Short Duration Rainfall Analysis for Punpun Basin

Analysis of short duration rainfall is essential for estimation of floods for small catchments. The time of concentration for such catchments may even range for few hours. For small catchments discharge data are rarely available, which are required for design of small dams, culverts, drop spillways etc. In the absence of the long term stream flow data, flood estimation may be carried out by estimating the design rainfall excess and convoluting it with the unit hydrograph (UH) ordinates of the catchment.

The present study deals with analysis of short duration rainfall for Punpun basin of Bihar. The analyses have been used to estimate the design storms which may be used for estimation of design flood of a small catchment. The rainfall data of 11 raingauge stations located in the basin has been used. Thiessen polygon method is used for computing the average areal rainfall for the study area. Depth-area-duration (DAD) curves have been prepared for the Punpun basin selecting the severemost storm. Depth-duration-frequency (DDF) curves have been prepared using L-moments based general extreme value (GEV) distribution, DDF curves give the design storm depth at various return periods for a specified duration.