The value of advanced flood models, damage costs and land use data in cost-effective climate change adaptation

Damage costs from coastal flooding are high and are expected to increase further due to rising sea levels. The associated risks suggest a need for developing methodologies and models to assess damage costs in coastal areas as a basis for decision-making on climate change adaptation. The accuracy of damage cost estimates is critical in cost-effective decision-making on adaptation measures, reflecting climate hazards, flood levels, and associated damage costs. However, detailed models require extended work compared to simpler models due to demands on input data, including land use, damage costs, and adaptation options and costs. In the paper, varying levels of resolution, damage costs and flood models are assessed for coastal flooding risks for two Danish urban areas. Two damage cost models are used: a detailed, context-specific model using local high-resolution land use- and flood damage cost data and a less detailed model with lower-resolution land use data and damage costs based on generic European cost curves. Two flood models are used for the assessment using the detailed damage cost model based on a dynamic and a static flood approach, respectively. For the coarser model, only a static flood model is used. Significant differences are identified between the modelling approaches: The flood area varies up to a factor of ten for static floods due to the digital elevation map (DEM) model alone and a factor of 17 when changing both the DEM and using a dynamic flood. Corresponding factors for resulting damage costs are four and five, respectively.