U.S. Department of the Interior

U.S. Geological Survey

TECHNIQUES FOR ESTIMATING

MAGNITUDE AND FREQUENCY OF

PEAK FLOWS FOR PENNSYLVANIA STREAMS

by Marla H. Stuckey and Lloyd A. Reed

Water-Resources Investigations Report 00-4189

prepared in cooperation with

PENNSYLVANIA DEPARTMENT OF TRANSPORTATION

Lemoyne, Pennsylvania

2000
ii

U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

The use of product names in this report is for identification purposes only and does not constitute endorsement by the

U.S. Government.

For additional information Copies of this report may be

write to: purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey Branch of Information Services

840 Market Street Box 25286

Lemoyne, Pennsylvania 17043-1586 Denver, Colorado 80225-0286

Email: dc_pa@usgs.gov Telephone: 1-888-ASK-USGS
iii

CONTENTS

Page

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

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

Purpose and scope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

Previous investigations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

Development of flood-frequency prediction equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

Description of stations used. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

Basin characteristics used in equation development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Regression analysis and resultant equations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

Limitations of regression equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Techniques for estimating magnitude and frequency of peak flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

Summary and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

References cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Appendix 1. Basin characteristics for streamflow-gaging stations used in the development

of the regional regression equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

Appendix 2. Flood-flow frequencies computed from streamflow-gaging data and regression

equations for streamflow-gaging stations used in analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

ILLUSTRATIONS

Figures 1-3. Maps showing:

1. Streamflow-gaging stations used in development of flood-flow regression

equations for Pennsylvania streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2. Carbonate regions in Pennsylvania. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3. Flood-frequency regions in Pennsylvania . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4-5. Graphs showing:

4. Comparison of 100-year flood-flow statistic (Q100) computed from

streamflow-gaging-station data and regression equation for flood

frequency Region A in Pennsylvania . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

5. Comparison of 100-year flood-flow statistic (Q100) computed from

streamflow-gaging-station data and regression equation for flood

frequency Region B in Pennsylvania . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
iv

TABLES

Page

Table 1. Regression coefficients for use with regression equations for peak flows

on Pennsylvania streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2. Equivalent period of record for regression equations developed for predicting

flood recurrance intervals in Pennsylvania. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3. Summary of the variables used to develop the regression equations for

flood frequency Regions A and B in Pennsylvania . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4. Streamflow-gaging stations in Pennsylvania with drainage areas less than

2,000 square miles and streamflow significantly affected by upstream

regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5. Streamflow-gaging stations in Pennsylvania with drainage areas less than

2,000 square miles and streamflow significantly affected by mining . . . . . . . . . . . . 15

CONVERSION FACTORS AND ABBREVIATIONS

Multiply By To obtain

Length

inch (in.) 2.54 centimeter

Area

square mile (mi2) 2.590 square kilometer

acre 0.4047 square hectometer

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second

Volume

acre-foot (acre-ft) 1,233 cubic meter
1

TECHNIQUES FOR ESTIMATING

MAGNITUDE AND FREQUENCY OF

PEAK FLOWS FOR PENNSYLVANIA STREAMS

By Marla H. Stuckey and Lloyd A. Reed

ABSTRACT

Regression equations for estimating the magnitude and frequency of floods on ungaged streams in

Pennsylvania with drainage areas less that 2,000 square miles were developed on the basis of peak-flow

data collected at 313 streamflow-gaging stations. All streamflow-gaging stations used in the development

of the equations had 10 or more years of record and include active and discontinued continuous-record

and crest-stage partial-record streamflow-gaging stations. Regional regression equations were developed

for flood flows expected every 10, 25, 50, 100, and 500 years by the use of a weighted multiple linear

regression model.

The State was divided into two regions. The largest region, Region A, encompasses about 78 percent of

Pennsylvania. The smaller region, Region B, includes only the northwestern part of the State. Basin

characteristics used in the regression equations for Region A are drainage area, percentage of forest cover,

percentage of urban development, percentage of basin underlain by carbonate bedrock, and percentage of

basin controlled by lakes, swamps, and reservoirs. Basin characteristics used in the regression equations

for Region B are drainage area and percentage of basin controlled by lakes, swamps, and reservoirs. The

coefficient of determination (R2) values for the five flood-frequency equations for Region A range from

0.93 to 0.82, and for Region B, the range is from 0.96 to 0.89.

While the regression equations can be used to predict the magnitude and frequency of peak flows for

most streams in the State, they should not be used for streams with drainage areas greater than

2,000 square miles or less than 1.5 square miles, for streams that drain extensively mined areas, or for

stream reaches immediately below flood-control reservoirs. In addition, the equations presented for

Region B should not be used if the stream drains a basin with more than 5 percent urban development.

INTRODUCTION

Flood-flow statistics are used in the design of bridges and flood-control structures as well as for floodplain management. It is important for engineers and planners to have access to methods that produce

reliable flood-flow statistics for inclusion in the design and implementation of these projects. Regional

regression equations as well as any available data from streamflow-gaging stations are used to estimate

flood-flow statistics for such projects. Commonly used flood-flow statistics in flood-related projects

include the flood flows expected every 10, 25, 50, 100, and 500 years (Q10, Q25, Q50, Q100, and Q500,

respectively). Regression equations for computing flood-flow frequencies for streams in Pennsylvania

were last developed by the U.S. Geological Survey (USGS) by use of peak-flow data collected through 1975

(Flippo, 1982). Analysis of these equations indicated the need to revise the flood-frequency equations by

use of the most recent flood-frequency data (Ehlke and Reed, 1999).

The USGS, in cooperation with the Pennsylvania Department of Transportation (PennDOT),

conducted an investigation to develop updated flood-flow regression equations for sites on ungaged

reaches of streams in Pennsylvania with drainage areas less than 2,000 mi2. Regression equations were

developed for Q10, Q25, Q50, Q100, and Q500 on the basis of streamflow records at gaging stations with 10 or

more years of record. Basin characteristics used in the development of the regression equations were

drainage area, percentage of forest cover, percentage of urban development, percentage of basin underlain
2

by carbonate bedrock, and percentage of basin controlled by lakes, swamps, and reservoirs. The

development of the regression equations produced two flood-flow regions; the larger region encompasses

most of Pennsylvania with the exception of the northwestern part of the State.

Purpose and Scope

This report presents equations that predict flood frequencies with return intervals of 10, 25, 50, 100,

and 500 years for ungaged streams in Pennsylvania. Flood-flow regression equations were developed by

use of data from 311 continuous-record and crest-stage partial-record streamflow-gaging stations (creststage stations) on streams in Pennsylvania and 2 in the adjacent states with 10 or more years of peak-flow

data generally through water year1 1997. The spatial distribution of the stations used in the development

of the equations is shown in figure 1. The spatial distribution of the streamflow-gaging stations represents

most of the various flow conditions and geology found throughout Pennsylvania. Although no major

regions are ungaged, only a few streamflow-gaging stations were available in the south central and

northeastern parts of the State (fig. 1).

Previous Investigations

Equations that could be used to predict flood frequencies for ungaged streams in Pennsylvania were

presented by Flippo in 1982. These equations were an updated form of previously published regression

equations by Flippo (1977). The flood-flow regression equations published in 1982 were evaluated by

Ehlke and Reed (1999) on the basis of a comparison between flood frequencies calculated from the

regression equations and peak-flow data collected through the 1996 water year. This comparison found

significant variation among flood-frequency statistics computed from the equations developed by Flippo

(1982) and peak-flow data, indicating that a revised or an updated version of these equations was

warranted.

DEVELOPMENT OF FLOOD-FREQUENCY PREDICTION EQUATIONS

Flood-frequency statistics were computed for all active and discontinued streamflow-gaging stations

in Pennsylvania with at least 10 years of peak-flow data by use of methods described in Water Resource

Council Bulletin 17B (Water Resources Council, Hydrology Committee, 1981). Drainage area and basin

characteristics were tabulated for each station with flood-frequency data. Regression equations for

predicting flood discharges were developed by weighting each data set with the number of years of peakflow data collected at the station. Following the first analysis, which included the entire State, departures

of predicted to observed flood frequencies were used to divide the State into regions and the development

of the regression equations was repeated on a regional basis.

Description of Stations Used

Peak-flow data from 313 continuous-record and crest-stage stations with 10 or more years of record

within Pennsylvania and the surrounding states were used in the development of the regression

equations. Some of these streamflow-gaging stations have a combined operational history that includes a

period when the station was operated as a continuous-record station and another period when it was

operated as a crest-stage station. Only stations with drainage areas less than 2,000 mi2 were used. Rivers

with drainage areas greater than 2,000 mi2 generally have an adequate number of streamflow-gaging

stations to represent all reaches of the river and have long periods of record to include the various flood

conditions. Flood-frequency statistics were computed using all available peak-flow data, generally

1 Water year refers to the 12-month period October 1 - September 30.
3

Figure 1. Streamflow-gaging stations used in development of flood-flow regression equations for Pennsylvania streams.
4

through water year 1997, as described in Water Resources Council Bulletin 17B (Water Resources Council,

Hydrology Committee, 1981). Five stations with short periods of record were greatly affected by

Hurricane Floyd in the fall of 1999. Because of this significant rainfall event, flood frequencies for these

stations were computed using data through water year 1999.

For most streamflow-gaging stations, the length of record was the period from the start of record to the

year flood frequencies were computed, or to the year the station was discontinued. Several stations were

operated before and after construction of large flood-control projects and these stations were assigned two

periods of record, one before and one after construction of the flood-control project. As an example, the

station on the Lackawaxen River at Hawley (01431500) was operated before and after construction of two

large flood-control reservoirs, which increased the percentage of basin controlled by lakes, swamps, and

reservoirs by 32 percent. Construction of the flood-control reservoirs affected the flood frequency and two

flood-frequency analyses were computed, one for before and one for after construction.

Period of record used in analysis for stations that have a gap in operational history was determined by

the total number of years the station was actually in operation. However, if a peak flow was determined

prior to the start of a station, which is coded as an historical peak, the total number of years from the

historical peak to the end of record are included in the period of record used in analysis, which would

include the period the station was not operating (Water Resources Council, Hydrology Committee, 1981).

This situation affects a small number of stations used in the analysis and usually adds only a few years to

the period of record used in analysis. For example, station 01543500, Sinnemahoning Creek at

Sinnemahoning, was started in 1939, but because an historical peak was recorded in 1936, the period of

record used in analysis includes the period between 1936 and 1939 that the station was not in operation.

Basin Characteristics Used in Equation Development

The basin characteristics used to develop the regression equations are drainage area, percentage of

forest cover, percentage of urban development, percentage of basin underlain by carbonate bedrock, and

percentage of basin controlled by lakes, swamps, and reservoirs. These basin characteristics are known to

affect flood flow. The basin characteristics for all streamflow-gaging stations used in the development of

the regression equations are listed in Appendix 1.

Other basin characteristics considered for use in the equations include channel slope and precipitation

index, two factors previously included in equations developed by Flippo (1982). Channel slope was found

to be significant for Flippo’s equations in only 1 region out of 10 regions, and that region was developed

entirely from New York stations (Flippo, 1977, 1982). Because of these findings, channel slope was not

included in the development of the present equations. A precipitation factor was not included in the

development of the equations because of a report by Reich and Jackson (1971) that found that estimates of

the 100-year flood were not improved with the inclusion of rainfall statistics.

Drainage area

Drainage areas for each of the streamflow-gaging stations were determined at the time the stations

were established, and most drainage areas were checked by use of the most recent topographic maps

available. These drainage areas are found in USGS Water-Resources Data Reports for the 1997 water year

(Durlin and Schaffstall, 1998a; Durlin and Schaffstall, 1998b; Coll and Siwicki, 1998). Drainage area for

ungaged sites can be determined from the most recent topographic maps.

Percentage of forest cover

Percentage of forest cover in the drainage basin upstream of each streamflow-gaging station was

determined from land-use data by use of Geographic Information Systems (GIS) methods (U.S. Geological

Survey, 1996) or from topographic maps. Values for percentage of forest cover in basins upstream of

streamflow-gaging stations still in operation and for streamflow-gaging stations recently discontinued

were determined from current land-use data.
5

Percentage of forest cover upstream of streamflow-gaging stations discontinued prior to about 1960

were determined from land-use data shown on 15-minute topographic maps produced from about 1920 to

about 1940. Not all 15-minute maps showed forest cover and estimates were made by use of 15-minute

maps of adjacent areas with similar topography or the oldest available 7.5-minute maps that showed forest

cover.

Percentage of urban development

Percentage of urban development in the drainage basin upstream of a streamflow-gaging station was

determined using the same methods used to determine percentage of forest cover. Percentage of urban

development was calculated as the land classified as low-intensity developed plus the land classified as

high-intensity residential, and the land classified as high-intensity commercial/industrial (U.S. Geological

Survey, 1996). Percentage of urban development in basins in which the streamflow-gaging station was

discontinued prior to about 1960 was determined from 15-minute topographic maps much the same as

was done for percentage of forest cover.

Percentage of basin underlain by carbonate rock

Percentage of the basin underlain by carbonate rock was computed by use of GIS methods

(Environmental Resources Research Institute, 1996). All calculations were made by use of GIS methods

except for a few streamflow-gaging stations in which the percentage carbonate bedrock in the basin was

obtained from Aron and Kibler (1981). Although not intended for determination of the carbonate bedrock

variable needed for input into the equations, figure 2 shows the areas underlain by carbonate bedrock for

the State.

Percentage of basin with controlled by lakes, swamps, and reservoirs

Percentage of drainage basin with streamflow controlled, or attenuated, by lakes, swamps, and

reservoirs was computed by use of the technique recommended by Aron and Kibler (1981). The technique

is based on two assumptions. The first assumption is that the temporary storage of 2.4 in. of runoff from

the area upstream of a lake, swamp, or reservoir can reduce flooding from storms that would, in an

uncontrolled basin, produce a flood with a recurrence interval of 100 years. The second assumption is that

the water-surface elevation in most unregulated lakes, swamps, and reservoirs will increase 24 in. during a

storm that would cause a flood with a recurrence interval of 100 years. Combining these assumptions into

an example, the water-surface elevation of an unregulated lake, swamp, or reservoir can increase 24 in.

during a large storm. As a result, a 10-acre lake, swamp, or reservoir can store 20 acre-feet of runoff,

enough storage to control the 100-year flood from a drainage area of 100 acres. If the drainage area above

the 10-acre lake or reservoir or swamp is larger than 100 acres, the percentage of the drainage area that is

controlled can be calculated by dividing 100 acres, the controlled area, by the total area in the basin.

To summarize, if the area of a watershed above a lake, swamp, or reservoir is more than 10 times the

surface area of the lake, swamp, or reservoir, the controlled area becomes the surface area multiplied by 10.

If the drainage area above the lake, swamp, or reservoir is smaller than 10 times the surface area of the

lake, swamp, or reservoir, the controlled area is equal to the drainage area above the lake, swamp, or

reservoir. A careful evaluation of streams with multiple lakes or swamps is required because double

counting of controlled areas must be avoided. Reservoirs built especially for flood control are assumed to

control the entire upstream basin for a flood with a recurrence interval of 100 years. The surface area of

lakes, swamps, and reservoirs, which determines the percentage of basin controlled by lakes, swamps, and

reservoirs, is determined from the most recent topographic maps.

As an example, a site on Middle Creek, at latitude 40°12'36" and longitude 76°15'05", has an upstream

reservoir with a surface area of 0.55 mi2. The drainage area at the reservoir is 7.59 mi2, and the drainage

area at the site is 23.3 mi2. Because the reservoir is not a flood-control reservoir and the drainage area at the

reservoir is greater than 10 times the surface area of the reservoir, the area controlled by the reservoir is

5.5 mi2 (10 times the surface area of the reservoir). The percentage of the basin controlled by lakes,

swamps, and reservoirs is 24 percent.
6

Figure 2. Carbonate regions in Pennsylvania (modified from Environmental Resources Research Institute, 1996).
7

Regression Analysis and Resultant Equations

The regression equations were developed by use of a multiple linear regression model from MathSoft,

Inc. statistics package S-Plus4. The flood-frequency discharges calculated for each streamflow-gaging

station were weighted as per the number of years in operation. In order to form a near linear relation

between differences in flood flow and differences in land use, all percentages were converted to the form

[1.0 + 0.01(percent of basin characteristic)] before the regression equations were developed.

A review of the records indicated most of the largest floods in the eastern part of the State occurred

during the summer and fall; most of the largest floods in the northwestern part of the State occurred in the

winter and spring. For example, the five largest floods on the Perkiomen Creek at Graterford, Pa. (station

number 01473000, latitude 40°13'46", longitude 75°27'07") occurred, from largest to smallest, on July 7,

1935; August 23, 1933; June 2, 1946; August 9, 1942; and November 25, 1950; on Brokenstraw Creek at

Youngsville, Pa. (station number 03015500, latitude 41°51'09", longitude 79°19'03"), a similar station in both

drainage area and period of record, the five largest floods occurred on March 25, 1913; April 5, 1947; March

22, 1948; January 22, 1959; and January 19, 1996. Serious flooding from tropical storms in the summer and

fall months is more common in the central and eastern part of the State.

An evaluation of the residuals from the initial regression analysis for 100-year recurrence interval

floods for the entire State indicated that the northwestern part of the State, including the headwaters of the

Allegheny River and the basins of Brokenstraw Creek, French Creek, Clarion River, Beaver Creek,

Redbank Creek, and Mahoning Creek, had consistently smaller flood flows (resulting in large negative

residuals) than streams in the rest of the State. These findings support the seasonal flooding differences

discussed previously.

Because flooding in the northwestern part of the State does not appear to be related to flooding in the

rest of the State, Pennsylvania was divided into two flood-flow regions, Region A and Region B (fig. 3).

Region A includes about 78 percent of the State. Region B encompasses the northwestern corner, about

22 percent of the State. Regression equations to predict the 10, 25, 50, 100, and 500-year floods were then

computed for Regions A and B. The basin characteristic coefficients and their residual standard error and

coefficient of determination (R2) are shown in table 1. The residual standard error provides a rough

estimate of reliability of the predicted discharges and R2 is a measure of the percentage of variance

explained by regression (Helsel and Hirsch, 1997). The R2 values range from 0.93 to 0.82 for Region A and

0.96 to 0.89 for Region B (table 1). The residual standard errors have some effect from the weighting and

should not be directly compared to standard errors from a non-weighted analysis (Freund and Littell,

1986). The calculated Q10, Q25, Q50, Q100, and Q500 from streamflow-gage data and regression equations

are listed in Appendix 2 for all streamflow-gaging stations used in the development of the regression

equations.

The regression model took the form:

(1)

where Log is log to base 10;

QT is return interval peak flow, in cubic feet per second;

A is the intercept;

DA is drainage area, in square miles;

 F is percentage of forest cover, in percent;

U is percentage of urban development, in percent;

C is percentage of basin underlain by carbonate rock, in percent;

CA is percentage of basin controlled by lakes, swamps, or reservoirs, in percent; and

b, c, d, e, f are basin characteristic coefficients of regression.

LogQ T = A bLogDA cLog ++ + + + ( ) 1.0 0.01 + F dLog( ) 1.0 0.01 + U eLog( ) 1.0 0.01 + C fLog( ) ( ) 1.0 0.01 + CA
8

Figure 3. Flood-frequency regions in Pennsylvania.
9

Table 1. Regression coefficients for use with regression equations for peak flows on Pennsylvania streams

[QT, discharge for the T-year flood; ft3/s, cubic feet per second; Q10, 10-year flood flow; Q25, 25-year flood flow;

Q50, 50-year flood flow; Q100, 100-year flood flow; Q500, 500-year flood flow; ---, basin characteristic coefficient not

used in regression equation]

QT return flow

(ft3/s)

Basin characteristic coefficients Residual standard

error

Coefficient of

determination

(R2) Intercept

(A)

Drainage

area

(b)

Percentage

forested area

(c)

Percentage

urban

development

(d)

Percentage

carbonate

area

(e)

Percentage

controlled

area

(f)

Log units Percent

Region A

Q10 2.5243 0.7770 -0.9712 1.0217 -1.7184 -0.5719 0.18 43 0.93

Q25 2.7145 .7556 -1.0324 .7608 -1.5302 -.5302 .19 45 .91

Q50 2.8441 .7414 -1.0821 .5785 -1.3955 -.4980 .21 50 .89

Q100 2.9665 .7278 -1.1342 .4040 -1.2691 -.4637 .23 55 .87

Q500 3.2294 .6994 -1.2666 .0208 -.9877 -.3834 .27 66 .82

Region B

Q10 2.3105 .7255 --- --- --- -1.2425 .12 28 .96

Q25 2.4418 .7108 --- --- --- -1.3700 .13 30 .95

Q50 2.5276 .7017 --- --- --- -1.4695 .14 33 .94

Q100 2.6069 .6932 --- --- --- -1.5677 .16 38 .92

Q500 2.7673 .6776 --- --- --- -1.8055 .19 45 .89

OR

Region A

Q10 = 334.4 DA .7770 (1 + .01F)

 -.9712 (1 + .01U)1.0217 (1+ .01C)-1.7184 (1 + .01CA)-.5719

Q25 = 518.2 DA .7556 (1 + .01F) -1.0324 (1 + .01U)

.7608 (1+ .01C)-1.5302 (1 + .01CA)-.5302

Q50 = 698.4 DA .7414 (1 + .01F)

 -1.0821 (1 + .01U).5785 (1+ .01C)-1.3955 (1 + .01CA)-.4980

Q100 = 925.8 DA .7278 (1 + .01F)

 -1.1342 (1 + .01U).4040 (1+ .01C)-1.2691 (1 + .01CA)-.4637

Q500 = 1,696 DA .6994 (1 + .01F) -1.2666 (1 + .01U)

.0208 (1+ .01C)-.9877 (1 + .01CA)-.3834

Region B

Q10 = 204.4 DA .7255 (1 + .01CA)

-1.2425

Q25 = 276.6 DA .7108 (1 + .01CA)

-1.3700

Q50 = 337.0 DA .7017 (1 + .01CA)

-1.4695

Q100 = 404.5DA .6932 (1 + .01CA)

-1.5677

Q500 = 585.2 DA .6776 (1 + .01CA)

-1.8055
10

Regression equations for Region A have five variables: drainage area, percentage of forest cover,

percentage of urban development, percentage of basin underlain by carbonate bedrock, and percentage of

basin controlled by lakes, swamps, and reservoirs and were developed from 270 streamflow-gaging

station records. All variables were significant predictors for the 10, 25, 50, 100, and 500-year floods at a

95-percent confidence level except percentage urban; percentage urban lost significance with the 100 and

500-year flood levels but was kept as a variable in the 100 and 500-year equations to provide consistency.

With larger floods, the amount of runoff due to urban areas does not influence the peak flood as much as

in smaller floods. If a 5-mi2 basin that was 30 percent forest cover with no carbonate area, no urban area,

and no controlled area was developed and percentage urban area increased 30 percent, the 10-year flood

would increase 31 percent but the 500-year flood would increase only 1 percent. In smaller floods the

runoff from pavement and roofs in urban areas makes up a substantial part of the peak, however, with

larger floods, unpaved areas become saturated and additional precipitation produces substantial runoff

from both paved and unpaved areas. A comparison between the Q100 computed from streamflow-gage

data and regression equations for Region A is shown in figure 4.

Regression equations for Region B were developed from 54 streamflow-gaging station records and

have 2 variables, drainage area and the percentage of basin controlled by lakes, swamps, and reservoirs.

The area of the State that comprises Region B does not contain any carbonate rocks (figs. 2 and 3). The

percentage urban area is consistently low for streamflow-gaging stations in Region B, without enough

stations with high percentage urban areas to produce meaningful results.2 Percentage forest was not a

significant variable and was dropped from the analysis. The comparison between the Q100 computed from

streamflow-gage data and regression equations for Region B is shown in figure 5.

2 When the percentage of urban area in a basin was included in the model for Region B, the regression coefficient was

-6.20, indicating a large reduction in the 100-year peak flow when going from an undeveloped to a fully developed basin.

Figure 4. Comparison of 100-year flood-flow statistic (Q100) computed

from streamflow-gaging- station data and regression equation for flood

frequency Region A in Pennsylvania.

0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000

Q100 COMPUTED FROM STREAMFLOW-GAGING-STATION DATA,

0

160,000

20,000

40,000

60,000

80,000

100,000

120,000

140,000

Q100 COMPUTED FROM REGION A REGRESSION EQUATION,

 IN CUBIC FEET PER SECOND

 IN CUBIC FEET PER SECOND
11

A t-test on signed-ranks was used to determine if the results from the regression equations were

significantly different than the flood frequencies computed from streamflow-gaging-station data (Helsel

and Hirsch, 1997). This analysis was done using a 95-percent confidence level. The results of the t-test on

signed-ranks showed that there was no significant difference between the flood frequencies predicted

from regression equations and those predicted from streamflow-gaging-station data.

Just as a streamflow-gaging station has a period of record that should be taken under consideration

when computing flood frequencies from the data for that station, the regression equations each have an

equivalent years of record that should be taken under consideration when using the equations to compute

flood frequencies. The equivalent years of record for the regression equations are computed from a factor

on the basis of the skew coefficient of the population of annual peaks at individual stations used in the

development of the regression equations, the standard deviation of the logs of the annual events at the

individual stations used in the development of the regression equations, and the standard error of

prediction of the regression equations. This methodology is presented by Hardison (1971). The equivalent

years of record for all the regression equations are shown in table 2. The Q100 equation developed for

Region A is comparable to a streamflow-gaging station that has been in operation for 10 years. The

equivalent period of record for Regions A and B range from 5 to 16 years (table 2).

Table 2. Equivalent period of record for regression equations

developed for predicting flood recurrence intervals in Pennsylvania

[Methodology used described by Hardison (1971)]

Flood recurrence interval

Equivalent period of record (years)

Region A Region B

10-year 5 5

25-year 6 5

50-year 8 8

100-year 10 10

500-year 16 13

Figure 5. Comparison of 100-year flood-flow statistic (Q100) computed from

streamflow-gaging-station data and regression equation for flood frequency

Region B in Pennsylvania.

0 20,000 40,000 60,000 80,000

Q100 COMPUTED FROM STREAMFLOW-GAGING-STATION DATA,

0

80,000

10,000

20,000

30,000

40,000

50,000

60,000

70,000

Q100 COMPUTED FROM REGION B REGRESSION EQUATION,

IN CUBIC FEET PER SECOND

IN CUBIC FEET PER SECOND
12

LIMITATIONS OF REGRESSION EQUATIONS

Several situations can limit the use of the regression equations presented for Regions A and B. The

equations should not be used if the drainage area is less than 1.5 mi2 or greater than 2,000 mi2. The

equations presented for Region B should not be used to predict flood flows from basins with more than

5 percent urban development because the largest percentage urban development in the data used to

develop the equations was 4.5 percent. Because the equations for Region B do not include a variable for

percentage of urban development, the equations do not incorporate the increased flooding that is likely to

be associated with urban areas. A summary of the range of variables used to develop the regression

equations for Regions A and B is presented in table 3.

The equations should not be used to predict flood flows if streamflow at the site of interest is

significantly affected by an upstream flood-control reservoir. The streamflow-gaging stations that were not

used to develop the regression model are listed in table 4, along with the associated controlled area and

flood frequencies computed from streamflow data. The 500-year flood is not listed in table 4 because the

storage capacity for some flood-control reservoirs may not be sufficient to store all the runoff that

contributes to the 500-year flood. The equations can be used to compute flood flows from basins that

contain lakes, swamps, and non-flood-control reservoirs, provided the controlled area is computed and

input to the regression equation.

The regression equations should not be used downstream of areas that have or have had significant

surface mining in the past. The streamflow-gaging stations that were not used to develop the regression

model due to extensive upstream surface mining are listed in table 5. Flood frequencies computed from

streamflow-gaging-station data using the entire period of record are reported by Ehlke and Reed (1999).

Extensive surface mining tends to reduce peak flood flows (Growitz and others, 1983). Reduced flooding

due to surface mining is most likely caused by increased permeability into the fractured rock and into

underground voids.

Table 3. Summary of the variables used to develop the regression equations for flood frequency Regions A and B

in Pennsylvania

[mi2, square miles]

Region

Number of

stations

used

Number of

records

used1

1 Some streamflow-gaging stations have two records because of the construction of reservoirs or other changes in land use.

Range

Drainage area

(mi2)

Years of

record

Percentage of basin

In forest cover In urban

development

Underlain

by

carbonate

bedrock

Controlled by

lakes, swamps,

and reservoirs

A 261 270 0.93 - 1,893 11- 109 1.8 - 100 0 - 86.7 0 - 98 0 - 94

B 52 54 2.12 - 1,608 11- 92 20. - ....96 0 - 4.5 0 - 0 0 - 89
 13

Table 4. Streamflow-gaging stations in Pennsylvania with drainage areas less than 2,000 square miles and streamflow significan

regulation

[Data from these streamflow-gaging stations was not included in the regression analysis; mi2, square miles; water year, 12-month 

September 30; ft3/s, cubic feet per second]

U.S.

Geological

Survey

streamflowgaging station

Station name

Drainage

area

(mi2)

Controlled

area

(percent)

Period of

record

(water

year)

Computed from 

stat

10-year

(ft3/s)

25-yea

(ft3/s)

101429000 West Branch Lackawaxen River at Prompton 59.7 100 1961-97 2,780 3,130 

101429500 Dyberry Creek near Honesdale 64.6 100 1960-97 2,050 2,290 101430000 Lackawaxen River near Honesdale 164 83 1960-97 6,020 7,070 

01447800 Lehigh River below Francis Walter near White Haven 290 99 1961-97 9,430 11,700 

101449500 Wild Creek at Hatchery 16.8 98 1959-78 400 532 

01449800 Pohopoco Creek below Beltzville Lake near Parryville 96.4 100 1971-97 1,680 1,840 01464645 North Branch Neshaminy Creek below Lake Galena near New Britain 16.2 94 1986-97 1,750 2,740 

101470960 Tulpehocken Creek at Blue Marsh Damsite near Reading 175 100 1978-97 4,030 4,920 101471000 Tulpehocken Creek near Reading 211 83 1979-97 4,480 5,550 

01480685 Marsh Creek near Downingtown 20.3 99 1974-97 638 786 

101518000 Tioga River at Tioga 282 100 1980-97 7,030 7,470 

01518700 Tioga River at Tioga Junction 446 90 1980-97 8,970 9,990 

101520000 Cowanesque River near Lawrenceville 298 100 1980-97 5,500 6,140 

01534300 Lackawanna River near Forest City 38.8 95 1960-97 1,040 1,180 

101541200 West Branch Susquehanna River at Curwensville 367 100 1966-97 6,230 7,000 

01541303 West Branch Susquehanna River at Hyde 474 77 1979-97 6,930 7,540 01544000 First Fork Sinnemahoning Creek near Sinnemahoning 245 99 1956-97 7,150 8,140 01545000 Kettle Creek near Westport 233 97 1962-97 6,420 7,130 

101547500 Bald Eagle Creek at Blanchard 339 100 1971-97 4,140 4,670 

01563200 Raystown Branch Juniata River below Raystown Dam near Huntingdon 960 100 1973-97 15,700 17,000 03020000 Tionesta Creek at Tionesta Dam 479 100 1941-91 9,440 10,800 03021520 French Creek near Union City 221 99 1972-91 3,530 4,040 03022554 Woodcock Creek at Woodcock Creek Dam 45.6 100 1978-93 872 990 03027500 East Branch Clarion River at East Branch Clarion River Dam 73.2 99 1953-91 1,170 1,570 03036000 Mahoning Creek at Mahoning Creek Dam 344 99 1939-91 7,800 9,400 

103039000 Crooked Creek at Crooked Creek Dam 278 99 1941-91 5,470 6,210 

03042280 Yellow Creek near Homer City 57.4 91 1971-97 3,960 6,320 
14

03044000 Conemaugh River at Tunnelton 1,358 100 1952-91 26,400 30,500 03047000 Loyalhanna Creek at Loyalhanna Dam 292 99 1942-91 5,440 6,190 03048500 Kiskiminetas River at Vandergrift 1,825 91 1971-97 28,000 31,800 03077500 Youghiogheny River at Youghiogheny River Dam 436 100 1944-91 7,860 9,200 03101500 Shenango River at Pymatuning Dam 167 95 1935-97 1,350 1,570 03103500 Shenango River at Sharpsville 584 100 1967-91 4,020 4,310 03106300 Muddy Creek near Portersville 51.2 98 1970-97 597 715 

1 Data collected from these stations prior to regulation by a reservoir are included in the analysis.

Table 4. Streamflow-gaging stations in Pennsylvania with drainage areas less than 2,000 square miles and streamflow significan

regulation—Continued

[Data from these streamflow-gaging stations was not included in the regression analysis; mi2, square miles; water year, 12-month 

September 30; ft3/s, cubic feet per second]

U.S.

Geological

Survey

streamflowgaging station

Station name

Drainage

area

(mi2)

Controlled

area

(percent)

Period of

record

(water

year)

Computed from 

stat

10-year

(ft3/s)

25-yea

(ft3/s)
15

TECHNIQUES FOR ESTIMATING MAGNITUDE AND FREQUENCY OF PEAK FLOWS

Four methods for computing flood-flow frequency discharges are discussed below and are dependent

on the location of the site: 1) not near a streamflow-gaging station, 2) at a streamflow-gaging station,

3) near a streamflow-gaging station, and 4) between two streamflow-gaging stations. The regression

equations presented in this report are used if the site of interest is not near a streamflow-gaging station.

Not near a streamflow-gaging station

If the site is not near a streamflow-gaging station, the appropriate flood-frequency regression equation

is used to compute the discharge.

Example 1. Not near a streamflow-gaging station

Calculate the 100-year flood frequency by use of the appropriate regional regression

equation for an ungaged site on Middle Creek at latitude 40°12'36" and longitude

76°15'05". The drainage area is 23.3 mi2, percentage of forest cover area is 58 percent,

percentage of urban development is 1.8 percent, percentage of carbonate bedrock in the

basin is 8.4 percent, and percentage of streamflow controlled by lakes, swamps, and

reservoirs is 24 percent (computed previously).

1. From figure 2 and the latitude and longitude, the site is in region A.

2. Substituting the basin characteristics into the regression equation for the 100-year flood

in Region A from table 1 produces:

logQ100=2.9665 + 0.7278*log(23.3) - 1.1342*log(1.58) + 0.4040*log(1.018) - 1.2691*log(1.084)

- 0.4637*log(1.24)

logQ100 = 2.9665 + 0.9952 - 0.2253 + 0.0031 - 0.0445 - 0.0433

logQ100 = 3.6517

Q100 = 4,480 ft3/s

At a streamflow-gaging station

When the site of interest is at a streamflow-gaging station, a weighting method is recommended by

Flippo (1977), Choquette (1987), and Water Resources Council, Hydrology Committee (1981). Because

peak-flow data reported for a streamflow-gaging station represents a specific time span, flood-frequency

values computed from streamflow-gaging-station data may contain some bias. The period of record for the

Table 5. Streamflow-gaging stations in Pennsylvania with

drainage areas less than 2,000 square miles and streamflow

significantly affected by mining

[Data from these streamflow-gaging stations was not included in the

regression analysis; mi2, square miles]

US Geological

Surveystreamflowgaging station

number

Station name Drainage area

(mi2)

01467500 Schuylkill River at Pottsville 53.4

01468500 Schuylkill River at Landingville 133

01534500 Lackawanna River at Archbald 108

01535500 Lackawanna River at Moosic 264

01536000 Lackawanna River at Old Forge 332

01537000 Toby Creek at Luzerne 32.4

01537500 Solomon Creek at Wilkes-Barre 15.7

01541308 Bradley Run near Ashville 6.77

01542000 Moshannon Creek at Osceola Mills 68.8

01554500 Shamokin Creek near Shamokin 54.2
16

streamflow-gaging station may or may not include years when large floods occurred in Pennsylvania,

such as 1936, 1955, 1972, 1977, and 1996. Inclusion of several large floods, or lack of any large floods, can

change flood-frequency values for streamflow-gaging stations, especially those with short periods of

record. Consequently, the flood-frequency discharge computed from streamflow data is weighted with the

flood-frequency discharges computed from regression equations on the basis of number of years in

operation for the streamflow-gaging station and equivalent period of record for the regression equations.

To use this method, the streamflow-gaging station should have at least 10 years of operation.

To obtain a weighted flood frequency for a site at a streamflow-gaging station, the flood frequency for

the station is multiplied by the years of record at the station (N), and the flood frequency computed from

the appropriate regional regression equation is multiplied by the equivalent years of record (NE) for the

regression equation from table 2. The two values are then added and divided by the sum of the years of

record to obtain a weighted flood frequency for the stream at the streamflow-gaging station. This equation

is shown below:

(2)

where WtdQT is the weighted discharge for return intervals T-years;

QT(G) is the T-year discharge computed from streamflow data, in cubic feet per second;

QT(R) is the T-year discharge computed from regression equations, in cubic feet per second;

N is the number of years of record at streamflow-gaging station; and

NE is the equivalent years of record for regional regression equations from table 2.

Example 2. At a streamflow-gaging station

Calculate the weighted flood frequency for streamflow-gaging station 01452300 on East

Branch Monocacy Creek near Bath, Pa., at latitude 40°43'10" and longitude 75°22'10". The

drainage area is 5.35 mi2, percentage of forest cover area is 26 percent, percentage of urban

development is 4.0 percent, percentage carbonate bedrock in the basin is 4.0 percent, and

7.5 percent of the basin is controlled by lakes, swamps, and reservoirs. The station was

operated from 1963 to 1968 as a continuous-record station and 1969 to 1980 as a crest-stage

station, for a total of 18 years. The reported Q100 determined from streamflow data is

1,540 ft3/s.

1. The Q100 computed from regional regression equations is 2,260 ft3/s (see Example 1 for

setup) and from table 2, the equivalent years of record for the regression equation is

10 years.

2. Substituting the discharges and number of years into equation 2 produces:

WtdQ100 = (1,540*18 + 2,260*10)/(18+10)

WtdQ100 = 1,800 ft3/s

Near a streamflow-gaging station on the same stream

Once a weighted flood frequency has been computed for the streamflow-gaging station, the flood

frequency can be applied to nearby sites within 0.5 to 1.5 times the drainage area of the streamflow-gaging

station, provided there is no significant change in land use or hydrologic conditions between the ungaged

site and streamflow-gaging station. This methodology is presented by Choquette (1987) for the state of

Kentucky and is cited as an acceptable transfer technique by the Federal Emergency Management Agency

(FEMA) (1995).

This method translates the weighted streamflow-gaging station flood discharges to the ungaged site of

interest by the use of a linear correction factor for the difference in drainage areas between the gaged and

ungaged sites. As the drainage area of the ungaged site nears either 0.5 or 1.5 times the drainage area of

the gaged site, the translated flood frequency nears the result of the regression equation. Using this

method prevents large changes in flood frequencies when going from a gage-regression weighted value to

WtdQ T Q T G( ) × N Q T ( ) R = ( ) + × NE ⁄ ( ) N + NE
17

a regression equation value. The equation to calculate this translated flood frequency is shown below:

(3)

where Cu is the correction factor for the ungaged site;

Cg is the weighted flood frequency for the gaged site (from equation 2) divided by the regression

estimate of flood frequency for the gaged site;

DAg is the drainage area at the streamflow gage, in square miles; and

DAu is the drainage area at the ungaged site, in square miles.

Example 3. Near a streamflow-gaging station on the same stream

Calculate the Q100 for an ungaged site on West Branch Clarion Creek at a latitude

41°29'55" and longitude 78°40'52". The drainage area for the ungaged site is 85.4 mi2.

There is an upstream streamflow-gaging station at Wilcox (station number 03028000) at a

latitude 41°34'45" and longitude 78°41'22". The streamflow-gaging station has 43 years of

operational history and a drainage area of 63.0 mi2. Neither site has any controlled area.

The Q100 computed from streamflow-gage data for the streamflow-gaging station is

7,410 ft3/s.

1. From the latitude and longitude and figure 2, both sites are in Region B.

2. Substituting the basin characteristics into the regression equations for Region B for the

ungaged site produces:

logQ100 = 2.6069 + 0.6932*log(85.4) - 1.5677*log(1)

Q100 = 8,830 ft3/s

and for the gaged site:

logQ100 = 2.6069 + 0.6932*log(63.0) - 1.5677*log(1)

Q100 = 7,150 ft3/s

3. Substituting the needed variables for the streamflow-gaging station into equation 2

results in a weighted discharge of Q100 = 7,360 ft3/s (see Example 2 for setup).

4. Substituting the needed variables into equation 3 produces:

Cu = (7,360/7,150) - (2*|63.0-85.4|)/63.0) * ((7,360/7,150)-1)

Cu = 1.029 - (44.8/63.0)*0.029

Cu = 1.008

5. Multiplying the correction factor for the ungaged site by the regression estimate for the

ungaged site produces:

Q100 = 1.008 * 8,830

Q100 = 8,900 ft3/s

Between two streamflow-gaging stations

If the ungaged site of interest is between two streamflow-gaging stations and within 0.5 to 1.5 times

both drainage areas (an upstream streamflow gage A and a downstream streamflow gage B), weighted

discharge data should be computed for each streamflow gage and moved from the streamflow gages to the

ungaged site of interest (C). The moved data should then be weighted proportional to the ratio of drainage

C u Cg

2 DAg DAu ( ) –

DAg

-------------------------------------

 Cg ( ) – 1 

 = –
18

areas between the site and the two streamflow gages. The equation for weighting the transferred data at

the ungaged site is shown below.

(4)

where QT(C) is the final weighted discharge at ungaged site C, in cubic feet per second;

QT(AC) is the weighted and moved discharge from upstream streamflow-gaging station (gage A),

in cubic feet per second;

QT(BC) is the weighted and moved discharge from downstream streamflow-gaging station

(gage B), in cubic feet per second;

DAA is the drainage area of the upstream streamflow gage A;

DAB is the drainage area of the downstream streamflow gage B; and

DAC is the drainage area of ungaged site C.

Example 4. Between two streamflow-gaging stations

Compute the Q100 for an ungaged site on Wissahickon Creek at a latitude 40°01'41" and

longitude 75°11'51" with a drainage area of 61.5 mi2. The basin is underlain by 17 percent

carbonate bedrock and has 41 percent forested area, 42 percent urban area, and has no

controlled area. Data from two streamflow-gaging stations are available, Wissahickon

Creek at Bells Mills Road (station number 01473950) at 40°04'50" 75°13'35" and

Wissahickon Creek at mouth (station number 01474000) at 40°04'45" 75°13'43". The

upstream station at Bells Mills Road drains 53.6 mi2, has 16 years in operation, 20 percent

of the basin underlain by carbonate bedrock, 39 percent forested area, 41 percent urban

area, and no area controlled by lakes or swamps. The Q100 for station number 01473950

computed from streamflow-gage data is 8,620 ft3/s. The downstream station at mouth

drains 64.0 mi2, has 34 years in operation, 16 percent of the basin underlain by carbonate

bedrock, 40 percent forested area, 42 percent urban area, and no area controlled by lakes

or swamps. The Q100 for station number 01474000 computed from streamflow-gage data

is 13,900 ft3/s.

1. From the latitudes and longitudes and figure 2, all three sites are in Region A

2. Substituting the basin characteristics into the regression equation for Region A results in:

(See Example 1 for setup)

01473950 Q100 = 10,500 ft3/s

01474000 Q100 = 12,400 ft3/s

ungaged site Q100 = 11,900 ft3/s

3. Substituting the regression estimates into equation 2 results in weighted discharges of:

(See Example 2 for setup)

01473950 wtdQ100 = 9,340 ft3/s

01474000 wtdQ100 = 13,600 ft3/s

4. Substitute these computed discharges into equation 3 and multiplying by the correction

factor results in: (See Example 3 for setup)

Q100(AC) = 11,000 ft3/s

Q100(BC) = 13,000 ft3/s

5. Substituting the variables into equation 4 to calculate the final discharge for the ungaged

site produces:

QT(C) = (11,000*(64.0-61.5)/(64.0-53.6)+(13,000*(61.5-53.6))/(64.0-53.6)

QT(C) = 2,644 + 9,875

QT(C) = 12,500 ft3/s

Q T ( ) C Q T ( ) AC

DAB DA C –

DAB DAA – ------------------------------- Q T ( ) BC × +

DAC DAA –

DAB DAA – = × -------------------------------
19

SUMMARY AND CONCLUSIONS

Regression equations for estimating the magnitude and frequency of floods on ungaged streams in

Pennsylvania were developed on the basis of peak-flow data collected at 313 streamflow-gaging stations.

All stations used in the development of the equations had 10 or more years of peak-flow record and were

either continuous-record or crest-stage stations. The equations were developed by dividing the State into

two flood-frequency regions, A and B. Region A generally is east and south of the Allegheny and Ohio

Rivers and region B generally is north and west of the Allegheny and Ohio Rivers. The reason for the

division was due to differing seasonal flooding that resulted in the initial run of the regression model

overestimating flood discharges in the northwestern part of the State. Equations were developed for flood

flows expected every 10, 25, 50, 100, and 500 years by the use of a weighted multiple linear regression

model. The regression equations were based on five variables—drainage area, percentage of forest cover,

percentage of urban development, percentage of basin underlain by carbonate rock, and percentage of

basin controlled by lakes, swamps, and reservoirs.

The regression equations developed for Region A produced residual standard errors that ranged from

0.18 to 0.27; for Region B, the standard errors ranged from 0.12 to 0.19. The R2 values ranged from 0.93 to

0.82 for Region A and 0.96 to 0.89 for Region B. The equations should only be used if the drainage area is

between 1.5 and 2,000 mi2. The equations should not be used to estimate flood flows immediately below

flood-control reservoirs, of for stream with upstream significant current or past surface-mining activity.

The equations developed for Region B should not be used if the basin has more than 5 percent urban

development.

REFERENCES CITED

Aron, G., and Kibler, D.F., 1981, Procedure PSU-IV for estimating design flood peaks on ungaged

Pennsylvania watersheds: Institute of Research on Land and Water Resources, FHWA/PA 81-013,

211 p.

Choquette, A.F., 1987, Regionalization of peak discharges for streams in Kentucky: U.S. Geological

Survey Water-Resources Investigations Report 87-4209, 105 p.

Coll, M.B., Jr., and Siwicki, R.W., 1998, Water-resources data, Pennsylvania, water year 1997-Volume 3,

Ohio River and St. Lawrence River Basins: U.S. Geological Survey Water-Data Report PA-97-3,

339 p.

Durlin, R.R., and Schaffstall, W.P., 1998a, Water-resources data, Pennsylvania, water year 1997-Volume 1,

Delaware River Basin: U.S. Geological Survey Water-Data Report PA-97-1, 372 p.

_____1998b, Water-resources data, Pennsylvania, water year 1997-Volume 2, Susquehanna and Potomac

River Basins: U.S. Geological Survey Water-Data Report PA-97-2, 439 p.

Ehlke, M.H., and Reed, L.A., 1999, Comparison of methods for computing streamflow statistics for

Pennsylvania streams: U.S. Geological Survey Water-Resources Investigations Report 99-4068, 80 p.

Environmental Resources Research Institute, 1996, Areas of carbonate lithology: Pennsylvania

Department of Environmental Protection, accessed September 19, 2000, at URL

http://www.pasda.psu.edu/access/compendium.shtml.

Federal Emergency Management Agency, 1995, Flood insurance study guidelines and specifications for

study contractors: Federal Emergency Management Report January 1995 FEMA 37, 200 p.

Flippo, H.N., Jr., 1977, Floods in Pennsylvania: Harrisburg, Pa., Pennsylvania Department of

Environmental Resources, Water Resources Bulletin No. 13, 59 p.

_____1982, Evaluation of the streamflow data program in Pennsylvania: U.S. Geological Survey Water

Resources Investigations 82-21, 56 p.

Freund, R.J., and Littell, R.C., 1986, SAS system for regression: Cary, N.C., SAS Institute, Inc., 165 p.
20

REFERENCES CITED—CONTINUED

Growitz, D.J., Reed, L.A., and Beard, M.M., 1983, Reconnaissance of mine drainage in the coal fields of

eastern Pennsylvania: U.S. Geological Survey Water-Resources Investigations Report 83-4274, 54 p.

Hardison, C.H., 1971, Prediction error of regression estimates of streamflow characteristics at ungaged

streams: U.S. Geological Survey Professional Paper 750-C, p. C228-C236.

Helsel, D.R., and Hirsch, R.M., 1997, Statistical methods in water resources: New York, Elsevier Science

Publishing Co., Inc., 529 p.

Reich, B.M., and Jackson, D.R., 1971, Flood prediction methods for Pennsylvania highway crossings:

University Park, Pa., The Pennsylvania State University, 200 p.

Water Resources Council, Hydrology Committee, 1981, Guidelines for determining flood flow

frequencies: Washington, D.C., Bulletin 17B, variously paged.

U.S. Geological Survey, 1996, National land cover data Pennsylvania: U.S. Geological Survey, accessed

September 14, 2000, at URL http://edcwww.cr.usgs.gov/programs/kcp/nationallandcover.html
21

APPENDIXES
22Appendix 1. Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations

[ddmmss, degrees, minutes, and seconds; mi2, square miles; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging station

Latitude

(ddmmss)

Longitude

(ddmmss) Station name

Drainage

area

(mi2)

Period of

record used

in analysis

(water year)

Number

of years

used in

analysis

Percentage

forested

area

(percent)

Perc

urba

(pe

01427650 414157 750958 North Branch Calkins Creek near Damascus, Pa. 7.02 1962-81 20 78 001428750 414028 752235 West Branch Lackawaxen River near Aldenville, Pa. 40.6 1975-97 23 74 01429000 413514 751938 West Branch Lackawaxen River at Prompton, Pa. 59.7 1945-60 16 70 01429300 413926 751712 Dyberry Creek above Reservoir near Honesdale, Pa. 45.8 1975-97 23 85 01429500 413626 751603 Dyberry Creek near Honesdale, Pa. 64.6 1944-59 16 75 01430000 413343 751454 Lackawaxen River near Honesdale, Pa. 164 1949-59 11 70 01430500 412910 751115 Lackawaxen River at West Hawley, Pa. 206 1922-42 21 72 01431000 412905 751320 Middle Creek near Hawley, Pa. 78.4 1945-86 42 77 01431500 412834 751021 Lackawaxen River at Hawley, Pa. 290 1909-59 51 72 

1960-97 38 72 

01431680 412315 751420 Mill Brook near Paupack, Pa. 4.84 1960-80 20 93 101438300 411935 744750 Vandermark Creek at Milford, Pa. 5.36 1962-97 33 85 201439500 410515 750220 Bush Kill at Shoemakers, Pa. 117 1909-96 88 90 01440300 410950 751600 Mill Creek at Mountainhome, Pa. 5.84 1961-97 37 94 201440400 410505 751254 Brodhead Creek near Analomink, Pa. 65.9 1958-96 39 95 01441000 405845 751205 McMichael Creek near Stroudsburg, Pa. 65.3 1911-55 45 50 101442500 405955 750835 Brodhead Creek at Minisink Hill, Pa. 259 1951-96 46 83 401446600 405400 751208 Martins Creek near East Bangor, Pa. 10.4 1961-86 26 84 01447500 410749 753733 Lehigh River at Stoddartsville, Pa. 91.7 1942-97 56 93 201447680 410355 753114 Tunkhannock Creek near Long Pond, Pa. 18 1965-96 32 86 01447720 410505 753621 Tobyhanna Creek near Blakeslee, Pa. 118 1962-96 35 89 201448000 410225 754542 Lehigh River at Tannery, Pa. 322 1917-59 43 86 201448500 410208 753237 Dilldown Creek near Long Pond, Pa. 2.39 1949-96 48 98 01449000 404945 754220 Lehigh River at Lehighton, Pa. 591 1982-97 16 83 201449360 405351 753010 Pohopoco Creek at Kresgeville, Pa. 49.9 1967-96 30 68 401449500 405522 753332 Wild Creek at Hatchery, Pa. 16.8 1941-58 18 70 01450000 404954 754053 Pohopoco Creek near Parryville, Pa. 109 1941-70 29 70 01450500 404822 753554 Aquashicola Creek at Palmerton, Pa. 76.7 1940-96 57 70 101451000 404525 753612 Lehigh River at Walnutport, Pa. 889 1947-60 14 80 

1961-97 37 85 2

01451500 403456 752900 Little Lehigh Creek near Allentown, Pa. 80.8 1946-97 52 33 11 
23

01451650 403547 752828 Little Lehigh Creek at 10th St Bridge at Allentown, Pa. 98.2 1987-97 11 29 18 01451800 403942 753738 Jordan Creek near Schnecksville, Pa. 53.0 1967-97 31 33 101452000 403723 752858 Jordan Creek at Allentown, Pa. 75.8 1945-97 53 34 301452300 404310 752210 East Branch Monocacy Creek near Bath, Pa. 5.35 1963-80 18 26 401452500 403828 752247 Monocacy Creek at Bethlehem, Pa. 44.5 1945-97 53 19 12 01453000 403655 752245 Lehigh River at Bethlehem, Pa. 1,279 1902-60 55 75 1

1961-97 37 64 5

01454600 403405 751945 Polk Valley Run at Hellertown, Pa. 2.14 1965-80 16 84 101454700 404009 751412 Lehigh River at Glendon, Pa. 1,359 1967-97 31 66 601458900 402814 750813 Tinicum Creek near Ottsville, Pa. 14.7 1962-80 19 78 01459500 402601 750701 Tohickon Creek near Pipersville, Pa. 97.4 1936-73 38 55 1

1974-97 24 59 3

01460000 402525 750400 Tohickon Creek at Point Pleasant, Pa. 107 1884-1913 29 61 301465000 401518 750159 Neshaminy Creek at Rushland, Pa. 134 1885-34 32 39 19 01465500 401026 745726 Neshaminy Creek near Langhorne, Pa. 210 1933-96 64 39 18 01465770 400755 745940 Poquessing Creek at Trevose Rd, Philadelphia, Pa. 5.08 1965-81 17 20 73 01465785 400522 745937 Walton Run at Philadelphia, Pa. 2.17 1965-78 14 23 63 01465790 400501 745857 Byberry Creek at Chalfont Road, Philadelphia, Pa. 5.34 1966-78 13 17 66 01465798 400325 745908 Poquessing Creek at Grant Ave, Philadelphia, Pa. 21.4 1966-97 32 18 67 01467042 400523 750410 Pennypack Creek at Pine Rd, Philadelphia, Pa. 37.9 1965-81 17 20 71 01467043 400527 750315 Unnamed tributary to Pennypack Creek at

Philadelphia, Pa.

1.20 1965-80 16 9.8 87 

01467048 400300 750159 Pennypack Creek at Lower Rhawn St Bridge,

Philadelphia, Pa.

49.8 1966-97 32 33 55 

01467050 400319 750122 Wooden Bridge Run at Philadelphia, Pa. 3.35 1965-81 17 20 71 01467086 400247 750640 Tacony Creek above Adams Ave, Philadelphia, Pa. 16.6 1966-86 21 25 68 01467087 400057 750550 Frankford Creek at Castor Ave, Philadelphia, Pa. 30.4 1982-97 16 20 73 01467089 400025 750533 Frankford Creek at Torresdale Ave, Philadelphia, Pa. 33.8 1966-81 16 20 74 01469500 404825 755820 Little Schuylkill River at Tamaqua, Pa. 42.9 1920-97 78 77 201470500 403121 755955 Schuylkill River at Berne, Pa. 355 1948-97 50 72 301470720 403423 755234 Maiden Creek tributary at Lenhartsville, Pa. 7.46 1962-80 18 30 01470756 403051 755300 Maiden Creek at Virginville, Pa. 159 1973-95 23 40 1

Appendix 1. Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations—Continued[ddmmss, degrees, minutes, and seconds; mi2, square miles; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging station

Latitude

(ddmmss)

Longitude

(ddmmss) Station name

Drainage

area

(mi2)

Period of

record used

in analysis

(water year)

Number

of years

used in

analysis

Percentage

forested

area

(percent)

Perc

urba

(pe
24

01470779 402448 761019 Tulpehocken Creek near Bernville, Pa. 66.5 1975-96 23 13 301470853 402024 760837 Furnace Creek at Robesonia, Pa. 4.18 1983-97 15 74 0 01470960 402200 760116 Tulpehocken Creek at Blue Marsh, Pa. 175 1965-78 14 30 301471000 402208 755846 Tulpehocken Creek near Reading, Pa. 211 1951-78 28 28 301471510 402005 755612 Schuylkill River at Reading, Pa. 880 1902-30 29 60 2

1980-97 18 49 4

01471800 402443 754402 Pine Creek near Manatawny, Pa. 15.6 1961-82 20 85 0 01471980 401622 754049 Manatawny Creek near Pottstown, Pa. 85.5 1975-97 23 56 101472000 401430 753905 Schuylkill River at Pottstown, Pa. 1,147 1902-78 77 50 5

1979-97 19 50 5

01472157 400905 753606 French Creek near Phoenixville, Pa. 59.1 1969-97 29 64 101472174 400522 753750 Pickering Creek near Chester Spring, Pa. 5.98 1967-83 17 63 01472198 402338 753057 Perkiomen Creek at East Greenville, Pa. 38.0 1982-97 16 54 201472199 402226 753122 West Branch Perkiomen Creek at Hillegass, Pa. 23.0 1982-97 16 61 101472500 401630 752720 Perkiomen Creek near Frederick, Pa. 152 1885-1913 29 20 301472620 402414 751405 East Branch Perkiomen Creek near Dublin, Pa. 4.05 1984-99 16 42 01473000 401346 752707 Perkiomen Creek at Graterford, Pa. 279 1915-97 83 50 201473100 401226 752157 Zacharias Creek near Skippack, Pa. 7.27 1960-80 21 41 601473120 400952 752601 Skippack Creek near Collegeville, Pa. 53.7 1966-94 29 37 19 01473169 400445 752740 Valley Creek at Pa Turnpike Bridge near Valley Forge, Pa. 20.8 1983-99 17 48 28 01473470 400738 752043 Stony Creek at Norristown, Pa. 20.4 1971-94 21 30 38 01473880 400813 751121 Pine Run Trib at Fort Washington, Pa. 2.01 1962-79 18 33 51 01473950 400450 751335 Wissahickon Creek at Bells Mill Rd, Philadelphia, Pa. 53.6 1966-81 16 39 41 01474000 400445 751343 Wissahickon Creek at Mouth, Philadelphia, Pa. 64.0 1966-99 34 40 42 01474500 395804 751120 Schuylkill River at Philadelphia, Pa. 1,893 1932-97 66 48 10 01475300 400121 752520 Darby Creek at Waterloo Mills near Devon, Pa. 5.15 1972-97 26 52 39 01475510 395544 751622 Darby Creek near Darby, Pa. 37.4 1964-90 27 38 51 01475530 395829 751649 Cobbs Creek at U.S. 1 at Philadelphia, Pa. 4.78 1965-81 17 20 73 01475550 395502 751452 Cobbs Creek at Darby, Pa. 22.0 1964-90 27 15 77 01475850 395837 752610 Crum Creek near Newtown Square, Pa. 15.8 1981-97 17 61 15 01476480 395458 752413 Ridley Creek at Media, Pa. 30.5 1987-97 11 58 14 

Appendix 1. Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations—Continued[ddmmss, degrees, minutes, and seconds; mi2, square miles; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging station

Latitude

(ddmmss)

Longitude

(ddmmss) Station name

Drainage

area

(mi2)

Period of

record used

in analysis

(water year)

Number

of years

used in

analysis

Percentage

forested

area

(percent)

Perc

urba

(pe
25

01476500 395410 752335 Ridley Creek at Moylan, Pa. 31.9 1932-55 24 58 15 01477000 395203 752431 Chester Creek near Chester, Pa. 61.1 1932-97 66 55 19 01478200 394654 754803 Middle Branch White Clay Creek near Landenberg, Pa. 12.7 1960-91 32 31 301480300 400422 755140 West Branch Brandywine Creek near Honey Brook, Pa. 18.7 1960-97 38 31 101480500 395908 754940 West Branch Brandywine Creek at Coatesville, Pa. 45.8 1944-97 37 42 201480610 395820 755106 Sucker Run near Coatesville, Pa. 2.57 1964-96 33 45 12 01480617 395742 754806 West Branch Brandywine Creek at Modena, Pa. 55.0 1970-97 28 42 201480675 400552 754431 Marsh Creek near Glenmoore, Pa. 8.57 1967-97 31 55 101480680 400358 754338 Marsh Creek near Lyndell, Pa. 17.8 1960-71 12 46 201480700 400205 754232 East Branch Brandywine Creek near Downingtown, Pa. 60.6 1974-99 26 46 101480800 400020 754220 East Branch Brandywine Creek At Downingtown, Pa. 81.6 1958-68 11 46 501480870 395807 754025 East Branch Brandywine Creek below

Downingtown, Pa.

89.9 1974-99 26 47 6

01481000 395211 753537 Brandywine Creek at Chadds Ford, Pa. 287 1912-97 78 35 301516350 414734 770444 Tioga River near Mansfield, Pa. 153 1972-96 21 74 01516500 414727 770054 Corey Creek near Mainesburg, Pa. 12.2 1955-96 42 47 01516800 414919 770550 Manns Creek near Mansfield, Pa. 3.01 1960-77 17 53 0 01517000 414854 765755 Elk Run near Mainesburg, Pa. 10.2 1955-78 24 52 0 01518000 415430 770747 Tioga River at Tioga, Pa. 282 1939-77 39 63 301518420 415033 771625 Crooked Creek below Catlin Hollow at Middlebury

Center, Pa.

74.3 1985-97 13 55 

01518500 415408 770855 Crooked Creek at Tioga, Pa. 122 1954-74 21 60 01518862 415523 773156 Cowanesque River at Westfield, Pa. 90.6 1984-96 12 64 01519200 415915 771809 Cowanesque River at Elkland, Pa. 235 1980-97 18 63 01520000 415948 770825 Cowanesque River near Lawrenceville, Pa. 298 1952-78 27 66 201532000 414225 762906 Towanda Creek near Monroeton, Pa. 215 1914-96 83 68 101532200 413525 762600 South Branch Towanda Creek at New Albany, Pa. 13.3 1963-95 30 55 01532850 415145 760026 Middle Branch Wyalusing Creek Trib near

Birchardsville, Pa.

5.67 1960-79 20 78 

01533250 414225 760710 Tuscarora Creek near Silvara, Pa. 11.8 1963-95 33 63 01533500 413150 760922 North Branch Mehoopany Creek near Lovelton, Pa. 35.2 1941-58 18 60 0 01533800 414810 753840 Butler Creek at Gibson, Pa. 7.38 1963-79 15 68 

Appendix 1. Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations—Continued[ddmmss, degrees, minutes, and seconds; mi2, square miles; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging station

Latitude

(ddmmss)

Longitude

(ddmmss) Station name

Drainage

area

(mi2)

Period of

record used

in analysis

(water year)

Number

of years

used in

analysis

Percentage

forested

area

(percent)

Perc

urba

(pe
26

01533950 413429 753832 South Branch Tunkhannock Creek near Montdale, Pa. 12.6 1961-78 18 74 001534000 413330 755342 Tunkhannock Creek near Tunkhannock, Pa. 383 1914-96 83 68 01538000 410333 760538 Wapwallopen Creek near Wapwallopen, Pa. 43.8 1920-96 77 83 501538800 411840 760850 Huntington Creek near Pikes Creek, Pa. 4.94 1960-80 21 96 0 01539000 410441 762553 Fishing Creek near Bloomsburg, Pa. 274 1939-96 58 71 01539500 410450 763040 Little Fishing Creek at Eyers Grove, Pa. 56.5 1941-58 18 50 01540000 410010 762750 Fishing Creek at Bloomsburg, Pa. 355 1914-31 18 45 01540200 405110 761648 Trexler Run near Ringtown, Pa. 1.77 1959-79 21 90 0 01541000 405349 784038 West Branch Susquehanna River at Bower, Pa. 315 1914-97 84 50 101541200 405741 783110 West Branch Susquehanna River at Curwensville, Pa. 367 1956-67 12 78 201541500 405818 782422 Clearfield Creek at Dimeling, Pa. 371 1914-97 84 84 101542000 405058 781605 Moshannon Creek at Osceola Mills, Pa. 68.8 1941-93 52 83 101542500 410703 780633 West Branch Susquehanna River at Karthaus, Pa. 1,462 1940-60 21 50 1

1966-97 32 80 1

01542720 411258 783500 Wilson Run at Penfield, Pa. 8.34 1962-95 34 65 0 01542810 413444 781734 Waldy Run near Emporium, Pa. 5.24 1964-97 34 99 0 01543000 412448 781150 Driftwood Br Sinnemahoning Creek at Sterling Run, Pa. 272 1914-96 83 80 01543500 411902 780612 Sinnemahoning Creek at Sinnemahoning, Pa. 685 1936-97 62 93 01543700 413108 780140 First Fork Sinnemahoning Creek at Wharton, Pa. 182 1984-97 14 93 01544450 413849 773922 Germania Branch at Germania, Pa. 2.40 1964-79 11 71 01544500 412833 774934 Kettle Creek at Cross Fork, Pa. 136 1941-96 56 96 0 01545600 412322 774128 Young Womans Creek near Renovo, Pa. 46.2 1965-96 32 100 0 01546000 405630 774740 North Bald Eagle Creek at Milesburg, Pa. 119 1911-28 18 60 01546400 405001 774940 Spring Creek at Houserville, Pa. 58.5 1985-96 12 37 801546500 405323 774740 Spring Creek near Axemann, Pa. 87.2 1936-96 57 37 801547100 405554 774713 Spring Creek at Milesburg, Pa. 142 1967-96 30 40 601547200 405635 774712 Bald Eagle Creek below Spring Creek at Milesburg, Pa. 265 1957-96 40 61 401547500 410306 773617 Bald Eagle Creek at Blanchard, Pa. 339 1955-69 15 60 701547700 410334 773622 Marsh Creek at Blanchard, Pa. 44.1 1956-96 41 78 01547800 410126 775415 South Fork Beech Creek near Snow Shoe, Pa. 12.2 1959-81 23 97 201547950 410642 774209 Beech Creek at Monument, Pa. 152 1968-97 30 68 1

Appendix 1. Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations—Continued[ddmmss, degrees, minutes, and seconds; mi2, square miles; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging station

Latitude

(ddmmss)

Longitude

(ddmmss) Station name

Drainage

area

(mi2)

Period of

record used

in analysis

(water year)

Number

of years

used in

analysis

Percentage

forested

area

(percent)

Perc

urba

(pe
27

01548005 410451 773259 Bald Eagle Creek near Beech Creek Station, Pa. 562 1971-97 25 71 201548020 410030 771935 Bull Run near Loganton, Pa. 1.99 1963-81 19 99 01548500 413118 772652 Pine Creek at Cedar Run, Pa. 604 1919-96 78 83 101549000 411845 772245 Pine Creek near Waterville, Pa. 750 1909-20 12 90 01549500 412825 771352 Blockhouse Creek near English Center, Pa. 37.7 1941-97 57 78 01549700 411625 771928 Pine Creek below Little Pine Creek near Waterville, Pa. 944 1958-96 39 98 101549780 412504 770946 Larrys Creek at Cogan House, Pa. 6.80 1960-78 19 75 0 01550000 412506 770159 Lycoming Creek near Trout Run, Pa. 173 1914-98 85 80 01551000 411515 770040 Grafius Run at Williamsport, Pa. 3.14 1940-53 14 40 501552000 411930 765446 Loyalsock Creek at Loyalsockville, Pa. 443 1926-98 73 82 01552100 412010 765745 Mill Creek near Warrensville, Pa. 11.9 1961-78 18 81 01552500 412125 763206 Muncy Creek near Sonestown, Pa. 23.8 1941-96 56 92 0 01553050 410705 770400 White Deer Hole Creek near Elimsport, Pa. 18.2 1961-95 33 98 0 01553130 410331 770437 Sand Spring Run near White Deer, Pa. 4.93 1968-81 14 95 301553600 410457 763917 East Branch Chillisquaque Creek near

Washingtonville, Pa.

9.48 1960-78 19 41 1

01553700 410342 764050 Chillisquaque Creek at Washingtonville, Pa. 51.3 1980-96 17 31 01555000 405200 770255 Penns Creek at Penns Creek, Pa. 301 1930-97 68 67 101555500 403640 765444 East Mahantango Creek near Dalmatia, Pa. 162 1930-97 68 53 101555800 402235 782555 McDonald Run near East Freedom, Pa. 1.54 1959-78 20 73 201556000 402747 781200 Frankstown Br Juniata River at Williamsburg, Pa. 291 1889-1997 109 70 101556400 403347 782035 Sandy Run near Bellwood, Pa. 5.58 1962-81 20 75 14 01556500 403740 781738 Little Juniata River at Tipton, Pa. 93.7 1946-81 36 75 601557100 404000 781500 Schell Run at Tyrone, Pa. 1.68 1958-81 23 86 301557500 404101 781402 Bald Eagle Creek at Tyrone, Pa. 44.1 1940-97 58 91 101558000 403645 780827 Little Juniata River at Spruce Creek, Pa. 220 1936-97 60 77 601559000 402905 780109 Juniata River at Huntingdon, Pa. 816 1896-97 96 50 201559500 403125 775815 Standing Stone Creek near Huntingdon, Pa. 128 1930-58 29 65 01559700 395840 783708 Sulphur Springs Creek near Manns Choice, Pa. 5.28 1962-78 17 80 0 01560000 400418 782934 Dunning Creek at Belden, Pa. 172 1936-97 62 56 101561000 395720 781515 Brush Creek at Gapsville, Pa. 36.8 1930-58 29 70 01562000 401257 781556 Raystown Branch Juniata River at Saxton, Pa. 756 1912-97 86 60 

Appendix 1. Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations—Continued[ddmmss, degrees, minutes, and seconds; mi2, square miles; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging station

Latitude

(ddmmss)

Longitude

(ddmmss) Station name

Drainage

area

(mi2)

Period of

record used

in analysis

(water year)

Number

of years

used in

analysis

Percentage

forested

area

(percent)

Perc

urba

(pe
28

01562500 402100 780750 Great Trough Creek near Marklesburg, Pa. 84.6 1930-57 28 65 001563000 402535 780147 Raystown Branch Juniata River near Huntingdon, Pa. 957 1946-71 26 67 101563800 400520 780255 Elders Branch near Hustontown, Pa. 3.46 1960-78 19 40 0 01564500 401245 775532 Aughwick Creek near Three Springs, Pa. 205 1939-97 59 60 01565000 403917 773500 Kishacoquillas Creek at Reedsville, Pa. 164 1936-98 63 63 101565700 403620 771840 Little Lost Creek at Oakland Mills, Pa. 6.52 1960-81 22 29 101565920 402115 773855 Lick Run near East Waterford, Pa. 8.38 1962-81 20 76 01566000 403055 772510 Tuscarora Creek near Port Royal, Pa. 214 1912-90 50 70 01566500 403355 770705 Cocolamus Creek near Millerstown, Pa. 57.2 1930-58 29 55 01567500 402215 772409 Bixler Run near Loysville, Pa. 15.0 1954-97 44 49 01568000 401924 771009 Sherman Creek at Shermans Dale, Pa. 207 1927-97 71 68 01568500 402737 764506 Clark Creek near Carsonville, Pa. 22.5 1938-96 59 95 0 01569000 402246 765431 Stony Creek near Dauphin, Pa. 33.2 1938-74 16 90 01569340 400740 773250 Newburg Run at Newburg, Pa. 5.29 1964-95 32 34 101569800 401405 770823 Letort Spring Run near Carlisle, Pa. 21.6 1976-97 22 8.1 21 01570000 401508 770117 Conodoguinet Creek near Hogestown, Pa. 470 1912-96 64 35 401571000 401830 765100 Paxton Creek near Penbrook, Pa. 11.2 1940-50 11 25 3

1974-94 21 38 29 

01571500 401329 765354 Yellow Breeches Creek near Camp Hill, Pa. 216 1910-97 55 55 901572000 403215 762240 Lower Little Swatara Creek at Pine Grove, Pa. 34.3 1920-84 18 59 01572900 402425 763315 Reeds Creek near Ono, Pa. 8.63 1962-81 20 41 15 01573000 402409 763439 Swatara Creek at Harper Tavern, Pa. 337 1919-97 79 54 101573086 401924 762900 Beck Creek near Cleona, Pa. 7.87 1964-81 18 17 101573160 402034 763346 Quittapahilla Creek near Bellegrove, Pa. 74.2 1975-93 19 17 13 01573500 402350 764235 Manada Creek at Manada Gap, Pa. 13.5 1938-58 21 89 01573560 401754 764005 Swatara Creek near Hershey, Pa. 483 1975-97 23 40 801574000 400456 764313 West Conewago Creek near Manchester, Pa. 510 1929-97 69 34 101574500 395243 765113 Codorus Creek at Spring Grove, Pa. 75.5 1930-66 37 15 3

1967-97 31 28 3

01574800 394857 763759 East Branch Codorus Creek Trib near Winterstown, Pa. 5.17 1960-75 16 26 

Appendix 1. Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations—Continued[ddmmss, degrees, minutes, and seconds; mi2, square miles; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging station

Latitude

(ddmmss)

Longitude

(ddmmss) Station name

Drainage

area

(mi2)

Period of

record used

in analysis

(water year)

Number

of years

used in

analysis

Percentage

forested

area

(percent)

Perc

urba

(pe
29

01575000 395514 764457 South Branch Codorus Creek near York, Pa. 117 1928-71 44 20 1

1972-95 24 29 2

01575500 395646 764520 Codorus Creek near York. Pa. 222 1947-97 51 28 501576085 400841 755920 Little Conestoga Creek near Churchtown, Pa. 5.82 1982-95 14 20 01576320 401244 760730 Stony Run at Reamstown, Pa. 3.55 1964-95 32 34 16 01576500 400300 761639 Conestoga River at Lancaster, Pa. 324 1929-97 69 27 12 01576754 395647 762205 Conestoga River at Conestoga, Pa. 470 1985-97 13 23 17 01577500 394621 761858 Muddy Creek at Castle Fin, Pa. 133 1929-72 15 40 101578200 395035 761145 Conowingo Creek near Buck, Pa. 8.71 1963-97 33 20 01578400 395341 760650 Bowery Run near Quarryville, Pa. 5.98 1963-81 19 22 0 01600700 395535 783940 Little Wills Creek at Bard, Pa. 10.2 1961-81 21 83 0 01601000 394843 784300 Wills Creek below Hyndman, Pa. 146 1952-86 35 87 01603500 394723 783848 Evitts Creek near Centerville, Pa. 30.2 1933-82 50 74 01613050 395354 780757 Tonoloway Creek near Needmore, Pa. 10.7 1963-96 33 70 0 01613500 394323 780338 Licking Creek near Sylvan, Pa. 158 1931-41 11 65 01614090 395548 772623 Conococheague Creek near Fayetteville, Pa. 5.05 1961-81 21 97 0 01638900 394745 771150 White Run near Gettysburg, Pa. 12.4 1961-80 20 17 603007800 414907 781735 Allegheny River at Port Allegany, Pa. 248 1975-97 23 88 03009680 414835 782550 Potato Creek at Smethport, Pa. 160 1972-97 24 93 03010655 415742 781154 Oswayo Creek at Shinglehouse, Pa. 98.7 1975-97 23 86 

03011020 420923 784256 Allegheny River at Salamanca, N.Y. 1,608 1904-95 92 86 03011800 414559 784308 Kinzua Creek near Guffey, Pa. 46.4 1966-96 31 96 1

03015000 415617 790800 Conewango Creek at Russell, Pa. 816 1936-97 62 52 203015080 415555 790538 Ackley Run near Russell, Pa. 9.64 1962-81 20 87 03015390 415629 793841 Hare Creek near Corry, Pa. 12.3 1964-85 21 58 03015500 415109 791903 Brokenstraw Creek at Youngsville, Pa. 321 1910-96 87 45 03017500 413607 790301 Tionesta Creek at Lynch, Pa. 233 1938-79 42 96 03019000 412825 792305 Tionesta Creek at Nebraska, Pa. 469 1910-40 19 90 03020440 414531 793408 West Branch Caldwell Creek near Grand Valley, Pa. 4.37 1964-81 17 77 03020500 412854 794144 Oil Creek at Rouseville, Pa. 300 1910-96 87 40 03021350 420055 794658 French Creek near Wattsburg, Pa. 92.0 1975-97 23 56 

Appendix 1. Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations—Continued[ddmmss, degrees, minutes, and seconds; mi2, square miles; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging station

Latitude

(ddmmss)

Longitude

(ddmmss) Station name

Drainage

area

(mi2)

Period of

record used

in analysis

(water year)

Number

of years

used in

analysis

Percentage

forested

area

(percent)

Perc

urba

(pe
30

03021410 420454 795102 West Branch French Creek near Lowville, Pa. 52.3 1975-94 20 57 003021700 415553 800502 Little Conneauttee Creek near Mckean, Pa. 3.60 1961-78 18 58 0 03022500 414250 800850 French Creek at Saegerstown, Pa. 629 1913-39 27 30 03022540 414126 800226 Woodcock Creek at Blooming Valley, Pa. 31.1 1975-95 21 64 03023000 414020 801255 Cussewago Creek near Meadville, Pa. 90.2 1911-38 28 20 03024000 412615 795722 French Creek at Utica, Pa. 1,028 1933-71 39 52 1

1972-97 26 52 1

03025000 412543 795248 Sugar Creek at Sugarcreek, Pa. 166 1933-79 47 71 03025200 412520 795059 Patchel Run near Franklin, Pa. 5.69 1961-78 18 77 03026400 411053 794125 Richey Run at Emlenton, Pa. 5.88 1963-81 19 61 203026500 413752 783437 Sevenmile Run near Rasselas, Pa. 7.84 1952-96 45 94 03028000 413445 784122 West Branch Clarion River at Wilcox, Pa. 63.0 1954-96 43 91 03028500 412910 784043 Clarion River at Johnsonburg, Pa. 204 1953-94 42 93 03029200 411917 790439 Clear Creek near Sigel, Pa. 8.67 1960-81 22 95 03029400 412016 791250 Toms Run at Cooksburg, Pa. 12.6 1960-78 19 94 03029500 411950 791233 Clarion River at Cooksburg, Pa 807 1936-97 62 92 103030500 411133 792625 Clarion River near Piney, Pa. 951 1948-96 49 90 103031000 410857 793937 Clarion River at St. Petersburg, Pa. 1,246 1942-53 12 90 03031780 411453 785008 Mill Creek near Brockway, Pa. 2.12 1965-81 17 50 03031950 405930 790526 Big Run near Sprankle Mills, Pa. 7.38 1964-81 18 53 03032500 405940 792340 Redbank Creek at St. Charles, Pa. 528 1910-97 88 40 03034000 405621 790031 Mahoning Creek at Punxsutawney, Pa. 158 1936-96 61 71 203034500 405010 790637 Little Mahoning Creek at Mccormick, Pa. 87.4 1940-98 59 73 03035000 405405 791335 Mahoning Creek near Dayton, Pa. 321 1917-40 24 40 03038000 403917 792056 Crooked Creek at Idaho, Pa. 191 1936-97 62 68 03039000 404313 793042 Crooked Creek at Crooked Creek Dam, Pa. 278 1910-39 30 50 03039200 400249 785000 Clear Run near Buckstown, Pa. 3.68 1961-78 18 99 0 03039925 401558 790101 North Fork Bens Creek at North Fork Reservoir, Pa. 3.45 1985-97 11 99 03040000 401708 785515 Stonycreek River at Ferndale, Pa. 451 1914-97 82 68 103041000 402037 785307 Little Conemaugh at East Conemaugh, Pa. 183 1936-97 62 77 303041500 402509 790135 Conemaugh River at Seward, Pa. 715 1936-97 62 72 3

Appendix 1. Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations—Continued[ddmmss, degrees, minutes, and seconds; mi2, square miles; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging station

Latitude

(ddmmss)

Longitude

(ddmmss) Station name

Drainage

area

(mi2)

Period of

record used

in analysis

(water year)

Number

of years

used in

analysis

Percentage

forested

area

(percent)

Perc

urba

(pe
31

03042000 402824 791101 Blacklick Creek at Josephine, Pa. 192 1952-96 45 77 103042170 403631 790949 Stoney Run at Indiana, Pa. 4.39 1964-76 13 34 52 03042200 403345 785644 Little Yellow Creek near Strongstown, Pa. 7.36 1961-87 19 88 03042500 403102 791019 Two Lick Creek at Graceton, Pa. 171 1952-68 17 72 3

1969-97 29 72 3

03043000 402825 791215 Blacklick Creek at Black Lick, Pa. 390 1905-51 47 50 03045000 401733 792027 Loyalhanna Creek at Kingston, Pa. 172 1940-97 52 81 03045500 402340 792555 Loyalhanna Creek at New Alexandria, Pa. 265 1920-40 19 50 03047500 403205 792755 Kiskiminetas River at Avonmore, Pa. 1,723 1884-1937 48 50 03049000 404257 794159 Buffalo Creek near Freeport, Pa. 137 1941-96 55 67 103049100 404557 794601 Little Buffalo Creek at Cabot, Pa. 4.66 1959-81 23 80 0 03049800 403113 795618 Little Pine Creek near Etna, Pa. 5.78 1963-96 33 80 803070420 394551 793514 Stony Fork Trib near Gibbon Glade, Pa. .93 1978-89 12 77 03072000 394533 795815 Dunkard Creek at Shannopin, Pa. 229 1941-96 56 78 03072590 394744 794747 Georges Creek at Smithfield, Pa. 16.3 1964-78 15 60 403072840 395951 800231 Tenmile Creek near Clarksville, Pa. 133 1969-79 11 56 103072880 395627 801721 Browns Creek near Nineveh, Pa. 17.5 1963-85 23 59 03073000 395523 800422 South Fork Tenmile Creek at Jefferson, Pa. 180 1932-95 64 63 103074300 395204 794140 Lick Run at Hopwood, Pa. 3.80 1959-78 20 97 03074500 395848 794552 Redstone Creek at Waltersburg, Pa. 73.7 1943-96 54 58 803078500 394334 790255 Big Piney Run near Salisbury, Pa. 24.5 1933-86 51 68 03079000 395135 791340 Casselman River at Markleton, Pa. 382 1915-96 82 40 03080000 394913 791918 Laurel Hill Creek at Ursina, Pa. 121 1914-97 84 81 03081000 394940 792225 Youghiogheny River below Confluence, Pa. 1,029 1942-97 56 68 03082200 400059 792533 Poplar Run near Normalville, Pa. 9.27 1961-78 18 79 03082500 400103 793538 Youghiogheny River at Connellsville, Pa. 1,326 1943-97 55 69 03083000 400618 793001 Green Lick Run at Green Lick Reservoir, Pa. 3.07 1929-79 51 70 03083500 401424 794824 Youghiogheny River at Sutersville, Pa. 1,715 1943-97 55 67 203083600 401359 794906 Gillespie Run near Sutersville, Pa. 4.04 1959-81 21 68 403084000 402701 794250 Abers Creek near Murrysville, Pa. 4.39 1949-93 45 59 27 03084500 402309 794555 Turtle Creek at Trafford, Pa. 55.9 1917-55 37 68 14 

Appendix 1. Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations—Continued[ddmmss, degrees, minutes, and seconds; mi2, square miles; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging station

Latitude

(ddmmss)

Longitude

(ddmmss) Station name

Drainage

area

(mi2)

Period of

record used

in analysis

(water year)

Number

of years

used in

analysis

Percentage

forested

area

(percent)

Perc

urba

(pe
32

03085500 402402 800548 Chartiers Creek at Carnegie, Pa. 257 1916-96 71 50 203086100 403627 800949 Big Sewickley Creek near Ambridge, Pa. 15.6 1963-78 16 84 303100000 413045 802815 Shenango River near Turnersville, Pa. 152 1912-22 11 30 03101000 412950 802755 Sugar Run at Pymatuning Dam, Pa. 9.34 1935-55 21 30 03102500 412519 802235 Little Shenango River at Greenville, Pa. 104 1914-96 80 30 03102850 412113 802353 Shenango River near Transfer, Pa. 337 1966-97 32 40 203103000 411840 802840 Pymatuning Creek near Orangeville, Pa. 169 1914-63 48 30 03104000 411355 803035 Shenango River at Sharon, Pa. 608 1910-32 23 30 03104500 410000 802105 Shenango River at New Castle, Pa. 792 1913-32 20 30 03104760 411110 801938 Harthegig Run near Greenfield, Pa. 2.26 1969-80 12 28 1

03106000 404901 801433 Connoquenessing Creek near Zelienople, Pa. 356 1916-96 81 56 403106500 405302 801402 Slippery Rock Creek at Wurtemburg, Pa. 398 1912-69 58 25 

1970-97 28 56 1

03108000 403740 802016 Raccoon Creek at Moffatts Mill, Pa. 178 1916-96 70 68 3

03111150 401154 802428 Brush Run near Buffalo, Pa. 10.3 1961-85 21 28 

04213000 415534 803618 Conneaut Creek at Conneaut, Ohio 175 1923-95 60 20 04213040 415642 802651 Raccoon Creek near West Springfield, Pa. 2.53 1961-95 34 63 204213200 420554 800435 Mill Creek at Erie, Pa. 9.16 1969-85 17 51 4

Appendix 1. Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations—Continued[ddmmss, degrees, minutes, and seconds; mi2, square miles; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging station

Latitude

(ddmmss)

Longitude

(ddmmss) Station name

Drainage

area

(mi2)

Period of

record used

in analysis

(water year)

Number

of years

used in

analysis

Percentage

forested

area

(percent)

Perc

urba

(pe
33

Appendix 2. Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging

stations used in analysis

[All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging

station

Period of

record used

in analysis

(water year)

Floodflow

region

Computed from streamflow-gaging-station data Predicted from regression e

10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 10

01427650 1962-81 A 990 1,310 1,580 1,890 2,730 841 1,210 1,540 01428750 1975-97 A 3,450 4,190 4,740 5,310 6,690 3,100 4,320 5,410 01429000 1945-60 A 4,820 6,010 6,990 8,030 10,800 4,180 5,800 7,250 01429300 1975-97 A 3,550 4,440 5,150 5,910 7,850 3,170 4,390 5,470 01429500 1944-59 A 8,540 12,600 16,600 21,400 37,500 4,540 6,270 7,790 01430000 1944-59 A 12,900 17,100 20,700 25,000 37,200 9,140 12,400 15,300 101430500 1922-42 A 14,800 22,100 29,300 38,300 68,600 10,700 14,400 17,700 201431000 1945-86 A 5,510 7,530 9,260 11,200 16,600 4,800 6,620 8,220 101431500 1909-59 A 17,200 23,800 29,800 36,900 58,600 14,000 18,700 22,800 2

1960-97 A 11,300 13,900 15,800 17,900 22,900 12,300 16,600 20,400 2

01431680 1960-80 A 380 460 530 600 790 516 746 956 01438300 1962-97 A 310 400 480 570 800 639 919 1,170 01439500 1909-96 A 4,310 6,200 8,010 10,300 17,700 5,580 7,650 9,470 101440300 1961-97 A 880 1,290 1,650 2,080 3,370 673 962 1,220 01440400 1958-96 A 6,480 8,930 11,000 13,300 19,800 4,140 5,670 6,990 01441000 1911-55 A 2,910 3,730 4,410 5,150 7,110 5,620 7,780 9,690 101442500 1951-96 A 20,100 29,500 38,600 49,700 86,600 13,500 17,800 21,400 201446600 1961-86 A 1,130 1,640 2,120 2,700 4,520 883 1,280 1,640 01447500 1942-97 A 6,700 10,700 14,800 20,200 39,300 4,690 6,430 7,950 01447680 1965-96 A 565 681 770 860 1,080 1,190 1,710 2,200 01447720 1962-96 A 7,060 9,690 11,900 14,300 20,800 5,490 7,500 9,270 101448000 1917-59 A 17,500 26,800 36,000 47,700 88,200 13,300 17,700 21,500 201448500 1949-96 A 320 450 560 690 1,040 308 452 584 01449000 1982-97 A 23,900 30,400 35,600 41,100 55,000 21,400 28,300 34,100 401449360 1967-96 A 1,860 2,280 2,600 2,920 3,720 4,270 5,840 7,200 01449500 1941-58 A 1,620 2,520 3,390 4,470 8,000 1,810 2,550 3,210 01450000 1941-70 A 3,780 5,030 6,070 7,220 10,300 7,300 9,940 12,200 101450500 1940-96 A 5,100 7,190 9,080 11,300 18,000 5,390 7,400 9,160 101451000 1947-60 A 49,000 69,100 87,400 109,000 176,000 32,100 42,000 50,400 5

1961-97 A 33,200 41,600 48,100 54,800 71,500 27,400 36,100 43,400 5
34

01451500 1946-97 A 4,970 8,220 11,500 15,600 29,700 3,730 5,530 7,250 01451650 1987-97 A 5,830 9,560 13,400 18,400 36,400 4,360 6,400 8,320 101451800 1967-97 A 5,050 6,900 8,500 10,300 15,300 5,550 7,770 9,760 101452000 1945-97 A 6,910 10,000 12,900 16,300 26,900 6,210 8,700 10,900 101452300 1963-80 A 730 1,020 1,270 1,540 2,280 919 1,350 1,760 01452500 1945-97 A 1,740 2,790 3,860 5,240 10,100 2,390 3,630 4,830 01453000 1902-60 A 51,800 73,100 92,500 115,000 185,000 41,900 55,000 66,100 7

1961-97 A 43,700 54,700 63,400 72,400 94,900 40,600 53,500 64,500 7

01454600 1965-80 A 340 530 720 970 1,800 337 496 642 01454700 1967-97 A 45,200 55,300 63,000 70,800 89,600 40,500 53,100 63,900 701458900 1962-80 A 4,910 6,980 8,860 11,100 17,700 1,550 2,190 2,760 01459500 1936-73 A 12,000 15,300 18,000 21,000 29,000 7,690 10,500 13,000 1

1974-97 A 12,700 17,100 20,900 25,200 37,200 5,750 7,940 9,890 1

01460000 1884-1913 A 6,810 8,800 10,500 12,500 18,400 8,090 10,900 13,400 101465000 1885-34 A 7,310 9,080 10,500 12,200 16,600 12,800 16,800 20,100 201465500 1933-96 A 20,400 26,800 32,400 38,500 55,600 16,900 22,100 26,600 301465770 1965-81 A 1,320 1,710 2,040 2,420 3,520 1,620 2,090 2,480 01465785 1965-78 A 1,110 1,380 1,590 1,820 2,430 823 1,090 1,320 01465790 1966-78 A 1,420 1,790 2,110 2,450 3,390 1,770 2,300 2,730 01465798 1966-97 A 5,840 7,460 8,790 10,200 14,100 5,180 6,530 7,620 01467042 1965-81 A 4,270 5,200 5,940 6,720 8,700 8,110 10,000 11,500 101467043 1965-80 A 620 840 1,030 1,230 1,790 666 869 1,040 01467048 1966-97 A 6,100 7,580 8,750 9,980 13,100 8,370 10,500 12,100 101467050 1965-81 A 1,650 2,150 2,570 3,030 4,320 1,240 1,610 1,920 01467086 1966-86 A 4,080 5,000 5,700 6,410 8,160 3,980 5,020 5,860 01467087 1982-97 A 9,620 11,300 12,500 13,800 16,800 6,950 8,570 9,850 101467089 1966-81 A 9,670 11,200 12,300 13,400 16,100 7,600 9,350 10,700 101469500 1920-97 A 3,280 4,360 5,220 6,120 8,390 3,620 4,960 6,140 01470500 1948-97 A 22,500 29,400 35,200 41,500 58,300 19,600 25,600 30,700 301470720 1962-80 A 1,310 1,980 2,600 3,340 5,640 1,240 1,810 2,340 

Appendix 2. Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging

stations used in analysis—Continued

[All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging

station

Period of

record used

in analysis

(water year)

Floodflow

region

Computed from streamflow-gaging-station data Predicted from regression e

10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 10
35

01470756 1973-95 A 9,660 13,100 16,300 19,900 30,900 9,500 13,300 16,600 201470779 1975-96 A 5,070 7,440 9,570 12,000 19,400 2,910 4,520 6,140 01470853 1983-97 A 470 600 700 810 1,080 593 861 1,110 01470960 1965-78 A 11,000 16,300 21,100 26,800 44,000 8,130 11,800 15,200 101471000 1951-78 A 9,340 12,200 14,600 17,200 24,600 9,610 13,800 17,700 201471510 1902-30 A 36,400 47,400 56,600 66,900 95,600 30,700 41,200 50,300 6

1980-97 A 30,700 40,100 48,000 56,500 79,800 30,300 40,800 50,100 6

01471800 1961-82 A 710 880 1,020 1,160 1,520 1,360 1,950 2,470 01471980 1975-97 A 5,780 7,310 8,530 9,830 13,200 4,760 6,780 8,620 101472000 1902-78 A 39,900 51,300 60,600 70,700 97,400 42,400 56,100 67,900 8

1979-97 A 36,200 45,400 52,700 60,600 81,000 39,200 52,100 63,400 7

01472157 1969-97 A 5,850 8,630 11,200 14,400 24,400 4,790 6,600 8,190 101472174 1967-83 A 1,930 2,920 3,820 4,890 8,080 844 1,220 1,570 01472198 1982-97 A 5,370 7,320 8,980 10,800 15,900 3,630 5,060 6,330 01472199 1982-97 A 3,080 4,120 5,000 5,970 8,670 2,250 3,180 4,010 01472500 1885-1913 A 7,190 8,540 9,630 10,800 13,800 13,600 18,700 23,200 201472620 1984-99 A 1,870 2,490 3,000 3,550 5,030 712 1,050 1,360 01473000 1915-97 A 28,000 35,200 40,500 45,900 58,600 16,700 22,400 27,400 301473100 1960-80 A 5,110 7,360 9,410 11,800 19,200 1,200 1,710 2,170 01473120 1966-94 A 12,900 18,800 24,600 31,700 55,800 6,520 8,670 10,500 101473169 1983-99 A 2,620 3,830 4,990 6,450 11,300 1,320 1,920 2,490 01473470 1971-94 A 12,900 18,400 23,300 29,000 45,800 3,700 4,860 5,840 01473880 1962-79 A 470 620 730 860 1,190 668 900 1,100 01473950 1966-81 A 5,300 6,540 7,550 8,620 11,400 5,600 7,390 8,920 101474000 1966-99 A 6,760 9,140 11,300 13,900 22,000 6,580 8,600 10,300 101474500 1932-97 A 76,500 96,900 113,000 130,000 172,000 70,100 90,400 107,000 1201475300 1972-97 A 1,420 1,880 2,250 2,660 3,750 1,110 1,480 1,810 01475510 1964-90 A 4,890 6,000 6,870 7,770 10,000 6,200 7,820 9,140 101475530 1965-81 A 2,160 3,380 4,610 6,180 11,600 1,660 2,130 2,520 01475550 1964-90 A 4,270 5,260 6,030 6,840 8,850 5,790 7,170 8,270 

Appendix 2. Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging

stations used in analysis—Continued

[All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging

station

Period of

record used

in analysis

(water year)

Floodflow

region

Computed from streamflow-gaging-station data Predicted from regression e

10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 10
36

01475850 1981-97 A 1,920 2,510 3,010 3,570 5,080 2,060 2,820 3,480 01476480 1987-97 A 2,950 4,400 5,780 7,480 13,000 3,480 4,700 5,750 01476500 1932-55 A 3,010 4,560 6,100 8,050 14,800 3,600 4,870 5,950 01477000 1932-97 A 6,910 10,200 13,400 17,400 30,500 6,340 8,400 10,100 101478200 1960-91 A 2,260 3,180 4,000 4,940 7,730 1,770 2,550 3,260 01480300 1960-97 A 4,360 7,680 11,400 16,600 38,000 2,440 3,490 4,440 01480500 1944-97 A 4,820 7,170 9,360 12,100 20,600 4,770 6,630 8,280 101480610 1964-96 A 840 1,240 1,610 2,050 3,380 327 499 664 01480617 1970-97 A 6,220 8,900 11,300 14,000 22,200 5,510 7,620 9,500 101480675 1967-97 A 560 790 990 1,230 1,930 864 1,270 1,650 01480680 1960-71 A 980 1,170 1,320 1,470 1,860 1,910 2,740 3,500 01480700 1974-99 A 4,450 5,870 7,020 8,250 11,500 4,830 6,730 8,430 101480800 1958-68 A 4,720 5,330 5,800 6,270 7,440 6,630 9,160 11,400 101480870 1974-99 A 5,940 7,710 9,180 10,800 15,000 6,090 8,440 10,500 101481000 1912-97 A 12,900 16,800 20,100 23,700 33,500 18,300 24,900 30,600 301516350 1972-96 A 20,300 31,400 42,400 56,100 102,000 9,660 13,000 15,900 101516500 1955-96 A 2,160 3,320 4,450 5,870 10,600 1,610 2,300 2,940 01516800 1960-77 A 560 690 790 890 1,140 528 779 1,010 01517000 1955-78 A 1,440 2,100 2,740 3,520 6,040 1,360 1,960 2,500 01518000 1939-77 A 25,500 37,700 49,100 62,700 106,000 17,100 22,700 27,500 301518420 1985-97 A 11,400 15,900 19,800 24,200 36,600 6,200 8,540 10,600 101518500 1954-74 A 8,560 12,200 15,600 19,700 32,700 8,990 12,200 15,000 101518862 1984-96 A 10,700 15,600 19,800 24,600 38,000 6,820 9,300 11,500 101519200 1980-97 A 20,600 26,500 31,200 36,000 48,300 14,500 19,400 23,700 201520000 1952-78 A 24,100 33,800 42,600 52,800 83,400 17,400 23,000 27,700 301532000 1914-96 A 24,400 36,100 47,200 60,700 104,000 12,900 17,200 20,800 201532200 1963-95 A 1,360 1,900 2,390 2,960 4,740 1,620 2,320 2,940 01532850 1960-79 A 1,020 1,430 1,770 2,150 3,190 732 1,050 1,350 01533250 1963-95 A 1,060 1,420 1,720 2,050 2,910 1,330 1,900 2,430 01533500 1941-58 A 6,640 10,700 14,800 20,000 37,500 3,290 4,610 5,780 

Appendix 2. Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging

stations used in analysis—Continued

[All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging

station

Period of

record used

in analysis

(water year)

Floodflow

region

Computed from streamflow-gaging-station data Predicted from regression e

10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 10
37

01533800 1963-79 A 1,120 1,700 2,270 2,980 5,350 853 1,240 1,590 01533950 1961-78 A 1,530 1,970 2,320 2,700 3,660 1,330 1,890 2,400 01534000 1914-96 A 24,100 29,500 33,500 37,400 46,300 17,900 23,900 29,100 301538000 1920-96 A 2,510 3,350 4,050 4,810 6,870 3,450 4,720 5,830 01538800 1960-80 A 1,030 1,430 1,760 2,130 3,110 601 864 1,100 01539000 1939-96 A 17,300 23,600 28,900 34,900 51,900 15,500 20,700 25,100 301539500 1941-58 A 3,150 3,700 4,100 4,510 5,470 5,120 7,100 8,850 101540000 1914-31 A 22,400 28,400 33,000 37,800 49,300 22,100 29,600 36,000 401540200 1959-79 A 190 320 460 640 1,290 280 411 533 01541000 1914-97 A 13,900 17,800 21,200 24,800 35,000 19,600 26,200 31,800 301541200 1956-67 A 14,500 17,700 20,200 22,700 28,600 19,100 25,000 30,000 301541500 1914-97 A 12,500 15,700 18,300 21,100 28,400 17,800 23,400 28,100 301542000 1941-93 A 2,430 3,110 3,670 4,270 5,850 5,080 6,900 8,470 101542500 1940-60 A 45,600 54,500 61,100 67,600 83,000 63,800 82,500 98,200 11

1966-97 A 37,300 48,900 58,900 70,200 102,000 47,200 60,700 71,900 8

01542720 1962-95 A 390 470 540 605 770 563 866 1,160 01542810 1964-97 A 410 560 690 840 1,260 620 889 1,130 01543000 1914-96 A 18,700 25,900 32,300 39,700 61,100 14,400 19,200 23,100 201543500 1936-97 A 36,300 49,000 60,100 72,600 109,000 28,800 37,300 44,300 501543700 1984-97 A 9,770 13,000 15,700 18,800 27,400 9,970 13,300 16,100 101544450 1964-79 A 170 200 230 260 340 395 581 753 01544500 1941-96 A 7,790 10,800 13,400 16,400 25,400 7,900 10,600 12,900 101545600 1965-96 A 2,430 3,700 4,920 6,430 11,400 3,330 4,560 5,630 01546000 1911-28 A 13,100 16,900 20,200 23,800 33,700 7,850 10,800 13,400 101546400 1985-96 A 1,170 1,680 2,170 2,750 4,610 2,370 3,590 4,780 01546500 1936-96 A 1,940 3,050 4,170 5,630 10,800 3,020 4,580 6,100 01547100 1967-96 A 3,270 4,900 6,450 8,350 14,500 4,470 6,680 8,800 101547200 1957-96 A 11,100 15,200 18,800 22,800 34,600 8,830 12,500 15,800 101547500 1955-69 A 7,560 9,350 10,800 12,200 15,800 11,300 15,800 19,800 201547700 1956-96 A 3,100 4,640 6,120 7,940 13,900 3,600 4,960 6,160 

Appendix 2. Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging

stations used in analysis—Continued

[All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging

station

Period of

record used

in analysis

(water year)

Floodflow

region

Computed from streamflow-gaging-station data Predicted from regression e

10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 10
38

01547800 1959-81 A 690 950 1,180 1,440 2,220 1,260 1,760 2,210 01547950 1968-97 A 5,380 7,180 8,710 10,400 15,100 10,100 13,500 16,500 101548005 1971-97 A 10,530 13,500 16,100 19,000 27,100 13,800 19,200 24,100 201548020 1963-81 A 160 240 310 400 700 292 428 552 01548500 1919-96 A 25,800 35,600 44,300 54,300 84,200 27,000 35,200 42,100 401549000 1909-20 A 34,400 40,700 45,200 49,600 59,300 30,900 40,000 47,500 501549500 1941-97 A 3,920 5,340 6,560 7,930 11,800 3,230 4,470 5,560 01549700 1958-96 A 42,800 58,700 72,700 88,600 135,000 31,700 40,900 48,600 501549780 1960-78 A 570 810 1,040 1,300 2,110 863 1,240 1,580 01550000 1914-96 A 14,100 19,100 23,500 28,400 42,500 10,300 13,800 16,700 201551000 1940-53 A 710 1,000 1,240 1,500 2,190 613 897 1,160 01552000 1926-98 A 28,400 37,200 44,800 53,200 76,600 20,300 26,700 32,200 301552100 1961-78 A 990 1,470 1,920 2,480 4,280 1,290 1,830 2,310 01552500 1941-96 A 4,190 6,000 7,660 9,600 15,500 2,000 2,800 3,500 01553050 1961-95 A 1,640 2,400 3,070 3,840 6,070 1,630 2,270 2,840 01553130 1968-81 A 590 1,010 1,440 2,000 3,990 615 879 1,120 01553600 1960-78 A 2,220 3,400 4,550 5,970 10,700 1,380 2,000 2,560 01553700 1980-96 A 3,480 4,100 4,560 5,030 6,150 4,710 6,700 8,520 101555000 1930-97 A 12,300 17,300 21,900 27,200 43,300 12,100 16,700 20,800 201555500 1930-97 A 11,300 17,300 23,300 31,200 58,900 11,400 15,400 18,900 201555800 1959-78 A 220 300 370 450 680 281 415 538 01556000 1889-1997 A 12,700 16,800 20,100 23,900 34,100 12,200 16,600 20,600 201556400 1962-81 A 520 780 1,020 1,310 2,230 653 938 1,200 01556500 1946-81 A 5,030 6,450 7,580 8,780 11,800 6,320 8,560 10,500 101557100 1958-81 A 230 310 380 450 640 289 421 542 01557500 1940-97 A 2,930 3,820 4,560 5,350 7,420 3,180 4,380 5,430 01558000 1936-97 A 12,200 17,900 23,400 30,100 52,300 9,840 13,300 16,400 101559000 1896-1997 A 28,300 38,600 47,600 58,000 88,600 26,000 35,600 44,200 501559500 1930-58 A 4,610 5,920 7,010 8,210 11,500 8,240 11,200 13,900 101559700 1962-78 A 770 1,130 1,470 1,860 3,040 678 978 1,250 

Appendix 2. Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging

stations used in analysis—Continued

[All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging

station

Period of

record used

in analysis

(water year)

Floodflow

region

Computed from streamflow-gaging-station data Predicted from regression e

10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 10
39

01560000 1936-97 A 9,020 12,400 15,400 18,800 29,000 10,700 14,600 18,100 201561000 1930-58 A 2,610 4,110 5,620 7,540 14,200 3,320 4,610 5,740 01562000 1912-97 A 27,800 35,900 42,400 49,400 67,500 29,200 39,100 47,800 501562500 1930-57 A 3,610 5,020 6,290 7,770 12,200 6,460 8,830 10,900 101563000 1946-71 A 23,400 27,400 30,200 32,800 38,600 34,700 46,000 55,700 601563800 1960-78 A 340 460 550 660 940 643 951 1,240 01564500 1939-97 A 14,200 20,000 25,100 31,100 49,000 12,300 16,700 20,500 201565000 1936-98 A 6,540 9,560 12,400 15,800 26,700 7,510 10,500 13,200 101565700 1960-81 A 630 980 1,330 1,780 3,350 605 946 1,280 01565920 1962-81 A 960 1,550 2,150 2,920 5,620 814 1,190 1,530 01566000 1912-90 A 11,300 14,400 17,000 19,800 27,200 10,600 14,500 17,900 201566500 1930-58 A 4,610 5,810 6,740 7,700 10,000 4,710 6,570 8,230 101567500 1954-97 A 3,300 6,060 9,300 14,000 34,200 1,380 2,030 2,650 01568000 1927-97 A 15,900 22,500 28,600 35,600 57,100 10,600 14,600 18,000 201568500 1938-96 A 1,030 1,700 2,380 3,260 6,400 1,590 2,240 2,830 01569000 1938-74 A 2,760 4,880 7,260 10,600 24,100 2,710 3,750 4,660 01569340 1964-95 A 890 1,460 2,060 2,860 5,950 928 1,360 1,750 01569800 1976-97 A 670 1,060 1,460 1,980 3,880 1,240 1,950 2,660 01570000 1912-96 A 13,000 16,900 20,300 24,100 35,000 17,900 25,100 31,600 301571000 1940-50 A 1,900 2,270 2,540 2,810 3,440 1,470 2,170 2,820 

1974-94 A 3,350 4,640 5,760 7,040 10,700 1,700 2,350 2,920 

01571500 1910-97 A 5,960 8,660 11,300 14,500 25,300 9,280 12,900 16,100 101572000 1920-84 A 2,700 3,750 4,700 5,820 9,210 3,360 4,700 5,880 01572900 1962-81 A 2,650 3,580 4,370 5,250 7,700 1,480 2,070 2,590 01573000 1919-97 A 17,900 23,700 28,900 34,700 51,700 19,900 26,400 32,100 301573086 1964-81 A 1,320 3,150 5,710 9,990 33,000 511 840 1,180 01573160 1975-93 A 2,200 3,280 4,320 5,620 10,000 3,530 5,320 7,060 01573500 1938-58 A 1,780 2,810 3,820 5,080 9,280 1,350 1,900 2,390 01573560 1975-97 A 20,000 26,400 32,100 38,600 57,600 26,100 34,600 41,900 501574000 1929-97 A 29,400 40,100 49,900 61,600 98,700 29,000 38,900 47,500 5

Appendix 2. Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging

stations used in analysis—Continued

[All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging

station

Period of

record used

in analysis

(water year)

Floodflow

region

Computed from streamflow-gaging-station data Predicted from regression e

10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 10
40

01574500 1930-66 A 4,620 6,670 8,610 11,000 18,500 6,560 9,410 12,100 1

1967-97 A 4,930 8,040 11,400 15,900 33,100 5,010 7,220 9,270 1

01574800 1960-75 A 1,070 2,230 3,740 6,130 18,300 952 1,410 1,830 01575000 1928-71 A 5,410 8,060 10,700 13,900 24,700 11,200 15,500 19,400 2

1972-95 A 11,900 18,600 25,300 34,000 64,400 10,600 14,500 18,000 2

01575500 1947-97 A 9,250 13,400 17,300 22,000 37,700 12,200 17,000 21,400 201576085 1982-95 A 1,550 2,060 2,480 2,930 4,120 763 1,170 1,570 01576320 1964-95 A 1,030 1,320 1,560 1,810 2,450 622 906 1,170 01576500 1929-97 A 16,000 22,000 27,300 33,400 51,000 14,200 20,000 25,300 301576754 1985-97 A 18,500 22,800 26,300 29,900 39,000 17,300 24,300 30,700 301577500 1929-72 A 12,100 17,500 22,600 28,800 49,200 10,600 14,500 17,900 201578200 1963-97 A 1,240 1,950 2,660 3,580 6,840 1,500 2,200 2,850 01578400 1963-81 A 2,000 3,440 5,040 7,270 16,300 743 1,140 1,530 01600700 1961-81 A 1,170 1,770 2,350 3,060 5,390 1,140 1,620 2,050 01601000 1952-86 A 8,660 11,300 13,600 16,100 23,000 8,720 11,700 14,200 101603500 1933-82 A 2,120 2,940 3,640 4,430 6,670 2,090 3,010 3,840 01613050 1963-96 A 900 1,230 1,520 1,830 2,680 1,260 1,800 2,280 01613500 1931-41 A 12,200 18,800 25,300 33,400 61,400 8,260 11,400 14,200 101614090 1961-81 A 300 470 630 840 1,560 612 879 1,120 01638900 1961-80 A 3,350 5,000 6,570 8,490 14,700 1,870 2,690 3,460 03007800 1975-97 B 8,740 10,400 11,700 13,000 16,100 11,000 13,800 15,900 103009680 1972-97 B 7,000 8,810 10,300 11,900 16,400 8,020 10,100 11,700 103010655 1975-97 B 3,530 4,180 4,640 5,090 6,100 5,640 7,120 8,300 

03011020 1904-95 B 37,000 44,600 50,500 56,700 72,200 41,700 50,400 57,300 603011800 1966-96 B 3,110 4,300 5,340 6,500 9,800 3,200 4,070 4,780 

03015000 1936-97 B 11,900 13,800 15,100 16,500 19,600 19,200 22,800 25,500 203015080 1962-81 B 930 1,040 1,120 1,200 1,380 1,060 1,380 1,650 03015390 1964-85 B 1,330 1,660 1,920 2,200 2,940 1,140 1,460 1,730 03015500 1910-96 B 11,900 14,100 15,600 17,100 20,600 10,700 13,000 14,800 103017500 1938-79 B 10,600 13,200 15,200 17,300 22,500 10,700 13,300 15,400 1

Appendix 2. Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging

stations used in analysis—Continued

[All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging

station

Period of

record used

in analysis

(water year)

Floodflow

region

Computed from streamflow-gaging-station data Predicted from regression e

10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 10
41

03019000 1910-40 B 13,900 16,100 17,800 19,400 23,000 17,700 21,900 25,200 203020440 1964-81 B 470 560 630 690 860 596 789 948 03020500 1910-96 B 12,800 15,400 17,500 19,600 24,700 12,000 14,900 17,100 103021350 1975-97 B 5,940 6,810 7,420 7,980 9,200 4,500 5,580 6,430 03021410 1975-94 B 6,120 8,060 9,700 11,500 16,600 3,380 4,280 5,000 03021700 1961-78 B 540 680 800 920 1,240 518 687 828 03022500 1913-39 B 17,500 21,100 23,900 26,700 33,700 18,400 22,300 25,200 203022540 1975-95 B 2,280 2,860 3,320 3,780 4,900 2,200 2,800 3,270 03023000 1911-38 B 2,540 3,130 3,610 4,130 5,500 4,640 5,790 6,700 03024000 1933-71 B 19,600 22,100 23,800 25,500 29,200 24,800 29,500 33,100 3

1972-97 B 16,500 18,300 19,400 20,500 22,700 19,900 23,100 25,500 2

03025000 1933-79 B 8,580 10,100 11,200 12,200 14,500 7,540 9,370 10,800 103025200 1961-78 B 620 920 1,210 1,560 2,680 722 952 1,140 03026400 1963-81 B 640 710 760 810 900 739 974 1,170 03026500 1952-96 B 1,140 1,710 2,240 2,890 4,950 911 1,200 1,430 03028000 1954-96 B 4,180 5,390 6,370 7,410 10,100 4,130 5,260 6,170 03028500 1953-94 B 6,900 8,660 10,100 11,600 15,800 6,630 7,980 8,990 103029200 1960-81 B 690 1,030 1,350 1,740 3,020 980 1,280 1,530 03029400 1960-78 B 620 760 860 970 1,220 1,280 1,670 1,990 03029500 1936-97 B 32,000 41,100 48,600 56,800 78,900 23,200 28,100 31,900 303030500 1948-96 B 40,100 50,600 59,100 68,200 91,800 26,600 32,200 36,600 403031000 1942-53 B 41,700 48,800 54,000 59,000 70,400 35,600 43,300 49,300 503031780 1965-81 B 230 300 350 400 520 353 472 571 03031950 1964-81 B 900 1,120 1,270 1,420 1,780 871 1,150 1,370 03032500 1910-97 B 23,200 31,100 38,000 46,000 69,300 19,300 23,800 27,400 303034000 1936-96 B 8,920 12,200 15,300 18,800 29,700 8,050 10,100 11,800 103034500 1940-98 B 5,300 6,470 7,380 8,320 10,700 5,240 6,630 7,760 03035000 1917-40 B 12,200 15,000 17,200 19,700 26,200 13,500 16,700 19,300 203038000 1936-97 B 8,890 11,300 13,300 15,400 21,300 8,490 10,500 12,200 103039000 1910-39 B 15,200 17,900 19,800 21,700 25,700 12,100 15,100 17,500 2

Appendix 2. Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging

stations used in analysis—Continued

[All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging

station

Period of

record used

in analysis

(water year)

Floodflow

region

Computed from streamflow-gaging-station data Predicted from regression e

10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 10
42

03039200 1961-78 A 260 340 400 470 650 474 685 875 03039925 1985-97 A 170 220 270 320 440 449 650 831 03040000 1914-97 A 22,800 30,700 37,400 44,800 65,500 22,500 29,600 35,500 403041000 1936-97 A 12,900 18,500 23,600 29,700 48,600 10,700 14,300 17,400 203041500 1936-97 A 39,800 55,800 70,000 86,400 135,000 33,100 42,900 51,200 603042000 1952-96 A 13,800 19,200 24,200 30,000 48,000 11,600 15,400 18,600 203042170 1964-76 A 460 530 580 630 740 1,200 1,590 1,910 03042200 1961-87 A 1,150 1,760 2,360 3,120 5,710 867 1,240 1,570 03042500 1952-68 A 8,980 11,200 12,900 14,800 19,700 11,100 14,700 17,800 2

1969-97 A 11,300 18,000 24,800 33,400 64,000 9,330 12,500 15,300 1

03043000 1905-51 A 22,300 30,000 36,800 44,700 67,900 23,000 30,600 37,100 403045000 1940-97 A 12,200 16,400 20,100 24,400 36,800 10,200 13,600 16,500 103045500 1920-40 A 16,000 22,400 28,300 35,100 55,900 16,800 22,500 27,400 303047500 1884-1937 A 74,900 97,900 117,000 139,000 202,000 73,600 94,800 113,000 1303049000 1941-96 A 7,360 9,390 11,100 12,900 17,600 9,410 12,700 15,600 103049100 1959-81 A 340 380 400 430 480 620 896 1,150 03049800 1963-96 A 1,160 2,160 3,310 4,930 11,700 818 1,150 1,450 03070420 1978-89 A 110 140 160 180 250 181 271 356 03072000 1941-96 A 12,200 14,700 16,600 18,500 22,900 13,000 17,400 21,000 203072590 1964-78 A 1,210 1,520 1,770 2,030 2,700 1,950 2,740 3,440 03072840 1969-79 A 10,800 15,800 20,600 26,300 44,300 9,700 13,200 16,200 103072880 1963-85 A 2,320 3,250 4,040 4,900 7,240 1,970 2,790 3,520 03073000 1932-95 A 10,200 12,000 13,300 14,500 17,300 12,200 16,300 19,900 203074300 1959-78 A 350 490 610 750 1,160 494 713 913 03074500 1943-96 A 3,900 4,830 5,570 6,340 8,300 6,670 8,940 10,900 103078500 1933-86 A 2,500 3,610 4,630 5,820 9,460 2,340 3,290 4,130 03079000 1915-96 A 20,600 27,200 32,900 39,400 58,000 24,200 32,300 39,300 403080000 1914-97 A 7,090 8,690 9,910 11,100 14,100 7,520 10,200 12,400 103081000 1942-97 A 28,400 36,100 42,400 49,400 68,300 35,800 47,000 56,500 603082200 1961-78 A 1,150 1,460 1,730 2,010 2,790 1,080 1,550 1,960 

Appendix 2. Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging

stations used in analysis—Continued

[All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging

station

Period of

record used

in analysis

(water year)

Floodflow

region

Computed from streamflow-gaging-station data Predicted from regression e

10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 10
43

03082500 1943-97 A 46,000 60,000 71,800 84,800 121,000 45,300 59,000 70,600 803083000 1929-79 A 590 870 1,120 1,430 2,390 480 704 909 03083500 1943-97 A 57,300 74,600 89,000 105,000 147,000 67,700 86,200 102,000 1103083600 1959-81 A 490 750 1,000 1,310 2,340 616 887 1,130 03084000 1949-93 A 900 1,160 1,370 1,590 2,120 850 1,170 1,450 03084500 1917-55 A 4,260 5,380 6,260 7,180 9,460 5,390 7,170 8,670 103085500 1916-96 A 10,100 12,400 14,100 15,900 19,900 16,800 22,500 27,300 303086100 1963-78 A 1,320 1,790 2,180 2,630 3,870 1,650 2,290 2,860 03100000 1912-22 B 6,170 8,100 9,710 11,500 16,400 4,260 5,030 5,570 03101000 1935-55 B 1,430 2,050 2,610 3,230 5,020 1,010 1,310 1,560 03102500 1914-96 B 4,510 5,610 6,470 7,340 9,490 4,900 6,080 6,990 03102850 1966-97 B 5,360 5,720 5,950 6,140 6,520 8,270 9,740 10,800 103103000 1914-63 B 5,010 5,970 6,650 7,290 8,680 3,840 4,440 4,840 03104000 1910-32 B 15,700 19,800 22,900 26,200 34,200 13,600 16,000 17,800 103104500 1913-32 B 16,500 21,300 25,300 29,700 41,600 18,100 21,400 23,900 203104760 1969-80 B 340 430 500 580 760 316 416 497 03106000 1916-96 B 12,600 15,100 17,000 19,000 23,800 14,300 17,700 20,400 203106500 1912-69 B 13,200 16,100 18,400 20,600 26,000 14,400 17,700 20,300 2

1970-97 B 8,900 9,930 10,600 11,300 12,600 12,600 15,200 17,200 1

03108000 1916-96 A 6,820 8,490 9,770 11,100 14,300 11,800 15,800 19,100 2

03111150 1961-85 A 1,240 1,670 2,010 2,380 3,310 1,590 2,310 2,980 

04213000 1923-95 B 11,100 13,600 15,500 17,400 21,900 7,680 9,510 11,000 104213040 1961-95 B 280 370 440 520 710 256 326 380 04213200 1969-85 B 1,380 1,700 1,940 2,190 2,780 1,020 1,340 1,590 

Appendix 2. Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging

stations used in analysis—Continued

[All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

U.S.

Geological

Survey

streamflowgaging

station

Period of

record used

in analysis

(water year)

Floodflow

region

Computed from streamflow-gaging-station data Predicted from regression e

10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 10