1. SS Load = Discharge * SS Concentration
Acoustic Backscatter as a Surrogate for Suspended Sediment Concentration
Measure Acoustic backscatter (ABS) and velocity with uplooking acoustic Doppler current profiler (ADCP)
Relate ABS to SSC
Develop index-velocity rating
ADCP
Hudson is tidal 150 miles so we can’t use conventional methods to measure SS Load
Use a relatively new application of existing technology - ABS as surrogate for SSC
Measure ABS with ADCP
ABS is a measure of the how “loud” the returning echo of the ADCP is.
Use ADCP to measure ABS and vel, develop an ABS – SSC rating and a V – Q rating
Combine these two to compute SS Load
For this project, have deployed an uplooking ADCP near Poughkeepsie in 60 ft of water, make a measurement every 15 min.
Limitations, computations?
SS Load = Discharge * SS Concentration

2. Suspended Sediment Data Collection
We use a fairly unique data collection to develop the ABS-SSC rating
We collect a point water sample with a P-61 at the same time as we make an ADCP measurement, correlating to a single bin at the same depth

3. Suspended Sediment Rating
ABS and water temperature contribute to rating
Slight cross-sectional variability which we account for (box coefficient)
Uplooker more representative at high flows (coef~1)

4. Discharge Rating and Verification Measurements
Uplooker velocity and wind stress contribute to the rating
Rating formed using “standard” boat-mounted ADCP measurements (only one transect per meas because of rapidly changing conditions
Measurements not contributing to the rating show that we’re generally within 10-15%
For more information go see poster session or acoustics ii