Determination of stream discharge, hydrodynamics and sediment transport variation at the estuarine section of the Hudson River and Estuary, NY

Tidal forces play a dominant role in controlling the sediment transport and water quantity and quality changes along the estuarine section of the Hudson River and Estuary (HRE), NY-a system of major ecological and economic importance. We present concurrent hydrodynamic and acoustic backscatter data collected through the River and Estuary Observatory Network (REON), with Acoustic Doppler Current Profilers (ADCP) installed on both a moored platform and research vessel to quantify tidal effects on this section of the HRE. Using index-velocity method, the concurrent datasets captured over a tidal cycle were used to develop rating curves for continuous estimation of stream discharge as a function of the current velocity and river stage height. These rating curves were used to estimate discharges during another tidal cycle which are in good agreement with those measurements with the vessel mounted ADCP. This demonstrated the applicability of using moored-ADCP datasets to generate continuous real-time estimates of stream discharges using the rating curves. In addition, concurrent determination of bed shear stress from ADCP-measured current profile and measurements of suspended solid concentration provides evidence of periodic occurrence of tidal-driven sediment re-suspension events. Significant variability in water current over each tidal cycle including strong vertical gradient in current at peak ebb tide and bi-directional movement of water at slack tide were observed. These hydrodynamic and suspended sediment variability will have significant impacts on nutrient dynamics, sediment and contaminant transport, water quantity and quality variation along the estuary and so, ecosystem managers needs to consider the tidal effects for conservation and management of this valuable ecosystem.