Comparative analysis of routed flood frequency for reservoirs in parallel incorporating bivariate flood frequency and reservoir operation

Abstract

AbstractFlood frequency is commonly defined by natural flood characteristics such as flood peak, volume and duration. However, for floods at reservoir site, reservoir operation will significantly alter the natural flood process and flood frequency. This article presents a framework of routed flood frequency which incorporates multi‐reservoir flood correlation and considers the effect of reservoir operation. Aggregated flood volume during reservoir operation has been adopted as indicator for the routed flood frequency curve (RFFC). A comparison has been made with a 62‐year series of historic flood inflows observed at two parallel reservoirs in Eastern China. By comparing the derived RFFC with traditional univariate and bivariate flood frequency results, it can be seen that the RFFC results provide a reasonable estimation of flood frequency. A sensitivity analysis indicated that the reservoir maximum release allocation has significant impact on RFFC, and a balanced allocation of flood peak can greatly decrease the overtopping risk. The “peak–peak” contour lines of the RFFC show that there are different flood combination zones which need different operation strategies in real‐time operation. Our findings improve the understanding of flood frequency concepts when considering the impact of reservoir operation and provide reference to manage real‐time reservoir operation.