Protective structures as adaptive management strategy in Nature-based Solutions to mitigate sea level rise effects

Resúmen

Nature-based Solutions (NbS) that integrate salt marshes with traditional coastal protection structures are gaining interest in the face of ongoing climate change. However, major uncertainties remain about the combined impact of sea level rise and marsh-supporting management measures (e.g. nourishments and brushwood dams) on vegetation establishment. This study presents inundation percentages, bed level changes and vegetation characteristics of the dominant pioneer species of the constructed Marconi salt marsh for the growing season of 2021. This field data identified hydrodynamic and morphodynamic thresholds for vegetation establishment: <12% monthly inundation, and −0.8 cm < monthly bed level change < 1.4 cm. The existing morphodynamic DET-ESTMORF model was extended with these thresholds for vegetation establishment. A scenario analysis with this model revealed that the implementation of a brushwood dam accommodates the vegetation to establish further seaward. On the long term, until 2100, predicted sea level rise was found to cause the vegetation to retreat, but this retreat was substantially delayed by the presence and positioning of a protective structure. These results emphasize the need for adaptive management of NbS.