Highlights:
The Dhaka-Kasiani-Gopalganj railway line, a major new transport link in the country, is facing "significant risks" of land subsidence that could jeopardise its long-term safety, according to a recent scientific study.
Researchers from the University of Tokyo used advanced satellite-based monitoring technology to discover that extensive sections of the 150-kilometre railway are gradually sinking, particularly where the line traverses soft deltaic and alluvial soils.
The study, titled "Instability Mapping of Dhaka-Kasiani-Gopalganj Railway Line in Bangladesh with InSAR Time Series Analysis," claims to be the first scientific assessment of ground subsidence on the country's linear rail infrastructure.
Bangladesh Railway authorities say they have not found any problem like this. They, however, say they will investigate whether there are any such problems in the spots based on the research data.
Embankments sinking up to 16mm per year
By analysing Sentinel-1 satellite data and InSAR time-series analysis from January 2020 to October 2023, the researchers monitored ground movement along the route. Their findings showed an average subsidence rate of 10-16 millimetres per year.
The most affected areas lie outside Dhaka, specifically near Mawa, Kasiani, and Chapta. In these zones, the railway embankments were constructed on soft soils – such as deltaic silt, alluvial clay, and marsh peat – which are highly susceptible to settling under the weight of the elevated tracks.
The study warned that embankments built on these soil types "should be prioritised for inspection," noting that instability is most pronounced where the line passes through paddy fields.
Concerns for future rail expansion
The Dhaka-Gopalganj line, construction of which began in 2016, is a flagship project under Bangladesh's Railway Master Plan (2016-2045) aimed at improving regional connectivity. However, the findings have raised broader concerns about the safety of new railway routes being built across the country's soft deltaic terrain.
Bangladesh lies on one of the most subsidence-prone deltas in the world, where natural sediment compaction, unregulated groundwater extraction, and rapid urbanisation contribute to land sinking. Earlier studies have detected ground subsidence of up to 18 millimetres per year on the outskirts of Dhaka.
The researchers highlighted that InSAR technology enables large-scale, cost-effective monitoring compared to conventional field surveys, which are often expensive and labour-intensive. "Satellite-based structural health monitoring can provide early warning signals and help prioritise maintenance," the study said, recommending that such data be integrated into Bangladesh Railway's inspection system to identify subsidence hotspots before significant damage occurs.
Call for proactive monitoring and soil stabilisation
The study urged Bangladesh Railway and the railways ministry to adopt proactive maintenance measures, including regular subsidence monitoring and soil stabilisation in high-risk areas. It also advised that future rail projects incorporate geotechnical mapping and soil improvement during the design and construction phases to mitigate settlement risks.
Nearly 40% of the railway corridor passes through cropland areas, which show the highest vertical displacement rates. The authors warned that reclaimed agricultural land used for infrastructure remains unstable even after compaction.
Experts believe that such satellite-based analyses could help policymakers enhance the resilience of critical infrastructure, not just railways but also roads, bridges, and pipelines across Bangladesh's deltaic regions. As climate change increases flooding and sediment shifts, these findings could inform national strategies for transport safety and sustainable development.
The researchers noted that integrating InSAR data into railway maintenance planning can serve as an early damage indicator, helping authorities "allocate inspection resources effectively and prevent major failures."
Experts have called for urgent action. Adil Mohammed Khan, president of the Bangladesh Institute of Planners, told The Business Standard that the matter "must be investigated" based on the research. He suggested the sinking could be due to either poor construction quality or the country's natural geological tendency for land to subside.
"If the line continues to sink every year from a specific spot, it could cause a major accident," he warned. "The railway authority should take the matter seriously and quickly find the cause and the solution."
What authorities say
Md Arman Hossain, director (procurement) of the Bangladesh Railway, told this newspaper, "One pair of trains is running on that line, and we have not received any notice regarding any problems with the line. We do not have information about the research mentioned. No such problem has been identified on that line from our side yet."
However, officials indicated a willingness to investigate the findings. Farid Ahmed, general manager (west zone) of the Bangladesh Railway, Rajshahi, said, "We do not have any information that the line is sinking every year. Train traffic is normal on that line... Even then, we will investigate whether there are any such problems in the spots based on the research data."