Werden die Hochwasser größer? Ursachen, Trends und Handlungsoptionen

The risk of river flooding is being discussed with growing concern, particularly whether this risk has increased and will continue to rise in the coming years. This article examines three key contributing factors. The first are land use changes such as deforestation, urbanization, and soil compaction. These changes can lead to reduced water infiltration and therefore higher flood peaks in small catchments. In larger river basins, however, soil saturation is more important, so land use has a smaller impact. The second are hydraulic engineering interventions including river training, levees and dams. These primarily influence mediumsized flood events downstream. The third is climate change. More frequent and intense short-duration rainfall increases flood risks in small catchments. In larger catchments, long-duration rainfall events are more relevant, and their changes are more complex. Additional processes such as evaporation and snowmelt can result in either increasing or decreasing flood trends. Effective risk management requires a nuanced understanding of all three factors. A major challenge lies in coping with so-called mega floods, where nonstructural measures play a crucial role.