Shoreline variation and wave energy fluxes at southern beaches of Mar del Plata, Argentina

BILLET, CAROLINA; BACINO, GUIDO; ALONSO, GUADALUPE; DRAGANI, W.C.

Congreso; IV LatWaves; 2022

: Mar del Plata city, located in the province of Buenos Aires, is the most important location on the Argentinean Atlantic coast. It can quadruplicate its population in summer due to tourism. This work aims to study the variability of the shoreline at the southern beaches of Mar del Plata by means of satellite images (1986-2020). CoastSat open package, Google Earth Engine (GEE) database, and satellite images from Landsat and Sentinel 2 missions were used in this work. Monthly series of beach width variations were obtained in 26 transects along 11 km of shoreline, and wave energy fluxes were used to explain the coast variability. SWAN model was implemented in a very high-resolution (100 m x 100 m) computational domain, which spans from 38.05⁰ to 38.20⁰, and from 57.39⁰ to 57.69⁰ W. Refraction and shoaling coefficients were computed along the studied coast considering all possible combinations of directions and periods, and running the wave model in stationary mode. Both computed coefficients were used to transform the wave parameters from the nearest Global Ocean Waves Reanalysis WAVERYS (1993-2020) node to the outer surf zone along the study area. Longshore and normal wave energy fluxes were estimated at each location where the transects were developed. As a result of this investigation, it was found that the highest accretion is observed in summer and the lowest in winter, at the northern sector of Punta Mogotes Bay. In addition, maxima accretion is appreciated in autumn and the minimum in spring, at the southern sector of Punta Mogotes Bay. Maxima accretion was inferred in winter and the minimum in summer, at the northern extreme of Faro Norte Bay, and vice versa at the southern extreme of this bay. Consequently, the phenomenon named “beach rotation” could be occurring in this area of the coast. Seasonal changes in beach width seem to be related to seasonal variations in the longshore wave energy flux. In addition, trends in the beach width variation (erosion-accretion) seem to be related to the alongshore and the normal wave energy fluxes.