Modeling synthetic unit hydrograph parameters with geomorphologic parameters of watersheds

This study was undertaken in two medium sized agricultural watersheds and their sub watersheds located in Midnapore and Bankura districts of West Bengal state in India. Runoff hydrographs were generated from flow data and unit hydrographs (UH) were obtained for 1 and 2 h duration. UH parameters such as time to peak (tp), time base (tb), and peak discharge were modeled with geomorphologic parameters of the watershed such as channel parameters as well as basin parameters. Basin parameters were obtained from the Survey of India maps using geographical information system (GIS) techniques and drainage network were updated from Indian remote sensing satellite digital images. A correlation matrix between UH parameters and geomorphologic parameters was generated and geomorphologic parameters having higher degree of correlation with UH parameters were selected. Regression equations were developed between individual UH parameters and one of the geomorphologic parameters obtained in the previous step. Out of various forms of equations, power law equations gave the highest values of the coefficient of determination (R2). Based on higher values of R2 geomorphologic parameters were selected. Then non-linear regression models were developed between UH parameters and the above-selected geomorphologic parameters based on Aikaike's information criterion (AIC) and higher R2 value. All developed models for Tarafeni watershed and its sub watersheds were tested using different statistical tests for different rainfall events. Also these models were validated for nearby Bhairabbanki watershed and its sub watersheds. These models can be suitable for small and medium agricultural sub tropical sub humid basins having similar geohydrological conditions.