Beach-Dune Frontal Limit Variability between 2012-2022 at Cassino Beach, Southern Brazil

Sá, L.P.; Oliveira, U.R.; Albuquerque, M.G.; Façanha, M.C., and Cruz, L.F., 2024. Beach-dune frontal limit variability between 2012-2022 at Cassino beach, southern Brazil. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 351-355. Charlotte (North Carolina), ISSN 0749-0208. The coastal zone faces natural and anthropic challenges, with beaches highly susceptible to extreme events. In southern Brazil, frontal systems and extratropical cyclones have caused significant changes in beach dynamics. This study aims to characterize the variation of the beach-dune limit adjacent to Cassino beach, southern Brazil, over the last decade. Based on a time series satellite images (GeoEye Sensor) from 2012, 2015, 2019, and 2022, it was possible to characterize whether the sections of the urban perimeter of Cassino beach are subject to accretion, retraction, or remain stable. From the beach-dune limit vectorization, the seasonal movement process was characterized using a method that emulates the Digital Shoreline Analysis System (DSAS) tool. The study area was divided into three sectors: north, middle, and south, each with 20, 30, and 20 transects, respectively. The results show that the average movement over a decadal was 21.3 meters of progradation. The southern sector presented the highest accretion rate, totaling approximately 35.4 meters, while the northern sector recorded the lowest rates (6.01 meters). The central portion of the study area presented 22.2 meters of accretion. The period from 2012-2015 was where the greatest progradation occurred, a total of 15.3 meters for the period, followed by the period from 2019-2022, totaling 7 meters prograded. The interval between 2015 and 2019 recorded retreat rates of 6.8 meters in the northern sectors, and 2.02 meters in the central portion. On the other hand, the southern sector presented an average progradation of 8.2 meters, totaling for the period an average of 0.4 meters retreated. Cassino beach presents a sedimental balance predominantly positive, although sporadic retreat episodes can occur. Finally, this study offers perspectives for coastal management and the prediction of future changes, as the locality is among the most sought after by users in the summer season.