Mr. Ken Leahy:

I would like to speak about the options that were considered. There has been talk about outdated solutions and about what works well in other locations. When any flood relief scheme is being considered, the most important thing is the best solution for the location in question, bearing in mind all of the location's constraints and objectives. It is very dangerous to try to compare the solution we are proposing with other solutions in other countries. It is untrue to say that countries like the Netherlands do not look at walled solutions or direct defence solutions. Direct defences make up a significant proportion of the Dutch solutions. They are integrated with other elements. The solution for Cork is no different from that. It has been suggested that the design of the scheme will funnel even faster waters through the city, but that is incorrect. A fundamental part of the design of the scheme is the optimisation of the use of the dams to reduce the flow into the city and therefore reduce the velocities and the flows through the city. The scheme will reduce rather than increase this risk. When factors like the flood forecasting system, the operation of the dam and the regulation of the flow between the north and south channels are taken into account, it is clear that direct defences comprise just one small part of a very integrated approach to flood risk management in the city, which deals with both fluvial and tidal flooding.

When we speak about the various possible solutions, including the tidal barrier, it is important to ensure everyone has clarity. We must make sure we are comparing apples with apples. The front page of the HR Wallingford report is of interest because it confirms what the report is and is not. Essentially, it is a high-level cost estimate of the barrier concept being advocated by the Save Cork City group. The HR Wallingford report notes that navigation, sedimentation and environmental issues would all warrant significant analysis and consideration in order to establish the size of the gates required. It notes that the cost estimate is extremely sensitive to those factors. That is very much the case. Rather than designing or sizing those gates, those who drew up the HR Wallingford report took the Save Cork City concept and worked from there. I am not privy to the details behind that. As the location proposed by Save Cork City is over 1 km in width, the flow through that portion of the channel has 1 km to pass through. The Save Cork City proposal would narrow that opening to 150 m, or one eighth of its current width. This would fundamentally alter the dynamics and velocities in the harbour. It is likely that it would have significant impacts on navigation, shipping, erosion, sedimentation and the environmentally designated sites - the special protection areas and the special areas of conservation - which are immediately proximate to it. Therefore, it is not at all reasonable to assume that the barrier, as costed, would be technically viable.

As part of the work we are undertaking and finalising, which has involved discussions with the Port of Cork, we have engaged in detailed modelling of velocities. It is likely that the barrier would have to be significantly wider, which would cause the cost of it to increase. The HR Wallingford cost estimate of €140 million relates to the cost of construction only. It must be acknowledged that there would be a significant maintenance cost in addition to that. It has been estimated that the overall cost would come to €165 million when the cost of 25 years of maintenance is included. OPW schemes provide for 50 years of maintenance. If a barrier were constructed purely as a tidal scheme, it would deal with the issue of tidal flooding and not with the fluvial flood risk to the west of Cork city where tide is not an influence. The cost of the damage arising from tidal-only flooding tends to be between €40 million and €50 million. At a cost of €165 million, the proposed barrier it would have a cost-benefit ratio of 0.3. Clearly, it is not economically viable as a stand-alone tidal scheme. The additional cost of dealing with the fluvial problem to the west of the city, as part of a combined fluvial scheme, would drive up the overall cost significantly. Even allowing for the total combined damages or benefit of the scheme of €185 million, it would remain non-cost-beneficial.

When we look at this proposal, we have to consider when a tidal barrier might become viable and consider what else is needed as part of it. Mr. Sydenham mentioned the N25 and the railway line. At the location proposed by the Save Cork City group, there is a bypass route to the north along the railway line and the N25. Therefore, further ancillary works would be needed to defend those areas directly and that costing would have to be included. At that location, there is reasonable storage for upstream waters to flow into the River Lee from the River Glashaboy in the current scenario. In the mid-range future scenario, which is based on a 20% to 30% increase in flows and a 0.5 m sea level rise, a barrier at that location would start to run out of storage capacity. That would not be the optimum location if a 1 m sea level rise were to occur in the context of longer-term climate change. In addition, it would not protect Midleton, which is also is at significant tidal flood risk. That risk will increase in the future scenario. It is probable that in the longer-term scenario, a barrier either side of Great Island would be more viable while also being more expensive. The question of whether a barrier will be a viable option at some point arises in this context. It may well become a viable option if sea levels rise by between 0.5 m and 1 m, but it is not viable at present.

I would like to make another point about the climate change scenario. If direct defences are not built in the city, the level at which flooding occurs will remain at approximately 2.5 m. If a sea level rise of 1 m occurs at the point at which a barrier becomes viable, the barrier will have to be closed every day to protect the city from flooding. This would have huge implications for navigation, the environment and the operation of the harbour.

In reality any future tidal barrier will only work in conjunction with raised defences in the east of the city and they will work together to ensure that the barrier would only need to be closed in extreme events, with the defence walls protecting against the more frequent events. In the short term, the direct defences are cost beneficial, are the correct solution for Cork protecting against both fluvial and tidal flooding. They are the first step and in 50 years or more it might be necessary to run a tidal barrier in conjunction with them. It is important that we compare like with like. A tidal barrier is not cost beneficial at the moment and is not viable. It has been studied in detail. All the issues that the HR Wallingford report said needed to be considered have been in our assessment, and were considered to an extent in the precursor to this work which was the Lee catchment flood risk assessment and management study, CFRAMS, by Halcrow which is another reputable international consultant.