Global Warming: The 9 Most Vulnerable Cities

Aerial view of modern skyline of Guangzhou, China
Guangzhou, China. Over 100 million people live in the Pearl River delta region, where climate change is expected to significantly increase flooding risks. dowell/Moment/Getty Images

The changes associated with global warming are increasing the risk of flooding in coastal cities. The rise in sea levels has been leading to salt water intrusion and infrastructure damage from storm surges. Intensifying rainfall events elevate the risk of urban flooding. At the same time, urban populations are growing, and the value of economic investments in cities is skyrocketing. Further complicating the situation, many coastal cities are experiencing subsidence, which is a lowering of the ground level.

It often occurs because of extensive draining of wetlands and heavy pumping of aquifer water. Using all these factors, the following cities have been ranked in order of average expected economic losses from climate change induced flooding:

1. Guangzhou, China. Population: 14 million. Located on the Pearl River Delta, this booming south China city has an extensive transportation network and a downtown area located right on the banks of the estuary.

2. Miami, United States. Population: 5.5 million. With its iconic row of high-rise buildings right on the water’s edge, Miami is certainly expected to feel the sea level rise.  The limestone bedrock on which the city sits is porous, and salt water intrusion associated with rising seas is damaging foundations. In spite of Senator Rubio’s and Governor Scott’s denial of climate change, the city has recently addressed it in its planning efforts, and is exploring ways to adapt to higher sea levels.

3. New York, United States. Population: 8.4 million, 20 million for the entire metropolitan area. New York City concentrates a phenomenal amount of wealth and a very large population right at the mouth of the Hudson River on the Atlantic. In 2012, Hurricane Sandy’s damaging storm surge overtopped floodwalls and caused $18 million in damage in the city alone.

This renewed the city’s commitment to step up preparation for increased sea levels.  

4. New Orleans, United States. Population: 1.2 million. Famously sitting below sea level (parts of it are, anyway), New Orleans is continuously fighting an existential struggle against the Gulf of Mexico and the Mississippi River. Hurricane Katrina’s storm surge damage prompted significant investments in water control structures to protect the city from future storms.

5. Mumbai, India. Population: 12.5 million. Sitting on a peninsula in the Arabian Sea, Mumbai receives phenomenal amounts of water during the monsoon season, and has an outdated sewer and flood control systems to deal with it.

6. Nagoya, Japan. Population: 8.9 million. Heavy rainfall events have become much more severe in this coastal city, and river floods are a major threat.

7. Tampa – St. Petersburg, United States. Population: 2.4 million. Spread around Tampa Bay, on the Gulf side of Florida, much of the infrastructure is very near sea level and particularly vulnerable to rising seas and storm surges, particularly from hurricanes.

8. Boston, United States. Population: 4.6 million. With a lot of development right on the shores, and relatively low sea walls, Boston is at risk of severe damage to its infrastructure and transportation systems.

The impact of Hurricane Sandy on New York City was a wake up call for Boston and improvements to the city’s defenses against storm surges are being made.

9. Shenzhen, China. Population: 10 million. Located approximately 60 miles further down the Pearl River estuary from Guangzhou, Shenzhen has a dense population concentrated along tidal flats and surrounded by hills.

This ranking is based on losses, which are highest in rich cities like Miami and New York. A ranking based on the losses relative to the cities Gross Domestic Product would show a predominance of cities from developing countries.

Source

Hallegatte et al. 2013. Future Flood Losses in Major Coastal Cities. Nature Climate Change.