River confluences intensify large floods, altering flood severity along river basins.
River confluences can impact the severity of floods by combining flood waves from tributaries and main rivers. A study analyzed the 6-10 largest floods in four German river basins to track flood waves and calculate return periods at different points along the rivers. The results show that the contribution of confluences to flood severity varies by event, with some confluences only affecting lower parts of the river basin and high return periods in upper parts not always leading to high return periods downstream.
