INFLUENCE OF SUBMERGED UNDULATIONS ON THE DEVELOPMENT OF A HORN-EMBAYMENT SYSTEM: A CASE OF STUDY IN SOUTHERN SPAIN

摘要

Progradational sedimentary bodies are common features of inner shelves worldwide. These features are sandy bodies deposited beyond the shoreface in steep inner shelves, and usually present an undulating geometry. They can affect the wave propagation patterns and hence, the sediment dynamics and shoreline morphology. However, few studies have analyzed the relationship between the nearshore morphodynamics and the characteristics of the adjacent shelf in wave-dominated coasts. This work analyzes the effects of submerged undulations on wave propagation under the action of a varying wave climate in a horn-embayment system located at Carchuna beach (Southern Spain). This beach exhibits a series of large-scale cuspate features with a non-uniform alongshore spacing of hundreds of meters. Moreover, the horns present in the coasts show an asymmetric shape. The sediment is characterized by the presence of a wide range of sizes, ranging from gravel to sand, and the beach slope varies form 0.04 at the embayments to 0.3 in the horns. The analysis is carried out using detailed bathymetric measurements, observational data and numerical wave propagations. The nearshore wave results are used to compute the forcing of a morphodynamic model which uses the alongshore sediment transport gradients to compute the time evolution of the shoreline. These gradients are obtained trough a new expression obtained for curvilinear coasts that considers alongshore variations both in sediment size and beach slope. The results of the morphodynamic model show that a shoreline with a series of large-scale cuspate features non-uniformly distributed arises from an initially straight coast. The model also reproduces the asymmetries of the horns and the spacing between them.