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Radars Pointing Rivers Water Surface Velocity & Bed Profiling

Radars Pointing Rivers Water Surface Velocity & Bed Profiling. OUTLOOK. Following monitoring practice in ocean and atmosphere  river monitoring moves toward remote sensing practices

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Radars Pointing Rivers Water Surface Velocity & Bed Profiling

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  1. Radars Pointing RiversWater Surface Velocity & Bed Profiling

  2. OUTLOOK • Following monitoring practice in ocean and atmosphere  river monitoring moves toward remote sensing practices • USGS has put forth a team (Hydro 21) for remote, non-contact, river monitoring to replace the over 7,000 stream gages • Remote sensing might revolutionize the current multi-task (discharge – velocity – depth - slope) river monitoring practice • Intensive and extensive developments needed to overcome practical implementation

  3. MEASUREMENT CANDIDATES Wave-based techniques: electromagnetic radiation and sound (magnetic and pressure waves): radars, image velocimetry, sonars http://www.geocities.com/kbachhuber2000/ems.html http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html

  4. RADARS • Most extensive tested so far for riverine environment • Wavelenghts from microwaves to radio waves • Doppler (coherent) or non-Doppler systems • Various configurations • Measurement objectives: • free-surface velocities • bathymetry • stage

  5. OPERATING PRINCIPLE • Velocity: Bragg scattering • Issues: • what represents v? • how to relate v to velocity in the water column? • how to get the proper free-surface wavelength (only one detected for a given radar wavelength) KOWACO

  6. OPERATING PRINCIPLE • Configurations: Monostatic (same antenna for emission and reception) • Scanning strategy • Assumptions: • Velocity constant over spot • Streamwise direction known

  7. OPERATING PRINCIPLE Configurations: Bistatic (distinct antennas)

  8. RADARS: PROs & CONs

  9. OPERATING PRINCIPLE • Ground Penetrating Radar (GPR) for Bathymetry: reflection of pulsed high-frequency electromagnetic waves • Issues: • Site specific f(surface and subsurface permittivity) • Performance f(speed of sound in the measured media, reflectivity, depth of investigation, resolution, interferences, calibration) http://fate.clu-in.org/gpr.asp?techtypeid=41

  10. GP RADARS: PROs & CONs

  11. SELECTED RADAR CONFIGURATIONS & MEASUREMENTS • Microwave Water Surface Current Meter (KOWACO) • UHF RiverSonde Radar (CODAR) • Ground Penetrating Radars (MALA GeoScience AB) • Flo-Dar (Marsh-McBirney Inc.) DEMO

  12. Microwave Water Surface Current Meter (MWSCM-KOWACO)

  13. MWSCM SPECIFICATIONS • Detection Method : • Microwave, Doppler effect • Frequency : 10 GHz • Measurement Range : 0.5~10m/s • Measurement Angle : • Vertical : 20 ~ 45° • Horizontal : 0 ~ 10° • Weight • Antenna : 4.9Kg, Signal processor : 4.2Kg

  14. MWSCM VERIFICATION Korea Institute of Construction Technology

  15. MWSCM MEASUREMENTS Daechung Dam

  16. RIVERSONDE RADAR Transmitter Receiver Barrick et al. (2003)

  17. GPR USGS Measurements with MALA GPR Haeni et al. (2003)

  18. DEMOFLO-DAR (Marsh-McBirney Inc.) Doppler 24 GHz radar • http://www.marsh-mcbirney.com/classes/flo-dar_technology/

  19. DEMOFLO-DAR (Marsh-McBirney Inc.) Instrument control: FFT of the Doppler shift • Output: channel discharge

  20. VALIDATIONFLO-DAR (Marsh-McBirney Inc.) • Best measurements: continuous foam layer (errors up to 10 %) • Good results: floating particles (2-3 mm diameter) • Poor results: controlled waves (errors up to 40%) • Not reliable: natural free surface waviness and lower than 0.5 m/s

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