Regional Flood Frequency Analysis Using L-moments for Sone Subzone-1 (d) of India

Data of 12 stream flow gauging sites of Sone Subzone-1 (d) of India are screened using the discordancy measure (D_i) and homogeneity of the region is then tested employing the L-moments based heterogeneity measure (H). It is observed that the data of 10 out of 12 stream flow gauging sites constitute a homogeneous region. Comparative regional flood frequency analysis studies are conducted using the various L-moments based frequency distributions. Based on the L-moments ratio diagram and |Z_i^dist| -statistic criteria, GEV distribution is identified as the robust distribution for the study area. Regional flood frequency relationships are developed for gauged catchments using the L-moments based GEV distribution. For estimation of floods of various return periods for ungauged catchments, a regional relationship between mean annual peak flood and catchment area is developed and the same is coupled with the regional flood frequency relationship derived for the gauged catchments. Flood frequency estimates of gauged and ungauged catchments obtained using the data of 10 gauging sites are compared with those obtained using the data of 12 gauging sites, without meeting the criteria of regional homogeneity.