山区小流域洪水分布式模拟与危险性评估

Distributed Simulation and Hazard Assessment of Flash Floods in Small Mountainous Catchment

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。

The temporal and spatial heterogeneity of flash flood is strong,and it is of great significance to accurately assess the rainfall and flood characteristics and flood hazard for the prevention and control of flash flood disasters.Seven rainfall characteristic indices and six flood characteristic indices were used to describe the rainfall and flood variability of flash flood events respectively,and China Flash Flood hydrological model was used to simulate the flood processes,combined with flood frequency indices to 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 rate of flood rising and declining 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 of the three catastrophic flash flood events were both characterized by great magnitude,high intensity,short duration,and storm centers located near the catchment outlet.In the calibration and validation periods,the average relative errors of runoff depth were both within 9%,the average relative errors of peak flow were both within 11%,the average errors of time to peak flow were both 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 magnitude of 0.0%~93.3% of river reaches reached the general flood hazard grade and above,and the overall flood hazard grade was the highest for the three catastrophic flood events,with the flood magnitude of 80.0%,35.0% and 1.7% of reaches reached high flood hazard grade and above,respectively.The research can provide technical supports for flood hazard assessment,flood disasters response and flash flood review in small mountain catchments.