'The stolen space': A history of channelization, reduction of riverine areas and related management issues. The lower Scrivia River case study (NW Italy)

In this research, we present the lower Scrivia River planform changes occurred from 1878 to 2016. furthermore, we illustrate the channelization-works development and the land-use changes registered close to the riverbed after the 1950s. The Scrivia River is among the most relevant right-bank tributaries of the Po River; it is about 90 km long and origins from the Ligurian-Piedmontese Appennines. The study reach is about 16 km long, close to the Po River, and generally shows a single-thread, sinuous and deep-incised channel. Nowadays the lower Scrivia River presents many bank retreat processes that involve surrounding areas, creating serious management issues. The aim of this research is to outline in detail the active-channel morphological evolution over the last 100-150 years, and characterize channelization and riverscape changes, with a specific focus on the occupation of the areas of fluvial pertinence. A quantitative multi-temporal analysis supported by field surveys and based on historical maps, aerial photographs and satellite images was performed in a GIS environment through automated and semi-automated procedures. The active channel experienced a well-defined sequence of morphological evolutionary phases. They were substantially characterized by a gradual increase of the active-channel stability and a reduction of the active-channel width, up to the end of the 20th century. Since the 2000s, morphological evolutionary trends have changed. Anthropic pressures on the river system, and in particular bank protections, are documented to have played a key role in driving the active-channel changes, and consequently, the near-riverbed land-property and land-use changes. In this respect, on the basis of cadastral data, the past legal framework is also identified as a relevant conditioning factor of the river-corridor morphological evolution. The ongoing dynamics most probably represent the morphological response to the documented, severe anthropic alterations, and are currently raising serious management issues.