HISTORIC CHANNEL CHANGE ON ESOPUS CREEK, UPSTREAM OF THE ASHOKAN RESERVOIR, CATSKILLS, NEW YORK

We studied historic channel change on Esopus Creek in the Catskill Mountains of New York, with the goal of gaining a better understanding of the stream's processes and their potential impacts to Ashokan Reservoir, part of New York City's drinking water supply system. Channel change was quantified through analysis of planform morphology interpreted from georectified aerial imagery from 1959, 1980 and 2001. Measured changes in channel width, sinuosity, channel index and meander migration were correlated with the hydrologic record from gaging stations with the goal of determining the influence of flood peaks and flow duration on channel processes. Channel index, a measure of anastomosis, increased 11.5% during the study period, providing evidence of a trend toward an anabranching planform along much of the creek. Measured changes in active channel width tied to bank erosion, bar deposition, vegetation encroachment on bar surfaces and the establishment and abandonment of secondary channels, exhibited a positive correlation with the timing, frequency and duration of peak and bankfull discharges. Calculated meander migration rates and the identification of dynamic stream segments with the potential to degrade water quality through fine-sediment loading provide important data for future stream management decisions.