Evaluation of probability distributions for estimation of peak flood discharge using FFA approach

Abstract

The estimation of Peak Flood Discharge (PFD) for a specific return period is of paramount importance in hydrological studies for the planning, design, and management of civil and hydraulic structures. This research investigates the evaluation of probability distributions through statistical tests, viz., the Chi-Square, Kolmogorov-Smirnov, and D-index. These tests aid in estimating the PFD using the Flood Frequency Analysis (FFA) approach for the Tapi River at Prakasha Barrage. In this analysis, various distributions from the extreme value family such as Extreme Value Type-1, Extreme Value Type-2, Generalized Extreme Value (GEV), and Pareto, were employed in the FFA. The distribution parameters are determined by standard techniques, such as the method of moments, Maximum Likelihood Method (MLM), and the Method of L-Moments (LMO). A qualitative assessment, along with the D-index value, was employed to select the most suitable distribution for the analyzed data. This study demonstrates that among the four distributions adopted in FFA, the GEV (LMO) distribution exhibits the best fit. Furthermore, this research suggests the use of PFDs derived from the GEV (LMO) distribution for design purposes.