OVERLAND FLOW DUE TO TIME VARIANT RAINFALL EXCESS

Abstract

1t or surface profile and surface runoff hydrograph under varying rainfall excess, have been obtained using method of characteristics. The varying rainfall excesses are divided into small time interval and the average value of the rainfall excesses are considered to remain uniform In each respective time intervals, The time variant infiltration values are calculated by using Horton Infiltration equation and Green I and Ampts Infiltration equation. From these time variant infiltration values, the varying rainfall excesses are found out and these values are used to find the water surface profile and surface runoff hydrographs, Study is made to find the effect of initial soil moisture on the overland flow hydrograph, by using the Green and .tempt Infiltration equation. It is found that the initial soil moisture has significant influence on the flow hydrograph. PUso the effect of slope on discharge rate has been analysed. Under same rainfall excess and same initial soil moisture, the catchment having higher slope contributes higher flow within shorter time and the flow continues for smaller durat ion compared to the catchment having flatter slope, This is because the detention storage for catchment having higher slope is less than that of the catchment having flatter slope.