Evolution of flood protection levels and flood vulnerability in Europe since 1950 estimated with vine-copula models

Abstract

The magnitude of flood losses is regulated not only by hydrometeorological hazard and exposure, but also flood protection levels (primarily from structural flood defenses) and vulnerability (relative loss at given intensity of hazard). Here, we infer the variation of both factors from data on historical riverine, coastal and compound floods and their impacts in 42 European countries over the period 1950–2020 obtained from the HANZE database. We contrast actual damaging floods, which imply flood protection was locally inadequate, with modelled potential floods, i.e. events that were hydrologically extreme but did not lead to significant impacts, which imply that flood protection was sufficient to prevent losses. Further, we compare the reported magnitude of impacts (fatalities, population affected, and economic losses) with potential impacts computed with a uniform, static approach. We finally derive the spatial and temporal drivers of both flood protection and vulnerability through a multivariate statistical analysis. We apply vine-copulas to derive the best predictors out of a long list of candidate variables, including hydrological parameters of floods, exposure to floods, socioeconomic development, and governance indicators. Our results show that flood protection improved since 1950, particularly for coastal floods. However, riverine protection levels are shown to be much lower than assumed in previous pan-European studies. A strong decline in flood vulnerability over time is also observed for all three indicators of relative losses, suggesting improved flood adaptation. However, there are very large variations in both flood protection and vulnerability between subnational regions in Europe.