A detailed, quantitative, multitemporal analysis of historical maps, aerial photos, and satellite images was performed to investigate the channel planform changes that occurred along the Scrivia River floodplain from 1878 to 2016. Various channel planform features, including channel length, area, width, braiding, sinuosity, lateral migration, activity, and stability, were computed through an innovative geographic information system–based procedure, starting from manually digitized active-channel polygons. Three active-channel morphological evolution stages are evident from: (1) 1878 to the 1950s; (2) the 1950s to the end of 1990s; and (3) the end of 1990s onward. In the first period, the river was generally able to migrate in its floodplain, shaping the riverscape. Active-channel narrowing and increasing channel stability characterize the second period. The most recent phase shows an inversion of the morphological evolutionary trend. This last phase is characterized by a slight generalized widening related to the reactivation of stabilized surfaces and to bank-erosion processes. Particularly from the 1950s to the 1990s, in-channel sediment mining and channelization with consequent occupation of riverine areas strongly affected the Scrivia River. These factors, together with floods, are thought to be the most likely causes of such consistent and fast morphological changes.

This paper presents a quantitative multi-temporal analysis performed in a GIS environment and based on different spatial information sources. The research is aimed at investigating the land use transformations that occurred in a small coastal terraced basin of Eastern Liguria from the early 1950s to 2011. The degree of abandonment of cultivated terraced slopes together with its influence on the distribution, abundance, and magnitude of rainfall-induced shallow landslides were accurately analysed. The analysis showed that a large portion of terraced area (77.4%) has been abandoned over approximately sixty years. This land use transformation has played a crucial role in influencing the hydro-geomorphological processes triggered by a very intense rainstorm that occurred in 2011. The outcomes of the analysis revealed that terraces abandoned for a short time showed the highest landslide susceptibility and that slope failures affecting cultivated zones were characterized by a lower magnitude than those which occurred on abandoned terraced slopes. Furthermore, this study highlights the usefulness of cadastral data in understanding the impact of rainfall-induced landslides due to both a high spatial and thematic accuracy. The obtained results represent a solid basis for the investigation of erosion and the shallow landslide susceptibility of terraced slopes by means of a simulation of land use change scenarios.

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.

From the 1990s onwards several Italian rivers have experienced a recent phase characterized by active-channel widening and, generally, by bed-level stability or slight aggradation. However, its triggering factors and its diffusion, along with the relationship between active-channel planform dynamics and vertical adjustments, are still quite debated and only few studies are available. This research deals with the active-channel planform changes occurred along the Scrivia River floodplain reach (NW Italy) over the period 1999–2019 and it aims at investigating in detail the ongoing geomorphological processes under the river management perspective. The study is based on a quantitative multitemporal analysis of aerial photographs and satellite images performed in a GIS environment and supported by field surveys. The outcomes revealed a generalized trend of gentle active-channel widening together with widespread bank instability and several (26% of total banks) intense and localized bank retreats involving both the modern floodplain and the recent terrace. In the investigated 20-year period, the active-channel area has increased by 22.7% (from 613.6 to 753.0 ha), its mean width by 25% (from 151.5 to 189.3 m), whereas no relevant length variations have been noticed. These morphological dynamics have been more or less pronounced both at reach scale and over time. The extreme floods occurred in the investigated period can be considered the most important triggering factor of the active-channel planform changes, most probably together with an increase of the reach-scale unit stream power due to changes in the channel geometry occurred over the 20th century.