Coastal region of Bangladesh possesses a fragile ecosystem and is exposed to hazards like cyclones, floods, storm surges, and water-logging. A detail understanding on the impact of water-logging due to various natural, man-made and climate change scenarios is still lacking. Considering this research gap, the present research is aimed to study impacts of these scenarios inside polders-24 and 25 which are situated on the western part of the coastal region. In this Study as natural scenario, sedimentation in the Hari River; as man-made scenario, new polders in the south-central region and as SLR scenario, an extreme sea level rise of 1.48m are considered. Long-term satellite images are analyzed, and numerical model is applied in the study area. The result shows that water-logging is more acute inside polder-25 compared to polder-24. Sedimentation in Hari River aggravates the water-logging condition. Dredging in Hari River does improve the situation.
Journal of Engineering Science 12(3), 2021, 73-83
Abstract
Water-logging is a major challenge for Dhaka city, the capital of Bangladesh. The rapid, unregulated, and unplanned urbanization, as well as detrimental social, economic, infrastructural, and environmental consequences, not to mention diseases like dengue, challenge the several crash programs combating water-logging in the city. This study provides a brief contextual analysis of the Dhaka’s geomorphology and natural plain, as well as, storm water drainage systems, before concentrating on the man-made causes and effects of water-logging, ultimately exploring a few remedial measures.
Understanding the interactions between shallow saline groundwater and surface water is crucial for managing water logging in deltaic islands. Water logging conditions result in the accumulation of salt in the root zone of crops and detrimentally affect agriculture in the economically and socially backward deltaic region of West Bengal and Bangladesh. In this paper, we undertook a modeling study of surface water–groundwater interactions in the Gosaba Island of Sundarbans region of the Ganges delta using MODFLOW followed by comprehensive parameter sensitivity analysis. Further, scenario analyses (i.e., no-drain, single drain, three drains) were undertaken to evaluate the effectiveness of drainage infrastructure to reduce saline water logging conditions. The evaluation indicated that installation of three drains can remove water at a rate of up to −123.3 m3day−1 and lower the water table up to 0.4 m. The single drain management scenario could divert water at the rate of −77.9 m3day−1 during post monsoon season, lowering the shallow saline groundwater table up to 0.1 m. This preliminary modeling study shows encouraging results to consider drainage management as to solve the increasing challenge of water logging and salinity management in the deltaic region. The insights will be useful for farmers and policymakers in the region for planning various sustainable saline groundwater management. Building drainage infrastructure could potentially be part of initiatives like the national employment guarantee scheme in India. In the future, this model can be coupled with solute transport models for understanding the current status and future expansion of salinity in the study area. Further modeling and optimization analysis can help identify the optimal depth and spacing of drains.
A hybrid model of two multi-criteria decision making techniques specifically, the analytical hierarchy process method and the technique for order preference by similarity to an ideal solution method was proposed to select the best site for constructing an underground dam to control the groundwater table rising or water-logging in the center of Al-Zubair city, southern Iraq. Six influencing factors were selected and prepared depending on the nature of the problem to be resolved the siting of the underground dam, and data availability. These are elevation, slope, curvature, aquifer transmissivity and specific yield, and distance to the water-logging body. Applying the hybrid system proved that approximately 50% of the study area is suitable for constructing the underground dam. Due to the expected high cost of constructing an underground dam in the study area as well as the technical challenges in implementing the project, the proposed design is digging a trench with limited width (meter or half a meter) and shallow depth (not more than 5 m) and fill the hole with an impermeable material (clay for example). It is preferred to drill wells in the headwater of the dam for pumping excess water and used it for another usage.
Impact of Human Intervention and Sea Level Rise on Water-Logging Scenarios inside Polders-24 And 25 of Bangladesh
