Shipboard measurements of sediment stability using a small annular flume—Core Mini Flume (CMF)

Abstract

Estimates of bed stability in coastal environments are essential to physical, biological, and chemical investigations of cohesive sediments. The Core Mini Flume (CMF), a 200 mm diameter annular flume has been designed to undertake sediment stability experiments on collected intact sediment box cores. Bed properties were assessed for replicate box cores at 3 contrasting sites in UK coastal waters (Tyne [in 2011 and 2012], Plymouth and Celtic Deep), each covering a maximum area of 80 m2. No significant horizontal spatial variations were found for grain size, bulk density, porosity, or oxygen penetration at the sites. Resuspension experiments performed on replicate cores yielded highly replicable results for each site, giving average erosion thresholds of 0.33 ± 0.02 (Tyne 2011), 0.215 ± 0.03 (Tyne 2012), 0.23 ± 0.01 (Plymouth), and 0.09 ± 0.006 (Celtic Deep) Pa and erosion depths of 10.7 ± 1.7, 6.63 ± 1.10, 3.65 ± 0.95, and 4.6 ± 0.5 mm. Using an already established methodology, the CMF allowed detailed replicate experiments to be performed on‐board ship rapidly after sediment collection, while minimizing the time spent at each station. The use of intact box cores minimized the disturbance to the bed often associated with recovering material to a laboratory or remoulding a bed. We have demonstrated that the convenience of laboratory‐based methodologies can be combined with the benefit of prompt investigations on undisturbed beds complete with overlying in situ water to produce robust measurements of sediment stability.

Physical behaviour of Cretaceous calcareous nannofossil ooze: Insight from flume studies of disaggregated chalk

“…(). It has been used to obtain τ c in sandy and cohesive/adhesive muddy sediments (Amos et al ., ; Widdows et al ., ; Thompson et al ., ). However, for the Mini‐Flume experiments with variable‐porosity beds, the fitting of this trendline yielded very low correlation coefficient values due to different erosion types, and the threshold for erosion is, therefore, defined as a value between the velocity steps at which the onset of erosion was observed.…”

Hindered erosion: The biological mediation of noncohesive sediment behavior

“…Six identical 20 L benthic chambers (290 mm diameter × 250 mm high) with rotating paddles were used in this study (Figure ). The device is an improved version of the UMCES Gust Erosion Microcosm System (U‐GEMS) [ Thomsen and Gust , ] and Core Mini Flume (CMF) [ Thompson et al ., ], comprising a benthic device with flow capability used for determining sediment erosion thresholds. A small island was placed (150 mm in diameter) at the center of the test bed in order to: (1) limit the effect of the flow vortices, often produced in the central region of the flow field, affecting the center of the bed; (2) provide a more evenly distributed shear stress over the outer annular test region (assessed using a simplified model and three‐dimensional Doppler Velocimetry (Vectrino Profiler, Nortek AS), see supporting information Figure S2 for more details).…”

The effect of cyclic variation of shear stress on non‐cohesive sediment stabilization by microbial biofilms: the role of ‘biofilm precursors’

“…Surface sediment at Site S7 in winter (see site information in Chen et al, 2017b). (Thomsen and Gust, 2000) and Core Mini Flume (CMF) (Thompson et al, 2013). [Colour figure can be viewed at wileyonlinelibrary.com] X. CHEN ET AL.…”

“…[Colour figure can be viewed at wileyonlinelibrary.com] X. CHEN ET AL. (Thomsen and Gust, 2000) and Core Mini Flume (CMF) (Thompson et al, 2013). The chamber was used for both biosedimentary bed cultivation and for determining sediment erosion thresholds by adjusting the rotation speed of the paddle.…”