变化环境下宣恩城区洪水变异及其成因分析

Flood variation and its cause analysis of Xuanen district under changing environment

作为调蓄城市洪水的主要工程手段,城市上游水库和城市河道整治工程在保护沿岸居民不受侵害的同时,也改变了天然河道洪水槽蓄关系,再加上气候变化的影响,导致城市洪水的形成、演变及时空分布规律发生了变异。利用水文变异诊断系统和谢才-曼宁公式,分析了宣恩城区变化环境下洪水的变异形式、程度及其成因。结果发现:1956年-2010年面平均年最大月雨量序列在1998年发生了跳跃向下的中变异,说明气候变化影响下降雨呈减少趋势;宣恩站实测年最大日流量序列在1999年发生了跳跃向下的中变异,其洪峰流量呈减少趋势;流域洪水变异是气候变化和人类活动双重影响的结果,但前者影响仅为后者的41%;渠化改造导致宣恩站洪水流量减少,加剧了洪水变异,因此其防洪预警预案需要适应环境变化而进行调整。

As themain engineering means of controlling urban flood, river and upst ream reservoir regulations which protect people against flood disasters can change river channel storage and lead to the variations of the formation, evolution, and spatial and temporal distribution of urban flood due to climate change. In this st udy, hydrological variation diagnosis system and the formula of Ch zy-manning w ere used to determine the f lood variation form, degree, and causes of Xuanen dist rict under the changing en-vironment. The results show ed that(1) the average annual maximum monthly rainfall series from 1956 to 2010 have a moderat e variation w ith downw ard jump in 1998, which indicates t hat rainfall decreases under the changing environment;(2) the annual maximum daily flow series from 1962 to 2013 have a moderate variation with dow nw ard jump in 1999, which indicates that peak flow decreases; (3) The dual effects of climate change and human activities cause the flood variation, but the former effects are only 41% of the lat ter; and(4) river canalization result s in the decreasing of t he flood flow and exacerbation of flood variation, therefore t he flood w arning plan needs to adapt to the changing environment .