Shanghai is the most vulnerable major city in the world to serious flooding, a study suggests.
Despite its economic wealth, the Chinese city is considered to be more exposed to the risk of flooding than much poorer cities such as Dhaka.
As well as evaluating a city’s physical attributes, the study also considers social and economic factors when rating an area’s vulnerability.
Details of the research appear in the journal Natural Hazards.
A team of scientists from the UK and the Netherlands has developed a Coastal City Flood Vulnerability Index (CCFVI) based on exposure, susceptibility and resilience to coastal flooding.
Co-author Nigel Wright, from the University of Leeds’ School of Civil Engineering, said that current methods tended to be two dimensional.
“Very often we look at these sorts of things in a very deterministic way,” he explained.
“We look at physical exposure, so if you live by a river you are exposed to the risk of flooding.”
Prof Wright said that the CCFVI used a range of data, consisting of 19 components.
“We still use the physical ones but also economic and social ones, such as how much attention is given by local or national governments to protect citizens and citizens’ property through investing in various forms of resilience,” he told BBC News.
These included the percentage of a city’s population living close to the coastline; the amount of time needed for a city to recover from flooding; the amount of uncontrolled development along the coastline, as well as the volume of measures to physically prevent floodwater entering a city.
Same but different
“What this index tries to do is to widen this out and look at social indicators too,” Prof Wright added.
“You can have people who live in the same area but their vulnerability is actually different.
“Age is one of those things; if you are over 65 or under 18 then you are more vulnerable than an adult because you are not able to take the actions necessary to protect yourself or evacuate.”
He explained that past experiences played a role in a region’s attitude towards the risk of flooding.
“Economies that are developing rapidly have not had to implement resilience in the past because there has not been the economic output to protect.
“At the other end of the scale, somewhere like the Netherlands, where there have been serious floods in the past that have had an impact so they know they need to do it.”
While flooding has a local, physical impact, the economic consequences can be felt globally.
Prof Wright observed: “After the Japanese tsunami a lot of hard disk manufacturing was moved to Bangkok, then there were the floods in Bangkok and the price of hard disks went up dramatically because the factories had to close down and there was a shortage of hard disks.”
The team’s paper focused on nine coastal cities built on river deltas, including Shanghai, Dhaka (Bangladesh), Casablanca (Morocco), Buenos Aires (Argentina), Calcutta (India) and Rotterdam (the Netherlands).
