Optimal Pre-storm Flood Hedging Releases for a Single Reservoir

Flood hedging reservoir operation is when a pre-storm release creates a small flood downstream to reduce the likelihood of a more damaging but uncertain larger flood in the future. Such pre-storm releases before a flood can increase reservoir storage capacity available to capture more severe flood flows, but also can immediately increase downstream flood damage and reduce stored water supply. This study develops an optimization model for prestorm flood hedging releases and examines some necessary theoretical conditions for optimality, considering hydrologic uncertainty from flood forecasts and engineering uncertainty from flood failures. Theoretically, the ideal optimality condition for pre-storm flood hedging releases is where the current marginal damage from the hedging release equals the future expected marginal damage from storm releases. Additional water supply losses due to prestorm releases tend to reduce pre-storm flood hedging releases. The overall flood damage cost to be minimized must be a convex function of pre-storm hedging releases for flood hedging to be optimal. Such convexity is determined by the overall flood risk together with the probability distribution of storm forecasts. Increasing the convexity of the failure probability function can induce more pre-storm hedging release. Categorized by flood risk likelihood downstream, forecasted storms that are large, but not yet overwhelming flood management systems, drive Water Resour Manage DOI 10.1007/s11269-016-1472-x * Rui Hui [email protected] Jay Lund [email protected] Jianshi Zhao [email protected] Tongtiegang Zhao [email protected] 1 Center for Watershed Sciences, Department of Civil and Environmental Engineering, University of California-Davis, Davis, CA 95616, USA 2 State Key Laboratory of Hydro-Science and Engineering, Department of Hydraulic Engineering, Tsinghua Univeristy, Beijing 100084, China optimal flood hedging operation. Awide range of near-optimal hedging releases is observed in numerical examples, providing options for more rational water resources management decisions.