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Brahmaputra River System

The Brahmaputra (/ˌbrɑːməˈpʊtrə/), also known as the Yarlung Tsangpo in Tibet, the Siang/Dihang River in Arunachal Pradesh, and Luit in Assamese, is a trans-boundary river which flows through Tibet, India, and Bangladesh. It is the 9th largest river in the world by discharge, and the 15th longest.

Path of the River Brahmaputra

From Sanskrit ब्रह्मपुत्र (brahmaputra, “son of Brahma”)

Majuli Proposal

CPGB, in collaboration with the Indian Institute of Technology - Guwahati(IITG), organized an International conference titled “Seeking Sustainable Solutions for the Brahmaputra: Challenges and Solutions” at Guwahati on December 18-19, 2010. The conference  was sponsored by the Government of Assam and attended by 200 Professionals, Private Consultants and Engineers from the Water Resources Department (WRD), Government of Assam. The meeting was successful with 34 technical papers presented in six following topics and sessions:

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  • Session 1: Mitigation Strategy for the Flood and River Bank Erosion problem in the Brahmaputra River.

  • Session 2: Global Climate Change Effects and Water Resources Management in the Brahmaputra River.

  • Session 3: Reclamation of Flood Plain land and Agricultural Water Management in the Brahmaputra River.

  • Session 4: Watershed Management in the Brahmaputra River Basin, Scope and Strategies.

  • Session 5: Groundwater Management in the Brahmaputra Basin.

  • Session 6: Polices and Governances Related to water Resources Management in the Brahmaputra Basin.

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Out of above diverse important issues discussed, the Flood and River Bank Erosion of the Brahmaputra was considered as the most critical. A group of Engineers under Dr. Arvind Phukan’s chairmanship, met at the end of the meeting on December 19, 2010. Dr. Phukan presented a summary of the CPGB’s comprehensive review of the severe river bank erosion of the Brahmaputra River that occurred at numerous locations in Assam during past six decades. The group identified mitigation of chronic River Bank erosion of Majuli Island as a “Piot Project” to proceed with development of a comprehensive plan for protection of the Island.  Accordingly, a detailed technical proposal titled “Sustainable Design Solutions for Mitigation of Flooding and River Bank Erosion of Majuli Island of Brahmaputra” was prepared by the group of CPGB Engineers and Scientists under Dr. Phukan’s leadership The proposal includes work efforts by four Task Groups as identified  below:

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  1. Data and Information system Group

  2. Geology and Geomorphology Study Group

  3. Mathematical Modeling Group

  4. Sustainable Design Solutions Group

 

The proposal was submitted to the Secretary, Ministry of Water Resources Department (MoWRD), Govt. of India on March 25, 2011 for funding authorization with development of the plan. After two years of reviews, correspondences, submissions of additional information requested by the reviewers and meetings with MoWRD officials, no indication of authorization of the proposal was received. 

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In the interim on February 6, 2015, through the kind assistance of Honorable Minister of State Mr. Sonowal, Dr. Phukan had an opportunity to meet Hon. Ms. Uma Bharti, Union Minister of Water Resources, River Development and Ganga Rejuvenation (MoWR, RD & GR) at Guwahati, and apprised her of the efforts of CPGB toward solution of the Majuli problem. He later provided a detailed presentation to her and her staff at Delhi on February 26, 2015 and handed over a copy of CPGB’s technical proposal on Majuli. CPGB received positive comments from Hon. Minister Bharti and her staff.  However, no approval of the proposal was received.

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In 2015, Dr. Phukan was appointed an Adviser to the WRD, Govt. of Assam. He was invited to deliver the keynote speech at a symposium organized by the WRD, Govt. of Assam to stress upon the Thrust Areas of the first 100 days’ agenda of Hon. Chief Minister Sonowal on July 30, 2016. A paper titled “Challenges and Sustainable Solutions for Mitigation of Flooding and River Bank Erosion on the Majuli Island”, written by Dr. Phukan with Co-authors, Ananta Nath, David Williams and Bruce Sharky (members of CPGB’s design team) was published in the souvenir of that event. 

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On May 2016, Dr. Phukan provided a presentation on the CPGB’s proposal to Dr. Amarjit Singh, I.A.S, Special Secretary, MoWR and his staff in Delhi.  Dr. Singh was pleased with the presentation and asked Dr. Phukan to re-submit the proposal in collaboration with IIT Guwahati (IITG). Accordingly, a Memorandum of Agreement was developed between CPGB and IITG, and the proposal was re-submitted in coordination with Prof. Chandan Mahanta of IITG and with a sponsoring letter signed by the Director of Research of IITG.

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Dr. Singh also coordinated with Dr. Phukan to make a presentation on the proposal to the members of the Brahmaputra Board and Central Water Commission (CWC) on November 1, 2017 in New Delhi. The committee members swayed away from considering the CPGB proposal as pilot project for Majuli, and remarked that “the Brahmaputra Board has taken up a scheme for protection of Majuli at an estimated cost of Rs.233.57 crores (Funded by MoDNER for Rs.207 Crores) and tenders have been finalized. The physical work for execution of the scheme is expected to start shortly and construction to be completed by March 2019.”

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Dr. Phukan visited Majuli in February 2018 to observe the progress of the project performed by the contractor TK Engineering Consortium Ltd. He was very surprised to know from the contractor’s representative that there was no design drawing on the project from the Brahmaputra Board. They bid the project based on estimated numbers of geo-bags to be filled with sand/silt and the number of RCC porcupines to be installed. Dr. Phukan visited the office of the Brahmaputra Board in Majuli and was shown a preliminary sketch illustrating the bank revetment with geo-bags. He was also told that the project would involve construction of RCC porcupines in 41 locations between Tekeliphuta and Chamaguri and bank revetment in 11 vulnerable reaches by using geo-bags filled with sand/silt.

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geo_bags.jpg

On a visit to observe the performance of the new revetments in November 2019, Dr. Phukan saw only remnants of geo-bags and porcupines at several sites built with the same age-old inefficient techniques. One of his notable observations was the absence of adequate armoring of the toes of bank slopes to the design scour depths for protection against bank failures. The first wave of 2019 floods had strewn away considerable portions of the geo-bags without much abatement of the continuing bank erosion in the island. Had the erosion protection measures proposed by CPGB were implemented, an investment of public funds of over Rs. 233 Crores wouldn’t have been washed away. 

Failed geo-bag revetments and eroded banks within months of placement in 2019

After the lull of the Corona Virus pandemic worldwide, and not having heard of any responses from the authorities, CPGB has submitted a letter to the Honorable Chief Minister of Assam in March 2022 apprising him the critical need of implementing sound technical measures to curb the riverbank erosion havoc of Majuli. The Government has proposed immediate construction of infrastructures involving a bridge, an university and a network of improved roads in the island.  The letter emphasized that such well-intended investment of large funds may not bear long term welfare to the residents unless the devastating saga of floods and riverbank erosion is curbed to save the very physical existence of the island. The group is eagerly waiting for a response. 

Our Approach

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​Mitigation measures of flooding and erosion problem must be selectively developed with the most efficient solutions possible while considering the available resources and constructability. The mitigation of erosion control can involve both structural and non-structural measures. The design team will evaluate the results of the inventory of available resources as well as the fluvial geo morphologic information and the numerical hydrodynamic modeling results. This information will be used as the basis for formulating sustainable design solutions to the flooding and the bank erosion problem. It is recognized that each strategic location may require a combination of measures to mitigate each identified erosion problem instead of applying one solution to solve all problems.

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Initial Development of the Mitigation Plan:

  1. Based on all available information from past initiatives of Brahmaputra Board, Central Water Commission and Water Resources Department, Govt. of Assam including community inputs, determine flood prone areas in the Island

  2. Assess the extent of flood prone areas and generate the flood prone map with priority areas across the Majuli Island.

  3. Evaluate the structural integrity of all embankments built on the Island considering the following factors:

  • Susceptibility to failure from inadequately designed river erosion protection measures or geotechnical instability

  • Inadequate maintenance of the embankments in terms of local erosion due to surface water runoff, piping and depression due to differential settlements, etc.

  • Gaps where the tributary streams enter the existing embankments from the landside

  • Record of the maximum flood levels across the Island in 100 years, if available

 

​It is to be recognized that the complex braided channel pattern including the erratic shifting nature of the Brahmaputra River have important implications on flood control by embankments. Given the high rates of channel migration and bank erosion in many places along the Brahmaputra River, unprotected embankments cannot be expected to remain immune to river erosion for many years, even if they are initially set back some distance from the banks. Also, the shifting channel pattern means that at many locations, flood flows can strike the banks or embankments at severe angles of attack, producing deep scour in the river bed and there by undermining the banks causing erosion.

Structural Measures

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  1. ​These measures can comprise of techniques that have a long history of success locally and throughout the world. These techniques may include:

  2. Channelization by dredging at a limited scale. The long-term success of dredging in the Brahmaputra river system of channels is unproven.

  3. Diversion of currents by Bendway (Submerged) weirs constructed with A-Jack concrete units.

  4. Bank Revetments (e.g., articulated concrete blocks, gabions, concrete lining, geo-web, etc.)

  5. Anchored Bulk Head or Tie-Back Steel Sheet Piles

  6. Stream cutoffs structures

  7. Grade control structures

Non-Structural Measures

​There are many factors contributing to the web of large scale riverbank erosion problems in the Majuli Island . Structural strategies of engineered measures to mitigate flood and river bank erosion may not be implemented in all stretches of the river and its tributaries in the Island.  Hence a holistic approach with inclusion of non-structural measures can provide a variety of proven erosion control measures in many areas of the island. Such measures can be through strategic establishment of native plant species and site specific or condition specific land management practices. Native plants have the advantage of being naturally adapted to environmental conditions within the region and sub-regions of the Island. Improving the management of upland soils such as agricultural lands as well as the application of best management practices for reducing surface water run-off will be included in the design recommendations.

Photos

The following pictures show typical River bank erosion of the Majuli Island at various locations.

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