A flood defence planned for south inner city Dublin will fail with a "catastrophic" deluge, it has been claimed.
A local environmental group has warned that a 1.3km flood barrier designed to protect low-lying areas from rising tides will not be enough to prevent disaster.
They insist that only a massive scheme like London's Thames barrier can stop the city getting swamped by rising sea levels.
Dublin City Council is planning to build a 900mm-high retaining wall along a stretch of the south quays, 1.8m from the edge of the quay wall.
It will apply to An Bord Pleanala for permission for the South Campshires Flood Protection project later this year.
The proposals come five years after the OPW carried out the Dublin Coastal Flood Protection Report, which identified the threat to homes and businesses in the city centre. It identified several locations where the level of flood protection was insufficient to deal with the projected sea-level rise.
The report had followed major flooding in 2002, when the River Dodder flooded Sandymount, Ringsend and Irishtown, with the south Liffey quays also flooding.
After carrying out an Environmental Impact Statement for the scheme, the city council will start work on the flood wall in 2011, if its application is successful.
Damien Cassidy of the Ringsend, Irishtown and Sandymount Environmental Group said the wall would not solve the flood threat.
"What is needed is a Thames-type barrier to stop the height of the tide invading the city of Dublin, because rising sea levels will eventually overtake all the low-lying areas," he said.
"Water will always find a way out. If they build this new flood defence the water will back up through the sewers and flood the low-lying areas along the quays."
A Dublin City Council spokesman said: "The project hasn't been designed yet, plans will be presented to An Bord Pleanala in summer and it would be premature to comment in advance of that."