Analysis of long- and short-term shoreline change dynamics: A study case of Joao Pessoa city in Brazil

摘要

The coastal area of Joao Pessoa city, Paraiba, Brazil, is densely populated and has a large flow of trade and services. More recently, this region has been suffering from the advance of the sea, which has caused changes in the shoreline and caused a decrease in the beach area and damage to various urban facilities. Thus, the spatiotemporal changes of the short- and long-term characteristics of the shoreline of Joao Pessoa city over the past 34 years (1985-2019) were calculated and the forcing mechanisms responsible for the shoreline changes were analyzed. Remote sensing data (Landsat 5-TM and 8-OLI) and statistical techniques, such as endpoint rate (EPR), linear regression rate (LRR) and weighted linear regression (WLR), using Digital Shoreline Analysis System (DSAS), were used. In this study, 351 transects ranging from ～1.1 km to ～6 km were analyzed within four zones (Zones 1 to IV), and the main controlling factors that influence the shoreline changes in these zones, such as sea level, tidal range, wave height, beach morphology and ocean currents, were discussed. The long-term change from 1985 to 2019 showed primarily accretion on the shoreline of Joao Pessoa city, with the rate of 0.55 m/year (WLR method); 282 transects showed accretion. The results showed that Zone-I, which was located in the south of the study area, was the only zone that primarily recorded erosion from 1985 to 2019, with a mean rate of-0.23 m/year according to the WLR method. According to the short-term shoreline change analysis, a cyclical pattern of erosion was observed in the 1985-1990,1993-1999, 2005-2011 and 2014-2019 periods, and accretion was observed in the 1990-1993,1999-2005 and 2011-2014 periods. It was inferred that the patterns of all analyzed zones were similar, i.e., when majority accretion was detected within a zone, the other zones also recorded accretion, except for during the period from 2014 to 2019, when Zone-Ⅰ showed different behavior. Finally, the long- and short-term analyses showed that the coastal area of Joao Pessoa city is influenced by various forcing mechanism responsible for the shoreline changes.