DIRECT TSS MONITORING OF SHORT-DURATION TRANSPORT IN THE HUDSON RIVER

Short-duration hydrologic events in the upper Hudson and Mohawk River basins have great influence on the transport of suspended sediment downstream. In an effort to highlight and quantify the impact of such events, we have continuously monitored total suspended sediment concentration (TSS) at three sites: in the Mohawk River at Erie Canal Guard Gate 2, the upper Hudson River at Champlain Canal Lock 2, and in the tidal Hudson at Albany, downstream of the confluence with the Mohawk. These three locations enable us to characterize the event-specific influence of the Mohawk and major upper Hudson tributaries on total sediment loading to the tidal Hudson. We are also using our filter-based TSS data to calibrate Acoustic Doppler Current Profiler (ADCP)-derived measurements of acoustic backscatter for use as a site-specific TSS proxy.

The TSS data from this study reveal the importance of short-duration sediment transport events in the basin. For example, a single storm event in Fall 2005 accounts for roughly 20% of the total sediment transport in that year. We have captured similar significant, post-freshet events in each year since the study began in 2004. Furthermore, weight loss on ignition (WLOI) data suggest that the character of sediment from each basin often evolves over the course of a short-duration event as basin soils and bottom sediments are mobilized.

Our extensive data set underscores the importance of post-freshet events in the mobilization of sediment. These short-duration events are of great concern in the Hudson Basin, as hotspots of contamination exist in areas upstream of the tidal Hudson River.