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Stream flowing (A) through the debris fan and (8) in the channel about 200 m upstream in Lightning Canyon near East Layton, Utah, on 13 June 1984. This stream typically flowed only after a rainstorm event and rapidly dried up until the 14 May 1984 debris-flow event.
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Numerous debris-flow events occurred along the Wasatch Front near Salt Lake City, Utah, during the springs of 1983 and 1984.
These flows were distinctly different from the previous damaging flows of 1923 and 1930 which were related to cloudburst thunderstorms.
The 1983 and 1984 flows were related to the rapid melting of an above average snow pack....
Citations
... Similarly, it is noticed with the rapid snow melt which get saturates more to the hillside soil and recharged the shallow fractured basement. It raises pore fluid pressure beneath regolith, thus triggering the landslide (Mathewson et al. 1990). ...
Slope movement, the surface expressions as seated scars are the variety of surface deformation mechanisms on the earth’s outer crust. These slow-deformation mechanisms can be visualized easily, if in-situ geotechnical observations, GNSS synopticity (regional), and space-borne (Microwave) spatio-temporal data structured and interpreted accordingly. Globally, several techniques are adapted for the slope failure analysis and their zonation. Thus, the most directed with geospatial technologies. Wide area assessment, mapping, and monitoring are some complex tasks only possible and could be addressed with the space borne datasets. Their outcomes help users to implement area strategies viz. in susceptibility and vulnerability. Landslide Susceptibility mapping (LSM) quantify the problem very effectively. In LSM, soft computing analytical skills among various participatory and triggering factors for the application of complex models are required for ground simulation. In this article critical review of LSM over Uttarakhand Himalaya was primarily focussed which analyze various sections including- participatory/triggering factors, datasets, different models, and validation practices. The study exhibits multiple avenues and future pathways for various research windows, such as LSM-SAR refinement, orographic climatic and changing factor relationship, high-quality data coupling with drone/Unmanned Aerial Vehicle (UAV) data, etc. Such analysis implicates the cost-effectiveness of strategies in effective planning and management.
... Slope instability due to snowmelt is therefore not a rare phenomenon in the world [14][15][16][17][18][19]. Rainfall or snowmelt events usually increase the pore water pressure in the slope [20][21][22][23], and the effective normal stress is subsequently reduced [24,25]. Compared to the usual short duration of rain infiltration, a more continuous supply of water can be provided by the snow-melting process over a longer period [26]. ...
The Ludoialm landslide, which is located in the municipality of Münster in Tyrol, Austria, represents a large-scale translational landslide in glacial soil sediments characterised by an exceptionally low inclined basal shear zone of only 12°. Although a temporal coincidence between meteorological events and slope displacement is obvious, the hydromechanical coupled processes responsible for the initial landslide formation and the ongoing movement characteristics have not yet been identified. This article provides a comprehensive analysis of the predisposition factors and the initial failure mechanism of this landslide from geological and geotechnical perspectives. We use a prefailure geometry of the cross section to simulate the initial slope failure process by a limit equilibrium analysis (LEA), a strength-reduction finite element method (SRFEM), and a finite element limit analysis (FELA). The shape and location of the computationally obtained basal sliding zone compare well with the geologically assumed one. Based on the computational study, it turns out that a high groundwater table probably caused by snow melting in combination with different permeabilities for the different layers is needed for the formation of the exceptionally low inclined basal shear zone. This paper presents the failure mechanism of the Ludoialm landslide and discusses the role of the shear band propagation in the process of slope destabilization.
... topography, geology and human activities, Arca et al., 2018) and trigger processes (e.g. rainfall, glacial melting, stream and coastal erosion, earthquakes and volcanic eruptions, Lichkov, 1938;Crandell et al., 1984;Keefer, 1984;Mathewson et al., 1990;McInnes, 1996;Suarez, 1996). Moreover, several researchers have argued that urbanization impacts landslide risk by influencing the severity and frequency of landslides, as well as the extent and value of building exposure and the degree of vulnerability to damage (Smyth & Royle, 2000;Douglass et al., 2005;Fedeski & Gwilliam, 2007;Mandasari et al., 2016;Zope et al., 2016). ...
Anthropogenic modifications of the landscape (e.g. urbanization, deforestation and agricultural activities) act as geomorphic processes, producing fast changes and instabilities, which often lead to landslides along hillslopes and floodings in low-lands. Anthropogenic modifications have increased with the progress of civilization; therefore, coupling historical information and geomorphological data can provide key information to determine the anthropogenic impacts on landscape evolution. The case of Castel Frentano, a village in the Abruzzo Region (Central Italy), has been analysed to shed light on the causes of its destruction in 1881: during the summer of that year, the village was heavily damaged by a peculiar succession of paroxysmal events, i.e. a mas-sive landslide followed by a strong earthquake. This earthquake induced additional damages to the buildings, due to seismic shak-ing and slide reactivation. This study involved geomorphological and geological surveys, which were aimed at mapping and defin-ing the main presently active geomorphic processes in the area of interest; moreover, we researched 19th-century historical docu-ments to reconstruct the genesis and evolution of the events that led to landsliding in 1881. Although the study area has always been prone to instability phenomena (due to its local geological and geomorphological characteristics), our results revealed that sliding was most likely triggered by human activities that had strongly modified the hillslope. Historical sources revealed a general hillslope instability that progressively evolved in the 1881 landslide because of deforestation. That deforestation had been carried out for agricultural exploitation on a previously stable territory. In this view, the case of Castel Frentano exemplifies the relationship between human activities, landscape modifications and their consequences in Italy in terms of risks to both natural and anthropo-genic environments. This is particularly important to assess at present: in a historical period characterized by economic growth, strong demographic expansion and the consequent fast colonization of natural spaces
... Rainfall is considered as one of the major causes of landslides. The penetration of stormwater through the soil layers increases the weights per unit volume of soil particles; thus slope stability rapidly decreases with the shear stress reduction of the soil [5][6][7][8][9][10][11][12][13][14][15]. Other direct and indirect causes of landslides include topography, geological features, and vegetation [16][17][18][19]. ...
Landslides, which often occur on natural slopes of mountainous areas and artificial slopes around urban areas during summer in South Korea, are mostly caused by localized heavy rainfalls and typhoons. A survey was conducted, and the characteristics of landslide occurrences in different geological conditions—in this case, granite soils in Sangju area and gneiss soils in Yangu area—were analyzed. Soil characteristics in the landslide and non-landslide areas and the surroundings of each geological condition were also evaluated. Triggering factors, namely permeability coefficients (k), shear strength with cohesion (c), and internal friction angle (φ) of soils that are closely linked to landslides around weathered soil layers were extracted based on the examined characteristics and a statistics method. The study used regression analysis to formulate equations to estimate the permeability coefficients and shear strength. Ultimately, the permeability coefficients showed significant results in terms of void ratio (e), the effective size of grains (D10), and uniformity coefficient (cu), while shear strength correlated with the proportion of fine-grained soil (Fines), uniformity coefficient (cu), degree of saturation (S), dry weight density (rd), and void ratio (e).
... [3] Shallow groundwater flow in fractured bedrock can lead to upward seepage and increased pore water pressure in the soil layer around the bedrock springs, while shallow confined aquifers in permeable bedrock can induce excess pore pressures. Both processes may result in localized slope failure [Everett, 1979; Mathewson et al., 1990; Montgomery et al., 2002]. Thus, bedrock infiltration and exfiltration processes influence the triggering of landslides and determine landslide intensity, volume, and runout distance [Onda et al., 2004; Matsushi and Matsukura, 2007; Katsura et al., 2008]. ...
[1] Shallow landslides pose substantial risks to people and infrastructure in mountain areas. Their occurrence is influenced by groundwater dynamics and bedrock characteristics. The bedrock may drain or contribute to groundwater in the overlying soil mass, depending on the hydraulic conductivity, degree of fracturing, saturation, and hydraulic head. Here, we present a detailed case study for a slope from Central Switzerland, where soil-bedrock interactions were responsible for triggering shallow landslides in the past. The bedrock in the study area represents a succession of heavily fissured conglomerate-sandstone beds and weathered marlstone layers, which are overlain by a clayey soil layer. There is evidence of a temporally confined aquifer in bedrock fractures from a severe storm event in August 2005. We derived a detailed geological model of the slope from electrical resistivity tomography surveys, borehole data, and bedrock outcrops. Then, the groundwater response to 32 rainfall events was monitored in the soil layer and in different bedrock layers from November 2010 to November 2011. We observed a fast and substantial rise of the hydraulic head in the bedrock, which was in contrast to the low permeability of the soil layer. The data suggest that rapid groundwater flow through bedrock fractures caused the immediate increase of the hydraulic head. Our observations document how water pressure builds up in fractured bedrock below a low permeability soil cover during heavy rainfall, which may trigger shallow landslides.
... Investigaciones realizadas en otras cadenas montañosas del planeta han demostrado que en años con precipitaciones níveas excepcionalmente altas, la probabilidad de que ocurran movimientos en masa generados por fusión nival aumenta de manera considerable (KAWAGOE et al. 2009). La fusión nival puede elevar el nivel freático en materiales fuertemente fracturados y aumentar la presión de agua en los poros provocan- do su desestabilización y posterior colapso (MATHEWSON et al. 1990). ...
Se estudia un movimiento en masa complejo ocurrido en la cuenca superior del Río Elqui, con el fi n
de evidenciar los factores desencadenantes e interpretar su relación con la dinámica geomorfológica,
criogénica y climática actual. Mediante el análisis de imágenes satelitales, fotografías áreas y trabajo
de campo se determinan algunos parámetros morfológicos del evento y se estima de manera aproximada
la fecha de origen del fenómeno. El deslizamiento rotacional y el fl ujo detrítico asociado ocurrieron
entre los años 1987-1988, afectaron un área de 0.22 km² y movilizaron un volumen aproximado de
materiales de 2.4-3.2x106 m³. La sobreelevación de los depósitos (run up) de entre 15 y 50 metros
permite estimar que el fl ujo detrítico habría alcanzado velocidades máximas de 31 m/s en el contacto
con los glaciares rocosos de la zona. Se advierte el importante rol que puede jugar el deshielo en
años excepcionalmente nivosos en la génesis o evolución de los movimientos en masa y la utilidad
de la información meteorológica, de los catálogos sísmicos y de las imágenes satelitales históricas en
el análisis geomorfológico retrospectivo. Se destaca fi nalmente el rol de los glaciares rocosos como
agentes reguladores del transporte de detritos en las áreas de alta montaña y la importancia que pueden
tener fenómenos de gran magnitud y poca frecuencia, como el movimiento en masa analizado, en el
suministro detrítico de estas formas.
... All three of the m values greater than 0.4 recorded in the area that failed are from piezometers located at these fracture zones. Hence, the hydrologically active bedrock fracture system at CB1 influenced thespatial variability and maximum values of pore pressure achieved in the overlying colluvial soil, as hypothesized in prior studies both elsewhere [Wilson and Dietrich, 1987; Johnson and Sitar, 1990; Mathewson et al., 1990; Anderson and Sitar, 1995; Fannin and Jaakkola, 1999; Onda et al., 2001; Uchida et al., 2002 Uchida et al., , 2003 and at CB1 [Montgomery et al., 1997. Further investigating and/or modeling of how artesian pore pressures propagate through colluvial soil lie beyond the scope of the present study. ...
The middle of a hillslope hollow in the Oregon Coast Range failed and mobilized as a debris flow during heavy rainfall in November 1996. Automated pressure transducers recorded high spatial variability of pore water pressure within the area that mobilized as a debris flow, which initiated where local upward flow from bedrock developed into overlying colluvium. Postfailure observations of the bedrock surface exposed in the debris flow scar reveal a strong spatial correspondence between elevated piezometric response and water discharging from bedrock fractures. Measurements of apparent root cohesion on the basal (Cb) and lateral (Cl) scarp demonstrate substantial local variability, with areally weighted values of Cb = 0.1 and Cl = 4.6 kPa. Using measured soil properties and basal root strength, the widely used infinite slope model, employed assuming slope parallel groundwater flow, provides a poor prediction of hydrologic conditions at failure. In contrast, a model including lateral root strength (but neglecting lateral frictional strength) gave a predicted critical value of relative soil saturation that fell within the range defined by the arithmetic and geometric mean values at the time of failure. The 3-D slope stability model CLARA-W, used with locally observed pore water pressure, predicted small areas with lower factors of safety within the overall slide mass at sites consistent with field observations of where the failure initiated. This highly variable and localized nature of small areas of high pore pressure that can trigger slope failure means, however, that substantial uncertainty appears inevitable for estimating hydrologic conditions within incipient debris flows under natural conditions.
... The soil samples from sites M1, M2, D1, and D2 are also shown with open circle and open triangle notation Environ Geol several of field visits. The role of bedrock fractures and ground water accumulation in relation to landslides and debris flows was well reviewed by Mathewson et al. (1990) in metamorphic and sedimentary terrains and by Onda (2004) in granitic terrains. Wilson and Dietrich (1987) described the bedrock hydrology and pore pressure development in topographic hollows covered by colluvium. ...
... In modeling with SEEP/W, bedrock hydrology was not incorporated (e.g., Casagli et al. 2006; Dapporto et al. 2005; Crosta and Dal Negro 2003). However, the role of bedrock seepages in slope failures and debris flows is well described in the literature (Mathewson et al. 1990; Onda 2004; Wilson and Dietrich 1987). Therefore, to ascertain the applicability of bedrock seepage in modeling, site M1 (crown of Matatirtha landslide) was simulated with both scenarios of seepage through rock (M1 simulation) and no seepage through rock (M1NFB simulation), i.e., as a null flux boundary on soil-bedrock contact. ...
In the Himalaya, people live in widely spread settlements and suffer more from landslides than from any other type of natural
disaster. The intense summer monsoons are the main factor in triggering landslides. However, the relations between landslides
and slope hydrology have not been a focal topic in Himalayan landslide research. This paper deals with the contributing parameters
for the rainfall-triggered landslides which occurred during an extreme monsoon rainfall event on 23 July 2002, in the south-western
hills of Kathmandu valley, in the Lesser Himalaya, Nepal. Parameters such as bedrock geology, geomorphology, geotechnical
properties of soil, and clay mineralogy are described in this paper. Landslide modeling was performed in SEEP/W and SLOPE/W
to understand the relationship of pore water pressure variations in soil layers and to determine the spatial variation of
landslide occurrence. Soil characteristics, low angle of internal friction of fines in soil, medium range of soil permeability,
presence of clay minerals in soil, bedrock hydrogeology, and human intervention were found to be the main contributing parameters
for slope failures in the region.
... However, field observations of fresh debris flow scarps suggest that shallow landslide initiation may be controlled by flow though bedrock fractures (e.g. Mathewson et al., 1990) or by flow in soil pipes (e.g. Uchida et al., 2001). ...
Simultaneous measurements of runoff, soil pore water pressure, soil temperature, and water chemistry were taken to evaluate the spatial and temporal nature of flowpaths in a steep 0·1 ha unchannelled hollow in the Tanakami Mountains of central Japan. Tensiometers showed that a saturated area formed and a downward hydraulic gradient existed continuously in the area near a spring. The amplitude of the soil–bedrock interface temperature difference near the spring was smaller than that in the upper hollow, although soil depth near the spring was smaller than in the upper hollow. This suggests that, in the small perennially saturated area near the spring, water percolates through the vadose zone mixed with water emerging from the bedrock. During summer rainstorms, the soil–bedrock interface temperature increased as the ground became saturated. Silica and sodium concentrations in the transient saturated groundwater during these episodes were significantly lower than those in the perennial groundwater, suggesting that both rainwater and shallow soil water had important effects on the formation of transient saturated groundwater on the upper slope. In this case, the streamflow varied with the soil pore water pressure on the upper slope; the soil pore water pressure in the area near the spring remained nearly constant. Moreover, the spring water temperature was almost the same as the transient groundwater temperature on the upper slope. This indicates that the transient groundwater in the upper slope flowed to the spring via lateral preferential paths. The relative inflow of bedrock groundwater to the spring decreased as rainfall increased. Copyright © 2003 John Wiley & Sons, Ltd.
... This flow is assumed to travel downslope following surface topography. Several workers, however, have suggested a significant role of shallow fracture flow on landslide initiation [Pierson, 1977; Everett, 1979; Wilson and Dietrich, 1987; Mathewson et al., 1990; Montgomery et al., 1997] . A substantial influence of shallow fracture flow on the piezometric response of colluvial soils and on debris flow initiation would help to explain: (1) shallow landslides that occur on planar and convex hill- slopes [Reneau and Dietrich, 1987; Ellen et al., 1988]; (2) differences in the timing and occurrence of landslides in topographically similar locations; and (3) variations in the frequency and location of landslides with bedrock type. ...
Experimental observations comparing two steep unchanneled valleys in the Oregon Coast Range, one intensively instrumented (CB1) and the other monitored for runoff but which produced a debris flow (CB2), shed light on the mechanisms of shallow flow in bedrock, its interaction with the vadose zone, and its role in generating landslides. Previous work at CB1 led to the proposal that during storms pulses of rainfall transmit pressure waves through the vadose zone and down to the saturated zone to create rapid pore pressure response and runoff [Torres et al., 1998]. Here, we document the associated rapid pore pressure response in the shallow fractured bedrock that underlies these colluvium-mantled sites and examine its influence on the generation of storm flow, seasonal variations in base flow, and slope stability in the overlying colluvial soil. Our observations document rapid piezometric response in the shallow bedrock and a substantial contribution of shallow fracture flow to both storm flow and seasonal variations in base flow. Saturated hydraulic conductivity in the colluvial soil decreases with depth below the ground surface, but the conductivity of the near-surface bedrock displays no depth dependence and varies over five orders of magnitude. Analysis of runoff intensity and duration in a series of storms that did and did not trigger debris flows in the surrounding area shows that the landslide inducing storms had the greatest intensity over durations similar to those predicted by a simple model of piezometric response. During a monitored storm in February 1992, the channel head at the base of the neighboring CB2 site failed as a debris flow. Automated piezometric measurements document that the CB2 debris flow initiated several hours after peak discharge, coincident with localized development of upward spikes of pressure head from near-surface bedrock into the overlying colluvial soil in CB1. Artesian flow observed exfiltrating from bedrock fractures on the failure surfaces at CB2 further implicates bedrock fracture flow in both runoff generation by subsurface storm flow and suggests a connection to landslide initiation. Our observations show that the timing of shallow landslide initiation can be delayed relative to both peak rainfall and peak runoff and support the argument that the influence of fracture flow on shallow landsliding helps explain the wide variability in the occurrence of slope instability in topographically analogous locations.
