Featured Project: Water Quality

Stony Clove - Warner Creek stream restoration project immediately after construction, fall 2014.

Stony Clove-Warner Creek stream restoration project immediately after construction.

 

The Stony Clove Creek-Warner Creek Confluence stream restoration project was constructed in 2014 in the hamlet of Chichester, NY to address erosion and stream stability concerns.  The project site is located at the confluence of Stony Clove Creek and Warner Creek and extends downstream ending before the Silver Hollow Rd. bridge.

This reach of of the stream is extremely steep – the slope is about 4%, and the channel is confined within the streambanks during high flow events. Over the years, fast flows had cut through the stream channel bottom, causing the stream banks to slump. Large cracks appeared in the banks, indicating the potential for mass failure. If left unchecked, bank erosion would threaten both Route 214 and Silver Hollow Rd.

History of the Site

According to the Stony Clove Creek Stream Management Plan, the project site was the historic location a railroad trestle for the Stony Clove and Kaaterskill rail line that began operations in 1883. Prior to this, the Warner Creek and Stony Clove valleys had been logged. Both activities probably impacted the  project site significantly. While the location of the stream channel remained fairly stable over time, the bed itself steadily eroded downward causing the adjacent banks to destabilize.

Between 1980 and 2000, rip-rap revetment (a lining of large rock) was placed on the stream’s right bank, which during the 1996 floods appeared to trigger severe erosion on the left stream bank where erosive flows were now concentrated. Afterward, the left bank was also rip-rapped. The Town, NYSDOT, and nearby landowners installed and repaired the rip-rap walls over the years. Still, about 1,366 feet of streambank was actively eroding by 2001 when the AWSMP conducted a stream feature inventory. At that time, 1,103 feet of banks were lined with rock revetment. Floods in 2010 further destabilized the stream bed and banks. Recent removal of an old abutment may have added to instability of the bed at the Stony Clove’s confluence with Warner Creek.

Stony Clove - Warner Creek Stream Restoration Project during construction, August 2014.

Stony Clove – Warner Creek Stream Restoration Project during construction, August 2014.

Stream Restoration

The Stony Clove Creek Stream Management Plan recommended full restoration of the site. Recommendations included installation of a series of large rock step and pool structures to control the stream’s grade and direct erosive forces away from the banks. Another recommendation was to install a floodplain bench between the active channel and eroding banks, and then stabilize the bench with tree and shrub plantings.

The construction firm Baker Brothers Excavating of West Hurley, NY was hired to install the series of large rock structures to prevent channel erosion. The structures look like rock “steps” found in steep streams throughout the Catskills. The engineering firm Milone & MacBroom, Inc (MMI) designed the project. MMI and the Ulster County Soil and Water Conservation District provided construction oversight.

To further stabilize the channel bed and prevent its erosion, thick metal sheet-piling was driven 10-23 feet into the ground with one of the largest excavator-mounted pneumatic hammers available. The piling was buried under native boulders and fill that restored the bed to a stable elevation. With the stream bed restored to a stable elevation, flows now access a small floodplain along the bank. The rock steps in the channel and floodplain absorb the energy of fast flows.

At project end, the stream banks and floodplain were re-vegetated with native trees and shrubs to hold any exposed soil and provide cover for migrating fish. Although this steep section of the Stony Clove is believed to provide limited habitat for fish, the construction crews observed large trout at the site.