scholarly journals Propagation Characteristics of Debris Flows Considering Entrainment Effect

2018 ◽  
Vol 7 (3.34) ◽  
pp. 122
Author(s):  
Seokil Jeong ◽  
Junseon Lee ◽  
Chang Geun Song ◽  
Seung Oh Lee
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Flow Behavior ◽  
Prediction Method ◽  
Heavy Rain ◽  
Accurate Analysis ◽  
Propagation Length ◽  
2D Simulation ◽  
Entrainment Effect ◽  
The Relationship

Background/Objectives: Due to the extreme climate and the localized heavy rain, the frequency of debris flow has been increasing. Therefore, there is a growing expectation for accurate numerical analysis.Methods/Statistical analysis: We present a prediction method that can calculate the propagation length of the debris flow. This analysis indicates the relationship between the potential energy and the propagation length of the debris flow. To study the behavior of the debris flow accurately, the change in the momentum force must be considered; otherwise the calculation accuracy of the debris flow behavior is inevitably low.Findings: Entrainment is a common behavior in a debris flow that leads to changes in the momentum force. Here, we analyzed the change in the momentum force using a 2D simulation model that included entrainment. The results show how the debris flow behaves with changes in the momentum force. When entrainment is considered, the propagation length tends to be underestimated. With detailed information, the uncertainty in the prediction accuracy can be reduced.Improvements/Applications: If studies on the material properties of debris flow would be added, it will be possible to carry out various and accurate analysis of the debris flow  

scholarly journals Dimensionless Assessment Method of Landslide Dam Formation Caused by Tributary Debris Flow Events

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Kun-Ting Chen ◽  
Xiao-Qing Chen ◽  
Gui-Sheng Hu ◽  
Yu-Shu Kuo ◽  
Yan-Rong Huang ◽  
...  
Keyword(s):  
Debris Flow ◽  
Water Depth ◽  
Debris Flows ◽  
Landslide Dam ◽  
Assessment Method ◽  
Main Stream ◽  
Deposition Thickness ◽  
The Relationship ◽  
Prepared Response

In this study, we develop a dimensionless assessment method to evaluate landslide dam formation by considering the relationship between the run-out distance of a tributary debris flow and the width of the main stream, deposition thickness of the tributary debris flow, and the water depth of the main stream. Based on the theory of debris flow run-out distance and fan formation, landslide dam formation may result from a tributary debris flow as a result of two concurrent formation processes: (1) the run-out distance of the tributary debris flow must be greater than the width of the main stream, and (2) the minimum deposition thickness of the tributary debris flow must be higher than the in situ water depth of the main stream. At the confluence, one of four types of depositional scenarios may result: (1) the tributary debris flow enters into the main stream and forms a landslide dam; (2) the tributary debris flow enters into the main stream but overflow occurs, thus preventing complete blockage of the main stream; (3) the tributary debris flow enters into the main stream, does not reach the far bank, and sediment remains partially above the water elevation of the main stream; or (4) the tributary debris flow enters into the main stream, does not reach the far bank, and sediment is fully submerged in the main stream. This method was applied to the analysis of 11 tributary debris flow events during Typhoon Morakot, and the results indicate that the dimensionless assessment method can be used to estimate potential areas of landslide dam formation caused by tributary debris flows. Based on this method, government authorities can determine potential areas of landslide dam formation caused by debris flows and mitigate possible disasters accordingly through a properly prepared response plan, especially for early identification.

scholarly journals The importance of erosion for debris flow runout modelling from applications to the Swiss Alps

2015 ◽  
Vol 3 (4) ◽  
pp. 2379-2417 ◽  
Author(s):  
F. Frank ◽  
B. W. McArdell ◽  
C. Huggel ◽  
A. Vieli
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Field Data ◽  
Hazard Analysis ◽  
Maximum Shear Stress ◽  
Swiss Alps ◽  
Erosion Model ◽  
Practical Applications ◽  
Bed Erosion ◽  
The Relationship

Abstract. This study describes an investigation of channel-bed erosion of sediment by debris flows. An erosion model, developed using field data from debris flows at the Illgraben catchment, Switzerland, was incorporated into the existing RAMMS debris-flow model, which solves the 2-D shallow-water equations for granular flows. In the erosion model, the relationship between maximum shear stress and measured erosion is used to determine the maximum potential erosion depth. Additionally, the maximum rate of erosion, measured at the same field site, is used to constrain the erosion rate. The model predicts plausible erosion values in comparison with field data from highly erosive debris flow events at the Spreitgraben torrent channel, Switzerland in 2010, without any adjustment to the coefficients in the erosion model. We find that by including channel erosion in runout models a more realistic flow pattern is produced than in simulations where entrainment is not included. In detail, simulations without channel bed erosion show more lateral outflow from the channel where it has not been observed in the field. Therefore the erosion model may be especially useful for practical applications such as hazard analysis and mapping, as well as scientific case studies of erosive debris flows.

Assessment of the 2019 Chamoson debris flow event (Swiss Alps)

2020 ◽  
Author(s):  
Marc-Henri Derron ◽  
Valérie Baumann ◽  
Tiggi Choanji ◽  
François Noël ◽  
Ludovic Baron ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Heavy Rain ◽  
Peak Discharge ◽  
Swiss Alps ◽  
Mitigation Measures ◽  
Size Classification ◽  
Cone Apex ◽  
The Right ◽  
The Village

<p>Debris flows triggered by heavy rain are common and can cause huge damages in Alpine valleys. In this case we documented the changes occurred in the Losentsé valley after the 11 August 2019 event, which caused two death and several damages to the village of Chamoson. The Chamoson basin is located in the Alps on the right side of the Rhône valley. Three main rivers drain the Chamoson basin, the Losentsé, the Cry and the Tsené. The main debris flow event occurred in the Losentsé sub-basin. The Losentsé River is 9 km long from the sources at 3000 m until the alluvial cone apex at 600 m. In the upper part of the Chamoson basin thick loose debris cones and glacial deposits lie on steep slopes, the geology of the middle basin is formed by unstable clayey shales with several active landslides on both lateral valley slopes.</p><p>The village of Chamoson is located on the huge alluvial cone built with torrential events from the three main rivers. Since the XIX century, several big debris flow events (1898, 1923, 2003, 2018) were recorded in this area and mitigation measures were built in the principal rivers. Unfortunately, the 2019 debris flows overflowed the channels limit when the flows reached the alluvial cone apex, reaching the road and took a car with 2 persons inside. Upstream in the middle basin 2 wood bridges were destroyed and many concrete or stone walls (mitigation measures) along the river were damaged.</p><p>After the event we acquired pictures with a drone from the sources area and the Losentsé river valley in order to have a post event image. With this image we could analyse and map the source areas and the inundated areas in the Losentsé channel. We did also field observation along the river.</p><p>After comparing the pre- and post-event images we mapped the middle and upper basin inundated areas by the 2019 event and the described the deposits and eroded sections along the river. We calculated the peak discharge of 1000 m<sup>3</sup>/s for this event using the inundated transversal profile area near the cone apex and the flow velocity obtained from a movie. The peak discharge corresponds to 4 in the size classification for debris flows (Jacob et al., 2005).</p><p>Reference:</p><p>Jakob, M. (2005). A size classification for debris flows. Engineering geology, 79(3-4), 151-161.</p>

The role of the phase shift of fine particles on debris flow behavior: an numerical simulation for a debris flow in Illgraben, Switzerland

2021 ◽  
Vol 58 (1) ◽  
pp. 23-34
Author(s):  
Taro Uchida ◽  
Yuki Nishiguchi ◽  
Brian W. McArdell ◽  
Yoshifumi Satofuka
Keyword(s):  
Numerical Simulation ◽  
Phase Shift ◽  
Debris Flow ◽  
Simulation Model ◽  
Debris Flows ◽  
Flow Behavior ◽  
Flow Characteristics ◽  
Simulation Models ◽  
Fine Sediment ◽  
Physically Based

Physically based numerical simulation models have been developed to predict hazard area relating to debris flows. Since fine sediments are expected to behave as a part of the fluid rather than solid phase in stony debris flows, several models have recently included this process of the phase shift from solid to fluid in the context of fine sediment. However, models have not been fully tested regarding the ability to reproduce a variety of debris flow characteristics. We therefore tested (i) applicability of a numerical simulation model for describing debris flow characteristics and (ii) the effect of phase shift of fine sediment on debris flow behaviors. Herein we applied a numerical simulation model to a well-documented dataset from the Illgraben debris flow observation station in Switzerland. Based on the stony debris flow concept, we physically modeled effects of the phase shift of sediment on transport capacity and flow resistance. We successfully reproduced the observed bulk density, erosion and deposition patterns, front velocity, and erosion rate, although we had to tune the ratio of fine sediment that behaves as a fluid. Considering the effects of the phase shift of sediments, we conclude that physically based numerical simulation models can describe a variety of debris flow behaviors.

scholarly journals A Case Study on the Closed-Type Barrier Effect on Debris Flows at Mt. Woomyeon, Korea in 2011 via a Numerical Approach

Energies ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7890
Author(s):  
Shin-Kyu Choi ◽  
Tae-Hyuk Kwon
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Flow Behavior ◽  
Hazard Mitigation ◽  
Flow Characteristics ◽  
Numerical Approach ◽  
Closed Type ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Terrain Elevation

Debris flows are capable of flowing with high velocities and causing significant economic and infrastructural damage. As a hazard mitigation measure, physical barriers are frequently installed to dissipate the energy of debris flows. However, there is a lack of understanding on how barriers affect and interact with debris-flow behavior (e.g., velocity and volume). This study investigated the changes in debris-flow characteristics depending on the installation location of barriers. Mt. Woomyeon, which is located in Seoul, Korea, was the site of a major debris-flow event in 2011. This study modeled this event using DAN3D, numerical software based on smoothed particle hydrodynamics (SPH). Our numerical approach assessed changes in debris-flow behavior, including velocity and volume, as the debris flow interacts with four closed-type barriers installed at separate points along the flow path. We used DAN3D to model the barriers via terrain elevation modifications. The presence of a closed-type barrier results in the reduction in the debris-flow velocity and volume compared to when no barrier is present. Most notably, the closer a barrier is installed to the debris source, the greater the velocity decrease. By contrast, a barrier that is constructed further downstream allows the debris flow to undergo entrainment-driven growth before confronting the barrier, resulting in a larger debris deposition volume that can often cause overflow, as shown at our particular study site. The presented results highlight the effectiveness of barriers as a method of hazard mitigation by providing insight into how such installations can alter debris-flow behavior. In addition, the findings can provide a reference for future debris-flow barrier designs, increasing the effectiveness and efficiency of such barrier systems.

scholarly journals Effect of Ground Conditions and Mesh Size of Net-type Barrier on Debris Flow Behavior

2021 ◽  
Vol 21 (1) ◽  
pp. 101-110
Author(s):  
Hyeong-Jin Kim ◽  
Ji-Sung Lee ◽  
Yun-Tae Kim
Keyword(s):  
Experimental Study ◽  
Debris Flow ◽  
Debris Flows ◽  
Heavy Rainfall ◽  
Flow Behavior ◽  
Mesh Size ◽  
Front Velocity ◽  
Fine Content ◽  
Mountain Valley ◽  
Ground Conditions

Debris flow is a type of landslide that occurs mainly in mountain valley areas during heavy rainfall. Various types of barriers have been installed in South Korea to reduce the damage caused by debris flows. However, there is no reasonable design standard when installing the barrier, and an experimental study for the performance evaluation of barriers is insufficient. In this study, the performance of the net-type barrier was evaluated by analyzing the effect of the ground conditions and mesh size of the net-type barrier on the debris flow behavior by reducing the front velocity and deposition volume. As a result, for areas with less fine content, the efficiency of the net-type barrier increased as the mesh size of the net-type barrier decreased. Accordingly, the ground conditions and mesh size of the net-type barrier significantly influence the performance of the net-type barrier. The damage caused by debris flow can be sufficiently reduced through the reasonable design of a net-type barrier.

scholarly journals Influence of biopolymers on the rheological properties of seafloor sediments and the runout behavior of submarine debris flows

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jun Kameda ◽  
Hamada Yohei
Keyword(s):  
Rheological Properties ◽  
Debris Flows ◽  
Extracellular Polymeric Substances ◽  
Flow Behavior ◽  
Mass Movement ◽  
Rheological Parameters ◽  
Natural Environments ◽  
Natural Systems ◽  
Chemical Conditions ◽  
Seafloor Sediments

AbstractSubmarine debris flows are mass movement processes on the seafloor, and are geohazards for seafloor infrastructure such as pipelines, communication cables, and submarine structures. Understanding the generation and run-out behavior of submarine debris flows is thus critical for assessing the risk of such geohazards. The rheological properties of seafloor sediments are governed by factors including sediment composition, grain size, water content, and physico-chemical conditions. In addition, extracellular polymeric substances (EPS) generated by microorganisms can affect rheological properties in natural systems. Here we show that a small quantity of EPS (~ 0.1 wt%) can potentially increase slope stability and decrease the mobility of submarine debris flows by increasing the internal cohesion of seafloor sediment. Our experiments demonstrated that the flow behavior of sediment suspensions mixed with an analogue material of EPS (xanthan gum) can be described by a Herschel–Bulkley model, with the rheological parameters being modified progressively, but not monotonously, with increasing EPS content. Numerical modeling of debris flows demonstrated that the run-out distance markedly decreases if even 0.1 wt% of EPS is added. The addition of EPS can also enhance the resistivity of sediment to fluidization triggered by cyclic loading, by means of formation of an EPS network that binds sediment particles. These findings suggest that the presence of EPS in natural environments reduces the likelihood of submarine geohazards.

scholarly journals Learning Case Study of a Shallow-Water Model to Assess an Early-Warning System for Fast Alpine Muddy-Debris-Flow

Water ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 750
Author(s):  
Antonio Pasculli ◽  
Jacopo Cinosi ◽  
Laura Turconi ◽  
Nicola Sciarra
Keyword(s):  
Debris Flow ◽  
Shallow Water ◽  
Early Warning ◽  
Debris Flows ◽  
Early Warning System ◽  
Warning System ◽  
Extreme Weather Events ◽  
Water Model ◽  
Computational Time ◽  
Processing Unit

The current climate change could lead to an intensification of extreme weather events, such as sudden floods and fast flowing debris flows. Accordingly, the availability of an early-warning device system, based on hydrological data and on both accurate and very fast running mathematical-numerical models, would be not only desirable, but also necessary in areas of particular hazard. To this purpose, the 2D Riemann–Godunov shallow-water approach, solved in parallel on a Graphical-Processing-Unit (GPU) (able to drastically reduce calculation time) and implemented with the RiverFlow2D code (version 2017), was selected as a possible tool to be applied within the Alpine contexts. Moreover, it was also necessary to identify a prototype of an actual rainfall monitoring network and an actual debris-flow event, beside the acquisition of an accurate numerical description of the topography. The Marderello’s basin (Alps, Turin, Italy), described by a 5 × 5 m Digital Terrain Model (DTM), equipped with five rain-gauges and one hydrometer and the muddy debris flow event that was monitored on 22 July 2016, were identified as a typical test case, well representative of mountain contexts and the phenomena under study. Several parametric analyses, also including selected infiltration modelling, were carried out in order to individuate the best numerical values fitting the measured data. Different rheological options, such as Coulomb-Turbulent-Yield and others, were tested. Moreover, some useful general suggestions, regarding the improvement of the adopted mathematical modelling, were acquired. The rapidity of the computational time due to the application of the GPU and the comparison between experimental data and numerical results, regarding both the arrival time and the height of the debris wave, clearly show that the selected approaches and methodology can be considered suitable and accurate tools to be included in an early-warning system, based at least on simple acoustic and/or light alarms that can allow rapid evacuation, for fast flowing debris flows.

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