Simulating Runoff Using the Method of Characteristics with Unsteady Rainfall Events

Abstract

AbstractThis investigation presents the solution of kinematic wave equations for overland flow, in which the lateral term is determined from unsteady rainfall and the infiltration φ index model [1], in which the rate of abstractions is constant, yielding an excess rainfall hyetograph with a total depth that equals the depth of direct runoff over the watershed. Lateral inflow is inferred by the unit step function to represent an unsteady rainfall event; the solution uses the method of characteristics. Part of the discharge hydrograph that satisfies the boundary condition is semi-analytically solved, by a reduced, simple procedure, which does not require the use of numerical method such as finite difference. The analysis presented herein this investigation deals with both rising and falling stages. Example calculations, water surface profiles, and discharge hydrographs are also presented.