The city council’s head of environment insists the Lower Lee Flood Relief Scheme is the only solution, writes Eoin English.
Opponents of the €140m Cork flood defence scheme have been accused of ignoring or denying its holistic approach to minimising flood risk.
The city council’s head of environment, Valerie O’Sullivan, made the comment at a design progress briefing for city councillors on Monday.
She insisted that the Lower Lee Flood Relief Scheme is the only solution now, that its design is based on best modern practice and legislative duties, rather than on outdated concepts, and that alternatives put forward by opponents are simply not viable now.
Despite this, she said unfair comparisons persist and that 2m-high walls alleged to be in the scheme “simply do not exist”.
“Real engagement would be much more productive, where all concerned can have constructive conversations about real things and not fake news,” she said.
“I felt it was time some of the myths abroad, which are very frustrating for the experts who now live and breathe this scheme, who have been in continuous consultation with heritage, landscape, public realm, and conservation stakeholders, and who have been both empathetic, sympathetic, and expert in their handling of the future of the river and the city, are put right by the facts.”
Councillors were told that following months of analysis of public feedback on the original scheme, architects and engineers have unveiled substantial design changes in several key locations.
Ms O’Sullivan set out the five core elements of the overall defence scheme, which she described as a “holistic solution” — a fact she said is “either being ignored or denied” by its opponents.
The overall approach will include the statutory use of the dams to reduce the impact of flood events before they happen, and to minimise the impact of flood events as they are occurring by using reduced levels for storage, thereby reducing the amount of water that will reach the city.
There will be extensive use of washlands to the west of the city, which will see areas of agricultural land falling within the floodplain being designated as temporary storage areas for water during a flood event, again reducing the volume of water that needs to be moved through the city.
An early-warning flood system will be introduced. It will include installation of a network of real-time sensors to give warning days in advance of a flood event. The 24/7 system will be constantly fed with live data.
A public information system will be introduced for river users, residents, and businesses.
Ms O’Sullivan said that, in specific areas where these four measures will not fully address flooding, some direct flood defences will be installed.
“Because of the first four measures, the height of these defences has significantly reduced from what would have been required,” she said.
She also took a swipe at Save Cork City’s (SCC) social media messaging for not comparing like with like.
“Every location is different, with different hydrologies, topographies, catchments, and characteristics,” she said. “What is good for one country, or indeed for one river, can be completely undeliverable for another.
“Because of this, a range of distorted views has been created and consumed by making completely inappropriate comparisons. The Lee Valley is a fast catchment. Rainfall in the upper catchment reaches Cork City within six to eight hours of falling.
“Many of the catchments used by SCC as a comparator to Cork are slow catchments, where this process can take weeks.
“So solutions which work in a slow catchment are completely inadequate in a fast one, making such comparisons incapable of direct comparison. But the comparisons persist.”
Ms O’Sullivan said some of the proposed alternatives, including open quays, may have been acceptable in the 1800s, but like most other aspects of life in a modern city, realities have moved on.
“Things that were acceptable then are simply not acceptable now and in many instances, could even be illegal,” she said.
Much of the controversy about the OPW’s flood defence scheme advertised more than 18-months ago focused on its reliance on raising quay walls, particularly along the historically important areas of the North Mall and Sullivan’s Quay.
However, following the consideration of feedback from the public and various stakeholders, it has now been confirmed that demountable barriers will be used along both quays instead of walls.
The historic quayside railings and the trees at both locations will be retained.
Micro-piles will be driven into the ground, between the roots of the trees, to allow for the installation of a ground-level fixing system, into which the demountable barriers can be installed ahead of flood events.
Engineers said that the information about ‘demountables’ will be fed by the OPW back to insurers, and that the use of demountable barriers should not pose a difficulty from an insurance point of view.
Tree surveys have been conducted along the entire flood defence scheme route, and have found that most of the trees at both quays can be retained.
There may even be an opportunity to plant new trees in both areas, the landscape architect Andrew Haley said.
The footpath along North Mall will be repaved, with architects saying that once the entire scheme is finished, the street will look better than it has done for years.
There may also be an opportunity to create improved public areas around the Shandon pedestrian footbridge, and around St Mary’s Church on Pope’s Quay.
Flood defences will be integrated into a new civic space at Ferry Walk, alongside the Shakey Bridge at the western end of Fitzgerald’s Park.
The area will be accessed via a 3m-wide ramp or a series of steps which will lead onto a new plaza which will built from reclaimed granite setts overlooking the river.
The area will include another set of steps leading down to the water.
The historic railings will be restored, and the possibility of installing a coffee pod in the shadow of the Shakey Bridge is being considered.
The riverside path leading from this area east towards the city will be retained at existing levels, but stepped and landscaped terraces will be constructed between the river and Fitzgerald’s Park.
Architects said that the integration of flood defences here, into a new civic space, will create a wonderful new civic area for the city when combined with the restoration of the Shakey Bridge. It will also promote more interaction with the river here than is currently available.
Talks with Sunday’s Well Tennis and Boating Club have led to the creation of a new pathway, with seating integrated along a wall, as well as a new raised patio area on the riverside of their premises, with glazed screens to provide defences.
The design will ensure connected walking and cycling routes from the Lee Fields can be developed.
Work is due to get underway early next year on the complete refurbishment and restoration of Shakey Bridge.
Architects working on the flood-defence scheme said the investment in flood defences provides an opportunity at this location to enhance and promote citizens’ interaction and engagement with the river.
At other locations downstream, city-centre quayside steps will be opened up for use again but some will be sealed off with a glazed screen.
A flood-defence embankment, or a ‘bund’, with a slope no greater than one-in-three and with a rounded crest, will be built along the Lee Fields riverbank.
The car park will be relocated slightly westward, and raised to the top of the embankment, with access to the existing 3m-wide riverside walkway via steps or a sloped path. It is hoped that the raised car park could also become a viewing area for those watching river-based activities.
The existing slipway alongside the current car park will be improved to encourage more use of the river, and a small area for the public will be developed at the entrance to the car park.
A 4m-wide tree-lined avenue will be built parallel to the Carrigrohane Road to allow people to walk or cycle in safety the length of the Lee Fields, freeing up the shared bus/ cycle lane on the Carrigrohane Road for buses only.
It is also planned to use the regular flooding of the Lee Fields area to help create wetlands and a bogland area, and to promote biodiversity.
The architects say that the design treatment of this area is another example of how investment in the city’s flood defences can promote better engagement with the river and lead to the creation of new public spaces.
This area was devastated during the 2009 flood, with the Kingsley Hotel completely inundated and forced to close for several years.
The County Library across the road in the basement of County Hall also suffered extensive damage from flood waters.
A demountable flood barrier has been proposed for along the quay edge at the Grand Parade boardwalk.
A new raised lawn area will be installed outside the Electric bar and restaurant, along with new seating to ensure that people can still enjoy the area as a public space.
The war memorial will be relocated to a central location within the new lawned area. The granite slabs will be retained and incorporated in the new setting as per the current design. The space will be accessed via a flush threshold on the South Mall.
Provision has also been made in the latest designs for the treatment of the area around Crosses Green, to factor in a proposed new pedestrian bridge, which is set to provide access to the long-awaited events centre on the former Beamish & Crawford site.
The design of the scheme around Morrison’s Island is being pursued through a different process following a successful legal challenge.
The delivery of defences in this part of the city is now being advanced under the Part 10 planning process through An Bord Pleanála.
The rest of the scheme is being advanced under the Arterial Drainage Acts, which will require Ministerial approval.
A new plaza will be created at Grenville Place with a glazed floodwall.
The plaza will be integrated with existing changes to the streetscape around the Mercy University Hospital.
The quay wall, running from the Lee Maltings towards St Vincent’s footbridge, will be lifted and raised to new levels. Individual stones will be numbered, lifted, and repositioned to retain the historic integrity. Seats will be incorporated into the riverside of the wall, between the wall and the glazed floodwall, to create a resting point with views upstream.
Gaps in the wall will be provided to encourage pedestrian permeability.
The design of the scheme around St Vincent’s footbridge, which is currently being restored, and around UCC’s Distillery Fields complex on the North Mall, has also been amended to include lower flood walls and floodgates.
It includes plans to install a 600mm flood wall, running between the pedestrian walkway and the access road to the UCC campus, to which demountable barriers can be attached.
A breach in the quay wall at Grenville Place during the 2009 flood led to a huge inundation of flood waters into vast swatches of Cork’s inner city.
The Mercy University Hospital came within minutes of a full evacuation, but thanks to the efforts of Cork City Fire Brigade and the Defence Forces, power to the hospital was maintained.
A tidal barrier to protect Cork from tidal flooding will not become economically viable for at least 50 years, experts working on the city’s flood defence scheme have said.
When and if a tidal barrier becomes viable, the optimum location is likely to be either side of Great Island at Monkstown and Marloge, not the Little Island location proposed by opponents of the scheme, because of environmental and navigation impacts.
To suggest that the dams on the River Lee have enough storage to avoid direct defences in the city centre “is simply not true”, city councillors have been told.
And the ‘farming the flood’ approach which would allow land upstream to flood during flood events could take decades to achieve given the size of the catchment and the number of landowners involved.
The comments were made during a detailed briefing for city councillors on the progress of the €140m Lower Lee flood relief scheme, which is the largest flood-defence scheme in the history of the State. The city council’s director of services in the environmental directorate, Valerie O’Sullivan, again said various alternatives put forward by opponents of the OPW scheme are not viable.
She said the OPW and its consultants prepared a detailed pre- feasibility study to investigate the potential for a tidal barrier in Cork to explain why two previous studies — the Lee Catchment Flood Risk Assessment and Management study and the Lower Lee Flood Relief Scheme Options Study — had concluded that a tidal barrier is not a viable solution.
The pre-feasibility report found that a tidal barrier will not become economically viable for at least 50 years, and would cost more than €1bn versus a potential benefit of less than €200m, meaning it is not cost beneficial. She said that many of the comparators used by opponents of the OPW scheme are “wholly inappropriate”.
Ms O’Sullivan said: “Barriers elsewhere used as examples by this cohort are built in shallow river or harbour settings, and either do not need to accommodate shipping to pass or represent only one of a number of entry points to a port (so if they are blocked, there are alternatives).
“This is not the case with Cork and the Lee.”
The Little Island barrier, proposed by Save Cork City, would pose numerous challenges in terms of environmental and navigation impacts, she said.
Given the 50-year horizon for a tidal barrier, Ms O’Sullivan said that, as responsible citizens charged with protecting the city from flood, talk of a tidal barrier cannot “unduly influence decisions” which must be made now.
“Low-level, quay-side defences in Cork, as per the OPW exhibited Scheme, remain the optimum (and indeed only viable) solution to protect against tidal flooding in Cork for at least the next 50 years,” she said.
“Even if a tidal barrier were to be built in 50 years, low-level defences are still needed now anyway. They are an element of the long-term scheme and climate- change strategy to manage flooding in Cork.”
Ms O’Sullivan also addressed claims that the dams can manage flood events on their own.
That premise is based on a number of incorrect assumptions, including a proposed dam-operating regime which would actually jeopardise dam safety, she said.
“They also do not address the residual risks associated with events greater than the one-in-100-year event,” she said.
“International best practice dictates that events up to the 10,000-year event must be capable of being safely passed through the dams at all times. The magnitude of a developing flood event cannot be established with enough certainty beforehand to advocate an approach that completely fills the reservoirs during events up to the one-in-100-year event as has been proposed by some third parties.
“This scheme as exhibited proposes revised rules which have been optimised following extensive detailed analysis of all the real-world constraints, to maximise the benefit of the dams.
“These revised rules result in almost a 40% reduction in peak flows reaching the city, meaning that required defence heights can be minimised. However, due to the limited size of the reservoirs, the revised rules cannot on their own provide the required standard of protection and therefore these rules can only be utilised in conjunction with direct defences as proposed.”