TECHNIQUES for ESTIMATING MAGNITUDE and FREQUENCY of PEAK FLOWS for PENNSYLVANIA STREAMS by Marla H

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 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: [email protected] Telephone: 1-888-ASK-USGS

ii 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

iii 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

iv 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 flood- plain 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

1 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 (crest- stage 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 peak- flow 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.

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

3 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.

4 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.

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

6 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:

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

7 Flood-frequency regions in Pennsylvania. Figure 3.

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

3 [QT, discharge for the T-year flood; ft /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]

Residual standard Basin characteristic coefficients error Coefficient of QT return flow Percentage Percentage Percentage 3 Drainage Percentage determination (ft /s) Intercept urban carbonate controlled 2 area forested area Log units Percent (R ) (A) development area area (b) (c) (d) (e) (f) 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 .7770 -.9712 1.0217 -1.7184 -.5719 Q10 = 334.4 DA (1 + .01F) (1 + .01U) (1+ .01C) (1 + .01CA) .7556 -1.0324 .7608 -1.5302 -.5302 Q25 = 518.2 DA (1 + .01F) (1 + .01U) (1+ .01C) (1 + .01CA) .7414 -1.0821 .5785 -1.3955 -.4980 Q50 = 698.4 DA (1 + .01F) (1 + .01U) (1+ .01C) (1 + .01CA) .7278 -1.1342 .4040 -1.2691 -.4637 Q100 = 925.8 DA (1 + .01F) (1 + .01U) (1+ .01C) (1 + .01CA) .6994 -1.2666 .0208 -.9877 -.3834 Q500 = 1,696 DA (1 + .01F) (1 + .01U) (1+ .01C) (1 + .01CA) Region B .7255 -1.2425 Q10 = 204.4 DA (1 + .01CA) .7108 -1.3700 Q25 = 276.6 DA (1 + .01CA) .7017 -1.4695 Q50 = 337.0 DA (1 + .01CA) .6932 -1.5677 Q100 = 404.5DA (1 + .01CA) .6776 -1.8055 Q500 = 585.2 DA (1 + .01CA)

9 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.

160,000

140,000

120,000

100,000

80,000

60,000 IN CUBIC FEET PER SECOND 40,000

20,000 COMPUTED FROM REGION A REGRESSION EQUATION, COMPUTED FROM 100 Q 0 0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000

Q100 COMPUTED FROM STREAMFLOW-GAGING-STATION DATA, IN CUBIC FEET PER SECOND

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.

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.

10 80,000

70,000

60,000

50,000

40,000

30,000 IN CUBIC FEET PER SECOND 20,000

10,000 COMPUTED FROM REGION B REGRESSION EQUATION, COMPUTED FROM 100 Q 0 0 20,000 40,000 60,000 80,000

Q100 COMPUTED FROM STREAMFLOW-GAGING-STATION DATA, IN CUBIC FEET PER SECOND

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.

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)]

Equivalent period of record (years) Flood recurrence interval Region A Region B 10-year 5 5 25-year 6 5 50-year 8 8 100-year 10 10 500-year 16 13

11 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.

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

[mi2, square miles]

Range Percentage of basin Number of Number of Region stations records Underlain Drainage area Years of Controlled by used used1 2 In urban by (mi ) record In forest cover lakes, swamps, development carbonate and reservoirs bedrock 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 1 Some streamflow-gaging stations have two records because of the construction of reservoirs or other changes in land use.

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.

12 /s) 3 ft by upstream by 100-year /s) 3 (ft 50-year /s) station data 3 (ft 25-year /s) 3 (ft Computed from streamﬂow-gaging- 10-year year) (water record Period of area (percent) Controlled , square miles; water year, 12-month period October 1- year, , square miles; water 2 ) 2 area (mi Drainage Station name /s, cubic feet per second] cubic feet /s, 3

Streamflow-gaging stations in Pennsylvania with drainage areas less than 2,000 square miles and streamflow significantly affected significantly affected areas less than 2,000 square miles and streamflow with drainage stations in Pennsylvania Streamflow-gaging U.S. Survey 0142950001430000 near Honesdale Dyberry Creek Lackawaxen River near Honesdale01449500 at Hatchery Creek Wild 0147096001471000 at Blue Marsh Damsite near Reading Creek Tulpehocken near Reading Creek Tulpehocken 01518000 River at Tioga Tioga 01520000 Cowanesque River near Lawrenceville01541200 175 Branch Susquehanna River at Curwensville West 164 64.6 10001547500 100 1978-97 83 at Blanchard Bald Eagle Creek 4,030 1960-97 1960-97 4,920 2,050 16.8 6,020 211 2,290 5,590 7,070 367 98 6,290 2,450 7,83003039000 298 83 2,600 1959-78 Dam Creek at Crooked Creek Crooked 8,570 100 1979-97 400 100 1966-97 4,480 282 532 1980-97 6,230 5,550 5,500 7,000 100 6,400 643 6,140 7,580 7,280 1980-97 764 6,610 339 8,160 7,030 7,080 7,470 100 7,760 1971-97 278 8,030 4,140 4,670 99 5,050 1941-91 5,420 5,470 6,210 6,730 7,220 01429000 Branch Lackawaxen River at Prompton West 59.7 100 1961-97 2,780 3,130 3,630 4,150 01447800 near White Haven Lehigh River below Francis Walter 0144980001464645 below Beltzville Lake near Parryville Pohopoco Creek below Lake Galena near New Britain North Branch Neshaminy Creek 01480685 near Downingtown Marsh Creek 16.201518700 290 Junction River at Tioga Tioga 9401534300 96.4 City Lackawanna River near Forest 1986-97 9901541303 1,75001544000 100 Branch Susquehanna River at Hyde West 1961-97 2,74001545000 near Sinnemahoning First Fork Sinnemahoning Creek 9,430 1971-97 near Westport Kettle Creek 3,690 11,700 1,68001563200 13,500 4,840 03020000 1,840 Raystown Branch Juniata River below Dam near Huntingdon 15,400 03021520 Dam at Tionesta Creek Tionesta 1,95003022554 near Union City Creek French 96003027500 Dam Creek at Woodcock 2,060 Creek Woodcock 03036000 20.3 East Branch Clarion River at Dam 245 100 Dam at Mahoning Creek Mahoning Creek 03042280 99 1973-97 446 near Homer City Creek Yellow 474 15,700 99 38.8 1974-97 17,000 1956-97 17,800 90 95 638 73.2 77 7,150 18,600 1980-97 1960-97 786 8,140 1979-97 99 8,970 1,040 6,930 8,850 233 898 9,990 1,180 1953-91 45.6 7,540 9,550 1,010 479 10,700 1,170 1,270 7,980 344 11,500 100 97 1,570 221 1,360 8,400 100 1978-93 1962-97 1,910 99 6,420 1941-91 99 2,310 872 7,130 9,440 1939-91 1972-91 990 10,800 57.4 7,800 7,640 3,530 11,700 1,070 9,400 8,120 4,040 12,600 91 10,700 1,150 4,400 12,000 1971-97 4,740 3,960 6,320 8,730 11,800 1 1 1 1 1 1 1 1 1 1 1 Geological streamflow- gaging station September 30; ft Table 4. Table regulation analysis; mi not included in the regression stations was [Data from these streamflow-gaging

13 /s) 3 ft by upstream by 100-year /s) 3 (ft 50-year /s) station data 3 (ft 25-year /s) 3 (ft Computed from streamﬂow-gaging- 10-year year) (water record Period of area (percent) Controlled , square miles; water year, 12-month period October 1- year, , square miles; water 2 ) 2 area (mi Drainage Station name /s, cubic feet per second] cubic feet /s, 3

Continued

14 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 Surveystreamﬂow- Drainage area Station name gaging station (mi2) number 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

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 3 Q100 = 4,480 ft /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

15 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: WtdQ ()Q × N Q × NE ⁄ ()N + NE (2) T = TG() + T ()R 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. 3 1. The Q100 computed from regional regression equations is 2,260 ft /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) 3 WtdQ100 = 1,800 ft /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

16 a regression equation value. The equation to calculate this translated flood frequency is shown below: () 2DAg – DAu  () Cu = Cg – ------ Cg – 1 (3) DAg 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) 3 Q100 = 8,830 ft /s and for the gaged site:

logQ100 = 2.6069 + 0.6932*log(63.0) - 1.5677*log(1) 3 Q100 = 7,150 ft /s 3. Substituting the needed variables for the streamﬂow-gaging station into equation 2 3 results in a weighted discharge of Q100 = 7,360 ft /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 3 Q100 = 8,900 ft /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

17 areas between the site and the two streamﬂow gages. The equation for weighting the transferred data at the ungaged site is shown below.

DA – DA DA – DA Q = Q × B C + Q × ------C A (4) T ()C T ()AC ------T ()BC DAB – DAA DAB – DAA 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) 3 01473950 Q100 = 10,500 ft /s 3 01474000 Q100 = 12,400 ft /s 3 ungaged site Q100 = 11,900 ft /s 3. Substituting the regression estimates into equation 2 results in weighted discharges of: (See Example 2 for setup) 3 01473950 wtdQ100 = 9,340 ft /s 3 01474000 wtdQ100 = 13,600 ft /s 4. Substitute these computed discharges into equation 3 and multiplying by the correction factor results in: (See Example 3 for setup) 3 Q100(AC) = 11,000 ft /s 3 Q100(BC) = 13,000 ft /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 3 QT(C) = 12,500 ft /s

18 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.

19 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

20 APPENDIXES

21 area (percent) controlled Percentage bedrock (percent) carbonate Percentage (percent) urban area Percentage area forested (percent) Percentage used in of years Number analysis 1960-97 38 72 .8 0 59 1961-97 37 85 2.0 4.0 43 Period of Period in analysis record used (water year) (water ) 2 area (mi Drainage Station name , square miles; water year, 12-month period October 1-September 30] 2 Longitude (ddmmss) Latitude (ddmmss)

Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations of the regional regression stations used in the development streamflow-gaging Basin characteristics for U.S. Survey 014276500142875001429000 41415701429300 414028 75095801429500 413514 near Damascus, Pa. North Branch Calkins Creek 75223501430000 413926 Branch Lackawaxen River near Aldenville, Pa. West 75193801430500 413626 Pa. Branch Lackawaxen River at Prompton, West 75171201431000 413343 above Reservoir near Honesdale, Pa. Dyberry Creek 75160301431500 412910 near Honesdale, Pa. Dyberry Creek 40.6 751454 412905 7.02 Lackawaxen River near Honesdale, Pa. 75111501431680 412834 Pa. Hawley, Lackawaxen River at West 59.7 1975-97 45.8 1962-81 75132001438300 Pa. near Hawley, Middle Creek 75102101439500 412315 Pa. 1945-60 Lackawaxen River at Hawley, 1975-97 23 2001440300 411935 75142001440400 410515 near Paupack, Pa. Mill Brook 744750 16 2301441000 410950 Pa. at Milford, Creek Vandermark 750220 74 7801442500 410505 164 Bush Kill at Shoemakers, Pa. 64.6 75160001446600 405845 206 at Mountainhome, Pa. Mill Creek 751254 70 8501447500 405955 1944-59near Analomink, Pa. Creek Brodhead 1949-59 751205 0.201447680 405400 .1 Pa. near Stroudsburg, McMichael Creek 1922-42 75083501447720 410749 at Minisink Hill, Pa. Creek Brodhead 751208 78.4 16 290 1101448000 410355 .1 .2 Pa. near East Bangor, Martins Creek 753733 2101448500 410505 Lehigh River at Stoddartsville, Pa. 0 1945-86 753114 001449000 410225 1909-59 near Long Pond, Pa. Creek Tunkhannock 753621 75 7001449360 410208 5.36 near Blakeslee, Pa. Creek Tobyhanna 754542 4.84 0 72 0 4201449500 404945 Pa. 51 Lehigh River at Tannery, 753237 1962-97 65.9 24 01450000 405351 7.1 65.3 117 1960-80 5.84 near Long Pond, Pa. Dilldown Creek 75422001450500 405522 .1 .5 Lehigh River at Lehighton, Pa. 753010 259 28 77 1958-96 22 01451000 404954 1961-97 33 .5 1911-55 72 Pa. at Kresgeville, Pohopoco Creek 20 1909-96 753332 404822 10.4 Pa. at Hatchery, Creek Wild 754053 1801451500 404525 39 1951-96 37 45 near Parryville, Pa. Pohopoco Creek 753554 0 0 91.7 88 85 .2 1961-86 at Palmerton, Pa. Aquashicola Creek 93 753612 .5 118 0 403456 1965-96 Pa. 46 Lehigh River at Walnutport, 1942-97 95 94 50 26 752900 18 90 26 2.8 1962-96 2.39 near Allentown, Pa. Little Lehigh Creek 32 1.7 26 0 56 322 83 0 1949-96 2.2 1.0 35 .8 84 591 49.9 .2 86 1917-59 0 109 33 93 0 48 4.5 27 1967-96 1982-97 76.7 89 16.8 .1 43 0 0 0 1941-70 30 .2 16 0 2.1 1940-96 889 80.8 98 16 33 1941-58 0 2.9 29 86 1946-97 19 57 9.6 2.6 0 1947-60 68 18 58 83 0 .2 0 15 52 70 14 2.0 0 70 55 4.7 70 2.3 94 58 0 33 80 .2 69 1.2 0 .2 0 0 11 17 .2 47 0 5.0 0 4.2 50 63 4.0 1.6 8.8 0 0 10 Geological streamflow- gaging station

Appendix 1. [ddmmss, degrees, minutes, and seconds; mi

22 area (percent) controlled Percentage bedrock (percent) carbonate Percentage (percent) urban area Percentage

Continued area forested (percent) Percentage used in of years Number analysis 1961-97 371974-97 64 24 5.8 59 13 3.6 30 0 75 Period of Period in analysis record used (water year) (water ) 2 1.20 1965-80 16 9.8 87 0 0 49.8 1966-97 32 33 55 1.0 0 area (mi Drainage Station name , square miles; water year, 12-month period October 1-September 30] 2 Philadelphia, Pa. Philadelphia, Pa. Longitude (ddmmss) Latitude (ddmmss)

Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations— of the regional regression stations used in the development streamflow-gaging Basin characteristics for U.S. Survey 014546000145470001458900 40340501459500 404009 751945 402814 Run at Hellertown, Pa. Polk Valley 75141201460000 402601 Lehigh River at Glendon, Pa. 75081301465000 near Ottsville, Pa. Creek Tinicum 75070101465500 402525 near Pipersville, Pa. Creek Tohickon 01465770 401518 75040001465785 401026 at Point Pleasant, Pa. Creek Tohickon 75015901465790 400755 at Rushland, Pa. Neshaminy Creek 74572601465798 400522 near Langhorne, Pa. Neshaminy Creek 74594001467042 400501 Rd, Philadelphia, Pa. at Trevose Poquessing Creek 74593701467043 400325 2.14 Run at Philadelphia, Pa. Walton 745857 400523 at Chalfont Road, Philadelphia, Pa. Byberry Creek 1,359 1965-80 74590801467048 400527 14.7 97.4 Philadelphia, Pa. at Grant Ave, Poquessing Creek 750410 5.08 at Pine Rd, Philadelphia, Pa. Pennypack Creek 10701467050 750315 400300 16 1967-97 1962-80 1936-73 at Unnamed tributary to Pennypack Creek 01467086 1965-81 210 134 750159 5.3401467087 400319 1884-1913 31 at Lower Rhawn St Bridge, Pennypack Creek 19 21.4 3801467089 400247 84 1966-78 17 750122 1933-96 2901469500 400057 1885-34 37.9 Bridge Run at Philadelphia, Pa. Wooden 1966-97 75064001470500 400025 Philadelphia, Pa. above Adams Ave, Creek Tacony 66 750550 78 13 5501470720 404825 2.17 64 1.0 1965-81 32 Philadelphia, Pa. at Castor Ave, Creek Frankford 20 750533 32 6101470756 403121 Philadelphia, Pa. Ave, at Torresdale Creek Frankford 755820 1965-78 403423 Pa. Little Schuylkill River at Tamaqua, 17 6.6 755955 17 1.0 16.6 403051 .6 39 73 39 Schuylkill River at Berne, Pa. 755234 18 0 3.4 14 33.8 tributary at Lenhartsville, Pa. Maiden Creek 30.4 755300 1966-86 3.35 66 Pa. at Virginville, Maiden Creek 20 18 16 19 1966-81 1982-97 0 67 0 1965-81 23 21 0 4.0 0 71 16 16 28 17 0 42.9 63 0 2.3 25 0 2.4 7.46 0 1.0 0 20 1920-97 20 1962-80 20 0 68 0 7.4 355 0 0 78 0 159 18 74 73 71 1948-97 0 1973-95 77 0 30 0 50 0 0 23 0 2.4 0 .6 72 0 40 0 0 0 3.8 0 1.3 0 0 0 16 0 0 014516500145180001452000 40354701452300 403942 75282801452500 403723 at 10th St Bridge Allentown, Pa. Little Lehigh Creek 75373801453000 404310 near Schnecksville, Pa. Creek Jordan 752858 403828 at Allentown, Pa. Creek Jordan 752210 98.2 403655 near Bath, Pa. East Branch Monocacy Creek 752247 at Bethlehem, Pa. Monocacy Creek 752245 1987-97 Lehigh River at Bethlehem, Pa. 11 53.0 5.35 29 1963-80 1967-97 75.8 44.5 18 18 31 1945-97 1,279 1945-97 53 26 33 1902-60 70 53 55 34 4.0 1.1 19 0 75 3.7 12 4.0 0 1.0 11 7.5 69 0 13 0 2.0 0 Geological streamflow- gaging station

Appendix 1. [ddmmss, degrees, minutes, and seconds; mi

23 area (percent) controlled Percentage bedrock (percent) carbonate Percentage (percent) urban area Percentage

Continued area forested (percent) Percentage used in of years Number analysis 1980-97 181979-97 49 19 4.3 50 19 5.1 20 19 15 Period of Period in analysis record used (water year) (water ) 2 area (mi Drainage Station name , square miles; water year, 12-month period October 1-September 30] 2 Longitude (ddmmss) Latitude (ddmmss)

Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations— of the regional regression stations used in the development streamflow-gaging Basin characteristics for U.S. Survey 014718000147198001472000 402443 401622 75440201472157 401430 Pa. near Manatawny, Pine Creek 75404901472174 near Pottstown, Pa. Manatawny Creek 75390501472198 400905 Schuylkill River at Pottstown, Pa.01472199 400522 75360601472500 402338 near Phoenixville, Pa. Creek French 75375001472620 402226 near Chester Spring, Pa. Pickering Creek 75305701473000 401630 Pa. at East Greenville, Perkiomen Creek 75312201473100 402414 at Hillegass, Pa. Branch Perkiomen Creek West 75272001473120 401346 Pa. near Frederick, Perkiomen Creek 85.5 75140501473169 401226 15.6 near Dublin, Pa. East Branch Perkiomen Creek 75270701473470 400952 1,147 Pa. at Graterford, Perkiomen Creek 1975-97 75215701473880 400445 1961-82 near Skippack, Pa. Zacharias Creek 75260101473950 400738 23.0 5.98 59.1 near Collegeville, Pa. Skippack Creek 752740 1902-78 2301474000 400813 38.0 Pa. Forge, Bridge near Valley at Pa Turnpike Creek Valley 20 752043 1967-8301474500 400450 1982-97 1969-97 at Norristown, Pa. Stony Creek 4.05 751121 20.8 7701475300 400445 1982-97 Pa. at Fort Washington, Pine Run Trib 751335 56 15201475510 395804 17 1984-99 16 at Bells Mill Rd, Philadelphia, Pa. Creek Wissahickon 85 29 751343 1983-9901475530 400121 16 at Mouth, Philadelphia, Pa. Creek Wissahickon 751120 1885-1913 5001475550 395544 279 16 Schuylkill River at Philadelphia, Pa. 752520 1.501475850 395829 17 63 61 53.6 Mills near Devon, Pa. at Waterloo Darby Creek 0 64 751622 29 7.27 53.701476480 395502 Pa. 54 near Darby, Darby Creek 1915-97 751649 395837 5.1 1966-81 42 at U.S. 1 Philadelphia, Pa. Cobbs Creek 1960-80 751452 1966-94 395458 48 64.0 26 1.9 Pa. at Darby, Cobbs Creek .5 752610 1.0 20 83 2.01 2.0 Pa. 16 near Newtown Square, Creek Crum 752413 6.7 21 20.4 1966-99 29 19 5.15 at Media, Pa. Ridley Creek 1962-79 28 .4 1,893 0 1971-94 3.0 50 4.0 1972-97 34 0 39 .2 0 41 18 3.0 37 0 1932-97 21 4.78 26 0 65 0 2.0 41 40 0 1.6 1965-81 2.4 6.6 19 33 0 66 15.8 37.4 30 52 0 17 42 0 1981-97 1964-90 0 1.7 51 20 22.0 48 0 38 39 0 17 27 20 30.5 1964-90 10 16 10 0 0 0 1987-97 27 0 61 73 38 0 0 0 11 14 15 0 51 15 0 0 0 58 77 3.0 0 0 14 0 0 0 0 0 0 0 014707790147085301470960 40244801471000 402024 76101901471510 402200 near Bernville, Pa. Creek Tulpehocken 760837 402208 at Robesonia, Pa. Furnace Creek 760116 402005 at Blue Marsh, Pa. Creek Tulpehocken 755846 near Reading, Pa. Creek Tulpehocken 755612 Schuylkill River at Reading, Pa. 66.5 175 1975-96 211 4.18 1965-78 23 1983-97 1951-78 880 14 15 13 28 1902-30 30 74 3.7 29 28 3.0 0 60 82 3.6 42 2.0 42 0 0 0 19 0 0 0 Geological streamflow- gaging station

Appendix 1. [ddmmss, degrees, minutes, and seconds; mi

24 area (percent) controlled Percentage bedrock (percent) carbonate Percentage (percent) urban area Percentage

Continued area forested (percent) Percentage used in of years Number analysis Period of Period in analysis record used (water year) (water ) 2 5.67 1960-79 20 78 .1 0 0 89.9 1974-99 26 4774.3 1985-97 6.4 13 8.7 55 22 .1 0 0 area (mi Drainage Station name , square miles; water year, 12-month period October 1-September 30] 2 Downingtown, Pa. Center, Pa. Center, Pa. Birchardsville, Longitude (ddmmss) Latitude (ddmmss)

Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations— of the regional regression stations used in the development streamflow-gaging Basin characteristics for U.S. Survey 014765000147700001478200 39541001480300 395203 75233501480500 394654 at Moylan, Pa. Ridley Creek 75243101480610 400422 Pa. near Chester, Chester Creek 75480301480617 395908 Pa. near Landenberg, Middle Branch White Clay Creek 75514001480675 395820 Pa. near Honey Brook, Branch Brandywine Creek West 75494001480680 395742 at Coatesville, Pa. Branch Brandywine Creek West 755106 12.701480700 400552 Sucker Run near Coatesville, Pa. 754806 18.701480800 400358 at Modena, Pa. Branch Brandywine Creek West 1960-91 75443101480870 400205 Pa. near Glenmoore, Marsh Creek 1960-97 754338 400020 45.8 Pa. near Lyndell, Marsh Creek 754232 32 395807 near Downingtown, Pa. East Branch Brandywine Creek 754220 38 1944-97 At Downingtown, Pa. East Branch Brandywine Creek 61.1 754025 31.9 55.0 below East Branch Brandywine Creek 60.6 31 37 1932-97 1932-55 1970-97 31 81.6 1974-99 2.57 66 24 3.6 1958-68 28 42 26 1.5 8.57 1964-96 11 55 58 1967-97 17.8 42 2.2 33 4.6 46 3.1 1960-71 31 46 19 15 2.2 0 45 1.8 1.0 12 0 55 5.4 12 0 0 1.0 0 46 .1 1.1 6.0 0 0 36 0 2.6 33 0 0 0 0 68 33 014810000151635001516500 39521101516800 414734 75353701517000 414727 Pa. at Chadds Ford, Brandywine Creek 77044401518000 414919 River near Mansfield, Pa. Tioga 77005401518420 414854 Pa. near Mainesburg, Creek Corey 770550 415430 near Mansfield, Pa. Manns Creek 76575501518500 415033 Pa. Elk Run near Mainesburg, 77074701518862 Pa. River at Tioga, Tioga 77162501519200 415408 below Catlin Hollow at Middlebury Creek Crooked 01520000 415523 287 77085501532000 415915 Pa. at Tioga, Creek Crooked 77315601532200 415948 Pa. Cowanesque River at Westfield, 771809 1912-9701532850 414225 Cowanesque River at Elkland, Pa. 153 770825 413525 12.2 Pa. Cowanesque River near Lawrenceville, 76290601533250 78 415145 Pa. near Monroeton, Creek Towanda 762600 3.0101533500 1955-96 1972-96 Pa. at New Albany, Creek South Branch Towanda 76002601533800 414225 1960-77 10.2 near Trib Creek Middle Branch Wyalusing 413150 35 42 21 760710 414810 near Silvara, Pa. Creek 1955-78 Tuscarora 760922 17 282 298 13.3 near Lovelton, Pa. North Branch Mehoopany Creek 90.6 753840 3.0 47 74 at Gibson, Pa. Butler Creek 122 235 24 1939-77 1963-95 1984-96 1952-78 53 215 35.2 1954-74 1980-97 39 30 52 .1 .5 12 7.6 27 1914-96 1941-58 0 21 18 63 55 83 0 3.5 64 66 18 11.8 0 0 60 63 0 1963-95 3.3 68 2.3 .2 60 .4 0 0 0 7.38 33 .2 .3 0 1.7 1963-79 0 0 0 0 0 0 63 15 0 0 0 0 0 0 0 0 .2 68 0 0 5.8 7.6 0 .3 13 0 19 Geological streamflow- gaging station

Appendix 1. [ddmmss, degrees, minutes, and seconds; mi

25 area (percent) controlled Percentage bedrock (percent) carbonate Percentage (percent) urban area Percentage

Continued area forested (percent) Percentage used in of years Number analysis 1966-97 32 80 1.3 0 28 Period of Period in analysis record used (water year) (water ) 2 area (mi Drainage Station name , square miles; water year, 12-month period October 1-September 30] 2 Longitude (ddmmss) Latitude (ddmmss)

Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations— of the regional regression stations used in the development streamflow-gaging Basin characteristics for U.S. Survey 015427200154281001543000 41125801543500 413444 78350001543700 412448 Run at Penfield, Pa. Wilson 78173401544450 411902 Run near Emporium, Pa. Waldy 78115001544500 413108 at Sterling Run, Pa. Driftwood Br Sinnemahoning Creek 78061201545600 413849 at Sinnemahoning, Pa. Sinnemahoning Creek 78014001546000 412833 272 at Wharton, Pa. First Fork Sinnemahoning Creek 77392201546400 412322 Germania Branch at Germania, Pa. 77493401546500 405630 Fork, Pa. at Cross Kettle Creek 1914-96 77412801547100 405001 near Renovo, Pa. Creek Womans Young 77474001547200 405323 182 685 Pa. at Milesburg, North Bald Eagle Creek 774940 8301547500 405554 at Houserville, Pa. Spring Creek 77474001547700 405635 near Axemann, Pa. Spring Creek 1984-97 774713 1936-97 5.2401547800 410306 8.34 Pa. at Milesburg, Spring Creek 774712 8001547950 410334 1964-97 Pa. at Milesburg, below Spring Creek Bald Eagle Creek 773617 14 1962-95 62 410126 Pa. at Blanchard, Bald Eagle Creek 773622 410642 2.40 46.2 265 Pa. at Blanchard, Marsh Creek 119 775415 34 34 .1 near Snow Shoe, Pa. South Fork Beech Creek 136 774209 1964-79 93 93 1965-96 at Monument, Pa. Beech Creek 1957-96 1911-28 99 11 1941-96 65 32 58.5 0 40 18 .1 87.2 .3 56 1985-96 142 0 12.2 71 100 0 1936-96 339 61 60 0 12 1959-81 0 0 1967-96 96 57 1955-69 44.1 0 .1 0 23 4.0 30 0 .1 152 37 1956-96 15 0 0 0 37 97 0 1968-97 41 0 40 0 46 8.6 0 60 7.0 8.3 30 0 2.2 78 6.8 0 0 0 76 0 7.1 83 68 0 .2 78 0 0 45 1.7 0 0 0 0 0 0 0 0 015339500153400001538000 41342901538800 413330 75383201539000 410333 near Montdale, Pa. Creek South Branch Tunkhannock 75534201539500 411840 Pa. near Tunkhannock, Creek Tunkhannock 76053801540000 410441 Pa. near Wapwallopen, Creek Wapwallopen 76085001540200 410450 12.6 Pa. near Pikes Creek, Huntington Creek 76255301541000 410010 Pa. near Bloomsburg, Fishing Creek 76304001541200 405110 1961-78 Pa. at Eyers Grove, Little Fishing Creek 76275001541500 405349 Pa. at Bloomsburg, Fishing Creek 383 76164801542000 405741 18 Run near Ringtown, Pa. Trexler 784038 43.801542500 405818 Pa. Branch Susquehanna River at Bower, West 783110 405058 1914-96 Branch Susquehanna River at Curwensville, Pa. West 782422 1920-96 410703 74 at Dimeling, Pa. Clearfield Creek 4.94 781605 83 at Osceola Mills, Pa. Moshannon Creek 780633 367 274 77 1960-80 56.5 Branch Susquehanna River at Karthaus, Pa. West 315 0.4 1941-58 68 1956-67 21 1939-96 355 83 1914-97 1,462 18 12 58 1.77 0 1914-31 96 84 .8 5.8 1940-60 68.8 1959-79 371 18 50 78 71 1941-93 21 9.1 0 50 21 1914-97 0 0 45 52 2.3 .1 .2 50 84 1.0 90 23 0 13 83 .1 0 1.0 0 84 0 0 0 0 1.3 1.5 0 .1 0 0 3.1 0 0 0 2.3 0 0 0 2.9 12 Geological streamflow- gaging station

Appendix 1. [ddmmss, degrees, minutes, and seconds; mi

26 area (percent) controlled Percentage bedrock (percent) carbonate Percentage (percent) urban area Percentage

Continued area forested (percent) Percentage used in of years Number analysis Period of Period in analysis record used (water year) (water ) 2 9.48 1960-78 19 41 1.0 0 0 area (mi Drainage Station name , square miles; water year, 12-month period October 1-September 30] 2 Washingtonville, Pa. Washingtonville, Longitude (ddmmss) Latitude (ddmmss)

Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations— of the regional regression stations used in the development streamflow-gaging Basin characteristics for U.S. Survey 015480050154802001548500 41045101549000 410030 77325901549500 413118 Station, Pa. near Beech Creek Bald Eagle Creek 77193501549700 411845 Bull Run near Loganton, Pa. 77265201549780 412825 at Cedar Run, Pa. Pine Creek 77224501550000 411625 Pa. near Waterville, Pine Creek 77135201551000 412504 Pa. near English Center, Blockhouse Creek 771928 56201552000 412506 Pa. near Waterville, below Little Pine Creek Pine Creek 77094601552100 411515 at Cogan House, Pa. Larrys Creek 77015901552500 411930 1971-97 Run, Pa. 944 near Trout Creek Lycoming 77004001553050 412010 Pa. Grafius Run at Williamsport, 76544601553130 412125 at Loyalsockville, Pa. Loyalsock Creek 25 765745 1958-9601553600 410705 37.7Pa. near Warrensville, Mill Creek 763206 410331 near Sonestown, Pa. Muncy Creek 770400 1.99 410457 39 604 1941-97 750 near Elimsport, Pa. White Deer Hole Creek 71 770437 Pa. Sand Spring Run near White Deer, 1963-81 763917 near East Branch Chillisquaque Creek 1919-96 57 173 1909-20 98 6.80 2.4 19 443 78 1960-78 12 1914-98 78 3.14 1.1 18.2 1926-98 99 28 19 11.9 1940-53 85 83 23.8 90 1961-95 .1 4.93 73 1961-78 14 0 1941-96 61 75 .4 33 80 1968-81 1.1 18 .2 82 56 40 0 18 14 0 98 .1 0 81 0 92 0 .8 5.0 95 0 0 0 0 0 .2 0 0 0 3.1 0 0 0 0 0 0 0 9.0 0 0 0 0 8.6 0 015537000155500001555500 41034201555800 405200 76405001556000 403640 Pa. at Washingtonville, Chillisquaque Creek 77025501556400 402235 Pa. at Penns Creek, Penns Creek 76544401556500 402747 near Dalmatia, Pa. East Mahantango Creek 78255501557100 403347 Pa. McDonald Run near East Freedom, 78120001557500 403740 Pa. Frankstown Br Juniata River at Williamsburg, 78203501558000 404000 Sandy Run near Bellwood, Pa. 781738 51.301559000 404101 Pa. Little Juniata River at Tipton, 78150001559500 403645 Pa. Schell Run at Tyrone, 781402 1980-96 16201559700 402905 291 Pa. at Tyrone, Bald Eagle Creek 78082701560000 403125 Pa. Creek, Little Juniata River at Spruce 78010901561000 395840 301 17 1889-1997 1930-97 Juniata River at Huntingdon, Pa. 775815 1.5401562000 400418 near Huntingdon, Pa. Standing Stone Creek 783708 109 395720 1959-78 near Manns Choice, Pa. Sulphur Springs Creek 1930-97 782934 68 401257 31 at Belden, Pa. Dunning Creek 781515 at Gapsville, Pa. Creek Brush 781556 20 70 68 93.7 5.58 Raystown Branch Juniata River at Saxton, Pa. 53 220 .5 128 1962-81 1946-81 5.28 44.1 73 1.5 67 1936-97 1.1 1.68 816 1962-78 1930-58 20 36 1940-97 6.0 756 1958-81 60 2.5 1.0 21 17 29 1896-97 58 75 0 75 1912-97 23 172 5.8 96 77 24 80 36.8 65 0 0 91 14 86 1936-97 6.5 86 0 1930-58 50 6.3 0 0 62 .5 0 1.5 60 29 17 3.9 8.0 2.0 21 56 .8 4.9 1.0 70 4.6 0 0 0 32 0 1.0 0 0 0 14 .5 0 0 6.7 0 0 0 0 Geological streamflow- gaging station

Appendix 1. [ddmmss, degrees, minutes, and seconds; mi

27 area (percent) controlled Percentage bedrock (percent) carbonate Percentage (percent) urban area Percentage

Continued area forested (percent) Percentage used in of years Number analysis 1974-94 21 38 291967-97 11 31 0 28 3.5 19 31 Period of Period in analysis record used (water year) (water ) 2 area (mi Drainage Station name , square miles; water year, 12-month period October 1-September 30] 2 Longitude (ddmmss) Latitude (ddmmss)

Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations— of the regional regression stations used in the development streamflow-gaging Basin characteristics for U.S. Survey 015715000157200001572900 40132901573000 403215 76535401573086 402425 near Camp Hill, Pa. Creek Breeches Yellow 76224001573160 402409 Pa. at Pine Grove, Lower Little Swatara Creek 76331501573500 401924 near Ono, Pa. Reeds Creek 76343901573560 402034 Pa. at Harper Tavern, Swatara Creek 76290001574000 402350 near Cleona, Pa. Beck Creek 76334601574500 401754 Pa. near Bellegrove, Quittapahilla Creek 764235 216 400456 34.3 at Manada Gap, Pa. Manada Creek 76400501574800 395243 Pa. near Hershey, Swatara Creek 764313 1910-97 Pa. 1920-84 near Manchester, Conewago Creek West 765113 394857 Pa. at Spring Grove, Creek Codorus 55 18 763759 337 Pa. near Winterstown, Trib Creek East Branch Codorus 74.2 1919-97 8.63 510 55 59 5.17 1975-93 13.5 7.87 1962-81 79 1960-75 483 1929-97 19 1938-58 9.6 1964-81 .3 20 75.5 16 69 1975-97 54 21 18 17 1930-66 34 41 23 0 26 34 1.7 37 89 17 13 15 0 40 0 .5 1.8 15 1.1 1.2 .8 74 8.5 0 3.0 0 6.0 82 .8 0 0 13 0 0 19 0 0 0 .5 0 015625000156300001563800 40210001564500 402535 78075001565000 400520 Pa. near Marklesburg, Creek Trough Great 78014701565700 401245 Raystown Branch Juniata River near Huntingdon, Pa. 78025501565920 403917 Elders Branch near Hustontown, Pa. 77553201566000 403620 Springs, Pa. near Three Aughwick Creek 773500 95701566500 402115 at Reedsville, Pa. Kishacoquillas Creek 77184001567500 403055 at Oakland Mills, Pa. Little Lost Creek 77385501568000 403355 1946-71 84.6 Pa. Lick Run near East Waterford, 77251001568500 402215 near Port Royal, Pa. Creek Tuscarora 77070501569000 401924 1930-57 near Millerstown, Pa. Cocolamus Creek 26 77240901569340 402737 Bixler Run near Loysville, Pa. 205 77100901569800 402246 at Shermans Dale, Pa. Sherman Creek 28 3.46 76450601570000 400740 164 near Carsonville, Pa. Clark Creek 67 76543101571000 401405 1939-97 1960-78 near Dauphin, Pa. Stony Creek 773250 401508 6.52 Pa. Run at Newburg, Newburg 65 1936-98 770823 401830 59 19 Letort Spring Run near Carlisle, Pa. 1.0 1960-81 770117 214 57.2 8.38 near Hogestown, Pa. Conodoguinet Creek 765100 63 Pa. near Penbrook, Paxton Creek 0.1 1962-81 22 1912-90 1930-58 60 40 207 12 63 20 15.0 50 29 29 1927-97 22.5 0 0 .4 470 1954-97 1.0 33.2 1.2 1938-96 76 71 70 55 21.6 1.2 5.29 44 1912-96 0 1938-74 59 5.8 1976-97 0 1964-95 68 25 11.2 .2 .1 .1 64 16 46 49 22 32 1940-50 0 95 0 .9 0 35 11 90 12 5.0 11 0 .1 34 8.1 0 4.0 12 21 0 0 .2 25 0 1.9 19 0 38 0 3.0 98 0 0 0 43 0 11 0 0 0 0 Geological streamflow- gaging station

Appendix 1. [ddmmss, degrees, minutes, and seconds; mi

28 area (percent) controlled Percentage bedrock (percent) carbonate Percentage (percent) urban area Percentage

Continued area forested (percent) Percentage used in of years Number analysis 1972-95 24 29 2.2 1.0 5.7 Period of Period in analysis record used (water year) (water ) 2 area (mi Drainage Station name , square miles; water year, 12-month period October 1-September 30] 2 Longitude (ddmmss) Latitude (ddmmss)

Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations— of the regional regression stations used in the development streamflow-gaging Basin characteristics for U.S. Survey 0301102003011800 420923 414559 784256 Allegheny River at Salamanca, N.Y. 784308 Pa. near Guffey, Kinzua Creek 1,608 1904-95 46.4 92 1966-96 31 86 96 .6 1.0 0 0 3.1 2.8 015755000157608501576320 39564601576500 400841 76452001576754 401244 Pa. near York. Creek Codorus 75592001577500 400300 Pa. near Churchtown, Little Conestoga Creek 76073001578200 395647 Stony Run at Reamstown, Pa. 76163901578400 394621 Pa. Conestoga River at Lancaster, 76220501600700 395035 Conestoga River at Conestoga, Pa. 76185801601000 395341 at Castle Fin, Pa. Muddy Creek 76114501603500 395535 near Buck, Pa. Conowingo Creek 760650 5.8201613050 394843 Bowery Run near Quarryville, Pa. 78394001613500 394723 Pa. at Bard, Creek Little Wills 1982-95 78430001614090 395354 below Hyndman, Pa. Creek Wills 783848 22201638900 394323 near Centerville, Pa. Evitts Creek 780757 1403007800 395548 Pa. near Needmore, Creek Tonoloway 780338 32403009680 394745 1947-97 near Sylvan, Pa. Licking Creek 470 3.55 77262303010655 414907 near Fayetteville, Pa. Conococheague Creek 771150 20 414835 1964-95 1929-97 133 Pa. White Run near Gettysburg, 51 781735 1985-97 415742 Pa. Allegheny River at Port Allegany, 8.71 78255003015000 5.98 32 69 at Smethport, Pa. Potato Creek 781154 1929-7203015080 .1 1963-97 13 at Shinglehouse, Pa. Oswayo Creek 28 146 1963-8103015390 415617 10.2 10.703015500 415555 15 30.2 5.05 33 34 27 79080003017500 415629 19 23 1961-81 1952-86 at Russell, Pa. Conewango Creek 23 5.9 1963-96 79053803019000 415109 1961-81 1933-82 Ackley Run near Russell, Pa. 158 79384103020440 413607 40 16 12 Pa. 20 21 35 near Corry, Creek Hare 248 791903 33 1703020500 412825 22 21 50 Pa. at Youngsville, Creek Brokenstraw 12.4 790301 13 0 03021350 414531 1931-41 Pa. at Lynch, Creek Tionesta 792305 412854 1975-97 1.0 at Nebraska, Pa. 83 Creek 87 Tionesta 1961-80 98.7 160 793408 .9 70 14 420055 44 0 97 Pa. 11 74 near Grand Valley, Branch Caldwell Creek West 794144 59 46 23 1975-97 at Rouseville, Pa. Oil Creek 794658 20 1972-97 Pa. near Wattsburg, Creek 0 French 0 .3 816 0 65 0 0 0 0 23 .1 4.37 26 0 88 24 321 17 1936-97 1964-81 9.64 0 0 0 .2 86 1910-96 0 12.3 0 18 93 1962-81 0 0 62 .6 6.3 17 233 469 1964-85 87 20 0 16 0 .1 0 0 52 .4 1938-79 1910-40 77 0 92.0 21 0 0 300 45 87 42 19 1975-97 0 2.0 0 1910-96 58 .1 0 30 .8 23 .2 96 90 .2 87 1.2 0 .5 1.0 0 56 0 40 .7 .1 0 29 0 0 .4 20 .5 0 0 0 8.9 0 0 0 0 17 5.3 01575000 395514 764457 Pa. near York, Creek South Branch Codorus 117 1928-71 44 20 1.0 1.0 2.7 Geological streamflow- gaging station

Appendix 1. [ddmmss, degrees, minutes, and seconds; mi

29 area (percent) controlled Percentage bedrock (percent) carbonate Percentage (percent) urban area Percentage

Continued area forested (percent) Percentage used in of years Number analysis 1972-97 26 52 1.4 0 44 Period of Period in analysis record used (water year) (water ) 2 area (mi Drainage Station name , square miles; water year, 12-month period October 1-September 30] 2 Longitude (ddmmss) Latitude (ddmmss)

Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations— of the regional regression stations used in the development streamflow-gaging Basin characteristics for U.S. Survey 030250000302520003026400 41254303026500 412520 79524803028000 411053 Pa. at Sugarcreek, Sugar Creek 79505903028500 413752 Patchel Run near Franklin, Pa. 79412503029200 413445 Richey Run at Emlenton, Pa. 78343703029400 412910 Sevenmile Run near Rasselas, Pa. 78412203029500 411917 Pa. Branch Clarion River at Wilcox, West 78404303030500 412016 Pa. Clarion River at Johnsonburg, 79043903031000 411950 near Sigel, Pa. Clear Creek 79125003031780 411133 Pa. Run at Cooksburg, Toms 79123303031950 410857 Pa Clarion River at Cooksburg, 79262503032500 411453 Pa. Clarion River near Piney, 166 79393703034000 405930 Pa. Clarion River at St. Petersburg, 785008 63.003034500 405940 5.69 Pa. near Brockway, Mill Creek 79052603035000 405621 1933-79 7.84 Big Run near Sprankle Mills, Pa. 792340 1954-96 5.88 1961-7803038000 405010 at St. Charles, Pa. Redbank Creek 790031 20403039000 405405 1952-96 47 Pa. at Punxsutawney, 1963-81 Mahoning Creek 79063703039200 403917 43 18 at Mccormick, Pa. Little Mahoning Creek 79133503039925 404313 1953-94 45 near Dayton, Pa. Mahoning Creek 792056 1903040000 400249 71 807 at Idaho, Pa. Creek 8.67 Crooked 12.6 793042 1,24603041000 401558 91 77 42 Dam, Pa. Creek at Crooked Creek Crooked 78500003041500 401708 1960-81 951 94 1960-78 Clear Run near Buckstown, Pa. 790101 61 1936-97 402037 1942-53 Pa. at North Fork Reservoir, North Fork Bens Creek .2 785515 402509 158 2.12 22 93 .6 River at Ferndale, Pa. Stonycreek 1948-96 .2 785307 19 7.38 528 87.4 62 Little Conemaugh at East Conemaugh, Pa. 12 790135 .1 2.9 1965-81 1964-81 Pa. Conemaugh River at Seward, 1936-96 1940-98 49 278 3.45 1910-97 0 95 321 94 .6 92 0 17 0 90 18 1985-97 61 59 0 1910-39 0 88 90 1917-40 191 .1 8.4 11 .3 183 1.0 50 0 0 53 30 0 71 .5 73 3.68 24 40 1936-97 0 1.0 0 451 1936-97 1961-78 99 0 36 .2 50 0 0 2.1 715 .4 62 40 1914-97 .3 0 62 .5 18 0 .1 1936-97 82 0 11 68 .1 0 0 0 .5 0 77 99 1.0 0 0 62 8.8 68 0 .7 0 0 3.5 0 0 0 0 0 72 0 1.8 0 0 0 0 3.4 0 0 0 7.0 6.6 0 0 7.7 1.7 030214100302170003022500 42045403022540 415553 79510203023000 414250 near Lowville, Pa. Creek Branch French West 80050203024000 414126 near Mckean, Pa. Little Conneauttee Creek 800850 414020 at Saegerstown, Pa. Creek French 800226 412615 Pa. at Blooming Valley, Creek Woodcock 801255 near Meadville, Pa. Cussewago Creek 795722 at Utica, Pa. Creek French 52.3 1975-94 3.60 1961-78 20 31.1 629 18 1975-95 90.2 57 1913-39 1911-38 21 58 27 1,028 0.8 28 64 0 1933-71 30 20 0 39 .2 0 .2 .2 5.5 52 0 0 0 0 1.4 9.9 15 12 0 21 Geological streamflow- gaging station

Appendix 1. [ddmmss, degrees, minutes, and seconds; mi

30 area (percent) controlled Percentage bedrock (percent) carbonate Percentage (percent) urban area Percentage

Continued area forested (percent) Percentage used in of years Number analysis 1969-97 29 72 3.9 0 35 Period of Period in analysis record used (water year) (water ) 2 area (mi Drainage Station name , square miles; water year, 12-month period October 1-September 30] 2 Longitude (ddmmss) Latitude (ddmmss)

Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations— of the regional regression stations used in the development streamflow-gaging Basin characteristics for U.S. Survey 030430000304500003045500 40282503047500 401733 79121503049000 402340 at Black Lick, Pa. Blacklick Creek 79202703049100 403205 at Kingston, Pa. Loyalhanna Creek 79255503049800 404257 at New Alexandria, Pa. Loyalhanna Creek 79275503070420 404557 Pa. Kiskiminetas River at Avonmore, 79415903072000 403113 Pa. near Freeport, Creek Buffalo 79460103072590 394551 at Cabot, Pa. Creek Little Buffalo 79561803072840 394533 near Etna, Pa. Little Pine Creek 79351403072880 394744 near Gibbon Glade, Pa. Stony Fork Trib 79581503073000 395951 265 at Shannopin, Pa. Creek Dunkard 794747 39003074300 395627 172 at Smithfield, Pa. Creek Georges 80023103074500 395523 1,723 near Clarksville, Pa. Creek Tenmile 1920-40 80172103078500 395204 1905-51 near Nineveh, Pa. Creek Browns 800422 1940-9703079000 395848 1884-1937 Pa. at Jefferson, Creek South Fork Tenmile 794140 1903080000 394334 137 Lick Run at Hopwood, Pa. 47 79455203081000 395135 52 48 Pa. at Waltersburg, Redstone Creek 4.66 79025503082200 394913 .93 Pa. Big Piney Run near Salisbury, 1941-96 791340 5003082500 394940 5.78 1959-81 Casselman River at Markleton, Pa. 50 1978-89 791918 22903083000 400059 81 50 at Ursina, Pa. Hill Creek Laurel 792225 1963-96 5503083500 400103 180 133 16.3 River below Confluence, Pa. Youghiogheny 23 792533 1203083600 400618 1941-96 .1 Poplar Run near Normalville, Pa. 793538 .103084000 401424 33 17.5 1964-78 River at Connellsville, Pa. .8 Youghiogheny 1932-95 .5 793001 1969-79 6703084500 401359 56 Pa. Lick Reservoir, Lick Run at Green 80 Green 794824 77 402701 1963-85 River at Sutersville, Pa. Youghiogheny 73.7 15 794906 64 0 11 80 402309 1,029 Gillespie Run near Sutersville, Pa. 0 794250 1.1 24.5 0 0 78 1943-96 382 near Murrysville, Pa. 3.80 Abers Creek 0 23 794555 .1 Pa. at Trafford, Creek Turtle 60 1942-97 63 56 1,326 8.9 1933-86 1959-78 2.0 121 54 1915-96 0 3.07 2.1 59 0 0 .3 56 51 20 1943-97 9.27 4.3 0 1,715 1914-97 1.4 0 1929-79 1.1 82 58 0 1961-78 55 .2 68 0 84 51 1943-97 68 97 0 0 40 4.04 0 0 18 0 0 8.4 0 4.39 55 69 1959-81 81 70 .9 0 .3 .5 0 1949-93 79 .2 55.9 0 0 0 21 0 67 .9 45 .4 .1 1917-55 0 0 0 0 .4 68 0 2.2 0 37 59 0 42 0 0 5.3 0 4.4 0 0 27 68 0 33 5.3 0 14 0 0 0 0 2.5 0 0 0 030420000304217003042200 40282403042500 403631 791101 403345 at Josephine, Pa. Blacklick Creek 790949 403102 Stoney Run at Indiana, Pa. 785644 Pa. near Strongstown, Creek Little Yellow 791019 at Graceton, Pa. Lick Creek Two 7.36 192 1961-87 1952-96 171 4.39 19 45 1964-76 1952-68 88 13 77 17 .2 34 1.4 72 52 0 3.9 0 0 0 0 0 0 0 Geological streamflow- gaging station

Appendix 1. [ddmmss, degrees, minutes, and seconds; mi

31 area (percent) controlled Percentage bedrock (percent) carbonate Percentage (percent) urban area Percentage

Continued area forested (percent) Percentage used in of years Number analysis 1970-97 28 56 1.5 0 20 Period of Period in analysis record used (water year) (water ) 2 area (mi Drainage Station name , square miles; water year, 12-month period October 1-September 30] 2 801938 Pa. Harthegig Run near Greenﬁeld, 2.26 1969-80 12 28 1.8 0 13 Longitude (ddmmss) 11110 Latitude (ddmmss)

Basin characteristics for streamflow-gaging stations used in the development of the regional regression equations— of the regional regression stations used in the development streamflow-gaging Basin characteristics for U.S. Survey 03111150 401154 802428 Pa. Run near Buffalo, Brush 10.3 1961-85 21 28 .2 0 0 0310600003106500 40490103108000 405302 801433 near Zelienople, Pa. Connoquenessing Creek 80140204213000 403740 Pa. at Wurtemburg, Slippery Rock Creek 04213040 80201604213200 415534 Mill, Pa. at Moffatts Raccoon Creek 415642 803618 420554 356 at Conneaut, Ohio Conneaut Creek 802651 Springfield, Pa. near West Raccoon Creek 800435 at Erie, Pa. Mill Creek 398 1916-96 1912-69 81 178 58 2.53 56 175 1916-96 1961-95 25 1923-95 70 4.5 34 60 .2 68 0 9.16 63 20 1969-85 3.5 0 2.0 1.4 17 .5 0 7.3 0 51 0 2.6 44 4.5 10 0 0 030855000308610003100000 40240203101000 403627 80054803102500 413045 at Carnegie, Pa. Chartiers Creek 80094903102850 412950 near Ambridge, Pa. Big Sewickley Creek 80281503103000 412519 Pa. Shenango River near Turnersville, 80275503104000 412113 Sugar Run at Pymatuning Dam, Pa. 80223503104500 411840 Pa. Little Shenango River at Greenville, 80235303104760 411355 Pa. Shenango River near Transfer, 802840 410000 near Orangeville, Pa. Pymatuning Creek 803035 4 Pa. Shenango River at Sharon, 802105 15.6 Shenango River at New Castle, Pa. 257 152 1963-78 104 1916-96 9.34 1912-22 16 169 1935-55 1914-96 337 71 11 1914-63 84 21 80 1966-97 792 608 50 30 48 3.8 32 30 30 1913-32 1910-32 2.5 30 .2 20 40 23 0 .2 .2 0 .2 30 0 2.1 30 0 0 0 1.5 63 0 .2 .2 0 17 2.3 89 52 0 0 33 44 Geological streamflow- gaging station

Appendix 1. [ddmmss, degrees, minutes, and seconds; mi

32 Computed from streamflow-gaging-station dataComputed from streamflow-gaging-station equations Predicted from regression 10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 100-year 500-year flow region Flood- 1960-97 A 11,300 13,900 15,800 17,900 22,900 12,300 16,600 20,400 24,7001961-97 37,100 A 33,200 41,600 48,100 54,800 71,500 27,400 36,100 43,400 51,500 74,100

Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging equations for data and regression frequencies computed from streamflow-gaging Flood-flow of Period in analysis record used (water year) (water U.S. station gaging Survey 0142765001428750 1962-8101429000 1975-9701429300 A 1945-6001429500 A 1975-9701430000 A 1944-5901430500 990 A 1944-59 3,45001431000 A 1922-42 4,82001431500 1,310 A 1945-86 3,550 4,190 A 1909-59 8,540 6,01001431680 12,900 A 1,580 4,44001438300 4,740 14,800 12,600 A 1960-8001439500 6,990 17,100 1962-97 5,51001440300 5,150 1,890 22,100 17,200 16,600 A 1909-96 5,31001440400 20,700 A 1961-97 8,030 7,53001441000 29,300 23,800 2,730 A 1958-96 5,91021,40001442500 6,690 380 25,000 A 1911-55 10,80001446600 9,26029,800 310 38,300 A 1951-96 4,310 37,50001447500 7,850 37,200 A 1961-86 46001447680 880 8413,100 36,900 68,600 11,200 A 1942-97 6,480 4006,200 4,18001447720 A 1965-96 2,910 4,54001448000 1,2104,320 3,170 1,290 20,100 16,60058,600 9,140 A 530 1962-96 5,800 8,93001448500 8,010 10,700 A 480 1917-59 1,130 6,270 3,73001449000 4,39012,400 1,5405,410 29,500 A 1,650 1949-96 6,700 14,400 7,250 11,00001449360 14,000 10,300 4,800 A 1982-97 600 7,79015,300 1,64001449500 1,9406,670 4,41038,600 5,470 565 17,700 10,700 A 1967-96 570 7,060 18,700 8,920 13,30001450000 2,080 17,500 17,700 6,620 18,500 A 1941-58 9,530 10,400 01450500 6,710 21,300 2,120 3,130 49,700 14,800 22,800 13,800 790 A 1941-70 5,150 6819,69001451000 19,800 26,800 320 27,900 23,900 8,220 14,600 8003,370 A 1940-96 10,300 31,800 27,400 86,600 5,580 A 1947-60 2,70020,200 1,860 11,900 7,110 10,100 36,000 30,400 A 770 1,620 450 40,500 5164,140 7,650 A 3,780 39,300 2,280 15,400 14,300 4,520 35,600 63967313,500 47,700 5,100 2,520 5,670 5,620 49,000 9,470 746 560 860 17,800 5,030 20,800 2,600 41,100 88,200 919962 7,190 4,690 7,780 3,390 6,990 69,100 11,600 21,400 883 1,080 6,070 956 55,000 1,1701,220 6902,920 6,430 17,600 8,51025,500 9,08087,400 9,690 5,49013,300 1,280 4,470 1,200 1,4701,530 7,220 17,700 7,950 11,900 12,800 36,600 109,000 1,0403,720 7,500 1,19021,400 11,300 1,640 8,000 1,960 21,500 18,300 2,370 2,430 10,300176,000 28,300 9,700 1,710 9,270 18,000 2,060 25,800 4,270 34,100 14,800 308 11,300 2,200 1,810 32,100 3,370 37,900 7,300 5,840 40,600 17,200 5,390 4522,55042,000 2,770 9,940 58,700 7,200 7,400 50,400 3,210 4,540 12,200 584 8,740 59,500 9,160 3,99014,900 13,200 742 11,200 84,800 22,400 6,290 17,000 1,230 Geological streamflow-

Appendix 2. stations used in analysis [All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

33 Computed from streamﬂow-gaging-station dataComputed from streamﬂow-gaging-station equations Predicted from regression 10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 100-year 500-year

Continued ﬂow region Flood- 1961-97 A 43,7001974-97 54,700 A 63,400 12,700 72,400 17,100 94,900 20,900 40,600 25,200 53,500 37,200 64,500 76,800 5,750 112,000 7,940 9,890 12,200 18,900

Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging equations for data and regression frequencies computed from streamflow-gaging Flood-flow of Period in analysis record used (water year) (water U.S. station gaging Survey 0145150001451650 1946-9701451800 1987-9701452000 A 1967-9701452300 A 1945-9701452500 A 1963-80 4,97001453000 A 1945-97 5,830 A 1902-60 5,050 8,22001454600 A 6,910 9,56001454700 A 1965-80 6,900 11,50001458900 730 10,000 1967-97 1,740 13,40001459500 51,800 A 1962-80 15,600 8,500 1,020 12,900 A 1936-73 2,790 18,40001460000 73,100 A01465000 29,700 340 1884-1913 10,300 45,200 A 1,270 16,30001465500 36,400 3,86092,500 1885-34 4,910 A01465770 55,300 12,000 15,300 1933-96 26,900 53001465785 115,000 1,540 3,730 A 1965-81 5,240 6,98001465790 6,810 63,000 15,300 4,360 A 1965-78 185,00001465798 5,530 2,280 5,550 A 720 1966-78 7,310 10,100 6,21001467042 6,400 8,86018,000 8,800 70,800 20,400 A 1966-9701467043 7,250 7,770 41,900 A 1965-81 1,320 8,700 9,08001467048 10,500 8,320 26,800 21,000 89,600 11,100 A 1965-80 970 1,110 2,39001467050 55,000 9,340 919 9,76010,900 A 1966-97 1,420 10,600 10,500 1,71001467086 32,400 12,500 17,70029,000 A 1965-81 5,840 3,630 66,100 1,380 16,100 01467087 1,800 1,350 12,10013,600 40,500 18,000 A 1966-86 4,270 1,790 12,20001467089 2,040 38,500 18,400 78,400 A 1982-97 53,100 4,830 7,460 19,100 21,400 01469500 1,590 1,760 620 1,5507,690 A 1966-81 6,100 5,200 113,000 01470500 16,600 2,110 55,600 63,900 A 1920-97 2,420 1,650 337 6,31001470720 10,500 2,260 8,790 2,190 8,090 A 1948-97 1,820 4,080 8407,580 75,900 5,940 11,300 A 1962-80 2,450 9,620 13,000 2,150 12,800 3,520 49610,900 3,820 16,900 10,200 2,760 109,000 A 9,670 5,000 2,430 1,0308,750 16,800 15,800 11,300 A 6,720 3,280 22,100 13,400 3,390 2,570 22,500 14,100 3,420 11,200 642 5,700 20,100 24,000 1,620 16,200 12,500 26,600 1,2309,980 1,310 4,360 8,700 29,400 12,300 5,380 3,030 823 23,900 2,090 81631,500 24,200 1,770 5,180 6,41013,800 13,100 1,980 1,790 5,22035,200 34,200 1,090 13,400 45,200 4,320 2,300 2,480 1,350 8,110 6,530 16,800 8,160 2,600 41,500 1,320 6,120 16,100 10,000 8,370 2,910 2,730 7,620 666 1,240 58,300 10,500 11,500 1,570 3,340 6,950 8,390 3,220 4,070 3,980 8,790 7,600 8691,610 13,100 12,100 2,280 8,570 5,640 5,020 4,530 11,900 19,600 9,350 13,900 17,300 1,0401,920 3,620 25,600 9,850 5,860 10,700 18,600 4,960 1,2302,260 1,240 30,700 11,200 6,76012,200 1,810 36,200 6,140 1,740 3,190 14,700 16,000 9,130 51,200 7,470 2,340 11,300 2,980 5,000 Geological streamflow-

Appendix 2. stations used in analysis— [All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

34 Computed from streamﬂow-gaging-station dataComputed from streamﬂow-gaging-station equations Predicted from regression 10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 100-year 500-year

Continued ﬂow region Flood- 1980-97 A 30,7001979-97 40,100 A 48,000 36,200 45,400 56,500 52,700 79,800 60,600 30,300 81,000 40,800 50,100 39,200 60,700 52,100 91,400 63,400 76,000 112,000

Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging equations for data and regression frequencies computed from streamflow-gaging Flood-flow of Period in analysis record used (water year) (water U.S. station gaging Survey 0147075601470779 1973-9501470853 1975-9601470960 A 1983-9701471000 A 1965-7801471510 A 1951-78 9,660 A 1902-30 5,07001471800 13,100 A01471980 470 11,000 A 1961-82 7,44001472000 16,300 1975-97 9,340 16,300 36,400 A 1902-78 60001472157 9,570 12,200 A 19,90001472174 21,100 47,400 A 1969-9701472198 710 12,000 14,600 700 1967-83 5,780 30,90001472199 56,600 26,800 39,900 A 1982-9701472500 19,400 A 1982-97 17,200 8807,31001472620 51,300 1885-1913 66,900 44,000 A 810 5,850 9,50001473000 A 1984-99 1,930 24,600 A01473100 1,0208,53060,600 95,600 13,300 2,910 1915-97 5,370 8,63001473120 1,080 8,130 A 1960-80 3,080 2,92001473169 7,190 16,600 70,700 4,520 A 1966-94 1,1609,830 7,320 11,200 9,61001473470 11,800 30,700 A 1983-99 1,870 20,500 4,12001473880 3,820 8,540 28,000 97,400 13,800 6,140 A 1971-94 13,200 593 41,200 15,200 14,40001473950 1,520 8,980 32,300 A 1962-79 5,110 2,49001474000 5,000 17,700 35,200 12,900 8,180 19,300 9,630 50,300 A 1966-81 4,89001474500 24,400 861 42,400 10,800 A 1966-99 2,620 22,300 7,360 4,76001475300 60,500 3,00040,500 18,800 15,200 32,300 1,360 12,900 A 1932-97 5,97010,800 56,10001475510 8,080 1,110 15,900 36,700 A 1972-97 6,780 3,830 89,900 01475530 1,950 9,410 24,600 18,400 470 4,790 45,900 67,900 A 1964-90 3,550 5,300 13,80001475550 8,670 1,400 A 1965-81 6,760 8,620 6,600 81,100 4,99023,300 2,470 31,700 76,500 58,60011,800 3,630 A 1964-90 844 6206,540 5,030 2,290 10,800 118,000 13,600 A 1,420 9,140 3,080 8,190 96,900 2,250 29,000 19,200 55,800 5,060 1,220 A 6,450 4,890 18,700 7,550 17,400 16,700 730 2,160 10,000 1,880 11,300113,000 3,180 4,900 45,800 6,330 1,570 4,270 11,300 712 22,400 23,200 6,000 15,300 1,200 6,520 8,620130,000 3,380 13,900 2,250 4,010 7,80028,400 27,400 1,050 1,980 860 5,260 6,870 172,000 1,710 8,670 3,700 11,400 1,320 22,000 4,98033,000 4,610 12,100 44,000 1,360 2,660 3,230 1,190 6,030 10,500 4,860 2,170 7,770 1,920 49,000 7,850 70,100 1,740 6,180 12,600 5,600 3,750 6,580 2,720 5,840 6,840 10,000 90,400 2,490 18,400 2,920 11,600 668 7,390 8,600 107,000 6,920 4,380 3,160 8,850 1,110 126,200 8,92010,300 6,200 900 9,920 5,280 178,000 1,660 1,480 10,50012,400 7,820 1,100 5,790 2,130 1,810 15,400 17,400 9,140 7,170 1,320 2,520 2,170 10,500 8,270 1,950 2,940 3,170 14,300 9,430 4,060 12,500 Geological streamflow-

Appendix 2. stations used in analysis— [All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

35 Computed from streamﬂow-gaging-station dataComputed from streamﬂow-gaging-station equations Predicted from regression 10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 100-year 500-year

Continued ﬂow region Flood-

Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging equations for data and regression frequencies computed from streamflow-gaging Flood-flow of Period in analysis record used (water year) (water U.S. station gaging Survey 0147585001476480 1981-9701476500 1987-9701477000 A 1932-5501478200 A 1932-9701480300 A 1960-91 1,92001480500 A 1960-97 2,95001480610 A 1944-97 3,010 2,51001480617 A 1964-96 6,910 4,40001480675 A 1970-97 2,260 4,56001480680 3,010 10,200 A 1967-97 4,36001480700 5,780 A 1960-71 4,820 3,18001480800 6,100 13,400 A 1974-99 3,570 7,68001480870 840 A 1958-68 7,480 6,220 7,17001481000 4,000 A 1974-99 8,05017,400 11,40001516350 5,080 560 1,240 A 1912-97 13,000 8,90001516500 9,360 980 A 1972-96 4,940 4,450 14,80030,500 16,60001516800 A 1,610 1955-96 4,720 790 11,30001517000 2,060 12,100 1,170 A 1960-77 5,940 5,870 3,48001518000 7,73038,000 12,900 A 1955-78 5,330 3,6006,340 14,00001518420 2,820 2,050 20,300 20,600 A 9901,320 1939-77 4,700 7,71001518500 7,020 16,800 A 1985-97 2,160 4,8708,40001518862 22,200 5,800 3,480 31,400 1,7702,440 3,380 A 1954-74 5,75001519200 9,18020,100 1,2301,470 560 10,100 4,770 A 1984-96 8,250 1,440 5,950 3,32001520000 2,5503,490 4,230 42,400 25,500 A 1980-97 6,270 6,94001532000 12,100 5,510 10,80023,700 11,400 6,630 1,9301,860 A 1952-78 11,500 7,170 6902,10001532200 4,450 3,2604,440 37,700 6,370 327 56,100 10,300 A 1914-96 8,560 17,500 01532850 7,440 7,620 15,900 10,700 15,00033,500 8,280 10,600 A 1963-9501533250 102,000 5,570 2,74049,100 4,110 20,600 12,200 499 A 790 1960-79 5,870 1,910 4,83001533500 10,200 19,800 9,500 15,600 864 24,100 A 1963-95 26,500 6,720 9,040 6,63018,300 62,700 24,400 15,600 6,090 2,740 A 1941-58 3,520 10,600 6,730 11,700 15,900 1,270 19,800 664 33,800 9,660 24,200 A 890 1,360 24,900 106,000 9,160 31,200 36,100 8,440 18,100 A 3,500 19,700 1,020 13,000 8,430 6,040 42,600 1,650 24,600 36,600 30,600 868 1,060 1,900 11,400 1,610 1,140 47,200 10,500 36,000 10,400 15,900 4,400 6,640 32,700 1,430 17,100 2,12037,200 52,800 38,000 14,000 1,540 2,300 13,000 1,420 19,100 2,390 16,300 1,360 60,700 48,300 22,700 10,700 6,200 7,160 56,500 1,770 3,590 21,500 83,400 20,200 528 2,940 28,200 8,990 104,000 1,960 1,720 27,500 8,540 14,800 6,820 2,960 14,500 12,200 2,150 3,69032,800 779 2,50010,600 17,400 9,300 2,05020,000 19,400 12,900 4,740 15,000 47,600 23,000 12,900 5,980 3,190 3,140 1,010 11,500 17,200 23,700 37,500 18,200 2,910 27,700 19,800 13,900 1,29028,400 20,800 5,100 1,620 27,400 33,000 21,000 732 24,900 41,800 3,290 2,320 2,170 1,330 47,700 36,300 1,050 4,610 1,900 2,940 1,350 5,780 3,680 2,430 1,690 7,140 3,050 5,920 11,200 2,740 4,930 Geological streamflow-

Appendix 2. stations used in analysis— [All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

36 Computed from streamﬂow-gaging-station dataComputed from streamﬂow-gaging-station equations Predicted from regression 10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 100-year 500-year

Continued ﬂow region Flood- 1966-97 A 37,300 48,900 58,900 70,200 102,000 47,200 60,700 71,900 84,100 117,000

Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging equations for data and regression frequencies computed from streamflow-gaging Flood-flow of Period in analysis record used (water year) (water U.S. station gaging Survey 0153380001533950 1963-7901534000 1961-7801538000 A 1914-9601538800 A 1920-9601539000 A 1960-80 1,12001539500 A 1939-96 1,53001540000 24,100 A 1941-58 1,70001540200 A 1914-31 2,510 1,97001541000 29,500 A 1959-79 1,03001541200 2,270 17,300 A 1914-97 3,35001541500 2,32033,500 A 1956-67 3,150 1,43001542000 23,600 22,400 A 1914-97 2,98001542500 4,050 37,400 A 1941-93 2,700 3,700 1,76028,900 28,400 190 13,900 A 1940-6001542720 5,350 14,500 46,300 A 4,81001542810 3,660 4,100 33,000 17,800 34,900 12,500 A 1962-95 2,130 32001543000 17,700 1964-97 2,43001543500 6,870 21,200 15,700 17,900 37,800 45,600 51,900 A 1914-96 4,510 85301543700 3,110 20,200 1,330 A 460 1936-97 23,900 3,11001544450 18,300 54,500 24,800 49,300 1,240 A 1984-9701544500 5,470 1,890 390 3,45015,500 22,700 29,100 A 1964-7901545600 3,67061,100 410 21,100 18,700 35,000 A 1941-96 1,590 640 601 20,70001546000 4,720 34,800 2,400 22,100 36,300 28,600 A 1965-96 47001546400 25,900 5,120 67,600 28,400 25,100 A 2,000 4,270 1911-28 9,770 29,600 560 51,100 01546500 1,290 864 2,990 5,830 49,000 19,600 A 1985-9601547100 7,100 30,000 32,300 170 19,100 83,000 36,000 13,000 A 540 1936-96 7,790 3,280 26,20001547200 5,850 7,080 60,100 1,100 4,780 17,800 A 690 1967-96 2,430 25,000 43,700 01547500 43,300 8,850 39,700 13,100 15,700 31,800 10,800 A 1957-96 280 23,400 200 10,700 01547700 1,380 63,800 72,600 30,000 A 1955-69 605 1,170 10,900 3,700 64,000 38,200 16,900 5,080 61,100 13,400 28,100 A 1956-96 84018,800 1,940 82,500 109,000 35,500 411 2,210 16,800 A 230 3,270 1,680 56,200 6,900 33,300 4,92020,200 11,100 98,200 770 A 16,400 27,400 3,050 50,500 1,260 14,400 533 7,560 4,900 115,400 47,700 28,800 2,170 8,470 15,200 23,800 2606,430 3,100 25,400 19,200 4,170 163,000 37,300 10,200 9,350 9,970 677 6,45018,800 563 33,700 23,100 2,750 11,400 620 4,640 44,300 13,300 15,300 340 5,630 10,800 7,900 27,600 1,120 22,800 866 8,350 52,000 4,610 889 6,120 16,100 10,600 7,850 10,800 39,800 3,330 12,200 34,600 72,600 1,160 14,500 19,200 10,800 1,13012,900 395 7,940 4,560 15,800 2,370 27,700 1,530 15,400 13,400 3,020 1,410 8,830 581 13,900 5,630 4,470 3,590 16,400 22,500 2,730 4,580 11,300 12,500 2,250 6,680 6,830 7534,780 25,200 15,800 6,10015,800 3,600 10,200 8,800 6,240 19,800 19,700 960 4,960 7,980 11,400 24,600 11,100 31,500 14,200 1,600 6,160 19,800 38,700 7,530 11,500 Geological streamflow-

Appendix 2. stations used in analysis— [All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

37 Computed from streamﬂow-gaging-station dataComputed from streamﬂow-gaging-station equations Predicted from regression 10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 100-year 500-year

Continued ﬂow region Flood-

Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging equations for data and regression frequencies computed from streamflow-gaging Flood-flow of Period in analysis record used (water year) (water U.S. station gaging Survey 0154780001547950 1959-8101548005 1968-9701548020 A 1971-9701548500 A 1963-8101549000 A 1919-9601549500 690 A 1909-20 5,38001549700 10,530 A 1941-9701549780 A 1958-96 9507,18001550000 13,500 160 25,800 A 1960-7801551000 34,400 A 1914-9601552000 1,1808,71016,100 35,600 A 1940-53 3,920 24001552100 40,700 42,800 A 1926-9801552500 44,300 10,40019,000 A 1961-78 1,440 5,34001553050 45,200 58,700 570 14,100 A 310 1941-9601553130 54,300 15,10027,100 A 1961-9501553600 2,220 6,560 72,700 19,100 710 49,600 28,400 A 1968-81 81001553700 84,200 A 1960-78 40001555000 23,500 37,200 990 10,10013,800 88,600 1,000 59,300 A 1980-96 7,930 4,19001555500 1,040 1,260 A 1930-97 1,640 13,50019,20001555800 135,000 44,800 27,000 28,400 1,470 700 A 1,240 1930-97 11,800 6,00001556000 1,760 590 30,900 16,50024,100 A 1959-78 1,300 2,220 35,200 2,40001556400 1889-1997 53,200 42,500 A 1,920 3,480 40,000 31,70001556500 19,800 29,800 7,660 2,210 1,500 1,010 12,300 42,100 A 1962-81 3,400 3,230 A01557100 2,110 3,070 292 76,600 11,300 40,900 47,500 1946-81 4,100 29,000 47,000 01557500 2,720 49,500 2,480 17,300 10,300 2,190 A 1,440 1958-81 9,600 12,700 4,47001558000 55,600 4,550 48,600 17,300 220 428 A 1940-97 3,840 13,800 69,900 01559000 4,56021,900 4,210 20,300 16,800 4,280 A 1936-97 15,500 863 56,900 5,560 77,500 01559500 23,300 2,000 520 1896-1997 16,700 A 5,970 5,030 26,700 30001559700 6,070 552 613 27,200 20,100 79,400 1,240 A 1930-58 5,030 6,810 A 20,000 230 31,200 32,200 3,990 1962-78 2,930 10,700 1,290 7806,450 2,000 12,200 43,300 10,400 897 A 699 370 1,580 23,900 28,300 29,300 6,150 38,200 1,630 58,900 1,830 A 2,800 3103,820 1,0207,580 17,900 38,600 1,990 1,160 4,610 1,150 34,100 54,700 1,380 2,270 61512,100 2,310 450 3,500 4,56023,400 770 4,710 11,400 47,600 1,470 380 1,3108,780 3,210 2,00016,700 5,920 2,840 12,200 879 2,870 15,400 4,310 6,700 30,100 1,130 20,800 680 5,35058,000 2,450 11,800 2,560 2,230 16,600 3,490 7,010 18,900 1,120 450 4,520 6,680 25,600 8,520 52,300 1,470 88,600 3,230 20,600 7,420 22,900 5,380 1,390 8,210 10,700 39,500 6,320 281 25,000 640 653 5,310 34,200 1,860 17,200 9,84026,000 2,210 11,500 8,560 38,000 3,180 415 93813,30035,600 10,500 3,040 4,380 289 16,40044,200 8,240 12,700 5381,200 5,430 19,80054,000 11,200 421 18,800 1,500 678 686 6,630 13,900 29,600 82,900 542 2,410 978 1,140 16,900 10,100 25,500 685 1,250 1,570 1,120 2,530 Geological streamflow-

Appendix 2. stations used in analysis— [All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

38 Computed from streamﬂow-gaging-station dataComputed from streamﬂow-gaging-station equations Predicted from regression 10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 100-year 500-year

Continued ﬂow region Flood- 1974-94 A 3,350 4,640 5,760 7,040 10,700 1,700 2,350 2,920 3,570 5,490

Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging equations for data and regression frequencies computed from streamflow-gaging Flood-flow of Period in analysis record used (water year) (water U.S. station gaging Survey 0156000001561000 1936-9701562000 1930-5801562500 A 1912-9701563000 A 1930-5701563800 A 1946-71 9,02001564500 A 1960-78 2,61001565000 27,800 12,400 A 1939-9701565700 A 1936-98 3,610 4,11001565920 35,900 23,400 15,400 A 1960-8101566000 A 1962-81 5,02001566500 5,62042,400 27,400 340 14,200 A 1912-90 18,80001567500 A 1930-58 6,54001568000 6,29030,200 20,000 49,400 A 1954-97 7,540 29,000 46001568500 630 A 1927-97 9,56001569000 25,100 960 32,800 67,500 11,300 A 1938-96 7,770 14,20001569340 10,700 A 550 1938-74 4,610 12,400 98001569800 14,400 31,100 1,550 38,600 A 1964-95 3,300 12,20001570000 14,600 29,200 15,900 A 1976-97 5,810 3,320 15,80001571000 1,33017,000 49,000 A 2,150 1912-96 660 1,030 39,100 18,100 6,060 22,500 34,700 A 1940-50 2,760 4,610 6,46001571500 26,700 6,740 19,800 22,000 47,800 A 1,780 46,000 1,70001572000 9,30028,600 2,920 890 12,300 940 A 1910-97 8,830 5,740 4,88001572900 57,500 670 33,600 13,000 27,200 55,700 1920-84 7,700 16,70001573000 3,350 2,380 7,510 14,00035,600 1,460 10,900 5,620 A 1962-81 1,900 7,050 85,300 01573086 66,400 7,260 16,900 1,060 20,500 A 1919-97 10,000 10,50001573160 13,200 64310,600 34,20057,100 10,900 A 2,060 1964-81 3,260 5,960 2,270 96,800 01573500 24,900 20,300 10,600 13,200 A 1,460 1975-93 2,700 605 14,500 20,000 01573560 814 951 A 1938-58 2,650 8,660 37,300 4,71001574000 6,400 16,400 2,540 2,860 10,600 24,100 17,900 24,100 17,900 1,380 A 1975-97 3,750 9461,190 1,980 A 1929-97 1,240 1,320 6,57014,600 3,580 11,300 25,700 21,800 23,700 35,000 2,030 5,950 A 2,810 2,200 4,700 1,2801,530 1,590 18,000 3,880 2,710 A 1,590 1,780 8,230 3,150 33,000 14,500 4,37028,900 20,000 2,650 3,280 3,440 2,240 1,7101,95022,000 17,900 29,400 3,750 10,200 5,820 2,690 2,810 25,300 5,710 26,400 928 34,700 3,400 5,250 1,240 25,100 33,400 4,320 2,830 40,100 3,150 3,210 15,800 4,660 9,210 1,360 3,82032,100 1,470 51,700 31,600 5,760 1,950 9,990 7,700 3,520 49,900 9,280 5,690 5,620 2,170 39,200 1,750 38,600 2,660 5,080 33,000 12,900 5,560 3,36019,900 61,600 8,670 10,000 62,300 2,220 2,820 1,480 57,600 16,100 3,570 26,400 9,280 4,700 98,700 2,070 3,61019,900 3,700 511 32,100 6,710 3,530 5,880 26,100 31,000 38,400 2,590 6,140 1,35029,000 8405,32034,600 7,250 38,900 56,100 1,900 3,200 41,900 1,1807,060 11,300 47,500 50,100 2,390 4,990 1,6309,200 57,200 73,300 2,960 16,300 3,260 85,300 4,620 Geological streamflow-

Appendix 2. stations used in analysis— [All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

39 Computed from streamﬂow-gaging-station dataComputed from streamﬂow-gaging-station equations Predicted from regression 10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 100-year 500-year

Continued ﬂow region Flood- 1967-97 A1972-95 4,930 A 8,040 11,900 11,400 18,600 15,900 25,300 33,100 34,000 64,400 5,010 7,220 10,600 14,500 9,270 18,000 11,700 22,000 19,500 33,900

Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging equations for data and regression frequencies computed from streamflow-gaging Flood-flow of Period in analysis record used (water year) (water U.S. station gaging Survey 0301102003011800 1904-95 1966-96 B B 37,000 3,110 44,600 4,300 50,500 5,340 56,700 72,200 6,500 9,800 41,700 50,400 3,200 57,300 4,070 64,400 82,400 4,780 5,540 7,500 01574500 1930-660157480001575000 A 1960-75 1928-7101575500 A 4,62001576085 A 1947-9701576320 1982-95 1,070 6,67001576500 A 1964-95 5,41001576754 A 1929-97 2,23001577500 8,610 A 1985-97 9,250 8,06001578200 A 1929-72 1,55001578400 3,740 11,000 13,400 A 1963-97 1,030 10,70001600700 16,000 A 1963-81 2,06001601000 18,500 18,500 17,300 A 1961-81 6,130 1,320 13,90001603500 22,000 12,100 A 1952-8601613050 2,480 22,800 A 1933-82 22,000 1,240 18,30001613500 24,700 1,56027,300 17,500 6,560 A 1963-96 2,00001614090 26,300 A 1931-41 2,930 1,170 37,700 1,95001638900 22,600 33,400 9,410 A 1961-81 1,810 8,660 3,440 11,20003007800 29,900 952 A 1961-80 2,120 1,77003009680 4,120 2,660 12,100 28,800 51,000 15,500 11,300 12,200 A 1975-9703010655 2,450 5,040 900 1,410 12,200 39,000 A 1972-97 15,200 2,940 17,000 2,350 19,400 49,200 13,600 1975-97 3,580 B 18,800 300 14,200 1,830 1,230 25,100 7,270 B 3,350 763 23,900 21,40003015000 3,640 17,300 3,06016,100 B 622 20,000 8,74003015080 6,840 25,300 10,600 2,340 26,500 37,300 1,170 1,520 1936-97 16,300 24,300 7,000 4705,00003015390 25,300 10,400 1962-81 4,430 23,000 14,500 3,53003015500 5,390 906 42,000 33,400 3,970 30,700 1964-85 1,570 B 8,81003017500 31,400 6,570 1,830 1,500 17,900 11,700 630 1910-96 B 4,180 6,670 38,200 1,170 61,400 743 11,900 2,060 1938-79 B 50,300 8,720 10,300 2,200 21,800 1,140 2,680 8,490 B 13,000 61,200 1,480 4,640 1,140 13,800 930 11,700 840 B 3,720 1,330 33,300 1,620 11,900 2,850 2,090 11,900 8,260 14,700 16,100 14,200 2,460 15,100 1,530 1,040 10,600 1,260 5,090 1,660 1,560 3,010 16,400 3,630 11,400 2,050 14,100 17,100 13,200 2,020 16,500 1,800 11,000 1,120 14,200 1,870 6,100 2,550 3,840 6,100 1,92015,600 25,000 13,800 15,200 8,020 3,650 19,600 17,500 2,280 612 2,690 4,820 4,040 1,200 17,100 2,200 10,100 15,900 26,900 5,640 17,300 2,850 3,460 879 7,790 19,200 20,600 18,200 11,7001,380 2,940 7,120 22,500 4,550 4,380 22,800 1,120 13,400 24,200 8,300 10,700 25,500 1,060 7,270 17,900 1,400 1,14010,700 13,000 9,580 28,200 1,380 13,300 2,250 1,460 14,800 12,900 34,500 15,400 1,650 16,600 1,730 17,700 1,950 21,000 2,020 23,500 2,720 2,750 Geological streamflow-

Appendix 2. stations used in analysis— [All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

40 Computed from streamﬂow-gaging-station dataComputed from streamﬂow-gaging-station equations Predicted from regression 10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 100-year 500-year

Continued ﬂow region Flood- 1972-97 B 16,500 18,300 19,400 20,500 22,700 19,900 23,100 25,500 27,900 33,200

Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging equations for data and regression frequencies computed from streamflow-gaging Flood-flow of Period in analysis record used (water year) (water U.S. station gaging Survey 0301900003020440 1910-4003020500 1964-8103021350 1910-96 B03021410 1975-97 B03021700 13,900 1975-94 B03022500 1961-78 B03022540 16,100 470 12,800 1913-39 B03023000 1975-95 B 5,94003024000 17,800 15,400 B 1911-38 6,120 560 1933-71 B 6,81003025000 17,500 540 19,400 17,500 B 8,06003025200 1933-79 B 630 2,28003026400 7,420 21,100 19,600 23,000 1961-78 2,540 68003026500 9,700 19,600 1963-81 B 2,86003028000 23,900 24,700 1952-96 B 6907,980 3,13003028500 22,100 17,700 11,500 1954-96 B 800 8,58003029200 3,320 26,700 1953-94 B 21,90003029400 9,200 3,610 23,800 620 12,000 16,600 10,100 860 1960-81 B03029500 640 33,700 25,200 1960-78 B 920 3,780 1,140 14,90003030500 25,500 11,200 1936-97 B 4,130 4,180 92003031000 28,700 4,500 17,100 1948-96 B 3,380 6,900 7101,71003031780 1,2404,900 18,400 596 29,200 1942-53 B 12,200 5,390 37,800 03031950 5,500 5,580 19,400 1,210 690 4,280 1965-81 B 22,300 8,66003032500 2,240 620 32,000 1964-81 B 789 760 14,500 25,400 03034000 6,370 6,430 2,20024,800 1,030 40,100 5,000 25,200 1910-97 B 1,560 518 10,10003034500 41,100 4,640 41,700 1936-96 B 2,890 29,500 76003035000 2,800 7,31028,300 948 50,600 5,780 1940-98 B 1,350 8107,41003038000 7,540 2,680 11,600 5,790 687 48,600 48,800 230 33,100 1917-40 B 35,800 03039000 4,950 1,120 59,100 3,270 900 9,510 23,200 7,760 1936-97 B 860 10,100 9,370 15,800 36,800 54,000 6,700 1,740 56,800 900 1910-39 B 828 8,920 300 3,780 31,100 1,590 68,200 1,120 10,800 B 5,300 722 45,700 7,650 59,000 12,200 78,900 12,200 3,020 B 970 911 4,130 983 12,300 38,000 5,070 6,630 91,800 3501,270 8,890 6,470 10,000 952 15,000 739 15,200 70,400 15,300 1,200 5,260 16,200 1,220 7,980 1,390 23,200 46,000 11,300 7,38017,200 1,140 1,420 17,900 98026,600 974 1,430 40018,800 28,100 6,170 8,990 35,600 69,300 13,300 32,200 1,280 1,350 19,800 1,280 19,700 31,900 1,780 1,690 1,170 8,320 29,700 43,300 7,150 10,000 36,600 520 15,400 1,670 35,800 1,530 1,900 19,300 21,700 26,200 49,300 12,400 1,380 2,360 10,700 9,690 41,100 21,300 23,800 45,600 8,050 1,810 55,700 1,990 871 25,700 1,940 52,400 35313,500 10,100 27,400 71,900 5,240 1,150 2,340 2,530 16,700 8,490 31,200 11,800 12,100 472 6,630 1,370 3,260 10,500 19,300 15,100 13,500 40,900 7,760 1,620 22,100 57112,200 17,500 18,100 8,970 13,900 29,200 20,000 2,270 681 12,100 18,200 26,500 974 Geological streamflow-

Appendix 2. stations used in analysis— [All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

41 Computed from streamﬂow-gaging-station dataComputed from streamﬂow-gaging-station equations Predicted from regression 10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 100-year 500-year

Continued ﬂow region Flood- 1969-97 A 11,300 18,000 24,800 33,400 64,000 9,330 12,500 15,300 18,400 27,300

Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging equations for data and regression frequencies computed from streamflow-gaging Flood-flow of Period in analysis record used (water year) (water U.S. station gaging Survey 0303920003039925 1961-7803040000 1985-9703041000 A 1914-9703041500 A 1936-9703042000 A 1936-9703042170 260 A 1952-9603042200 170 22,800 A 1964-7603042500 12,900 A 1961-87 340 30,700 39,800 A 1952-68 22003043000 18,500 13,800 A03045000 37,400 55,800 A 400 1905-5103045500 23,600 19,200 460 270 1940-97 1,15003047500 70,000 44,800 A 1920-40 8,98003049000 24,200 1884-1937 29,700 A 470 5301,76003049100 86,400 22,300 65,500 11,200 A 1941-96 320 A03049800 30,000 12,200 48,600 1959-8103070420 135,000 2,360 30,000 16,000 12,900 650 A 580 1963-96 74,90003072000 16,400 22,500 48,000 440 A 1978-8903072590 36,800 22,400 10,700 97,900 A 1941-96 3,12014,800 7,360 29,600 33,10003072840 20,100 A 1964-78 630 14,30003072880 28,300 340 117,000 474 11,600 44,700 42,900 35,500 A 1969-79 1,160 19,700 9,39003073000 5,710 449 24,400 17,400 A 1963-85 15,400 139,00003074300 42,100 51,200 110 35,100 12,200 67,900 740 685 A 1932-95 3802,160 11,10003074500 20,800 36,800 18,600 650 11,100 A 1959-78 1,210 202,000 60,200 60,300 03078500 14,700 10,800 55,900 A 1943-96 867 140 30,300 12,90003079000 14,700 22,200 3,310 875 23,000 84,700 A 400 1933-86 2,320 1,200 1,52003080000 16,600 831 15,800 10,200 10,200 73,600 1,240 A 1915-96 30,600 17,800 32,200 03081000 17,600 1,100 16,800 1,590 A 160 1914-97 4,930 13,600 3,25003082200 94,800 1,050 1,77020,600 12,000 350 18,500 21,200 37,100 A 1942-97 1,570 430 3,900 22,500 1,770 16,500 113,000 A 1961-78 1,910 2,500 11,700 44,400 4,04013,300 1,690 30,600 9,410 26,300 20,600 22,900 27,400 A 1,970 180 2,030 132,000 4904,830 19,800 480 A 2,280 7,090 12,700 3,610 65,000 33,000 27,200 185,000 14,500 28,400 44,300 4,900 3,130 29,000 2,700 5,570 13,000 818 15,600 250 610 1,150 3,280 8,690 49,000 4,63032,900 36,100 17,300 17,400 7,240 18,800 620 1,150 9,700 6,340 1,460 9,91042,400 1,950 39,400 21,000 7505,820 28,000 13,200 181 12,200 1,450 896 8,300 2,740 25,200 1,730 1,970 49,400 58,000 11,100 16,300 16,200 1,1609,460 1,790 271 1,150 36,600 2,790 3,440 14,10068,300 19,700 19,900 2,010 6,67024,200 2,790 1,440 4,25023,800 356 3,520 29,600 2,340 494 32,300 2,790 8,940 35,800 7,520 2,340 35,000 3,290 4,390 6,650 39,300 458 47,000 10,900 71310,200 47,200 4,130 6,970 1,080 13,100 56,500 12,400 779 913 69,800 1,550 67,100 5,110 19,300 15,000 1,150 96,800 1,960 7,990 22,200 1,850 2,450 3,900 Geological streamflow-

Appendix 2. stations used in analysis— [All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]

42 Computed from streamﬂow-gaging-station dataComputed from streamﬂow-gaging-station equations Predicted from regression 10-year 25-year 50-year 100-year 500-year 10-year 25-year 50-year 100-year 500-year

Continued ﬂow region Flood- 1970-97 B 8,900 9,930 10,600 11,300 12,600 12,600 15,200 17,200 19,300 24,400

Flood-flow frequencies computed from streamflow-gaging data and regression equations for streamflow-gaging equations for data and regression frequencies computed from streamflow-gaging Flood-flow of Period in analysis record used (water year) (water U.S. station gaging Survey 03111150 1961-85 A 1,240 1,670 2,010 2,380 3,310 1,590 2,310 2,980 3,770 6,260 0308250003083000 1943-9703083500 1929-7903083600 A 1943-9703084000 A 1959-8103084500 46,000 A 1949-9303085500 A 1917-5503086100 60,000 590 57,300 A 1916-9603100000 A 1963-7803101000 71,800 74,600 490 A 1912-22 87003102500 900 A 1935-55 4,26003102850 89,000 84,800 10,100 1914-96 B 75003103000 1,120 1,160 1966-97 B 1,320 5,380 105,00003104000 121,000 12,400 1914-63 B 6,17003104500 1,000 1,370 1910-32 1,430 B 147,000 1,430 1,79003104760 6,26014,100 1913-32 B 4,510 45,300 8,10003106000 1969-80 1,310 B 5,360 2,05003106500 2,390 2,180 1,590 15,900 59,000 67,700 1916-96 7,180 B 5,010 5,610 9,710 15,700 1912-69 B 5,72003108000 2,340 86,200 70,600 2,610 19,900 16,500 2,120 2,630 B 5,970 9,460 6,470 19,800 11,500 102,000 1916-96 B 480 83,30004213000 5,950 21,300 340 12,600 3,230 118,00004213040 3,870 119,000 16,800 6,65022,900 13,200 16,400 A 1923-95 616 7,34004213200 704 162,000 8505,390 25,300 15,100 1961-95 6,140 22,500 430 5,020 16,100 26,200 1969-85 B 6,820 7,290 1,1707,170 887 9,490 1,650 17,000 29,700 27,300 909 B 4,260 6,520 18,400 34,200 11,100 B 500 8,490 2,290 8,680 32,800 1,1301,4508,670 1,010 19,000 41,600 5,030 1,150 13,600 280 4,900 20,600 1,380 10,300 48,200 1,4201,760 9,770 2,860 1,310 8,27013,600 23,800 5,570 1,910 580 6,080 15,500 3,84018,100 26,000 15,000 16,000 3701,700 3,510 2,300 2,670 9,740 1,560 11,100 6,110 21,400 4,440 6,990 14,300 17,400 17,800 760 10,800 5,400 1,840 1,940 14,400 14,300 23,900 7,270 440 17,700 7,940 19,500 4,840 21,900 11,800 17,700 26,300 2,550 20,400 2,190 10,300 23,400 5,230 11,800 14,100 316 20,300 520 32,000 23,200 7,680 15,800 2,780 23,000 6,010 416 30,600 19,100 9,510 710 29,800 22,800 497 11,000 1,020 33,200 12,500 1,340 256 585 16,300 1,590 326 812 1,880 380 2,620 437 572 Geological streamflow-

Appendix 2. stations used in analysis— [All flood flows in cubic feet per second; water year, 12-month period October 1-September 30]