Estimation of Peak Flood Discharge for the Ungauged Catchments in the Tributaries of River Sutlej using Synthetic Unit Hydrograph Approach

C. Srishailam; N VIVEKANANDAN

Abstract

Estimation of peak flood discharge (PFD) for a given return period is of utmost importance for planning and design of hydraulic structures, river protection works, and development of integrated water resources management projects which can be computed by applying various approaches viz., flood frequency analysis, rational formula, envelope curve and synthetic unit hydrograph (SUH). In this paper, SUH approach is adopted for estimation of PFD for the ungauged catchments viz. Saisso Khad up to Giabong village, Saisso Khad between Giabong and Rushkling villages, and Kannam Nallah up to Kannam Village (viz. Kannam Khad) in the tributaries of river Sutlej in Tehsil Pooh, Kinnaur District, Himachal Pradesh. For this purpose, rainfall depth (i.e., 24-hour maximum rainfall) is considered as one of the inputs which can be estimated through extreme value analysis (EVA) by fitting Extreme Value Type-1, 2-parameters Log Normal and Log Pearson Type-3 (LP3) distributions to the annual 1-day maximum rainfall data series. The estimators of the parameters of the distributions are determined by method of moments and used for estimation of rainfall for different return periods. Goodness-of-Fit (viz. Chi-square and Kolmogorov-Smirnov) and diagnostic (viz., D-index) tests are applied for checking the adequacy of fitting probability distributions adopted in EVA. The rainfall depth is computed by multiplying the estimated 1-day maximum rainfall using LP3 with 1.15 and used as an input for estimation of PFD. The paper presents the procedures adopted in estimation of PFD for the ungauged catchments in the tributaries of river Sutlej using SUH and the results obtained thereon.