Estimation of Maximum Flood Discharge Using Gamma and Extreme Value Family of Probability Distributions

Estimation of Maximum Flood Discharge (MFD) for a given return period is important for planning, design and management of hydraulic structures for the project. This can be achieved through Flood Frequency Analysis (FFA) by fitting of probability distributions to the recorded Annual Maximum Discharge (AMD) data. In this paper, Gamma and Extreme Value family of probability distributions are adopted for FFA. Method of Moments is used for determination of parameters of six probability distributions. Goodness-of-Fit tests such as Chi-square and Kolmogorov-Smirnov are applied for checking the adequacy of fitting of probability distributions to the recorded AMD data. Diagnostic test of D-index is used for the selection of suitable distribution for estimation of MFD. The study showed that the Gamma distribution is found to be better suited amongst six distributions adopted in the estimation of MFD at Dedtalai and Pearson Type-3 distribution for Ghala.