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Other Surrogates for Sediment

Other Surrogates for Sediment. by Jim Selegean, Ph. D., P.E., P.H. U.S. Army Corps of Engineers Great Lakes Hydraulics and Hydrology Office. What is a Sediment Surrogate?. The measurement one thing in order to make an inference of another thing: Temperature of the room

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Other Surrogates for Sediment

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  1. Other Surrogates for Sediment by Jim Selegean, Ph. D., P.E., P.H. U.S. Army Corps of Engineers Great Lakes Hydraulics and Hydrology Office

  2. What is a Sediment Surrogate? • The measurement one thing in order to make an inference of another thing: • Temperature of the room • Leaving the lecture room • Stage for precipitation

  3. Sediment Surrogates • Differential Pressure • Impact Sensor/Geophones • Hydrophones • Optical Backscatter (OBS) • Laser Diffraction

  4. SSC by Density Difference Method Rio Puerco near Bernardo, New Mexico

  5. Hydrophones and Geophones Hydrophone Geophone • Senses Vibrations • Underwater microphone – listens passively for sound • More sensitive – can pick up nearby traffic • Senses Vibrations • Geophone needs to be struck to record the sound • Less sensitive

  6. Continuous Bed Load Monitoring by Impact Sensors Accelerometer Geophone Hydrophone Sedimentation and River Hydraulics Group Bureau of Reclamation, Technical Service Center Denver, CO

  7. Aerial photo after weir installation on Elwha River near Port Angeles, Washington

  8. After repair, Sept. 2009

  9. Diagram of impact sensor configuration

  10. Hydrophones Source: BoR This technique is still in its infancy. Lab (flume) tests and field tests continue to resolve this field: - Initiation of motion - Bedload transport rate (m/T) ? - Gradation ?

  11. Optical Backscatter (OBS) • Light directed at sample will backscatter if SS is present • Empirical calibration is used to calculate concentration • Readily available and inexpensive

  12. Laser Diffraction and LISST Technology Source: Mark N. Landers

  13. Diffraction – the apparent bending of light around an object. Diffraction occurs with all waves, included sound waves, water waves and elecromagnetic waves (laser). Light Diffracting Around a Particle Water Wave Diffraction Source: Johnvagabondscience.com Particle and wavelength need to be comparable

  14. LD Technology Basics • All LD technology provides PSD and Concentration of an ensemble of particles • ‘A view in a flash’ • LISST and all other LD instruments gives a volumetric measure of SSC, NOT a mass measure of SSC.

  15. 3 Types of Laser Diffraction Devices Benchtop Streamside In situ Source: ga.gov.au Source: Selegean Source: Sequoia Source: Selegean Source: Selegean

  16. Laser Diffraction • Gives real-time particle size distribution • Gives real-time SSC (volumetrically) • Temperature sensitive

  17. USACE PICS (Particle Imaging Camera System) Source: Smith - USACE

  18. Spherical Dia Orientation Major/Minor Axis Image Analysis • Parameters measured • Settling Velocity • Size (to 30 um) • Orientation • Can be deployed from vessel, hydrofoil or fixed Source: Smith - USACE

  19. ISSDOTv2: ERDC has developed a method for computing bedload from sequential bathymetry measurements. Difference Plot showing scour (red) and deposition (blue). Bedload transport can be computed from these plots using ISSDOTv2 Missouri River, Nebraska City Site, raw bathymetric data. At least two sequential swaths are needed.

  20. Questions?? Jim Selegean, Ph.D., P.E., P.H. USACE – Detroit District 477 Michigan Ave Detroit, MI 48226 313.226.6791 James.p.selegean@usace.army.mil

  21. www.streamsidesystems.com

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