1Assistant Research Officer, Central Water and Power Research Station, Pune, Maharashtra
2Scientist B, Central Water and Power Research Station, Pune, Maharashtra
3Scientist C, Central Water and Power Research Station, Pune, Maharashtra
4Scientist E, Central Water and Power Research Station, Pune, Maharashtra
Online published on 17 August, 2022.
Estimation of Peak Flood Discharge (PFD) for a given return period is considered as one of the most important parameter for planning and design of hydraulic structures, river protection works, and development of integrated water resources management projects. This can be achieved by adopting various methods viz., flood frequency analysis, rational formula, envelope curves and Synthetic Unit Hydrograph (SUH) approach. Out of which, rational formula is used for estimation of PFD for ungauged catchments with catchment area less than 25 km2 while SUH approach is adopted for ungauged catchments with catchment area more than 25 km2. This paper presents a study on estimation of PFD using rational formula and SUH approach for ungauged catchments of river Beas upto Aut gauge-discharge site. From the topography and catchment characteristics of the study area, it is determined that the study area consists of 37 ungauged catchments wherein the catchment area of 22 catchments are less than 25 km2 and the remaining 15 catchments are more than 25 km2. In this paper, the annual 1-day maximum rainfall (AMR) series is extracted from the daily rainfall data observed at Manali rain-gauge site for the period 1990 to 2019 and used for rainfall estimation by adopting Extreme Value Type-1 (EV1) distribution. The adequacy of fitting EV1 distribution to the AMR series is evaluated by using Goodness-of-Fit tests viz., Chi-square and Kolmogorov-Smirnov. The 1-hour distributed rainfall is computed from the 24-hour maximum rainfall that is obtained by multiplying the 1-day maximum rainfall with 1.15. In addition to above, the physiographic parameters are retrieved from the Digital Elevation Model of National Remote Sensing Centre for estimation of PFD. The estimated 25-year, 50-year and 100-year return period PFDs given by SUH approach are used for derivation of flood hydrograph of the respective catchment. The paper presents the methodology adopted in rainfall data analysis using EV1, estimation of PFD using rational formula and SUH approach, and the results obtained thereon.
