Coastal environment is a dynamic system in which numerous natural processes are continuously actuatingand interacting among them. As a result, geomorphologic, physical and biological characteristics of coastalenvironments are constantly changing. Such dynamic balance is nowadays seriously threatened by the strong andincreasing anthropic pressure that favors erosion processes, and the associated loss of environmental, ecologic andeconomic aspects. Sandy beaches are the most vulnerable environments in coastal areas.The aim of this work was to reconstruct the historical evolution of the Mediterranean coastline of Andalusia,Spain. The investigated area is about 500 km in length and includes the provinces of Cadiz, Malaga, Granadaand Almeria. It is essentially composed by cliffed sectors with sand and gravel pocket beaches constitutingindependent morphological cells of different dimensions.This study was based on the analysis of aerial photos and satellite images covering a period of 55 years, between1956 and 2011. Aerial photos were scanned and geo-referenced in order to solve scale and distortion problems.The shoreline was considered and mapped through the identification of the wet / dry sand limit which coincideswith the line of maximum run-up; this indicator - representing the shoreline at the moment of the photo - isthe most easily identifiable and representative one in microtidal coastal environments. Since shoreline positionis linked to beach profile characteristics and to waves, tide and wind conditions at the moment of the photo,such parameters were taken into account in the calculation of shoreline position and changes. Specifically,retreat/accretion changes were reconstructed applying the DSAS method (Digital Shoreline Analysis System)proposed by the US Geological Survey.Significant beach accretion was observed at Playa La Mamola (Granada), with +1 m/y, because the constructionof five breakwaters, and at Playa El Cantal (Almeria) and close to Garrucha harbor, with values of +2 m/y.Erosion rates ranged from -0.4 m/y (at Playa Casarones, Rubite) and -0.7 m/y (at Playa Castillos de Baños,Granada) to c. -2 m/y (at Punta de los Hornicos, Almeria).The analysis of coastline evolution revealed as the distribution of erosion areas is strictly related to the incorrectdesign of coastal structures and their negative effects on downdrift areas. Obtained results clearly evidenced as, inorder to evaluate the efficiency of emplaced coastal defense structures, a continuous coastal evolution monitoringplan should be implemented.
|Numero di pagine||1|
|Stato di pubblicazione||Published - 2015|