In 1867, after several days of rain, the Tennessee River surged over its banks and water rushed into Chattanooga, Tennessee. The devastating flood remains the worst in the river’s history since record-keeping began.

But Lisa Davis of the University of Alabama is digging in the dirt and finding evidence of even larger floods in the more distant past.

When flood waters recede, they leave behind minerals.

“And so we search for these deposits and we date them and we build a chronology of events,” she says. “And in some cases, we’re actually able to reconstruct what the height or the size of the flood was.”

At their research site in northern Alabama, her team has found evidence of several Tennessee River floods larger than the flood of 1867. And she says such events could happen again.

As the climate warms, extreme rainfall is growing more common in the Tennessee River Valley.

So Davis says it’s important for planners to understand what they could be up against in the future. That requires knowing what’s happened in the past – not just in recent centuries, but over millennia.

“That information can be used to figure out whether or not dams have been adequately designed,” she says. “Has anything happened that’s bigger than what they have imagined?”.

Reporting credit: Sarah Kennedy/ChavoBart Digital Media.