The snow leopard lives in the high mountains of Asia. Threats currently facing the species are being poached for its high-valued fur and being killed by herders in retaliation for livestock predation. However, climate change also has an impact on the snow leopard’s mountain habitats as tree line height and the average temperature have increased in Asian mountains. This thesis analyzes the near-future threats from climatic changes against snow leopards and what impact human activities have on the species. Fragmentation of habitats have a huge effect on the survival of snow leopards because the connectivity routes may be reduced or lost. The general process of assessment by the IUCN was examined alongside the assessment of the snow leopard. Both anthropogenic activities and global warming lead to fragmented habitats and may isolate snow leopard populations from each other. An estimated 30 - 65 % of the snow leopard’s habitats may disappear in future scenarios. Climate change is not a threat by itself but creates new threats. Therefore, climate change needs to be taken into consideration in future assessments by IUCN due to its growing impact. The recently released IPBES report makes it apparent what destructive force human activities have on biodiversity.

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.

When radio echo sounding polar ice sheets weak stratified reflections are visible deep inside the ice sheets. These reflections are often called internal layers. Previously it has been suggested as a result of glacier flow models that these reflections can be treated as surfaces of equal age. In order for a reflection to be related to a single age feature in an ice sheet a one dimensional wave model must be adequate to model the propagation of a wavelet down to the feature and back to the surface. In this thesis four different one dimensional models are constructed each including different physics. It is shown that for the frequencies of interest to radio echo sounding it is sufficient to use the non-dispersive high frequency values of permittivity and conductivity for the ice in the models. The models are used on data from two drill sites. The first site is Berkner Island where I constructed an instrument to measure the electrical conductivity of the 181 metre long ice core. The second site is the Greenland Ice Core Project (GRIP) site at Summit of length 3028 metres. For both sites permittivity and conductivity profiles inside the ice sheet are calculated and put into the models with an estimate of the transmitted wavelet to produce expected radio echo profiles at the sites. For Berkner despite altering many parameters no match between model result and radar data was obtained. For GRIP a satisfactory match was obtained between model result and radar data. It is concluded that the weak, specular (plane like), st Ratified reflections at depth can be treated as isochrones. The strong reflections at shallow depths are a result of a combination of spherical reflection surfaces and interference between many closely spaced layers and cannot necessarily be treated as isochrones.

Tyres are used in everyday life for a variety of practical and recreational tasks. Frictional behaviour of tyres on any surface is important for vehicle safety and control; this behaviour becomes more important when that surface is snow. The interaction of rubber and a snow surface is complex and a deeper understanding of both is needed in order to help develop better tyres. Outdoor full scale tyre test results were compared to results from indoor laboratory tests using a linear tribometer and a surface of compacted artificial snow; these were in excellent correlation allowing a systematic and comprehensive study of rubber friction on snow to be conducted in the laboratory. Rubber samples of varied rubber compositions and geometries were used to gain an understanding of friction on snow. Samples with varying glass transition temperature (Tg), dynamic rigidity (G*) and Payne effect (dependence of the dynamic moduli on the amplitude of the applied strain) were investigated along with samples with and without sipes. The rubber friction coefficient (μ) was measured as a function of velocity and temperature. The siped samples exhibited a higher μ than those without sipes. FE simulations, rubber friction tests for varying contact pressures and steel blade force tests were performed to evaluate contributions from ‘surface’ friction and ploughing separately. The increased μ was attributed to the ploughing force from the front edges of the ‘subblocks’ created by the sipes. Although it is well known in the industry that siped tyres grip well, this is the first time it has been explained how sipes grip effectively through a combination of ploughing and rubber snow interaction. A comprehensive study of varying rubber properties (Tg, G* and Payne effect) was conducted to better understand their impact on snow friction. The findings were evaluated using the WLF shift factor to account for the running frequency of the rubber from the snow surface roughness. G* was found to be the dominant parameter for rubber μ when considering running frequency. Increased μ values were exhibited by rubbers with a lower G*. The decreased G* makes the rubber more compliant, thus increasing the contact area between the rubber and the snow, in turn increasing μ. A better knowledge of the surface roughness of snow will aid the understanding of the interaction between rubber and snow for tyres. A method was developed to characterise the artificial snow surface utilising sectioning and imaging of chemically stabilised snow samples. From images of the snow surface before friction testing the average indentor size can be found, this is used to analyse the running frequency of the rubber. Qualitatively comparing the surfaces before and after rubber friction testing shows a decrease in surface profile aggressivity after a test; this is attributed to melting of the snow from frictional heating and snow grain fracture. Friction tests were conducted to directly compare rubber friction on snow and ice using round edged samples. Again it was found that the rubber with the decreased G* exhibited higher friction; this was seen on both snow and ice confirming G* as the dominant rubber property for both surfaces, regardless of the surface roughness change. It was found that at low temperatures ice had a higher μ than snow, while at high temperatures snow exhibited a higher μ than ice. It is hypothesised that this intriguing switch is due to the surface roughness change leading to differing contact areas both with and without melt water. This switch is not seen when a simple heat transfer model is used, confirming the effect as a surface roughness change. The use of a modified Hertz model shows that indentation is the dominant mechanism at low velocities on snow. It is hypothesised that at high velocities melt water dominates on both snow and ice while adhesion may have a more significant role on ice at low velocities. These findings provide knowledge that can be used in the design of tyres for snow and ice in the future.

Ce travail de thèse propose une méthodologie d’instrumentation reposant sur plusieurs outils hydrologiques, géophysiques et géochimiques afin de quantifier l’apport nival dans les débits du Lignon. Cette instrumentation consiste en un suivi des échanges aux différents compartiments/interfaces hydrologiques que forment l’atmosphère, la neige, le sol et les cours d’eau au cours des saisons. La neige, et surtout l’équivalent en eau liquide qu’elle représente, est fondamentale pour la compréhension du fonctionnement des sources du Lignon, situées à l’aval direct d’une congère de grand volume. Ce volume d’eau est stocké durant la saison froide pour être restitué lors de la fonte printanière. Cette restitution est loin d’être homogène dans le Haut Lignon, en raison de la forte variabilité spatio-temporelle des paramètres qui la pilotent.L’infiltration de l’eau alors produite est une étape clef dans le comportement hydrologique du Lignon au printemps. La structure du sol à proximité des sources explique également la forte dépendance des sources du Lignon par rapport aux précipitations neigeuses. Cette dépendance est particulièrement visible lors de la fonte de la neige, qui modifie à très court terme les débits aux sources. Cette relation neige-pluie-débit met en évidence une alimentation superficielle pluvio-neigeuse prépondérante par rapport aux débits issus d’eau plus profonde, mais variable au cours de l’année.La méthode d’instrumentation employée, adaptée à l’hydrologie locale employée, permet de corroborer les résultats obtenus avec une précision appréciable, tout en ouvrant de nouvelles perspectives d’application à d’autres bassins versants d’altitude. / This work proposes a methodology for an instrumentation based on several hydrological, geophysical and geochemical tools, to quantify the contribution of snowmelting proportions in the Lignon. This instrumentation is a monitoring of the different compartments / hydrological interfaces made up by atmosphere, snow, soil and rivers throughout the seasons.Snow, and especially the snow water equivalent, is fundamental to a better hydrological understanding of the sources of the Lignon, located directly downstream of a large snowdrift. This amount of water is stored during the cold season, to be returned during the spring melting. This return is heterogeneous in the top of the Lignon, due to the high spatial and temporal variability of parameters leading the melting.The infiltration of water therefore produced is a key step in the hydrological behavior of the Lignon during the spring time, which can be potentially more affected by the freezing of the ground, which significantly increases surface runoff.Soil structure near sources also explains the strong dependence of the sources of the Lignon towards snowfalls and rains. This dependence is especially noticeable at the snow melting that changes with very short term the flows at the sources.This snow-rainfall-runoff relationship highlights a predominant rain-snow surface supply, in comparison with the deeper water flows, and variable during the year.This instrumentation method, adapted to the local scale hydrology, allows corroborating the results obtained with a good accuracy, while opening new opportunities for application to other altitude watersheds.

Travel over snow by vehicle in Arctic and mountainous terrain is one of the most difficult problems of our Armed Forces and other public and private agencies. agencies whose services demand over-snow travel find little or no adequate means of transport. Those vehicles which are available, are either economically infeasible in construction and operating costs, or have serious operational limitations. A great amount of research has been done, but as yet, no vehicle has been produced to successfully meet the varied problems of over-snow transportation. The Utah State Agricultural College, and its affiliated organization, the Utah Scientific Research Foundation, in cooperation with other public and private agencies, has sponsored several research projects which have attempted to produce a satisfactory over-snow vehicle.

Snow melt is an important component of Western US water resources, accounting for about 50-80% of the annual runoff. Prediction of runoff from snowmelt in heterogeneous watersheds requires the quantification of physical processes accounting for the effects of forest canopy on snow accumulation, melt and sublimation. The forest canopy intercepts snowfall that resulting in smaller snow accumulations in forest area than in open area. The forest canopy also modifies the energy exchange between snow surface and the atmosphere, and alters the sublimation and melting of sub-canopy snow relative to open area. This dissertation has examined ways to improve snowmelt modeling capability to better account for canopy effects and has presented enhancements to an energy balance model that include i) an improved representation of the transmission of radiation through the canopy, ii) an improved representation of the atmospheric transport of heat and water vapor between the snow on the ground, in the canopy and the atmosphere above, and iii) an improved representation of the processes of canopy snow interception and unloading. These enhancements were evaluated against 4 years of field data (2006-2010) collected at the TW Daniels Experimental Forest (TWDEF) located 30 miles N-E of Logan. Observations included continuous automated climate and snow depth measurements supported by periodic field measurements of snow water equivalent and temperature in four different vegetation classes (grass, shrubs, coniferous forest, deciduous forest). The enhanced canopy components were included into the Utah Energy Balance Snowmelt model and provide improved capability to predict the surface water input and runoff from snowmelt in heterogeneous watersheds using a parsimonious approach that can be used with practically available information.

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Thesis (M.M.S.)--Memorial University of Newfoundland, 2005. / Bibliography: leaves 85-91.