The Application of a Three-Dimensional Deterministic Model in the Study of Debris Flow Prediction Based on the Rainfall-Unstable Soil Coupling Mechanism

As debris flow is one of the most destructive natural disasters in many parts of the world, the assessment and management of future debris flows with proper forecasting methods are crucial for the safety of life and property. So increasing attention has been paid to the forecasting methods on debris flows. A debris flow forecasting method based on the rainfall-unstable soil coupling mechanism (R-USCM) is presented in the current study. This method is based on the debris flow formation mechanism. The density of sediment is introduced as an evaluation index to determine the susceptibility of debris flow occurrence. The forecasting method includes two phases: (1) rainfall and soil coupling and (2) runoff and unstable soil coupling. Scoops3D, a three-dimensional (3D) model for analyzing slope stability, was introduced into the debris flow forecasting method. In order to test the forecasting accuracy of this method, Jiaohe County was selected as a research area, and the serious debris flow disasters attributed to strong rainfall on 20 July 2017 were taken as the research case. By comparing the forecasting results with the debris flow distribution map for Jiaohe County, the method based on the R-USCM is feasible for forecasting debris flows at the regional scale. The application of the Scoops3D model can more reasonably analyze the slope stability than the traditional two dimensional (2D) method and improve the forecasting ability of debris flows.

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The temporally varying roles of rainfall, snowmelt and soil moisture for debris flow initiation in a snow-dominated system

Hydrology and Earth System Sciences ◽

10.5194/hess-22-3493-2018 ◽

2018 ◽

Vol 22 (6) ◽

pp. 3493-3513 ◽

Cited By ~ 10

Author(s):

Karin Mostbauer ◽

Roland Kaitna ◽

David Prenner ◽

Markus Hrachowitz

Keyword(s):

Soil Moisture ◽

Debris Flow ◽

High Intensity ◽

Debris Flows ◽

Regional Scale ◽

Early Summer ◽

Temporal Separation ◽

Antecedent Soil Moisture ◽

Trigger Mechanisms ◽

Debris Flow Initiation

Abstract. Debris flows represent frequent hazards in mountain regions. Though significant effort has been made to predict such events, the trigger conditions as well as the hydrologic disposition of a watershed at the time of debris flow occurrence are not well understood. Traditional intensity-duration threshold techniques to establish trigger conditions generally do not account for distinct influences of rainfall, snowmelt, and antecedent moisture. To improve our knowledge on the connection between debris flow initiation and the hydrologic system at a regional scale, this study explores the use of a semi-distributed conceptual rainfall–runoff model, linking different system variables such as soil moisture, snowmelt, or runoff with documented debris flow events in the inner Pitztal watershed, Austria. The model was run on a daily basis between 1953 and 2012. Analysing a range of modelled system state and flux variables at days on which debris flows occurred, three distinct dominant trigger mechanisms could be clearly identified. While the results suggest that for 68 % (17 out of 25) of the observed debris flow events during the study period high-intensity rainfall was the dominant trigger, snowmelt was identified as the dominant trigger for 24 % (6 out of 25) of the observed debris flow events. In addition, 8 % (2 out of 25) of the debris flow events could be attributed to the combined effects of low-intensity, long-lasting rainfall and transient storage of this water, causing elevated antecedent soil moisture conditions. The results also suggest a relatively clear temporal separation between the distinct trigger mechanisms, with high-intensity rainfall as a trigger being limited to mid- and late summer. The dominant trigger in late spring/early summer is snowmelt. Based on the discrimination between different modelled system states and fluxes and, more specifically, their temporally varying importance relative to each other, this exploratory study demonstrates that already the use of a relatively simple hydrological model can prove useful to gain some more insight into the importance of distinct debris flow trigger mechanisms. This highlights in particular the relevance of snowmelt contributions and the switch between mechanisms during early to mid-summer in snow-dominated systems.

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A probabilistic model for assessing debris flow propagation at regional scale: a case study in Campania region, Italy

10.5194/egusphere-egu21-2224 ◽

2021 ◽

Author(s):

Luca Crescenzo ◽

Gaetano Pecoraro ◽

Michele Calvello ◽

Richard Guthrie

Keyword(s):

Debris Flow ◽

Debris Flows ◽

Regional Scale ◽

Erosion And Deposition ◽

Campania Region ◽

Source Areas ◽

Model Input ◽

Travel Path ◽

Debris Avalanches ◽

Modelling Approach

Debris flows and debris avalanches are rapid to extremely rapid landslides that tend to travel considerable distances from their source areas. Interaction between debris flows and elements at risk along their travel path may result in potentially significant destructive consequences. One of the critical challenges to overcome with respect to debris flow risk is, therefore, the credible prediction of their size, travel path, runout distance, and depths of erosion and deposition. To these purposes, at slope or catchment scale, sophisticated physically-based models, appropriately considering several factors and phenomena controlling the slope failure mechanisms, may be used. These models, however, are computationally costly and time consuming, and that significantly hinders their applicability at regional scale. Indeed, at regional scale, debris flows hazard assessment is usually carried out by means of qualitative approaches relying on field surveys, geomorphological knowledge, geometric features, and expert judgement.In this study, a quantitative modelling approach based on cellular automata methods, wherein individual cells move across a digital elevation model (DEM) landscape following behavioral rules defined probabilistically, is proposed and tested. The adopted model, called LABS, is able to estimate erosion and deposition soil volumes along a debris flow path by deploying at the source areas autonomous subroutines, called agents, over a 5 m spatial resolution DEM, which provides the basic information to each agent in each time-step. Rules for scour and deposition are based on mass balance considerations and independent probability distributions defined as a function of slope DEM-derived values and a series of model input parameters. The probabilistic rules defined in the model are based on data gathered for debris flows and debris avalanches that mainly occurred in western Canada. This study mainly addresses the applicability and the reliability of this modelling approach to areas in southern Italy, in Campania region, historically affected by debris flows in pyroclastic soils. To this aim, information on inventoried debris flows is used in different study areas to evaluate the effect on the predictions of the model input parameter values, as well as of different native DEM resolutions.

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Debris-flow forecasting at regional scale by combining susceptibility mapping and radar rainfall

Natural Hazards and Earth System Science ◽

10.5194/nhess-15-587-2015 ◽

2015 ◽

Vol 15 (3) ◽

pp. 587-602 ◽

Cited By ~ 24

Author(s):

M. Berenguer ◽

D. Sempere-Torres ◽

M. Hürlimann

Keyword(s):

Debris Flow ◽

Debris Flows ◽

Regional Scale ◽

Early Warning Systems ◽

Warning Systems ◽

Susceptibility Assessment ◽

Radar Rainfall ◽

Eastern Pyrenees ◽

Rainfall Map ◽

Rainfall Estimates

Abstract. This work presents a technique for debris-flow (DF) forecasting able to be used in the framework of DF early warning systems at regional scale. The developed system is applied at subbasin scale and is based on the concepts of fuzzy logic to combine two ingredients: (i) DF subbasin susceptibility assessment based on geomorphological variables and (ii) the magnitude of the rainfall situation as depicted from radar rainfall estimates. The output of the developed technique is a three-class warning ("low", "moderate" or "high") in each subbasin when a new radar rainfall map is available. The developed technique has been applied in a domain in the eastern Pyrenees (Spain) from May to October 2010. The warning level stayed "low" during the entire period in 20% of the subbasins, while in the most susceptible subbasins the warning level was at least "moderate" for up to 10 days. Quantitative evaluation of the warning level was possible in a subbasin where debris flows were monitored during the analysis period. The technique was able to identify the three events observed in the catchment (one debris flow and two hyperconcentrated flow events) and produced no false alarm.

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Debris-flow activity in five adjacent gullies in a limestone mountain range

Geochronometria ◽

10.1515/geochr-2015-0007 ◽

2015 ◽

Vol 42 (1) ◽

Cited By ~ 10

Author(s):

Klaus Schraml ◽

Markus Oismüller ◽

Markus Stoffel ◽

Johannes Hübl ◽

Roland Kaitna

Keyword(s):

Debris Flow ◽

Debris Flows ◽

National Park ◽

Regional Scale ◽

Field Investigation ◽

Mountain Range ◽

Sediment Sources ◽

Aerial Vehicle ◽

Flow Activity ◽

Local Variability

Abstract Debris-flows are infrequent geomorphic phenomena that shape steep valleys and can repre-sent a severe hazard for human settlements and infrastructure. In this study, a debris-flow event chro-nology has been derived at the regional scale within the Gesäuse National Park (Styria, Austria) using dendrogeomorphic techniques. Sediment sources and deposition areas were mapped by combined field investigation and aerial photography using an Unmanned Aerial Vehicle (UAV). Through the analysis of 384 trees, a total of 47 debris-flows occurring in 19 years between AD 1903 and 2008 were identified in five adjacent gullies. Our results highlight the local variability of debris-flow activi-ty as a result of local thunderstorms and the variable availability of sediment sources.

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GIS-based modelling of landslide and debris flow hazard in mountainous terrain of Agra Khola watershed, central Nepal

Journal of Nepal Geological Society ◽

10.3126/jngs.v34i0.31886 ◽

2006 ◽

Vol 34 ◽

pp. 117-128

Author(s):

P. B. Thapa ◽

T. Esaki ◽

B. N. Upreti

Keyword(s):

Debris Flow ◽

Prediction Model ◽

Debris Flows ◽

Flow Distribution ◽

Spatial Prediction ◽

Distribution Map ◽

Central Nepal ◽

Landslides And Debris Flows ◽

Debris Flow Hazard ◽

Hazard Levels

A comprehensive GIS-based analytical approach was followed to derive a spatial database of landslides and debris flows in the Agra Khola watershed of central Nepal which suffered from the hydrological disaster of 1993. For this purpose, the landslides and debris flows occurring in that area between 1993 and 2006 were delineated. From the database, the influence of geological and geomorphic variables was quantified and a spatial prediction model for landslide and debris flow hazard was worked out. In this process, quantitative statistical analysis (bivariate, multivariate) as applied to predict elements or observations between stable and unstable zones. The predicted results were classified into various hazard levels m a hazard map and were validated by comparing it with the landslide and debris flow distribution map of the Agra Khola watershed. Also the GIS-based hazard prediction model has objectivity in the procedure and reproducibility of the results in the mountainous terrains.

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Debris-Flow Hazard Assessments: A Practitioner's View

Environmental and Engineering Geoscience ◽

10.2113/eeg-d-20-00110 ◽

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.

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Debris flow hazard modelling on medium scale: Valtellina di Tirano, Italy

Natural Hazards and Earth System Science ◽

10.5194/nhess-10-2379-2010 ◽

2010 ◽

Vol 10 (11) ◽

pp. 2379-2390 ◽

Cited By ~ 40

Author(s):

J. Blahut ◽

P. Horton ◽

S. Sterlacchini ◽

M. Jaboyedoff

Keyword(s):

Debris Flow ◽

Debris Flows ◽

Flow Direction ◽

Hazard Analysis ◽

Regional Scale ◽

Aerial Photographs ◽

Hazard Zonation ◽

Conditioning Factors ◽

Medium Scale ◽

Debris Flow Hazard

Abstract. Debris flow hazard modelling at medium (regional) scale has been subject of various studies in recent years. In this study, hazard zonation was carried out, incorporating information about debris flow initiation probability (spatial and temporal), and the delimitation of the potential runout areas. Debris flow hazard zonation was carried out in the area of the Consortium of Mountain Municipalities of Valtellina di Tirano (Central Alps, Italy). The complexity of the phenomenon, the scale of the study, the variability of local conditioning factors, and the lacking data limited the use of process-based models for the runout zone delimitation. Firstly, a map of hazard initiation probabilities was prepared for the study area, based on the available susceptibility zoning information, and the analysis of two sets of aerial photographs for the temporal probability estimation. Afterwards, the hazard initiation map was used as one of the inputs for an empirical GIS-based model (Flow-R), developed at the University of Lausanne (Switzerland). An estimation of the debris flow magnitude was neglected as the main aim of the analysis was to prepare a debris flow hazard map at medium scale. A digital elevation model, with a 10 m resolution, was used together with landuse, geology and debris flow hazard initiation maps as inputs of the Flow-R model to restrict potential areas within each hazard initiation probability class to locations where debris flows are most likely to initiate. Afterwards, runout areas were calculated using multiple flow direction and energy based algorithms. Maximum probable runout zones were calibrated using documented past events and aerial photographs. Finally, two debris flow hazard maps were prepared. The first simply delimits five hazard zones, while the second incorporates the information about debris flow spreading direction probabilities, showing areas more likely to be affected by future debris flows. Limitations of the modelling arise mainly from the models applied and analysis scale, which are neglecting local controlling factors of debris flow hazard. The presented approach of debris flow hazard analysis, associating automatic detection of the source areas and a simple assessment of the debris flow spreading, provided results for consequent hazard and risk studies. However, for the validation and transferability of the parameters and results to other study areas, more testing is needed.

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Coupled prediction of flood response and debris flow initiation during warm and cold season events in the Southern Appalachians, USA

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-10-8365-2013 ◽

2013 ◽

Vol 10 (7) ◽

pp. 8365-8419 ◽

Cited By ~ 1

Author(s):

J. Tao ◽

A. P. Barros

Keyword(s):

Slope Stability ◽

Debris Flow ◽

Debris Flows ◽

Warning System ◽

Cold Season ◽

Southern Appalachians ◽

Winter Storm ◽

Headwater Catchments ◽

Flood Response ◽

Debris Flow Initiation

Abstract. Debris flows associated with rainstorms are a frequent and devastating hazard in the Southern Appalachians in the United States. Whereas warm season events are clearly associated with heavy rainfall intensity, the same cannot be said for the cold season events. Instead, there is a relationship between large (cumulative) rainfall events independently of season, and thus hydrometeorological regime, and debris flows. This suggests that the dynamics of subsurface hydrologic processes play an important role as a trigger mechanism, specifically through soil moisture redistribution by interflow. The first objective of this study is to investigate this hypothesis. The second objective is to assess the physical basis for a regional coupled flood prediction and debris flow warning system. For this purpose, uncalibrated model simulations of well-documented debris flows in headwater catchments of the Southern Appalachians using a 3-D surface-groundwater hydrologic model coupled with slope stability models are examined in detail. Specifically, we focus on two vulnerable headwater catchments that experience frequent debris flows, the Big Creek and the Jonathan Creek in the Upper Pigeon River Basin, North Carolina, and three distinct weather systems: an extremely heavy summertime convective storm in 2011; a persistent winter storm lasting several days; and a severe winter storm in 2009. These events were selected due to the optimal availability of rainfall observations, availability of detailed field surveys of the landslides shortly after they occurred, which can be used to evaluate model predictions, and because they are representative of events that cause major economic losses in the region. The model results substantiate that interflow is a useful prognostic of conditions necessary for the initiation of slope instability, and should therefore be considered explicitly in landslide hazard assessments. Moreover, the relationships between slope stability and interflow are strongly modulated by the topography and catchment specific geomorphologic features that determine subsurface flow convergence zones. The three case-studies demonstrate the value of coupled prediction of flood response and debris flow initiation potential in the context of developing a regional hazard warning system.

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Why are some alpine catchments debris-flow active and others not? - the influence of geomorphology on debris-flow initiation

10.5194/egusphere-egu2020-7805 ◽

2020 ◽

Author(s):

Philipp Aigner ◽

Leonard Sklar ◽

Markus Hrachowitz ◽

Roland Kaitna

Keyword(s):

Debris Flow ◽

Debris Flows ◽

Regional Scale ◽

Alpine Regions ◽

Order Of Magnitude ◽

Elevation Changes ◽

Alpine Catchments ◽

Flow Activity ◽

The Impact ◽

Debris Flow Susceptibility

Processes like flash floods or debris flows, which typically occur in small headwater catchments, represent a substantial natural hazard in alpine regions. Due to the entrainment of sediment, the discharge of debris flows can be up to an order of magnitude larger compared to 100-year fluvial flood events in the same channel, which poses a great threat to affected communities. Besides the triggering rainfall, the initiation of debris flows depends on the watershed&#8217;s hydrological and geomorphological susceptibility, which makes it hard to predict and understand where and when debris flows occur.In this study we aim to quantify the influence of geomorphologic characteristics and long-term sediment dynamics on debris flow activity in the Austrian Alps. Based on a database of debris-flow events within the last 60+ years, a geomorphological assessment of active and non-active sub-catchments in different study regions is carried out. In a first step, we derive geomorphological characteristics, such as terrain roughness, Melton number as well as weathering potential of geological units found within the watersheds. Based on the findings of the terrain shape analysis, a set of representative watersheds will be selected for systematic monitoring of surface elevation changes over the project period of three years. This will be achieved by comparing digital surface models based on photogrammetric UAV surveys and monitoring of channel reaches with cameras.In order to project these findings onto a larger regional scale, the derived terrain parameters will be used to integrate and extend a previously designed hydro-meteorological debris-flow susceptibility model (Prenner et al., 2018) with a sediment-disposition-model. This will form the basis for an advanced debris flow forecasting tool and help to better assess the impact of climate change on the magnitude and frequency of future debris flows.&#160;<div>References:</div><div>Prenner, D., Kaitna, R., Mostbauer, K., & Hrachowitz, M. ( 2018). The value of using multiple hydrometeorological variables to predict temporal debris flow susceptibility in an Alpine environment. Water Resources Research, 54, 6822&#8211; 6843. </div>&#160;

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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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