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