Retention areas flooding Brandenburg

The flood events in recent years at Oder and Elbe, which also affected the Land of Brandenburg, showed that the timing of the flood wave was significantly shortened compared to previous events, resulting in a higher amplitude, i.e. higher water levels. One of the main causes of this is a drastic decline in natural retention areas caused by increased water drainage close to the surface in the catchment areas and by the reduction of natural flooding areas close to rivers. Retention in the hydrological sense refers to the reduction, inhibition or delay of discharge. These processes can directly affect the flood wave in the flowing waters and their flooding areas (water retention) or control the formation of a flood wave in the catchment area (territory retention). Measures to preserve and extend retention spaces on the river itself are the most effective method of mitigating the water level in the event of flood discharge in a water, as the flood wave is deformed during its course in the river bed and in the floodplain by various restraint mechanisms (Böhm et al. 1999). The technical flood protection (dikes, retention basins, dams) is limited, since restraint basins cannot be built at any size and dikes cannot always be built higher. (National Environment Agency 2003). The territorial retention, on the other hand, aims to reduce the flow wave by preventing the water from draining as far as possible at the site of the precipitation or by delaying the drainage (Böhm et al. 1999). A goal of flood prevention must therefore be to prevent outflow-enhancing and drain-accelerating measures and to reverse or at least mitigate any negative effects that have already occurred. This requires knowledge of suitable potential retention areas.