バングラディシュの更新世台地の地形と地質

With regards to the origin and evolution of the Pleistocene tracts (Lalmai, Madhupur and Barind tracts) of Bangladesh, two trends of thoughts are common. Most of the authors believed that the Madhupur, Barind and Lalmai tracts represent tectonically uplifted surface. Some researchers have different opinion and they believed that the Lalmai hills and the Madhupur locality represent tectonically uplifted blocks but the whole Barind tract and the major portion of the Madhuput tracts are not tectonically uplifted, rather these are originated by erossional-depositional processes. In order to solve the problems associated with origin and evolution of Pleistocene tracts of Bangladesh, further study is needed. Borehole data may be collected and fusion images can be prepared from aerial photographs and setellite images to detect netectonic imprins and geomorphological signatures of the areas. Elaborate laboratory analysis of sediment deposits, radiocarbon dating my indicate a new dimension about the origin and evolution of these tracts

A Review on the Quaternary Characteristics of Pleistocene Tracts of Bangladesh

With regards to the origin and evolution of the Pleistocene tracts (Lalmai, Madhupur and Barind tracts) of Bangladesh, two trends of thoughts are common. Most of the authors believed that the Madhupur, Barind and Lalmai tracts represent tectonically uplifted surface. Some researchers have different opinion and they believed that the Lalmai hills and the Maclhupur locality represent tectonically uplifted blocks but the whole Barind tract and the major pOl1ion of the Madhuput tracts are not tectonically uplifted, rather these are originated by erossional-depositional processes. In order to solve the problems associated with origin and evolution of Pleistocene tracts of Bangladesh, fU11her study is needed. Borehole data may be collected and fusion images can be prepared from aerial photographs and satell ite images to detect neotectonic imprints and geomorphological signatures of the areas. Elaborate laboratory analysis of sediment deposits, radiocarbon dating may indicate a new dimension about the origin and evolution of these tracts

Assessment of CMIP6 global climate models in reconstructing rainfall climatology of Bangladesh

This study evaluated the rainfall historical simulations of 15 Global Climate Models (GCMs) of the Coupled Model Intercomparison Project phase 6 (CMIP6) in replicating annual and seasonal rainfall climatology, their temporal variability and trends in Bangladesh for the period 1979–2014, considering ERA5 (ECMWF Reanalysis 5th Generation) reanalysis as the reference dataset. Shannon's Entropy decision-analysis was employed for GCMs' rating based on eight statistical indicators and a comprehensive rating metric for the final grading of the GCMs. The majority of the CMIP6 GCMs accurately reproduced the spatial feature of ERA5 rainfall. However, the GCMs underestimated annual rainfall by an average of 190.5 mm, with the highest underestimation in monsoon (131.76 mm) and least in winter (3.52 mm) seasons. Most GCMs also underestimated rainfall variability for all seasons except winter. Besides, the GCMs showed an increasing trend in pre-monsoon and a decreasing trend in post-monsoon rainfall like ERA5, but an opposite (negative) to ERA5 trend (positive) in monsoon season rainfall. The ensemble mean of the GCMs showed higher skill in reconstructing rainfall climatology, temporal variability and trends than the individual GCMs. The study identified MPI-ESM1-2-LR, MPI-ESM1-2-HR, and GFDL-ESM4 as the most effective GCMs in reproducing precipitation over Bangladesh. The selected models' simulation can be used for climate change impact assessment in Bangladesh after bias minimization

Integrating subsurface stratigraphic records with satellite images to investigate channel change and bar evolution: a case study of the Padma River, Bangladesh

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. Landsat data and stratigraphic records were employed to determine channel changes and bar evolution of a selected reach of the Padma River in Bangladesh. Analysis of multi-temporal images showed that the selected reach of the Padma River has undergone significant morphological changes since 1973. The mean width of the river has almost doubled, having increased from 5458 m in 1973 to 10,638 m in 2014. Bank erosion, totalling 281 km 2 , was more than double the accretion (123 km 2 ), and the left bank experienced higher levels of erosion than the right bank. Analysis of the stratigraphy of the bar head, middle and tail sections revealed that erosion occurred in the head section, but that the middle section seemed to be stable, whereas accretion was estimated to be high in the tail section of the bar. Sedimentary facies analysis indicated that bar evolution is largely influenced by the variation of both water and sediment flows, as bar areas tend to accrete substantially following large floods. However, the erosion–accretion process of both bars and river banks appeared to be stable during the periods when the river experiences no major flooding. The relationship between bank erosion and bar area expansion showed a moderately positive correlation (r 2  = 0.64, p = 0.016), while a strong correlation was observed (r 2  = 0.80; p = 0.008) between channel width and area of the bar, suggesting that river width is highly influenced by bank erosion. This implies that the growth of bars within the reach is largely determined by materials flowing from bank failure.