Cork city flood defence scheme will make the river safer, says OPW
The team behind the Cork city flood defence scheme say the latest design images show again how it will make the river safer and more open.
The OPW and its engineering consultants, Arup, have also criticised campaign group Save Cork City’s (SCC) tidal barrier proposal, insisting that it fails on all technical criteria and would cost €966m - and not €200m as has been claimed.
The latest computer-generated images of key parts of the €150m Lower Lee Flood Relief Scheme (LLFRS) show the proposed interventions at Mardyke Walk, Anderson’s Quay, on the riverside walkway behind the Kingsley Hotel, and at the Grand Parade boardwalk. Following extensive public consultation, it is now proposed to:
- build a new slipway on Mardyke Walk immediately west of Daly’s Bridge;
- deploy demountable barriers to protect the Grand Parade boardwalk area during flood events, and to raise the ground around the cenotaph;
- install new seats and a knee-high wall topped with railings along Anderson’s Quay;
- and to maintain river views along the walkway behind the Kingsley Hotel, with a wall to be built on the road-side of the path.
In a statement, the team said the visuals again show that claims the LLFRS features high walls that will block views of the river are “simply incorrect”.
The images come just weeks after SCC published visuals of its tidal barrier proposal at Little Island.
But the OPW and Arup said the SCC images differ significantly from the group's original “sketch”, with larger gates and other features which would significantly increase the costs.
They said hydrology experts, HR Wallingford, based their €140m cost estimate on SCC's 2017 tidal barrier proposal on a “sketch” and stressed that detailed hydrodynamic, navigational safety and environmental assessment work would be required before cost certainty could be provided.
“The only detailed pre-feasibility study undertaken on these critical matters has been carried out by LLFRS and the 200-page report is available on the project website. SCC has not undertaken this work, nor has anyone on their behalf," the LLFRS team said.
They also said that Prof SN Jonkman of Delft University, engaged by SCC in 2018 to review the OPW cost estimated methods, has co-authored a technical paper recently on how the US Army Corp of Engineers (USACE) has costed flood defence options for New York - the world’s largest flood defence scheme - which found that as well as reflecting current best international practice, the USAEC methods are “very similar” to the methods used by the LLFRS team in 2017.
“Even if SCC’s proposed tidal barrier at Little Island did not fail on all technical criteria, as it does, and, hypothetically, was progressed, the USACE method as recommended by Jonkman, yields an estimated whole life cost of over €966m, not under €200m as has been claimed by SCC,” they said.
“Using the same USACE method, the cost of a viable tidal barrier, located at Great Island, and future-proofed for climate change would be close to €2bn."
That's within 2% of the OPW’s original estimate.
“If the various initiatives to combat climate change in the coming decades are unsuccessful and if a tidal barrier becomes necessary in the future, the currently proposed quayside defences will be an essential component of such a solution,” the LLFRS team said.
SCC said its concept images, prepared by Vindenvisual.com, give a “visual representation of the emerging design proposal”, give a "realistic impression of the physical infrastructure of a tidal barrier at Little Island", and consider previous cost estimates.
It said building a barrier at Little Island would protect the most amount of property for the least investment and would still retain all the advantages of maintaining lower flood water levels in the city - a design solution it claimed is more than 30 times safer than the LLFRS scheme.
“We estimate the maintenance cost of the tidal barrier at Little Island over a 25 year period conservatively at €30m or €1.25m per year,” it said.
