RECENT HUMAN-INDUCED COASTAL CHANGES IN THE GUADALFEO RIVER DELTAIC SYSTEM (SOUTHERN SPAIN)

Deltas are located at the transition between terrestrial and aquatic environments, consequently, they respond rapidly to both natural and human-induced disturbances. Mediterranean deltaic systems are particularly sensitive to changes in the coastline and in the sea level. This work addresses the evolution of the Guadalfeo Delta during the last fifteen years, focusing on the impact of the construction of Rules' reservoir in the coastal system. To this end, topographic, bathymetric and grain size measurements were analyzed and correlated with the fluvial and maritime forcing agents. In addition, we estimated the volume of sediment transported as bedload and accumulated in the delta for two different scenarios: real scenario, based on the flows drained by Rules' dam; and natural scenario, considering the flow upstream of the reservoir. Coastline and beach profile evolution were also analyzed. The results indicate that the delta dynamics is dominated by fluvial sediment supply during storm events, which are transported alongshore by the prevailing waves. We also found a similarity between the granulometric characteristics of the sediment transported as bedload and the coastal sediment. The damming of the natural river channel close to its mouth has considerably reduced the pulses of sediment towards the coast. These sediments have accumulated as delta deposits in the reservoir upstream, whereas the delta has lost sediments and receded.