EFFECTS OF GROUNDWATER ON SLOPE FAILURE IN THE STONY CLOVE BASIN, CATSKILL, NY

The Ashokan Reservoir provides 40% of the water for over 9 million residents of New York City and surrounding areas. In recent years the reservoir has seen an increase in suspended sediment, making the water more turbid and degrading the water quality. The Stony Clove Creek has been identified as the primary contributor of these sediments. The turbidity results from erosion of sediments along the banks of the creek, especially in areas of slope failure. The purpose of this research project is to evaluate the factors contributing to slope failure along the Stony Clove Creek. Methods of study have included periodic observation of the stream bank, Geographic Information System (GIS) mapping, and the installation and monitoring of piezometers within the site area. Hydrostatic pressure and the type of geologic materials within the stream bank both play a significant role in exacerbating slope instability. The study suggests that alternating beds of clay and sand - and the variations in structural strength and permeability that they incur – are influencing slope failure in the basin. The data also suggest a positive correlation between hydrostatic pressure and erosion, but further research may be needed before this claim can be properly confirmed or dismissed. This research and further research in this area may aid in the design of restoration projects along the stream and help to ensure the protection of water quality of the Ashokan Reservoir.