The state irrigation department sent a detailed project report (DPR) to the state government on Friday on the plan to dredge the Teesta riverbed.

Due to the GLOF (glacial lake outburst flood) due to the outburst of the South Lhonak Lake in Sikkim in October last year which led to a flash flood in the Teesta, heavy silt deposits have been found in the riverbed.

“Because of such silt deposits, the height of the riverbed has increased. As a result, the river’s capacity to hold water has reduced and during this year’s monsoon, we have noticed that whenever there has been a rise in the water levels due to downpours in upper catchment areas, the river has spilt over its banks and flooded low lying areas. That is why, dredging is required to lower the riverbed,” said Krishnendu Bhowmik, the chief engineer (northeast) of the state irrigation department.

Sources said that after last year’s flash flood, the state government had instructed the department to prepare a DPR for dredging the river bed.

In the DPR, engineers of the irrigation department recommended dredging along a 32km stretch of the Teesta, starting from Sevoke to Bakali in Mainaguri block of Jalpaiguri.

“Dredging has to be done in at least 20 spots along this stretch. While in some locations, silt deposit has to be cleared up to a depth of around 2.5 metres, there are places where such deposits have to be cleared over a width of 400 metres,” said a source.

The DPR adds that around 20.20 crore cubic metres or 7.14 crore metric tonnes of silt, which include sand, pebbles and boulders, have to be taken out of the Teesta.

“This will augment the water holding capacity of the river. Around ₹567 crore will be needed for this work. We have sent the report. It is up to the state to decide on the issue,” said an engineer.

A senior official of the department said after the extraction, the sand can be tested and used for construction work.