CS(AR)-210 : Derivation of GIUH for small catchments of upper Narmada and Tapi subzone (subzone 3c) Part-II

Abstract

The computations of flood hydrographs have always been one of the major concerns of the water resources engineers and scientists. For the purpose of rainfall-runoff process simulation, mathematical modelling is often resorted to. Continued research in this field has resulted in numerous types of rainfall-runoff models. For simulation and design flood evaluation, conceptual models and physically based models are widely used. The linearity principle of unit hydrograph theory has been widely applied for the simulation of rainfall-runoff process, particularly for small and medium sized catchments. Derivation of unit hydrograph has been extensively investigated by many researchers since Sherman gave the principle of unit graph in 1932. For the gauged catchments the unit hydrographs can be derived by analysing the historical rainfall-runoff records. However, for ungauged catchments some indirect approaches have been used for the derivation of the unit hydrographs. Due to scarcity of data, particularly for small and medium sized catchments, physically based models are very difficult to be implemented. Greater emphasis is now being given to the concept of models based on geomorphological characteristics. Geomorphological instantaneous unit hydrograph is one among the various approaches available for the simulation of flood events, especially for the ungauged catchments. Many investigators have tried to relate the parameters of the conceptual models to the geomorphological characteristics of the catchments:

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. Earlier this model was implemented on the Kolar sub-basin of river Narmada and three small catchments of Upper Narmada and Tapi Sub-zone 3c. In this part of the study the model is applied on seventeen small catchments of the sub-zone 3c.

Various event based conceptual models and the models for ungauged catchments have been reviewed. The description of the study area alongwith the availability of the data for the present study has also been presented. The methodology is fully explained and analysis has been carried out by using the computer software developed for this approach. Since the data for historical flood events and stream gauging could not be obtained the model is applied to obtain the unit hydrographs for various small catchments corresponding to different velocities of flow. Flood events may be simulated by having an indirect estimate of velocity of flow corresponding to the rainfall intensity of the event. Conclusions drawn have been presented alongwith the suggestions for further work in the direction of improvement of the methodology.