Short and medium-term evolution of a coastal sector in Cadiz, SW Spain

The present paper is a combined study on the medium and short-term evolution of the littoral between Chipiona and Rota (SW Spain). The analysis of coastal evolution over a period of 24 years (i.e. medium-term), was carried out using six, well temporally spaced, photogrammetric flights. Cliff top and dune toe were used as shoreline indicators to solve problems related to the use of watermark in tidal environments. Short-term littoral variations were monitored monthly by means of an electronic theodolite over a period of 2 years. The width variations of the dry beach were surveyed by always using a constant, average value for the mean sea level position derived from the numerous surveys carried out. The obtained data was representative of both seasonal and annual variations. Over medium-term, most of the littoral recorded erosion, while accretion has been recorded over recent years in the southern part. Coastal erosion was related to the impact of several storms and dune accretion was linked to the action of eastern winds. Over the short-term time frame, about the same percentage of coastal erosion and accretion was recorded. Most of the important accretion trends were observed at the central and southern parts of the littoral, the largest amount of erosion being recorded in the southern end of the littoral, in a nourished beach. All the studied beaches (except Punta Candor dunes) showed more short-term changes than medium-term ones, because of different factors, essentially the great seasonal variability of the studied beaches. The partial discrepancy between the medium and the short-term trends was related to the applied methodology, which demonstrates the problem of comparing different coastal features (dunes and cliffs on one hand, and beaches on the other) and to the implications of 2-3 years of lasting fair weather conditions that favoured beach and dune accretion, within an historical retreat tendency related to storm actions. (C) 2006 Elsevier B.V. All rights reserved.