Recent human-induced coastal changes in the Guadalfeo river deltaic system (southern Spain).

Rafael J Bergillos, Cristóbal Rodríguez-Delgado, Alejandro López-Ruiz, Agustín Millares, Miguel Ortega-Sánchez, Miguel Á. Losada

Friday 3 july 2015

8:45 - 9:00h at Oceania (level 0)

Themes: (T) Managing deltas, (ST) Impacts of urbanization and land reclamation

Parallel session: 14K. Managing deltas - Impacts

Deltaic systems are particularly sensitive to coastline changes as they allocate numerous activities and have high ecological, economic, and social importance. The Guadalfeo river catchment (southern Spain) has an area of 1252 km2, includes the highest peaks on the Iberian Peninsula (~3400 m.a.s.l.) and is fed by one of the most high-energy drainage systems along the Spanish Mediterranean coast. The topographic gradients, in combination with the high variability of precipitation and temperature distributions, may lead to large contributions of a wide range of sediment sizes as bedload. During the 90’s the river was regulated altering the natural behavior of the system. As a consequence, nowadays the delta presents erosion problems and a severe coastline retreat. For this reason, several artificial replenishments have been done near the river mouth in recent years. This work studies the influence of the construction of Rules’ reservoir in the coastal area surrounding the Guadalfeo river deltaic system. The sediment loss in the coastal system has been correlated with the sediment volume retained in the Rules’ reservoir based on: (1) fluvial and maritime data, (2) sediment transport formulations and (3) topographic, bathymetric and granulometric measurements. These measurements have been made both at Rules reservoir and at the coast since the construction of the dam to the present. Our results indicate that the coastal changes in the delta, both in the plan form and cross-shore profiles, are controlled by the sediment supply reaching the coastal domain. The damming of the natural river channel close to its mouth has considerably reduced these pulses of sediment on the coast, which have been accumulated as delta deposits in the reservoir upstream. The erosion problems in the delta may be exacerbated by the expected increase in sea level in the coming years. Management practices in the river basin and on the coast will be analyzed and discussed in the conference.