Hurricane Harvey

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.

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

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.

“Either it settles to the bottom, degrades or just gets diluted by all the water,” Velinsky said. “In the Houston area, it will take everything a while to flush out into the Gulf of Mexico.”

Part of the danger, especially in a port town like Houston, are the industrial and commercial sites that get flooded.

“You have a lot of stuff that gets inadvertently dumped along the site,” Velinsky said. “Then, imagine 20 inches of rain there, or more, and it gets flushed away.”

So that means that it might be a good idea to avoid bodies of water for a bit of time after flooding like what Houston is experiencing. That includes even catching seafood, which might absorb or accumulate some of the harmful things in the water.

Velinsky sees this flooding as something becoming more common as a result of climate change. As catastrophic as it is, it might become more of the norm as we move forward in a warming world.

“This is unprecedented,” Velinsky said. “It’s a 500-year storm, but there could be another  500-year storm in three years from now, given the changing climate.”


Post by Frank Otto

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