With increasing flood risk due to climate change and socioeconomic trends, governments are under pressure to continue implementing flood protection measures, such as dikes, to reduce flood risk. However, research suggests that a sole focus on government-funded flood protection leads to an adverse increase in exposure as people and economic activities tend to concentrate in protected areas. Moreover, governmental flood protection can reduce the incentive for autonomous adaptation by local households, which paradoxically results in more severe consequences if an extreme flood event occurs. This phenomenon is often referred to as the ‘safe development paradox’ or ‘levee effect’ and is generally not accounted for in existing flood risk models used to assess developments in future flood risk under climate change. In this study we assess the impact of extreme flood events for the European Union using a large-scale agent-based model (ABM). We quantify how the safe development paradox affects (1) population growth and the increase in exposed property values, (2) the reduction in investments to flood-proof buildings as public protection increases, and (3) the increase in potential damage should a flood occur. For this analysis, we apply an ABM that integrates the dynamic behaviour of governments and residents into a large-scale flood risk assessment framework, in which we include estimates of changing population growth. We find that the impact of extreme flood events increases considerably when governments provide high protection levels, especially in large metropolitan areas. Moreover, we demonstrate how policy that stimulates the flood-proofing of buildings can largely counteract the effects of the safe development paradox.

由于气候变化和社会经济趋势导致洪水风险增加，各国政府承受着继续实施堤防等防洪措施以降低洪水风险的压力。但是，研究表明，由于人们和经济活动往往集中在保护区，因此仅集中于政府资助的防洪措施会导致暴露的不利增加。此外，政府的防洪措施可以减少当地家庭自主适应气候变化的动力，如果发生极端洪灾事件，反而会导致更严重的后果。这种现象通常被称为“安全发展悖论”或“堤坝效应”，通常在用于评估气候变化下未来洪水风险发展趋势的现有洪水风险模型中并未加以考虑。在这项研究中，我们使用大型基于主体的模型（ABM）评估了极端洪灾事件对欧盟的影响。我们量化了安全发展悖论如何影响（1）人口增长和裸露的财产价值的增长；（2）随着公共保护的增加，对防洪建筑的投资减少；（3）洪灾可能造成的破坏增加发生。在此分析中，我们应用了ABM，将政府和居民的动态行为整合到大规模洪水风险评估框架中，其中包括人口增长变化的估计。我们发现，当政府提供高水平的保护时，特别是在大都市地区，极端洪水事件的影响会大大增加。而且，