Monitoring the Coastline Change of Moheshkhali Island Using Remote Sensing Techniques

Bangladesh is a riverine country with several estuarial islands, these islands are subjected to dynamic erosion and accretion. Increased sea level could consume about 26% of land in low lying zone like Bangladesh by 2100. In this alarming situation, monitoring coastline dynamics is obligatory to assess the current status of coastline so that essential measures can be taken to compensate the damage. In this study remote sensing and geographical information system (GIS) techniques have been used to quantify the erosion and accretion of land along the coastline of Moheshkhali Island, Bangladesh. Satellite images form Thematic Mapper(TM) has been used from 1996 to 2016. Modified Normalized Water Index (MNDWI) algorithm has been applied to separate land from water and on screen digitization has been adopted to extract coastline form images of 1996, 2006 and 2016 respectively. Finally, overlaying the digitized maps, the erosion and accretion has been quantified. The result shows that the western and the south-eastern part of the island faced total accretion of 4830 hectares. Erosion on the other hand was not so dominant in the study area during the 20 year time span. The finding contradicts previous works done for estuarine islands as estuarine island face both erosion and accretion.The root of this anomaly is engraved in a tidal swamp forest named “mangrove”.