Morphological behaviour of costa da caparica beaches monitored during nourishment operations

Abstract

Coastal erosion is a common problem along sandy shores in Europe, a result of its dynamic nature, anthropogenic influences and the effects of climate change. The coastal stretch Cova do Vapor-Costa da Caparica, located south from Tagus River, evidences chronic erosion problems since the 60's. It was necessary to construct a series of defence structures that more or less stabilized the beaches for nearly 30 years, although subjected to occasional overtopping and to increasing urban pressure and tourism. A worsening of the erosion situation from the winter of 2000/01 required a new intervention, which was envisaged in several phases, including the rehabilitation of the structures and the annual nourishment of the beaches. The nourishment operations were accompanied by a topo-hydrographic monitoring program, which complemented a database for the time period between 2001 and 2010. In this paper, the morphological behaviour of the sector is investigated making use of these data. A procedure for the analysis of its volumetric evolution is presented, following the test of different methods for volume variations estimation. Some conclusions about the behaviour of the sector and the lifetime of the nourishments are drawn, together with recommendations concerning topo-hydrographic monitoring. A morphological model and a medium to long-term coastline change model are being implemented at the site. Their implementation is intended to support the test, cost-effectiveness analysis and selection of interventions, for this site or others to which the analysis procedure may be exported. Â(c) Coastal Education & Research Foundation 2013.