Frequency Analysis of Annual Maximum Flood Discharge Using Method of Moments and Maximum Likelihood Method of 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 in FFA. Method of Moments and Maximum Likelihood Method are used for determination of parameters of six probability distributions. Goodness-of-Fit tests such as Chi-square and KolmogorovSmirnov 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 a suitable distribution for estimation of MFD. The study showed that the exponential distribution (using MLM) is found to be better suited amongst six distributions adopted in estimation of MFD at Dedtalai and gamma distribution (using MLM) for Ghala.