The contribution of spatial images in the prevention of natural flood risk and its effects on human societies

International audienceWe know that global climate change has many local impacts on environment and populations, particularly through increased flooding. These affect more and more great cities. The consequences are devastating with important stakes on several plans: society, human, economic, financial and environmental. Reduce damage and protect populations at risk of flooding is essential. This relationship "nature-society" can only be interdisciplinary as factors to control are numerous and complex. The objective is to provide an early warning system for floods that combining the waterside communities and their needs, the political decisionmakers and different scientific fields (geography, remote sensing, hydraulic, mathematics, modeling...).The experience takes place on two ponds hillsides tributaries of the Garonne in the south of France. Variable areas (500 to 1000 km ²) with lengths of 50 to 70 km, these two rivers converge to on the large city of Toulouse. But what prognostic issue without understanding the past and present of the contemporary evolution of land use, rural landscapes and the growth of urban areas ; all these key factors of flood hazards and the spatial extension of water during floods. The retrospective spatial analysis by means of satellite images with fine resolutions allows to establish a reliable, perceptible and quantifiable diagnosis to meet the needs of populations. All these data are then integrated into a chain of forward-looking models.Nous savons que le changement climatique a de nombreux impacts sur l'environnement et les populations, en particulier sur l'augmentation des inondations. Elles touchent de plus en plus les grandes villes. Réduire les préjudices et protéger les populations à risque est essentiel. L'objectif est de procurer un système de prévention contre les inondations qui associe les communautés et leurs besoins, les décisionnaires et différents domaines scientifiques (géographie, télédétection, mathématiques, modélisation ...). L'étude a lieu dans la région sud-ouest de la France, en amont de la grande agglomération de Toulouse traversée par le fleuve La Garonne