The approach is cost-effective when applied to small, slow-flowing rivers
When riverbank erosion—one of Bangladesh’s major natural disasters—displaces thousands of families each year, state-sponsored bamboo and bio-engineering intervention, to mitigate riverbank erosion, provides significant prospects to reduce the destruction.
Erosion and channel-shifting during the monsoon—more specifically, during the rising and recession stage—results in serious damage to livelihoods in Bangladesh. However, the problems can be reduced by constructing low-cost bamboo structures; with the added advantages of agricultural land reclamation as well as navigational channel development, experts say.
As typical riverbank protection methods with sand-filled mattresses or concrete cubes are expensive, the cost-effective, local technology—using locally-available material and manpower—provides a sustainable way to stem river erosion, they claim.
“Conventionally, spurs, groynes, revetments—or a combination of them—are used to manage and mitigate river erosion and related problems. However, these structures are too expensive to adapt to the longer reaches of the large-scale alluvial rivers of Bangladesh,” said Moniruzzaman Khan Eusufzai, a senior scientific officer of the River Research Institute (RRI) under the Ministry of Water Resources.
“A 100-meter conventional structure costs Tk40 crore, a 100-meter bamboo structure costs only Tk4 lakhs. Therefore, bamboo bandals [bundles] are important as a low-cost alternative that can be adaptive when necessary; with local socio-economic and environmentally- friendly conditions,” Moniruzzaman told the Dhaka Tribune.
According to RRI research, the key mechanism of bandals is their ability to shift sediment loads, towards the bank line, where water flows at a reduced velocity.
“This bank-shifting is also utilized to divert water flows towards the center line of the channel, to facilitate natural dredging; reducing riverbank erosion,” Moniruzzaman explained adding that: “on the basis of empirically-understood working principles of bandals, they are used to mitigate riverbank erosion and navigation problems.”
After receiving positive results from the protective experimental work— using bamboo structures in different districts over the last couple of years—now the government has been implementing another pilot project on a tributary of Brahmaputra in Rowmari upazilla under Kurigram district.
Financed by the Climate Change Trust Fund (CCTF), the Tk1.6 crore project—consisting of three bamboo structures of 4.9km—began in Bolodmara Kheyaghat, Phuluarchar, and its surrounding area, in mid-October.
The project will be completed in March, 2019.
An exclusive project
Taherul Islam, a resident of North Phuluarchar village, has had to shift his residence seven times, since 1988, due to frequent riverbank erosion.
While talking to the Dhaka Tribune, he said: “Protecting bank erosion with bamboo structures is a good initiative. But the way the work is advancing will only benefit the people of Kurirchar, Baghmara, and Rowmari; not the people of Phuluarchar who are the most vulnerable. It is Phuluarchar that has been most-ravaged by river erosion.”
While asked about the exclusive design of the project, Taherul said that there were few political leaders and public representatives in southern Phuluarchar, while most of them—including the Union Parishad Member, Upazila Chairman, and Member of Parliament—reside in Baghmara, Kurirchar, and Rowmari—on the eastern side of the embankment.
“Since the influential leaders are from those areas, the project has been designed according to their instructions,” he told the Dhaka Tribune.
Another villager of North Phuluarchar Md Shamesh Uddin said: “As the project has begun, I believe a protective embankment will be built on our side in future.”
When asked, RRI Officer Moniruzzaman, also the project director, said: “Since the project was funded by CCTF, they had a condition that it must be implemented with the participation of local people. So we had to carry out the project with local representatives.”
“If there is public demand, we will seek more funding from the CCTF to expand the project. Perhaps, we can request the government to provide funding from its Annual Development Programme (ADP),” he told the Dhaka Tribune.
Limitations of bamboo structures
Despite being low-cost, eco-friendly, and effective for land reclamation, the most crucial limitation of bamboo structures is their lack of sustainability, experts say.
Center for Environmental and Geographic Information Services (CEGIS) Deputy Executive Director Dr Maminul Haque Sarker described this method as unsustainable and not effective for major rivers.
“This is an ancient method which was initiated during the British period in India. This method is often used locally but it cannot protect bank erosion along major rivers,” he said.
“Bamboo structures are comparatively weak and cannot exist in rivers with high water flow. However, they can work in minor rivers,” CEGIS’s river, delta and coastal morphology expert Maminul told the Dhaka Tribune.
RRI Scientific Officer Moniruzzaman echoed Maminul’s conclusion.
He said: “This method is not appropriate for rivers with a high current. Therefore, we are implementing the project in a tributary where water flow, or velocity, is low.”
Several pilot projects have been successfully completed in the: Rajbari, Faridpur, Sirajganj, Netrokona, Jamalpur, Mymensingh and Barisal districts, he said.
“In some areas in Islampur under Jamalpur district, land has been reclaimed with this method and people are now cultivating crops there. Previously, these areas faced erosion,” he told the Dhaka Tribune.