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Topic 5 - Numerical Modelling of Debris Flows

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Topic 5 - Numerical Modelling of Debris Flows
Cellular Automata models are a promising solution for the simulation of debris flows moving over a 3D topography. In this paper, an extensive review of SCIDDICA, a Cellular Automata model based on the equivalent fluid approach, is presented. Moreover, the main steps in the development of SCIDDICA are described with a chronological criterion. The last version of SCIDDICA (SS2) is suitable for the simulation of completely subaerial, completely subaqueous and combined subaerial-subaqueous debris flows. Main fe
Topic 5 - Numerical Modelling of Debris Flows
Recent advances in downscaling climate model precipitation predictions now yield spatially explicit patterns of rainfall that could be used to estimate shallow landslide susceptibility over large areas. In California, the United States Geological Survey is exploring community emergency response to the possible effects of a very large simulated storm event and to do so it has generated downscaled precipitation maps for the storm. To predict the corresponding pattern of shallow landslide susceptibility across
Topic 5 - Numerical Modelling of Debris Flows
The mountain hazards like snow avalanches, landslides, rock falls, debris flows all have strong destructive power which seriously threaten human lives and belongings. Therefore, it is necessary to study more about the happenings and developments of these disasters. Among the important and common features of the debris flow, the entrainment is the one that can increase the volume of debris flow and affects significantly the flow motion. These influences usually result in a more harmful and stronger destructi
Topic 5 - Numerical Modelling of Debris Flows
Pore-fluid pressure plays a crucial role in debris flows because it counteracts normal stresses at grain contacts and thereby reduces intergranular friction. Pore-pressure feedback accompanying debris deformation is particularly important during the onset of debrisflow motion, when it can dramatically influence the balance of forces governing downslope acceleration. We consider further effects of this feedback by formulating a new, depth-averaged mathematical model that simulates coupled evolution of granul
Topic 5 - Numerical Modelling of Debris Flows
A GIS-based cell model is proposed for the simulation of the routing and deposition phases of debris flow on a fan. Flow pattern is discretized by square cells, 2m size, which coincide with the DEM cells and the mixture is assumed a monophasic continuum. Flow exchange between adjacent cells is ruled by uniform flow or broad-crested weir laws and by continuity equation. Flow occurs from cells with higher surface to those with lower surface and is simulated by uniform flow law if the elevation of the formers
Topic 5 - Numerical Modelling of Debris Flows
Bouldery debris flows exhibit a rich variety of dynamics including complex fluid-like behaviour and spontaneous pattern formation. A predictive model for these flows is elusive. Among the complicating factors for these systems, mixtures of particles tend to segregate into dramatic patterns whose details are sensitive to particle property and interstitial fluids, not fully captured by continuum models. Further, the constitutive behaviour of particulate flows are sensitive to the particle size distributions.
Topic 5 - Numerical Modelling of Debris Flows
A kinematic model is developed to estimate the velocity and runout distance of a gravitative debris flow. The characteristics and the different stages of development of a gravitative flow are first described. The equations governing the motion during the flow are then derived based on the Newtonian translation motion with some simplified assumptions on the erosion process along the flow path. After the motion is initiated, the debris is considered to behave as a frictional material with the friction angle d
Topic 5 - Numerical Modelling of Debris Flows
We present a quasi three-dimensional numerical model to simulate debris flows accounting for a continuum non-Newtonian fluid phase composed by water and fine sediments, and a non-continuum phase for large particles such as boulders. Particles are treated in a Lagrangian frame of reference using the 3D Discrete Element Method. The fluid phase flow equations are solved by the RiverFLO- 2D computational model which is based on the 2D depth-averaged shallow water approximation and uses the Finite Element Method
Topic 5 - Numerical Modelling of Debris Flows
2D muddy debris flow has been simulated according to a dam break like problem along a slope. The two sets of equations related to the fluid and solid phases, as considered by the debris flow mixture theory, have been simplified in only one set of equations, considering just one equivalent material. Then the Herschel- Bulkley fluid constitutive equations have been selected. The correct parameters of the Hersch el-Bulkley model have been chosen in order to correctly simulate the behaviour of mudflows. The fin
Topic 5 - Numerical Modelling of Debris Flows
Previous studies have shown that numerical simulation models commonly used for debris flows may not be applicable for large-scale debris flows. In this study, we developed a technique for simulation of large-scale stony debris flows. For this purpose, we tested the hypothesis that the motion of fine sediment in these debris flows is similar to that of the interstitial water. We developed key parameters to simulate large-scale debris flows, such as sediment concentration, fluid density, and representative pa
Topic 5 - Numerical Modelling of Debris Flows
In mountainous area, cross drainage culvert is commonly used to allow water and debris to pass underneath road or embankment. Flood and debris flows typically undergo a sudden change of the flow depth in the open channel with culvert due to the discontinuity of the bottom slope and the cross-sectional area near the culvert inlet, which can result in culvert failure due to blockage. In this study, we seek to improve our understanding of the culvert flow and its transition in such open channel. A second-order
Topic 5 - Numerical Modelling of Debris Flows
The aim of the work is to develop a system capable of providing debris flow warnings in areas where historical events data are not available as well as in the case of changing environments and climate. For these reasons, critical rainfall threshold curves are derived from mathematical and numerical simulations rather than the classical derivation from empirical rainfall data. The possible formation of debris flow is simulated through infinite-slope stability analysis. Land instability is governed by the inc
Topic 5 - Numerical Modelling of Debris Flows
This work examines dam-break flows of dry granular material and investigates the suitability of the depth-averaged models with particular attention being given to the description of the shear stresses and pressure terms. The experimental results of dam-break flows down a gently sloped channel have been reported. Tests were carried out on both a smooth Plexiglas bed as well as a rough one. Measurements of the flow depth profiles and the front wave position were obtained using two digital cameras. In order to
Topic 5 - Numerical Modelling of Debris Flows
Recently, debris-flow kinds of phenomena have been reproduced by means of Lagrangian methods, such as Distinct Element Method (DEM) or Lagrangian Finite Element Method (LFEM). Among the others, meshless, Lagrangian numerical method, known as Smoothed Particle Hydrodynamics (SPH), is here applied to simulate debris-flow initiation and propagation over the slope of a mountain located in the city of Nocera Inferiore (Southern Italy). Debris-flows have been simulated since long time for hazard mitigation assess
Topic 5 - Numerical Modelling of Debris Flows
Earthquakes and heavy rainfall result in the formation of landslide dams following a massive collapse or landslide. Landslide dams can result in catastrophic outburst floods or debris flows when the dam breaches with overtopping erosion. Therefore, it is important to determine the discharge rate and area of flooding due to overtopping erosion to mitigate disasters triggered by landslide dams. This study applied a two-layer model that incorporates a slope-collapse model to the erosion process at landslide da
Topic 5 - Numerical Modelling of Debris Flows
The Campania Region (southern Italy) is characterized by a frequent occurrence of volcaniclastic debris flows causing extreme loss of life and property damage where a large population occupies alluvial fans. In 1954 the small town of Maiori was struck by several debris flows initiated as soil slips triggered by prolonged rainfalls. Historical sources report seaward shift of the coastline of some tens of metres during major flood events, also documented by air photographs taken soon after the disaster. The 1
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