Numerical Simulations of Debris Flows and Its Application in Hazard Assessments

2017 ◽  
pp. 571-576
Author(s):  
K. T. Chau
Keyword(s):  
Numerical Simulations ◽  
Debris Flows ◽  
Hazard Assessments

Numerical simulations of flow motion and deposition characteristics of granular debris flows

2009 ◽  
Vol 50 (3) ◽  
pp. 623-650 ◽  
Author(s):  
Der-Guey Lin ◽  
Sen-Yen Hsu ◽  
Kuang-Tsung Chang
Keyword(s):  
Numerical Simulations ◽  
Debris Flows ◽  
Flow Motion

scholarly journals Debris-Flow Hazard Assessments: A Practitioner's View

2021 ◽  
Author(s):  
Matthias Jakob
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Three Dimensional ◽  
Extreme Value Statistics ◽  
Major Life ◽  
Two Factors ◽  
Hazard Assessments ◽  
Cost Efficient ◽  
Multi Phase ◽  
Debris Flow Hazard

ABSTRACT Substantial advances have been achieved in various aspects of debris-flow hazard assessments over the past decade. These advances include sophisticated ways to date previous events, two- and three-dimensional runout models including multi-phase flows and debris entrainment options, and applications of extreme value statistics to assemble frequency–magnitude analyses. Pertinent questions have remained the same: How often, how big, how fast, how deep, how intense, and how far? Similarly, although major life loss attributable to debris flows can often, but not always, be avoided in developed nations, debris flows remain one of the principal geophysical killers in mountainous terrains. Substantial differences in debris-flow hazard persist between nations. Some rely on a design magnitude associated with a specific return period; others use relationships between intensity and frequency; and some allow for, but do not mandate, in-depth quantitative risk assessments. Differences exist in the management of debris-flow risks, from highly sophisticated and nation-wide applied protocols to retroaction in which catastrophic debris flows occur before they are considered for mitigation. Two factors conspire to challenge future generations of debris-flow researchers, practitioners, and decision makers: Population growth and climate change, which are increasingly manifested by augmenting hydroclimatic extremes. While researchers will undoubtedly finesse future remote sensing, dating, and runout techniques and models, practitioners will need to focus on translating those advances into practical cost-efficient tools and integrating those tools into long-term debris-flow risk management.

scholarly journals Hazard assessment of debris flows for Leung King Estateof Hong Kong by incorporating GIS with numericalsimulations

2004 ◽  
Vol 4 (1) ◽  
pp. 103-116 ◽  
Author(s):  
K. T. Chau ◽  
K. H. Lo
Keyword(s):  
Hong Kong ◽  
Debris Flow ◽  
Numerical Simulations ◽  
Computer Simulations ◽  
Debris Flows ◽  
Potential Hazard ◽  
Expert Opinions ◽  
Flow Parameters ◽  
Digital Elevation ◽  
Elevation Model

Abstract. As over seventy percent of the land of Hong Kong is mountainous, rainfall-induced debris flows are not uncommon in Hong Kong. The objective of this study is to incorporate numerical simulations of debris flows with GIS to identify potential debris flow hazard areas. To illustrate this approach, the proposed methodology is applied to Leung King Estate in Tuen Mun. A Digital Elevation Model (DEM) of the terrain and the potential debris-flow sources were generated by using GIS to provide the required terrain and flow source data for the numerical simulations. A theoretical model by Takahashi et al. (1992) improved by incorporating a new erosion initiation criterion was used for simulating the runout distances of debris flows. The well-documented 1990 Tsing Shan debris flow, which occurred not too far from Leung King Estate, was used to calibrate most of the flow parameters needed for computer simulations. Based on the simulation results, a potential hazard zone was identified and presented by using GIS. Our proposed hazard map was thus determined by flow dynamics and a deposition mechanism through computer simulations without using any so- called expert opinions, which are bounded to be subjective and biased.

scholarly journals Numerical Simulation of Failure Behavior of Granular Debris Flows Based on Flume Model Tests

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Jian Zhou ◽  
Ye-xun Li ◽  
Min-cai Jia ◽  
Cui-na Li
Keyword(s):  
Numerical Simulation ◽  
Debris Flow ◽  
Numerical Simulations ◽  
Failure Mode ◽  
Debris Flows ◽  
Fine Particles ◽  
Model Tests ◽  
Failure Behavior ◽  
Medium Sand ◽  
Grain Sizes

In this study, the failure behaviors of debris flows were studied by flume model tests with artificial rainfall and numerical simulations (PFC3D). Model tests revealed that grain sizes distribution had profound effects on failure mode, and the failure in slope of medium sand started with cracks at crest and took the form of retrogressive toe sliding failure. With the increase of fine particles in soil, the failure mode of the slopes changed to fluidized flow. The discrete element methodPFC3Dcan overcome the hypothesis of the traditional continuous medium mechanic and consider the simple characteristics of particle. Thus, a numerical simulations model considering liquid-solid coupled method has been developed to simulate the debris flow. Comparing the experimental results, the numerical simulation result indicated that the failure mode of the failure of medium sand slope was retrogressive toe sliding, and the failure of fine sand slope was fluidized sliding. The simulation result is consistent with the model test and theoretical analysis, and grain sizes distribution caused different failure behavior of granular debris flows. This research should be a guide to explore the theory of debris flow and to improve the prevention and reduction of debris flow.

scholarly journals Debris-flow deposition zones – an example from the southern slopes of Stara Planina Mountain (village of Anton area)

2020 ◽  
Vol 81 (3) ◽  
pp. 192-194
Author(s):  
Zornitsa Dotseva
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Preliminary Analysis ◽  
Field Observations ◽  
Geological Characteristics ◽  
Mountain Village ◽  
Raster Analysis ◽  
Hazard Assessments ◽  
Flow Activity

The analysis of the deposition zones is one of the main steps in the debris flows hazard assessments. For the area located north and northeast of Anton village is known that in the last 100 years there is at least one debris flow event. Field observations, geological characteristics, and raster analysis for prediction of possible sediment accumulations over the fans, related with debris flow activity were performed for preliminary analysis of the debris flows hazard in the area.

scholarly journals Impact of a Random Sequence of Debris Flows on Torrential Fan Formation

Geosciences ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 64 ◽  
Author(s):  
Nejc Bezak ◽  
Jošt Sodnik ◽  
Matjaž Mikoš
Keyword(s):  
Debris Flow ◽  
Numerical Simulations ◽  
Rheological Properties ◽  
Debris Flows ◽  
Random Sequence ◽  
Rheological Parameters ◽  
Model Parameters ◽  
Maximum Height ◽  
Wide Range ◽  
The Impact

Debris flows with different magnitudes can have a large impact on debris fan characteristics such as height or slope. Moreover, knowledge about the impact of random sequences of debris flows of different magnitudes on debris fan properties is sparse in the literature and can be improved using numerical simulations of debris fan formation. Therefore, in this paper we present the results of numerical simulations wherein we investigated the impact of a random sequence of debris flows on torrential fan formation, where the total volume of transported debris was kept constant, but different rheological properties were used. Overall, 62 debris flow events with different magnitudes from 100 m3 to 20,000 m3 were selected, and the total volume was approximately 225,000 m3. The sequence of these debris flows was randomly generated, and selected debris fan characteristics after the 62 events were compared. For modeling purposes, we applied the Rapid Mass Movement Simulations (RAMMS) software and its debris flow module (RAMMS-DF). The modeling was carried out using (a) real fan topography from an alpine environment (i.e., an actual debris fan in north-west (NW) Slovenia formed by the Suhelj torrent) and (b) an artificial surface with a constant slope. Several RAMMS model parameters were tested. The simulation results confirm that the random sequence of debris flow events has only some minor effects on the fan formation (e.g., slope, maximum height), even when changing debris flow rheological properties in a wide range. After the 62 events, independent of the selected sequence of debris flows, the final fan characteristics were not significantly different from each other. Mann–Whitney (MW) tests and t-tests were used for this purpose, and the selected significance level was 0.05. Moreover, this conclusion applies for artificial and real terrain and for a wide range of tested RAMMS model rheological parameters. Further testing of the RAMMS-DF model in real situations is proposed in order to better understand its applicability and limitations under real conditions for debris flow hazard assessment or the planning of mitigation measures.

Direct Numerical Simulations of Gas–Liquid Multiphase Flows

2001 ◽  
Author(s):  
Grétar Tryggvason ◽  
Ruben Scardovelli ◽  
Stéphane Zaleski
Keyword(s):  
Numerical Simulations ◽  
Multiphase Flows ◽  
Direct Numerical Simulations

Saturation mechanism and generated viscosity in gravito-turbulent accretion disks

2020 ◽  
Vol 640 ◽  
pp. A53
Author(s):  
L. Löhnert ◽  
S. Krätschmer ◽  
A. G. Peeters
Keyword(s):  
Growth Rate ◽  
Numerical Simulations ◽  
Accretion Disks ◽  
Gravitational Instability ◽  
Turbulent Viscosity ◽  
Radial Distance ◽  
Maximum Growth ◽  
Wave Number ◽  
Radiative Cooling ◽  
Mixing Length

Here, we address the turbulent dynamics of the gravitational instability in accretion disks, retaining both radiative cooling and irradiation. Due to radiative cooling, the disk is unstable for all values of the Toomre parameter, and an accurate estimate of the maximum growth rate is derived analytically. A detailed study of the turbulent spectra shows a rapid decay with an azimuthal wave number stronger than ky−3, whereas the spectrum is more broad in the radial direction and shows a scaling in the range kx−3 to kx−2. The radial component of the radial velocity profile consists of a superposition of shocks of different heights, and is similar to that found in Burgers’ turbulence. Assuming saturation occurs through nonlinear wave steepening leading to shock formation, we developed a mixing-length model in which the typical length scale is related to the average radial distance between shocks. Furthermore, since the numerical simulations show that linear drive is necessary in order to sustain turbulence, we used the growth rate of the most unstable mode to estimate the typical timescale. The mixing-length model that was obtained agrees well with numerical simulations. The model gives an analytic expression for the turbulent viscosity as a function of the Toomre parameter and cooling time. It predicts that relevant values of α = 10−3 can be obtained in disks that have a Toomre parameter as high as Q ≈ 10.

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