Design flood estimation using GIS supported GIUH approach

Quantitative understanding and prediction of the processes of runoff genera tion and its transmission to the outlet represent one of the most basic and challenging areas of hydrology. Traditional techniques for design flood es timation use historical rainfall-runoff data for unit hydrograph derivation . Such techniques have been widely applied for the estimation of design flo od hydrograph at the sites of gauged catchment. For ungauged catchments, un it hydrograph may be derived using either regional unit hydrograph approach or alternatively Geomorhological Instantaneous Unit Hydrograph (GIUH) appr oach. The unit hydrograph thus derived may be used for the simulation of fl ood events for the ungauged catchments. In this study Gambhiri dam catchmen t located in Rajasthan, India is selected for applying this approach. Gambh iri river is a small tributary of the Berach/Banas river of the Chambal bas in in Rajasthan, India. The objective of the present study is to apply Geog raphical Information System (GIS) supported GIUH approach for the estimatio n of design flood. A mathematical model has been developed at the National Institute of Hydrology, which enables the evaluation of the Clark Model par ameters using geomorphological characteristics of the basin. This model has been applied for the present study. From this study it is observed that th e peak characteristics of the design flood are more sensitive to the variou s storm pattern as well as method of critical sequencing followed for the c omputation of design storm patterns. Earlier estimates for the peak and tim e to peak hydrograph was 9143.74 cumec and 18 hrs. respectively. However, t he estimates for the peak characteristics of design flood hydrograph obtain ed from the GIUH based approach are 11870.6 cumec and 19 hrs. respectively considering the same design storm pattern.