Homes may need to be abandoned due to water risk
Homes may have to be abandoned and swathes of agricultural land given over to water storage to help prevent catastrophic flood damage.
And flood risk management plans produced by the Office of Public Works (OPW) suggest that, in some cases, completing flood defences may result in increased risk in some areas, including parts of Co Cork.
Among the areas highlighted as being at risk are 18 holiday homes in Clifden, Co Galway, with OPW sources saying that while abandoning homes was a "live issue", no decisions had yet been made.
Official plans to manage rising waters also warn there could be a "slight increase" in flood risk in parts of Ballymakeery/Ballyvourney in Co Cork if defences are installed.
And plans also say that creation of flood storage schemes, where water is contained in agricultural lands before being slowly released back into watercourses, may need to be considered. This could be required near Naas in Co Kildare, where flood storage facilities of 39 million litres are identified. This would result in loss of land currently earmarked for new development.
"The idea is that a stream would run through the location in the normal course of events, and when it hits a certain level you back up the stream into a storage facility," said Mark Adamson of the OPW. "When the flood has passed, you can start releasing those stored waters.
"There's an example in Clonakilty, which was brought forward in 2012 because of really bad flooding. In the normal course of events, you could farm the land. Floods are rare enough, and apart from the Shannon and turloughs, they're quite short-lived, so the area that would be used for storage during a flood would only be flooded on rare occasions."
There could be no question of houses and businesses being developed in areas at risk, given that thousands of properties were currently at risk of flooding, he added. "What's critically important is not creating new problems," Mr Adamson said.
"In town centres, which need to grow and redevelop, there is a justification test to allow that kind of development to go ahead."
Flood Defence Works Interactive Map
This tool sets out the cost of installing flood defences, the damages which might arise and number of properties under threat, in the most at-risk areas across the State.
It is based on data from the draft Flood Risk Management Plans, produced by the Office of Public Works (OPW), following extensive surveys of 90 coastal communities, and more than 6,500kms of river channel.
The country is divided into 29 Units of Management (UoMs), which are areas covered by a single river basin or covered by a group of smaller rivers. Given its size, works required along the Shannon are set out in three UoM.
Clicking on the icons show the works required in each area.
The urban area is highlighted at the top, and the UoM beneath. The cost of proposed works is set out in €m. The ‘damage uncapped’ figure relates to the total cost of damages to properties and infrastructure which would arise if nothing was done.
The ‘damage’ figure is based on the value of the properties at risk. This figure is used to determine if a scheme should go ahead – if the cost of the damage is less than the cost of providing defences, the scheme may not go ahead. This is the cost-benefit ratio. If it’s less than one, the scheme doesn’t make financial sense.
The final figure is the number of properties protected.
Some icons contain less information. For example, Tullig in Kerry is part of the Castleisland flood defence scheme so no information is contained. The OPW has also identified other areas as being at low risk, or says the existing flood defence regime should be maintained. In other cases it notes the need for a forecasting system, or says if a scheme is underway.
Further information is at http://maps.opw.ie/floodplans/
He said local authorities were generally completing flood risk assessments on lands proposed for development, and some councils have been issued with legally-binding directions from the Department of Housing forbidding them to allow development on flood plains.
Limerick City and County Council was issued with one in 2015 relating to Adare, a town in need of €10m of defences and where 120 properties are at risk. Directions were also issued in relation to land zonings in Midleton, Co Cork, in 2013, where more than 240 properties are at risk, and Mountmellick in Laois in 2012.