Taming the Jamuna: Effects of river training in Bangladesh

<p style="margin: 0cm 0cm 10pt;">The 10 km wide Jamuna river in Bangladesh is one of the most morphologically active rivers in the world, with bank erosion rates of up to 500 m per year (Mutton and Haque 2004). Such extreme river migration in the center of Bangladesh, one of the most densely populated and impoverished regions in the world, displaces roughly 60,000 people per year (Mutton and Haque 2004). To alleviate this, the Government of Bangladesh has committed to stabilizing and narrowing it’s major rivers with the Flood and Riverbank Erosion Risk Management Investment Program (FRERMIP) (ADB 2016). FRERMIP is investigating numerous training scenarios and final stabilized widths (4-8 km). These scenarios are combinations of works (spur dikes, dredging) at different locations and activation rates (i.e. construction schedules) which FRERMIP seeks to optimize for cost, navigation, bank erosion prevention and flood mitigation. However, little is understood about how these proposals may affect the sediment balances in Bangladesh. The Jamuna combines with the Ganges and Upper Meghna to form the world’s second largest delta: the Bengal delta. Due to the high sediment load delivered from these Himalayan rivers, accretion rates in the delta have been in the order of 5 km2/yr (Sarker et al. 2011). Changes in the supplied sediment to the delta may reduce this accretion, amplifying the consequences of sea level rise. A better understanding of how proposed trainings will affect the sediment supply to the delta can help decision makers weigh the pros and cons of implementation, and prepare for these impacts on the delta.