Thomas Beillouin

The concentration of population and human activities on coastlines is causing increasing coastal risks. With two-thirds of the world's population living less than 100 km from the coast, this “coastalization” is intensifying and risk situations are multiplying in the face of various hazards, with erosion, submersion, and flooding at the forefront. For a long time, the relationship between urbanization and natural coastal dynamics was regulated by the construction of “sea defense” structures. Today, these structures are being called into question both for their financial and environmental costs and because of the false sense of security they provide. In France, the storm Xynthia in 2010 and the brutal erosion of the Aquitaine coast during the winter of 2013-2014 dramatically revealed the vulnerability of coastal areas, stimulating research in the field of risk management. While geographers point to development as one of the main factors contributing to coastal risks, uncontrolled urbanization of the coastline and hinterland is evidence of a crisis in the model, exacerbated by the effects of climate change. Exploring the context of metropolitan France, this thesis posits not only that taking coastal hazards into account in development can serve as a model, but also that architects and urban planners can play a key role in its implementation, in close collaboration with geographers. Its central hypothesis is that, given the growing attractiveness of coastal areas, a qualitative reflection on their territorial depth is essential to mitigate risks while enhancing coastal landscapes. First, this work traces the links between 19th- and 20th-century development models and coastal dynamics, highlighting their role in the production of coastal risks. Next, the analysis of five coastal areas, diverse in terms of geography and urbanization, highlights the contrasting strategies currently being developed in France, from the most conventional to the most naturalistic: Le Barcarès, La Rochelle, Lacanau, Saint-Nazaire, and Salin-de-Giraud in the Camargue. Finally, after drawing lessons and identifying gaps, the third part questions the possibility of better integrating buildings and natural dynamics through a renewal of urban and architectural design tools in coastal areas.