545 research outputs found
Recent advancements of landslide hydrology
No full textOccurrence of rainfall-induced landslides is increasing worldwide, owing to land use and climate changes. Although the connection between hydrology and rainfall-induced landslides might seem obvious, hydrological processes have been only marginally considered in landslide research for decades. In 2016, an advanced review paper published in WIREs Water [Bogaard and Greco (2016), WIREs Water, 3(3), 439–459] pointed out several challenging issues for landslide hydrology research: considering large-scale hydrological processes in the assessment of slope water balance; including antecedent hydrological information in landslide hazard assessment; understanding and quantifying the feedbacks between deformation and infiltration/drainage processes; overcoming the conceptual mismatch of soil mechanics models and hydrological models. While little progress has been made on the latter two issues, a variety of studies have been published, focusing on the role of hydrological processes in landslide initiation and prediction. The importance of the identification of the origin of water to understand the processes leading to landslide activation is largely acknowledged. Techniques and methodologies for the definition of landslide catchments and for the assessment of landslide water balance are progressing fast, often considering the hydraulic effect of vegetation. The use of hydrological information in landslide prediction models has also progressed enormously. Empirical predictive tools, to be implemented in early warning systems for shallow landslides, benefit from the inclusion of antecedent soil moisture, extracted from different sources depending on the scale of the prediction, leading to significant improvement of their predictive skill. However, this kind of information is generally still missing in operational LEWS. This article is categorized under: Science of Water > Hydrological Processes.Water Resource
Invited perspectives: Hydrological perspectives on precipitation intensity-duration thresholds for landslide initiation: proposing hydro-meteorological thresholds
Get PDFMany shallow landslides and debris flows are precipitation initiated.
Therefore, regional landslide hazard assessment is often based on empirically
derived precipitation intensity-duration (ID) thresholds and landslide
inventories. Generally, two features of precipitation events are plotted and
labeled with (shallow) landslide occurrence or non-occurrence. Hereafter, a
separation line or zone is drawn, mostly in logarithmic space. The practical
background of ID is that often only meteorological information is available
when analyzing (non-)occurrence of shallow landslides and, at the same time,
it could be that precipitation information is a good proxy for both
meteorological trigger and hydrological cause. Although applied in many case
studies, this approach suffers from many false positives as well as limited
physical process understanding. Some first steps towards a more
hydrologically based approach have been proposed in the past, but these
efforts received limited follow-up.Therefore, the objective of our paper is to (a) critically analyze the
concept of precipitation ID thresholds for shallow landslides and debris
flows from a hydro-meteorological point of view and (b) propose a
trigger–cause conceptual framework for lumped regional hydro-meteorological
hazard assessment based on published examples and associated discussion. We
discuss the ID thresholds in relation to return periods of precipitation,
soil physics, and slope and catchment water balance. With this paper, we aim
to contribute to the development of a stronger conceptual model for regional
landslide hazard assessment based on physical process understanding and
empirical data
Effects of Anisotropy of Preferential flow on the Hydrology and Stability of Landslides
Get PDFInfiltration is one of the most important landslides triggering mechanisms and it is controlled by the hydraulic characteristics of the soil, which depend on degree of saturation, existence of preferential flow paths and anisotropy. In order to account for preferential flow that can have place in macro-pores and fissures, it is common to represent the soil matrix by means of the superimposition of two different domains: a soil matrix domain, which mainly accounts for the flow in the porous matrix, and preferential flow domain representing the flow through macro-pores and fissures. There have been recent investigations on the influences of preferential flow on slope stability; however, the combined effects of anisotropy and preferential flow on infiltration processes and on rainfall induced landslide mechanisms have not been studied yet, at our knowledge. Aiming at better understanding the effects that anisotropy combined with preferential flow has on the infiltration process, we investigated the stability of a hillslope using a numerical modelling approach. Results indicate that anisotropy affects the slope stability and its failure area
Is there Predictive Power in Hydrological Catchment Information for Regional Landslide Hazard Assessment?
Get PDFAbstractRegional landslide hazard assessment is often carried out by means of empirical meteorological thresholds, which reliability is sometimes limited by the lack of information about the hydrological processes which lead to landslide triggering in slopes. Hence, in this paper the inclusion of hydrological information at catchment scale in the definition of landslide triggering thresholds is applied to a catchment in the northern Apennines (Italy). In particular, an hydro-meteorological threshold based on event precipitation and catchment specific storage (H-S threshold) is proposed. The performance of the proposed threshold is compared with the one of the usually adopted precipitation Intensity-Duration (I-D) threshold. Although most of the landslide recorded in the observed period (2002-2013) were triggered by short and intense precipitation events with little influence of the slope conditions prior the precipitation, the H-Sthreshold performs slightly better than the I-D threshold
Potential use of satellite information on soil moisture to improve landslide forecasting: a numerical investigation
No full textWater Resource
Hydro-chemical anomalies in clay-rich landslides: evidences from case studies in the northern Apennines (Italy)
Get PDFThe presence of deep faults can affect the groundwater circulation. They can control the rising of deep fluids to
the ground surface. Normally, deep fluids have a chemical composition completely different from the shallow
groundwater; depending on the travel depth, temperature and pressure conditions, mineral composition of the
rocks crossed and time of interaction.
This can affect the hydro-chemical characteristics of near-surface groundwater. Eventually, it can change the
fingerprint of groundwater circulating in landslides and it can influence long-term pore-pressure fluctuations,
playing a role on slope stability.
In the northern Apennines of Italy, several large-scale earth slides – earth flows affecting faulted clayey formations
are believed to be somehow influenced by deep fluids. The study was aimed at detecting hydro-chemical anomalies
in groundwater circulating in 3 landslides that have resumed activity several times in the last decades, and that
are occurring in areas of potential deep-fluid influence (Silla, Ca’ Lita, Vedriano). More than 30 water-samples
were collected at different depth in the landslide body and in the underlying bedrock, owing to the presence
of several piezometers. Physical and chemical analyses comprised determination of temperature, conductibility,
pH, main cations and anions (K+, Na+, Cl, Ca2+, Mg2+, SO42 and HCO). Isotopic analyses (oxygen and
deuterium) are still ongoing. Results allowed discriminating between a Ca-Carbonate hydrotype (400-600 μS/cm),
that is interpreted as being directly connected with rainfall infiltration, and a Na-sulfate-rich hydrotype, that is
interpreted as the evidence of deep fluids upflow. This would actually be the result of the mixing between two
extreme hydrotypes: Na-bicarbonate water and Ca-sulfate waters, both characterized by high salinity, over 4000
μS/cm. The first is typical of geothermal water in the Apennines and is linked to the infiltration at great depth of
rain water and the subsequent long term interaction between water and rock masses that allows to degradation of
the Na-silicate. The second hydrotype, Ca-sulfate water, might be related to the presence of gypsum deposits in
the stratigraphic sequence of the Apennines chain
A rugged FBG-based pressure sensor for water level monitoring in dikes
Get PDFThis paper describes the implementation of an FBG sensor to measure water levels in a dike. The sensor is based on a 3D-printed mechanical transducer through which the external pressure is converted into longitudinal strain exerted on the fiber. An additional FBG integrated within the sensor measures temperature and is used to compensate for the temperature effects on the first FBG. By employing an aluminum alloy case, the sensor is suitable for operations in harsh environments and rough installation procedures. Four sensors of this kind have been successfully tested on a real scale dike at the Water Proof Holland facility in The Netherlands.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Hydraulic Structures and Flood RiskWater Resource
The influence of preferential flow on pressure propagation and landslide triggering of the Rocca Pitigliana landslide
No full textThe fast pore water pressure response to rain events is an important triggering factor for slope instability. The fast pressure response may be caused by preferential flow that bypasses the soil matrix. Currently, most of the hydro-mechanical models simulate pore water pressure using a single-permeability model, which cannot quantify the effects of preferential flow on pressure propagation and landslide triggering. Previous studies showed that a model based on the linear-diffusion equation can simulate the fast pressure propagation in near-saturated landslides such as the Rocca Pitigliana landslide. In such a model, the diffusion coefficient depends on the degree of saturation, which makes it difficult to use the model for predictions. In this study, the influence of preferential flow on pressure propagation and slope stability is investigated with a 1D dual-permeability model coupled with an infinite-slope stability approach. The dual-permeability model uses two modified Darcy-Richards equations to simultaneously simulate the matrix flow and preferential flow in hillslopes. The simulated pressure head is used in an infinite-slope stability analysis to identify the influence of preferential flow on the fast pressure response and landslide triggering. The dual-permeability model simulates the height and arrival of the pressure peak reasonably well. Performance of the dual-permeability model is as good as or better than the linear-diffusion model even though the dual-permeability model is calibrated for two single pulse rain events only, while the linear-diffusion model is calibrated for each rain event separately. In conclusion, the 1D dual-permeability model is a promising tool for landslides under similar conditions
Invited perspectives: Integrating hydrologic information into the next generation of landslide early warning systems
Get PDFAlthough rainfall-triggered landslides are initiated by subsurface hydro-mechanical processes related to the loading, weakening, and eventual failure of slope materials, most landslide early warning systems (LEWSs) have relied solely on rainfall event information. In previous decades, several studies demonstrated the value of integrating proxies for subsurface hydrologic information to improve rainfall-based forecasting of shallow landslides. More recently, broader access to commercial sensors and telemetry for real-time data transmission has invigorated new research into hydrometeorological thresholds for LEWSs. Given the increasing number of studies across the globe using hydrologic monitoring, mathematical modeling, or both in combination, it is now possible to make some insights into the advantages versus limitations of this approach. The extensive progress demonstrates the value of in situ hydrologic information for reducing both failed and false alarms through the ability to characterize infiltration during – as well as the drainage and drying processes between – major storm events. There are also some areas for caution surrounding the long-term sustainability of subsurface monitoring in landslide-prone terrain, as well as unresolved questions in hillslope hydrologic modeling, which relies heavily on the assumptions of diffuse flow and vertical infiltration but often ignores preferential flow and lateral drainage. Here, we share a collective perspective based on our previous collaborative work across Europe, North America, Africa, and Asia to discuss these challenges and provide some guidelines for integrating knowledge of hydrology and climate into the next generation of LEWSs. We propose that the greatest opportunity for improvement is through a measure-and-model approach to develop an understanding of landslide hydro-climatology that accounts for local controls on subsurface storage dynamics. Additionally, new efforts focused on the subsurface hydrology are complementary to existing rainfall-based methods, so leveraging these with near-term precipitation forecasts is a priority for increasing lead times.</p
- …
