Catalyst Fall 2018
Final Analysis

Far from the Coast, Floodwaters Rage

Photo: J.B. Forbes/St. Louis Post-Dispatch via AP
Inland flooding affects thousands of homes and businesses around the country every year. Here, a December 2015 storm inundated towns in and around St. Louis, Missouri.


When we think of flooding, those of us who live near the coast might naturally picture storm waves overwhelming shorelines and sending water flowing onto streets and homes, such as we saw in coastal communities in North and South Carolina with the recent devastation wrought by Hurricane Florence. But inland flooding is actually the most common type of natural disaster in the United States, and earlier this year, many landlocked communities such as Elkhart, Indiana, and Millville, West Virginia, were hit by dangerous and expensive floods that threatened—and in some cases, claimed—people’s lives, triggered evacuations, damaged infrastructure, and cost millions in rescue and cleanup operations.

In 2017 alone, inland US floods killed 25 people and caused more than $3 billion in property damage and ruined crops. Worse still, these floods are becoming more frequent and more destructive in some parts of the country. My team’s new fact sheet Climate Change, Extreme Precipitation, and Flooding: The Latest Science answers the questions inland residents might have about increased flooding, such as: Why is it happening? Is it because of climate change? And what can we do to prepare for more frequent and severe floods?

Flooding is a natural process that occurs when rivers or land don’t have enough capacity to absorb or drain large amounts of water from rain or melting snow. We’ve always experienced floods, but we haven’t always seen rainstorms with the frequency and intensity we are experiencing now, which often contribute to increased flooding. Nor have we always used our land the way we do today, allowing building in wetlands and covering vast tracts with nonporous asphalt. These two factors—increased extreme precipitation and changes in land use—contribute to worsening floods in certain US regions, especially the Midwest and Northeast.

Scientists are working now to better understand the links between extreme precipitation and climate change. Although some intense rainfall occurs as a function of natural variability, warmer air holds more moisture, so global warming can make increased rainfall more likely. In our analysis, however, we don’t just advocate for better policies to mitigate global warming—we make the case that preparedness is key. Because warmer temperatures will continue to drive heavier rainfall, triggering more frequent and intense floods in some areas of the United States, state and local governments must adopt science-based and commonsense land-use standards that protect wetlands from development, keep people and buildings out of harm’s way, and ensure that all new infrastructure is climate-resilient.

Astrid Caldas is a senior climate scientist at UCS. Read the full fact sheet—along with concrete suggestions for your local decisionmakers—at, and read more from Astrid on our blog, The Equation.