A new method to restore the impact of land‐use change on flood frequency based on the Hydrologic Engineering Center‐Hydrologic Modelling System model

Abstract

AbstractTo reveal the impacts of land‐use change on flood frequency distribution, a method to contradiction restore the largest‐gauged annual flood series to current land‐use conditions was proposed, based on the Hydrologic Engineering Center‐Hydrologic Modelling System (HEC‐HMS), with a newly developed iterative asymptotic method to calibrate the model parameters. Using the Xixi Basin on the southeastern coast of China as a case‐study, the HEC‐HMS model was applied to forward restore the largest annual floods between 1956 and 2011 by using the land‐use conditions of 2010. The flood peak flow series derived from forward restoration were used for flood frequency analysis. The results showed that (a) the iterative asymptotic method could calibrate the initial loss ratio and wave velocity relatively well. The physical meaning of the parameter values obtained was clear. The overall model simulation result was satisfactory, with Nash–Sutcliffe efficiency coefficients of 0.827 and 0.843 in the calibration and verification periods, respectively. (b) The calibration method effectively addressed the difficulty in determining the model parameters needed for resolving the restoration of the impacts of land‐use changes on the largest‐gauged annual flood peak flows and provided a newer HEC‐HMS‐based restoration approach for nonstationary flood frequency analysis. (c) Urbanization in the Xixi Basin caused a degradation in forested and arable lands, as well as in grasslands. Its main impact on the flood frequency distribution was that the average flood peak flow increased from 2,633.32 to 2,889.48 m3s−1and the changes in the coefficient of variation and coefficient of skewness were very small.