Dublin’s flood defenses are protection against rising sea levels

Dublin’s flood defenses are designed to protect the capital against sea level rise “until the end of the century”, according to Dublin City Council’s longest-serving flood expert.

A study by scientists at the University of Maynooth, published in the academic journal Ocean Science in recent days, has confirmed that the sea in Dublin Bay is rising at approximately twice the rate of global sea level.

The research project, led by the Hamilton Institute and the ICARUS Climate Research Center, found that sea levels in the bay are rising faster than climate change models had predicted.

Gerry O’Connell, of the council’s Flood and Flood Warning Projects division, said the division provided data to the project and had been aware of higher rates of sea level rise in the bay for many years.

“We have recorded about 130ml in Dublin Bay over the last 20 years or so, which is about twice the global average, but we have incorporated that into our flood designs and our flood responses.”

About 20,000 properties are at significant risk of flooding in the city, but most are already protected by flood defences. For areas where new defenses are planned, interim measures have been put in place to protect against flooding, O’Connell said.

“All the flood defenses took the estimated sea level rise to the end of the century,” O’Connell said, incorporating analysis of trends seen over the past 20 years.

“In some places we have new flood defenses planned, like at Sandymount and Clontarf, they will also be incorporated, but we currently have temporary measures that take care of the current sea level risk,” he said.

“We also have flood warning systems and can implement temporary measures and sandbags depending on the sea level and wave action we are anticipating.”

The board expects to begin work on flood defenses for the Sandymount Boardwalk later this year or early next year and is in the design phase for the flood scheme at Clontarf and north of the boardwalk at Sandymount.

In 2008, the council obtained permission from An Bord Pleanála for flood defenses in Clontarf, one of the main victims of extreme flooding in 2002. However, these were rejected by residents largely because they would hamper views of the bay.

The council offered to lower the height of the protective embankment, but that too was met with resistance. Eighteen months ago, it submitted a new scheme, which it hopes to present to An Bord Pleanála in 2023, after further public consultation. Meanwhile, large yellow sandbags remain parked along the coast.

Separate safeguards have been implemented and continue on Dublin’s three main rivers – the Liffey, Tolka and Dodder.

While cities by their nature have higher flood risks due to lower levels of vegetation and the extent of hard surfaces, Dublin has inherent disadvantages due to its extensive coastline and reclaimed land.

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