东西部城市洪涝灾害风险演变规律与适度防御阈值研究

Study on flood risk evolution and moderate flood control standard helps to solve fundamental problems for urban flood protection planning and comprehensive risk management improvement. At present, most research on flood risk evolution is based on statistical analysis, and urban flood control standard is mainly defined according to the importance of social and economic status or non-agricultural population. It is failed to fully consider temporal and spatial risk variation and reflect the actual situation, such as rapid urbanization process and differences of natural geographical features and economic development between the eastern and western regions in China. So this project intends to use several scientific methods including theoretical analysis, field survey, statistical analysis, scenario simulation and function construction to solve these problems. Urban flood risk evolution law theory model is put forward based on dualistic water cycle and flood risk system. The flood risk is expressed as S-shaped damage-return period function with fewer parameters and explicit physical meanings, which can be used to assess and predict flood risk rapidly. The turning points of D-R function curve can be utilized for moderate defense threshold definition and rational strategy development associated with flood hazards. The research results provide new concepts and new methods for adjusting “adaptive” urban flood protection standard to different conditions in terms of locality and time concerned.

把握洪涝灾害风险演变规律，选择适度的防洪标准，是制定城市防洪规划与完善综合风险管理中绕不开的科学问题。目前关于洪涝灾害风险演变的研究多基于统计分析，而我国城市防洪标准主要依据城市社会经济地位的重要性或非农业人口数量进行选择，未能充分考虑风险的时空变化，也就不能反映我国城市化进程迅猛，东西部地区自然特征与经济发展水平差异较大的实际情况。针对以上现状，本课题拟采用理论分析、实地调查、统计分析、情景模拟、函数构建等研究手段，基于“自然-社会”二元水循环与风险系统理论，提出城市洪涝灾害风险演变规律理论模型；构建具有物理意义的洪灾损失-重现期风险函数，实现对洪灾风险的快速评估与预测；识别风险管理的适度防御阈值，提出科学风险分级方法。研究成果可为制定城市防洪标准中，“度”的把握提供因地制宜、因时制宜的新理念和新方法。

把握洪涝灾害风险演变规律，选择适度的防洪标准，是制定城市防洪规划与完善综合风险管理中绕不开的科学问题。目前关于洪涝灾害风险演变的研究多基于统计分析，而我国城市防洪标准主要依据城市社会经济地位的重要性或非农业人口数量进行选择，未能充分考虑风险的时空变化，也就不能反映我国城市化进程迅猛，东西部地区自然地理特征与经济发展水平差异较大的实际情况。针对以上现状，本课题拟采用理论分析、实地调查、统计分析、情景模拟、函数构建等研究手段，基于“自然-社会”二元水循环与风险系统理论，提出城市洪涝灾害风险演变规律理论模型；构建具有物理意义的洪灾损失-重现期风险函数，实现对洪灾风险的快速评估与预测；识别风险管理的适度防御阈值，提出科学风险分级方法。研究结果表明：防洪排涝工程可有效降低防洪排涝标准内的洪灾风险，而对超标准暴雨洪水，其减灾效益并不明显。因此，仅依靠工程措施减灾效果有限，必须采取综合性减灾对策。东、西部城市社会经济水平差距较大，防御标准西部要低，且由于降雨较少，风险等级也较低。因此在防洪工程投入上也就较少。我国处于迅猛城镇化发展阶段，城镇地区洪涝风险急剧上升，安全保障需求大为提高，加大了洪涝灾害防治的复杂性与艰巨性。研究洪涝灾害的成灾机理，提出科学合理的风险评估与预测方法；构建具有物理意义的洪涝灾害损失函数，把握快速城镇化背景下洪涝风险的演变趋势；识别出适度防御阈值，可为完善洪涝灾害综合防治体系提供依据。该研究对建立健全高效的洪涝风险管理体制，具有重要的理论价值与实践意义。