Runoff Computation on River Omi Catchment Using Spatially Distributed Terrain

Rainfall runoff is an important component contributing significantly to the hydrological cycle, design of hydrological structures and morphology of the drainage system. Estimation of the same is required in order to determine and forecast its effects. Estimation of direct rainfall runoff is always efficient but is not possible for most of the location at desired time. Use of remote sensing and GIS technology can be used to overcome the problem of conventional method for estimating runoff caused due to rainfall. For the runoff computation, SCS method was adopted which is a function of rainfall (P), initial ion (Ia), and Potential maximum retention after runoff begins (S). Rainfall data were acquired from meteorological station near the study area, S is a function of CN which was chosen based on the land use characteristics of the study area and the soil type. Also, data for peak discharge were acquired which was related with computed runoff to obtained mathematical equation that relates runoff with discharge. This equation was then calibrated, stimulated and validated. The estimated monthly and yearly spatial runoffs using SCS method were obtained. The developed mathematical model was y = 11.49x2-116.82x+647.69 with a coefficient of regression of 98.61 %. The developed model performs at 70 % of coefficient of accuracy. The peak runoff of the catchment was obtained between the months of July -October. The mathematical relationship exist between discharged and runoff with 92 % of coefficient of regression. The design of hydraulic structures within the catchments should make use of the value of peak runoff in the month of September.