Slip sliding away: Alta Sierra resident says tree cutting causes landslides
February 21, 2014
An Alta Sierra resident with a background in biology is charging that a vegetation management program administered by Nevada County is responsible for several landslides in the neighborhood.
Virginia Moran, who owns a Grass Valley-based environmental consulting business and who has worked for several state and federal agencies as a biologist, said the removal of trees from steep slopes in the Clover Valley area near Fay Road induced several minor, and at least one major, landslide events.
“About five years ago, when the county was doing brush clearing and tree trimming, I noticed a correlation between where they cut the trees and where the slopes were failing,” Moran told The Union as she stood beside Fay Road in the Clover Valley portion of Alta Sierra.
“I can take you to tons of locations where this is happening. There is at least over 50.”
Moran ascribed part of the problem to how the subdivision, which was built in the 1960s, was laid out, with roads cut steeply into the contours of the rolling landscape.
“They needed to make the slope more gradual,” she said. “The taxpayers have to pay to clean up these landslides.”
Moran is partially right, said Steve Castleberry, director of Public Works for Nevada County.
While Castleberry grants the correlation between vegetation management and landslides in theory, he said that in practice, the frequent slides result more from the soil.
“There are landslides all over the county, and I don’t know if it has much to do with the road construction as much as what is going on with the underlying soil,” he said.
In winter 2010, there were three major landslides in the county — the one on Fay Road that Moran pointed out, a major one on Augustine Road in the Cement Hill area of Nevada City and another one in South County off Allison Ranch Road, Castleberry said.
All told, the cleanup operations conducted by the county totaled $213,000 for the year, which was a particularly bad year.
However, it was not an anomaly, as Nevada County spent about $150,000 on repairing another landslide that compromised Allison Ranch Road in 2006, largely due to the weathered rock, groundwater seepage and possibility of underground tunnels, shafts and vents left over from the mining period.
In each case, the cleanup and repair was done by county crews, Castleberry said.
Moran said the county did “a nice job” on its cleanup operations on Fay Road but persisted in her assertion that money could be saved if the county took into account the gradient of a particular area before eradicating vegetation that helps stem erosion and stabilize soil.
Castleberry said vegetation management is necessary for three reasons: It helps enhance sight lines for motorists when attempting to take turns onto roadways, it prevents old trees from divesting their branches onto the roadways and vehicles during storm events and it helps provide a natural fire break should a wildland fire move through the area.
Moran said the elimination of trees near the roadway would do little to prevent flying embers from leaping across the roadway and urged the county to keep the public informed regarding upcoming vegetation management projects in the county.
“There is no communication between the residents and the county regarding the trees,” she said. “We don’t know where, when or why they are getting cut.”
Castleberry said the county right-of-way typically extends about 50 or 60 feet beyond the roadway and in all three instances of major landslides in 2010, the landslides began on private property.