Hurricane Harvey: Even After Floodwaters Recede, They Hold Danger

By Frank Otto

Flooding during Hurricane Harvey in Texas. Photo by Jill Carlson from Roman Forest, Texas

August 31, 2017

Since Friday, Houston and its surrounding area has been hammered by more than 40 inches of rain, with more set to come. Flooding related to Hurricane Harvey has water cresting dams and forcing people to their rooftops all across the area.

Over the years, word has spread enough that most people know to stay out of the floodwaters spreading throughout southeast Texas (if they can). In addition to the apparent danger of drowning it poses, the water also picks up illness-causing bacteria and toxins.

But what happens when the floodwaters recede back into lakes, rivers and streams. Does that risk go away?

Not very quickly, according to David Velinsky, PhD, a professor in Drexel’s College of Arts and Sciences and vice president for Academy Science at the Academy of Natural Sciences.

“The rain just washes all the bacteria and contaminants like trace metals and organic toxins into the waterways,” he said. “And that may take days or weeks before it settles or dilutes out and flushes through.”

For Houston, in the case of Hurricane Harvey, it will likely take “a while” for that to happen.