Observations on soil-atmosphere interactions after long-term monitoring at two sample sites subjected to shallow landslides

Abstract

Soil-atmosphere interaction has implications in different scientific research contexts and is increasingly investigated through field measurements. This paper reports a detailed description of interaction between shallow soil and atmosphere at two test sites in Oltrepò Pavese area (Northern Italy). The two test sites are in the same climatic area but are characterised by different geological features. In fact, the first objective is to compare the behaviour of two different soils, namely a clayey-sandy silt (CL) and a silty clay (CH), under similar meteorological events. Soil-atmosphere interaction is studied on the basis of long-term (about 87 and 42 months for the two test sites, respectively) monitoring data of both volumetric water content and soil water potential, recorded at different depths along two vertical soil profiles in the first two metres from ground level. Field measurements, together with meteorological data such as precipitation and air temperature, allow for clear identification of the seasonal fluctuations of unsaturated soil hydraulic properties. To infer detailed information, the recorded data were processed and relationships between soil water potential and water content were investigated. Different time spans, from several months to a few days, even including single rainy events, are considered to show the hydraulic soil behaviour. The hysteretic cycles of water content with respect to soil water potential and non-equilibrium flow are highlighted. In particular, the measured soil water potential is in the range of 0–800 kPa and of 0–1500 kPa for the CL and CH soil, respectively. At both sites, the observed hysteretic cycles are more frequent in the hot season (summer) than in the cold season (winter) and tend to reduce with depth. The experimental results are compared with the soil water characteristic curves (SWCCs) to assess whether and to what extent the SWCCs are reliable in modelling the hydraulic behaviour of partially saturated soils, under atmospheric forcing, at least in the considered climatic contexts.

IoT-based hydrological monitoring of water-induced landslides: a case study in central Norway

“…In the cold season, from mid-October to almost April, the ground temperature increased with depth. Similar trends in ground temperature with depth were reported in the study of Bordoni et al (2021). For the 1-year monitoring data starting from August 2020, the total 12b, it can be seen that there was less rainfall from mid-November 2020 to mid-February 2021 in the winter period.…”

“…At the instant of water-induced landslide initiation, initiated slope might be either saturated with positive pore pressure due to perched water table or unsaturated with the presence of suction. Several studies performed hydrological monitoring in hillsides in order to clarify the underlying initiation mechanism of water-induced landslides (Bordoni et al 2021(Bordoni et al , 2015Crawford et al 2019;Godt et al 2009;Kim et al 2021;Smith et al 2014;Wei et al 2020). Hydrological monitoring can provide important insights into the hydrological processes occurring in similar slopes (Comegna et al 2016) such as water infiltration and corresponding changes in VWC and suction (Li et al 2005).…”

Analysis of the Role of Precipitation and Land Use on the Size of the Source Area of Shallow Landslides

“…A comprehensive multitemporal inventory of past landslide phenomena, which includes location, size, landslide classification and date of occurrence, is available for this area. The outer perimeters of the shallow landslides were outlined manually through the analysis of field surveys and of aerial and satellite images [40,41]. The landslides thatdeveloped on 27-28 April 2009, which make up all landslides in the SVC, were mapped manually through the use of high-resolution colour aerial photographs taken immediately after this event, with an image resolution of 15 cm (photo scale of 1:12,000), and were validated by repeated field surveys [42].…”

“…The SVC test site is characterised by poorly cemented sandstones and conglomerates overlying marls and evaporitic deposits. In the SVC, soils are mainly low plastic clayey or clayey-sandy silts, characterised by unit weight in the order of 16-19 kN/m 3 and saturated hydraulic conductivity in the order of 10 −5 -10 −7 m/s [40] (Table 2). In this area, soil thickness typically ranges between a few centimetres and about 2.5 m from ground level.…”

Impact of climate change on shallow ground hydro-thermal properties

“…Soil scientists have studied this issue from an agricultural point of view over many years, because plant growth is a direct function of the ground moisture. Ground-atmosphere interaction and associated hydro-mechanical-thermal processes have been thoroughly researched in soil mechanics domain as well (Wilson et al 1994;Swanson et al 2003;Kodikara et al 2020;Bordoni et al 2021;Cui 2022). Infiltration is well-understood in geomechanics literature compared to evaporation.…”