OPW rejects alternative Cork flood plans as 'just not viable'

Professor called for reservoir/downstream tidal barrier which he claims would be half the cost of €150m Lower Lee Flood Relief Scheme

Paul O’Driscoll handing out emergency flood protection sand bags from the Cork City Council depot on Anglesea Terrace. Picture: Dan Linehan

The Office of Public Works has rejected as "just not viable" a retired professor’s theory that a new upstream reservoir combined with a downstream tidal barrier can protect Cork from flooding for half the cost of its €150m Lower Lee Flood Relief Scheme (LLFRS).

As the city braced for the second major flood in less than two months, the OPW mounted a robust critique of a detailed paper presented by Philip O'Kane, a retired professor of civil engineering at University College Cork, at the recent National Hydrology Conference.

Prof O'Kane argued that a tidal barrier at any of four locations, to be operated in conjunction with the ESB dams on the River Lee, is a “realistic and viable alternative” to what he described as the OPW’s “14.5km of embankments, walls, walls with gaps and demountables, and groundwater pumps’ scheme” as proposed in its LLFRS.

He suggested his approach would be half the cost of the €150m LLFRS, would protect more of the city from fluvial, tidal, and groundwater flooding, would avoid the conversion of the city centre into a building site for the second time in a generation, and would conserve the character of the 800-year-old port city.

Drawing comparisons with Belfast and Singapore, he said the active controlling of water levels within the city could facilitate boating, windsurfing, kayaking, and dragon boating, on a coastal freshwater-supply and flood-control reservoir.

There are two parts to his theory.

Firstly, he suggests increasing the capacity of the existing reservoir at Carrigadrohid and the creation of a new reservoir at Dromcarra, further west, to help reduce the risk of river/fluvial flooding from the west.

The OPW said this was considered as part of the LLFRS and was ruled out on several grounds including technical difficulties with augmenting the Carrigadrohid dam without compromising dam safety, negatively impacting the internationally heralded designated environmental site at the Gearagh, displacing some 80 property owners, and negatively impacting both existing and proposed road infrastructure.

“Professor O’Kane’s proposal fails to meet the project objectives of being technically, socially, environmentally, and economically viable,” a spokesman said.

Secondly, Prof O’Kane suggests protecting the city from tidal flooding from the east by using a tidal barrier or barrage, working in combination with what the OPW said would be some of the largest pumps in the world, to effectively pump the River Lee at Tivoli.

Prof O'Kane makes comparisons with the tidal weir in Belfast and the tidal barrage in Singapore but the OPW said neither comparison was appropriate. “The tidal weir in Belfast is to keep water in at low tide, not to keep water out at high tide," the spokesman said.

"It does not and will not provide the required standard of tidal flood protection, and accordingly, like Cork, Belfast City Council has developed a tidal defence solution consisting of circa 8km of quayside parapet defences, the majority of which lie upstream of the weir.

“The scheme is currently out to tender for construction and so Belfast will soon have the necessary protection.

“This is an example of projects in other jurisdictions being purported entirely out of context, leading to unnecessary confusion.

“Equally so is the comparison to the large barrage and pumping station in Singapore, which cost hundreds of millions, and was constructed to turn the area into a fresh-water lake, to provide drinking water for half a million people.

Brock Lewin of Badger & Dodo, South Mall, Cork, collecting his emergency flood protection sand bags from the Cork City Council depot on Anglesea Terrace. Picture: Dan Linehan

“Its upstream catchment is less than one-tenth of Cork’s and is completely urbanised and densely populated.

“Whilst it does provide additional benefits such as tidal protection and recreation, the context and business case bear no relationship to Cork’s situation and needs.

Neither OPW nor Cork City Council foresee any scenario where turning the River Lee into a lake would be appropriate or acceptable.” 

The spokesman said Prof O’Kane acknowledged at the conference that his cost estimates were essentially his best guess.

The OPW said his costs did not include other capital project costs, or the enormous operational and maintenance costs, while its cost reports do.

“Technically viable options for a tidal surge barrier sufficiently far downstream to avoid the need for pumping have been studied at length as part of the LLFRS, with whole life costs estimated at about €2bn using robust cost estimation methodologies similar to these used by the City of New York," the spokesman said.

"A tidal barrier or barrage is not a viable option.

"Prof O’Kane’s work does not consider its adaptability for climate change or its resilience to design exceedance events, factors which were carefully considered in developing the LLFRS.

“In summary, Prof O’Kane’s proposal for the management of flooding from the River Lee is a combination of measures, all of which have already been assessed as part of the LLFRS and found not to be viable or appropriate to Cork’s specific problems.

"LLFRS represents the only viable solution."