Ballincollig's broken weir will be blocked off from the public after Cork County Council determined it was too expensive to repair it.
The historic weir collapsed in late 2014 having being built in the 1790s to divert water to the local Gundpowder mills.
The collapse has meant the weir is now accessible to the public and the water channels leading to the Mill have dried up.
Local Councillor Derry Canty (FG) told the Evening Echo that he feared it was only a matter of time before somebody was seriously injured or killed at the location which is a popular gathering spot for locals.
Recent good weather has seen people flock to the weir to sit on it or paddle in the water.
Mr Canty believes the weir should be fixed rather than merely blocked off.
“I've been told it will cost approximately €800,000 to fix,” said Councillor Canty.
“The canals have gone into disrepair. Cork County Council has washed their hands of it, it seems.
“It's an amenity that has been left to die,” he added.
JB Barry & Partners were commissioned by the local authority to examine options at the weir last year.
They identified four options, including a repair of the weir and a new fish pass mid-river, costing up to €500,000.
A second option included leaving the weir unrepaired, meaning the Mill Race channel would run dry with sheet piles installed upstream with the upstream sluice fully closed — costing up to a tenth the cost of a full repair.
A pumping station costing €60,000 and a low flow channel pipe to divert the flow of the Lee costing up to €67,500 were also options.
Repairing the weir was not considered desirable by the fisheries and diverting River Lee flows were met with resistance from Heritage Ireland.
However, Ballincollig-Carrigaline municipal district officer Kevin O'Regan said that blocking public access to the weir will be carried out this year and the Council is seeking quotations on the work.
“Following a recent review of the options available the Council has decided to undertake measures to limit access to the damaged weir, provide increased awareness to the general public of the dangers associated with the collapsed weir and reduce potential fish kills within the mill race associated with fluctuating water levels,” he said.
This work will close off access to the weir. Quotations for undertaking this work will now be sought with a view to having work undertaken this year,” he added.