山区小流域洪水分布模式模拟与危险性评估

流域暴雨山洪过程时空异质性强，准确评估雨洪变化特性和洪水危险性对山洪灾害防治具有重要意义。以7个降雨特征指标和6个洪水特征指标刻画流域场次雨洪特性，采用中国山洪水文模型和洪水频率指标相结合，模拟和评估口前流域洪水过程及其危险性。结果表明：场次洪水洪峰模数、洪峰时间偏度、高脉冲历时占比、涨落洪速率与降雨总量、平均雨量、最大雨强、雨峰位置系数、基尼系数等降雨特征指标显著相关，三场致灾洪水过程的降雨均呈现量级大、强度大、历时短、暴雨中心偏中下游的特点；率定期和验证期的平均径流深相对误差均在9%以内，平均洪峰流量相对误差均在11%以内，平均峰现时间误差均在1.7 h以内，平均Nash-Sutcliffe系数为0.80和0.76；各场次洪水有0.0%～93.3%的河段流量达到一般危险及以上等级，三场致灾洪水过程的危险性等级最高，分别有80.0%、35.0%和1.7%的小流域河段流量达到高危险及以上等级。研究可为山区小流域暴雨洪水危险性评估、灾害响应和复盘等提供技术支撑。

Distributed flood simulation and hazard assessment for small mountainous catchments

Due to the strong spatial and temporal heterogeneity of storm-flash flood process, accurate assessment of rainfall and flood variation characteristics and flood hazard is of great significance for flash flood prevention and control. Six rainfall characteristic indices and six flood characteristic indices were used to describe the rainfall and flood variability of flash flood events, and China Flash Flood hydrological model was combined with flood frequency indices to simulate the flood processes and assess the corresponding flood hazard in Kouqian catchment. Results showed that the modulus of flood peak, skewness of flood peak time, proportion of high pulse duration and rates of flood rising and declining processes were significantly correlated with rainfall characteristic indices, such as total rainfall depth, average rainfall depth, maximum rainfall intensity, rainfall peak location coefficient, and Gini coefficient. Specifically, the rainfall events of three catastrophic flash flood events were characterized by great magnitude, high intensity and short duration. In the calibration and validation periods, the average relative errors of runoff depth were within 9%, the average relative error of peak flow were within 11%, the average error of time to peak flow were within 1.7 h, and the average Nash-Sutcliffe efficiency coefficients were 0.80 and 0.76, respectively. For all the flood events, the flood magnitudes of 0.0%~93.3% of the river reaches were at the general hazard grade and above, and the hazard grades were the highest for the three catastrophic flood processes, with the flood magnitudes of 80.0%, 35.0% and 1.7% of river reaches at high hazard grade above respectively. The research can provide technical supports for flood hazard assessment, disaster response and review of storm-flash floods in small mountain catchments.