TR(BR)-1/98-99 : Application of GIUH and GIS based approach for design flood estimation

Abstract

Quantitative understanding and prediction of the processes of runoff generation and its transmission to the outlet represent one of the most basic and challenging areas of hydrology. Unit hydrograph techniques have been widely applied for the estimation of design flood hydrograph at the site of interest. Whenever adequate rainfall-runoff records are available, unit hydrograph for that catchment can be developed very easily analysing the available records. For ungauged catchments, unit hydrograph may be derived using either regional unit hydrograph approach or alternatively GIUH approach. The Geomorhological Instantaneous Unit Hydrograph (GIUH) approach may be applied for the simulation of flood events particularly fr the ungauged catchments.

The objective of the present study is to apply GIUH and GIS based approach for the estimation of design flood. For this purpose the design storm data of four dam catchments alongwith morphological characteristics are considered. In this study the geomorphological parameters and time area diagrams for each dam catchments were generated using Geographic Information System (GIS) package ILWIS (Integrated Land and Water Information System). The geopmorphological parameters together with time area diagramme forms important input for the GIUH based Clark model. This model has been applied for deriving the instantaneous unit hydrograph and thereby for estimation of design flood in four dam catchments located in Rajasthan viz. Jawai, Sei, Gamabhiri and Alnia, which are part of Luni and Chambal basins. A review of the previous studies carried out using GIUH approach has been presented. Further more a review is also presented for the studies carried out using GIS techniques.

The design flood estimates have been obtained for different scenarios of the design storm. These design flood estimates have been compared with the available design flood estimates in order to examine the applicability of the above approach. It was found that the velocity is one of the important design parameters. Its estimation for design condition is one of the most crucial issues, which require further investigation.