Will 100-Year Floods Become the Norm for Coastal Cities?

By Yessenia Funes Jun 08, 2017

A study released yesterday (June 7) by researchers from Princeton University and Rutgers University asserts that severe flooding in the United States is on course to become worse.

The paper, published in Environmental Research Letters, examines how climate change-driven sea level rise will impact flooding in coastal cities like Seattle, New York City and Charleston, South Carolina.

Sea level rise impacts not only the frequency of floods, but also their height. The impacts vary from state to state, but the number of 100-year floods (or floods that have a 1 percent chance of hitting annually) will see anywhere from a 1- to 1,314-fold increase with an average of 40-fold. For example, San Francisco and Seattle would experience a 100-year-flood annually, and Hawaii could see floods that are supposed to happen once every 100 years 130 times a year.

This is all by 2050—a mere 33 years away.

“Most coastal areas will experience relatively large increases in flooding events,” said Michael Oppenheimer, a Princeton climate scientist and co-author of the paper, to The Guardian. “A 40-fold increase on average is gigantic. Cities may not be able to defend themselves. They will have to spend a lot of money or there will be quite a lot of damage.”

Fast forward to 2100, and New York City could see a so-called 100-year flood event every other month. Natural disasters like Hurricane Sandy, on the other hand, are considered 500-year floods. The paper concludes that those will also increase in frequency, particularly on the West Coast.

Needless to say, communities of color will bear a disproportionate impact from such flooding, as happened with the flooding in Louisiana August 2016—a 1-in-1,000 year flood event. Such communities tend to live on lower-lying land more susceptible to flooding, and when it floods, they often lack the proper funds to deal with it and rebuild.

The study’s model assumes that business-as-model carbon emissions continue, which appears to be a part of the Trump administration’s agenda as it cuts methane regulations and stands by the fossil fuel industry, especially the coal industry.

Still, states, counties and cities across the country have joined forces to prevent such climate catastrophe—especially in light of President Donald Trump’s decision to pull out U.S. involvement in the international Paris Agreement, which would have set nonbinding greenhouse gas emission standards for the U.S.

Check out the complete study here.