How suitable are current approaches to simulate flood risk under future urbanization trends?

Abstract Flood risk in urban areas will increase massively under future urbanization and climate change. Urban flood risk models have been increasingly applied to assess impacts of urbanization on flood risk. For this purpose, different methodological approaches have been developed in order to reflect the complexity and dynamics of urban growth. To assess the state-of-the art in the application of flood risk models under urbanization scenarios, we conducted a structured literature review and systematically analyzed 93 publications with 141 case studies. Our review shows that hydrological and hydrodynamic flood models are the most commonly used approaches to simulate flood risk. Future urbanization is mostly considered as urban sprawl through the adjustment of land use maps and roughness parameters. A low number of approaches additionally consider transitions of urban structures and densification processes in their urbanization scenarios. High-resolution physically based flood models have been advanced and are well suited for describing quantifiable processes in data-rich contexts. In regions with limited data, we argue that reducing the level of detail in flood models and increasing the level of detail in urbanization patterns should be considered to improve the quality of flood risk projections under future urbanization. For this purpose, we also call for the development of integrative model structures such as causal network models that have greater explanatory power and enable the processing of qualitative data.