Saving Assam's Communities: A Scientific Approach to Riverbank Erosion

MONOJ GOGOI 

The riverbank erosion is one of the major problems in Assam. The riparian community in the Brahmaputra basin in Assam has been bearing the brunt of erosion for decades. They lose properties, houses, homestead land and agricultural lands to erosion. The riverbank erosion, sometimes, engulfs even an entire settlement or village and thus displaces thousands of people annually in the state. According to a report, the state has already lost more than 4.27 ha of land to the 

erosion caused by the Brahmaputra and its tributaries. There is no any mantra or strategy to stop suddenly the increasing trend of the erosion but scientific studies like “Mapping riverbank erosion and assessing it's impact on socio-economy and livelihood of people in selected villages in Lakhimpur and Majuli district: A case study for sustainable policy intervention to improve disaster and climate resilience of vulnerable communities”, prepared by Partha J Das (lead author) and Arup Kr. Das (remote sensing and GIS specialist) will definitely help the policy-makers in frameworking appropriate strategic approaches to deal with the erosion situation in Assam and such approaches may decelerate the owes of erosion vulnerable communities in Assam. 

(File photo: Flood and erosion protection measures on the bank of Singora river near Borsala in Lakhimpur district)

This technical report is concentrating on 20 erosion affected villages as study areas, 10 each in Majuli and Lakhimpur districts. The primary objectives of this report are to understand the situation of riverbank erosion and its impacts socio-economic and livelihood security of the communities in these 20 villages and also to explore the existing policy spectrum in the disaster management domain at the state and national level and examine their relevance to provide benefits to the erosion affected communities. The report terms erosion as a hydro-climatologically induced hazard and attempts to recommend effective strategies for communities and governments so that the affected people can adapt better to the hazard.

The selected villages, chosen as study zones, in the two districts are contiguous and riparian in nature. To prepare the maps of the area two data sources are used: The location of the river channels and the drainage pattern have been taken from the Survey of India Toposheet of 1963, while the riparian background is sourced from a Landsat satellite imagery of January 2023.

Shifting of river channels is observed in the study which is almost usual in the context of the tributaries of the Brahmaputra. Three decades ago, the report says, Gandhasoraiati and Dhunaguri, the two villages in the study zone in Lakhimpur closer to Ranganadi. Later the confluence of Ranganadi went upward and the downstream of Ranganadi channel was captured by the Subansiri. The villages in the study areas in Lakhimpur are either affected by the Subansiri of Dikrong river. In the Majuli study area, the villages are affected by the Brahmaputra river itself over the last four decades as the river has been intruding to the mainland Majuli from the south to the north.

Basic information about the villages, like population, number of households, land area, names in ASSAC data and local names of the villages are clearly stated for villages situated in the study areas in Lakhimpur and Majuli districts. To understand the erosion situation in the villages,  the villages are demarcated a circular zone of 5 km and examines the erosion and deposition processes. 

The methodology used for such a serious study plays a vital role in the outcomes of the entire study. For data acquisition and analysis, the Survey of India (SoI) Toposheet for the year 1963 were used, and medium to medium resolution satellite imagery for different time periods (e.i. for 1987, 1990, 1995, 2000, 2005, 2010, 2015 from Landsat ™  and for 2020 and 2023 from Landsat 8) were used. Moreover,  the study team also visited the study villages in the year 2023 and recorded the latitude and longitude of each village. The acquired data were preprocessed using advanced scientific and technological tools. The river channels in the study area of Lakhimpur were also analyzed digitizing the river channels from SOI Toposheet for the year 1963 and the satellite images for the year 1987, 1990, 1995, 2000, 2005, 2010, 2015, 2020 and 2023.

The methodology used in the study helps in bringing out the accuracy in findings in the study. 

An overview of the changes in the erosive landscape during the period of 1963 - 2023 is presented very distinctively through different maps for different time periods for the villages of Lakhimpur and Majuli. Besides the maps, specific notes are used in the study to make it easier to understand the erosion, accretion or unchanged situation in the area.

During the period of 1990-2023 land use and land cover analysis were done using geospatial techniques and changes in the landscape happened due to constant exposure to hydrogeomorphological actions and processes triggered by the rivers such as braiding,  meandering, flooding, bank erosion, sediment deposition and consequent human responses and forests, vegetation,wetlands etc. The village community, as expressed to the surveyors of People's Action for Development (PAD) and North East Affected Area Development Society (NEADS), attributed that climate change was affecting such changes.

To present the land use and land cover changes in the study area of Lakhimpur maps based on satellite imagery are used for different time periods. From 1990 onwards a map is used at a gap of every 5 years while the gap of the last map of 2023 is 3 years. These colourful maps distinctively presented the periodic LU and LC changes in the location. Moreover, numerical charts and bar graphs are also glittering in the study report. The study vividly stated village wise data of erosion, accretion, sand deposition etc.

In the context of villages in Majuli district, the author says the Brahmaputra has been intruding towards human habitats and making the villages more erosion prone from the year 1963 to 2023. To delineate the situation, 10 maps of 10 different years of the period are given which clearly show how the river channels come closer to human settlements and the increasing trend of erosion in the Majuli study area. A separate chapter is used for the Majuli study zone. The same methodology, as in the Lakhimpur study zone, is applied to understand the situation in the 10 villages of Majuli.

Analyzing the land use and land cover changes in the study area during 1976 - 2023 the report says that the changes mainly occur due to due to prevalence of active erosion and accretion processes caused mainly by channel migration triggered by intense braiding, annual flood cycles, and huge sediment flux driven by powerful hydrogeomorphological regime of river over the year. This causes shifting of human settlements, agricultural areas, social and economic infrastructure, and forests, vegetation, wetlands etc. 

To indicate the LU and LC changes in the area of Majuli, 10 separate satellite images (maps) of different years, from the year 1976 to 2023 have been used. These colourful maps distinctively given the landscape changes scenarios of the study area over the year. Bar graphs and numerical charts are also added to the report. Analyzing the findings from the LU - LC the report says agricultural land has decreased from 69.79% of the total study area (153.83ha) in Majuli to 45.95%, by about 23.84% equivalent to 36.66 ha. This happened due to river erosion and increase in sediment/sand deposition on agricultural land. Built up area, area under wetland, sand deposition area and grassland area in and around the river have found increased while area under active river channels containing water has decreased. The study cites, reduction in flow of the Brahmaputra could happen due to a combination of factors such as historical decline in flow from upstream sources in the upstream stretches in China (Tibet) and Arunachal Pradesh, more acute braiding with larger sediment loads and other factors which could affect the flow in the upstream areas. Additionally, climate change, manifested in the form of recession of glaciers in the Himalayas, irregular rainfall and the observed decline in monsoonal rainfall may be possible causes of declining flow of the Brahmaputra. 

In the Majuli study zone (7 km buffer area), it is found that maximum soil accretion (1514.06) occurred during 1963-1976 followed by 1976-1987 (1391.29 ha) and 2009-2014 (1152.04 ha). In the report, the erosion and accretion trend was also estimated for individual or cluster of villages for the period of 1963-2023 and the findings are presented visually. The area of erosion,  deposition and area undergoing no change are shown in maps and the estimated values are tabulated and graphically plotted in each figure.At the end of the chapter the findings are well summarized providing village wise erosion, accretion and area under no change with data to understand better.

In the chapter IV of this technical report, giving an overview on riverbank erosion and its mitigation in Assam, the report says in stable river system erosion takes place at slower pace and smaller scale but the Brahmaputra is unstable, it has exceedingly large flow, enormous volume of sediment load, continuous changes in channel morphology, rapid bed aggradation and bank line erosion and recession. The report points and explains every main cause behind erosion by the Brahmaputra. The Brahmaputra has been gradually widening mainly  due to losing terrestrial land through erosion processes. Previous studies, stated in this report, told that in the first survey in 1912-1928 the Brahmaputra covers an area of 3,870 Sq km which increased to 6,080 Sq km by 2006 found in the third survey. The increase rate was 57.11%. Erosion occurs in the tributaries of the Brahmaputra too in massive intensity. Due to erosion by the major tributaries it was found that 639 Sq km land area has been lost in the Brahmaputra river system during 1990 - 2008, out of this 223 Sq km and 416 Sq km area has been lost due southern tributaries and north bank tributaries respectively. All the findings on erosion by National Disaster Management Authority (NDMA), 2012, are presented in the report so that anyone can find an historical and present overview of erosion in the Brahmaputra basin.

Detrimental impacts of erosion are elaborated and states two ideal measures: structural measures and non-structural measures, are ideally applicable to mitigate or reduce erosion and its impacts. The report also discusses the legislations and policies at national level, state level and local level which were formulated to manage the erosion issue and mentions about streamlining legal and land use regulations, planning for vulnerable areas, developing emergency and evacuation plans, designing local and livelihood improvement programmes etc.

As per government rule, those who have lost their land to erosion, still have to pay land revenue. But among the communities there are two different opinions- one group wants to pay for lost land as they will have the legal right on the land if the land is recreated by normal processes of the river or structural measures. Another group opines that they don't want to go back to land although it is recreated because the land became unusable due to sand and hence they are not paying revenue or reluctant to pay. Few land regulations are stated here to understand the ownership of such lands.

Till the year 2021, erosion was not listed as a natural calamity in policy documents. Therefore erosion mitigation schemes were not considered eligible for funding under the National Disaster Response Fund (NDRF) and State Disaster Response Fund (SDRF) and the erosion victims are also not considered entitled to get compensation or rehabilitation under these funds. The Assam government tried to bring a change in policy by introducing ‘Chief Minister’s Special Scheme for Rehabilitation of Erosion Affected Families of Assam in 2015 but failed for not framing the detailed roles and funds were not allocated on time. But the NITI Ayog's intervention and acceptance of Fifth Finance Commission in 2020 helped the erosion victims to get compensation from the NDRF and SDRF. Another policy ‘Rehabilitation policy for erosion affected families of Assam,  2020’ which was issued by the government of Assam in January, 2021 sought to provide compensation and rehabilitation to the families affected by erosion. This was the first such state policy in Assam. 

Analysis of policies regarding erosion will definitely help all sections of people including policy makers, researchers, academicians, stakeholders etc.

Towards the end of the report, in chapter VI, some advocacy points and salient recommendations were made for erosion risk reduction in the study zones as well as in the entire Brahmaputra and Barak basins. In total, 27 recommendations, including structural and non-structural, suggested in the report to government departments,  agencies, reputed institutions, NGOs , stakeholders etc.

Under the supervision of the Lead Author of this technical report, a survey was conducted with a structured questionnaire in study zones of Majuli and Lakhimpur by the researchers of PAD and NEADS to know the extent of erosion and its impacts on various aspects of the lives and livelihood of the communities.  But failed to reach a conclusion because it was found that the information provided by the villagers were inadequate, inconsistent and unclear on many fronts. The survey was conducted during September and October, 2023. The author is hopeful and wants to conduct the exercise again in future so that the information provided by the villagers can be compared with the results of scientific assessment and can develop an integrated methodology for erosion impact assessment combining both geospatial techniques and local information. 

Dr Partha J Das, a well known water and climate expert who is also heads of Aaranyak's Water, Climate and Hazard (WATCH) programme is very much familiar with the water, river, climate, flood and erosion issues of Assam. For over two decades he has been extensively doing field works in the entire Brahmaputra and Barak Basins and these issues have been raised even in national and international forums. 

His experience and expertise is highly reflected in this technical report. This report will be an important asset for upcoming generations.