In 2005, the flood damage of the 136 major port cities included in the study was 6 billion dollars (4.5 billion euros).
The scientists had analyzed the current and future flood risk and flood protection for the individual cities. They calculated three scenarios – with no sea level rise at all, with a 20-centimeter sea level rise and with a 40-centimeter sea level rise by 2050. The data was then used to draw conclusions about the costs to be expected in the event of flooding. In addition to rising sea levels, the causes of the predicted massive increase in costs are land erosion and socio-economic factors such as growing populations in the affected regions. .
The chinese city of guangzhou will be hardest hit, having to pay a good 13 billion dollars a year for flood damage by 2050. India’s mumbai also faces tough financial consequences, study finds. U.S. Cities were also identified as particularly vulnerable: major cities such as miami, new york and boston were high up on the list of costs. If the expected costs are set in relation to the economic strength, poor countries in particular will suffer the most. This does not even include possible damage from other weather extremes such as heavy storms.
To avoid the huge increase in costs, each of the 136 cities would have to invest an average of 350 million dollars a year in flood protection – a total of around 50 billion dollars. It is not enough to adapt plants to environmental changes. They had to be raised more than simply to match sea level rise, study says. This could reduce the likelihood of flooding.
In the agyptian port city of alexandria on the mediterranean, for example, facilities had to be raised by 67 centimeters when sea levels were expected to rise by 60 centimeters. This was necessary because the costs of individual flood events were increasingly high in the future – and floods therefore had to be avoided more than ever before.
Even if alexandria reduced the probability of a flood by a factor of 2.7, the cost of flooding would triple to an estimated $51 billion by 2050. "The world’s coastal cities are thus becoming more dependent on flood defenses, but also more vulnerable once they fail and there is flooding after all," the report says.