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    降雨和外江水位变化对城市洪涝的联合影响分析——以武汉市为例

    Joint Impact of Rainfall and River Water Level on Urban Flooding: A Case Study of Wuhan City

    • 摘要: 降雨和外江水位是影响城市洪涝灾害的主要因素.为了更好地评估洪涝灾害风险,分析了降雨和外江水位变化对城市洪涝的联合影响.以武汉市为研究对象,采用Copula函数定量评估了不同时段降雨与外江水位的联合分布特征,并基于2016年典型降雨过程验证后的青山区SWMM模型,模拟了不同降雨和外江水位变化下武汉市青山区的洪涝过程.计算结果表明,同一重现期降雨下外江水位从21.7m升高至28.0m,研究区域的致涝率增加了0.5%~2.2%;相同外江水位下降雨重现期从5a增加至100a一遇,研究区域的致涝率增加了28.5%~29.1%,泵站运行对区域致涝率的消减作用从20.6%~21.0%减少至4.1%~4.9%;表明暴雨是区域内涝的主要因素,外江水位越高对区域内涝造成的不利影响越显著,且随降雨重现期增大泵站对区域的排涝作用越来越小.武汉市汛期降雨量和长江水位的联合风险率大于单个因素的风险率,且2010~2020年强降雨与高水位联合风险率和同现风险率相较于2000~2009年的均呈增加趋势,增长率超过了70%,表明近几年来极端降雨和高水位事件频发,且未考虑降雨和长江水位的联合作用可能会低估洪涝的危险程度.该研究成果可为沿江城市的防洪排涝规划设计提供技术参考.

       

      Abstract: Rainfall and river water level are the main factors to affect urban flood disaster.In order to assess flood risk better, the joint impact of rainfall and river water level on urban flooding should be considered.Taking the Wuhan City as a study area, the Copula functions were used to quantitatively evaluate the joint distribution characteristics of rainfall and river water level during different periods.The SWMM model for the Qingshan district of Wuhan City has been validated using the typical rainfall processes in 2016, and the validated model was used to simulate the effects of different rainfall and river water level processes on urban flooding.The results show that the waterlogging rate increased by 0.5%~2.2%, with the river water level increasing from 21.7m to 28.0m.With the rainfall return period increasing from 5-yr to 100-yr, the waterlogging rate increased by 28.5%~29.1%, and the reduction value of the waterlogging rate causing by the pump operation decreased from 20.6%~21.0% to 4.1%~4.9%.Apparently, urban inundation was mainly caused by heavy rainfall, and the increasing river water level could lead to more significant adverse effects on the regional waterlogging.Meanwhile, the effect of pump station on drainage became smaller with an increase in rainfall return period.The joint risk probability of rainfall in Wuhan and water level at Hankou of the Middle Yangtze River during flood seasons was greater than that of a single factor, implying that ignoring the correlation between rainfall and river water level could lead to the underestimation of flood risk.The comparison of the joint risk probability and encounter risk probability of heavy rainfall and high-water level during different periods of 2010~2020 and 2000~2009 show increasing trends, with the increasing rate more than 70%, indicating that the extreme events of intense rainfall and higher water level events have occurred frequently in recent years.Therefore, the results can provide technical reference for flood control and drainage planning and design in the cities along the Middle Yangtze River.

       

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