Measuring Two-Dimensional Surface Velocity Distribution
using Two RiverSondes
Ralph T ChengCODAR OS and U. S. Geological Survey
Jon R. Burau and James DeRoseU. S. Geological Survey
Donald E. Barrick, Calvin C. Teague and Peter M. Lilleboe
CODAR Ocean Sensors
OutlineRadar Technology for Surface Velocity
RiverSonde System
Multi-Dimensional Channel Flows
Two-RiverSonde for Two-Dimensional Surface Velocity DistributionProof-of-the-Concept Experiments Threemile Slough Sacramento River at Georgiana Slough, CADiscussion of Results
RiverSonde System• UHF radar: 0.7-m radar wavelength (435 MHz)
• 3-yagi antenna system on bank
• Bragg scatter from 0.35-m wavelength water waves
• Doppler shift gives radial velocity, water phase velocity known from their wavelength
• Time delay (time-gating) gives distance
• MUSIC direction finding gives direction
• Estimate along-channel flow from radial velocity
• Straight channel: assume flow parallel to banks
• Complex geometry: calculate total vectors using 2 RiverSondes
Typical
RiverSonde
Deployment
River Mean Flow
Radar
Example of Radial Vectors
Sacramento River near Walnut Grove, CADelta Cross-Channel, Georgiana Slough
Concept of Two RiverSondesfor Two-Dimensional Surface
Velocity DistributionRadar line of sight
RiverSonde A
RiverSonde B
O
B
A
C
River Bank
OA = Radial Velocity A
OB = Radial Velocity B
OC = Total Velocity
Continuing Development of RiverSonde at Three Mile Slough
San Francisco Bay-Delta(Cooperation with California District)
Threemile Slough, California•Straight channel between Sacramento and San Joaquin Rivers in California Delta•Tidally-dominated flow•In operation for several years with a single RiverSonde•One day proof-of-the-concept experiment (21 February 2007) with 2 RiverSondes•Antenna interference?•Antenna patterns measured in field
RiverSondes at Threemile Slough
North South
Velocity Time-series at TMS
Threemile Slough High Velocity
02/2119:30 GMT
02/2200:30 GMT
Threemile Slough, just Before Slack
Threemile Slough, just After Slack
BASIC FINDINGS:• Two-RiverSonde operating in close proximity
does not have interference issues
• Total vectors are generated with same software used in SeaSonde for ocean currents
• 5- or 10-m grid spacing
• Manual masking of river banks
• Observed complex flow pattern during tidal reversal
Proof-of-the-Concept II: April 23-25, 2007Sacramento River at Georgiana Slough, CA
• Tidally-influenced flow• Flow patterns affect fish migration• 2 RiverSondes
• 1.5 days with units on same bank
• 0.5 day with units on opposite banks
• Antenna patterns measured with a transponder on a boat
• USGS measurements• Boat-mounted ADCP transects every 30 min for 12 hours
• Four Flow Stations in the region
Two-RiverSonde Experiment for 2D Velocity Mapping
Proof-of-the-concept atGeorgiana Slough
View From Levee Site
Georgiana Slough
Sacramento RiverDWRG
LVEG
Data Coverage
Preliminary Results: Same Bank
Preliminary Results: Opposite Bank
Slack or reversal: Case 1
Slack or Reversal: Case 2
ADCP, USGS 2-RiverSonde, CODAR
Preliminary Results: April 24, 2007 13:06
ADCP, USGS
Numerical Hydrodynamic Model
B.C. specified
B.C. specified
B.C. specified
Model results compared
Model results compared
DCC Closed
Implementing a Detailed Numerical Model
Implementing a Detailed Numerical Model
•2-RiverSonde operation works well• Both units on same bank or on opposite bank
•Total vectors generated with same software used with SeaSonde for ocean currents
•Unfortunately ADCP transects did not overlap with the complex flow patterns observed by 2-RiverSonde
•Mistakes in the current experiment lead to a better design of the next experiment
•Further experiment and Comparisons with in-situ data and numerical model underway
Preliminary Conclusion
