Levees protect floodplain areas from frequent flooding, but they can paradoxically contribute to more severe flood losses. The construction or reinforcement of levees can attract more assets and people in flood-prone area, thereby increasing the potential flood damage when levees eventually fail. Moreover, structural protection measures can generate a sense of complacency, which can reduce preparedness, thereby increasing flood mortality rates. We explore these phenomena in the Jamuna River floodplain in Bangladesh. In this study area, different levels of flood protection have co-existed alongside each other since the 1960s, with a levee being constructed only on the right bank and its maintenance being assured only in certain places. Primary and secondary data on population density, human settlements, and flood fatalities were collected to carry out a comparative analysis of two urban areas and two rural areas with different flood protection levels. We found that the higher the level of flood protection, the higher the increase of population density over the past decades as well as the number of assets exposed to flooding. Our results also show that flood mortality rates associated with the 2017 flooding in Bangladesh were lower in the areas with lower protection level. This empirical analysis of the unintended consequences of structural flood protection is relevant for the making of sustainable policies of disaster risk reduction and adaptation to climate change in rapidly changing environments.

中文翻译：

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孟加拉国Jamuna河沿岸的结构性防洪，人口密度和洪水死亡率之间的相互作用。

堤防使洪泛区免受频繁的洪水侵袭，但它们却可能导致更严重的洪灾损失。堤防的建设或加固可以在易发洪水地区吸引更多的资产和人员，从而在堤防最终倒塌时增加潜在的洪灾破坏。此外，结构保护措施会产生自满感，从而减少备灾，从而提高洪水死亡率。我们在孟加拉国的贾木纳河（Jamuna）河漫滩中探索这些现象。在这个研究区域，自1960年代以来，不同级别的防洪并存并存，仅在正确的堤岸上修建了堤坝，仅在某些地方保证了堤坝的维护。有关人口密度，人类住区，并收集了洪水死亡人数，对防洪等级不同的两个城市地区和两个农村地区进行了比较分析。我们发现，防洪等级越高，过去几十年来人口密度的增加以及遭受洪水侵害的资产数量就越大。我们的结果还显示，在保护水平较低的地区，与2017年孟加拉国洪水有关的洪水死亡率较低。对结构性防洪的意外后果进行的实证分析与制定减少灾害风险和在快速变化的环境中适应气候变化的可持续政策有关。我们发现，防洪等级越高，过去几十年来人口密度的增加以及遭受洪水侵害的资产数量就越大。我们的结果还显示，在保护水平较低的地区，与2017年孟加拉国洪水有关的洪水死亡率较低。对结构性洪水保护的意想不到的后果进行的实证分析与制定减少灾害风险和在快速变化的环境中适应气候变化的可持续政策有关。我们发现，防洪等级越高，过去几十年来人口密度的增加以及遭受洪水侵害的资产数量就越大。我们的结果还显示，在保护水平较低的地区，与2017年孟加拉国洪灾相关的洪水死亡率较低。对结构性防洪的意外后果进行的实证分析与制定减少灾害风险和在快速变化的环境中适应气候变化的可持续政策有关。