Study of the sedimentation and dynamics of Modelo Beach (Northern Portugal)

Abstract

Coastal sandy systems exposed to the Atlantic Ocean are particularly vulnerable to erosion caused by intense winter storms, a phenomenon that is expected to intensify significantly due to the current trajectory of climate change and continuing human interventions in coastal and river systems. The objective of this research is therefore to characterize and quantify the sedimentary dynamics and evolution of Moledo beach (Northern Portugal) during an observation period, namely from 2004 to 2023. Both the orthophotos and the reference profiles will be used to calculate the movements of the shoreline or dune toe over time and thus derive the advance/retreat rates of the beach, which show a general downward trend of the shoreline in the southern part of the study area. The winter storms caused significant setbacks. The study of the beach of Moledo during the period 2004-2023 reveals a predominance of moderately selected medium- coarse grain sands with very low carbonate content, consistent with its high-energy ocean exposure and limited sedimentary contribution. The accumulated net balance is negative on most of the coast, which indicates that the dominant erosive dynamics is reinforced by artificial dune stabilization and reduced river sediment feeding. Despite this, there is some seasonal recovery of the beach in periods without intense storms, which shows a limited capacity for natural resilience. This scientific characterization justifies the need for coastal management measures to mitigate the progressive erosion in the southern sector imbalance observed in Moledo.