Taming the Jamuna: Effects of river training in Bangladesh

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.