On the use of acoustics for measuring shallow water suspended sediment processes

Thorne, Peter D.; Hardcastle, P.J.; Flatt, D.; Humphery, J.D.

doi:10.1109/48.289450

Cited by 22 publications

(8 citation statements)

References 11 publications

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“…Backscatter was further corrected for absorption due to suspended sediment, implementing the iterative algorithm described by Thorne et al . [] and applied, by Holdaway et al . [] on single‐frequency hydroacoustic data.…”

Section: Data Collection and Analysismentioning

confidence: 99%

With or against the tide: The influence of bed form asymmetry on the formation of macroturbulence and suspended sediment patterns

Kwoll

Becker

2014

Water Resources Research

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This study examines tide-dependent variations in the formation and dynamics of suspended sediment patterns coupled to mean flow and turbulence above asymmetric bed forms. In the Danish Knudedyb inlet, very large primary bed forms remain ebb-oriented during a tidal cycle while smaller superimposed bed forms reverse direction with each tidal phase. Hydroacoustic in situ observations reveal pronounced differences in suspended sediment transport patterns between tidal phases caused by the relative orientation of primary bed forms and the mean tidal flow and flow unsteadiness during a single tidal phase. When flow and primary bed form orientation are aligned, water-depth-scale macroturbulence develops in the bed form lee-sides in the presence of flow separation. Macroturbulent flow structures occur at high flow stages and are coupled to increased amounts of sediment in suspension. When flow and bed form orientation are opposed no evidence of flow separation associated with primary bed forms is found. Sediment-laden macroturbulence at high flow velocities is of a smaller scale and attributed to the superimposed secondary bed forms. The flow structures are advected along the primary bed form stoss-side (temporary hydraulic lee-side). The steep primary bed form lee-side (temporary hydraulic stoss-side) however, limits transport capabilities beyond the scale of primary bed forms.

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Section: Data Collection and Analysismentioning

confidence: 99%

With or against the tide: The influence of bed form asymmetry on the formation of macroturbulence and suspended sediment patterns

Kwoll

Becker

2014

Water Resources Research

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“…This is an advantage over the bottle and pumps sampling, as these techniques do not provide detail information on turbulence mechanics. The technique is suitable for deployment for measurements spanning over an extended period (Thorne et al , 1994, 1995).…”

Section: Acoustic Techniquementioning

confidence: 99%

A review of field methods for suspended and bedload sediment measurement

Nda

Adnan

Yosuff

et al. 2019

WJE

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Purpose Sediment measurement is usually accessible on a periodic or distinct basis. The measurement of sediment (suspended and bedload), especially in the field, is vital in keeping essential data of sediment transport and deposition. Various techniques for measuring sediment have been used over time each with its merits and demerits. The techniques discussed in this paper for suspended sediment include bottle, acoustic, pump, laser diffraction, nuclear and optical. Other techniques for bedload measurement are; River bedload trap (RBT), CSU/FU bedload trap, Helley–Smith, Polish Hydrological Services (PIHM) device, pit and trough, vortex tube, radioactive traces and bedload–surrogate technologies. However, the choice of technique depends on multiple factors ranging from budget constraint, availability of equipment, manpower and data requirement. The purpose of this paper is to present valuable information on selected techniques used in sediment measurement, to aid researchers/practitioners in the choice of sediment measurement technique. Design/methodology/approach This paper presents a general review of selected field techniques used in sediment measurement (suspended and bedload). Each techniques mode of operation, merits and demerits are discussed. Findings This paper highlights that each technique has its peculiar merits and demerits. However, two techniques are generally preferred over others; the bottle sampling and the Helley–Smith sampler for measuring suspended and bedload sediment. This is because the applicability of these techniques is quite widespread and time-tested. Originality/value This review paper provides an in-depth description and comparison of selected existing field sediment measurement techniques. The objective is to ease decision-making about the choice of technique, as well as to identify the suitability and applicability of the chosen technique.

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“…Only results from the OBS sensor at a height of 100 cm are reported here as it demonstrated the least interference. The backscatter from the four acoustic altimeters was used to measure bed level changes, bed form height, and sand in suspension using methods described by Thorne et al [1994] and Lee and Hanes [1995]. Hydrostatic pressure was converted to water depth (h) and wave height (H sig ) using the transform: where h sd is the standard deviation of water depth, Z p is height of pressure sensor above bed, is mean water depth and k is the wave number [ Green et al , 1997].…”

Section: Databasementioning

confidence: 99%

Origin of shore‐normal channels from the shoreface of Sable Island, Canada

Amos

Chiocci

et al. 2003

J. Geophys. Res.

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[1] A suite of modern, shore-normal channels was discovered on the southern shoreface of Sable Island, Canada. Repetitive multibeam and side scan surveys of these features, as well as box coring and sampling, showed that the depressions were perennial features of the shoreface. They occurred in fine and medium sand and were most abundant indepths less than 20 m. They were up to 1 m deep and 50 m wide, increased in size seawards, and generally followed the seabed slope. The channels dominated the inner shoreface becoming wider and deeper seawards to depths in excess of 40 m. There is a continuum of scales in width and depth of these channels, the smallest of which are equated with gutters preserved in the geological record. The internal structure of the shoreface sediments where the gutters are found is characterized by normally graded tempestites composed of cut-and-fill structures overlying an erosion surface. Thus, the environmental setting, internal structure, and scale are similar to ancient counterparts. Gutters have been interpreted to result from downwelling over palaeo-shorefaces during ancient storms [Myrow, 1992b]. The composition of gutter infill, as well as the stability, evolution, associated bed forms, and hydrodynamic conditions under which they formed, were examined to verify genetic interpretations of the ancient counterparts. The multisensor benthic lander RALPH was deployed within a field of shore normal channels for 17 days during late winter 1998. RALPH burst-sampled flow at hourly intervals while imaging the seabed. Resulting sequential imagery revealed the genesis of a group of five gutters during storm spin-down that was coincident with the formation of largescale wave ripples. This was followed by infilling of the gutters and wave ripple destruction within 20 hours by longshore sand transport. The gutters were located within, and parallel to, a larger channel (50 m wide and 0.50 m deep). They were formed by coastal set-up and subsequent downwelling that was triggered by the rotation of storm winds from seawards (onshore wind) to landwards (offshore wind). The gutters formed within 2-3 hours during spin-down of a winter storm under ''live-bed'' conditions of sand transport. Wave height and mean tidal flows were well below those of the storm peak and so they were not directly responsible for creating the gutters. The mechanism we propose for the evolution of gutters supports the geological interpretations; that is, a storm-driven, downwelling event as described by Swift and Niedoroda [1985]. However, the downwelling event appeared to take place suddenly (rapid acceleration in flow), briefly (few hours duration), and within narrow corridors guided by wider and deeper channels of the shoreface. High turbidity during the time of gutter formation leads us to believe that the phenomenon of inner shelf turbidity currents [as suggested by Walker, 1985] exists and may be instrumental in channel formation. INDEX TERMS: 4546

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On the use of acoustics for measuring shallow water suspended sediment processes

Cited by 22 publications

References 11 publications

With or against the tide: The influence of bed form asymmetry on the formation of macroturbulence and suspended sediment patterns

With or against the tide: The influence of bed form asymmetry on the formation of macroturbulence and suspended sediment patterns

A review of field methods for suspended and bedload sediment measurement

Origin of shore‐normal channels from the shoreface of Sable Island, Canada

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