Debris flow hazards due to land use change above source areas in torrent catchments. The case study of Les Arcs (Savoie, France)

For a few decades, land use has changed due to developments in mountainous regions and this has resulted in new pressures on the environment. Consequently, slope instabilities could be a physical expression of such imbalance. Since the 1960s, debris flows events have occurred with an increasing frequency on Les Arcs catchment as it never happened before. At the same time, a large skiing area has been expending on the upper slopes. The study of climatic series shows that rainfall events linked to debris flow triggering were not especially intense compared to the more extreme precipitations recorded in the area for the past middle century. This observation suggests that additional factors have taken part in the debris flow triggering for the last fifty years. Following this logic, the space-time study of land use has underlined the role of winter sport resort expansion on processes such as runoff and erosion affecting torrent banks and beds, directly at the origin of debris flow generation. A complementary analysis of effects on hydrology, supported by a hydrological modelling (PCRaster Software) has been carried out as well. According to modelling results, the land use conversion is responsible for a change of annual water balance resulting in a significant increase of torrent water flow. Particularly, these effects are emphasised by the localization of converted surfaces (roads, buildings, car parks, ski runs, sport facilities...) in the catchment recharge areas above steep slopes of torrent channels, where materials are liable to be mobilized. Indeed at this interface, during rainfall events the water flow and especially the peak flow are more intense than in the past, due to water rerouting and concentrating that may activate erosive processes above debris flow source areas. At the catchment scale, the increasing number of debris flow events seems to be the answer to this change

Les processus de métropolisation dans les capitales régionales européennes (agglomération de 500 000 à 1 000 000 d'habitants). Les cas de Bordeaux, Bristol, Montpellier, Saragosse et Toulouse

In the last three decades, cities have become the major recipients of economic globalisation. Urban mutations within this context have transformed the role and functions of these cities. Since the early 1990s this phenomenon, known as metropolisation, has been at the heart of pluridisciplinary studies. The definition of metropolisation initially applied to the large metropolises. However, smaller cities have also undergone substantial mutations. The aim of this thesis is to analyse the transformations that have occurred in those metropolises with a population of between 500,000 and 1,000,000 inhabitants, and to gauge whether these transformations are related to metropolisation processes. Based upon the comparative analysis of five European regional capitals, urban mutations are considered in the light of demographic, socio-economic and political change. The signs of metropolisation demonstrate that these cities play a leading role in the development of their countries, in particular by giving them access to international dynamics. However, these opportunities are fragile as they rely heavily upon economic trends and public politics.Depuis trois décennies, les villes sont devenues le réceptacle majeur de la mondialisation de l'économie. Les mutations urbaines liées à ce contexte ont transformé leurs rôles et fonctions : ce phénomène appelé processus de métropolisation a fait l'objet d'études pluridisciplinaires depuis le début des années 1990. La définition du concept de métropolisation s'est d'abord construite pour les grandes métropoles. Mais les villes de taille inférieure ont subi également des mutations profondes. L'objet de la thèse consiste à analyser les transformations subies par les métropoles dont l'agglomération est comprise entre 500 000 et 1 million d'habitants et à apprécier si elles s'apparentent à des processus de métropolisation. A partir d'une analyse comparative de cinq capitales régionales européennes, les mutations urbaines sont saisies au regard des évolutions démographiques, socio-économiques et politiques. Les manifestations de la métropolarisation montrent que ces villes jouent aussi un rôle moteur dans le développement de leurs pays notamment grâce à leur insertion dans des dynamiques internationales. Toutefois, ces capacités demeurent fragiles car fortement dépendantes de mouvements économiques généraux et des politiques publiques

New General Models for Evaluating Interactions in Non-Regular Solutions and Adsorption Energies Based on Both Hansen's and Drago's Parameters

This study aims at providing a model for the internal mixing energy of two liquids. The concerned variables are the solute molar volume V (cm3/mol.), the cohesion parameters and the Drago's parameters. The model is based on the following fundamental novelties: The fragmentation of molar cohesive energy ∆Ecoh (kJ/mol) into two distinct categories. Indeed, the dispersive and polar cohesion energies are magnetic and electrical in nature, and the cohesive energy of the chemical bonds (Hydrogen Bond) is due to charge transfer and orbital overlap. The origins of these two categories of energy are different, requiring two different treatments in use. For the first time, a relationship has been established between the cohesive energy from chemical bonds ∆Eh (kJ/mol) and Drago's parameters Ea, Eb, Ca, and Cb (KJ1/ 2mol-1/2). A simple equation has been proposed for the salvation energy of a gaseous solute in a liquid solvent. This equation contains a term for the perturbation energy of the solvent in the presence of the solute, namely the cavity formation energy, and different types of interaction energies between the solvent and the solute at infinite dilution. Based on calorimetric data published, the proposed model is compared with the classic model in terms of the mixing energy. The result shows a clear advantage of the new model over the old or conventional one. Clearly, this new model should provide a new method to determine the interaction parameters or interaction capacities of complex pharmaceutical molecules using a series of simple and well-chosen solvents