Optimization of gated spillways operation for flood risk management in multi-reservoir systems

Abstract

In this research, a flood control operation policy based on a simulation–optimization model is developed for minimizing flood damage downstream of multi-reservoir systems by using spillway gates. The operation policy is based on a multistage method used to control floods of various magnitudes in reservoirs with gated spillways. In this operation policy, it is assumed that the system has no flood forecast, and thus shapes and sizes of the inflow hydrographs are not prior known. In this method, the rate of flow released in each stage level is decided according to the current reservoir water level and determined in such a way that flood damage risk for downstream areas is minimized while the dams’ safety is maintained. For this purpose, an optimization algorithm is introduced in which the expected annual flood damage downstream of the river system is the objective function and the spillway release discharges in stage levels of spillways gates are the decision variables. A continuous genetic algorithm is utilized to solve this problem. As a case study, the Karun River system including multi-reservoir of Karun 4, Karun 3, Karun 1 and Gotvand is analyzed. Results obtained from the proposed model indicate dramatic decrease in the expected annual flood damage. Comparison of the results with other studies shows that the proposed model has a better ability in flood control and minimization of damage costs.