U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2013–3028

May 2013

Visualizing Flow Fields Using Acoustic Doppler Current Profilers 

and the Velocity Mapping Toolbox

Printed on recycled paper

Beyond Discharge

The purpose of this fact sheet is to provide examples of how the U.S. Geological Survey 

is using acoustic Doppler current profilers for much more than routine discharge 

measurements. These instruments are capable of mapping complex three-dimensional 

flow fields within rivers, lakes, and estuaries. Using the Velocity Mapping Toolbox 

to process the ADCP data allows detailed visualization of the data, providing 

valuable information for a range of studies and applications.

What Is an Acoustic Doppler Current Profiler and 

How Does it Work?

Much like a radar gun is used for determining the speed of 

a moving vehicle, the acoustic Doppler current profiler (ADCP) 

relies on the Doppler effect to measure the speed and direction of 

flowing water. The ADCP transmits pulses of sound at a known 

frequency into the water column along diverging beams (fig. 1). 

Particles being carried by currents reflect the sound back to the 

ADCP (much like a car reflects the radar gun signal). The ADCP 

receives the reflected sound using the same transducers that 

transmitted the original sound pulses and then analyzes these data. 

Changes in frequency of the sound returning to the ADCP are 

related to the speed at which each particle is moving (that is, the 

Doppler effect). Along with timing information, pitch and roll data, 

speed of sound estimates, and depth measurements, the ADCP uses 

sophisticated algorithms to measure a 3D velocity field based on 

information received from its four beams. The ADCP also records 

independent measurements of depth from each transducer for every 

sample. With the ability to sample several times a second, an ADCP 

provides a more efficient means of gathering detailed hydrodynamic data for studies within the U.S. Geological Survey (USGS).

The Velocity Mapping Toolbox (VMT)

The Velocity Mapping Toolbox (VMT) is a Matlab®-based 

software for processing and visualizing ADCP data collected in rivers or other bodies of water. VMT allows processing, visualization, 

and analysis of a range of ADCP datasets and includes utilities to 

export ADCP data to files compatible with ArcGIS®, Tecplot®, and 

Google Earth®. The software can be used to explore patterns of 3D 

fluid motion through several methods for calculation of secondary 

flows (Rhoads and Kenworthy, 1998; Lane and others, 2000). 

The software also includes capabilities for analyzing the acoustic 

backscatter and bathymetric data from the ADCP. A user-friendly 

graphical user interface (GUI) enhances program functionality and 

provides ready access to 2- and 3D plotting functions, allowing 

display and interrogation of velocity, backscatter, and bathymetry 

data. See Parsons and others (2013) for more information.

Figure 1. Schematic of a moving-boat acoustic Doppler current 

profiler measurement downstream from a levee breach on the 

Mississippi River near Cairo, Illinois. 

(Photograph by Robert Holmes, USGS)

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0 50 100 150 200 250 300 350 400

0

5

10

15

20

25

30

Bed Acoustic beams

Acoustic Doppler 

current profiler

Global positioning system 

(GPS) receiver

EXPLANATION

Slow

Water velocity

Fast
Mapping Depth- and Layer-Averaged Velocities

Spatial distributions of depth- and layer-averaged velocities 

are important when trying to understand large-scale circulation 

patterns in lakes and reservoirs. Because many lakes and reservoirs 

are thermally stratified for certain months of the year, a true 

understanding of the lake circulation requires an analysis of the 

currents on a layer-by-layer basis. VMT allows users to extract, 

average, and visualize velocity data from any user-defined layer of 

interest. In doing so, the user may find very different circulation 

patterns above and below the thermocline (fig. 2). These patterns 

may not be apparent when averaging data over the full depth of 

flow. 

In unstratified water bodies, such as rivers and well-mixed 

lakes, depth-averaged velocities can provide valuable information 

about flow structure, shear, and interaction of the flow with the 

bed, banks, and structures. Such interaction is evident in figure 3 in 

which the alongshore currents in Lake Erie interact with shoreline 

structures to produce a large zone of recirculation that traps inflow 

from a tributary (and the constituents transported therein) along a 

beach front. Circulation patterns are often hidden in the noise of the 

data, but the averaging routines in VMT reduce the noise and allow 

these patterns to be seen. VMT allows depth- and layer-averaged 

velocity data to be exported in a georeferenced format for direct 

comparison to output from hydrodynamic models or for inclusion 

in analyses using geographic information systems (GIS).

UTM NORTHING (meters) 4445000

 4445500

 4446000

 4446500

 4447000

0.07

0.13

0.20

0.26

0.33

0.39

0.46

0.52

UTM EASTING (meters)

345000 345500 346000 346500 347000 347500 348000

 4445000

 4445500

 4446000

 4446500

 4447000

0.03

0.07

0.10

0.13

0.16

0.20

Layer-averaged velocity (vectors), in feet per second

Surface-water temperature, in degrees Celsius

22.2 26.2

Near-Surface Water 

(0 to 8.2 feet depth)

Deep Water 

(8.2 to 25 feet depth)

Figure 2. Layer-averaged currents showing the thermal plume from a 

nuclear powerplant in one section of Clinton Lake, Illinois, a 5,000-acre cooling 

reservoir, October 6, 2008. Note the opposing currents in the two layers.

UTM Easting (meters)

UTM Northing (meters)

451500 452000 452500 453000 453500

 4603200

 4603400

 4603600

 4603800

 4604000

 4604200

 4604400

 4604600

 4604800

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Depth-averaged velocity (vectors), in feet per second

L a k e E r i e 

General circulation of 

Euclid Creek water

Alongshore Current

Euclid 

Creek

V i l l a A n g e l a B e a c h

20

25

10

10

20

25

18

16

14

12

18

16

14 12

Start Survey

08:26

End Survey

11:17

Euclid Creek

Specific conductance 

0.851 to 0.894 mS/cm

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

 ́

Specific conductance, in millisiemens

 per centimeter (mS/cm)

Combined sewer overflow (CSO)

permit point

EXPLANATION

8 Survey cross section

Bathymetric contour, in feet

0.298 – 0.299

0.299 – 0.300

0.300 – 0.301

0.301 – 0.302

0.302 – 0.303

0.303 – 0.304

0.297 – 0.298

N

0 850 1,700 FEET

0 100 200 300 400 METERS 

425

Figure 3. Depth-averaged currents and distribution of near-surface specific conductance in coastal Lake Erie in the vicinity of Villa Angela Beach 

and Euclid Creek, Ohio, on September 11, 2012. Produced in VMT using data from an ADCP and supplementary specific conductance data from an 

autonomous underwater vehicle that completed a simultaneous 3D survey.
White River

Wabash River

Figure 4. Depth-averaged velocity and primary and secondary velocities (Rozovskii definition) in the confluence of the White and Wabash Rivers along 

the Illinois and Indiana border, January 12, 2008. Produced in VMT using data from an ADCP and additional formatting using a graphics design program.

Mapping Primary and Secondary Circulation 

Patterns in Rivers

Velocities oriented perpendicular to the streamwise, or 

primary flow, direction are called secondary velocities and are 

important for understanding sediment transport and mixing in 

rivers. VMT computes primary and secondary velocities using 

several conventions (Lane and others, 2000) and allows users to 

easily switch between conventions. Some conventions, such as 

the Rozovskii definition, are generally best suited for bifurcations 

and confluences (fig. 4), while others like the “zero net secondary 

discharge” definition are best suited for meander bends (fig. 5). 

VMT allows users to place secondary flow vectors atop a contour 

variable, such as primary flow velocity or acoustic backscatter, 

for analysis.

Distance, in feet

Depth, in feet

2.8

0 500 1,000 1,500

0

5

10

15

100

110

120

Secondary velocity, Wabash River

in feet per second Cutoff water Plunging of high

suspended sediment

water Secondary circulation

Meander cutoff channel Main channel

Acoustic 

backscatter,

 in decibels

25

B

E E’

Figure 5. (A) An overview image of the Wabash River and a developing meander cutoff channel from June 2008 and (B) Acoustic backscatter (surrogate 

for suspended sediment) overlaid by secondary flow vectors at the confluence of the Wabash River and the cutoff channel, January 7, 2009. Produced 

in VMT using data from an ADCP and additional formatting using a graphics design program. Secondary flow vectors computed using the “zero net 

secondary discharge” definition.

Bathymetry From an ADCP

Each of the transducers of an ADCP serves as a single beam 

echo sounder and provides an independent measurement of the 

water depth. VMT allows the bathymetry data to be averaged 

to form a single representative bed profile at each cross section 

(fig. 6) or exported as individual point data from each transducer 

(corrected for heading, pitch, and roll). These data can be useful 

for understanding the morphology of a river or for developing 

hydrodynamic models.

Figure 6. Screen shot of average bed profiles through the confluence 

of the Wabash and Embarras Rivers, May 23, 2006, visualized in 3D in 

Google Earth®. Google Earth® KMZ files were exported from VMT (each 

section is an average of four transects collected with an ADCP).

Wabash River

Ohio

River

Cutoff channel

Cross section 

shown below

E

E’

0 3,000 FEET

0 800 METERS

Flow

Flow

Flow

A

Wabash River

Embarras

 River

Flow

Average bed profile

(from ADCP data; lifted out of the image plane)

Flow

Confluence scour hole
Utilizing a Geographic Information System (GIS) 

Framework for ADCP Data

Studies in natural and environmental science often require a 

cross-disciplinary approach and integration of geological, hydrological, hydrodynamic, biological, and meteorological datasets into 

a common framework for analysis. Because of the general spatial 

heterogeneity of these datasets, the GIS framework is often used 

due to its ability to handle georeferenced data from a variety of 

sources. Because many biological and morphological processes in 

surface-water bodies depend on currents, it is important that ADCP 

data be readily accessible to the GIS community. Using a standalone utility, VMT allows users to extract depth- or layer-averaged 

ADCP data to a GIS-compatible format for easy import into GIS 

software packages. Accessible data include not only 3D water 

velocity but also individual depth soundings from each ADCP 

transducer, acoustic backscatter (high backscatter can be correlated 

with high suspended sediment), and surface-water temperature 

measured using the thermistor in the head of the ADCP (see fig. 2). 

To reduce uncertainty of the data and provide a clearer representation of the flow, the VMT utility allows temporal averaging. Data 

input into this utility need not be transect based and can include, 

for example, streamwise profiles of rivers (Murphy and Jackson, 

2013), serpentine surveys of a reach (fig. 7) or water body, or a 

series of stationary at-a-point measurements.

A B C D

1.9 – 2.2

2.2 – 2.5

2.5 – 2.8

2.8 – 3.2

3.2 – 3.5

3.5 – 3.8

3.8 – 4.1

4.1 – 4.4

4.4 – 4.7

4.7 – 5.1

5.1 – 5.4

5.4 – 5.7

5.7 – 6

6 – 6.3

88 – 89

89 – 91

91 – 92

92 – 94

94 – 95

95 – 97

97 – 98

98 – 100

100 – 101

101 – 103

103 – 104

104 – 106

106 – 107

107 – 109

109 – 110

C. Depth-averaged velocity,

 in feet per second

EXPLANATION

D. Acoustic backscatter,

 in decibels

B. Water depth

Shallow

Deep

A. Shiptracks

0 1,800 FEET

0 500 METERS

wing 

dike

Flow

Figure 7. A 3-mile reach of the Mississippi River near St. Louis, 

Missouri, showing (A) survey shiptracks, (B) multibeam bathymetry, 

(C) depth-averaged velocity, and (D) acoustic backscatter. Data collected 

November 2–3, 2010, with an ADCP (127,000 samples averaged over 

20-second intervals). Note the acceleration of the flow in response to 

channel training structures and the associated increase in backscatter 

due to sediment resuspension. Evidence of the flow response to 

bedforms is also present.

Additional Examples of Applications of VMT and 

Similar Software

Find more examples, learn more about VMT, and download 

the program at http://hydroacoustics.usgs.gov/movingboat/VMT/

VMT.shtml.

Studies of Particular Interest:

Czuba, J.A., Best, J.L., Oberg, K.A., Parsons, D.R., Jackson, P.R., Garcia, 

M.H., and Ashmore, P., 2011, Bed morphology, flow structure, and 

sediment transport at the outlet of Lake Huron and in the upper 

St. Clair River: Journal of Great Lakes Research, v. 37, p. 480–493. 

Dinehart, R.L., and Burau, J.R., 2005, Averaged indicators of secondary 

flow in repeated acoustic Doppler current profiler crossings of bends: 

Water Resources Research, v. 41, 18 p. 

Acknowledgments

The author wishes to thank Kevin Johnson (U.S. Geological 

Survey), Jim Best and Bruce Rhoads (University of Illinois at 

Urbana–Champaign), and Dan Parsons (University of Hull, UK) for 

contributing data to this publication.

References Cited

Lane, S.N., Bradbrook, K.F., Richards, K.S., Biron, P.M., and Roy, A.G., 

2000, Secondary circulation cells in river channel confluences: 

Measurement artefacts or coherent flow structures?: Hydrological 

Processes, v. 14, no. 11–12, p. 2047–2071. 

Murphy, E.A., and Jackson, P.R., 2013, Hydraulic- and water-quality data 

collection for the investigation of Great Lakes tributaries for Asian carp 

spawning and egg-transport suitability: U.S. Geological Survey Scientific Investigations Report 2013–5106, 30 p. 

Parsons, D.R., Jackson, P.R., Czuba, J.A., Engel, F.L., Rhoads, B.L., 

Oberg, K.A., Best, J.L., Mueller, D.S., Johnson, K.K., and Riley, J.D., 

2013, Velocity Mapping Toolbox (VMT): A processing and visualization suite for moving-vessel ADCP measurements: Earth Surface 

Processes and Landforms, online Early View, 17 p., DOI: 10.1002/

esp.3367.

Rhoads, B.L., and Kenworthy, S.T., 1998, Time-averaged flow structure in 

the central region of a stream confluence: Earth Surface Processes and 

Landforms, v. 23, p. 171–191. 

Front page banner imagery: Visualization of flow (vectors) and acoustic backscatter (contours) in the Rio Paraná, near Santa Fe, Argentina, on September 18, 2009. High backscatter 

(red) can be correlated with high suspended sediment, and banner shows an ejection of 

sediment from the bed (red plume) as flow separates in the lee of a dune and the subsequent 

formation as a “boil” on the river surface. 

Front page boat photograph: Manned boat equipped with an ADCP and differential GPS 

receiver. The bow mount is stowed in the horizontal position for transport and is rotated to 

the vertical position for measurement. Photograph by Paul Baker, USGS.

Any use of trade, product, or firm names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

P. Ryan Jackson, Hydrologist 

U.S. Geological Survey, Illinois Water Science Center

pjackson@usgs.gov

For information contact:

U.S. Geological Survey, Office of Surface Water

415 National Center, Reston, VA 20192

(703) 648-5301, http://hydroacoustics.usgs.gov