Majuli Island of the Brahmaputra River in Assam: Origin and alteration in geomorphological features

by Rohan Nath

Introduction 

The mighty Brahmaputra River in Assam is home to the largest river island of the world,  Majuli Island which spans an area of 1255 km2(Fig 1, 2). The island is a subdivision of the  Jorhat district of Assam and is inhabited by around 153,000 people. “Vaisnavite” shrines,  popularly known as “Sattras” is present on this island which led it to become a principal  pilgrimage site for the last 400 years. However, flooding and severe bank erosion harm the  island at this current time. 

Fig. 1. Location of Majuli Island. (1917).  

Image Source: Sarma, J. N., & Phukan, M. K. (2004). Origin and some geomorphological  changes of Majuli Island of the Brahmaputra River in Assam,  India. Geomorphology, 60(1-2), 1-19.

Three important rivers bound the island, namely, the Subansiri River, Kherkutia Suti in the  north, and the Brahmaputra River in the south.  

The Majuli island is characterized by a spindle shape lying in NE-SW direction with an  altitude of 85.9m above sea level. Numerous lowlands and swamps of various shapes and  sizes occupy the plain topography with low relief. Few big rivers and several small streams  flow through the island. Alluvial fine loamy soils dominate the Majuli. The subtropical  monsoon climate brings an annual rainfall between 1494 to 2552 mm.

Fig. 2. Majuli Island of the Brahmaputra River. 

Image Source: https://timesofindia.indiatimes.com/travel/destinations/majulithe-worlds largest-river-island-might-just-disappear-in-the-future/as64012861.cms

There is a high mean annual flow and suspended sediment load of the Brahmaputra and  Subansiri (Table 1). 

Table 1. The mean annual flow and suspended sediment load of the Brahmaputra and  Subansiri. 

Year River Mean Annual Flow Annual Suspended Sediment Load
1975-1990 Brahmaputra 8829.5 m3/s 402 million metric tons during 1955- 1979
1956-1982 Subansiri 1671 m3/s 35.48 million tons annually

The mighty Brahmaputra leads to s severe bank erosion, which threatens the existence of  Majuli. 

The origin of Majuli 

According to historical surveys and reports, Majuli stretched between a location named  Banfang or Lakhu in the west and Bengmora in the east. In ancient histories of Assam, it had  been referred to as ‘Majali’ or a piece of land located in between two adjacent and parallel  rivers because the land was situated between the Luhit (Brahmaputra) in the north and its  tributary, the Dihing (Burhi Dihing) in the south.

The Brahmaputra River (formerly known as the Luhit or Luit) flowed to the north of the land  area of Majuli. The Dihing (one of the tributaries of the Brahmaputra) flowed south of Majuli  and met the Brahmaputra at Lakhu (Fig. 3). The land area of Majuli was converted into an  island when the Brahmaputra shifted its course southward and united with the Dihing near the  confluence point at Dihingmukh which is located around 190 km east of Lakhu, the former  confluence point. The southward shift of the Brahmaputra is believed to occur between 1661- 1696 due to a series of frequent floods and earthquakes.  

Fig. 3. The flow course of the Brahmaputra and the Dihing rivers before the  formation of Majuli. Image Source: Sarma, J. N., & Phukan, M. K. (2004). Origin and  some geomorphological changes of Majuli Island of the Brahmaputra River in Assam,  India. Geomorphology, 60(1-2), 1-19.

Following the formation of the Majuli island, the Brahmaputra was divided into two separate  branches. 

i. Luhit Suti or Kherkutia Suti – Brahmaputra (Luhit) flow to the north of Majuli. ii. Burhi Suti – The flow of Brahmaputra was directed to the south of Majuli through  the channel of the Dihing tributary. 

There was a natural event of channel shift when the major flow of the Brahmaputra was  diverted from the Kherkutia Suti into the Dihing leading to the enlargement of the channel (Fig. 4). 

Fig. 4. The flow course of the Brahmaputra and the Dihing rivers during the  formation of Majuli. Image Source: Sarma, J. N., & Phukan, M. K. (2004). Origin and  some geomorphological changes of Majuli Island of the Brahmaputra River in Assam,  India. Geomorphology, 60(1-2), 1-19.

Current scenario 

Currently, the Brahmaputra River resulted in an erosion in the southern boundary of the  Majuli island with a faster erosion in the southwestern part of the island. There has been a  noticeable increase in erosion during 1917-2001. The channel of Brahmaputra has widened  due to the erosion of both of its banks. The great Assam earthquake of 1950, further leads to  landslides in the eastern Himalayas which resulted in an increased flow of sediments into the  river. The high amount of sediment descended the plains, choked the channel of the river  which caused channel widening due to bank erosion. It has been reported that the width of the  Brahmaputra channel has increased up to 300% since 1917.  

The thick sand layer beneath the topsoil is undermined by the water which caused an increase  in erosion. The erosion is slower in locations where there is a presence of cohesive silty-clay  beds at the base of the banks.  

The Government of Assam is actively involved in assessing damage to agricultural land due  to sand deposition, the loss of property and life due to floods, and land area depletion due to  erosion, leading to the displacement of settlements and families from their location.  Therefore, it is an urgent need for the government to look upon it due to socioeconomic  issues associated with it. 

Reference 

1. Sarma, J. N., & Phukan, M. K. (2004). Origin and some geomorphological changes of  Majuli Island of the Brahmaputra River in Assam, India. Geomorphology, 60(1-2), 1- 19. 

Published by LakesOfIndia

Lakes of India is an E.F.I initiative aimed at sensitizing the larger public on freshwater habitats across the country. A blog platform where one can read about lakes across India. You can become a guest blogger to write about a lake in your hometown and initiate an action to protect that lake.

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