Hydrodynamic flood routing considering piedmont zone

Hydrodynamic models are generally used for routing flood in river. Sometimes, solution of hydrodynamic equation carried out without considering some important aspects, like existence of piedmont zone in the computational domain. It has been observed that a significant amount of flow may infiltrate in to the ground due to presence of piedmont zone in the river. A hydrodynamic flood routing model capable of handling the effect of a recharge zone in a river is presented in this paper. One dimensional continuity and momentum equation of unsteady free surface flow, coupled with Green-Ampt infiltration model has been used as governing equations. Second order finite difference explicit scheme is used for solution of the governing equation. Possible effect of piedmont zone on flood routing is analyzed by applying the model in a hypothetical non-prismatic river reach. Computational result obtained by considering the recharge zone is compared with the result without the recharge zone. From this canvass it has been observed that the hydrograph at downstream of the piedmont zone attenuate significantly because of the presence of recharge zone in the river. Similar effect has been also noticed in the water surface elevation. Results are found to be quite sensitive to hydraulic conductivity of the piedmont zone and therefore precise estimation of hydraulic conductivity is essential for reliable result.