Debris flow run-out simulation and analysis using a dynamic model

Abstract. Only two months after a huge forest fire occurred in the upper part of a valley located in central Portugal, several debris flows were triggered by intense rainfall. The event caused infrastructural and economic damage, although no lives were lost. The present research aims to simulate the run-out of two debris flows that occurred during the event as well as to calculate via back-analysis the rheological parameters and the excess rain involved. Thus, a dynamic model was used, which integrates surface runoff, concentrated erosion along the channels, propagation and deposition of flow material. Afterwards, the model was validated using 32 debris flows triggered during the same event that were not considered for calibration. The rheological and entrainment parameters obtained for the most accurate simulation were then used to perform three scenarios of debris flow run-out on the basin scale. The results were confronted with the existing buildings exposed in the study area and the worst-case scenario showed a potential inundation that may affect 345 buildings. In addition, six streams where debris flow occurred in the past and caused material damage and loss of lives were identified.

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Debris flow run-out simulation and analysis using a dynamic model

10.5194/nhess-2017-280 ◽

2017 ◽

Author(s):

Raquel Melo ◽

Theo van Asch ◽

José L. Zêzere

Keyword(s):

Debris Flow ◽

Dynamic Model ◽

Debris Flows ◽

Back Analysis ◽

Quantitative Information ◽

Rheological Parameters ◽

Case Scenario ◽

Worst Case ◽

Basin Scale ◽

Central Portugal

Abstract. Only two months after a huge wildfire occurred in the upper part of a valley located in Central Portugal, several debris flows were triggered by intense rainfall. The event caused infrastructural and economical damage, although no life was lost. The present research aims to simulate the run-out of two debris flows occurred during the event as well as to calculate by back-analysis the rheological parameters and the excess rain involved. Thus, a dynamic model was used, which integrates surface runoff, concentrated erosion along the channels, propagation and deposition of flow material. The rheological and entrainment parameters obtained for the most accurate simulation were then used to perform three scenarios of debris flows run-out at the basin scale. Due to the lack of quantitative information to validate these models, the results were compared with historical references of debris flow events in the study area. Six streams were identified, where debris flows occurred in the past and caused material damage and loss of lives. The worst-case scenario carried out at the basin scale shows a potential inundation that may affect 345 buildings at the present day.

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On the use of the calibration-based approach for debris-flow forward-analyses

Natural Hazards and Earth System Science ◽

10.5194/nhess-10-1009-2010 ◽

2010 ◽

Vol 10 (5) ◽

pp. 1009-1019 ◽

Cited By ~ 13

Author(s):

M. Pirulli

Keyword(s):

Debris Flow ◽

Debris Flows ◽

Single Phase ◽

Back Analysis ◽

Numerical Approach ◽

Rheological Parameters ◽

Trial And Error ◽

Back Calculation ◽

Selection Of ◽

Volume Size

Abstract. In the present paper the problem of modeling the propagation of potential debris flows is tackled resorting to a numerical approach. In particular, numerical analyses are carried out with the RASH3D code, based on a single-phase depth-averaged continuum mechanics approach. Since each numerical analysis requires the selection of a rheology and the setting of the rheological input parameters, a calibration-based approach, where the rheological parameters are constrained by systematic adjustment during trial-and-error back-analysis of full-scale events, has been assumed. The back-analysis of a 1000 m3 debris flow, located at Tate's Cairn, Hong Kong, and the forward-analysis of a 10 000 m3 potential debris flow, located in the same basin have been used to investigate the transferability of back-calculated rheological parameters from one case to another. Three different rheologies have been tested: Frictional, Voellmy and Quadratic. From obtained results it emerges that 1) the back-calculation of a past event with different rheologies can help in selecting the rheology that better reproduces the runout of the analysed event and, on the basis of that selection, can give some indication about the dynamics of the investigated flow, 2) the use of back-calculated parameters for forward purposes requires that past and potential events have similar characteristics, some of which are a function of the assumed rheology. Among tested rheologies, it is observed that the Quadratic rheology is more influenced by volume size than Frictional and Voellmy rheologies and consequently its application requires that events are also similar in volume.

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Identifying buildings at risk and pedestrian travel times to safety areas in a debris flow worst-case scenario

10.5194/egusphere-egu2020-2403 ◽

2020 ◽

Author(s):

Raquel Melo ◽

José Luís Zêzere ◽

Sérgio Oliveira ◽

Ricardo Garcia ◽

Sandra Oliveira ◽

...

Keyword(s):

At Risk ◽

Debris Flow ◽

Early Warning ◽

Debris Flows ◽

Case Scenario ◽

Worst Case ◽

Evacuation Modelling ◽

Worst Case Scenario ◽

Pedestrian Evacuation ◽

Pedestrian Travel

During the last two centuries, several debris flow events occurred in the upper part of the Z&#234;zere valley, which is located in the Estrela mountain, in Central Portugal. These events were responsible for material damage as well as for the loss of lives. Given the susceptibility of this area to the occurrence of debris flows, a methodology for pedestrian evacuation modelling was implemented, in order to identify buildings at risk and pedestrian travel times to safety areas in a debris flow worst-case scenario. Starting from a dynamic run-out model, developed in previous works, the potential debris flow intensity was estimated (e.g. flow depth, velocity and run-out distance). Sequentially, the buildings potentially affected by the impact of debris flows, as well as the ones where the evacuation would take longer than the debris flows arrival, were identified. In addition, the potentially exposed population was estimated by applying a dasymetric distribution to each residential building. This population distribution took into account the identification of the older residents as the most exposed to debris flows, which is critical to develop reliable pedestrian evacuation travel time scenarios. The pedestrian evacuation modelling was performed using the Pedestrian Evacuation Analyst, a GIS tool developed by the United States Geological Survey. The evacuation modelling was based on an anisotropic approach, which considers the influence of slope direction on travel costs, thus its application is suitable in a mountainous area. The implemented methodology is a critical step towards the implementation of a reliable early warning system to debris flows that can be reproduced elsewhere.Funding information: This work was financed by national funds through FCT&#8212;Portuguese Foundation for Science and Technology, I.P., under the framework of the project BeSafeSlide&#8212;Landslide Early Warning soft technology prototype to improve community resilience and adaptation to environmental change (PTDC/GES-AMB/30052/2017)&#160;and by the&#160;Research Unit UIDB/00295/2020. Pedro Pinto Santos is funded by FCT through the project with the reference CEEIND/00268/2017.

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Impact of Xylella fastidiosa subspecies pauca in European olives

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1912206117 ◽

2020 ◽

Vol 117 (17) ◽

pp. 9250-9259 ◽

Cited By ~ 17

Author(s):

Kevin Schneider ◽

Wopke van der Werf ◽

Martina Cendoya ◽

Monique Mourits ◽

Juan A. Navas-Cortés ◽

...

Keyword(s):

Xylella Fastidiosa ◽

Plant Diseases ◽

Disease Spread ◽

Economic Damage ◽

Climatic Suitability ◽

Case Scenario ◽

Worst Case ◽

Ongoing Research ◽

Phytosanitary Measures ◽

The Impact

Xylella fastidiosa is the causal agent of plant diseases that cause massive economic damage. In 2013, a strain of the bacterium was, for the first time, detected in the European territory (Italy), causing the Olive Quick Decline Syndrome. We simulate future spread of the disease based on climatic-suitability modeling and radial expansion of the invaded territory. An economic model is developed to compute impact based on discounted foregone profits and losses in investment. The model projects impact for Italy, Greece, and Spain, as these countries account for around 95% of the European olive oil production. Climatic suitability modeling indicates that, depending on the suitability threshold, 95.5 to 98.9%, 99.2 to 99.8%, and 84.6 to 99.1% of the national areas of production fall into suitable territory in Italy, Greece, and Spain, respectively. For Italy, across the considered rates of radial range expansion the potential economic impact over 50 y ranges from 1.9 billion to 5.2 billion Euros for the economic worst-case scenario, in which production ceases after orchards die off. If replanting with resistant varieties is feasible, the impact ranges from 0.6 billion to 1.6 billion Euros. Depending on whether replanting is feasible, between 0.5 billion and 1.3 billion Euros can be saved over the course of 50 y if disease spread is reduced from 5.18 to 1.1 km per year. The analysis stresses the necessity to strengthen the ongoing research on cultivar resistance traits and application of phytosanitary measures, including vector control and inoculum suppression, by removing host plants.

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Debris flow event on Osorno volcano, Chile, during summer 2017: new interpretations for chain processes in the southern Andes

Natural Hazards and Earth System Science ◽

10.5194/nhess-21-3015-2021 ◽

2021 ◽

Vol 21 (10) ◽

pp. 3015-3029

Author(s):

Ivo Janos Fustos-Toribio ◽

Bastian Morales-Vargas ◽

Marcelo Somos-Valenzuela ◽

Pablo Moreno-Yaeger ◽

Ramiro Muñoz-Ramirez ◽

...

Keyword(s):

Debris Flow ◽

Water Content ◽

Debris Flows ◽

Back Analysis ◽

High Sensitivity ◽

Initial Water Content ◽

Southern Andes ◽

Initial Water ◽

Geomorphological Mapping ◽

In Situ Data

Abstract. Debris flow generation in volcanic zones in the southern Andes has not been widely studied, despite the enormous economic and infrastructure damage that these events can generate. The present work contributes to the understanding of these dynamics based on a study of the 2017 Petrohué debris flow event from two complementary points of view. First, a comprehensive field survey allowed us to determine that a rockfall initiated the debris flow due to an intense rainfall event. The rockfall lithology corresponds to lava blocks and autobrecciated lavas, predominantly over 1500 m a.s.l. Second, the process was numerically modelled and constrained by in situ data collection and geomorphological mapping. The event was studied by back analysis using the height of flow measured on Route CH-255 with errors of 5 %. Debris flow volume has a high sensitivity with the initial water content in the block fall zone, ranging from 4.7×105 up to 5.5×105 m3, depending on the digital elevation model (DEM) used. Therefore, debris flow showed that the zone is controlled by the initial water content available previous to the block fall. Moreover, our field data suggest that future debris flows events can take place, removing material from the volcanic edifice. We conclude that similar events could occur in the future and that it is necessary to increase the mapping of zones with autobrecciated lava close to the volcano summit. The study contributes to the understanding of debris flows in the southern Andes since the Osorno volcano shares similar features with other stratovolcanoes in the region.

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On the application of kinematic models to simulate the diffusive processes of debris flows

Natural Hazards and Earth System Science ◽

10.5194/nhess-10-1689-2010 ◽

2010 ◽

Vol 10 (8) ◽

pp. 1689-1695 ◽

Cited By ~ 1

Author(s):

M. Arattano ◽

L. Franzi

Keyword(s):

Debris Flow ◽

Debris Flows ◽

Diffusion Processes ◽

Kinematic Model ◽

Wave Model ◽

Momentum Equation ◽

Case Scenario ◽

Kinematic Approximation ◽

Kinematic Models ◽

Frictional Forces

Abstract. Debris flows generally propagate along steep mountain torrents with dynamics primarily governed by gravitational and frictional forces. Thus, debris flows modelling can be successfully performed through the application of kinematic models, which consider only the effects of slope and friction and neglect the remaining terms of the momentum equation. However, the diffusion processes that can be observed in the field, such as the spreading of the debris flow wave as it flows downstream, can not be theoretically predicted by kinematic models, since diffusion is a second-order process neglected in the kinematic approximation. In this paper, this issue is discussed and an application for both a generalized diffusion wave model and a kinematic model is proposed of a debris flow which occurred in an Italian instrumented torrent to identify, in a real case scenario, the effective value of the neglected terms in the kinematic approximation.

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Anticipating cascading risks at the imminent Hochvogel peak failure

10.5194/egusphere-egu21-9581 ◽

2021 ◽

Author(s):

Johannes Leinauer ◽

Manfred Meindl ◽

Benjamin Jacobs ◽

Verena Stammberger ◽

Michael Krautblatter

Keyword(s):

Debris Flow ◽

Debris Flows ◽

Point Clouds ◽

Volume Estimation ◽

Rock Fall ◽

Recent Case ◽

Hazard Evaluation ◽

Event Analysis ◽

Worst Case ◽

Cascading Effects

Climatic changes are exacerbating the risk of alpine mass movements for example through more frequent and extreme heavy precipitation events. To cope with this situation, the monitoring, anticipation, and early warning of rock slope failures based on process dynamics is a key strategy for alpine communities. However, only investigating the release area of an imminent event is insufficient, as the primary hazard can trigger or increase secondary hazards like debris flows or the damming of a river. Nevertheless, recent case studies dealing with successive hazards are rarely existent for the Calcareous Alps. In this study, we precisely investigate the cascading effects resulting from an imminent rock fall and perform a pre-event analysis instead of back-modelling of a past event.The Hochvogel summit (2592 m&#160;a.s.l., Allg&#228;u Alps, Germany/Austria) is divided by several pronounced clefts that separate multiple instable blocks. 3D-UAV point clouds reveal a potentially instable mass of 260,000&#160;m&#179; in six main subunits. From our near real time monitoring system (Leinauer et al. 2020), we know that some cracks are opening at faster pace and react differently to heavy rainfall, making a successive failure of subunits likely. However, pre-deformations are not yet pronounced enough to decide on the exact expected volume whereas secondary effects are likely as the preparing rock fall mass will be deposited into highly debris-loaded channels. Therefore, we developed different rock fall scenarios from the gathered monitoring information, which we implemented into a RAMMS modelling of secondary debris flows. To obtain best- and worst-case results, each scenario is calculated with different erosion parameters in the runout channel. The models are calibrated with a well-documented debris flow event at Ro&#223;bichelgraben (10&#160;km NW and similar lithology) and are supported by field investigations in the runout channel including electrical resistivity tomography profiles (ERT) for determination of the depth of erodible material as well as a drone survey for mapping the area and the generation of an elevation model.Here we show a comprehensive scenario-based assessment for anticipating cascading risks at the Hochvogel from initial rock failure volume estimation to debris flow evolution and potential river damming. This recent case study from an alpine calcareous peak is an excellent and rare chance to gain insights into cascading risks modelling and an improved hazard evaluation.

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Simplified simulation of rock avalanches and subsequent debris flows with a single thin-layer model. Application to the Prêcheur river (Martinique, Lesser Antilles)

10.5194/egusphere-egu21-2752 ◽

2021 ◽

Author(s):

Marc Peruzzetto ◽

Clara Levy ◽

Yannick Thiery ◽

Gilles Grandjean ◽

Anne Mangeney ◽

...

Keyword(s):

Debris Flow ◽

Thin Layer ◽

Debris Flows ◽

Initial Conditions ◽

Rock Avalanche ◽

Numerical Code ◽

Lesser Antilles ◽

Rheological Parameters ◽

Model Parameters ◽

High Discharge

This work focuses on the use of thin-layer models for simulating fast gravitational flows for hazard assessment. Such simulations are sometimes difficult to carry out because of the uncertainty on initial conditions and on simulation parameters. In this study, we aggregate various field data to constrain realistic initial conditions and to calibrate the model parameters. By using the SHALTOP numerical code, we choose a simple and empirical rheology to model the flow (no more than two parameters), but we model more finely the geometrical interactions between the flow and the topography. We can thus model both a rock avalanche, and the subsequent remobilization of the deposits as a high discharge debris flow.Using the Pr&#234;cheur river catchment (Martinique, Lesser Antilles) as a case study, we focus on extreme events with a high potential to impact populations and infrastructures. We use geological and geomorphological data, topographic surveys, seismic recordings and granulometric analysis to define realistic simulation scenarios and determine the main characteristics of documented events. The latter are then reproduced to calibrate rheological parameters. With a single rheological parameter and the Coulomb rheology, we thus model the emplacement and main dynamic characteristics of a recent rock avalanche, as well as the travel duration and flooded area of a documented high discharge debris flow. Then, in a forward prediction simulation, we model a possible 1.9x106 m3 rock avalanche, and the instantaneous remobilization of the resulting deposits as a high-discharge debris flow. We show that successive collapses allow to better reproduce the dynamics of the rock avalanche, but do not change the geometry of the final deposits, and thus do not influence the initial conditions of the subsequent debris flow simulation. A progressive remobilization of the materials slows down the debris flow and limits overflow, in comparison to instantaneous release. However, we show that high discharge debris flows, such as the one considered for model calibration, are better reproduced with an instantaneous initiation. The range of travel times measured for other significant debris flows in the Pr\^echeur river is consistent with our simulation results, with various rheological parameters and the Coulomb or Voellmy rheology.

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Numerical simulation of debris flows

Canadian Geotechnical Journal ◽

10.1139/t99-089 ◽

2000 ◽

Vol 37 (1) ◽

pp. 146-160 ◽

Cited By ~ 117

Author(s):

H Chen ◽

C F Lee

Keyword(s):

Hong Kong ◽

Debris Flow ◽

Numerical Solution ◽

Dynamic Model ◽

Debris Flows ◽

Soil Column ◽

Three Dimensional ◽

Landslide Risk ◽

Lumped Mass ◽

Runout Distance

A key requirement in the assessment of landslide risk in such densely populated urban areas as Hong Kong consists of the prediction of potential runout distance or the extent of the subsequent debris flow. This paper presents a three-dimensional dynamic model of unsteady gravity-driven debris flow. The Lagrangian Galerkin finite element method is used to determine the nodal velocity and depth of soil column elements within the sliding mass, with the momentum and mass conservation mathematically closed within the soil column elements. The numerical solution also features a lumped mass matrix and a volume-weighted procedure. The method of least squares approximation plays a smoothing role which enhances stability and efficiency of the numerical solution scheme. The nodal elevation during sliding is obtained via a dynamic bilinear interpolation of the elevation function for the base of the sliding mass. Furthermore, the accuracy, robustness, and generality of this method are validated by experimental results. Its application to the Shum Wan Road landslide and the Fei Tsui Road landslide, both of which occurred during a heavy rainstorm in Hong Kong on 13 August 1995 and involved fatalities, gives reasonable results in comparison to the field observations. A variety of rheological constitutive relationships have already been coded in the present program to provide flexibility and adaptability in practical applications.Key words: debris flows, three-dimensional dynamic model, runout distance.

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Assessing potential debris flow runout: a comparison of two simulation models

Natural Hazards and Earth System Science ◽

10.5194/nhess-8-961-2008 ◽

2008 ◽

Vol 8 (4) ◽

pp. 961-971 ◽

Cited By ~ 34

Author(s):

M. Pirulli ◽

G. Sorbino

Keyword(s):

Debris Flow ◽

Back Analysis ◽

Simulation Models ◽

Numerical Code ◽

Rheological Parameters ◽

Rheological Parameter ◽

Safe Side ◽

Study Sites ◽

Comparison Of The Results ◽

Parameter Values

Abstract. In the present paper some of the problems related to the application of the continuum mechanics modelling to debris flow runout simulation are discussed. Particularly, a procedure is proposed to face the uncertainties in the choice of a numerical code and in the setting of rheological parameter values that arise when the prediction of a debris flow propagation is required. In this frame, the two codes RASH3D and FLO2D are used to numerically analyse the propagation of potential debris flows affecting two study sites in Southern Italy. For these two study sites, a lack in information prevents that the rheological parameters can be obtained from the back analysis of similar well documented debris flow events in the area. As a prediction of the possible runout area is however required by decision makers, an alternative approach based on the analysis of the alluvial fans existing at the toe of the two studied basins is proposed to calibrate rheological parameters on the safe side. From the comparison of the results obtained with RASH3D (where a Voellmy and a Quadratic rheologies are implemented) and FLO2D (where a Quadratic rheology is implemented) it emerges that, for the two examined cases, numerical analyses carried out with RASH3D assuming a Voellmy rheology can be considered on the safe side respect to those carried out with a Quadratic rheology.

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