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Ireland’s interface with climate change: extreme flooding

Office of Public Works delivers eye-catching assessment of risk posed to Dublin from extreme flooding event

A simulation of O’Connell Street, Dublin, overwhelmed by flooding due to rising sea levels. Graphic: Eddie Sheanon/Midas Productions

Eoin Burke-Kennedy's face
Eoin Burke-Kennedy
Sun Mar 24 2024 - 14:29

Buried in the recesses of a 2018 report by the Office of Public Works (OPW) is an eye-catching assessment of the risk posed to Dublin from an extreme flooding event. For Ireland, climate change-induced weather events are more likely to manifest as flooding.

The OPW’s “Flood Risk Management Plan for the Liffey and Dublin Bay River Basin” sets out the at-risk areas in Dublin, which include coastal areas such as Howth, Sutton, Clontarf and parts of Dublin city (including Ringsend) but also inland areas at risk of pluvial or river flooding such as Blessington, Baldonnel, Clane and Leixlip.

The estimated costs associated with various future flooding scenarios (in the absence of mitigation measures) are also laid out. Flooding damage (without an extreme weather scenario) costs city authorities (or did back then) €25 million a year.

However, in what the report classifies as a “mid-range future scenario” flooding event, a one-in-ten year event, which entails a 20 per cent increase in rainfall and 0.5 metre increase in sea level, the cost jumps to €333 million with up to 2,800 residential properties impacted.

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In a high-end risk scenario, in other words a one-in-100 year event, involving a 30 per cent increase in rainfall and a one metre sea level rise, the cost jumps to €2.9 billion and involves 15,500 homes and almost 3,000 business premises being damaged.

But here’s the sting. While a one-in-100 year event doesn’t seem like something to get too worked up about, these types of events are expected to occur more frequently as global temperatures rise. According to experts, they could happen every year by 2100 due to what the Intergovernmental Panel on Climate Change (IPCC) describes as “continuing deep ocean warming”.

IFAC estimates that Government tax revenues could fall by as much as €2.5 billion a year by 2030 as a result of lower taxes from fuel and energy use amid the switch to renewables and EVs.

“Due to relative sea level rise, extreme sea level events that occurred once per century in the recent past are projected to occur at least annually at more than half of all tide gauge locations by 2100 and risks for coastal ecosystems, people and infrastructure will continue to increase beyond 2100,” it said in a report last year.

And remember the OPW’s risk assessment analysis is for Dublin only. Experts say parts of Cork and Limerick and other areas are more at risk and could potentially suffer more damage with big costs for the exchequer.

[ Ireland has a chance to influence the world’s response to the climate emergency ]

Emeritus Professor of Geography at Maynooth University John Sweeney, one of Ireland’s foremost climate scientists, has warned that Ireland has been lucky “so far in that we’ve had storm surges when the tide has been out or we haven’t had a depression arriving at the same time as the storm surge”.

He warns that there will come a time “when the dice will fall badly and we will get that kind of joint probability going the wrong way and that’s when we get the big problems”.

Sweeney cites the floods in Midleton, Co Cork last October as an example.

Extreme weather events – wildfires, droughts, heat waves, cold snaps - triggered by rising global temperatures are now part of the annual calendar.

“The fact that the tide was out enabled a large part of the town to dodge a bullet. But the situation is still that with higher sea levels the probability of a higher storm surge is on an increasing trend, as is the probability of more severe (though not necessarily more frequent) storms arriving,” he says.

The heavy rainfall which caused the flooding in Midleton and other parts of east Cork is more than twice as likely to occur at current global temperatures in comparison with pre-industrial times.

Extreme weather events – wildfires, droughts, heatwaves, cold snaps – triggered by rising global temperatures are now part of the annual calendar.

Every big global climate record was broken last year and 2024 promises to be worse the World Meteorological Organisation warned last week, while highlighting rising sea temperatures and shrinking sea ice as particular concerns.

[ Climate change: ‘How can we feed the world while not damaging it?’ ]

The United Nations (UN) weather agency said in its annual State of the Global Climate report that average temperatures hit the highest level in 174 years of record-keeping by a clear margin, reaching 1.45 degrees above pre-industrial levels.

The EU’s climate change monitoring service Copernicus indicated earlier this month that the global average temperature for the past 12 months – between March 2023 and February 2024 – was the highest on record at 1.56 degrees above pre-industrial levels.

That puts the world – perhaps temporarily but nonetheless worryingly – above the 1.5 degrees tipping point that scientists warn will usher in more extreme and unpredictable climate events.

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The Irish Fiscal Advisory Council (Ifac) has been utilising the OPW flood risk findings in its own work to estimate and warn about the likely fiscal impact of climate change here.

The watchdog estimates that Government tax revenues could fall by as much as €2.5 billion a year by 2030 as a result of lower taxes from fuel and energy use amid the switch to renewables and EVs while grants for retrofitting, assisting agricultural transition and other supports could lead to additional Government spending of between €1.6 billion and €3 billion a year from 2026 to 2030.

These fiscal challenges don’t include the estimated expenditure needed for building and reinforcing flood defences. Without the latter we run the risk of incurring billions each year in flood damages, up to €1.15 billion per year by 2050, according one estimate by the Department of the Environment.

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