Assessing damage cost estimation of urban pluvial flood risk as a mean of improving climate change adaptations investments

Estimating the expected annual damage (EAD) due to flooding in an urban area is of great interest for urban water managers and other stakeholders. It is a strong indicator for a given area showing how it will be affected by climate change and how much can be gained by implementing adaptation measures. This study investigates three different methods for estimating the EAD based on a loglinear relation between the damage costs and the return periods, one of which has been used in previous studies.
The results show with the increased amount of data points there appears to be a shift in the log-linear relation which could be contributed by the Danish design standards for drainage systems. Three different methods for estimating the EAD were tested and the choice of method is less important than accounting for the log-linear shift. This then also means that the statistical approximation of the EAD used in previous studies appears to be valid and is a good assumption. The EAD estimation can be simplified by having a single unit cost per flooded area which is multiplied with the extent of the flood. It does however depend on the lower threshold chosen in the estimation of the flood extent.