Magnitude and Frequency of Floods in Western Oregon · A method for estimating the magnitude and frequency of floods is presented for un regulated streams in western Oregon. Equations
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Magnitude and Frequency of Floods in Western Oregon
By D. D. Harris, Larry L. Hubbard, and Lawrence E. Hubbard
U.S. GEOLOGICAL SURVEY Open-File Report 79-553
Prepared in cooperation with theOREGON DEPARTMENT OF TRANSPORTATION,HIGHWAY DIVISION
1979
UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary
GEOLOGICAL SURVEY H. William Menard, Director
For additional information write to:
U.S. GEOLOGICAL SURVEY P.O. Box 3202 Portland, Oregon 97208
ContentsPage
ABSTRACT ------------------------------------------ 1
INTRODUCTION --------------------------------------- 1
Purpose and scope --------------------------------- 2
Previous studies ----------------------------------- 2
GENERAL DESCRIPTION OF THE AREA ---------------------- 2
ANALYTICAL TECHNIQUE ------------------------------- 4
Drainage-basin characteristics --------------------------- 4
Magnitude and frequency of floods at gaged sites -------------- 5
Regression analysis --------------------------------- 5
APPLICATION OF RESULTS ------------------------------ 6
Method used ------------------------------------ 6
Evaluation of estimates ------------------------------ 8
Illustrative problems -------------------------------- 10
Limitations ------------------------------------- 13
SUMMARY ----------------------------------------- 14
SELECTED REFERENCES -------------------------------- 15
in
IllustrationsPage
Plate 1. Map showing locations of gaging stations in western Oregon - - - - In pocket
2. Map showing isopluvial of 2-year, 24-hour precipitation in tenthsof an inch for western Oregon --------------------- In pocket
Figure 1. Index map showing flood-frequency regions of western Oregon - - 3
2. Graph showing maximum observed peak discharges in relationto drainage areas ----------------------------- 9
3. Graph showing flood-frequency curve developed by regionalanalysis for the Willamette Region ------------------ 12
Tables
Page
Conversion factors ----------------------------- v
Table 1. Regional flood-frequency equations ------------------- 7
2. Basin characteristics used in multiple regression ----------- 16
3. Maximum discharges at gaging stations used in western Oregonflood-frequency analysis ------------------------ 23
4. Discharges for selected flood frequencies at gaging stations - - - - 29
IV
Conversion factors for inch-pound system and International System Units (SI)
[For use of those readers who may prefer to use metric units rather than inch-pound units, the conversion factors for the terms used in this report are listed below:]
Multiply inch-pound units By To obtain metric unit
Length
inch (in.) foot (ft) mile (mi)
25.40 0.3048 1.609
millimeter (mm) meter (m) kilometer (km)
Area
square mile (mi2 ) 2.590 square kilometer (km2 )
Specific combinations
cubic foot per second (ft 3 /s) 0.0283 cubic meter per second(m3 /s)
Afagnitude and Frequency of Floods in Western Oiegon
By D. D. Harris, Larry L. Hubbard, and Lawrence E. Hubbard
ABSTRACT
A method for estimating the magnitude and frequency of floods is presented for un regulated streams in western Oregon. Equations relating flood magnitude to basin charac teristics were developed for exceedance probabilities of 0.5 to 0.01 (2- to 100-year recur rence intervals). Separate equations are presented for four regions: Coast, Willamette, Rogue-Umpqua, and High Cascades.
Also presented are values of flood discharges for selected exceedance probabilities and of basin characteristics for all gaging stations used in the analysis. Included are data for 230 stations in Oregon, 6 stations in southwestern Washington, and 3 stations in north western California. Drainage areas used in the analysis range from 0.21 to 7,280 square miles. Also included are maximum discharges for all western Oregon stations used in the analysis.
INTRODUCTION
A special need for updated flood-frequency information for Oregon results from recent emphasis on flood-plain zoning, flood insurance, and design adequacy of hydraulic struc tures. Studies of flood magnitude and frequency are based on analyses of available stream- flow records. Very few long-term records for streams with less than 10 mi2 of drainage area were available when the last flood-frequency reports were prepared for Oregon by the U.S. Geological Survey. Many data have been collected since a small-stream flood-data program was started in 1952 in cooperation with the Oregon State Highway Commission (now Oregon Department of Transportation, Highway Division). This program was ex panded in 1965, through funds provided by the U.S. Forest Service, to include many pre viously unsampled areas in national forests. Inclusion of these data has enlarged the flood- data base, both areally and in range of basin size.
This analysis was limited to western Oregon, because of the large number of gaging- station records available for the western part of the State and the deficiency of peak-flow information for many areas of the eastern part. Limiting the analysis to western Oregon allows timely use of urgently needed flood information in a rapidly developing area. An eastern Oregon flood-frequency analysis will be presented in a later report.
In describing flood frequency in this report, the term "exceedance probability" is used in preference to the term "recurrence interval." However, both terms are used in most of the tables, graphs, and illustrative problems. For example, a flood with a 0.01 exceedance probability is a flood that has one chance in a hundred of being exceeded in any one year. This is a 100-year flood under the "recurrence interval" terminology.
1
Purpose and Scope
This report describes methods for evaluating the magnitude and frequency of floods at sites on streams with natural flow. The purpose is to provide a method to estimate flood magnitude and frequency at ungaged sites in western Oregon. The report is based on data from all unregulated streams (or data from regulated streams prior to their regulation) where gaging stations have been operated for at least 10 years.
Records at the gaging stations provided the basis for estimating flood-peak discharges and frequency of occurrence at ungaged sites. Stations used in this analysis have records ranging from 10 to 70 years. Peak-flow records of 230 gaging stations are available for western Oregon, 73 of which are crest-stage gaging stations that have drainage areas as small as 0.21 mi2 . Locations of the gaging stations are shown on plate 1.
The magnitude of a flood is influenced by physiographic characteristics of the drainage basin. These characteristics, which include climate, topography, geography, soils, and vege tation, are referred to as basin characteristics throughout this report.
Multiple-regression analysis was used to correlate flood discharges with selected basin characteristics and to develop appropriate regional relation equations. Although many basin characteristics were determined and investigated, the number retained in the equations was reduced for simplicity and practicality, without undue sacrifice of the accuracy of the flow estimate. The characteristics used were selected on the basis of the results of prior investi gations, ease of determination, and the results of the regression analysis.
Previous Studies
A previous flood-frequency report by Hulsing and Kallio (1964), covering the Pacific slope basins in Oregon and lower Columbia River basin, contains peak-flow records for 173 gaging stations in western Oregon. Of these, 22 are for crest-stage gaging stations on small streams.
Regression equations for flood-peak discharge are presented in a report, "Evaluation of the streamflow data program in Oregon" (Lystrom, 1970), that is based on data from all stations with 10 or more years of record of unregulated flow through the 1967 water year (October 1966 through 1967).
GENERAL DESCRIPTION OF THE AREA
The area studied includes all that part of Oregon west of the crest of the Cascade Range. The principal physiographic areas in western Oregon include the Coast and Cascade Ranges and the Willamette, Rogue, and Umpqua River valleys, as shown in figure 1.
The western slope of the Coast Range is influenced directly by ocean-spawned storms and weather. Annual precipitation is commonly 60 to 80 in. in the area; some coastal mountains receive as much as 200 in. (U.S. Weather Bureau, 1964). Snowmelt is not nor mally a major factor in flooding.
In the Willamette, Rogue, and Umpqua River valleys, high streamflows are created by storms from the Pacific Ocean. High flows in some streams draining from the Cascade Range frequently are caused by runoff from snowmelt in combination with direct rainfall runoff. The proportional contributions from each source are difficult, if not impossible, to identify. Annual precipitation amounts range from lows of less than 20 in. in the Rogue River basin to more than 100 in. in the lower elevations of the Cascade Range.
In the higher elevations of the Cascade Range, flood peaks are predominantly from snow- melt runoff combined with heavy rainfall runoff. Much of the precipitation in this area falls as snow in late fall, winter, and early spring. Annual precipitation ranges from less than 20 in. in the south to more than 100 in. in the north.
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ANALYTICAL TECHNIQUE
Flood-frequency characteristics for gaged sites were related to drainage-basin charac teristics by the multiple-regression technique to define regional flood magnitude- frequency relations.
Drainage-Basin Characteristics
The drainage-basin characteristics computed for each gaging station and used as an independent variable in the multiple-regression study are listed in table 2 at the back of the report and are defined as follows:1. Drainage area (A), in square miles, the total contributing area upstream from the
gaging-station site, as shown in the latest Geological Survey water-resources data reports.
2. Main-channel slope (S), in feet per mile, determined from elevations at points 10 and 85 percent of the distance along the channel from the gaging station to the divide. This index was described and used by Benson (1962b, 1964).
3. Main-channel length (L), in miles, from the gaging station to the basin divide,measured in accordance with guidelines given by the U.S. Water Resources Council (1968) or taken in part from the various River Mile Index publications prepared by the Hydrology and Hydraulics Committee of the Pacific Northwest River Basins Commission (1963-68).
4. Mean basin elevation (E), in feet above mean sea level, determined by the gridmethod from quadrangle map of a practical scale by laying a grid over the map, recording the elevation at each grid intersection, and averaging those elevations. The grid spacing was selected to give at least 25 intersections within the basin boundary.
5. Area of lakes and ponds (ST), expressed as a percentage of the drainage area, determined from the most recent quadrangle maps available.
6. Forest cover (F), expressed as the percentage of the drainage area covered by forests, as shown on the most recent quadrangle maps available.
7. The values of soils index (SI), determined from a map compiled from computed values of soils indexes according to procedures described by the Soil Conserva tion Service (1959, 1964). Data for these computations were derived from soils- association and land-use maps included in the Columbia North-Pacific Framework Study (unpub. manuscript). Data were also furnished by the Soil Conservation Service staff, State office, Portland, Oreg.
8. Azimuth (AZ), in degrees from north, of a straight line connecting points 85 and 10 percent of distance from gage to divide.
9. Latitude at gage (LAT). Latitude of stream-gaging station in decimal degrees.10. Longitude of gage (LONG). Longitude of stream-gaging station in decimal degrees.11. Mean annual precipitation (P), in inches, determined from an isohyetal map pre
pared by the National Weather Service River Forecast Center, Portland, Oreg., (U.S. Weather Bureau, 1964), using adjusted climatological data (1930-57) and values derived by correlation with other physiographic factors.
12. Precipitation intensity (I), defined as the maximum 24-hour rainfall having a recur rence interval of 2 years (2-year, 24-hour rainfall), expressed in inches. These values were determined by the grid method, using plate 2 which was prepared by U.S. National Oceanic and Atmospheric Administration (NOAA) (1973).
13. Temperature index (TI), the mean minimum January temperature, in degrees Fah renheit, in the basin. This value was determined from a U.S. Weather Bureau publication (Sternes, 1960).
Magnitude and Frequency of Floods at Gaged Sites
Methods for estimating flow frequencies at gaged sites, presented in "Guidelines for Determining Flood Flow Frequency," published by the U.S. Water Resources Council (1977) were used in this study. Data from 230 gaging stations in Oregon, 6 in south western Washington, and 3 in northern California, representing basins that have virtually natural flow conditions and 10 years or more of record, provided the basic dependent variables (annual peak discharge). Historic flood information was used, when available, to supplement the systematic gaging-station record. For each station, the logarithms of the annual peaks were used to compute the mean, standard deviation, and skew co efficient that describe a log-Pearson Type-Ill distribution.
Frequency data from the log-Pearson Type-Ill frequency curve for each station are presented in table 4 at the back of the report. It lists flows for exceedance probabi lities of Q0 . 5 (2 yr), Q0 .2 (5 yr), Q0 . 10 (10 yr), Q0 . 04 (25 yr), Q0 . 02 (50 yr), and Q0>01 (100 yr). The figures in parentheses are the corresponding recurrence intervals. As an example, if a flow of 900 ft3 /s is shown under an exceedance probability of 0.5 in the table, it means that there is a 50 percent chance that the flow at the gaging station will exceed 900 ft 3 /s in any one year. Another way of describing the same peobability is that a 900-ft 3 /s flow has a 2-year recurrence interval. A flow shown under an exceedance probability of 0.01 has a 1 percent chance of being exceeded in any one year. (It could be described as having a 100-year recurrence interval.)
Regression Analysis
Multiple-regression analyses were used to define equations expressing flood discharges of selected exceedance probabilities as a function of the basin characteristics. This relation may be expressed by the mathematical model
QT=K Ci a C2 b C3 C . . . Cnnin which Qj is the discharge for a selected exceedance probability, T; K is a regression constant; C l , C 2 , C 3 , and Cn are basin characteristics; and a, b, c, and n are regression coefficients. A step-backward regression analysis of the variables was made using a STATPAC data matrix. The least significant independent variable (basin characteristic) was deleted at each step. An evaluation of the standard errors for the various steps of the multiple regression was made to determine the most suitable regional equation.
The program computes the logarithms of the regression constant, the exponents of the independent variables, and the logarithm of the standard error of estimate.
Data for the 230 gaging stations in western Oregon were used for the "first try" of regression equations. The residuals (the difference between the logarithms of the flood discharges estimated from the gaging-station record and the logarithms of the flood dis charges estimated from the regression equations) were plotted on a map of western Oregon. This plot and topographic maps were evaluated to delineate the boundaries of the four flood-frequency regions selected for use in the regression analysis. These four regions (Coast, Willamette, Rogue-Umpqua, and High Cascades) are shown in figure 1. Flood-frequency equations were then developed for each of these regions.
Few gaging-station data for the extreme southern end of the Oregon coast are usable for flood-frequency analysis. Peak-flow and basin-characteristics data for three gaging stations at the extreme northern end of the California coastal area were used to supplement the Oregon coast data. To determine the flood-frequency equations for the Coast Region, data from 37 stations in Oregon and three in California were used in the multiple-regression analysis.
To develop the flood-frequency equation for the Willamette Region, peak-flow and basin-characteristics data from six stations across the Columbia River in Washington were used to supplement data from 105 stations in Oregon.
Data from 60 Oregon stations in the Rogue-Umpqua Region and from 28 Oregon stations in the High Cascades Region were used to develop the respective regional equations.
The final regression equations for each of the four regions are shown in table 1. These equations relate floods having exceedance probabilities of Q0 5 , Q0 2 > QOIO' Q004 , Q002 , and Q001 to selected basin characteristics in each of the flood-frequency regions shown in figure 1. The general form of the equation and the standard error of estimate is also shown in table 1.
Drainage area (A) and precipitation intensity (I) were selected as the most signi ficant independent variables for the flood-frequency equation for the Willamette Region. Drainage area, precipitation intensity, and area of lakes and ponds (ST) were selected as the most significant independent variables for the Coast and Rogue-Umpqua Regions. For the High Cascades Region, drainage area, area of lakes and ponds, pre cipitation intensity, and nonforested areas proved to be the most significant indepen dent variables to use in the flood-frequency equation. In the frequency equation for the High Cascades Region, nonforested area is expressed as a function of forest cover (F).
Soils index and azimuth were not used in the final regression analysis. These two basin characteristics were not found to be significant in preliminary analysis, which was based strictly on data for Oregon stations.
APPLICATION OF RESULTS
Method Used
The design flow or peak discharge for selected exceedance probabilities (or recurrence intervals) can be estimated for sites on unregulated streams in Oregon by using the method described below.1. Locate the site on the map (pi. 1, in pocket) and determine which region it is in and
if it is on a gaged stream.a. If the site is at a gaging station used in this analysis or is on the same stream as
a gaging station used in this analysis and has a drainage area within 5 percent of that at the gaged site, USE THE GAGING-STATION DATA DIRECTLY FROM TABLE 4.
b. If the site is on a stream that has a gaging station listed in this report but has a drainage area estimated at 5 to 25 percent different from that at the gaging station, adjust the peak discharges of the gaged site (table 4) on the basis of drainage area by using the following equation: Qu =Qg (Au/Ag)a , where Qu and Qg are the discharges at the ungaged and gaged sites, Au and Ag are the drainage areas, and "a" is an exponent. The value for "a" can be selected from the expo nents for the drainage area (A) given in the equation in table 1.
2. If the site is on an ungaged stream or if the site is on a gaged stream shown in table 4 but the drainage area at the site differs by more than an estimated 25 percent from the drainage area at the gaging station, thena. Inspect the applicable regional equations in table 1 and identify which basin
characteristics are needed to estimate discharge for selected exceedance probabi lities.
Table {.-Regional flood-frequency equations
General form of equation QT=KAa(ST+l)b(101-F)cId where Qj=discharge for selected exceedance probability,K = regression constant,A = drainage area, in square miles,
ST = area of lakes and ponds, in percent,F = forest cover, in percent, andI = precipitation intensity, in inches.
(When the functions of F and ST are not significant, the factors (ST+l)b and (101-F)C are omitted from the equation.)
Exceedanceprobability
(RDL/
Qo.s(2)Qo. 2 (5)QQ j(10)
Qo.04 (25)Qo.o 2 (50)Q0 . 01 (100)
Equation
Percentstandard
error
(1) COAST REGION (40 stations)
4.59A°-96 (ST+l)-°-4S I 1 - 916.27A°-9S (ST+l)-°-4S I 1 - 9S7.32A°-94 (ST+l)-°-4s I 1 - 978.71A°-93 (ST+l)-°-4S I 1 - 999.73A°-93 (ST+l)-°-44 I 2 - 0110.7A°-92 (ST+l)-°-44 I 2 - 02
333233343537
(2) WILLAMETTE REGION (111 stations)
Qo.s(2)Qo. 2 (5)Q0 j(10)
Qo.04 (25)Qo.02 (50)Q0 . 01 UOO)
8.70A0 - 87 ! 1 - 7115. 6A°-88 I 1 - 5521. 5A0 - 88 ! 1 -4630.3A0 - 88 ! 1 - 3738.0A0 - 88 ! 1 - 3146.9A0 - 88 ! 1 - 25
3333
33343637
(3) ROGUE-UMPQUA REGION (60 stations)
Qo.s(2)Qo. 2 (5)Qo.i( 10 )
Qo.04 (25)Qo.02 (50)Qo.oidOO)
24.2A°-86 (ST+1)- 1 - 16 I 1 - 1536.0A°- 88 (ST+1)- 1 - 2S I 1 - 1544.8A°- 88 (ST+1)- 1 - 28 I 1 - 1456.9A°- 89 (ST+1)- 1 - 31 I 1 - 1266.7A°- 90 (ST+1)- 1 - 33 I 1 - 1077.3A°-90 (ST+1)- 1 - 34 I 1 - 08
4443444649
51
(4) HIGH CASCADES REGION (28 stations)
Qo.s(2)Qo. 2 (5)QoaOO)Qo.o4 (25)Qo.o 2 (50)Qo.oiOOO)
4.75A°-90 (ST+l)-°-62 (101-F)0 - 11 I 1 - 178.36A°- 86 (ST+l)-°- 81 (lOl-F) 0 - 08 ! 1 - 3011.3A0 - 8s (ST+l)-°-92 (101-F) 0 - 07 I 1 - 3715.4A°- 83 (ST+1)- 1 - 03 (101-F)°-OS I 1 -4618.8A°-82 (ST+1)- 1 - 10 (101-F)°-04 I 1 - S222.6A°- 81 (ST+1)- 1 - 17 (101-F)°-03 I 1 - S7
55505359
6672
]_/ Numbers in parentheses refer to recurrence intervals in years.
7
b. Determine the appropriate basin-characteristic values as follows:Drainage area (A) Compute the drainage area, in square miles, within the
surface-water divide upstream from the desired site on the stream, using the best available topographic map, generally U.S. Geological Survey ll/2- or 15- minute quadrangle maps. Determine the drainage area by planimetering.
Area of lakes and ponds (ST) Compute the percentage of the total drain age area occupied by lakes and ponds, using a planimeter or a transparent grid overlay on T/2- or 15-minute topographic maps. In the equation, the value (ST+1) is used to avoid introducing zero values that cannot be accom modated in the equations used in this study.
Forest-cover index (F) Compute the percentage of the total drainage area covered by brush or trees, as indicated by the extent of green overprint (vegetation) shown on U.S. Geological Survey topographic maps.
The value of 101-F is used in the equation for the High Cascades Region to reflect the percentage of "nonforest" cover. The value 101 is used rather than 100 to avoid having to deal with the logarithm of zero values. The use of nonforest cover rather than forest cover provided the most prac tical equation fit.
Precipitation intensity (I) Determine the maximum 2-year, 24-hour precipi tation, in inches, on plate 2 of this report by using the grid method as des cribed under drainage-basin characteristics section for mean basin elevation on page 11.
c. Compute the peak discharge for the desired exceedance probabilities, or recur rence intervals, directly through the use of the appropriate regional equations.
d. Compare, for reasonableness, the estimated peak discharge values particularlythose for small probabilities (long recurrence intervals) with (1) maximum peak discharges for nearby streams (table 3 at the back of the report) and (2) other maximum observed discharges (fig. 2).
Peak discharges for exceedance probabilities between 0.5 and 0.01, other than those shown in the equations, can be determined either by plotting station values from table 4 or by plotting computed values from the equa tions on probability paper and drawing a smooth curve through the points. Peak discharges for other exceedance probabilities can then be estimated from the curve.
Extrapolation of peak discharges for exceedance probabilities greater than 0.01 (the 100-year flood) exceeds the limits of this study. Such derived values should be qualified and used judiciously.
Evaluation of Estimates
Peak discharges estimated from the regression equation can be evaluated for credibi lity by comparison to maximum observed peak discharges for streams with similar drain age areas in the same regions. Maximum observed peak discharges for all gaging stations used in the analysis are listed in table 3. Figure 2 shows the maximum observed peak discharges for long-term gaging stations in western Oregon in relation to drainage area. Figure 2 also shows a maximum envelope curve developed by Matthai (1969). For drain age areas between 1 and 200 mi 2 , the equation for the Matthai curve is Q=11,OOOA°-61 . Also shown are the observed discharges that have the highest unit runoff measured in
Oregon and the highest peak discharges observed throughout the United States. Figure 2 can be used to judge the reasonableness or uniqueness of flood-peak discharges esti mated by use of flood-frequency equations. For example, if the 0.02 (50-year) flood discharge estimated for a site with a drainage area of 10 mi2 was 10,000 ft 3 /s, a com parison with figure 2 indicates the discharge could be too high for western Oregon. The user might then check the computations and also decide that the regional equations are not applicable if the basin being studied is not typical of the region.
On some streams the geology of the drainage basin can have a large effect on the magnitude of the flood peak. An example is the Clearwater River above Trap Creek near Toketee Falls (14314500) in the Umpqua River basin. Most of the Trap Creek drainage is located in a geologic area of recent volcanics (Wells and Peck, 1961). Ob served flood peaks at the Clearwater River above Trap Creek gaging station are much smaller in magnitude than are indicated by the regional equation. It appears that
1,000,000
UPPER LIMIT OF 1965 DATA (MATTHAI, 1969)
A North Carolina
EXPLANATION
Record peaks National
Record peaks Oretqon
1. Butter Creek tributary near Echo, OR2. Lane Canyon near Ecnp, OR3. Meyers Canyon near Mitchell, OR
O Maximum peaks at all stations in Western Oregon with at least 50 years of record and 10 square mile drainage areas, or 25 years of record and 10 square mile drainage area
10 100 DRAINAGE AREA, IN SQUARE MILES
1000 10,000
Figure 2.-Maximum observed peak discharges in relation to drainage areas.
peaks at this gaging station are greatly diminished because of temporary ground-water storage. Numerous springs along the Clearwater River above Trap Creek tend to support this assumption. Other streams in similar recent volcanic geology will probably respond in the same manner. Therefore, the geology map should be consulted to evaluate the possibility of the actual flood peaks differing from those indicated by the regional equation because of the local geology.
Some of the older peak discharges used in this analysis were based on once or twice daily gage readings which may be lower than the actual instantaneous peak and there fore would not represent the highest discharge during the day. The effect of such peaks on the analysis has not been thoroughly evaluated; however, because only about 2 percent of the peaks were determined in this manner, their use likely has little influence on the resulting equations.
Weather stations are sparsely located in the High Cascades Region; therefore, the precipitation intensity values shown on plate 2 are probably somewhat less reliable for the High Cascades than for the other three flood-frequency regions, where there are more precipitation gages. This lack of basic precipitation data probably contributed to the higher standard error for the High Cascades Region. This higher standard error may also be attributed to the lack of regional snowpack information. No basin charac teristics for snowpack were available for the regression analysis; however, it would be reasonable to assume that snowpack would influence the flood-frequency equations for the High Cascades.
Illustrative Problems
The method for estimating discharges of selected recurrence intervals is shown by thefollowing examples:
Example 1. (Determining a single flood in an ungaged area)Determine the discharge for an exceedance probability of 0.01 (100-year flood) for
a site in the Coast Region, where the drainage area is 20 mi2 and the area of lakes and ponds is 1.2 percent of the drainage area. According to the precipitation intensity map (pi. 2, in pocket), the site is at a location where the average 2-year, 24-hour precipita tion intensity over the drainage basin is 4.0 in.
From the Coast Region equation (see table 1), the 0.01 exceedance probability flood is:Q0 . 01 =10.7A0 -92 (ST+l)-°-44 I 2 -02
=(10.7)(20)°-92 (2.2)-°-44 (4) 2 -02
=(1Q.7)(15.7)(16.4)(1.41)
= 1,950 ft3 /s
Example 2. (Determining two floods in an ungaged area)Determine the discharge for exceedance probabilities of 0.5 and 0.1 (2- and 10-year
floods) for a site on a stream in the High Cascades Region. The drainage area is 9.8 mi2 ; the area of lakes and ponds (ST) is 2.5 percent; forest cover (F) is 96 percent; and the average 2-year, 24-hour precipitation intensity is 3.2 in.
From the High Cascades Region equation, the 0.5 exceedance probability flood is:
.17Q05 =4.75A0 - 90 (ST+l)-°-62 (101-F)0 - 11 I 1J=4.75(9.8)0 - 90 (2.5+l)-°-62 (101-96)0 - 11 (3.2) 1 - 17
=(4.75)(7.80)(0.46)(1.19)(3.90) =79 ft 3 /s
10
From the High Cascades Region equation, the 0.1 exceedance probability flood is:
= 11.3(9.8)0 - 85 (2.5+l)-°-92 (101-96)0 - 07 (3.2) 1 - 37
= 11.3(6.96)(0.32)(1. 12)(4.92)= 139 ft3 /s
Example 3. (Developing a flood-frequency curve)Develop a flood-frequency curve for a site in the Willamette Region. The drainage
area is 230 mi2 ; and the average 2-year, 24-hour precipitation intensity is 3.1 in.Based on the above basin characteristics, develop a flood-frequency curve by com
puting the flood discharges for Q0 5 , Q0 2 , Q 0 A , Q04 , Q 0 . 02 > m & QO.OI exceedance probabilities, as shown below:
=8.70(230)°- 87 (3.1) 1 - 71
=(8.70)(1 13)(6.92) =6,800 ft 3 /s
= 15.6(230)°-88 (3.1) 1 - 55
=(15.6)(120)(5.78) = 10,800 ft 3 /s
Q0 . 1 =21.5(A)°- 88 (I) 1 -46 =21.5(230)°- 88 (3.1) 1 - 46
=(21.5)(120)(5.22) = 13,500 ft 3 /s
Q0 . 04 =30.3(A)°- 88 (I) 1 - 37=30.3(230)°- 88 (3.1) 1 - 37
=(30.3)(120)(4.71) = 17,100 ft 3 /s
=38.0(230)°- 88 (3.1) 1 - 31
=(38.0)(120)(4.40) =20,100 ft 3 /s
Q0 . 01 =46.9(A)°-88 (I) 1 -25=46.9(230)°- 88 (3.1) 1 - 25
=(46.9)(120)(4.11) =23,100 ft 3 /s
11
Then plot the flood discharges on probability paper at the respective exceedance positionsand draw a smooth curve through the points, as shown in figure 3.Example 4. (Determining the exceedance probability or recurrence interval for a selecteddischarge)
Using the curve developed in example 3 (fig. 3), determine the exceedance probability and recurrence interval for a peak discharge of 16,000 ft3 /s.
At the 16,000-ft3 /s discharge magnitude on the graph, project horizontally to the frequency curve. Project up vertically at the intersection with the curve and read an ex ceedance probability of 0.05 and project down vertically and read a recurrence interval of 20 years.
EXCEEDANCE PROBABILITY
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mD O
LU O QC
I O
100,000
50,000
0.01
20,000
10,000 -
5,000
2,000
1,0005 10 25
RECURRENCE INTERVAL, IN YEARS
100
Figure 3. Flood-frequency curve developed by regional analysis for an example computation at an ungaged site in the Willamette Region (example 3).
12
Example 5. (Determining a flood on a stream near an existing gaging station)Determine the discharge for an exceedance probability of 0.01 (the 100-year flood)
for a site upstream from the existing long-term gaging station on Salmon Creek near Oakridge (No. 1414650) in the Willamette Region. The gaged site has a drainage area of 117 mi2 , and the selected site has a drainage area of 100 mi2 . Therefore, the drainage areas differ by more than 5 percent but less than 25 percent. The flood for an exceed ance probability of 0.01 at the gaged site (table 4) is 14,000 ft3 /s. Use the relationship Q =Q (Au/Ag)a . The exponent "a" for an exceedance probability of 0.01 in the Willamette Region is 0.88.
Qu =Qg (Au/Ag)
=(14,000)(0.85) =(14,000)(0.87)
= 12,200 ft3 /s
0.88
Limitations
The equations in this report, developed through regional analysis, are usable, under certain limitations, for estimating flood magnitudes of selected exceedance probabilities or recurrence intervals at ungaged sites in western Oregon.
The equations are based on data representing natural flood conditions and are not appli cable to streams where storage or artificial structures have modified the flow appreciably such as sites downstream from large storage reservoirs. In general, the equations are not appli cable at any site where flow from 10 percent or more of the drainage basin is controlled.
Ranges of characteristics used for defining equations for each region are:
Region
1.2.3.4.
Drainagearea(A)
(mi2 )
Area oflakes and
ponds(ST)
(percent)
Forestcover
(F)(percent)
Precipitationintensity
(I)(in.)
Coast 0.27- 667 0-18.81 - - 3.0-6.2Willamette 0.37-7,280 - - - - 2.3-5.0Rogue-Umpqua 0.75-3,939 0- 4.40 - - 2.5-6.2High Cascades 0.21- 650 0- 3.65 48-100 1.4-4.3
Extrapolation beyond the limits of the data used for defining relationships is not advisable. Such extrapolations could produce erroneous discharge values. However, if extrapolations are made they should be used judiciously and qualified accordingly.
13
SUMMARY
The study describes a method for estimating the magnitude and frequency of floods on natural streams in western Oregon. The equations were developed by regional multiple- regression analysis. An evaluation of the differences between the flood discharges estimated from the gaging-station records and the discharges determined from the general regression equation were used to help delineate boundaries for four flood-frequency regions in western Oregon.
Drainage-area size was the most significant basin characteristic for all four of the flood- frequency regions in western Oregon. Precipitation intensity was also a significant basin characteristic for all the regions. By utilizing only the drainage-area size and precipitation intensity for the Willamette Region, the standard error of estimate ranged from 33 to 37 percent, as shown in table 1. The area of lakes and ponds was used in addition to drainage- area size and precipitation intensity in the flood-frequency equation for the Coast and Rogue- Umpqua Regions. The standard error of estimate ranged from 32 to 37 percent in the Coast Region and from 43 to 51 percent in the Rogue-Umpqua Region.
The standard errors of estimate were greatest in the High Cascades Region, where the range was 50 to 72 percent. Four basin characteristics (drainage area, precipitation inten sity, area of lakes and ponds, and forest cover) were required to reduce the standard error significantly in this region.
When used within the range of data used to define the relationships, the regional flood- frequency equations provide reasonably accurate estimates of floodflows of specified ex- ceedance probabilities.
14
SELECTED REFERENCES
Benson, M. A., 1962a, Evolution of methods for evaluating the occurrence of floods: U.S.Geological Survey Water-Supply Paper 1580-A, 29 p.
____1962b, Factors influencing the occurrence of floods in a humid region of diverseterrain: U.S. Geological Survey Water-Supply Paper 1580-B, 64 p.
____1964, Factors affecting the occurrence of floods in the Southwest: U.S. Geological Survey Water-Supply Paper 1580-D, 72 p.
Columbia Basin Inter-Agency Committee, 1963, River mile index-Willamette River, ColumbiaRiver basin, Oregon: Hydrology Subcommittee report, 57 p.
_____1966, River mile index - Umpqua River and tributaries, Umpqua River basin, Oregon:Hydrology Subcommittee report, 25 p.
____1967, River mile index - Rogue River, Pacific slope basin, Oregon: Hydrology Subcommittee report, 28 p.
Friday, John, 1974, Cres,t-stage gaging stations in Oregon, A compilation of peak datacollected from October 1952 to September 1974: U.S. Geological Survey open-filereport, 160 p.
Hardison, C. H., 1971, Prediction error of regression estimates of streamflow characteristics atungaged sites, in Geological Survey Research, 1971: U.S. Geological Survey ProfessionalPaper 750-C, p. C228-C236.
Hulsing, Harry, and Kallio, N. A., 1964, Pacific slope basins in Oregon and lower ColumbiaRiver basin, part 14 of Magnitude and frequency of floods in the United States: U.S.Geological Survey Water-Supply Paper 1689, 320 p.
Lystrom, D. J., 1970, Evaluation of the streamflow-data program in Oregon: U.S. GeologicalSurvey open-file report, 28 p.
Matthai, H. F., 1969, Floods of June 1965 in South Platte River basin, Colorado: U.S.Geological S.urvey Water-Supply Paper 1850-B, 64 p.
Pacific Northwest River Basins Commission, 1968, River mile index - Coastal tributaries,Pacific coast basin, Oregon: Hydrology and Hydraulics Committee report, 84 p.
Riggs, H. C., 1968, Some statistical tools in hydrology: U.S. Geological Survey Techniques ofWater-Resources Investigations, book 4, chap. Al, 39 p.
_____1968, Frequency curves: U.S. Geological Survey Techniques of Water-Resources In vestigations, book 4, chap. A2, 15 p.
_____1973, Regional analyses of streamflow characteristics: U.S. Geological Survey Techniques of Water-Resources Investigations, book 4, chap. B3, 15 p.
Sternes, G. L., 1960, Climates of the States, Oregon, in Climatography of the United States:U.S. Weather Bureau, no. 60-35, p. 17.
Thomas, D. M., and Benson, M. A., 1970, Generalization of streamflow characteristics fromdrainage-basin characteristics: U.S. Geological Survey Water-Supply Paper 1975, 55 p.
U.S. Dept. of Agriculture, Soil Conservation Service, 1959, State engineering handbook, Oregon,sec. 4 in Hydrology: 10 p.
_____ 1964, Watershed planning, pt. 1 in Watershed planning, sec. 4 in Hydrology: U.S.Dept. Agriculture SCS Handb.
U.S. National Oceanic and Atmospheric Administration, 1965, Climates of the States Washing ton, of Climatology of the United States no. 60-45: Washington, D. C., 27 p.
_____1973, Precipitation-frequency atlas of the Western United States, NOAA Atlas 2,volume X - Oregon: Silver Spring, Md., 43 p.
U.S. Water Resources Council, 1967 [rev. 1977], A uniform technique for determining floodflow frequencies: Washington, D. C., U.S. Water Resources Council Bulletin 15, 15 p.
____1977, Guidelines for determining flood flow frequency: Washington, D.C., WaterResources Council Bulletin 17A, 26 p.
U.S. Weather Bureau, 1964, Mean annual precipitation, 1930-57, State of Oregon: Portland,Oreg., U.S. Soil Conservation Service Map M-4161.
Wells, F. G., and Peck, D. L., 1961, Geologic map of Oregon west of the 121st meridian: U.S.Geological Survey Miscellaneous Investigations Map 1-325, scale 1:500,000.
15
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Table 2. Basin characteristics used in multiple regressions continued
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1.00.77
0.000.000.00
0.00.27
0.000.00.19
95.692.292.098.498.0
94.085.050.097.0100.0
96.095.096.097.090.0
94.0100.090.091.098.0
92.079.097.092.091.0
95.093.083.087.084.0
96.096.0100.091.0100.0
96.090.092.085.086.0
5.65.55.65.65.6
5.43.2
5.65.25.55.04.6
4.93.23.83.73.2
4.33.43.23.22.6
3.23.12.83.85.1
5.65.55.65.65.6
5.65.33.82.84.6
320275330295265
30075
3155
300270265
29545
270260250
315345145290310
330335
5295210
300335320275295
40175240225260
45.3245.3945.4545.5045.41
45.6245.6145.5843.6043.67
43.6843.7243.7343.7643.76
43.8043.8643.9743.9443.97
44.0043.6443.7143.7443.79
43.7443.7843.8344.0544.18
44.0544.1444.2244.2144.21
44.1844.1244.1544.0944.11
121.95122.13121.8^122.01122.17
122.20122.30122.40122.46122.43
122.37122.44122.42122.37122.51
122.56122.68122.64122.77122.76
122.91123.08122.74122.87122.99
122.98123.00123.04123.03122.13
122.22122.25122.24122.26122.26
122.28122.47122.57122.96123.05
808512012596
10070446055
5858606258
5850556264
5856496056
5756555486
6570
11810490
11783927079
4.04.14.54.5
3.5
4.03.93.03.53.0
3i43.43.43.43.8
3.53.54.04.04.0
3.73.83.03.43.4
3.33.33.63.54.3
3.83.94.04.04.0
4.34.24.33.84.2
23.026.028.029.029.0
28.029.031.024.029.0
24.024.021.02**.02b.O
25.031.030.031.032.5
28.533.031.031.031.3
32.032.533.031.020.0
23.024.026.025.726.0
26.223.031.032.030.0
17
Table 2. Basin characteristics used in multiple regressions continued
Stationnumber
0
«r'« 55 ""'
A
^~ 'Ec e'
~ c,
EJfra c/is
s
"3 .crS .SJ3 ~ 0 M
.E F?3 >
S
L
>"3c
s § .2S ~
E
ac0a. a
3-* OS c
j> ^_*- *<
ST
c
E.
>o0
£10u.
F
X0 a cJ2'oC/3
SI
0V
CO11T3
3
.E_SJ<
AZ
-SJ
00
T3
a
.t^"^J
LAT
"s
1 a" a3
co
LONG
a 'o
a
c S .l§ "cao *->s
p
ccco ra .£
'o £"2- 35OH
I
X
T3C'«
3
s.~Eod> * *H
TI
(2| WILLAMETTE REGION
1416650014167000141697001417050014171000
1417150014172000141723001417350014174000
1417410014178000141788001417900014181500
1418170014182500141830001418490014185000
1418580014185900141860001418700014187500
1418880014189000141895001419000014190200
1419050014190600141910001419210014192200
1419250014192800141930001419330014194000
89.395.15.1914.6159
107105
5.06372
4640
15.22161.03106453
.411126551.35174
10499.2271
51.8640
109179034.3115
3.46
240.57
72802.724.83
1331.8164.727.4502
13.110.967.5
277.013.4
4.064.6
221.021.1
18.323.35.37.8
37.7
22.8
7407308571510925
63030.5 20604.172.9
877955
18.8 154.0 2230
10.593.3
1420.0180.066.3
529.077.453.3
714.0102.0
100.0107.071.6
129.035.7
88.036.2115.039.5
138.0
17.8124.0
15.5 26135.7 37201.5 3010
21.8 372049.1 3510
1.4 144029.5 264068.5 33501.9 1780
23.5 2870
22.0 330021.2 320032.4 297013.6 248049.4 2560
27.0 190096.8 247015.2 131028.73.7
44.91.1
1010874
910365
11.2 189.0 2150256.0227.0
40.5284.0124.0120.09.4
3.2<».o
21.12.415.19.7
49.9
630595
95062510601720750
.070.000.00
78.060.054.0
0.00 100.00.00
.030.000.000.00.03
.30
.60
82.0
42.087.059.031.071.0
0.092.0
0.00 100.0.19.33
91.590.0
0.00 100.0.36.24
95.089.6
0.00 100.0.03 92.0
.30 100.00.00 100.0.02
0.00.02
.03
.090.000.000.00
0.000.00.02
0.00.10
.080.000.000.00.10
96.083.086.0
90.078.095.089.083.0
78.014.070.037.034.0
84.054.085.099.947.0
1.91.71.23.21.9
1.04.3.8
1.93.1
.95.45.65.55.6
1.24.55.03.25.5
5.65.65.24.74.5
3.34.03.31.8.6
2.1.6
3.2.6.6
3.2.9
3.65.62.1
15340140110315
15295305300330
320160340270315
19025530510
280
300265275305285
2852905513535
9055
340105100
31540200
95
44.0544.0244.1644.5044.53
44.5044.3544.4744.6244.64
44.6444.7144.7644.7544.75
44.7544.7944.7944.3944.39
44.5244.5444.4644.3744.50
44.7144.7244.7244.7444.87
44.7844.7044.9444.9544.97
45.0545.0445.1444.9745.17
123.42123.25123.35123.44123.33
123.33122.79122.96123.13123.11
123.07122.10122.12122.13122.30
122.39122.58122.62122.51122.51
122.37122.43122.52122.62122.82
122.77123.01123.50123.42123.41
123.23123.22123.04123.08123.07
123.50123.47123.49123.45123.21
6743489178
5089505660
4280777781
69978668
101
1101101067190
5578917480
7241644344
10170.8811578
3.63.23.53.84.0
3.54.22.93.33.6
2.54.13.53.74.2
4.04.44.13.44.7
5.05.04.73.94.3
3.53.94.64.34.2
4.44.63.72.62.5
5.02.54.94.93.9
31.032.532.031.031.0
32.031.033.033.031.0
33.020.021.023.022.0
26.527.027. P28.027.0
28.02^.026.030.028.0
28.027.030.030.030.0
31.033.031.032.032.0
30.029.029.028.530.0
18
Table 2. Basin characteristics used in multiple regressions continued
Stationnumber
a
CS
S^i"§Q"
A
^
|| 5^ a-s "
s
~s ^-g£ S-c0 6GC Cs"
L
>~s 03 ' 4
XI ^
g§S ~
E
oc0o. oi ^ ^£ c°s2 o-L* ~^<
ST
e
iD.
u<
0 0
£o
u.
F
X o e
'oC/)
SI
^<uoo o
.c3E'N
<
AZ
~SJCD0
T3
-a3
3LAT
^ _
0
1 o0 a3 a
!LONG
,,i..£ 'osQ.
3 gC ^ a c
O C '-C3
S~
P
c ut:co ^
S^ §^
£
I
X oe'o
22
IF£~TI
(2) WILLAMETTE REGION
1419500014196500141970001419730014198500
1419970014200000142010001420150014202000
14202500142030001420350014203faOO14204000
1420410014204500142055001420600014206500
1420750014208000142095001420990014210000
1421080014211500142118001422350014243500
6.7048.866.83.1997.0
4.16323204
58.7479
51.043.3
1254.3133.2
1.2766.143.027.6
568
706136479
2.52671
2.2526.51.46
198.92
335.0147.095.4
518.083.1
192.040.572.3
104.023.6
96.187.376.5
121.0127.0
467.071.296.7
136.012.9
4.3136.095.3
227.060.9
107.031.9
538.073.0
375.0
5.1 23209,8 1400
12.3 12702.6 1400
17.8 2910
3.8 90944.0 191035.4 128028.6 167067.7 859
20.3 126015.9 109023.8 12603.2 940
10.5 1310
2.4 114019.3 10BO13.1 112011.1 108051.5
83.0
750
65519.3 390030.5 35703.3 1010
55.2 3350
3.013.81.6
576520818
45.2 18802.0 700
0.000.000.000.00
.02
.04
.03
.04
.01
.02
.03
.18
.09
.23
.03
0.00.03.03.03.02
.02
.22
.350.00
.29
0.00.07
0.00.01
0.00
93.978.072.5a9.080.2
71.669.947.3b3.730,1
37.348.342.392.349.2
86.659.684.680.245.7
44.297.092.12.0
91.0
25.035.899.398.098.0
4.02.52.03.23.8
.82.31.82.51.5
2.22.11.75.63.8
3.22.51.92.21.7
1.55.65.3
.94.6
.9
.7
.9
1308595
105290
345315345305
15
11512595
175115
120130175170100
110330325330315
255270
35
45.3145.3745.3745.3145.01
45.1745.2445.0645.1045.23
45.4445.4645.4745.6745.64
45.6345.5645.6345.6345.45
45.3545.02*5.1245.2845.30
45.4445.4845.5646.0446.26
123.37123.29123.25123.35122.48
122.48122.69122.83122.74122.75
123.17123.15123.12123.29123.27
123. 2b123.1ft123.04122.97122.95
122.67121.92122.07122.34122.35
122.48122.51122.74122.80122.90
10588809191
5168607355
7666596670
6563484848
4691796077
4443408280
3.54.34.03.84.0
2.53.43.33.62.9
3.92.53.43.63.6
3.53.62.62.72.8
2.73.93.83.03.8
2.82.82.34.04.8
28.029.029.028.027.0
32.031.031.031.033.0
29.029.030.02d.O28.0
29.029.031.032.031.0
32.020.023.031.025.0
32.032.034.029.039.0
14245000 119 49.0 28.8 1390 .08 99.0 46.15 122.90 69 3.5 31.0
19
Table 2. Basin characteristics used in multiple regressions continued
Stationnumber
Sa
llQ """
A
^ 3 'ge *-"a ^
If«
S
~ .c
cS
If1"
L
,>
"5
c ^n C.c
a °%*
E
73CO
a
i00
-X -~2
3. co *\L
<~
ST
^_,
0
c.~^
5!p
S3o
tu
F
X
73
'3C/1
SI
~
£to3w=
|<
AZ
~0
to73
073 3
3
LAT
5aCJ a~
73
ao
LONG
o. 'o
o.
1.1c ~~^
c!S~
P
cV
cc.2 ^~13 c
.|x
£
I
X
73 C-^
PTo
If£~
TI
(3) ROGUE-UMPQUA REGION
1430770014308000143085001430870014308900
1430900014309500143100001431070014310900
1431100014311200143115001431200014312100
1431220014312300143135001431450014315500
1431600014316500143167001431750014317600
1431780014318000143185001431860014319200
1431950014320600143207001432100014321900
1432200014322400143227001433800014339000
152449
54.455.336.9
78.086.9
45643.93.16
54.261.3
15816702.42
53.21.25
17041.6
339
68.8475227886
97.4
56.9177
1210.75
16.4
13401.28210
368026.0
10461.95.13
1331220
27.587.1
133.0460.0168.0
73.352.518. R
128.0545.0
42.3146.026.819.3
274.0
115.0236.090.5
257.069.0
187.063.660.769.6
164.0
210.0139.058.2
517.055.9
47.5188.054.66.1
23.0
28.023.0
163.0121.034.2
21.8J9.810.013.511.1
20.020.349.515.03.1
20.510.226.994.02.5
14.21.9
24.69.8
40.0
13.848.024.279.017.2
14.023.979.5
1.57.4
108.02.3
28.8170.0
7.7
19.513.23.8
20.579.5
35703130290016802100
29201990683
19601550
20501740143022301130
1080750
567051805130
48804870264039802800
2700259035201180902
3480810
13102480
700
1020800
128031003930
0.00.09.60
0.000.00
0.000.000.00
.01
.63
.020.00
.03
.020.00
.030.004.40
.162.42
.171.77
.02
.96
.02
0.00.10.44
0.00.04
.650.000.00
.25
.30
.040.000.000.001.14
97.598.091.794.098.2
95.599.395.885.776.6
84.190.777.091.978.5
48.230.294.695.695.5
95.295.899.097.179.5
84.089. b90.049.345.0
86.921.958.385.936.6
55.090.048.298.695.9
5.25.35.62.12.6
4.25.03.73.11.2
2.43.62.33.4.6
1.4.6
13.811.212.5
3.29.44.17.14.6
5.64.96.62.8
.8
5.91.82.34.11.8
2.24.72.23.53.9
245240340230350
305275350250140
22535
120270325
315230285
0270
345275210270195
225275275185285
270120255290
5
3255560
210235
42.9542.9342.8942.9742.92
42.8242.8042.9243.0343.09
43.0443.0443.1343.1343.20
43.2243.2543.3243.2443.26
43.2343.3043.3543.3343.35
43.2243.2543.3143.3243.39
43.2743.4443.4043.5943.62
43.6443.7043.6342.6642.52
122.83122.95122.92123.17123.27
123.18123.61123.43123.19123.20
123.26123.54123.461P3.40123.35
123.29123.40122.19122.29122.42
122.45122.54122.73123.00122.99
123.02123.02123.12123.17123.30
123.41123.31123.36123.55123.29
123.30123.28123.37122.75122.84
4945523739
5483593730
3548474631
3330436553
5152575256
4551503840
4945464743
4340453943
3.13.13.42.82.9
3.34.43.52.62.5
2.83.23.53.22.5
2.62.83.23.43.4
3.63.43.b3.44.1
3.53.53.53.03.0
3.43.03.33.33.0
3.33.23.03.33.2
30.031.031.032.532.0
32.030.031.033.033.0
33.030.530.532.033.0
33.033.018.020.524.0
24.020.030.027.032.0
33.032.530.033.034.0
33.534.033.732.034.0
34.034.034.028.025.0
20
Table 2. Basin characteristics used in multiple regressions continued
Station number
2aM. .
|lQ
A
£ 'gH *^j=^
||s"1
S
13 CTE Ex £5 cs"
L
E"u
c'j?S
c §s"
E
ocoo. a
V ^ ^£ co £^<^
ST
"^
C
11 '
"o
U-
F
X
T3
1'5
SI
<u ubfi
S
£3E<
AZ
1on
3 a3
3
LAT
aj
a"tT a3'Si
c3
LONG
D. 'o
D.
3.5C ^S. c
.2s"
P
cIU
co /^a ^c I'S
£ S
I
X a'u
3'H
l£
TI
(3) ROGUE-UMPQUA REGION
1433920014359000143595001436130014362000
1436300014366000143685001436980014370000
1437020014371500143723001437250014375000
1437550014377000143775001437780014376000
6.422050116
7.41223
302483
8.603.0731.4
3.1622.1393942.376.2
42.4364
22.01.62665
72.030.3158.0334.0166.0
95.364.7
475.0376.0180.0
332.0132.022.0
308.0170.0
128.0112.0333.01240.0
38.1
5.192.319.34.117.5
28.437.15.03.1
10.4
2.710.3
189.09.715.1
9.726.96.82.5
48.3
15703560271019804280
39003660322017602160
16303480310039003910
25002930337030502780
0.00.16
0.000.00.09
.07
.040.000.000.00
0.000.00.08.04.05
.02
.04
.040.00.02
48.385.099.092.894.4
95.192.195.683.790.9
99.199.689.098.196.9
92.087.096.592.087.3
1.23.63.33.22.1
2.63.23.23.23.2
3.21.23.33.23.6
3.23.23.2.6
3.1
17523523020535
30156095
140
140205250
0330
200
250200345
42.5142.4442.5842.4442.06
42.1742.2442.2742.3442.36
42.3842.6442.5842.0042.15
42.0442.2142.2642.2842.38
122.89122.99123.02123.29123.11
123.05123.14123.29123.57123.52
123.50123.21124.06123.62123.47
123.75123.66123.45123.69123.81
1835402935
3229383845
3453407457
8066434258
2.52.93.03.03.5
3.43.12.93.03.5
3.03.22.75.34.1
6.24.83.64.64.6
29.025.030.030.027.0
28.028.528.031.031.0
30.531.027.029.027.0
31.029.028.431.029.0
21
Table 2. Basin characteristics used in multiple regressions continued
Stationnumber
ua
^^
11C
A
~ly £c "^03 ^,
5.2«
S
u .dr5 E£^c cs"
L
1<uc _a £s|s~
E
acoa aS<G
-* ^~ so 'sia> ft<~
ST
c
fti_>00
1o u.
F
X ac
1
SI
1?
&o3.53E<
AZ
^$o3 a 2
'a
LAT
£
1 a' a 2
'5iico
LONG
ft '0
S, ' T*S sc ^^- c« 0C 'C
jjl **
p
c(U
co ^M.C
IS-£"
I
X a cu3
ItH
TI
(4) HIGH CASCADES REGION
141340001413450014145&901414740014158250
1415850014208500142088501420900014209100
1432749014327500143280001433050014331000
1433200014333000143335001433500014335500
1433750014339500143415001434250014343000
143470001435300014353500
8.7054.01.511.52
.21
92.454.02.30
1263.75
19.3156312
52.026.0
83.856.545.5
650138
24516.6
13820.843.8
26910.58.14
590.0135.0
1260.0670.0
1590.0
76.647.6
388.087.5
343.0
243.076.659.1
138.0311.0
134.0242.0220.061.0
141.0
109.0108.0182.0127.0217.0
144.0617.0535.0
5.215.62.02.5
.9
12.39.82.0
19.23.8
12.628.244.717.49.0
17.915.315.153.816.4
29.87.5
22.36.8
17.2
31.35.86.2
48004000413028504630
41203740423037503400
52005200490052304850
51505310529047003950
35205350444065204820
388051205040
0.00.11
0.000.000.00
.651.590.00
.080.00
0.00.16.08.84.17
.68
.360.00
.18
.34
.20
.05
.013.651.73
.360.000.00
93.193.091.376.648.0
89.097.785.286.990.1
100.096.396.698.399.2
98.599.297.796.596.6
95.398.866. 570.183.6
82.099.599.1
5.65.65.63.25.6
4.95.65.65.65.6
3.64.15.35.65.6
5.65.65.75.04.2
3.35.63.65.65.1
2.95.65.6
180325265320160
340295230265330
260225215330280
330295265255260
285285285260275
2852510
45.2745.2243.6643.8844.40
44.3645.1245.1445.0745.07
43.0042.9342.7742.7042.70
42.7142.7342.7842.7042.54
42.6542.3442.4142.3842.40
42.4742.1442.15
121.72121.86122.21122.37122.12
121.99121.80121.90121.95121.96
122.36122.43122.50122.38122.38
122.39122.40122.43122.59122.55
122.69122.36122.60122.36122.54
122.73122.72122.71
6885565095
8170606960
6056545058
5356545036
3626223431
262122
4.34.13.43.53.5
4.23.74.03.63.5
3.53.43.43.63.5
3.63.63.53.43.3
3.21.42.63.03.0
2.63.03.0
22.522.022.029.423.0
21.021.023.022.023.0
24.023.023.020.021.0
20.021.020.023.022.5
24.022.025.022.024.0
25.027.026.0
22
Table 3.-Maximum discharges at ganinu stations used in western Oregon flood-freuuency analysis
Station number
1153085011531000115330001413400014134500
1413500014137000141388001413885014141500
1414350014144000141446001414480014144870
1414490014145500141456901414600014146500
1414740014147500141480001414870014150300
1415100014151500141520001415250014153900
1415450014155500141560001415650014157000
1415800014158250141585001415900014159200
1415950014161200141615001416160014162000
Yec
Station name rec
ars f 3rd Date
MIDDLE FK SMITH RIVER TRIB. NR OBRIEN,OR 12 12-22-64MIDDLE FK SMITH RIVER AT GASQUET,CA 16 12-22-6*LOPEZ CREEK NEAR SMITH RIVER, CA 12 03-02-72SALMON RIVER NEAR GOVERNMENT CAMP, OREG. 51 12-23-64SALMON RIVEH BELOW LINNEY CREEK, OREG. 23 03-31-31
SALMON RIVER AT WELCHES, ORtG. 13 03-31-31SANDY RIVER NEAR MARMOT, OREG. 65 12-22-64BLAZED ALDER CREEK NEAR RHODODENDRON, OREG. 13 12-22-64BULL RUN R NR MULTNOMAH FALLS, OREG. 10 01-20-72LITTLE SANDY RIVER NEAR BULL HUN, OREG. 58 12-20-74
WASHOUGAL RIVER NR WASHOUGAL, WA 28 01-20-72LITTLE WASHOUGAL R NR WASHOUGAL, WA 17 12-22-64GROENVELD CREEK NEAR CAMAS, WA 15 12-22-64MIDDLE FORK WILLAMETTE RIVE* NR OAKRIDGE OREG i b 12-22-6*MIDDLE FK WILLAMETTE R TRIB NR OAKRIDGE , OREG. 16 12-22-6*
HILLS CR AB HILLS CR RES, NR OAKRIDGE , OREG. 18 12-22-64M F WILLAMETTE R AB SALT CR., NR OAKRIOGE, OREG 26 12-28-45SWAMP CREEK NEAR MCCREDIE SPRINGS, OREG. 10 12-22-64SALT CREEK NEAR OAKRIDGE , ORtG. 19 10-29-50SALMON CREEK NEAR OAKRIDGE , OREG. 50 12-22-64
TUMBLE CREEK NEAR WESTF IP, OREG. 11 12-22-64N FK OF M FK WILLAMETTE R NR OAKR IDGE ,OREG. 46 12-22-64MF WILLAMETTE R NR OAKRIDGE OREG 39 12-28-45FERN CREEK NEAR LOWELL,OREG. 21 02-10-61FALL CR. NEAR LOwELL, OREG. 13 01-21-72
FALL CREEK BL WINBERRY CR N« FALL CR,OREG. 30 12-11-56LITTLE FALL CREEK NEAR FALL CREEK OREG. 13 12-28-45MF WILLAMETTE R AT JASPER OREG 10 11-23-09COAST FORK WILLAMETTE RIVER AT LONDON, OREG. 41 12-22-6*PRATHER CREEK NEAR DISSTON, OREG. 12 02-10-61
ROW RIVER ABOVE PITCHER CREEK, NEAR DORENA,OREG. 41 12-22-64ROW RIVER NEAR COTTAGE GROVE, OREG. 11 12-28-45MOSBY CREEK NEAR COTTAGE GROVE, OREG. 11 12-28-45MOSBY CR AT MOUTH, NR COTTAGE GROVE, OREG. 30 12-22-64COAST FK WILLAMETTE R AT SAGINAW OREG. 19 02-20-27
WILLAMETTE RIVER AT SPRINGFIELD, OREG. 36 12-29-45HACKELMAN CREEK NR UPPER SODA, OREG. 16 12-11-56MCKENZIE RIVER AT OUTLET OF CLEAR LAKE, OREG. 32 12-23-64MCKENZIE R AT MCKENZIE BRIDGE, OREG. 49 01-06-23S FK MCKENZIE R AB COUGAR LK NR RAINBOW, OREG. 19 12-22-64
SOUTH FORK MCKENZIE RIVER NR RAINBOW, OREG. 16 12-28-45LOOKOUT CR TRI NO 3 NR BLUE RIVER OREG. 11 12-20-57LOOKOUT C NR BLUE R OREG 19 12-22-64LOOKOUT CR TRIB NR BLUE R,OREG. 15 12-11-56BLUE RIVER NR BLUE RIVER, OREG. 30 12-22-64
Discharge (ft'/s)
10241100
57013003670
1300061400261086104280
2260024300
10339800
82
1070034000
120450011600
982440081800
5212100
247006110
9400012500
326
331002140085201410032500
140000102
33001650018400
2450052
666075
19600
23
Table 3. Maximum discharges at gaging stations used in western Oregon flood-frequency analysis continued
Station number
14162500 14163000 14165000 14165500 14166500
14167000 14169700 14170500 14171000 14171500
14172000 14172300 14173500 14174000 14174100
14178000 14178800 14179000 14181500 14181700
14182500 14183000 14184900 14185000 14185800
14185900 14186000 14187000 14187500 14188800
14189000 14189500 14190000 14190200 14190500
14190600 14191000 14198100 14192200 14192500
14192800 14193000 14193300 14194000 14195000
Ye o
Station name re«
ars f >rd Date
MCKENZIE R NR VIDA OREG 38 12-28-45 GATE CREEK AT VIDA. OREG. 24 l?-22-64 MOHAWK RIVER MR SPRINGFIELD* OREG. 31 IP-22-64 MCKENZIE RIVER NEAR C06URG,OREG. 18 IP-29-45 LONG TOM RIVFR NEAR NOTI. 03EG. 41 1P-P2-55
COYOTE CREEK NEAR CROW, OREG. 36 02-10-61 BEAR CREEK NEAR CHESHIRE. OREG. 20 01-15-74 HOCK CREEK NEAR PHILOMATH* OREG. 18 IP-24-64 MARYS RIVER NEAR PHILOMATH, OREG. 36 1P-P2-64 MUDDY CREEK NEAR CORVALLIS. OREG. 10 12-22-64
CALAPOOIA R AT HOLLEY 0»EG 41 12-22-64 BUTTE CR NR PLAINVIEW,OREG. 14 11-24-60 CALAPOOIA RIVER AT ALBANY, OREG. 36 12-22-55 WILLAMETTE RIVER AT ALBANY, OREG. 56 12-04-61 COX CREEK AT ALBANY, OPEG. 16 12-21-64
NORTH SANTIAM R BEL BOULDER CR NR DETROIT, OREG. 51 12-22-64 WIND CP NR DETROIT. OREG. 23 12-21-64 8REITEN8USH R A8V CANYON CR NR DETROIT, OREG. 44 IP-22-64 NORTH SANTIAM RIVER AT NIAGARA .OPEG. 26 11-22-09 N SANTIAM RIVER TRIB NR GATES, OREG. 17 01-30-65
LITTLE NORTH SANTIAM RIVER NEAR MEHAMA, OREG. 44 12-22-64 NORTH SANTIAM RIVER AT MEHAMA, OREG. 37 12-28-45 SHEEK CREEK NEAR CASCAOI A .OREG. 24 IP-22-64 SOUTH SANTIAM RIVER BELOW CASCADIA, OREG. 41 12-22-64 MIDDLE SANTIAM R NEAR CASCAOI A , OREG. 13 12-22-64
QUARTZVILLE CREEK NEAR CASCADIA, OREG. 13 IP-22-64 MIDDLE SANTIAM RIVER NEAR FOSTER, OREG. 16 12-P8-45 WILEY CREEK NEAR FOSTER, OREG. 26 01-21-72 SOUTH SANTIAM RIVER AT WATERLOO, OREG. 45 12-22-64 THOMAS CREEK NEAR SCIO.OREG. 14 12-22-64
SANTIAM R AT JFFFERSON OREG 23 11-21-21 LUCKIAMUTE RIVER NEAR HOSKINS, OREG. 42 IP-14-46 LUCKIAMUTE R AT PEDEE OREG 30 12-P2-64 WAYMIRE CR NR FALLS CITY, OREG. 15 12-22-64 LUCKIAMUTE RIVER NEAR SUVER. OREG. 42 IP-22-64
SOAP CREEK TRIBUTARY NEAR SJVER»OREG. 24 03-02-72 WILLAMETTE RIVER AT SALEM, OREG. 51 IP-04-61 GLENN CREEK NEAR SALEM, OREG. 25 12-21-55 GIBSON CREEK NEAR SALEM, OREG. 15 IP-23-64 SOUTH YAMHILL RIVER NEAR WILLAMINA, OREG. 42 12-22-64
SOUTH YAMHILL R TRIB NR WILLAMINA ,ORF.G. 23 12-21-55 WILLAMINIA CREEK NEAR WILLAMINA ,OREG. 43 12-22-64 MILL CREEK NEAR WILLAMINA, OREG. 15 12-22-64 SOUTH YAMHILL RIVER NEAR WHITESON,OREG. 36 12-23-64 HASKINS CREEK NEAR MCMINNVILLE, OREG. 21 03-31-31
Discharge (ft 3 /s)
64400 7140 13000 88200 6990
10600 530
2500 13600 6040
12600 647
32700 340000
1070
26700 231
16900 63200
132
36000 76600
116 27600 22900
36500 41800 9640
95200 27400
202000 5560 15700
598 32900
86 500000
172 434
19600
420 10BOO 6170
47200 610
24
Table 3. Maximum discharges at gaging stations used in western Oregon flood-frequency analysis continued
Station number
1419650014197000141973001419850014199700
1420000014201000142015001420200014202500
1420300014203500142038001420400014P04100
14P0450014205500142060001420650014207500
1420800014208500142088501420900014209100
1420950014209900142100001421080014211500
1421180014223500142435001424500014248700
1425150014299000142995001430020014301000
1430140014301500143025001430300014303600
Years of
Station name record
NORTH YAMHILL RIVER NR PIKE» OREG. 11NORTH YAMHILL R AT PIKE. OREG. 25PANTHER CHEEK NEAR CARLTON,OREG. 16MOLALLA R AB PC NR WILHOIT, OREG. 41HULL CR NR COLTON,OREG. 13
MOLALLA R NR CAMBY» OREG. 44PUDDING PIVER NEAR MOUNT ANGEL* OREG. 26BUTTE CREEK AT MONI TOR, OREG. 22PUDDING RIVER AT AURORA. OREG. 38TUALATIN RIVFR NR GASTON,OR£G. 20
SCOGGIM CREEK NEAR GASTON. OxEG. 34TUALATIN RIVF.R NEAR DILLEY, OREG. 37BEAVER CREEK NEAP GLENWOOD.OKFG. 17GALES CREEK NR GALES CREEK, OREG. 17BATEMAN CHEE.K NEAR GLENWOOD ,OREG. 25
GALES CREEK NEAR FOREST GROVE, OREG. 22EAST FORK DAIRY CREEK AT MOUNTA INDALE » OREG. 11MCKAY CREEK NEAR NORTH PLAINS, OREG. 11TUALATIN RIVER AT FARMINGTON,OREG. 19TUALATIN RIVF.R AT WEST LINN, OREG. 46
CLACKAMAS RIVFR AT BIG BOTTOM, OREG. 50OAK GROVE FORK AT TIMOTHY MEADOWS, OREG. 16EAST FORK SHELLROCK CR NR GOVT CAMP, OREG. 10OAK GROVE FORK ABOVE POWERPLANT INTAKE, OREG. 43KINK CR NR GOVERNMENT CAMP, OREG. 19
CLACKAMAS RIVER ABOVE THREE LYNX CREEK, OREG. 38DUBOIS CREEK AT ESTACADA.OREG. 20CLACKAMAS RIVER AT ESTACADA, OREG. 47ROCK CR NR BORING OREG. 10JOHNSOM CHEEK AT SYCAMORE, OREG. 36
SALTZMAN CREEK AT PORTLAND, OREG. 25KALAMA R BL ITALIAN CR NR KALAMA,WA 26DELAMETER CREEK NEAR CASTLE ROCK, WA 19COWEMAN RIVER NEAR KELSO, WA 22BEAR CREEK NEAR SVENSEN.OREG. 10
YOUNGS RIVER NEAR ASTORIA, OREG. 31so FK NECANICUM RIVER NEAR SEASIDE, OREG. i&ASBURY CREEK NEAR CANNON BEACH, OREG. 25OAK RANCH CR NR VERNONIA OREG. 10NEHALEM RIVER NEAR FOSS. OREG. 37
PATTERSON CREEK AT BAY CITY, OREG. 17WILSON RIVER NEAR TILLAMOOK, OREG. 46TRASK RIVER NEAR TILLAMOOK, OREG. 37NESTUCCA RIVER NEAR MCMINNVILLE, OREG. 16NESTUCCA R NR BEAVER OREG 11
Discharge Date (ft3 Is)
02-10-49 478012-21-55 9530IP-21-64 612IP-22-64 2430011-24-60 293
12-22-64 4360012-22-64 1670001-21-72 731001-07-23 27900IP-21-55 8170
IP-21-55 5320IP-22-64 17100OP-02-63 472IP-22-64 397012-21-55 145
02-17-49 6410OP-17-49 142002-17-49 210012-22-55 24200IP-23-33 29300
12-22-64 1120001-07-23 97012-24-64 11801-07-23 5000IP-21-64 94
03-31-31 3480012-22-64 50803-31-31 6080011-20-62 28012-22-64 2620
12-21-55 30601-20-72 1790001-19-62 242011-20-62 972001-11-72 342
02-10-49 475001-25-64 3040OP-10-61 31412-21-64 51401-20-72 46900
01-28-65 30001-20-72 3600011-20-21 3000012-22-33 148001-11-72 29400
25
Table 3. Maximum discharges at gaging stations used in western Oregon flood-frequency analysis continued
Station number
1430370014305500143061001430640014306500
1430670014306800143068101430683014307500
1430755014307610143077001430800014308500
1430870014308900143090001430950014310000
1431070014310900143110001431120014311500
1431200014312100143122001431230014313500
1431450014315500143160001431650014316700
1431750014317600143178001431800014318500
1431860014319200143195001432060014320700
Years of
Station name recordDischarge
Date (ft 3 /s)
ALDER BROOK NR ROSE LODGE.OREG. 23 01-21-72 218SILETZ RIVER AT SILETZ, OREG. 60N FK ALSEA R AT ALSEA. OREG. 18
11-20-21 4080012-22-64 14100
FIVE RIVERS NR FISHER. OREG. 14 01-21-72 17200ALSEA RIVER NEAR TIDEWATER. OREG. 37 12-22-64 41800
NEEDLE BRANCH NEAR SALAD0.03EG. 15 01-11-72 64FLYNN CREEK NEAR SALADO.OREG. 15 01-21-72 139DEF.R CREEK NEAP SALAOO.OREG. 15 01-28-65 201LYNDON CREEK NEAR WALDPORT .OREG. 11 01-28-65 162LAKE CREEK AT TRIANGLE, OR 32 01-15-74 4640
DEADWOOD CREEK TRI8 AT ALPHA, OR 12 12-22-64 89SIUSLAW R TRI8 NR RAINROCK ,OREG. 20 01-21-72 62JACKSON CREEK NEAR TILLER, OREG. 21SOUTH UMPQUA RIVER AT TILLER, OREG. 38ELK CREEK NEAR DREW, OREG. 22
12-22-64 2110012-22-64 6020012-22-64 8880
DAYS CREFK AT DAYS CREEK, OREG. 17 02-21-56 3450CANYON CREEK AT CANYONVlLLE. OREG. 15 IP-21-55 3810COW CREEK NEAR AZALEA. OREG. 48 01-15-74 10600WEST FORK COW CREEK NEAR GLENDALE ,OREG. 21COW CREEK NEAR RIDDLE, OREG. 22
SOUTH MYRTLE CREEK NEAR MYRTLE CREEK, OREG. 17W F FROZEN CR NR MYRTLE CREEK, OREG. 14NORTH MYRTLE CREEK NEAR MYRTLE CREEK, OREG. 21OLALLA CREEK NEAR TENMILE. OREG. 17LOOKINGGLASS CREEK AT BROCKWA Y ,OREG. 21
SOUTH UMPQUA RIVER NEAR BROCKWAY, OREG. 46PARROTT CREEK AT ROSEBURG.OREG. 25DEER CREEK NEAR ROSE8URG,OREG. 17MARKS CREEK NEAR ROSEBURG.OREG. 17NORTH UMPQUA R 8L LEMOLO LK NR T FALLS, OREG. 27
CLEARWATER RIVER AS TRAP CR NR TOKETTE FLS, OR 49NORTH UMPQUA RIVER AT TOKETEE FALLS OREG. 24FISH CP AT 6IG C R STATION NR T FLS, OREG. 28NO UMPQUA R AB COPELAND CR NR T FLS.OREG. 27STEAMBOAT CREEK NEAR GLIDE, OREG. 21
N UMPQUA RIVER AB ROCK CR NR GLIDE OWEG 23ROCK CREEK NEAR GLIDE, OREG. 17CAVITT CREEK NEAR PEEL, OREG. 12LITTLE RIVER AT PEEL, OREG. 22NORTH UMPQUA RIVER NEAR GLIDE, OREG. 20
NORTH UMPQUA R TRIB NR GLIDE OREG. 12SUTHERLIN CR AT SUTHERLIN OREG. 12NORTH UMPQUA R. AT WINCHESTER. OREG. 11CABIN CR TRIB NR OAKLAND, OREG. 19CALAPOOYA CREEK NEAR OAKLAND. OREG, 18
12-22-64 1570010-29-50 41100
12-11-56 305012-26-55 30001-20-64 326001-03-66 916012-26-55 35000
12-23-64 12500012-21-55 290IP-28-65 7910OP-10-61 26006-09-33 1190
12-23-64 102012-31-42 508012-22-64 12100IP-22-64 4070012-22-64 S1000
12-22-55 6800012-22-64 2280012-11-56 1060012-11-56 2110011-22-09 94000
12-26-55 188OP-10-61 225012-22-64 15000011-23-61 24611-23-61 26600
26
Table 3. Maximum discharges at gaging stations used in western Oregon flood-frequency analysis continued
Station number
14321000 14321900 143P2000 14322400 14322700
14323200 14323300 14324500 14324600 14324700
14324900 14325000 14326500 14326600 14326800
14327000 14327100 14327240 143P7400 14327490
14327500 14328000 14330500 14331000 14332000
14333000 14333500 14335000 14335500 14337500
14338000 14339000 14339200 14339500 14341500
14342500 14343000 14347000 14353000 14353500
14359000 14359500 14361300 14362000 14363000
Ye c
Station name rec<
ars f 3rd Date
UMPQUA RIVER NEAR ELKTON, 0*EG. 70 12-23-64 YONCALLA CR NR YONCALLA OREG. 12 02-10-61 ELK CREEK NEAR DRAIN* ORES. 22 02-10-61 PASS CREEK NEAR DRAIN, ORES. 12 02-10-61 BEAR CREEK NEAR DRAIN, OREG. 14 02-10-61
TENMILE CREEK NEAR LAKESIDE , OREG. 19 12-26-64 EEL CREEK AT LAKESIDE, OREG. 19 01-17-74 WEST FORK MILLICOMA RIVER NEAR ALLEGANY, OREG. 22 ll-P.4-60 S FK COQUILLE R AB PANTHER CR, NR ILLAHE,OREG. 14 IP-22-64 SOUTH FORK COQUILLE RIVER NEAR ILLAHE,OREG. 16 12-22-64
SF COQUILLE R NR POWERS OREG 14 12-22-64 SOUTH FORK COQUILLE RIVER AT POWERS, OREG. 58 12-22-64 MIDDLE FK COQUILLE R NR MYRTLE POINT OREG. 17 10-31-24 GETTYS CREEK NEAR MYRTLE POINT, OREG. 24 OP-10-61 NORTH FORK COQUILLE RIVER NR FAIRVIEW»OREG. 13 03-02-72
N FK COQUILLE R NR MYRTLE POINT, OREG. 24 12-23-64 GEIGER CREEK NEAR BANDON,OREG. 16 02-10-61 MIL8URY CREEK NEAR PORT ORFORD,OREG. 11 01-04-66 DRY RUN CR NR PORT ORFORD»OREG. 22 01-18-71 NATIONAL CREEK NEAR UNION CREEK, OREG. 11 12-22-64
ROGUF RIVER ABOVE BYBEE CREEK, NR UNION CR, OREG 22 11-29-42 ROGUE RIVER ABOVE PROSPECT, OREG. 55 12-22-64 S FK ROGUE R AB IMNAHA CR NR PROSPECT OREG. 18 IP-01-42 IMNAHA CREEK NEAR PROSPECT, OREG. 18 02-13-45 SOUTH PORK ROGUE RIVER NEAR PROSPECT, OREG. 34 IP-22-64
MIDDLE FK ROGUE RIVER NR PROSPECT OREG. 30 12-22-55 RED BLANKET CREEK NEAR PROSPECT, OREG. 50 02-13-45 ROGUE R BL S FK ROGUE R NR PROSPECT OREG. 34 12-22-64 SOUTH FORK BIG BUTTE CR NR BUTTE FALLS, OREG. 56 IP-22-64 bIG BUTTE CREEK NFAR MCLEOD»OREG. 20 12-22-55
ELK CREEK NEAR TRAIL, OREG. 31 12-22-64 ROGUE R AT DODGE RR NR EAGLE POINT, OKEG. 38 12-22-64 CONSTANCE CR NR SAMS VALLEY OREG. 10 12-02-62 S FK LITTLE BUTTE CR AT BIG ELK RG STA,OR 22 05-25-42 SOUTH FORK LITTLE BUTTE CR NR LAKECREEK,OREG. 55 12-02-62
NO FK LITTLE BUTTE CR AT F L NR LAKECREEK ,OREG. 59 07-17-59 NO FK LITTLE BUTTE CR NR LAKECREEK, OWEG. 51 12-22-64 LITTLE BUTTE CREEK AB EAGLE POINT OREG. 10 10-30-24 W FK ASHLAND CREEK NEAR ASHLAND, OREG. 19 01-15-74 EAST FK ASHLAND CREEK NEAR ASHLAND, OREG. 19 01-15-74
ROGUE RIVER AT RAYGOLD, NEAR CENTRAL POINT, OREG 71 12-23-64 EVANS CR NR BYBEE SPRINGS NR ROGUE R OREG. 13 02-20-27 JONES CREEK NEAR GRANTS PASS, OREG. 25 OP-22-56 APPLEGATE RIVER NEAR COPPER, OREG. 38 01-15-74 APPLEGATE RIVER NEAR RUCH, OREG. 31 02-20-27
Discharge (ft3 /s)
265000 IS70
19000 10300
674
3330 316
8100 8840 12000
29600 48900 31800
245 7760
38400 206 286 213 475
4430 22400 2170 500
7010
3230 9900
55000 12600 8950
19200 87600
950 145
7660
163 1750 7000 4780 5630
131000 11100 1350
29800 20000
27
Table 3.-Maximum discharges at gaging stations used in western Oregon flood-frequency analysis-continued
Station number
1436600014368500143698001437000014370200
1437150014372300143725001437500014375500
14377000143775001437780014378000
Years of
Station name record
APPLEGATE RIVER NEAR APPLEGATE, OREG. 38POWELL CREEK NEAR WILLIAMS, OREG. 124UTCHF.RKNIFE CREEK NEAR WONDER, OREG. 16SLATE CREEK AT WONDER, OREG. 19ROUND PRAIRIE CREEK NR WILDERVILLE.OREG. 16
GRAVE CREEK AT PEASE 6PIDGE.NEAR PLACER, OREG. 34ROGUE RIVER NEAR AGNESS.OREG. 16E F ILLINOIS RIVER NEAR TAKILMA ,OREG. 39SUCKER CREEK MEAR HOLLAND, ORES. 24¥ FK ILLINOIS R RL ROCK CR NR 09PIEN. OR 22
ILLINOIS RIVER AT KERBY, OREG. 35DEF-R CREEK NEAR DRYDEN, OREG. 15SNAILBACK CR NR SELMA,ORFG. 17ILLINOIS R NP SELMA, OREG. 12
Discharge Date (ft'/s)
01-15-74 3720001-18-53 111001-03-66 43212-22-64 465001-03-66 375
12-22-64 624012-23-64 29000012-22-64 1570012-22-64 1750012-24-64 16100
12-22-55 5680001-18-53 500012-21-64 32912-22-64 160000
28
Table 4. Discharges for selected flood-frequencies at gaging stations
Station number
Peak discharge, in cubic feet per second, t'or selected exceedance probabilities (indicated recurrence interval)
0.50 (2-yr)
0.20 (5-yr)
0.10 (10-yr)
0.04 (2 5-yr)
0.02 (50-yr)
0.01 (100-yr)
(1) COAST REGION
11530850115J1000115330001424870014251500
1429900014299500143002001430100014301400
1430150014302500143030001430360014303700
1430550014306100143064001430650014306700
1430680014306810143068301430750014307550
1430761014323200143233001432450014324600
1432470014324900143250001432650014326600
1432680014327000143271001432724014327400
4014600
152147
2960
1900£12285
27900109
1740012900
72714500
88
2090051208680
2060030
6310355
223053
252190164
538037ao
4850131001530014800
137
498013400
95111107
6021100
286207
3590
2360253415
35200164
22600169001130
20100132
266007350
1200027300
39
8613588
340071
372910219
71504900
6650168002190021100
190
681021000
1^1190158
7425500
393249
3980
2650277509
39800205
26000195001440
24000163
302008S801420031700
45
101156112
424082
463340253
32405560
7760190002620025000
223
796026200
170256191
9130800
546304
4450
3000306636
45500259
30100229001880
28900204
34300109001710037100
51
12018?144
536096
573860293
95506330
9080215003160029700
262
933032800
206357231
10434800
671348
4780
3260327736
49600303
33200254002240
32600236
37300124001920041000
56
135201170
6230106
664220321
105006850
10000232003550033100
290
1030037800
232447261
11738700
805393
5110
3510347841
53600349
36300279002620
36300269
40200140002130045000
61
149219197
7140116
754560348
114007340
10900248003940036300
316
1120042700
257548289
29
Table 4.-Discharges for selected flood-frequencies at gaging stations-continued
Station number
Peak discharge, in cubic feet per second, for selected exceedance probabilities (indicated recurrence interval)
0.50 (2-yr)
0.20 (5-yr)
0.10 (10-yr)
0.04 (25-yr)
0.02 (50-yr)
0.01 (100-yr)
(2) WILLAMETTE REGION
14135000141370001*1388001413885014141500
1414350014144000141446001414480014144870
1414490014145500141460001414650014147500
1414800014148700141503001415100014151500
1415200014152500141539001415450014155500
1415600014156500141570001415800014159000
1415920014159500141612001416150014161600
1416200014162500141630001416500014165500
549014000118061602270
13500125042
314025
201011700167031507350
2690023
614097002470
455003700207
1120011100
3570486018300555006360
49809500
331860
35
59202830029705820
49bOO
759021300165071803200
16600171057
1370044
333020800?830530011500
4490034
9640150004250
814005960288
1690017300
58207450
24300785009330
758015300
452850
55
89004010046108570
68700
899026600198077803850
185002020
6618300
59
4380284003760702014800
5920043
12300190005710
1110007670344
2090022000
75709360
284009450011400
948019800
543570
70
111004830058301050081800
1080033700239084704700
207002410
7724900
81
5890398005120952019300
7980053
16100245007880
15700010100
4172640028500
10100120003360011600014200
1210026200
664570
90
140005890075401320099000
1210039400270089405350
223002700
8630600
100
7170498006270
1160023000
9710062
19200290009750
19700012000
4753070033800
12100141003750013200016300
1420031400
755360107
1630067000894015300
112000
1340045300302094006030
238002990
9436900
122
8570610007550
1400027000
11600071
226003370011800
24200014100534
3510039500
144QO163004150014900018500
1640037000
846190124
18800753001040017500
126000
30
Table 4.-Discharges for selected flood-frequencies at gaging stations-continued
Station number
Peak discharge, in cubic feet per second, for selected exceedano: probabi (indicated recurrence interval)
0.50 (2-yr)
0.20 (5-yr)
0.10 (10-yr)
0.04 (2 5-yr)
0.02 (50-yr)
ities
0.01 (100-yr)
(2) WILLAMETTE REGION
1416650014167000141697001417050014171000
1417150014172000141723001417350014174000
14174100U178000141788001417900014181500
1418170014182500141830001418490014165000
1418580014185900141660001418700014167500
1418880014189000141895001419000014190200
1419050014190600141910001419210014192200
1419250014192800141930001419330014194000
3150413023410705990
32205620237
12500106000
b337510
866260
21300
t>l1350034100
5511700
821012000209003410
37500
82507700030206410248
1180044
16500072
139
9520129
38503060
22300
4710768035315108630
419082/0391
20100160000
75011600
1278890
34700
661890048600
8017500
1180017900284005300
54200
12900120000
39608700384
1710060
241000117212
12300199
52404100
28300
5790106004191820
10500
482010200512
26000199000
90314600
1571070044900
1032270058500
9821700
1430022100336006730
65900
16500152000458010300486
2100071
298000152267
14100252
6210478033100
721014900
556222012900
561012800
68R34200
254000
111018700
1961310059300
1242760071200
12227300
1770027900402008730
81500
21500199000536012300
628
2630086
376000203343
16400324
75005660
38500
830018500649
252014700
620014800
83741000
299000
1?6021900
2261490071000
1413140080800
14131700
2020032400453001040093700
25600237000
594013900
744
3050097
439000246405
18000382
84906330
42600
941022600
746284016600
6790169001000
48200346000
143025400
2571670083600
1583530090600
16136300
22900372005050012100
106000
30000278000
653015500
867
34900108
507000293472
19700444
95307000
46800
31
Table 4. Discharges for selected flood-frequencies at gaging stations continued
Station number
Peak discharge, in cubic feet per second, for selected exceedance probabilities (indicated recurrence interval)
0.50 (2-yr)
0.20 (5-yr)
0.10 (10-yr)
0.04 (25-yr)
0.02 (50-yr)
0.01 (100-yr)
(2) WILLAMETTE REGION
1419500014196500141970001419730014198500
1419970014200000142010001420150014202000
1420250014203000142035001420380014204000
1420410014204500142055001420600014206500
1420750014208000142095001420990014210000
1421080014211500142118001422350014243500
28727704060224
7660
11613800b08030808650
2940181050902001890
6131701150954
10200
101003010
1690084
24400
1511170104
103001260
39735505630325
10800
1952020094704610136UO
3990261075302B9
2880
87464012901250
15000
147004750
25100163
37600
2341800168
129001770
47340606730399
13100
25724BOO12000573017500
470031909360360
3630
106571013RO1440
18500
180006030
30700231
46900
2962250217
145002110
57447108190499
16100
34631100155007260
22800
562039«0
11900468
4670
132717014701680
23300
224007780
38100335
59300
3792840287
165002560
65151909330579
18500
42136000164008480
27300
6330462014000
5615520
152833015401870
27100
259009170
43700426
68900
4463300344
179002910
732567010500664
20900
502412002140097bO
32100
7050530016300
6686420
173955016102050
31100
296001060049300
5?978700
5163770406
194003260
14245000 4860 6340 7300 8510 9410 10300
32
Table 4. Discharges for selected flood-frequencies at gaging stations continued
Station number
Peak discharge, in cubic feet per second, for selected exceedance probabilities (indicated recurrence interval)
0.50 (2-yr)
0.20 (5-yr)
0.10 (10-yr)
0.04 (25-yr)
0.02 (50-yr)
0.01 (100-yr)
(3) ROGUE-UMPQUA REGION
1430770014308000143085001430870014308900
1430900014309500143100001431070014310900
1431100014311200143115001431200014312100
1431220014312300143135001431450014315500
1431600014316500143167001431750014317600
1431780014318000143185001431860014319200
1431950014320600143207001432100014321900
1432200014322400143227001433800014339000
577017900291015802530
24307300
214001830147
203039201150049400
163
4000132710320
2560
21007750
15000245006270
35209740
3950055
1310
49300152
11700945001250
56004040370
550021100
9680?8600507023703140
449010200313002510232
250066001790076100
187
5390198929421
3560
379013700226003710010300
60901450057400
871920
74700217
19700141000
1490
106006720492
897035500
1280036600680029403510
609012100377002960294
27808620
2260094400
202
63002441070492
4250
522018700281004630013400
81501790069900
1112330
92900262
25800173000
1640
149008780572
1160046800
1720047500932036903960
833014500455003520380
31101140028800118000
218
7430305
1260586
5180
743026200357005870017800
112002250086400
1442880
117000320
34500216000
1810
2150011700
6731530063100
20900563001140042804280
10100162005120039SO449
33501360033700135000
229
8270353
1390660
5890
938032700418006870021500
137002600099100
1703300
136000364
41700249000
1930
2730014100
7471840076700
25000655001380048904590
1200017900567004370521
35801600038800153000
240
91104021530736
6640
1160040100483007910025500
1650029800112000
1983730
156000409
49400284000
2050
3380016700822
2170091600
33
Table 4. Discharges for selected flood-frequencies at gaging stations continued
Station number
Peak discharge, in cubic feet per second, for selected exceedance probabilities (indicated recurrence interval)
0.50 (2-yr)
0.20 (5-yr)
0.10 (10-yr)
0.04 (25-yr)
0.02 (50-yr)
0.01 (100-yr)
(3) ROGUE-UMPQUA REGION
1433920014359000143595001436130014362000
1436300014366000143685001436980014370000
1437020014371500143723001437250014375000
1437550014377000143775001437780014378000
425262003860319
6710
<t9409110<tlO228
2600
1801690
10600041903200
5840248001950157
54<tOO
6314650073<*0533
13300
977018700
937348
4070
3192840
18200063406150
8280381003500227
78600
7756330010200
6931R700
13800267001430431
5110
4273680
23600077908530
9810470004680273
94100
9658870014500
91226600
19900389002230538
6470
5804810
308000963011900
11700582006330329
113000
1110111000161001090
33300
25000492002960620
7520
7045690
363000110001480U
13000665007640370
127000
1260136000221001270
40600
30700605003800702
8580
8376600
4180001240017800
14200746009030410
140000
34
Table 4. Discharges for selected flood-frequencies at gaging stations continued
Station number
Peak discharge, in cubic feet per second, for selected exceedance probabilities (indicated recurrence interval)
0.50 (2-yr)
0.20 (5-yr)
0.10 UO-yr)
0.04 (25-yr)
0.02 (50-yr)
0.01 (100-yr)
(4) HIGH CASCADES REGION
14134000141345001414569014147400I4lb8250
1415850014208500142088501420900014209100
1432749014327500143280001433050014331000
1433200014333000143335001433500014335500
1433750014339500143415001434250014343000
143470001435300014353500
2901380
123635
147050364
168049
17722504790735171
1050909569
9040618
3420104
1130121247
31009294
4442100
378060
203071293
243076
253307076201110286
187015101130
153001590
5540116
2290143
421
48502672/8
55926?0
6912479
?410855113
296095
307364098801380377
256019901680
20300?320
7170124
3310154573
6130467491
7173320135199106
29001040139
3660120
3814390132001760510
361027002620
279003560
9460132
4910167812
7880847900
8463860209271129
32701180159
4210140
4384970160002060622
453033003550
344004750
11300138
6330176
1030
927012401330
98244203133bO153
36401320179
4780161
4985560192002380745
559039604720416006210
13400144
7950183
1290
1070017601890
35
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