GUWAHATI: An indigenous river model BRAHMA-2D (Braided River Aid: Hydro-Morphological Analyzer) developed by the Hydrod-research team of Civil Engineering Department of Indian Institute of Technology Guwahati (IITG) successfully simulated the impact of vegetation on flow velocity to check river bank erosion in 450 meters areas from Charighoria to Bandarbari in Lower Majuli, Assam the second largest river island of the world.
The initiative was executed under the leadership of Prof Arup Kr Sarma.
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The area that was covered by the project experimentally was saved from river bank erosion in the last year.
“The villages like Bandarbari, Mohorichouk, Borjan, Charighoria, Kordoiguri and Barmukali were saved from the impact of river bank erosion in the last year,” said a resident of Bandarbari.
A team of researchers from the Water Resource Division of Civil Engineering Department of IITG led by Prof Sarma in collaboration with the Brahmaputra Board under the Ministry of Jal Shakti has developed the river model BRAHMA-2D, which can help to understand the flow Characteristics of large braided river like Brahmaputra, providing valuable insights to field engineers to design sustainable hydraulic structures like spurs, revetment and other river bank protection measures.
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“We have used coir bags, coir logs, coir mats, geo bags, bamboo poles and vegetation to check riverbank erosion. While geo bag appron checks the bed erosion at the depth of the river, to protect the sloping surface we planted five different species of grass with special root systems along with other materials. We also planted some saplings on the bank of the river. When they grow, they will stop the wind flow near the water surface which affects the river current and its course and thus check the erosion of the bank,” Dr Sarma told reporters during his visit to the project site in the last week.
“Our mathematical model combines highly complex mathematical modelling with challenging field-based research on large braided rivers. With this quasi-3D river flow model, we can understand how fast the water moves at different depths inside a river and its circulation around a structure like a spur installed for preventing river bank erosion,” Dr Sarma said.
The versatile model has further helped to design bioengineering methods for controlling river bank erosion. It has also been applied to understand the habitat suitability of aquatic species, especially endangered species, based on the availability of required depth and flow velocity.
“We will be happy to extend our project to other areas of Majuli. The plant and grass species chosen will also generate revenue if properly maintained. A society with local people should be formed to monitor the implementation and to maintain the project for its sustainability,” Dr Sarma also said.
“It is not correct that river bank erosion takes place only during monsoon or floods. Erosion also takes place after the water level of the river goes down. River orientation and winds have a significant effect on the flow of the river. The root system of the trees planted here will add additional strength to the bank. In addition, once grown, they would be able to counter the wind and thus help protect the area from erosion,” he also said.
“The bamboo pole used in this project anchors the coir log and also protects the area from the direct impact of water waves. The geo bags might settle down to protect the surface from erosion,” he added and thus needs maintenance.
“BRAHMA-2D integrates a two-dimensional model of water movement with a theory about entropy, a measure of disorder or randomness. The research also delves into how features like river banks, spurs, and sandbars affect the way water moves. Specifically, it observes a dip phenomenon near spurs where the flow of water underneath increases, a phenomenon absent in points away from these structures