Large‐scale nourishments and mega‐nourishments are increasingly employed as nature‐based solutions (NBS) to enhance coastal resilience. This study evaluates the hydrodynamic effects of nourishments and mega‐nourishments of varying radius (500 m–2 km) and elevation (2–3 m) in a macro‐tidal embayment in the United Kingdom, Morecambe Bay, using a hydrodynamic model developed in Delft3D. Offshore wave heights of 0.5–1 m were applied at the open boundary. The analysis focuses on the capacity of these interventions to dissipate wave energy and reduce water levels under typical offshore conditions. For the largest interventions, the results indicate wave height reductions within the nourished area of up to 0.7 m and maximum water level decreases of up to 0.8 m. For the smaller radius (500 m), increasing the footprint generally produced significantly greater reductions than increasing elevation alone, whereas at a radius of 1.5 km, the results were more variable. Higher offshore wave conditions further enhanced the dissipation effect. Changes outside the intervention were comparatively minor, reflecting localised energy dissipation via depth‐limited breaking and bottom friction. Sediment transport and morphological changes were not included in this analysis, which should be considered when interpreting the results. Although in some cases, absolute reductions remain modest, they can be relevant for hydraulic loading on both the nourishment and adjacent infrastructure, with potential benefits for overtopping, operational performance, and long‐term maintenance.
Leonardi et al. (Thu,) studied this question.