I 

I 0.1 0.1 f 

D1 10 100 

DAILY WATER DISCHARGE, IN CUBIC FEET PER SECOND 

FIGURE 14.-Continued. 
50 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

w 

a: 

u 

<{ 

a: 

w 

a.. 

en 

z 

0 

1-

z 

6 

_J 

w 

> 

1-

z 

w 

~ 

5 

w 

en 

6 

w 

0 

z 

w 

a.. 

en 

:::::> 

en 

_J 

<{ 

:::::> 

z 

z 

<{ 

w 

(!) 

<{ 

a: 

w 

~ 

50 

10 

5 

0.5 

0 

EXPLANATION 

DATA TREND 

POINT LINE 

0 ....................... . 

6 ----

() ------------ \7 

. ----

.& 

Williamsburg Run 

N. Branch Rock Creek 

Manor Run 

Bel Pre Creek 

Lutes Run 

NW. Branch Anacostia River 

5 10 

PERCENTAGE OF BASIN AREA UNDER CONSTRUCTION 

FIGURE 15.-Relation of suspended-sediment yieldto percentage of drainage basin under construction. 

100 

10 

15 

a: 

w 

1-

w 

~ 

0 

1-

u 

w 

I 

w 

a: 

<{ 

:::::> 

0 

en 

a: 

w 

a.. 

en 

w 

z 

z 

0 

1-

z 

6 

_J 

w 

> 

1-

z 

w 

~ 

5 

w 

en 

6 

w 

0 

z 

w 

a.. 

en 

:::::> 

en 

_J 

<{ 

:::::> 

z 

z 

<{ 

w 

(!) 

<{ 

a: 

w 

> <{ 
SEDIMENT DISCHARGE 51 

abies used in the regression equations affect the 

suspended-sediment yields of the basins. The lines 

on figure 15, which repres.ent the approximate relation between sediment yield and percentage of construction for different periods on individual basins, 

further illustrate the variation of sediment yields. 

Apparently, other basin factors such as slope or 

soil conditions caused substantially greater sediment 

yields in the Manor Run, North Branch Rock Creek, 

and Lutes Run basins than in the Bel Pre Creek 

and Williamsburg Run basins. 

CONSTRUCTION-SITE SEDIMENT YIELDS 

To evaluate the variation of suspended-sediment 

yields from construction sites, a simple arithmetic 

procedure was used to successively eliminate the 

part of each basin yield attributable to other 

land use/land cover, so that the remainder represented only the yield from construction sites. Land 

use/land cover in each period for each basin was 

first summarized in the following categories: Forest 

land, grass, crops, rural residential, urban residential, public and commerci.al, and construction. These 

categories represent the same general categories of 

table 2 except that the impervious category of farmland and parks was placed in the cropland category 

because most of this area consisted of dirt roads 

with unimproved roadside ditches. 

The next step was to estimate suspended-sediment 

yields. for the different land-us.e/land-cover categories with relatively low erosion potential. Williams and George (1968) determined that the sediment yield from basins in Pennsylvania with 100 

percent forest cover averaged 0.03 (ton/acre) /yr 

[ (0.07 t/hm2 ) /yr]. Sediment yields from forested 

watersheds in Missis.sippi were reported as 0.02 

(ton/acre)/yr [(0.04 t/hm2 )/yr] by Ursie and 

Dendy (1965). Wark and Keller (1963) found that 

forested areas in the Poto·mac River basin averaged 

about 0.03 (ton/acre) /yr [ (0.07 t/hm2 ) /yr]. On the 

basis of these previous investigations, the annual 

sediment yield from forested areas in the study 

basins was assumed to be 0.03 ton/acre (0.07 

t/hm2 ). 

Ursie and Dendy (1965) found the annual sediment yield of grazed pastures and abandoned fields 

in Mississippi averaged 1.6 and 0.12 tons/acre (3.6 

and 0.27 t/hm2 ), respectively. The grass category 

in this study is generally well-managed turf on golf 

courses, abandoned fields, or lightly grazed pastures. 

The·se conditions are probably comparable to the 

abandoned fields in Mississippi; therefore, an annual 

sediment yield of 0.2 ton/acre (0.45 t/hm2 ) was assumed for the grass category. 

The yields for rural residential and commercialpublic areas within the basins were assumed to be 

0.5 and 0.3 (ton/acre) /yr [ (1.1 and 0.7 t/hm2 ) /yr], 

respectively. The rural residential yield was ass.umed to be considerably higher than the yield for 

grass because a fairly large part of the rural residential area was used for large gardens and for 

grazing horses. Also, some of the roads and roadside ditches in these areas were unimproved. The 

yield for co·mmercial-public land was assumed to be 

somewhat lower than rural residential because• most 

of this land was in either well-managed turf or impervious .surfaces. It was assumed to be greater than 

grass, however, because of accelerated erosion in 

the stream channels immediately downstream 

caused by increased runoff from the impervious surfaces.. This subject will be discussed in more detail 

in the section on stream-channel erosion. 

Suspended-sediment yields for urban residential, 

cropland, and construction areas were determined by 

subtracting the assumed yields for forest land, pasture, rural residential, and public-commercial from 

the total sediment yields of each basin. For example, 

the sediment yield for cropland was determined for 

four basins during periods when there were no 

urban residential or construction areas. Example 1 

for Bel Pre Creek during the March 1963 to December 1964 sample period illustrates this method. 

EXAMPLE 1.-Bel Pre Creek, March 1963 to December 1964 

Average annual sediment yield= 295 tons; drainage area= 1,082 acres. 

(1) (2) (3) 

Land use/land cover Acres Sediment Columna 

yield (2) X (3) 

Forest --------------- 619 0.03 18.6 

Pasture ------------- 375 .2 75 

Rural residential ----- 18 .5 9 

Crops --------------- 70 

Sum 1,082 102.6 ----------- Annual sediment yield from cropland= (295-102.6) tons+ 

70 acres=2.7 tons/acre. 

The computed annual yields for cropland in the four basins 

were: 

Tons/Acre 

Batchellors Run ------------------ 0.65 

Bel Pre Creek -------------------- 2.7 

Nursery Run --------------------- 4.3 

Northwest Branch 

Anacostia River ----------------- 3.3 

Similarly, the annual yield for urban residential was 

determined by subtracting other known or assumed 

yields from the total yields of the basins during 

periods with no construction or only minimal construction activities (Example 2). 
52 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

EXAMPLE 2.-Lutes Run, June 1973 to September 1974 

Average annual sediment yield=664 tons, drainage area=301 acres. 

(1) (2) (3) 

Land use/land cover Acres Sediment 

yield 

Pasture --------- 17 0.2 

Forest land 54 .03 

Rural residential _ 48 .5 

Urban residential _ 163 

Commercial-public_ 15.5 .3 

Construction ----- 3.5 Assumed 10 

Sum ------- 301 

Annual sediment yield from urban land= 

(664-68.7) tons -7- 163 acres= 

3.65 tonsjacre. 

Columns 

(2) X (3) 

3.4 

1.6 

24 

4.7 

35 

68.7 

The annual suspended-sediment yields computed for 

Lutes Run and Manor Run were 3.6 and 3.9 tons/ 

acre (8.1 and 8.7 t/hm2 ), respectively. 

The computed values of cropland and urban residential were then used with the other assumed 

values to compute the construction-site sediment 

yield for ba.sins with active construction. If cropland 

or urban yields were computed for individual basins, 

these values were used; otherwise, the average of 

the yields computed for all basins were used. 

Construction-site sediment yields computed for 

the different time periods in the five basins with 

active construction ranged from 7.2 to 100.8 (tons/ 

acre)/yr [(16.1 to 226 t/hm2 )/yr] and averaged 

32.7 (tons/acre) /yr [ (73.3 t/hm2 ) /yr]. The yields 

are comparable to those found by previous investigators. Vice, Guy, and Ferguson (1969) reported 

that the yield from highway construction in northern Virginia was about 100 tons/acre (220 t/hm2 ). 

Guy and Ferguson (1962) estimated the yield from 

residential construction sites near Lake Barcroft, 

Va., to be 39 tons/acre (87 t/hm2 ). 

Several factors could affect the variation of construction-site yields. Slope conditions on the sites, 

proximity to stream channels, buffer zones of natural vegetation, ratio of the largest construction 

site to total construction area in the basin, and the 

percentage of construction area with sediment controls were factors considered for analysis. Other 

factors are probably significant, but could not be 

evaluated properly. Soils, particularly their relative 

erodibility, could result in substantial variation of 

sediment yields; however, the soil conditions were 

generally uniform except for one or two sites. The 

density of housing could affect the construction 

methods, but, again, the conditions in the basins 

were too uniform to detect significant differences. 

Another important factor that could not be evaluated for use in the analysis was the length of time 

that sites were not stabilized, as the period of nonstabilized construction activity varied among sites 

within an individual basin. 

Average slope on the construction sites was determined by using the average slope map shown in 

plate 1 as an overlay to the aerial photographs of 

the study basin. The construction area in each slope 

class was determined with a dot-grid, and a 

weighted average was calculated. This method averaged the slope conditions of different sites within 

the basins, which could obscure the influence of extreme conditions. However, it did provide a relative 

index of slope for evaluating the variation of yields 

among the basins. Average slopes ranged from 4.30 

to 7.34 percent. 

The amount of construction within 200 ft (61 m) 

of stream channels was selected as an arbitrary 

index of the proximity of construction to the drainage net. An overlay of streams shown on the U.S. 

Geological Survey quadrangles and U.S. Soil Conservation Service soil maps of the study basins was 

used with aerial photographs to measure the percentage of construction area within this category. 

Construction within 200 ft (61 m) of stream 

channels (hereafter referred to as the proximity 

factor) ranged from 17.4 to 64.8 percent of the total 

construction area in the basins. 

The existence of buffer zones of natural vegetation between the construction sites and the stream 

channels was also evaluated. The percentage of construction area without a 200 ft ( 61 m) strip of 

natural vegetation between the site and the natural 

drainage to the stream channels was determined 

from aerial photographs. This parameter ranged 

from 52 to 100 percent. 

The size of the construction sites was also considered as a possible source of variation of site 

yields. The area of the largest construction site as 

a percentage of the total construction area within 

each basin was used as an index of this parameter. 

The last parameter considered for analysis was 

the percentage of the construction sites with adequate sediment-control measures. This parameter 

was based on county-wide field surveys, which will 

be discussed in more detail in the section on sediment control. Some adjustments to, the average 

values determined by the field surveys were made 

in cases where observations by project personnel 

were available. These adjustments to the average 

values were particularly necessary during the initial 

periods of development when many sites did not 

have controls. Sites with control measures constituted 0 to 68 percent of the total construction 

area in the basins. 
SEDIMENT DISCHARGE 53 

Construction-site suspended-sediment yields and 

the corresponding site facto·rs are summarized in 

table 10. These data were analyzed graphically and 

with correlation and multiple regression techniques. 

to determine the relative effect of each site factor 

on construction-site yields. Graphical and correlation analyses indicate that there is a poor relationship between site yields and the individual site factors. Correlation coefficients between the logarithm 

of site yield amd the site factors are: 0.36 for average slope, 0.36 for the p·roximity factor, 0.28 for the 

percentage of construction area represented by one 

large site, 0.18 for construction sites without buffer 

zones, and -0.67 for the percentage of construction 

sites with sediment controls. The correlation coefficient for site yield amd percentage of controls is the 

only one significant at the 95 percent confidence 

level. 

The multiple effect of the site factors was evaluated with a multiple-regression model. The logarithm of construction-site sediment yield was the 

dependent variable and the site factors were the 

independent variables. Equations 2, 3, and 4 illustrate the results of the regression analysis. 

log Sv = 1.73-0.010 C, S.E.=0.24 log units (2) 

log Sv=0.86+0.143 S-0.010 C, S.E.=0.22 

log units (3) 

Jog Sv=0.67+0.143 8+0.002 B-0.010 C, S.E. 

= 0.22 Jog units ( 4) 

where 

Sv =construction site suspended-sediment 

yield, in tons per acre per yr; 

C= percentage of construction area with sediment control; 

S = average slope of construction sites, in percent; 

B =percentage of construction area without a 

buffer of natural vegetation. 

Equation 2 explains 45 percent of the variation of 

construction-site yield. Equations 3 and 4 explain 

59 and 60 percent of the variation, respectively. The 

use of additional variables did not significantly increase the explained variation of site yield. 

The analysis suggests that sediment controls used 

to limit erosion and sediment transport from the 

construction sites significantly reduced construeTABLE 10.-Construction-site sediment yields and related factors 

Ratio 

Average Construe- of Construe- ConstrueAverage tion area tion tion Construe- annual slope are& of area area 

ti'on sediment of within largest without with Period area yield construe- 200ft develop- 200ft adequate 

(acres) (tons/ tion of ment buffer sediment 

acres) area channel to zon<! control (percent) (percent) total (percent) (percent) 

(percent) 

Williamsburg Run near Olney, Md. 

Oct. 1966-Mar. 1968 (1) 109 20.6 5.45 25.3 99.3 96.6 10 

Apr. 1968- Mar. 1969 (2) 68 24.4 5.75 20.4 83.3 85.2 36 

Apr. 1969-Mar. 1971 (3) 45 22.8 5.97 26.1 39.8 52.0 42 

Apr. 1971-Dec. 1971 (4) 74 14.4 4.30 20.0 24.0 88.0 49 

Jan. 1972-Sept. 1973 (5) 90 8.6 5.15 17.4 39.0 75.6 60 

North Branch Rock Creek near Norbeck, Md.' 

Oct. 1966-Mar. 1968 (1) 87 46.4 6.70 52.1 45.1 88.7 5 

Apr. 1969-Mar. 1971 (2) 60 63.0 7.64 20.3 74.3 81.4 36 

Apr. 1971-Dec. 1971 (3) 63 12.5 7.34 29.2 58.3 91.7 49 

Jan. 1972-Dec. 1973 (4) 52 15.1 6.94 7.0 49.2 52.8 60 

Manor Run near Norbeck, Md. 

Mar. 1967-Sept. 1968 (1) 73 96.4 6.38 36.6 87.2 81.7 10 

Jan. 1969-Dec. 1969 (2) 62 100.8 6.72 41.7 88.9 100.0 15 

Apr. 1970-Dec. 1970 (3) 48 54.4 5.90 37.5 80.0 87.5 27 

Feb. 1971-Dec. 1972 (4) 30 21.2 7.28 22.2 46.1 88.6 52 

Bel Pre Creek at Layhill, Md. 

Jan. 1966-Dec. 1967 (1) 150 21.1 5.72 19.3 88.1 65.1 0 

Jan. 1968-Dec. 1969 (2) 113 26.4 5.92 32.4 92.4 93.8 35 

Jan. 1970-Dec. 1971 (3) 100 16.5 5.56 34.8 83.0 67.8 45 

Jan. 1973-Sept. 1974 (4) 142 7.2 5.58 25.0 91.7 97.0 68 

Lutes 

Oct. 1966-Jan. 1968 (1) 29.5 31.8 5.42 55.0 35.0 75.0 0 

Mar. 1968-Apr. 1970 (2) 13.0 17.0 6.58 64.8 66.7 78.5 38 

1 Represents North Branch Rock Creek near Norbeck excluding Williamsburg Run. 
54 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

tion-site suspended-sediment yields .. The slope of the 

construction sites was also a significant factor affecting the site yields. Construction on mild slopes 

resulted in lower sediment yields than construction 

on steep slopes. The relative size of the largest construction site in the basin and the amount of construction within 200ft (61 m) of the stream channel did not significantly affect the suspended-sediment yields. This outcome could be due to the small 

number of observations available, or due to the 

effect of other factors not analyzed in the regression 

analysis. 

Figure 16 illustrates the slope factor in two of 

the study basins. The average slope on construction 

sites in Bel Pre Creek basin was 5.72 percent during the January 1966 to December 1967 sampling 

period, and the average annual sediment yield was 

21.1 (tons/ acre) / yr [(47.3 t/ hm2 ) / yr]. In contrast, 

39" 

06' 

MANOR RUN BASIN 

EXPLANATION 

Construction area 

Average slope conditions 

in percent 

D o-3 

w 3- 8 

§ 8-15 

• 15-25 

-· · - Basin dra inage divide 

the average slope on the Manor Run construction 

sites was 6.38 percent and the average annual sediment yield was 96.4 (tons/ acre) / yr [ (216 t / hm2 ) I 

yr] between March 1967 and September 1968. Virtually all the construction in Bel Pre Creek was on 

slopes ranging from 3 to 8 percent, whereas a large 

part of the construction area in Manor Run was on 

slopes between 8 and 15 percent. Some sites had 

slopes greater than 15 percent. The photograph in 

figure 17 shows the severity of erosion on the long, 

steep slopes in the Manor Run basin. The extensive 

rill and gully erosion on slopes greater than 10 percent apparently resulted in the high sediment yield 

from this basin. 

The implementation of sediment controls is illustrated by aerial photographs of the Bel Pre Creek 

basin fo·r June 1966 and June 1974 (fig. 18). The 

1966 photograph shows 148 acres (60 hm2 ) of land 

~ l MU 

0 0.5 1 KILOMETER 

FIGURE 16.- Coristruction sites and average .slope conditions, Bel Pre Creek and Manor Run basins, June 1967. Land slope 

adapted from Soil Survey of Montgomery County, Md, (U.S. Dept, Agriculture, 1961) 
SEDIMENT DISCHARGE 55 

FIGURE 17.-Extensive erosion in the Manor Run basin, 1967. 

under construction with no sediment controls. The 

1974 photograph shows about the same amount of 

construction controlled by a network of five sediment 

basins. Some of the basins are temporary and others 

are designed as permanent stormwater management 

structures (fig. 19). The increased use of sediment 

basins and other control measures has substantially 

reduced the construction-site sediment yields of the 

study basins. For example, the average annual sediment yield delivered to the stream channels from 

construction sites shown in figure 18 was reduced 

from 26 to 7 tons/ acre (58 to 16 t / hm2 ) between 

1968 and 1974. 

To further examine the relation between construction-site sediment yields and various site factors, 

the relation between computed site yields and the 

yields estimated with equation 3 is shown in figure 

20. The scatter about the line of equality is significant, reflecting the large standard error of estimate of the regression equation. The data points 

with the greatest departure from the line of equality 

were probably influenced by other site factors not 

used in the equation. For example, the high computed yields for Manor Run sample periods 1, 2, 

and 3 probably result from grading activities adjacent to and within the stream channels (fig. 21). 

The proximity factor averaged 39 percent in Manor 

Run during these periods. In contrast, the relatively 

low proximity factors for period 1 in the Williamsburg Run and Bel Pre Creek basins, 25.3 and 19.3 

percent, are reflected by the low computed sediment 

yields. An earlier study in the same basins found 

that construction-site sediment yields from summer 

storms increased as the amount of construction 

within 100 and 300 ft (30 and 91 m) of stream 

channels increased (Yorke and Davis, 1972). The 

lower sediment yields from construction sites 

farther from stream channels represent the effects 

of filtering of sediment-laden runoff waters by vegetation. As runoff transporting sediment from a construction site passes through a heavily vegetated 

zone, velocity is reduced by an increase in friction. 
56 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

APPROXIMATE SCALE 1:24 000 

FIGURE lB.-Construction activities, A, without (1966 ) and, B, with (1974) sediment controls, Bel Pre Creek basin. Circles 

indicate locations of sediment basins. 

This action reduces the competence of the water to 

transport sediment. A less important factor in the 

reduction in competence is a loss of water through 

:Infiltration into the soil of the vegetated zone. As a 

consequence, much of the sediment is deposited 

before it enters the stream. 

The low computed yields in the Lutes Run basin, 

where the percentage of the construction area with 

sediment controls was lower than average and the 

slope of construction sites was higher than average, 

are indicative of another factor affecting site yields. 

One construction site in this basin was opened prior 

to 1963 and remained undeveloped through 1973 

(fig. 22). The low yields from the Lutes Run basin, 

in general, and this site in particular, probably resulted from the site being open long enough for 

natural stabilization to develop. As fine soil particles 

are eroded and transported from a site, the remaining large particles armor the soil mass. The 

gradual increase in the size of remaining soil particles results in decreased sediment yields because 

the particles are too large to be transported except 

by the very large storms. 

In summary, the degree of sediment control and 

the slope of construction sites are the most significant factors affecting construction-site sediment 

yields. Buffer zones of vegetation, proximity of construction to stream channels and the length of time 

the sites are not stabilized affect the annual yield 

to a lesser degree. 

STREAM-CHANNEL EROSION 

In anticipation of significant urbanization during 

the period covered by the project, three channel 

reaches were selected to study possible changes in 

channel geometry. The reaches are located immediately downstream from the gaging stations (fig. 1) 

on Manor Run, Northwest Branch Anacostia River 

at Norwood, and Batchellors Run. Drainage areas 

above the study reaches range from 0.47 to 2.45 
SEDIMENT DISCHARGE 57 

APPROXIMATE SCALE 1:24 000 

FIGURE 18.-Continued 

FIGURE 19.-Large sediment-stormwater management basin 

used to trap sediment before it can leave construction sites, 

Bel Pre Creek basin, 1974. 

mF ( 1.22 to 6.35 km 2 ) • The basins were basrically 

rural at the beginning of the study period with only 

small amounts of impervious area. 

Stream channels selected for study are incised in 

Wehadkee silt loam, which is commonly found in 

stream valleys of the study area. The texture of 

Wehadkee silt loam varies from a silty clay loam to 

a light silt loam, and the soil is susceptible to frost 

action and very erodible (U.S. Dept. of Agriculture, 

1961). The Manor Run and the Northwest Branch 

Anacostia River channels are typical U-shaped 

channels carved in flood-plain sediments. Low be,rms 

defining the low-water channel are generally absent 

except at the inside of meanders. In contrast, the 

Batchellors Run channel has distinct berms or terraces between the low-water channel and the flood 

plain (fig. 23). 

Channel-geometry reaches were established and 

surveyed in 1967. Cross sections in these reaches 
58 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

FIGURE 20.-Relation between construction-site sediment yields computed from observed data and those estimated by 

equation 3. 

were selected to represent typical conditions and 

variations in stream-channel geometry. Cross sections were defined by determining the elevation of 

selected points along a line perpendicular to the 

stream banks to the nearest 0.1 ft (0.03 m) with 

transit and rod. Elevations were determined at lor 2-ft (0.3- or 0.6-m) -horizontal intervals across 

the streambed, at 5-ft (1.5 m) intervals in the flood 

plain, and at breaks in slope. The position of the 

thalweg was located by azimuth and stadia; thalweg 

elevations were determined to the nearest 0.01 ft 

(0.003 m). 

The channel reaches were resurveyed in 1974 to 

determine changes in the cross sections and total 

volume of the active channels. Cross sections were 

located through the 1967 thalweg and perpendicular 

to the banks. Additional cross sections were measured in some reaches to facilitate computation of 

the channel volume. Changes in the cross sections 

typical of straight and curved reaches of the channels for each stream are shown in figure 24. 
SEDIMENT DISCHARGE 59 

FIGURE 21.-Grading for street right-of-way within the Manor 

Run stream channel, 1967. 

From the information obtained by the 1967 and 

1974 channel surveys, four channel-geometry parameters were chosen for study. These parameters 

include channel length, cross-sectional area, channel 

volume, and channel width. Channel length was defined as the total distance between successive thalweg locations in the study reaches. Cross-sectional 

area was determined by plotting the channel crosssections as determined from the survey field notes 

and planimetering the area below a line drawn between the top bank elevations. Total channel volume 

was calculated as the sum of the products of each 

cross-sectional area times one-half the distance between the thalweg of the section and the thalwegs 

of the preceding and succeeding sections. Channel 

width was determined as the horizontal distance, 

perpendicular to the channel, between the top of the 

low bank and the wall of the opposite bank. 

The effects of urbanization and the associated increa.se in flood peaks are illustrated by the differences in the channel-geometry parameters of Manor 

Run and the other two streams (table 11). Each of 

the parameters, except for channel length, increased 

in the Manor Run basin a.s the impervious area increased from 5.6 percent in 1966 to· 13.5 percent in 

1974. In the Northwest Branch Arnacostia River, 

all the channel parameters. increased slightly as the 

impervious area increased from 3.4 to 4.4 percent. 

In the Batchellors Run basin, channel parameters 

increased slightly, except for a slight decrease in 

channel cross-sectional area, as the impervious area 

increased from 11 to 12 acres (4.5 to 4.9 hm2 ), 3.6 

to 4.0 percent of the ba.sin area. 

The changes in the stream channel parameters are 

consistent with changes found in previous investigations. Leopold (1968) indicated that stream channels form in response to the regimen of the stream 

and will carry, without overflow, a discharge which 

is somewhat smaller than the average annual flood. 

Brown (1971) showed that the 5-year flood has a 

direct positive relationship with channel capacity. 

Because urbanization causes increased flood peaks, 

as discussed earlier, a substantial enlargement of 

the channels of urban streams should be expected. 

Apmann (1974) found that in any watershed in 

which the runoff volumes and flood peaks are increa.sing, the tendency will be for the stream channel 

to increase its cross-sectional area and length of 

meander. Hammer (1972) found that channel enlargement was related to the amount of impervious 

area, particularly impervious areas more than 4 

years old. 

The two parameters indicating a large difference 

between Manor Run and the other basins were the 

average cross-sectional area and channel volume. 

Channel cross-sectional area increased 28 percent 

in the Manor Run basin. It increased 5 percent and 

decreased 6 percent in the Northwest Branch Anacostia River and Batchellors Run basins, respectively. Statistical analysis indicated that the 1974 

cross sections for Manor Run were significantly 

larger than the 1967 cross sections at the 95-percent confidence level. The difference between the 

1967 and 1974 cross sections for the other two basins 

were not significant at the 95-percent confidence 

level. The volume of the Manor Run channel increased 34 percent between 1967 and 1974. Channel 

volume increased 12 percent in the Northwest 

Branch Anacostia River basin and increased 2 percent in the Batchellors Run basin during the same 

period. 

An examination of the individual cross sections 

and the streambed profiles of each channel reach indicated substantial differences between Manor Run 

and the other two streams. The increase in channel 

cross-sectional area in Manor Run resulted from a 

combination of bank erosion and degradation of the 

streambed. Each cross section wa.s deeper and all 

except one section had greater cross-sectional areas 

in 1974. In straight channel reaches, in particular, 

cross sections were scoured to a nearly rectangular 

shape instead of the V- or U-shaped sections common in 1967. In contrast, the cross sections of 

Batchellors Run and Northwest Branch Anacostia 

River did not exhibit any consistent pattern of bank 

erosion or bed degradation. The channels generally 
60 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

A APP ROXIMATE SCALE 1 :22 800 

B APPROXIMATE SCALE 1:24000 C APPROXIMATE SCALE 1:24 000 

FIGURE 22.-Construction site in the Lutes Run basin, 1964 (A), 1968 (B), and 1974 (C). 
SEDIMENT DISCHARGE 61 

FIGURE 23.-Stream channel-geometry 

reaches, 1974: Manor Run (A), Northwest Branch Anacostia River at Norwood (B), and Batchellors Run (C). 
62 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

f0 

8 

6 

4 

2 

STRAIGHT REACHES 

DISTANCE, IN METERS 

5 10 

SECTION 9 

15 

3 

2 

o '-----..l_ __ _l_ __ _j_ _ _ __L __ __j_ o 

~ 10 r-~~-,~~~,-~~,--L~-,~~~ 

3 u.. 

z 

'2, 

::J 

f-

<{ 

0 

>-

c: 

<{ 

c: 

t:: 

co 

c: 

<{ 

w 

> 

0 

co 

<{ 

z 

0 

i= 

:; 

w 

--' 

w 

Left bank 

8 

2 

6 

4 

2 

SECTION 8 

0 l_ __ L__ __ .L__ _ _ _j__ _ _ _L_ _ _ _l_ 0 

10 3 

Left bank 

8 

2 

6 

4 

2 

SECTION 4A 

10 20 30 40 

DISTANCE, IN FEET 

0 

8 

6 

4 

2 

Left bank 

.... 

CURVED REACHES 

DISTANCE, IN METERS 

5 10 

..... ______ , 

SECTION 5 

I 

I 

I 

I 

I 

I 

I 

15 

3 

2 

Q'----~~--'-~~~'----~~---'---~~-----'~~~---'--- 0~ 

10 3 ~ 

8 

6 

4 

2 

Left bank 

BATCHELLORS RUN 

' ------==:----.. '------, \ 

\ 

1974 

196/\ 

' ' ,_, SECTION 11 

'2 

z 

:i 

::J 

f-

<{ 

2 0 

>-

c: 

<{ 

c: 

fCii 

c: 

<{ 

w 

> 0 

co 

<{ 

z 

0 

i= 

0 '---~~--'-~~~L-~~--'-~~~'---~~---'--- 0 ~ --' 10 3 w 

6 

4 

2 

Left bank 

--.., 

I 

I 

) 

I 

I 

I 

I 

I 

I 

\ 

\ 

SECTION 9 

1974 

I 

I 

I 

I 

L---1967 

I 

2 

'------~----~---'-----_l_--~ 0 

0 10 20 30 40 50 

DISTANCE, IN FEET 

FIGURE 24.-Typical cross.,section changes between 1967 and 1974 in straight (sections 9, 8 , and 4A) and curved 

(sections 5, 11, and 9) reaches of three typical stream channels in the study area. 
SEDIMENT CONTROL 63 

TABLE 11.- Summary of stream-channel surveys 

Number Impervious Channel Average Average cross~ Channel Drainage channel of area length a.rea (percent) 

(mi") cros·s (ft) 

sections 

1966 1974 1967 

Manor Run near Norbeck 1.01 12 5.6 13.5 271 

N. W. Br. Anacostia River 

at Norwood 

Batchellors Run--

2.45 15 3.4 4.4 427 

at Oakdale --- .45 8 3.6 4.0 235 

retained their original shape within slight shifts of 

the meander pattern. Virtually all the increase in 

average cross-sectional area in the Northwest 

Branch Anacostia River channel was attributable to 

increases at three sections located on an active 

meander. 

The increase in suburban land area and impervious surfaces is apparently the only factor that 

could have caused the channel enlargement in Manor 

Run. Each of the streams is carved through similar 

soils, and the rainfall characteristics for the three 

basins were similar during the period of comparison (1967-74). 

The change in Manor Run channel volume over 7 

years has resulted in a removal of approximately 

5,300 fV (150 m3 ) of soil from the area of the 

stream channel. Based on an assumed density of 

100 lbs/ fV (1,600 kg/ m3 ), 265 tons (240 t) of soil 

was eroded from a channel reach 270 ft (82 m) 

long. This erosion is equivalent to about 1 ton per 

foot (3 t / m) of channel over 'l years. In other 

words, every 7 ft (2.1 m) of channel length contributed approximately 1 ton (0.9 t) of sediment to 

(he stream annually. Based on a total channel length 

of 5,000 ft (1,520 m) from the outlet of storm 

sewers in the upstream developments to the gaging 

station, the contribution of stream-channel erosion 

to· the total sediment load measured at the gaging 

station would be about 700 tons/ yr (640 t/ yr). 

Suspended-sediment load would probably represent 

about 90 percent of the to·tal load or about 630 

tons/ yr (570 t/ yr). Suburban land averaged about 

250 acres (101 hm2 ) between 1967 and 1974. If all 

the stream-channel erosion was attributable to increased runoff from impervious surfaces in this 

area, the sediment yield from stream channels would 

be about 2.5 tons/ yr (2.3 t / yr) for each acre (0.4 

hm2 ) of suburban land. This is a temporary source 

of sediment that would be expected to diminish to 

zero when the stream channel reached equilibrium 

with the post-development runoff regime. 

sectiona.il area volume width 

(ft) (ft ') (ft3) 

1974 1967 1974 1967 1974 1967 1974 

269 22.6 24.9 59.8 76.8 15,600 20,900 

444 32.6 34.5 104 109 45,200 50,500 

243 34.7 35.9 74.8 70.4 16,800 17,200 

SEDIMENT CONTROL 

In the past 10 years, sediment control has become 

an integral part of urban construction. Control programs have been implemented by all local jurisdictions in the Baltimore-Washington area. The impetus for these programs was a study begun by the 

Interstate Commission on the Potomac River Basin 

in the early 1960's. The Commission's study group 

recommended that sediment control become the started 

policy of local governments, that urban development 

be planned carefully, and that local ordinances be 

adopted to require developers to employ erosioncontrol measures on construction sites (Guy and 

others, 1963). 

The Montgomery County sediment-control program evolved from a Sediment Control Task Force 

formed to study the possibility of reducing sediment from developing areas in the Rock Creek 

watershed, which was being considered for a Public 

Law 566 flood-control project. The Task Force drew 

up a program for voluntary sediment control, and 

it was adopted as county policy in 1965. This action 

was followed by a mandatory program in 1967 that 

required developers to submit sediment control plans 

along with preliminary subdivision plans. This regulation provided for review of plans by the Montgomery County Soil Conservation District; however, 

there was no provision for field inspections to assure 

that the approved control measures were installed 

and properly maintained. In 1971, however, the 

Montgomery County Council enacted a Grading and 

Sediment Control ordinance, which established an 

enforcement unit within the county's Department 

of Environmental Protection. This unit has the responsibility of inspecting construction sites to insure 

that approved sediment-control measures are properly installed and adequately maintained throughout the construction period. 

The urban sediment-control program adopted by 

Montgomery County is similar to the program used 
64 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPO RT IN MARYLAND 

for many years in agricultural areas. The basic 

principles, as outlined by the Maryland-National 

Capital Park and Planning Commission (1967), 

are: 

1. The smallest pract.ical area of land should be 

exposed at any one time during development. 

2. When land is exposed during development, the 

exposure should be kept to the shortest practical period of time. 

3. Temporary vegetation and (or) mulching should 

be used to protect critical areas exposed during 

development. 

4. Sediment basins (debris basins, desilting basins, 

or silt traps) should be installed and maintained to remove sediment from runoff waters 

from land undergoing development. 

5. Provisions should be made to effectively accommodate the increased runoff caused by changed 

soil and surface conditions during and after 

development. 

6. The permanent final vegetation and structures 

should be installed as soon as practical in the 

development. 

7. The development plan should be fitted to the 

topography and soils so as to create the least 

erosion potential. 

8. Wherever feasible, natural vegetation should be 

retained and protected. 

FIELD APPLICATIONS 

The field application of the principles outlined 

above required a gradual training program for de~ 

velopers, engineers, and grading contractors. In the 

past, developers generally did all the rough grading 

on the site at one time to minimize expenses for 

heavy grading equipment. Engineers and grading 

contractors designed and built drainage systems to 

facilitate rapid runoff from the sites. Final road 

surfaces, drainage channels, and vegetative cover 

were installed after houses were sold and ready for 

occupancy. Major changes in these methods of 

operation were required to accomplish the principles 

of the sediment-control program. 

The first attempt at sediment control was the installation of sediment basins. These basins could be 

built at minimal cost at the same time heavy equipment was rough-grading street rights-of-way. They 

were generally located in small drainage swales at 

the edge of the development so they would not interfere with the standard construction methods. In 

general, they were small and underdesigned, as illustrated by figure 25. Many of these basins were 

FIGURE 25.-Typical sediment basin used in 1966. 

filled with sediment in one or two storms and were 

of no value thereafter. The net result was a generally ineffective program between 1965 and 1968. 

The lack of effective control during the early 

stages of the program occurred because it was a 

learning period for all concerned. Representatives 

of the Soil Conservation District and the county 

were trying to develop effective standards and specifications for measures that would control sediment 

transport from construction sites, but that would 

not place undue restrictions on construction activities. At the same time, developers and engineers 

were trying to control erosion without the benefit 

of adequate standards. As specifications became 

available, the program gradually improved: Better 

planning limited grading to the smallest practical 

area to reduce the amount of land exposed to erosion 

at any one time; straw mulch and temporary vegetation were used to protect exposed soils; diversion 

berms, level spreaders, and stabilized water-ways 

were used to reduce erosion on critical slopes; and 

properly designed sediment basins were used to trap 

the sediment before it could leave the construction 

site (U.S. Dept. of Agriculture, 1969). 

Between 1968 and 1971, most of the sedimentcontrol plans were implemented in the field; however, there were still problems with contractors unfamiliar with sediment control measures. Some 

control measures were installed improperly, and 

many others were not adequately maintained. There 

was also a lack of coordination between the different 
SEDIMENT CONTROL 65 

contractors involved in the housing developments. 

Rough-grading, utility installation, and paving were 

not coordinated so as to reduce the length of time 

that construction sites were subject to erosion. 

Sometimes utility contractors would remove or alter 

controls that were installed by the developer. For 

example, interceptor berms on rights-of-way were 

frequently removed during utility installation and 

not replaced after the utilities were in place. In 

other instances, the embankments of sediment basins 

were breached for installation of sewer lines and 

were not rebuilt, resulting in the subsequent discharge of sediments previously trapped by the basin 

(fig. 26). Photograph A in figure 26 shows a wellbuilt basin at one of the construction sites in the 

study area. Photographs B and C show the same 

basin after the embankment was breached for a 

sewer line. This embankment was eventually rebuilt, but not until much of the trapped sediments 

had been scoured by a series of storms. 

Another problem between 1968 and 1971 was a 

general lack of maintenance of control measures. 

Berms destroyed or altered by construction traffic 

were not replaced. Temporary vegetation and mulch 

were not maintained. Sediment basins, the prime 

means of control, were not maintained. When basins 

became filled, the accumulated sediments were not 

removed. As the trap efficiency is related to the 

ratio between the storage capacity of basins and 

the inflow, the accumulation of sediment greatly reduced the value of the basins. During some sto·rms, 

sediment-filled basins probably had a negative trap 

efficiency, as runoff scoured more sediment from the 

basins than was deposited in them (fig. 27). 

After the Sediment Control Section was established in the Montgomery County Depa.rtment of 

Environmental Protection, control measures improved markedly. Inspectors were on hand to see 

that controls were installed properly. Inspections at 

regular intervals throughout the period of construction ensured that controls were adequately maintained and that additional controls were installed as 

needed. Impmvements in the sediment control program are illustrated by the summary of field evaluations listed: 

FIGURE 26.-Sediment basin before (A) and after (B and 

C) it was breached for installation of a sewer line. Note the 

scour of previously accumulated sediments. 

/ 
66 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

Year Percentage of total con- struction area w ith 

approved sedimentcontrol measures 

1968 --- -------- - -------------- ----- 36 

1970 ------------ ------------------- 41 

1972 ------------------------------- 56 

1974 ------------------------------- 74 

These field evaluations were made by several groups. 

The 1968 and 1970 evaluations were made by members of the Montgomery County Sediment Control 

Task Force. The 1972 evaluation was made by the 

Montgomery County Sediment Control Section, and 

the 197 4 evaluation was made by representatives of 

the Sediment Control Section and U.S. Geological 

Survey personnel assigned to this project. All except 

the 1974 evaluation were countywide. The 1974 

evaluation considered only sites in the study area. 

EFFECTS OF SEDIMENT-CONTROL MEASURES 

The effectiveness of the sediment-control program 

was illustrated in the earlier discussion of construction-site sediment yields. The quantity of suspended 

sediment transported by the streams decreased 

markedly as the percentage of construction sites 

with approved controls increased. In the Bel Pre 

Creek basin, suspended-sediment yields from construction areas decreased from 26.4 tons/ acre (59.2 

t/ hm2 ), when there were minimal controls, to 7.2 

tons/ acre (16.1 t/ hm2 ), when about 70 percent of 

the construction area was adequately controlled. 

Similar decreases were observed in the other study 

basins. Sixty to eighty percent decreases were observed in the Williamsburg Run, North Branch Rock 

Creek, and Manor Run basins. 

Another example of reduced sediment yields from 

construction sites is shown in figure 28. The curves 

FIGURE 37.-Small sediment basin requiring maintenance. 

in figure 28 represent the average relation between 

storm runoff and suspended-sediment discharge in 

the Northwest Branch Anacostia River near Colesville for three periods: 1963-67 water years, when 

no controls were used on construction sites; 1968-71 

water years, when controls were mandatory; and 

1972-74 water years, when controls were mandatory 

and subject to inspection by the Sediment Control 

Section. The curves indicate a substantial reduction 

in sediment discharge during each succeeding 

period. An analysis of covariance found that the regression curves for the dormant-season storms were 

significantly different for all periods. The differences 

of the adjusted means of the dormant-season loads 

for the periods 1963- 67 versus 1968-71 and 1968-71 

versus 1972-74 were significant at the 95-percent 

confidence level. The difference between the 1963-67 

and 1972-7 4 adjusted means were significant at 

the 99-percent confidence level. Growing-season adjusted means were significantly different at the 99-

percent confidence level, except for the periods 

1963-67 and 1968-71, which were not significantly 

different at the 95- or 99-percent confidence level. 

Several factors could account for the reduced 

suspended-sediment discharge from the basin. A 

decrease in the amount of sediment source area 

would be the most obvious. Land under cons,truction averaged 2.87, 3.15, and 2.63 percent of the total 

basin area for 1963-67, 1968-71, and 1972-74, respectively. On the basis of construction area alone, 

a slight increase over the 1963-67 period would be 

expected in 1968-71 and a slight decrease expected 

between 1972 and 1974. However, a decrease was 

observed between 1968 and 1971. The large decrease 

in sediment discharge between 1972 and 1974 is 

not the likely result of the small decrease in construction area. Cropland decreased during the 

period, but the increase in new urban land was 

greater than the decrease in cropland. The sediment 

yield from these two sources probably did not 

change appreciably because the yield from urban 

land and stream channels downstream from urban 

land was greater than or equal to the cropland 

yields observed for the small study basins. 

Change·s in soil and slope conditions on construction sites and a decrease in the size or intens.ity of 

storms could also affect the sediment discharge, but 

these did not change significantly during the study 

period. Soil conditions were generally uniform except for the greater erodibility of the subsoil in the 

Manor series. A substantial decrease in construction on the Manor Soils was not observed. Slope 

varied between construction sites, but there was no 
SEDIMENT CONTROL 67 

STORM RUNOFF, IN CUBIC HECTOMETERS 

0.05 0.1 0.5 1 

1 0,000 ,.........___._+-'-........... J..,L-.,........--.-+-r.,--J---'-.....J.--'_.,_..-Y-........-...-+-.--

(f) 

z 

~ 

z 

5000 

w' 1000 (!) 

a: 

<( 

0 500 (f) 

0 

1-

z 

w 

~ 

0 

w 

(f) 100 

~ 

a: 

~ 50 (f) 

EXPLANATION 

1963--67. ······················ 

1968-71 ... -------- • 1972-74. ---

• 

A 

• 

5000 

(f) 

w 

z 

z 

0 

1-

1000 ~ 

w' 

(!) 

500 ~ 

100 

50 

:c 

u 

(f) 

0 

1-

z 

w 

~ 

0 

w 

(f) 

~ 

a: 

0 

1-

(f) 

10~--~~·~~~~--~__._~~~ 10 

1 0 50 1 00 500 1 000 

STORM RUNOFF, IN CUBIC FEET PER SECOND-DAYS 

STORM RUNOFF, IN CUBIC HECTOMETERS 

0.05 0.1 0.5 1 

1 0,000 ,_.J-.--L....,L-l.--'-,-L...l..f-,..........rl-r-r-1---'--+--'---'r-'--Y-.,....,--r+-.,.... 

EXPLANATION 

1963--67. ······················ 

5000 1968-71 ..__-----

(f) 

z 

0 

1-

z 

w' 1000 (!) 

a: 

<( 

:c 500 u 

(f) 

0 

1-

z 

w 

::?! 

0 

w 

(f) 100 

::?! • a: 

0 • 1- 50 (f) 

1972-74. --- •• 

• 

• 

/ 

/ . _,. ~· ....... -,/~ 

- • _li- .... 

• y 

#>_ • • 

, •. t . / ~*•· /. 

.. ,/. .. . ~···/ . . . . ..· / 

• .. II- ·· . 

/ 

~· . .. 

·-·~ ·:... .. . ·'/ ... . . 

• 

..... 

.·/ ... ·::. ' 

• •• • 

• 

8 

• 

5000 

(f) 

w 

z 

z 

0 

1-

1000 ~ 

w' 

(!) 

500 ~ 

:c 

u 

(f) 

0 

1-

z 

w 

~ 100 0 

w 

(f) 

50 ::?! 

a: 

0 

1-

(f) 

STORM RUNOFF, IN CUBIC FEET PER SECOND-DAYS 

FIGURE 28.-Relation between suspended sediment and storm 

runoff for dormant season (A) and growing season (B) 

storms, Northwest Branch Anacostia River near Colesville, 

1963-74. 

trend of decreasing slope conditions during the 12-

year period. Total precipitatioo varied during the 

periods, but the magnitude and intensity of storms 

did not decrease significantly. 

The use of sediment controls is the one factor 

that has changed appreciably during the three 

periods represented by the curves in figure 28. Total 

suspended-sediment discharge that would have occurred if each condition had existed throughout the 

12-year period was estimated as shown: 

Degree of 

sediment control 

None --------------------- Mandatory, no enforcement __ 

Mandatory, with enforce12-yr sediment load 

transported by storms 

Growing 

season 

(tons) 

114,000 

79,000 

Dormant 

season 

(tons) 

93,000 

60,000 

ment ------------------- 52,000 52,000 

The seasonal regression curves and the storm 

runoff for all significant storms that occurred between October 1962 and September 197 4, except for 

Hurricane Agnes, were used in the computations . 

The Agnes storm runoff was not used because it far 

exceeded the sample range of the 1963-67 and 1968-

71 periods. Suspended-sediment discharge of the 

storms used in the computations is 92 percent of the 

12-year total sediment discharge, excluding the 

load transported during Hurricane Agnes. The other 

8 percent represents the load transported during 

base flow and small storms for which no samples 

were collected . 

The estimated loads indicate that a substantial 

reduction in sediment discharge would have occurred if sediment controls had been used throughout the study period. Sediment yields under mandatory controls were estimated to be 33 percent lower 

than yields estimated for conditions of no control. 

A slightly larger reduction would have occurred 

during the dormant season. Enforcement of controls 

throughout the study period would have resulted 

in a total yield reduction of 103,000 tons (93,400 t), 

or 50 percent. The largest reduction under enforced 

controls occurred during the growing season. This 

is probably the result of an improvement in the designs of structures and better maintenance, which 

provided greater control of runoff during intense 

summer storms. Scheduled inspections of construction sites resulted in prompt replacement and maintenance of sediment controls damaged by normal 

construction traffic and a substantial reduction in 

sediment discharge. 

COST OF SEDIMENT CONTROLS 

Sediment-control measures implemented on urban 

construction .sites apparently have reduced the sedi-
68 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

ment.loads in the re.ceiving streams. The installation 

of these controls, however, represents an additional 

expense to developers, builders, and ultimately, the 

property owner. The standard control measures 

used in the field, the cost of the control program, and 

the· relative costs incurred due to sediment damage 

downstream from construction sites are discussed 

in this section. 

After standards and specifications for soil erosion 

and sediment control (U.S. Department of Agriculture, 1969) were prepared, sediment-control measures in the field have become fairly uniform. The 

conventional method used on most construction sites 

includes a combination of: 

1. Mulch and (or) te·mporary vegetation to protect 

exposed slopes. 

2. Interceptor dikes to reduce erosion on rights-ofway by diverting storm runoff to temporary 

outlets where the water can be transported 

with minimal erosion. 

3. Grassed waterways, level spreaders, and grade 

stabilization structures to convey storm runoff 

through the construction site without erosion. 

4. Diversion berms to divert storm runoff from 

areas with critical slopes. 

5. Sediment basins to trap and store sediment 

eroded from construction sites before it can 

enter the stream system. 

Complete descriptions and illustrations of these and 

other commonly used control measures are available 

in reports by the U.S. Department of Agriculture 

(1969), Thronson (1971), and Becker and Mills 

(1972). 

The cost of these conventional controls has been 

evaluated in several studies. Brandt and others 

(1972) interviewed developers in Montgomery 

County, Md., to determine the average cost of individual controls. Hotes and others ( 1973) obtained 

similar information for a cost comparison between 

sediment controls in northern Virginia and central 

California. The costs for the commonly used control 

measures in Maryland and northern Virginia were 

estimated as: 

Surface stabilization ___ ----$209-$567 I acre 

Diversion and intercepter 

dikes -------------------$1.25-$3.70/ln ft (linear foot) 

Sodded ditches -------------$4.50/ln ft 

Grade stabilization 

structures ---------------$2.80-$28/ln ft 

Level sp.readers ------------$1.36-$3.16/ln ft 

Sediment basins -----------$1,500-$2,560/basin 

The range in costs reflects differences in the type 

of materials used for the controls, differences in 

sediment-control specifications in Maryland and Virginia, and different time periods during which the 

costs were determined. 

An average unit cost of $1,026/acre for sediment 

control was estimated by Brandt and others ( 1972), 

based on sediment-control plans submitted by seven 

developers in Montgomery County. This rep·resents 

an average cost of $55/acre for engineering, plus 

$421/acre for structures and sediment basins, plus 

$500/acre for surface stabilization, plus $150/acre 

for maintenance of structures and repair of erosion 

damage, minus $100/acre for the residual value of 

surface stabilization. The significance of these costs 

can be shown by the total cost of sediment control 

in the Anacostia River basin. Between 1962 and 

1974, 1,900 acres of land was developed for houses, 

apartments, schools, and shopping centers. If an 

average cost of $1,026/acre is assumed, the total 

cost of sediment control would have been $1.9 million. This represents an approximate cost of $19 

for each ton (0.9 t) of sediment that would have 

been prevented from entering the stream system if 

mandatory controls had been enforced between 1962 

and 1974. 

The cost of onsite sediment control falls somewhere within the range o.f costs incurred for sediment removal from ponds, reservoirs, streets, basements, and sewers. These costs range from $2.50 I 

ton for removal of sediment from an urban pond 

(Becker and Mills, 1972) to $134/ton for removal 

from sewers (Hotes and others, 1973). Dredging 

cost can range from $0.11 to $9.00/ton depending 

on the amount of sediment to be dredged and the 

distance from the dredging operation to a suitable 

disposal site (Hotes and others, 1973). Many other 

costs are incurred as a result of increased sedimentation caused by urban construction ; however, an 

analysis of these costs is beyond the scope of this 

study. These include: increased water treatment 

costs, increased flooding, decreased commercial fish 

and shellfish harvests, decreased sport fishing, decreased esthetic values in streams and estuaries, 

and decreased shipping due to harbor shoaling. 

Most sediment damages and the related reduction 

in costs resulting from onsite sediment control can 

be calculated, but there are several damages that 

cannot be evaluated based on present knowledge. 

Several unanswered questions are: What are the 

toxic levels of turbidity, suspended sediment, and 

pollutants associated with suspended sediment for 

indigenous fish and other aquatic life in the local 

streams and ponds? What is the effect of estuarine 

sedimentation on marine life cycles? What is the 
SUMMARY 69 

acceptable level of turbidity and sedimentation for 

recreational use of streams and lakes? Will sediment 

controls reduce the impact of urban sediment on 

these conditions? When these questions are answered, local officials will be better able to determine whether the costs of sediment control are 

justified by the benefits. 

SUMMARY 

This report presents the results of a field investigation of the effects of urbanization and sedimentcontrol measures on streamflow and sediment transport in Montgomery County, Md. The study was made 

between 1962 and 1974 in a 32-mi 2 (83-km2 ) area 

in the headwaters of the Rock Creek and Anacostia 

River basins. Data from 9 streamflow-sediment stations, 9 recording rain gages, numerous nonrecording rain gages, 14 sets of aerial photographs, and 

channel surveys on 3 stream reaches were used for 

the study. 

Land use/land cover varied considerably in the 

study basins. Three subbasins remained virtually 

rural, the others underwent urban development with 

as much as 20 percent of one subbasin undergoing 

active construction at one time. Urban area ranged 

from 0 to 60 percent 'in the subbasins in 1974. 

Suburban land in the Anacostia River basin increased from 6 to 23 percent of the drainage area: 

between 1962 and 197 4. 

Precipitation and streamflow between October 

1962 and September 1974 were essentially the same 

as the long-term conditions in the study basins. 

Streamflow was higher than normal between 1966 

and 1974, and the increase in volume was mostly 

due to higher base flows. Urbanization did not affect 

median and low flows in the study basins; however, 

storm runoff and peak discharges were gr·eater in 

the urban basins. 

Suspended sediment transported from the Anacostia River basin averaged 14,800 tons (13,400 t) 

per year between 1962 and 1974. The annual suspended-sediment discharge ranged from 5,500 tons 

(4,990 t) in 1974, to 31,000 tons (28,100 t) in 1972, 

when the runoff from Hurricane Agnes. transported 

12,800 tons (11,600 t) in a 2-day period. Bedload 

was estimated to be 6 to 13 percent of the total 

load. Most of the load was transported during 

storms, 73 percent in 2.2 percent of the time and 

94 percent in 5.7 percent of the time. The te~mporal 

distribution of suspended sediment closely approximated the seasonal variability of the erosion index; 

high loads generally occurred in the late winte~r, 

early spring and midsummer, and low loads occurred 

in the fall and early winter. 

Sediment loads were highly variable from storm 

to storm. Loads were most closely related to the 

volume of storm runoff and peak discharge. Other 

factors affecting the load variation for individual 

streams include the relative basin area under construction, antecedent moisture levels, total precipitation, and an index of the storm intensity. Useful 

storm-intensity indices were maximum 15- or 30-

minute rainfall or the ratio of peak discharge to 

runoff volume. 

Cropland, urban land, and construction sites were 

the major sources of sediment. Suspended-sediment 

yields from land under cultivation ranged from 0.65 

to 4.3 tons/acre (1.5 to 9.6 t/hm2 ). Yields from 

forest lands and grasslands were estimated as 0.03 

ton/acre (0.07 t:/hm2 ) and 0.2 ton/acre (0.45 

t/hm2 ), respe~ctively. Urban land yielded about 3.7 

tons/acre (8.3 t/hm2 ), mostly from stream-channel 

erosion immediately downstream from newly completed residential and commercial areas. In one 

urban basin, channel surveys indicated that streamchannel erosion contributed 1 ton (0.9 t) of sediment per foot (0.3 m) of main channel length to 

the total sediment yield of the basin between 1967 

and 1974. 

Suspended-sediment yields from urban construction sites ranged from 7 to 100 tons/acre (16 to 

224 t/hm2 ) and averaged 33 tons/acre (74 t/hm2 ). 

Most of the variation in yields was attributable to 

the increased use of effective sediment-control measures in construction areas between 1966 and 1974. 

The average slope of the construction sites also was 

determined to be a significant factor affecting sediment yields. Other factors affecting sediment yields 

to a lesser extent were the proximity of construction to stream channels and the existence of buffer 

zones of undisturbed vegetation between construction sites and stream channels. 

Construction-site sediment yields decreased as use 

of sediment-control measures increased. Yields were 

reduced from 26 tons/ acre (58 t/hm2 ) to 7 tons/ acre 

(16 t/hm2 ) in the Bel Pre Creek basin. Sixty to 

eighty pe,rcent decreases were observed in the other 

subbasins. If controls had been used between 1963 

and 1974 in the Anacostia River basin, suspendedsediment discharge would have decreased about 

103,000 tons (93,400 t), or 50 percent between 1963 

and 1974. Reportedly, the cost of controlling sediment on the 1,900 acres developed during this 

period would have been $1,030/acre (0.4 hm2 ) or 

$19 for each ton (0.9 t) of sediment controlled. The 
70 EFFECTS OF URBANIZATION ON STREAMFLOW AND SEDIMENT TRANSPORT IN MARYLAND 

data indicate that control could be achieved at less 

expense if construction were limited to areas with 

slopes less than 10 percent and if sites immediately 

adjacent to stream channels were avoided. If construction were required in these. critical areas, substantial control could be achieved by limiting construction to the period of low erosion potential between September and January. These restrictions 

would reduce the direct cost of sediment control, 

but they may introduce additional costs whose evaluation is beyond the scope of this report. 

Standard cost-benefit methods can only be used to 

partly assess the effect of enforcing sediment-control 

measures or alternative restrictions on construction 

activities. Although costs of controlling sediment on 

site can be compared with the· costs of removing 

sediment at downstream locations, there are intangible damages associated with allowing sediment 

to leave the construction site. It is difficult to assign 

costs of increased flood potential, deterioration of 

the esthetic quality of streams, and damage to the 

flora and fauna of streams, lakes, and estuaries, but 

there can be little doubt that these costs are real. 

SELECTED REFERENCES 

Anderson, D. G., 1970, Effects of urban development on floods 

in northE:.tn Virginia: U.S. Geol. Survey Water-Supply 

Paper 2001-C, 22 p. 

Apmann, R. P., 1974, The influence of urbanization on stream 

channel behavior, in National Symposium on urban rainfall and runoff and sediment control, July 1974: Univ. 

of Kentucky Bull. 106, 246 p. 

Becker, B. C., 1and Mills, T. R., 1972, Guidelines for erosion 

and sediment control planning and implementation: U.S. 

Environmental Protection Agency Rept. EPA-R2-72-015, 

228 p. 

Brandt, G. H., and others, 1972, An economic analysis of 

erosion andi sediment control methods for watersheds 

undergoing urbanization: Dow Chemical Co. Rept. submitted to U.S. Dept. of Interior (Water Resources Research Contract No. 14-31-0001-3392), 181 p. 

Brown, D. A., 1971, Stream channels and flow relations: 

Water Resources Research, v. 7, no. 2, p. 304-310. 

Garter, R. W., and Davidian, Jacob, 1968, General procedures 

for gaging streams: U.S. Geol. Survey Techniques WaterResources Inv., book 3, chap. A6, 13 p. 

Guy, H. P., 1964, An analysis of some storm-period variables 

affecting stream sediment transport: U.S. Geol. Survey 

Prof. Paper 462-E, 46 p. 

--- 1965, Residential construction and sedimentation at 

Kensington, Maryland, in Federal Inter-Agency Sedimentation Conf. Proc., 1963: U.S. Dept. of Agriculture Misc. 

Pub. 970, p. 30-37. 

Guy, H. P., and Ferguson, G. E., 1962, Sediment in small 

reservoirs due to urbanization: Am. Soc. Civil Engr., 

Jour. Hydraulics Div., v. 88, no. HY2, p. 27-37. 

Guy, H. P., and Norman, V. W., 1970, Field methods for 

measurement of fluvial sediment: U.S. Geol. Survey Techniques Water-Resources Inv., book 3, chap. C2, 59 p. 

Guy, H. P., and others, 1963, A program for sediment control 

in the Washington metropolitan region: Interstate 

Comm. Potomac River Basin Tech. Bull., 1963-1, 48 p. 

Hammer, T. R., 1972, Stream channel enlargement due to 

urbanization: Water Resources Research, v. 8, no. 6, p. 

1530-1540. 

Hotes, F. L., and others, 1973, Comparative costs of erosion 

and sediment control, construction activities: U.S. Environmental Protection Agency Rept. EPA 430/9-73-

016, 205 p. 

Leopold, L. B., 1968, Hydrology for urban land planning-A 

guidebook on the hydrologic effects of urban land use: 

U.S. Geol. Survey Circ. 554, 18 p. 

Maryland-National Capital Park and Planning Commission, 

1967, Sediment control program for Montgomery County, 

Maryland: Maryland-National Capital Park and Planning Comm., 6 p. 

Miller, C. R., 1951, Analysis of flow-duration, sediment-rating 

curve method of computing sediment yield: U.S. Dept. of 

Interior, Bur. of Reclamation, 55 p. 

Putm~n, A. L., 1972, Effect of urban development on floods 

in the Piedmont province of North Carolina: U.S. Geol. 

Survey open- file report, 87 p. 

Searcy, J. K., 1959, Flow-'duration curves: U.S. Geol. Survey 

Water-Supply Paper 1542-A, 33 p. 

Sheppard, J. R., 1960, Investigation of Mey·er-Peter, Muller 

bedload formulas: U.S. Bur. of Reclamation, 22 p. 

Shulits, Sam, 1935, The Schoklitsch bedload formula: Engineering, v. 139, p. 644-646, 687. 

Thronson, R. E., 1971, Control of erosion and sediment deposition from construction of highways :and land development: U.S. Environmental Protection Agency, 50 p. 

U.S. Department of Agriculture, 1961, Soil Survey of Montgomery County, Maryland: U.S. De.pt. of Agriculture, 

Soil Conservation Service, 107 p. 

--- 1969, Standards and specifications for soil erosion and 

sediment control in urbanizing areas: U.S. Dept. of Agriculture, Soil Conservation Service, College Park, Md. 

--- 1970, Soil loss prediction guide for construction sites 

in Virginia; U.S. Dept. of Agriculture, Soil Conservation Service, Virginia. 

Ursie, S. J., and Dendy, F. E., 1965, Sediment yields from 

small watersheds under various land use and forest covers, 

in Federal Inter-Agency Sedimentation Conf. Proc., 1963: 

U.S. Dept. of Agriculture Mis.c. Pub. 970, p. 47-52. 

Vice, R. B., Guy, H. P., and Ferguson, G. E., 1969, Sediment 

movement in an area of suburban highway construction, 

Scott Run basin, Fairfax County, Virginia, 1961-64; U.S. 

Geol. Survey Water-Supply Paper 1591-E, 41 p. 

Wark, J. W., and Keller, F. J., 1963, Preliminary study of 

sediment sources and transport in the Potomac River 

basn: Interstate Comm. Potomac River Basin Tech. Bull., 

1963-11, 28 p. 

Williams, K. F., and George, J. R., 1968~ Preliminary appraisal 

of stream sedimentation in the Susquehanna River basin: 

U.S. Geol. Survey open-file report, 73 p. 

Wischmeir, W. H., and Smith, D. D., 1965, Predicting rainfall-erosion losses from cropland east of the Rocky Moun-
SELECTED REFERENCES 71 

tains: U.S. Dept. of Agriculture, Agriculture Handb. 

282,47 p. 

Wolman, M. G., 1955, The natural channel of Brandywine 

Creek Pennsylvania: U.S. Geol. Survey Prof. Paper 271, 

56 p. 

--- 1964, Problems posed by sediment derived from construction activities in Maryland: Rept. to the Maryland 

Water Pollution Control Comm., Annapolis, Md., 125 p. 

Yorke, T. H., and Davis, W. J., 1972, Sediment yields of urban 

construction sources, Montgomery County, Maryland: 

U.S. Geol. Survey open-file report, 39 p. 

n U.S. Government Printing Office: 1978-240·961/163