Flow patterns, sedimentation and deposit architecture under a hydraulic jump on a non‐eroding bed: defining hydraulic‐jump unit bars

Abstract

This paper presents results from two flume runs of an ongoing series examining flow structure, sediment transport and deposition in hydraulic jumps. It concludes in the presentation of a model for the development of sedimentary architecture, considered characteristic of a hydraulic jump over a non‐eroding bed. In Run 1, a hydraulic jump was formed in sediment‐free water over the solid plane sloping flume floor. Ultrasonic Doppler velocity profilers recorded the flow structure within the hydraulic jump in fine detail. Run 2 had identical initial flow conditions and a near‐steady addition of sand, which formed beds with two distinct characteristics: a laterally extensive, basal, wedge‐shaped massive sand bed overlain by cross‐laminated sand beds. Each cross‐laminated bed recorded the initiation and growth of a single surface feature, here defined as a hydraulic‐jump unit bar. A small massive sand mound formed on the flume floor and grew upstream and downstream without migrating to form a unit bar. In the upstream portion of the unit bar, sand finer than the bulk load formed a set of laminae dipping upstream. This set passed downstream through the small volume of massive sand into a foreset, which was initially relatively coarse‐grained and became finer‐grained downstream. This downstream‐fining coincided with cessation of the growth of the upstream‐dipping cross‐set. At intervals, a new bed feature developed above and upstream of the preceding hydraulic‐jump unit bar and grew in the same way, with the foreset climbing the older unit bar. The composite architecture of the superimposed unit bars formed a fanning, climbing coset above the massive wedge, defined as one unit: a hydraulic‐jump bar complex.

Hydraulic and sediment transport properties of autogenic avulsion cycles on submarine fans with supercritical distributaries

“…Hydraulic jumps quarantined a large amount of the sediment and comprised a good amount of the total deposition within a particular lobe. A small portion of sediment was sometimes transported through the entire hydraulic jump region, i.e., through the subcritical tailwater and out onto the lobe deposit, but was typically deposited quickly as in Macdonald et al []. The flow downstream of the hydraulic jump was initially completely depositional but regained some ability to move sediment as on the lee of the lobe (Figure d).…”

Turbulent shear stresses in hydraulic jumps, bores and decelerating surges

“…In a natural system, the formation and propagation of hydraulic jumps have a major impact on the channel bed and associated sediment transport (Macdonald et al, 2009). For example, in a mobile bed fl ume, Bellal et al (2003) observed the bed deformation associated with the upstream propagation of a positive surge until its stabilisation and ultimately its disappearance in response to a change in bed topography.…”

“…The formation of a hydraulic jump propagating upstream against a steep slope, its deceleration and vanishing were also associated with cyclic behaviour (Parker, 1996;Grant, 1997;Parker and Izumi, 2000;Yokokawa et al, 2009). Some pertinent studies included Carling (1995) and Macdonald et al (2009) with the stationary hydraulic jumps, and Chen et al (1990), Wolanski et al (2004) and Koch and Chanson (2008) in tidal bores. Other relevant studies encompassed the studies of bores generated by wave runup in the swash zone of the shoreline (Kobayashi, 2001;Barnes et al, 2009).…”

Alluvial stratification styles in a large, flash‐flood influenced dryland river: The Luni River, Thar Desert, north‐west India

“…(). Faint low‐angle bedding within massive deposits was observed previously in experimental studies of supercritical deposits, such as antidunes and hydraulic jumps (Alexander et al ., ; MacDonald et al ., , fig. 13 showing stream‐transverse bedding; Cartigny et al ., ).…”