Comparison of Probability Distributions for Estimation of Peak Flood Discharge

Abstract

Estimation of peak flood discharge (PFD) for a given return period is of utmost importance for planning and design of hydraulic structures in the project site. The peak value of a flood discharge having a pre-defined average return period is determined by frequency analysis, known as flood frequency analysis (FFA). The paper compares the eight probability distributions used for estimation of PFD for Malakkara and Neeleswaram. Maximum likelihood method is used for determination of parameters of the probability distributions. Goodness-of-Fit tests such as Anderson-Darling and Kolmogorov-Smirnov are applied for checking the adequacy of fitting of the distributions to the recorded annual maximum discharge. A diagnostic test of D-index is used for the selection of a most suitable distribution for FFA. Based on GoF and diagnostic test results, the study shows the EV1 distribution is better suited for estimation of PFD for Malakkara whereas LP3 for Neeleswaram.