前期土壤湿度和降雨对小流域山洪预警指标的影响评估

山洪灾害临界雨量预警指标受多种因素影响,尤其是前期土壤湿度状况和降雨变化。基于分布式水文模型和情景分析法确定安徽省岳西流域的山洪灾害临界雨量集合,评估前期土壤湿度状况、雨型和预警时段对临界雨量变化的影响。研究表明：① 中国山洪水文模拟系统在研究区内具有较好的适用性,率定期和验证期的平均径流深和洪峰流量相对误差均在15%以内,平均峰现时间误差在1h以内,平均Nash-Sutcliffe系数为0.79和0.77;② 60种情景模式下,池墩组村的临界雨量集合为141~528 mm;③ 前期土湿状况和雨型均显著影响临界雨量变化,随着土壤饱和率从0.20分别增加到0.50和0.80,临界雨量分别减少13.7%~16.2%和26.8%~31.8%;短历时预警时,临界雨量由大到小的相应雨型分别为减弱雨型、中间雨型和增强雨型。研究可为山洪灾害预报和早期预警提供理论支持,也为中国山洪灾害防治提供参考和借鉴。

Impact assessment of antecedent soil moisture conditions and rainfall variability on flash flood warning index at catchment scale

Flash flood disaster warning index is highly influenced by many factors, especially the antecedent soil moisture condition and the rainfall variability. In this study, the rainfall threshold assemble is determined in Yuexi catchment of Anhui province based on the distributed hydrological model and scenarios analysis. Moreover, the impact of these factors is assessed on the variation of the rainfall threshold assemble. The results showed that: (1) China Flash Flood-Hydrological Modelling System presented preferable performances in the study area. During the calibration and validation periods, the average relative errors of runoff and peak flow were less than 15%, the average errors of time to peak flow were no more than 1 h and the average Nash-Sutcliffe efficiency was 0.79 and 0.77, respectively. (2) The rainfall threshold assemble at Chidunzu village was determined as 141-528 mm under the 60 scenarios designed. (3) Both the antecedent soil moisture condition and rainfall pattern highly influenced the rainfall threshold assemble. The decrease ratios of rainfall threshold were in a range from -13.7% to -16.2% and from -26.8% to -31.8% as soil saturation increased from 0.2 to 0.5 and from 0.2 to 0.8. As for the early warning within 6 hours, the advanced rainfall patterns yielded the maximum rainfall threshold, followed by the intermediate pattern and delayed pattern. All studies are expected to provide theoretical supports for flash flood early-warning and forecasting, and also provide references for the national flash flood prevention and control in China.