Reservoir Lake Effects on Eroded Littoral Systems: The Case of the Bay of Marbella, Southern Spain

Del Rio, J.L.; Malvarez, G., and Navas, F., 2020. Reservoir lake effects on eroded littoral systems: The case of the Bay of Marbella, southern Spain. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 443-447. Coconut Creek (Florida), ISSN 0749-0208.The Bay of Marbella, in Western Costa del Sol (southern Spain), is one of the most artificialized coastal areas of the Mediterranean. Environmental factors, such as geology and climatic conditions, have supported a great variety of industrial activities over time. However, tourism industry positioned Marbella as an internationally renowned destination demanding the rapid artificialisation of its hinterland between the 1970s and the 1990s, relying such process on natural resources -mainly water- for urban sprawl. Small reservoir lakes were constructed in the 19th century for iron melting and irrigation industries, but the greatest water management infrastructure for the development of the tourism industry, La Concepcion Dam, was constructed in the 1970s in the lower reaches of the Rio Verde, the main river in the area. Although a significant amount of water is stored in the dam, the presence of steep slopes and the likely occurrence of heavy rainfall during winter generate torrential water runoff with high energy and high rates of sediment yield. The dam performs as a sediment trap and has induced the annulment of the main source of sediment supply to the littoral system, inducing severe coastal erosion processes which have not been successfully tackled yet. This paper presents a first order estimate of sediment yield in the Rio Verde watershed introducing sediment budget stored within La Concepcion reservoir. Results show that potential high sediment yield rates estimated in the Rio Verde watershed might have reached La Concepcion Dam and might have contributed to the siltation of the reservoir lake and direct coastal erosion. Whilst recognised as the main culprit, no action is undertaken by the decision-makers to extract and reutilise sediments silting coastal dams.