Shoreline evolution of an urbanized coastal dune: Médanos private neighborhood, Necochea, Argentina

Abstract

The shoreline evolution among three stages (before, during and after urbanization and anthropization of a dune) was analyzed in order to determine the influence of hard structures on coastal dune's dynamics. Through the comparison of the shoreline position extracted from aerial photographs and satellite images, the Digital Shoreline Analysis System tool was used to calculate the rates of evolution. In every coastal zone, the first line of dunes (foredune) is essential to beach dynamics. Problems arise when buildings and/or land parceling take place at these areas. This scenario requires planning, aiming to promote the equilibrium in the marine littoral stripe, and the protection and conservation of its resources. The specifics results of the studied area indicate an advance tendency of the shoreline during two periods before the anthropization (1.25 m/year). During the development of the neighborhood, a retreat tendency of the same magnitude is estimated. After the neighborhood's development, this trend changed into an advance of the order of 0.5 m/year. Through the extended analysis and the zoned beach, shoreline trends in the prior periods of the construction of the neighborhood were to advance. During the construction period, both the SW and NE sectors evidenced minimal movements of their shoreline with values close to zero and, the neighborhood center side showed a retreat. Finally, during the most recent stages (2004–2014 and 2014–2021), both sectors (SW-NE) showed slightly opposite trends, but also close to zero; center side showed an advance. This analysis, supported by oceanographic information on waves, tides and winds, suggests that during the period 1994–2004, there were no records that suggest an erosive potential. This shows a clear anthropic influence between 1994 and 2004 coincident with the neighborhood construction (1996) and dunes fixation.