Coastline change detection adjacent to Salli GN Division in Trincomalee, Sri Lanka

Abstract

Monitoring shoreline is importantt for planning and development in the coastal region. This research aims to detect and analyze the rate of shoreline changes in the Salli Grama Niladhari (GN) division between 1991 and 2021. In this study, the shoreline change rate along the coastline was analyzed using multi-temporal Landsat imagery and the Digital Shoreline Analysis System (DSAS). The analysis revealed a significant rate of both accretion and erosion along the coast of the study area. Remotely acquired, multi-temporal Landsat images with 30 m resolution were collected at 10-year intervals from 1991 to 2021. To perform the quantitative analysis of shoreline delineation, geometric and radiometric corrections were applied to all Landsat images. Shorelines were then automatically extracted in ArcGIS 10.8 using the Tasseled Cap (Landsat toolbox), and the rate of shoreline change was analyzed using the Digital Shoreline Analysis System extension. End Point Rates and Linear Regression Rates were used to calculate the net rate of shoreline change over 30 years from 1991-2021. The rates of shoreline change and net movement along transects were determined. Two hundred twenty-one transects at 20m intervals were cast for the entire coast of the study area, the bulk of which revealed coastline erosion (78.6%). The analysis showed that some parts of the research area experience remarkable shoreline changes (averagely 0.237m/yr accretion and -0.676 m/yr erosion base on Linear Regression Rates and 0.28 m/yr accretion and -0.671 m/yr erosion based on End Point Rates) between 1991 and 2021. The combined effects of the different natural and human activities on the coast of the study area have caused this shoreline change. An "erosion" type coast can be seen in the study area and coastal protection is therefore considered important for this area as well.