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A coupled stability and eco-hydrological model to predict shallow landslides
Full text linkKnowledge of spatio-temporal dynamics of soil water content, groundwater and infiltration processes is of considerable
importance for the understanding and prediction of landslides. Rainfall and consequent water infiltration
affect slope stability in various ways, mainly acting on the pore pressure distribution whose increase causes a decrease
of the shearing resistance of the soil. For such reasons rainfall and transient changes in the hydrological
systems are considered the most common triggers of landslides.
So far, the difficulty to monitor groundwater levels or soil moisture contents in unstable terrain have made modeling
of landslide a complex issue. At the present, the availability of sophisticated hydrological and physically based
models, able to simulate the main hydrological processes, has allowed the development of coupled hydrologicalstability
models able to predict when and where a failure could occur.
In this study, a slope-failure module, with capability to predict shallow landslides, implemented into an ecohydrological
model, tRIBS-VEGGIE (Triangulated Irregular Network (TIN)-based Real-time Integrated Basin
Simulator with VEGetation Generator for Interactive Evolution), is presented. The model evaluates the stability
dynamics in term of factor of safety consequent to the soil moisture dynamics, strictly depending on the textural
soil characteristics and hillslope geometry.
Failure criterion used to derive factor of safety equation accounts for the stabilizing effect of matric suction arising
in unsaturated soils. The eco-hydrological framework allows also to take into account the effect of vegetation with
its cohesive effect as well as its weight load.
The Mameyes basin, located in the Luquillo Experimental Forest in Puerto Rico, has been selected for modeling
based on the availability of soil, vegetation, topographical, meteorological and historic landslide data. A static
analysis based on susceptibility mapping approach was also carried out on the same area at a larger spatial scale,
providing the hot spot of landsliding area. Application of the model yields a temporal and spatial distribution of
predicted rainfall-induced landslides.
Moreover, stability dynamics have been assessed for different meteorological forcing and soil types, to better evaluate
the influence of hydrological dynamics on slope stability
A physically-based and distributed approach to analyze rainfall-triggered landslides at a watershed scale
Full text linkPhysically-based and distributed approach to analyze rainfall-triggered landslides at watershed scale
No full textLandslides are a serious threat to life and property throughout the world. The causes of landslides are various since multiple dynamic processes are involved in driving slope failures. One of these causes is prolonged rainfall, which affects slope stability in different ways. Water infiltrating in a hillslope may cause a rise of the piezometric surface, which, in turn, involves an increase of the pore water pressure and a decrease of the soil shear resistance. For this reason, knowledge of spatio-temporal dynamics of soil water content, infiltration processes and groundwater dynamics, is of considerable importance in the understanding and prediction of landslides dynamics.In this paper a spatially distributed and physically based approach is presented, which embeds a slope failure method in a hydrological model. The hydrological model here used is the tRIBS model (Triangulated Irregular Network Real-Time Integrated Basin Simulator) that allows simulation of most of spatial-temporal hydrologic processes (infiltration, evapotranspiration, groundwater dynamics and soil moisture conditions) that can influence landsliding. Slope stability is assessed by implementing the infinite slope model in tRIBS. The model, based on geotechnical and geomorphological characteristics, classifies each computational cell as unconditionally stable or conditionally stable. Soil moisture conditions resulting from precipitation can trigger landslides at conditionally stable locations. When a landslide occurs, the model also computes the amount of detached soil and its possible path downslope.Model performance has been initially tested on a small catchment with very steep slopes, located in the northern part of Sicily (Italy), after a sensitivity analysis concerning some model parameters
A physically-based and distributed approach to analyze soil erosion and rainfall triggered landslides at a watershed scale
No full textEffects of Initialization on Response of a Fully-Distributed Hydrologic Model
No full textKnowledge of initial conditions is very important to correctly model the basin response at the storm event scale. Of particular interest is the influence of topography and soil type on the principal hydrologic variables and runoff generation mechanisms as a function of antecedent wetness conditions. This study addresses the influence of initial states on the short-term hydrologic response and characterizes the effects of topography and soils on the dissipation of the influence of the initialization conditions. Two case studies are considered: a synthetic two-dimensional planar hillslope with various assumed slope magnitudes and soil types; and a real basin (∼800 km2) with actual land-surface characteristics. These case studies have been chosen in order to investigate the hydrological behavior at two different scales. Various precipitation rates and durations are used to force both domains, each initialized assuming different positions of spatially variable water table. The results illustrate the existence of complex mechanisms that modulate the watershed response depending on the catchment initial state and rainfall forcing. Factors contributing to the unsaturated zone soil moisture movement are discussed in relation to different soils and topographic properties. The role of rainfall intensity in determining the degree of control exerted by initial conditions on the total runoff as well as its partition into various mechanisms is examined for both case studies. Differences in the sensitivity of certain terrain locations to the initialization and the rainfall rates are revealed. In particular, the real case study points out that the effects of initial conditions strongly depend on rainfall intensity and that the spatial hydrologic variations is influenced by the initial groundwater position
Accounting for soil parameter uncertainty in a physically based and distributed approach for rainfall-triggered landslides
Full text linkIn this study we propose a probabilistic approach for coupled distributed hydrological-hillslope stability models that accounts for soil
parameters uncertainty at basin scale. The geotechnical and soil retention curve parameters are treated as random variables across the
basin and theoretical probability distributions of the Factor of Safety (FS) are estimated. The derived distributions are used to obtain the
spatio-temporal dynamics of probability of failure, in terms of parameters uncertainty, conditioned to soil moisture dynamics. The
framework has been implemented in the tRIBS-VEGGIE (Triangulated Irregular Network (TIN)-based Real-time Integrated Basin
Simulator-VEGetation Generator for Interactive Evolution)-Landslide model and applied to a basin in the Luquillo Experimental
Forest (Puerto Rico) where shallow landslides are common. In particular, the methodology was used to evaluate how the spatial and
temporal patterns of precipitation, whose variability is significant over the basin, affect the distribution of probability of failure, through
event scale analyses. Results indicate that hyetographs where heavy precipitation is near the end of the event lead to the most critical
conditions in terms of probability of failur
MODELING THE TERRAIN EVOLUTION AT BASIN SCALE: THE GEOMORPHIC COMPONENT OF TRIBS HYDROLOGICAL MODEL
No full textA spatially distributed and physically based tool to modelling rainfall-triggered landslides
Full text linkLandslides are a serious threat to lives and property throughout the world. Over the last few years the need to
provide consistent tools and support to decision-makers and land managers have led to significant progress in
the analysis and understanding of the occurrence of landslides. The causes of landslides are varied. Multiple
dynamic processes are involved in driving slope failures. One of these causes is prolonged rainfall, which
affect slope stability in different ways. Water entering the ground beneath a slope always causes a rise of the
piezometric surface, which in turn involves an increase of the pore-water pressure and a decrease of the soil
shear resistance. For this reason, knowledge of spatio-temporal dynamics of soil water content, groundwater and
infiltration processes is of considerable importance in the understanding and prediction of landslides dynamics.
Many methods and techniques have been proposed to estimate when and where rainfall could trigger slope failure.
In this paper a spatially distributed and physically based approach is presented, which integrates of a failure model
with an hydrological one. The hydrological model used in the study is the tRIBS model (Triangulated Irregular
Network (TIN-based) Real-Time Integrated Basin Simulator) that allows simulation of spatial and temporal
hydrological dynamics influencing the landsliding, in particular infiltration, evapotranspiration, groundwater
dynamics and soil moisture conditions. In order to evaluate the slope stability, the infinite slope model has been
implemented in tRIBS, making up a new component of the model. For each computational element, the model
is able to verify the stability condition as a function of the safety factor, splitting between the unconditionally
stable and the conditionally stable computational cells. The amount of detached soil and its possible path are also
estimated. The variations in elevation due to the landslides modify the basin morphology. The computational TIN
is updated when a threshold related to the changes in elevation is exceeded.
Model performance has been evaluated carrying out a setup case in a small catchment with very steep slopes,
located in the northern part of Sicily (Italy). The test has been useful to highlight weaknesses and strengths of the
model as well as to enhance the formulation. Another validation test is being carried out using landslides data
recorded in the island of Puerto Rico, a US territory, where landslide triggered by rainfall are the most common
type with one or two events per year
Modeling the mechanical and hydrological controls of vegetation in shallow landslides
Full text linkThis study proposes a methodology for integrating vegetation's mechanical control into a physically-based, eco-hydrological slope stability model by estimating apparent root cohesion via the Root Area Ratio (RAR). A synthetic case study demonstrates the approach's effectiveness in evaluating combined hydrological and mechanical controls
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