Poor water drainage systems, lack of silt management with India, and climate change have caused repeated flooding in the Sylhet region.
In addition to these two reasons, research attributes flooding to unplanned dams, roads, infrastructure construction, riverbed filling, and filling of various haors (wetlands).
The information has been revealed in a joint study conducted by geography professors from Dhaka, Chittagong, and Rajshahi universities.
Since May this year, Sylhet has experienced three bouts of floods.
Floodwaters have even entered many homes in Sylhet city.
As a result, floods have become a cause of anxiety for the people of the Sylhet region.
Prof Dr Mahbub Morshed, chairman of the Department of Geography and Environmental Science at Chittagong University, told Dhaka Tribune that housing in the lowland areas of Sylhet is increasing. Wetlands connected to Sylhet city are being filled up. The condition of the drains within Sylhet City Corporation is also not good.”
He emphasized the need to make these drains functional, dredge the Surma River, and prepare the haors to hold water. Otherwise, Sylhet will face even worse conditions in the future, leading to both humanitarian and climate-related disasters.
He mentioned that the research findings would soon be published as a booklet.
Geographical position
The study noted that the world's rainiest place, Cherrapunji in India's Meghalaya state, is only about 45 kilometers from Sylhet metropolis, located in a highland area.
This geographical location places Sylhet metropolis at risk of floods.
Heavy rainfall in Cherrapunji drains into the Surma-Kushiyara river system through the Meghna River into the Bay of Bengal.
The Surma River's northern bank developed as a commercial center, with numerous wetlands and canals once spread across the Sylhet metropolis.
These canals originated from the highlands to the north and flowed southward into the Surma River, facilitating the movement of many small and medium-sized boats.
Long history of floods
Floods are a major natural disaster for the Sylhet region, despite being a seasonal natural disaster for Bangladesh.
Historical records show significant floods in the western part of Sylhet in 1781, 1853, 1902, 1966, 1968, and 1988.
More recent floods of note occurred in 1998, 2000, 2004, 2007, 2010, 2012, 2015, 2016, 2017, 2019, and 2022.
Sylhet faces two types of floods: sudden floods caused by the Surma River and floods from local rainfall.
Heavy rainfall in the Khasi-Jaintia and Cherrapunji hills quickly flows into Sylhet's lowlands, causing sudden floods.
These waters follow the Surma-Kushiyara river system into the Meghna River, suddenly flooding the Sylhet metropolis.
Heavy rainfall
Sylhet also experiences the highest rainfall in Bangladesh, averaging around 4000 mm annually, causing local floods due to poor water drainage systems.
Sylhet's flood-prone lowlands are surrounded by hills, making flash floods a common natural disaster.
The region's flooding is significantly affected by heavy rains in Assam and Meghalaya in India. The study analyzes 27 years (1995-2022) of rainfall data, showing that 200mm of rain in Meghalaya and 400mm in Sylhet result in severe flash floods.
Rainfall between 200 and 99 mm strongly impacts total rainfall in Sylhet.
Meghalaya's heavy rainfall is a major cause of floods in Sylhet, linked to climate change.
Slit management
The study mentions 16 transboundary rivers between Bangladesh and India, with no joint silt management agreements.
India's control over water flow is another contributing factor. Other causes of flooding in Sylhet include unplanned dams, roads, infrastructure construction, riverbed filling, and filling of haors.
On a recent visit to flood-affected areas in Sylhet, State Minister for Water Resources Zahid Farooq mentioned that 1.2 million tons of silt come into Bangladesh's rivers from India annually, but no specific data on silt in Sylhet are available.
What experts say?
Prof Dr Jahir Bin Alam of Shahjalal University of Science and Technology (Sust) said: “Since 1971, the Surma River hasn't been fully dredged, leading to its siltation. Encroachment and construction along the river have further filled its bed. More silt accumulates in the riverbed than erosion.”
Prof Dr Abdur Rob of Dhaka University's Department of Environment said: “Riverbed filling and destruction of natural reservoirs are the main causes of floods in Sylhet. Activities along riverbanks and structural interventions increase erosion, depositing eroded materials on the riverbed, raising it and reducing water removal capacity. Scientific dredging and long embankments are needed. Haors should be preserved as natural reservoirs, and their capacity developed with advice from hydrologists. This issue is not just national but transboundary, requiring discussions at joint river commission meetings.”
Sharif Jamil, general secretary of Dhara and former general secretary of Bangladesh Poribesh Andolon (Bapa), said: “River filling in Sylhet is due to plastic waste, large projects without consulting locals, and authorities' neglect of problems.”
He stressed the need for comprehensive planning, including science, public involvement, and accountability, to free Sylhet from flood-waterlogging.