Mechanisms of failure on terraced slopes: the Valtellina case (northern Italy)

Abstract

Slopes that are terraced by means of dry-stone retaining walls are very common in the alpine environment. In Valtellina, a typical Italian alpine valley, these slopes are widespread and quite often involved in superficial mass movements that can result in severe damage and casualties. For an in-depth understanding of the processes that can trigger these events, numerical modeling of groundwater movement and a related stability analysis were performed on a detailed scale, based on an intensive monitoring of rainfall events and groundwater movement. Field observations suggest that the formation of a perched groundwater table at the contact between the bedrock and the backfill soil of walls as well as the concomitant saturation of this backfill soil are the determining factors of potential slope failure. The numerical models support these observations. In addition, the models are able to explain the mechanisms of formation of perched water tables, highlighting the factors that can influence groundwater levels and slope instabilities.

Catchment based hydrology under post farmland abandonment scenarios

“…Slow responses and long recession limbs usually indicate a large contribution of subsurface flows (Whipkey, 1965;Burch et al, 1987;Palleiro et al, 2014), favored by thick and well developed soils, both of which are found in the terraces and the natural forest catchments. Although relatively little is known about hydrological processes in terraced catchments, water flow within soils was shown to be important (Gallart et al, 1994;Nunes et al, 2016;Camera et al, 2014;Petri et al, 2017). Thus, despite the Munilla and San Salvador catchments having completely different vegetation covers (sparse shrubs and dense forest, respectively), their hydrological responses are somehow similar, perhaps due to similarities in their soil properties.…”

Modeling the stability of terraced slopes: an approach from Valtellina (Northern Italy)

“…However, all these studies have not developed a complete physically based approach that takes into account the hydrogeological and geotechnical processes that can affect terraced slopes. A first step in this direction is represented by the studies of Camera et al (2012Camera et al ( , 2014, who showed, working at the single terrace scale, how the main cause of failure in these environments is related to the building-up of saturated horizons in the backfill of the dry-stone wall. Due to the overpressure, the wall bulges at toe and then collapses, leading to the subsequent failure of the whole terrace.…”

Relationship between man-made environment and slope stability: the case of 2014 rainfall events in the terraced landscape of the Liguria region (northwestern Italy)

“…In Italy, terraces are widespread features (Agnoletti et al 2011;Cullotta and Barbera 2011;Camera et al 2014). Particularly, in Liguria region, anthropic terraces are widely spread throughout the territory, with and important presence on the valley flanks of the hills (Sereni 1997).…”

“…Its lack promotes water erosion processes, local collapses of vertical stone walls and an increase of soil loss and slope failure (Koulouri and Giourga 2007;Garcıa-Ruiz and Lana-Renault 2011;Dotterweich 2013;Tarolli et al 2014). Among these occurrences, shallow landslides are one of the most common phenomena that can arise on terraced territories (Crosta et al 2003;Canuti et al 2004;Camera et al 2014). Shallow landslides are small volume of earth featuring reduced thickness (less than 2 m).…”