Knowledge erosion: Floods and the regularisation of the river Tiber, 1870–1937

The historiography of urban rivers in Europe and North America has recognised that the development of infrastructure to harness rivers between the nineteenth and early twentieth centuries often resulted in increased flooding risks upstream or downstream to the point of intervention. The present article focuses on the city of Rome and the Tiber River, with its thousand-year history of flood-related memories and relationships. A comprehensive analysis of the extant literature, encompassing projects, public debates, the reports of scientific committees, and practical arrangements for coping with seasonal flooding between late nineteenth and early twentieth centuries, reveals that the development of novel vulnerabilities on the Tiber River floodplain occurred in conjunction with the erosion of a form of knowledge that had previously enabled the implementation of effective non-structural flood protection measures. This resulted in a continuous alteration of the river’s hydraulic regime, driven by the pursuit of a perceived permanent regulatory framework: a goal that repeatedly eluded achievement through new engineering projects.