REGIONALIZATION OF NEPALESE RIVER BASINS FOR FLOOD FREQUENCY ANALYSIS

Abstract

Regional flood frequency analysis which is applicable for estimating design flood at both gauged and ungaged sites needs grouping of river basins into hydrological homogeneous regions. Specific flood, timing of flood events and spatial location are significant in reflecting physiogrpahy and climate of any river basins. These three physiographic/climatic characteristics of 46 independent Nepalese river basins have been used successfully to delineate the homogeneous regions. This study uses a clustering algorithm as a starting point for partitioning the independent catchments. The regions thus formed are subsequently revised to improve the regional homogeneity after performing the L-moment based homogeneity test. Spatial proximity consideration has been used to delineate region for mountainous dependent river basins whereas subjective considerations have been made to delineate region for river basins of alluvial plain region.