Tidal River Siltation and its Impact in the Coastal Parts of Bangladesh

The study area is located in the south-western coastal part of Bangladesh and belongs to the lower deltaic plain of the Ganges delta system, which lies in the Rampal upazila of Bagherhat district. The area is more or less flat with elevation ranges from 1.0 to 2.0 m above mean sea level (MSL) and is blanketed with fluvio-tidal deposits of sandy silt, clayey silt and clay. Right now, water logging is one of the major problems in the area. The present paper is an attempt to expose the causes of water logging as well as its consequences. The satellite images of the last few decades, existing statistical records and simultaneous field checking were employed in this study, which reveals that natural as well as anthropogenic factors are responsible for water logging problem. The rivers and their link channels in the areas are influenced by tidal water regularly. The Water Development Board (WDB) was built embankments along the river courses as well as constructed sluice gates on the head of the tidal creeks to protect the area from regular tidal flooding and sea water intrusion. During monsoon, when rivers carry huge amount of water and sediments due to torrential rain, and these rising waters overtop the natural levees which were artificially modified and raised by coastal embankments. Consequently, the sediments drop down inside the channel and near channel bank rather in the nearby tidal plain. As a result, channels are gradually congested due to siltation, whereas tidal plain areas gradually lower due to subsidence and lack of sedimentation. Moreover, many sluice gates were constructed on the river courses in the coastal areas which also aggravate the situation. Daudkhali river is one of the main rivers in the study area. Image interpretation depicts that in 1977 the width of this river was nearly about 200 m all through its course and the river maintained this width up to 1990. But due to embankments the river starts to squeeze and the width of the river reached about 100 m in 2000. But in 2014, the river was nearly abandoned. A sluice gate was constructed on the course of the river about 30 years ago near Foila Bazar. The sediments carried by the river started to deposit in the mouth of the sluice gate which gradually choked the opening of the gate and now the gate is nearly blocked. During the rainy season,the river cannot carry excess water resulting flooding and water logging for long time. The presence of thick finer sediments in the subsurface as well as climate change further prolongates the situations. Finally, for sustainable development of the area,it is necessary to carry out different development activities with consideration of delta building processes

Climate Change Impact and Frequency of Cyclone Surge in Bangladesh Coast: Proper Plan to Address Sustainably

The Bay of Bengal (BoB) is a familiar ground for tropical cyclones. Consequently, cyclone surge and tidal inundation are very common in the Bangladesh coast which causes massive loss of human lives and properties. The present paper is an attempt to delineate the frequency of cyclones in the BoB, and loss of human lives and properties of Bangladesh coast on the basis of published reports, open source data and field checking, and finally to propose an effective way out to protect the area from cyclone surge. This study exposes that the frequency of cyclones in the area increased recently due to rise of global temperature. It further reveals that though the frequency of cyclones is increased, the loss of human lives is significantly decreased. Death toll in the last two decades decreased a lot for similar strength of cyclones comparing to the toll in last thirty or fifty years. Improvement in the early warning system, evacuation plan with proper training and construction of good number of cyclone shelter all over the coastal region are the main reason for this improvement. Though the loss of human lives is significantly reduced, the loss of economic resources in the coastal areas of the country is enormous as in earlier episodes. Therefore, adaptation for the Climate Change effect is needed to expedite with afforestation in the coastal region. Economic loss might also be reduced obstructing the cyclonic surge in the coastal region. Considering the cyclone path and tidal amplitude of cyclonic surge, upgradation or reconstruction of the coastal embankments all along the coast is essential. In this process, it is important to ensure that the tidal channels act as an inlet and outlets all over the coast to keep the natural processes active. An integrated approach including geoscientists, engineers, planners, policy makers, etc. is required to protect the resources as well as proper management of the coastal areas of the country

Causes of Acute Water Scarcity in the Barind Tract, Bangladesh

The Barind tract is an elevated landmass (about 11-48 m amsl) comprised with Pleistocene terraces and is situated in the northwestern part of Bangladesh. At present, this area faces scarcity of water. The present study is an attempt to unveil the causes of water scarcity of the area. Several aspects like change in climatic condition, irrigation practice and drainage characteristics of major rivers are the prime factors for water scarcity. Interpretation of recent satellite imagery and historical records reveal that the major rivers of the area like Ganges (Padma), Tista and Kosi have remarkably migrated from Barind tract during last few hundred years. Shifting of these rivers causes great change in hydrodynamics of the Barind tract. As a result, flow of other related rivers of the area like the Mahananda, Kulic, Tangon, Punarbhaba, Atrai, Little Jamuna, Karatoya and Nagar reduces remarkably in the dry season. As a result aquifers in the area are not recharged sufficiently by river water in the dry season. India constructed Farakka barrage on the Ganges (Padma) river in 1975 to divert the flow of water from Bangladesh to the other parts of India. This diversion of water also leads to the decreasing of water in the area. Climatic data interpretation of the last 50 years also reveals that annual rainfall in the area is decreasing while overall temperature is increasing. To boost up the cropping intensity (117% to 200% compared to national average of 174%) and to meet present demand 74% of cultivable lands are being irrigated with 96% share of groundwater owing to unavailability or scarcity of rainfall and hence surface water. Irrigation by groundwater has dramatically been increased (250 times) in the last 30 years. Due to over exploitation, water table progressively declined (av. rate 0.10 m/year) which ultimately leads the area to water scarcity zone. The aquifers are confined or semi-confined and do not get appreciable vertical recharge through clay beds. Recharge is mainly through the exposures of sandy strata in the river beds which are flooded in Monsoon season. All sorts of parameters for water scarcity indicate that this condition may aggravate further if no rescue measures are taken immediately

Metal(loid)s in tap-water from schools in central Bangladesh (Mirpur): Source apportionment, water quality, and health risks appraisals

Considering the health risks originating from the exposure of metal(loid)s in tap-water and the concomitant vulnerability of school-going students, 25 composite tap water samples from different schools and colleges of central Bangladesh (Mirpur, Dhaka) were analyzed by atomic absorption spectroscopic technique. Elemental abundances of Na, Mg, K, Ca, Cr, Mn, Fe, Co, Ni, Zn, As, Cd, and Pb in the studied tap water samples varied from 4520 to 62250, 2760–29580, 210–3000, 15780–78130, 1.54–5.32, 7.00–196, 2.00–450, 0.04–1.45, 8.23–24.4, 0.10–813, 0.10–10.5, 0.002–0.212, and 1.55–15.8 μgL−1, respectively. Dissolved metal(loid)s' concentrations were mostly within the national and international threshold values with few exceptions which were also consistent with the entropy-based water quality assessment. Multivariate statistical approaches demonstrated that hydro-geochemical processes like water-rock interactions mostly govern the major elemental (Na, Mg, K, Ca) compositions in tap water. However, anthropogenic processes typically control the trace elemental compositions where supply pipeline scaling was identified as the major source. Cluster analysis on sampling sites separated two groups of schools and colleges depending on their establishment years where tap water from older schools and colleges possesses relatively higher levels of metal(loid)s. Hence, gradual pipeline scaling on a temporal scale augmented the metal(loid)s' concentrations in tap-water. In terms of non-carcinogenic health risks estimation, studied tap-water seems to be safe, whereas elemental abundances of Pb and As can cause carcinogenic risks to school-going people. However, progressive deterioration of water quality by pipeline scaling will be supposed to cause significant health risks in the future, for which preventative measures should be adopted

Salinity-induced change in green vegetation and land use patterns using remote sensing, NDVI, and GIS techniques: A case study on the southwestern coast of Bangladesh

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

Consequences of catastrophic cyclone Amphan in the human-induced coastal plain ecosystems of Bangladesh

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

Assessment of radionuclides from coal-fired brick kilns on the outskirts of Dhaka city and the consequent hazards on human health and the environment

In a first-of-its-kind study, terrestrial radionuclide concentrations were measured in 35 topsoil samples from the outskirts of Dhaka using HPGe gamma-ray spectrometry to assess the radiological consequences of such a vast number of brick kilns on the plant workers, general as well as dwelling environment. The range of activity concentrations of 226Ra, 232Th, and 40K is found at 19 ± 3.04 to 38 ± 4.94, 39 ± 5.85 to 57 ± 7.41, and (430 ± 51.60 to 570 ± 68.40) Bq/kg, respectively. 232Th and 40K concentrations were higher than the global averages. Bottom ash deposition in lowlands, fly ash buildup in soils, and the fallout of micro-particles are all probable causes of the elevated radioactivity levels. 137Cs was found in the sample, which indicates the migration of 137Cs from nuclear accidents or nuclear fallout, or the contamination of feed coal. Although the effective dose received by the general public was below the recommended dose limit but, most estimates of hazard parameters surpass their respective population weighted global averages, indicating that brick kiln workers and nearby residents are not safe due to prolonged exposures to terrestrial radiation. In addition, the soil around sampling sites is found to be unsuitable for agricultural purposes