Optimal Control of Flood Waters with Sediment Transport in Watershed

This paper presents a simulation-based optimization model to perform optimal control of flood stages under complex channel geometries and sediment properties in channels and channel network of a watershed. The flood control is demonstrated by operating multiple gates to withdraw flood waters from the alluvial channels in the watershed. The optimal withdrawal hydrographs for the floodgate operations are obtained by this optimization model which contains flow and morphodynamic models to simulate hydrodynamic and morphodynamic processes. Based on the designated flood control criteria (the objective water stages), the optimal solutions for determining diversion flow rates are found by solving the nonlinear adjoint equations of the nonlinear one-dimensional Saint-Venant equations. Through study of optimal control of flows with sediment transport, it is found that the influence of morphological changes on flood control becomes critical under certain hydrological and morphological conditions, and the responses of morphology to the control actions can help select the best locations of the control facilities (i.e. floodgates).