The retreat of the delta: a geomorphological history of the Po river basin during the twentieth century
Résumé
The morphology of rivers and deltas, like many features of the Earth’s physical geography, is today subject to dramatic and rapid changes due to human actions. Deprived of sediment from their basins and besieged by rising sea levels, many deltas are at risk of complete disappearance. Despite a rich historical scholarship on rivers, we know little about the history of these important geomorphological processes. This paper sheds light on the geomorphological history of rivers by investigating the case of the Po River basin and its delta during the twentieth century. By combining the insights of fluvial geomorphology and a historical methodology, the paper analyses three main drivers of geomorphic alterations in the catchment that had an impact on the delta: hydroelectricity, sand and gravel mining, and methane extraction. In each case, it focuses on how experts, policy-makers, and overseers understood and regulated (or not) these geomorphic alterations. During much of the twentieth century, engineers and hydrologists monitored geomorphic processes with increasing detail, while state and business actors practiced multiple forms of sediment management. For most of the twentieth century, however, experts did not acknowledge the scale and nature of human-induced geomorphic alteration. Sediment management, moreover, did not take into account sediment scarcity until late in the century, and remained exclusively motivated by local concerns. Through this particular case, this paper offers insights on the historical limits to environmental expertise and policy when facing long term and large-scale geomorphic processes, and encourages a more sustained incorporation of fluvial geomorphology into the history of water systems.
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