Bien qu'appartenant à la zone « tempérée », la France et les îles Britanniques connaissent pourtant de nombreux excès climatiques. Parmi ceux-ci, les tempêtes hivernales font partie des aléas les plus destructeurs, en même temps qu'elles assurent un transfert d'énergie thermique de la zone tropicale vers les plus hautes latitudes. Pour mieux comprendre la climatologie de ce météore, une chronologie des tempêtes a été établie à partir des cartes des bulletins météorologiques quotidiens disponibles depuis la fin de l'année 1864. Plus de 2400 cas ont été identifiés, ce qui a permis d'évaluer la variabilité interannuelle et intra-annuelle de l'aléa. Les données de pression recueillies sur les cartes et leur analyse mettent en évidence le creusement des tempêtes au cours de la période. Les directions de vent figurées sur les cartes ont par ailleurs permis de réaliser des roses des vents pour une série de stations irlandaises, britanniques et françaises. La cartographie des minima de pression permet de faire apparaître des trajectoires privilégiées. L'étude climatologique s'achève par la recherche d'une cyclicité des tempêtes et par l'étude de leur lien avec l'ONA. Ce travail s'intéresse ensuite aux tempêtes qui ont fait événement pour les météorologues et/ou pour l'ensemble de la société du pays concerné. Ainsi sont mises en lumière les étapes de la compréhension de la météorologie des tempêtes. D'autre part, les tempêtes-événements retenues illustrent des évolutions économiques et sociales ainsi que les changements de gestion du risque tempête. Elles montrent aussi comment la culture du risque tempête s'est forgée et comment la mémoire du risque a parfois été réactivée. / Through France and the British Isles belong to the « temperate » zone, they both experience a lot of weather hazards. Among those hazards, winter storms are some of the most destructive ones, but in the same time they contribute to the thermal energy transfer from the tropical zone to the mid-latitudes. As a result, they play a major role in the world's thermal balance. In order to better understand the climatology of these meteors, a storm chronology has been established from the daily weather maps that are available since the end of 1864. More than 2400 cases have been identified which has allowed to measure the year-to-year and seasonal variability. Pressure data collected from the maps and their analysis show a deepening trend of their core pressures over the period. Wind directions displayed on the maps for different weather stations have been used to generate wind roses for a selection of Irish, British and French weather stations. The climatological study ends up in the calculation of the periodicity of storms as well as their link with the NAO. This study focuses then on a few storms that have been considered has events, either for the meteorologists or for the entire population of the country hit by the storm. Thus is highlighted the different stages of the meteorological understanding of wind storms in Europe. Moreover, the selected storms as social events underline economic and social evolutions as well as changes in the risk management of storms. These storms also show how a risk culture has emerged and how the risk memory has been re-activated.

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The aim of this thesis is to investigate the Chinese government’s disaster response over the past two decades, analyze any patterns or recurring management behaviors, and understand the government’s overall emergency response capability. Disaster response is one area that reflects the Chinese Communist Party’s ability to govern and exhibit performance legitimacy. As an authoritarian regime, the CCP relies on repression and performance to maintain its authority, especially so when national disasters occur. During times of crisis, the CCP is expected to maintain control and minimize potentially negative consequences. Not doing so results in a potential image crisis and loss of legitimacy. The cases studied in this thesis were the 2005 Songhua River benzene spill, the 2008 winter storms, the 2008 Wenchuan earthquake, the 2015 Tianjin warehouse explosions, and the 2016 June and July floods. The 2008 Wenchuan earthquake was the deadliest disaster in a generation and provides the most thorough example to investigate China’s government disaster response capabilities. Two of these crises were industrial chemical accidents near or in major Chinese cities. The remaining two were weather disasters spread over a large area that required a far-reaching and coordinated government response across multiple provinces. Each of these sets displays a type of national disaster that China experiences regularly. In conclusion, the investigation makes two conclusions about the government’s disaster response capabilities. First, the central government is able to make extensive use of its overall authority and hierarchical structure to mobilize state resources on a massive scale. This includes the CCP’s control of the People’s Liberation Army and state emergency personnel, the government’s economic authority to impose immediate regulatory measures, and ability to gather and distribute physical resources. Second, the CCP seeks to avert an image crisis to maintain a veneer of performance legitimacy. Two common tactics are repressing investigative journalism and jailing critics while molding an image of a paternalistic and protecting state through compassionate moral performance. However, the necessity for this last conclusions hints at why such practices are necessary in the first place. The CCP’s rush for economic growth, lack of accountability, and propensity for corruption among other things are the very factors that have allowed disasters to become crises. Extreme measures are necessitated because the system the Party has built is prone to crisis. Without fundamental change, the CCP will continue facing such crises in the foreseeable future.

This study examines wind generated waves during winter storms, their transformation/attenuation near the marsh edge, and the resulting saltmarsh edge erosion. A simple numerical model for wave generation, transmission and marsh edge erosion was developed and validated against observations from Lake Borgne, Louisiana. Results suggest that meteorological conditions modify the local water depth via wind or wave setup and atmospheric pressure, thus exerting a first order control on the location of wave attack, which in turn determines the type of wave forces (shear vs. impact) that dominate the erosion process. Scarp failure follows, at a location determined by water level, creating multiple erosive scarps and terraces. High measured erosion, likely due to marsh edge destabilization followed by subsequent frontal passage forces differential marsh erosion, exposing underlying substrate to further erosion. A conceptual model for marsh edge retreat is developed using these observations and supported further by model predictions.

The Northern Gulf of Mexico and coastal Louisiana are experiencing accelerated relative sea level rise rates; therefore, the region is ideal for modeling the global affects of sea level rise (SLR) on estuarine dynamics in a transgressive barrier island setting. The field methods and numerical modeling in this study show that as barrier islands are converted to inner shoals, tidal exchange increases between the estuary and coastal ocean. If marshes are unable to accrete at a pace comparable to SLR, wetlands will deteriorate and the tidal exchange and tidal prism will further increase. Secondary to hurricanes, winter storms are a primary driver in coastal morphology in this region, and this study shows that wind direction and magnitude, as well as atmospheric pressure change greatly affect estuarine exchange. Significant wetland loss and winter storm events produce changes in local and regional circulation patterns, thereby affecting the hydrodynamic exchange and resulting transport.

Cette thèse de doctorat porte sur l’analyse des dommages et sur l’évaluation des coûts induits sur les habitations par les submersions marines. L’étude se base sur les données d’assurance de deux évènements récents ayant touché la France et causé des submersions sur les côtes bretonnes et atlantiques : les tempêtes Johanna (mars 2008) et Xynthia (février 2010).Dans un premier temps, l’analyse des données d’expertise et d’indemnisation d’assurance, en lien avec celle des paramètres de l’aléa et des enjeux exposés, a eu pour but la meilleure compréhension des différents types de dommages, et l’explication des coûts observés. En parallèle, un travail de modélisation de l’aléa a été réalisé à une échelle régionale, afin de déterminer des indicateurs des forçages météo-marins, et à une échelle locale, afin de préciser les processus d’endommagement sur les sites étudiés pour les deux tempêtes. La caractérisation de la vulnérabilité et de la valeur des enjeux (coûts de construction) a été menée à l’aide de différents paramètres issus de bases de données nationales (INSEE et IGN) et de campagnes de terrain.Dans un second temps, les informations recueillies ont permis la construction de modèles empiriques de prédiction du coût des dommages aux habitations spécifiques à l’aléa submersion marine, outils aujourd’hui inexistants en France. Les différents types de modèles testés sont basés sur des approches statistiques univariées (fonctions d’endommagement) et multivariées. L’apport des données d’assurance à la réalisation de tels modèles est discuté, et des recommandations ainsi que des perspectives de recherche sont évoquées, afin de rendre ces modèles opérationnels et d’augmenter leur capacité de prédiction des coûts d’évènements catastrophiques futurs. / This PhD work aims at analysing damage and evaluating costs related to coastal flooding on residential buildings. The study is based on insurance data from two recent storm events, which caused coastal flooding in the Brittany and Atlantic regions in France: the storms Johanna (March 2008) and Xynthia (February 2010).At first, the analysis of insurance indemnities and loss adjustment data, in connection with hazard parameters, and exposed assets characteristics, allowed a better understanding of the different types of damage and costs observed. At the same time, hazard models were carried out at a regional level, in order to identify meteorological forcing indicators, and at a local level, in order to link damages to the associated physical flooding processes on the studied sites. The characterization of the asset’s vulnerability and values (construction costs) was conducted using different parameters from national databases (INSEE and IGN) and field survey.In a second step, empirical cost-assessment models were built on the basis of the data analysed, using univariate (damage functions) and multivariate statistical approaches. This study is the first attempt in France to elaborate models for the prediction of damage costs linked to coastal flooding on housing. The contribution of insurance data to the implementation of such models is discussed, and recommendations and research perspectives are expressed, in order to make the models operational and to increase their capacity to predict future catastrophic events costs.