摘要：Flood risk assessments are typically based on scenarios whichassume homogeneous return periods of flood peaks throughout the catchment.This assumption is unrealistic for real flood events and may bias riskestimates for specific return periods. We investigate how three assumptionsabout the spatial dependence affect risk estimates: (i) spatiallyhomogeneous scenarios (complete dependence), (ii) spatially heterogeneousscenarios (modelled dependence) and (iii) spatially heterogeneous butuncorrelated scenarios (complete independence). To this end, the model chainRFM (regional flood model) is applied to the Elbe catchment in Germany,accounting for the spatio-temporal dynamics of all flood generation processes,from the rainfall through catchment and river system processes to damagemechanisms. Different assumptions about the spatial dependence do notinfluence the expected annual damage (EAD); however, they bias the riskcurve, i.e. the cumulative distribution function of damage. The widespreadassumption of complete dependence strongly overestimates flood damage of theorder of 100 % for return periods larger than approximately 200 years. Onthe other hand, for small and medium floods with return periods smaller thanapproximately 50 years, damage is underestimated. The overestimationaggravates when risk is estimated for larger areas. This study demonstratesthe importance of representing the spatial dependence of flood peaks anddamage for risk assessments.
