摘要：This study explores the uncertainty introduced inglobal assessments of coastal flood exposure and risk when not accounting forwater-level attenuation due to land-surface characteristics. We implement arange of plausible water-level attenuation values for characteristicland-cover classes in the flood module of the Dynamic and IntegratedVulnerability Assessment (DIVA) modelling framework and assess thesensitivity of flood exposure and flood risk indicators to differences inattenuation rates. Results show a reduction of up to 44 % in areaexposure and even larger reductions in population exposure and expected flooddamages when considering water-level attenuation. The reductions vary bycountry, reflecting the differences in the physical characteristics of thefloodplain as well as in the spatial distribution of people and assets incoastal regions. We find that uncertainties related to not accounting forwater attenuation in global assessments of flood risk are of similarmagnitude to the uncertainties related to the amount of sea-level riseexpected over the 21st century. Despite using simplified assumptions toaccount for the process of water-level attenuation, which depends on numerousfactors and their complex interactions, our results strongly suggest that animproved understanding and representation of the temporal and spatialvariation of water levels across floodplains is essential for future impactmodelling.
