Fractional-Step Method Solution of Diffusive Wave Equation

Flood routing modeling of one-dimensional unsteady flow in open channels is sometimes based on the numerical solution of the diffusive wave equation. This paper presents a computational method for the solution of the diffusive wave problem with lateral inflow, based on the fractional-step technique. This method converts the diffusive wave problem into two single problems by utilizing separate equations for convection and diffusion. This separation is well adapted for computerization in distributed hydrological models. The applicability and the accuracy of this method are studied by mathematical analysis. Results show that this method provides an efficient and accurate resolution of the diffusive wave equation under some conditions on space and time steps and on spatial and temporal distribution of lateral inflow.