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Mount Washington landslide mitigation begins as climate challenges increase

Trees, debris, and mud cover the hillside around a house that was destroyed from a landslide in 2018.
Keith Srakocic
Greenleaf Street, one of the three project sites on Mt. Washington, was the site of a major landslide in 2018 that destroyed at least one home.

Monongahela has been translated from Lenape to mean "high banks or bluffs, breaking off and falling down in places," or "many landslides." Hovering above the Monongahela River next to Station Square, Mt. Washington’s slouching slopes are getting a lift.

Earlier this month, work began on William Street as part of a $10 million project to sturdy Mt. Washington’s hillsides, funded mostly by Federal Emergency Management Agency dollars. Using techniques such as “pinning,” which bolts unstable rock faces to prevent them from slipping, this work sets out to prevent future landslides.

The region’s climate change projections show such work could become more common. Pittsburgh got doused with more than double its average rainfall in April. And climate scientists predict the region will continue to get wetter.

Heavy rainfall is “probably the most important” catalyst for landslides to slide, according to Dan Bain, associate professor of geology and environmental science at the University of Pittsburgh. Thick layers of clay stone lie under Pittsburgh’s soil and when they get wet, they deteriorate fast. Coupled with steep slopes, Pittsburgh is a land of landslides.

“It's like a perfect storm,” Bain said. “You've got the right soils, you've got the right slopes, and you've got the right amount of rainfall.”

Predicting landslides is tricky. The conditions could be right and yet the hill holds. Public works agencies and researchers have only patchy past records to rely on to understand local trends. But projects out of Pittsburgh’s universities — in partnership with local government agencies — could fill in the gaps to sturdy the region’s hillsides.

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Wet and unpredictable

Allegheny County has gotten 24” of rain so far this year, which is 10.5” above the average total for the Jan. 1 to May 16 time period, according to the National Weather Service. The past two decades have been the wettest on record in the region.

The wettest year was 2018, when 58 inches of rain drenched the region. The wet spring triggered 25 landslides in Allegheny County alone. It was “a wake up call to most in the region,” Bain said. And he said during another wet year in 2019, budgets for emergencies like landslides were spent early. “And the landslides kept coming.”

It’s hard to see a trend in the region’s landslides, because researchers have only recently begun to track them. The U.S. Geological Survey mapped landslides that occurred in 1972 following devastation from Hurricane Agnes, but it wasn’t until after 2018 that a consortium out of University of Pittsburgh Swanson School of Engineering started keeping a running inventory of landslides in the county. There isn’t much record of what occurred in between, according to Bain.

A map of past and current landslides is available on Allegheny County’s online landslide portal. Red for recent landslides, purple for rockfall threats — few places in the county are not colored with risk.

A prevention puzzle

Cracks in the soil. Asphalt seemingly melting off the roadway. Bent horizontal trees grasping at the hillside. Soil slumping down a hill, forming hollow lobes. These are some of the warning signs of a landslide. Trained engineers drive around on the county’s roads each month and look for sights like these as well as any clogged drainages, according to Stephen Shanley, director of the Allegheny County Department of Public Works. The engineers note any troubling changes to the landscape, free up drains. They prioritize projects based on factors such as amount of traffic on a roadway or number of residences at risk.

“We don't get into the weather predictions,” Shanley said. “We just react and try to be proactive to prevent any landslides from happening on our roads.”

Major projects to stabilize hillsides — like the one going on on Mt. Washington — cost millions of dollars and funding is thin. “If we can mitigate it on the front end, that's the one thing,” said Randy Padfield, director of the Pennsylvania Emergency Management Agency, the state agency responsible for such projects. “But it takes a significant amount of funding to be able to do that. We always have more hazard mitigation projects than we have funding available to us.”

There could be more efficient and cheaper ways to catch a landslide before it takes down a hill, according to Karen Lightman, the executive director of Metro21 — a civic research institute at Carnegie Mellon University. One of Metro21’s projects used cameras on buses to track changes on roads. Lightman said equipping every public works truck or city bus on regular routes could be a first step in helping to monitor local slides. “It's capturing images and it's showing the change over time,” Lightman said. “You could actually see the deterioration. You could see the cracks in the road. You can see the start of a sinkhole. You can see the start of a landslide. And then they can be prevented.”

Metro21 is now working with the City of Pittsburgh Department of Mobility and Infrastructure, the Pittsburgh Water and Sewer Authority and researchers at Penn State on a new pilot project to use existing fiber optic cables — like those used for the internet — as sensors to monitor underground hazards in Pittsburgh at a low-cost. The cables register small vibrations and other changes and can be “first an indicator and then a predictor of climate, erosion, flooding and even landslides,” Lightman said.

The region’s past land use decisions haunt present day residents. “We don't get to make our decisions about how we're going to change the way we live,” Bain said. “We inherit it. We inherit the way the roads are laid out. We inherit where houses have been built. We have these soils. We have these hills. We can't escape that. But previously I think that we as a society were a little bit arrogant about the ways in which we sighted things.”

Bain recommended residents check the location of their homes against the county’s colorful landslide map. Right now, there is no insurance provider in the region that offers coverage for landslide damage. But help for homeowners could be on the way. Democrat Emily Kinkead and Republican Valerie Gaydos introduced a bill in February to the state legislature that could help shore up this gap.