FLOOD ROUTING USING APPROXIMATE DIFFUSION MODEL

Abstract

The present study aims to develop a simplified channel routing method based on the Approximate Diffusive (AD) wave equation for routing flood waves in different prismatic channels. This method is derived directly from the diffusive wave equation developed from the Saint-Venant equations without considering lateral inflow and outflow. The benchmark solutions required for comparative evaluation of the proposed routing method were obtained using the well known software package HEC-RAS version (5.0.1). To evaluate the routing capability of the proposed method, a set of 25 types of channels with each set of channels characterised by the trapezoidal, rectangular and triangular channel sections and each of these channels characterised by a unique slope, selected from the range of 𝑆𝑜 =0.0001 to 0.002, and a unique roughness coefficient selected from the range of n=0.01 to 0.06 are used for routing the given hypothetical stage hydrographs using the proposed method. The routed stage hydrograph and the corresponding estimated discharge hydrographs arrived at using the proposed method are compared with the respective benchmark solutions based on the reproduction of some pertinent characteristics of the benchmark stage and discharge hydrographs using the appropriate evaluation measures. It is inferred from the routing results of reproducing the benchmark stage and discharge hydrographs, that the proposed AD routing method is capable of reproducing the benchmark stage and discharge hydrographs closely with NSE of ≥ 0.99 when the absolute magnitude of (1𝑆𝑜⁄)(𝜕𝑦𝜕𝑥⁄)≤0.5.