Waterlogging is one of the major global problems which affects agro-economic activities around the world. In the coastal areas of Bangladesh, especially the southwestern coast, drainage congestion and waterlogging are very common which makes the area uninhabitable. Therefore, timely checking of drainage systems and surface water, and conveying data on the dynamics of drainages and surface water are important for plan and supervisory processes. The present study took an effort to illustrate the waterlogging and morphological change of the rivers in the southwestern coast of Bangladesh through the Modification Normalized Difference Water Index (MNDWI) values which are valuable indicators for monitoring the water area and land use pattern change. Landsat images (Landsat L8 Oli TIRS, Landsat ETM+, Landsat TM) were used in the research. The study reveals that from 1989 to 2020, the shallow water area (mostly covered with rivers) decreased by ^∼14.30 km² yr⁻¹, whereas the wet-land area (mostly covered with beels and water logging areas) increased by ^∼ 67.12 km² yr⁻¹. The bare land area also increased at a rate of ^∼ 36.90 km² yr⁻¹. On the other hand, the green vegetation decreased at a rate of ^∼166.1 km² yr⁻¹, whereas the moderate green vegetation area increased by ^∼ 69.77 km² yr⁻¹ for the same period. In the coastal zones of Bangladesh, the polders, embankments, upstream dams, etc., enhance more sedimentation within the channels rather than in the nearby tidal plains. As a result, the shallow water area which is mostly covered by rivers is gradually decreasing. Moreover, due to increase in wet-land areas with salinity intrusions which affect the vegetation. Therefore, the green vegetation area is regularly declining due to demolition or conversion to moderate green vegetation. The findings of the research will be supportive for coastal scientists worldwide, policy makers & planners, and finally supportive for sustainable management of the coastal areas including Bangladesh.

This study attempts to analyse the historical records and satellite images, and determines the dynamic morphological changes using Remote Sensing (RS) and Geographic Information System (GIS) techniques in order to delineate the paleo-course and the dimensions of the Brahmaputra River. Additionally, land transformations due to route change from Old Brahmaputra-Meghna to Jamuna River were also evaluated. The study revealed that owing to the route changes, the Jamuna River grabbed about 2817 km² of invaluable land resources that were well developed. Whereas Brahmaputra-Meghna river course was associated with ∼4563 km² newly developed lands which are currently being used for settlement, business, and agricultural purposes. Thus, if the river system changes its route again and follows the former path, the lands associated with the Brahmaputra-Meghna river course may again be scoured by the river. Hence, it is suggested that the necessary preparations should be adopted to maintain the current flow of the Brahmaputra through the Jamuna River which may help to protect the newly developed landmasses. Since the present route is straighter than the old Brahmaputra course, it would be easier to manage and maintain the current route of the Brahmaputra via the Jamuna River. Finally, a sustainable river basin management approach may be lucrative for both local as well as international communities.

This research assesses radioactivity in soil and coal samples around the Barapukuria coal-fired thermal power plant using a high-purity germanium detector. The range of activity of ²²⁶Ra, ²³²Th, and ⁴⁰K in the studied soil samples were 14–75, 16–112, and 132–460 Bqkg⁻¹, respectively and the respective activity in coal samples ranged from 14–30, 16–39 and 72–182 Bqkg⁻¹. The majority of the hazard indices (absorbed dose rate, gamma index, effective dose and excess lifetime cancer risk) were higher than the world average, which shows that long-term exposure to terrestrial ionising radiation is not safe for coal miners and the local community. The presence of minerals like monazite and zircon, granitic type parent rock, bottom ash discharged adjacent on lowlands, fly ash deposition, different geochemical and physicochemical properties, dominant wind directions, the artificial contamination, meteorological conditions, leaching caused by rainwater- may have a crucial influence on NORM distributions. The quantitative results of this study have important implications for planning a larger and more modern coal-fired power plant, and this study’s findings inspire municipal officials to restrict and monitor the release of fly ash nearby coal-fired power plants. In addition, it is essential to monitor the health of individuals (workers and locals) near the power plant.

Erosion of banks and channel migration are usually common phenomenon and recurring geo-hazardous problem in the Brahmaputra-Jamuna river system of Bangladesh. The present study intensively analyzed multi-temporal Landsat satellite imageries (Landsat MSS, Landsat TM, Landsat ETM+, Landsat OLI TIRS), historical documents (Hunter maps), and literature information employing Remote Sensing and Geographic Information System techniques, and estimation of braiding and sinuosity indices especially emphasizing channel bar development, braiding, and bank-line migration of the river. The computed braiding indices of the river were 1.5, 10.3, 13.4, 11.0, 10.6 and 14.6 for the year of 1853-1857, 1977, 1989, 2000, 2014 and 2018, respectively (overall deciphering increasing trend). Similar to the braiding indices, the sinuosity indices (2.58, 7.02, 9.92, 8.31, 7.42 and 11.25 for the same selected years) of the river have also been changed over time. During 1853-1857 to 2018, 766.7 and 1624.2 km² of lands extensively eroded on the east and west bank, respectively at a rate of 4.8 and 10.1 km² yr^-1. However, from 1977 to 2018, the erosion rates were 14.4 and 12.5 km² yr^-1, respectively. High discharges, sediment transport associated with random bars formation related braiding expansion, and weak bank materials are presumably the governing factors for causing such simultaneous severe bank erosion and remarkable bank-line migration phenomenon. Although, from 1853-1857 to 1977 the erosion of the river followed the river flow direction. It is expected that the outcomes of this research can contribute further research on morphodynamic characteristics of the braided river for better understanding the river characteristics, the river hydromorphology, water and sediment transport, its bank erosion, and formulating protective measurement plan for their sustainable current flow path maintenance.