Can we predict, maybe prevent, the next Rockfish Gap landslide?
Hindsight being what it is, Chuck Bailey, professor of structural geology at William & Mary, would have predicted the May 3 landslide on Rockfish Gap, if asked.
What does this say for the future of rockfalls in the area, an important connection point between the Shenandoah Valley and central Virginia?
“You could argue that if we look to the future, we could identify places on the mountainside that maybe have the greatest likelihood of slipping, and then think about trying to do something proactive rather than reactive,” said Bailey, who turned out to be crossing the area a day before the landslide that shut down the US 250 for the foreseeable future, as VDOT engineers are working overtime trying to stabilize the slope.
“I actually had to go to the valley that day, so I ended up crossing on route 250. I hadn’t done it in months and months and months, so it was a little unusual lately. I was in a rush and was going up the hill, really just off the Albemarle-Nelson line, and I noticed some trees that were little cattywampus and then some rocks that were kind of lying in the gutter by the side of the road. . And immediately I was like, hmm, we’ve got some sort of mass movement going on here, ”Bailey said.
“It’s not uncommon to see a little piece of rock fall off, and like I said, I zoomed in on it, and it kind of backed up in the rearview mirror. I say to myself, I wonder if this is going to become a big deal. And that was the next day when some of my friends from Williamsburg that have relatives in the Augusta County area were, like, the road is closed, everything is going down hill. And that’s when I realized it was a big deal.
It is also almost inevitable that this sort of thing will happen, given the complicated geology of Rockfish Gap, a low point in the Blue Ridge, with an elevation of 1,903 feet.
The Blue Ridge Mountains typically have an elevation of 3,000 feet or more, so the Rockfish Gap has long been considered a link between east and west, dating back to the days when Claudius Crozet was in charge of try to build a rail tunnel across the gap. back to the 19th century.
The problem is, it’s not perfect, geologically speaking of the region.
“When you look at the scenery on this side of the hill, on the east side of Rockfish Gap, it’s pretty steep to start with, and to get these roads, and also the railroad below, to the kind of slope that they wanted. Basically, the construction engineers had to remove a lot of rock, and they used that rock in places to fill in the little valleys and hollows, ”Bailey said.
“Sure enough, human activity has overstepped some of the slopes there. It’s a natural consequence of building these roads, ”Bailey said.
This is something Bailey witnessed firsthand during a recent visit to the site, after the slide.
“What I noticed when I was examining the slide is that over there it’s cut into a very steep part of the hill,” Bailey said. “I don’t think I enjoyed how steep it was until I got there. These are not the highest road cuts. If you are on the highway, some of them are just beautiful, geologically speaking. They are big, they are wide. These are smaller and older, but they’re still very, very steep.
What this translates to: “If you were to kind of predict where you might expect the landslide to occur, the places that have the steepest cuts would be the ones to look at,” Bailey said.
The area of the most recent slide is one of a dozen that Bailey says seems like a great place to slide in the near future, which is why trying to get ahead of future slides is probably a good idea, even if the VDOT is consumed in the here and now when trying to correct the problem in question.
The last thing any of us want to happen is a major slide that closes Interstate 64, which crosses about 100 meters above the site of the current slide that closed US 250 between Route 6 and Route 151.
The VDOT in 2016 set the average annual daily traffic for Interstate 64 on Afton Mountain at 18,000 vehicles per day eastbound and westbound in 2016, with an additional 6,700-7,000 vehicles using the US $ 250 stretch between lines. Nelson County and Albemarle County which is currently closed to traffic.
Losing I-64 would be a state of emergency given the economic ties between the valley and central Virginia.
The good news: According to Bailey, it doesn’t look like the current landslide is expected to impact the grade the highway crosses.
“VDOT has its hands full with the big mess just over 250,” Bailey said. “Part of their remediation is going to be making sure they can go down the slope so that it’s no longer a significant risk to 250, and at the same time, not allowing this landslide to collapse and collapse. ascend. It is still probably 100 meters or more to approach the freeway. At first glance it doesn’t seem to be going up the slope so that’s a good thing.
Chris Graham story