Results and experiences gathered at the Rebaixader debris-flow monitoring site, Central Pyrenees, Spain

Abstract. The use of ground vibration sensors for debris-flow monitoring has increased in the last two decades. However, the correct interpretation of the seismic signals produced by debris flows still presents many uncertainties. In the Rebaixader monitoring site (Central Pyrenees, Spain) two different ground vibration stations with different characteristics in terms of recording systems and site-specific factors have been compared. The shape of the time series has been recognised as one of the key parameters to identify events and to distinguish between different types of torrential processes. The results show that the site-specific factors strongly influence on the ground vibration registered at each geophone. The attenuation of the signal with the distance has been identified as linear to exponential. In addition, the assembly of the geophones to the terrain also has an important effect on the amplification of the signal. All these results highlight that the definition of ground vibration thresholds for debris-flow detection or warning purposes is a difficult task which is clearly influenced by site-specific conditions of the geophones.

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Rockfalls detached from a lateral moraine during spring season. 2010 and 2011 events observed at the Rebaixader debris-flow monitoring site (Central Pyrenees, Spain)

Landslides ◽

10.1007/s10346-011-0314-4 ◽

2012 ◽

Vol 9 (3) ◽

pp. 385-393 ◽

Cited By ~ 17

Author(s):

Marcel Hürlimann ◽

Clàudia Abancó ◽

José Moya

Keyword(s):

Debris Flow ◽

Monitoring Site ◽

Lateral Moraine ◽

Spring Season ◽

Flow Monitoring ◽

Central Pyrenees

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Debris-Flow Monitoring at the Rebaixader Torrent, Central Pyrenees, Spain. Results on Initiation, Volume and Dynamic Behaviour

Engineering Geology for Society and Territory - Volume 2 ◽

10.1007/978-3-319-09057-3_76 ◽

2015 ◽

pp. 469-472

Author(s):

Hürlimann Marcel ◽

Abancó Clàudia ◽

Moya Jose

Keyword(s):

Debris Flow ◽

Dynamic Behaviour ◽

Flow Monitoring ◽

Central Pyrenees

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Application of a combined and automated monitoring and early warning system for debris flows at the Dawinbach

10.5194/egusphere-egu21-10280 ◽

2021 ◽

Author(s):

Tobias Schöffl ◽

Richard Koschuch ◽

Philipp Jocham ◽

Johannes Hübl

Keyword(s):

Debris Flow ◽

Early Warning ◽

Pulse Compression ◽

Mitigation Measures ◽

Heavy Rainfall Event ◽

Monitoring Site ◽

Traffic Lights ◽

The Road ◽

Pulse Compression Radar ◽

Monitoring And Early Warning

After a heavy rainfall event on August 31st, 2019, a debris flow at the Dawinbach in the municipality of Strengen (Tyrol, Austria) caused a blockage of the culvert below the provincial road B-316 and deposition in the residential area. The debris deposition raised up to 2 to 3 meters on the road and led to property damage to real estate. The total volume of the debris flow was approximately 15&#160;000 cubic meters.In order to control a further debris flow of this magnitude, the Austrian Service of Torrent and Avalanche Control started to construct mitigation measures. They include a channel relocation in order to significantly increase the channel crosssection. Hence the construction company STRABAG is also relocating the provincial road bridge.Since the risk for this road section and for the workers on site is particularly high during the construction period, a combined monitoring and early warning concept was developed and implemented by the BOKU, Vienna and the company IBTP Koschuch.The monitoring site consisting of a pulse compression radar and a pull rope system was installed 800m upstream from the fan. The combination of the two sensors now results in three major advantages.<ul><li>At sensor level, the system operates redundantly.</li> <li>A more reliable differentiation between increased discharge or debris flow is given.</li> <li>In the event of a false alarm, the system provides easier diagnosis and assignment of the fault.</li> </ul>Two events of increased runoff occurred during the deployment period. Both were successfully detected by the pulse compression radar. Here, the first event was used for threshold validation of the radar unit. Thus, an alarm could already be sent out automatically for the second one. The road is controlled by an integrated light signal system consisting of three traffic lights. A siren near the construction site can warn workers of an impending event by means of an acoustic signal. The reaction time after the alarm has been triggered is between 75 and 150 seconds, depending on the speed of the debris flow. The responsible authorities are informed by sending an SMS chain, which includes details about the type of process and the type of the activated triggering system.

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Analysis of debris-flow recordings in an instrumented basin: confirmations and new findings

Natural Hazards and Earth System Science ◽

10.5194/nhess-12-679-2012 ◽

2012 ◽

Vol 12 (3) ◽

pp. 679-686 ◽

Cited By ~ 27

Author(s):

M. Arattano ◽

L. Marchi ◽

M. Cavalli

Keyword(s):

Debris Flow ◽

Alluvial Fan ◽

Seismic Network ◽

Low Flow ◽

Main Peak ◽

Flow Monitoring ◽

Irregular Pattern ◽

New Findings ◽

Seismic Recording ◽

Seismic Networks

Abstract. On 24 August 2006, a debris flow took place in the Moscardo Torrent, a basin of the Eastern Italian Alps instrumented for debris-flow monitoring. The debris flow was recorded by two seismic networks located in the lower part of the basin and on the alluvial fan, respectively. The event was also recorded by a pair of ultrasonic sensors installed on the fan, close to the lower seismic network. The comparison between the different recordings outlines particular features of the August 2006 debris flow, different from that of events recorded in previous years. A typical debris-flow wave was observed at the upper seismic network, with a main front abruptly appearing in the torrent, followed by a gradual decrease of flow height. On the contrary, on the alluvial fan the wave displayed an irregular pattern, with low flow depth and the main peak occurring in the central part of the surge both in the seismic recording and in the hydrographs. Recorded data and field evidences indicate that the surge observed on the alluvial fan was not a debris flow, and probably consisted in a water surge laden with fine to medium-sized sediment. The change in shape and characteristics of the wave can be ascribed to the attenuation of the surge caused by the torrent control works implemented in the lower basin during the last years.

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Debris flow monitoring in the French Alps

River Flow 2014 ◽

10.1201/b17133-211 ◽

2014 ◽

pp. 1589-1595

Author(s):

C Bel ◽

F Liébault ◽

H Bellot ◽

F Fontaine ◽

D Laigle ◽

...

Keyword(s):

Debris Flow ◽

French Alps ◽

Flow Monitoring

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Analysis of the ground vibration generated by debris flows and other torrential processes at the Rebaixader monitoring site (Central Pyrenees, Spain)

Natural Hazards and Earth System Science ◽

10.5194/nhess-14-929-2014 ◽

2014 ◽

Vol 14 (4) ◽

pp. 929-943 ◽

Cited By ~ 20

Author(s):

C. Abancó ◽

M. Hürlimann ◽

J. Moya

Keyword(s):

High Frequency ◽

Debris Flows ◽

Low Frequency ◽

Ground Vibration ◽

Monitoring Site ◽

Velocity Signal ◽

Vibration Sensors ◽

Definition Of ◽

Flow Detection ◽

Central Pyrenees

Abstract. Monitoring of debris flows using ground vibration sensors has increased in the last two decades. However, the correct interpretation of the signals still presents ambiguity. In the Rebaixader monitoring site (Central Pyrenees, Spain) two different ground vibration stations are installed. At the first station the ground velocity signal is transformed into an impulses-per-second signal (low frequency, 1 Hz). The analysis of the data recorded at this station show that the shape of the impulses signal is one of the key parameters to describe the evolution of the event. At the second station the ground velocity signal is directly recorded at high frequency (250 Hz). The results achieved at this station show that the differences in time series and spectral analysis are helpful to describe the temporal evolution of the events. In addition, some general outcomes were obtained: the attenuation of the signal with the distance has been identified as linear to exponential; and the assembly of the geophones to the terrain has an important effect on the amplification of the signal. All these results highlight that the definition of ground vibration thresholds for debris-flow detection or warning purposes is a difficult task; and that influence of site-specific conditions is notable.

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Debris-flow monitoring and warning: Review and examples

Earth-Science Reviews ◽

10.1016/j.earscirev.2019.102981 ◽

2019 ◽

Vol 199 ◽

pp. 102981 ◽

Cited By ~ 10

Author(s):

Marcel Hürlimann ◽

Velio Coviello ◽

Coraline Bel ◽

Xiaojun Guo ◽

Matteo Berti ◽

...

Keyword(s):

Debris Flow ◽

Flow Monitoring

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Outlining a stepwise, multi-parameter debris flow monitoring and warning system: an example of application in Aizi Valley, China

10.5194/egusphere-egu2020-4306 ◽

2020 ◽

Author(s):

Ningsheng Chen

Keyword(s):

Debris Flow ◽

Early Warning ◽

Pressure Sensors ◽

Warning System ◽

Point Of View ◽

Economic Point ◽

Flow Monitoring ◽

Vibration Sensors ◽

Wide Range ◽

Critical Rainfall

Abstract: In recent years, the increasing frequency of debris flow demands enhanced effectiveness and efficiency are essential not only from an economic point of view but are also considered as a frontline approach to alleviate hazards. Currently, the key issues are the imbalance between the limited lifespan of equipment, the relatively long period between the recurrences of such hazards, and the wide range of critical rainfall that trigger these disasters. This paper attempt to provide a stepwise multi-parameter debris flow warning system after taking into account the shortcomings observed in other warning systems. The whole system is divided into five stages. Different warning levels can be issued based on the critical rainfall thresholds. Monitoring starts when early warning is issued and it continues with debris flow near warning, movement warning and hazard warning stages. For early warning, historical archives of earthquake and drought are used to choose a debris flow susceptible site for further monitoring, Secondly, weather forecasts provide an alert of possible near warning. Hazardous precipitation, model calculation and debris flow initiation tests, pore pressure sensors and water content sensors are combined to check the critical rainfall and to publically announce a triggering warning. In the final two stages, equipment such as rainfall gauges, flow stage sensors, vibration sensors, low sound sensors and infrasound meters are used to assess movement processes and issue hazard warnings. In addition to these warnings, community-based knowledge and information is also obtained and discussed in detail. The proposed stepwise, multi-parameter debris flow monitoring and warning system has been applied in Aizi valley China which continuously monitors the debris flow activities.

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