A survey of the Karnaphuli River, the lifeline waterway of the port city, finds it changing course with its two north tributaries accumulating sand, its flow interrupted by the pillars of the Shah Amanat Bridge in Southern Chattogram.
The depth of the river has come down to 7.7 feet between pillar-1 and pillar-2 on the north side under the bridge, which was once over 25 feet, while the depth tripled to 78.6 feet on the south side, between pillar-4 and pillar-5, narrowing the river to less than half its earlier size, the survey found.
Initiated by river campaigners of the Karnaphuli River and Canal Protection Movement, Chittagong University of Engineering and Technology University Civil Engineering Department, Professor Dr Swapan Kumar Palit, Karnaphuli expert, Professor Idris Ali, and Marine Fisheries Academy Bangladesh Professor, Noman Ahmad Siddiki, conducted the survey from 1 March to 30 April this year.
According to the survey, the width of the river has now come down to 410 metres from 930.31 metres in 2000, meaning that 520 metres of the river disappeared in 22 years. Land has emerged as char areas, where various types of establishments such as fish markets, ice factories and slums have been established.
"A large portion of the river filled up on the northern side under the bridge, making a sharp flow to the south," Professor Noman Ahmed, who led the survey, told The Business Standard.
"If the riverbed is not dredged immediately, and the water flow brought back to normal, the bridge [Shah Amanat] at risk of collapsing," he added.
"Sand from two tributaries is accumulating and filling up the riverbed there," said Swapan Kumar palit.
Former Chattogram City Corporation mayor Mohiuddin Chowdhury once led a movement for a hanging bridge on the Karnaphuli River instead of the then proposed pillar-backed Shah Amanat Bridge, fearing the disruption in water flow on this waterway lifeline.
Such damage to the river also took place after building the Kalurghat Bridge back in 1930; it created a large char, now familiar as Kulagaon Char, in the middle of the river.
After 80 years, the government built the third Karnaphuli bridge at Tk380 crore and named it after 18th century Sufi Muslim figure Shah Amanat.
According to the survey, the gradual change in the river direction threatens to bring down the bridge, the only means of communication between Chattogram and nearby districts Cox's Bazar and Bandarban.
However, the Roads and Highways Department (RHD) denies any such risk to the bridge collapsing.
"We have recently visited the bridge," Mohammad Jahed Hossain, RHD chief engineer for Chattogram division, told The Business Standard.
"We found it all okay. None of the pillars of the bridge appeared to be at risk." There was 255 feet of piling in the 78 feet deep portion of the river, he added.
The depth was found normal, from 24 to 25 feet on average, in Patharghata, Firingi Bazar and Bridgeghat, as the authorities were dredging the areas on a regular basis, while it was abnormal in the areas of the Chaktai and Rajakhali estuaries.
In the Chaktai estuary, the north side river was gauged only 2 feet deep, midpoint 13.6 feet, and south side 48 feet.
The midpoint depth was only 7 feet in the Rajakhali estuary, but it was found to be 60.9 feet under the Shah Amanat bridge, which means the riverbed has lost its normal shape and form.