Beach nourishment : assessing its validity and benefits in the Maltese islands

Abstract

The coastal zone has been the focus of human civilization for centuries and beach nourishment has proven to sustainably improve the relationship between the coast and development when properly designed, managed and monitored. The dynamic character of the coasts has provided coastal scientists, developers and managers with several challenges in trying to adapt beach nourishment to the natural environment of the coast under development. The three parameters: design, management and monitoring have been examined for both nourishments under study: St. George's Bay, St. Julians and Perched Beach at Bugibba. Beach nourishment on St. George's Bay was expected to be more effective than beach nourishment on the Ix-Xtajta ta' Bugibba due to the natural character of the coastline, being, a pocket beach and a high energy coastline respectively. Primarily, the pivotal point of success or failure of a project is said to be the nourishment material and so the case studies in question were examined particularly, with respect to the choice of the nourishment material, its behavior to the natural dynamics and its relationship with the native beach material. Being both in an erosional state before the commencement of the nourishment projects, erosion control had to be a key factor in all the phases of the nourishment designs. Erosional estimates may be predicted by analyzing the distribution of the nourishment material and the original beach material (D. Reeve et.al. 2004). For this reason, the sand distribution of both the nourishment material and the natural sand material were regularly monitored for St. George's Bay for approximately eighteen months by on-site observation and sand profiling. The Bugibba Perched Beach, being a high energy shore platform, could not be examined from this point of view as prior to the project it lacked natural sand. As a result, the primary objective of the fieldworks was to identify a pattern of movement for the seasonal distribution of the artificial nourishment material outside the Perched Beach boundaries. The initial predictions for both case studies were sustained throughout the research, however, an interesting pattern evolved in the case of St. ( George's Bay, St . Julians, where the volume of the natural sand was found to be more abundant on the bay and extended further out from the coast beyond the waterline after the beach nourishment project. The results revealed an interesting element of beach nourishment where while the sediment budget was recharged by the nourishment material, the volume of the native sand was recuperated. This may be explained by the fact that the coarseness of the nourishment material allowed it to settle on top of the natural sand, and protecting it from erosion by absorbing the wave energy upon contact. Another advantage was the fact that the bay extended further on the sea bed and produced a shallower coast, which allow for the deflection of the waves by friction. Therefore the choice of grain size in this nourishment project was the key element for its success.