The Use of Imagery in Laboratory Experiments

Tal, Michal; Frey, Philippe; Kim, Wonsuck; Lajeunesse, É.; Limare, Angela; Métivier, François

doi:10.1002/9781119940791.ch13

Cited by 11 publications

(7 citation statements)

References 69 publications

(89 reference statements)

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“…We quantify this by tracking the fraction of the delta top covered by active flow ( f w ) and the roughness of the shoreline ( R SL ) each hour (Figures b and c). f w is computed from wet/dry maps of experimental surfaces generated from overhead photos captured every 0.25 h [ Tal et al ., ]. We quantify R SL with the coefficient of variation for distances measured from points defining the shoreline to the basin entrance

R_{normalS normalL} = \sqrt{\frac{1}{N} {\sum_{i = 1}^{N} (\frac{r_{i} - \overset{r}{true}}{\overset{true¯}{r}})}^{2}}

where N is the total number of points defining the shoreline, r i are the individual distance measurements, and

\overset{r}{true}

is the mean distance from basin entrance to shoreline for that run hour.…”

Section: Resultsmentioning

confidence: 99%

“…We quantify this by tracking the fraction of the delta top covered by active flow (f w ) and the roughness of the shoreline (R SL ) each hour (Figures 1b and 1c). f w is computed from wet/dry maps of experimental surfaces generated from overhead photos captured every 0.25 h [Tal et al, 2012]. We quantify R SL with the coefficient of variation for distances measured from points defining the shoreline to the basin entrance…”

Section: Resultsmentioning

confidence: 99%

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Influence of sediment cohesion on deltaic shoreline dynamics and bulk sediment retention: A laboratory study

Straub

Benson

2015

Geophysical Research Letters

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While boundary and forcing conditions influence the average location of a shoreline in deltaic systems, internal morphodynamics can drive high‐magnitude deviations from the long‐term trend. Here we explore the role of sediment cohesion on these morphodynamics using physical experiments. Specifically, we explore the role of sediment cohesion on the scales of autogenic shoreline transgressions and regressions. Results indicate that sediment cohesion enhances the time and space scales associated with autogenic cycles of channel formation, elongation, and abandonment. In systems with high sediment cohesion, this cycle can drive shoreline transgressions that produce flooding surfaces in the resulting stratigraphy which could be confused with surfaces produced by increases in sea level rise or subsidence rates. Enhanced channelization resulting from sediment cohesion also increases the pumping of fine‐grained sediment into the marine realm, where it can bypass the delta foreset, thus decreasing total delta sediment retention rate.

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R_{normalS normalL} = \sqrt{\frac{1}{N} {\sum_{i = 1}^{N} (\frac{r_{i} - \overset{r}{true}}{\overset{true¯}{r}})}^{2}}

where N is the total number of points defining the shoreline, r i are the individual distance measurements, and

\overset{r}{true}

is the mean distance from basin entrance to shoreline for that run hour.…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Influence of sediment cohesion on deltaic shoreline dynamics and bulk sediment retention: A laboratory study

Straub

Benson

2015

Geophysical Research Letters

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“…Measuring T ch is accomplished using wet/dry maps of experimental surfaces generated from overhead photos. Using a threshold blue luminosity value, we separate dry regions from wet regions on each delta‐top image [ Tal et al ., ]. The threshold value used for this operation was picked by identifying a value that on visual inspection appeared to correctly separate the two regions.…”

Section: Resultsmentioning

confidence: 99%

Influence of water and sediment supply on the stratigraphic record of alluvial fans and deltas: Process controls on stratigraphic completeness

Straub

Esposito

2013

JGR Earth Surface

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[1] Stratigraphy contains the most complete record of information necessary to quantitatively reconstruct paleolandscape dynamics, but this record contains significant gaps over a range of time and space scales. These gaps result from stasis on geomorphic surfaces and erosional events that remove previously deposited sediment. Building on earlier statistical studies, we examine stratigraphic completeness in three laboratory experiments where the topography of aggrading deltas was monitored at high temporal and spatial scales. The three experiments cover unique combinations in the absolute magnitudes of sediment and water discharge in addition to generation of accommodation space through base-level rise. This analysis centers on three time scales: (1) the time at which a record is discretized (t), (2) the time necessary to build a deposit with mean thickness equivalent to the maximum roughness on a surface (T c ), and (3) the time necessary for channelized flow to migrate over all locations in a basin (T ch ). These time scales incorporate information pertaining to the time-variant topography of actively changing surfaces, kinematics by which the surfaces are changing, and net deposition rate. We find that stratigraphic completeness increases as a function of t/T c but decreases as a function of T c /T ch over the parameter space covered in the experiments. Our results suggest that environmental signals disconnected from a sediment routing system are best preserved in systems with low T c values. Nondimensionalizing t by T c , however, shows that preservation of information characterizing system morphodynamics is best preserved in stratigraphy constructed by systems with low water to sediment flux ratios.Citation: Straub, K. M., and C. R. Esposito (2013), Influence of water and sediment supply on the stratigraphic record of alluvial fans and deltas: Process controls on stratigraphic completeness,

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“…Grains were colored based on five size classes, which had median grain diameters of 2.4, 4.5, 8.0, 15.4, and 27.2 mm ( D 16 = 2.0, 3.4, 6.7, 12.4, and 24.0 mm and D 84 = 2.8, 5.7, 10.3, 19.7, and 31.3 mm, respectively). Surface GSDs were measured through image analysis at the same time intervals as cumulative sediment output (with discharge briefly suspended to make measurements), by identifying the proportions of different grain colors from distortion‐corrected photographs of the bed surface and using the median diameters of each size class to calculate a grain size distribution [ Tal et al , ].…”

Section: Experimental Designmentioning

confidence: 99%

Coarser and rougher: Effects of fine gravel pulses on experimental step-pool channel morphodynamics

Johnson

Aronovitz

Kim

2015

Geophys. Res. Lett.

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Understanding how steep mountain rivers respond to natural and anthropogenic sediment supply perturbations is important for predicting effects of extreme events (e.g., floods and landslides) and for restoring rivers to more natural conditions. Using flume experiments, we show that stabilized step‐pool‐like channel beds can respond to pulses of finer gravel by becoming even coarser and rougher than before. Adding finer gravel initially reduces bed roughness and also increases the mobility of previously stable bed grains. Small‐ and intermediate‐diameter clasts are then preferentially winnowed from the bed surface, leaving behind higher concentrations of even larger clasts. Ultimately, this results in both a coarser and rougher bed. Our experiments demonstrate that steep river beds become stable through the coevolution of bed roughness and surface grain size distribution and that these morphological variables can be sensitive to the history of upstream sediment supply.

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The Use of Imagery in Laboratory Experiments

Abstract: International audienceno abstrac

Cited by 11 publications

References 69 publications

Influence of sediment cohesion on deltaic shoreline dynamics and bulk sediment retention: A laboratory study

Influence of sediment cohesion on deltaic shoreline dynamics and bulk sediment retention: A laboratory study

Influence of water and sediment supply on the stratigraphic record of alluvial fans and deltas: Process controls on stratigraphic completeness

Coarser and rougher: Effects of fine gravel pulses on experimental step-pool channel morphodynamics

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