||Computer Program for Statistical Analysis of Annual Flood Data by the Log-Pearson Type III Method.
Bower, C. Edward ;
Pabs, Arthur F. ;
Larso, Steven P. ;
||Minnesota Univ., Minneapolis. St. Anthony Falls Hydraulic Lab.
||OWRR-A-020-MINN; 08187,; A020-MINN(1)
( Flood forecasting ;
Statistical analysis) ;
( Flood control ;
Data processing) ;
Computer programs ;
Curve fitting ;
FORTRAN 4 programming language
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The adoption of a uniform method of establishing flood flow frequencies by use of the log-Pearson Type III distribution by the Water Resources Council was discussed. The objective was to obtain consistent estimates of flood frequencies. The method used first transforms the natural data to their logarithms and then computes the statistical parameters. The basic equations associated with the log-Pearson Type III distribution were included although it is not necessary to go through the process of solving these equations since the dimensionless probability distribution was provided in table form. With the table available the primary problem was determinization of logarithms of the floods and the mean, standard deviation, and skewness of the logarithms. The computer program used was written in Fortran IV language and was included in the appendix. The example used illustrated the input and output data for annual floods on two Minnesota streams. The log-Pearson Type III distribution appeared to have an advantage over other distributions commonly used in flood frequency analysis in that it could be used with data having skewness coefficients other than one. To illustrate its use, it was applied to selected streams in the United States.