Wednesday 28 January 2009

Building houses on flood plains is destroying natural defences, says expert

THE practice of building houses and other concrete structures on flood plains is destroying Ireland’s natural flood defences, according to one of the country’s leading experts on coastal engineering.

“If you look at the rainfall patterns over the last 20 years, you will find that there has been a marked change. We are now getting severe bursts of rain rather than precipitation being spread out,” said Dr Jimmy Murphy, coastal engineering manager with the Hydraulics and Maritime Research Centre, University College Cork (UCC).

Dr Murphy attributed much of this change to global warming which has lead to great uncertainty in predicting climate change.

“We have better technology and that means we know more, but the problem is we don’t know what to do about it because we don’t know what the climate will be in the next decade. That is the problem facing us and it is a real challenge.”

“That poses a difficulty in designing coastal defences for an event that might only occur once in several decades. We design structures for extreme events that might happen once in every 50 years while in the Netherlands, they design structures for climatic events that might occur once in every 10,000 years.”

Dr Murphy, who hosts a seminar on flood defences at UCC on Friday, said that, despite the uncertainty in predicting weather patterns, he was not in favour of constructing massive flood defences.

“We do not want huge structures that cost a fortune. It is far better if we find solutions that provide effective early warning systems so we can be prepared for extreme events.”

“There are great challenges and great opportunities and lateral thinking is required when it comes to solving problems. Making our coastal defences climate proof, requires a different kind of thinking. It must be more an ongoing process, a system that needs revisiting from time to time and regular maintenance.

“Recent weather patterns are putting Ireland’s flood defence and coastal infrastructure under increasing pressure. Flooding of cities and towns is now a common occurrence and UCC studies have shown that rainfall patterns have changed considerably in recent years. In addition many of Ireland’s coastal defences may be found to be under designed given future storm and sea level predictions.

“The coastline is coming under increasing threat as is indicated by the recent breaching of the sand dunes on Rossbeigh Beach, Co Kerry. There is an urgent need for decision-makers to understand the challenges facing the country and how best to meet them.”

However, Dr Murphy said he was hopeful for the future. “The design and management methodologies for flood defence systems and coastal structures has developed considerably in recent years. Through monitoring, mapping and modelling there is now a greater understanding of basic system behaviour yet great uncertainty exists as to the nature and magnitudes of environmental loadings. The challenge now is to seek solutions that are both sustainable and cost-effective in the long-term whilst providing sufficient protection against extreme events, such as we have witnessed over the past week.” It is opportune that this seminar brings experts from Ireland, Britain and the Netherlands to discuss these latest developments and possible future trends, he said.

lThe seminar will run from 9.30am to 5pm in the Cavanagh Pharmacy Building, UCC on Friday. To register for this seminar or obtain more information please contact Cora Edwards, Hydraulics and Maritime Research Centre, on (021) 4250021 or email

Irish Examiner

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