Shoreline and coastal morphological changes induced by the 2004 indian ocean tsunami in the Katchal Island, Andaman and Nicobar – A study using archived satellite images

Abstract

The December 24, 2004 Sumatra earthquake and Tsunami had caused large damage to the coastal environment in the Indian Ocean countries. Continuous monitoring of shorelines are needed to understand the causes and consequences of recent changes and to assess the long term impact of tsunami waves. Assessment of the shoreline and coastal morphological changes due to tsunami in Katchal Island have been lacking due to obstacles in the field data acquisition owing to their remote location. As access to the ground information is limited, the only possibility is the monitoring of shorelines from multi-temporal satellite images. In this study, we demonstrate the methods used in extracting shorelines and analyzing their changes using the data from Indian Remote Sensing (IRS) satellites, the EO1-ALI and Landsat images in a GIS environment. Eight satellite images acquired between 2004 and 2014 where used for the shoreline change and coastal morphology analysis in the Katchal Island. The results showed that the island experienced extensive erosion and significant loss in land area of about 20 km2. Erosion has been more prevalent than accretion at an average linear regression rate of ~ −13 m/year between 2004 and 2010. Net shoreline movement of more than 4 km landward has been observed at the western coast of the island. Regions of high net shoreline movements were associated with bay-mouth areas, and regions linked with coastal inlets. This study demonstrates the strong potential of archived satellite images for detecting shoreline movements in far-off islands. The results will likewise help in understanding the response and recovery of shorelines in Indian Ocean regions after the 2004 tsunami.