The 400-year history of Dhaka says that the city once had several well-known natural canals (khals) that drained stormwater and graywater. In addition to city’s combined sewer system, these water bodies offered an essential natural drainage system that allowed to manage the monsoon rainfall effectively. However, over the past three decades, due to rapid urbanization, these khals have significantly depleted to the point where they are no longer capable of draining the city’s monsoon runoff. Using past, present, and future Land Use and Land Cover (LULC) and urban drainage modeling, this study identified the effects of such LULC change on pluvial flooding of the northern part of the city. Analysis shows that the rapid and extensive changes in LULC over the past decades have resulted in significant shrinkage of these khals, consequently leading to escalated rates of urban flooding in this region. The western part of Turag thana, low-lying areas close to the Baunia Khal depression, and the upstream region of Abdullahpur Khal are highly vulnerable to future urban floods. The projected LULC change indicates an increase of 8.47%, 8.11%, and 4.05% in the total inundation area by 2042 for rainfall events with return periods of 50 years, 25 years, and 2.33 years, respectively. The findings also indicate that 11% more area is likely to experience long-duration flooding due to LULC change.

Surface water pollution from rapid urbanization, industrialization, inadequate sanitation, and excessive agrochemical use is a global crisis. In developing countries, water quality is one of the most urgent environmental issues. The presence of pathogenic extended spectrum β-lactamase (ESBL) producing E. coli in surface water poses a critical public health concern by increasing the risk of waterborne diseases and spreading multidrug-resistant (MDR) infections. This study addresses the severity of surface water pollution in urban Bangladesh, focusing on the molecular characterization of ESBL E. coli in surface waters from the Goranchatbari sub-catchment of Dhaka. Isolates of ESBL E. coli underwent analysis for the major ESBL and pathogenic genes, antibiotic susceptibility, biofilm formation, and genetic diversity. However, the existence of E. coli was confirmed in every sample. Among 266 isolates, 62 (23.31 %) were phenotypically positive for ESBL, with 58 (93.55 %) carrying at least one of the four ESBL genes: CTX-M, TEM, SHV, and OXA. CTX-M was the most prevalent, found in 55 (88.71 %) isolates. Regarding pathogenicity, 25 (40.32 %) isolates were enteric pathogens, including 24 ETEC and a single EIEC. Four non-diarrheagenic isolates were extraintestinal pathogenic E. coli (ExPEC), capable of causing diseases beyond enteric infections. All ESBL isolates were MDR, with high resistance to β-lactam antibiotics, and capable of forming biofilms at 25 °C and 37 °C. ERIC-PCR analysis grouped the isolates into 14 distinct clusters at a 75 % similarity matrix. These water sources critically threaten public health by contaminating nearby freshwater sources with ESBL-producing pathogenic isolates, leading to various hard-to-treat waterborne diseases and risking aquatic biota by deteriorating water quality. Immediate public awareness, proper water treatment, and precise environmental management are needed before using this water for any purpose.

The World Health Organization has recommended the development of new antimicrobials against Acinetobacter baumannii , one of the six highly significant pathogens. In this study, 28 wastewater samples were collected from the Goranchatbari sub-catchment area in Dhaka city over several periods. The samples were characterized for the presence of Acinetobacter spp. The isolates showing cream, opaque colonies on CHROMagar ^TM ESBL plates were considered positive for ESBL production. They were further characterized for major antibiotic resistance and pathogenic genes, biofilm production and antibiotic susceptibility testing. Furthermore, the isolates were phylogenetically clustered based on their Enterobacterial Repetitive Intergenic Consensus (ERIC) profiles and correlation matrix analysis was performed. Out of 28 samples, 27 were positive for Acinetobacter spp. and a total of 106/249 (42.6%) sample representative isolates were positive for ESBL production. Out of these 106 isolates, 97 (91.5%) were genotypically confirmed to belong to the Acinetobacter spp . and of which, 72 (74.2%) were genotypically confirmed as Acinetobacter baumannii . Among the distribution of β-lactamase genes, bla _TEM was the most prevalent being present in 40/72 (55.6%) isolates, followed by bla _SHV in 3/72 (4.2%) isolates. With respect to the pathogenic genes, pgaB and bfmS were the most prevalent being present in 80.6% and 69.4% of the isolates, respectively. The antibiotic susceptibility testing revealed a diverse range of resistance patterns with high levels of intermediate resistance being observed for cefotaxime and ceftriaxone. The biofilm formation screening revealed that 48.6% and 44.4% of isolates formed strong biofilms at 37°C and 25°C, respectively. The phylogenetic clustering of the A. baumannii isolates resulted in the formation of 10 clusters at 60% similarity index, and the correlation matrix helped reveal important associations between genotypic and phenotypic traits. These results demonstrate the continued prevalence of A. baumannii within these environmental reservoirs and its ability to persist despite seasonal variations, prioritizing changes in environmental health policies that aim to reduce the widespread prevalence of these pathogens.

As the threat of unstable braided river geomorphology to the resilience of local communities grows, a better understanding of the morphological changes in a river subject to climate is essential. However, little research has focused on the long-term planform change of the braided reaches and its response to hydrological changes. The reach around Majuli Island (Majuli Reach), the first and typical braided reach of the Brahmaputra River emerging from the gorge, experiences intense geomorphological change of the channels and loss of riparian area every year due to the seasonal hydrological variability. Therefore, focusing on the Majuli Reach, we quantitatively investigate changes in its planform morphology from 1990 to 2020 using remote sensing images from the Landsat dataset and analyze the influence of discharge in previous years on channel braiding. The study shows that the Majuli Reach is characterized by a high braiding degree with an average Modified Plan Form Index (MPFI) of 4.39, an average reach width of 5.58 km, and the development of densely migrating bars and active braided channels. Analysis shows a control point near Borboka Pathar with little morphological change, and the braided channel shows contrasting morphological changes in the braiding degree, bars, and main channel between the reach upstream and downstream of it. The area of the riparian zone of the Majuli Reach decreased by more than 50 km² during the study period due to migration of the main channel toward the island. The braiding degree of Majuli Reach is positively correlated with the discharge in previous years, with the delayed response time of the MPFI to discharge being just 3–4 years, indicating the unstable feature of the Majuli Reach with varied hydrology conditions.