By Catherine A. Cardno, Ph.D.
A $2-billion embankment project in Bangladesh is under way to protect the nation's coastal residents from tidal and storm surges-not to mention sea level changes.
Squatters have created homes and communities along the embankments that protect Bangladesh’s low-lying land from tidal water ingress. A $2-billion project is under way to strengthen the nation’s embankments. © Royal HaskoningDHV
February 3, 2015—Bangladesh, located at the point at which three transhimalayan rivers—the Ganges, the Brahmaputra, and the Meghna—join together, has a long history of flooding. Much as California is crisscrossed by a network of fault lines associated with the San Andreas fault, Bangladesh is crisscrossed by approximately 200 rivers and tributaries that create estuaries, tidal inlets, and tidal creeks, all related in one way or another to these three major rivers. The nation's coastal river delta is one of the largest, and youngest, in the world, according to the World Bank.
Beginning in the 1960s, embankments built to protect low-lying coastal areas from tidal inundation brought immense benefit to people by creating polders—low-lying areas rimmed with dikes for protection. Over time, however, poor maintenance and storm damage have exceeded the limitations of these dikes, threatening some 42 million coastal residents and their communities. So a plan was developed to construct $2 billion worth of improvements, and the first phase of this construction project is now under way. When the project is completed, the existing embankments along the sea, estuaries, and rivers-and their associated drainage channels and systems-will have been upgraded to offer greater protection from tidal activity, storm surges, and sea level rise.
The Government of the People's Republic of Bangladesh is paying for the project—known as Coastal Embankment Improvement Project, Phase-1 (CEIP-1)—with funds borrowed from the World Bank and grant monies issued by the bank under its pilot program for climate resilience.
Engineering consultancy Royal HaskoningDHV, a company based in Amersfoort, the Netherlands, has signed a contract with the government to provide the engineering design and project management for this first phase, which encompasses 17 polders covering approximately 1,000 sq km of the nation. This phase will take six years to complete and will upgrade 618 km of embankments that protect the polders.
Bangladesh’s system of embankments was initially constructed beginning in the 1960s to protect low-lying land from incoming tides. Poor maintenance and storm damage have exceeded the limitations of the original embankment designs. © Royal HaskoningDHV
The original embankment program that began more than 50 years ago within Bangladesh "started as a simple protection to make agriculture possible," explains Roelof Moll, the project director of CEIP-1 for Royal HaskoningDHV and the director of the company's advisory group on rivers, deltas, and coasts. Moll is based at the company's Nijmegen, Netherland, office.
Moll says, "The recently started project will bring these embankments up to the level of present flood-safety requirements" as established by the Bangladeshi government, while at the same time serving water-management functions.
The geotechnical work involved in upgrading the embankments will be multifaceted. Soil will be used to increase the height and width of the embankments, locally produced concrete blocks or geotubes will offer slope reinforcement, and, where possible, mangrove and other salt-tolerant species will be planted to further reinforce the foreland of embankments with vegetation.
In addition to the geotechnical work, sluice gates associated with the existing embankments and their respective drainage channels will be updated, according to Moll. "There are now agricultural requirements for the use of the sluices," he says, that require that they be used not only for outlet purposes, but also for ingress in times of drought—"to let water in," he notes. The new sluice gates incorporated into the embankments as part of the project will include sliding gates that will enable the sluices to function in both ways so that they can be used as part of local water management operations.
Because of the remote location of the coastal areas that are being worked on—many of which must be accessed by boat, particularly in the rainy season-all materials will be locally sourced to the greatest extent possible, according to Moll. This means that the soil will be drawn from so-called "borrow" pits located outside the embankments. When possible, soil drawn from drainage channels—known as
—that have silted up over time will also be used, if the recovered soil is strong enough, Moll notes.
The geotechnical work involved in upgrading the embankments will rely on soil to increase the height and width of the embankments, concrete blocks or geotubes for slope reinforcement, and salt-tolerant vegetation. © Royal HaskoningDHV
Private landowners will be compensated for any lands acquired for the enlargement of the embankments, according to material released by the World Bank. At the same time, the rights of squatters who have created communities upon the embankments themselves, which are considered public land, will also be protected.
"Bangladesh has a large population, so every part, every parcel of land has high value and is immediately brought into use," Moll explains. Those squatters who must be relocated during construction will be given money to assist with their relocation within the community, according to the World Bank. Because the squatters do not have legal titles that can be used for their claims, video footage documenting the location and type of dwellings that will be dismantled is being taken. Although permanent relocation is desired, it will not be enforced, and people will be allowed to return to the embankments once construction is complete.
In total, approximately 129 polders will be upgraded as a part of the project. "The World Bank has reserved a large amount—about U.S.$2 billion—to invest in coastal protection to make the economic development of the country sustainable," Moll says. "Bangladesh has steady economic growth and is self-sufficient in food, [but] they need the protection against the frequent flooding to make this growth sustainable."
Additional companies that will be working on phase one of the embankment project include the Hørsholm-based Danish Hydraulic Institute, as well as three companies based in Dhaka, Bangladesh: DevConsultants, Design Planning & Management Consultants, and the Institute of Water Modeling.
Royal HaskoningDHV's project office for phase one is currently being set up, according to Moll. The work will be carried out in three overlapping batches, he says, with each batch taking approximately two years to complete. "The size of the works to be carried out in a relatively short period forms a major challenge," Moll says. "A huge number of designs will have to be produced in parallel, [and] quality control will be set up using the strengths of the Bangladeshi and the international experts in an effective way," he says.
Currently, Bangladesh has a coastal embankment system comprising 139 polders protected by approximately 3,430 km of embankments and overseen by the Bangladesh Water Development Board, according to the World Bank. Once phase one is complete in 2020, later phases will already have begun.