3.2. Geological setting
The studied area is located on the side of the youngest structural division in the western Indo-Burman Range of the folded flank (Kresic, 2006; Nahin, Basak, Alam, & Environment, 2019). The elevation of this area is very low from the other areas of Bangladesh. The majority of the land is found in hilly reason. In the east boundary which is covered in low hilly ranges (100m elevations) and west side is covered by Bay of Bengal. Bakkhali estuary and Maheshkhali channel are found in the north and south. The landform types of this area are divided into two categories flooded and coastal plain. The beach plain unit has been consisted of dunes, tidal creeks and beach. The floodplain unit has been consisted of the Tertiary hills between the hilly reason. The flat surface mainly consisted of sandy clay and sand size is larger in continuously higher on the depth.