Design flood estimation using GIS supported GIUH approach

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. Traditional techniques for design flood estimation use historical rainfall-runoff data for unit hydrograph derivation. Such techniques have been widely applied for the estimation of design flood hydrograph at the sites of gauged catchment. For ungauged catchments, unit hydrograph may be derived using either regional unit hydrograph approach or alternatively Geomorhological Instantaneous Unit Hydrograph (GIUH) approach. The unit hydrograph thus derived may be used for the simulation of flood events for the ungauged catchments. In this study Gambhiri dam catchment located in Rajasthan, India is selected for applying this approach. Gambhiri river is a small tributary of the Berach/Banas river of the Chambal basin in Rajasthan, India. The objective of the present study is to apply Geographical Information System (GIS) supported GIUH approach for the estimation of design flood. A mathematical model has been developed at the National Institute of Hydrology, which enables the evaluation of the Clark Model parameters using geomorphological characteristics of the basin. This model has been applied for the present study. From this study it is observed that the peak characteristics of the design flood are more sensitive to the various storm pattern as well as method of critical sequencing followed for the computation of design storm patterns. Earlier estimates for the peak and time to peak hydrograph was 9143.74 cumec and 18 hrs. respectively. However, the estimates for the peak characteristics of design flood hydrograph obtained from the GIUH based approach are 11870.6 cumec and 19 hrs. respectively considering the same design storm pattern.