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Warning of whole cities being lost to flooding
IT IS a scene that could be taken from the movie set of The Day After Tomorrow.
Cities across the world disappearing under water as floods decimate the world’s coastlines after the melting of ice sheets sparks rising sea-levels.
But according to a Southampton researcher, the chances of it becoming reality are greater than ever.
The study, co-authored by Professor Robert Nicholls from the University of Southampton, has revealed that climate change combined with rapid population increases, economic growth and land subsidence could lead to a more than nine-fold increase in the global risk of flooding in large port cities between now and 2050.
Future Flood Losses in Major Coastal Cities explores the policy implications of flood risks due to climate change and economic development and urges action to improve flood defences before it is too late.
The authors estimate present and future flood losses – or the global cost of flooding – in 136 of the world’s largest coastal cities, taking into account existing coastal protections.
Average global flood losses in 2005, estimated at about six billion US dollars per year, could increase to 52 billion US dollars by 2050 with projected socio-economic change alone.
The cities ranked most at risk, measured by annual average losses due to floods, include Miami, New York, Vancouver and Mumbai – no UK cities were in the list.
Robert Nicholls, Professor of Coastal Engineering at the University of Southampton and co-author of the study, said: “This work shows that flood risk is rising in coastal cities globally due to a range of factors, including sea-level rise.
“Hence there is a pressing need to start planning how to manage flood risk now.”
To estimate the impact of future climate change the study assumes that mean sea-level, including contributions from melting ice sheets, will rise 0.2-0.4 metres by 2050.
An important finding of this study is that, because flood defences have been designed for past conditions, even a moderate rise in sea-level would lead to soaring losses in the absence of adaptation. Failing to take action is not an option as it could lead to losses in excess of one trillion US dollars.
Therefore, coastal cities will have to improve their flood management, including better defences, at a cost estimated at around 50 billion US dollars per year for the 136 cities.
Even with better protection, the magnitude of losses will increase, often by more than 50 per cent, when a flood does occur.
The report also notes that large increases in port city flood risk may occur in locations that are not vulnerable today, catching citizens and governments off-guard, including Naples in Italy.
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