Back-analysis of geophysical flows using three-dimensional runout model

Koo, R.C.H.; Kwan, J.S.H.; Lam, Carlos; Goodwin, George Robert; Choi, Clarence Edward; Ng, Charles Wang Wai; Yiu, Jack; Ho, Ken; Pun, W. K.

doi:10.1139/cgj-2016-0578

Cited by 30 publications

(2 citation statements)

References 28 publications

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“…This is especially pertinent since the clay content of submarine debris flows is expected to change from the initiation of a submarine landslide to its final deposition. Without rational rheological models that can capture the effects of clay content, then the practical value of numerical tools for vulnerability assessments will be limited (Koo et al., 2018).…”

Section: Discussionmentioning

confidence: 99%

Mechanisms of Submarine Debris Flow Growth

Song

et al. 2022

JGR Earth Surface

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Submarine debris flows are among the largest types of landslide on planet Earth. They occur under the cloak of the sea so little is known about how they reach such large volumes. Field evidence suggests that the entrainment from the sediment‐rich sea floor enables the growth of submarine debris flows. However, there is a dearth of understanding of the dynamic processes of entrainment. In this study, a new entrainment model is proposed for submarine debris flows with different clay contents. The entrainment model considers the relative contributions from basal grain friction and fluid viscous stresses that drive the entrainment process, and the effects of hydroplaning. To evaluate the new model, a new experimental setup is developed to simulate submarine debris flows, with clay contents from 4% to 12%, overriding and entraining a loose sand bed. The clay content is found to have profound effects on the entrainment dynamics. Flows with high clay contents (i.e., ≥10%) hydroplane, which enhances the mobility of the flow but reduces its entrainment potential. The predicted entrainment depths from the proposed model are consistent with the measured ones from the experiments. The proposed theoretical model and unique experimental evidence can be used as guiding tools to progress toward the inclusion of entrainment in vulnerability assessments of offshore infrastructure.

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Section: Discussionmentioning

confidence: 99%

Mechanisms of Submarine Debris Flow Growth

Song

et al. 2022

JGR Earth Surface

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“…However, knowledge of the runout and lateral deposition of such flows is essential. 2D runout simulation models have proven to be suitable tools for creating detailed delineation of typical mass movement deposits in torrent catchments, e.g., in [6][7][8][9][10][11], supporting the development of hazard maps and the estimation of process parameters for the design of protective measures [12]. However, the a priori estimation of process parameters as well as the magnitude of hillslope processes is typically associated with large uncertainties.…”

Section: Introductionmentioning

confidence: 99%

2D Runout Modelling of Hillslope Debris Flows, Based on Well-Documented Events in Switzerland

et al. 2020

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In mountain areas, mass movements, such as hillslope debris flows, pose a serious threat to people and infrastructure, although size and runout distances are often smaller than those of debris avalanches or in-channel-based processes like debris floods or debris flows. Hillslope debris-flow events can be regarded as a unique process that generally can be observed at steep slopes. The delimitation of endangered areas and the implementation of protective measures are therefore an important instrument within the framework of a risk analysis, especially in the densely populated area of the alpine region. Here, two-dimensional runout prediction methods are helpful tools in estimating possible travel lengths and affected areas. However, not many studies focus on 2D runout estimations specifically for hillslope debris-flow processes. Based on data from 19 well-documented hillslope debris-flow events in Switzerland, we performed a systematic evaluation of runout simulations conducted with the software Rapid Mass Movement Simulation: Debris Flow (RAMMS DF)-a program originally developed for runout estimation of debris flows and snow avalanches. RAMMS offers the possibility to use a conventional Voellmy-type shear stress approach to describe the flow resistance as well as to consider cohesive interaction as it occurs in the core of dense flows with low shear rates, like we also expect for hillslope debris-flow processes. The results of our study show a correlation between the back-calculated dry Coulomb friction parameters and the percentage of clay content of the mobilised soils. Considering cohesive interaction, the performance of all simulations was improved in terms of reducing the overestimation of the observed deposition areas. However, the results also indicate that the parameter which accounts for cohesive interaction can neither be related to soil physical properties nor to different saturation conditions.

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Investigation of Debris Flow Impact Mechanisms and Designs

Ng,

Poudyal,

Liu

et al. 2023

Progress in Landslide Research and Technology

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Debris flows are catastrophic landslides increasing in severity in recent decades due to the more frequent and intense rainfall events under climate change. Debris flows pose a serious threat to infrastructure, settlements, and the natural environment in mountainous regions around the world causing considerable economic losses every year. To mitigate debris flows, single and multiple rigid and flexible barriers are constructed along the predicted debris flow paths. Compared with single barriers, multiple barriers are more advantageous in mitigating large debris flow volumes by progressively retaining and decelerating the flow with much smaller barrier sizes. These smaller barriers are not only easier to construct on steep hillslopes but also reduce the carbon footprint compared to large single barriers. However, current understanding of debris flow impact mechanisms on single and multiple barriers is limited due to the complex composition and scale-dependent nature of debris flow. The need of using different barrier configurations further adds to this complexity and the impact mechanisms of debris flow against single and multiple barriers are yet to be elucidated, thereby hindering the development of scientific design guidelines. This paper examines the impact mechanisms of water, dry granular and two-phase debris flows on barriers of varying stiffness, openings and numbers based on physical and numerical results, and provides recommendations for design of debris-resisting single and multiple barriers.

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Back-analysis of geophysical flows using three-dimensional runout model

Cited by 30 publications

References 28 publications

Mechanisms of Submarine Debris Flow Growth

Mechanisms of Submarine Debris Flow Growth

2D Runout Modelling of Hillslope Debris Flows, Based on Well-Documented Events in Switzerland

Investigation of Debris Flow Impact Mechanisms and Designs

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