Changes in channel morphology in response to two flood events were measured within three reaches on the Sainte Marguerite River, Quebec. The first event was the spring freshet---peaking in mid-May, 1996---while the second event---peaking on July 20, 1996---was the largest flood on record for the region. The resultant channel adjustments can be classified as either bedform evolution---in which a clear, systematic pattern of adjustment is evident---or as bedform change, in which local hydraulic and sedimen tologic conditions produce a seemingly random pattern of channel mobilization. Where bedform evolution has occurred, it is consistent with the existing paradigm for meander development. Sediment transport calculations based on the 'inverse' or 'morphologic' method were strongly correlated to reach average mobility ratios. The average rate of transport in response to the larger flood approached those reported by others for a braided system (Goff and Ashmore, 1994). Potential spawning zones within the three reaches were all subjected to significant net scour and/or fill following the second event; several potential spawning zones were significantly affected by the first event The presence of bank protection upstream of a potential spawning zone seems to be a determinant 10 the severity of the impact by promoting erosion of these zones.

Thesis (M.E.S.)--The Evergreen State College, 2007. / Title from title screen (viewed 1/23/2008). "A thesis: essay of distinction submitted in partial fulfillment of the Master of Environmental Studies, The Evergreen State College, June 2007." Includes bibliographical references (leaves 66-70).

Ce travail de thèse vise à reconstituer les conditions paléo-environnementales ayant eu lieu dans la vallée de l’Oisans à partir des archives naturelles représentées par les sédiments lacustres. Par une approche multi-marqueurs, nous visons à reconstituer tout à la fois : i) les fluctuations glaciaires en Oisans; ii) les modifications des activités humaines en montagne et leurs influence sur les flux de matière lors d’événements extrêmes ; iii) comprendre la relation entre changements climatiques, changements d’usage et évolution des aléas en haute montagne. Cette étude a permis de mettre en évidence les changements globaux, regroupant la variabilité climatique et les pratiques humaines, ayant influencés l’érosion autour des lacs de La Muzelle et du lac du Lauvitel durant les derniers millénaires.Les résultats principaux ont montrés que l’érosion du lac de la Muzelle a été largement dominé par l’activité glaciaire notamment avec la présence à certaines époques de fines particules détritiques liées à l’abrasion sous glaciaire. Ces dernières ont révélées une relation aux pluies torrentielles encore jamais observées auparavant, leur présence en période d’extension glaciaire étant synonyme d’une augmentation du nombre de dépôts lacustres de crues. Les activités humaines, en majeure partie représentées par l’utilisation agro-pastorale de l’espace avoisinant les lacs, ne sont clairement identifiables que lors des 300 dernières années au lac de la Muzelle. Le lac de Lauvitel est situé à une altitude moindre, dont la majorité du bassin versant est maintenant une réserve intégrale. Les études palynologiques ont mis en évidence certaines périodes d’activités humaines plus marquées. Les événements extrêmes enregistrés dans les sédiments dulac regroupent d’une part les crues, dont l’enregistrement permet une comparaison régionale de l’occurrence de ces événements et de mettre en évidence les changements de circulations atmosphériques à l’échelle des Alpes. D’autre part, les avalanches de neige lourde, dont peu d’enregistrements sont disponibles dans la bibliographie. Nous les avons identifiés grâce à l’utilisation du CT scan l’élaboration d’une nouvelle méthodologie basée sur la différence de densité relative des sédiments. Le comptage et la quantification des apports de matériel détritique grossier aux seins d’une matrice de sédiment lacustre fin, a permis d’identifier les apports liés à cet aléa au cours du temps. Nous avons ensuite reconstitué les événements d’avalanche de neige lourde déposés dans le lac de Lauvitel sur les derniers 3500 ans, dont l’occurrence intervient préférentiellement lors des périodes de retraits glaciaires. / This doctoral thesis aims to a paleo-environmental reconstitution of the Oisans valley based on the natural archive of lake sediments. From a multi-proxy approach, we aim to reconstruct: i) Glacial fluctuation reconstruction in Oisans valley; ii) human activities evolution in mountain area and their influences on sediment fluxes especially during extreme events; iii)understand the relationship between climate change, use of mountain lands and natural hazard.Through this study, we identified processes of global change, comprising natural climate variability and human practices, which affected erosion patterns around Lakes Muzelle and Lauvitel during the last millennia. Main results have shown that erosion in the lake Muzelle watershed was dominated in the past by glacial activity, in particular with the presence of fine detrital particles related to subglacial abrasion. They were identified to have a relationship never observed before; during glacial extension their presence is triggering a higher number of flood deposits. At this location, human activities were identified through agro-pastoral activities and more precisely by the coprophilous fungi spore counting, revealing cattle presence since 300 years. Lake Lauvitel is located at lower altitude, which most of the watershed is now situated in an Integral Reserve. Palynological investigations lead to identification of periods of higher human activities in the valley. Extreme events recorded in Lake Lauvitel sediment are on the one hand torrential floods, which allowed a comparison with other reconstructions highlighting changes in the climatic settings in the Alps. On the other hand, wet avalanches deposits were identified with the use of a CT scan and the development of a new methodology based on relative density differences in the sediment. The counting and the quantification of coarse detrital matter within the lacustrine fine sediment matrix allowed income identification of this hazard though time. We then reconstructed wet avalanches events deposited in Lake Lauvitel during the last 3500 years, which occurrence is preferentially during glacial retreats.

This thesis provides a novel investigation into rainfall-runoff processes occurring within a unique two-tiered depth-driven overland flow physical modelling environment, as well as within a numerical model context where parameterisation and DEM/building resolution influences have been investigated using an innovative de-coupled methodology. Two approaches to simulating urban rainfall-runoff responses were used. Firstly, a novel, 9 m2 physical modelling environment consisting of a: (i) a low-cost rainfall simulator component able to simulate consistent, uniformly distributed rainfall events of varying duration and intensity, and; (ii) a modular plot surface layer was used. Secondly, a numerical hydroinundation model (FloodMap2D-HydroInundation) was used to simulate a short-duration, high intensity surface water flood event (28th June 2012, Loughborough University campus). The physical model showed sensitivities to a number of meteorological and terrestrial factors. Results demonstrated intuitive model sensitivity to increasing the intensity and duration of rainfall, resulting in higher peak discharges and larger outflow volumes at the model outflow unit, as well as increases in the water depth within the physical model plot surface. Increases in percentage permeability were also shown to alter outflow flood hydrograph shape, volume, magnitude and timing due to storages within the physical model plot. Thus, a reduction in the overall volume of water received at the outflow hydrograph and a decrease in the peak of the flood event was observed with an increase in permeability coverage. Increases in the density of buildings resulted in a more rapid receding limb of the hydrograph and a steeper rising limb, suggesting a more rapid hydrological response. This indicates that buildings can have a channelling influence on surface water flows as well as a blockage effect. The layout and distribution of permeable elements was also shown to affect the rainfall-runoff response recorded at the model outflow, with downstream concentrated permeability resulting in statistically different hydrograph outflow data, but the layout of buildings was not seen to result in significant changes to the outflow flood hydrographs; outflow hydrographs appeared to only be influenced by the actual quantity and density of buildings, rather than their spatial distribution and placement within the catchment. Parameterisation of hydraulic (roughness) and hydrological (drainage rate, infiltration and evapotranspiration) model variables, and the influence of mesh resolution of elevation and building elements on surface water inundation outputs, both at the global and local level, were studied. Further, the viability of crowdsourced approaches to provide external model validation data in conjunction with dGPS water depth data was assessed. Parameterisation demonstrated that drainage rate changes within the expected range of parameter values resulted in considerable losses from the numerical model domain at global and local scales. Further, the model was also shown to be moderately sensitive to hydraulic conductivity and roughness parameterisation at both scales of analysis. Conversely, the parameterisation of evapotranspiration demonstrated that the model was largely insensitive to any changes of evapotranspiration rates at the global and local scales. Detailed analyses at the hotspot level were critical to calibrate and validate the numerical model, as well as allowing small-scale variations to be understood using at-a-point hydrograph assessments. A localised analysis was shown to be especially important to identify the effects of resolution changes in the DEM and buildings which were shown to be spatially dependent on the density, presence, size and geometry of buildings within the study site. The resolution of the topographic elements of a DEM were also shown to be crucial in altering the flood characteristics at the global and localised hotspot levels. A novel de-coupled investigation of the elevation and building components of the DEM in a strategic matrix of scenarios was used to understand the independent influence of building and topographic mesh resolution effects on surface water flood outputs. Notably, the inclusion of buildings on a DEM surface was shown to have a considerable influence on the distribution of flood waters through time (regardless of resolution), with the exclusion of buildings from the DEM grid being shown to produce less accurate results than altering the overall resolution of the horizontal DEM grid cells. This suggests that future surface water flood studies should focus on the inclusion and representation of buildings and structural features present on the DEM surface as these have a crucial role in modifying rainfall-runoff responses. Focus on building representation was shown to be more vital than concentrating on advances in the horizontal resolution of the grid cells which make up a DEM, as a DEM resolution of 2 m was shown to be sufficiently detailed to conduct the urban surface water flood modelling undertaken, supporting previous inundation research.

Security of citizens is one of the fundamental responsibilities of the state. Therefore, the crisis management system in the Czech Republic is one of the forms of the population protection guaranteed by the state. During its creation and operation cooperate appropriate bodies of the public administration, as well as legal and natural persons. In this thesis the readiness of smaller administrative units is assessed, such as municipality type I. (a municipality), municipality type II. (a municipality with authorized authority ) and especially municipality type III. (a municipality with extended scope). Despite the fact that the crisis management system in the Czech Republic is constantly evolving and is also supported by the legislative side, it is largely neglected at lower levels. Activities in this area are in many cases either postponed or in worse cases considered completely useless and their implementation will not take place. In relation with the exceptional situations the municipal authorities were entrusted with certain powers to deal with such situations. But on the other hand, different levels of municipalities are not distinguished in the cases of dealing with crisis situations. Problems arise in the areas of expertise, material and human resources, especially when the municipalities type I. do not have such resources to be capable of adequately respond in the event of a crisis situation. After all, there are better conditions in municipalities with extended scope, which are able, also due to the larger budgets within its administrative area, to ensure better crisis preparedness of municipality to an exceptional or crisis situation and its subsequent solutions associated with minimizing damages and eliminate the consequences of the action of an exceptional or crisis situation.The main objective of this thesis is to characterize the crisis management system in the Czech Republic. With the help of legislation and professional literature the theoretical part is focused on the explanation of basic terms, such as crisis management, a system of integrated rescue system, emergency and crisis planning, characteristics of the exceptional and crisis situation or crisis management authorities. Furthermore, the thesis is focused on the field of crisis management at the level of municipalities with extended scope, which describes both the scope and the various municipal bodies. It addresses the individual procedures of primarily smaller local government units in the prevention of municipality preparation for exceptional situations, participation of municipality on rescue and relief works and operations implemented in connection with the population protection. At last, the theoretical part contains the financial security operations related to the preparation of exceptional or crisis situations and to the rescue and relief work implementation.To meet the objectives of the thesis were established two research questions that address both the preparedness of humanitarian worker, as well as the possibility of drafting a proposal for a methodological procedure in dealing with crisis situation.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O presente estudo objetiva contribuir para a construção de uma metodologia que possa integrar as abordagens da presença e da circulação da água em ambientes urbanos, destacando o caso das enchentes, por meio da criação de um mapeamento que consiga espacializar em detalhe o fenômeno. Além disso, uma análise que permita uma visão integrada da água - sua circulação, armazenamento e interações sócio-ambientais, que se estabeleceram ao longo da história, relacionando-a às transformações urbanas oriundas também das intervenções governamentais. Essa perspectiva de análise foi inserida na área da Grande Tijuca Zona Norte do município do Rio de Janeiro (RJ) - densamente habitada, com histórico de utilização da água apresentando problemas desde o processo de ocupação inicial. Hoje, problemas relacionados ao abastecimento de água pela rede geral da cidade e ligados à circulação superficial das águas em épocas de chuvas intensas, ocasionando as freqüentes enchentes urbanas; assolam a população. O que se busca identificar é a intensidade das mudanças ocorridas no ambiente no que diz respeito aos problemas relacionados à água: o aumento na demanda por abastecimento da rede geral de água; o saneamento básico; ao aporte de efluente de esgoto sobre os canais de drenagem principais e sobre a rede geral de esgoto; além do escoamento superficial das águas pluviais, que ocasionam as enchentes. Foram utilizadas como metodologia: o levantamento histórico da evolução urbana e a presença da água nos bairros, assim como o levantamento das características físicas do ambiente, a análise de políticas públicas e como a circulação da água nos bairros da Grande Tijuca se integra no espaço. Para a presença e o uso dos recursos hídricos, recorreram-se aos dados censitários do IBGE, visando uma análise evolutiva de 1991 a 2000, que resultaram em mapeamentos. Além disso, foi realizada uma inédita Carta de Enchentes de 2006, que espacializa o fenômeno em uma escala de 1:8000 e que permite uma análise rica em detalhes, como a extensão e a variabilidade do nível das enchentes na Grande Tijuca, rua a rua pelos bairros. As muitas enchentes urbanas na Grande Tijuca seriam a resposta do ambiente às transformações que se deram ao longo do tempo. Com a diminuição da qualidade de vida, a Grande Tijuca - e a cidade do Rio de Janeiro como um todo - vai ser alvo de políticas visando o controle desse processo atuante. No entanto, essas não parecem vislumbrar a totalidade do sistema, e se apresentam como obras desconexas e pontuais, uma vez que não foram observados o controle e eliminação das enchentes. O exemplo da Grande Tijuca, evidencia a necessidade de uma visão mais abrangente do planejamento e gestão não só dos recursos hídricos, mas do espaço urbano como um todo, inserida em uma gestão que leve a um real desenvolvimento local integrado / This research objects to contribute in the construction of a methodology that can integrate the boarding of the presence and the circulation of the water in urban environments, detaching the case of floods, with the creation of a mapping that obtains to specialize in detail the phenomenon. Besides, it aims to realize an analysis that allows to an integrated vision of the water - its circulation, storage, and its social-environmental interactions, that were established through the history, relating it to the urban transformations which were derived also by the governmental interventions. This perspective of analysis was inserted in the area of the Grande Tijuca - North Zone of the city of Rio de Janeiro - densely inhabited, with description of waters use shows problems since the initial occupation process. Nowadays, the problems related to the water supply by the general net of the city and the ones related on to the superficial circulation of waters at times of intense rains (that causes frequent urban floods) devastate the population. This work searches to identify the intensity of the changes that happened in the environment concerning to the problems related to the water: the increase in the demand for supplying of the general water net; the basic sanitation; the inputs of sewage effluent on the main canals of draining and the general net of sewer; beyond the superficial draining of the pluvial waters, which causes the floods. It was used as methodology: a historical review of the urban evolution and the presence of the water in the quarters, as well as the review of the physical characteristics of the environment, the analysis of public politics and as the way that the circulation of the water in the quarters of the Grande Tijuca integrates in the space. In order to study the presence and the use of the water resources it was used the census data of the IBGE, aiming at an evolutionary analysis from1991 to 2000 that they had resulted in mappings. Moreover, an unpublished Floods Chart of 2006 was realized, which specializes the phenomenon in a 1:8000 scale and allows a rich analysis in details, as the extension and the variability of the level of floods on the street by street of the quarters. The many urban floods in the Grande Tijuca would be the reply of the environment to the transformations that occurs for long time. With the reduction of the quality of life, the Grande Tijuca - and the city of Rio de Janeiro as a whole will be white of politics aiming at the control of this operating process. However, these do not seem to glimpse the totality of the system, and they present themselves as disconnected and pointed repairs, because they dont object the control and elimination of the floods. The example of the Tijuca, not only evidences the necessity of a more including vision of the planning and management of the water resources, as well as the urban space as a whole, inserted in a management that has led to a real integrated local development.

Made available in DSpace on 2016-06-02T20:00:13Z (GMT). No. of bitstreams: 1 DissJQB.pdf: 5149396 bytes, checksum: 18f319148c3d9512b4dbca810e39ae4e (MD5) Previous issue date: 2006-05-26 / Financiadora de Estudos e Projetos / The present work proposes a debate that interrelates three areas of knowledge urbanization, urban drainage and social segregation and has the main purpose to analyze the occupation of river marginal areas in urban places as the main cause for temporary social segregation. It also proposes a discussion about this impact caused by the occurrence of floods. The research strategy used is the study of an exploratory single case made in the city of São Carlos-SP, more specifically in the central area belonging to the Gregório River Basin, characterized for having solid occupation with great commercial activity. Besides theoretical basis, we have done a research on how many floods have occurred during 1995 and 2005, in the works fulfilled by the City Government, and also interviews with five groups of social actors. The results obtained with the conclusion of the work had, in its greatest parts, a social and educational value, involving consciousness of the necessity of environment preservation; of the eventually irreversible damages caused by the occupation of environmentally fragile areas, such as floodable fertile valleys. The research has also been detached as a relevant instrument to subsidize new debates and researches. As far as the social actors are included, we have verified that the most damaged ones in the cases of floods, in the unity of analysis, were the businessmen, and 70% of these consider themselves victims of temporary social segregation. This way, it was possible to confirm the main hypothesis of the work: temporary social segregation can be considered a consequence of inadequate occupation of river marginal areas in urban places, and this may involve lots of situations, including the ones that do not refer to the condition of poverty and misery. / A presente pesquisa se insere em um debate que inter-relaciona três áreas de conhecimento urbanização, drenagem urbana e exclusão social e tem como objetivo principal analisar a ocupação de fundos de vale em áreas urbanas como agente indutor da exclusão social temporária, propondo uma discussão sobre esse impacto causado pela ocorrência de inundações. A estratégia de pesquisa utilizada é a de estudo de caso único exploratório realizado na cidade de São Carlos SP, mais especificamente, na região central pertencente à Bacia do Córrego do Gregório, caracterizada por possuir ocupação consolidada, com grande atividade comercial. Além do embasamento teórico, foram realizados levantamentos das inundações ocorridas no período entre 1995 a 2005, das obras realizadas pela Prefeitura Municipal e também, entrevistas com cinco grupos de atores sociais. Os resultados obtidos com a conclusão da pesquisa foram, em grande parte, de valor social e educacional, envolvendo a conscientização com relação à necessidade da preservação ambiental; aos danos causados - muitas vezes irreversíveis - pela ocupação de áreas ambientalmente frágeis, como as várzeas inundáveis e, também se configurou como instrumento relevante para subsidiar novas pesquisas e debates. Com relação aos atores sociais, verificou-se que os maiores prejudicados com as inundações na unidade de análise são os comerciantes e 70% desses, se consideraram vítimas da exclusão social temporária. Nesse sentido, foi possível comprovar a hipótese principal de pesquisa: A exclusão social temporária pode ser considerada uma conseqüência da ocupação inadequada das áreas urbanas de fundo de vale, podendo abranger inúmeras situações, inclusive as que não se referem à condição de pobreza e miséria.

Made available in DSpace on 2016-06-02T20:00:48Z (GMT). No. of bitstreams: 1 5002.pdf: 13532825 bytes, checksum: 924825e2affc2f847a47a3786263245f (MD5) Previous issue date: 2013-01-24 / Financiadora de Estudos e Projetos / Over past years, in the period of greatest rainfall - between december and march the cities suffer from floods. There are various motives for the urban floods, including the changes in the hydrological cycle and the disordered process of urban land use and occupation. Floods cause impacts to the population subject to the phenomenon, whose mitigation is fundamental and is based an action that balances urban development with environmental conditions. The present work aims to identify the main factors which act directly or indirectly in floods from the perspective of the areas vulnerable to flooding, with case study in the city of Sao Jose do Rio Preto-SP. From the analysis of the literature review were selected four parameters related to the areas vulnerable to flooding: the use and occupation of urban land, the river basin, the urban drainage, and the vulnerability. A method of evaluation of areas with the main features to be parsed assigning scores to the same, with the intention of quantifies and qualifies them. As a result were obtained a diagnoses form the selection area with their respective scores, degree of vulnerability, recommendations and suggestions, as well as map overview and representation schematic of the area. / Nos últimos anos, no período de maior precipitação - entre dezembro e março - cidades sofrem com as enchentes, cada vez mais frequentes, devido às inúmeras alterações no ciclo hidrológico natural e ao processo desordenado de uso e ocupação do solo urbano. As enchentes implicam uma série de impactos negativos à população sujeita ao fenômeno, cuja mitigação é fundamental e baseia-se em ações que equilibra o desenvolvimento urbano com as condições ambientais. Deste modo, o presente estudo objetiva identificar os principais fatores que atuam direta ou indiretamente na sistemática das enchentes sob a ótica das áreas vulneráveis a enchentes, tendo como estudo de caso a cidade de São José do Rio Preto SP. Foram selecionados quatro parâmetros relacionados às áreas vulneráveis a enchentes, a partir da análise da revisão bibliográfica, a saber: uso e ocupação do solo urbano, bacia hidrográfica, drenagem urbana e vulnerabilidade. A partir disso, foi elaborado um método de avaliação dessas áreas com as principais características a serem analisadas, atribuindo pontuação às mesmas, com a intenção de quantifica-las e qualifica-las. Como resultado foram obtidos diagnósticos da região selecionada com as respectivas pontuações, grau de vulnerabilidade, recomendações e sugestões para cada trecho, bem como mapa síntese e cortes esquemáticos.

Com a urbanização crescente no Brasil, o mapeamento de eventos perigosos mostra-se cada vez mais necessário para que se reduzam transtornos socioeconômicos nos municípios brasileiros. O objetivo principal da pesquisa foi elaborar mapas de suscetibilidade a eventos perigosos de natureza geológica e hidrológica, para a área urbana e de expansão urbana (148,97 km²) do município de São Carlos – SP. A análise foi feita em ambiente de SIG (Sistemas de Informação Geográfica), e combinou abordagens qualitativas e quantitativas de mapeamento de eventos perigosos, propostas pelo Working Group Committee on Risk Assessment (1997). Como método, analisou-se a freqüência dos eventos históricos em função da área (km²) dos condicionantes cartografados nos mapas temáticos (probabilidades iniciais). Os condicionantes foram analisados isoladamente e combinados, na forma de classes de terreno. O inventário dos registros históricos (482 registros) dos eventos foi feito com os dados de jornais, defesa civil e imagens de satélite entre os anos de 1965 a 2016. Foram elaborados os mapas de suscetibilidade para: movimentos de encosta, erosão pluvial, solos colapsíveis e enchentes/inundações. O método utilizado mostrou-se eficiente, visto que os objetivos da pesquisa foram alcançados. Foi possível validar os mapas de suscetibilidade, com as características do meio físico observadas em trabalhos de campo e dados de ensaios geotécnicos. Os eventos mais críticos para o município são as enchentes/inundações e alagamentos, erosões pluviais e movimentos de encostas causam pequenos transtornos, principalmente em consequência do relevo suave da região. Apesar da base cartográfica estar na escala 1:10.000, os mapas são apresentados na escala 1:20.000, com o objetivo destes serem impressos em papéis no formato A1. / With the increasing urbanization in Brazil, hazardous events mapping has become increasingly necessary to reduce socioeconomic disorders in Brazilian citys. The main goal of the research was to elaborate susceptibility maps to dangerous events of geological and hydrological nature, for the urban area and urban expansion (148,97 km²) to the city of São Carlos - SP. The analysis was done in a GIS environment (Geographic Information Systems), and combined qualitative and quantitative approaches of hazardous events mapping, proposed by the Working Group Committee on Risk Assessment (1997). The frequency of historical events was analyzed according to the area of the conditioners mapped on the thematic maps (prior probabilitys). The conditioners were analyzed separately and then combined, in the form of land classes. The inventory of historical records (482 records) of events was done with acquired data from newspapers, civil defense and satellite images between the years 1965 to 2016. Susceptibility maps were developed for slope movements, water erosion, collapsible soils and floods. This method proved to be efficient, since the research objectives were achieved. It was possible to validate the susceptibility maps, with the characteristics of the physical environment observed in field work and geotechnical data. The most critical events in São Carlos are floods, rainfall erosions and slope movements cause minor damage, as a result of the region\'s soft relief. Although the cartographic base is in the 1:10.000 scale, the maps are presented in the 1:20.000 scale, with the purpose of being printed on A1 format paper.

Ce travail de thèse a pour ambition de comprendre les mécanismes et les processus qui régissent l’action en situation decrise, c’est-à-dire dans des conditions de gestion fortement marquées par l’urgence et la nécessité d’agir vite en situationd’incertitude. Le constat d’une vulnérabilité du réseau routier face aux crues rapides nous conduit à la question suivante :quelles sont les modalités de gestion de crise lors d’événements pluvieux violents ayant pour conséquences des fermetures, des coupures ou des submersions du réseau routier et quelles sont les conditions de l’efficacité de gestion ? Notre étude souhaite montrer comment les acteurs en charge de la gestion du réseau routier dans un département régulièrement impacté par les inondations « gèrent » ces périodes de turbulences, avec quelles ressources et avec quels outils (plans, logiciels, dispositifs techniques, fiches actions etc.). Ce que nous souhaitons montrer, ce n’est pas tant qu’il existe des décalages entre le travail prescrit et le travail réel des opérateurs en temps de crise, mais bien les modalités de ces déplacements. En ce sens, c’est la question de l’efficacité qui est au coeur de notre démarche. Au sens étymologique, l’efficacité est une « vertu », une « force » (du latin efficacitas), elle doit nous permettre dans ce travail de saisir les décalages entre se qui se rapporte d’un côté à la planification et à une gestion organisée des crises, et de l’autre ce qui se rattache à la métis, c’est-à-dire l’intelligence pratique des acteurs en charge de l’exécution des tâches planifiées. Plutôt que d’identifier des défaillances, nous souhaitons montrer ce qui semble efficace du point de vue des acteurs, ce qui est « porteur » pour l’action, ce qui fait sens (Jullien, 1996, 1992). Quels sont les mécanismes vertueux que les acteurs mettent en place afin d’assurer une certaine efficacité de gestion, et de « faire tenir » ce moment de crise caractérisé, d’après une partie de la littérature, par la perte de repères pour l’action ? Approcher les conditions de l’efficacité demande d’une part d’analyser les pratiques des acteurs (rapport à la confiance, à l’adaptation, à l’improvisation, à l’interprétation de l’environnement et des informations), d’autre part de connaître les plans d’action qui les prescrivent. / This PhD dissertation aims at a better understanding of the mechanisms and processes which dictate the actions taken ina situation of crisis, that is to say, in a context very much characterized by urgency, and the necessity to act quickly inan unpredictable situation. After assessing the vulnerability of the road network in the event of a rapid rise in the waterlevel, we were led to raise the following questions : what are the various modes of crisis management in the event of violentrainstorms leading up to closings, interruptions or submersion of the road network ? What are the required conditions foran efficient management ? Our study intends to show the modus operandi of the actors in charge of the road networkmanagement in a district subject to frequent flooding to « manage » those times of trouble and the means and tools given tothem (maps, softwares, technical devices etc). What we originally aimed at was not so much emphasizing the gap betweenthe stipulated work and the effective work of operators in a time of crisis but rather focusing on the modalities of these« moves ». In a sense, matters of efficiency are at the heart of our approach. In its etymological meaning, efficiency is avirtue, a strength (from latin efficacitas) and it should enable us in this work to grasp the discrepancies between whatis linked on one side to the planning and organized managing of crises and on the other to metis, that is, the practicalintelligence of the actors in charge of the execution of the devised tasks. Instead of identifying the deficiency, we intend tohighlight what seems efficient from the actors’ point of view, what is « bearing » to the action, what makes sense (Jullien,1996, 1992). What are the virtuous mechanisms that the actors can devise in order to secure some kind of managementefficiency and to "hold together" this moment of crisis characterized, according to some writings, by the loss of a sense ofdirection in action ? This approach of the conditions of efficiency entails on the one hand the analysis of the actors’ practices(trust, adaptation, improvisation, interpretation of the surroundings and of information), and on the other, the knowledgeand understanding of the plans of action that prescribe them.