scholarly journals Numerical simulation of debris flows triggered from the Strug rock fall source area, W Slovenia

2006 ◽  
Vol 6 (2) ◽  
pp. 261-270 ◽  
Author(s):  
M. Mikoš ◽  
R. Fazarinc ◽  
B. Majes ◽  
R. Rajar ◽  
D. Žagar ◽  
...  
Keyword(s):  
Debris Flow ◽  
Mathematical Models ◽  
Debris Flows ◽  
Model Calibration ◽  
Source Area ◽  
Rock Fall ◽  
One Dimensional ◽  
Engineering Measures ◽  
The Village ◽  
Extreme Scenario

Abstract. The Strug landslide was triggered in December 2001 as a rockslide, followed by a rock fall. In 2002, about 20 debris flows were registered in the Kosec village; they were initiated in the Strug rock fall source area. They all flowed through the aligned Brusnik channel, which had been finished just before the first debris flow reached the village in April 2002. Debris flow events were rainfall-induced but also governed by the availability of rock fall debris in its zone of accumulation. After 2002 there was not enough material available for further debris flows to reach the village. Nevertheless, a decision was reached to use mathematical modeling to prepare a hazard map for the village for possible new debris flows. Using the hydrological data of the Brusnik watershed and the rheological characteristics of the debris material, 5 different scenarios were defined with the debris flow volumes from 1000 m3 to a maximum of 25 000 m3. Two mathematical models were used, a one-dimensional model DEBRIF-1D, and a two-dimensional commercially available model FLO-2D. Due to the lack of other field data, data extracted from available professional films of debris flows in 2002 in the Kosec village were used for model calibration. The computational reach was put together from an 800-m long upstream reach and 380-m long regulated reach of the Brusnik channel through the village of Kosec. Both mathematical models have proved that the aligned Brusnik channel can convey debris flows of the volume up to 15 000 m3. Under the most extreme scenario a debris flow with 25 000 m3 would locally spill over the existing levees along the regulated Brusnik channel. For this reason, additional river engineering measures have been proposed, such as the raising of the levees and the construction of a right-hand side sedimentation area for debris flows at the downstream end of the regulated reach.

Alternative approach for works controlling stony debris flows

2020 ◽  
Author(s):  
Carlo Gregoretti ◽  
Matteo Barbini ◽  
Martino Bernard ◽  
Mauro Boreggio
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
High Elevation ◽  
Valley Bottom ◽  
Check Dams ◽  
Retention Basin ◽  
Retention Basins ◽  
Solid Liquid ◽  
The Impact ◽  
The Village

<p>Many sites of the Dolomites are threatened by channelized debris flows: solid-liquid surges initiated by the entrainment of large quantities of sediments into the abundant runoff at the head of channel incised on fans, can dramatically increase their volume along the downstream routing. This is the case of the Rovina di Cancia site where solid-liquid surges forming in the upper part of the basin can increase their volume up and over 50000 m<sup>3</sup>, seriously impacting the downstream village of Borca di Cadore. The debris-flow channel ends just upstream the village that in the past was hit by four debris flows (three in the recent years) that caused victims and destructions. Control works built until now are not sufficient to protect the village from high magnitude debris flows and a definitive solution calls to be planned. Present works are a flat deposition area, 300 m downstream the initiation area, an open dam under construction downstream it, and  two retention basins at the end of the channel. Between the open dam and the upstream retention basin, there are the rest of eight check-dams made of gabions, built in the 60s and progressively damaged or destroyed by the debris flows occurred after their construction. This series of check-dams limited the entrainment of solid material and the occurrence of localized scours. The initial plan is the substitution of the check-dams with concrete structures and the widening of the dowsntream retention basin through the raising of high elevation embankment downstream it and the following demolition of the actual dyke. Finally, a channel crossing the village and national route on the valley bottom will deliver the fluid phase from the widened basin to the Boite river. All these control works have a very high cost for construction and maintenance and severely impact the village with the presence of a non-negligible residual risk. These drawbacks call for an alternative solution that is searched looking at to the morphology. Downstream of the open dam and on its right side, there is a deep impluvium that ends on a large grass sloping area. The novel solution requires the construction of a channel through the right high bank that deviates the debris flow into the impluvium. The impluvium, widened through the excavation of the surrounding slopes, is closed at the outlet by  an open dam. Downstream the open dam, a channel will lead to a retention basin, where most of storage volume is obtained from the excavation of the grass sloping area, limiting the elevation of the dykes At the end of this basin an open dam will deliver the debris-flow fluid part to a channel passing under the national route and joining the Boite river. Such a solution composed of a deviatory channel, two retention basins (the deep impluvium and that excavated on the sloping grass area) and the channels between and downstream them, has quite a lower costs of construction and maintenance, eliminating the impact on the village because occupying uninhabited areas without interrupting the main roads.</p>

scholarly journals Parameterization of a numerical 2-D debris flow model with entrainment: a case study of the Faucon catchment, Southern French Alps

2012 ◽  
Vol 12 (10) ◽  
pp. 3075-3090 ◽  
Author(s):  
H. Y. Hussin ◽  
B. Quan Luna ◽  
C. J. van Westen ◽  
M. Christen ◽  
J.-P. Malet ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Debris Flow ◽  
Debris Flows ◽  
Source Area ◽  
European Alps ◽  
Actual Process ◽  
French Alps ◽  
Modeling Software ◽  
Entrainment Process

Abstract. The occurrence of debris flows has been recorded for more than a century in the European Alps, accounting for the risk to settlements and other human infrastructure that have led to death, building damage and traffic disruptions. One of the difficulties in the quantitative hazard assessment of debris flows is estimating the run-out behavior, which includes the run-out distance and the related hazard intensities like the height and velocity of a debris flow. In addition, as observed in the French Alps, the process of entrainment of material during the run-out can be 10–50 times in volume with respect to the initially mobilized mass triggered at the source area. The entrainment process is evidently an important factor that can further determine the magnitude and intensity of debris flows. Research on numerical modeling of debris flow entrainment is still ongoing and involves some difficulties. This is partly due to our lack of knowledge of the actual process of the uptake and incorporation of material and due the effect of entrainment on the final behavior of a debris flow. Therefore, it is important to model the effects of this key erosional process on the formation of run-outs and related intensities. In this study we analyzed a debris flow with high entrainment rates that occurred in 2003 at the Faucon catchment in the Barcelonnette Basin (Southern French Alps). The historic event was back-analyzed using the Voellmy rheology and an entrainment model imbedded in the RAMMS 2-D numerical modeling software. A sensitivity analysis of the rheological and entrainment parameters was carried out and the effects of modeling with entrainment on the debris flow run-out, height and velocity were assessed.

scholarly journals Quantitative Analysis of the Debris Flow Societal Risk to People Inside Buildings at Different Times: A Case Study of Luomo Village, Sichuan, Southwest China

2021 ◽  
Vol 8 ◽  
Author(s):  
Li Wei ◽  
Kaiheng Hu ◽  
Jin Liu
Keyword(s):  
Quantitative Analysis ◽  
Debris Flow ◽  
Debris Flows ◽  
Evaluation Model ◽  
Alluvial Fan ◽  
Economic Losses ◽  
Rural Settlements ◽  
Societal Risk ◽  
Flow Intensity ◽  
The Village

Debris flows, which cause massive economic losses and tragic losses of life every year, represent serious threats to settlements in mountainous areas. Most deaths caused by debris flows in China occur in buildings, and the death toll is strongly dependent on the time people spend indoors. However, the role of time spent indoors in the quantitative analysis of debris flow risk has been studied only scarcely. We chose Luomo village in Sichuan atop a debris flow alluvial fan to study the influence of the temporal variation in the presence of people inside buildings on the societal risk. Two types of days (holidays vs. workdays) and two diurnal periods (daytime vs. nighttime) were considered in our risk evaluation model. A questionnaire survey was conducted for each family in the village, and the probability of the temporal impact of a debris flow on every household was calculated based on the average amount of time each member spent in the house. The debris flow hazard was simulated with FLO-2D to obtain the debris flow intensity and run-out map with return periods of 2, 10, 50, and 100 years. The risk to buildings and societal risk to residents were calculated quantitatively based on the probabilities of debris flow occurrence, the probability of the spatial impact, and the vulnerabilities of buildings and people. The results indicated that societal risk on holidays is always higher than that on weekdays, and societal risk at night is also much higher than that in the daytime, suggesting that the risk to life on holidays and at night is an important consideration. The proposed method permits us to obtain estimates of the probable economic losses and societal risk to people by debris flows in rural settlements and provides a basis for decision-making in the planning of mitigation countermeasures.

Anticipating cascading risks at the imminent Hochvogel peak failure

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

<p>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.</p><p>The Hochvogel summit (2592 m a.s.l., Allgäu 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 m³ 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 Roßbichelgraben (10 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.</p><p>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.</p>

scholarly journals Simulation of Debris-Flow Runout Near a Construction Site in Korea

2020 ◽  
Vol 10 (17) ◽  
pp. 6079 ◽  
Author(s):  
Byung-Gon Chae ◽  
Ying-Hsin Wu ◽  
Ko-Fei Liu ◽  
Junghae Choi ◽  
Hyuck-Jin Park
Keyword(s):  
Debris Flow ◽  
Landslide Susceptibility ◽  
Debris Flows ◽  
Source Area ◽  
Flow Path ◽  
Construction Site ◽  
Landslide Prediction ◽  
Runout Distance ◽  
Susceptibility Analysis

This study analyzed landslide susceptibility and numerically simulated the runout distance of debris flows near a construction site in Korea. Landslide susceptibility was based on a landslide prediction map of the study area. In the prediction map, 3.5% of the area had a 70–90% landslide probability, while 0.79% had over 90% probability. Based on the landslide susceptibility analysis, debris flows in four watersheds were simulated to assess possible damage to the construction site. According to the simulations, debris flow in Watershed C approaches to within 9.6 m of the site. Therefore, the construction site could be impacted by debris flow in Watershed C. Although the simulated flows in Watersheds A and D do not directly influence the construction site, they could damage the nearby road and other facilities. The simulations also show that debris runout distance is strongly influenced by the volume of debris in the on-slope source area and by the slope angles along the debris-flow path.

scholarly journals A two-phase model for numerical simulation of debris flows

2014 ◽  
Vol 2 (3) ◽  
pp. 2151-2183 ◽  
Author(s):  
S. He ◽  
W. Liu ◽  
C. Ouyang ◽  
X. Li
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Volume Fraction ◽  
Solid Phase ◽  
Fluid Phase ◽  
Viscous Drag ◽  
Finite Volume Scheme ◽  
Viscous Stress ◽  
Two Phase ◽  
One Dimensional

Abstract. Debris flows are multiphase, gravity-driven flows consisting of randomly dispersed interacting phases. The interaction between the solid phase and liquid phase plays a significant role on debris flow motion. This paper presents a new two-phase debris flow model based on the shallow water assumption and depth-average integration. The model employs the Mohr–Coulomb plasticity for the solid stress, and the fluid stress is modeled as a Newtonian viscous stress. The interfacial momentum transfer includes viscous drag, buoyancy and interaction force between solid phase and fluid phase. We solve numerically the one-dimensional model equations by a high-resolution finite volume scheme based on a Roe-type Riemann solver. The model and the numerical method are validated by using one-dimensional dam-break problem. The influences of volume fraction on the motion of debris flow are discussed and comparison between the present model and Pitman's model is presented. Results of numerical experiments demonstrate that viscous stress of fluid phase has significant effect in the process of movement of debris flow and volume fraction of solid phase significantly affects the debris flow dynamics.

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>

Runout modeling based debris flow risk assessment: a case study from Garhwal Himalaya, India

2020 ◽  
Author(s):  
Rajesh Kumar Dash ◽  
Debi Prasanna Kanungo
Keyword(s):  
Risk Assessment ◽  
Debris Flow ◽  
Debris Flows ◽  
Back Analysis ◽  
Source Area ◽  
Quantitative Information ◽  
Source Zone ◽  
Garhwal Himalayas ◽  
Model Input ◽  
Input Parameters

<p>Debris flows are one of the most frequently occurring and destructive hazards in Indian Himalayas which are often initiated by rainfall.  To minimize the losses due to the destructive power of the debris flows, demarcation of debris flow risk zones is an effective practice for risk reduction. In the present study, site specific debris flow risk assessment has been carried out based upon runout behaviour modeling. Tangni debris flow is an active debris flow in the Chamoli district of Garhwal Himalayas, India which is responsible for disrupting the traffic by blocking the road for days. This debris flow is repetitive in nature and occurs many a times every year in the monsoon during the months between June to September. The Tangni debris flow is categorized as a hill slope debris flow and the failure is considered as a block failure. Runout modeling of Tangni debris flow has been carried out using a Voellmy approach based continuum model. Quantitative information on debris flow intensity parameters such as flow velocity, height and pressure was obtained from the numerical simulation. The calibration of model input parameters was done by back analysis of an event from a particular source area that took place in 2013. Depending upon the amount of materials present in different source areas in the entire source zone and using the calibrated model input parameters, several simulations were performed to assess the flow behaviour of at different possible scenarios. Thus, Tangni debris flow risk assessment has been carried out based on its runout effect modeling. This study revealed that there may be a possibility of damming of river as well as blocking of the National Highway which are located at the downstream of the debris flow.</p><p>Key words:  Debris flow, Risk assessment, Runout modeling, Garhwal Himalayas, Voellmy model</p>

scholarly journals Risk Identification of Lijiadagou Landslide and Debris Flow Hazards Chain in Yong'an Town, Fengjie County of Chongqing City

2021 ◽  
pp. 1-12
Author(s):  
Q. H. Song ◽  
S. C. Ren ◽  
X. L. LI ◽  
B. L. Chen ◽  
K. Li ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Social Impact ◽  
Source Area ◽  
Economic Loss ◽  
Soil Mass ◽  
Mechanical Analysis ◽  
Field Investigation ◽  
Risk Identification ◽  
Alternate Control

Lijiadagou landslide and debris flow hazards chain in Yong’an Town of Fengjie county is one of the representative geohazards. By using satellite remote sensing technology, field investigation and observation, survey and analysis, mechanical analysis and other technical means, this paper makes qualitative or semi quantitative analysis on the hazard environment, instability probability, vulnerability analysis of elements at risk, risk loss, etc. The risk factors of Lijiadagou landslide and debris flow were identified. The conclusion shows that the unique landform and climate of Lijiadagou lay a foundation for the occurrence of multiple debris flows in the history. Under the alternate control of multiple factors such as the nature of the rock and soil mass, the stratum structure that controls the sliding, the complex geomorphic environment, continuous heavy rainfall and the rise and fall of the water level, there are high risks of landslides and debris flows, threatening about  6,000 residents in the middle and front range of Lijiadagou. The risk economic loss of hazards is about 80 million yuan, and will cause serious social impact. It is urgent to strengthen monitoring and early warning, and at the same time take targeted measures against the landslide source  area to cut off the hazards chain from the source, so as to achieve a multiplier effect with half the effort.

scholarly journals The December 2012 Mayo River debris flow triggered by Super Typhoon Bopha in Mindanao, Philippines: lessons learned and questions raised

2016 ◽  
Vol 16 (12) ◽  
pp. 2683-2695 ◽  
Author(s):  
Kelvin S. Rodolfo ◽  
A. Mahar F. Lagmay ◽  
Rodrigo C. Eco ◽  
Tatum Miko L. Herrero ◽  
Jerico E. Mendoza ◽  
...  
Keyword(s):  
Climate Change ◽  
Debris Flow ◽  
Population Growth ◽  
Debris Flows ◽  
Lessons Learned ◽  
Loss Of Life ◽  
River Watershed ◽  
Super Typhoon ◽  
Future Events ◽  
The Village

Abstract. Category 5 Super Typhoon Bopha, the world's worst storm of 2012, formed abnormally close to the Equator, and its landfall on Mindanao set the record proximity to the Equator for its category. Its torrential rains generated an enormous debris flow in the Mayo River watershed that swept away much of the village Andap in the New Bataan municipality, burying areas under rubble as thick as 9 m and killing 566 people. Established in 1968, New Bataan had never experienced super typhoons and debris flows. This unfamiliarity compounded the death and damage. We describe Bopha's history, debris flows and the Mayo River disaster, and then we discuss how population growth contributed to the catastrophe, as well as the possibility that climate change may render other near-Equatorial areas vulnerable to hazards brought on by similar typhoons. Finally, we recommend measures to minimize the loss of life and damage to property from similar future events.

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