极端暴雨下黄土高原小流域洪水特征及风险分析

为研究极端暴雨下小流域的洪水特性，采用二维全水动力数值模型模拟流域洪水演进过程，计算不同重现期下典型断面的水力要素，并进行流域洪水风险分析。结果表明：500 a重现期对应洪峰流量增长速率最大，高达51.38%；而1 000 a重现期对应洪峰流量增长速率降低至7.61%，洪峰流量增长速率随降雨重现期的增大呈现先上升后降低规律。各断面的最大水深增幅小于其对应的洪峰流量增幅。流域洪水淹没面积随重现期增加变化较小。为使社会经济效益达到最大化，建议该小流域使用500 a重现期下洪峰流量推算新建公路和铁路桥涵孔径尺寸，研究成果可为小流域应对极端暴雨和进行防洪评价提供必要参考。

Flood characteristics and risk analysis of a small watershed in the Loess Plateau under extreme rainstorm conditions

In order to study the flood characteristics of small watersheds under extreme rainstorm conditions, a two-dimensional full hydrodynamic numerical model is used to simulate the flood routing process of a small watershed, with which the hydraulic elements of typical sections under different return periods were calculated, and the flood risk analysis of the watershed was conducted. The results show that the peak flow growth rate corresponding to the return period of 500 a is the largest, up to 51.38%, which drops dramatically to 7.61% when the return period is increased to 1 000 a, because the peak flow growth rate increases first and then decreases with the increase of rainfall return period. Moreover, the maximum water depth increment of each section is smaller than its corresponding peak flow increment, and the flood inundation area of the watershed changes little with the increase of the return period. In order to maximize the social and economic benefits, it is recommended that the peak flow under the return period of 500 a should be adopted for the calculation of aperture size of highway and railway bridges and culverts in small watersheds. The research results can provide some necessary reference for the management of extreme rainstorms and evaluation of flood control in small watersheds.