Ask Us: What if Huntsville got 17 inches of rain?

Paul Gattis | By Paul Gattis |
Email the author | Follow on Twitter
on May 26, 2010 at 9:03 AM, updated May 26, 2010 at 9:14 AM

Q: What if Huntsville received 17 inches of rain like Nashville did? What would Huntsville look like? Does anybody know just how bad it would be? And does Huntsville have a plan in place? - Harold Dosdall, Huntsville

A: Marty Calvert, a hydrologist for the City of Huntsville, said it's difficult to project what impact a similarly heavy rain would have, because there are variations that could make a difference. Was it a heavy rain or a slow, steady rain? Was the amount of rainfall just in Huntsville or widespread along the Tennessee River?

"There is no way of saying," Calvert said. "If somebody said, 'What happened to me if I lived in a certain location and 13 inches of rain fell in a day's time,' I might could give them an estimate of what would happen.

"Downtown, where I am sitting, I would still be dry. If I lived on the Tennessee River, I probably wouldn't be. If I lived along the bank of Aldridge Creek or Peavey Creek or Dallas Branch, I'd probably get wet.

"It's hard to say what would actually happen unless you had some specifics. We've never experienced that much rainfall. You would have to assume it would be the worst flood that Huntsville's ever had."

To date, Calvert said the city's worst flood came in March 1973 when about seven inches of rain fell in 24 hours.

"You can see in pictures around town," he said, "(that) they had boats out on the Parkway. That was before the Parkway had overpasses, but you would probably have boats out again.

"With Nashville, they had the Cumberland River that goes through their town. We don't have a river system that goes through the middle of town. It's a lot different. A lot along the Cumberland River was protected by dikes and berms that were breached during the flood.
"You could say it would be devastating just about to any city if they had 17 inches of rain. To say who would be affected, that would be pretty hard to do."

Even along the Tennessee River, other factors would have to fall into place to cause major flooding problems.

"The Tennessee River doesn't rise unless you have a widespread rainfall," Calvert said. "If it just rains 17 inches in Huntsville, it wouldn't affect the Tennessee River unless it rained 17 inches in Chattanooga and Scottsboro and Knoxville, because they feed the Tennessee River.
"You have the dams (controlling water levels), and it takes a large watershed to affect the Tennessee River. Rainfall over a large area, not just one little isolated area, would cause the Tennessee River to rise."

And what about Big Spring International Park?

"Usually, Big Spring Park is affected by a short downburst thunderstorm," Calvert said. "It all has to do with timing. If you have 17 inches spread out over two days and it was a slow rain, you wouldn't ever see it. But if you have five inches in an hour, then Big Spring would go up, and it would probably get up on the roads and then it would drop back down."

The heavier the rain, the more water is available as runoff to cause levels to rise.

"During a heavy rain, there is more discharge produced per acre," Calvert said. "You have a lot of rainfall that comes off in a small area. Big Spring Park has a small tributary area. It takes a heavy rainfall to make it go up. Light rainfall doesn't produce a lot of runoff. The bigger the river, the bigger the creek, the larger an area it takes to affect it."


Got a questionSubmit it to or phone it in to 536-8255. Include your name, hometown and phone number.

