Flood Frequency Analysis Calculator: Log-Pearson Type III Distribution NOTE: Only enter data/edit yellow cells; do not alter white or blue cellsUSGS Gaging Station Name: USGS Site ID:Step 1: On separate sheet, sort PeakQ with date, from highest to lowest; Step 2: Paste sorted dates and Qpeak into Col B and C, respectively

RANK LOGQ_cfs1 no data no data no data no data2 no data no data no data no data3 no data no data no data no data4 no data no data no data no data5 no data no data no data no data6 no data no data no data no data7 no data no data no data no data8 no data no data no data no data9 no data no data no data no data

10 no data no data no data no data11 no data no data no data no data

12 no data no data no data no data13 no data no data no data no data14 no data no data no data no data15 no data no data no data no data16 no data no data no data no data17 no data no data no data no data18 no data no data no data no data19 no data no data no data no data20 no data no data no data no data21 no data no data no data no data22 no data no data no data no data

23 no data no data no data no data24 no data no data no data no data25 no data no data no data no data26 no data no data no data no data27 no data no data no data no data28 no data no data no data no data29 no data no data no data no data30 no data no data no data no data31 no data no data no data no data32 no data no data no data no data33 no data no data no data no data34 no data no data no data no data35 no data no data no data no data36 no data no data no data no data37 no data no data no data no data38 no data no data no data no data39 no data no data no data no data40 no data no data no data no data41 no data no data no data no data42 no data no data no data no data43 no data no data no data no data44 no data no data no data no data

YEAR OF PEAK FLOW

PEAK_FLOW_VALUE_Q(cfs)

(log Q – avg(logQ))^2

(log Q – avg(logQ))^3

Return Period (n+1)/m

45 no data no data no data no data46 no data no data no data no data47 no data no data no data no data48 no data no data no data no data49 no data no data no data no data50 no data no data no data no data51 no data no data no data no data52 no data no data no data no data53 no data no data no data no data54 no data no data no data no data55 no data no data no data no data56 no data no data no data no data57 no data no data no data no data58 no data no data no data no data59 no data no data no data no data60 no data no data no data no data61 no data no data no data no data62 no data no data no data no data63 no data no data no data no data64 no data no data no data no data65 no data no data no data no data66 no data no data no data no data67 no data no data no data no data68 no data no data no data no data69 no data no data no data no data70 no data no data no data no data71 no data no data no data no data72 no data no data no data no data73 no data no data no data no data74 no data no data no data no data75 no data no data no data no data76 no data no data no data no data77 no data no data no data no data78 no data no data no data no data79 no data no data no data no data80 no data no data no data no data81 no data no data no data no data82 no data no data no data no data83 no data no data no data no data84 no data no data no data no data85 no data no data no data no data86 no data no data no data no data87 no data no data no data no data88 no data no data no data no data89 no data no data no data no data90 no data no data no data no data91 no data no data no data no data92 no data no data no data no data93 no data no data no data no data94 no data no data no data no data

95 no data no data no data no data96 no data no data no data no data97 no data no data no data no data98 no data no data no data no data99 no data no data no data no data

100 no data no data no data no data101 no data no data no data no data102 no data no data no data no data103 no data no data no data no data104 no data no data no data no data105 no data no data no data no data106 no data no data no data no data107 no data no data no data no data108 no data no data no data no data109 no data no data no data no data110 no data no data no data no data111 no data no data no data no data112 no data no data no data no data113 no data no data no data no data114 no data no data no data no data115 no data no data no data no data116 no data no data no data no data117 no data no data no data no data118 no data no data no data no data119 no data no data no data no data

NOTE: Only enter data/edit yellow cells; do not alter white or blue cells

Step 1: On separate sheet, sort PeakQ with date, from highest to lowest; Step 2: Paste sorted dates and Qpeak into Col B and C, respectively

no data No. Years in Record 0.00no data Avg_Qpeak_cfs #DIV/0!no data Avg_LogQ_cfs #DIV/0!no data Sum {(log Q – avg(logQ))^2} 0.000no data Sum {(log Q – avg(logQ))^3 0.000no data Variance_LogQ_cfs #DIV/0!no data Stdev_LogQ_cfs #DIV/0!no data Skewness (Cs) #DIV/0!no data Skew Coefficient (Cm) 0.00 **Determine from skew coefficient Map of USno data Variance of Regional Skewness V(Cm) 0.302 **Constant for U.S. = 0.302no data

no data Variance of Station Skewness (V(Cs): Err:502no data A value #DIV/0!no data B value #DIV/0!no data Weighting Factor (W) Err:502 **W=V(Cm)/[V(Cs)+V(Cm)]no data Weighted Skewness (Cw) Err:502 **Cw = [W*Cs] + [(1-W)*Cm]no datano datano data Table Cw upper **Paste value here from K factor table belowno data Table Cw lower **Paste value here from K factor table belowno data Calculated Cw Value Err:502no data

no data Tr K lower K upper Slopeno data 2 #DIV/0!no data 5 #DIV/0!no data 10 #DIV/0!no data 25 #DIV/0!no data 50 #DIV/0!no data 100 #DIV/0!no data 200 #DIV/0!no datano data *Note: paste K lower and upper values from K factor table belowno datano datano data Frequency Factors K for Gamma and log-Pearson Type III Distributions (Haan, 1977, Table 7.7)no datano data Recurrence Interval In Yearsno data WEIGHTED 1.0101 2 5no data SKEW COEFFICIENT Percent Chance (>=) = 1-Fno data Cw 99 50 20no data 3 -0.667 -0.396 0.42no data 2.9 -0.69 -0.39 0.44no data 2.8 -0.714 -0.384 0.46no data 2.7 -0.74 -0.376 0.479

Exceedence Probability (1/Tr)

**V(Cs)=10[A-B*(log(n/10))]

no data 2.6 -0.769 -0.368 0.499no data 2.5 -0.799 -0.36 0.518no data 2.4 -0.832 -0.351 0.537no data 2.3 -0.867 -0.341 0.555no data 2.2 -0.905 -0.33 0.574no data 2.1 -0.946 -0.319 0.592no data 2 -0.99 -0.307 0.609no data 1.9 -1.037 -0.294 0.627no data 1.8 -1.087 -0.282 0.643no data 1.7 -1.14 -0.268 0.66no data 1.6 -1.197 -0.254 0.675no data 1.5 -1.256 -0.24 0.69no data 1.4 -1.318 -0.225 0.705no data 1.3 -1.383 -0.21 0.719no data 1.2 -1.449 -0.195 0.732no data 1.1 -1.518 -0.18 0.745no data 1 -1.588 -0.164 0.758no data 0.9 -1.66 -0.148 0.769no data 0.8 -1.733 -0.132 0.78no data 0.7 -1.806 -0.116 0.79no data 0.6 -1.88 -0.099 0.8no data 0.5 -1.955 -0.083 0.808no data 0.4 -2.029 -0.066 0.816no data 0.3 -2.104 -0.05 0.824no data 0.2 -2.178 -0.033 0.83no data 0.1 -2.252 -0.017 0.836no data 0 -2.326 0 0.842no data -0.1 -2.4 0.017 0.846no data -0.2 -2.472 0.033 0.85no data -0.3 -2.544 0.05 0.853no data -0.4 -2.615 0.066 0.855no data -0.5 -2.686 0.083 0.856no data -0.6 -2.755 0.099 0.857no data -0.7 -2.824 0.116 0.857no data -0.8 -2.891 0.132 0.856no data -0.9 -2.957 0.148 0.854no data -1 -3.022 0.164 0.852no data -1.1 -3.087 0.18 0.848no data -1.2 -3.149 0.195 0.844no data -1.3 -3.211 0.21 0.838no data -1.4 -3.271 0.225 0.832no data -1.5 -3.33 0.24 0.825no data -1.6 -3.88 0.254 0.817no data -1.7 -3.444 0.268 0.808no data -1.8 -3.499 0.282 0.799no data -1.9 -3.553 0.294 0.788no data -2 -3.605 0.307 0.777no data -2.1 -3.656 0.319 0.765no data -2.2 -3.705 0.33 0.752no data -2.3 -3.753 0.341 0.739

no data -2.4 -3.8 0.351 0.725no data -2.5 -3.845 0.36 0.711no data -2.6 -3.899 0.368 0.696no data -2.7 -3.932 0.376 0.681no data -2.8 -3.973 0.384 0.666no data -2.9 -4.013 0.39 0.651no data -3 -4.051 0.396 0.636no datano datano datano datano datano datano datano datano datano datano datano datano datano datano datano datano datano data

**Determine from skew coefficient Map of US**Constant for U.S. = 0.302

**W=V(Cm)/[V(Cs)+V(Cm)]**Cw = [W*Cs] + [(1-W)*Cm]

**Paste value here from K factor table below**Paste value here from K factor table below

K calculatedErr:502 Err:502 Err:502Err:502 Err:502 Err:502Err:502 Err:502 Err:502Err:502 Err:502 Err:502Err:502 Err:502 Err:502Err:502 Err:502 Err:502Err:502 Err:502 Err:502

*Note: paste K lower and upper values from K factor table below

Frequency Factors K for Gamma and log-Pearson Type III Distributions (Haan, 1977, Table 7.7)

10 25 50 100 200

10 4 2 1 0.51.18 2.278 3.152 4.051 4.97

1.195 2.277 3.134 4.013 4.9041.21 2.275 3.114 3.973 4.847

1.224 2.272 3.093 3.932 4.783

LogQTr_cfs QTr_cfs

1.238 2.267 3.071 3.889 4.7181.25 2.262 3.048 3.845 4.652

1.262 2.256 3.023 3.8 4.5841.274 2.248 2.997 3.753 4.5151.284 2.24 2.97 3.705 4.4441.294 2.23 2.942 3.656 4.3721.302 2.219 2.912 3.605 4.298

1.31 2.207 2.881 3.553 4.2231.318 2.193 2.848 3.499 4.1471.324 2.179 2.815 3.444 4.0691.329 2.163 2.78 3.388 3.991.333 2.146 2.743 3.33 3.911.337 2.128 2.706 3.271 3.8281.339 2.108 2.666 3.211 3.745

1.34 2.087 2.626 3.149 3.6611.341 2.066 2.585 3.087 3.575

1.34 2.043 2.542 3.022 3.4891.339 2.018 2.498 2.957 3.4011.336 1.993 2.453 2.891 3.3121.333 1.967 2.407 2.824 3.2231.328 1.939 2.359 2.755 3.1321.323 1.91 2.311 2.686 3.0411.317 1.88 2.261 2.615 2.9491.309 1.849 2.211 2.544 2.8561.301 1.818 2.159 2.472 2.7631.292 1.785 2.107 2.4 2.671.282 1.751 2.054 2.326 2.576

1.27 1.716 2 2.252 2.4821.258 1.68 1.945 2.178 2.3881.245 1.643 1.89 2.104 2.2941.231 1.606 1.834 2.029 2.2011.216 1.567 1.777 1.955 2.108

1.2 1.528 1.72 1.88 2.0161.183 1.488 1.663 1.806 1.9261.166 1.448 1.606 1.733 1.8371.147 1.407 1.549 1.66 1.7491.128 1.366 1.492 1.588 1.6641.107 1.324 1.435 1.518 1.5811.086 1.282 1.379 1.449 1.5011.064 1.24 1.324 1.383 1.4241.041 1.198 1.27 1.318 1.3511.018 1.157 1.217 1.256 1.2820.994 1.116 1.166 1.197 1.216

0.97 1.075 1.116 1.14 1.1550.945 1.035 1.069 1.087 1.097

0.92 0.996 1.023 1.037 1.0440.895 0.959 0.98 0.99 0.9950.869 0.923 0.939 0.946 0.9490.844 0.888 0.9 0.905 0.9070.819 0.855 0.864 0.867 0.869

0.795 0.823 0.83 0.832 0.8330.711 0.793 0.798 0.799 0.80.747 0.764 0.768 0.769 0.7690.724 0.738 0.74 0.74 0.7410.702 0.712 0.714 0.714 0.7140.681 0.683 0.689 0.69 0.69

0.66 0.666 0.666 0.667 0.667

Frequency Factors K for Gamma and log-Pearson Type III Distributions (Haan, 1977, Table 7.7)

Recurrence Interval In YearsWeighted 1.0101 2 5 10 25 50 100 200SKEW COEFFICIENT Percent Chance (>=) = 1-FCw 99 50 20 10 4 2 1 0.5

3 -0.667 -0.396 0.42 1.18 2.278 3.152 4.051 4.972.9 -0.69 -0.39 0.44 1.195 2.277 3.134 4.013 4.9042.8 -0.714 -0.384 0.46 1.21 2.275 3.114 3.973 4.8472.7 -0.74 -0.376 0.479 1.224 2.272 3.093 3.932 4.7832.6 -0.769 -0.368 0.499 1.238 2.267 3.071 3.889 4.7182.5 -0.799 -0.36 0.518 1.25 2.262 3.048 3.845 4.6522.4 -0.832 -0.351 0.537 1.262 2.256 3.023 3.8 4.5842.3 -0.867 -0.341 0.555 1.274 2.248 2.997 3.753 4.5152.2 -0.905 -0.33 0.574 1.284 2.24 2.97 3.705 4.4442.1 -0.946 -0.319 0.592 1.294 2.23 2.942 3.656 4.372

2 -0.99 -0.307 0.609 1.302 2.219 2.912 3.605 4.2981.9 -1.037 -0.294 0.627 1.31 2.207 2.881 3.553 4.2231.8 -1.087 -0.282 0.643 1.318 2.193 2.848 3.499 4.1471.7 -1.14 -0.268 0.66 1.324 2.179 2.815 3.444 4.0691.6 -1.197 -0.254 0.675 1.329 2.163 2.78 3.388 3.991.5 -1.256 -0.24 0.69 1.333 2.146 2.743 3.33 3.911.4 -1.318 -0.225 0.705 1.337 2.128 2.706 3.271 3.8281.3 -1.383 -0.21 0.719 1.339 2.108 2.666 3.211 3.7451.2 -1.449 -0.195 0.732 1.34 2.087 2.626 3.149 3.6611.1 -1.518 -0.18 0.745 1.341 2.066 2.585 3.087 3.575

1 -1.588 -0.164 0.758 1.34 2.043 2.542 3.022 3.4890.9 -1.66 -0.148 0.769 1.339 2.018 2.498 2.957 3.4010.8 -1.733 -0.132 0.78 1.336 1.993 2.453 2.891 3.3120.7 -1.806 -0.116 0.79 1.333 1.967 2.407 2.824 3.2230.6 -1.88 -0.099 0.8 1.328 1.939 2.359 2.755 3.1320.5 -1.955 -0.083 0.808 1.323 1.91 2.311 2.686 3.0410.4 -2.029 -0.066 0.816 1.317 1.88 2.261 2.615 2.9490.3 -2.104 -0.05 0.824 1.309 1.849 2.211 2.544 2.8560.2 -2.178 -0.033 0.83 1.301 1.818 2.159 2.472 2.7630.1 -2.252 -0.017 0.836 1.292 1.785 2.107 2.4 2.67

0 -2.326 0 0.842 1.282 1.751 2.054 2.326 2.576-0.1 -2.4 0.017 0.846 1.27 1.716 2 2.252 2.482-0.2 -2.472 0.033 0.85 1.258 1.68 1.945 2.178 2.388-0.3 -2.544 0.05 0.853 1.245 1.643 1.89 2.104 2.294-0.4 -2.615 0.066 0.855 1.231 1.606 1.834 2.029 2.201-0.5 -2.686 0.083 0.856 1.216 1.567 1.777 1.955 2.108-0.6 -2.755 0.099 0.857 1.2 1.528 1.72 1.88 2.016-0.7 -2.824 0.116 0.857 1.183 1.488 1.663 1.806 1.926-0.8 -2.891 0.132 0.856 1.166 1.448 1.606 1.733 1.837-0.9 -2.957 0.148 0.854 1.147 1.407 1.549 1.66 1.749

-1 -3.022 0.164 0.852 1.128 1.366 1.492 1.588 1.664-1.1 -3.087 0.18 0.848 1.107 1.324 1.435 1.518 1.581-1.2 -3.149 0.195 0.844 1.086 1.282 1.379 1.449 1.501-1.3 -3.211 0.21 0.838 1.064 1.24 1.324 1.383 1.424

-1.4 -3.271 0.225 0.832 1.041 1.198 1.27 1.318 1.351-1.5 -3.33 0.24 0.825 1.018 1.157 1.217 1.256 1.282-1.6 -3.88 0.254 0.817 0.994 1.116 1.166 1.197 1.216-1.7 -3.444 0.268 0.808 0.97 1.075 1.116 1.14 1.155-1.8 -3.499 0.282 0.799 0.945 1.035 1.069 1.087 1.097-1.9 -3.553 0.294 0.788 0.92 0.996 1.023 1.037 1.044

-2 -3.605 0.307 0.777 0.895 0.959 0.98 0.99 0.995-2.1 -3.656 0.319 0.765 0.869 0.923 0.939 0.946 0.949-2.2 -3.705 0.33 0.752 0.844 0.888 0.9 0.905 0.907-2.3 -3.753 0.341 0.739 0.819 0.855 0.864 0.867 0.869-2.4 -3.8 0.351 0.725 0.795 0.823 0.83 0.832 0.833-2.5 -3.845 0.36 0.711 0.711 0.793 0.798 0.799 0.8-2.6 -3.899 0.368 0.696 0.747 0.764 0.768 0.769 0.769-2.7 -3.932 0.376 0.681 0.724 0.738 0.74 0.74 0.741-2.8 -3.973 0.384 0.666 0.702 0.712 0.714 0.714 0.714-2.9 -4.013 0.39 0.651 0.681 0.683 0.689 0.69 0.69

-3 -4.051 0.396 0.636 0.66 0.666 0.666 0.667 0.667

Alsea ExampleCw = 0.1092