降雨量空间分布对山洪临界雨量的影响

山洪临界雨量是山洪灾害预报预警的重要基础,受降雨、土壤含水量以及下垫面的影响,其中降雨量空间分布是重要的影响因素之一。以湖北省崇阳县高堤河流域为例,采用HEC-HMS分布式水文模型计算设计洪水,试算法计算临界雨量,提出了降雨量空间分布系数,分析了降雨量空间分布系数与临界雨量的关系,探讨了降雨空间分布对临界雨量的影响。结果表明:当降雨从上游到下游逐渐减少时,达到相同成灾流量对应的临界雨量最大,暴雨中心在下游时临界雨量最小,说明降雨量空间分布对临界雨量影响显著。由分析可知,在山洪灾害预警实践中应根据实际的降雨空间分布对预警指标适当修正,对山洪进行动态雨量预警。

Influence of rainfall spatial distribution on critical rainfall calculation for early warning of flash floods

Critical precipitation is an important basis for flash flood early warning, which is affected by precipitation, soil water content and underlying surface characteristics, and the spatial distribution of precipitation is one of the important factors. Taking Gaotihe Watershed in Chongyang County, Hubei Province as an example, we discussed the influence of precipitation spatial distribution on critical rainfall for early warning of flash floods. The distributed hydrological model(HEC-HMS) and trial method were respectively used to calculate the designed flood and critical precipitation, the precipitation spatial distribution coefficient was proposed and the relationship between precipitation spatial distribution coefficient and critical rainfall was analyzed. The results show that the critical rainfall is the largest when the precipitation reduces from upstream to downstream, while it is the smallest when the rainstorm center is located in the downstream, indicating that the precipitation spatial distribution has a significant effect on critical rainfall. Therefore, in the flood warning practice, we should adjust early warning index based on the actual precipitation spatial distribution.