110 W. New York Ave.
DeLand, FL 32720
Beware as rains follow drought
By Pat Andrews
posted Jan 28, 2013 - 7:15:54pm
As sinkholes go, it isn’t spectacular. However, it could be the harbinger of more yawning holes opening up in the ground.
The sinkhole that appeared at 4733 Mills Road in DeLeon Springs Jan. 24 gobbled up some fencing, a tree and a few power lines.
David Griffis, director of the University of Florida-Volusia County Extension Office, keeps up with local sinkholes. Volusia County Fire Services checked out the Mills Road sinkhole, and estimated it at 25-30 feet in diameter and about 20 feet deep, he said.
Griffis also looked at photos of the sinkhole, and talked to the landowner, a man who identified himself only as “Jerry,” Griffis said.
Griffis said the property owner didn’t seem panicked or worried about the sinkhole.
“It’s a normal, average sinkhole,” he said.
Because it’s on private property and didn’t endanger any homes or structures, Griffis said, neither he nor any other agency will take further action.
Sinkholes collapse suddenly and dramatically. When a depression forms gradually, it isn’t a sinkhole, he said.
“I’m surprised that we haven’t had more sinkholes with the drought that we’ve been having,”
Tom Carey, groundwater-resources manager for Volusia County, agreed with Griffis.
For the calendar year 2012, rainfall was down almost 8 inches, Carey said. For Volusia County, the average annual rainfall is 55 inches.
Over the past four years, the rainfall shortage has totaled just over 25 inches.
“That comes out to about 523 trillion gallons of rain that haven’t fallen on Volusia County,” Carey said.
When it does start raining after a drought, sinkhole activity increases, especially with heavy rains, he said.
Here’s why: During a drought, the groundwater levels drop, and underground limestone caverns don’t have hydraulic pressure holding them in place anymore. They become weak and crumbly.
With heavy rains, the caverns can’t sustain the weight of the saturated ground above, in combination with the sudden influx of groundwater. The cavern collapses, forming a sinkhole.
“Nice, moderate rains” will ease the drought without contributing to sinkhole development, Carey said.
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