€5m plan to map flood risk

A 3-D map of Dublin city is to be created showing how water flows through the capital's streets to help officials avoid the widespread flooding which hit the city in August.

The ambitious €5m project will show officials the route water takes, and allow them to plan installation of gullies and drains so the water can be removed from the city's streets without causing chaos.

And it will result in developers having to design housing schemes with fewer hard surfaces, which siphon water on to public roads, and with more green areas.

City engineer Tom Leahy said yesterday that "radical" measures would have to be taken to avoid the devastating floods which left parts of the city underwater earlier this year.

"The drainage system in Ireland was built up over time," he said. "The standards were to deal with a normal storm, but we're now at a situation where weather patterns are changing. The amount of rain falling has remained static for years, but it's falling in more intense bursts.

"The 3-D modelling is very advanced, and has never been done elsewhere on the same scale.

"The new thinking is to avoid putting water into the river, but to provide surface routes. We need to think in a radically different way.

"You're more likely to be flooded at the top of a hill because you're more exposed. If you're planning anything, no longer is there low and high risk. Fluvial (river) flooding can hit anywhere, the risks have to be assessed."

Radar

The project, part of an EU-wide Flood Resilient Cities Project, would divide the city into cells and use radar to map each area. Half the €5m cost will be funded by the EU.

For example, in Christchurch water naturally flows down Fishamble Street and into the River Liffey, but it could take a left -- depending on the ground conditions -- and go into the basement of Dublin City Council. The council is also to invest in new high-capacity pumps for use during flood events.

"We're looking at purchasing high-capacity pumps which can pump water 3km away," Mr Leahy said. "You can drive at 30kph and the hose comes out the back. Very few parts of the city are more than 3km from the sea or a river. They cost €1.5m each."

The mapping will show the 'at risk' areas across the city, and could result in a ban on use of tarmac and brick pavements, as they allow water to flow out on the road.

Paul Melia
Irish Independent

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