Climate change experts have backed calls for tighter planning restrictions to prevent new building on flood plains after the worst national flooding crisis in a generation.
After a major study of city floods around the world, academics at University College Cork, the London School of Economics, and Oxford University found no evidence that cities, their economic hubs, or large population centres relocate after large floods.
Full economic activity has usually resumed in the flood-prone zones, usually within a year, they said.
The study also warned that modern cities with high population concentrations in low-lying areas face greater flood risk as sea levels rise and extreme rainfall episodes become more frequent.
“At a minimum, tighter planning restrictions are required to prevent new building on existing flood plains,” said co-author Tom McDermott, of UCC’s school of economics and the Environmental Research Institute — one of Ireland’s leading climate change research centres.
Extreme rainfall during December resulted in widespread flooding across parts of Ireland and the UK, with some estimates putting the cost of the devastation to the British economy alone at close to £3bn (€4.07bn). In Ireland, the repair bill could top €100m.
Over the past 30 years, floods worldwide have killed more than 500,000 people and displaced over 650m people.
In the new study, Mr McDermott and his colleagues looked at the effects o f more than 50 large floods, which displaced at least 100,000 people each in more than 1,800 cities in 40 countries from 2003 to 2008.
They found that the low-lying urban areas hit more often by large floods are also the areas with the higher density of economic activity.
However, while these areas sustain more flood damage and recover quickly, the economic activity does not move to safer locations.
Mr McDermott said part of the problem is that many cities were built in flood-prone locations at a time when access to a river or the coast was economically important.
However, the cities have remained in flood-risk locations even when modern land transport reduced the importance of access to waterways.
The study also said that because governments bear much of the costs of building and maintaining flood defences and compensating flood victims, private developers can build on cheap, flood-prone land without bearing the full cost of their actions.
This has resulted in too many people ending up living in these flood-risk areas.
“As a society we appear to be overly exposed to flood risk — there are various reasons why developers and house builders do not take full account of flood risk when deciding where to build,” said Mr McDermott.
“Rising sea levels and more extreme rainfall episodes as a result of climate change will lead to greater flood risk — more frequent flooding of existing flood-prone areas or an expansion of areas at risk.
“We, as a society, must look at ways of mitigating that risk, and not building on flood plains would be a good place to start.”
Last month, the Oireachtas environment committee also called for a ban on new buildings on flood plains.
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