Indicators on the ecosystem service “regulation service of floodplains”

Abstract The capacity to absorb and retain surface waters in the floodplain in case of floods and thus prevent or reduce threats to settlement areas through flooding is an important aspect among others within the ecosystem service “Regulation service of floodplains”. Two simplified indicators for measuring the potential flood retention in Germany are proposed here: the “Area for flood retention” on the one hand and the “Proportion of built-up areas in the current floodplain” on the other. The results for the 79 largest rivers of Germany, which are also presented in the form of a map, show among other things that only around 35% of the morphological floodplain in Germany still serve for natural flood retention. In the short period between 2010 and 2015 alone, the area for flood retention decreased by 7.3 km 2 (0.13%) nationwide due to the increase in the settlement and traffic area. Capturing the ecosystem service of floodplains also for smaller rivers would make sense from a flood protection perspective. It is also necessary to regularly capture any change of the current floodplain due to embankments and dyke relocations that currently cannot be deduced from available geodata. A political aim in Germany is to significantly increase the retention areas within the next few years. Our results show that huge efforts are necessary in order to reach this aim, which would directly contribute to the prevention of flood damage.