Morphodynamics of intermittent coastal lagoons in Southern Spain: Zahara de Los Atunes

Coastal lagoons are valuable water bodies since they are of great ecological and economic interest throughout the world. Their existence is controlled by variations in sea level and the geological substrate of their location. Their morphology is linked to local topography, alternation of high and low pressure, the presence of a river, as well as tidal regime. All these factors influence lagoons along the coastline in the south of Spain. The main morphological characteristics of such lagoons are the following: intermittence, one-dimensional morphology, small size, shallow waters, high area/depth ratio, no flood- or ebb tide deltas, overwash of their low barriers during storms, high evaporation rates and feeding by rivers. Effective management of these systems requires the evaluation not only of their hydrodynamics and opening and closure rate, but also the prediction of possible future scenarios as a response to meteorological events. This paper describes the behavior of a coastal lagoon in Zahara de los Atunes (Cadiz) by means of a numerical model implemented with the objective of serving as a tool for optimizing the coastal zone management. Although the coastal lagoon at Zahara de los Atunes is closed most of the year, it is artificially opened at the beginning of the summer. The results of our study showed that during this period, the lagoon is flood-dominated with a pumping-mode response. It naturally tends to close since it is a trap for littoral drift sediments. The precise date of closure depends on the events that take place during the autumn, which determine whether the sediments deposited in the inlet by the littoral drift are flushed out by the river flow or flushed in by the waves. (C) 2010 Elsevier B.V. All rights reserved.