July 25, 2018

New UCS Fact Sheet Shows Midwest, Northeast Experiencing More Floods

Storms Now Dumping More Rain While Number of Heavy Precipitation Events Also Rising

The eastern U.S. has been pummeled by relentless rain and widespread flash floods. The Union of Concerned Scientists (UCS) released a new synthesis report examining the frequency and intensity of extreme precipitation and inland flooding events, as well as the role of climate change in driving current and future trends. This analysis summarizes the latest science, making it ideal for citing in future stories on such events when a scientific source is needed.

According to the report:

  • Some regions in the U.S.—such as the Midwest and Northeast—have experienced an increase in the number of floods over the last 50 years, while other areas—including the Pacific Northwest, Rocky Mountains, Southwest and Southeast—have seen a decrease.
  • The frequency and intensity of extreme precipitation events across most U.S. regions has also increased since the middle of the 20th century.
    • The eastern half of the U.S. has seen a 50 percent (or more) increase in extreme rainfall event frequency.
    • The entire country has seen an increase in the amount of rain falling during the most intense events.  

“While climate change is likely not the sole cause for this uptick in supercharged weather events, it can be a significant contributing factor,” said Astrid Caldas, senior climate scientist at UCS. “We know warmer air holds more moisture, meaning there’s more water in the air that can potentially fall as rain. Climate attribution science is starting to identify the role of global warming in specific extreme events. The devastating 2016 Louisiana rains, for example, which flooded thousands of businesses and homes, were considered 40 percent more likely to occur and 10 percent more intense because of human-induced climate change. Hurricanes are also bringing more rain with them to both coastal and inland communities, with Harvey being a prime example of a ‘supercharged’ tropical storm.”

Click here to check out a new UCS fact sheet released in June that examines the science connecting extreme weather events to climate change.

The United States has a long history of enduring devastating floods in both rural and urban areas. However, land use practices such as increased development in floodplains and extensive paved urban areas mean these places are less able to accommodate more frequent, heavy rainfall, increasing their risk of floods and the resulting impacts. Despite the human and economic toll, the nation has not yet implemented the policies and resources needed to adequately respond to the magnitude and severity of the problem.

“With climate change possibly worsening flood risks over time, it’s critical we establish new policies and reform existing ones, to limit both costs and harms to communities and to target resources effectively,” said Shana Udvardy, climate resilience analyst at UCS. “Congress has an opportunity this summer to make much needed reforms to the National Flood Insurance Program, including modernizing outdated flood maps, ensuring flood insurance rates reflect current risks, maintaining affordability for policy holders, and expanding resources to help communities reduce their flood risk.”

The Union of Concerned Scientists puts rigorous, independent science to work to solve our planet's most pressing problems. Joining with people across the country, we combine technical analysis and effective advocacy to create innovative, practical solutions for a healthy, safe, and sustainable future.