Researchers have revealed that the biggest cities in the U.S. are at far greater risk of experiencing serious flooding in the decades to come than previously believed and this has something to do with a "triple threat" associated with climate change.
For the new study published in the journal Nature Climate Change on Monday, Steven Meyers, from the University of South Florida, and colleagues reported that a combination of storm-surge, sea-level rise and heavy rainfall, all of which are functions of climate change, places Los Angeles, New York, Houston, San Francisco, Boston and San Diego at increased risk of compound flooding.
The research showed that how scientists traditionally analyzed heavy rainfall and storm surge, which primarily drives flooding in coastal communities, underestimates the risks of flood in the U.S.
Disaster experts used to analyze high rainfall and storm surges when defining flood zones and making preparedness plans, but the findings of the study revealed that this method underestimated the combined risks of high rainfall and storm surges when they occur at the same time, which they refer to as a compound event.
"Usually it requires an extreme storm surge to cause flooding or an extreme rainfall event," said study researcher Thomas Wahl, from the University of South Florida. "But the combination of two events that are not really extreme on their own may cause larger damages than one of the two events alone."
The researchers said that the biggest driver of increased flooding risks remains the long-term rise of sea level. Wahl said that if sea levels continue to rise, it would have an impact on storm surges, which also affect compound flooding.
The researchers likewise noted that the compound events have being occurring more often over the past century. In the case of New York City, for instance, the risks of flooding have more than doubled over the past six decades because of the combination of storm surge and high rainfall.
About 40 percent of the population of the U.S. resides in coastal cities, where flooding has already proved to have costly consequences, particularly in low-lying, heavily developed and densely populated areas.
"When storm surge and heavy precipitation co-occur, the potential for flooding in low-lying coastal areas is often much greater than from either in isolation," Meyers and colleagues wrote. "Knowing the probability of these compound events and understanding the processes driving them is essential to mitigate the associated high-impact risks."
Photo: U.S. Geological Survey | Flickr
