Shoreline Temporal Variability Inferred from Satellite Images at Mar del Plata, Argentina

Sandy beaches are fragile and dynamic coastal areas exposed to numerous environmental forcings. Systematic long-term data acquisition programs and exhaustive data series analyses are fundamental for a comprehensive understanding of the coastal processes. The software CoastSat was implemented to detect the shoreline position at beaches located to the south of Mar del Plata city (Buenos Aires Province, Argentina), by means of satellite images (period: 1986-2020). Tides in this area are mixed semidiurnal with a mean range of 1.74 m. The most frequent waves are characterized by significant wave heights from 0.5 to 2 m and periods of around 8 s propagating mainly from SSE. Seasonal and interannual variability and long-term trends of the shoreline position were investigated at Punta Mogotes (PM) bay, Faro Norte (FN) bay, and Ensenada Mogotes (EM). Seasonal cycles were noticed in the beach width variation series. In general, maximum accumulation was observed in summer and maximum erosion in winter. Exceptions were appreciated at southern PM bay (maximum accretion in autumn and maximum erosion in spring) and at FN bay (beach rotation on a seasonal scale). The drivers of seasonal variation are likely seasonal variations in the significant wave height and direction. PM bay showed a strong interannual variability with a clear alternating pattern between the northern and southern sectors of the bay, in an 8 +/- 1.2 years period. Long-term trends showed a generalized erosion along 9 of the 12 km of the analyzed coast.