I Effects of Agricultural

- Conservation Practices on the

I

\ Hydrology of Corey Creek Basin 

I Pennsylvania, 1954-60

>

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1532-C

5

d

Prepared in cooperation with 

the Pennsylvania Department of 

Agriculture, State Soil and 

Water Conservation Commission
PROPERTY OF GROUND WATER BRANCH 

. OKLAHOMA DISTRICT

Effects of Agricultural 

Conservation Practices on the 

Hydrology of Corey Creek Basin 

Pennsylvania, 1954-60

By BENJAMIN L. JONES

HYDROLOGIC EFFECTS OF LAND USE

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1532-C

Prepared in cooperation with 

the Pennsylvania Department of 

Agriculture, State Soil and 

Water Conservation Commission

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1966
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

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

Washington, D.C. 20402 - Price 25 cents (paper cover)
CONTENTS

Page

Abstract_______________________________________________________ Cl

Introduction._____________________________________________________ 2

Previous studies.______________________________________________ 3

Acknowledgments _____________________________________________ 3

Instrumentation and data collection.____--_-_____________---__-_ 3

Description of the basins. __________________________________________ 6

Physiography and topography_________________________________ 7

Geology------______----_-__-___-________-______-_________-___ 8

Soils.-----_------------------_-----_------_-----_---_-----_-- 9

Climate...______________________________________________ 10

Hydrology_ _____________________________________________________ 10

Precipitation and runoff._______________________________________ 11

Runoff peakedness ___________________________________________ 12

Relation of runoff to land use and land treatment.________________ 15

Sedimentation. _ __ _________________________________________________ 16

Suspended-sediment transport_________________________________ 17

Analysis of sediment-transport variables.___---_-_-_--_----_-- 17

Seasonal analysis of daily data__---_-_--_--_---_---_-__- 18

Analysis of storm data for Corey Creek basin _____________ 21

Size distribution of suspended sediment._____--__-_____----__ 23

Stream-channel changes----..---------.-------------------- 26

Subbasin sediment yields for Corey Creek basin_...__._-_.____ 30

Trends in sediment discharge.___________----_-_-_____---_.- 36

Relation of sedimentation to land use and land treatment. _________ 37

Effects of diversion terrace construction___..-___-______--____ 40

Water chemistry._________________________________________________ 46

Summary and conclusions. -______-___-_-_____--__-----_-____-______ 50

Selected references.______---_________----_____-__--_---__--___--- 54

ILLUSTRATIONS

 Page

FIGURE 1. Map showing instrument sites and data collection points. C4

2. Photograph of newly constructed farm pond ___________ 7

3. Photograph showing the typical rolling topography of

Corey Creek basin________________________________ 8

ni
IV CONTENTS

FIGURES 4^9. Graphs showing: Page

4. Monthly variation in precipitation and runoflf.___ C12

5. Duration curves of daily mean water discharge. _ 13

6. Double-mass relation of precipitation.__________ 14

7. Double-mass relation of runoff.________________ 15

8. Double-mass relation of storm runoff and peakedness factor._______________________________ 16

9. Seasonal suspended-sediment-transport curves _ _ _ 20

10. Diagram showing percentages of sand, silt, and clay in

suspended-sediment samples_______________________ 25

11. Graphs showing relation of the sand, silt, and clay discharge to instantaneous water discharge.____________ 26

12. Sketches showing changes in stream cross sections at

selected ranges._____-____---________----_________ 28

13. Photograph of Elk Run, showing typical bed material_ 29 

14-20. Graphs showing:

14. Relation between scouring or filling and stream

slope at ranges..___________________________ 29

15. Double-mass comparisons of discharges from 

Corey Creek basin with sediment discharges 

from subbasins.___________________________ 31

16. Relation between storm-sediment loads fcr daily

station and intermittent stations.____________ 32

17. Cumulative frequency curve of daily sediment

discharge-______-----____-_-------_--____- 33

18. Double-mass comparison of sediment discharge __ 36

19. Double-mass comparisons of monthly sediment

discharge for growing and dormant seasons.--- 38

20. Relation of relative erosion potential to sedimentdischarge ratio___________________________ 41

21. Photograph showing construction of a diversion terrace.. 42 

22-27. Graphs showing:

22. Change in erosion potential produced by terrace

construction..______-_____________----_-___ 44

23. Time distribution of diversion terrace construction and effect of diversion terrace construction. 46

24. Adjusted erosion potential versus the sedimentdischarge ratio___________________________ 47

25. Relation of instantaneous water discharge to concentration and discharge of dissolved solids..,. 49

26. Relation of dissolved-solids concentration and

hardness to specific conductance-____________ 51

27. Relation of specific conductance to instantaneous

water discharge______----_____---------__-_ 52
CONTENTS V

TABLES

Page 

TABLE 1. Land use in the Corey Creek and Elk Run basins.---------- C5

2. Agronomic practices in the Corey Creek and Elk Run basins. 6

3. Engineering practices in the Corey Creek and Elk Run basins. 6

4. Most efficient regression equations for daily suspended-sediment concentration and discharge for water discharges of 

10 cfs or greater..______________________________________ 19

5. Simple correlation coefficients and level of significance for daily

water discharge of 10 efs or greater._____________________ 21

6. Simple correlation coefficients and level of significance for

storm data___-________________________-____-_-______- 24

7. Changes in cross-sectional area of aggradation-degradation

ranges-______________________________________________ 27

8. Computation of average annual suspended-sediment discharges, 

Corey Creek near Mainesburg, Corey Creek at Mainesburg, 

and North Branch Corey Creek at Mainesburg-__________ 34

9. Comparison of average annual suspended-sediment discharges

from subbasins within Corey Creek basin_________________ 35

10. Chemical analyses of water, Corey Creek and Elk Run near

Mainesburg, 1956-61__________-_________-___---_------ 48
HYDROLOGIC EFFECTS OF LAND USE

EFFECTS OF AGRICULTURAL CONSERVATION

PRACTICES ON THE HYDROLOGY OF COREY CREEK

BASIN, PENNSYLVANIA, 1954-60

By BENJAMIN L. JONES

ABSTRACT

Analyses of data collected from two small basins in northern Pennsylvania 

during the period May 1954 to September 1960 indicated that changes ir land 

use and land treatment have affected, suspended-sediment discharge from the 

basins. Extensive land use and land-treatment changes have taken plr<?e in 

the 12.2-square-mile Oorey Creek study basin, whereas such changes in the 

10.2-square-mile Elk Run basin, which is adjacent to the northeast, have been 

relatively slight. Elk Run basin, which is topographically and hydrologically 

similar to Gorey Creek basin, was used as an external control for the Corey 

Creek basin study.

Multiple-regression analysis showed that of all the variables, runoff correlated 

most highly with the sediment yield of each basin.

Surveys at selected cross-sections of the two streams indicated that most 

channel changes were in the banks rather than in the bed. At points where 

the stream channel slope was greater than 70 feet per mile, the average annual 

change in cross-sectional area at the measured ranges was less than ±2.5 

square feet. Filling of the stream channel occurred where the slope was 70 

feet per mile or less, and such filling was greater in Corey Creek than rr Elk 

Run.

Trend analyses of data, from both basins indicated no persistent chanf^s in 

quantity of runoff, precipitation, or runoff intensity (peakedness), although 

similar analyses indicated significant changes in the rate of susipended-sed'ment 

discharge from both basins. During the period September 1957 to September 

1960, sediment discharge from Corey Creek basin decreased by 11 percent 

relative to the sediment discharge from Elk Run. All, or most, of this decrease 

was the result of a decrease in sediment discharge during the May to October 

growing seasons. No significant trends were detected in data collected during 

the November to April dormant season.

A factor, termed the relative erosion potential, was formulated for evaluating 

the effects of changes in the hydrologic cover conditions. This factor was 

adjusted for- the effects of diversion terrace construction in the Corey Creek 

basin. A rank correlation test of the adjusted relative erosion potential versus 

the growing season Corey Creek-Elk Run suspended-sediment discharge ratio

Cl
C2 HYDROLOGIC EFFECTS OF LAND USB

resulted in a correlation coefficient, r=0.71, significant at the 3 percent level. 

The least-squares regression equation derived from the same data was

Y=0.276Jf 6.89,

where Y was the Corey Creek-Elk Run sediment-discharge ratio and X was the 

adjusted relative erosion potential. The correlation coefficient v^as 0.65, significant at the 12 percent level. Standard error of estimate was 0.44, or about 

±20 percent of the observed variation in the sediment-discharge ratio.

INTRODUCTION

The purpose of the investigation was to measure and explain the 

hydrologic and sedimentation characteristics of two small Pennsylvania watersheds with respect to changing land use and agronomic 

practices. Well documented, quantitative information regarding the 

effects of conservation practices in natural basins is vital to the effective and efficient planning of conservation programs.

In November 1953, the Corey Creek basin was selected by the U.S. 

Soil Conservation Service for extensive conservation treatment under 

the Federal Watershed Protection Law (P.L. 566) Pilot Watershed 

Program. The conservation plan provided for collection and evaluation of hydrologic data by the U.S. Geological Survey during and 

after conservation treatment. Because no major flood-control structures were planned for the Corey Creek basin, the study afforded an 

excellent opportunity to correlate the hydrologic data with the changes 

in land use and land treatment. Where installed, flood-control structures tend to be the dominant factors in hydrologic changes and, therefore, increase the difficulty of evaluating the effects of other practices.

The study necessitated collection and evaluation of data on precipitation, streamflow, suspended sediment, water chemistry, land use, and 

agronomic and engineering practices.

Elk Eun, an adjacent basin of similar size, topography, and hydrologic characteristics, was chosen as a control for the study because 

changes in land use and treatment were expected to take place at a 

much slower rate than in Corey Creek basin. Elk Run data were used, 

therefore, as a means of estimating the probable behavior of the Corey 

Creek basin under the influence of a less intensive conservation 

program.

This report presents an evaluation of data collected during the 

period May 1954 to September 1960. The analyses presented were used 

to define the relationships between precipitation, streamflov^, and sedimentation. Each of these variables was tested for change in trend 

and, in addition, a test was made of the relation between land use and 

the trend in sediment discharge.
OOREY CREEK BASIN, PENNSYLVANIA, 1954-60 C3 

PREVIOUS STUDIES

The Tioga County Soil Conservation District watershed work plan 

(1954) outlined the conservation problems and suggested the remedial 

practices to be initiated.

Culbertson (1957) made a preliminary evaluation of hydrologic data 

from the two basins, using information collected during the first year 

and a half of the study.

The techniques developed for analyses of the data, and a brief Hstory 

of the project were reported by Jones and Unger (1962).

ACKNOWLEDGMENTS

The investigation was conducted by the U.S. Geological Survey in 

cooperation with the Pennsylvania Department of Agriculture, State 

Soil and Water Conservation Commission, Charles F. Hess, Director. 

The project is under the general supervision of Norman H. B^amer, 

district chemist, U.S. Geological Survey, Philadelphia, Pa., anc1 John 

E. George, geologist-in-charge, Harrisburg subdistrict office.

INSTRUMENTATION AND DATA COLLECTION

Continuous records of streamflow were obtained at the downstream 

limit of each study area, and suspended-sediment data were coHected 

at the stream-gaging station. In addition, sediment data and records 

of water stage were collected at several upstream locations in each 

watershed. The water-stage data were obtained on an intermittent, 

or storm, basis and were used to compute suspended-sedimert discharge contributed from each part of the basin. Figure 1 shows the 

instruments sites and data collection points in the two basins.

Cross-sectional area of the stream channels was measured each year 

at selected permanent sites as an aid in determining the channel contribution to suspended-sediment discharge. The difference in area 

from one year to the next revealed whether the channel was filling or 

scouring at the section. Special note was made of any change in the 

type of channel materials.

There was a rain gage for every 2 square miles in the basin. This 

density insured accuracy and maintained the record during periods 

when one or more gages were inoperative. These gages were at elevations representative of the variations in basin topography. Eecording rain gages, centrally located in each basin, were used to determine the intensity as well as quantity of precipitation.

Specific conductance and pH of the water were measured on tH 1st,

217-102
C4 HYDROLiOGIC EFFECTS OF LAND USE

llth, and 21st day of each month. Complete chemical analyses were 

performed at less frequent intervals.

Land use and agronomic and engineering practices were determined 

yearly for each farm in the Corey Creek and Elk Eun basins. This 

information was collected from the county tax offices, Soil Conservation district offices, and Agricultural Stabilization Conservation 

Committee offices and from studies of aerial photographs and field 

tours of the basins. Each farm was located by a grid system that was 

keyed to an overlay. This overlay corresponded to an aerial photo 

mosaic on which farm boundaries were shown. In addition, each farm 

was located by subbasin.

2 MILES

Location of Corey Creek 

and Elk Run watersheds

A Daily sediment sampling and 

stream-gaging station

A Intermittent sediment 

sampling station

 Recording rain gage

O Nonrecording rain gage

 Aggradation-degradation range

FIGURE 1. Map of Corey Creek and Elk Run basins, showing instrument sites and data'

collection points.
COREY CREEK BASEST, PENNBYiLVANlIA, 1954-60 C5

A computer punchcard system was devised to facilitate the classification and analysis of the data. This system was discussed by Jones 

(1964).

In Corey Creek basin, 132 individual parcels of land were in the 

area being evaluated, whereas in Elk Run basin there were 79. Part 

of this difference was caused by the greater number of small urban 

properties in the town of Mainesburg, which was included in the 

Corey Creek study area.

Designation of both time and location for the land-use data was 

somewhat different from that for the hydrologic data; because of the 

sources of land-use data, calendar years were used in this record.

Tables 1-3 are yearly summaries of land use, agronomic practices, 

and engineering practices in the two basins. The major lard-use 

categories (table 1) are cropland, woodland, grassland, urban land, 

idle land, and wildlife. The sum of these categories equals the total 

area surveyed. Because of the several sources of information, and 

the possibility of multiple uses of the same acreage, it was not always 

possible to balance pasture and hayland against the total grassland.

In Corey Creek basin, 160,000 feet of diversion terrace and seven 

farm ponds of 24 acre-feet total capacity were installed betweer 1954 

and 1960, whereas in Elk Run basin, 19,460 feet of diversion terrace 

and one farm pond of 4 acre-feet capacity were constructed. A. similar contrast between the two basins can be seen in the rate of p.pplication of agronomic practices. Figure 2 shows a newly constructed 

farm pond.

TABLE 1. Land use, in acres

Year

Permanent haySpring

grain Crops Hay

Urban

settlement

Idle Wooded

Pasture Grass

Wildlife

Corey Creek basin

1954.. ..........

1956 

1956 

1957

1958 .......

1959 .......

I960 ....

103

111

111

105

159

490

536

94

79

90

94

85

105

54

2,388

2,388

2,364

2,356

2,266

1,981

2,052

436

436

437

416

374

713

667

99.9

99.9

99.9

100.9

100.9

100.9

100.9

262

257

259

235

212

197

300

2,336

2,345

2,355

2,373

2,438

2,419

2,470

2,405

2,385

2,380

2,271

2,233

2,178

1,915

2,609

2,605

2,617

2,630

2,678

2,997

2,771

23

23

23

23

23

23

24

Elk Run basin

1954. .......

1956 

1956 

1957

1958

1959

I960 

20

20

20

23

23

23

56

2,288

2,288

2,312

2,312

2,312

2,312

2,278

20

20

20

OQ

OO

OO

56

26

26

26

26

26

26

26

390

390

390 ion

ion

ion

390

2,113

2,113

2,110

2,110

2,110

9 1fU

2,104

1,075

1,075

1,054

1,054

1,054

998

998

1,445

1,445

1,424

1,424

1,424

1,430

1,464
C6 HYDROLOGIC EFFECTS OF LAND USE

TABLE 2. Agronomic practices 

[Measurements In acres unless otherwise indicated]

Year I 

w.g

SB

 oS

Ssa 

M

8

Corey Creek basin

1954..-

1955 

1956. _

1957..-

1958---

1959 

I960 

326

592

662

475

120

47

10

16

28

38

8

398

497

471

343

462

17

204

323

501

641

278

130

1

7

13

42

238

148

3

8

42

42

17

129

236

402

550

557

130

5

35

61

277

304

7

74

65

346

72

274

72

23

64

58

26

12

16

10

2

116

19

11

109

9

2

10

13

17

Elk Run basin

1954. _

1955.--

1956..-

1957..-

1958-.-

1959-.- 

1960-.-

29

2 

4 

3 

39

354 

277 

321 

420 

30

15

52

41

2

41

15

45

8

17

35

3 is

19

10

10

3

6

1 17

TABLE 3. Engineering practices

Year

Open drains Impoundments Closed drains Grassed outlets 

and waterways

Corey Creek basin

1954 

1955 .

1956 -

1957 

1958 

1959 

I960 

1,600

400

82

5

1,300

52,605

19, 020

19,985

38, 275

16,785

6,320

7,010

0.3

2 9

.7

.3

.6

4.0

25.5

14.0

8.0

8 n

0.3

2.2

.8

.3

.6

1.5

12.7

2.7

1.6

2.7

715

400

2

1

1,950

2,370

670

600

150

500

48

222

5

90

Elk Run basin

1954 

1955 

1956 -

1957 

1958 

1959 

I960 

1,000

3,835

725

5,045

8,854

0.7 7.0 0.5 4.0

750 15

300 18

DESCRIPTION OF THE BASINS

Corey Creek and Elk Run occupy adjacent basins in north-central 

Pennsylvania (fig. 1). Corey Creek flows from its source on Armenia 

Mountain, approximately 10 miles to its confluence with Tioga River
OOREY CREEK BASIN, PENNSYLVANIA, 1954-60 C7

FIGURE 2. A newly constructed farm pond, Elk Run basin.

at Mansfield. The main gaging station is 4.2 miles upstream from the 

mouth of Corey Creek. The basin area above the gage is 12.2 square 

miles.

Elk Run flows into Mill Creek, a tributary of Tioga River, and 

has a total length of about 10 miles. The gaging station is 5.5 miles 

upstream from the mouth. Drainage area above the gage is 10.2 

square miles.

PHYSIOGRAPHY AND TOPOGRAPHY

Both basins have rolling to steep topography (fig. 3), and the 

elevation ranges from approximately 1,300 feet above mean sea level 

at the gaging stations to about 2,400 feet at the divide. Mean elevation and mean slope of the basins are as follows:

Mean elevation Mean lasin slope 

above sea level (percent)

(feet)

Corey Creek______________________ 1,750 15 

Elk Run_________________________ 1,800 17

The basins lie within the folded part of the Appalachian Plateaus 

Province. This part of the Province is a greatly dissected high plain, 

the two dominant structural features being the Wellsboro anticline and 

Pine Creek syncline, both of which trend northeast-southwest and
C8 HYDROLOGIC EFFECTS OF LAND USE

FIGURE 3. View of the typical rolling topography of Corey Creek basin.

distance is the basin divide.

Ridge in the

plunge northeastward. Both Elk Run and Corey Creek rise southeast 

of the axis of the Wellsboro anticline and flow across the northwest 

limb toward the axis of the Pine Creek syncline, which underlies the 

hills to the northwest. Corey Creek, Elk Run, and most other streams 

in the area exhibit a modified dendritic pattern.

GEOLOGY

The streams traverse two rock formations. Both streams rise in the 

Catskill Formation of Late Devonian and Early Mississippian age and 

flow across the Chemung Formation of Late Devonian age. The Catskill is composed of greenish-gray sandy shales, fine-grained greenishgray sandstones and some fresh-water and marine red shales. The 

underlying Chemung consists of similar rocks but locally may contain 

thin layers of impure limestone.

The basins have been subjected to continental glaciation at least 

three times. Evidence of the latest, or Wisconsin, glaciation can be 

found in deposits mantling the consolidated rock and in glacial outwash deposits formed in the flooded streams during times of glacial 

melting and retreat (Lohman, 1939). This fill largely consists of 

fragments of sandstone or conglomerate in the gravel and cobble size 

range (2-256 mm).
OOREY CREEK BASIN, PENnST/SYLVANIA, 1954-60 C9

SOILS

Soil characteristics are determined by the interaction of five frotors: 

climate, parent material, biological activity, slope or relief, anc! time. 

Land utilization by man may also be a soil modifying factor. Factors 

of importance in evaluating or predicting the sediment yield from a 

specific locality are slope of the soil surface, infiltration capacity, permeability, and erodibility of the soil. Infiltration capacity and permeability of the soil, as well as degree and length of slope, are important in determining the amount of surface runoff and soil erosion 

during a given storm. Infiltration capacity is determined largely by 

the texture, structure, organic matter content, dispersibility, and moisture conditions of the surface soil. Permeability is affected by texture, 

structure, mineral composition, and chemical characteristics of the soil 

profile. During prolonged periods of rainfall, the ultimate infiltration capacity of the soil profile is determined by the least permeable 

horizon.

More than 90 percent of the soils in each of the two basins may be 

classified as channery silt loams. Approximately two-thirds of these 

soils are well drained to moderately well drained and have a surface 

soil consisting of a strongly acid friable channery silt loam less than 

1 foot thick, a subsoil of channery silt loam or silt loam to al out 2 

feet deep, and a substratum of channery silty clay loam or silty clay 

loam. About one-third are fragipan soils and have poor internal 

drainage. The surface soil consists of a friable channery silt loam 

to a depth of 8 inches; a subsoil of silt loam is underlain at a depth 

of 15 inches by a fragipan which is very firm and dense while in place 

but brittle when removed. Both these situations are important agriculturally because much of the cropland is on the well-drained soil; 

the more poorly drained soil is devoted to pasture and grassland.

On the hill tops, the soil is thinner. Much of the forested Ir.nd is 

either gravelly silt loam or rocky silt loam, which are similar soils 

except that the surface and subsoils of the rocky silt loam contain 

angular cobbles and glacial boulders. The remainder of the timberland is rough stony land that has extensive outcrops of bedrock and 

areas of loose slab rock.

Less extensive than the channery silt loams, but still agriculturally 

important, are the silt loams of the flood plains. The surface soil is 

a very friable silt loam as much as a foot in thickness, and the subsoil 

is silty clay or silty clay loam extending to a depth of 24 inches. The 

substratum is a sandy or silty clay which contains some gravel. The 

bottom lands that are composed of this type soil are extensively 

cultivated.

Small areas of poorly drained loam occur on gentle slopes or flats 

near the streams in both basins. These soils have a dark-gr^y to
CIO HYDROLOGIC EFFECTS OF LAND USE

reddish-gray silt loam surface and a subsoil of gray to bluish-gray 

plastic silty clay or clay. The surface soil is 3-6 inches thick, and 

the subsoil may extend to a depth of 36 inches or more. The areas 

underlain by these soils are used largely for pasture or woodland.

In general, soils in the Corey Creek and Elk Eun basins are similar 

in type, distribution, and abundance.

CLIMATE

The climate of the study area is typical of continental climate in 

the North Temperate Zone. The minimum temperatures in winter 

are below 0°F, and the maximum summer temperatures may exceed 

100°F. The mean temperature for the month of January is 26°F, 

and the mean for July is 71°F (Wellsboro, Pa., data, U.S. Weather 

Bureau, 1960).

Frost depth is almost at the surface under grasslands or forest cover 

and extends as much as 3 feet beneath bare cropland during severe 

winters. If a long period of subf reezing weather precedes the first 

snowfall, the soil under all cover conditions may be frozer. During 

many winters, however, the soil remains unfrozen in those areas protected by heavy forest cover. The average frost-free growing season 

is 118 days.

HYDROLOGY

Mean annual precipitation and runoff of the two basins for the 

period October 1954 to September I960 were as follows:

Precipitation Runoff 

(inches) (inches)

Corey Creek______________________ 37.94 15.05 

Elk Run_________________________ 40.69 17.56

In Corey Creek basin, mean annual runoff was 40 percent of mean 

annual precipitation, whereas in Elk Run basin, runoff was 43 percent 

of precipitation.

Considerable variation exists in the precipitation-runoff relation 

from year to year and from season to season. Figure 4 shows the 

mean monthly precipitation and runoff in the two basinr Higher 

average elevation of the Elk Run basin probably influences the quantity of precipitation. Elk Run basin receives an average of about 0.2 

inch per month more precipitation than Corey Creek basin.

During months of high streamflow (as in March and /pril), the 

runoff from Elk Run basin is greater than that from Ccrey Creek 

basin, but during months of recession and low flow (as in May to September), runoff from Elk Run basin is less than that from Corey 

Creek basin.
OOREY CREEK BASIN, PENNSYLVANIA, 1954-60 Cll

The higher average streamflows during the dormant season can be 

partially accounted for by the somewhat greater precipitatior in the 

Elk Run basin, but the lower base flow indicates that the Elk Run- basin 

has less capacity for retaining precipitation in ground-water storage. 

Reasons for this smaller capacity probably include the greater proportion of cropland and somewhat steeper slopes in the Elk Run basin.

Difference in runoff from the two basins is also reflected in the duration curves of mean daily water discharge shown in figure 5. Although the Elk Run basin is 18 percent smaller than the Corey Creek 

basin, mean flow at Elk Run is only 1.5 percent less than at Corey 

Creek, and median flow is only 12 percent less. Flows that oc^ur less 

than 4 percent of the days are greater at Elk Run, and these that 

occur 4 percent or more of the days are of lesser magnitude than those 

at Corey Creek.

Monthly runoff bears no fixed relationship to precipitation, as is 

shown by figure 4. During the summer, most of the precipitation is 

lost through evaporation, is used and returned to the atmosphere by 

vegetation, or is allowed to percolate downward to the water table. 

Beginning with the dormant season in October, more of the precipitation is available as overland runoff because of decreased evaporation 

and plant use. During the winter, the base flow of the streams remains moderately high, even though most of the precipitation is 

stored in the form of snow. The snow melts in March and Ap^il, and 

runoff during these months often exceeds precipitation. The month 

of May usually is a transitional period of declining streamflow as 

rising temperatures and the demands of growing plants again become 

the dominant factors.

It is necessary to detect and explain variations in precipitation and 

streamflow because these factors are important to the production and 

transportation of sediment. A trend analysis of precipitation and 

streamflow follows.

PRECIPITATION AND RUNOFF

The double-mass-curve technique described by Searcy and Hardison 

(1960) was used to test for changes in the hydrologic characteristics of 

each basin. Figure 6 shows the double-mass relation of precipitation 

for the Corey Creek and Elk Run basins, and figure 7 shows the doublemass relation of runoff. These figures indicate that the relative rates 

of accumulation of both precipitation and runoff have been very 

uniform.

Further tests were made of cumulative precipitation and runoff 

versus time for each basin. The rates of accumulation by quarters of 

the 6-year period agreed within 2 percent. These tests indicated that 

there has been no persistent change in the time rate of precipitation 

or runoff in either of the basins.

217-102 Q 66 3
C12 HYDROLOGIC EFFECTS OF LAM> USE

§ 5

IE 4

O

UJ

^x 3

AVERAGE MONTH

INT

2> roiEx1

i

Y//////////A

Vs

V///////////

£

i

Y777/77/////,

ITTI

Y///////////

W?1

V/////////A X//////////A

\

\

\

^ 

^

1

V/////////A

^

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Y///////////

RN

5r

EXPLANATION

u_

0 Z , 4

=3

o:

_i XXUJ o J

1- O

Z Z

AVERAGE l\ir

D ri 

-

1

Jan

_j\^l

1

F*7

^

$

^

\

X

Y77/77/77,

KV

§

^ 0

§

y////////.

m

Corey Creek

ra

bd

Elk Run

IL^^ii i

Feb Mar Apr May June July Aug Sept Oct Nov Dec

FIGURE 4. Average monthly precipitation and runoff, Corey Creek and Elk Run basins, 

October 1954 to September 1960.

RUNOFF PEAKEDNESS

Runoff peakedness, as used in this report, is the ratio of the peak 

rate of direct water discharge to the mean direct water discharge for a 

given storm. High peakedness indicates a more rapid runoff from the 

basin, and the rapid runoff usually results in a higher suspendedsediment discharge. Most soil conservation practices are designed to 

decrease runoff peakedness by slowing overland runoff and extending 

the time required for storm water to reach the stream channel. The 

decrease in runoff generally increases the retention of water as soil 

moisture. Decreasing runoff peakedness results in lower peak stages 

and, therefore, less flooding.

To test whether there had been a change in runoff peakedness at 

Corey Creek, TO storms were analyzed. Each storm resulted in a rainfall of one-half inch or more. The peakedness factor (P) was computed as

in which QP is the instantaneous peak water discharge, QT> is base flow, 

and Qm is the time- weighted mean flow for the storm period.
OOREY CRE'EK BASIN, PENNSYLVANIA, 1954-60 C13

1UUU

o. i r\r\ SECONI I

DC.

LU

Q.

1-

LU

LU

U_

0

QD

ID

O

T

)ISCHARGE, II

0

i_j 

o:

LU1-

<

5

z

<

LU

5

>-

_l

<

Q 1

--

^s

- Cc

_

~~

_

_

_

__

E

1

1 1

>

3rey Cree

1 1

1 II 1

\ Elk Run

k ^«x

 Su

'^ \

Y1

Me

MM

I I

t

t\<\

\\<\

an vt Mean

\

\

^

Median 

I I I

I I I

r Median

\\

ML

\

X9* »

A

* \

»>\N\

\

i i i

i

^

\\it \

-

-

-

_

_

-

-

0.01 0.1 1 10 50 90 99 99.99 

PERCENTAGE OF DAYS INDICATED DISCHARGE WAS EQUALED OR EXCEEDED

FIGURE 5. Duration curves of daily mean water discharge, Corey Creek and lllk Run 

near Mainesburg, October 1954 to September I960.

Two methods were used to analyze for a change in peakedness 

factor: first, a double-mass curve was constructed relating peakedness 

to mean water discharge; and second, the rank correlation method, as 

discussed by Guy (1957), was used to test for any change in peakedness 

with time.
C14

250

HYDROLOGIC EFFECTS OF LAND USE

0 50 100 150 200 250 

CUMULATIVE PRECIPITATION, IN INCHES, COREY CREEK BASIN

FIGURE 6. Double-mass relation of precipitation, Corey Creek and Tlk Bun

basins, 1954-60.

Kunoff was used in the double-mass analysis because it is an independent variable with no change in trend. Figure 8 shows this 

double-mass curve. There are fluctuations in the rate of accumulation 

which probably are caused by seasonal variations in the irtensity of 

rainfall; however, no persistent change in trend is apparent in these 

data.

For the rank correlation analysis, the largest peakedness factor was 

designated as 1, proceeding to the smallest peakedness factor, 70. 

These factors were then arranged in order of time sequence. The 

method resulted in a rank correlation coefficient (T) of 0.15, significant at the 10 percent level, which suggests an increase rather than a 

decrease in peakedness with time. The 5 percent level of significant 

is generally considered to be the upper limit for which any degree of 

certainty can be ascribed to a correlation; so, evidence for increasing 

peakedness is not conclusive. The results do serve as strong evidence 

against any significant decrease in runoff peakedness.
OOREY CREEK BASIN, PENNSYLVANIA, 1954-60 C15

30

28

! 26

f

! 24

I

|| 22 

'm 20

Oo: 18

-co

UJ >-

CCQ 14 

< i 10

co o 12

10

10 12 14 16 18 20

CUMULATIVE WATER DISCHARGE, IN THOUSANDS 

PER SECOND-DAYS, COREY CREEK

22 24 26 28 30

OF CUBIC FEET 

BASIN

FIGURE 7. Double-mass relation of runoff, Corey Creek and Illk Run near Main°sburg,

1954-60.

RELATION OF RUNOFF TO LAND USE AND LAND TREATMENT

Trend analyses indicated no significant change

of runoff or in the peakedness of runoff during; storm eventr The 

practices initiated during the conservation program have r.ffected 

runoff characteristics very little or else the various effects of the 

changes have been such as to balance one another.

The study by Schneider and Ayer (1961) showed that ever in extensively reforested basins the changes in runof ' characteristics take 

place rather gradually. Although there have been extensive land-use 

changes in the Corey Creek basin, nothing approaching the magnitude 

of a complete reforestation has been attempted. About 2 percent of 

the basin area was planted in trees through 1960, but even when the 

trees mature, they probably will have little effect on the runoff characteristics of the entire basin.

Of all the conservation practices initiated, diversion terracing might 

be expected to exert the greatest effect on runoff characteristics. About

sither in the quantity
HYDROLOGIC EFFECTS OF LAND USE

0 500 1000 1500 2000 2500 

CUMULATIVE DIRECT STORM RUNOFF, IN CUBIC FEET PER SECOND-DAYS

FIGURE 8. Double-mass relation of storm runoff and peakedness factor, Corey Creek

near Mainesburg, 1954^60.

19 percent of the Corey Creek basin area was affected by diversion terrace construction between 1953 and 1960. The increase in evaporation 

of water released to the terraces, as well as the increase in the effective 

permeability of the slope above the terraces, should have resulted in a 

reduction in streamflow, but apparently this reduction, if present, is 

too small to be detected.

SEDIMENTATION

When erosion removes the fertile upper layer of the soil, a valuable 

resource has been lost and cannot be replaced quickly or easily. If 

soil erosion exceeds the rate of soil formation, the result is reduction of
OOREY CREEK BASIN, PENNSYLVANIA, 1954-60 C17

the land's ability to support crops. In addition to the effects on the 

soil itself, eroded material chokes stream channels and causes flooding, 

fills, reservoirs, renders the stream incapable of supporting desirable

animal and plant life, and reduces the usefulness 

dustrial or domestic purposes.

SUSPENDED-SEDIMENT TRANSPORT

In this report, no attempt is made to estimat 

basins, but instead it is assumed that any changes 

the quantity of sediment reaching the stream and 

will be reflected in the measured suspended-sediment discharge

Suspended-sediment discharge varies with changes 

affecting both erosion and sediment transport. It 

fore, to examine these factors before any meaningful 

be made between the rate of suspended-sediment 

effects of conservation treatment.

ANALYSIS OF SEOTMENTVrRANSCPORT VARIABLES

In most natural streams, a relation exists between 

and suspended-sediment discharge. This relation 

as an average curve, or sediment-transport curve 

determining the sediment-transport relation involves 

discharge versus sediment discharge and drawing 

through the scatter of points. The general relation 

discharge and water discharge is

of the water for ins soil erosion in the 

in erosion will alter 

that these changes

in the factors 

is necessary, therecorrelations can 

discharge and the

water discharge 

may be expressed

This method of 

plotting water 

an average, curve 

between sediment

where Qs is sediment discharge, in tons per day; Qw is water discharge, 

in cubic feet per second; and a> and n are constants. The ecnation 

may be adjusted for other factors which affect phe relation, such as

season, runoff peakedness, and rainfall intensity by using thQ, multiple-regression technique described by Linsley, ohler, and Paulhus

(1949).

Because many of the computations used in tjiis report were performed by a digital computer and a standar

program, the above equation was transformed to 

tion by taking the logarithm of both sides

logio Qs=logw a+n Iog10 Qw. 

Variables, such as temperature (T7 ), which

multiple-regression 

a straight-line funcbear a straight-line 

relationship to Iog10 Q8 were not transformed so that the form of the

equation becomes

logio Qs=logw a+n Iog10 Qw+bT 

where & is a constant.

The data analyzed by computer for this pro ^ress report were of 

two major types: (1) daily data collected at Core7 Creek near Mainesburg, Pa., and Elk Run near Mainesburg, Pa., and (2) storm data,
CIS HYDROLOGLC EFFECTS OF LAND USE

Corey Creek near Mainesburg, Pa., (daily sampling station), and 

Corey Creek at Mainesburg, Pa., (intermittent sampling station).

SEASONAL ANALYSIS OF DAILY DATA

Preliminary plotting indicated that the daily streamflow and sediment data should be classed by dormant season (November to April) 

and by growing season (May to October). Within these classes, the 

data were divided by streamflow because the sediment-transport characteristics at low flows were found to be different from thoee at high 

flows. The point at which this change occurred was at a m°-an daily 

water discharge of about 10 cfs for both stations. At flows below 10 

cfs, suspended-sediment concentration varied only slightly with water 

discharge; at flows above 10 cfs, concentration increased rapidly with 

increasing water discharge. More than 99 percent of annual sediment 

discharge from the basins is transported by daily streamflows of 10 

cfs or greater, and therefore, this part of the sediment-transport relation was used in determining trends in the amount of sediment being 

transported. The complete grouping of daily data was ar follows:

A. Dormant season (November to April)

1. Water discharge=0-9.9 cfs

a. Suspended-sediment concentration 

b. Suspended-sediment discharge

2. Water discharge=10 cfs or greater

a. Suspended-sediment concentration 

b. Suspended-sediment discharge 

B. Growing season (May to October)

1. Water discharge=0-9.9 cfs

a. Suspended-sediment concentration 

b. Suspended-sediment discharge

2. Water discharge =10 cfs or greater

a. Suspended-sediment concentration 

b. Suspended-sediment discharge.

The following variables were used in this analysis: 

A. Dependent variables:

Log 10 Qs =logarithm of daily suspended-sediment discharge, in

tons per day 

Log 10 C'=logarithm of mean daily concentration of suspended

sediment, in parts per million 

B. Independent variables:

M=month of observation (1-12) 

F=year of observation (1954-60) 

i=& measure of time duration, in days, since the beginning of

record (first day of record = 1)

Log 10 Qw=logarithm of mean daily water discharge, in cubic feet 

per second
OOREY CKE'EK BASEST, PENTSTSTLVANttA, 1'9 5 4-60 C19

Log 10 Qttp=logarithm of mean water discharge on the day 

previous to the one being measured (a measure of 

antecedent streamflow conditions), in cubic feet 

per second

T daily water temperature, in degrees Fahrenheit.

In the first computations, all the independent variables were used 

in the equation. The least significant independent variable was eliminated in each successive computation. These eliminations wore continued until sediment discharge or concentration was shown only as 

functions of the most significant independent variable.

Figure 9 shows the average sediment-transport curves for streamflows of 10 cfs or greater. The curves have somewhat steeper slopes 

for the dormant season than for the growing season. The slopes of 

both curves for the Elk Eun basin are steeper than the sloper of the 

Corey Creek curves, indicating a higher rate of sediment discharge 

per unit water discharge in Elk Eun.

The equations that can be used to estimate sediment concentration 

or sediment discharge with the smallest degree of error are tiH most 

efficient. Table 4 gives the most efficient equations for water discharges of 10 cfs and greater and the standard error of estimate of 

the dependent variable for each equation.

TABLE 4. Most efficient regression equations for daily suspended-sedimen4, concentration and discharge for water discharges of 10 cfs or greater

Season

Standard 

error 

(logio units)

Equation

Corey Creek near Mainesburg

Growing __ _

Dormant. __.

0. 5564

.4630

. 4750

.4047

Lo 0-23061o Q +001957T-0

3.830.

Logio (7=1.216 logio Q«, + 0.01252 T-0

0.04810 F+ 1.896.

Log10 Q,=2.4411og10 Qu,-0.31881ogioQ U)

0.02405M-O.On4r-2.110.

Logio C=1.5231og10 Q u,-0.33501ogioQ.

0.01333r-0.0003119? + 0.4130.

.49911og, 0 Q»p-

.45311ogioQu,p 

p -0.0002862; -

BJ,-0.02512MElk Run near Mainesburg

Growing

Dormant, ___

0. 4512

.3536

. 4304

. 3883

Lo 0-252610 Q +0 01692T-(

3.992.

Logio C=1.5391og10 Qu, + 0.01244T-C

0.2974 F-0.0008764Z- 17.17.

Logio Qs =2.6011ogioQu,-0.41861ogioQ

0.03088 F- 1.326.

Logio C= 1.6541ogio Qw - 0.37861ogio Q

0.01484M+ 1.965.

).47001og, 0 Q«,p-

.42201ogioQ»p4

^p-O.OU.OSMU)P -0.04670F217-102 O 66
OJ

 fU uj

a g a B 0 PS

B ~

^ «

?< C

CO

gH3 

PS S 

p' &

s s.

^1

si

01 S *-.§

HO

SUSPENDED-SEDIMENT DISCHARGE, IN 

8
OOREY CREEK BASIN, PENNSYLVANIA, 1954-60 C21

The independent variables having the highest degree of correlation 

with the dependent variables are water discharge and the previous 

day's water discharge. During the growing season, the daily water 

temperature shows a high degree of correlation, but it is less significant during the dormant season. The measures of time, duration, and 

season (?', J/, and Y) exhibit varying degrees of significance.

Table 5 lists the simple correlation coefficients of all the variables 

and the level of significance of each.

TABLE 5. Simple correlation coefficients and level of significance for daily water 

discharge of 10 cfs or greater, 1954-60

i LogioO,^ T LogioP, LogioC Logio9» Y

COREY CREEK NEAR MAINESBURG

Growing season

Af 

Y.. -..-

T. ....... ..

1-0.2145

i .9968

2 . 1639

-.02498

.02691

1-.3548

.05831

2-0.1427

3 . 06951

i . 2893

1-.3150

4-. 1099

1-.3734

2 0. 1414

1-.3606

1-.2089

* . 1382

4.1089

2 0. 1659

. 01381

i .7108

1.6849

2 0. 1934

_ OSQ71

i . 3274

0.09036

2.1556

1-0.2911

Dormant season

AfY..........

T.-. .......

3-0. 03077

1.9785

i .1061

1-.1544

2-. 07691

1-.1657

0.006457

i . 5189

i .2026

1.3156

1 . 1799

i 0. 1450

1 1QCT9

i . 1374

3.1028

03649

1-0.1063

-. 05230

1.8142

i . 5397

«-0. 05871

1-.1362

i . 3919

0. 002464

2.1047

1-0.2280

ELK RUN NEAR MAINESBURG

Growing season

Af 

Y..........

T. .........

1-0.2012

i .9972

.01864

-.008495

1-.3920

4 . 1137

-0.09604

4.1192

i . 2917

1-.2042

-.04686

1-.3157

1-.4017

i _ ^039

2 . 1515

.06657

2 0. 1802

-0. 02073

i .8024

i .9028

10.2367

.0009311

i . 5987

4 0. 1331

.09970

1-0.2726

Dormant season

M.. ..______

Y..........

T..........

i-0. 1424

1 . 9777

i . 2003

2.09110

i . 1320

*-. 07878

i . 1185

-0. 02879

M229

i . 5007

i . 2356

i . 3002

.02295

i 0. 1574

2-. 1093

-. 005353

. 05832

-. 007093

-0. 05645

i . 1394

i . 8781

i . 8390

-0. 007384

2.08864

i . 6785

-0.03485

1.2009

1-0.3461

1 Significant at 0.01 level.

2 Significant at 0.05 level.

3 Absence of a qualifying note indicates level of significance at greater than 0.10.

4 Significant at 0.10 level.

ANALYSIS OF STORM DATA FOR COREY CREEK BASIN

The sediment sampling program at the upstream, or intermittent, 

locations in Corey Creek basin was designed to provide coverage of 

the major storm events. The multiple-regression technique WFS used
C22 HYDROLOGIC EFFECTS OF LAND TJSE

to analyze hydrologic data collected during these storm events. The 

analyses were performed on data representing 21 storm events sampled at the daily station, Corey Creek near Mainesburg, Pa., (drainage area, 12.2 sq mi) and at the largest intermittent station, Corey 

Creek at Mainesburg, Pa. (drainage area, 8.44 sq mi) .

The following variables were used in this analysis : 

A. Dependent variables :

Log10(7M,=

logarithm of mean water-weight sediment concentraLog10 (7Ml = tion for daily and intermittent stations, respectively, computed as

C'«=7r^W where

Vwt&

Qs= storm sediment load, in tons,

QW(=tota\ storm runoff, in cubic feet p<>r seconddays,

K=a, constant which varies with the length of

the storm. 

B. Independent variables:

Mt=time, in months (January 1954=1)

Qwd= logarithm of direct storm runoff (Qn Q&) for

daily and intermittent stations, respectively, 

in cubic feet per second-days 

rai =mean air temperature (°F) for 10 days previous to storm 

Ta2 =mean air temperature (°F) for 30 days previous to storm 

(data from U.S. Weather Bureau Wellsboro, Pa., station) 

Logio jRs=logarithm of rainfall quantity during storm period,

in inches 

Logio jRi=logarithm of rainfall intensity for the most intense

period of the storm, in inches per hour

PandP!=peakedness factor for daily and intermittent stations, respectively, defined as

%?~%> where

vtfm vtf&

Qm = time-weighted mean storm runoff, in cubic

feet per second

(^6= base flow, in cubic feet per second 

Qp= instantaneous peak runoff, in cubic feet

per second.
OOREY CRE'EK BASIN, PENlSTSYLVAOSflEA, 1954-60 C23

Suspended-sediment concentration, rather than discharge, was used 

because the length of storms varied. Water-weighted sediment concentration provided a more direct comparison, regardless of storm 

duration. The number of the month in which the storm o^-curred 

was used to indicate time duration since the beginning of the record.

Because air temperature is related to season and thus to storn characteristics, a test was devised to determine if the temperature conditions prior to a storm runoff were significant. Two periods of 

antecedent air temperature were considered to determine if the temperature conditions for a specific period prior to a storm were significant to the storm characteristics. Both measures of antecedent 

temperature conditions were about equally significant, indicating that 

temperature is probably largely a measure of season. After th^ initial 

computations, only To, 1 was retained for the remaining computations.

The most efficient equations are shown in the following tab!?,:

Station

Corey Creek near 

Mainesburg. 

Corey Creek at 

Mainesburg.

Standard 

error 

(logio units)

0.3883 

.3699

Equation

Logio C w =0.5129 logio Qwd+Q.W701Tai +0.8542

Logio CWl =0.31971ogio QM)(il -0.008204M< + 0.9574 

logio (100# a) + 0.1017 Pi + 0.5439

Direct storm runoff was the most important variable affecting 

suspended-sediment concentration at both stations. At the upstream 

station, the month in which a storm occurred seemed to be more significant than the antecedent air temperature, which was the significant 

seasonal variable at the downstream station. The retention of runoff 

peakedness and rainfall quantity as significant variables in the equation 

for the upstream location may be a reflection of the less complex 

drainage system of the smaller area, which causes a mor? direct 

response to precipitation. There was a wider variation in runoff 

peakedness at the upstream location, and the average per.kedness 

factor was 4.3, compared with an average of 3.5 at the downstream 

(daily) station.

The simple correlation coefficients between all variables and the 

levels of significance are shown in table 6.

SIZE DISTRIBUTION OF SUSPENDED SEDIMENT

Size distribution of the suspended sediment was an important 

characteristic measured during the study. The proportion of sand, 

silt, and clay being carried by the stream gives some indication of the
TABLE 6. Simple correlation coefficients and level of significance for storm data, Corey Creek nea

1954-60

LogioC^ ---

Log # ,<*-- --

Af,__ -_.._..

T£________-.

L^10 (100fi,)~

Log10 (100fi«)~

P.. ____.-___

LogioC^j--- -

Log #«,<*! -

Pi

!-0. 0008376

-. 2434

. 1068

.3245

.2869

.1719

. 03058

2. 8126

. 2718

-. 3262

LogioQwd,

2 0. 5963

2. 9311

-. 08262

3-. 4571

2 -. 4695

. 03321

«. 3951

-. 07281

«. 4129

LogioC,,,,

3 0. 4524

*. 3921

-. 1682

. 1641

. 1305

3. 4684

2. 6881

3. 4501

P

0. 1822

-. 03131

. 08567

.2218

. 2142

4. 4214

. 1569

Login (lOOtf )

0. 3469

*. 3713

. 05005

. 2792

.3131

2. 5510

Logio (lOQRi)

0. 2173

-. 003887

.2625

4. 3930

«. 4340

1 Absence of a qualifying rate indicates significance at a level greater than 0.10.

2 Significant at O.Ol level.

»S ignificant at 0.05 leve

1 Significant at 0.10 leve
OOREY CREEK BASIN, PENNOTLVAiNILA., 1954-60 C25

type of soil being eroded. Significant changes in these proportions 

might also be indicative of changing basin conditions. Figure 10 

shows the proportion of sand, silt, and clay as percent of tl Q, total 

weight in suspended-sediment samples from the two basins. Most of 

these samples contain more than 50 percent silt. The shaded area in 

figure 10 indicates the silt loam soil texture, which is the predcminant 

textural class in the Corey Creek and Elk Bun basins. Mo^e than 

three-fourths of the suspended-sediment size analyzes correspond to 

this soil class.

Differences between the two basins seem to be the relative content 

of sand and clay. Suspended sediment from Corey Creek basin has a 

higher clay content, and suspended sediment from Elk Kun has a 

higher sand content; however, there is enough similarity in the 

particle-size composition so that some general relation can be formulated by combining the analyses from the two basins.

The water discharges represented by the data points in figure 10 

were relatively high and were at least 10 times the mean water discharge. Although streamflow of this magnitude or larger occrrs only 

about 2 percent o| the time, 70 percent or more of the annual sediment 

discharge occurs during these high flow periods. Figure 11 shows the

EXPLANATION

 

Corey Creek

Elk Run

EXAMPLE 

Sand 18 percent 

Silt 48 percent 

Clay 34 percent

.jAYyyyyyyVWWv / V V V V V V V '"' '""

vvvvvvvv

o ~o ~o *o 

PERCENTAGE OF SAND (0.062-2.000 MILLIMETERS)

FIGURE 10. Percentages of sand, silt, and clay in suspended-sediment samples, 

Corey Creek and Elk Run near Mainesburg, 1955-60. Shaded area indicates 

silt loam soil texture.
HYDROLOGIC EFFECTS OF LAND USE

Clay

8 §

O

8

o " o 

INSTANTANEOUS WATER DISCHARGE, IN CUBIC FEET PER SECOND

FIGURE 11. Relation of the sand, silt, and clay discharge to instantaneous water 

discharge for Corey Creek and Elk Run near Mainesburg, 1955^-60.

relationship between suspended-sediment discharge and water discharge for each size range. The discharge of sand increases more 

rapidly with water discharge than does the discharge of either silt or 

clay.

The steeper slope of the sediment-transport curve of sand may be 

caused by the immediate availability of sand-size sediment in the 

stream channel or may result because sand is deposited near the stream 

channel during the smaller runoff events.

STREAM-CHANNEL CHANGES

Generally, the aggradation-degradation ranges in Corey Creek show 

a tendency toward deposition of sediment throughout the period of this 

study. Of the 14 ranges surveyed, 10 were filling and 4 were scouring.

Most changes have taken place in the streambanks by addition or 

removal of material of sand size or finer. Undercutting and slumping of streambanks are commonly observed in both basins. Changes 

in bed elevation generally have been very slight, and, in the se places 

where the bed elevation has changed, the change usually has been a 

result of filling rather than scouring.
OOREY CREEK B'ASEST, PEOSFNSYLVAlNIIA, 1'9 5 4-60 C27

In Elk Run, changes at the cross sections were almost evenly divided between scour and fill. Table 7 summarizes the resultr of the 

surveys for both basins. The locations of the ranges are si own in 

figure 1. Range 5 in Elk Run basin is on an actively migrating 

meander and, therefore, represents a type of channel regimen different from that at the other ranges.

The distribution of changes in the cross sections is indicated in 

figure 12.

In both stream channels, the bed is composed mostly of material 

that is gravel size (2.0-64 mm) or larger (fig. 13). The range data 

indicate that there has been very little redistribution of this naterial 

within the measured cross sections.

Figure 14 shows the relationship between the average annual scouring or filling and the slope of the stream channel at each range. 

Ranges on slopes of greater than 70 feet per mile in either basin

TABLE 7. Changes in cross-sectional area of aggradation-degradation

ranges, 1954-60

Raage

Scour (sq ft)

Net change Average 

annual change

Fill (sq ft)

Net change Average 

annual change

Corey Creek

1 - --

3

4_

5

B-----__ --__-_-

8-_-____----_______

9__________________

5.29

8.40

. 54

. 15

0.88

1. 40

. 09

.02

12. 507

7.26

20.47

39. 55

9. 22

4. 96

55.67

9.98

2. 04

4. 11

2. 08

1. 21

3 41

6 59

1.54

.83

9 28

1. 66

. 34

. 68

Elk Run

1

3

4

5__-_______________.

6-___________-__-__.

7___________________

8-_-_________-______

9___________________

10___-_-___-________

12__________________

13____--___-__._____

79. 86

1.77

2. 28

4. 14

3. 84

13. 31

. 30

. 38

1. 03

. 64

8. 33

2. 16

4. 53

8. 37

3. 73

8. 06

1 39

36

91

2 09

62

1. 54
C28 HYDROLOGIC EFFECTS OF LAND USE 

COREY CREEK 

Range 1

FEET 

10r

10 FEET

Range 7

Range 11

EXPLANATION

1954 

T960"

Scour Fill

ELK RUN 

Range 1

Range 11

FIGURE 12. Changes in stream cross sections at selected ranges in the Corey 

'Creek and Elk Run basins, 1954-60. Location of ranges is shown in figure 1.
OGRE'Y CREEK BASIN, PENNSYLVANIA, 1954-60 C29

FIGURE 13. Elk Run, showing bed material typical of both stream channels. Note 

undercutting of trees on right bank.

50 100 150 200 

CHANNEL SLOPE AT RANGE, IN FEET PER MILE

UJ

0

Z

cc

*f

CHANGE I

^

UJ

C£

<

Z

z

UJ

cc

UJ

It)

10

_J

uj 5

UJ 

UUJ

cc

3 °

Z

^5

O

o

10

15

1 1 1 1 1

- .n

Y

~ X B

v ^^^^^. Q 7 "lQ^

18 !«x 12 8xxf, 15*^ 

10

EXPLANATION

X

Elk Run

Corey Creek

1 1 1 1 1

250

FIGURE 14. Relation between average annual scouring or filling and stream slope at 

Corey Creek and Elk Run aggradation-degradation ranges, 1954-60.
C30 HYDROLiOGIC EFFECTS OF LAND USE

showed an average annual scour or fill of less than 2.5 square feet. 

Filling of the stream channels occurred where the slope was TO feet 

per mile or less. At such locations, the amount of filling was greater 

in Corey Creek than in Elk Run.

SUBBASIN SEDIMENT YIEGLDS FOR CCXKEY CREEK BASIN

The average annual suspended-sediment discharges from the major 

Corey Creek subbasins were computed by using data from the upstream sampling stations. This computation was made to determine 

the variations in the sediment-transport characteristics within the 

basin.

Two methods were used for the computations. In the first method, 

double-mass curves were constructed comparing sediment discharge 

for individual storms at the downstream station with that at each 

upstream station (fig. 15). The average slope of this double-mass 

curve was taken as the proportion of the basin sediment discharge 

being contributed by each subbasin.

In the second method, the sediment discharge for individual storms 

at each intermittent station was related to the daily station sediment 

discharge for the same storm. The average relation (fig. 16) then 

was used with a cumulative frequency curve of sediment discharge 

(fig. 17) to compute an average annual sediment discharge.

Table 8 shows this second method of calculation. Percentage intervals were selected from figure 17, and the sediment discharges corresponding to the midordinate of the percentage intervals were 

tabulated. The corresponding values of sediment discharge for the 

intermittent stations were then read from the curves in figure 16 and 

tabulated. Each of these was then multiplied by the percentage interval and the sum of the products was the mean daily sediment 

discharge, which was multiplied by 365 to obtain the annual sediment 

discharge.

Table 9 compares the suspended-sediment discharges computed Fj 

the two methods. Results agree within a few percent. The computed sediment discharge from the remainder of the basin is the 

difference between the measured basin discharge and the sum of the 

computed subbasin discharges. This remaining part of the basin 

includes most of the urban land and has the highest proportion of 

cropland and the lowest proportion of woodland. In view of these 

facts, the relatively high computed yield is not unrealistic, as will be 

demonstrated in the discussion of land-use effects.

Data from the third intermittent sampling station (South Branch 

Corey Creek at Mainesburg) were not used in this evaluation, but the 

drainage area for this sampling station is included in the area of 

the largest intermittent station (Corey Creek at Mainesburg).
OOREY CREEK BASIN, PENNSYLVANIA, 1954-60 C31

1000

s r) a: 0 8

io

500

1000 2000 3000 4000

3000

2000

1000

2000 4000 6000

CUMULATIVE SUSPENDED-SEDIMENT DISCHARGE, IN TONS

COREY CREEK NEAR MAINESBURG

8000

FIGURE 15. Double-mass comparisons of storm suspended-sediment discharges from 

the Corey Creek basin with storm suspended-sediment discharges from the Corey 

Creek subbasins.
C32 HYDROLOGIC EFFECTS OF LAND USE

100

10

OH

H V)

Q 

LLJ i_

9<

0.1

o.oi

\ I

North Branch Corey Creek 

at Mainesburg

I I I I I I I I I

0.1 1 10

STORM SUSPENDED-SEDIMENT DISCHARGE, IN TONS PER 

SQUARE MILE, COREY CREEK NEAR MAINESBURG

100

FIGURE 16. Relation between storm suspended-sediment loads for daily station and 

intermittent stations, Corey Creek basin, 1954-60.
COREY CRE'EK BASIN, PENNSYLVANIA, 1954-60 

5000

C33

1000

100

10

0.1 J_L

0.1

\ \ \ J__L

1 10 50 90 99 

PERCENTAGE OF DAYS INDICATED SEDIMENT 

DISCHARGE WAS EQUALED OR EXCEEDED

99.99

FIGURE 17>. Cumulative frequency curve of daily suspended-sediment discharge, 

Corey Creek near Mainesburg, October 1954 to September 1967.
TABLE 8. Computation of average annual suspended-sediment discharges, Corey Creek n

and North Branch Corey Creek at Mainesburg, 193

0.0-0.1.

0.1-0.2.

0.2-0.3.

0.3-0.5.

0.5-0.7.

0.7-1.0.

1.0-3..

3-5. _

5-7..

7-10_

10-15.

15-20_

20-30.

30-40.

40-50.

Percentage limits

Mean daily discharge. __ .tons.

Mean annual discharge

(daily X 365) ______ _tons_

Percentage 

interval

0. 1

. 1

. 1

. 2

. 2

. 3

2. 0

2.0

2. 0

3. 0

5. 0

5. 0

10

10

10

Percentage 

midordinate

0. 05

. 15

. 25

. 4

. 6

. 85

2

4

6

8. 5

12. 5

17.5

25

35

45

Suspended-sediment disc

(tons per day)

Corey Creek

near 

Mainesburg

1,450

740

430

330

200

130

44

14

6. 4

2. 7

1. 1

. 5

. 3

. 2

. 1

Corey Creek

at 

Mainesburg

N

C

at 

710

330

180

135

77

48

14

5. 5

1.2

. 6

. 2
TABLE 9. Comparison of average annual suspended-sediment discharges from subbasins w

methods, 1954-60

Station

North Branch Corey Creek at Mainesburg

Remainder of basin (bv difference)

Drainage area 

(sq mi)

12. 2 

8. 44 

2. 13

1. 63

Mean annual susp

discharge 

Double-masscurve method

800 

400

790

Su
C36 HYDROLOGIC EFFECTS OF LAND USE

TRENDS IN SEDIMENT1 DISCHARGE

Data collection for this study was not initiated until after the beginning of the construction phase of the conservation program in 

Corey Creek basin. As will be shown, the soil disturbed during the 

construction phase of the program undoubtedly affected the rate of 

suspended-sediment discharge; thus, no data are available to allow 

a precise determination of the rate of sediment discharge in Corey 

Creek basin during a period of normal activity.

Compared to Corey Creek basin, Elk Eun basin has received relatively little conservation treatment. Suspended-sediment data from 

Elk Eun provide the best available estimate of the sediment-discharge 

rate under relatively undisturbed conditions. In the following trend 

analyses the Elk Eun data used as a base against the Corey Creek data 

were evaluated.

Double-mass curves were constructed to detect any change in the 

rate of suspended-sediment discharge from the two basins. Figure 

18 is a double-mass comparison of suspended-sediment discharge from 

both basins. The curve shows that definite changes occurred in the 

relationship in December 1956 and again in December 1958. Comparison of the first and last parts of the curve indicates a relative 

decrease of about 11 percent from the Corey Creek basin but a temporary sharp increase during the middle period.

8000

2000 4000 6000 8000 10,000 

CUMULATIVE SEDIMENT DISCHARGE, IN TONS, ELK CREEK B^SIN

FIGURE 18. Double-mass comparison of suspended-sediment discharge for Corey Creek 

and Elk Run near Mainesburg, October 1954 to September 1960.
OOREY CREEK BASIN, PENNSYLVANIA, 1954-60 C37

To investigate seasonal distribution of the trends, double-mass 

curves were constructed for the growing season (May to October) 

and the dormant season (November to April).

Data for October 1955 were eliminated because the sediment discharge for that month was abnormally high at both stations and 

amounted to a significant proportion of the total sediment discharge 

for the period of record. Data for April 1957 were eliminated from 

the dormant season curve for the same reason.

The curves in figure 19 compare the rates of sediment discharge 

from the two basins by season. The dormant season curve stows no 

significant long-term change in the relation.

The double-mass curve for the growing season indicates three distinct periods in the relative rate of sediment discharge from the two 

basins:

Average slope of

double-muss curve

(percent)

May 1954 to May 1955________________________ 83

June 1955 to May 1958________________________ 200

June 1958 to September 1960____________________ 41

Comparison of the slope of the curve for the May 1954 to May 1955 

period with the slope for the June 1958 to September 1960 pericd indicates a relative decrease of 51 percent in sediment discharge from the 

Corey Creek basin. Approximately 25 percent of the total suspendedsediment discharge from the Corey Creek basin occurred during the 

growing season. The maximum possible contribution of the growing 

season trend in sediment discharge was, therefore, 13 percent, which 

was more than sufficient to have produced the previously indicated 

overall trend of 11 percent. This fact, along with the fact that no 

significant trend was indicated in the double-mass relation for the 

dormant season, serves as strong evidence that the significant changes 

in suspended-sediment discharge have occurred during the growing 

season,

RELATION OF SEDIMENTATION TO LAND USE AND LAITO

TREATMENT

The trend analyses of sediment discharge indicated a sigrificant 

decrease in the suspended-sediment discharge from Corey Creek 

basin during the growing season. It was necessary to use statistical 

techniques in relating this decrease to the agronomic changes which 

have taken place in the basin. The techniques used were rank correlation and least-squares regression. Both these techniques required a 

numerical evaluation of the effects of changing land use and agronomic 

practices.
CUMULATIVE SUSPENDED-SEDIMENT DISCHARGE, 
OOREY CREEK BASIN, PEINNSYLVAMEA, 1954-60 C39

The changes taking place in the basins are of two general kinds: 

changes in the type and density of vegetative cover, and changes in the 

physical or topographic characteristics of the land.

Land-use changes are considered first. Because each of these 

changes affects the erosion potential of the basins to a different degree, 

it was necessary to evaluate their combined effects. To estimate the 

relative erosion under different cover conditions, relative erosion 

factors were assigned for different types of cover :

Factor

Woodland _________________________ 1 

Idle land __________________________ 2 

Grassland _ _ _____________ _ ___ _ _ _____ 6

Urban land __________________ __ 50 

Cropland _______ . _________________ 100

The numbers assigned to the various land-use categories are dimensionless. The values are based on the cover factors used by Musgrave 

(1947) for computing erosion losses. The values indicate that urban 

land, for example, has 50 times the erosion potential of woodland.

The relative erosion potential for each type of cover can be computed 

with the formula

where E-R is the relative erosion potential, Fe is the relative erosion 

factor, and P is the percent of the basin area in a specific type cf cover. 

The summation of erosion potentials for all types of hydrologic cover 

is then the relative erosion potential for the whole basin.

The annual relative erosion potentials computed for each b-r.sin are 

as follows:

Relative erosion 'potential

Year 

1954.. ________ _ ______

l955---___--___----_-_-

1956__-_-___-___-__.___

1957-.

1958-_____________---_-

1959_-_____.___________

1960----------___------

Corey Creek basin E 

____-____--_ 34.1

____________ 340

____________ 33.8

----__----_- 33.5

_--___--_--_ 32.5

29.2

----___--_-_ 29.8

Efe Run bc*in 

38 5 

38 5 

38 5 

38 8 

38.8 

38 8 

38 5

These figures represent the relative degree of erosion that theoretically would occur if the forces causing erosion were constant with 

time; however, these, forces are seldom, if ever, constant. The sediment discharge of a stream at any given time can be related to the 

erosion potential of the basin only if the proper adjustment is made 

to account for the variations .in the factors acting to produce erosion
C40 HYDROLOGIC EFFECTS OF LAND USE

and transportation. The sediment-discharge data from Elk Kun 

basin, where there has been little change in land use, wer^, used to 

adjust the Corey Creek basin data. The factor used was th^ average 

monthly ratio of the growing season suspended-sediment discharge 

from Corey Creek basin to the sediment discharge from Elk Pun basin. 

This method is another way of expressing the mean annual slope of 

the growing season double-mass curve. These factors are as follows:

Suspended-sedimentYear discharge ratio 

1954._____________._______________________ 1. 66

1955 _____________________________________ 2. 70 

1956________ _ _________ _ __________________ 1. 54

1957____________________________________ 3. 40 

1958____________________________________ 1. 52 

1959_________________ _ _________________ 1. 44 

1960___________________________________ 1.15

Data used for the correlation of relative erosion potential with 

sediment-discharge ratio were limited to the growing season because 

the computed erosion potential is based on growing season conditions 

and because during the dormant season, other factors such as temperature, snow cover, and depth of frost affect both the cover conditions 

and the relations between precipitation, runoff, and sediment discharge.

Figure 20 shows the relation of the relative erosion potential to 

the sediment-discharge ratio. The rank correlation coefficient was 

0.62, significant at the 0.07 level.

It was evident from this test that the fluctuations in the sedimentdischarge ratio could not be accounted for by the crop changes alone, 

as evaluated by the relative erosion potential. Other conservation 

practices that affect the sediment yield also were considered.

EFFECTS OF DIVERSION TERRACE CONSTRUCTION

The changes next considered were those associated with engineering 

practices. More diversion terraces were installed than any other 

practice. In the Corey Creek basin, 160,000 feet of diversion terraces were constructed between 1954 and 1960. In the Elk Run basin, 

19,460 feet of terraces were constructed during the same period. Diversion terrace construction accounted for about 90 percent of the 

engineering practices, on the basis of acreage affected.

A somewhat unusual aspect of these diversion terraces is tiKt many 

were constructed for the purpose of improving the drainage characteristics of those soils having impermeable substrata. By constructing a terrace to intersect these substrata, drainage of thQ. surface
OOREY CRE'EK B'A'SENl, PENNSYiLVJAMA, 1'9 5 4-60 C41

'

2 uj

uj cc 

0-0 <f> Q

,1957

,1955

1959

1958

01954 

'1956

,1960

29 30 31 32 33

RELATIVE EROSION POTENTIAL

34 35

FIGURE 20. Relation of relative erosion potential to Corey Creek-Elk Bnn 

sediment-discharge ratio, 1954-60 growing seasons.

soil above the terrace is more rapid. Interception of the water by the 

terraces also decreases the amount of water reaching the lower parts 

of the slope. The slope immediately below each terrace receives the 

most benefit from this treatment, and the effect of the improvement 

in drainage may extend for one-third of the way down the slope between terraces. The improved drainage may allow a more deeply 

rooted type of vegetation to be grown on this part of the slone, and 

this vegetation, in turn, should eventually increase the permeability 

of the substratum. Seepage of water from the soil above the terraces 

may occur almost continuously throughout the spring and early 

summer. The usual result is an increase in soil moisture in the 

terrace, and generally, this seepage between storms does not resell the
C42 HYDROLOGIC EFFECTS OF LAND USE

outlet waterways but evaporates or is transpired by tin terrace 

vegetation.

The average drainage area of terraces in the Corey Cr°!ek basin 

(including the drainage above the uppermost terrace) is 9 acres per 

1,000 linear feet of terrace. The average length of slop^ between 

terraces is 400 feet, of which about 70 feet represents the width affected by terrace construction. Therefore, about 17.5 perc3nt of the 

terrace drainage area is distributed during terrace construction 

(fig. 21).

Approximately 80 percent of the terraces in the basin were constructed on grassland, and 20 percent were constructed on cropland. 

The average erosion factor for the terraced areas before terrace construction was

JFe =0.8(6)+0.2(100)=24.8.

During construction, 17.5 percent of the terrace drainage area was 

disturbed, and for this part the erosion factor became 100. The 

increase in erosion potential caused by this soil disturbance was

(17.5X100) + (82.5X24.8)

 1=0.53, (100X24.8)

or approximately 50 percent.

A method of estimating the effect of terraces after maximum stabilization of the soil was suggested by Van Doren and Bartelli (1956).

FIGUEE 21. Construction of a diversion terrace In the Corey Creek basin.
OOREY CREEK BASIN, PENNSYLVANIA, 1954-60 C43

In that study, erosion losses from silt loam soils in Illinois' were 

computed as the 0.6 power of the slope length (Z) for slopes over 

200 feet long.

In Corey Creek basin, the average length of slope before terracing 

was 1,600 feet (an average of three terraces in a series). The average 

slope of terraced areas was 12 percent. For this order of slope of 

Flanigan silt loam in Illinois, Van Doren and Bartelli estima ted the 

soil loss factor as 0.65, or a reduction in soil loss of 35 percent due to 

terracing alone.

Using the combined factors for slope length and terracing, the 

computed reduction in potential after terrace stabilization was

,600°- 6 -400°- 6>

?B=1-0.65 =0.72, 1,600°- 6 

or approximately 70 percent.

Observations of terraces constructed during the early stagers of the 

program indicated that maximum cover conditions were attained 

after about 5 years.

Figure 22 represents graphically the effect of cover establishment 

after construction of a single set of terraces. The coefficient of adjustment is the ratio of the erosion potential produced by terrace 

construction to the erosion potential of the undisturbed slope. The 

reduction in erosion potential is greatest during the first growing 

season because of the combined effect of reduction in length of slope 

and the beginning of vegetation growth. In the following ye^-rs, the 

reduction in erosion potential is the result of increased cover density, 

and therefore, additional decreases are shown as taking place only 

during the growing seasons. In figure 22, it is assumed that the terraces were constructed during May, the beginning of the growing 

season. To compute the effects of terraces constructed in Jrne, the 

curve must be shifted to intersect the vertical line representir g June 

at the 1.50 line.

As an example, the following table shows the use of the curve in 

computing the cumulative effect of construction. In this example, it 

is assumed that no terraces have been installed during the periods 

between the months shown, that the average drainage area is 9 acres 

per 1,000 linear feet of terrace, and that the total basin area is 12.2 

square miles, or 7,808 acres.

Date of construction

May, 1st year_

2d year____

Terraces 

constructed 

(feet)

10, 000 

14, 000 

9,000

Basin area affected

Acres

90 

126

81

Percent

1.2 

1. 6 

1. 0

Adjustment 

coefficient

1.50 

1.50 

1. 50

Adjustment 

coefficient times 

percentage of basin 

affected

1.8 

2. 4 

1.5
C44 HYDROLOGLC EFFECTS OF LAND USE

1.8

1.6

LU O

1.4

1.2

.

°2 0.8

nfi LL. 0.6 ^J £; 0°

a

0.4

0.2

1234 

TIME SINCE DIVERSION TERRACE CONSTRUCTION, IN YEAR?

FIGUBE 22. Adjustment for the change in erosion potential produced by diversion terrace

construction.

The cumulative effect of the terraces may now be computed. From 

the curve, the reduction in erosion potential is 45 percent during the 

first growing season, and 35 percent during the second growin g season. 

The values, therefore, are as follows :

Terrace construction

during 

2d year_

3d year. _

Adjustment

1st 

year

1.8

1.3

. 8

coefficient time 

of basin afiectec

2d 

year

2.4

1. 7

s percentage

3d 

year

1. 5

S Percentage 

of basin times

coefficient

1.8

3. 7

4.0

Cumulative 

percentage of

basin affected

1. 2

2. 8

3. 8

The difference between the computed erosion effects and th°, percent 

of the basin affected is the adjustment factor to be applied to the previously computed relative erosion potential (p. C39) ; for example, if, 

for the third year, the relative erosion potential were 35.0, the adjustment applied would be

and the adjusted value would be 35.1.
OOREY CREEK BASIN, PENNSYLVANIA, 1954-60 C45

Figure 23 presents the results of such computations for th*, Corey 

Creek basin. The vertical distance between the two curves in the 

figure is the adjustment, in percent, to be applied to the relative erosion 

potential. During the early part of the program, the construction 

phase dominated and the positive adjustment increased the erosion 

potential. As more of the soil became stabilized, the construction 

effect on the erosion potential decreased until June 1957, when the conditions were about equal to those before construction. After June 

1957, the adjustment factor become negative, causing a progressive 

decrease in the erosion potential. The adjustment factor is projected 

through 1964 on the basis of the average construction rate in 1959-60.

The bar graph in the lower part of figure 23 shows the distribution 

of terrace construction within the study period.

The following table table gives the mean annual terrace adjustment 

factors and the relative erosion potential after adjustment for terrace 

construction:

Year

1954.

1955.

1956.

1957.

1958.

1959.

1960.

Terrace adjustment 

factor (percent of 

relative erosion 

potential)

+ 1.07

+ 3.24

+ 1. 13

-.56

-1.86

-5. 59

-7.76

Adjusted relative 

erosion potential

34.5

35. 1

34.2

33.3

32. 9

27.6

27. 5

Figure 24 is a plot of the adjusted relative erosion potential against 

the Corey Creek-Elk Run sediment-discharge ratio. The rrnk correlation coefficient is 0.71 and is significant at the 0.03 level. There 

are 97 chances in 100 that true positive correlation exists between the 

ranks of the two variables. This correlation is evidence that the sediment-discharge ratio has decreased with decreasing relative erosion 

potential in the Corey Creek basin. It should be emphasized, however, that the rank correlation method only defines the degree of correlation between the ranks and gives no quantitative information 

about one variable with respect to the other.

The curve in figure 24 is the computed least-squares regression line 

of best fit through the scatter of points. The equation of this curve is

r=0.276X-6.89,

where T is the Corey Creek-Elk Run sediment-discharge rrtio and 

X is the adjusted relative erosion potential.
C46 HYDROIjOGIC EFFECTS OF LAND USE

z o <f>

O CCZ

ev C/3 en

111 Z i

> O O

I 

Predicted adjustment 

factor

EXPLANATION

Percentage adjustment

to relative erosion

potential

Positive Negative

Cumulative percentage of 

basin affected

Computed cumulative 

 n effect

1954 ' 1955 ' 1956 ' 1957 1958 ' 1959 ' 1960 ' 1961 1962' 1963 ' 1964

FIGURE 23. Time distribution of diversion terrace construction and the computed 

effect of diversion terrace construction for Corey Creek basin, 1953-6O.

The standard error of estimate of T is 0.44. This means that, if Y 

is estimated from a computed value of X, using the equation given, the 

average estimated value of Y will be within ±O.M units of the true 

value of Y about 66 percent of the time. This amounts to ±20 percent 

of the observed range of Y.

The coefficient of correlation for the equation is 0.65, s: gnificant 

at the 0.12 level, which indicates one chance in eight that a coefficient 

of this size may be the result of chance.

The foregoing analyses indicate a general relationship between the 

effects of conservation practices, as estimated by the relative erosion 

potential, and the observed changes in the Corey Creek-Elk Run 

sediment-discharge ratio. The rank correlation test indicates a significant qualitative correlation between the two variables. The correlation coefficient obtained in the regression analysis is indicative of 

the degree to which the computed relative erosion potential measures 

the effects of the conservation practices on sedimentation.

WATER CHEMISTRY

Information on the chemical characteristics of the water is necessary for an understanding of the hydrologic environment. Such information is used to evaluate the suitability of the water fcr various 

uses, estimate the behavior of the sediment under different hydro-
OOREY CREEK BASIN, PENNSYLVANIA, 1'9 5 4-60 C47

O z 1 "

o c/>

CD

5 LlJ LlJ 

 Crt

Q Q 

UJ C3 Z

,1957

1955

1958

,195* 

1956 

27 28 29 30 31 32 33 34 35 36

RELATIVE EROSION POTENTIAL, ADJUSTED FOR 

EFFECTS OF DIVERSION TERRACES

FIGURE 24. Adjusted relative erosion potential versus the ratio of/Corey Creek suspendedsediment discharge to Elk Run suspended-sediment discharge, 1954-60 growing 

seasons.

logic conditions, and estimate the magnitude of chemical weathering 

and erosion.

The waters of Corey Creek and Elk Run are similar in chemical 

composition and in total amount of dissolved solids (table 1C). The 

principal ions present are calcium, bicarbonate, and sulfate. During 

periods of low flow, a large proportion of streamflow is from groundwater sources. This water has percolated through the carbon dioxide 

rich soil profile and has been in contact with soluble materials in the 

relatively unleached zone below the soil. Ground water, therefore, 

contains a much higher concentration of dissolved solids than does 

overland runoff. During storm events, most of the streamflow is derived from precipitation. The surface runoff from precipitation is 

normally low in dissolved solids and dilutes the water in the stream 

to a lower dissolved-solids concentration.
C48 HYDROLOGIC EFFECTS OF LAND USE

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OGREY CREEK BASIN, PENNSYLVANIA, 1*9 5 4-60 C49

The general relation between water discharge and total dissolvedsolids concentration is shown in figure 25. The average curve has a 

negative slope, and this slope indicates that dissolved-solids concentration decreases as water discharge increases; however, dissolvedsolids discharge increases with increasing water discharge, because 

even though the water is more dilute at higher flows, the dilution effect 

is not enough to offset the increasing volume. The increased k ad may 

come from solids dissolved by surface runoff, from increased groundwater discharge during storm periods, or from dissolved solids present 

in the precipitation. The load-discharge relation is shown in the 

lower set of curves in figure 25. These load-discharge curves and

1000

0.01

1 IT I I

CONCENTRAT/ONe "~~^^

A®

I I 1

1 I I I L

COREY CREEK BASIN

 ® Concentration

 Discharge 

ELK RUN BASIN

 --A Concentration

---x Discharge

I I I I I I I

0.1 1 10 100

INSTANTANEOUS WATER DISCHARGE, IN CUBIC FEET PER SECOND

1000

FIGURE 25. Relation of instantaeous water discharge to concentratioa and discharge 

of dissolved solids, Corey. Creek and Elk Run near Mainesburg, June 1956 to 

October 1961.
C50 HYDROLOGIC EFFECTS OF LAND USE

flow-duration curves were used to compute the data and tl °, average 

annual discharge of dissolved solids in the following table. The results indicate that the average annual dissolved-solids discharge is 

approximately one-half the average annual suspended-sediment 

discharge.

Basin

Corev Creek. _ 

Elk Run______

Average annual 

dissolved-solids 

discharge

Tons

1,000

818

Tons per 

square 

mile

82 

80

Average 

waterweighted 

dissolved-solids concentration (ppm)

75 

63

Average 

total hardnessasCaCOs 

(ppm)

52

54

In addition to the complete chemical analysis performed, specific 

conductance and pH were measured for more than 300 samples from 

each basin. Measured specific conductance of the water ranged from 

60 to 235 micromhos in Corey Creek and from 61 to 206 micromhos 

in Elk Run. Measured pH of the water ranged from 6.£ to 8.3 in 

Corey Creek and from 6.6 to 8.7 in Elk Run.

The ability of water to conduct an electric current is dependent upon 

the concentration of dissolved solids in the water; therefore, specific 

conductance can be used as an indirect method of determining dissolved-solids content. Figure 26 is the relation of specific conductance 

to dissolved-solids concentration and to hardness. Both dissolvedsolids content and hardness can be estimated from these curves if the 

specific conductance is known.

Because specific conductance is directly related to dissolved-solids 

concentration, it follows that the relation between water discharge and 

conductance will be similar to the water discharge-dissolved-solids 

concentration relation. The curves in figure 27 can be used to estimate 

the specific conductance (and thus, the dissolved-solids concentration) 

for any given rate of water discharge.

SUMMARY AND CONCLUSIONS

Data collected during the period 1954-60 have been us^d in this 

report to describe the differences and similarities in both the natural 

and artificially created environments of Corey Creek and Elk Run 

basins. Changes occurring within each basin have been evaluated, 

and some projections have been made concerning the probable effects 

of future changes.
SPECIFIC CONDUCTANCE, IN MICROM

ho co -t^ <ji 

3 o o o o

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B

B 0.
C 25° AT MICROMHOS IN CONDUCTANCE, SPECIFIC 

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T 1 I I I I I 

I I l I I I I 

I I I I I 

i I 
COREY CREEK BASIN', PENNSYLVANIA, 1954-60 C53

The mean elevation is somewhat higher and slopes are somewhat 

steeper in Elk Run basin. These factors may cause the observed 

difference in precipitation, which has averaged 2.75 inches more per 

year in Elk Bun basin than in Corey Creek basin.

About 90 percent of the soils in the two basins are classified as silt 

loam. The size distribution of suspended sediments generally corresponds to this soil texture.

The aggradation-degradation ranges in both basins indicate an 

average change in cross-sectional area of less than ±2.5 square feet 

for ranges on portions of the stream channels having slopes greater 

than 70 feet per mile. On slopes of less than 70 feet per mile, the 

range data indicate filling, especially in the Corey Creek basin. Most 

changes have taken place in the banks rather than in the streambeds.

Of the independent variables tested by regression analyses, those 

correlating most highly with sediment yield were quantity of runoff, 

precipitation, and temperature. Tests of temperature as a variable 

indicated that it was largely an indicator of variations in seagons. 

Precipitation and runoff peakedness were the two most important 

variables determining storm- suspended-sediment concentration for 

the intermittent station, Corey Creek at Mainesburg.

During the period 1954-60, there was no significant change in 

precipitation, total runoff, or direct runoff in either basin. Doublemass curves and rank correlation analysis indicated no significant 

change in the peakedness of runoff in the Corey Creek basin during 

the study period.

The rate of suspended-sediment discharge has changed in both 

basins. The trend since 1957 has been toward decreasing sediment 

discharge, but the decrease has been greater in the Corey Creek basin. 

The net decrease in Corey Creek basin with respect to Elk Run has 

been about 11 percent. The double-mass analyses indicated this 

change was the result of a 51-percent relative decrease during the 

growing season, when about 25 percent of the average annual suspended-sediment discharge occurred. There was little or no change 

during the dormant season.

The application of conservation practices has been an important 

factor in decreasing the suspended-sediment discharge from the two 

basins; the most important change probably has been the shift from 

cropland to grassland. The rank correlation test indicated a significant correlation between the adjusted relative erosion potential 

of Corey Creek basin and Corey Creek-Elk Run sediment-discharge 

ratio during the growing season.

Although diversion terraces affected about 19 percent of th°> Corey 

Creek basin and reduced the relative erosion potential by about 8 per-
C54 HYDROLQGIC EFFECTS OF LAND USE

cent through 1960, the data indicate that the terraces have 1 ^,d little 

or no effect on runoff characteristics.

The generalizations used in formulating the relative erosion potential obviously did not account for all of the subtle variations in cover 

conditions within the two basins. Measurement of the total effect of 

the conservation practices may be possible only after the major construction and land use changes in the basins have ceased. Few data, 

along with that presently available, could be analyzed by other techniques, such as that suggested by Van Doren and Bartelli (1956), to 

obtain a more quantitative solution of the erosion-sedimentation, 

relationship.

During the period 1954 through 1958, there was an intensive application of conservation techniques in the Corey Creek basin. The 

temporary sharp rise in sediment yields that resulted from the construction phase of the program probably would not be observed in 

an area where treatment progressed at a slower, more uniform rate.

The reduction in sediment yield was not directly proportional to 

the intensity of conservation activity. Elk Run basin showed a reduction in sediment yield of more than half that in Corey Creek basin, 

while receiving only about one-tenth as much treatment.

Improvements in land treatment often are aimed at increased crop 

yields as well as soil conservation, and these techniques are, therefore, 

applied more intensively during the growing season. More, than 75 

percent of the sediment discharge from the two basins, however, 

occurs during the dormant season. If a further reduction in annual 

erosion is desirable, attention might be given to increasing acreage 

and density of ground cover during the dormant season.

SELECTED REFERENCES

Culbertson, J. K., 1957, Progress report of hydrology and sedimentation in

Bixler Run, Corey Creek and Elk Run watersheds, Pennsylvania: U.S.

Geol. Survey open-file report, 44 p. 

Guy, H. P., 1957, The trend of suspended-sediment discharge of the F-andywine

Creek at Wilmington, Del., 1947-1955: U.S. Geol. Survey open-file report,

p. lb-12b. 

Hendrickson, B. H., Burke, R. T. A., Goodman, K. V., and Smith, P. L., 1929,

Soil survey of Tioga County, Pennsylvania: U.S. Dept. Agriculture, Bur.

Chemistry and Soils, Soil Survey Rept. 30,47 p. 

Jones, B. L., 1964, Sedimentation and land use in Corey Creek anl Elk Run

basins, Pennsylvania 1954-1960 (a progress report) : U.S. Geol. Survey

open-file report, 112 p. 

 1965, Conservation effects in a small watershed: Soil and Water Conserv.

Jour., v. 20, no. 1, p. 26-28. 

Jones, B. L., and Unger, D. G., 1962, Measuring effects of conservation: Soil

and Water Conserv. Jour., v. 17, no. 4, p. 172-174.
COREY CREEK BASIN, PENNSYLVANIA, 1954-60 C55

Linsley, R. K., Kohler, Max A., and Paulhus, L. H., 1949, Applied hydrology: 

New York, McGraw-Hill Book Co., 689 p.

Lohman, S. W., 1939, Ground water in north-central Pennsylvania: Pennsylvania Topog. and Geol. Survey Bull. W-6, p. 8-15.

Musgrave, G. W., 1947, The quantitative evaluation of factors in water erosion 

a first approximation: Soil and Water Conserv. Jour., v. 2, no. 3, p. 133-138.

Schneider, W. J., and Ayer, G. R., 1961, Effect of reforestation on streamflow 

in central New York: U.S. Geol. Survey Water-Supply Paper le^, 61 p.

Searcy, J. K., and Hardison, C. H., 1960, Double-mass curves: U.S. Geo1 - Survey 

Water-Supply Paper 1541-B, 66 p.

Tioga County Soil Conservation District, 1954, Work plan Corey Creek watershed protection project: Wellsboro, Pa., 43 p.

U.S. Weather Bureau, 1960, Climates of the States, Pennsylvania: U.S. Dept. 

Commerce, Weather Bur. Climatography of the United States No. 60-36.

Van Doren, C. A., and Bartelli, L. J., 1956, A method of forecasting soU losses: 

Agr. Eng., v. 37, no. 5, p. 335-341.

U.S. GOVERNMENT PRINTING OFFICE: 1966 O 217-102