scholarly journals The Importance of Hail Events for Landslides and Bedload Transport in Austrian Alpine Torrents

2021 ◽  
Author(s):  
Mario Schritter ◽  
Thomas Glade
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Control Unit ◽  
Bedload Transport ◽  
Weather Data ◽  
Process Dynamics ◽  
Triggering Conditions ◽  
Thiessen Polygons ◽  
Trigger Mechanisms ◽  
Local Weather

Abstract Landslides and bedload transport can be a threat to people, infrastructure, and vegetation. Many detailed hydrometeorological trigger mechanisms of such natural hazards are still poorly understood. This is in particular valid concerning hail as a trigger of these processes. Therefore, this study aims to determine the influence of hail on landslides and bedload transport in alpine torrents. Based on a generated table from an event register of mountain processes maintained by the Avalanche and Torrent Control Unit (WLV) and weather data provided by the Centre for Meteorology and Geodynamics (ZAMG), 1,573 observed events between 1980 and 2019 in 79 Austrian alpine sites are analysed. Thiessen polygons are used to regionalise local weather data to adjacent regions. The spatial extend of these regions are merged with the registered torrential events. As a result of a stepwise filtering of the used data, the final inventory was created.The results show that 95.1% of the investigated torrential processes triggered by hailstorms are debris flows or debris flow-like transports. Within the study period, a peak of hail-triggered landslides and bedload transport can be recognised in the first 10 days of August in all 39 years. Furthermore, the results suggest that hail is rather a direct than an indirect trigger for landslides and bedload transport.Overall, we conclude that the influence of hail on landslides and bedload transport is significant. Respective hydrometeorological triggering conditions should be included in any regions. Further research for this topic is required to explore the process dynamics in greater detail.

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

2018 ◽  
Vol 22 (6) ◽  
pp. 3493-3513 ◽  
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.

scholarly journals Triggering conditions and depositional characteristics of a disastrous debris flow event in Zhouqu city, Gansu Province, northwestern China

2011 ◽  
Vol 11 (11) ◽  
pp. 2903-2912 ◽  
Author(s):  
C. Tang ◽  
N. Rengers ◽  
Th. W. J. van Asch ◽  
Y. H. Yang ◽  
G. F. Wang
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Field Investigation ◽  
Gansu Province ◽  
Northwestern China ◽  
Catastrophic Event ◽  
Catchment Areas ◽  
Triggering Conditions ◽  
Geomorphological Features ◽  
Triggering Rainfall

Abstract. On 7 August 2010, catastrophic debris flows were triggered by a rainstorm in the catchments of the Sanyanyu and Luojiayu torrents, Zhouqu County, Gansu Province northwestern China. These two debris flows originated shortly after a rainstorm with an intensity of 77.3 mm h−1 and transported a total volume of about 2.2 million m3, which was deposited on an existing debris fan and into a river. This catastrophic event killed 1765 people living on this densely urbanised fan. The poorly sorted sediment contains boulders up to 3–4 m in diameter. In this study, the geomorphological features of both debris flow catchment areas are analyzed based on the interpretation of high-resolution remote sensing imagery combined with field investigation. The characteristics of the triggering rainfall and the initiation of the debris flow occurrence are discussed. Using empirical equations, the peak velocities and discharges of the debris flows were estimated to be around 9.7 m s−1 and 1358 m3 s−1 for the Sanyanyu torrent and 11 m s−1 and 572 m3 s−1 for the Luojiayu torrent. The results of this study contribute to a better understanding of the conditions leading to catastrophic debris flow events.

scholarly journals The temporally varying roles of rainfall, snowmelt and soil moisture for debris flow initiation in a snow dominated system: the compound trigger concept

2017 ◽  
Author(s):  
Karin Mostbauer ◽  
Roland Kaitna ◽  
David Prenner ◽  
Markus Hrachowitz
Keyword(s):  
Soil Moisture ◽  
Debris Flow ◽  
High Intensity ◽  
Debris Flows ◽  
Late Summer ◽  
Early Summer ◽  
Temporal Separation ◽  
Antecedent Soil Moisture ◽  
Trigger Mechanisms ◽  
Debris Flow Initiation

Abstract. Debris flows represent a severe hazard 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 and to overcome the above limitations, 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, western Austria. The model was run on a daily basis between 1953 and 2012. Analyzing 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 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 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, rather than their absolute values, 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 in a compound trigger concept, highlighting in particular the relevance of snowmelt contributions and the switch between mechanisms in early- to mid-summer in snow dominated systems.

scholarly journals Sediment budget monitoring of debris-flow and bedload transport in the Manival Torrent, SE France

2012 ◽  
Vol 12 (3) ◽  
pp. 731-749 ◽  
Author(s):  
J. I. Theule ◽  
F. Liébault ◽  
A. Loye ◽  
D. Laigle ◽  
M. Jaboyedoff
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Laser Scanning ◽  
Sediment Budget ◽  
Bedload Transport ◽  
High Order ◽  
Time Shift ◽  
Catchment Scale ◽  
Sediment Routing ◽  
Budget Analysis

Abstract. Steep mountain catchments typically experience large sediment pulses from hillslopes which are stored in headwater channels and remobilized by debris-flows or bedload transport. Event-based sediment budget monitoring in the active Manival debris-flow torrent in the French Alps during a two-year period gave insights into the catchment-scale sediment routing during moderate rainfall intensities which occur several times each year. The monitoring was based on intensive topographic resurveys of low- and high-order channels using different techniques (cross-section surveys with total station and high-resolution channel surveys with terrestrial and airborne laser scanning). Data on sediment output volumes from the main channel were obtained by a sediment trap. Two debris-flows were observed, as well as several bedload transport flow events. Sediment budget analysis of the two debris-flows revealed that most of the debris-flow volumes were supplied by channel scouring (more than 92%). Bedload transport during autumn contributed to the sediment recharge of high-order channels by the deposition of large gravel wedges. This process is recognized as being fundamental for debris-flow occurrence during the subsequent spring and summer. A time shift of scour-and-fill sequences was observed between low- and high-order channels, revealing the discontinuous sediment transfer in the catchment during common flow events. A conceptual model of sediment routing for different event magnitude is proposed.

scholarly journals Direct field observations of massive bedload and debris-flow depositions in open check dams

2018 ◽  
Vol 40 ◽  
pp. 03003 ◽  
Author(s):  
Guillaume Piton ◽  
Firmin Fontaine ◽  
Hervé Bellot ◽  
Frédéric Liébault ◽  
Coraline Bel ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Time Lapse ◽  
Bedload Transport ◽  
The Other ◽  
Field Observations ◽  
Sediment Trapping ◽  
Check Dams ◽  
Protection Systems ◽  
Detention Basins

Sediment detention basins, also called SABO dams, are key facilities in flood protection systems of mountain catchments, specifically in torrents prone to massive bedload transport or debris flows. A better understanding of the processes generating sediment trapping is required to optimize their functioning. Two monitoring stations have been implemented in the French Alps on two torrents: the Manival (Saint-Nazaire-Les-Eymes) and the Claret (Saint-Julien-Mont-Denis). Time-lapse photos show an event depositing 10,000 m3of debris flow in a basin in less than six minutes and several events partially filling the other basin with gravel, impairing its capacity to store debris flows later. After a presentation of the catchments, this paper qualitatively analyzes the dynamics of the depositions. It highlights and stresses the consistency and differences between bedload and debris-flow deposition. Overall, despite clear differences of geomorphic activity, deposits tend to fill the trap basins just enough to enable the sediment transport continuity reestablishment through the basin. The open check dams thus play a role only provided that this continuity precondition is completed. These observations enhance our comprehension of massive sediment trapping in torrents and our capacity to better adjust trap maintenance and design to the objective sought in each site.

scholarly journals Headwater sediment dynamics in debris flow catchment: implication of debris supply using high resolution topographic surveys

2016 ◽  
Author(s):  
A. Loye ◽  
M. Jaboyedoff ◽  
J. I. Theule ◽  
F. Liébault
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Laser Scanning ◽  
Early Spring ◽  
Bedload Transport ◽  
Sediment Dynamics ◽  
Power Law Distribution ◽  
Sediment Reworking ◽  
Sediment Budgets ◽  
Sediment Transfer

Abstract. Debris flows have been recognized to be linked to amounts of material temporary stored in torrent channels. Consequently, sediment production, debris supply and storage changes from low-order channels of the Manival catchment (French Alps) were surveyed periodically during 16 months using terrestrial laser scanning (TLS) to study the coupling between sediment dynamics and torrent responses in terms of debris flow events, which happened twice during the monitoring period. Sediment transfer in the main torrent was monitored with cross-section surveys. Sediment budgets were generated seasonally using sequential TLS data differencing and morphological extrapolations. Debris production depends strongly on rockfall occurring during winter–early spring season, following power law distribution for volumes of rockfall events above 0.1 m3, while hillslope sediment reworking dominates debris recharge from spring to autumn. Both debris flows originate in channels exclusively, but their occurrence is linked to recharge from previous debris pulses coming from the hillside and from bedload transport. Headwater debris sources display an equivocal behaviour in sediment transfer: despite of rainstorms inducing debris flows in torrent, low geomorphic activity occurred in production zone. Still, a general reactivation of sediment transport in headwater channels was observed in autumn without new debris supply, suggesting no exhaustion of debris storages. The seasonal cycle of sediment yield seems therefore to depend not only on debris supply and runoff (flow capacity), but also on geomorphic conditions that destabilize remnant debris stocks. This study shows that a monitoring of torrent in-channel storage changes coupled to debris supply can readily improve knowledge on recharge threshold leading to debris flow, so their prediction.

scholarly journals Learning Case Study of a Shallow-Water Model to Assess an Early-Warning System for Fast Alpine Muddy-Debris-Flow

Water ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 750
Author(s):  
Antonio Pasculli ◽  
Jacopo Cinosi ◽  
Laura Turconi ◽  
Nicola Sciarra
Keyword(s):  
Debris Flow ◽  
Shallow Water ◽  
Early Warning ◽  
Debris Flows ◽  
Early Warning System ◽  
Warning System ◽  
Extreme Weather Events ◽  
Water Model ◽  
Computational Time ◽  
Processing Unit

The current climate change could lead to an intensification of extreme weather events, such as sudden floods and fast flowing debris flows. Accordingly, the availability of an early-warning device system, based on hydrological data and on both accurate and very fast running mathematical-numerical models, would be not only desirable, but also necessary in areas of particular hazard. To this purpose, the 2D Riemann–Godunov shallow-water approach, solved in parallel on a Graphical-Processing-Unit (GPU) (able to drastically reduce calculation time) and implemented with the RiverFlow2D code (version 2017), was selected as a possible tool to be applied within the Alpine contexts. Moreover, it was also necessary to identify a prototype of an actual rainfall monitoring network and an actual debris-flow event, beside the acquisition of an accurate numerical description of the topography. The Marderello’s basin (Alps, Turin, Italy), described by a 5 × 5 m Digital Terrain Model (DTM), equipped with five rain-gauges and one hydrometer and the muddy debris flow event that was monitored on 22 July 2016, were identified as a typical test case, well representative of mountain contexts and the phenomena under study. Several parametric analyses, also including selected infiltration modelling, were carried out in order to individuate the best numerical values fitting the measured data. Different rheological options, such as Coulomb-Turbulent-Yield and others, were tested. Moreover, some useful general suggestions, regarding the improvement of the adopted mathematical modelling, were acquired. The rapidity of the computational time due to the application of the GPU and the comparison between experimental data and numerical results, regarding both the arrival time and the height of the debris wave, clearly show that the selected approaches and methodology can be considered suitable and accurate tools to be included in an early-warning system, based at least on simple acoustic and/or light alarms that can allow rapid evacuation, for fast flowing debris flows.

scholarly journals Numerical Simulation of Non-Homogeneous Viscous Debris-Flows Based on the Smoothed Particle Hydrodynamics (SPH) Method

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2314 ◽  
Author(s):  
Shu Wang ◽  
Anping Shu ◽  
Matteo Rubinato ◽  
Mengyao Wang ◽  
Jiping Qin
Keyword(s):  
Debris Flow ◽  
Water Content ◽  
Smoothed Particle Hydrodynamics ◽  
Debris Flows ◽  
Sph Method ◽  
Particle Hydrodynamics ◽  
Sph Model ◽  
Smoothed Particle ◽  
The Impact ◽  
Kinetic And Potential Energies

Non-homogeneous viscous debris flows are characterized by high density, impact force and destructiveness, and the complexity of the materials they are made of. This has always made these flows challenging to simulate numerically, and to reproduce experimentally debris flow processes. In this study, the formation-movement process of non-homogeneous debris flow under three different soil configurations was simulated numerically by modifying the formulation of collision, friction, and yield stresses for the existing Smoothed Particle Hydrodynamics (SPH) method. The results obtained by applying this modification to the SPH model clearly demonstrated that the configuration where fine and coarse particles are fully mixed, with no specific layering, produces more fluctuations and instability of the debris flow. The kinetic and potential energies of the fluctuating particles calculated for each scenario have been shown to be affected by the water content by focusing on small local areas. Therefore, this study provides a better understanding and new insights regarding intermittent debris flows, and explains the impact of the water content on their formation and movement processes.

The Debris Flow Disaster Faster-Than-Early Forecast System (DFS) with Multi-Sensors Integrated Wireless Sensor Networks

2013 ◽  
Vol 347-350 ◽  
pp. 975-979
Author(s):  
Rong Zhao ◽  
Cai Hong Li ◽  
Yun Jian Tan ◽  
Jun Shi ◽  
Fu Qiang Mu ◽  
...  
Keyword(s):  
Wireless Sensor Networks ◽  
Sensor Networks ◽  
Debris Flow ◽  
Real Time ◽  
Debris Flows ◽  
Base Station ◽  
Base Stations ◽  
Wireless Sensor ◽  
Forecast System ◽  
Debris Flow Disaster

This paper presents a Debris Flow Disaster Faster-than-early Forecast System (DFS) with wireless sensor networks. Debris flows carrying saturated solid materials in water flowing downslope often cause severe damage to the lives and properties in their path. Faster-than-early or faster-than-real-time forecasts are imperative to save lives and reduce damage. This paper presents a novel multi-sensor networks for monitoring debris flows. The main idea is to let these sensors drift with the debris flow, to collect flow information as they move along, and to transmit the collected data to base stations in real time. The Raw data are sent to the cloud processing center from the base station. And the processed data and the video of the debris flow are display on the remote PC. The design of the system address many challenging issues, including cost, deployment efforts, and fast reaction.

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