Blame it on the rain

North Georgia residents who found a key Lookout Mountain route to Chattanooga closed over the weekend will be allowed on Scenic Highway this morning following a weekend rock slide.

In total, three geological mishaps have closed roads, caused millions of dollars in damage and rerouted motorists. The latest, and decidedly the most minor, occurred Saturday on Scenic Highway on Lookout Mountain.

That slide resulted in massive boulders the size of pickup trucks falling into a ditch about two miles north of Ruby Falls. Chattanooga officials closed the road Saturday evening but reopened it less than 24 hours later.

Rain and cold weather often contribute to slides, and more precipitation is expected today in Georgia and Tennessee.

“Just by the geography of our mountains, there are multiple layers of rocks — some are strong, some are weak — and when there is a lot of rain, the moisture gets into the rock and breaks down the weak layers,” said Jennifer Flynn, TDOT region spokeswoman.

Freezing temperatures followed by a thaw — and even the minor earthquakes the area has experienced recently — can contribute to the slides, Ms. Flynn said.

“There was an earthquake that measured 3.0 in Bradley County on Nov. 1, and then on Nov. 10 there was a rock slide in neighboring Polk County,” Ms. Flynn said. “That could be a cause.”

The Polk County disaster will take two months to clean up at a cost of $2.1 million.

Even for mountain residents who are used to occasional road closures, the number of slides this fall seems high.

“Occasionally a tree will fall across the road or something of that nature — not anything like this,” said Don Stinnett, who has lived on East Brow Road overlooking the Lookout slide for 38 years.

A rock slide on Oct. 25 closed a section of Interstate 40 northwest of Asheville in North Carolina.

Since then a Nov. 10 rock slide in Polk County closed U.S. Highway 64, and it won’t reopen until at least mid-January. Then a slide collapsed a section of Signal Mountain Boulevard on Wednesday. Those two events are being cleaned up by the Tennessee Department of Transportation. This weekend’s slide was cleared by Chattanooga.

“We will clean the ditch line out along the right of way, and we’ll leave the big rocks right where they are,” said Tony Boyd, assistant director of citywide services.

Assessing the scene without the help of a geologist, Mr. Boyd said the Lookout rock slide appeared stable and unlikely to produce more slides. An expert is expected to examine the area today.

Meanwhile, on Signal Mountain on Sunday, workers still were dumping massive loads of rock into a crater created in the Wednesday washout there, Ms. Flynn said. That’s a $400,000 to $500,000 effort, she said.

That road was closed at 10 p.m. Friday and will reopen at 6 a.m. today.

“They are on schedule and still dumping rock,” Ms. Flynn said Sunday afternoon, adding that the one lane that will reopen Monday will be loose gravel.

The weekend closure of Signal Mountain access caused serious congestion at times on the W Road, an alternative route off the mountain that is fraught with hairpin turns.

“It’s been extremely congested,” said Peter Hetzler, the mayor of Walden. “The W Road, at the peak times, had a very long wait to get up.”

Walden residents, whose town is just north of the town of Signal Mountain, use the W Road as their primary route off the mountain, Mr. Hetzler said. The road requires some negotiation on the part of motorists.

“Particularly for people who are not experienced with the road, it can cause some trouble,” said Mr. Hetzler, a lifelong Walden resident. “You have to stop and wait and allow others to come down.”