Damage-Cost Modelling of Coastal Floods : Assessing the Value of Detailed Data and Advanced Flood Models as a Basis for Cost-Effective Decision-Making on Climate Adaptation

Damage costs from coastal flooding are currently 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 geographical resolution and accuracy of damage-cost estimates are critical factors in decision-making on cost-effective adaptation measures based on risk assessments, reflecting the likelihood of climate hazards, flood levels, and associated damage costs. However, detailed and context-specific models require extended work compared with simpler models due to demands on input data regarding flood probabilities, land use, damage costs, and adaptation options and costs. In the paper, data and models with different levels of resolution and localised data on floods and damage costs are assessed for coastal flooding risks for two Danish urban areas. Two different damage cost models are used: a detailed, context-specific model developed by the Danish Technical University (DTU) and a generic and less detailed EU model. For the DTU model, two flood models are used based on a dynamic and a static flood approach, respectively. Significant differences are identified between the two modelling approaches: The flood area varies between models up to a factor of 10 for static floods, due to the digital elevation model (DEM) alone, and a factor of 17 when changing both the DEM and using a dynamic flood model for a similar scenario and return period. Corresponding factors for resulting damage costs are 4 and 5, respectively