Evaluating coastal multifunctionality: sand nourishment strategies at decadal timescales

Globally, there is a growing societal need for multifunctional coastal climate adaptation of sandy shores in the coming decades. Sand nourishment strategies are increasingly regarded as promising nature-based approaches, as they may increase flood safety and mitigate erosion while enhancing recreational and ecological functioning. However, their multifunctional potential has not yet been assessed under diverse climate impacts at decadal scales. This study aimed to identify the effects of beach, shoreface and mega-nourishment strategies on coastal multifunctionality using a systems-based approach. We identified indicators for recreational, ecological and flood safety functions through a structured literature review, and integrated these into a process-based sand distribution model for dissipative coastal profiles. We simulated indicator states as the coastal profile responded to the nourishment strategies under five sea level rise scenarios and three erosion rates, and calculated the extent to which coastal functions and multifunctionality were supplied over six decades. We found that all three nourishment strategies could supply coastal multifunctionality to a high extent, although the drivers of this potential differed per strategy. These findings imply that sand nourishment strategies are viable approaches for multifunctional coastal climate adaption in the coming decades, that require prioritising specific coastal features and functions. While sand nourishment strategies remain high-impact interventions, they also allow for creating coastal landscapes that may not only prevent floods but also enhance the environmental and societal functions and features we desire of sandy shores worldwide.