Improved flow velocity estimates from moving-boat ADCP measurements

Vermeulen, B.; Sassi, M.G.; Hoitink, A.J.F.

doi:10.1002/2013wr015152

Cited by 36 publications

(42 citation statements)

References 41 publications

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“…Method A is based on a methodological approach developed by Vermeulen et al (2014b). Method A is based on a methodological approach developed by Vermeulen et al (2014b).…”

Section: Discussionmentioning

confidence: 99%

“…In this section, we describe the two different methodological approaches used in this study to estimate Cartesian velocity components: (1) Method A, the Vermeulen et al (2014b) method; and (2) Method B, the conventional method. Common to all methods is the assumption that data are available from repeat measurement of the same cross-section, as has been shown to be critical for obtaining reliable estimates of secondary circulation from aDcp data (Szupiany et al, 2007), particularly when single transect measurements are not close enough together.…”

Section: Methods For Estimating Cartesian Velocity Components From Admentioning

confidence: 99%

“…Method A: based on Vermeulen et al (2014b) Application of the Vermeulen et al (2014b) method requires mapping of radial beam velocity data onto a predefined mesh. This mesh requires both a bottom topography or bathymetric model, and an upper limit just below the water surface.…”

Section: Methods For Estimating Cartesian Velocity Components From Admentioning

confidence: 99%

“…The Vermeulen et al (2014b) method includes in the transformations an explicit treatment of the random errors due to internal and external factors and the bias (systematic errors) caused by the measurement system and the nature of river flow (Tsubaki et al, 2012). To obtain the raw beam velocities, we use matrix transformations obtained from the raw data to transform measured velocities in XYZ coordinates into beam velocities.…”

Section: Methods For Estimating Cartesian Velocity Components From Admentioning

confidence: 99%

“…Marsden and Ingram, 2004) through a Taylor expansion of the coordinate transform used to determine the Cartesian velocity components. This method strongly reduces the volume over which homogeneity should be assumed and Vermeulen et al (2014b) found that this significantly impacted interpretations of secondary velocities in the presence of strong shear. Vermeulen et al (2014b) developed and tested a second solution.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of aDcp processing options for secondary flow identification at river junctions

Moradi

Vermeulen

Rennie

et al. 2019

Earth Surf Processes Landf

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Secondary circulation in river confluences results in a spatial and temporal variation of fluid motion and a relatively high level of morphodynamic change. Acoustic Doppler current profiler (aDcp) vessel‐mounted flow measurements are now commonly used to quantify such circulation in shallow water fluvial environments. It is well established that such quantification using vessel‐mounted aDcps requires repeated survey of the same cross‐section. However, less attention has been given to how to process these data. Most aDcp data processing techniques make the assumption of homogeneity between the measured radial components of velocity. As acoustic beams diverge with distance from the aDcp probe, the volume of the flow that must be assumed to be homogeneous between the beams increases. In the presence of secondary circulation cells, and where there are strong rates of shear in the flow, the homogeneity assumption may not apply, especially deeper in the water column and close to the bed. To reduce dependence on this assumption, we apply a newly‐established method to aDcp data obtained for two medium‐sized (~60–80 m wide) gravel‐bed river confluences and compare the results with those from more conventional data processing approaches. The comparison confirms that in the presence of strong shear our method produces different results to more conventional approaches. In the absence of a third set of fully independent data, we cannot demonstrate conclusively which method is best, but our method involves less averaging and so in the presence of strong shear is likely to be more reliable. We conclude that it is wise to apply both our method and more conventional methods to identify where data analysis might be impacted upon by strong shear and where inferences of secondary circulation may need to be made more cautiously. © 2019 John Wiley & Sons, Ltd.

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“…Method A is based on a methodological approach developed by Vermeulen et al (2014b). Method A is based on a methodological approach developed by Vermeulen et al (2014b).…”

Section: Discussionmentioning

confidence: 99%

Section: Methods For Estimating Cartesian Velocity Components From Admentioning

confidence: 99%

Section: Methods For Estimating Cartesian Velocity Components From Admentioning

confidence: 99%

Section: Methods For Estimating Cartesian Velocity Components From Admentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Evaluation of aDcp processing options for secondary flow identification at river junctions

Moradi

Vermeulen

Rennie

et al. 2019

Earth Surf Processes Landf

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Sharp bends associated with deep scours in a tropical river: The river Mahakam (East Kalimantan, Indonesia)

et al. 2014

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Autogenic scouring in sharp river bends has received ample attention in laboratory and modeling studies. These studies have significantly advanced our understanding of how flow processes are influenced by strong curvature and how they affect the bathymetry. Here we present a 300 km reach of the Mahakam River in Indonesia, which features several sharp bends (W/R > 0.5), providing a unique field data set to validate existing knowledge on sharp bends. Scour depths were found to strongly exceed what can be expected based on existing understanding of sharp bends and are highly correlated with curvature. A comprehensive stream reconnaissance was carried out to compare the occurrence of sharp bends and deep scours with lateral bank migration. Histograms of the occurrence of erosive, stable, advancing, and bar‐type banks as a function of curvature quantify the switch from a mildly curved bend regime to a sharp bend regime. In mild bends, outer banks erode and inner banks advance. In sharp bends the erosion pattern inverts. Outer banks stabilize or advance, while inner banks erode. In sharply curved river bends, bars occur near the outer banks that become less erosive for higher curvatures. Inner banks become more erosive for higher curvatures but nevertheless accommodate the larger portion of exposed bars. No relation was found between the land cover adjacent to the river and the occurrence of sharp bends. Soil processes may play a crucial role in the formation of sharp bends, which is inferred from iron and manganese concretions observed in the riverbanks, indicating ferric horizons and early stages of the formation of plinthic horizons. Historical topographic maps show the planform activity of the river is low, which may relate to the scour holes slowing down planimetric development.

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Flow structure caused by a local cross‐sectional area increase and curvature in a sharp river bend

2015

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Horizontal flow recirculation is often observed in sharp river bends, causing a complex three-dimensional flow structure with large implications for the morphological and planimetric development of meanders. Several field observations in small-scale systems show that sharp bends are often found in association with a strong increase in cross-sectional area, the deposition of outer bank benches, and reattachment bars near the inner bank. Recent studies show that these bends can also occur in large-scale systems. In this study, we present field measurements of a sharp bend in the Mahakam River, East Kalimantan, Indonesia. The cross-sectional area increases by a factor of 3 compared with the reach-averaged cross-sectional area. Along a river reach of about 150 km, cross-sectional area correlates strongly with curvature. The field measurements are analyzed together with the results from numerical simulation with a three-dimensional finite element model, which yields a comprehensive view of the intricate flow structure. In turn, the model is used to validate a new equation that captures the water surface topography dependence on cross-sectional area variation and curvature. The results show the importance of the increase in cross-sectional area in the development of horizontal recirculation. Vertical acceleration of the flow into the scour causes the pressure to deviate from a hydrostatic pressure distribution. Strong downflow (up to 12 cm s −1 ) advects longitudinal momentum toward the bed, causing the flow to concentrate in the lower part of the cross section. This increases the velocity magnitude throughout the cross section, which is expected to maintain the large scour depth found in several bends along the Mahakam River.

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Improved flow velocity estimates from moving-boat ADCP measurements

Cited by 36 publications

References 41 publications

Evaluation of aDcp processing options for secondary flow identification at river junctions

Evaluation of aDcp processing options for secondary flow identification at river junctions

Sharp bends associated with deep scours in a tropical river: The river Mahakam (East Kalimantan, Indonesia)

Flow structure caused by a local cross‐sectional area increase and curvature in a sharp river bend

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