Considerations on the design of shellfish reef against coastal erosion

The Catterline Bay in Scotland (UK) is regularly subjected to storm surges during spring tide periods which had led to coastal erosion and landslides. As a response to the local population whose material properties and lives are at risk, we have investigated the potential of design and construction of Nature-Based Solutions (NBS) against the geo-hydro-climatic hazards posed by a changing climate. This paper assesses theoretically the wave attenuation ca-pacity of an off-shore shellfish reef, as an NBS, which could be implement-ed in Catterline. Although less rigid than a traditional, ‘grey' solution, this strategy plays on the depth reduction created by its organic structure to break the wave before it reaches the shore. Through numerical modelling using R Studio, we calculated the wave breaking probability (Qb) and the distribution of the wave energy flux (P) from the sea to the shore. Then, we compared two possible scenarios: the current conditions without a shellfish reef and a scenario with a constructed shellfish reef at three different locations and with different dimensions. The modelled NBS showed high wave breaking proba-bility for each wave height trend. Moreover, the reef was shown to be more effective when located furthest from the shore. For maximum wave breaking effectiveness, the reef was shown to require relatively short length when lo-cated the furthest from the shore. Finally, based on the design and construc-tion requirements, we offer recommendations about the reefs dimensions, and the shellfish species to implement as well as its management throughout the design life.