Long-Term Shoreline and Islands Change Detection with Digital Shoreline Analysis Using RS Data and GIS

Abstract

This study concerned the assessment of changes in the coastline of Kavvayi beach and its nine islands in a tropical coastal wetland using remote sensing (RS) data and geographic information systems (GIS), as this sedimentary environment is still poorly characterized. The satellite data used were from LANDSAT images (30 m spatial resolution) (MSS—volume 5, TM, ETM, and ETM+ volume 6) for the period of the last 25 years (1990 to 2014). Band 5 in Landsat (MSS) and band 6 (ETM 24- OLI) were used because they clearly distinguish the boundaries between land and water. The Digital Shoreline Analysis System (DSAS) was used to understand shoreline changes such as erosion and accretion processes by calculating the net shift in shoreline (NSM), end point rate (EPR), and linear regression rate (LRR) for the period of 25 years. The results showed significant changes over the studied period, leading to erosion and accretion. Coastal processes had an impact in the period from 2005 to 2014, leading to the development of a new island in the northern part of the wetland due to the construction of a new breakwater. In addition, the causes of the shoreline changes on the islands, including anomalies and the formation of new structures in the wetland, were investigated and discussed. These analyses confirmed that the islands studied were subjected to marine transgression and vice versa. Among this, Kavvayi was subject to marine transgression over the period, and Achanthurti Island showed erosion to a lesser extent. This can be considered as a feature of wetlands in combating sea level rise at local levels and possible reasons for the changes along with the coastal zone management plans were also discussed.