Recent coastline changes at the eastern part of the Meghna Estuary using PALSAR and Landsat images

Abstract

In the present paper, we have focused on the recent coastline changes at the eastern part of the Meghna Estuary of Bangladesh through the application of PALSAR (The Phased Array L-band Synthetic Aperture Radar) and Landsat images. The area under concern is very dynamic where the combined processes of erosion and accretion take place under the influence of river discharge with heavy sediment load, wind waves and tides. It falls under the macro-tidal zone with tidal range varying from 4 m to 6 m or even higher. Many parts of the area is covered with intertidal mudflats. They are inundated during the high tides and get exposed during the low tides. So for the detection coastline change consideration of tidal phase is quite important which has been done in the present study. Coastline change from the year 2007 to 2013 has been presented in this paper. From the analyses of satellite images the areas of erosion and accretion of the four major offshore islands have been calculated during the above mentioned period. It has been found that the annual rate of accretion of Urir Char island has decreased from 5.84 km2 per year between 2007~2010 to 1.05 km2 per year between 2010~2013. On the other hand, Sandwip island has been eroding at a higher rate of 3.15 km2 per year between 2010~2013 compared to 0.34 km2 per year between 2007~2010. Overall, the total area of Urir Char, Sandwip and Jahajir Char island increased by about 120 km2 from 2007 to 2013, mainly contributed by the drastic expansion of Jahajir Char island during this period.