Historical study of the Rhône river floods (France) and their consequences on the land use evolution

Abstract:

This work aims to study the co-evolution of the flooding risk and land use to better understand how, through land use patterns, human societies have adapted to their environment or influenced it. A rereading of the coevolution of floods and society is important to understand both the nature and society and question the issue of land use and human activities in flood areas. River morphology evolution and extreme events occurrence during the last 200 years have been analyzed focusing on the influence of anthropic constructions during the same period of time. We have used these data sets to discuss the co-evolution of nature and societies. The Rhone valley has been significantly constructed (dam, embankment, nuclear power station). These constructions have been built since 1850-1860 in relation with the economic development but also after the decision to better control flooding events which have been taken after the 1856 floods.

If the first traces of civilization, especially in the Rhone Valley, show that man has established safe from floods - on the high altitude points, for example - several factors (hydrological period of calm, high population and economic activities growth...) led them to develop their cities and activities in areas submitted to flood risks. If the urbanization of flooding areas has happened and continues to happen, that is mean that some factors have a more decisive influence on the choice of location than the risk presence. Why and when the human has been installed in areas liable to natural hazards? The idea is to identify these factors and prioritize them. In other cases, some major flood could permanently change the human implantation strategies on its territory: according to the impact of floods and the human risk perception, some communities have chosen to leave the risk areas or to change their land uses (agriculture / housing). This study aims to clarify these choices and understand their construction.