Those worst affected by this week's flooding are asking why it caused such mayhem. Conor Lally reports
Dublin City Council is undertaking a €7 million review of the drainage system in the capital, the surrounding counties of Meath and Kildare, and parts of north Wicklow. It is aimed at preventing floods like those seen in so many parts of Dublin this week.
Dublin City Council's head engineer, Mr Michael Phillips, said yesterday it was expected that "hundreds of millions of euro" would be needed to implement the review's recommendations.
"We can never guarantee that there won't be any more floods but what we will try to do is use the recommendations to minimise flooding," he said.
He added there was nothing the council could have done to prevent the floods seen in Dublin this week. While a lot of the underground drainage system in the capital dated back to the 1880s it was in good condition and could still cope with large volumes of storm water, he said.
"But what we have seen lately is very localised rain, almost tropical storms, coming down in sheets in certain areas. It is an abnormal level of rain."
He said the greater Dublin drainage strategy study had been ongoing for around 12 months and was being undertaken by a consortium of consultants. Recommendations arising from the review will be published next June.
The study will look at practical ways to prevent flooding and will also examine the manner in which development on flood plains and in other areas has impacted on natural drainage systems. It is expected to make a number of recommendations relating to sustainable development.
It is also examining the effects of global warming on flooding.
Mr Phillips said while the city council was "very well resourced" to respond to flooding, traffic on Dublin's streets was a major impediment to relief efforts this week. "Even with Garda escorts it was very hard to get trucks with sandbags through," he said. "And in some places there were cars parked over shores which were blocked by sheets of leaves".
Mr Pat Clarke, a meteorologist at Met Éireann, believes if many rivers were fitted with gauges to measure water levels, residents around waterways might get a warning as to when flooding should be expected.
However, he said it was a combination of weather factors over the past six weeks which caused Thursday's flooding and not simply sudden rainfall.
Much heavier rain than normal in October and the first half of November meant the water table in many areas was already very high before the heavy rainfall of Wednesday and Thursday. In effect, the "soakage factor" provided by terrain was already exhausted.
"In a case like that the rain that falls simply has nowhere to go," Mr Clarke said.
"In October and the first two weeks of November combined, Dublin got 14 inches of rain compared with a usual 29-inch annual national average. The monthly average rainfall in November is around 64 millimetres but on Wednesday and Thursday 86 millimetres fell in some parts of Dublin."
Many places around the country have already had their usual level of annual rainfall and "with global warming very wet episodes may become more regular", he said.
The storms seen this week came from Spain, up through England and then across the Irish Sea, hitting the Leinster coast north of Wicklow. Generally storms come from the Atlantic from a wide area between Ireland and Iceland and it is usually the north and west coasts which bear the full brunt of those weather fronts, making flooding on the eastern seaboard more unusual.
While onshore winds and high tides can exacerbate flooding, it was not clear if this had been the case this week. The tides of 3.5 metres to 3.75 metres seen on Thursday were not unusually high but even normal tides meeting swollen rivers can cause flooding.
Many locals in the worst flood-affected areas of Drumcondra expressed concern yesterday that some local flood plains have been lost to housing and commercial developments in recent years. It was a factor, some said, which resulted in houses which had never been flooded before succumbing to the flood waters seen this week.
Ms Karin Dubsky of Coastwatch Europe said the 1948 Land Reclamation Act, reinforced in the 2000 Planning Act, had allowed the destruction of wetlands along many rivers. "These are most valuable for their capacity to retain flood waters," she said.
"What are we doing to them? We in-fill."
Mr Kevin Gilna, a spokesman for the Construction Industry Federation, said developers build properties only where planning permission has been granted by a local authority.
However, he conceded that local authorities needed to draw up plans of flood plains in their catchment areas in order to prevent those lands being developed.