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

“…The latter approach needs the incorporation of a trigger into the recording algorithm and the correct definition of its value. Different types of triggers can be found in the literature, such as (a) level triggers: fixed value of the ground velocity (LaHusen, 2005a) or fixed values of a transformed signal (Badoux et al, 2009;Hürlimann et al, 2013); or (b) more sophisticated thresholds based on the frequency content of the signal (Bessason et al, 2007). The type of trigger applied mainly depends on the data recording system implemented at the site.…”

Section: Abancó Et Al: Analysis Of the Ground Vibration Generatedmentioning

confidence: 99%

“…The debris flows and debris floods analysed in this study are mostly triggered by convective storms in the summer, which are characterised by short and intense rainfalls. However, it has also been observed that rainfalls of lower intensities accompanied by snowmelt can also trigger events in spring (Hürlimann et al, 2013).…”

Section: General Settingmentioning

confidence: 99%

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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)

Abancó

Hürlimann

Moya

2014

Nat. Hazards Earth Syst. Sci.

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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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“…These local, intense, convective rainfalls (Underwood et al, submitted) produce abundant runoffs at the feet of rocky headwater walls that are able to entrain large quantities of sediments and debris flows. Runoffgenerated debris flows, initially observed in laboratory facilities (Gregoretti, 2000a,b;Tognacca et al, 2000), are common both in the Alpine region (Berti and Simoni, 2005;Gregoretti and Dalla Fontana, 2008;Theule et al, 2012;Tiranti and Deangeli, 2015) and in other mountainous regions such as the Pyrenees (Hurlimann et al, 2014), Japan Alps (Imaizumi et al, 2006;Okano et al, 2012), Colorado and California (Cannon et al, 2008;Coe et al, 2008;Kean et al, 2012). The routing of debris flow in settled areas can cause damage and casualties.…”

Section: Introductionmentioning

confidence: 99%

Comparative analysis of the differences between using LiDAR and contour-based DEMs for hydrological modeling of runoff generating debris flows in the Dolomites

2015

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Present work aims to explore the differences in hydrological modeling when using digital elevation models (DEMs) generated by points from LiDAR surveys and those digitized on the contour lines of the regional technical map (RTM) and their relevance for the simulation of debris flow triggering. Hydrological models for mountainous areas are usually based on DEMs. DEMs are used to determine the flow path from each pixel, by which the basin is discretized, to the outlet. Hydrological simulations of runoff that triggered debris flows occurred in two rocky headwater basins of Dolomites, Fiames Dimai (area approximately 0.03 km 2 ), and Cancia (area approximately 0.7 km 2 ) are carried out using a DEM-based model designed for simulating runoff that descends from headwater areas. For each basin, the runoff is simulated using DEMs that are generated using points from LiDAR, and those digitized on the contour lines of the regional technical map, respectively. The results show that the peak discharge values corresponding to the simulations carried out using the LiDAR-based DEMs are higher than those corresponding to the simulations carried out using the RTM-based DEMs. Larger differences are observed for the Dimai basin, where the area corresponding to the RTM-based DEM is markedly smaller than the area corresponding to LiDAR-based DEM, whereas for the Cancia basin, the two areas are similar. Both the differences in the peak discharge and the basin area are due to the poor accuracy of the contour-based DEM (i.e., elevation accuracy), that is, a poor representation of the morphological features that leads to errors on the watershed divide and simplifications of the flow paths from each cell to the outlet. This result is highly relevant for estimating the triggering conditions of runoff generated debris flows. An incorrect simulated value of peak discharge can lead to errors both in planning countermeasures against debris flows and in predicting their occurrence.

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

Cited by 80 publications

References 41 publications

Recent debris flows in the Portainé catchment (Eastern Pyrenees, Spain): analysis of monitoring and field data focussing on the 2015 event

Recent debris flows in the Portainé catchment (Eastern Pyrenees, Spain): analysis of monitoring and field data focussing on the 2015 event

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

Comparative analysis of the differences between using LiDAR and contour-based DEMs for hydrological modeling of runoff generating debris flows in the Dolomites

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