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Les risques naturels en montagne font l'objet de mesures de prévention, souvent liées à des démarches de prévision. Dans certaines situations, la prévision de la survenue d'évènements liés à ces risques, voire la simple connaissance des processus physiques qui leur est associé, constitue un enjeu scientifique important compte-tenu de la grande complexité et de la forte hétérogénéité de ce milieu. La connaissance des mécanismes de formation des crues rapides sur les petits bassins versants englacés, ainsi que la perspective de leur prévision, est un exemple de ces risques difficilement maitrisables. La diversité des facteurs influençant les débits des rivières, leur complexité individuelle ainsi que celle de la manière dont ils interagissent, la forte variabilité spatio-temporelle des conditions météorologiques de la montagne ainsi que les modifications ayant lieu sur le long terme en raison du changement climatique font que ce phénomène nécessite une étude approfondie mobilisant des compétences pluri-disciplinaires, allant de la mesure de terrain au développement de modèles numériques prenant en compte les divers phénomènes liés à ce risque. Cette thèse s'inscrit dans le cadre d'un projet mis en oeuvre en partenariat avec les collectivités locales oevrant dans la vallée de Chamonix, voué à apporter un appui scientifique à la maitrise de ce risque. Au sein de ce projet, cette thèse porte sur le développement et le déploiement d'un modèle hydrologique prenant en compte la neige et les glaciers. Ce modèle se veut avoir deux objectifs : 1) servir d'outil de recherche permettant par exemple d'exploiter les mesures de terrain réalisées, en les confrontant aux résultats produits par ce modèle, et plus généralement de servir d'outil d'étude et de compréhension du fonctionnement de ce bassin, et 2) servir d'outil d'aide à la prévision des crues, en étant en mesure de fournir une prévision des débits de l'Arve à Chamonix à partir des données de prévision météorologique. L'exploitation des possibilités toujours grandissantes de la modélisation à bases physiques fait également partie des objectifs de cette thèse. En particulier, l'utilisation d'un modèle de neige à bilan d'énergie permettant notamment une représentation détaillée de l'interaction neige-glace a été mise en oeuvre, associée à l'exploitation des nombreuses mesures de terrain pour une évaluation en profondeur des résultats du modèle. Enfin, un déploiement expérimental de ce modèle en prévision a eu lieu à la fin de cette thèse. / Natural hazards in mountain are subject to prevention measures, which often partly rely on a forecasting component. In some situations, forecasting these hazards and understanding their underlying physical processes is a major scientifical issue, considering the great complexity and the strong heterogeneity of these backgrounds. Knowing underlying mechanisms of flash-floods on little catchments with glacier cover, and the perspective to forecast be able to forecast it, is an example of these risks difficult to master. The diversity of contributions to river discharge, their individual complexity and the one of the way they interact, the strong spatio-temporal variability of meteorological conditions of mountain and long-terms modifications occuring due to climate change make that this phenomenon needs to be deeply studied within a plury- disciplinary work, going from terrain measurement to development of computationnal models taking into account the diversity of physical phenomenons relating to this risk. This thesis belongs to a research project conducted in collaboration with local authorities operating in the Chamonix Valley. The goal is to provide a scientific support to help managing this hazard. The role of this thesis in this research project is to develop, test and deploy an hydrologic model taking snow and ice into account. This model is intended to be used as a research tool among other research tools of this projects (terrain measurements for example) and also to be able to help forecasting floods, when being driven by forecast meteorological data. This thesis benefitted from the continuous development of new possibilities from physically-based simulation. We have used an energy-balance multi layer snowpack model that permits a detailled representation of glacier accumulation and melt, and snow-ice interaction. It was possible to perform a multi-criteria evaluation of the model, thanks to the numerous in-situ field measurements in the Arve valley, especially glaciers mass balance measurements. Finally, this model has been deployed and tested as a pre-operationnal forecast tool.

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Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 67-73). Also available on the World Wide Web.

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Drainage systems on cold-based glaciers are often thought to be simple systems that can be approximated from the supraglacial components of temperate glaciers. Most studies concerning cold-based glacier drainage systems have only considered one facet of the system, with little regard for how the system components interact. Studying each component independently of the whole system constrains our ability to model drainage system function and development. This in turn restricts our potential to predict how drainage systems of cold glaciers may respond to environmental change. The overarching aim of this thesis was to understand drainage system development of a cold-based glacier, and to assess whether our current understanding of supraglacial hydrological systems is consistent with the drainage systems that form on cold-based glaciers. This thesis evaluated the drainage system of the Wright Lower Glacier, McMurdo Dry Valleys, Antarctica, during the 2004/05, 2005/06 and 2006/07 ablation seasons. The study incorporated field, laboratory and numerical analyses, which resulted in a deeper understanding of the spatial and temporal variability of meltwater generation, drainage pathways, water stores and bulk discharge from the glacier. The findings showed that melt variability was driven by sediment and topographic variations, and that water storage in the form of cryoconite holes, intergranular flow, supraglacial ponds and refreezing dictated meltwater transmission to the glacier outlet. These results indicated that the structure, function and variability of the drainage system were inherently more complex than previous studies on supraglacial drainage systems had suggested. These new insights were combined together to construct a new conceptual model of the drainage system structure of a cold-based glacier. However, before the conceptual model can be used to produce a numerical model of drainage system function or development on cold-based glaciers, several issues need to be addressed. These include: refined methods for quantifying meltwater generation in cold, arid environments; methods to measure water storage on and under the glacier surface; further understanding of the development of permeable ice; and a better technique to quantify cryoconite hole connectivity.

Thesis (M. Sc.)--University of Alberta, 2009. / Title from pdf file main screen (viewed on Dec. 2, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science, Department of Earth and Atmospheric Science, University of Alberta." Includes bibliographical references.

Thesis (M.S.)--University of Delaware, 2009. / Principal faculty advisor: Michael A. O'Neal, Dept. of Geography. Includes bibliographical references.