Effect of alongshore sediment supply gradients on projected shoreline position under sea-level rise (northwestern Portuguese coast)

• Published in: Estuarine, coastal and shelf science coastal and shelf science, 2022-07, Vol.271, p.107876, Article 107876
• Main Authors: López-Olmedilla, Laura, Almeida, Luis Pedro, de Figueiredo, Salette Amaral, Fontán-Bouzas, Ángela, Silva, Paulo A., Alcántara-Carrió, Javier
• Format: Article
• Language: English
• Subjects: Beach nourishment; Climate change; Coastal modelling; Sediment budget; Shoreline response
• ISSN: 0272-7714; 1096-0015
• DOI: 10.1016/j.ecss.2022.107876

Shoreline changes are associated with natural and anthropic factors, such as sea-level rise, sediment budget, and beach fills. Shoreline retreat is mainly related to sediment deficit and sea-level rise. Some studies show that by the end of the 21st century some beaches may be lost, with the erosion of sandy beaches becoming predominant across the globe. The main purpose of this work is to model the shoreline evolution for 2050 and 2100 along a sandy coastal stretch in the NW Portugal, considering different scenarios of sea-level rise, to evaluate the influence this parameter and sediment budget have on shoreline displacement, as well as estimate the nourishment volume necessary to hold the shoreline in case of shoreline retreat. For this, we applied the stochastic version of the Random Shoreface Translation Model (RanSTM), in four cross-shore topo-bathymetric profiles, which are representative of alongshore coastal compartments. The overall results indicate that the key drivers in shoreline migration along the coastal stretch are not the same for the different profiles; in areas with a sediment supply deficit, shoreline recession increases, and hence the volume of sand required to hold the shoreline position in those zones is much greater. In contrast, positive sediment budgets can mitigate or reverse the erosion caused by sea-level rise. •RanSTM model applied to forecast future shoreline displacement under climate change.•Sediment budget can intensify or diminish shoreline recession under sea level rise.•Highest shoreline recession distances are observed in sectors with the greatest sediment deficit.•Sediment budget plays an important role in the estimation of nourishment volume to mitigate coastal erosion.•The results contribute to determine or adapt the best interventions to protect the coastal areas.