Analysis of the Bank Assessment for Non-point Source Consequences of Sediment (BANCS) Approach for the Prediction of Streambank Stability and Erosion along Stony Clove Creek in the Catskills

New York City's Ashokan Reservoir provides much of the drinking water for the New York metropolitan area. Storm events occasionally increase reservoir suspended sediment to levels that exceed the regulatory limit. As a result, reservoir discharge must be treated with aluminum sulfate. Streambanks within the Stony Clove Creek subbasin were thought to be a significant source of suspended sediment during these storm events. Twenty-seven bank erosion monitoring sites (BEMS) were established on the Stony Clove Creek by the Green County Soil and Water Conservation District (GCSWCD) in 2001. Stream cross-sections were surveyed and the Bank Assessment for Non-point source Consequences of Sediment (BANCS) model was used to assess streambank erosion and predict future erosion at each BEMS.;The BEMS cross-sections were resurveyed in 2012 by Syracuse University in order to assess erosion and the validity of the BANCS model in predicting streambank stability and erosion along the Stony Clove Creek. Single-factor analysis of variance comparing erosion potential revealed that there was a significant difference between the eroded areas of moderate, high and very high risk streambanks at a 90% confidence level. Plots of mean lateral erosion and eroded area as a function of near bank stress (NBS) gave a positive relationship for high/very high erosion potential bank erosion monitoring sites, with R 2 values of 0.3453 and 0.3726, respectively. These R 2 values demonstrate a correlation between streambank erosion and NBS, but with a poor fit. Net streambank erosion at the BEMS was determined to be responsible for less than 3% of the total estimated suspended sediment flux from the Stony Clove subbasin. While some BANCS variables correlate with streambank erosion, current results are not conclusive enough to predict future streambank erosion along the Stony Clove Creek.