No abstract

The study attempted to assess the changes in shoreline and erosion-accretion of newly formed island at the mouth of the Meghna river estuary in Bangladesh using multi temporal satellite images and GIS techniques. The current study used NDWI an MNDWI to delineate land and water boundary to extract the shoreline and also used some overlay analysis to measure the erosion-accretion. DSAS extension is used for analyzing the shifting of the shoreline. The results (1990-2015) show that the island has 1192 hectares of land accreted during this time period, and about 1 km of its shoreline lost during this time period as it has broken in few places. Most accretion found in the northwestern part and erosion in southeastern and southwestern part. The study area was divided into four different segments and about 115 transects were constructed, of which about 74 shows the seaward movement and 44 shows landward movement. Seaward movement and rate of shoreline shifting is higher in the northwestern part where net shoreline movement (NSM) is +1897 meters and end point rate (EPR) is +73 m/year. Landward movement and the rate of shoreline shifting are higher in southeastern and southwestern part of which net shoreline movement (NSM) is about -2680 meters and end point rate (EPR) is about -129 m/year. The highest landward movement is found as -2680 meters and highest seaward movement as +1897 meters. Accretion process is dominant while erosion process discontinued the shoreline in some places.

No abstract

In Southkhali Union of Bagerhat district in Bangladesh about 47% of the total population is living beyond the service area of cyclone shelters (CS) not only for the carrying capacity of CS but also for the accessibility. Location-allocation tool of Network Analyst tool in ArcGIS determined the service area of each CS in the study area based on its shelter capacity and accessibility. People residing outside the service area of cyclone shelter are highly vulnerable due to low elevation of land and poor housing structure. The location-allocation tool of Network Analyst provided the proper evacuation plan that would identify the shelter location for each household or cluster of population and the evacuation route also. It would also help to find the proper location to build new shelters for unserved community. Asiat. Soc. Bangladesh, Sci. 44(2): 137-148, December 2018

Erosion and accretion rate are found very high in the estuary of an active delta which can be observed by satellite imageries. According to the multispectral satellite imageries it is found that accretion of Domar Char (a little island belongs to Meghna estuary) was more than 1192 hectares in last 25 years. The study was conducted in five years interval from 1990 to 2015 using spatial analyst extension of ArcGIS. It is revealed that accretion rate is about 208 hectares/year and erosion is about 160 hectares/year, which indicates the dynamic nature of the island. According to Landsat imageries about 2500 hectares of land rose in five years (1990 to 1995) and again lost 2300 hectares of land in next five years (1995 to 2000). Though the total area of intertidal zone has decreased, the area of barren land, vegetation and sand dune has increased over the time. Asiat. Soc. Bangladesh, Sci. 42(2): 219-228, December 2016