REAL-TIME MONITORING OF SUSPENDED SEDIMENT TRANSPORT IN THE UPPER HUDSON RIVER

The transport of suspended sediment in the upper Hudson River is very closely tied to hydrologic events in the many tributaries and sub-basins of this area of the river. Transport events are typically of shorter duration and have less attenuation than transport in the lower, tidal Hudson. We have recently explored the use of Acoustic Doppler Current Profilers (ADCPs) to monitor these transport events in "real time" using acoustic backscatter as a proxy for suspended sediment concentration. In the summer of 2004, we deployed ADCPs in the upper Hudson at Champlain Canal Lock 2 near Mechanicville, and in the tidal Hudson at Albany, approximately 10 miles downstream from the confluence with the Mohawk River. The high sampling resolution afforded by ADCP monitoring has revealed details of short-duration transport events in the upper Hudson, and has allowed us to study the onset of tidal attenuation just below the head of tide.

Discrete water samples collected from both the Albany and Lock 2 sites -- as well as a site on the Mohawk just above the confluence with the Hudson -- provide a daily time series of total suspended sediment concentrations (TSS) for calibration of the ADCP-derived acoustic backscatter intensity measurements. Preliminary calibrations indicate the utility and sensitivity of ADCP monitoring techniques in the upper Hudson, and point out the importance of post-freshet, event-driven transport. Daily TSS sampling also highlights the fact that between our two ADCP sites, the Mohawk River contributes the majority of sediment transported in the tidal Hudson.