For more than a month, millions of tons of earth and millions of dollars in property value have been inching down a Keene Valley mountainside. As 82 acres of trees and homes continue to break loose, a state geologist says other Adirondack slopes could fail.
The slow-moving landslide on the side of Little Porter Mountain is unnerving residents in the town of Keene, which includes the hamlets of Keene and Keene Valley. The year-round population of 1,000 is nearly doubled in summer by wealthy seasonal residents, many who live upslope for the lofty views of the High Peaks.
Four half-million-dollar houses at the top of the slide have been affected—pried wholly from their foundations or partially destabilized—and at least one vacation home appears to be in its path below. The value of the land in motion is expected to be reduced from about $3 million to zero, while sales of similar properties are thrown into limbo. Supervisor Bill Ferebee said the town has begun to seek emergency state reimbursement to help make up anticipated losses in property tax.
Andrew Kozlowski, associate state geologist with the New York State Museum, says the slide is the largest in state history. It’s nothing like the quick tumble of trees and thin humus familiar on high Adirondack terrain. This one started as a subtle shift below 2,000 feet on a 25–35 degree slope. It was triggered by the melting of deep snowpack compounded by more than a foot of rain in April and May. The slide does not seem to pose a risk to human life, but it is reactivated when new rains slip into soil cracks that are growing wider every day. Because it’s logistically difficult to drill borings in shifting soils to measure their depth, Kozlowski can’t estimate when the mass will stop moving; he says it could be months or years.
A dirt road runs parallel to the top of the landslide. Keene residents are questioning whether mountainside building is responsible for altering drainage patterns. “Does the development help? Probably not. Was it the actual cause? Probably not,” Kozlowski said.
There were pre-existing conditions, he explained. He detected on the site signs of a landslide hundreds or thousands of years ago. At the end of the last ice age, Keene Valley was submerged by a glacial lake, and deep sand on the hillsides is evidence of 12,000-year-old beaches.
LiDAR (Light Detection and Ranging) imagery collected by aerial survey can provide high-resolution digital images and help identify shifty soils, he said. Eight New York counties have collected LiDAR data but none in northern New York, which has the state’s steepest topography. Keene Supervisor Ferebee said aerial images could be useful to all towns in Essex County, and he is exploring how the county might cover the $150,000 cost.
Residents are also concerned about the future of homes on other Keene mountainsides. “There is danger of this happening elsewhere,” Kozlowski told a group of two dozen citizens who gathered at the community’s K–12 school earlier this month. “Will it happen on this scale? We don’t know.”
Real Estate and Rain
Annual rainfall in the Lake Champlain watershed is three inches greater on average than it was during the mid 20th century, when the first houses were built on the side of Little Porter Mountain, according to United States Historical Climatology Network data. A range of climate models predict the Champlain Basin could receive 4 to 6 inches more precipitation a year by the end of this century, with heavy storms becoming more frequent, according to a 2010 report by The Nature Conservancy’s Adirondack and Vermont chapters.
The Little Porter slide has suddenly become an unforeseen example of something other Adirondack mountain communities must consider in a potentially wetter future.
“Throughout the Adirondacks there is going to be a lot more concern about this now,” said Martha Lee Owen, who owns vacant land on the failed slope. She is a real-estate broker whose father, Adrian Edmonds, lived at the base of Little Porter and pioneered homebuilding on Keene’s mountainsides. “He’d be just heartbroken,” she said. “It’s just terrible that it’s affected so many homeowners.”
Owen said it never occurred to her to recommend that potential buyers hire a geologist to evaluate slope stability, but she will recommend it now. She would also like to see LiDAR data collected for Essex County. “Of course it’s a huge concern to me in terms of selling properties, not just my own but selling any properties,” she said. “So far buyers aren’t asking a lot of questions, although everyone is just sort of shocked by this. You have to get used to it before you take it all in.”
Jane Bickford, a Saranac Lake resident who has a summer home beneath and — she hopes — outside the projected path of the slide, said the mountain-climbing mecca of Keene Valley is more than an investment to people who own property there. “The piece that’s important is, Can we keep living there?” she said. “The financials are pretty terrible but Keene Valley represents to people a touchstone. It’s where my kids grew up and where they are bringing their own kids up. This is where children’s values are developed. To the people who go to Keene Valley it’s not just a house. It’s a place where families get together and where bonding happens.”
Photograph courtesy of Curt Stager.
Link to video of the landslide site.