Catastrophic Coastal Floods Could Become Much More Likely

A new study predicts a median 40-fold increase in flood frequency by 2050

San Diego
Once rare floods could afflict cities like San Diego more often in the future, a new study finds. russellstreet - Flickr/Creative Commons

There’s not much that can stand in the way of a flood—a disaster that can put lives at risk, contaminate drinking water and sweep away animals’ habitats. For many coastal cities, the risks of catastrophic floods are relatively low. But not for long. As The Guardian’s Oliver Milman reports, a group of scientists has a dire message for coastal cities: If greenhouse gas emissions don’t fall, floods that once seemed rare could become much more frequent.

A sobering new study published in the journal Environmental Research Letters suggests that major floods may occur much more frequently in the future. Researchers assumed that greenhouse gas emissions would continue at their current pace—causing the atmosphere to warm, melting glaciers and raising sea levels. They combined those predictions with historical flood frequency data and data about current weather patterns.

The result was a predicted median 40-fold increase of hundred-year floods along the United States coastline by 2050. Since the concept of flood recurrence is confusing at best, here’s a quick refresher. The term “hundred-year flood” does not refer to the severity of a flood, just its frequency. It means the probability that a flood will reach a certain level once in a hundred years. By definition, a hundred-year flood has a one-percent chance of occurring in any given year.

So what does a 40-fold increase in a hundred-year flood mean? Essentially it would push the chance of a flood reaching a certain level in any given year to 40 percent. And the probability of flooding could be even higher in places like New York, Baltimore, Washington, D.C. and Key West. In places like San Diego, Los Angeles and Seattle, the researchers predict, low-level flooding would likely occur more often than it does now.

Scientists already know that sea levels are rising faster than ever before, but are still teasing out the connections between human activity and floods. As reported in 2015, the Atlantic coast is thought to be at particular risk of severe flooding as sea levels rise and severe weather increases. And just last month, another group of researchers predicted that a rise of just under eight inches will double the risk of storm surges, large waves and severe coastal flooding along every coast on Earth.

It is still possible to curb greenhouse gas emissions and try to slow future damage to Earth’s glaciers. But the study’s real takeaway is that it’s time to prepare for the probability of flooding in places that haven’t really been affected by catastrophic floods thus far. As once rare floods become more common, a new reality could settle in for coastal cities—and the time to minimize damage is before a flood hits, not after. There’s still a lot to learn about how climate change could affect floods, but it never hurts to be prepared.

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