Conceptualising the effect of preferential flow on slow-moving landslides: from experiments to concepts and models.

2021 ◽  
Author(s):  
Thom Bogaard
Keyword(s):  
Preferential Flow ◽  
Water Levels ◽  
Spatial And Temporal Variation ◽  
Flow Paths ◽  
Groundwater Levels ◽  
Multiple Origins ◽  
Preferential Flow Paths ◽  
Landslide Body ◽  
Slow Moving ◽  
The Impact

<p>Precipitation is one of the main causes for the initiation or reactivation of deep seated slow moving landslides. Preferential flow paths can have multiple origins, they can be due to changes in soil water content such as desiccation, due to mechanical movement or due to biological activity. The overarching characteristic is that they strongly alter the hydraulic properties of the landslide material. This results in a complex hydrological behaviour of deep-seated slow moving landslides. Research has shown that for instance the porosity of the soil, the fissure distribution and fissure connectivity are very important to predict the behaviour of the hydrological response of precipitation within a landslide body. However, due to large heterogeneity of landslide lithology and spatial and temporal variation of a landslide, it is hard to model water levels in landslides. Cracks and fissures inside the landslide are the cause of preferential flow paths, which can work as infiltration networks to the groundwater, but also as drainage networks lowering the (perched) groundwater levels.</p><p>In the last decades, both methodological progress has been made and several case studies have been published. However, most are still somewhat anecdotic examples and a more overarching conceptualisation has not been made yet. In this overview I want to highlight the progress as well as obstacles and challenges ahead of us when assessing and quantifying the impact of preferential flow paths on the mechanisms of a slow moving deep-seated landslide and to improve our understanding and modelling of complex landslides.</p>

scholarly journals A model of hydrological and mechanical feedbacks of preferential fissure flow in a slow-moving landslide

2013 ◽  
Vol 17 (3) ◽  
pp. 947-959 ◽  
Author(s):  
D. M. Krzeminska ◽  
T. A. Bogaard ◽  
J.-P. Malet ◽  
L. P. H. van Beek
Keyword(s):  
Slope Stability ◽  
Preferential Flow ◽  
Water Pressure ◽  
Flow Paths ◽  
Landslide Activity ◽  
Hydrological Responses ◽  
Preferential Flow Paths ◽  
Slow Moving ◽  
Groundwater Drainage ◽  
Opening And Closing

Abstract. The importance of hydrological processes for landslide activity is generally accepted. However, the relationship between precipitation, hydrological responses and movement is not straightforward. Groundwater recharge is mostly controlled by the hydrological material properties and the structure (e.g., layering, preferential flow paths such as fissures) of the unsaturated zone. In slow-moving landslides, differential displacements caused by the bedrock structure complicate the hydrological regime due to continuous opening and closing of the fissures, creating temporary preferential flow paths systems for infiltration and groundwater drainage. The consecutive opening and closing of fissure aperture control the formation of a critical pore water pressure by creating dynamic preferential flow paths for infiltration and groundwater drainage. This interaction may explain the seasonal nature of the slow-moving landslide activity, including the often observed shifts and delays in hydrological responses when compared to timing, intensity and duration of precipitation. The main objective of this study is to model the influence of fissures on the hydrological dynamics of slow-moving landslide and the dynamic feedbacks between fissures, hydrology and slope stability. For this we adapt the spatially distributed hydrological and slope stability model (STARWARS) to account for geotechnical and hydrological feedbacks, linking between hydrological response of the landside and the dynamics of the fissure network and applied the model to the hydrologically controlled Super-Sauze landslide (South French Alps).

scholarly journals A 2D model for simulating heterogeneous mass and energy fluxes through melting snowpacks

2016 ◽  
Author(s):  
Nicolas R. Leroux ◽  
John W. Pomeroy
Keyword(s):  
Water Flow ◽  
Liquid Water ◽  
Preferential Flow ◽  
Initial Conditions ◽  
Surface Fluxes ◽  
Porous Media Flow ◽  
Accurate Estimation ◽  
Flow Paths ◽  
Preferential Flow Paths ◽  
The Impact

Abstract. Accurate estimation of the water flux through melting snowpacks is of primary importance for runoff prediction. Lateral flows and preferential flow pathways in porous media flow have proven critical for improving soil and groundwater flow models, but though many physically-based layered snowmelt models have been developed, only 1D matrix flow over level ground is currently accounted for in snow models. Snowmelt models that include these processes may improve snowmelt discharge timing and contributing area calculations in hydrological models. A two-dimensional snow model (SMPP – Snowmelt Model with Preferential flow Paths) is presented that simulates heat and water flows through both snowpack matrix and preferential flow paths, as well as snowmelt and refreezing of meltwater. The model assumes thermodynamic equilibrium between solid and liquid phases and uses the latest improvements made in snow science to estimate snow hydraulic and thermal properties. A finite volume method is applied to solve for the 2D heat and water equations. The use of a water entry pressure for dry snow combined with consideration of the impact of heterogeneities in surface fluxes and internal snow properties – density, grain size and layer thickness – allowed calculation of the formation of preferential flow paths in the snowpack. The simulation of water flow through preferential flow paths resulted in liquid water reaching the base of the snowpack earlier than for a homogeneous wetting front. Moreover, the preferential flow paths in the model increased the exchange of energy between the snow surface and the internal snowpack, resulting in faster warming of the snowpack. A sensitivity analysis, conducted on the snow internal properties showed that initial conditions such as density and temperature, should be carefully measured in the field to accurately estimate liquid water percolating through the snowpack. Furthermore, two empirical coefficients used in the water flow equation were showed to greatly impact model outputs. This heterogeneous flow model is an important tool to help understand snowmelt flow processes in complex and level terrains and to demonstrate how uncertainty in snowmelt-derived runoff calculations might be reduced.

scholarly journals A conceptual model of the hydrological influence of fissures on landslide activity

2011 ◽  
Vol 8 (6) ◽  
pp. 11039-11073 ◽  
Author(s):  
D. M. Krzeminska ◽  
T. A. Bogaard ◽  
Th. W. J. van Asch ◽  
L. P. H. van Beek
Keyword(s):  
Slope Stability ◽  
Preferential Flow ◽  
Hydrological Regime ◽  
Temporal Variations ◽  
Hydrological Processes ◽  
Flow Paths ◽  
Meteorological Forcing ◽  
Landslide Activity ◽  
Preferential Flow Paths ◽  
Slow Moving

Abstract. Hydrological processes control the behaviour of many unstable slopes and their importance for landslide activity is generally accepted. In slow-moving landslides differential displacement complicates the hydrological regime due to continuous opening and closing of the fissures and cracks, creating dynamic preferential flow path systems. The consequences of the appearance and destruction of these preferential flow paths is thus closely related to the formation of critical pore pressure and the resulting movement and persistence of fissure systems. This interaction may account for the seasonal nature of the slow-moving landslide activity, including the often observed shifts and delays. This research aims to investigate this interaction between slope stability and spatial and temporal variations in fissure patterns, which makes fissures act both as preferential flow paths for infiltration and as lateral groundwater drains. To this end, the hydrological processes that control exchange of water between the fissure network and the matrix has been included in a spatially distributed hydrological and slope stability model. The ensuing feedbacks in landslide activity were explored by running the model with the meteorological forcing of one year until a dynamic steady-state was achieved. The effect of fissure dynamics was evaluated by comparing simulations with static fissure patterns to those in which these patterns deform as function of the local stability.

scholarly journals A model of hydrological and mechanical feedbacks of preferential fissure flow in a slow-moving landslide

2012 ◽  
Vol 9 (10) ◽  
pp. 11161-11197 ◽  
Author(s):  
D. M. Krzeminska ◽  
T. A. Bogaard ◽  
J.-P. Malet ◽  
L. P. H van Beek
Keyword(s):  
Slope Stability ◽  
Preferential Flow ◽  
Water Pressure ◽  
Flow Paths ◽  
Landslide Activity ◽  
Hydrological Responses ◽  
Preferential Flow Paths ◽  
Slow Moving ◽  
Groundwater Drainage ◽  
Opening And Closing

Abstract. The importance of hydrological processes for landslide activity is generally accepted. However, the relationship between precipitation, hydrological responses and movement is not straightforward. Groundwater recharge is mostly controlled by the hydrological material properties and the structure (e.g. layering, preferential flow paths such as fissures) of the unsaturated zone. In slow-moving landslides, differential displacements caused by the bedrock structure complicate the hydrological regime due to continuous opening and closing of the fissures, creating temporary preferential flow paths systems for infiltration and groundwater drainage. The consecutive opening and closing of fissure aperture control the formation of a critical pore water pressure by creating dynamic preferential flow paths for infiltration and groundwater drainage. This interaction may explain the seasonal nature of the slow-moving landslide activity, including the often observed shifts and delays in hydrological responses when compared to timing, intensity and duration of precipitation. The main objective of this study is to model the influence of fissures on the hydrological dynamics of slow-moving landslide and the dynamic feedbacks between fissures, hydrology and slope stability. For this we adapt the spatially distributed hydrological and slope stability model (STARWARS) to account for geotechnical and hydrological feedbacks, linking between hydrological response of the landside and the dynamics of the fissure network and applied the model to the hydrologically controlled Super-Sauze landslide (South French Alps).

scholarly journals The Role of Management of Stream–Riparian Zones on Subsurface–Surface Flow Components

Water ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1905 ◽  
Author(s):  
Steiness ◽  
Jessen ◽  
Spitilli ◽  
van’t Veen ◽  
Højberg ◽  
...  
Keyword(s):  
Preferential Flow ◽  
Groundwater Discharge ◽  
Surface Flow ◽  
Flow Paths ◽  
Flow Measurements ◽  
Preferential Flow Paths ◽  
Flow Components ◽  
Anthropogenic Alterations ◽  
The Impact ◽  
Geoelectrical Methods

A managed riparian lowland in a glacial landscape (Holtum catchment, Denmark) was studied to quantify the relative importance of subsurface and surface flow to the recipient stream. The hydrogeological characterization combined geoelectrical methods, lithological logs, and piezometric heads with monthly flow measurements of springs, a ditch, and a drain, to determine seasonality and thereby infer flow paths. In addition, groundwater discharge through the streambed was estimated using temperature and water-stable isotopes as tracers. The lowland received large groundwater inputs with minimal seasonal variations from adjacent upland aquifers. This resulted in significant amounts of groundwater-fed surface flow to the stream, via man-made preferential flow paths comprising ditches, drainage systems, and a pond, and via two natural springs. Roughly, two thirds of the stream gain was due to surface flow to the stream, mainly via anthropogenic alterations. In contrast, direct groundwater discharge through the streambed accounted for only 4% of the stream flow gain, although bank seepage (not measured) to the straightened and deepened stream potentially accounted for an additional 17%. Comparison to analogous natural flow systems in the catchment substantiate the impact of anthropogenic alterations of riparian lowlands for the subsurface and surface flow components to their streams.

scholarly journals The impact of soil development, rainfall intensity and vegetation complexity on subsurface flow paths along a glacial chronosequence of 10 millennia

2021 ◽  
Author(s):  
Anne Hartmann ◽  
Markus Weiler ◽  
Konrad Greinwald ◽  
Theresa Blume
Keyword(s):  
Bulk Density ◽  
Vegetation Cover ◽  
Preferential Flow ◽  
Landscape Evolution ◽  
Subsurface Flow ◽  
Flow Paths ◽  
Hydrologic Processes ◽  
Preferential Flow Paths ◽  
Irrigation Intensity ◽  
The Impact

Abstract. Hydrologic processes play an important role in the hydro-pedo-geomorphological feedback cycle of landscape evolution. Soil properties and subsurface flow paths change over time, but due to lack of observations important hydrologic processes such as water flow paths are often not properly considered in soil and landscape evolution studies. We investigated the evolution of subsurface flow paths during landscape development in the calcareous glacier forefield at the Griessfirn in the Swiss Alps. While the main focus was on flow path evolution and the formation of preferential flow paths with soil development, we also looked at the impact of irrigation intensity and vegetation complexity (in what way does the vegetation complexity defined by degree of vegetation cover and functional diversity at each age class relate to subsurface structures and flow path initialization?). We chose four glacial moraines of different ages (110, 160, 4 900, and 13 500 years) and conducted dye tracer experiments with Brilliant Blue (4 g l−1) on three plots at each moraine. The three plots at each age class differed by their degree of vegetation complexity (low, medium, and high) and each was further divided into three equal subplots where dyed water was applied with three different irrigation intensities (20, 40, and 60 mm h−1) and an irrigation amount of 40 mm. Dye pattern characteristics in form of volume density and surface area density were derived by digital image analysis and compared via statistical analysis.Volume density was used to classify the observed dye patterns into specific flow type categories. The effect of soil formation and thus changing soil characteristics on flow types were investigated by the analysis of structural and textural parameters in form of grain size distribution, porosity, bulk density, and loss on ignition. A change in flow types with increasing moraine age was observed from a rather homogeneous matrix flow to heterogeneous matrix and finger flow. Along the soil chronosequence, a reduction in particle sizes and an ongoing vegetation development resulted in an accumulation of organic matter in the topsoil and an increase in water storage capacity (decrease in bulk density and increase in porosity). Differences in irrigation intensity only had an effect on flow types at the oldest moraine, where the frequency of finger flow decreased with increasing irrigation intensity. A relation between vegetation complexity and flow types was only observed at the older moraines, which had a dense vegetation cover. With increasing vegetation complexity the proportion of preferential flow paths in form of finger flow also increased.

Visualizing Preferential Flow Paths using Ammonium Carbonate and a pH Indicator

2002 ◽  
Vol 66 (2) ◽  
pp. 347 ◽  
Author(s):  
Zhi Wang ◽  
Jianhang Lu ◽  
Laosheng Wu ◽  
Thomas Harter ◽  
William A. Jury
Keyword(s):  
Preferential Flow ◽  
Ammonium Carbonate ◽  
Ph Indicator ◽  
Flow Paths ◽  
Preferential Flow Paths

Equation for Describing Solute Transport in Field Soils with Preferential Flow Paths

2005 ◽  
Vol 69 (2) ◽  
pp. 291-300 ◽  
Author(s):  
Young-Jin Kim ◽  
Christophe J. G. Darnault ◽  
Nathan O. Bailey ◽  
J.-Yves Parlange ◽  
Tammo S. Steenhuis
Keyword(s):  
Solute Transport ◽  
Preferential Flow ◽  
Flow Paths ◽  
Preferential Flow Paths ◽  
Field Soils

Dynamic Modeling of Channel Formation During Fluid Injection Into Unconsolidated Formations

SPE Journal ◽  
2015 ◽  
Vol 20 (04) ◽  
pp. 689-700 ◽  
Author(s):  
S.. Ameen ◽  
A. Dahi Taleghani
Keyword(s):  
Preferential Flow ◽  
Volume Fraction ◽  
Injection Pressure ◽  
Internal Erosion ◽  
Fluid Injection ◽  
Critical Threshold ◽  
Model Parameters ◽  
Flow Paths ◽  
Preferential Flow Paths ◽  
Stress Changes

Summary Injectivity loss is a common problem in unconsolidated-sand formations. Injection of water into a poorly cemented granular medium may lead to internal erosion, and consequently formation of preferential flow paths within the medium because of channelization. Channelization in the porous medium might occur when fluid-induced stresses become locally larger than a critical threshold and small grains are dislodged and carried away; hence, porosity and permeability of the medium will evolve along the induced flow paths. Vice versa, flowback during shut-in might carry particles back to the well and cause sand accumulation inside the well, and subsequently loss of injectivity. In most cases, to maintain the injection rate, operators will increase injection pressure and pumping power. The increased injection pressure results in stress changes and possibly further changes in channel patterns around the wellbore. Experimental laboratory studies have confirmed the presence of the transition from uniform Darcy flow to a fingered-pattern flow. To predict these phenomena, a model is needed to fill this gap by predicting the formation of preferential flow paths and their evolution. A model based on the multiphase-volume-fraction concept is used to decompose porosity into mobile and immobile porosities where phases may change spatially, evolve over time, and lead to development of erosional channels depending on injection rates, viscosity, and rock properties. This model will account for both particle release and suspension deposition. By use of this model, a methodology is proposed to derive model parameters from routine injection tests by inverse analysis. The proposed model presents the characteristic behavior of unconsolidated formation during fluid injection and the possible effect of injection parameters on downhole-permeability evolution.

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