scholarly journals Debris Flow Modelling Using RAMMS Model in the Alpine Environment With Focus on the Model Parameters and Main Characteristics

2021 ◽  
Vol 8 ◽  
Author(s):  
Matjaž Mikoš ◽  
Nejc Bezak
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Mass Movement ◽  
Friction Model ◽  
Economic Damage ◽  
Model Parameters ◽  
Comprehensive Overview ◽  
Alpine Environment ◽  
Flow Modelling ◽  
Parameter Ranges

Debris flows are among the natural hazards that can occur in mountainous areas and endanger people’s lives and cause large economic damage. Debris flow modelling is needed in multiple applications such as design of protection measures or preparation of debris flow risk maps. Many models are available that can be used for debris flow modelling. The Rapid Mass Movement Simulation (RAMMS) model with its debris flow module, (i.e. RAMMS-DF) is one of the most commonly used ones. This review provides a comprehensive overview of past debris flow modelling applications in an alpine environment with their main characteristics, including study location, debris flow magnitude, simulation resolution, and Voellmy-fluid friction model parameter ranges, (i.e. μ and ξ). A short overview of each study is provided. Based on the review conducted, it is clear that RAMMS parameter ranges are relatively wide. Furthermore, model calibration using debris-flow post-event survey field data is the essential step that should be done before applying the model. However, an overview of the parameters can help to limit the parameter ranges. Particularly when considering the similarity between relevant case studies conducted in similar environments. This is especially relevant should the model be applied for estimating debris-flow hazard for potential future events. This model has been used mostly in Europe, (i.e. Alpine region) for modelling small and extremely large debris flows.

Uncertainty in debris flow rainfall thresholds

2021 ◽  
Author(s):  
Matteo Berti ◽  
Alessandro Simoni
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Measurement Errors ◽  
Critical Conditions ◽  
Model Parameters ◽  
Average Intensity ◽  
Rainfall Thresholds ◽  
Sources Of Uncertainty ◽  
Time Space ◽  
Physically Based

<p>Rainfall is the most significant factor for debris flows triggering. Water is needed to saturate the soil, initiate the sediment motion (regardless of the mobilization mechanism) and transform the solid debris into a fluid mass that can move rapidly downslope. This water is commonly provided by rainfall or rainfall and snowmelt. Consequently, most warning systems rely on the use of rainfall thresholds to predict debris flow occurrence. Debris flows thresholds are usually empirically-derived from the rainfall records that caused past debris flows in a certain area, using a combination of selected precipitation measurements (such as event rainfall P, duration D, or average intensity I) that describe critical rainfall conditions. Recent years have also seen a growing interest in the use of coupled hydrological and slope stability models to derive physically-based thresholds for shallow landslide initiation.</p><p>In both cases, rainfall thresholds are affected by significant uncertainty. Sources of uncertainty include: measurement errors; spatial variability of the rainfall field; incomplete or uncertain debris flow inventory; subjective definition of the “rainfall event”; use of subjective criteria to define the critical conditions; uncertainty in model parameters (for physically-based approaches). Rainfall measurement is widely recognized as a main source of uncertainty due to the extreme time-space variability that characterize intense rainfall events in mountain areas. However, significant errors can also arise by inaccurate information reported in landslide inventories on the timing of debris flows, or by the criterion used to define triggering intensities.</p><p>This study analyzes the common sources of uncertainty associated to rainfall thresholds for debris flow occurrence and discusses different methods to quantify them. First, we give an overview of the various approaches used in the literature to measure the uncertainty caused by random errors or procedural defects. These approaches are then applied to debris flows using real data collected in the Dolomites (Northen Alps, Itay), in order to estimate the variabilty of each single factor (precipitation, triggering timing, triggering intensity..). Individual uncertainties are then combined to obtain the overall uncertain of the rainfall threshold, which can be calculated using the classical method of “summation in quadrature” or a more effective approach based on Monte Carlo simulations. The uncertainty budget allows to identify the biggest contributors to the final variability and it is also useful to understand if this variability can be reduced to make our thresholds more precise.</p><p> </p>

scholarly journals 2D Runout Modelling of Hillslope Debris Flows, Based on Well-Documented Events in Switzerland

Geosciences ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 70 ◽  
Author(s):  
Florian Zimmermann ◽  
Brian W. McArdell ◽  
Christian Rickli ◽  
Christian Scheidl
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Mass Movement ◽  
Clay Content ◽  
Systematic Evaluation ◽  
Mountain Areas ◽  
Flow Processes ◽  
Friction Parameters ◽  
Cohesive Interaction ◽  
Hillslope Debris Flow

In mountain areas, mass movements, such as hillslope debris flows, pose a serious threat to people and infrastructure, although size and runout distances are often smaller than those of debris avalanches or in-channel-based processes like debris floods or debris flows. Hillslope debris-flow events can be regarded as a unique process that generally can be observed at steep slopes. The delimitation of endangered areas and the implementation of protective measures are therefore an important instrument within the framework of a risk analysis, especially in the densely populated area of the alpine region. Here, two-dimensional runout prediction methods are helpful tools in estimating possible travel lengths and affected areas. However, not many studies focus on 2D runout estimations specifically for hillslope debris-flow processes. Based on data from 19 well-documented hillslope debris-flow events in Switzerland, we performed a systematic evaluation of runout simulations conducted with the software Rapid Mass Movement Simulation: Debris Flow (RAMMS DF)—a program originally developed for runout estimation of debris flows and snow avalanches. RAMMS offers the possibility to use a conventional Voellmy-type shear stress approach to describe the flow resistance as well as to consider cohesive interaction as it occurs in the core of dense flows with low shear rates, like we also expect for hillslope debris-flow processes. The results of our study show a correlation between the back-calculated dry Coulomb friction parameters and the percentage of clay content of the mobilised soils. Considering cohesive interaction, the performance of all simulations was improved in terms of reducing the overestimation of the observed deposition areas. However, the results also indicate that the parameter which accounts for cohesive interaction can neither be related to soil physical properties nor to different saturation conditions.

scholarly journals Modeling debris-flow runout patterns on two alpine fans with different dynamic simulation models

2015 ◽  
Vol 15 (7) ◽  
pp. 1483-1492 ◽  
Author(s):  
K. Schraml ◽  
B. Thomschitz ◽  
B. W. McArdell ◽  
C. Graf ◽  
R. Kaitna
Keyword(s):  
Numerical Simulation ◽  
Debris Flow ◽  
Mass Movement ◽  
Simulation Models ◽  
Realistic Model ◽  
Three Dimensions ◽  
Model Parameters ◽  
Alpine Regions ◽  
Digital Elevation ◽  
Higher Sensitivity

Abstract. Predicting potential deposition areas of future debris-flow events is important for engineering hazard assessment in alpine regions. To this end, numerical simulation models are commonly used tools. However, knowledge of appropriate model parameters is essential but often not available. In this study we use two numerical simulation models, RAMMS–DF (rapid mass movement system–debris-flow) and DAN3D (dynamic analysis of landslides in three dimensions), to back-calculate two well-documented debris-flow events in Austria and to compare the range and sensitivity of input parameters for the Voellmy flow model. All simulations are based on the same digital elevation models and similar boundary conditions. Our results show that observed deposition patterns are best matched with a parameter set of μ [–] and ξ [m s-2], ranging between 0.07 to 0.11 and 200 to 300 m s-2, respectively, for RAMMS–DF, and between 0.07 to 0.08 and 300 to 400 m s-2, respectively, for DAN3D. Sensitivity analysis shows a higher sensitivity of model parameters for the DAN3D model than for the RAMMS–DF model. This contributes to the evaluation of realistic model parameters for simulation of debris-flows in steep mountain catchments and highlights the sensitivity of the models.

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

2018 ◽  
Vol 18 (2) ◽  
pp. 555-570 ◽  
Author(s):  
Raquel Melo ◽  
Theo van Asch ◽  
José L. Zêzere
Keyword(s):  
Debris Flow ◽  
Dynamic Model ◽  
Debris Flows ◽  
Back Analysis ◽  
Rheological Parameters ◽  
Economic Damage ◽  
Case Scenario ◽  
Worst Case ◽  
Basin Scale ◽  
Central Portugal

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.

Tree rings and debris flows: Recent developments, future directions

2010 ◽  
Vol 34 (5) ◽  
pp. 625-645 ◽  
Author(s):  
Michelle Bollschweiler ◽  
Markus Stoffel
Keyword(s):  
Debris Flow ◽  
Tree Rings ◽  
Debris Flows ◽  
Mass Movement ◽  
Wide Field ◽  
Mountain Areas ◽  
Additional Information ◽  
Recent Developments ◽  
Spatial Positioning ◽  
The Impact

The sudden and unpredictable occurrence of debris flows poses major problems in many mountain areas in the world. For a realistic hazard assessment, knowledge of past events is of crucial importance. As archival data is generally fragmentary, additional information sources are needed for an appraisal of past and contemporary events as well as for the prediction of potential future events. Tree rings represent a very valuable natural archive on past debris-flow occurrence as they may record the impact of events in their tree-ring series. In the past few years, dendrogeomorphology has evolved from a pure dating tool to a broad range of applications. Besides the reconstruction of frequencies, tree rings allow — if coupled with spatial positioning methods — the determination of spread and reach of past events. Similarly, the wide field of applications includes the identification of magnitudes and triggers of debris-flow events. Besides demonstrating recent developments in the use of tree rings for debris-flow research, this contribution also provides a short overview on the application of tree rings for other mass-movement processes and highlights further possibilities of the method. Established techniques can be applied to related processes such as debris floods, flash floods or lahars. Data obtained can also be used to calibrate modeling approaches. The impact of past and future climatic changes on debris-flow occurrence is furthermore an important aspect where tree rings can be of help.

scholarly journals Simulation of debris flows in the watershed of the Putih River, Indonesia using SIMLAR 2.1

2021 ◽  
Vol 930 (1) ◽  
pp. 012034
Author(s):  
J Ikhsan ◽  
R Ardiansyah ◽  
D Legono
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Rainfall Data ◽  
River Watershed ◽  
Volcanic Material ◽  
Flow Modelling ◽  
Dam Building ◽  
Sediment Data ◽  
The Impact

Abstract In 2010, the eruption of Mount Merapi produced a huge volcanic material for debris flows. One area affected by the debris flows is the watershed of Putih River. To predict the impact caused by debris flows can be done by using software such as the Simulation Lahar (SIMLAR) 2.1. In this paper, debris flow modelling will be carried out using SIMLAR 2.1 in conditions without sabo dams and using sabo dams. This simulation aims to determine the effectiveness of the sabo dams in reducing the impact of debris flows. The data used are rainfall data, DEM and sediment data in Putih River. The results show that the sabo dam building can slow down the velocity of debris flow. In addition, sabo dams also function as a barrier to riverbed erosion in the Putih River watershed. Based on the results above, it can be concluded that SIMLAR 2.1 can predict the impact of debris flows in the Putih River watershed.

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

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

<p>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.</p><p>Using the Prêcheur 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 1.9x10<sup>6 </sup>m<sup>3</sup> 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.</p>

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.

Comparing a newly developed DEM-based runout model for hillslope debris flows with full-scale experiments and historical events

2020 ◽  
Author(s):  
Adel Albaba ◽  
Niels Hollard ◽  
Christoph Schaller ◽  
Massimiliano Schwarz ◽  
Luuk Dorren
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Residential Buildings ◽  
Full Scale ◽  
Swiss Alps ◽  
Model Parameters ◽  
Historical Events ◽  
Margin Of Error ◽  
Hillslope Debris Flow ◽  
Good Agreement

<p>The increasing urbanization of mountainous areas increased the risk imposed on residential buildings and infrastructure. In Switzerland, shallow landslides and hillslope debris flows are responsible every year for high infrastructure damage, blocking of important highways, evacuations and deaths. Up till now, the assessment of these processes has been mainly based on the experience of experts, especially in the assessment of their run-out extent and expected damage. In this research we present a new computationally efficient Discrete Element Model (DEM) which has been developed for the aim of simulating the run-out of hillslope debris flows.</p><p>YADE-DEM open source code has been extended and an elasto-plastic adhesive contact law have been implemented, which partially account for the presence of the fluid composed of water and find material. This is achieved through the adhesive aspect of the contact law, which would indirectly take the presence of such fluid into account, as this fluid would increase the cohesion of the flowing mass. A parametric study has been carried out to define the most sensitive model parameters, which were found to be the microscopic basal friction angle (Φ<sub>b</sub>) and the ratio between stiffness parameters (loading and unloading) of the flowing particles <img src="data:image/png;base64,%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" alt="">. Data of full-scale experiments of hillslope debris flows were used to compare the flow kinematics with the model’s prediction. A good agreement between the model and experiments was observed concerning the mean front velocity (average margin of error of 8%) and the maximum applied pressure (average margin of error of 5%), with less agreement of the flow height (average margin of error of 13%). Detailed comparisons of pressure evolution between different selected experiments and simulations revealed the model’s capability of reproducing observed pressure curves, especially during the primary loading phase, leading to maximum pressure.</p><p>In order to test the model’s prediction of run-out distance of hillslope debris flow, hundreds of past hillslope debris flow events in the Swiss Alps were analyzed and 30 cases were selected representing different situations (i.e. different release volumes, slopes and forest cover). Due to the discrete nature of results in YADE, a GIS algorithm was developed in order to create envelopes representing the temporal evolution of the simulated propagating processes, which were compared to the those of the historical events. Results of the comparison revealed that, with the calibration of the two sensitive parameters in YADE, a fair to very good agreement was observed between the envelopes of the model and those of historical events for 87% of the tested cases. Difficulties in reproducing the envelopes of the rest of the cases are linked to the uncertainties in the mapping of the envelopes of past events, the role of the forest which is not taken into account in the model, and the lack of direct representation of fluid in the model.</p>

scholarly journals Modeling debris-flow runout patterns on two alpine fans with different dynamic simulation models

2015 ◽  
Vol 3 (2) ◽  
pp. 1397-1425 ◽  
Author(s):  
K. Schraml ◽  
B. Thomschitz ◽  
B. W. McArdell ◽  
C. Graf ◽  
R. Kaitna
Keyword(s):  
Numerical Simulation ◽  
Debris Flow ◽  
Initial Conditions ◽  
Mass Movement ◽  
Simulation Models ◽  
Realistic Model ◽  
Three Dimensions ◽  
Sensitivity Analyses ◽  
Model Parameters ◽  
Alpine Regions

Abstract. Predicting potential deposition areas of future debris-flow events is important for engineering hazard assessment in alpine regions. For this, numerical simulation models are commonly used tools. However, knowledge of appropriate model parameters is essential but often not available. In this study we use two numerical simulation models, RAMMS-DF (Rapid Mass Movement System – Debris Flow) and DAN3D (Dynamic Analysis of Landslides in Three Dimensions), to back-calculate two well-documented debris-flow events in Austria and to compare the range and sensitivity of input parameters for the Voellmy flow model. All simulations are based on the same digital elevation model with a 1 m resolution and similar initial conditions. Our results show that both simulation tools are capable of matching observed deposition patterns. The best fit parameter set of μ [–] and ξ [m s−2] range between 0.07–0.11 and 200–300 m s−2, respectively, for RAMMS-DF, and 0.07–0.08 and 300–400 m s−2, respectively, for DAN3D. Sensitivity analyses show a higher sensitivity of model parameters for the DAN3D model than for the RAMMS-DF model. This study shall contribute to the evaluation of realistic model parameters for simulation of debris-flows in steep mountain catchments and highlights the sensitivity of the models.

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