Storylines of the impacts in the Netherlands of alternative realizations of the Western Europe July 2021 floods

Abstract

The 2021 summer flooding was an extremely rare event, driven by precipitation extremes that exceed Dutch design levels for flood protection of relatively small rivers and waterways. However, similar events in neighboring locations cannot be ruled out in the near future. The implications of such extreme rainfall amounts will vary by region, subject to local topography, water systems, and societal exposure. We explore the diversity of potential flood impacts induced by a similar event by constructing impact-oriented event storylines for characteristic water management regions in the Netherlands. The plausibility of the storylines is underlined by using physical evidence, proven impact-modelling concepts, and expert judgment successfully assessing the (sometimes unexpected) outcomes. The approach supports impact assessment and risk management of extraordinary rainfall and flood events. The outcomes show the relevance for crisis management and spatial policies, and confirms the need for in depth-analysis to assess concrete adaptation options.