West Kill Stream Restoration Project Phase I Stream Corridor Assessment Summary


	Greene County Soil & Water Conservation District West Kill Stream Restoration Project Phase I Stream Corridor Assessment Summary A Phase I assessment provides a rapid assessment of the overall stream corridor health and provides the basis for selecting sites for additional assessment and monitoring.


	In the Fall of 2000, District staff conducted a Phase I Assessment of the main stem of the West Kill Stream. To complete this assessment, the District uses a GPS unit during a stream walkover to locate and inventory Level I Rosgen stream types, as well as a number of other items related to the streams condition. The West Kill assessment team of Joel DuBois, Jake Buchanan and Amy DeGaetano walked the entire main stem, from the head of the valley to the confluence with the Schoharie Creek, over a two week period. The walk over allowed the team to observe existing stream conditions and to look for signs which may indicate stream instability. The team uses Global Positioning Satellites (GPS), later integrated with a GIS platform, to inventory actively eroding streambanks, stream bed incisement, channel aggradation, obstructions, high slope failure and other items. The GPS inventory is also used to locate any evidence of past stream work such as cribbing, riprap and channelization activities and photo points are set up for monitoring the streams features.


	West Kill: The Problems Based on general observation of GCSWCD staff over the past 12 years, as well as observations made during the Phase I Assessment process, it has been shown that the West Kill is experiencing several classic stream related problems. While the GCSWCD will be undertaking surveys and other monitoring in the spring to confirm these processes, a general description of these problems is provided here. In the West Kill stream corridor, one quickly notes that the stream is experiencing two primary problems. Aggradation: In stream systems, aggradation is the process by which a stream channel is built up and generally due to a stream reach losing its ability to transport its sediment load. In aggraded stream reaches, the stream is often characterized by multi-channels, which constantly shift during larger flow events. As the stream reach loses its ability to transport its bedload, the materials are deposited out and the stream becomes "built up". This often causes problems as the flood surface elevation can be raised and the constant shifting of the channel through the depositional materials can promote excessive streambank erosion on the outer banks of the stream In several areas, the West Kill is experiencing Aggradation. This is most notable in the lower Spruceton area above the NYS 42 bridge and in the broader section of the valley across from the Red Bear Inn. Aggradation is an indication that the streams morphology is not capable of moving bedload and deposition results in a stream channel subject to rapid horizontal shifts and excessive streambank erosion. Degradation: In other reaches of the West Kill, the stream has experiences some severe impacts from the process of down cutting, known as Degradation. Like most Greene County mountaintop streams, the West Kill generally has a shallow cobble or gravel streambed pavement, under laid by deep glacial lake clays. When the protection of this streambed cover is lost, either by a storm event or in-channel grading with heavy equipment, the clays are exposed to the erosive forces of the stream, and the channel quickly cuts deeper into the landform. When the streambed cuts into these clays, the results are significant destabilization of the adjoining streambanks as well as severe water quality problems. in significant water quality problems as well as destabilization of the streambanks as seen on CRT 6 with the slippage of the roadway. In some areas, degradation of the stream channel appears to be a major contributing factor to massive failures of the streambanks and the GCSWCD will soon be confirming these observations during the Phase II Assessment process.


	Aerial view of braided reach on the lower West Kill. Braided, multiple channels with excess depositions of loose gravel is characteristic of a stream channel that can no longer transport its sediment load


	As shown, this scour under Baker Road bridge is a good visual indicator of stream down cutting or degradation.


	When highly erosive glacial lake clays become exposed in the stream bottom, the channel is easily incised, or degraded by stream action .


	During the winter 2000-01, the GCSWCD will be reviewing the Level I Stream Assessment data and developing a Level II Assessment strategy which will involve extensive field measurements. The GCSWCD will use Level II assessment to monitor both stable and unstable sections of the stream.


	Slope failures such as this one on the lower West Kill (also picture at top of page) present not only a major water quality problem, but also results in serious destabilization of the stream in that area.


	Level I Assessment summary of specific stream reaches of the West Kill


	West Kill Project Directory West Kill Project Home Page Stream Classification Map Stream Stability Assessment Flood Mitigation Projects West Kill Photo Page Project Partnerships & Funding Stream Corridor Planning Stream Restoration Home GCSWCD Home


	Throughout the West Kill, there are numerous examples of past stream management activities that may have a negative impact on the stream system beyond the area of the work. While protection of property is an essential component of any stream management plan, the District will be working with landowners to address their stream stability concerns in a manner that will not promote additional instability.