Learning from floods to mitigate flood risk

BACKGROUND AND OBJECTIVES Flood risk is expected to increase in large parts of the world due to climate change and globally increasing exposure. Efficient integrated flood risk management needs to be implemented to counteract this trend. Societies can learn from floods, and consequently improve their risk management. Objective of this study is to increase our knowledge on how societies learn from floods and what measures they implement to reduce their flood risk. METHOD Societal learning can occur through 'focusing events', i.e. events that provide a sudden, strong push for action (Kreibich et al. 2011). Thus, we undertook a semi-quantitative assessment of eight paired flood events around the world, i.e. consecutive floods that occurred in the same catchments, with the second flood causing significantly lower damage. We present these eight success stories of risk reduction and unravel what risk management concepts were implemented after the first flood and how these changed the flood risk and thus the resulting damage of the second flood. RESULTS AND CONCLUSIONS Across all case studies, we find that lower damage caused by the second event was mainly due to significant reductions in vulnerability. The role of changes in exposure is less apparent; positive and negative changes are reported. In some cases, significant investments in flood protection between the floods have played a large role in exposure and damage reduction. Reduction of vulnerability seems to be a key for better risk reduction via integrated flood risk management. Thus, efforts need to be redoubled to improve our understanding of vulnerability.