Incorporating the Effects of Complex Soil Layering and Thickness Local Variability into Distributed Landslide Susceptibility Assessments

Abstract

Incorporating the influence of soil layering and local variability into the parameterizations of physics-based numerical models for distributed landslide susceptibility assessments remains a challenge. Typical applications employ substantial simplifications including homogeneous soil units and soil-hydraulic properties assigned based only on average textural classifications; the potential impact of these assumptions is usually disregarded. We present a multi-scale approach for parameterizing the distributed Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability (TRIGRS) model that accounts for site-specific spatial variations in both soil thickness and complex layering properties by defining homogeneous soil properties that vary spatially for each model grid cell. These effective properties allow TRIGRS to accurately simulate the timing and distribution of slope failures without any modification of the model structure. We implemented this approach for the carbonate ridge of Sarno Mountains (southern Italy) whose slopes are mantled by complex layered soils of pyroclastic origin. The urbanized foot slopes enveloping these mountains are among the most landslide-prone areas of Italy and have been subjected to repeated occurrences of damaging and deadly rainfall-induced flow-type shallow landslides. At this scope, a primary local-scale application of TRIGRS was calibrated on physics-based rainfall thresholds, previously determined by a coupled VS2D (version 1.3) hydrological modeling and slope stability analysis. Subsequently, by taking into account the spatial distribution of soil thickness and vertical heterogeneity of soil hydrological and mechanical properties, a distributed assessment of landslide hazard was carried out by means of TRIGRS. The combination of these approaches led to the spatial assessment of landslide hazard under different hypothetical rainfall intensities and antecedent hydrological conditions. This approach to parameterizing TRIGRS can be adapted to other spatially variable soil layering and thickness to improve hazard assessments.

Towards a National-Scale Dataset of Geotechnical and Hydrological Soil Parameters for Shallow Landslide Modeling

“…The main one is the limited availability, for large areas, of detailed information on geotechnical and hydraulic properties of soils (e.g., cohesion, internal friction angle, soil unit weight, hydraulic conductivity, and so on) [11][12][13]. It is widely known that these parameters, although quasi-static (i.e., with values that can be reasonably considered constant in time), have a large spatial variability and even two spots close to each other may exhibit very different values [14][15][16]. As a consequence, if distributed slope stability models have to be applied over large areas, a large number of measures would be needed to have a sufficient characterization of the physical properties of the involved materials [17][18][19].…”

Hydraulic Efficiency of Green-Blue Flood Control Scenarios for Vegetated Rivers: 1D and 2D Unsteady Simulations

“…The geo-hydrological and ecohydraulic challenges linked to current and future climate processes [1][2][3][4][5][6] highlight the growing need to protect water resources quantitatively and qualitatively in an ever more decisive way, especially in sensitive areas within both natural and urban territories [7,8]. In this context, the hydraulic conveyance of vegetated open channels intersecting anthropogenic settlements is dramatically affected by the temporal evolution of riverine vegetation properties [9][10][11], mainly associated with riverine plants' growth, foliage, and density overall [12,13].…”

Improved Method of Defining Rainfall Intensity and Duration Thresholds for Shallow Landslides Based on TRIGRS

“…TRIGRS must input the soil thickness, which significantly influences the stability simulation results [44] and the hydrological response of slope [62,63]. Using a fixed soil thickness may give unreasonable results in some areas.…”