Abstract. As products of both natural and social systems, rivers are highly complex historical objects. We show in this paper that historical analysis works on two different levels: one level, which we call "structural", shows the materiality of the riverine environment as the spatial-temporal product of natural factors and human impacts (bed and course alterations, pollution, etc.). On a second level -"semiotic" -we show that river systems are also social constructs and the subjects of ancient and diverse management practices. The quality of a river will be a function of the dialectical interaction between both levels. Historical analysis can uncover the inherited constraints that bear upon current management practices. To help substantiate this analytical framework, we analyse the case of the Moselle river in eastern France by using archival sources and statistical data. Severely impaired by industrial discharges from iron, coal and salt industries between the 1875s and the early 1980s, the waters of the Moselle became the subject of a social consensus between stakeholders that prevented the implementation of efficient pollution management policies until the 1990s. The example urges caution on the pervasiveness of participatory approaches to river management: social consensus does not necessarily benefit the environment.

Abstract. As products of both natural and social systems, rivers are highly complex historical objects. We show in this paper that historical analysis works on two different levels: one level, which we call "structural", shows the materiality of the riverine environment as the spatial-temporal product of natural factors and human impacts (bed and course alterations, pollution, etc.). On a second level – "semiotic" – we show that river systems are also social constructs and the subjects of ancient and diverse management practices. The quality of a river will be a function of the dialectical interaction between both levels. Historical analysis can uncover the inherited constraints that bear upon current management practices. To help substantiate this analytical framework, we analyse the case of the Moselle river in eastern France by using archival sources and statistical data. Severely impaired by industrial discharges from iron, coal and salt industries between the 1875s and the early 1980s, the waters of the Moselle became the subject of a social consensus between stakeholders that prevented the implementation of efficient pollution management policies until the 1990s. The example urges caution on the pervasiveness of participatory approaches to river management: social consensus does not necessarily benefit the environment.

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International audienceThe present study examines the geoarchaeological history of an oasis in Kharga Depression in central Egypt. El-Deir is renowned for its Ptolemaic temple and Roman fortress on the road from former Hibis (Kharga) to the Nile Valley. During the survey, spring mounds and irrigation soils belonging to an ancient agricultural zone were discovered, and further documented by ceramics found on the site. Our methodology combines the geomorphological interpretation of landforms (especially yardangs) with ceramics and 14C-dated charcoal to distinguish and date former agricultural areas in El-Deir. The results show that the oasis experienced several phases of soil accretion and destruction through time. Playa sediments were deposited in the humid early Holocene and severely eroded by deflation before the onset of irrigated agriculture between Pharaonic and Persian times. Very fast vertical soil accretion occurred in the Ptolemaic period, but irrigation soils were later destroyed during the Roman period by a combination of wind deflation and flash floods (second to fourth century A.D.), suggesting a period of climate instability. The case of El-Deir invites reevaluation of constructive agencies for the development of irrigated land and destructive agencies as limiting factors for the sustainability of agricultural practices in late antiquity