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Université de Fribourg

Gap‐filling algorithm for ground surface temperature data measured in permafrost and periglacial environments

Staub, Benno ; Hasler, Andreas ; Noetzli, Jeannette ; Delaloye, andReynald

In: Permafrost and Periglacial Processes, 2017, vol. 28, no. 1, p. 275–285

Ground surface temperatures (GST) are widely measured in mountain permafrost areas, but their time series data can be interrupted by gaps. Gaps complicate the calculation of aggregates and indices required for analysing temporal and spatial variability between loggers and sites. We present an algorithm to estimate daily mean GST and the resulting uncertainty. The algorithm is designed to...

Université de Fribourg

Geomorphology of the Hérens valley (Swiss Alps)

Lambiel, Christophe ; Maillard, Benoît ; Kummert, Mario ; Reynard, Emmanuel

In: Journal of Maps, 2016, vol. 12, no. 1, p. 160–172

This paper presents a geomorphological map of the Hérens valley in the Western Swiss Alps. With an area of 270 km2 and altitudes ranging from 470 to 4357 m a.s.l., this valley is one of the main secondary catchments of the Upper Rhône valley. The high differences in altitudes, combined with a varied geology, create an important geomorphic diversity. The main processes active in mountain...

Université de Fribourg

Internal structure and permafrost distribution in two alpine periglacial talus slopes, Valais, Swiss Alps

Scapozza, Cristian ; Lambiel, Christophe ; Baron, Ludovic ; Marescot, Laurent ; Reynard, Emmanuel

In: Geomorphology, 2011, vol. 132, no. 3-4, p. 208-221

In order to determine the spatial extension and the characteristics of permafrost within alpine talus slopes, two sites located in the western part of the Swiss Alps were studied using borehole drilling and electrical resistivity tomography (ERT) profiles. Three boreholes were drilled along an upslope–downslope transect in both talus slopes. In both sites, frozen sediments are present only in...

Université de Fribourg

Surface subsidence and uplift above a headrace tunnel in metamorphic basement rocks of the Swiss Alps as detected by satellite SAR interferometry

Strozzi, Tazio ; Delaloye, Reynald ; Poffet, Damien ; Hansmann, Jürgen ; Loew, Simon

In: Remote Sensing of Environment, 2011, p. -

Surface subsidence associated with the construction of a headrace tunnel in the Swiss Alps at more than 2000 m above sea level (a.s.l.) has been detected at two locations with satellite differential Synthetic Aperture Radar (SAR) interferometry. At the first location, a subsidence trough of about 4 cm in the satellite line-of-sight direction following the headrace tunnel axes has been measured...

Université de Fribourg

Unraveling the patterns of late Holocene debris-flow activity on a cone in the Swiss Alps: chronology, environment and implications for the future

Stoffel, Markus ; Conus, Delphine ; Grichting, Michael A. ; Lièvre, Igor ; Maître, Gilles

In: Global and Planetary Change, 2008, vol. 60, no. 3-4, p. 222-234

Debris-flow activity on the forested cone of the Ritigraben torrent (Valais, Swiss Alps) was assessed from growth disturbances in century-old trees, providing an unusually complete record of past events and deposition of material. The study of 2246 tree-ring sequences sampled from 1102 Larix decidua Mill., Picea abies (L.) Karst. and Pinus cembra ssp. sibirica trees allowed reconstruction of 123...

Université de Fribourg

Dynamics in debris-flow activity on a forested cone — A case study using different dendroecological approaches

Bollschweiler, Michelle ; Stoffel, Markus ; Schneuwly, Dominique M.

In: Catena, 2008, vol. 72, no. 1, p. 67-78

Dendrogeomorphological analyses of trees affected by debris flows have regularly been used to date past events. However, this method has always been limited to forested cones where trees registered the impact of previous events. The minimum age dating of trees growing in the debris deposits can, in contrast, provide information on the latest possible moment of past activity. In this paper, we...

Université de Fribourg

Differentiating past events on a cone influenced by debris-flow and snow avalanche activity - a dendrogeomorphological approach

Stoffel, Markus ; Bollschweiler, Michelle ; Hassler, Gion-Reto

In: Earth Surface Processes and Landforms, 2006, vol. 31, no. 11, p. 1424 - 1437

Dendrogeomorphology was used to investigate past events on a cone affected by both debris flows and snow avalanches. We report on results of 520 cores from 251 injured Larix decidua Mill. and Picea abies (L.) Karst. trees sampled on the Birchbach cone (Swiss Alps). Detailed analysis of tree-ring sequences allowed dating of 561 growth disturbances in individual trees for a 252 yr...

Université de Fribourg

Assessing the protective effect of mountain forests against rockfall using a 3D simulation model

Stoffel, Markus ; Wehrli, André ; Kühne, Roderick ; Dorren, Luuk K.A. ; Perret, Simone ; Kienholz, Hans

In: Forest Ecology and Management, 2006, vol. 225, p. 1-3

We used one of the few rockfall models explicitly taking trees into account and compared the results obtained with the 3D simulation model RockyFor with empirical data on tree impacts at three mountain forests in Switzerland. Even though we used model input data with different resolutions at the study sites, RockyFor accurately predicted the spatial distribution of trajectory frequencies at all...

Université de Fribourg

Seasonal timing of rockfall activity on a forested slope at Täschgufer (Swiss Alps) – a dendrochronological approach = Saisonale Steinschlagverteilung auf einem bewaldeten Hang im Täschgufer (Schweizer Alpen) – ein dendrochronologischer Ansatz.

Stoffel, Markus ; Lièvre, Igor ; Monbaron, Michel ; Perret, Simone

In: Zeitschrift für Geomorphologie, 2005, vol. 49(1), p. 89-106

La dendrochronologie a été utilisée pour étudier 25 ans d’activités de chutes de pierres sur le versant boisé de Täschgufer, à Täsch (Alpes suisses). Une nouvelle approche, basée sur l’apparition de tissu calleux et de canaux résinifères résultant d’impacts dus à des chutes de pierres, permet de déterminer la saison des événements. Les résultats issus de l’analyse de 270...