Impacts of Dredging on Fluvial Geomorphology in the Jamuna River, Bangladesh

Abstract

Jamuna, a major braided river in Bangladesh, has an enormous hydrological impact on the surrounding areas and streams. Erosion and sedimentation in the Jamuna river cause a large flow fluctuation and floods round the year. Bangladesh Water Development Board has initiated a pilot capital dredging project in the Jamuna river in 2011-2012, aiming to guide the flow to reduce the risk of failure of the city area and right guide bundh of the Jamuna Bridge. This study explores the long-term role of dredging on river morphology using erosion-sedimentation numerical modeling approaches. Primary data were employed in numerical models to estimate the erosion-sedimentation and compared outputs with the real-time cross-sectional variation at selected sections along the reach during 2012-2013. The analysis suggested that the rate of sedimentation is higher (60% to 80%), where the dredging alignment crosses through the existing sandbar/char. Moreover, a cross-section comparison revealed that the channel near Sirajganj Hardpoint shifted towards the left (east) bank, and the channel within the study area developed very fast along the right (west) bank. However, satellite image analysis revealed that the major bankline shifting occurred from 2000 to 2010 and the channel shifting was observed from 2014 to 2018 along the reach, mostly, after the construction of some river training works. The variation of the channel persistence (40% -100%) selected part of the study area in the channel incidence map, indicating the rapid dynamic behavior of the river morphology. This study showed a promise that numerical approaches can predict the long-term hydrodynamic behavior of a braided river.

Caste System Turns into A Social Curse and Social Discrimination: A Study of Mulk Raj Anand’s Untouchable in the Perspective of Post-independence Bangladesh

“…This research shows that education and knowledge are powerful means to break down the deep-seated prejudices of the caste system. While, (Rahman, 2016) recommends urgent legislative modifications, such as the implementation of a law that opposes discrimination. Efforts aimed at promoting comprehension and compassion among communities have the capability to interrupt the harmful pattern of prejudice, creating surroundings that flourish on inclusiveness and fairness.…”

“…As a move, the government took proactive steps by introducing legal actions to address such practices. Nevertheless, obstacles in putting these initiatives into action, combined with deeply rooted societal beliefs, impeded the complete achievement of these policies' influence on the lives of disadvantaged populations (Rahman, 2016) Looking at things from a comparative perspective helps us see the complex patterns of caste in both India and Bangladesh. Although the two countries have similarities with respect to their past as British colonies, origins, cultures and many the paths they took after gaining independence have resulted in different ways in which caste-related prejudice is demonstrated.…”

Enhancing Riverbank Protection along the Jamuna River, Bangladesh: Review of Previous Countermeasures and Morphological Assessment through Groyne-based Solutions using Numerical Modeling

“…The iRIC Nays2DH software was employed for morphological verification through simulation, incorporating bathymetry data of the Jamuna River and implementing interventions such as cross bars around Sirajganj, dredging, and filling [28]. The validation utilized a discharge value of 72,661 m 3 /s for the upstream boundary derived from post-crossbar installation data (2011-2012).…”

Evaluation of Groynes Installation at the Vulnerable Bank of a Braided River

“…Various model studies explored groyne types and patterns in braided rivers, including sediment exchange between main channel and groyne fields 7) , turbulent flows around a single groyne 8) , and erosion and deposition processes along a 180° open canal bend in arbitrary topography 9) . In the specific case of the Jamuna River, various studies have been undertaken, such as the historical assessment of morphodynamic conditions 10) , an overview of bank protection structures including groynes in the Brahmaputra-Jamuna River 11) , the interaction between braided bars and adjacent channels 12) , and the impact of dredging in the Jamuna River 13) . However, most of the previous studies have been conducted for the purpose of planning and designing the groynes in the Jamuna River, and few studies have been conducted to quantitatively compare and evaluate the effects and impacts of actually installed groynes with the real data measured after the groynes installation.…”