Four sinkholes open up at Top of the Rock golf course

Mother Nature added four new holes at Top of the Rock Golf Course in Branson.

Engineers were at the course Friday.

Gary Pendergrass, a geological engineer and principal with GeoEngineers, said the largest sinkhole of the four that opened was 60 feet by 80 feet wide, and 35 feet deep.

Pendergrass said the initial focus was to ensure the safety of the public and the facilities and determined that the largest hole was "medium-sized."

Pendergrass said the next step was to drain the water from a nearby pond to avoid more water flowing into the sinkhole and making it worse.

Martin MacDonald, director of conservation for Bass Pro Shops, was also at the course Friday to survey the damage.

MacDonald noted that karst topography is a major feature of the Ozarks. Water is constantly circulating through bedrock below the ground, creating Missouri's many caves — and sometimes, sinkholes.

Pendergrass said engineers will conduct a more in-depth investigation next week to determine the best way to replace the 7,000 cubic feet of material that's been displaced.

Filling the hole — when and if it's done — would likely take a week or two, Pendergrass said.

MacDonald said before that, they were going to "do a little exploration" to see if there was a possibility of using the hole as a teaching lesson about karst topography.

"From the Top of the Rock perspective, it's not what you want to have," MacDonald said. "But we'll see if we've got anything unique down there."

MacDonald was also thankful that the sinkhole opened near the practice area and driving range and that scheduled golf games wouldn't be affected.

"If they were going to have a place for a sinkhole to open," MacDonald said, "that was not bad."

Doug Gouzie, associate professor of geology and sinkhole expert at Missouri State University, studied a photo of the largest of the four sinkholes.

"Sinkholes that develop with steep walls are probably only 5 to 8 percent of the sinkholes we see in Missouri," Gouzie told the News-Leader Friday. "Any time you see a big collapse with vertical walls, that quite possibly is the result of a cave below that collapsed."

Recent heavy rains in the area likely played "a huge role" in the sinkhole's formation, Gouzie said. Rain will flow downward, following cracks in the rock below, eventually working its way to the cave roof.

Rain will carry soil particles with it, eventually creating a small collapse that can grow into a very large one when the cave roof gives way.

Could there be more collapses at the golf course?

"That's the magic question," Gouzie said. "If there are other vertical cracks in the rocks where water can wash through, then potentially yes."

Gouzie said it would be unwise to move heavy equipment near the sinkhole or allow people to approach it because the sinkhole walls likely will continue to slough into the hole and the hole will grow wider.

A sinkhole's growth can be stopped by packing it with rocks of different sizes, as was done when a very large sinkhole opened beneath a house in Nixa several years ago. Gouzie said he planned to visit the sinkhole Saturday to get a better idea of its size and scale.

The Missouri Department of Natural Resources has extensive information about sinkholes in the Environmental Geology section on its website.