Warmer weather, increased rainfall and already saturated ground have left several areas of the county prone to mudslides and rockfalls, with several occurring locally Friday morning in various areas.
Emergency crews were dispatched to trees and electrical wires down along Route 26 in Miller Township at “Riling’s Curve,” a minor mudslide and trees down at the intersection of Schoolhouse Hollow and Route 22 and a more major mudslide along Route 22 in Henderson Township near Huston Ford.
Huntingdon County Emergency Management Agency (EMA) director Joe Thompson stated that several areas in the county are more susceptible to mudslides and rockfalls due to the terrain.
“In the area of Jack’s Narrows from the county line to the east side of Sand Plant Hill, especially where it’s narrowed down to two lanes, PennDOT has taken steps with the rock fence to help prevent rock slides,” Thompson said. “Generally anywhere in through there would be an area of concern. There was some stabilization work performed by PennDOT on the east side of Sand Plant Hill.”
Other points of concern include the area surrounding Water Street and Route 453.
“In the Water Street area, there could be concern with rocks. Parts of Route 453 would be on our concern list, especially in the area between Huntingdon Furnace Road and to the county line at Hundred Springs Road,” said Thompson. “That is definitely an area we do see land, tree and rockslides — everything from small pieces coming down because the cut of the embankment is so steep with the road to large vehicle-sized boulders coming off of there.”
Thompson added that some of the very points where issues arose Friday are also areas of concern.
“There were two areas, just east of Ardenheim and another one further up toward Huntingdon at the intersection of Schoolhouse Hollow Road and Route 22. There’s very little there to hold any of that dirt and you can see the dirt embankment and there’s very little to hold that back,” said Thompson. “The Route 26 North area, has been stabilized by PennDOT several times and I know they had several issues including Friday morning in that area. That’s just somewhere that there’s not a lot of vegetation and support to hold things back from sliding down.”
Mudslides and rockfalls can make for a difficult cleanup for area fire companies and maintenance crews.
“The initial response from the fire companies is to assist with traffic control, and if it’s something that can be cleaned up quickly by the fire companies or with some PennDOT assistance to get the road way open back up again safely,” said Thompson.
Matt Powell, associate professor of geology at Juniata College, believes that the recent weather was a contributing factor to the recent mudslides.
“Around here, it’s steep slopes in combination with a lot of rain and snowmelt. On any hillside or slope, gravity is always pulling downwards, but the hillside is held back basically by inertia and friction,” Powell said. “When you add water into it, it seeps into the ground from the snowmelt and the rain, or, as we just saw, the combination of the two of them. There’s different ways it can do it, but it overcomes that inertia and friction and the slope fails.”
Thompson observed the current conditions created a perfect recipe for mudslides and rockfalls.
“The warm, cold, freeze, thaw, rain, snow, windy, all of the weather conditions combined with a lack of vegetation and other ground root support to otherwise help stabilize can make for some pretty dangerous situations, at least some concerning situations,” said Thompson.
The soil composition of the region also contributes to the possibility of instability.
“The main things around here is adding that extra water adds weight to the hillside and at some point it overcomes gravity and pulls it down,” he said. “It’s also possible for water to swell the clays, so the clays actually expand ad they can weaken the hillside.”
He also cited that in times of freeze and thaw, areas can be affected if rocks and walls have cracks that allow water to infiltrate.
“When water seeps into those cracks and it expands, it expands with tremendous pressure — I think it’s close to 120,000 PSI — there’s virtually nothing that can withstand that and it will crack those walls apart from the inside,” Powell said. “Once it breaks that apart, it’s added more space for water to infiltrate and that can make the probability of slope failure even worse.”
Changing climate increases the likelihood of similar events in the future.
“Right now in Huntingdon County, we get maybe three or four days per year that have more than an inch of rain, but with climate change, that’s expected to almost double,” said Powell. “Whatever the factors that are causing it, we should expect to have more slope failures and mudslides.”