Investigation on Farmland Abandonment of Terraced Slopes Using Multitemporal Data Sources Comparison and Its Implication on Hydro-Geomorphological Processes

Abstract

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.

Short-Term GIS Analysis for the Assessment of the Recent Active-Channel Planform Adjustments in a Widening, Highly Altered River: The Scrivia River, Italy

“…However, aiming to precisely define the ongoing morphological dynamics, the most suited time span to consider for analyzing the riverbed adjustments ranges from the present-day to approximately 10-25 years ago [11,22,23].Previous studies concerning the morphological evolution of Italian rivers outlined their main morphological tendencies over the last two centuries, that is substantially before the occurrence of the most intense and widespread anthropic interventions on fluvial systems. As reported by several authors [18,[24][25][26][27][28], three evolutionary phases can be recognized: (i) the first one, from the last decades of the 19th century to the 1950s, is generally characterized by gentle narrowing and incision albeit, in some cases, no large-scale dominant processes are recognizable up to the beginning of the 20th century [18]; (ii) the second one, from the 1950s to the 1990s, presents the most relevant channel adjustments related to fast, severe and generalized narrowing and incision processes, coupled with a reduction in braiding degree and with an increase of sinuosity; (iii) the third one, from the 1990s onwards, shows a reversal trend since it is characterized by active-channel widening and by an overall slight aggradation or bed-level stability; however, this latter phase is documented only along some rivers [25,29,30].The causes behind the 20th century channel changes are now widely documented [18,21] and have been recognized in the reduction of the sediment budget due to in-channel quarrying activity [19,31], occupation of areas of fluvial pertinence [21,32], channelization [19,33,34], land-use changes at catchment scale [16,30,[35][36][37][38] and building of cross works such as weirs and dams [39][40][41]. On the contrary, the triggering factors of the most recent phase are still quite debated in the scientific literature…”

“…The causes behind the 20th century channel changes are now widely documented [18,21] and have been recognized in the reduction of the sediment budget due to in-channel quarrying activity [19,31], occupation of areas of fluvial pertinence [21,32], channelization [19,33,34], land-use changes at catchment scale [16,30,[35][36][37][38] and building of cross works such as weirs and dams [39][40][41]. On the contrary, the triggering factors of the most recent phase are still quite debated in the scientific literature [29,30] and according to previous research could be related to: (i) the end of the in-channel sediment mining for commercial purposes, which is dated back around the late 1980s-early 1990s [20,42,43], (ii) changes in the riverbed geometry resulting in an increase of unit stream power [44], and/or (iii) the occurrence of large flood events [21,24,25,29,30].…”

Large-scale geomorphology of the Entella River floodplain (Italy) for coastal urban areas management

“…As shown in the geology sketch map, the bedrock consists mainly of marl, silty marl, sandstone, shale and, secondarily, of ophiolite and chaotic complex. As documented for neighbouring areas (Brandolini et al, 2017;Pepe, Mandarino, Raso, Scarpellini, et al, 2019), the inlands experienced an intense abandonment of cultivated terraced slopes mainly due to the socio-economic growth occurred over the last century (Brandolini, 2017;Roccati, Faccini, Luino, Turconi, & Guzzetti, 2018).…”

Critical Environmental Issues Confirm the Relevance of Abandoned Agricultural Land

“…There are still many open questions concerning the abandonment of terraced landscapes: what is the frequency of terrace collapse and what are the temporal drivers [78]? To what extent and under which conditions can the original drainage network be reinstalled?…”