Project context and challenge
The coast of Bangladesh stretches over 710 km and is home to some 35 million people. It is one of the most dynamic deltas in the world: rivers meander, islands form and disappear, and while some stretches gain land, others lose it at rates of up to 10 metres per year. Cyclones and erosion threaten homes, farmland, embankments and roads, and annual losses from coastal hazards are estimated at around USD 3 billion.
Coastal protection in Bangladesh has traditionally relied on proven local practice, with limited use of advanced modelling or alternative concepts. The World Bank therefore launched a technical assistance programme to help the Government of Bangladesh develop innovative, integrated and low maintenance solutions for coastal erosion. The aim was to close knowledge gaps, show what such solutions could look like on real erosion hotspots, and give decision makers practical recommendations for future investments.
CDR’s approach and contribution
CDR led the assignment together with Deltares and the Bangladeshi Institute of Water Modelling, working in close consultation with the Bangladesh Water Development Board and other stakeholders through workshops and field visits.
The team first reviewed existing coastal protection practices and analysed the coastal system, dividing it into four zones with distinct erosion processes. In consultation with stakeholders, three hotspots were selected that together represent the main erosion mechanisms along the coast: river bank erosion at Polder 35/1, beach erosion at Kuakata Sea Beach in Polder 48, and shifting shorelines along Cox’s Bazar and the Marine Drive.
For each hotspot, CDR developed concept designs and tested them with numerical models. At Polder 35/1, the team proposed dredging a new channel in the Baleshwar River to speed up a natural shift in the main flow away from the eroding bank, combined with bank protection and an erosion early warning system. When Cyclone Amphan breached embankments in May 2020, the team analysed the failure mechanisms to strengthen the design. At Kuakata, a combination of groynes, sand nourishment and a multifunctional embankment, inspired by the boulevard in Scheveningen, protects the beach while making it more attractive for tourism. Along Cox’s Bazar, sand nourishments that work with the natural sand transport were combined with multifunctional embankments.
Risk and economic assessments supported each design. In the final phase, the lessons were scaled up into general strategies for other locations along the coast with similar erosion mechanisms.
Result
The project delivered showcase designs for three representative erosion hotspots and a method to identify and address erosion elsewhere along the Bangladesh coast. It showed that hybrid solutions, which combine nature based measures with structural protection, deliver the greatest benefits for safety, livelihoods and the local economy.
Concepts such as sand nourishment and multifunctional embankments were introduced to Bangladesh for the first time, and the recommendations were shared with decision makers to guide future coastal investment programmes.
