In the book of Genesis we learn how Noah built the ark to save the world from a catastrophic flood. The world has known catastrophic flooding since biblical times but the gravity and frequency of such events is likely to increase because of climate change.
We have known about global warming and its consequences for decades, but action to halt it has been dilatory. It now seems it will be impossible to hold the rise in temperature by 2050 to 1.5 degrees above pre-industrial levels; holding it to 2 degrees also looks unlikely. If temperatures were to stabilise at that level, the negative consequences would continue to play out over the following century or more.
There will be an inevitable rise in sea level. That will continue long after global warming has been halted. It represents a major threat to our island.
Greenland’s ice cap is already melting, and will continue to do so well into the 22nd century, irrespective of global climate action – the die is already cast. While it would take many centuries for all of Greenland’s ice to disappear, were that to happen, the volume of meltwater would raise world sea level by seven meters. Much of Ireland would be swamped in that eventuality, leaving a much shrunken island. Fortunately, ice melts slowly, so that the rise in sea level by 2100 could be around 0.3 meters.
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While not enough to swamp Ireland, it will mean we will face an increasing risk of major coastal flooding, when higher sea levels are combined with more frequent and violent storms. By the end of this century, much of the centres of Dublin, Limerick and Galway could be at risk of periodic coastal flooding, with devastating economic and social consequences.
Significant thought, but much less action, has been put into preventing river flooding. A recent paper by Ronan Lyons of TCD and colleagues from NUIG has shown that the publication in 2011 of flood-risk maps for river basins resulted in a 4 per cent price discount for dwellings at risk of flooding.
When flooding actually takes place, as along the east coast recently, the effects on individual households are devastating. It is not just that everything gets wet; the mixture of water and sewage that comes with such flooding requires massive refurbishment of homes, and it also represents an environmental hazard. While investment to prevent river flooding is going to be expensive, its long-term benefits will also be significant.
In 2019, the Climate Change Advisory Council highlighted the anomaly that while the Office of Public Works (OPW) was responsible at that time for action to prevent river flooding, it was the relevant local councils that dealt with coastal flooding, with responsibility in Dublin shared by its three coastal local authorities. Since then, the OPW has been given a co-ordinating role for preventing coastal flooding.
[ Most ‘priority’ flood defences have still not entered planning after eight yearsOpens in new window ]
This is important, as, by 2100, the danger to our low-lying cities from the sea could be greater than that from river flooding. It is likely, too, that action to protect areas from the sea could be much more expensive and take longer to deliver.
One of the obstacles to taking action to keep the sea out is that people like sea views. However, if you can see the sea, the sea can also see you.
While raising barriers around Dublin Bay will be unpopular, they will be essential to avoid huge damage from flooding that will otherwise be inevitable. The periodic swamping of the Dart at Blackrock is already causing major dislocation to many people’s lives.
Building defences to protect this vital artery will make the views from the Dart less interesting, but at least it will continue running.
A greater threat probably stems from the possibility of a tidal surge in the Liffey swamping the city centre. London put in place a movable barrier across the Thames 40 years ago that has proved vital. Indeed, it will need to be enlarged to protect London over the rest of the 21st century. However, protecting Dublin will not be as simple.
The Thames barrier is in the relatively narrow river. To protect Dublin and its port could require a more substantial and expensive solution which could take decades to construct. That makes early action necessary.
[ Inside the Dublin data centres consuming an unknown amount of energyOpens in new window ]
The people of the Netherlands have spent the past millennium fighting to preserve their country from the sea. It has required massive investment and dykes are not always pretty.
Action to prevent the sea taking over the centres of our cities will likely be disruptive and very costly. However, as Noah realised, building an Ark takes time and needs to be finished before the flood comes.
