Flood magnification on the River Rhine

Flooding on the German Rhine during the 20th century was tested for trends and assessed to identify causal mechanisms driving worsening of flooding. A review of previous research outlines the range of impacts due to climate change, land-use shifts, and river regulation. Analysis of hydrologic data, especially of the long record at Cologne, documents statistically significant increases in both flood magnitudes and frequencies. Specific-gauge analysis, which isolates the effects of channel modification, documents that 20th century river engineering has caused little of the observed increase in flooding on the German Rhine. Precipitation records from the Rhine basin confirm that flood magnification has been driven by upstream factors, including an increase in flood-producing precipitation of roughly 25% during the past 100 years and increases in runoff yields. In addition, agricultural land-use records suggest that flood magnification can be partially explained by 20th century trends documenting intensification and industrialization of German agriculture.