Work in Stony Clove Creek may help with flooding, turbidity

The “Bowl of Doom” is under assault by heavy equipment. A portion of this problematic stretch of the Stony Clove Creek in Chichester is being modified to protect roads and properties from flooding, and one project is expected to be completed this week. The Shandaken town board has approved a resolution to seek bids from contractors for two more projects along the creek, addressing issues of flooding and turbidity that have had impacts as far downstream as Phoenicia’s Main Street and the lower Esopus Creek.

The stream modifications are a result of planning by the Shandaken Area Flood Assessment and Remediation Initiative (SAFARI), a group that has been working since the 2010 floods to devise methods of flood protection throughout the town. The group includes representatives from the Town of Shandaken, New York City Department of Environmental Protection (DEP), New York State Department of Environmental Conservation (DEC), Ulster County Soil and Water Conservation District (UCSW), Ulster County Department of Transportation, and Cornell Cooperative’s Ashokan Watershed Stream Management Program (AWSMP).

The project that’s nearing completion is estimated to cost $775,000, said Cory Ritz, Stream Project Manager for UCSW. Funding will be provided by National Resources Conservation Service (NRCS), part of the U.S. Department of Agriculture. The NRCS covers 75 percent of repairs due to declared emergencies, and the AWSMP, funded by New York City, will pick up the rest of the tab, said Ritz.

“I know people get frustrated with the city,” he commented, “but I don’t know how else we could have paid for this.”

As the Stony Clove Creek tumbles down the valley alongside Route 214, it has carved out steep slopes of clay and rubble that wash into the watercourse during storms, explained Ritz. The rocks and pebbles are carried along until they reach Phoenicia’s Main Street bridge, where the flatter topography and backwash from the junction of the Esopus Creek cause the rubble to fall to the stream bottom, raising the stream bed and contributing to three instances of flooding on Main Street over the past two years.

Dredging in the area of the bridge has deepened the channel in an effort to prevent future floods, but the channel will fill up quickly unless measures like the projects now underway can reduce the amount of rocky material sent downstream in high water events.

The stream modifications now being made just below Silver Hollow Road involve creating a gentler slope down to the water. The new slope will be planted with vegetation to further stabilize the bank and reduce the amount of material being washed into the water — including the clay that makes the Esopus creek run brown for weeks after a storm.

The remediation may even affect the recent battles between the DEP and Ulster County over the muddy water that has been siphoned off into the lower Esopus Creek from the Ashokan Reservoir. The DEP says its needs to dump the turbidity in order to protect New York City drinking water, but residents of Saugerties and the Town of Esopus say their creek and streambank properties are being ruined. One major source of the turbidity is the eroding clay banks of the Stony Clove, which should be reduced by the stream modifications.

The natural process of a stream is to change course, deepening and spreading at different points, as storms bring extra water down the mountain. This natural action creates problems for the humans settled along the banks, as the rushing water undercuts roads and properties where houses have been built. In the past, riprap was the main remedy for firming up banks, but big rocks can have unintended negative impacts up and downstream. In recent years, engineers have devised other methods for stopping erosion.

“We’re preventing the stream from cutting into the bottom of the channel,” said Ritz. A deepened channel runs faster, making a greater impact as the water hits the S-curves of the stream and undermines the banks.

In an attempt to stabilize the stream bottom and the banks, structures have been put into place such as partially buried root wads that deflect impact on the banks, and arrangements of rocks called “vanes,” carefully placed to direct water flow away from banks and slow its course along the center of the stream.