Channel inception in cohesionless sediment by seepage erosion

Pornprommin, Adichai; Takei, Yoshihiro; Wubneh, Atinkut Mezgebu; Izumi, Norihiro

doi:10.1016/j.jher.2009.10.011

Cited by 33 publications

(12 citation statements)

References 24 publications

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“…It is found that channels were bifurcated when the sediment size is large and the slope is small. Our results that a milder slope induces bifurcation confirms the results of [4]. Nevertheless, the reason that we can see bifurcation for a smaller d50 of 0.56 mm is not clearly understood.…”

Section: Resultssupporting

confidence: 89%

“…In this study, we have extended the experiments by [3] & [4]. In their experiments, there were no initial channels at the downstream scarp.…”

Section: Introductionmentioning

confidence: 73%

“…Thus, the competition between two processes provides the channelization with the characteristic spacing. More experiments have been done by [4], and they found that channel bifurcation location is farther from a scarp when the chamber slope becomes steeper.…”

Section: Introductionmentioning

confidence: 99%

“…In [3] and [4], water fed to the experimental chambers at the far upstream end. Channel bifurcation by uniform rain on the sediment surface has been studied by [5].…”

Section: Introductionmentioning

confidence: 99%

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Experiment of Channelization Due to Seepage Erosion

Thaisiam¹

2018

GEOMATE

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ABSTRACT:We have investigated channelization due to seepage erosion using two sizes of coarse sand (d50 = 0.86 and 0.56 mm), two chamber slopes (S = 0 and 3%) and three upstream water depths (H = 15, 17 and 19 cm). Water was fed at the far upstream end of a sand layer, and a small incipient channel was made at the center of the downstream scarp. Thus, groundwater flow converged into the central channel, promoted erosion and caused the development in both width and length. At the beginning, the retreat rates of channel heads were rapid but decreased after a while. A higher H induced a faster retreat and a larger size of the center channel. In the experiments with S = 0%, channel head bifurcation was always observed for d50 = 0.86 mm but not d50 = 0.56 mm. Thus, not only the characteristics of groundwater flow field soil properties but the sediment properties also affect the shapes of evolving channels. For S = 3%, however, bifurcation was only found in the experiment with d50 = 0.86 mm and H = 15 cm. It implies that H also controls bifurcation. In addition, new channels were initiated at the downstream scarp when S = 3%. An increase in the streamwise discharge due to a steeper slope may weaken the convergence of the groundwater flow into the center channel. Using the concept of network circularity, we can divide the channel development of our experiments into the initiation and extension phases.

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Section: Resultssupporting

confidence: 89%

“…In this study, we have extended the experiments by [3] & [4]. In their experiments, there were no initial channels at the downstream scarp.…”

Section: Introductionmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 99%

“…In [3] and [4], water fed to the experimental chambers at the far upstream end. Channel bifurcation by uniform rain on the sediment surface has been studied by [5].…”

Section: Introductionmentioning

confidence: 99%

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Experiment of Channelization Due to Seepage Erosion

Thaisiam¹

2018

GEOMATE

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“…Recent experiments by Izumi and collaborators [20,21] have also shown channel bifurcation by using coarse sand and a weak slope [20]. The authors attribute this occurrence to the important role of the geometry of groundwater flow and the "resistibility of sediment material to slope failure."…”

Section: Introductionmentioning

confidence: 96%

Shape and dynamics of seepage erosion in a horizontal granular bed

et al. 2012

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We investigate erosion patterns observed in a horizontal granular bed resulting from seepage of water motivated by observation of beach rills and channel growth in larger scale landforms. Our experimental apparatus consists of a wide rectangular box filled with glass beads with a narrow opening in one of the side walls from which eroded grains can exit. Quantitative data on the shape of the pattern and erosion dynamics are obtained with a laser-aided topography technique. We show that the spatial distribution of the source of groundwater can significantly impact the shape of observed patterns. An elongated channel is observed to grow upstream when groundwater is injected at a boundary adjacent to a reservoir held at constant height. An amphitheater (semi-circular) shape is observed when uniform rainfall infiltrates the granular bed to maintain a water table. Bifurcations are observed as the channels grow in response to the ground water. We further find that the channels grow by discrete avalanches as the height of the granular bed is increased above the capillary rise, causing the deeper channels to have rougher fronts. The spatio-temporal distribution of avalanches increase with bed height when partial saturation of the bed leads to cohesion between grains. However, the overall shape of the channels is observed to remain unaffected indicating that seepage erosion is robust to perturbation of the erosion front.

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Initiation of Channel Head Bifurcation by Overland Flow

2017

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Channel head bifurcation is a key factor for generating complexity of channel networks. Here we investigate incipient channel head bifurcation using linear stability analysis. Channel heads are simplified as circular hollows, toward which surface sheet flow accelerates in the radial direction. Sinusoidal perturbations in the angular direction with different angular wave numbers k are imposed on the bed, and their growth rates truenormalΩ~ are computed. Because the channel head radius trueR~c is extending over time, the base state (circular hollow in the absence of perturbations) also evolves continuously. With the use of the momentary stability concept, the evolving base state is defined as momentarily unstable to the imposed perturbation if the disturbance is growing faster than the evolution of the base state. It was found that in the range of sufficiently small trueR~c, bifurcation cannot be initiated. As trueR~c increases, bifurcation starts to be possible with k≈ 3–5. A higher k implies bifurcation with a narrower channel junction angle (θ = 2π/k). The average junction angle of the Colorado High Plains for the smallest drainage area is about 85° with a standard deviation of 35° (Sólyom and Tucker, 2007). Our predicted angles (75°–120°) agree qualitatively with the observed angles. Finally, we propose a simple criterion to compute the threshold trueR~c for the onset of bifurcation.

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Channel inception in cohesionless sediment by seepage erosion

Cited by 33 publications

References 24 publications

Experiment of Channelization Due to Seepage Erosion

Experiment of Channelization Due to Seepage Erosion

Shape and dynamics of seepage erosion in a horizontal granular bed

Initiation of Channel Head Bifurcation by Overland Flow

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