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Jabaloy-Sanchez A.,University of Granada | Lobo F.J.,Csic Instituto Andaluz Of Ciencias Of La Tierra | Azor A.,University of Granada | Barcenas P.,University of Malaga | And 3 more authors.
Geomorphology | Year: 2010

The recent evolution of the Adra River delta in southeastern Spain has been reconstructed from historical maps, aerial photographs, and submarine multibeam bathymetric data. We have distinguished three main evolutionary stages whose development took place as a direct response to the main anthropic and natural influences on the river system. The first stage (4000. BC to 1872. AD) represents the natural behavior of the deltaic system with negligible anthropic influence. This long stage is characterized by coastline advance with the formation of a small asymmetric triangular delta in the natural river mouth and a typical prodeltaic deposit. In contrast, the second and third stages are characterized by anthropic interventions in the catchment and the river mouth, which heavily modified the natural dynamics of the deltaic system. The second stage (1872. AD to 1972. AD) coincided with damming of the natural river channel very close to its mouth and the construction of two successive artificial channels to deviate the river flow. The coastal dynamics changed during this second stage with erosion of the original delta and the formation of a new, asymmetrical delta at the mouth of the artificial channels. This younger eastern delta comprises two infralittoral wedges in the submarine realm, which recorded changes of lateral redistribution processes and enhanced influence of energetic events and can only be explained if the sediment supply from the river source was reduced during this period. The third stage (1972. AD to present-day) started with the damming of the trunk river in the central sector of the catchment, thus drastically reducing sediment flow to the coastal realm and triggering general erosion and coastline retreat. © 2010 Elsevier B.V.

Lobo F.J.,Csic Instituto Andaluz Of Ciencias Of La Tierra | Maldonado A.,Csic Instituto Andaluz Of Ciencias Of La Tierra | Noormets R.,University Center in Svalbard
Earth Surface Processes and Landforms | Year: 2010

A previously unknown field of large-scale sedimentary bodies has been mapped and studied on the continental shelf off the Cape Trafalgar near the Strait of Gibraltar with particular emphasis on the relationship between large-scale sediment bodies and the superimposed bedforms. This study is based on a grid of 975 km of high-resolution seismic profiles collected at water depths ranging between 15 and 60 m. High variability of large-scale sedimentary bodies is attributed to the complex interaction of hydrodynamic agents. The most prominent sedimentary features are sand banks and ridges that indicate long-term southwest and southward-directed sediment transport patterns, possibly due to the interplay of two dominant current systems flowing southward and westward. These sediment bodies evolve laterally to distinct external geometries, such as sand shoals in shallow water and sand sheets in the vicinity of larger sand banks that indicate moderate current velocities. In addition, pre-existing physiography is considered to play a role in the generation of certain sediment bodies, developed over inclined surfaces or confined laterally by elevations. Relationships between superimposed bedforms (mostly very large dunes) and underlying sediment bodies vary across the study area. Most superimposed bedforms occur over the complex mosaic of sediment banks and sheets, suggesting the interaction of several high-energy currents with different directions, such as tidal and/or wind-driven currents. © 2010 John Wiley & Sons, Ltd.

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