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Jeannee N.,GEOVARIANCES | Bardou E.,CREALP | Faucheux C.,GEOVARIANCES | Ornstein P.,CREALP
Mathematical Geosciences | Year: 2013

The Glacier Bonnard is a rock glacier located in the State of Valais, Switzerland. It overhangs a settlement and its slow downward constant creep constitutes an environmental hazard. It is therefore important to understand the glacier's internal structure, particularly in terms of ice content, in order to evaluate its current global dynamic and future evolution. Following preliminary geophysical investigations, several boreholes have been drilled to measure the thickness of the glaciated mass and the vertical distribution of lithology and ice content. These new data are helpful in assessing the amount of ice within the Glacier Bonnard. Two geostatistical modeling approaches are considered: a direct modeling of ice content and an indirect approach linking together lithology and ice content by the use of the plurigaussian algorithm. Comparisons between these approaches are made in terms of ice content prediction and of global ice mass within the sampled area; they underline the benefit of the geostatistical modeling and particularly the advantages of the indirect approach. © 2013 International Association for Mathematical Geosciences.

Bottelin P.,ISTerre | Jongmans D.,ISTerre | Baillet L.,ISTerre | Hantz D.,ISTerre | And 5 more authors.
Near Surface Geoscience 2012 | Year: 2012

The dynamic response of four prone-to-fall compartments exhibiting diverse morphology, rupture mechanism, geological context and volumes has been studied using the resonance frequency technique. All sites exhibit well-defined spectral energy peaks, both in specific directions and at given frequencies. A predominant peak has been systematically measured at the lowest frequency, which has been interpreted as the first resonance frequency (f1) of the unstable compartment. The observation that the vibration direction at f1 is perpendicular to the rear main fracture at the four sites supports this interpretation and suggests that the first vibration mode is probably bending. These results show that the spectral analysis of the seismic noise might provide valuable information on unstable compartments, in various geological contexts. The first resonant frequency has also been monitored over a few months and did not show irreversible variations linked to damaging. By contrast, all sites exhibited reversible changes in fundamental frequency, clearly related to temperature variations but showing different patterns. These results suggest that the origin and control of the resonance depends on the site characteristics (volume, geology, morphology and rupture mechnism).

Bardou E.,CREALP | Favre-Bulle G.,CREALP | Faucheux C.,Geovariances | Jeannee N.,Geovariances | Ornstein P.,CREALP
Earth Surface Processes and Landforms | Year: 2015

Complex para-glacial systems may show signs of destabilization leading to frequent and potentially hazardous debris-flows. Understanding creeping permafrost displacement over a period of time is therefore crucial for hazard management and risks assessment. This paper presents our methodology for estimating creeping permafrost displacement based upon data derived from various survey methods and demonstrates its relevance on the Glacier Bonnard system in southern Switzerland. Geostatistical processing allowed estimation of the displacement intensity over the area of interest, as well as assessment of the interpolation quality. Although the local measurement network needs to be refined, the results largely improve the understanding of the Bonnard para-glacial system, though highlighting the need to locally refine the measurement network. In the present case, the destabilized front advances at ~1m/a and the upstream creeping part at ~0.4m/a. Variance analysis also provide objective thresholds that could be used to distinguish underlying physical processes. © 2015 John Wiley & Sons, Ltd.

Hernandez J.G.,CREALP | Claude A.,CREALP | Paredes Arquiola J.,Polytechnic University of Valencia | Roquier B.,Hydro Cosmos S.A | Boillat J.-L.,Ecole Polytechnique Federale de Lausanne
Swiss Competences in River Engineering and Restoration - Special Session on Swiss Competences in River Engineering and Restoration of the 7th International Conf. on Fluvial Hydraulics, RIVER FLOW 2014 | Year: 2014

A complex hydrologic-hydraulic model has been developed for the Upper Rhone River basin in Switzerland. It is currently operational in the Canton of Valais for real-time flood forecasting and management, providing automatic warnings to the crisis cell of the Canton as well as proposing preventive emptying operations of dam reservoirs to reduce potential flood damage. The system is connected with a database for real-time data transfer and a website has been created to provide information for flood management, such as warning levels, hydrological forecasts at the main control points of the Rhone River and its tributaries, precipitation forecasts over the whole basin, snow cover state and reservoirs water levels. Besides, a hydrological call center has been established for supporting the crisis cell during risked event situations. © 2014 Taylor & Francis Group, London.

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