城市韧性承洪理论--另一种规划实践的基础

A Theory on Urban Resilience to Floods——A Basis for Alternative Planning Practices

滨河城市面对水患问题需要一种基于韧性理论的管理方法,而不是简单地修建防洪工程来抵御。通过堤、坝和渠化的防洪工程来抵御洪水,忽略了人与自然互动时所产生的不确定因素,也无法回应因气候变化而不断增加的极端灾害,因此不是解决洪水安全问题的长期有效的方法。通过运用韧性理论提升系统存续能力,笔者提出了"城市韧性承洪"理论,作为替代目前主流方式的城市洪水灾害管理体系。该理论明确了一个城市的承洪力,以及对潜在的物质财产损失和社会经济中断等情况的预警辨识力,从而防止伤亡和保持现有的社会经济特征。通过在周期性洪水中积累经验,可以应对城市的极端洪水灾害。城市韧性承洪理论挑战了"城市如不防洪即无法生存"的传统理念,实际上传统的防洪工程破坏了应对洪水的韧性。为将此理论运用于规划实践中,笔者提出了"可浸区百分比"这一指标,用以评估城市的承洪韧性。应用自然的洪泛区功能建立城市承洪韧性,提升对洪水的适应性以替代防洪工程,将减轻洪水的危害。

River cities require a management approach based on resilience to floods rather than on resistance.Resisting floods by means of levees,dams,and channelization neglects inherent uncertainties arising from human-nature couplings and fails to address the extreme events that are expected to increase with climate change,and is thereby not a reliable approach to longterm flood safety.By applying resilience theory to address system persistence through changes,I develop a theory on ＂urban resilience to floods＂ as an alternative framework for urban flood hazard management.Urban resilience to floods is defined as a city＇s capacity to tolerate flooding and to reorganize should physical damage and socioeconomic disruption occur,so as to prevent deaths and injuries and maintain current socioeconomic identity.It derives from living with periodic floods as learning opportunities to prepare the city for extreme ones.The theory of urban resilience to floods challenges the conventional wisdom that cities cannot live without flood control,which in effect erodes resilience.To operationalize the theory for planning practice,a surrogate measure—the percent floodable area—is developed for assessing urban resilience to floods.To enable natural floodplain functions to build urban resilience to floods,flood adaptation is advocated in order to replace flood control for mitigating flood hazards.