Sediment is physical matter and, as such, is usually studied in the physical and natural sciences, such as chemistry, geomorphology, or hydraulics and hydrology. However, sediment is also deeply embedded in society and politics. Sediment flows are affected by river transformation and, in turn, affect river management. This article highlights the changing ways in which society has considered sediment in the Rhône River (France). In the early-modern historical period (16e-18e c.) sediment was generally considered a blessing. However, the contemporary evolution of the Rhône's industrialisation, river engineering, and governance has challenged this perspective. Today sediment is more likely to be viewed as a threat. The concept of the hydrosocial cycle is a useful framework within which to describe the variety of ways societies have understood river sediment. The variation is caused by, and in turn affects, the meaning and representation of sediment, the structure of land and water governance, the nature of sedimentary and water resources, and the materiality of sediment and water, mediated by technology. This article aims to open the issue of sediment to the social sciences through a dialogue between history, human geography, and political science.

En 1599, Henri IV promulgue un édit en faveur de l’assèchement des lacs et des marais de France avec pour objectif de repeupler les zones humides du royaume et d’accroître la production céréalière. Par leur diffusion et leurs dimensions dans la France méridionale, les assèchements s’apparentent à une forme d’aménagement du territoire. Les dessiccateurs, essentiellement des financiers parisiens proches du pouvoir central, ont tiré profit du cadre légal très favorable fourni par la monarchie, soucieuse de favoriser les opérations de drainage, mais aussi de son soutien judiciaire. Toutefois, les promoteurs des assèchements recherchaient également leur enrichissement personnel sur le court terme et l’accroissement de leur patrimoine. De la sorte, les assèchements méridionaux montrent que le succès des politiques d’aménagement réside dans la convergence entre l’intérêt de l’État et celui de ses dirigeants.

SUMMARY: Between 1599 and the end of the 1650s, the French Crown sustained a policy of land reclamation at a large scale. It was led by the French aristocracy who were helped by representatives of the merchant elites of Amsterdam, such as Hieronimus van Uffelen and Jean Hoeufft. The works in both Arles (Provence) and Petit Poitou (Poitou) show that land reclamation involved a radical change in society, reinforced the authority of the Crown in the areas concerned, and disrupted the former social balances built around the marshes. Thus, land reclamation aroused several conflicts which revealed its deep impact on the environment. So, this article demonstrates how the making of the modern state, backed by the development of European trade and banking, caused ecological and social changes by connecting the political and financial powers on a European scale.In the long-term history of wetlands, the sixteenth century represents a turning point as at that time very large funds were injected into a new system of drainage. 1 In the Low Countries and in northern Italy more than anywhere else, the conquest of the wetlands turned into an extensive business. 2 The change was particularly marked in Holland, where people were obliged to manage the consequences of the intensive mining of peat which had occurred during the Middle Ages. 3 To drain the lakes created by the * I should like to thank Alice Arnould, Daniel Dessert, Christelle Rabier, Géraldine Vaughan, and Marjolein 't Hart, who helped me put this essay into good order.

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