U.S. Geological Survey Office of Surface Water

Partnership to Develop ADCP Standards ERDC Coastal and Hydraulics Laboratory USGS Office of Surface Water

ADCP 101 ADCP Conventional current meter Depth Cell ADCP’s can be deployed from a boat or mounted on the streambed. This particular graphic shows an upward looking ADCP mounted on the stream bed. We mentioned the the ADCP measured a complete velocity profile. It is comparable to having a whole string of velocity meters deployed. It measures the velocity in discrete water layers by range gating the reflected acoustic energy. In other words it processes small parts of the entire echo individually thus producing multiple velocity measurements. The water layer is frequently referred to as a depth cell or bin. A measurement consisting of a single ping (burst of acoustic energy) can be made in less than a second. Typically a single profile measurement consist of several pings averaged together. Still the typical time for a profile measurement is 3-5 seconds.

Why ADCPs allow unprecedented data collection capabilities ADCPs can collect inaccurate data if misapplied USGS are using ADCPs in their operational program

Corps Data Collection Effort

Flow Homogeneity HOMOGENEOUS NONHOMOGENEOUS Remember the Doppler shift is directional. The ADCP can only measure velocity parallel to the beams. To be useful we need to resolve those radial velocities into horizontal and vertical components. To do this, the assumption is made that all 4 beams are measuring a homogeneous volume of water. Remember the instrument is looking at four beams not the entire volume of water contained inside the boundary of the four beams. What are the potential sources of error? A vortex or eddy in one beam Random errors The error velocity gives a an indication or the flow homogeneity and is an indicator of the validity of the assumptions used to compute the horizontal and vertical velocity components.

Corps Data Collection Effort

Heave, Pitch, Roll Heave => Vertical Velocity Pitch => Second Order Error Roll => Second Order Error

Unmeasured Top and Bottom The drawing shows the limitations of the measured velocity profile. Depth is lost near the water surface for the draft of the instrument and the blanking distance or dead band. All acoustic instruments have this dead band. It is the distance that sound travels while the ceramics of the transducer stop vibrating from having transmitted and reach a state that they can begin listening from a reflected acoustic energy. Near the bottom the side lobe of the acoustic energy reflects of the stream bottom creating reflected acoustic energy that is of the same magnitude as the reflection of the main lobe off the scatterers in the water column near the bed. For most riverine systems this is 6% of the depth.

Who CHL USGS Michael Winkler Thad Pratt Terry Waller David Mueller Chad Wagner Kevin Oberg

Recommendations I Field Data Collection Field crew needs to understand the use of the data Compass must be calibrated Slow boat speed Collect single ping data Field methods documented

Recommendations II Data Processing – ASCII Output Review every transect in WinRiver Set appropriate thresholds to filter data Account for side lobe interference Spatial averaging must use vector averaging Based on : Instrument noise Flow field Desired spatial resolution Account for unmeasured areas Data processing methods documented

Recommendations III Data Processing – Raw Data Files Must apply Boat speed Compass heading/corrections Side lobe interference Generally not recommended unless you fully understand raw data files.

Test Plan Deliverables What Test Plan Deliverables Technical Report on Discharge Measurements Technical Report on Velocity Measurements Processing Software (If Additional Funded) Quick sheets for Discharge Quick sheets for Velocity Note Sheets for Discharge Note Sheets for Velocity Quick Sheets for Velocity Processing

When Oct 2006 Deliverables: TechNote (Study Plan) Draft Discharge Sections: Introduction Predeployment Field Procedures Initiate Software Development (if funds are available). Feb 2007 TechNote on Field Notes for Discharge Quick sheets for Q measurements Jul 2007 Velocity Software (if funding available) Draft of remaining discharge report sections (less uncertainty) Oct 2007 Uncertainty method for discharge (tentative) Draft Discharge Measurement Guidance

POC’s USGS, Mr. Dave Muelller dmueller@usgs.gov Corps, Mr. Michael Winkler michael.f.winkler@usace.army.mil

Corps Navigation Mission Provide safe,reliable,efficient,effective and environmentally sustainable waterborne transportation systems for movement of commerce, national security needs, and recreation.

Lock and Dam 3 Barge sunk in dam gates August 1,1993 The outdraft current sweeps across the lock approach toward the gated part of the dam. This makes downbound navigation very difficult during outdraft conditions, and has caused many navigation accidents. Towboat pilots consider Lock and Dam 3 the most dangerous site on the upper river. Only 4 roller gates 11 into-dam accidents since 1968

No Flow Entering Lock Approach Outdraft ETL 1110-2-562 - Basham Outdraft is defined as the flow in the upper lock approach that cannot be passed under or through the guard wall, and thereby moves across the upper lock approach or around the end of the guard wall and towards the dam. The outdraft, if severe, tends to move the head (bow) of the tow out of alignment with the guard wall and requires that the pilot increase maneuvering. EM 1110-2-1611 The effects on currents due to structures placed in a river depends principally on the configuration and alignment of the channel upstream and downstream therefrom and the amount of contraction and expansion in channel width produced by the obstruction. The usual effect of the sudden channel contraction in the upper approach to the locks is an outdraft or crosscurrent that affects the movement of a tow at a time when its rudder power is reduced because of reduced speed with respect to river currents. The intensity of the crosscurrents is dependent on the total discharge affected by the structure and is a function of the velocity of currents approaching the structure, channel depth, and width of channel affected by the structure, and, in some cases, by flow along the adjacent overbank. Since no two reaches of a stream are identical, the intensity of the crosscurrents in the upper lock approach will vary according to the site selected and the orientation of the structures with respect to the alignment of the channel and currents. No Flow Entering Lock Approach

Tom Bevill Outdraft Outdraft Currents

Tom Bevill – Confetti Picture Can anyone locate the Outdraft Here?? Notice the Outdraft: Why we are here Upstream View of the Model

Bull Nose Guard Wall

H-ADCP Doppler Unit 3 – Beam ADCP

H-ADCP Mount H-ADCP Mounted

Separate Velocity Measurements - BINS ADCP Measurements Separate Velocity Measurements - BINS

Wind Meter

ADCP/Wind Control Station

Control Workstation

Current Vectors on IENC

Current Vectors on IENC