CHARACTERIZING THE FLUVIAL GEOMORPHOLOGY OF A MOUNTAIN RIVER WATERSHED USING MULTI-SCALE METHODS

The New York City Department of Environmental Protection (DEP) ensures high quality water standards are met through watershed management and protection. Warner Creek is located within the Ashokan watershed in the eastern Catskill Mountains of New York, and has been identified as a contributor of sediment loading. The Ashokan Reservoir is the second largest source of water for New York City, making turbidity reduction a main goal for the DEP. During the SUNY New Paltz Research Experience for Undergraduates (REU) program, students collaborated with the DEP throughout the summer of 2010 to conduct a full stream assessment. Working from a regional, watershed scale down to a local, field scale, students identified locations and geomorphic processes contributing to turbidity in Warner Creek. At the watershed scale, remotely sensed data were used to delineate reaches, watershed boundary, stream corridor, and predict hydraulic geometry and stream profile of the entire 14.5 km of Warner Creek. Data included a ten meter digital elevation model, historic ortho-imagery, and the United States Geological Survey web-based program StreamStats. Possible anthropogenic influence was also documented by digitizing cleared land in ArcGIS. At the stream scale, major stream features were located and inventoried including large woody debris (LWD), bedform, fine sediment sources, bank erosion, revetments, culverts, and bridges along the length of the stream. Multiple cross sections were surveyed to measure hydraulic geometry at locations within the stream. LWD was found to entrain sediment and in some cases cause scouring. Vadose zone processes have influenced sediment loss along the channel banks; this has lead to hill slope failures which are a major contributor to turbidity in the system. Most of the geomorphic changes along the length of Warner Creek were located adjacent to cleared land. Understanding the controls on channel stability and locating fine sediment sources was achieved through the use of multi-scale methods. This information can be used further by the DEP to implement a stream management plan directed towards minimizing sediment loading in the Ashokan Reservoir.