LANESVILLE – A substantial source of fine sediment in the Stony Clove Creek has become the latest in a series of stream restoration projects constructed by the Ashokan Watershed Stream Management Program.
The project is located about a mile north of Lanesville in Greene County along State Route 214.
The Stony Clove Creek is the largest tributary to the upper Esopus Creek, which supplies water to the Ashokan Reservoir, a component of New York City’s drinking water supply.
Construction extends along 1,600 feet of stream length and will cost just over $2 million, making this one of the largest stream restoration projects completed in the Ashokan watershed.
The project is managed by the Ulster County Soil and Water Conservation District with funding and technical support from the NYC Department of Environmental Protection.
At the project site, the Stony Clove Creek channel has historically snaked from side to side across a shallow floodplain. The channel eventually shifted to the edge of a large hillslope of mixed sand, clay, and till soils. The escarpment began to slump and fail in dramatic fashion.
The site eventually became the largest producer of fine sediment in the Stony Clove Creek subbasin and rose to the top priority for treatment as part of New York City’s Filtration Avoidance Determination to maintain an unfiltered drinking water supply.
Fine sediments cloud drinking water and lead to additional treatment costs and health hazards. Fines can also deposit on stream bottoms and smother habitat for aquatic organisms.
Construction of the Stony Clove Creek stream restoration project began in June and will end by September 2022 if high flows don’t cause delays.
The design process for this project was complicated compared to other recent projects, according to SWCD Project Manager Adam Doan. “The fast water velocities combined with abundant sediment deposition made the design challenging. But the wider valley bottom at the site gave project designers more room to work when choosing a new channel alignment,” said Doan. Wider floodplains are hard to find in the region’s narrow and developed valleys.
The stream channel will be reshaped and relocated by project end. Grading will soften the steepest banks to arrest active slope failures. Instream rock riffles and large wood revetments will be installed to stabilize the channel bed and banks. These features naturally occur in Catskill streams and provide structure for fish habitat. The final important step will be to plant and restore native trees and shrubs to “bioengineer” long-term bank protection.
Previous studies have identified the Stony Clove Creek as the largest contributor of suspended sediment and turbidity to the upper Esopus Creek. But according to monitoring results published by the U.S. Geological Survey, the average amount of suspended sediment in stream flows has substantially decreased in the Stony Clove watershed since 2010 when a series of stream restoration projects began.
