Development of Regional Flood Frequency Relationship for Narmada Basin using Index Flood Procedure

Abstract

Water Resources decision making problems such as flood plain zoning, design of hydraulic structures etc. are based on design flood estimate, defined as discharge for a specified probability of exceedance. Flood Frequency Analysis helps to estimate the flood value for a specific return period. This procedure requires sufficient length of observed data of floods on river gauging sites which many a time is not available. In India major rivers have very few gauging sites and their tributaries are mostly ungauged. When quantiles have to be estimated for ungauged sites, Flood Frequency Analysis is neither possible nor reliable. Regional Flood Frequency Analysis is the means to overcome such problems, reasonably quantifying flood estimates at desired frequencies for sites within a more or less hydrological homogeneous region. Narmada Basin located in central India covers an area about 98,976 sq. km, drained by a large number of tributaries, most of which are ungauged, has been considered as the case. Index Flood method utilizing Gumbel’s EV-1 distribution have been used in the present study to develop the Regional flood frequency relationship. The Annual Peak Flood data of 16 gauging sites of Narmada Basin, having record length of 12 to 17 years, is utilized for flood estimation. Flood frequency curves for the considered gauging stations are generated. Development of regional flood frequency relationship leads to the estimation of different return period flood.