International engineering and hydraulics company, HR Wallingford, believes a tidal barrier would protect more of the city from flood risk than the OPW’s controversial Lower Lee flood relief scheme — the single largest investment in flood defences in the history of the State.

The news comes as the OPW finalises its analysis of the 1,250 public submissions made on its Cork City flood defence plan. Its reliance on raised quay walls has sparked controversy, with the Save Cork City campaign group a vocal opponent. It has called for its alternative plan to be considered — a downstream tidal barrier and upstream catchment management measures.

The OPW has consistently ruled out its proposals, saying a tidal barrier could cost up to €1bn, and that the upstream measures would not provide adequate protection against fluvial flooding.

However, in a report commissioned by Save Cork City and due to be launched today, HR Wallingford experts David Ramsbottom and Peter Hunter, said the alternative plan is viable and provides many benefits over the OPW’s plan.

They say a 950m sector and sluice gate tidal barrier, similar to storm surge barriers in New Orleans, could be built 10km downstream of Cork City for €140m based on 2017 figures. They said it would avoid the need to build or maintain flood defences in the city centre, avoid the disruption caused by such construction, and eliminate the visual impact of raised walls.

Save Cork City spokesman John Hegarty: “We want the right solution for flood relief in Cork that reflects the ambition of the city.”

Tidal barrier ‘cheaper and better protection for Cork’

A tidal barrier could be built in Cork for €140m and would protect more of the city from flood risk than the OPW’s controversial Lower Lee flood defence scheme, international experts have said.

HR Wallingford, a civil engineering and environmental hydraulics firm based in England, said the alternative tidal barrier plan proposed by the Save Cork City group, which has been ruled out by the OPW on mostly cost grounds, is viable and would work.

The campaign group’s alternative plan has the major benefit of not requiring the construction of raised walls along the city’s quays, it would help to maintain the historic landscape of the city, and would avoid the disruption caused by construction, the firm says.

“The alternative scheme would also avoid the scenario of overtopping or failure of flood walls in the city, which could cause a serious risk to life as well as damage to the city,” it says.

Image taken from teh report by HR Wallingford on the Cork City tidal barrier

The details are contained in a report by two of the firm’s leading experts, who were commissioned by Save Cork City to examine their proposal. It will be launched today.

The OPW is in the final stages of analysing more than 1,200 submissions from the public on its Lower Lee flood relief scheme — the largest single investment in flood defences in the history of the State.

Save Cork City is opposed to the scheme’s reliance on raised quay walls and has suggested an alternative plan — the construction of a downstream tidal barrier combined with upstream catchment management.

The OPW has consistently ruled out a barrier on cost grounds, suggesting that it could cost somewhere between €500m and €1bn, and warning that it would do nothing to protect the city from fluvial flood risk upstream.

The campaigners commissioned Oxford-based HR Wallingford to provide an independent cost estimate for their alternative plan.

The firm’s technical director, David Ramsbottom, who was involved in the technical development of the Thames Estuary 2100 Plan, and civil engineer Peter Hunter, who was a project manager on the Cardiff Bay Barrage and who is the lender’s supervisor for a group of European banks for the $3bn St Petersburg Flood Defence Barrier, examined the campaigner’s proposal.

Their report says a tidal barrier could be built 10km downstream of Cork City, at a location proposed by Save Cork City between Little Island and Horse Head, for an estimated €140m based on 2017 figures.

The proposed structure would be about 950m-long and would consist of an embankment with a 60m wide navigation opening and a number of smaller gates.

“The main cost elements are the gates and the embankment, but the costs also include environmental mitigation measures and public amenity facilities,” they said.

“Further study will be needed to develop the design for a barrier and refine the cost estimates.”

They said a tidal barrier will provide tidal flood protection for the city without the need to provide and maintain flood defences in the city’s urban area.

“This will avoid the disruption that construction of the walls would cause and also avoid the impacts that walls would have on the city landscape,” they said.

They also said a tidal barrier will protect more of the city and more infrastructure from tidal flooding as it includes significant areas to the east of the OPW’s walls proposal.

Save Cork City spokesman John Hegarty welcomed the report which he said confirms what they have been saying all along.

“We want the right solution for flood relief in Cork that reflects the ambition of the city,” he said.

“The walls scheme would set a new and dangerous precedent for Cork with water pumping systems and many kilometres of walls ensuring the likelihood of a future dangerous breach in the defences leaving the city more likely to be flooded in the future.

“A tidal barrier provides faster flood relief and is environmentally the better choice for the city.

“It represents better value for money for the taxpayer.

“In design terms it represents a more predictable set of circumstances so the outcome and costs are predictable too. A tidal barrier is a far safer solution for people at risk of flooding by reducing that risk.”