USE OF DIGITAL SHORELINE ANALYSIS SYSTEM TO IDENTIFY SEASONAL/ROTATIONAL EFFECTS FROM 2015 TO 2021 IN THE ARPOADOR-LEBLON BEACH ARC, RJ

Abstract

Studies on shoreline variations generally aim to demonstrate medium- and long-term trends. However, understanding short-term displacements is essential for comprehending the morphodynamics of embayed beaches, aiding in the assessment of vulnerability to extreme events and in coastal management, especially in urbanized waterfronts. The rotational effect is a phenomenon that can occur seasonally, where sediment exchange takes place within its own beach arc, transporting sediments from one end of the beach to the other. This study investigates the interannual behavior of the shoreline in the Leblon-Arpoador (RJ) beach arc between 2015 and 2021, using Google Earth Pro images analyzed with the Digital Shoreline Analysis System (DSAS). The main objective is to evaluate the occurrence of the rotational effect, characterized by the alternating migration of sediments between the arc’s ends, in response to wave climate seasonality. The results indicate accumulation in the west and slight retreat in the east during summer; in winter, the opposite occurs, confirming the rotational behavior based on seasonal wave climate variation. Though not designed for this purpose, with proper procedures the DSAS proved efficient in identifying short-term variations, generating consistent data that highlight seasonal shoreline changes and demonstrate its potential for short-term coastal dynamics studies.