Survival of the Strong and Dense: Field Evidence for Rapid, Transport‐Dependent Bed Material Abrasion of Heterogeneous Source Lithology

Pfeiffer, Allison M.; Morey, Susannah; Karlsson, H.; Fordham, Edward M.; Montgomery, David R.

doi:10.1029/2021jf006455

Cited by 7 publications

(4 citation statements)

References 38 publications

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“…The 3D model in Figure 5 shows the rocks that will remain if there is continued landward abrasion. Climatological and geological factors influence this condition in the research area, affecting seawater and the rock structure of the coastal zone [5], [7], [10], [41]- [43]. This modeling displays the subsurface condition of the research location with a resistivity value of >250 Ωm in the form of clay this rock is not homogeneously distributed in the coastal area, so the land conditions are inserted in an abstract and undefined form.…”

Section: Resultsmentioning

confidence: 99%

Coastal vulnerability assessment using electrical resistivity tomography in Padang Betuah, Central Bengkulu

Suhendra,

Halauddin,

Lizalidiawati

et al. 2023

IJAAS

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Abrasion disaster in the coastal area of Padang Betuah Beach has a high level of abrasion in Central Bengkulu. The local community utilizes abrasion in the coastal area as a tourist attraction and becomes local revenue in the research location. The location that becomes a tourist attraction is decreasing because the coastal area’s land has been abraded. After conducting research using the electrical resistivity tomography (ERT) method in 2D and 3D, it was found that claystone dominated the coastal area at the research location with a resistivity value of 16-200 Ωm at a depth of 15-20 m. The coastal area in Padang Betuah Beach is composed of clay shale rocks (207-220 Ωm), and the depth is 2-14.8 m. Clay shale rocks are not abraded in stones with resistivity values >250 Ωm. This is caused by clay shale, which has low porosity, so it has a compact rock density. Seawater is identified at a depth of 21-63 m with a resistivity value of 2.225-10.2 Ωm. The depth of seawater determined follows the average height of the cliffs in the research location. The abrasion process can be slowed down by making jetties, water breakers, and mangrove cultivation.

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Section: Resultsmentioning

confidence: 99%

Coastal vulnerability assessment using electrical resistivity tomography in Padang Betuah, Central Bengkulu

Suhendra,

Halauddin,

Lizalidiawati

et al. 2023

IJAAS

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“…The coarse fraction of material introduced by debris flows certainly contributes to the annual SSL, even though our analysis does not account for it explicitly (Figure 7). The debris flow deposits along Chocolate and Dusty creeks are, on average, 22% fine (<2 mm) sediment, though the coarse material is exceptionally weak and prone to rapid abrasion during transport (Pfeiffer et al, 2022). The fine fraction of the terrace material, when eroded, would rapidly transport downstream and contribute to the anomalously high sediment load of the basin recorded at the downstream gauge.…”

Section: Discussionmentioning

confidence: 99%

“…If we assume that erosion into the 2003 debris flow deposit is roughly representative of sediment supply from the high‐magnitude events along Chocolate and Dusty creeks, we can begin to evaluate their role in explaining the anomalous sediment yield of the basin. We will assume that the erosion happens efficiently in the years after deposition (Major et al, 2021), that these events occur with a 9.3‐year recurrence interval, that 22% of the eroded material is fine grained and that 60% of the coarse material is, over many years of gradual transport, converted to fines via bed material abrasion (Pfeiffer et al, 2022). This yields an average rate of 104 000 t/year of fine‐grained material contributed to the fine sediment budget, most of which would be eroded or gradually abraded during the highest peak flow events.…”

Section: Discussionmentioning

confidence: 99%

Section: Debris Flow Triggers and Implications For Climate-change Imp...mentioning

confidence: 99%

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Recurrent debris flows and their downstream fate: Geomorphic drivers of an anomalous sediment load, Suiattle River, Washington State, USA

Fordham¹,

Pfeiffer

Bunn

et al. 2023

Earth Surf Processes Landf

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Alpine mass wasting events have impacts that extend past their headwater origins, sometimes reaching populated lowlands. Understanding the processes driving these sediment pulses, and how they contribute to basin‐scale sediment fluxes, is important for hazard assessment and aquatic habitat management. The Suiattle River, which drains Glacier Peak stratovolcano in Washington State, is a dominant contributor of suspended sediment in the region. Normalized for drainage area, it supplies more suspended sediment than nearly any other river in the area and more than twice as much as the White Chuck River, which drains the opposite flank of the volcano. Despite its importance to the regional sediment budget, geomorphic processes in the basin have received relatively little attention in the literature. In this study, we build on previous work to explore the magnitude, timing and triggering mechanisms of sediment loading events in the basin. We find that outburst flood‐triggered debris flows from Chocolate Glacier are of widely varying magnitude and coincide with high temperatures in the late summer. Major debris flow activity initiated in the late 1930s, with at least eight valley‐filling debris flows since then. Smaller, more recent debris flows, likely also driven by outburst floods, occur in five of seven years of complete data. In total, the small debris flows and the subsequent autumn flushing events explain ~21% of the ‘anomalous’ sediment load in the basin, while reworking and abrasion of the historic events may explain another ~26%. We speculate that some of the remaining unexplained ‘anomalous’ load could be the result of a feedback between channel lateral instability (originally triggered by the valley‐spanning debris flows) and bluff erosion.

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A mathematical model for bedrock incision in near‐threshold gravel‐bed rivers

Gabel,

Tucker,

Campforts

2024

Earth Surf Processes Landf

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Gravel‐bed rivers that incise into bedrock are common worldwide. These systems have many similarities with other alluvial channels: they transport large amounts of sediment and adjust their forms in response to discharge and sediment supply. At the same time, the occurrence of bedrock incision implies behaviour that falls on a spectrum between fully detachment‐limited ‘bedrock channels’ and fully transport‐limited ‘alluvial channels’. Here, we present a mathematical model of river profile evolution that integrates bedrock erosion, gravel transport and the formation of channels whose hydraulic geometry is consistent with that of near‐threshold alluvial channels. We combine theory for five interrelated processes: bedload sediment transport in equilibrium gravel‐bed channels, channel width adjustment to flow and sediment characteristics, abrasion of bedrock by mobile sediment, plucking of bedrock and progressive loss of gravel‐sized sediment due to grain attrition. This model contributes to a growing class of models that seek to capture the dynamics of both bedrock incision and alluvial sediment transport. We demonstrate the model's ability to reproduce expected fluvial features such as inverse power law scaling between slope and area, and width and depth consistent with near‐threshold channel theory, and we discuss the role of sediment characteristics in influencing the mode of channel behaviour, erosional mechanism, channel steepness and profile concavity.

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Survival of the Strong and Dense: Field Evidence for Rapid, Transport‐Dependent Bed Material Abrasion of Heterogeneous Source Lithology

Cited by 7 publications

References 38 publications

Coastal vulnerability assessment using electrical resistivity tomography in Padang Betuah, Central Bengkulu

Coastal vulnerability assessment using electrical resistivity tomography in Padang Betuah, Central Bengkulu

Recurrent debris flows and their downstream fate: Geomorphic drivers of an anomalous sediment load, Suiattle River, Washington State, USA

A mathematical model for bedrock incision in near‐threshold gravel‐bed rivers

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