Physical environment and landform change of the Bengal lowland

Masatomo UMITSU
1997 Tropics  
Regional characteristics of the landform changes in the Bengal lowland, including Ganges delta are closely related to the characteristics of the floods and storm surges of the region. Due to the remarkable increase of the discharge in a rainy season, most part of Bangladesh except Hill Tract is covered by floods. The flooding condition in the Bengal lowland shows regional differences. Landforms of the southem Ganges delta are characterized as the deltaic and tidal lowlands with low and flat
more » ... ace. Ground height of the region is 2-3 m. The flooding inundation depth in the delta region facing the Bay of Bengal is not so deep and the coast line along the region except around the mouth of the Meghna is almost stable during these several decades. In the region of the active delta around the mouth of the Meghna (mouth of the Ganges), landforms are extremely unstable due to the strong river flow and large supply of sediments. The region is characterized by low and flat land with deltaic islands such as Hatia, Bora, Sandwip and so on. Height of the islands is lower than 3 m, and mostly 1-2 m above mean sea level. Sediments of the islands are very soft unconsolidated silt and clay, Then the landforms of the active delta are extremely temporal and have been easily changed in their forms owing to the flood flow and attack of cyclones. Especially, the islands around the mouth of the Meghna have been easily eroded by river flow and wave action. The region along the southeastern coast of Bangladesh from Feni to Cox's Bazar is a coastal plain. Landforms of the plain are characteized by rows of beach ridges and low tidal plains. Two or three obscure rows of beach ridges can be seen in the region between Feni and Chittagong. Broad tidal plain is seen in the region south of Chittagong. Rows of beach ridges and coastal sand dune are also seen in the region near Cox's Bazar. Regional characteristics of the coastal changes of the Ganges delta are closely related to the flooding and landform conditions. Landforms of the central and westem coastal regions of the Ganges delta are characterized as the tidal and deltaic lowlands with mangrove vegetation. Abundant growth of mangrove vegetation in the region west of the active delta is effective for the deposition of sediments. The mangrove forests in the region are also effective against the tidal surge erosion caused by cyclones.
doi:10.3759/tropics.6.189 fatcat:ejbkb3uxzvd5heqk5qhqqigxnm