Debris flow enlargement from entrainment: A case study for comparison of three entrainment models

Shen, Ping; Zhang, Limin; Wong, Ho Fai; Peng, Dalei; Zhou, Shengyang; Zhang, Shuai; Chen, Chen

doi:10.1016/j.enggeo.2020.105581

Cited by 21 publications

(10 citation statements)

References 43 publications

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“…The integrated model EDDA (Erosion-Deposition Debris Flow Analysis), developed by Chen and Zhang (2015), Shen et al (2020), and Zhou et al (2019) was employed in this study to reproduce the geo-hazard chain process. In EDDA, the volumetric sediment concentration of the flow mixture, , V C is employed to indicate the flow types of the mixture in a chain process.…”

Section: Simulation Of the Geo-hazard Chainmentioning

confidence: 99%

The Landslide Hazard Chain in the Tapovan of the Himalayas on 7 February 2021

Jiang

Zhang

Peng

et al. 2021

Geophysical Research Letters

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On February 7, 2021, a catastrophic landslide occurred in Chamoli, India on the southern hills of the Himalayas (  30.37 N,  79.73 E). About 28 × 10 6 m 3 of landslide mass detached from the mountain face, entrained deposits in the valley and riverbed, and generated a huge debris flood along the Dhauliganga River. In this study, the geomorphological and volumetric characteristics of the disaster chain were interpreted from satellite images. The full process of the disaster chain and the erosion, deposition and flow discharge processes were reproduced using a cell-based analysis program, Erosion-Deposition Debris Flow Analysis (EDDA). The results indicate a peak flow discharge of the debris flood at Tapovan Hydropower Station of about 25,000-28,000 m 3 /s. The main erosion and deposition zones are distributed along the valley floor and the Dhauliganga River, respectively. This study serves as basis for understanding the disaster chain dynamics in high mountain areas.Plain Language Summary Catastrophic geo-disasters become more frequent in the Himalayan region due to the global climate change, and pose threats to the local residents and infrastructure. A large landslide happened in the Tapovan area in the south of the Himalayas on February 7, 2021, which triggered a large avalanche down the valley, entrained the deposits and river water, and evolved into a catastrophic debris flood in the Dhauliganga River, causing fatalities and severe damage to the local infrastructure. This study reconstructs the entire geo-disaster process, and reveals key characteristics including the landslide source, erosion and deposition features, and the transformation of hazard types. The outcome from this study helps understand and manage the risk of catastrophic geohazards in high mountain areas, especially in the Himalayas and other areas of the Tibetan Plateau. JIANG ET AL.

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Section: Simulation Of the Geo-hazard Chainmentioning

confidence: 99%

The Landslide Hazard Chain in the Tapovan of the Himalayas on 7 February 2021

Jiang

Zhang

Peng

et al. 2021

Geophysical Research Letters

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“…Debris flow erosion is essentially the failure of bed soil under the influence of external stresses (P. Song & Choi, 2021). It is widely accepted that erosion of debris flow occurs when the total basal shear stress exceeds the shear resistance inside the bed material (Iverson, 2012; Shen et al., 2020). After shear failure occurs, soil particles slide along a failure plane, moving with overriding flows.…”

Section: Test Resultsmentioning

confidence: 99%

“…In contrast, flows interacting with wet hydrophobic beds always yield Γ > 1, with flow velocities evolved and more material entrained to increase the flow volume simultaneously. According to Equation 8, impact force is also governed by the impacting velocity and flow depth, considering that the flow width is equal to the constant width of channel and the flow density is simplified as unchanged value during erosion (Iverson, 2012; Shen et al., 2020). As captured by PIV analysis (Figure 6), large amount of sediment gets mobilized and accelerated while impacting the barrier along with overriding flows.…”

Section: Discussionmentioning

confidence: 99%

Effects of Bed Hydrophobicity on Post‐Fire Debris Flow Entrainment and Momentum Growth

Zheng

Liu

et al. 2022

JGR Earth Surface

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Forest wildfires leave vast areas with burned topsoil that is water repellent, susceptible to erosion by surface runoff and a potential source of debris flow. To mitigate post‐fire debris flow hazards, debris resisting barriers are usually constructed in the flow path. However, the fundamental interaction mechanisms of debris flow on a water repellent bed and the momentum exchange process that governs the destructive potential of debris flows have yet to be elucidated. This study investigates the influence of bed sediment hydrophobicity on entrainment by debris flows and the impact force on a downstream barrier using a series of physical flume tests. Bed sediment with increasing contact angles (50°–130°) were used to model bed hydrophobicity from wettable to hydrophobic conditions, and volumetric water content (0%–30%) to simulate the natural unsaturated condition after rainfall in fire‐burned hillslopes. Compared to a wettable bed, a hydrophobic bed exhibits a failure pattern with slab‐by‐slab entrainment and en masse failure with a sixfold increase in the average erosion depth. A new dimensionless number is proposed to quantify the effects of contact angle on soil erosion. The flow momentum increases up to 21% after entrainment of hydrophobic bed compared to non‐erodible bed. The peak impact force on the downstream barrier can increase up to 80% for hydrophobic bed as a consequence of momentum gains after entrainment. The hydrodynamic coefficient for estimating impact force reveals the inadequacy of current design criteria of debris resisting barriers for fire‐prone vegetated hillslopes, suggesting further investigations are needed.

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“…Flow momentum decrease is also associated with the entrainment potential of the debris flow, with a progressive reduction in erosion depth toward the debouchment area. Even though the estimation of eroded material is affected by larger uncertainties than the landslides and on-channel debris volume, the debris flow's sediment yield came mostly from the entrainment of material from channel bed and lateral banks, which is a common characteristic of large debris flows worldwide (e.g., Marchi et al 2009;Gabet and Sternberg 2008;Bennet et al 2013;Shen et al 2020).…”

Section: Discussionmentioning

confidence: 99%

Characterization of a landslide-triggered debris flow at a rainforest-covered mountain region in Brazil

et al. 2021

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Debris flows represent great hazard to humans due to their high destructive power. Understanding their hydrogeomorphic dynamics is fundamental in hazard assessment studies, especially in subtropical and tropical regions where debris flows have scarcely been studied when compared to other mass-wasting processes. Thus, this study aims at systematically analyzing the meteorological and geomorphological factors that characterize a landslide-triggered debris flow at the Pedra Branca catchment (Serra do Mar, Brazil), to quantify the debris flow’s magnitude, peak discharge and velocity. A magnitude comparison with empirical equations (Italian Alps, Taiwan, Serra do Mar) is also conducted. The meteorological analysis is based on satellite data and rain gauge measurements, while the geomorphological characterization is based on terrestrial and aerial investigations, with high spatial resolution. The results indicate that it was a large-sized stony debris flow, with a total magnitude of 120,195 m3, a peak discharge of 2146.7 m3 s−1 and a peak velocity of 26.5 m s−1. The debris flow was triggered by a 188-mm rainfall in 3 h (maximum intensity of 128 mm h−1), with an estimated return period of 15 to 20 years, which, combined with the intense accumulation of on-channel debris (ca. 37,000 m3), indicates that new high-magnitude debris flows in the catchment and the region are likely to occur within the next two decades. The knowledge of the potential frequency and magnitude (F–M) can support the creation of F–M relationships for Serra do Mar, a prerequisite for reliable hazard management and monitoring programs.

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Debris flow enlargement from entrainment: A case study for comparison of three entrainment models

Cited by 21 publications

References 43 publications

The Landslide Hazard Chain in the Tapovan of the Himalayas on 7 February 2021

The Landslide Hazard Chain in the Tapovan of the Himalayas on 7 February 2021

Effects of Bed Hydrophobicity on Post‐Fire Debris Flow Entrainment and Momentum Growth

Characterization of a landslide-triggered debris flow at a rainforest-covered mountain region in Brazil

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