考虑水文趋势影响的珠江流域非一致性洪水风险分析

Non-stationary flood risk analysis in Pearl River Basin,considering the impact of hydrological trends

基于两参数对数正态分布和指数趋势模型建立了非一致性洪水频率计算模型,分析了珠江流域28个测站年最大日流量序列趋势性对洪水频率分析的影响。结果表明:1从空间分布来看,珠江流域中北部年最大日流量序列呈增加趋势,东部和南部年最大日流量序列呈减小趋势;从时间变化来看,1981-2010年年最大日流量呈显著性增加趋势的站点数较多,占总站点数的20%~25%,1966-1990年年最大日流量呈显著性减小趋势的站点数较多,占总站数的25%~30%;2珠江流域洪水放大因子(未来T年一遇设计流量与现在T年一遇设计流量比值)和重现期都受到趋势性的显著影响。西江中北部和北江洪水放大因子大于1,意味着原有的防洪工程设计标准可能无法满足未来防洪需求,存在防洪隐患;洪水放大因子较大和较小的地区集中在西江干流和东江干流;3非一致性条件下,同一场洪水过去、现在和未来重现期是不同的。非平稳性条件下,珠江流域近20年来20~50年一遇洪水发生站次相比平稳性条件下在减小。

Based on two parameter Log-Normal distribution and exponential trend model, this study attempts to explore the impacts of hydrological trends on stationarity of hydrological series. The results indicate that:(1) Increasing maximum daily streamflow is observed in the north-central parts of the Pearl River Basin, and decreasing trends in the eastern and southern parts of the Pearl River Basin; stations with significant increasing trends during 1981-2010 are more than those with significant decreasing trends during 1966-1990, accounting for 20%-25%and 25%-30% of the total number of stations, respectively;(2) Flood magnification factor(the ratio of the T-year flood in future to the T-year today) and return period are significantly affected by hydrological trends. Flood magnification factors in the West River North-Central and North River are greater than 1. Flood magnification factor smaller than 1 is found mainly along the mainstream of the West River and in the East River basin, suggesting a decreasing flood risk;(3) Compared with stationary condition, floods with return periods of 20-50 years are increasing. The mitigation standards of the flood-mitigation infrastructure will be improved to mitigate increasing flood risks in the river basins with flood magnification factor being larger than 1.