Increasing stress on disaster-risk finance due to large floods

Recent major flood disasters have shown that single extreme events can affect multiple countries simultaneously(1-3), which puts high pressure on trans-national risk reduction and risk transfer mechanisms(4-6). So far, little is known about such flood hazard interdependencies across regions(7,8) and the corresponding joint risks at regional to continental scales(1,9). Reliable information on correlated loss probabilities is crucial for developing robust insurance schemes(5) and public adaptation funds(10), and for enhancing our understanding of climate change impacts(9,11,12). Here we show that extreme discharges are strongly correlated across European river basins. We present probabilistic trends in continental flood risk, and demonstrate that observed extreme flood losses could more than double in frequency by 2050 under future climate change and socio-economic development. We suggest that risk management for these increasing losses is largely feasible, and we demonstrate that risk can be shared by expanding risk transfer financing, reduced by investing in flood protection, or absorbed by enhanced solidarity between countries. We conclude that these measures have vastly different efficiency, equity and acceptability implications, which need to be taken into account in broader consultation, for which our analysis provides a basis.