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This systematic review attempts to delineate a synthesis of the main drainage characteristics of the Bengal basin through the study of historical data, old maps, reports, records, satellite images, water and sediment discharge, etc. In doing so, especial emphasize is given on the changing scenery of the river courses (paleo-present), sediment supply and water resources as well as downstream impact on socio-economy and valuable landforms (e.g., agricultural, settlement, urban, sub-urban, municipality, industry, forest, etc.). Nevertheless, impacts on biodiversity, ecosystem, water discharge and suspended sediment transport to deltas, eco-environment, human-life etcetera were also considered in evaluating the drainage characteristics. With continuing earlier custom, till now, human lives, valuable landforms and national economy have continuously been negatively affected by the rapid and frequently changing flow path of the largest rivers (Padma, Jamuna, Meghna) with the consequential river bank erosion. Furthermore, the polders, embankments, river training, and upstream barrages/dams lead to cause and enhance undesired channel siltation, land subsidence, severe erosion, sudden catastrophic floods, water logging, salinity, etc., and also hinder sediment transportation / delivery and water discharge to the basin. Finally, it has a huge impact on the basin's human-life, landforms, biodiversity, ecosystem, eco-environment, etc.

The Amphan, a super cyclone, hit the Bangladesh coast on May 20, 2020. This study conducted on the worst calamity-affected areas of southwestern coast of Bangladesh through field investigation, and Modification of Normalized Difference Water Index, and Normalized Difference Vegetation Index analysis. The study disclosed that most of the areas were submerged by tidal saline water during the cyclone. The people in the areas were taken refuge on embankments and in cyclone shelters. The vegetation was fully or partially damaged/dead due to undesired inundation. Domestic animals are completely absent in the area due to the unavailability of freshwater.

Coal-fly-ash is one of the major byproducts of coal-based power plant in which naturally occurring radioactive materials (NORMs) are drastically enriched compared to those of feed coals. Thus, improper management of fly-ash may introduce additional radioactivity to the surrounding environment and cause radiological risk. So, in order to study the distribution of radionuclides in soil around a coal-based power plant and to evaluate their radiological risk, soil, coal and fly-ash samples were analyzed by using a HPGe detector for U-238, Ra-226, Th-232 and K-40 radioactivity concentrations. Furthermore, soil minerals were also studied by X-ray diffractometer to assess the mineralogical provenance of the radionuclides. Mean radioactivity concentrations (in Bq·kg−1) of U-238, Ra-226, Th-232 and K-40 in soil samples are 102.9±41.4, 63.6±7.4, 103.4±13.9 and 494.2±107.5, respectively which are comparatively higher than the typical world mean value. Elevated levels of radioactivity are likely due to the presence of illite, kaolinite, monazite, rutile and zircon minerals in the soil samples rather than technogenic contributions from the power plant. Furthermore, mean soil contamination factor (CF) are close to unity and mean pollution load index (PLI) is below unity while the average radium equivalent activity (Raeqin Bq·kg−1), external hazard index (Hex), absorbed γ dose rate (D in nGyh−1), annual effective dose rate (E in mSv·y−1) and excess lifetime cancer risk (ELCR in Sv−1) are 249.5±21.7, 0.67±0.06, 114.2±9.4, 0.20±0.02, 4.9×10−4±0.4×10−4, respectively, which are within the permissible limit. Thus, in terms of radioactivity concentrations and associated environmental and radiological indices, the effect of the power plant is insignificant.

This study measured the salinity in the surface water, groundwater, and soils of the southwestern coast of Bangladesh to illustrate the changes in vegetation patterns of the area by NDVI values through RS and GIS. The top soils are found more saline than the sub-soils, and the salinity decreased with soil depths mostly towards the river's flow paths. Almost 50, 86, 100, and 72% of samples of the pond, Gher/agricultural field, river/Khal, and groundwater, respectively are identified as brackish. From the year of 1989–2020, the saline-rich waterlogging area was found to increase while the green vegetation decreased considerably.

•Elemental abundances of soil & water samples from a southern part of Bangladesh are presented.•Natural radioactivity of soil & physicochemical parameters of water samples are reported.•Base-line data for our studied pre-industrial area (Rampal) has been established.•Statistical approaches have been used to assess the measured analytical data.•Using environmental and radiological indices environmental geochemistry has been evaluated.

•Using INAA, elemental abundances of soil samples from ship-breaking yards and an adjacent island were determined.•Heavy minerals from similar geochemical settings were also analyzed for elemental composition by INAA.•Environmental indices, inter-element correlation study and PCA were performed to evaluate the elemental distribution.•Elemental enrichments in ship-breaking yards are higher than UCC while Sandwip island possesses crustal origin.•Acknowledging the anthropogenic input, heavy mineral’s distribution is also accountable for elemental distribution.