A NEW METHOD FOR MEASURING THREE-DIMENSIONALFLOW STRUCTURES AROUND RIVER BANK USING ADCP
Masaru Koshiishi1, Tatsuhiko Uchida2 and Shoji Fukuoka3

ABSTRACT
Detailed mapping of velocity using Acoustic Doppler Current Profiler (ADCP) mounted on a sliding
platform was carried out around a revetment in the experimental meandering channel constructed inthe Jyoganji River. To measure detailed velocity distributions around revetments using ADCP, wedeveloped a new method to improve the low spatial resolution of the conventional method by using
individual beam data of different directions. We demonstrated the accuracy of the new method
through the comparison with velocity distributions measured by the Electromagnetic Current Meter(ECM) in the Asa River. Results indicated that the new method was reliable to understand three
dimensional flow structures in flow attacking zones with steep velocity gradients and local scouring
around revetments.

1.

INTRODUCTION

Revetments are constructed to protect the bank against the erosion. However, they also tend to cause
severe bed scouring along revetments (Osada et al., 2007). One of the authors has developed naturefriendly bank protection works using natural bars protected with large stones in flow attacking areasof the Jyoganji River (Fujimoto et al., 2010). It is necessary for a reliable bank protection, not only
to reveal flow structures around river constructions, but also to develop a calculation method thatcan reproduce these flows. Uchida and Fukuoka (2012) proposed a new depth integrated model that
calculates three-dimensional flow structures by using depth integrated vorticity equations without
the assumption of the shallow water flow. However, very few data of detailed velocity distributionsin actual flood scale flows have been measured for the validity check of models and understanding
three-dimensional flow structures. For example, because of large hydrodynamic forces acting on theprobe of an anemometer at deep water or high velocity conditions, it is difficult to measure velocity
distributions in flows attacking on revetments by an anemometer which measures by means of asingle point such as an ECM. Recent advancements in ADCP measuring vertical velocity
distributions from the water surface have provided the means for measuring flood discharge andvelocity distributions (Nihei et al., 2008). But some studies have revealed that measuring errors
could be seen in the steep bank of the cross-section, because the ADCP measurements are conducted1
Graduate Student, Graduate School of Science and Engineering, Chuo University,
1-13-27 Kasuga, Bunkyo-ku, Tokyo, Japan, 1-13-27 (masaru-k@civil.chuo-u.ac.jp)
2
Associate Professor, Research and Development Initiative, Chuo University,
1-13-27 Kasuga, Bunkyo-ku, Tokyo, Japan, 1-13-27 (utida@tamacc.chuo-u.ac.jp)
3
Professor, Research and Development Initiative, Chuo University,
1-13-27 Kasuga, Bunkyo-ku, Tokyo, Japan, 1-13-27 (sfuku@tamacc.chuo-u.ac.jp)

by averaged beam data from four transducers in different directions (Nihei et al., 2008, Gunawan etal., 2010). On the other hand, Detert et al. (2008) presented fairly good results in vertical
distributions of streamwise velocity which are calculated by one beam data (1D-ADCP) in therectangular experimental channel. This follows that the spatial error caused by averaged individual
beam data from four transducers of different directions reduces the accuracy of measuring resultscollected by ADCP.
This paper proposes a new method for measuring velocity distributions in flow attacking areas
by using ADCP. We investigate the accuracy of the new method through the comparison withvelocity distributions measured by the ECM in the Asa River. This paper also presents the structureof the 3D flow attacking a revetment in the field experiment with actual floods scale.

2.

A NEW METHOD FOR MEASURING THREE-DIMENSIONAL FLOWSTRUCTURES USING ADCP

(a)

(b)

(c)

Stream-wise(Longitudinal)

0.0m

BEAM2

BEAM1



BEAM 3

BEAM 250cm

Span-wise(Lateral)

87cm

BEAM 1xzyv2

BEAM 4x123cm

1.0m

1.5mvzzFocus spot Lv10.5myvy

160cm

L2.0m
depth

Figure 1 Calculation of velocity with ADCP beams and Focus spot L.
ADCP method has been used for the measurement of three dimensional velocity distributions using
Doppler shift (Teledyne RD Instruments, 2006). Figures 1 (a) and (b) show the definition of eachbeam direction and span-wise (lateral) sectional view, respectively. The conventional ADCP method
gives longitudinal, lateral and vertical velocities vx , vy , vz in equation (1) by using four individual
beam data v1 - v4 with an assumption of constant velocity in the focus spot L (Fig. 1).

vx  v3  v 4v v v v
 v v, v y  1 2 , vz   1 2  3 4  / 22 sin 2 sin  2 cos 2 cos (1)However, the conventional method cannot give accurate velocity distributions of flows with local
velocity gradients and deep water depth, because of velocity variations within the focus spot L that
expand towards the vertical direction by the angle of 20 degrees as shown in Fig. 1 (c).
In this paper, it is assumed that variations of stream-wise velocity component vx in the focus
spot L are negligibly-small compared with those of the lateral and vertical direction. Thus, only thestream-wise velocity vx is calculated by equation (1) with the assumption of constant velocity in thefocus spot L. But, lateral and vertical velocity at any point are calculated by equation (2) usingsuperimposing spatially-interpolated individual beam data v1 , v2 which are measured continuouslyin lateral direction and averaged over time (Fig. 2).

vy  v1in  v2inv v, v z  1in 2in
2 sin 2 cos

(2)

Here, v1in: interpolated v1, v2in: interpolated v2. For the above method, we introduce the assumptionof little variation in mean velocity during the measurement. The measurement should be conductedwith the appropriate sampling time and space for averaging procedure.
Continuous measuringzinterpolation of v1yx

interpolation of v2
Figure 2 Concept of the new method.

Where one of the beam data cannot be obtained such as near wall or bed, velocity can be calculatedby the others three beam data (Teledyne RD Instruments, 2006). Also, in this case, the new ADCP
method will lead to an increase in the precision of velocity calculation compared to the conventional
ADCP method by using three available beams directly.

3.

APPLICATION TO THREE-DIMENSIONAL FLOW FIELD IN THE ASA RIVER
AND VALIDATION OF THE NEW METHOD

3.1 Summary of Field Observation in the Asa River
12.2kmFlow

12.0km

11.8kmzy
Hagiwara bridge

11.6km

11.4kmxAsa River bridge
Measured cross-section

Figure 3 Location of the observed site in the Asa River.
The field measurement was carried out at the flow attacking zone along right bank located in thevicinity of 11.75km of the Asa River (Fig. 3). The low-water channel in the experimental field iscurved and has revetment works with a gradual slope (Fig. 4).

Elevation[m]Figure 4 Picture of the observation.
0.25

(A)

(B) (C)
Cross-section‐0.25

Water level‐0.75

Measurement pointsof ECM
Measurement area ofADCP

‐1.25

‐1.75
1112131415161718Lateral distance[m]Figure 5 Measurement area and points by ADCP and ECM.
Hydraulic conditions during the velocity measurement were mean depth: 0.55m, water surface
width: 9.13m, mean velocity: 0.37m/s and discharge: 1.86m3/s. The observation was conductedusing a Workhorse ADCP Rio Grande manufactured by RD Instruments, Inc. and two-dimensional
Electromagnetic Current Meter, AEM213-D manufactured by JFE Advantech Co., Ltd. Velocity
data within the red line as shown in Fig. 5 were collected by using ADCP mounted on the sliding
platform as shown in Fig. 4 (time constant: 10.0s, cross-sectional interval: 0.1m). Black Crosspoints in Fig. 5 show measurement points by using ECM (time constant: 30.0s, cross-sectional
interval: 0.5m).
3.2 Comparisons of the Measurement Results between the Conventional Method and theNew Method

Figures 6 and 7 show measured results by the ECM, the conventional ADCP method and the newADCP method in the Asa River. Figure 6 shows distributions of primary flow contours andsecondary flow vectors. Secondary flow vectors by the ECM show only the y-component because
the instrument is 2-dimensional (x-y) type. Both ADCP results give similar results to the ECM inthat the maximum velocity region of the primary flow occurs along the right bank. But, in thesecondary flow, the new method presents better results compared with that of the conventional
method. Vertical distributions of longitudinal and lateral direction velocities vx , vy are compared inFig. 7. Points (A), (B), (C) are shown in Fig. 5. Lateral velocity distributions by the new method
provide good agreement with that by the ECM compared with the conventional method. Especiallyin the deep portion of water depth, the new method makes it possible to measure detailed lateralvelocity distributions.

[m/s]

Elevation[m]0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1

0.5

[m/s]

-0.2
-0.4
-0.6
-0.8
-1-1.2

Electromagnetic Current Meter

-1.4
-1.6

8

9

10

1112

13

14

15

16

1718

Elevation[m]Lateral distance[m]Measuring area

-0.2
-0.4
-0.6

Unmeasurable
area

-0.8
-1-1.2

New ADCP method

-1.4
-1.6

8910111213

14

15

16

1718

Elevation[m]Lateral distance[m]Measuring area

-0.2
-0.4-0.6

Unmeasurablearea-0.8-1-1.2

Conventional ADCP method

-1.4
-1.6

8

910111213

1415

161718Lateral distance[m]Figure 6 Contours of longitudinal velocity and vectors of lateral velocity.

(B)

‐0.45

(C)
Elevation[m]Elevation[m]Longitudinalvelocity

Elevation[m]

(A)
‐0.4

‐0.6

‐0.4

‐0.6

‐0.65
‐0.8

‐0.8

‐1.0

‐1.0

‐1.2

‐1.2

‐0.85

‐1.05

‐1.4

‐1.25
0.0

0.5

1.00.0

1.5

0.5

‐1.4

1.50.00.5

1.0

‐0.4

‐0.6

1.5vx[m/s]Elevation[m]‐0.45

1.0vx[m/s]Elevation[m]Lateralvelocity

Elevation[m]vx[m/s]

‐0.4

‐0.6

‐0.65
‐0.8

‐0.8

‐1.0

‐1.0

‐1.2

‐1.2

‐0.85

‐1.05

‐1.25

‐1.4
‐0.6

‐0.2

0.2

0.6

‐1.4
‐0.6

‐0.2

vy[m/s]Electromagnetic Current Meter

0.2

0.6

vy[m/s]
New method

‐0.6

‐0.2

0.2

0.6

vy[m/s]Conventional method

Figure 7 Comparisons of longitudinal velocity vx and lateral velocity vy.

4.

APPLICATION TO MEASURED VELOCITY DISTRIBUTION IN THE JYOGANJI
RIVER

4.1 Summary of the Field Experiment in the Jyoganji River

The field experiment in the Jyoganji River in 2011 had a twofold purpose. One was to investigate
characteristics of erosion and bed scouring beside revetment works (Koikeda et al., 2012). The otherwas to obtain the detailed data for validating the new depth integrated calculation method for bed
scouring in flow attacking area. Figure 8 shows plan view of the experimental meandering channel.
The experiments were conducted in a compound meandering channel, and the configurations aretotal channel length: 170.0m, total channel width: 20.0m, main channel width: 4.0m, main channel
depth: 1.0m and bed slope: 1/200. There are vertical revetments made with concrete wall in two
flow attacking zones around meandering sections (Fig. 8, 9). We conducted the experiments inascending order of discharges, about 7.0m3/s (exp1), 7.6m3/s (exp2), 13.7m3/s (exp3).
Flow attacking zone 1
No.5

No.3

JyoganjiRiverFlow
No.14 No.13 No.12 No.11 No.10 No.9

No.8

No.7 No.6

No.4No.2

No.1

No.0

Flow attacking zone 2

Figure 8 Plan view of the experimental channel in the Jyoganji River.

Revetment
Revetment

Figure 9 Picture of the velocity measurement on flow attacking zone 1.
Fig. 10 shows cross-sectional form changes and water level around flow attacking zones 1, 2 in eachcase. Natural bars with large stones were prepared in the flow attacking zone 1 before theexperiment. And, velocity measurements were conducted around the zone 1 under the condition oflittle change in cross-sectional form as shown at No.5 station of Fig. 10. In the flow attacking zone 2,
natural bars without large stones were arranged at first, and large stones with restored bars werearranged after exp. 1 (Fig. 10 No. 11). It aimed for investigating characteristics of erosion and bed
scouring around the revetment. As a result, Koikeda et al. (2012) reported that bar erosion in a broad
scale was developed around bars (Fig. 10 No. 11). For this reason, flow attacking zone 1 is protectedagainst erosion and bed scouring by large stones, but there are large hydrodynamic forces caused.
Fig. 9 shows a picture of velocity measurements.

Elevation[m]Elevation[m]

No.5
12.0

Revetment

11.5

No.11

11.6

Revetment

11.1

10.6

11.0

Large
stones10.5

10.1

Set out largestones after exp1

9.6

10.0
-4-3-2-1012

3-3

4-2-1

012

Lateral distance[m]345Lateral distance[m]Cross-section of initial

Cross-section after exp1

Cross-section before exp2

Cross-section after exp2

Cross-section before xp3

Cross-section after xp3

Water level of exp1

Water level of exp2

Water level of exp3

Figure 10 Cross-sectional form changes on flow attacking zones 1, 2.
Velocity data were measured by using ADCP mounted on the sliding rail at cross-sections a-g as
shown in Fig. 11. The draft of the ADCP was a little deep for cutting down effects of bubble,
because there are hard flow conditions with high velocity in contrast with observation in the Asa
River as shown in Fig. 12. Therefore, velocity data couldn’t be collected in the range of about 0.4m
depth from water surface. In the cross-sections c and e, velocity data to 0.15m from water surface
are measured by using the ECM for interpolating. Instruments were same as the Asa Riverobservation.
4.2 Measurement Results in the Flow attacking zone 1 at exp2(m)

In Fig. 11, black vector and red vector show bottom velocity by the new ADCP method and surface
velocity by the ECM, respectively. The bottom velocity is defined as averaged velocity around 80
percent of depth. Surface velocity is measurement value of the ECM at 0.15m from surface.
-210.2 10.4 10.6 10.8 11 11.2 11.4

2 (m/s)(m)

revetment

0Large stones
24
68
10g
110

105fe
100

d cb95a90(m)

Figure 11 Surface (red) and bottom (black) velocity on flow attacking zone 1 of exp2.

(m)

(m)

Bottom velocity along the inner bank of the main channel is high between cross-section a and d.
Secondary flow can be seen around cross-section c and e, in which surface velocity and bottom
velocity are towards the right bank and inner bank, respectively.
11.8

Revetment

11.8

Revetment

11.6

11.6

11.4

11.4

11.2

11.2

1111

10.8

10.8

10.6
10.4

10.6

Section a6

5Section e

10.4

4

32

10-1

6

54

32

10-1

11.8

Revetment

11.6

(m)

(m)

(m)

(m)

11.4

11.4

11.2

11.2

1111

10.8

10.8

10.6

10.6
10.4

Revetment

11.6

Section b6

54

3

2

10

Large
stonesSection f

10.4
10.2

-1

6

54

32

10-1(m)

(m)

(m)

(m)
11.8

Revetment

11.6

Revetment

11.6

11.4

11.4

11.2

11.2

1111

10.8

10.8

10.6
10.4

10.6
10.4

Large
stonesSection c6

5Section g

10.2
4

3

2

10-1

76

54

321(m)

(m)

0(m)

11.8

Revetment
11.6
11.4
11.2
110.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2(m/s)

2 (m/s)

10.8
10.6
10.4

Section d65432

10-1(m)Figure 12 Velocity distributions on flow attacking zone 1 of exp2.
Fig. 12 shows vertical velocity distributions of primary flow as contour and secondary flow as
vector by the new ADCP method. With regard to primary flow, high velocity regions are occurredalong the inner bank between cross-section a and b. Their regions gradually shift towards the rightbank between cross-section c and g. In the cross-section f and g, high velocity regions occur near thebottom. The reason for this is that the secondary flow beside revetments along right bank transports
momentum of primary flow from surface of the inner bank to bottom of the right bank. The abovealso induces the result that bottom velocity, which plays important role in the sediment transport, isaccelerated beside revetments with small friction. Furthermore, the flows become concentrated more
severely as bank erosion and bed scouring develop by the process.

5CONCLUSIONSThe new method provides fairly good measuring results in flow attacking zones compared with theprevious method by ADCP. Especially in the portion of maximum scouring area around a revetment
with the considerable erosion and scouring energy where the previous method could not be applied,
the measuring method makes it possible to measure detailed distributions of three dimensional flows.
Furthermore, this paper supplies detailed data of velocity distributions in flow attacking zones by thefield experiment in the Jyoganji River. Experiments proved that the new method is reliable tounderstand three dimensional flow structures in concentrated zones with local scouring in ameandering channel.

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Fukuoka, S. (2005) “Flood Hydraulics and River Channel Design”, Morikita publishing company.
Fujimoto, M., Ookuma, Y., Hatanaka, Y. and Fukuoka, S. (2010) “A Study on New
Countermeasures against Embankment Erosion in the Jyoganji River”, Advances in River
Engineering, JSCE, Vol.16, pp.413-418.
Gunawan, B., Sterling, M., Tang, X., Knight, D. W. (2010) “Measuring and Modelling Flow
Structures in a Small River”, River Flow, pp.179-186.
Koikeda, S., Ishii, A., Iwai, H., Ishikawa, T., and Fukuoka, S. (2012) “Nature Friendly Bank
Protection Works Using Sandbars with Boulders in the Jyoganji River”, Advances in River
Engineering, JSCE, Vol.18, pp.233-238.
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Engineering, vol.64, No.2, pp.99-114.
Osada, K., Abe, T., and Fukuoka, S. (2007) “Formation Mechanism of Channels Developing along
the Low Water Revetment in Gravel Bed Rivers”, Advances in River Engineering, JSCE,
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Practical Primer”.
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without Shallow Water Assumption”, Annual Journal of Hydraulic Engineering, JSCE, Vol.56,
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