Long-Term Monitoring and Forecasting of Teesta Riverbank Dynamics Using Remote Sensing and GIS
This study utilizes remote sensing and GIS tools to analyze 35 years of Teesta Riverbank dynamics, revealing significant left-bank erosion and right-bank accretion, and employs Kalman filter forecasting to predict continued migration trends through 2044 for improved river management and disaster mitigation.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Rivers are not static lines on a map; they are living, breathing entities that constantly reshape the land they flow through. In places like Bangladesh, where over six hundred rivers crisscross the landscape, the movement of water is a primary force that builds and destroys the very ground people live on. Two opposing forces drive this change: erosion, where the river eats away at the soil, and accretion, where the river drops sediment to build new land. When a riverbank erodes, it can swallow homes, farms, and entire villages in a matter of years, leaving behind a loss that can never be recovered. Understanding how these banks move is not just an academic exercise; it is a matter of survival for communities living on the edge of the water. To track these changes over decades, scientists now look to the sky, using satellite images to create a time-lapse history of the river's path, allowing them to measure exactly how much ground has been gained or lost and to guess where the river might go next.
In a recent study focused on the Teesta River in northern Bangladesh, researchers used this satellite perspective to trace the river's behavior from 1989 to 2024. The Teesta is a massive, transboundary river that enters Bangladesh from India and flows south, known for its chaotic and shifting nature. The team, led by Md Rayhan of the Bangladesh University of Engineering and Technology, gathered a series of satellite photographs taken every five years over thirty-five years. They selected images taken during the winter months to ensure the water levels were consistent and the views were clear of clouds. By carefully tracing the edge of the water in each photo, they created a digital record of where the riverbank stood at each point in time. This allowed them to see the river not as a single line, but as a moving boundary that has been in a constant state of flux for decades.
To make sense of this complex history, the researchers divided the river into hundreds of small, straight lines running from the bank out into the water. They measured how far each point on the bank had moved over the years, calculating the total distance of change and the average speed of that movement. They found a striking difference between the two sides of the river. On the left bank, the dominant story is one of loss. The data showed that nearly 70 percent of the measured sections of the left bank were retreating, with the land being eaten away at a rate of up to 74 meters per year in the most severe spots. This side of the river is a place of relentless erosion, where the soil is constantly being washed away, threatening the stability of the land and the people who depend on it.
In contrast, the right bank tells a story of growth. Here, the river is mostly building land rather than destroying it. The researchers observed that about 59 percent of the sections on the right side were gaining ground, with some areas accumulating new soil at a remarkable rate of over 154 meters per year. This side of the river is expanding, creating new land through the deposition of sediment. However, this growth is not uniform; there are still pockets of erosion along the right bank, and the pattern of where the land builds up and where it disappears varies significantly from one section to another. The river is essentially shifting its weight, carving out the left side while piling up the right, a process that reshapes the entire floodplain.
Looking beyond the past, the researchers used a statistical method to project where these banks might be in the future, specifically for the years 2034 and 2044. This method takes the historical trends of movement and extends them forward, assuming that the river will continue to behave as it has in the past. The projections suggest that the current patterns will likely continue: the left bank will keep retreating in many areas, while the right bank will continue to expand in others. These forecasts are not absolute predictions of the future, as they cannot account for sudden events like extreme floods, changes in how dams upstream release water, or other human interventions that could alter the river's path. Instead, they serve as a guide, showing the most probable direction of the river's movement if no major changes occur.
The implications of these findings are clear for anyone living in the Teesta basin. The river is not moving as a single unit; it is acting differently on each side, requiring different strategies for protection and planning. On the left, where the land is disappearing, the focus must be on preventing further loss through embankments and vegetation to hold the soil in place. On the right, where new land is forming, the challenge is to manage the sediment so that it does not block the flow of water or alter the river's course in dangerous ways. By understanding the specific dynamics of each bank, local authorities can make better decisions about where to build, where to farm, and how to protect communities from the inevitable shifts of the river. This study provides a crucial map of the past and a window into the future, offering a way to navigate the changing landscape of one of Bangladesh's most vital waterways.
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