From perception to modelling: Nature-based solutions as a tool for coastal risk management

Coastal nature-based solution (NBS) projects have been on the rise over the past few years. In France, the expression is being increasingly used at a local level, and new projects are developing on the coast. However, they face various limitations, involving both technical challenges and social acceptability issues. Based on data from the perception survey conducted by the DIGUES research programme in the Authie Bay in 2021 and a numerical model used to assess the efficiency of flood protection measures developed as part of a flood action and prevention programme, this study aimed to highlight the gap between perceptions and misconceptions surrounding NBS-like scenarios and more objective modelling data. It offers a cross-comparison of these two datasets. For this purpose, the scenarios used to assess public perception in the DIGUES survey were translated in the numerical model to study the difference between perceived protection and actual protection in the Authie Bay, the opportunity for dyke relocation in an NBS scenario, and the effectiveness of the NBSs according to their scale. Overall, these results demonstrated a real benefit for implementing dyke relocation through breaches, compared to other scenarios for the Authie Bay.