Applying Socioeconomic Optimisation on Blue-Green Climate Adaptation Projects in an Urban Catchment

Climate adaptation projects are often conducted without assessing the socioeconomic losses or benefits associated with the project. Methods for conducting socioeconomic assessments and optimisations have been proposed in various articles, but these methods often include more simulations than what is feasible for the common climate adaptation project. Identifying the optimum service or protection level for climate adaptation is important to avoid over or under investments, to understand the residual risks, and for informed decision-making and communication. This study develops a methodology for socioeconomic optimisation and applies it to the Kildeskovsrenden catchment in Gentofte, Denmark. The methodology requires many simulations to optimise the return period for climate adaptation. This study aims to reduce the number of simulations by defining the acceptable water level on terrain in collaboration with stakeholders. The return period combined with an acceptable water level on terrain constitutes the dimensioning criteria for the climate adaptation projects. Three return periods of 20, 50 and 100 years in year 2100 make up the optimisation exercise of identifying the optimum service level. Following its application, a set of recommendations are developed to accompany the optimisation and strengthen the methodology, including the use of the risk density curve during initial assessment of the catchment. Although the optimisation is built on a reduced amount of simulations, the methodology still requires large resources for modelling and assessments of investment and damage costs.