The influence of shelf-indenting canyons and infralittoral prograding wedges on coastal morphology: The Carchuna system in Southern Spain

Submarine canyons and progradational sedimentary bodies are common features of continental margins worldwide. Few studies have analyzed the relationship between the coastal morphology and the morphology and sedimentary characteristics of the adjacent shelf in wave-dominated coasts; or the potential role played by shelf-indenting canyons as inducers of sediment deposition in shallow waters. This work presents a study that correlates the coastal morphology with the characteristics of the adjacent offshore shallow shelf in an area with a complex inner bathymetry: the Carchuna system, Spain. The study area is characterized by large-scale non-rhythmic cuspate features in the coastline, whereas the inner bathymetry exhibits a shallow-water infralittoral prograding wedge (IPW) and a shelf-indenting canyon that has tributaries located a short distance from the coastline. Using detailed bathymetric measurements, observational data and wave propagation modeling, the influence of the different bathymetric elements was quantified, and a mechanism proposed for the generation of the Carchuna IPW. The wave propagation results show that the canyon is the main source of the alongshore modulation of nearshore waves and that it plays a major role in the generation of the large-scale cuspate features in the shoreline. Additionally, these results suggest that the long-term coastal erosion associated with extreme storms yielded sufficient sediment which when subsequently transported eastward, the dominant littoral drift direction, formed the IPW. Once formed the IPW modified the wave propagation patterns and contributed to the development and reinforcement of the shoreline features.