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Summary
The effects of land-use changes on flooding include both the direct (by changes in the production and confluence parameters) and indirect (by changes in rainfall) effects. In this study, three periods of land-use data were used to analyze the spatiotemporal characteristics of land-use changes in different urbanization periods. The Weather Research and Forecasting (WRF) model was then coupled with the MIKE model to analyze the total effects of land-use changes on watershed flood during different urbanization periods in the Qianshan River Basin, China, including both the direct and indirect effects. In addition, the previous research methods that only consider the direct effects were evaluated by quantifying the proportions of the direct and indirect effects, so as to provide more scientific ideas and references for future related research. The results show that land-use changes increase the peak water level, peak flow, submergence areas, and risk areas in both the pre- and posturbanization period, with the increase in posturbanization exceeding that in preurbanization. This is consistent with the temporal characteristics of urban expansion in the Qianshan River Basin. Moreover, the proportions of the direct and indirect effects of land-use changes on the peak water level and peak discharge are similar, while the direct effects on the submergence and risk areas dominate those of the indirect effects. When only considering the direct effects, the increases in peak water level, peak discharge, submergence areas, and risk areas are reduced by 45%-55%, 57%-62%, 23%, and 19%, respectively. Therefore, both the direct effects and indirect effects of land-use changes must be considered in future related research.
