The crisis is exacerbated by a lack of major dredging operations
The navigability of rivers in Sylhet district is at an all-time low, due to the inflow of silt carried by Indian floodwaters.
A lack of regular dredging efforts has also contributed significantly to this particular problem.
Numerous river islands have appeared in almost all rivers across the district; especially in the Surma, one of the largest rivers in Sylhet division.
This phenomenon has caused the river flow to further decrease in the dry season.
According to information from the Sylhet divisional commissioner's office, Maharam Patla river of Sunamganj's Tahirpur upazila is nearly dead because of the sediment.
The biodiversity of Sunamganj's Jadukata, Rakti, Patlai, Boulai, and Maharam rivers is threatened by the illegal and unplanned occupation of river islands and land surrounding the river.
Biodiversity of rivers endangered
There are 36 rivers in Sylhet division, according to information published on the website of the divisional commissioner.
They are the: Surma, Piyain Gange, Sari Gowain, Bagra Gange, Naowa Gange, Shyola, Dhamalia, Monai, Borodal, Juri Monu, Dholai, Longla, Karangi, Khowai, Sutang, Kushiyara, Madhabpur, Mahasing, Khajanchi, Bhottokhal, Kalni, Jamalpur, Boraba river, Lobha, Hari, Bogapani, Dhariyana, Dhoyai, Jadukata, Dhola-Dholai Gange, Gopla-Longol, Mogai-Chalti, Rakti, Poinda, Bhera Mohona, and Dhanu Bolai.
Sylhet Additional Divisional Commissioner Mrinal Kanti Deb told the Dhaka Tribune: "Drives are being conducted in Habiganj, Sunamganj, and Moulvibazar—as well as in Sylhet's Bishwanath upazila—to evict the illegal occupiers from the river islands."
He said there will be a meeting by the River Protection Commission in Sylhet this month; where they will discuss the steps necessary in order to protect the rivers.
National River Protection Commission Chairman Mujibur Rahman Howladar, at one of the commission's meetings a few days ago, said: "As Bangladesh is geographically lower than its neighbouring country, India, the country faces many natural disasters, including flash floods, due to mudslides from hilly areas."
Consequently, rivers face navigability issues and their direction flow changes as the depth of the water decreases. This is because river islands emerge as sediment amasses on the river beds, he added.
National River Protection Commission General Member Md Alauddin said the rivers' environmental balance is being disrupted by the emergence of these river islands and their illegal acquisition, threatening the biodiversity of those rivers.
Bangladesh Water Development Board's (BWDB) Executive Engineer of Sylhet unit Md Sirajul Islam said: "I believe that, every year, the navigability of Sylhet's rivers decreases by half a metre due to the inflow of silt from India."
He furthered that India's Barak river flows into streams through the Surma and Kushiyara at Bangladesh's Amalsid point. As the Surma river's source has filled with silt, most of the water flows through the Kushiyara river, resulting in horrific erosion on the river banks.
River water flow disrupted
The BWDB official also said the Piyain river—the trans-boundary river of India and Bangladesh that used to flow down from India's Omghat—has already filled with sediment. Thus, this river is flowing through the Dawki river.
At Amalsid point, the Surma river is flowing in the opposite direction and has taken a right turn; and Kushiyara is also flowing in the same alignment.
Some 60% of the water inflow from India flows through the Surma river and the remaining 40-35% flows through the Kushiyara river; the inconsistency of water flow is causing the silt deposits and erosion.
Huge river islands have started to emerge at the source of the Surma river, almost killing the upper Surma. Of the 53 kilometres of this river, 26 kilometres flow along the border—which is creating immense pressure on the Kushiyara river—causing river erosion on its banks, the BWDB official added.
Sirajul Islam furthered: "If dredging operations are executed on the upper Surma river— with the consent of both India and Bangladesh's government—then the navigability crisis, environmental-ecological problems, and other inconveniences might be averted.
"All the silt from landslides, mudslides, or flow from upstream is depositing on Bangladesh's side of the river."
He said since water flow is higher in the upper Surma channel—than its capacity to uphold the flow—river islands are being created near the piers of all the bridges on the channels, while the velocity of the flow decreases.
Due to this, a whole town of Kanaighat was flooded in three hours last year, he added.
Describing basin management as the key to the river’s condition, the BWDB executive engineer said: "The river basin is not in my country, so how should I manage that? This problem does not even have a scientific solution."
According to information on river research by Sylhet Agricultural University's Soil Science Department Professor, also the Dean of the Faculty of Agriculture, Dr Md Abul Kashem, every year 800,000,000 million tonnes of sand and silt are deposited in Bangladesh.
Bangladesh is facing frequent floods now, whereas it only used to flood every five to seven years due to the overflowing river bodies.
He stated that apart from Sunamganj, Moulvibazar, and Habiganj, silt from India flows through 57 upazilas of seven districts—including Brahmanbaria, Kishoreganj and Netrokona—into the Meghna river, crossing near Brahmanbaria's Titas, old Brahmaputra, and Bhairab.
However, the depth of all three points through which silt is carried has decreased, causing frequent flooding every year.
He said: "There have been no major dredging operation on rivers in the eastern region of Bangladesh, because of this, it is difficult to avoid the crisis."