Global Changes of Flood Hazard in Cities
Beveren, Jasper van
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As the climate changes, weather patterns are expected to shift. Stakeholders (e.g. policymakers, investors, water managers and planners) are interested in how strong and how frequent future storm events might become and what this means for the climate hazard cities face. Hence, there is need for a global assessment approach that can aid policymakers and investors in determining the city’s most at risk of certain climate hazards. Risk is here defined as the product of the probability of the hazard and a measure of the associated consequence (Risk = Hazard * Exposure * Vulnerability). Climate scientists can estimate changes in climate with global top-down models. However, they can’t trust on the reliability of these models on local scales like cities, they often have difficulties determining hydrological extremes which are especially important for stakeholders. This research aims to contribute to the climate risk assessment of cities, by proposing a new approach to contribute to decision making in determining the city’s most at risk of flooding under different climate conditions. Adding to the assessment of where climate adaptation is deemed necessary. The approach used in this research moves away from conventional top-down approaches and builds on existing bottom-up approaches, utilizing a new methodology by using global datasets, and hydrological models that can simulate the hydrological extremes stakeholders are interested in. The results show the developed workflow by testing it on the study area of Bangkok for riverine flooding under historic, climate variability and climate change conditions. Although the approach still requires work when assessing the impact of climate change, it already is in a state in which it can raise many interesting discussions about methodologies for climate risk assessments, and possibly can become an established approach in climate risk assessments. A main achievement related to scientific and management implications is that not only steps have been made to improve the reliability of rapid, global flood hazard methodologies but rather a shift in the approach on how to model climate change has started, addressing city-wide resilience issues from a holistic, global perspective. The constructed approach is a solution for the coarse scale and the misinterpretation of hydrological extremes that comes with top-down approaches. Additionally, when adding the exposure and vulnerability components of risk to the suggested approach it can provides opportunities for cities to explore whether climate disasters could have a major impact on society beyond the immediate knowledge of experts and policymakers. This information will be crucial for stakeholders identifying which cities benefit most from adaptations to climate risk under several climate conditions.