Evolution of beach-dune fields systems following the construction of jetties in estuarine mouths (Cantabrian coast, NW Spain)

摘要

The morphology of many Spanish estuarine mouths has been modified over recent decades to improve access to the harbours located inside. The normal practice has been the construction of jetties along one or both sides of the mouth to improve the flow though the main estuarine channel and thereby prevent the formation of bars in the main channel bed and ebb-tidal delta lobes or mouth bars in the mouths. The new wave refraction/diffraction dynamics created by these structures induces a strong modification of the beach-dune systems. In the zones adjacent to the jetties, a rapid migration occurs until the beach profile and the associated dune field stabilise, which occurs when the confined space is unable to retain more sediment. This process may include the reworking of outer sandy bottoms and the generation of new stabilised bars. A portion of the sand used by waves to form this accretion is supplied by erosive processes occurring during the same period on the beaches and dune fronts located in areas further away from the jetties, which in many cases are heavily used. The aim of this paper was to analyse the accretion geometries and rates of beach-dune systems in several estuaries that drain into the Cantabrian coast and the subsequent erosion in the outer dune belt, testing a conceptual model formulated to explain the factors that determine the beach-dune response to human actions. The methodology applied can be exportable to other regions to facilitate the prediction of anthropic effects from harbour development and coastal management policies and the subsequent conservation of these environments.