An Empirical Formula for Design Flood Estimation of Un-Gauged Catchments in Brahmani Basin, Odisha

Abstract

Several statistical methods, viz. flood frequency analysis and hydro-meteorological methods (i.e., unit hydrograph approach) are available for estimation of design flood in un-gauged catchments. Till today, the empirical formulae are relevant as the latest methods require adequate field observation and collection of sufficient data. The available formulae such as Dicken’s formula, Ryves formula and Inglis formula are applicable, respectively, to Northern India, Western India and Southern India. But no such empirical formula is available for eastern India, especially for Odisha region, for which designers depend on the established formulae for other regions. This necessitated developing an empirical formula for computation of design flood for this zone. An empirical formula is developed for computation of design flood of un-gauged catchments in Brahmani Basin of Odisha and presented in this paper. Relation between the peak discharges of the unit hydrograph and the design discharges of individual sub-basins is established. Eight sub-basins are considered for this study. The derived formula is validated through upper and lower envelope curves for probable maximum flood for Mahanadi and adjoining river basins, recommended by Central Water Commission. This would provide guideline in planning any future water resources projects in Brahmani basin. The study would form a part of final work of derivation of a general equation applicable to the State/Eastern zone of India.