台风和非台风暴雨混合影响下的流域洪水特征及其频率分析方法研究

Floods in the southeastern coastal area of China are usually generated by two different mechanisms. One is the typhoon induced rainstorm. The other is dominated by the frontal rainstorms and categorized as non-typhoon induced rainstorm. The two rainstorm types have different spatial and temporal variation characteristics, leading to significant distinctions between the floods caused by two types of rainstorms. The flood differences between two types have not been well studied. To reveal the different characteristics of the two flood types, a few meso-scale watersheds influenced by both typhoon and non-typhoon induced rainstorms will be selected for studies. The spatial and temporal variation characteristics of typhoon and non-typhoon induced rainstorm-flood are analyzed using indices describing the spatial and temporal heterogeneity, respectively. A multiple regression analysis will be used to estimate the relationship between flood peak discharges and the rainstorm indices. .The flood time-series generated by two different mechanisms will be tested for its trend. For the series exhibiting a decreasing or increasing trend, two approaches for frequency estimation of non-stationary time series will be used respectively. One of the approaches is based on the forward reproduction combined with the simulation of distributed watershed model, and the other is directly based on the non-stationary hydro-meteorological extremes. Since the conventional hydrological frequency analysis based on the stationary assumption may be invalid for floods generated by two different mechanisms, a mixed distribution will be employed to analyze the non-stationary flood frequency. The results will reveal the spatial and temporal variation characteristics of typhoon and non-typhoon induced rainstorms and the differences in the generation mechanisms of the two kinds of flood. The appropriate type of mixed distribution for the frequency analysis in the region will be determined.

我国东南沿海地区的暴雨洪水，可以分为台风暴雨洪水和以锋面暴雨为主的非台风暴雨洪水。生成暴雨的天气系统不同，暴雨的时空变化特征也有很大差异；两类暴雨生成的流域洪水特征也应有很大的差异。选择福建省沿海多个台风和非台风暴雨影响都比较显著、且观测资料系列比较长的中小流域为研究区，通过（1）流域台风和非台风暴雨时空变化特征及其洪水响应的统计分析，（2）重点应用分布式水文模型进行洪水还现与基于非一致性极值序列直接分析的两种频率分析方法，与成因不一致洪水序列的混合分布分析相结合,探讨变化环境影响下的不一致与成因不一致共同影响下的洪水混合分布频率分析方法，揭示流域尺度台风和非台风暴雨的时空变化特征及其洪水响应特点、差异，阐明台风和非台风暴雨洪水成因不一致性对洪水频率总体分布的影响。其成果将进一步丰富区域洪水规律认识，完善非一致性条件下洪水频率计算问题研究，具有重要的理论意义与应用价值。

我国东南沿海地区的暴雨洪水，可以分为台风暴雨洪水和以锋面暴雨为主的非台风暴雨洪水。生成暴雨的天气系统不同，暴雨的时空变化特征有很大差异，两类暴雨生成的流域洪水特征也应有很大的差异。选择福建省及其沿海的晋江、西溪、山美水库集水区等台风和非台风暴雨影响都比较显著、且观测资料系列比较长的中小流域为研究区，开展了台风和非台风暴雨时空变化及其洪水响应分析，台风非台风暴雨、洪水的混合频率分布研究，基于分布式水文模型还现的非一致频率分析和非一致台风与非台风洪水极值序列的模拟与频率分析等4个方面的研究。.结果表明，（1）台风非台风暴雨时空变化特征差异显著；流域洪水过程、洪峰序列，以及场次洪水模拟的HEC-HMS关键参数的变化，都显示洪水对台风和非台风暴雨的响应规律明显不同。（2）区分台风非台风暴雨、洪水进行混合频率分析，估计结果的安全性和不确定性方面表现较好；样本分布形态的非一致性是影响暴雨、洪水混合频率分析适用性的主要因素。（3）提出了基于HEC-HMS模型还现土地利用变化对洪水过程影响，进而分析现状土地利用条件下洪水频率分布的新方法。城市化导致的频率分布变化主要表现在还现洪水系列洪峰流量均值高于实测洪水系列，参数Cv和Cs变化较小；区分台风和非台风暴雨洪水，可以更合理揭示土地利用变化对台风和非台风暴雨混合洪水频率分布的影响。（4）基于Vine-Copula函数，结合MMFA模型，建立了台风非台风洪峰模拟和混合频率分析方法。台风非台风洪峰峰前雨型区域特征差异为长重现期的洪峰估计带来更大不确定性；非台风洪峰对雨型区域组合特征的变化更加敏感，雨型对非台风洪峰上尾部特征的影响显著，也相应影响台风非台风混合洪峰分布的特征。.这些成果进一步丰富东南沿海区域洪水规律认识，提出的方法是变化环境下非一致性洪水频率计算问题的重要补充，区分台风非台风暴雨的洪水研究，可望成为深化区域气候水文研究的重要特色方向。