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Sample records for abstract debris flows

  1. Orbital Debris Shape Characterization Project Abstract

    NASA Technical Reports Server (NTRS)

    Pease, Jessie

    2016-01-01

    I have been working on a project to further our understanding of orbital debris by helping create a new dataset previously too complex to be implemented in past orbital debris propagation models. I am doing this by creating documentation and 3D examples and illustrations of the shape categories. Earlier models assumed all orbital debris to be spherical aluminum fragments. My project will help expand our knowledge of shape populations to 6 categories: Straight Needle/Rod/Cylinder, Bent Needle/Rod/Cylinder, Flat Plate, Bent Plate, Nugget/Parallelepiped/Spheroid, and Flexible. The last category, Flexible, is still up for discussion and may be modified. These categories will be used to characterize fragments in the DebriSat experiment.

  2. The physics of debris flows

    USGS Publications Warehouse

    Iverson, R.M.

    1997-01-01

    Recent advances in theory and experimentation motivate a thorough reassessment of the physics of debris flows. Analyses of flows of dry, granular solids and solid-fluid mixtures provide a foundation for a comprehensive debris flow theory, and experiments provide data that reveal the strengths and limitations of theoretical models. Both debris flow materials and dry granular materials can sustain shear stresses while remaining static; both can deform in a slow, tranquil mode characterized by enduring, frictional grain contacts; and both can flow in a more rapid, agitated mode characterized by brief, inelastic grain collisions. In debris flows, however, pore fluid that is highly viscous and nearly incompressible, composed of water with suspended silt and clay, can strongly mediate intergranular friction and collisions. Grain friction, grain collisions, and viscous fluid flow may transfer significant momentum simultaneously. Both the vibrational kinetic energy of solid grains (measured by a quantity termed the granular temperature) and the pressure of the intervening pore fluid facilitate motion of grains past one another, thereby enhancing debris flow mobility. Granular temperature arises from conversion of flow translational energy to grain vibrational energy, a process that depends on shear rates, grain properties, boundary conditions, and the ambient fluid viscosity and pressure. Pore fluid pressures that exceed static equilibrium pressures result from local or global debris contraction. Like larger, natural debris flows, experimental debris flows of ???10 m3 of poorly sorted, water-saturated sediment invariably move as an unsteady surge or series of surges. Measurements at the base of experimental flows show that coarse-grained surge fronts have little or no pore fluid pressure. In contrast, finer-grained, thoroughly saturated debris behind surge fronts is nearly liquefied by high pore pressure, which persists owing to the great compressibility and moderate

  3. The physics of debris flows

    NASA Astrophysics Data System (ADS)

    Iverson, Richard M.

    1997-08-01

    Recent advances in theory and experimentation motivate a thorough reassessment of the physics of debris flows. Analyses of flows of dry, granular solids and solid-fluid mixtures provide a foundation for a comprehensive debris flow theory, and experiments provide data that reveal the strengths and limitations of theoretical models. Both debris flow materials and dry granular materials can sustain shear stresses while remaining static; both can deform in a slow, tranquil mode characterized by enduring, frictional grain contacts; and both can flow in a more rapid, agitated mode characterized by brief, inelastic grain collisions. In debris flows, however, pore fluid that is highly viscous and nearly incompressible, composed of water with suspended silt and clay, can strongly mediate intergranular friction and collisions. Grain friction, grain collisions, and viscous fluid flow may transfer significant momentum simultaneously. Both the vibrational kinetic energy of solid grains (measured by a quantity termed the granular temperature) and the pressure of the intervening pore fluid facilitate motion of grains past one another, thereby enhancing debris flow mobility. Granular temperature arises from conversion of flow translational energy to grain vibrational energy, a process that depends on shear rates, grain properties, boundary conditions, and the ambient fluid viscosity and pressure. Pore fluid pressures that exceed static equilibrium pressures result from local or global debris contraction. Like larger, natural debris flows, experimental debris flows of ˜10 m³ of poorly sorted, water-saturated sediment invariably move as an unsteady surge or series of surges. Measurements at the base of experimental flows show that coarse-grained surge fronts have little or no pore fluid pressure. In contrast, finer-grained, thoroughly saturated debris behind surge fronts is nearly liquefied by high pore pressure, which persists owing to the great compressibility and moderate

  4. Hydroplaning and submarine debris flows

    NASA Astrophysics Data System (ADS)

    de Blasio, Fabio V.; Engvik, Lars; Harbitz, Carl B.; ElverhøI, Anders

    2004-01-01

    Examination of submarine clastic deposits along the continental margins reveals the remnants of holocenic or older debris flows with run-out distances up to hundreds of kilometers. Laboratory experiments on subaqueous debris flows, where typically one tenth of a cubic meter of material is dropped down a flume, also show high velocities and long run-out distances compared to subaerial debris flows. Moreover, they show the tendency of the head of the flow to run out ahead of the rest of the body. The experiments reveal the possible clue to the mechanism of long run-out. This mechanism, called hydroplaning, begins as the dynamic pressure at the front of the debris flow becomes of the order of the pressure exerted by the weight of the sediment. In such conditions a layer of water can intrude under the sediment with a lubrication effect and a decrease in the resistance forces between the sediment and the seabed. A physical-mathematical model of hydroplaning is presented and investigated numerically. The model is applied to both laboratory- and field-scale debris flows. Agreement with laboratory experiments makes us confident in the extrapolation of our model to natural flows and shows that long run-out distances can be naturally attained.

  5. Debris Flows and Related Phenomena

    NASA Astrophysics Data System (ADS)

    Ancey, C.

    Torrential floods are a major natural hazard, claiming thousands of lives and millions of dollars in lost property each year in almost all mountain areas on the Earth. After a catastrophic eruption of Mount St. Helen in the USA in May 1980, water from melting snow, torrential rains from the eruption cloud, and water displaced from Spirit Lake mixed with deposited ash and debris to produce very large debris flows and cause extensive damage and loss of life [1]. During the 1985 eruption of Nevado del Ruiz in Colombia, more than 20,000 people perished when a large debris flow triggered by the rapid melting of snow and ice at the volcano summit, swept through the town of Armero [2]. In 1991, the eruption of Pinatubo volcano in the Philippines disperses more than 5 cubic kilometres of volcanic ash into surrounding valleys. Much of that sediment has subsequently been mobilised as debris flows by typhoon rains and has devastated more than 300 square kilometres of agricultural land. Even, in Eur opean countries, recent events that torrential floods may have very destructive effects (Sarno and Quindici in southern Italy in May 1998, where approximately 200 people were killed). The catastrophic character of these floods in mountainous watersheds is a consequence of significant transport of materials associated with water flows. Two limiting flow regimes can be distinguished. Bed load and suspension refer to dilute transport of sediments within water. This means that water is the main agent in the flow dynamics and that the particle concentration does not exceed a few percent. Such flows are typically two-phase flows. In contrast, debris flows are mas s movements of concentrated slurries of water, fine solids, rocks and boulders. As a first approximation, debris flows can be treated as one-phase flows and their flow properties can be studied using classical rheological methods. The study of debris flows is a very exciting albeit immature science, made up of disparate elements

  6. Segregation dynamics in debris flows

    NASA Astrophysics Data System (ADS)

    Hill, K. M.; Fei, M.

    2014-12-01

    Debris flows are massive flows consisting of mixtures of particles of different sizes and interstitial fluids such as water and mud. In sheared mixtures of different-sized (same density) particles, it is well known that larger particles tend to go up (toward the free surface), and the smaller particles, down, commonly referred to as the "Brazil-nut problem" or "kinetic sieving". When kinetic sieving fluxes are combined with advection in flows, they can give rise to a spectacular range of segregation patterns. These segregation / advection dynamics are recognized as playing a role in the coarsening of a debris flow front (its "snout") and the coarsening of the self-formed channel sides or levees. Since particle size distribution influences the flow dynamics including entrainment of bed materials, modeling segregation dynamics in debris flows is important for modeling the debris flows themselves. In sparser systems, the Brazil-nut segregation is well-modeled using kinetic theory applied to dissipative systems, where an underlying assumption involves random, uncorrelated collisions. In denser systems, where kinetic theory breaks down we have recently developed a new mixture model that demonstrates the segregation fluxes are driven by two effects associated with the kinetic stress or granular temperature (the kinetic energy associated with velocity fluctuations): (1) the difference between the partitioning of kinetic and contact stresses among the species in the mixture and (2) a kinetic stress gradient. Both model frameworks involve the temperature gradient as a driving force for segregation, but kinetic theory sends larger particles toward lower temperatures, and our mixture model sends larger particles away from lower temperatures. Which framework works under what conditions appears to depend on correlations in the flow such as those manifested in clusters and force chains. We discuss the application of each theoretical framework to representing segregation dynamics

  7. Detecting debris flows using ground vibrations

    USGS Publications Warehouse

    LaHusen, Richard G.

    1998-01-01

    Debris flows are rapidly flowing mixtures of rock debris, mud, and water that originate on steep slopes. During and following volcanic eruptions, debris flows are among the most destructive and persistent hazards. Debris flows threaten lives and property not only on volcanoes but far downstream in valleys that drain volcanoes where they arrive suddenly and inundate entire valley bottoms. Debris flows can destroy vegetation and structures in their path, including bridges and buildings. Their deposits can cover roads and railways, smother crops, and fill stream channels, thereby reducing their flood-carrying capacity and navigability.

  8. Debris flow study in Malaysia

    NASA Astrophysics Data System (ADS)

    Bahrin Jaafar, Kamal

    2016-04-01

    The phenomenon of debris flow occurs in Malaysia occasionally. The topography of Peningsular Malysia is characterized by the central mountain ranges running from south to north. Several parts of hilly areas with steep slopes, combined with high saturation of soil strata that deliberately increase the pore water pressure underneath the hill slope. As a tropical country Malaysia has very high intensity rainfall which is triggered the landslide. In the study area where the debris flow are bound to occur, there are a few factors that contribute to this phenomenon such as high rainfall intensity, very steep slope which an inclination more than 35 degree and sandy clay soil type which is easily change to liquidity soil. This paper will discuss the study of rainfall, mechanism, modeling and design of mitigation measure to avoid repeated failure in future in same area.

  9. Evaluating tsunami hazards from debris flows

    USGS Publications Warehouse

    Watts, P.; Walder, J.S.; ,

    2003-01-01

    Debris flows that enter water bodies may have significant kinetic energy, some of which is transferred to water motion or waves that can impact shorelines and structures. The associated hazards depend on the location of the affected area relative to the point at which the debris flow enters the water. Three distinct regions (splash zone, near field, and far field) may be identified. Experiments demonstrate that characteristics of the near field water wave, which is the only coherent wave to emerge from the splash zone, depend primarily on debris flow volume, debris flow submerged time of motion, and water depth at the point where debris flow motion stops. Near field wave characteristics commonly may be used as & proxy source for computational tsunami propagation. This result is used to assess hazards associated with potential debris flows entering a reservoir in the northwestern USA. ?? 2003 Millpress,.

  10. Debris-flow susceptibility map of Slovenia

    NASA Astrophysics Data System (ADS)

    Komac, M.; Kumelj, Š.; Ribičič, M.

    2009-04-01

    Until now debris-flow susceptibility was relatively poorly investigated in Slovenia. Regarding lack of such studies »Map of debris-flow susceptibility in Slovenia in scale 1.250.000« was elaborated using GIS and the latest spatial data was used; among them the latest lithological map of Slovenia in scale 1:250.000. For the creation of debris-flow susceptibility map of Slovenia in scale 1:250.000 seven considered most important factors were used that were divided into two groups: 1) initial factors that precondition debris-flows: lithology, slope angle, slope potential, 48-hours precipitation and 2) transport factors that contribute to higher probability of the transport of debris-flow material: terrain convexity, energy potential of streams, distance to surface water. Using linear weighted sum the precondition information layer was derived, and the same principal was used to derive transport information layer. Both layers were joined into final susceptibility assessment, again with consideration of their importance to contribute to debris-flow occurrence. Different weights were applied to chosen parameters, which resulted in several different models that were evaluated according to historical or recent debris-flow phenomena. Expert estimation was used to define the torrential areas with high probability of the debris-flow occurrence. The emphasis was on location rather than on the time of the debris-flow occurrence. There were unfortunately no adequate representative data about debris-flow in Slovenia (debris flow cadastre does not exist and not many historical studies have been done so far) for the quantitative statistical analysis. Hence only expert estimation approach was possible, based on the experience and historical events gathered from chronicles and eyewitness. Such an approach is mainly limited by subjectivity and has difficulties with sound argumentation, but at the given state it was the only possible approach. Based upon spatial analyses of four

  11. Debris flows: behavior and hazard assessment

    USGS Publications Warehouse

    Iverson, Richard M.

    2014-01-01

    Debris flows are water-laden masses of soil and fragmented rock that rush down mountainsides, funnel into stream channels, entrain objects in their paths, and form lobate deposits when they spill onto valley floors. Because they have volumetric sediment concentrations that exceed 40 percent, maximum speeds that surpass 10 m/s, and sizes that can range up to ~109 m3, debris flows can denude slopes, bury floodplains, and devastate people and property. Computational models can accurately represent the physics of debris-flow initiation, motion and deposition by simulating evolution of flow mass and momentum while accounting for interactions of debris' solid and fluid constituents. The use of physically based models for hazard forecasting can be limited by imprecise knowledge of initial and boundary conditions and material properties, however. Therefore, empirical methods continue to play an important role in debris-flow hazard assessment.

  12. Erosion of steepland valleys by debris flows

    USGS Publications Warehouse

    Stock, J.D.; Dietrich, W.E.

    2006-01-01

    Episodic debris flows scour the rock beds of many steepland valleys. Along recent debris-flow runout paths in the western United States, we have observed evidence for bedrock lowering, primarily by the impact of large particles entrained in debris flows. This evidence may persist to the point at which debris-flow deposition occurs, commonly at slopes of less than ???0.03-0.10. We find that debris-flow-scoured valleys have a topographic signature that is fundamentally different from that predicted by bedrock river-incision models. Much of this difference results from the fact that local valley slope shows a tendency to decrease abruptly downstream of tributaries that contribute throughgoing debris flows. The degree of weathering of valley floor bedrock may also decrease abruptly downstream of such junctions. On the basis of these observations, we hypothesize that valley slope is adjusted to the long-term frequency of debris flows, and that valleys scoured by debris flows should not be modeled using conventional bedrock river-incision laws. We use field observations to justify one possible debris-flow incision model, whose lowering rate is proportional to the integral of solid inertial normal stresses from particle impacts along the flow and the number of upvalley debris-flow sources. The model predicts that increases in incision rate caused by increases in flow event frequency and length (as flows gain material) downvalley are balanced by rate reductions from reduced inertial normal stress at lower slopes, and stronger, less weathered bedrock. These adjustments lead to a spatially uniform lowering rate. Although the proposed expression leads to equilibrium long-profiles with the correct topographic signature, the crudeness with which the debris-flow dynamics are parameterized reveals that we are far from a validated debris-flow incision law. However, the vast extent of steepland valley networks above slopes of ???0.03-0.10 illustrates the need to understand debris-flow

  13. Assessment and prediction of debris-flow hazards

    USGS Publications Warehouse

    Wieczorek, Gerald F.

    1993-01-01

    Study of debris-flow geomorphology and initiation mechanism has led to better understanding of debris-flow processes. This paper reviews how this understanding is used in current techniques for assessment and prediction of debris-flow hazards.

  14. The debris-flow rheology myth

    USGS Publications Warehouse

    Iverson, R.M.; ,

    2003-01-01

    Models that employ a fixed rheology cannot yield accurate interpretations or predictions of debris-flow motion, because the evolving behavior of debris flows is too complex to be represented by any rheological equation that uniquely relates stress and strain rate. Field observations and experimental data indicate that debris behavior can vary from nearly rigid to highly fluid as a consequence of temporal and spatial variations in pore-fluid pressure and mixture agitation. Moreover, behavior can vary if debris composition changes as a result of grain-size segregation and gain or loss of solid and fluid constituents in transit. An alternative to fixed-rheology models is provided by a Coulomb mixture theory model, which can represent variable interactions of solid and fluid constituents in heterogeneous debris-flow surges with high-friction, coarse-grained heads and low-friction, liquefied tails. ?? 2003 Millpress.

  15. VISCOPLASTIC FLUID MODEL FOR DEBRIS FLOW ROUTING.

    USGS Publications Warehouse

    Chen, Cheng-lung

    1986-01-01

    This paper describes how a generalized viscoplastic fluid model, which was developed based on non-Newtonian fluid mechanics, can be successfully applied to routing a debris flow down a channel. The one-dimensional dynamic equations developed for unsteady clear-water flow can be used for debris flow routing if the flow parameters, such as the momentum (or energy) correction factor and the resistance coefficient, can be accurately evaluated. The writer's generalized viscoplastic fluid model can be used to express such flow parameters in terms of the rheological parameters for debris flow in wide channels. A preliminary analysis of the theoretical solutions reveals the importance of the flow behavior index and the so-called modified Froude number for uniformly progressive flow in snout profile modeling.

  16. Morphodynamics of debris flow-dominated channels

    NASA Astrophysics Data System (ADS)

    Huebl, Johannes

    2013-04-01

    The mountain environment is mainly shaped by mass movements and glacial, debris flow and fluvial erosion. Therefore the landform ensemble of torrential catchments includes features of several thousand years. Many of them contribute as debris sources to the development of debris flow activity. But the torrential channel is not formed by different types of slope failures only, channel erosion itself plays a dominant role in the development of debris flows. Today LIDAR data allow us to identify different types of debris sources and subsequent channel features. In combination with the lithological setting this information helps us to understand the general morphodynamics of mountain channels. A deeper insight into the development of mountain channels lacks of consistent data sets. Different approaches try to estimate erosional rates of torrents during design events. These methods are mainly based on field survey and on the experience of the person doing this job. To decrease the uncertainty of these data, the collected data have to be checked against already existing data of documented former events. The development of the erosional processes in torrents is directly linked with the dominating morphodynamic process, leading to essential estimates of debris flow hydrographes.

  17. Amplification of postwildfire peak flow by debris

    NASA Astrophysics Data System (ADS)

    Kean, J. W.; McGuire, L. A.; Rengers, F. K.; Smith, J. B.; Staley, D. M.

    2016-08-01

    In burned steeplands, the peak depth and discharge of postwildfire runoff can substantially increase from the addition of debris. Yet methods to estimate the increase over water flow are lacking. We quantified the potential amplification of peak stage and discharge using video observations of postwildfire runoff, compiled data on postwildfire peak flow (Qp), and a physically based model. Comparison of flood and debris flow data with similar distributions in drainage area (A) and rainfall intensity (I) showed that the median runoff coefficient (C = Qp/AI) of debris flows is 50 times greater than that of floods. The striking increase in Qp can be explained using a fully predictive model that describes the additional flow resistance caused by the emergence of coarse-grained surge fronts. The model provides estimates of the amplification of peak depth, discharge, and shear stress needed for assessing postwildfire hazards and constraining models of bedrock incision.

  18. Density Estimations in Laboratory Debris Flow Experiments

    NASA Astrophysics Data System (ADS)

    Queiroz de Oliveira, Gustavo; Kulisch, Helmut; Malcherek, Andreas; Fischer, Jan-Thomas; Pudasaini, Shiva P.

    2016-04-01

    Bulk density and its variation is an important physical quantity to estimate the solid-liquid fractions in two-phase debris flows. Here we present mass and flow depth measurements for experiments performed in a large-scale laboratory set up. Once the mixture is released and it moves down the inclined channel, measurements allow us to determine the bulk density evolution throughout the debris flow. Flow depths are determined by ultrasonic pulse reflection, and the mass is measured with a total normal force sensor. The data were obtained at 50 Hz. The initial two phase material was composed of 350 kg debris with water content of 40%. A very fine pebble with mean particle diameter of 3 mm, particle density of 2760 kg/m³ and bulk density of 1400 kg/m³ in dry condition was chosen as the solid material. Measurements reveal that the debris bulk density remains high from the head to the middle of the debris body whereas it drops substantially at the tail. This indicates lower water content at the tail, compared to the head and the middle portion of the debris body. This means that the solid and fluid fractions are varying strongly in a non-linear manner along the flow path, and from the head to the tail of the debris mass. Importantly, this spatial-temporal density variation plays a crucial role in determining the impact forces associated with the dynamics of the flow. Our setup allows for investigating different two phase material compositions, including large fluid fractions, with high resolutions. The considered experimental set up may enable us to transfer the observed phenomena to natural large-scale events. Furthermore, the measurement data allows evaluating results of numerical two-phase mass flow simulations. These experiments are parts of the project avaflow.org that intends to develop a GIS-based open source computational tool to describe wide spectrum of rapid geophysical mass flows, including avalanches and real two-phase debris flows down complex natural

  19. Debris-flow mobilization from landslides

    USGS Publications Warehouse

    Iverson, R.M.; Reid, M.E.; LaHusen, R.G.

    1997-01-01

    Field observations, laboratory experiments, and theoretical analyses indicate that landslides mobilize to form debris flows by three processes: (a) widespread Coulomb failure within a sloping soil, rock, or sediment mass, (b) partial or complete liquefaction of the mass by high pore-fluid pressures, and (c) conversion of landslide translational energy to internal vibrational energy (i.e. granular temperature). These processes can operate independently, but in many circumstances they appear to operate simultaneously and synergistically. Early work on debris-flow mobilization described a similar interplay of processes but relied on mechanical models in which debris behavior was assumed to be fixed and governed by a Bingham or Bagnold rheology. In contrast, this review emphasizes models in which debris behavior evolves in response to changing pore pressures and granular temperatures. One-dimensional infinite-slope models provide insight by quantifying how pore pressures and granular temperatures can influence the transition from Coulomb failure to liquefaction. Analyses of multidimensional experiments reveal complications ignored in one-dimensional models and demonstrate that debris-flow mobilization may occur by at least two distinct modes in the field.

  20. Debris flow hazards mitigation--Mechanics, prediction, and assessment

    USGS Publications Warehouse

    Chen, C.-L.; Major, J.J.

    2007-01-01

    These proceedings contain papers presented at the Fourth International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction, and Assessment held in Chengdu, China, September 10-13, 2007. The papers cover a wide range of topics on debris-flow science and engineering, including the factors triggering debris flows, geomorphic effects, mechanics of debris flows (e.g., rheology, fluvial mechanisms, erosion and deposition processes), numerical modeling, various debris-flow experiments, landslide-induced debris flows, assessment of debris-flow hazards and risk, field observations and measurements, monitoring and alert systems, structural and non-structural countermeasures against debris-flow hazards and case studies. The papers reflect the latest devel-opments and advances in debris-flow research. Several studies discuss the development and appli-cation of Geographic Information System (GIS) and Remote Sensing (RS) technologies in debris-flow hazard/risk assessment. Timely topics presented in a few papers also include the development of new or innovative techniques for debris-flow monitoring and alert systems, especially an infra-sound acoustic sensor for detecting debris flows. Many case studies illustrate a wide variety of debris-flow hazards and related phenomena as well as their hazardous effects on human activities and settlements.

  1. Evaluating tsunami hazards from debris flows

    NASA Astrophysics Data System (ADS)

    Walder, J.; Watts, P.

    2003-04-01

    Water-wave hazards associated with debris flows entering water depend on the location of the affected area relative to the debris-flow entry point. Three distinct regions (splash zone, near field, and far field) may be identified may be identified on hydrodynamic grounds. The splash zone is nearly always small compared to the overall domain of interest. In the case of debris-flow generated tsunamis in lakes and reservoirs, commonly the entire water body lies within the near field, that is, beyond the zone of complex splashing but close enough to the source that wave-propagation effects do not predominate, in contrast to the case of tsunamis in the ocean. Scaling analysis of the equations governing water-wave propagation shows that near-field wave amplitude and wavelength should depend on specific measures of debris-flow dynamics and volume. The scaling analysis motivates a successful collapse (in dimensionless space) of data from two sets of flume experiments with solid-block "wavemakers." To first order, measured near-field wave amplitude/water depth depends simply on a dimensionless measure of the quantity (submerged travel time/wavemaker volume per unit width). This functional relationship also does a good job of describing wave-amplitude data from previous laboratory investigations with both rigid and deformable wavemakers. The characteristic wavelength/water depth for all our experiments is simply proportional to dimensionless wavemaker travel time, which is itself given approximately by a simple function of wavemaker length/water depth. Wavemaker shape and rigidity do not otherwise influence wave features. These scaling relations for near-field amplitude, wavelength, and submerged travel time, when combined with a correction for near-field wavefront speading in actual water bodies (which are rarely flume-like), allow us to construct a proxy source for computational tsunami propagation. We apply our results to assess hazards associated with potential debris

  2. Assessment of Debris Flow Hazards, North Mountain, Phoenix, AZ

    NASA Astrophysics Data System (ADS)

    Reavis, K. J.; Wasklewicz, T. A.

    2014-12-01

    Urban sprawl in many western U.S. cities has expanded development onto alluvial fans. In the case of metropolitan Phoenix, AZ (MPA), urban sprawl has led to an exponential outward growth into surrounding mountainous areas and onto alluvial fans. Building on alluvial fans places humans at greater risk to flooding and debris flow hazards. Recent research has shown debris flows often supply large quantities of material to many alluvial fans in MPA. However, the risk of debris flows to built environments is relatively unknown. We use a 2D debris flow modeling approach, aided by high-resolution airborne LiDAR and terrestrial laser scanning (TLS) topographic data, to examine debris flow behavior in a densely populated portion of the MPA to assess the risk and vulnerability of debris flow damage to the built infrastructure. A calibrated 2D debris flow model is developed for a "known" recent debris flow at an undeveloped site in MPA. The calibrated model and two other model scenarios are applied to a populated area with historical evidence of debris flow activity. Results from the modeled scenarios show evidence of debris flow damage to houses built on the alluvial fan. Debris flow inundation is also evident on streets on the fan. We use housing values and building damage to estimate the costs assocaited with various modeled debris flow scenarios.

  3. GENERAL SOLUTIONS FOR VISCOPLASTIC DEBRIS FLOW.

    USGS Publications Warehouse

    Chen, Cheng-lung

    1988-01-01

    Theoretical velocity profile and theoretical pressure and concentration distributions for (steady) uniform debris flow in wide channels are derived from a generalized viscoplastic fluid (GVF) model without imposing R. A. Bagnold's assumption of constant grain concentration. Good agreement between the theoretical velocity profile and the experimental data of Japanese scientists strongly supports the validity of both the GVF model and the proposed method of solution from the model. It is shown that both E. C. Bingham and Bagnold versions (or submodels) of the GVF model can be used to simulate debris flow at the dynamic state. Although Bagnold's dilatant submodel appears to fit the Japanese data better than the Bingham submodel for flow of noncohesive grains, the choice between them is by no means clear-cut.

  4. GENERALIZED VISCOPLASTIC MODELING OF DEBRIS FLOW.

    USGS Publications Warehouse

    Chen, Cheng-lung

    1988-01-01

    The earliest model developed by R. A. Bagnold was based on the concept of the 'dispersive' pressure generated by grain collisions. Some efforts have recently been made by theoreticians in non-Newtonian fluid mechanics to modify or improve Bagnold's concept or model. A viable rheological model should consist both of a rate-independent part and a rate-dependent part. A generalized viscoplastic fluid (GVF) model that has both parts as well as two major rheological properties (i. e. , the normal stress effect and soil yield criterion) is shown to be sufficiently accurate, yet practical for general use in debris-flow modeling. In fact, Bagnold's model is found to be only a particular case of the GVF model. analytical solutions for (steady) uniform debris flows in wide channels are obtained from the GVF model based on Bagnold's simplified assumption of constant grain concentration.

  5. Mitigation of Debris Flow Damage--­ A Case Study of Debris Flow Damage

    NASA Astrophysics Data System (ADS)

    Lin, J. C.; Jen, C. H.

    Typhoon Toraji caused more than 30 casualties in Central Taiwan on the 31st July 2001. It was the biggest Typhoon since the Chi-Chi earthquake of 1999 with huge amounts of rainfall. Because of the influence of the earthquake, loose debris falls and flows became major hazards in Central Taiwan. Analysis of rainfall data and sites of slope failure show that damage from these natural hazards were enhanced as a result of the Chi-Chi earthquake. Three main types of hazard occurred in Central Taiwan: land- slides, debris flows and gully erosion. Landslides occurred mainly along hill slopes and banks of channels. Many dams and houses were destroyed by flooding. Debris flows occurred during typhoon periods and re-activated ancient debris depositions. Many new gullies were therefore developed from deposits loosened and shaken by the earthquake. This paper demonstrates the geological/geomorphological background of the hazard area, and reviews methods of damage mitigation in central Taiwan. A good example is Hsi-Tou, which had experienced no gully erosion for more than 40 years. The area experienced much gully erosion as a result of the combined effects of earth- quake and typhoon. Although Typhoon Toraji produced only 30% of the rainfall of Typhoon Herb of 1996, it caused more damage in the Hsi-Tou area. The mitigation of debris flow hazards in Hsi-tou area is discussed in this paper.

  6. Debris flow hazard mapping, Hobart, Tasmania, Australia

    NASA Astrophysics Data System (ADS)

    Mazengarb, Colin; Rigby, Ted; Stevenson, Michael

    2015-04-01

    Our mapping on the many dolerite capped mountains in Tasmania indicates that debris flows are a significant geomorphic process operating there. Hobart, the largest city in the State, lies at the foot of one of these mountains and our work is focussed on identifying areas that are susceptible to these events and estimating hazard in the valley systems where residential developments have been established. Geomorphic mapping with the benefit of recent LiDAR and GIS enabled stereo-imagery has allowed us to add to and refine a landslide inventory in our study area. In addition, a dominant geomorphic model has been recognised involving headward gully retreat in colluvial materials associated with rainstorms explains why many past events have occurred and where they may occur in future. In this paper we will review the landslide inventory including a large event (~200 000m3) in 1872 that affected a lightly populated area but since heavily urbanised. From this inventory we have attempted volume-mobility relationships, magnitude-frequency curves and likelihood estimates. The estimation of volume has been challenging to determine given that the area of depletion for each debris flow feature is typically difficult to distinguish from the total affected area. However, where LiDAR data exists, this uncertainty is substantially reduced and we develop width-length relationships (area of depletion) and area-volume relationships to estimate volume for the whole dataset exceeding 300 features. The volume-mobility relationship determined is comparable to international studies and in the absence of reliable eye-witness accounts, suggests that most of the features can be explained as single event debris flows, without requiring more complex mechanisms (such as those that form temporary debris dams that subsequently fail) as proposed by others previously. Likelihood estimates have also been challenging to derive given that almost all of the events have not been witnessed, some are

  7. Debris-flow generation from recently burned watersheds

    USGS Publications Warehouse

    Cannon, S.H.

    2001-01-01

    Evaluation of the erosional response of 95 recently burned drainage basins in Colorado, New Mexico and southern California to storm rainfall provides information on the conditions that result in fire-related debris flows. Debris flows were produced from only 37 of 95 (~40 percent) basins examined; the remaining basins produced either sediment-laden streamflow or no discernable response. Debris flows were thus not the prevalent response of the burned basins. The debris flows that did occur were most frequently the initial response to significant rainfall events. Although some hillslopes continued to erode and supply material to channels in response to subsequent rainfall events, debris flows were produced from only one burned basin following the initial erosive event. Within individual basins, debris flows initiated through both runoff and infiltration-triggered processes. The fact that not all burned basins produced debris flows suggests that specific geologic and geomorphic conditions may control the generation of fire-related debris flows. The factors that best distinguish between debris-flow producing drainages and those that produced sediment-laden streamflow are drainage-basin morphology and lithology, and the presence or absence of water-repellent soils. Basins underlain by sedimentary rocks were most likely to produce debris flows that contain large material, and sand- and gravel-dominated flows were generated primarily from terrain underlain by decomposed granite. Basin-area and relief thresholds define the morphologic conditions under which both types of debris flows occur. Debris flows containing large material are more likely to be produced from basins without water-repellent soils than from basins with water repellency. The occurrence of sand-and gravel-dominated debris flows depends on the presence of water-repellent soils.

  8. The Effect of Debris-Flow Composition on Runout Distance

    NASA Astrophysics Data System (ADS)

    Haas, T. D.; Braat, L.; Leuven, J.; Lokhorst, I.; Kleinhans, M. G.

    2014-12-01

    Estimating runout distance is of major importance for the assessment and mitigation of debris-flow hazards. Debris-flow runout distance depends on debris-flow composition and topography, but state-of-the-art runout prediction methods are mainly based on topographical parameters and debris-flow volume, while composition is generally neglected or incorporated in empirical constants. Here we experimentally investigated the effect of debris-flow composition and topography on runout distance. We created the first small-scale experimental debris flows with self-formed levees, distinct lobes and morphology and texture accurately resembling natural debris flows. In general, debris-flow composition had a larger effect on runout distance than topography. Enhancing channel slope and width, outflow plain slope, debris-flow size and water fraction leads to an increase in runout distance. However, runout distance shows an optimum relation with coarse-material and clay fraction. An increase in coarse-material fraction leads to larger runout distances by increased grain collisional forces and more effective levee formation, but too much coarse debris causes a large accumulation of coarse debris at the flow front, enhancing friction and decreasing runout. An increase in clay fraction initially enlarges the volume and viscosity of the interstitial fluid, liquefying the flow and enhancing runout, while a further increase leads to very viscous flows with high yield strength, reducing runout. These results highlight the importance and further need of research on the relation between debris-flow composition and runout distance. Our experiments further provide valuable insight on the effects of debris-flow composition on depositional mechanisms and deposit morphology.

  9. The effect of debris-flow composition on runout distance

    NASA Astrophysics Data System (ADS)

    de Haas, Tjalling; Braat, Lisanne; Leuven, Jasper; Lokhorst, Ivar; Kleinhans, Maarten

    2015-04-01

    Estimating runout distance is of major importance for the assessment and mitigation of debris-flow hazards. Debris-flow runout distance depends on debris-flow composition and topography, but state-of-the-art runout prediction methods are mainly based on topographical parameters and debris-flow volume, while composition is generally neglected or incorporated in empirical constants. Here we experimentally investigated the effect of debris-flow composition and topography on runout distance. We created the first small-scale experimental debris flows with self-formed levees, distinct lobes and morphology and texture accurately resembling natural debris flows. In general, the effect of debris-flow composition on runout distance was larger than the effect of topography. Enhancing channel slope and width, outflow plain slope, debris-flow size and water fraction leads to an increase in runout distance. However, runout distance shows an optimum relation with coarse-material and clay fraction. An increase in coarse-material fraction leads to larger runout distances by increased grain collisional forces and more effective levee formation, but too much coarse debris causes a large accumulation of coarse debris at the flow front, enhancing friction and decreasing runout. An increase in clay fraction initially enlarges the volume and viscosity of the interstitial fluid, liquefying the flow and enhancing runout, while a further increase leads to very viscous flows with high yield strength, reducing runout. These results highlight the importance and further need of research on the relation between debris-flow composition and runout distance. Our experiments further provide valuable insight on the effects of debris-flow composition on depositional mechanisms and deposit morphology.

  10. Mapping debris-flow hazard in Honolulu using a DEM

    USGS Publications Warehouse

    Ellen, Stephen D.; Mark, Robert K.

    1993-01-01

    A method for mapping hazard posed by debris flows has been developed and applied to an area near Honolulu, Hawaii. The method uses studies of past debris flows to characterize sites of initiation, volume at initiation, and volume-change behavior during flow. Digital simulations of debris flows based on these characteristics are then routed through a digital elevation model (DEM) to estimate degree of hazard over the area.

  11. Debris-flow susceptibility of watersheds recently burned by wildfire

    USGS Publications Warehouse

    Cannon, S.H.

    2004-01-01

    Evaluation of the erosional response of 95 recently burned watersheds in Colorado, New Mexico, and southern California to storm rainfall established the factors that best differentiate between debris-flow producing basins and those that produced other flow responses. These factors are drainage-basin morphology and lithology, and the presence or absence of water-repellent soils. Basins underlain by sedimentary rocks were most likely to produce debris flows that contain large material, and sand- and gravel-dominated debris flows were generated primarily from terrain underlain by decomposed granite. Basin-area and relief thresholds define the morphologic conditions under which both types of debris flows occurred. Debris flows containing large material were more likely to be produced from basins without water-repellent soils than from basins with water repellency. The occurrence of sand and gravel-dominated debris flows depended on the presence of water repellent soils. Copyright 2004 ASCE.

  12. Debris flow, debris avalanche and flood hazards at and downstream from Mount Rainier, Washington

    USGS Publications Warehouse

    Scott, Kevin M.; Vallance, J.W.

    1995-01-01

    Mount Rainier volcano has produced many large debris flows and debris avalanches during the last 10,000 years. These flows have periodically traveled more than 100 kilometers from the volcano to inundate parts of the now-populated Puget Sound Lowland. Meteorological floods also have caused damage, but future effects will be partly mitigated by reservoirs. Mount Rainier presents the most severe flow risks of any volcano in the United States. Volcanic debris flows (lahars) are of two types: (1) cohesive, relatively high clay flows originating as debris avalanches, and (2) noncohesive flows with less clay that begin most commonly as meltwater surges. Three case histories represent important subpopulations of flows with known magnitudes and frequencies. The risks of each subpopulation may be considered for general planning and design. A regional map illustrates the extent of inundation by the case-history flows, the largest of which originated as debris avalanches and moved from Mount Rainier to Puget Sound. The paleohydrologic record of these past flows indicates the potential for inundation by future flows from the volcano. A map of the volcano and its immediate vicinity shows examples of smaller debris avalanches and debris flows in the 20th century.

  13. Sources of debris flow material in burned areas

    USGS Publications Warehouse

    Santi, P.M.; deWolfe, V.G.; Higgins, J.D.; Cannon, S.H.; Gartner, J.E.

    2008-01-01

    The vulnerability of recently burned areas to debris flows has been well established. Likewise, it has been shown that many, if not most, post-fire debris flows are initiated by runoff and erosion and grow in size through erosion and scour by the moving debris flow, as opposed to landslide-initiated flows with little growth. To better understand the development and character of these flows, a study has been completed encompassing 46 debris flows in California, Utah, and Colorado, in nine different recently burned areas. For each debris flow, progressive debris production was measured at intervals along the length of the channel, and from these measurements graphs were developed showing cumulative volume of debris as a function of channel length. All 46 debris flows showed significant bulking by scour and erosion, with average yield rates for each channel ranging from 0.3 to 9.9??m3 of debris produced for every meter of channel length, with an overall average value of 2.5??m3/m. Significant increases in yield rate partway down the channel were identified in 87% of the channels, with an average of a three-fold increase in yield rate. Yield rates for short reaches of channels (up to several hundred meters) ranged as high as 22.3??m3/m. Debris was contributed from side channels into the main channels for 54% of the flows, with an average of 23% of the total debris coming from those side channels. Rill erosion was identified for 30% of the flows, with rills contributing between 0.1 and 10.5% of the total debris, with an average of 3%. Debris was deposited as levees in 87% of the flows, with most of the deposition occurring in the lower part of the basin. A median value of 10% of the total debris flow was deposited as levees for these cases, with a range from near zero to nearly 100%. These results show that channel erosion and scour are the dominant sources of debris in burned areas, with yield rates increasing significantly partway down the channel. Side channels are

  14. Acoustic module of the Acquabona (Italy) debris flow monitoring system

    NASA Astrophysics Data System (ADS)

    Galgaro, A.; Tecca, P. R.; Genevois, R.; Deganutti, A. M.

    2005-02-01

    Monitoring of debris flows aimed to the assessment of their physical parameters is very important both for theoretical and practical purposes. Peak discharge and total volume of debris flows are crucial for designing effective countermeasures in many populated mountain areas where losses of lives and property damage could be avoided. This study quantifies the relationship between flow depth, acoustic amplitude of debris flow induced ground vibrations and front velocity in the experimental catchment of Acquabona, Eastern Dolomites, Italy. The analysis of data brought about the results described in the following. Debris flow depth and amplitude of the flow-induced ground vibrations show a good positive correlation. Estimation of both mean front velocity and peak discharge can be simply obtained monitoring the ground vibrations, through geophones installed close to the flow channel; the total volume of debris flow can be so directly estimated from the integral of the ground vibrations using a regression line. The application of acoustic technique to debris flow monitoring seems to be of the outmost relevance in risk reduction policies and in the correct management of the territory. Moreover this estimation is possible in other catchments producing debris flows of similar characteristics by means of their acoustic characterisation through quick and simple field tests (Standard Penetration Tests and seismic refraction surveys).

  15. NOAA-USGS Debris-Flow Warning System - Final Report

    USGS Publications Warehouse

    ,

    2005-01-01

    Landslides and debris flows cause loss of life and millions of dollars in property damage annually in the United States (National Research Council, 2004). In an effort to reduce loss of life by debris flows, the National Oceanic and Atmospheric Administration's (NOAA) National Weather Service (NWS) and the U.S. Geological Survey (USGS) operated an experimental debris-flow prediction and warning system in the San Francisco Bay area from 1986 to 1995 that relied on forecasts and measurements of precipitation linked to empirical precipitation thresholds to predict the onset of rainfall-triggered debris flows. Since 1995, there have been substantial improvements in quantifying precipitation estimates and forecasts, development of better models for delineating landslide hazards, and advancements in geographic information technology that allow stronger spatial and temporal linkage between precipitation forecasts and hazard models. Unfortunately, there have also been several debris flows that have caused loss of life and property across the United States. Establishment of debris-flow warning systems in areas where linkages between rainfall amounts and debris-flow occurrence have been identified can help mitigate the hazards posed by these types of landslides. Development of a national warning system can help support the NOAA-USGS goal of issuing timely Warnings of potential debris flows to the affected populace and civil authorities on a broader scale. This document presents the findings and recommendations of a joint NOAA-USGS Task Force that assessed the current state-of-the-art in precipitation forecasting and debris-flow hazard-assessment techniques. This report includes an assessment of the science and resources needed to establish a demonstration debris-flow warning project in recently burned areas of southern California and the necessary scientific advancements and resources associated with expanding such a warning system to unburned areas and, possibly, to a

  16. Systems and Sensors for Debris-flow Monitoring and Warning

    PubMed Central

    Arattano, Massimo; Marchi, Lorenzo

    2008-01-01

    Debris flows are a type of mass movement that occurs in mountain torrents. They consist of a high concentration of solid material in water that flows as a wave with a steep front. Debris flows can be considered a phenomenon intermediate between landslides and water floods. They are amongst the most hazardous natural processes in mountainous regions and may occur under different climatic conditions. Their destructiveness is due to different factors: their capability of transporting and depositing huge amounts of solid materials, which may also reach large sizes (boulders of several cubic meters are commonly transported by debris flows), their steep fronts, which may reach several meters of height and also their high velocities. The implementation of both structural and non-structural control measures is often required when debris flows endanger routes, urban areas and other infrastructures. Sensor networks for debris-flow monitoring and warning play an important role amongst non-structural measures intended to reduce debris-flow risk. In particular, debris flow warning systems can be subdivided into two main classes: advance warning and event warning systems. These two classes employ different types of sensors. Advance warning systems are based on monitoring causative hydrometeorological processes (typically rainfall) and aim to issue a warning before a possible debris flow is triggered. Event warning systems are based on detecting debris flows when these processes are in progress. They have a much smaller lead time than advance warning ones but are also less prone to false alarms. Advance warning for debris flows employs sensors and techniques typical of meteorology and hydrology, including measuring rainfall by means of rain gauges and weather radar and monitoring water discharge in headwater streams. Event warning systems use different types of sensors, encompassing ultrasonic or radar gauges, ground vibration sensors, videocameras, avalanche pendulums

  17. Risk assessment of debris flow hazards in natural slope

    NASA Astrophysics Data System (ADS)

    Choi, Junghae; Chae, Byung-gon; Liu, Kofei; Wu, Yinghsin

    2016-04-01

    The study area is located at north-east part of South Korea. Referring to the map of landslide sus-ceptibility (KIGAM, 2009) from Korea Institute of Geoscience and Mineral Resources (KIGAM for short), there are large areas of potential landslide in high probability on slope land of mountain near the study area. Besides, recently some severe landslide-induced debris flow hazards occurred in this area. So this site is convinced to be prone to debris flow haz-ards. In order to mitigate the influence of hazards, the assessment of potential debris flow hazards is very important and essential. In this assessment, we use Debris-2D, debris flow numerical program, to assess the potential debris flow hazards. The worst scenario is considered for simulation. The input mass sources are determined using landslide susceptibility map. The water input is referred to the daily accumulative rainfall in the past debris flow event in study area. The only one input material property, i.e. yield stress, is obtained using calibration test. The simulation results show that the study area has po-tential to be impacted by debris flow. Therefore, based on simulation results, to mitigate debris flow hazards, we can propose countermeasures, including building check dams, constructing a protection wall in study area, and installing instruments for active monitoring of debris flow hazards. Acknowledgements:This research was supported by the Public Welfare & Safety Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Science, ICT & Future Planning (NRF-2012M3A2A1050983)

  18. Experiments With Small-scale Debris Flow Breakers

    NASA Astrophysics Data System (ADS)

    Hübl, J.; Steinwendtner, H.

    In Austria debris flow breakers are a common countermeasure against debris flows since several decades. Although a lot of practical experience exists, there is a gap on general design criteria for this kind of measure. To close this gap some flume experi- ments were carried out. The model tests are designed to analyse interactions of debris flows with structures under controlled conditions. The tests were performed to inves- tigate maximal possible dynamic loads by the impact of viscous and granular debris flows as well as to optimise the design of debris flow breakers. The experimental de- sign consists of a 4,0 m long and 0,3 m wide channel with variable slope and different check dam models. Ultrasonic sensors are used for the measurement of flow velocity and flow depth. Impact forces are recorded using strain gauges. Debris flow matrix consists of Xanthan, a thickener in food technology, and loam and water, respectively. As rigid phase PVC granulars and natural debris with different grain size distribution is used. To check the different interactions the mixtures (matrix and rigid phase) are varied in sediment concentration and grain size distribution. To determine flow be- haviour and rheological parameters a conveyor channel was used. This special exper- imental design enables to study the behaviour of debris flow material with maximum grain diameter up to 20mm. The results show that the main criteria for the deposition of debris flows is the width of the opening between the panels. The structural design of the waterfront plays a minor role in the stopping process.

  19. Simulation of long-term debris flow sediment transport based on a slope stability and a debris flow routing model

    NASA Astrophysics Data System (ADS)

    Müller, T.; Hoffmann, T.

    2012-04-01

    Debris flows play a crucial role in the coupling of hillslope-sediment sources and channels in mountain environments. In most landscape evolution models (LEMs), the sediment transport by debris flows is (if at all) often represented by simple empirical rules. This generally results from the mismatch of the coarse resolution of the LEMs and the small scale impacts of debris flow processes. To extend the accuracy and predictive power of LEMs, either a higher resolution of LEMs in combination with process-based debris flow models or a better parametrisation of subpixel scale debris flow processes is necessary. Furthermore, the simulation of sediment transport by debris flows is complicated by their episodic nature and unknown factors controlling the frequency and magnitude of events. Here, we present first results using a slope stability model (SINMAP) and an event-based debris flow routing model (SCIDDICA-S4c) to simulate the effects of debris flows in LEMs. The model was implemented in the XULU modelling platform developed by the Department of Computer Science at the University of Bonn. The combination of the slope stability model and the event-based routing and mass balance model enables us to simulate the triggering and routing of debris flow material through the iteration of single events over several thousand years. Although a detailed calibration and validation remains to be done, the resulting debris flow-affected areas in a test elevation model correspond well with data gained from a geomorphological mapping of the corresponding area, justifying our approach. The increased computation speed allows to run high resolution LEM in convenient short time at relatively low cost. This should encourage the development of more detailed LEMs, in which process-based models should be incorporated.

  20. Volcanic debris flows in developing countries - The extreme need for public education and awareness of debris-flow hazards

    USGS Publications Warehouse

    Major, J.J.; Schilling, S.P.; Pullinger, C.R.; ,

    2003-01-01

    In many developing countries, volcanic debris flows pose a significant societal risk owing to the distribution of dense populations that commonly live on or near a volcano. At many volcanoes, modest volume (up to 500,000 m 3) debris flows are relatively common (multiple times per century) and typically flow at least 5 km along established drainages. Owing to typical debris-flow velocities there is little time for authorities to provide effective warning of the occurrence of a debris flow to populations within 10 km of a source area. Therefore, people living, working, or recreating along channels that drain volcanoes must learn to recognize potentially hazardous conditions, be aware of the extent of debris-flow hazard zones, and be prepared to evacuate to safer ground when hazardous conditions develop rather than await official warnings or intervention. Debris-flow-modeling and hazard-assessment studies must be augmented with public education programs that emphasize recognizing conditions favorable for triggering landslides and debris flows if effective hazard mitigation is to succeed. ?? 2003 Millpress,.

  1. Listening to debris flows: What can ground vibrations tell us about debris-flow entrainment and flow density?

    NASA Astrophysics Data System (ADS)

    Kean, J. W.; Coe, J. A.; Coviello, V.; Smith, J. B.; McCoy, S. W.; Arattano, M.

    2015-12-01

    Debris flows generate seismic waves as they travel downslope and can grow in size and destructive potential by entraining sediment along their paths. Recent observations from the Chalk Cliffs monitoring site in central Colorado show there is a systematic relation between the magnitude of seismic waves and both (1) the amount of erodible sediment beneath the flow, and (2) the density of the flow. Specifically, we observed that the spectral power of debris-flow induced ground motion increased by two orders of magnitude after a 34-cm layer of bed sediment was eroded from a bedrock channel. We also observed that high-density (sediment-rich) debris-flow surges generate about two orders of magnitude greater spectral power than low-density (water-rich) surges of similar thickness. These observations lead us to the hypothesis that the recorded ground motions are generated primarily by the impacts of grains on bedrock sections of the channel. This hypothesis is supported by ball drop tests which showed that impacts on deformable loose bed sediment in the channel (if present) generate negligibly small surface waves compared to impacts on bedrock. We thus expect debris-flow induced ground motion to increase as sediment entrainment exposes bedrock in channel, and as the flow density (and number of grains) increase. We explored the connection between ground motions and debris-flow entrainment/density by adapting a model from fluvial seismology [Tsai et al., GRL, 2012]. We used the adapted model to estimate rates of sediment entrainment and the density of flows over bare bedrock channels. Our estimates of sediment entrainment compared favorably with previous direct measurements of entrainment rates at the site. Estimates of flow density are sufficiently accurate to distinguish between three density levels: low (<1200 kg/m3), medium (1200-1600 kg/m3), and high (<1600 kg/m3). Although more testing is needed, these initial results suggest the approach may be a new indirect way to

  2. Modeling sediment concentration in debris flow by Tsallis entropy

    NASA Astrophysics Data System (ADS)

    Singh, Vijay P.; Cui, Huijuan

    2015-02-01

    Debris flow is a natural hazard that occurs in landscapes having high slopes, such as mountainous areas. It can be so powerful that it destroys whatever comes in its way, that is, it can kill people and animals; decimate roads, bridges, railway tracks, homes and other property; and fill reservoirs. Owing to its frequent occurrence, it is receiving considerable attention these days. Of fundamental importance in debris flow modeling is the determination of concentration of debris (or sediment) in the flow. The usual approach to determining debris flow concentration is either empirical or hydraulic. Both approaches are deterministic and therefore say nothing about the uncertainty associated with the sediment concentration in the flow. This paper proposes to model debris flow concentration using the Tsallis entropy theory. Verification of the entropy-based distribution of debris flow concentration using the data and equations reported in the literature shows that the Tsallis entropy-proposed model is capable of mimicking the field observed concentration and has potential for practical application.

  3. Predicting sediment delivery from debris flows after wildfire

    NASA Astrophysics Data System (ADS)

    Nyman, Petter; Smith, Hugh G.; Sherwin, Christopher B.; Langhans, Christoph; Lane, Patrick N. J.; Sheridan, Gary J.

    2015-12-01

    Debris flows are an important erosion process in wildfire-prone landscapes. Predicting their frequency and magnitude can therefore be critical for quantifying risk to infrastructure, people and water resources. However, the factors contributing to the frequency and magnitude of events remain poorly understood, particularly in regions outside western USA. Against this background, the objectives of this study were to i) quantify sediment yields from post-fire debris flows in southeast Australian highlands and ii) model the effects of landscape attributes on debris flow susceptibility. Sediment yields from post-fire debris flows (113-294 t ha- 1) are 2-3 orders of magnitude higher than annual background erosion rates from undisturbed forests. Debris flow volumes ranged from 539 to 33,040 m3 with hillslope contributions of 18-62%. The distribution of erosion and deposition above the fan were related to a stream power index, which could be used to model changes in yield along the drainage network. Debris flow susceptibility was quantified with a logistic regression and an inventory of 315 debris flow fans deposited in the first year after two large wildfires (total burned area = 2919 km2). The differenced normalised burn ratio (dNBR or burn severity), local slope, radiative index of dryness (AI) and rainfall intensity (from rainfall radar) were significant predictors in a susceptibility model, which produced excellent results in terms identifying channels that were eroded by debris flows (Area Under Curve, AUC = 0.91). Burn severity was the strongest predictor in the model (AUC = 0.87 when dNBR is used as single predictor) suggesting that fire regimes are an important control on sediment delivery from these forests. The analysis showed a positive effect of AI on debris flow probability in landscapes where differences in moisture regimes due to climate are associated with large variation in soil hydraulic properties. Overall, the results from this study based in the

  4. Debris-flow deposition: Effects of pore-fluid pressure and friction concentrated at flow margins

    USGS Publications Warehouse

    Major, J.J.; Iverson, R.M.

    1999-01-01

    Measurements of pore-fluid pressure and total bed-normal stress at the base of several ???10 m3 experimental debris flows provide new insight into the process of debris-flow deposition. Pore-fluid pressures nearly sufficient to cause liquefaction were developed and maintained during flow mobilization and acceleration, persisted in debris-flow interiors during flow deceleration and deposition, and dissipated significantly only during postdepositional sediment consolidation. In contrast, leading edges of debris flows exhibited little or no positive pore-fluid pressure. Deposition therefore resulted from grain-contact friction and bed friction concentrated at flow margins. This finding contradicts models that invoke widespread decay of excess pore-fluid pressure, uniform viscoplastic yield strength, or pervasive grain-collision stresses to explain debris-flow deposition. Furthermore, the finding demonstrates that deposit thickness cannot be used to infer the strength of flowing debris.

  5. Fire-related debris flows in the Iberian Range, Spain

    NASA Astrophysics Data System (ADS)

    García-Ruiz, José M.; Arnáez, José; Gómez-Villar, Amelia; Ortigosa, Luis; Lana-Renault, Noemí

    2013-08-01

    Debris flows occurred three weeks after a wildfire in August 1986 in the Najerilla River valley in the Iberian Range, northern Spain. The flows were triggered by a brief, intense rainstorm (approximately 25 mm h- 1 over 15 min) in a small area with steep slopes covered by a thick colluvium of quartzite clasts. This storm resulted in the development of several unconfined hillslope debris flows and the formation of an alluvial fan at the mouth of the Pítare stream, which partially blocked the Najerilla River. We analysed the conditions that led to the development of the debris flows, and estimated the rainfall threshold for the debris flows to occur as well as the total volume of mobilised sediment. Four factors contributed to the debris flows: (i) the occurrence of a rainstorm three weeks after a wildfire, which had removed the plant cover from the soil; (ii) the steep slopes in the area (> 30°), which were the most affected by debris flows; (iii) the presence of quartzite scarps on the hillslopes, which favoured the development of a 'firehose effect' involving channelised surface runoff; and (iv) the low plasticity index values of the fine material of the colluvium (indices of 7 to 8), which enabled rapid liquefaction. Estimates of rainfall intensity derived from the estimated peak flow in the Pítare stream suggests that around 80 mm of rainfall fell in approximately 15 min, although this is clearly an overestimated value given the high proportion of sediment load transported during the peak flow. Various equations estimated a rainfall-threshold of approximately 25 mm h- 1 considering a concentration time of 15 min. The total sediment transported by the debris flows was 10,500 m3 (15,750 Mg, 6800 Mg km- 2), and the Pítare stream alone transported a minimum of 4000 m3 (6000 Mg, 2500 Mg km- 2). These results suggest that the rainfall threshold for initiating debris flows decreases following a wildfire, such that an ordinary rainstorm is able to trigger a severe

  6. A real two-phase submarine debris flow and tsunami

    SciTech Connect

    Pudasaini, Shiva P.; Miller, Stephen A.

    2012-09-26

    The general two-phase debris flow model proposed by Pudasaini is employed to study subaerial and submarine debris flows, and the tsunami generated by the debris impact at lakes and oceans. The model, which includes three fundamentally new and dominant physical aspects such as enhanced viscous stress, virtual mass, and generalized drag (in addition to buoyancy), constitutes the most generalized two-phase flow model to date. The advantage of this two-phase debris flow model over classical single-phase, or quasi-two-phase models, is that the initial mass can be divided into several parts by appropriately considering the solid volume fraction. These parts include a dry (landslide or rock slide), a fluid (water or muddy water; e.g., dams, rivers), and a general debris mixture material as needed in real flow simulations. This innovative formulation provides an opportunity, within a single framework, to simultaneously simulate the sliding debris (or landslide), the water lake or ocean, the debris impact at the lake or ocean, the tsunami generation and propagation, the mixing and separation between the solid and fluid phases, and the sediment transport and deposition process in the bathymetric surface. Applications of this model include (a) sediment transport on hill slopes, river streams, hydraulic channels (e.g., hydropower dams and plants); lakes, fjords, coastal lines, and aquatic ecology; and (b) submarine debris impact and the rupture of fiber optic, submarine cables and pipelines along the ocean floor, and damage to offshore drilling platforms. Numerical simulations reveal that the dynamics of debris impact induced tsunamis in mountain lakes or oceans are fundamentally different than the tsunami generated by pure rock avalanches and landslides. The analysis includes the generation, amplification and propagation of super tsunami waves and run-ups along coastlines, debris slide and deposition at the bottom floor, and debris shock waves. It is observed that the

  7. Scaling and design of landslide and debris-flow experiments

    USGS Publications Warehouse

    Iverson, Richard M.

    2015-01-01

    Scaling plays a crucial role in designing experiments aimed at understanding the behavior of landslides, debris flows, and other geomorphic phenomena involving grain-fluid mixtures. Scaling can be addressed by using dimensional analysis or – more rigorously – by normalizing differential equations that describe the evolving dynamics of the system. Both of these approaches show that, relative to full-scale natural events, miniaturized landslides and debris flows exhibit disproportionately large effects of viscous shear resistance and cohesion as well as disproportionately small effects of excess pore-fluid pressure that is generated by debris dilation or contraction. This behavioral divergence grows in proportion to H3, where H is the thickness of a moving mass. Therefore, to maximize geomorphological relevance, experiments with wet landslides and debris flows must be conducted at the largest feasible scales. Another important consideration is that, unlike stream flows, landslides and debris flows accelerate from statically balanced initial states. Thus, no characteristic macroscopic velocity exists to guide experiment scaling and design. On the other hand, macroscopic gravity-driven motion of landslides and debris flows evolves over a characteristic time scale (L/g)1/2, where g is the magnitude of gravitational acceleration and L is the characteristic length of the moving mass. Grain-scale stress generation within the mass occurs on a shorter time scale, H/(gL)1/2, which is inversely proportional to the depth-averaged material shear rate. A separation of these two time scales exists if the criterion H/L < < 1 is satisfied, as is commonly the case. This time scale separation indicates that steady-state experiments can be used to study some details of landslide and debris-flow behavior but cannot be used to study macroscopic landslide or debris-flow dynamics.

  8. Vulnerability Assessment of Rainfall-Induced Debris Flow

    NASA Astrophysics Data System (ADS)

    Lu, G. Y.; Wong, D. W.; Chiu, L. S.

    2006-05-01

    Debris flow is a common hazard triggered by large amount of rainfall over mountainous areas. A debris flow event results from a complex interaction between rainfall and topographical properties of watersheds. Heavy rainfall facilitates this process by increasing pore water pressure, seepage force and reducing effective stress of soils (normal stress carried by soil particles at the points of contact). Since debris flow events are closely related to topography and rainfall, the goal of this research is to assess debris flow vulnerability related to these two factors. Objectives of this research are to: (1) examine new spatial interpolation techniques to estimate high spatial rainfall data relevant to debris flows. (2) develop topographical factors using Geography Information System (GIS) and remote sensing (RS) approaches and (3) combine the estimated rainfall and topographical factors to assess the vulnerability of debris flow. We examined three spatial interpolation techniques: adaptive inversed distance weight (AIDW), simple kriging and spatial disaggregation using wind induced-topographic effect that incorporates gauge measurements, satellite remote sensing data (TRMM). The topographical factors are derived from high resolution digital elevation model (DEM), and adopt fuzzy-based topographical models proposed by Tseng (2004). Estimated rainfall and topographical factors are processed by self-organizing maps (SOM) to provide vulnerability assessment. To demonstrate our technique, rainfall data collected by 39 rain gauges in the central part of Taiwan during the passage of Typhoon Tori-Ji around July 29, 2001 were used. Results indicate that the proposed spatial interpolation methods outperform existing methods (i.e. kriging, inverse distance weight, and co-kriging methods). The vulnerability assessment of 187 debris flows watersheds in the study area will be presented. Keyword: Debris flow, spatial interpolation, adaptive inverse distance weight, TRMM, self

  9. High-density turbidity currents: Are they sandy debris flows?

    SciTech Connect

    Shanmugam, G.

    1996-01-01

    Conventionally, turbidity currents are considered as fluidal flows in which sediment is supported by fluid turbulence, whereas debris flows are plastic flows in which sediment is supported by matrix strength, dispersive pressure, and buoyant lift. The concept of high-density turbidity current refers to high-concentration, commonly non-turbulent, flows of fluids in which sediment is supported mainly by matrix strength, dispersive pressure, and buoyant lift. The conventional wisdom that traction carpets with entrained turbulent clouds on top represent high-density turbidity currents is a misnomer because traction carpets are neither fluidal nor turbulent. Debris flows may also have entrained turbulent clouds on top. The traction carpet/debris flow and the overriding turbulent clouds are two separate entities in terms of flow rheology and sediment-support mechanism. In experimental and theoretical studies, which has linked massive sands and floating clasts to high-density turbidity currents, the term high-density turbidity current has actually been used for laminar flows. In alleviating this conceptual problem, sandy debris flow is suggested as a substitute for high-density turbidity current. Sandy debris flows represent a continuous spectrum of processes between cohesive and cohesionless debris flows. Commonly they are rheologically plastic. They may occur with or without entrained turbulent clouds on top. Their sediment-support mechanisms include matrix strength, dispersive pressure, and buoyant lift. They are characterized by laminar flow conditions, a moderate to high grain concentration, and a low to moderate mud content. Although flows evolve and transform during the course of transport in density-stratified flows, the preserved features in a deposit are useful to decipher only the final stages of deposition. At present, there are no established criteria to decipher transport mechanism from the depositional record.

  10. Dynamics of unusual debris flows on Martian sand dunes

    NASA Astrophysics Data System (ADS)

    Miyamoto, Hideaki; Dohm, James M.; Baker, Victor R.; Beyer, Ross A.; Bourke, Mary

    2004-07-01

    Gullies that dissect sand dunes in Russell impact crater often display debris flow-like deposits in their distal reaches. The possible range of both the rheological properties and the flow rates are estimated using a numerical simulation code of a Bingham plastic flow to help explain the formation of these features. Our simulated results are best explained by a rapid debris flow. For example, a debris flow with the viscosity of 102 Pa s and the yield strength of 102 Pa can form the observed deposits with a flow rate of 0.5 m3/s sustained over several minutes and total discharged water volume on the order of hundreds of cubic meters, which may be produced by melting a surface layer of interstitial ice within the dune deposits to several centimeters depth.

  11. [Relations of landslide and debris flow hazards to environmental factors].

    PubMed

    Zhang, Guo-ping; Xu, Jing; Bi, Bao-gui

    2009-03-01

    To clarify the relations of landslide and debris flow hazards to environmental factors is of significance to the prediction and evaluation of landslide and debris flow hazards. Base on the latitudinal and longitudinal information of 18431 landslide and debris flow hazards in China, and the 1 km x 1 km grid data of elevation, elevation difference, slope, slope aspect, vegetation type, and vegetation coverage, this paper analyzed the relations of landslide and debris flow hazards in this country to above-mentioned environmental factors by the analysis method of frequency ratio. The results showed that the landslide and debris flow hazards in China more occurred in lower elevation areas of the first and second transitional zones. When the elevation difference within a 1 km x 1 km grid cell was about 300 m and the slope was around 30 degree, there was the greatest possibility of the occurrence of landslide and debris hazards. Mountain forest land and slope cropland were the two land types the hazards most easily occurred. The occurrence frequency of the hazards was the highest when the vegetation coverage was about 80%-90%.

  12. What is the velocity profile of debris flows?

    NASA Astrophysics Data System (ADS)

    Walter, Fabian; McArdell, Brian

    2015-04-01

    The distribution of flow velocity within a debris flow is difficult to determine at full scale in the field due to the large forces and inherently destructive nature of the flow. However, knowledge of the distribution of velocity within a flow would be helpful to constrain rheological models and to better understand the internal dynamics of such flows. Here we describe recent efforts to determine the velocity of debris flows as a function of distance from the channel bed. Measurements were made at the Illgraben, Switzerland, which exhibits a wide variety of flows, ranging from turbulent debris floods to flows which resemble laminar mud flows to more classical debris flows with a clear granular front. The Illgraben observation station is therefore an ideal location to investigate debris flow dynamics. Our measurements were made using sensors embedded on a 14 m long, 2.5 m tall steel-reinforced concrete wall constructed flush with the torrent channel walls. The main instrumentation consists of 18 geophones (10 Hz natural frequency) installed on square steel plates with a side length of 0.3 m. Each steel plate is acoustically isolated from the wall and the other plates through the use of elastomer elements. The geophone plates are arranged in six rows of three sensors with a dimension of 1.8 m in the vertical direction and 1.5 m in the horizontal direction (i.e. parallel to the flow direction). A sensorless plate separates each plate in the horizontal direction. The data are collected at 2 kHz using a high-speed (synchronous) capture card in a pc. The elevation of the flow surface is determined at a cross-stream distance 1 m away from the wall, using a laser sensor installed on a bridge above the wall. We present a processing approach for the geophone data with the goal to track particle sliding across the sensor plates. For signals near or above the sensors' natural frequency (10 Hz), the measured time series are poorly correlated between sensors. Therefore, we use a

  13. Debris-flow observations in the Zermatt Valley

    NASA Astrophysics Data System (ADS)

    Graf, Christoph

    2015-04-01

    In the Alps, a multitude of unstable slopes is located at altitudes of ~2700 m asl, where sediment transfers typically happen outside the range of humans or their infrastructure. The situation is slightly different in the Zermatt Valley, a high-elevation, north-south oriented glacial valley in the Swiss Alps, where the detachment of melting permafrost results in rock falls on steep slopes and debris flows in high-gradient gullies through which till is transferred directly to the inhabited valley floor at elevations between 1100 (N) and 1600 m asl (S). As a result of the excellent database on past disasters in the valley, recent developments and measurements in the local rock glacier bodies and current torrential events, I show data from some debris-flow torrents to document impacts of past, ongoing and possible future changes of debris flows originating from periglacial environments. Debris flows are typically initiated by the abrupt input of considerable quantities of water. The water-saturated masses of fragmented rock and soil slump down mountainsides into gullies which in turn mobilize stored sediment in the channels. In addition to triggering by extreme rainstorms, debris flows have also been reported to be released by rapid snowmelt, rain-on-snow storms, or the sudden emptying of glacier water bodies or through the rupture of landslide dams. More frequently, debris flows occur as a result of high-intensity, convective rainstorms of short duration or low-intensity advective precipitation events over several days. Displacement rates and instability of rock glaciers have increased further recently to show movement rates without historical precedents. At Grabengufer (Dorfbach) e.g., increasing air and ice temperatures have favoured the development of annual displacement rates from just a few decimetres in the past decades to 80 m in 2010. Similar behaviour was observed in catchments nearby. As a consequence of the enhanced movement of these permafrost bodies and

  14. Use of acoustic monitoring system for debris flow discharge evaluation

    NASA Astrophysics Data System (ADS)

    Galgaro, A. G.; Tecca, P. R.; Genevois, R.; Deganutti, A. M.

    2003-04-01

    In 1997 an automated system for monitoring of debris flows has been installed in the Acquabona channel Dolomites, Italy. Induction geophones, with a specific frequency of 10 Hz, measure the amplitude of vertical ground vibrations generated by the passage of a flowing mass along the channel. Continuous acoustic logs and ultrasonic hydrograph recorded at the lower-channel measurement station for the debris flow of August 17, 1998, show a striking correspondence. This correspondence, already observed in different flow sites, is represented by the best fit between flow depth and flow sensor amplitude. Average front velocity for surges, calculated from the signal peak time shift and the distance between the sensors along the flow path, range between 2.00 and 7.7 m/s. As the ultrasonic sensor provides a way to measure the variation of the flow section area with the flow depth, the debris flow peak discharge may be estimated; obtained values of debris flow peak discharge range from 4 and 30 m3/s. Volumes were calculated by integrating instantaneous discharges through the hydrograph and by integrating the geophone log (acoustic flux). Volumes of 13700 m3 and 15500 m3 have been respectively obtained. The slight difference between the two values may result from the fact that acoustic records: i) are sensitive to the high frequencies, typical of the debris flow tails; ii) sum up the contributions sent by the whole flowing mass, while the ecometer detect the flow depth at every time at only one section. As a consequence the rising of the whole geophone log gives a higher value at the integration result. This only acoustic system can give a reasonably proxy for discharge and total volumes involved, which are among the most important parameters for debris flow hazard assessment and planning countermeasures. This methodology can be used in other debris flow sites if they are calibrated by the acoustic characterization of debris, obtained by both seismic surveys and SPT tests, and

  15. Field observations of a debris flow event in the Dolomites

    NASA Astrophysics Data System (ADS)

    Berti, Matteo; Genevois, Rinaldo; Simoni, Alessandro; Tecca, Pia Rosella

    1999-09-01

    A debris flow event occurred in June 1997 in the Dolomites (Eastern Alps, Italy). The phenomenon was directly observed in the field and recorded by a video camera near its initiation area. The debris flow originated shortly after an intense rainstorm (25 mm in 30 min) whose runoff mobilised the loose coarse debris that filled the bottom of the channel in its upper part. The analysis of the steep headwater basin indicates a very short concentration time (9-14 min) that fits the quick hydrological response observed in the field. The debris flow mobilisation was not contemporaneous with the arrival of the peak water discharge in the initiation area probably due to the time required for the saturation of the highly conductive channel-bed material. Channel cross-section measurements taken along the flow channel indicate debris flow peak velocity and discharge ranging from 3.1 to 9.0 m/s and from 23 to 71 m 3/s, respectively. Samples collected immediately after deposition were used to determine the water content and bulk density of the material. Channel scouring, fines enrichment and transported volume increase testify erosion and entrainment of material along the flow channel. Field estimates of the rheological properties based on open channel flow of Bingham fluid indicate a yield strength of 5000±400 Pa and relatively low viscosity (60-326 Pa s), probably due to a high percentage of fines (approx. 30%).

  16. Estimating rates of debris flow entrainment from ground vibrations

    NASA Astrophysics Data System (ADS)

    Kean, J. W.; Coe, J. A.; Coviello, V.; Smith, J. B.; McCoy, S. W.; Arattano, M.

    2015-08-01

    Debris flows generate seismic waves as they travel downslope and can become more dangerous as they entrain sediment along their path. We present field observations that show a systematic relation between the magnitude of seismic waves and the amount of erodible sediment beneath the flow. Specifically, we observe that a debris flow traveling along a channel filled initially with sediment 0.34 m thick generates about 2 orders of magnitude less spectral power than a similar-sized flow over the same channel without sediment fill. We adapt a model from fluvial seismology to explain this observation and then invert it to estimate the level of bed sediment (and rate of entrainment) beneath a passing series of surges. Our estimates compare favorably with previous direct measurements of entrainment rates at the site, suggesting the approach may be a new indirect way to obtain rare field constraints needed to test models of debris flow entrainment.

  17. Emerging insights into the dynamics of submarine debris flows

    NASA Astrophysics Data System (ADS)

    Elverhøi, A.; Issler, D.; de Blasio, F. V.; Ilstad, T.; Harbitz, C. B.; Gauer, P.

    2005-08-01

    Recent experimental and theoretical work on the dynamics of submarine debris flows is summarized. Hydroplaning was first discovered in laboratory flows and later shown to likely occur in natural debris flows as well. It is a prime mechanism for explaining the extremely long runout distances observed in some natural debris flows even of over-consolidated clay materials. Moreover, the accelerations and high velocities reached by the flow head in a short time appear to fit well with the required initial conditions of observed tsunamis as obtained from back-calculations. Investigations of high-speed video recordings of laboratory debris flows were combined with measurements of total and pore pressure. The results are pointing towards yet another important role of ambient water: Water that intrudes from the water cushion underneath the hydroplaning head and through cracks in the upper surface of the debris flow may drastically soften initially stiff clayey material in the "neck" of the flow, where significant stretching occurs due to the reduced friction at the bottom of the hydroplaning head. This self-reinforcing process may lead to the head separating from the main body and becoming an "outrunner" block as clearly observed in several natural debris flows. Comparison of laboratory flows with different material composition indicates a gradual transition from hydroplaning plug flows of stiff clay-rich material, with a very low suspension rate, to the strongly agitated flow of sandy materials that develop a pronounced turbidity current. Statistical analysis of the great number of distinguishable lobes in the Storegga slide complex reveals power-law scaling behavior of the runout distance with the release mass over many orders of magnitude. Mathematical flow models based on viscoplastic material behavior (e.g. BING) successfully reproduce the observed scaling behavior only for relatively small clay-rich debris flows while granular (frictional) models fail at all scales

  18. Traking of Laboratory Debris Flow Fronts with Image Analysis

    NASA Astrophysics Data System (ADS)

    Queiroz de Oliveira, Gustavo; Kulisch, Helmut; Fischer, Jan-Thomas; Scheidl, Christian; Pudasaini, Shiva P.

    2015-04-01

    Image analysis technique is applied to track the time evolution of rapid debris flow fronts and their velocities in laboratory experiments. These experiments are parts of the project avaflow.org that intends to develop a GIS-based open source computational tool to describe wide spectrum of rapid geophysical mass flows, including avalanches and real two-phase debris flows down complex natural slopes. The laboratory model consists of a large rectangular channel 1.4m wide and 10m long, with adjustable inclination and other flow configurations. The setup allows investigate different two phase material compositions including large fluid fractions. The large size enables to transfer the results to large-scale natural events providing increased measurement accuracy. The images are captured by a high speed camera, a standard digital camera. The fronts are tracked by the camera to obtain data in debris flow experiments. The reflectance analysis detects the debris front in every image frame; its presence changes the reflectance at a certain pixel location during the flow. The accuracy of the measurements was improved with a camera calibration procedure. As one of the great problems in imaging and analysis, the systematic distortions of the camera lens are contained in terms of radial and tangential parameters. The calibration procedure estimates the optimal values for these parameters. This allows us to obtain physically correct and undistorted image pixels. Then, we map the images onto a physical model geometry, which is the projective photogrammetry, in which the image coordinates are connected with the object space coordinates of the flow. Finally, the physical model geometry is rewritten in the direct linear transformation form, which allows for the conversion from one to another coordinate system. With our approach, the debris front position can then be estimated by combining the reflectance, calibration and the linear transformation. The consecutive debris front

  19. Propagation and deposition of stony debris flows at channel confluences

    NASA Astrophysics Data System (ADS)

    Stancanelli, L. M.; Lanzoni, S.; Foti, E.

    2015-07-01

    The fluid dynamics of stony debris flows generated in two small tributaries adjacent to each other and flowing into a main receiving channel was analyzed experimentally at a laboratory scale. The analysis on the propagation along the tributaries and deposition in the main channel provide information about sediment-water mobility, dangerous damming, and potential hazard. Debris flows were generated by releasing a preset water discharge over an erodible layer of saturated gravels material. As a consequence, the debris flow sediment concentration varied accordingly to the entrainment rate which, in turn, was strongly controlled by the tributary slope. The data collected by acoustic level sensors, pore fluid pressure transducers, and a load cell were used to characterize the evolution of bulk density and solid concentration of the sediment-water mixture. These two parameters were relevant to assess the stony debris flow mobility which contributes to determine the shape of sediment deposits in the main channel. The detailed bed topography surveys carried out in the main channel at the end of each experiment provided information on the morphology of these deposits and on the interplay of adjacent confluences. The influences of confluence angle, tributary slopes, and triggering conditions have been investigated, for a total of 18 different configurations. Within the investigated range of parameters, the slope angle was the parameter that mainly influences the stony debris flow mobility while, for adjacent confluences, the degree of obstruction within the receiving channel was strongly influenced by the triggering scenario.

  20. Generation of Martian chaos and channels by debris flows

    NASA Astrophysics Data System (ADS)

    Nummedal, D.; Prior, D. B.

    1981-01-01

    A debris flow mechanism is proposed to account for the formation of chaos and the large channels debouching into Crysae Planitia from the adjacent southern uplands of Mars. Based on considerations of the juxtaposition of individual channel environments, the morphological assemblages within each environment and flow dynamics, it is suggested that the debris flows were triggered by the large-scale failure of subsurface sediments, possibly initiated by a seismic event. During the initial, slow-moving phase of the flow, the debris would have formed gently sinuous channels with multiple side-wall slumps, grooves and ridges, and elongate erosional remnants. The flow would have gained mobility as the debris moved downslope, producing travel distances greatly in excess of those characteristic of terrestrial examples, and eroded, streamlined remnants at the distal reaches of the channel. Finally, due to internal and boundary friction, the flow would have been slowed down once it entered the Chryse plains, resulting in a thin debris blanket with no depositional relief.

  1. SATURATED ZONE FLOW AND TRANSPORT MODEL ABSTRACTION

    SciTech Connect

    B.W. ARNOLD

    2004-10-27

    The purpose of the saturated zone (SZ) flow and transport model abstraction task is to provide radionuclide-transport simulation results for use in the total system performance assessment (TSPA) for license application (LA) calculations. This task includes assessment of uncertainty in parameters that pertain to both groundwater flow and radionuclide transport in the models used for this purpose. This model report documents the following: (1) The SZ transport abstraction model, which consists of a set of radionuclide breakthrough curves at the accessible environment for use in the TSPA-LA simulations of radionuclide releases into the biosphere. These radionuclide breakthrough curves contain information on radionuclide-transport times through the SZ. (2) The SZ one-dimensional (I-D) transport model, which is incorporated in the TSPA-LA model to simulate the transport, decay, and ingrowth of radionuclide decay chains in the SZ. (3) The analysis of uncertainty in groundwater-flow and radionuclide-transport input parameters for the SZ transport abstraction model and the SZ 1-D transport model. (4) The analysis of the background concentration of alpha-emitting species in the groundwater of the SZ.

  2. Debris flow hazard assessment for the Oregon Caves National Monument

    USGS Publications Warehouse

    Friday, John

    1983-01-01

    After experiencing a devastating debris flow in the Oregon Caves National Monument, the National Park Service needs an evaluation of the hazard of additional flows. Soil properties at six random sites were compared with those at the source of the debris flow. Although all sites had soils that could become unstable with sufficient moisture, soil at one site had properties similar to those at the scar and the potential for another flow was confirmed. The report suggests that winter weather conditions be closely monitored and compared to the antecedent conditions prior to the known failure. When the threshold for additional mass wasting is believed imminent, appropriate action can be taken to insure the safety of work personnel and the public. The peak streamflow that preceded the 5,200 cu yds of debris is estimated to have a 0.5 percent chance of being equaled or exceeded in any given year. (USGS)

  3. Rainfall Generated Debris flows on Mount Shasta: July 21, 2015

    NASA Astrophysics Data System (ADS)

    Mikulovsky, R. P.; De La Fuente, J. A.; Courtney, A.; Bachmann, S.; Rodriguez, H.; Rust, B.; Schneider, F.; Veich, D.

    2015-12-01

    Convective storms on the evening of July 21, 2015 generated a number of debris flows on the SE flank of Mount Shasta Volcano, Shasta-Trinity National Forest. Widespread rilling, gullying and sheet erosion occurred throughout the affected area. These storms damaged roads by scouring drainage ditches, blocking culverts, eroding road prisms, and depositing debris where streams emerged from their incised channels and flowed over their alluvial fans. Effects were limited geographically to a narrow band about 6 miles wide trending in a northeasterly direction. Debris flows were identified at Pilgrim Creek and nearby channels, and Mud Creek appears to have experienced sediment laden flows rather than debris flows. Doppler radar data reveal that the storm cells remained nearly stationary for two hours before moving in a northeasterly direction. Debris flows triggered by convective storms occur often at Mount Shasta, with a similar event recorded in 2003 and a larger one in 1935, which also involved glacial melt. The 1935 debris flow at Whitney Creek buried Highway 97 north of Weed, CA, and took out the railroad above the highway. In September, 2014, a large debris flow occurred in Mud Creek, but it was associated solely with glacial melt and was not accompanied by rain. The 2014 event at Mud Creek filled the channel and parts of the floodplain with debris. This debris was in turn reworked and eroded by sediment laden flows on July 21, 2015. This study was initiated in August, 2015, and began with field inventories to identify storm effects. Lidar data will be used to identify possible avulsion points that could result in unexpected flash flooding outside of the main Mud Creek channel and on adjacent streams. The results of this study will provide critical information that can be used to assess flash flood risk and better understand how to manage those risks. Finally, some conclusions may be drawn on the kinds of warning systems that may be appropriate for possible flash

  4. Mount Baker lahars and debris flows, ancient, modern, and future

    USGS Publications Warehouse

    Tucker, David S; Scott, Kevin M.; Grossman, Eric E.; Linneman, Scott

    2014-01-01

    Holocene lahars and large debris flows (>106 m3) have left recognizable deposits in the Middle Fork Nooksack valley. A debris flow in 2013 resulting from a landslide in a Little Ice Age moraine had an estimated volume of 100,000 m3, yet affected turbidity for the entire length of the river, and produced a slug of sediment that is currently being reworked and remobilized in the river system. Deposits of smaller-volume debris flows, deposited as terraces in the upper valley, may be entirely eroded within a few years. Consequently, the geologic record of small debris flows such as those that occurred in 2013 is probably very fragmentary. Small debris flows may still have significant impacts on hydrology, biology, and human uses of rivers downstream. Impacts include the addition of waves of fine sediment to stream loads, scouring or burying salmon-spawning gravels, forcing unplanned and sudden closure of municipal water intakes, damaging or destroying trail crossings, extending river deltas into estuaries, and adding to silting of harbors near river mouths.

  5. Debris-flow initiation from large, slow-moving landslides

    USGS Publications Warehouse

    Reid, M.E.; Brien, D.L.; LaHusen, R.G.; Roering, J.J.; de la Fuente, J.; Ellen, S.D.

    2003-01-01

    In some mountainous terrain, debris flows preferentially initiate from the toes and margins of larger, deeper, slower-moving landslides. During the wet winter of 1997, we began real-time monitoring of the large, active Cleveland Corral landslide complex in California, USA. When the main slide is actively moving, small, shallow, first-time slides on the toe and margins mobilize into debris flows and travel down adjacent gullies. We monitored the acceleration of one such failure; changes in velocity provided precursory indications of rapid failure. Three factors appear to aid the initiation of debris flows at this site: 1) locally steepened ground created by dynamic landslide movement, 2) elevated pore-water pressures and abundant soil moisture, and 3) locally cracked and dilated materials. This association between debris flows and large landslides can be widespread in some terrain. Detailed photographic mapping in two watersheds of northwestern California illustrates that the areal density of debris-flow source landsliding is about 3 to 7 times greater in steep geomorphically fresher landslide deposits than in steep ground outside landslide deposits. ?? 2003 Millpress.

  6. Debris-flow initiation experiments using diverse hydrologic triggers

    USGS Publications Warehouse

    Reid, Mark E.; LaHusen, Richard G.; Iverson, Richard M.

    1997-01-01

    Controlled debris-flow initiation experiments focused on three hydrologic conditions that can trigger slope failure: localized ground-water inflow; prolonged moderate-intensity rainfall; and high-intensity rainfall. Detailed monitoring of slope hydrology and deformation provided exceptionally complete data on conditions preceding and accompanying slope failure and debris-flow mobilization. Ground-water inflow and high-intensity sprinkling led to abrupt, complete failure whereas moderate-intensity sprinkling led to retrogressive, block-by-block failure. Failure during ground-water inflow and during moderate-intensity sprinkling occurred with a rising water table and positive pore pressures. Failure during high-intensity sprinkling occurred without widespread positive pore pressures. In all three cases, pore pressures in most locations increased dramatically (within 2-3 seconds) during failure. In some places, pressures in unsaturated materials rapidly 'flashed' from zero to elevated positive values. Transiently elevated pore pressures and partially liquefied soil enhanced debris-flow mobilization.

  7. Granular Dilatancy and its Effect on Debris-flow Dynamics

    NASA Astrophysics Data System (ADS)

    Iverson, R. M.; George, D. L.

    2012-12-01

    Landslides and debris flows commonly exhibit the effects of variable granular dilatancy, but incorporation of these effects in predictive models of debris-flow dynamics has been lacking. We have developed a depth-averaged model of debris-flow initiation and motion that includes the effects of variable dilatancy without stipulating its influence on rheology. Instead, the apparent rheology of Coulomb-frictional debris evolves during coupled evolution of the grain concentration m, basal pore-fluid pressure, flow thickness, and flow velocity. The dilatancy angle ψ plays an intermediary role in this evolution and obeys the simple relationship tan ψ = m-meq, where meq is the grain concentration in equilibrium with the ambient stress state and flow rate. Results of recent stress-controlled rheometric experiments by Boyer et al. (DOI: 10.1103/PhysRevLett.107.188301) provide our basis for estimating meq. Relaxation of m toward meq, coupled with evolution of pore pressure, allows our model to simulate a smooth transition from static limiting equilibrium of slopes to disequilibrium flow dynamics. Use of variable friction coefficients or dam-break initial conditions is unnecessary. We have evaluated predictions of our model in three ways: (1) by examining physical implications of exact solutions of simplified model equations, (2) by comparing numerical solutions with results of controlled experiments at the USGS debris-flow flume, and (3) by comparing numerical predictions with the behavior of a large (~50 million m3) debris flow that occurred at Mt. Meager, British Columbia, in 2010. Model predictions depend mostly on initial conditions, flow-path topography, and the value of a single dimensionless parameter that represents the ratio of two key timescales. One timescale governs downslope, gravity-driven motion of debris, and the other governs pore-pressure diffusion. Values of these timescales are readily calculated from source-area geometry and standard geotechnical

  8. Simulated tornado debris tracks: implications for inferring corner flow structure

    NASA Astrophysics Data System (ADS)

    Zimmerman, Michael; Lewellen, David

    2011-11-01

    A large collection of three-dimensional large eddy simulations of tornadoes with fine debris have been recently been performed as part of a longstanding effort at West Virginia University to understand tornado corner flow structure and dynamics. Debris removal and deposition is accounted for at the surface, in effect simulating formation of tornado surface marks. Physical origins and properties of the most prominent marks will be presented, and the possibility of inferring tornado corner flow structure from real marks in the field will be discussed. This material is based upon work supported by the National Science Foundation under Grants No. 0635681 and AGS-1013154.

  9. Effects of the Basal Boundary on Debris-flow Dynamics

    NASA Astrophysics Data System (ADS)

    Iverson, R. M.; Logan, M.; Lahusen, R. G.; Berti, M.

    2006-12-01

    Data aggregated from 37 large-scale experiments reveal some counterintuitive effects of bed roughness on debris-flow dynamics. In each experiment 10 m3 of water-saturated sand and gravel, mixed with 1 to 12% silt and clay by dry weight, was abruptly released from a gate at the head of a 2-m wide, 1.2-m deep, 82.5-m long rectangular flume inclined 31° throughout most of its length and adjoined to a gently sloping, planar runout surface at its toe. The flume's basal boundary consisted of either a smooth, planar concrete surface or a concrete surface roughened with a grid of conical bumps. Tilt-table tests with dry debris-flow sediment showed that this roughness imparted a basal friction angle of 38°, comparable to the sediment's internal friction angle of 38-42°, whereas the smooth-bed friction angle was 28°. About 20 electronic sensors installed in the flume yielded data on flow speeds and depths as well as basal stresses and pore pressures. Behavior observed in all experiments included development of steep, unsaturated, coarse-grained debris-flow snouts and tapering, liquefied, fine-grained tails. Flows on the rough bed were typically about 50% thicker and 20% slower than flows on the smooth bed, although the rough bed caused snout steepening that enabled flow fronts to move faster than expected, given the increased bed friction. Moreover, flows on rough beds ran out further than flows on smooth beds owing to enhanced grain-size segregation and lateral levee formation. With the rough bed, measured basal stresses and pore pressures differed little from values expected from static gravitational loading of partially liquefied debris. With the smooth bed, however, measured basal stresses and pore pressures were nearly twice as large as expected values. This anomaly resulted from flow disturbance at the upstream lips of steel plates in which sensors were mounted. The lips produced barely visible ripples in otherwise smooth flow surfaces, yet sufficed to generate

  10. On predicting debris flows in arid mountain belts

    NASA Astrophysics Data System (ADS)

    Stolle, Amelie; Langer, Maria; Blöthe, Jan Henrik; Korup, Oliver

    2015-03-01

    The use of topographic metrics for estimating the susceptibility to, and reconstructing the characteristics of, debris flows has a long research tradition, although largely devoted to humid mountainous terrain. The exceptional 2010 monsoonal rainstorms in the high-altitude mountain desert of Ladakh and Zanskar, NW India, were a painful reminder of how susceptible arid regions are to rainfall-triggered flash floods, landslides, and debris flows. The rainstorms of August 4-6 triggered numerous debris flows, killing 182 people, devastating 607 houses, and more than 10 bridges around Ladakh's capital of Leh. The lessons from this disaster motivated us to revisit methods of predicting (a) flow parameters such as peak discharge and maximum velocity from field and remote sensing data, and (b) the susceptibility to debris flows from catchment morphometry. We focus on quantifying uncertainties tied to these approaches. Comparison of high-resolution satellite images pre- and post-dating the 2010 rainstorm reveals the extent of damage and catastrophic channel widening. Computations based on these geomorphic markers indicate maximum flow velocities of 1.6-6.7 m s- 1 with runout of up to ~ 10 km on several alluvial fans that sustain most of the region's settlements. We estimate median peak discharges of 310-610 m3 s- 1, which are largely consistent with previous estimates. Monte Carlo-based error propagation for a single given flow-reconstruction method returns a variance in discharge similar to one derived from juxtaposing several different flow reconstruction methods. We further compare discriminant analysis, classification tree modelling, and Bayesian logistic regression to predict debris-flow susceptibility from morphometric variables of 171 catchments in the Ladakh Range. These methods distinguish between fluvial and debris flow-prone catchments at similar success rates, but Bayesian logistic regression allows quantifying uncertainties and relationships between potential

  11. Studies of fluid instabilities in flows of lava and debris

    NASA Technical Reports Server (NTRS)

    Fink, Jonathan H.

    1987-01-01

    At least two instabilities have been identified and utilized in lava flow studies: surface folding and gravity instability. Both lead to the development of regularly spaced structures on the surfaces of lava flows. The geometry of surface folds have been used to estimate the rheology of lava flows on other planets. One investigation's analysis assumed that lava flows have a temperature-dependent Newtonian rheology, and that the lava's viscosity decreased exponentially inward from the upper surface. The author reviews studies by other investigators on the analysis of surface folding, the analysis of Taylor instability in lava flows, and the effect of surface folding on debris flows.

  12. Rheological changes induced by clast fragmentation in debris flows

    NASA Astrophysics Data System (ADS)

    Caballero, Lizeth; Sarocchi, Damiano; Soto, Enrique; Borselli, Lorenzo

    2014-09-01

    On the basis of rotating drum analogue experiments, we describe a fragmentation process acting within debris flows during transport and its influence on rheologic behavior. Our hypothesis is based on a detailed textural analysis including granulometry, clast morphology, and rheologic properties of the fluid matrix. Results of the experiments point out that breakage of certain granulometric classes produces fine particles like fine sand and silt. The population growth of fine clasts with time leads to an increase in yield strength and viscosity that progressively modifies the rheologic behavior. From a textural point of view, this is reflected in a bimodal granulometric distribution. Up to now this characteristic has been explained as the effect of bulking and/or sedimentation processes during transport. Our experimental results show that the type of fragmentation depends on particle size and is the consequence of strong clast-clast interaction and clast-fluid interactions. Coarse particles develop small fractures which cause the loss of sharp edges and asperities. Medium-sized particles develop through-going fractures that cause them to break apart. The latter process explains why intermediate granulometric classes progressively diminish with time in debris flows. Analogue experiments enable us to study the efficacy of clast fragmentation in modifying the textural character and flow behavior of debris flows without the influence of external factors such as erosion and sedimentation. The obtained results constitute the base of a new approach for modeling debris flow dynamics.

  13. Pebble orientation on large, experimental debris-flow deposits

    USGS Publications Warehouse

    Major, J.J.

    1998-01-01

    Replicable, pronounced orientation of discoid pebbles (??? 8 mm) embedded on surfaces of large (??? 10 m3) experimental debris-flow deposits reveals that strongly aligned, imbricate fabric can develop rapidly over short distances in mass flows. Pebble long axes aligned subparallel to deposit margins as well as subparallel to margins of surge waves arrested within the deposits. Pebble alignment exhibited modes both parallel to (a(p)), and normal to (a(t)), the primary flow direction; intermediate axes dipped preferentially inward from surge-wave margins (b(i) orientation). Repetitive development of margin-parallel, imbricate fabric distributed across deposit surfaces provides compelling evidence that deposits formed dominantly through progressive incremental accretion rather than through simple en masse emplacement. Pronounced fabric along deposit and arrested surge-wave margins reflects significant grain interaction along flow margins. This sedimentological evidence for significant marginal grain interaction complements theoretical analyses (Iverson, 1997) and other experimental data (Major, 1996: Iverson, 1997) that indicate that resistance along flow margins is an important factor affecting debris-flow deposition. The fabric on the experimental deposits demonstrates that debris flows can develop strongly imbricate particle orientation that mimics fabric developed during fluvial deposition. Particle shape and local stress fields appear to have more control over fabric development than does general depositional process. Other criteria in addition to particle orientation are needed to discriminate mass flow from fluvial gravel deposits and to unravel depositional history. ?? 1998 Elsevier Science B.V. All rights reserved.

  14. Experimental testing of flexible barriers for containment of debris flows

    USGS Publications Warehouse

    DeNatale, Jay S.; Iverson, Richard M.; Major, Jon J.; LaHusen, Richard G.; Fliegel, Gregg L.; Duffy, John D.

    1999-01-01

    In June 1996, six experiments conducted at the U.S. Geological Survey Debris Flow Flume demonstrated that flexible, vertical barriers constructed of wire rope netting can stop small debris flows. All experimental debris flows consisted of water-saturated gravelly sand with less than two percent finer sediment by weight. All debris flows had volumes of about 10 cubic meters, masses of about 20 metre tons, and impact velocities of 5 to 9 meters per second. In four experiments, the debris flow impacted pristine, unreformed barriers of varying design; in the other two experiments, the debris flow impacted barriers already loaded with sediment from a previous flow. Differences in barrier design led to differences in barrier performance. Experiments were conducted with barriers constructed of square-mesh wire-rope netting with 30centimeter, 20centimeter, and 15 centimeter mesh openings as well as 30centimeter diameter interlocking steel rings. In all cases, sediment cascading downslope at the leading edge of the debris flows tended to spray through the nets. Nets fitted with finer-mesh chain link or chicken wire liners contained more sediment than did unlined nets, and a ring net fitted with a synthetic silt screen liner contained nearly 100 percent of the sediment. Irreversible net displacements of up to 2 meters and friction brake engagement on the support and anchor cables dissipated some of the impact energy. However, substantial forces developed in the steel support columns and the lateral and tie-back anchor cables attached to these columns. As predicted by elementary mechanics, the anchor cables experienced larger tensile forces when the support columns were hinged at the base rather than bolted rigidly to the foundation. Measured loads in the lateral anchor cables exceeded those in the tie-back anchor cables and the load cell capacity of 45 kilo-Newtons. Measurements also indicated that the peak loads in the tie- back anchors were highly transient and occurred at

  15. Dendrochronological analysis of debris flow disturbance on Rishiri Island

    NASA Astrophysics Data System (ADS)

    Yoshida, Keiji; Kikuchi, Shun-ich; Nakamura, Futoshi; Noda, Masato

    1997-09-01

    Abies sachalinensis dominates the alluvial fan head of the Ochiushinai Gully on Rishiri Island, Japan. This species is able to adapt to frequent disturbances by debris flows. Even-aged stands composed of A. sachalinensis or Alnus maximowiczii were found along the channel, and standing dead trees buried by debris flows were discovered at the alluvial fan head. We used dendrochronological data in order to analyse the geomorphic history of the fan head. We determined the master ring-width chronology by synchronizing ring-width variations in living trees. This master chronology was used to cross-date the establishment and death of the buried trees. Results indicated that most of the buried trees were established in the 1870s and died in the early 1950s. Further, debris flow was estimated to have occurred in the 1890s and the late 1960s based upon the distribution of even-aged stands seen in aerial photos. The ring-width variations of the trees adjacent to the channel indicate a low correlation for synchronization, while those located on the hillslope have a high correlation. A low correlation in the riparian trees can be attributed to the instability of geomorphic surfaces caused by debris flow disturbances.

  16. Latest Pleistocene-Holocene debris flow activity, Santa Catalina Mountains, Arizona; Implications for modern debris-flow hazards under a changing climate

    NASA Astrophysics Data System (ADS)

    Youberg, Ann M.; Webb, Robert H.; Fenton, Cassandra R.; Pearthree, Philip A.

    2014-08-01

    Hazard mitigation for extreme events such as debris flows requires geologic mapping and chronologic information, particularly for alluvial fans near mountain fronts in the southwestern United States. In July 2006, five consecutive days of monsoonal storms caused hundreds of debris flows in southeastern Arizona, particularly in the southern Santa Catalina Mountains north of Tucson. Before 2006, no historical debris flows from the Santa Catalina Mountains reached the populated mountain front, although abundant evidence of prehistoric debris flows is present on downslope alluvial fans. We used a combination of surficial geologic mapping and 10Be exposure dating to produce a debris-flow history for Pima and Finger Rock Canyons. The largest debris flows, of latest Pleistocene to early Holocene age, covered much of the apices of alluvial fans formed at the mouths of these canyons and extended up to 3 km downslope. These debris-flow deposits were inset against higher and older alluvial surfaces with few debris-flow deposits of late Pleistocene age. The 10Be ages in this study have considerable scatter for surfaces believed to be of uniform age, indicating the dual possibilities of inheritance from previous cosmic-ray exposure, as well as the potential for composite deposits derived from numerous debris flows. We then used an empirical inundation model, LAHARZ, to assess probable magnitudes of the older debris flows to evaluate possible initiation mechanisms. In-channel and terrace storage within the canyons is not sufficient to generate volumes likely needed to produce the larger late Pleistocene to early Holocene debris-flow deposits. The abundance of latest Pleistocene and early Holocene deposits suggests that large debris flows were generated during the instability associated with climate and vegetation changes at the Pleistocene-Holocene transition. Under present watershed conditions with limited sediment supplies, modern debris-flow hazards are generally limited to

  17. Transformation of dilative and contractive landslide debris into debris flows-An example from marin County, California

    USGS Publications Warehouse

    Fleming, R.W.; Ellen, S.D.; Algus, M.A.

    1989-01-01

    The severe rainstorm of January 3, 4 and 5, 1982, in the San Francisco Bay area, California, produced numerous landslides, many of which transformed into damaging debris flows. The process of transformation was studied in detail at one site where only part of a landslide mobilized into several episodes of debris flow. The focus of our investigation was to learn whether the landslide debris dilated or contracted during the transformation from slide to flow. The landslide debris consisted of sandy colluvium that was separable into three soil horizons that occupied the axis of a small topographic swale. Failure involved the entire thickness of colluvium; however, over parts of the landslide, the soil A-horizon failed separately from the remainder of the colluvium. Undisturbed samples were taken for density measurements from outside the landslide, from the failure zone and overlying material from the part of the landslide that did not mobilize into debris flows, and from the debris-flow deposits. The soil A-horizon was contractive and mobilized to flows in a process analogous to liquefaction of loose, granular soils during earthquakes. The soil B- and C-horizons were dilative and underwent 2 to 5% volumetric expansion during landslide movement that permitted mobilization of debris-flow episodes. Several criteria can be used in the field to differentiate between contractive and dilative behavior including lag time between landsliding and mobilization of flow, episodic mobilization of flows, and partial or complete transformation of the landslide. ?? 1989.

  18. Empirical model for the volume-change behavior of debris flows

    USGS Publications Warehouse

    Cannon, S.H.

    1993-01-01

    The potential travel down hillsides; movement stops where the volume-change behavior of flows as they travel down hillsides ; movement stops where the volume of actively flowing debris becomes negligible. The average change in volume over distance for 26 recent debris flows in the Honolulu area was assumed to be a function of the slope over which the debris flow traveled, the degree of flow confinement by the channel, and an assigned value for the type of vegetation through which the debris flow traveled. Analysis of the data yielded a relation that can be incorporated into digital elevation models to characterize debris-flow travel on Oahu.

  19. A study of methods to estimate debris flow velocity

    USGS Publications Warehouse

    Prochaska, A.B.; Santi, P.M.; Higgins, J.D.; Cannon, S.H.

    2008-01-01

    Debris flow velocities are commonly back-calculated from superelevation events which require subjective estimates of radii of curvature of bends in the debris flow channel or predicted using flow equations that require the selection of appropriate rheological models and material property inputs. This research investigated difficulties associated with the use of these conventional velocity estimation methods. Radii of curvature estimates were found to vary with the extent of the channel investigated and with the scale of the media used, and back-calculated velocities varied among different investigated locations along a channel. Distinct populations of Bingham properties were found to exist between those measured by laboratory tests and those back-calculated from field data; thus, laboratory-obtained values would not be representative of field-scale debris flow behavior. To avoid these difficulties with conventional methods, a new preliminary velocity estimation method is presented that statistically relates flow velocity to the channel slope and the flow depth. This method presents ranges of reasonable velocity predictions based on 30 previously measured velocities. ?? 2008 Springer-Verlag.

  20. GIS-based numerical simulations of the July 2014 Nagiso debris flow in Nagano Prefecture, Japan

    NASA Astrophysics Data System (ADS)

    Wang, Chunxiang; Fukuoka, Hiroshi

    2015-04-01

    A debris flow disaster took place in Nagiso, Nagano Prefecture of Japan in the later afternoon of 9 July 2014 triggered by 76 mm torrential rain associated with the typhoon Neoguri. This debris flow killed one resident and completely destroyed several houses. Although the source of the debris flows, especially the origin of their large boulders exceeding 5 m, are not clear, it seems that those debris flows initiated in the two upstream torrents and they joined Nashisawa torrent. Finally the debris flow ran and deposited in the Kiso River. The downstream residents are much aware of the many historical cases on similar debris flow disasters in the torrents in Nagiso and surrounding communities. Most of the residents could evacuate immediately after they felt the ground tremors induced by the running debris flow. Authors used LAHARZ (Schilling 1998) to simulate the Nagiso debris flow using 5-meter resolution Digital Elevation Model and several debris-flow volumes for the calibration. We also performed a numerical simulation to predicting the runout distance and to get insight into the behavior of the debris flow movement. A GIS-based depth-averaged 2D numerical model using a coupled viscous and Coulomb type law is used to simulate a debris flow from initiation to deposition. We compared the two simulation results and suggested the more appropriate coefficients of equations in LAHARZ for calculating the cross sectional area and planimetric area for application to the July 2014 Nagiso debris flows.

  1. Debris Flows Within The Greater Caucasus Northern Slope

    NASA Astrophysics Data System (ADS)

    Panova, S.

    Debris flows are recorded everywhere within the Greater Caucasus northern slope. In last decades studies of debris flows appeared to be very important due to an intensive anthropogenic activity in the mountainous areas. Debris flow spatial distribution, as well as their genesis and means of protection are critical, too. The studied terri- tory has significant absolute altitudes, especially in the central and eastern parts. Also large amount of atmospheric precipitation with maximum in a warm period is typical for the region. Modern glaciation with soil-covered moraine deposits of modern and Holocene age is developed in the region. Geological and geomorphological conditions lead to debris flows formation within the entire territory. However, the amount of atmospheric precipitation drastically decreases from west to east and in the eastern part (Dagestan) debris flow is less active than in the central even under the presence of enormous amounts of loose detrital material of different genesis. In the western part debris flows are less developed due to insignificant altitudes and considerable forest coverage and soil-cover. Powerful modern glaciation with vast development of purely moraine and fluvial-glacial deposits results in intensive debris flow activity in the central part of the northern slope (the Terek river basin). In the upper reaches of all the Terek tributaries moraine deposits reach up to several dozen meters. They are widespread at altitudes higher than 2000 m (above the forest boundary) and almost everywhere uncovered by soils. They are a key source of sediments under debris flow formation. Within the Greater Caucasus northern slope there are 1700 debris flow basins with the total area about 7000 km2. Their average area is 4.0 km2 with minimum 0.20 km2 and maximum 173.8 km2. Moreover, there are many riverbeds in the area where form mountain mud floods more than 3000 km long. Debris flows occur between January and October with clear altitudinal zoning

  2. Flood and Debris Flow Hazard Predictions in Steep, Burned Landscapes

    NASA Astrophysics Data System (ADS)

    Rengers, Francis; McGuire, Luke; Kean, Jason; Staley, Dennis

    2016-04-01

    Post-wildfire natural hazards such as flooding and debris flows threaten infrastructure and can even lead to loss of life. The risk from these natural hazards could be reduced if floods and debris flows could be predicted from modeling. Our ability to test predictive models is primarily constrained by a lack of observational data that can be used for comparison with model predictions. Following the 2009 Station Fire in the San Gabriel Mountains, CA, USA, we conducted a study with high-resolution topography and hydrologic measurements to test the effectiveness of two different hydrologic routing models to predict flood and debris flow timing. Our research focuses on comparing the performance of two hydrologic models with differing levels of complexity and efficiency using high-resolution, lidar-derived digital elevation models. The simpler model uses the kinematic wave approximation to route flows, while the more complex model uses the full shallow water equations. In both models precipitation is spatially uniform and infiltration is simulated using the Green-Ampt infiltration equation. Input data for the numerical models was constrained by time series data of soil moisture, and rainfall collected at field sites as well as high-resolution lidar-derived digital elevation models. We ran the numerical models and varied parameter values for the roughness coefficient and hydraulic conductivity. These parameter values were calibrated by minimizing the difference between the simulated and observed flow timing. Moreover, the two parameters were calibrated in two different watersheds, spanning two orders of magnitude in drainage area. The calibrated parameters were subsequently used to model a third watershed, and the results show a good match with observed timing of flow peaks for both models. Calibrated roughness coefficients are generally higher when using the kinematic wave approximation relative to the full shallow water equations, and decrease with increasing spatial

  3. Debris flows in Grand Canyon National Park, Arizona: magnitude, frequency and effects on the Colorado River

    USGS Publications Warehouse

    Melis, Theodre S.; Webb, Robert H.; ,

    1993-01-01

    Debris flows are recurrent sediment-transport processes in 525 tributaries of the Colorado River in Grand Canyon. Arizona. Initiated by slope failures in bedrock and (or) colluvium during intense rainfall, Grand Canyon debris flows are high-magnitude, short-duration floods. Debris flows in these tributaries transport very large boulders into the river where they accumulate on debris fans and form rapids. The frequency of debris flows range from less than 1 per century to 10 or more per century in these tributaries. Before regulation by Glen Canyon Dam in 1963, high-magnitude floods on the Colorado River reworked debris fans by eroding all particles except large boulders. Because flow regulation has substantially decreased the river's competence, debris flows occurring after 1963 have increased accumulation of finer-grained sediments on debris fans and in rapids.

  4. Effects of debris flow composition on runout, depositional mechanisms, and deposit morphology in laboratory experiments

    NASA Astrophysics Data System (ADS)

    Haas, Tjalling; Braat, Lisanne; Leuven, Jasper R. F. W.; Lokhorst, Ivar R.; Kleinhans, Maarten G.

    2015-09-01

    Predicting debris flow runout is of major importance for hazard mitigation. Apart from topography and volume, runout distance and area depends on debris flow composition and rheology, but how is poorly understood. We experimentally investigated effects of composition on debris flow runout, depositional mechanisms, and deposit geometry. The small-scale experimental debris flows were largely similar to natural debris flows in terms of flow behavior, deposit morphology, grain size sorting, channel width-depth ratio, and runout. Deposit geometry (lobe thickness and width) in our experimental debris flows is largely determined by composition, while the effects of initial conditions of topography (i.e., outflow plain slope and channel slope and width) and volume are negligible. We find a clear optimum in the relations of runout with coarse-material fraction and clay fraction. Increasing coarse-material concentration leads to larger runout. However, excess coarse material results in a large accumulation of coarse debris at the flow front and enhances diffusivity, increasing frontal friction and decreasing runout. Increasing clay content initially enhances runout, but too much clay leads to very viscous flows, reducing runout. Runout increases with channel slope and width, outflow plain slope, debris flow volume, and water fraction. These results imply that debris flow runout depends at least as much on composition as on topography. This study improves understanding of the effects of debris flow composition on runout and may aid future debris flow hazard assessments.

  5. Internal characteristics of refractive-index matched debris flows

    NASA Astrophysics Data System (ADS)

    Gollin, Devis; Bowman, Elisabeth; Sanvitale, Nicoletta

    2016-04-01

    Debris flows are channelized masses of granular material saturated with water that travel at high speeds downslope. Their destructive character represents a hazard to lives and properties, especially in regions of high relief and runoff. The characteristics that distinguish their heterogeneous, multi-phase, nature are numerous: non-uniform surge formation, particle size ranging from clay to boulders, flow segregation with larger particles concentrating at the flow front and fluid at the tail making the composition and volume of the bulk varying with time and space. These aspects render these events very difficult to characterise and predict, in particular in the area of the deposit spread or runout - zones which are generally of most interest in terms of human risk. At present, considerable gaps exist in our understanding of the flow dynamics of debris flows, which originates from their complex motion and relatively poor observations available. Flume studies offer the potential to examine in detail the behaviour of model debris flows, however, the opaque nature of these flows is a major obstacle in gaining insight of their internal behaviour. Measurements taken at the sidewalls may be poorly representative leading to incomplete or misleading results. To probe internally to the bulk of the flow, alternative, nonintrusive techniques can be used, enabling, for instance, velocities and solid concentrations within the flowing material to be determined. We present experimental investigations into polydisperse granular flows of spherical immersed particles down an inclined flume, with specific attention directed to their internal behavior. To this end, the refractive indices of solids and liquid are closely matched allowing the two phases to be distinguished. Measurements are then made internally at a point in the channel via Plane Laser Induced Fluorescence, Particle Tracking Velocimetry, PTV and Particle Image Velocimetry, PIV. The objective is to to increase our

  6. Contrasting rainfall generated debris flows from adjacent watersheds at Forest Falls, southern California, USA

    USGS Publications Warehouse

    Morton, D.M.; Alvarez, R.M.; Ruppert, K.R.; Goforth, B.

    2008-01-01

    Debris flows are widespread and common in many steeply sloping areas of southern California. The San Bernardino Mountains community of Forest Falls is probably subject to the most frequently documented debris flows in southern California. Debris flows at Forest Falls are generated during short-duration high-intensity rains that mobilize surface material. Except for debris flows on two consecutive days in November 1965, all the documented historic debris flows have occurred during high-intensity summer rainfall, locally referred to as 'monsoon' or 'cloudburst' rains. Velocities of the moving debris range from about 5??km/h to about 90??km/h. Velocity of a moving flow appears to be essentially a function of the water content of the flow. Low velocity debris flows are characterized by steep snouts that, when stopped, have only small amounts of water draining from the flow. In marked contrast are high-velocity debris flows whose deposits more resemble fluvial deposits. In the Forest Falls area two adjacent drainage basins, Snow Creek and Rattlesnake Creek, have considerably different histories of debris flows. Snow Creek basin, with an area about three times as large as Rattlesnake Creek basin, has a well developed debris flow channel with broad levees. Most of the debris flows in Snow Creek have greater water content and attain higher velocities than those of Rattlesnake Creek. Most debris flows are in relative equilibrium with the geometry of the channel morphology. Exceptionally high-velocity flows, however, overshoot the channel walls at particularly tight channel curves. After overshooting the channel, the flows degrade the adjacent levee surface and remove trees and structures in the immediate path, before spreading out with decreasing velocity. As the velocity decreases the clasts in the debris flows pulverize the up-slope side of the trees and often imbed clasts in them. Debris flows in Rattlesnake Creek are relatively slow moving and commonly stop in the

  7. Seafloor imagery from the BIG'95 debris flow, western Mediterranean

    NASA Astrophysics Data System (ADS)

    Lastras, G.; Canals, M.; Hughes-Clarke, J. E.; Moreno, A.; de Batist, M.; Masson, D. G.; Cochonat, P.

    2002-10-01

    Seafloor backscatter data are used to image the product of one of the youngest major mass-wasting events in the northwestern Mediterranean Sea: a 26 km3 debris-flow deposit that covers 2000 km2 of the Ebro continental slope and base of slope, offshore Spain. Backscatter images provide unprecedented insights on debris-flow dynamics in the deep sea. A pattern of low-backscatter patches represents large sediment blocks that moved while keeping their internal coherence. High-backscatter alignments restricted to topographic lows that represent coarse sediment pathways separate the blocks. The results presented prove the occurrence of large catastrophic sediment failures near heavily populated coastal areas even in continental margins considered to be geodynamically quiet, such as those of the northwestern Mediterranean.

  8. Volcanic Debris Flows in the Elysium Region of Mars

    NASA Technical Reports Server (NTRS)

    Christiansen, E. H.; Ryan, M. P.

    1985-01-01

    Photogeologic studies of the Elysium volcanic province appear to provide a specific example of the importance of volcanic-ice interaction to produce the channels of Hrad and Granicus Valles. In addition, these studies shows that the channels lie on the surface of a large sedimentary deposit which is interpreted as an accumulation of volcanic debris flows or lahars. In spite of some similarities with Martian outflow channels, this latter difference may distinguish the Elysium channels from other types of Martian channels. Geologic relations are described which demonstrate that the debris flows formed amidst other volcanic activity in the Elysium region thereby suggesting that the magmatism was important to the generation of the mobilizing liquid. The lahars resulted from the melting of ground ice and liquefaction of subsurface materials. The intersection of this fluid reservoir with the regional fracture system lead to the rapid expulsion of a muddy slurry down the steep western slope of the province.

  9. Impact of permafrost degradation on debris flow initiation - a case study from the north Italian Alps

    NASA Astrophysics Data System (ADS)

    Damm, Bodo; Felderer, Astrid

    2014-05-01

    ): Impact of atmospheric warming on permafrost degradation and debris flow initiation - a case study from the eastern European Alps. E&G Quaternary Science Journal 62/2: 136-149. Damm, B. & Langer, M. (2006): Kartierung und Regionalisierung von Permafrostindikatoren im Rieserfernergebiet (Südtirol/Osttirol). Mitteilungen der Österreichischen Geographischen Gesellschaft 148: 295-314. IPCC (2012): Managing the risks of extreme events and disasters to advance climate change adaption. http://ipcc-wg2.gov/SREX/. Langer, M., Damm, B. (2008): CRYOSNOW - An approach for mapping and simulation of mountain permafrost distribution based on the spatial analyses of perennial snow patches. Geophysical Research Abstracts, Vol. 10: EGU2008-A-11263.

  10. Landslides and debris flows in Ephraim Canyon, central Utah

    SciTech Connect

    Baum, R.L.; Fleming, R.W.

    1989-01-01

    The geology of 36 km{sup 2} in Ephraim Canyon, on the west side of the Wasatch Plateau, central Utah, was mapped at a scale of 1:12,000 following the occurrence of numerous landslides in 1983. The geologic map shows the distribution of the landslides and debris flows of 1983-86, as well as older landslide deposits, other surficial deposits, and bedrock. Several of the recent landslides are described and illustrated by means of maps or photographs.

  11. Dendrogeomorphic evidence of debris flow frequency and magnitude at Mount Shasta, California

    NASA Astrophysics Data System (ADS)

    Hupp, C. R.

    1984-06-01

    Debris-flow deposits and woody vegetation adjacent to and growing within the channels of Whitney, Bolam, Mud, Ash, and Panthe creeks provide a 300-year record of debris-flow frequency at Mount Shasta Dendrochronologic (tree-ring) dating methods for the debris flows proved consistent with available documented records of debris flows Nine debris flows not reported in the historic record were documented and dated dendrochronologically. The oldest tree-ring date for a mudflow was about 1670 Combined geomorphic and botanical evidence shows that debris flows are a common occurrence at Mount Shasta Debris flows traveling at least 2 km have occurred at the rate of about 8 3 per century Smaller debris flows occur substantially more frequently and usually do not proceed as far downslope as larger debris flows. Cyclic scouring and filling by debris flows, in and adjacent to the stream channels, is suggested by dendrogeomorphic evidence and appears to be related to their magnitude and frequency Debris flows, small and large, may be the major surficial geomorphic agent in the vicinity of mount Shasta, sculpturing the channels and developing large alluvial fans

  12. Dendrogeomorphic evidence of debris flow frequency and magnitude at Mount Shasta, California

    USGS Publications Warehouse

    Hupp, C.R.

    1984-01-01

    Debris-flow deposits and woody vegetation adjacent to and growing within the channels of Whitney, Bolam, Mud, Ash, and Panthe creeks provide a 300-year record of debris-flow frequency at Mount Shasta Dendrochronologic (tree-ring) dating methods for the debris flows proved consistent with available documented records of debris flows Nine debris flows not reported in the historic record were documented and dated dendrochronologically. The oldest tree-ring date for a mudflow was about 1670 Combined geomorphic and botanical evidence shows that debris flows are a common occurrence at Mount Shasta Debris flows traveling at least 2 km have occurred at the rate of about 8 3 per century Smaller debris flows occur substantially more frequently and usually do not proceed as far downslope as larger debris flows. Cyclic scouring and filling by debris flows, in and adjacent to the stream channels, is suggested by dendrogeomorphic evidence and appears to be related to their magnitude and frequency Debris flows, small and large, may be the major surficial geomorphic agent in the vicinity of mount Shasta, sculpturing the channels and developing large alluvial fans ?? 1984 Springer-Verlag New York Inc.

  13. Debris flow laterites and bauxites at Naredi, Kutch, western India

    SciTech Connect

    Chitale, D.V.

    1986-05-01

    Reworked laterites and bauxites at Naredi, India, occur as lateritic pebbly mudstone underlain by bauxitic bouldery mudtone and nodular bauxites. The boundary between lateritic pebbly mudstone and bauxitic bouldery mudstone is wavy and sharp, suggesting deposition in two distinct phases. The bouldery bauxites share a diffuse boundary with nodular bauxites. The laterite pebbles float in a yellowish-brown muddy matrix. The boulders and nodules of bauxite are embedded in a massive white clayey matrix. The pebbles and boulders are randomly oriented and are either internally massive or composed of smaller clasts. The occurrence of bauxite boulders over bauxite nodules gives an appearance of inverse bedding. Based on these characteristics, a debris-flow mechanism is proposed for the deposition of laterites and bauxits at Naredi. Deposition occurred as two debris-flow pulses. The bauxites were deposited first, followed by laterites. Smaller clasts are present within the larger clasts, which suggests that the bauxite and laterite clasts had been reworked several times before finally being deposited. The residual, insitu laterites and bauxites capping the hills around Naredi were apparently source rocks for the debris-flow deposits. Deposition is speculated to have occurred during the Miocene-Pliocene.

  14. Debris flow deposition and reworking by the Colorado River in Grand Canyon, Arizona

    USGS Publications Warehouse

    Yanites, B.J.; Webb, R.H.; Griffiths, P.G.; Magirl, C.S.

    2006-01-01

    Flow regulation by large dams affects downstream flow competence and channel maintenance. Debris flows from 740 tributaries in Grand Canyon, Arizona, transport coarse-grained sediment onto debris fans adjacent to the Colorado River. These debris fans constrict the river to form rapids and are reworked during river flows that entrain particles and transport them downstream. Beginning in 1963, flood control operations of Glen Canyon Dam limited the potential for reworking of aggraded debris fans. We analyzed change in debris fans at the mouths of 75-Mile and Monument Creeks using photogrammetry of aerial photography taken from 1965 to 2000 and supplemented with ground surveys performed from 1987 to 2005. Our results quantify the debris fan aggradation that resulted from debris flows from 1984 to 2003. Volume, area, and river constriction increased at both debris fans. Profiles of the two debris fans show that net aggradation occurred in the middle of debris fans at stages above maximum dam releases, and surface shape shifted from concave to convex. Dam releases above power plant capacity partially reworked both debris fans, although reworking removed much less sediment than what was added by debris flow deposition. Large dam releases would be required to create additional reworking to limit the rate of debris fan aggradation in Grand Canyon.

  15. Topographic Controls on Landslide and Debris-Flow Mobility

    NASA Astrophysics Data System (ADS)

    McCoy, S. W.; Pettitt, S.

    2014-12-01

    Regardless of whether a granular flow initiates from failure and liquefaction of a shallow landslide or from overland flow that entrains sediment to form a debris flow, the resulting flow poses hazards to downslope communities. Understanding controls on granular-flow mobility is critical for accurate hazard prediction. The topographic form of granular-flow paths can vary significantly across different steeplands and is one of the few flow-path properties that can be readily altered by engineered control structures such as closed-type check dams. We use grain-scale numerical modeling (discrete element method simulations) of free-surface, gravity-driven granular flows to investigate how different topographic profiles with the same mean slope and total relief can produce notable differences in flow mobility due to strong nonlinearities inherent to granular-flow dynamics. We describe how varying the profile shape from planar, to convex up, to concave up, as well how varying the number, size, and location of check dams along a flow path, changes flow velocity, thickness, discharge, energy dissipation, impact force and runout distance. Our preliminary results highlight an important path dependence for this nonlinear system, show that caution should be used when predicting flow dynamics from path-averaged properties, and provide some mechanics-based guidance for engineering control structures.

  16. A comparative assessment of two different debris flow propagation approaches - blind simulations on a real debris flow event

    NASA Astrophysics Data System (ADS)

    Stancanelli, L. M.; Foti, E.

    2015-04-01

    A detailed comparison between the performances of two different approaches to debris flow modelling was carried out. In particular, the results of a mono-phase Bingham model (FLO-2D) and that of a two-phase model (TRENT-2D) obtained from a blind test were compared. As a benchmark test the catastrophic event of 1 October 2009 which struck Sicily causing several fatalities and damage was chosen. The predicted temporal evolution of several parameters of the debris flow (such as flow depth and propagation velocity) was analysed in order to investigate the advantages and disadvantages of the two models in reproducing the global dynamics of the event. An analysis between the models' results with survey data have been carried out, not only for the determination of statistical indicators of prediction accuracy, but also for the application of the Receiver Operator Characteristic (ROC) approach. Provided that the proper rheological parameters and boundary conditions are assigned, both models seem capable of reproducing the inundation areas in a reasonably accurate way. However, the main differences in the application rely on the choice of such rheological parameters. Indeed, within the more user-friendly FLO-2D model the tuning of the parameters must be done empirically, with no evidence of the physics of the phenomena. On the other hand, for the TRENT-2D the parameters are physically based and can be estimated from the properties of the solid material, thus reproducing more reliable results. A second important difference between the two models is that in the first method the debris flow is treated as a homogeneous flow, in which the total mass is kept constant from its initiation in the upper part of the basin to the deposition in a debris fan. In contrast, the second approach is suited to reproduce the erosion and deposition processes and the displaced mass can be directly related to the rainfall event. Application of both models in a highly urbanized area reveals the

  17. A comparative assessment of two different debris flow propagation approaches - blind simulations on a real debris flow event

    NASA Astrophysics Data System (ADS)

    Stancanelli, L. M.; Foti, E.

    2014-11-01

    A detailed comparison between the performances of two different approaches to debris flow modelling has been carried out. In particular, the results of a mono-phase Bingham model (FLO-2D) and these of a two phase model (TRENT-2D) obtained from a blind test have been compared. As a benchmark test the catastrophic event of 1 October 2009 which struck Sicily causing several fatalities and damages has been chosen. The predicted temporal evolution of several parameters of the debris flow (as the flow depths and the propagation velocities) has been analyzed in order to investigate the advantages and disadvantages of the two models in reproducing the global dynamics of the event. Analysis between the models results with survey data have been carried out, not only for the determination of statistical indicators of prediction accuracy, but also for the application of the Receiver Operator Characteristic (ROC) approach. Provided that the proper rheological parameters and boundary conditions are assigned, both models seem capable of reproducing the inundation areas in a fairly good way. However, the main differences in the application rely in the choice of such rheological parameters. Indeed, within the more user friendly FLO-2D model the tuning of the parameters must be done empirically, with no evidence of the physics of the phenomena. On the other hand, for the TRENT-2D the parameters are physically based and can be estimated from the properties of the solid material, thus reproducing more reliable results. A second important difference between the two models is that in the first method the debris flow is treated as homogeneous flow, in which the total mass is kept constant from initiation in the upper part of the basin up to the deposition on debris fan. On the contrary, the second approach is suite to reproduce the erosion and deposition processes and the displaced mass can be directly related to the rainfall event. Application of both models in an highly urbanized area

  18. Debris flow impact estimation on a rigid barrier

    NASA Astrophysics Data System (ADS)

    Vagnon, Federico; Segalini, Andrea

    2016-07-01

    The aim of this paper is to analyse debris flow impact against rigid and undrained barrier in order to propose a new formulation for the estimation of acting force after the flow impact to safe design protection structures. For this reason, this work concentrates on the flow impact, by performing a series of small scale tests in a specifically created flume. Flow characteristics (flow height and velocity) and applied loads (dynamic and static) on barrier were measured using four ultrasonic devices, four load cells and a contact surface pressure gauge. The results obtained were compared with main existing models and a new equation is proposed. Furthermore, a brief review of the small scale theory was provided to analyse the scale effects that can affect the results.

  19. Scaling up debris-flow experiments on a centrifuge

    NASA Astrophysics Data System (ADS)

    Hung, C.; Capart, H.; Crone, T. J.; Grinspum, E.; Hsu, L.; Kaufman, D.; Li, L.; Ling, H.; Reitz, M. D.; Smith, B.; Stark, C. P.

    2013-12-01

    Boundary forces generated by debris flows can be powerful enough to erode bedrock and cause considerable damage to infrastructure during runout. Formulation of an erosion-rate law for debris flows is therefore a high priority, and it makes sense to build such a law around laboratory experiments. However, running experiments big enough to generate realistic boundary forces is a logistical challenge to say the least [1]. One alternative is to run table-top simulations with unnaturally weak but fast-eroding pseudo-bedrock, another is to extrapolate from micro-erosion of natural substrates driven by unnaturally weak impacts; hybrid-scale experiments have also been conducted [2]. Here we take a different approach in which we scale up granular impact forces by running our experiments under enhanced gravity in a geotechnical centrifuge [3]. Using a 40cm-diameter rotating drum [2] spun at up to 100g, we generate debris flows with an effective depth of over several meters. By varying effective gravity from 1g to 100g we explore the scaling of granular flow forces and the consequent bed and wall erosion rates. The velocity and density structure of these granular flows is monitored using laser sheets, high-speed video, and particle tracking [4], and the progressive erosion of the boundary surfaces is measured by laser scanning. The force structures and their fluctuations within the granular mass and at the boundaries are explored with contact dynamics numerical simulations that mimic the lab experimental conditions [5]. In this presentation we summarize these results and discuss how they can contribute to the formulation of debris-flow erosion law. [1] Major, J. J. (1997), Journal of Geology 105: 345-366, doi:10.1086/515930 [2] Hsu, L. (2010), Ph.D. thesis, University of California, Berkeley [3] Brucks, A., et al (2007), Physical Review E 75, 032301, doi:10.1103/PhysRevE.75.032301 [4] Spinewine, B., et al (2011), Experiments in Fluids 50: 1507-1525, doi: 10.1007/s00348

  20. Hydrometeorological triggers of periglacial debris flows in the Zermatt valley (Switzerland) since 1864

    NASA Astrophysics Data System (ADS)

    Schneuwly-Bollschweiler, Michelle; Stoffel, Markus

    2012-06-01

    The triggering of debris flows depends on a critical combination of available unconsolidated material and water supply. In periglacial environments, debris flows are generally triggered by liquefaction of loose material in a channel, or by progressive erosion during a large release of water. Here, we link an unusually dense and highly resolved database on periglacial debris flows with meteorological records dating back to AD 1864 to reconstruct ˜150 yr of rainstorms that triggered debris flows at high-elevation sites (source area elevations ranging from 2000 to 4545 m a.s.l.) in the Swiss Alps. Analysis is based on a tree ring-derived frequency series of debris flows from eight torrents, as well as on daily records from three meteorological stations and runoff data from four river gauging stations. Results show that the debris-flow season at these high-altitude sites now is much longer (May to October) than it used to be in the late nineteenth century when activity was limited to June-September. Debris flows early in the season are generally triggered by lower rainstorm totals (<20 mm/day) than those occurring later in the season because early season snowmelt adds considerable amounts of water to the system and therefore facilitates debris-flow formation. Debris flows in May, June, July, and August are triggered primarily by short-duration high-intensity rainstorms (local thunderstorms) whereas late season (September, October) debris flows are commonly related to longer-lasting advective rainstorms.

  1. Variation in initiation condition of debris flows in the mountain regions surrounding Beijing

    NASA Astrophysics Data System (ADS)

    Ma, Chao; Wang, Yu-jie; Du, Cui; Wang, Yun-qi; Li, Yun-peng

    2016-11-01

    Debris flows in the mountain regions surrounding Beijing have been occurring for a long time and have resulted in great economic losses. In this study, 23 rainstorm events, surficial sediments, and debris flow deposits were analyzed to quantify the area's rainfall threshold and to investigate how such conditions may be used to predict debris flow in this region. Rainfall threshold of intensity-duration (I-D) functions after vegetation recovery was higher than before recovery and also higher than I-D levels in other regions where debris flows are closely associated with runoff. Field investigations revealed that surficial sediments were characterized by coarse-grained sediments and that debris flow deposits lacked fine particles. Local debris flows can be triggered by runoff; however, no single standard equation is used to predict the conditions that lead to runoff-triggered debris flow; and commonly used equations give different values. Here, we propose an empirical function that takes into account peak discharge per width and particle diameter. This model should be verified with further investigations so that it can be used as a reference to analyze the conditions that lead to debris flow in the study area. Finally, debris flows may have been related to occasional storms in the study area, which has been experiencing substantially increased temperatures and decreased annual precipitation. This work provides important information about the conditions that initiated debris flow in the Beijing mountain regions in the last few decades.

  2. Debris Flow Occurrence and Sediment Persistence, Upper Colorado River Valley, CO.

    PubMed

    Grimsley, K J; Rathburn, S L; Friedman, J M; Mangano, J F

    2016-07-01

    Debris flow magnitudes and frequencies are compared across the Upper Colorado River valley to assess influences on debris flow occurrence and to evaluate valley geometry effects on sediment persistence. Dendrochronology, field mapping, and aerial photographic analysis are used to evaluate whether a 19th century earthen, water-conveyance ditch has altered the regime of debris flow occurrence in the Colorado River headwaters. Identifying any shifts in disturbance processes or changes in magnitudes and frequencies of occurrence is fundamental to establishing the historical range of variability (HRV) at the site. We found no substantial difference in frequency of debris flows cataloged at eleven sites of deposition between the east (8) and west (11) sides of the Colorado River valley over the last century, but four of the five largest debris flows originated on the west side of the valley in association with the earthen ditch, while the fifth is on a steep hillslope of hydrothermally altered rock on the east side. These results suggest that the ditch has altered the regime of debris flow activity in the Colorado River headwaters as compared to HRV by increasing the frequency of debris flows large enough to reach the Colorado River valley. Valley confinement is a dominant control on response to debris flows, influencing volumes of aggradation and persistence of debris flow deposits. Large, frequent debris flows, exceeding HRV, create persistent effects due to valley geometry and geomorphic setting conducive to sediment storage that are easily delineated by valley confinement ratios which are useful to land managers.

  3. Debris Flow Occurrence and Sediment Persistence, Upper Colorado River Valley, CO.

    PubMed

    Grimsley, K J; Rathburn, S L; Friedman, J M; Mangano, J F

    2016-07-01

    Debris flow magnitudes and frequencies are compared across the Upper Colorado River valley to assess influences on debris flow occurrence and to evaluate valley geometry effects on sediment persistence. Dendrochronology, field mapping, and aerial photographic analysis are used to evaluate whether a 19th century earthen, water-conveyance ditch has altered the regime of debris flow occurrence in the Colorado River headwaters. Identifying any shifts in disturbance processes or changes in magnitudes and frequencies of occurrence is fundamental to establishing the historical range of variability (HRV) at the site. We found no substantial difference in frequency of debris flows cataloged at eleven sites of deposition between the east (8) and west (11) sides of the Colorado River valley over the last century, but four of the five largest debris flows originated on the west side of the valley in association with the earthen ditch, while the fifth is on a steep hillslope of hydrothermally altered rock on the east side. These results suggest that the ditch has altered the regime of debris flow activity in the Colorado River headwaters as compared to HRV by increasing the frequency of debris flows large enough to reach the Colorado River valley. Valley confinement is a dominant control on response to debris flows, influencing volumes of aggradation and persistence of debris flow deposits. Large, frequent debris flows, exceeding HRV, create persistent effects due to valley geometry and geomorphic setting conducive to sediment storage that are easily delineated by valley confinement ratios which are useful to land managers. PMID:27059223

  4. Debris flow occurrence and sediment persistence, Upper Colorado River Valley, CO

    USGS Publications Warehouse

    Grimsley, Kyle J; Rathburn, Sara L.; Friedman, Jonathan M.; Mangano, Joseph F.

    2016-01-01

    Debris flow magnitudes and frequencies are compared across the Upper Colorado River valley to assess influences on debris flow occurrence and to evaluate valley geometry effects on sediment persistence. Dendrochronology, field mapping, and aerial photographic analysis are used to evaluate whether a 19th century earthen, water-conveyance ditch has altered the regime of debris flow occurrence in the Colorado River headwaters. Identifying any shifts in disturbance processes or changes in magnitudes and frequencies of occurrence is fundamental to establishing the historical range of variability (HRV) at the site. We found no substantial difference in frequency of debris flows cataloged at eleven sites of deposition between the east (8) and west (11) sides of the Colorado River valley over the last century, but four of the five largest debris flows originated on the west side of the valley in association with the earthen ditch, while the fifth is on a steep hillslope of hydrothermally altered rock on the east side. These results suggest that the ditch has altered the regime of debris flow activity in the Colorado River headwaters as compared to HRV by increasing the frequency of debris flows large enough to reach the Colorado River valley. Valley confinement is a dominant control on response to debris flows, influencing volumes of aggradation and persistence of debris flow deposits. Large, frequent debris flows, exceeding HRV, create persistent effects due to valley geometry and geomorphic setting conducive to sediment storage that are easily delineated by valley confinement ratios which are useful to land managers.

  5. Debris Flow Occurrence and Sediment Persistence, Upper Colorado River Valley, CO

    NASA Astrophysics Data System (ADS)

    Grimsley, K. J.; Rathburn, S. L.; Friedman, J. M.; Mangano, J. F.

    2016-07-01

    Debris flow magnitudes and frequencies are compared across the Upper Colorado River valley to assess influences on debris flow occurrence and to evaluate valley geometry effects on sediment persistence. Dendrochronology, field mapping, and aerial photographic analysis are used to evaluate whether a 19th century earthen, water-conveyance ditch has altered the regime of debris flow occurrence in the Colorado River headwaters. Identifying any shifts in disturbance processes or changes in magnitudes and frequencies of occurrence is fundamental to establishing the historical range of variability (HRV) at the site. We found no substantial difference in frequency of debris flows cataloged at eleven sites of deposition between the east (8) and west (11) sides of the Colorado River valley over the last century, but four of the five largest debris flows originated on the west side of the valley in association with the earthen ditch, while the fifth is on a steep hillslope of hydrothermally altered rock on the east side. These results suggest that the ditch has altered the regime of debris flow activity in the Colorado River headwaters as compared to HRV by increasing the frequency of debris flows large enough to reach the Colorado River valley. Valley confinement is a dominant control on response to debris flows, influencing volumes of aggradation and persistence of debris flow deposits. Large, frequent debris flows, exceeding HRV, create persistent effects due to valley geometry and geomorphic setting conducive to sediment storage that are easily delineated by valley confinement ratios which are useful to land managers.

  6. Analyzing debris flows with the statistically calibrated empirical model LAHARZ in southeastern Arizona, USA

    USGS Publications Warehouse

    Magirl, Christopher S.; Griffiths, Peter G.; Webb, Robert H.

    2010-01-01

    Hazard-zone delineation for extreme events is essential for floodplain management near mountain fronts in arid and semiarid regions. On 31 July 2006, unprecedented debris flows occurred in the Santa Catalina Mountains of southeastern Arizona following extreme multiday precipitation (recurrence interval > 1000 years for 4-day precipitation). Most mobilized sediment contributing to debris flows was derived from shallow-seated failures of colluvium on steep slopes. A total of 435 slope failures in the southern Santa Catalina Mountains released 1.34 million Mg of sediment into the channels of 10 drainage basins. Five drainages produced debris flows that moved to the apices of alluvial fans on the southern edge of the mountain front, damaging infrastructure and aggrading channels to reduce future flood conveyance. Using the statistically calibrated, empirical debris-flow model LAHARZ and modified model coefficients developed to better match conditions in southeastern Arizona, we predicted the approximate area of deposition and travel distance in comparison to observed depositional areas and travel distance for seven debris flows. Two of the modeled debris flows represented single slope failures that terminated downslope with no additive influence of other debris flows or streamflow flooding. Five of the simulated debris flows represented the aggregation of multiple slope failures and streamflow flooding into multiple debris-flow pulses. Because LAHARZ is a debris-flow hazard-zone delineation tool, the complexity of alternating transport and deposition zones in channels with abrupt expansions and contractions reduces the applicability of the model in some drainage basins.

  7. On the connection of permafrost and debris flow activity in Austria

    NASA Astrophysics Data System (ADS)

    Huber, Thomas; Kaitna, Roland

    2016-04-01

    Debris flows represent a severe hazard in alpine regions and typically result from a critical combination of relief energy, water, and sediment. Hence, besides water-related trigger conditions, the availability of abundant sediment is a major control on debris flows activity in alpine regions. Increasing temperatures due to global warming are expected to affect periglacial regions and by that the distribution of alpine permafrost and the depth of the active layer, which in turn might lead to increased debris flow activity and increased interference with human interests. In this contribution we assess the importance of permafrost on documented debris flows in the past by connecting the modeled permafrost distribution with a large database of historic debris flows in Austria. The permafrost distribution is estimated based on a published model approach and mainly depends of altitude, relief, and exposition. The database of debris flows includes more than 4000 debris flow events in around 1900 watersheds. We find that 27 % of watersheds experiencing debris flow activity have a modeled permafrost area smaller than 5 % of total area. Around 7 % of the debris flow prone watersheds have an area larger than 5 %. Interestingly, our first results indicate that watersheds without permafrost experience significantly less, but more intense debris flow events than watersheds with modeled permafrost occurrence. Our study aims to contribute to a better understanding of geomorphic activity and the impact of climate change in alpine environments.

  8. Critical Rainfall Conditions Triggering Shallow Landslides or Debris Flows in Torrents - Analysis of Debris Flow events 2012, 2013 and 2014 in Austria

    NASA Astrophysics Data System (ADS)

    Moser, Markus; Mehlhorn, Susanne; Janu, Stefan

    2015-04-01

    Generally, debris flows are caused by both small-scale intensive precipitation and long lasting rainfalls with lower intensity but high pre-wetting or both combined. The triggering mechanism of the debris flow events in Austria 2012, 2013 and 2014 were mass movements (rapid shallow landslides) on steep slopes in the upper catchments. Those masses slide with very high velocity into the torrent beds provoking hyperconcentrated flows or debris flows. In areas of the geologically unstable Greywacke zone, the torrents were cleared up onto the bedrock and the debris was deposited in the storage areas of existing debris flow breakers or in torrents without technical protection measures the debris caused catastrophic damage to residential buildings and other infrastructural facilities on the alluvial fan. Following the events, comprehensive documentation work was undertaken comprising precipitation analysis (rainfall data, weather radar data), identification and quantification of the landslide masses, cross profiles along the channel and of deposition in the storage areas or on the fan. The documentation and analysis of torrential events is an essential part of an integrated risk management. It supports the understanding of the occurred processes to mitigate future hazards. Unfortunately, the small-scale heavy rain events are not detected by the precipitation stations. Therefore, weather radar data (INCA-Data) analysis was used to determine the - usually very local - intensities which caused those catastrophic landslides and debris flows. Analysis results showed an agreement with the range of the previously known precipitation thresholds for debris flow triggering in the Alps.

  9. Dynamic Modelling of Erosion and Deposition Processes in Debris Flows With Application to Real Debris Flow Events in Switzerland

    NASA Astrophysics Data System (ADS)

    Deubelbeiss, Y.; McArdell, B. W.; Graf, C.

    2011-12-01

    The dynamics of a debris flow can be significantly influenced by erosion and deposition processes during an event because volume changes have a strong influence on flow properties such as flow velocity, flow heights and runout distances. It is therefore worth exploring how to include these processes in numerical models, which are used for hazard assessment and mitigation measure planning. However, it is still under debate, what mechanism drives the erosion of material at the base of a debris flow. There are different processes attributed to erosion: it has been proposed that erosion correlates with the stresses due to granular interactions at the front, which in turn strongly depend on particle size or it may be related to basal shear forces. Because it is expected that larger flow heights result in larger stresses one can additionally hypothesize that there is a correlation between erosion rate and flow height. To test different erosion laws in a numerical model and its influence on the flow behavior we implement different relationships and compare simulation results with field data. Herefore, we use the numerical model, RAMMS (Christen et al., 2010), employing the Voellmy-fluid friction law. While it has already been shown that a correlation of erosion with velocity does not lead to a satisfying result (too high entrainment in the tail) a correlation with flow height combined with velocity (momentum) has been successfully applied to ice-avalanches. Currently, we are testing the momentum-driven and for comparison we reconsider the simple velocity-driven erosion rate. However, these laws do not consider processes on a smaller scale such as particle fluctuations resulting in energy production, which might play an important role. Therefore, we additionally consider an erosion model that has potential to draw new insights on the erosion process in debris flows. The model is based on an extended Voellmy model, which additionally employs an equation, which is a measure

  10. Estimated probabilities and volumes of postwildfire debris flows, a prewildfire evaluation for the upper Blue River watershed, Summit County, Colorado

    USGS Publications Warehouse

    Elliott, John G.; Flynn, Jennifer L.; Bossong, Clifford R.; Char, Stephen J.

    2011-01-01

    The subwatersheds with the greatest potential postwildfire and postprecipitation hazards are those with both high probabilities of debris-flow occurrence and large estimated volumes of debris-flow material. The high probabilities of postwildfire debris flows, the associated large estimated debris-flow volumes, and the densely populated areas along the creeks and near the outlets of the primary watersheds indicate that Indiana, Pennsylvania, and Spruce Creeks are associated with a relatively high combined debris-flow hazard.

  11. Debris flows from tributaries of the Colorado River, Grand Canyon National Park, Arizona

    USGS Publications Warehouse

    Webb, R.H.; Pringle, P.T.; Rink, G.R.

    1987-01-01

    A reconnaissance of 36 tributaries of the Colorado River indicates that debris flows are a major process by which sediment is transported to the Colorado River in Grand Canyon National Park. Debris flows are slurries of sediment and water that have a water content < 40% by volume. Debris flows occur frequently in arid and semiarid regions. Slope failures commonly trigger debris flows, which can originate from any rock formation in the Grand Canyon. The largest and most frequent flows originate from the Permian Hermit Shale, the underlying Esplanade Sandstone of the Supai Group, and other formations of the Permian and Pennsylvanian Supai Group. Debris flows have reached the Colorado River on an average of once every 20 to 30 yr in the Lava-Chuar Creek drainage since about 1916. Two debris flows have reached the Colorado River in the last 25 yr in Monument Creek. The Crystal Creek drainage has had an average of one debris flow reaching the Colorado River every 50 yr, although the debris flow of 1966 has been the only flow that reached the Colorado River since 1900. Debris flows may actually reach the Colorado River more frequently in these drainages because evidence for all debris flows may not have been preserved in the channel-margin stratigraphy. Discharges were estimated for the peak flow of three debris flows that reached the Colorado River. The debris flow of 1966 in the Lava-Chuar Creek drainage had an estimated discharge of 4,000 cu ft/sec. The debris flow of 1984 in the Monument Creek drainage had a discharge estimated between 3,600 and 4,200 cu ft/sec. The debris flow of 1966 in the Crystal Creek drainage had a discharge estimated between 9,200 and 14,000 cu ft/sec. Debris flows in the Grand Canyon generally are composed of 10 to 40% sand by weight and may represent a significant source of beach-building sand along the Colorado River. The particle size distributions are very poorly sorted and the largest transported boulders were in the Crystal Creek

  12. Debris flows as geomorphic agents in the Huachuca Mountains of southeastern Arizona

    USGS Publications Warehouse

    Wohl, E.E.; Pearthree, P.P.

    1991-01-01

    Numerous debris flows occurred in the Huachuca Mountains of southeastern Arizona during the summer rainy season of 1988 in areas that were burned by a forest fire earlier in the summer. Debris flows occurred following a major forest fire in 1977 as well, suggesting a causal link between fires and debris flows. Abundant evidence of older debris flows preserved along channels and in mountain front fans indicates that debris flows have occurred repeteadly during the late Quaternary in this environment. Soil development in sequences of debris-flow deposits indicates that debris flows probably recur over time intervals of several hundred to a thousand years in individual drainage basins in the study area. Surface runoff in the steep drainage basins of the Huachuca Mountains is greatly enhanced following forest fires, as the hillslopes are denuded of their vegetative cover. Water and sediment eroded from the hillslope regolith are rapidly introduced into the upper reaches of tributary channels by widespread rilling and slope wash during rainfall events. This influx of water and sediment destabilizes regolith previously accumulated in the channel, triggering debris flows that scour the channel to bedrock in the upper reaches. Following a debris flow, the scoured, trapezoidally-shaped channel gradually assumes a swale shape and the percentage of exposed bedrock declines, as material is introduced from the slopes. Debris flows do a tremendous amount of work in a very short time, however, and are the major channel-forming events. Where the tributary channels enter larger, trunk channels, the debris flows serve as the main source of very coarse sediment. The local slope and coarse particle distribution of the trunk channel depend on the competence of water flows in the channel to transport the material introduced by debris flows. Where the smaller channels drain directly to the mountain front, debris flows create extensive alluvial fans which dominate the morphology of the

  13. Infiltration Control of Shallow Landslides and Debris Flows

    NASA Astrophysics Data System (ADS)

    Baum, R. L.; Godt, J. W.

    2011-12-01

    Empirical rainfall intensity-duration thresholds have been defined for many areas and are the basis for most operational landslide and debris-flow warnings; however, paucity of historical data on landslide occurrence is a major limitation in defining such thresholds. Infiltration theory provides a useful framework for examining the rainfall intensity-duration control of shallow landslides and debris flows. Dimensionless intensity, I* (I*=I/K, where I is rainfall intensity and K is saturated hydraulic conductivity), and duration, T* (T*=TKS, where T is duration, and S is a lumped storage parameter), groupings were defined by dimensional analysis of variables appearing in the equations governing unsaturated infiltration. Replotting empirical thresholds in terms of I* and T* reveals strong clustering of dimensionless thresholds into three main bands having relatively low, moderate, and high I*. The low I* band includes burned, logged, bedrock, and sparsely vegetated areas susceptible to debris flows. The moderate and high I* bands include areas susceptible to shallow landslides and debris flows. The high I* band includes thresholds for abundant (tens to hundreds) landslides whereas the moderate I* band includes minimum thresholds for few or isolated landslides. These bands are readily distinguishable when I* and T* have been computed using published hydrologic properties of the areas where the thresholds were developed. Dimensionless intensity and duration thresholds for low and moderate I* bands follow power laws as do most published empirical rainfall intensity-duration thresholds. Areas included in the low I* band are characterized by a much shallower penetration depth (millimeters to a few decimeters) than that observed in areas of the other bands (several decimeters to meters). Physically, rainfall intensity-duration thresholds can be understood in terms of some measure of the rate and depth of rainfall infiltration and its effect, through the law of effective

  14. Debris Flow as a Mechanism for Forming Martian Gullies

    NASA Astrophysics Data System (ADS)

    Conway, S. J.; Balme, M. R.; Murray, J. B.; Towner, M. C.

    2009-04-01

    The current low temperatures and pressures at the martian surface are not conducive to the stability of liquid water; hence the discovery of recently active, fluvial-like gullies [1, 2] presents an apparent paradox: how can these fluvial landforms have occurred if water is not stable at the surface? To approach this problem we have compared the morphometric properties of gullies in various settings on Earth to those of gullies on Mars. We have measured debris flows in Westfjords, Iceland [3] and gullies in La Gomera, Canary Islands [4]. The Iceland elevation data were generated from differential GPS and a LiDAR survey, and the La Gomera data from differential GPS. In addition we used elevation data from the Shuttle Radar Topography Mission (SRTM) extracted along previously mapped debris flows in the Taurids Mountains, Turkey [5] and the Colorado Front Range, USA [6]. We have compared these data to preliminary analyses of stereo HiRISE images of martian gullies in four locations using a method to extract point elevation data developed by Kreslavsky [7]. In all cases the elevation along the centre channel of the debris flow or gully was used for comparison to Mars. For Iceland and La Gomera we also extracted cross-profiles for comparison with martian gullies. Simply comparing the longitudinal profiles of gullies on Mars and different situations on the Earth highlights the variability between debris flow sites on Earth. The martian gully profiles are most similar to debris flows in the Taurids Mountains and in the Colorado Front Range. The overall slope is shallower on Mars compared to the Iceland debris flows and the ephemeral water flow gullies in La Gomera. The runout or total length of gullies is also more variable and greater for Mars than for Iceland and La Gomera. Caution should be taken in interpreting the cross profiles for Mars as the error on the elevation is at least 1m and there is low sampling density in comparison to the other datasets. The v-shaped La

  15. Remote sensing of rainfall for debris-flow hazard assessment

    USGS Publications Warehouse

    Wieczorek, G.F.; Coe, J.A.; Godt, J.W.; ,

    2003-01-01

    Recent advances in remote sensing of rainfall provide more detailed temporal and spatial data on rainfall distribution. Four case studies of abundant debris flows over relatively small areas triggered during intense rainstorms are examined noting the potential for using remotely sensed rainfall data for landslide hazard analysis. Three examples with rainfall estimates from National Weather Service Doppler radar and one example with rainfall estimates from infrared imagery from a National Oceanic and Atmospheric Administration satellite are compared with ground-based measurements of rainfall and with landslide distribution. The advantages and limitations of using remote sensing of rainfall for landslide hazard analysis are discussed. ?? 2003 Millpress,.

  16. PRESENT STATUS OF RESEARCH IN DEBRIS FLOW MODELING.

    USGS Publications Warehouse

    Chen, Cheng-lung

    1985-01-01

    A viable rheological model should consist of both a time-independent part and a time-dependent part. A generalized viscoplastic fluid model that has both parts as well as two major rheological properties (i. e. , the normal stress effect and soil yield criteria) is shown to be sufficiently accurate, yet practical, for general use in debris flow modeling. Other rheological models, such as the Bingham plastic fluid model and the so-called Coulomb-viscous model, are compared in terms of the generalized viscoplastic fluid model.

  17. UAV remote sensing hazard assessment in Zhouqu debris flow disaster

    NASA Astrophysics Data System (ADS)

    Wen, Qi; He, Haixia; Wang, Xufeng; Wu, Wei; Wang, Lei; Xu, Feng; Wang, Ping; Tang, Tong; Lei, Yu

    2011-11-01

    On August 8, 2010 morning, a large debris flow occurred in Zhouqu County, Gannan Tibetan Autonomous Prefecture, Gansu Province, China, which has damaged Zhouqu County and its surrounding area seriously. An UAV and airplane were sent there the day after to acquire images of disaster area; UAV image of 0.2 meter resolution and aerial remote sensing image of 1 meter resolution were acquired. NDRCC compared pre-disaster and post-disaster remote sensing images of disaster area, preliminary analyzed and judged the damage condition and disaster trend. We partitioned the coverage and affected area of debris flow into 2457 girds in high resolution remote sensing images, hazard assessment expert group were sent to implement field investigation according to each grid. The disaster scope and extent of loss were defined again combined with field investigation data. Then we assessed the physical quantity of housing, infrastructure, land resource in detail and assessed the direct economic losses. It is for the first time that remote sensing images are integrated into the national catastrophe assessment flow of China as a major data source.

  18. SCDAP/RELAP5 Modeling of Heat Transfer and Flow Losses in Lower Head Porous Debris

    SciTech Connect

    E. W. Coryell; L. J. Siefken; S. Paik

    1998-09-01

    Designs are described for implementing models for calculating the heat transfer and flow losses in porous debris in the lower head of a reactor vessel. The COUPLE model in SCDAP/RELAP5 represents both the porous and nonporous debris that results from core material slumping into the lower head. Currently, the COUPLE model has the capability to model convective and radiative heat transfer from the surfaces of nonporous debris in a detailed manner and to model only in a simplistic manner the heat transfer from porous debris. In order to advance beyond the simplistic modeling for porous debris, designs are developed for detailed calculations of heat transfer and flow losses in porous debris. Correlations are identified for convective heat transfer in porous debris for the following modes of heat transfer; (1) forced convection to liquid, (2) forced convection to gas, (3) nucleate boiling, (4) transition boiling, and (5) film boiling. Interphase heat transfer is modeled in an approximate manner. A design is also described for implementing a model of heat transfer by radiation from debris to the interstitial fluid. A design is described for implementation of models for flow losses and interphase drag in porous debris. Since the models for heat transfer and flow losses in porous debris in the lower head are designed for general application, a design is also described for implementation of these models to the analysis of porous debris in the core region. A test matrix is proposed for assessing the capability of the implemented models to calculate the heat transfer and flow losses in porous debris. The implementation of the models described in this report is expected to improve the COUPLE code calculation of the temperature distribution in porous debris and in the lower head that supports the debris. The implementation of these models is also expected to improve the calculation of the temperature and flow distribution in porous debris in the core region.

  19. Field measurement of basal forces generated by erosive debris flows

    USGS Publications Warehouse

    McCoy, S.W.; Tucker, G.E.; Kean, J.W.; Coe, J.A.

    2013-01-01

    It has been proposed that debris flows cut bedrock valleys in steeplands worldwide, but field measurements needed to constrain mechanistic models of this process remain sparse due to the difficulty of instrumenting natural flows. Here we present and analyze measurements made using an automated sensor network, erosion bolts, and a 15.24 cm by 15.24 cm force plate installed in the bedrock channel floor of a steep catchment. These measurements allow us to quantify the distribution of basal forces from natural debris‒flow events that incised bedrock. Over the 4 year monitoring period, 11 debris‒flow events scoured the bedrock channel floor. No clear water flows were observed. Measurements of erosion bolts at the beginning and end of the study indicated that the bedrock channel floor was lowered by 36 to 64 mm. The basal force during these erosive debris‒flow events had a large‒magnitude (up to 21 kN, which was approximately 50 times larger than the concurrent time‒averaged mean force), high‒frequency (greater than 1 Hz) fluctuating component. We interpret these fluctuations as flow particles impacting the bed. The resulting variability in force magnitude increased linearly with the time‒averaged mean basal force. Probability density functions of basal normal forces were consistent with a generalized Pareto distribution, rather than the exponential distribution that is commonly found in experimental and simulated monodispersed granular flows and which has a lower probability of large forces. When the bed sediment thickness covering the force plate was greater than ~ 20 times the median bed sediment grain size, no significant fluctuations about the time‒averaged mean force were measured, indicating that a thin layer of sediment (~ 5 cm in the monitored cases) can effectively shield the subjacent bed from erosive impacts. Coarse‒grained granular surges and water‒rich, intersurge flow had very similar basal force distributions despite

  20. SCDAP/RELAP5 Modeling of Heat Transfer and Flow Losses in Lower Head Porous Debris

    SciTech Connect

    Siefken, Larry James; Coryell, Eric Wesley; Paik, Seungho; Kuo, Han Hsiung

    1999-07-01

    Designs are described for implementing models for calculating the heat transfer and flow losses in porous debris in the lower head of a reactor vessel. The COUPLE model in SCDAP/RELAP5 represents both the porous and nonporous debris that results from core material slumping into the lower head. Currently, the COUPLE model has the capability to model convective and radiative heat transfer from the surfaces of nonporous debris in a detailed manner and to model only in a simplistic manner the heat transfer from porous debris. In order to advance beyond the simplistic modeling for porous debris, designs are developed for detailed calculations of heat transfer and flow losses in porous debris. Correlations are identified for convective heat transfer in porous debris for the following modes of heat transfer; (1) forced convection to liquid, (2) forced convection to gas, (3) nucleate boiling, (4) transition boiling, and (5) film boiling. Interphase heat transfer is modeled in an approximate manner. Designs are described for models to calculate the flow losses and interphase drag of fluid flowing through the interstices of the porous debris, and to apply these variables in the momentum equations in the RELAP5 part of the code. Since the models for heat transfer and flow losses in porous debris in the lower head are designed for general application, a design is also described for implementation of these models to the analysis of porous debris in the core region. A test matrix is proposed for assessing the capability of the implemented models to calculate the heat transfer and flow losses in porous debris. The implementation of the models described in this report is expected to improve the COUPLE code calculation of the temperature distribution in porous debris and in the lower head that supports the debris. The implementation of these models is also expected to improve the calculation of the temperature and flow distribution in porous debris in the core region.

  1. Surge dynamics coupled to pore-pressure evolution in debris flows

    USGS Publications Warehouse

    Savage, S.B.; Iverson, R.M.; ,

    2003-01-01

    Temporally and spatially varying pore-fluid pressures exert strong controls on debris-flow motion by mediating internal and basal friction at grain contacts. We analyze these effects by deriving a one-dimensional model of pore-pressure diffusion explicitly coupled to changes in debris-flow thickness. The new pore-pressure equation is combined with Iverson's (1997) extension of the depth-averaged Savage-Hutter (1989, 1991) granular avalanche equations to predict motion of unsteady debris-flow surges with evolving pore-pressure distributions. Computational results illustrate the profound effects of pore-pressure diffusivities on debris-flow surge depths and velocities. ?? 2003 Millpress,.

  2. Finite volume methods for submarine debris flows and generated waves

    NASA Astrophysics Data System (ADS)

    Kim, Jihwan; Løvholt, Finn; Issler, Dieter

    2016-04-01

    Submarine landslides can impose great danger to the underwater structures and generate destructive tsunamis. Submarine debris flows often behave like visco-plastic materials, and the Herschel-Bulkley rheological model is known to be appropriate for describing the motion. In this work, we develop numerical schemes for the visco-plastic debris flows using finite volume methods in Eulerian coordinates with two horizontal dimensions. We provide parameter sensitivity analysis and demonstrate how common ad-hoc assumptions such as including a minimum shear layer depth influence the modeling of the landslide dynamics. Hydrodynamic resistance forces, hydroplaning, and remolding are all crucial terms for underwater landslides, and are hence added into the numerical formulation. The landslide deformation is coupled to the water column and simulated in the Clawpack framework. For the propagation of the tsunamis, the shallow water equations and the Boussinesq-type equations are employed to observe how important the wave dispersion is. Finally, two cases in central Norway, i.e. the subaerial quick clay landslide at Byneset in 2012, and the submerged tsunamigenic Statland landslide in 2014, are both presented for validation. The research leading to these results has received funding from the Research Council of Norway under grant number 231252 (Project TsunamiLand) and the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement 603839 (Project ASTARTE).

  3. Headwater sediment dynamics in a debris flow catchment constrained by high-resolution topographic surveys

    NASA Astrophysics Data System (ADS)

    Loye, Alexandre; Jaboyedoff, Michel; Theule, Joshua Isaac; Liébault, Frédéric

    2016-06-01

    Debris flows have been recognized to be linked to the amounts of material temporarily stored in torrent channels. Hence, sediment supply and storage changes from low-order channels of the Manival catchment, a small tributary valley with an active torrent system located exclusively in sedimentary rocks of the Chartreuse Massif (French Alps), were surveyed periodically for 16 months using terrestrial laser scanning (TLS) to study the coupling between sediment dynamics and torrent responses in terms of debris flow events, which occurred twice during the monitoring period. Sediment transfer in the main torrent was monitored with cross-section surveys. Sediment budgets were generated seasonally using sequential TLS data differencing and morphological extrapolations. Debris production depends strongly on rockfall occurring during the winter-early spring season, following a power law distribution for volumes of rockfall events above 0.1 m3, while hillslope sediment reworking dominates debris recharge in spring and autumn, which shows effective hillslope-channel coupling. The occurrence of both debris flow events that occurred during the monitoring was linked to recharge from previous debris pulses coming from the hillside and from bedload transfer. Headwater debris sources display an ambiguous behaviour in sediment transfer: low geomorphic activity occurred in the production zone, despite rainstorms inducing debris flows in the torrent; still, a general reactivation of sediment transport in headwater channels was observed in autumn without new debris supply, suggesting that the stored debris was not exhausted. The seasonal cycle of sediment yield seems to depend not only on debris supply and runoff (flow capacity) but also on geomorphic conditions that destabilize remnant debris stocks. This study shows that monitoring the changes within a torrent's in-channel storage and its debris supply can improve knowledge on recharge thresholds leading to debris flow.

  4. Transformation of cohesive and noncohesive debris flows in subaerial and subaqueous settings

    NASA Astrophysics Data System (ADS)

    Sohn, Y. K.

    2003-04-01

    Debris flows are an important means of sediment transport and deposition in subaerial and subaqueous settings. They commonly transform into dilute flow types (e.g., hyperconcentrated flow, concentrated density flow, or turbidity current) when they mix with ambient water. In subaerial settings, noncohesive debris flows transform easily into dilute flow types when they run over a streamflow, producing a transition facies composed of a hyperconcentrated-flow deposit overlain by a debris-flow deposit in one sedimentation unit. On the other hand, cohesive debris flows are able to maintain their coherence and textural uniformity over 100 km without transforming into dilute flows. The behavioral difference between the cohesive and the noncohesive flows is caused mainly by the difference in the miscibility of the flows with associated streamflows, which depends strongly on the mud content in the matrix. In subaqueous settings, cohesive debris flows can be efficiently diluted because their impermeable (muddy) matrix facilitates hydroplaning. In this case, they produce a transition facies similar to that of subaerial noncohesive debris flows. Noncohesive debris flows in subaqueous settings may transform into dilute flow types as readily as subaerial ones because of larger flow resistance and the lack of surface tension effects by interstitial water. Some studies suggest, however, that clast-rich debris flows may be subject to neither hydroplaning nor vigorous surface transformation, remaining as debris flows to their termini. Further study on the transformation processes and related sedimentary features is necessary for resolving a number of problems regarding hazard assessment of mass-movement processes, characterization of reservoir rocks, and the definition and classification of sediment gravity flows.

  5. Rheological properties of simulated debris flows in the laboratory environment

    USGS Publications Warehouse

    Ling, Chi-Hai; Chen, Cheng-lung; Jan, Chyan-Deng; ,

    1990-01-01

    Steady debris flows with or without a snout are simulated in a 'conveyor-belt' flume using dry glass spheres of a uniform size, 5 or 14 mm in diameter, and their rheological properties described quantitatively in constants in a generalized viscoplastic fluid (GVF) model. Close agreement of the measured velocity profiles with the theoretical ones obtained from the GVF model strongly supports the validity of a GVF model based on the continuum-mechanics approach. Further comparisons of the measured and theoretical velocity profiles along with empirical relations among the shear stress, the normal stress, and the shear rate developed from the 'ring-shear' apparatus determine the values of the rheological parameters in the GVF model, namely the flow-behavior index, the consistency index, and the cross-consistency index. Critical issues in the evaluation of such rheological parameters using the conveyor-belt flume and the ring-shear apparatus are thus addressed in this study.

  6. Magnitude and frequency of debris flows, and areas of hazard on Mount Shasta, northern California

    USGS Publications Warehouse

    Osterkamp, W.R.; Hupp, C.R.; Blodgett, J.C.

    1985-01-01

    Debris flows on Mount Shasta, northern California, have occurred frequently during the late Holocene in response to rapid runoff from melting snow and ice. Glacial-meltwater streams that deeply incise unstable pyroclastic and related flow deposits typically from debris flows when high discharge rates cause slope failures within steep-walled gorges. The landslide material either adsorbs streamflow quickly and becomes a slurry or it briefly dams the stream and converts to a debris flow as breaching occurs. All glacial-meltwater streams on Mount Shasta have been repeated debris-flow activity during the last 500 years. During this period, large-magnitude, potentially destructive flows on Mount Shasta have occurred at a rate of four per century, but smaller flows contained by stream channels may be 10 to 20 times more numerous. The smaller debris flows on Mount Shasta pose little hazard to human life or property, whereas larger, out-of-channel flows could cause minor damage. Only the City of McCloud and inhabited areas on the Whitney-Bolam fan appear to be threatened by possible debris-flow activity. None of the streams lacking glacial meltwater have had significant debris-flow activity during late Holocene time. Sediment yields from upper fan areas of Mount Shasta are very high, but most of the sediment, moved by debris flows from upper slopes is redeposited on lower fan areas, locally causing extensive and rapid aggradation of the fan surface. Little sediment enters a through-flowing stream network. Correspondingly high denudation rates in the sediment source areas for debris flows (the deep gorges) suggest that a high frequency of debris flows may be unique in recent centuries. (USGS)

  7. Headless Debris Flows From Mount Spurr Volcano, Alaska

    NASA Astrophysics Data System (ADS)

    McGimsey, R. G.; Neal, C. A.; Waythomas, C. F.; Wessels, R.; Coombs, M. L.; Wallace, K. L.

    2004-12-01

    Sometime between June 20 and July 15, 2004-and contemporaneous with an increase of seismicity beneath the volcano, and elevated gas emissions-a sudden release of impounded water from the summit area of Mt. Spurr volcano produced about a dozen separate debris flow lobes emanating from crevasses and bergschrunds in the surface ice several hundred meters down the east-southeast flank from the summit. These debris flows were first observed by AVO staff on a July 15 overflight and appeared to represent a single flooding event; subsequent snow cover and limited accessibility have prevented direct investigation of these deposits. Observed from the air, they are dark, elongate lobate deposits, up to several hundred meters long and tens of meters wide, draping the steep (up to ~45 degree) slopes and cascading over and into crevasses. A water-rich phase from the flows continued down slope of the termini of several lobate deposits, eroding linear rills into the snow and ice down slope. We infer that the dark material composing these flows is likely remobilized coarse lapilli from the June 1992 tephra fall produced by an eruption of Crater Peak, a satellite vent of Mt. Spurr located 3.5 km to the south. Between 1 and 2 meters of basaltic andesite tephra fell directly on the Spurr summit during the 1992 eruption. The exact mechanism for sudden release of water-laden remobilized tephra flows from the summit basin is not clear. However, observations in early August, 2004, of an 80 m x 110-m-wide pit in the summit area snow and ice suggest the possibility of a partial roof collapse of a summit meltwater basin, likely associated with subglacial melting due to recent heat flux. Such a collapse could have led to the hydraulic surge of meltwater, and rapid mixing with tephra to produce slurries. These slurries traveled down slope beneath the ice surface to emerge through existing crevasses and other easy points of exit on the steep inclines. Mount Spurr is an ice- and snow covered

  8. Entrainment of bed sediment by debris flows: results from large-scale experiments

    USGS Publications Warehouse

    Reid, Mark E.; Iverson, Richard M.; Logan, Matthew; LaHusen, Richard G.; Godt, Jonathan W.; Griswold, Julie P.

    2011-01-01

    When debris flows grow by entraining sediment, they can become especially hazardous owing to increased volume, speed, and runout. To investigate the entrainment process, we conducted eight largescale experiments in the USGS debris-flow flume. In each experiment, we released a 6 m3 water-saturated debris flow across a 47-m long, ~12-cm thick bed of partially saturated sediment lining the 31º flume. Prior to release, we used low-intensity overhead sprinkling and real-time monitoring to control the bed-sediment wetness. As each debris flow descended the flume, we measured the evolution of flow thickness, basal total normal stress, basal pore-fluid pressure, and sediment scour depth. When debris flows traveled over relatively dry sediment, net scour was minimal, but when debris flows traveled over wetter sediment (volumetric water content > 0.22), debris-flow volume grew rapidly and flow speed and runout were enhanced. Data from scour sensors showed that entrainment occurred by rapid (5-10 cm/s), progressive scour rather than by mass failure at depth. Overriding debris flows rapidly generated high basal pore-fluid pressures when they loaded and deformed bed sediment, and in wetter beds these pressures approached lithostatic levels. Reduction of intergranular friction within the bed sediment thereby enhanced scour efficiency, entrainment, and runout.

  9. Magnitude and frequency data for historic debris flows in Grand Canyon National Park and vicinity, Arizona

    USGS Publications Warehouse

    Melis, T.S.; Webb, R.H.; Griffiths, P.G.; Wise, T.J.

    1995-01-01

    Debris flows occur in 529 tributaries of the Colorado River in Grand Canyon between Lees Ferry and Diamond Creek, Arizona (river miles 0 to 225). An episodic type of flash flood, debris flows transport poorly-sorted sediment ranging in size from clay to boulders into the Colorado River. Debris flows create and maintain debris fans and the hundreds of associated riffles and rapids that control the geomorphic framework of the Colorado River downstream from Glen Canyon Dam. Between 1984 and 1994, debris flows created 4 new rapids and enlarged 17 existing rapids and riffles. Debris flows in Grand Canyon are initiated by slope failures that occur during intense rainfall. Three of these mechanisms of slope failure are documented. Failures in weathered bedrock, particularly in the Hermit Shale and Supai Group, have initiated many historic debris flows in Grand Canyon. A second mechanism, termed the fire-hose effect, occurs when runoff pours over cliffs onto unconsolidated colluvial wedges, triggering a failure. A third initiation mechanism occurs when intense precipitation causes failures in colluvium overlying bedrock. Multiple source areas and extreme topographic relief in Grand Canyon commonly result in combinations of these three initiation mechanisms. Interpretation of 1,107 historical photographs spanning 120 years, supplemented with aerial photography made between 1935 and 1994, yielded information on the frequency of debris flows in 168 of the 529 tributaries (32 percent) of the Colorado River in Grand Canyon. Of the 168 tributaries, 96 contain evidence of debris flows that have occurred since 1872, whereas 72 tributaries have not had a debris flow during the last century. The oldest debris flow we have documented in Grand Canyon occurred 5,400 years ago in an unnamed tributary at river mile 63.3-R. Our results indicate that the frequency of debris flows ranges from one every 10 to 15 years in certain eastern tributaries, to less than one per century in other

  10. Debris flow grain size scales with sea surface temperature over glacial-interglacial timescales

    NASA Astrophysics Data System (ADS)

    D'Arcy, Mitch; Roda Boluda, Duna C.; Whittaker, Alexander C.; Araújo, João Paulo C.

    2015-04-01

    Debris flows are common erosional processes responsible for a large volume of sediment transfer across a range of landscapes from arid settings to the tropics. They are also significant natural hazards in populated areas. However, we lack a clear set of debris flow transport laws, meaning that: (i) debris flows remain largely neglected by landscape evolution models; (ii) we do not understand the sensitivity of debris flow systems to past or future climate changes; and (iii) it remains unclear how to interpret debris flow stratigraphy and sedimentology, for example whether their deposits record information about past tectonics or palaeoclimate. Here, we take a grain size approach to characterising debris flow deposits from 35 well-dated alluvial fan surfaces in Owens Valley, California. We show that the average grain sizes of these granitic debris flow sediments precisely scales with sea surface temperature throughout the entire last glacial-interglacial cycle, increasing by ~ 7 % per 1 ° C of climate warming. We compare these data with similar debris flow systems in the Mediterranean (southern Italy) and the tropics (Rio de Janeiro, Brazil), and find equivalent signals over a total temperature range of ~ 14 ° C. In each area, debris flows are largely governed by rainfall intensity during triggering storms, which is known to increase exponentially with temperature. Therefore, we suggest that these debris flow systems are transporting predictably coarser-grained sediment in warmer, stormier conditions. This implies that debris flow sedimentology is governed by discharge thresholds and may be a sensitive proxy for past changes in rainfall intensity. Our findings show that debris flows are sensitive to climate changes over short timescales (≤ 104 years) and therefore highlight the importance of integrating hillslope processes into landscape evolution models, as well as providing new observational constraints to guide this. Finally, we comment on what grain size

  11. Holocene debris flows on the Colorado Plateau: The influence of clay mineralogy and chemistry

    USGS Publications Warehouse

    Webb, R.H.; Griffiths, P.G.; Rudd, L.P.

    2008-01-01

    Holocene debris flows do not occur uniformly on the Colorado Plateau province of North America. Debris flows occur in specific areas of the plateau, resulting in general from the combination of steep topography, intense convective precipitation, abundant poorly sorted material not stabilized by vegetation, and the exposure of certain fine-grained bedrock units in cliffs or in colluvium beneath those cliffs. In Grand and Cataract Canyons, fine-grained bedrock that produces debris flows contains primarily single-layer clays - notably illite and kaolinite - and has low multilayer clay content. This clay-mineral suite also occurs in the colluvium that produces debris flows as well as in debris-flow deposits, although unconsolidated deposits have less illite than the source bedrock. We investigate the relation between the clay mineralogy and major-cation chemistry of fine-grained bedrock units and the occurrence of debris flows on the entire Colorado Plateau. We determined that 85 mapped fine-grained bedrock units potentially could produce debris flows, and we analyzed clay mineralogy and major-cation concentration of 52 of the most widely distributed units, particularly those exposed in steep topography. Fine-grained bedrock units that produce debris flows contained an average of 71% kaolinite and illite and 5% montmorillonite and have a higher concentration of potassium and magnesium than nonproducing units, which have an average of 51% montmorillonite and a higher concentration of sodium. We used multivariate statistics to discriminate fine-grained bedrock units with the potential to produce debris flows, and we used digital-elevation models and mapped distribution of debris-flow producing units to derive a map that predicts potential occurrence of Holocene debris flows on the Colorado Plateau. ?? 2008 Geological Society of America.

  12. Development and maintenance of a telescoping debris flow fan in response to human-induced fan surface channelization, Chalk Creek Valley Natural Debris Flow Laboratory, Colorado, USA

    NASA Astrophysics Data System (ADS)

    Wasklewicz, T.; Scheinert, C.

    2016-01-01

    Channel change has been a constant theme throughout William L. Graf's research career. Graf's work has examined channel changes in the context of natural environmental fluctuations, but more often has focused on quantifying channel change in the context of anthropogenic modifications. Here, we consider how channelization of a debris flows along a bajada has perpetuated and sustained the development of 'telescoping' alluvial fan. Two-dimensional debris-flow modeling shows the importance of the deeply entrenched channelized flow in the development of a telescoping alluvial fan. GIS analyses of repeat (five different debris flows), high-resolution (5 cm) digital elevation models (DEMs) generated from repeat terrestrial laser scanning (TLS) data elucidate sediment and topographic dynamics of the new telescoping portion of the alluvial fan (the embryonic fan). Flow constriction from channelization helps to perpetuate debris-flow runout and to maintain the embryonic fan and telescoping nature of the alluvial fan complex. Embryonic fan development, in response to five debris flows, proceeds with a major portion of the flows depositing on the southern portion of the embryonic fan. The third through the fifth debris flows also begin to shift some deposition to the northern portion of the embryonic. The transfer of sediment from a higher portion of the embryonic fan to a lower portion continues currently on the embryonic fan. While channelized flow has been shown to be critical to the maintenance of the telescoping fan, the flow constriction has led to higher than background levels of sediment deposition in Chalk Creek, a tributary of the Arkansas River. A majority of the sediment from each debris flow is incorporated into Chalk Creek as opposed to being stored on the embryonic fan.

  13. Initiation of Recent Debris Flows on Mount Rainier, Washington: A Climate Warming Signal?

    NASA Astrophysics Data System (ADS)

    Copeland, E. A.; Kennard, P.; Nolin, A. W.; Lancaster, S. T.; Grant, G. E.

    2008-12-01

    The first week of November 2006 an intense rainstorm inundated the Pacific Northwest and triggered debris flows on many large volcanoes in the Cascade Range of Washington and Oregon. At Mount Rainier, Washington, 45.7 cm of rain was recorded in 36 hours; the storm was preceded by a week of light precipitation and moderate temperatures, so that rain fell on nearly-saturated ground with minimal snow cover. The November 2006 storm was exceptional in that it resulted in a 100-year flood and caused an unprecedented six-month closure of Mount Rainier National Park. It also focused inquiry as to whether debris flows from Cascade volcanoes are likely to occur more frequently in the future as glaciers recede due to climate warming, leaving unstable moraines and sediment that can act as initiation sites. We examined the recent history of debris flows from Mount Rainier using aerial photographs and field surveyed debris flow tracks. Prior to 2001, debris flows were recorded in association with rainfall or glacial outburst floods in 4 drainages, but 3 additional drainages were first impacted by debris flows in 2001, 2005, and 2006, respectively. We discovered that most of the recent debris flows initiated as small gullies in unconsolidated material at the edge of fragmented glaciers or areas of permanent snow and ice. Other initiation sites occur on steep-sided un-vegetated moraines. Of the 28 named glaciers on Mount Rainier, debris flows initiated near five glaciers in the exceptional storm of 2006 (Winthrop, Inter, Kautz-Success, Van Trump, Pyramid, and South Tahoma). Less exceptional storms, however, have also produced wide-spread debris flows: in September 2005, 15.3 cm of rain fell in 48 hours on minimal snow cover and caused debris flows in all except 2 of the glacier drainages that initiated in 2006. Debris flows from both storms initiated at elevations of 1980 to 2400 m, traveled 5 to 10 kilometers, and caused significant streambed aggradation. These results suggest a

  14. Catastrophic debris-flows: geological hazard and human influence

    NASA Astrophysics Data System (ADS)

    Del Ventisette, Chiara; Garfagnoli, Francesca; Ciampalini, Andrea; Battistini, Alessandro; Gigli, Giovanni; Moretti, Sandro; Casagli, Nicola

    2013-04-01

    Rainfall-induced landslides are widespread phenomena often affecting urbanized areas and causing intense damages and casualties. The management of the post-event phase requires a fast evaluation of the involved areas and triggering factors. The latter are fundamental to evaluate the stability of the area affected by landslides, in order to facilitate quick and safe activities of the Civil Protection Authorities during the emergency. On October 1st 2009, a prolonged and intense rainstorm triggered hundreds of landslides (predominantly debris flows) in an area of about 50 km2 in the north-eastern sector of Sicily (Italy). Debris flows swept the highest parts of many villages and passed over the SS114 state highway and the Messina-Catania railway, causing more than 30 fatalities. This work deals with the geological and hydro-geomorphological studies performed as a part of the post-disaster activities operated in collaboration with Civil Protection Authority, with the aim of examining landslides effects and mechanisms. The data were elaborated into a GIS platform, to evaluate the influence of urbanization on the drainage pattern and were correlated with the lithological and structural framework of the area. The case study of Giampilieri focuses the attention on the necessity of sustainable land use and reasonable urban management in areas characterized by a high hydrogeological hazard and on the tremendous destructive power of these phenomena, which are capable of causing a large number of victims in such small villages. Field surveys and stereo-photo geomorphological analysis revealed a significant human influence on determining landslide triggering causes, as well as the final amount of damage. In particular, destruction and injuries in the built-up area of Giampilieri were made even more severe by the main water flow lines made narrower due to building activity and enlargement of the urban area. The area maintains a high degree of hazard: deposits of poorly

  15. Control works in debris-flow channels: influence on morphology and sediment transfer

    NASA Astrophysics Data System (ADS)

    Marchi, L.

    2012-04-01

    Extensive torrent control works, such as grade-control dams, debris basins, deflecting walls, etc. have been implemented in the European Alps since the last decades of 19th century. These structural measures, aimed at stabilizing channels and to control sediment transport, are also widespread in Japan and are increasingly present in other mountain regions. As debris flows are one of the most destructive processes in steep mountain channels, hydraulic works are often intended to attenuate debris-flow hazard. Multi-temporal aerial photos and historic records permit evaluating the long term effects of torrent control works on the morphological settings of the channels and the delivery of sediment. The experience arising from over one century of torrent control works in debris-flow channels of the Alps permits also to improve the management of steep headwater catchments. A basic issue in the management of debris-flow channels is the recognition of success versus failure of engineering control works. Successful debris-flow control works provide benchmarks for further implementations, whereas the failure in reducing debris-flow hazard may lead to refinements in planning and design of control works or to the choice of preferring non-structural measures for coping with debris flows. Data from historical archives on debris-flow occurrence and on the performance of control works are the basic sources of information for these analyses. Moreover, when dealing with hydraulic structures for debris-flow control, it should be reminded that the artificial morphology resulting from the construction of check dams provides only a temporary stability to the channel and adjacent banks. This stresses the importance of evaluating the state of conservation and the effectiveness of control works and implies the need for their careful and continuous maintenance. Inventories of hydraulic structures, coupled with detailed data on catchment and channel topography, sediment sources and supply

  16. Hydraulic modeling of unsteady debris-flow surges with solid-fluid interactions

    USGS Publications Warehouse

    Iverson, Richard M.

    1997-01-01

    Interactions of solid and fluid constituents produce the unique style of motion that typifies debris flows. To simulate this motion, a new hydraulic model represents debris flows as deforming masses of granular solids variably liquefied by viscous pore fluid. The momentum equation of the model describes how internal and boundary forces change as coarse-grained surge heads dominated by grain-contact friction grade into muddy debris-flow bodies more strongly influenced by fluid viscosity and pressure. Scaling analysis reveals that pore-pressure variations can cause flow resistance in surge heads to surpass that in debris-flow bodies by orders of magnitude. Numerical solutions of the coupled momentum and continuity equations provide good predictions of unsteady, nonuniform motion of experimental debris flows from initiation through deposition.

  17. Runoff-generated debris flows: observations and modeling of surge initiation, magnitude, and frequency

    USGS Publications Warehouse

    Kean, Jason W.; McCoy, Scott W.; Tucker, Gregory E.; Staley, Dennis M.; Coe, Jeffrey A.

    2013-01-01

    Runoff during intense rainstorms plays a major role in generating debris flows in many alpine areas and burned steeplands. Yet compared to debris flow initiation from shallow landslides, the mechanics by which runoff generates a debris flow are less understood. To better understand debris flow initiation by surface water runoff, we monitored flow stage and rainfall associated with debris flows in the headwaters of two small catchments: a bedrock-dominated alpine basin in central Colorado (0.06 km2) and a recently burned area in southern California (0.01 km2). We also obtained video footage of debris flow initiation and flow dynamics from three cameras at the Colorado site. Stage observations at both sites display distinct patterns in debris flow surge characteristics relative to rainfall intensity (I). We observe small, quasiperiodic surges at low I; large, quasiperiodic surges at intermediate I; and a single large surge followed by small-amplitude fluctuations about a more steady high flow at high I. Video observations of surge formation lead us to the hypothesis that these flow patterns are controlled by upstream variations in channel slope, in which low-gradient sections act as “sediment capacitors,” temporarily storing incoming bed load transported by water flow and periodically releasing the accumulated sediment as a debris flow surge. To explore this hypothesis, we develop a simple one-dimensional morphodynamic model of a sediment capacitor that consists of a system of coupled equations for water flow, bed load transport, slope stability, and mass flow. This model reproduces the essential patterns in surge magnitude and frequency with rainfall intensity observed at the two field sites and provides a new framework for predicting the runoff threshold for debris flow initiation in a burned or alpine setting.

  18. Runoff-generated debris flows: Observations and modeling of surge initiation, magnitude, and frequency

    NASA Astrophysics Data System (ADS)

    Kean, Jason W.; McCoy, Scott W.; Tucker, Gregory E.; Staley, Dennis M.; Coe, Jeffrey A.

    2013-12-01

    during intense rainstorms plays a major role in generating debris flows in many alpine areas and burned steeplands. Yet compared to debris flow initiation from shallow landslides, the mechanics by which runoff generates a debris flow are less understood. To better understand debris flow initiation by surface water runoff, we monitored flow stage and rainfall associated with debris flows in the headwaters of two small catchments: a bedrock-dominated alpine basin in central Colorado (0.06 km2) and a recently burned area in southern California (0.01 km2). We also obtained video footage of debris flow initiation and flow dynamics from three cameras at the Colorado site. Stage observations at both sites display distinct patterns in debris flow surge characteristics relative to rainfall intensity (I). We observe small, quasiperiodic surges at low I; large, quasiperiodic surges at intermediate I; and a single large surge followed by small-amplitude fluctuations about a more steady high flow at high I. Video observations of surge formation lead us to the hypothesis that these flow patterns are controlled by upstream variations in channel slope, in which low-gradient sections act as "sediment capacitors," temporarily storing incoming bed load transported by water flow and periodically releasing the accumulated sediment as a debris flow surge. To explore this hypothesis, we develop a simple one-dimensional morphodynamic model of a sediment capacitor that consists of a system of coupled equations for water flow, bed load transport, slope stability, and mass flow. This model reproduces the essential patterns in surge magnitude and frequency with rainfall intensity observed at the two field sites and provides a new framework for predicting the runoff threshold for debris flow initiation in a burned or alpine setting.

  19. Influence of check dams on debris-flow run-out intensity

    NASA Astrophysics Data System (ADS)

    Remaã®Tre, A.; van Asch, Th. W. J.; Malet, J.-P.; Maquaire, O.

    2008-12-01

    Debris flows are very dangerous phenomena claiming thousands of lives and millions of Euros each year over the world. Disaster mitigation includes non-structural (hazard mapping, insurance policies), active structural (drainage systems) and passive structural (check dams, stilling basins) countermeasures. Since over twenty years, many efforts are devoted by the scientific and engineering communities to the design of proper devices able to capture the debris-flow volume and/or break down the energy. If considerable theoretical and numerical work has been performed on the size, the shape and structure of check dams, allowing the definition of general design criteria, it is worth noting that less research has focused on the optimal location of these dams along the debris-flow pathway. In this paper, a methodological framework is proposed to evaluate the influence of the number and the location of the check dams on the reduction of the debris-flow intensity (in term of flow thickness, flow velocity and volume). A debris-flow model is used to simulate the run-out of the debris flow. The model uses the Janbu force diagram to resolve the force equilibrium equations; a bingham fluid rheology is introduced and represents the resistance term. The model has been calibrated on two muddy debris-flow events that occurred in 1996 and 2003 at the Faucon watershed (South French Alps). Influence of the check dams on the debris-flow intensity is quantified taking into account several check dams configurations (number and location) as input geometrical parameters. Results indicate that debris-flow intensity is decreasing with the distance between the source area and the first check dams. The study demonstrates that a small number of check dams located near the source area may decrease substantially the debris-flow intensity on the alluvial fans.

  20. Debris flows from tributaries of the Colorado River, Grand Canyon National Park, Arizona

    USGS Publications Warehouse

    Webb, Robert H.; Pringle, Patrick T.; Rink, Glenn R.

    1989-01-01

    A reconnaissance of 36 tributaries of the Colorado River indicates that debris flows are a major process by which sediment is transported to the Colorado River in Grand Canyon National Park. Debris flows are slurries of sediment and water that have a water content of less than about 40 percent by volume. Debris flows occur frequently in arid and semiarid regions. Slope failures commonly trigger debris flows, which can originate from any rock formation in the Grand Canyon. The largest and most frequent flows originate from the Permian Hermit Shale, the underlying Esplanade Sandstone of the Supai Group, and other formations of the Permian and Pennsylvanian Supai Group. Debris flows also occur in the Cambrian Muav Limestone and underlying Bright Angel Shale and the Quaternary basalts in the western Grand Canyon. Debris-flow frequency and magnitude were studied in detail in the Lava-Chuar Creek drainage at Colorado River mile 65.5; in the Monument Creek drainage at mile 93.5; and in the Crystal Creek drainage at mile 98.2. Debris flows have reached the Colorado River on an average of once every 20 to 30 years in the Lava-Chuar Creek drainage since about 1916. Two debris flows have reached the Colorado River in the last 25 years in Monument Creek. The Crystal Creek drainage has had an average of one debris flow reaching the Colorado River every 50 years, although the debris flow of 1966 has been the only flow that reached the Colorado River since 1900. Debris flows may actually reach the Colorado River more frequently in these drainages because evidence for all debris flows may not have been preserved in the channel-margin stratigraphy. Discharges were estimated for the peak flow of three debris flows that reached the Colorado River. The debris flow of 1966 in the Lava-Chuar Creek drainage had an estimated discharge of 4,000 cubic feet per second. The debris flow of 1984 in the Monument Creek drainage had a discharge estimated between 3,600 and 4,200 cubic feet per

  1. The vulnerability assessment of rainfall-induced debris flows in Taiwan

    NASA Astrophysics Data System (ADS)

    Lu, George Yen-Hsu

    2007-12-01

    A debris flow vulnerability assessment which incorporates topographic and rainfall effects is developed. Rainfall at a scale compatible with the resolution of digital elevation model is obtained using a neural network estimation method with a wind induced topographic effect and rainfall derived from satellite rain estimates and an improved inverse distance weight method. The technique is tested using data collected during the passage of typhoon Tori-Ji on July 2001, which caused massive debris flows in central Taiwan. Numerous debris flows triggered by the typhoon were used as control for the study. The results show that the proposed wind-topography neural network (WTNN) technique outperforms other popular interpolation techniques, including inversed distance weight method (IDW), ordinary kriging (OK), co-kriging method, and multiple linear regression method. Multiple fuzzy-logic-based debris flow susceptibility factors are used to characterize watersheds. Self-organizing maps (SOM) was adopted for the debris flow vulnerability assessment by incorporating estimated rainfall and debris flow susceptibility factors. The result examined by contingency table agrees to the assessment proposed by Soil and Water Conservation Bureau of Taiwan and National Science and Technology Center for Hazard Reduction of Taiwan. An index of vulnerability representing the degrees of hazard is implemented in a GIS-based decision support system which decision maker can use to manage debris flow environmental issues. Key Words. Debris flow, spatial interpolation, vulnerability assessment, satellite rainfall, neural network, GIS.

  2. Differentiation of debris-flow and flash-flood deposits: implications for paleoflood investigations

    USGS Publications Warehouse

    Waythomas, Christopher F.; Jarrett, Robert D.

    1993-01-01

    Debris flows and flash floods are common geomorphic processes in the Colorado Rocky Mountain Front Range and foothills. Usually, debris flows and flash floods are associated with excess summer rainfall or snowmelt, in areas were unconsolidated surficial deposits are relatively thick and slopes are steep. In the Front Range and foothills, flash flooding is limited to areas below about 2300m whereas, debris flow activity is common throughout the foothill and alpine zones and is not necessarily elevation limited. Because flash floods and debris flows transport large quantities of bouldery sediment, the resulting deposits appear somewhat similar even though such deposits were produced by different processes. Discharge estimates based on debris-flow deposits interpreted as flash-flood deposits have large errors because techniques for discharge retrodiction were developed for water floods with negligible sediment concentrations. Criteria for differentiating between debris-flow and flash-flood deposits are most useful for deposits that are fresh and well-exposed. However, with the passage of time, both debris-flow and flash-flood deposits become modified by the combined effects of weathering, colluviation, changes in surface morphology, and in some instances removal of interstitial sediment. As a result, some of the physical characteristics of the deposits become more alike. Criteria especially applicable to older deposits are needed. We differentiate flash-flood from debris-flow and other deposits using clast fabric measurements and other morphologic and sedimentologic techniques (e.g., deposit morphology, clast lithology, particle size and shape, geomorphic setting).

  3. Debris flow cartography using differential GNSS and Theodolite measurements

    NASA Astrophysics Data System (ADS)

    Khazaradze, Giorgi; Guinau, Marta; Calvet, Jaume; Furdada, Gloria; Victoriano, Ane; Génova, Mar; Suriñach, Emma

    2016-04-01

    The presented results form part of a CHARMA project, which pursues a broad objective of reducing damage caused by uncontrolled mass movements, such as rockfalls, snow avalanches and debris flows. Ultimate goal of the project is to contribute towards the establishment of new scientific knowledge and tools that can help in the design and creation of early warning systems. Here we present the specific results that deal with the application of differential GNSS and classical geodetic (e.g. theodolite) methods for mapping debris and torrential flows. Specifically, we investigate the Portainé stream located in the Pallars Sobirà region of Catalonia (Spain), in the eastern Pyrenees. In the last decade more than ten debris-flow type phenomena have affected the region, causing considerable economic losses. Since early 2014, we have conducted several field campaigns within the study area, where we have employed a multi-disciplinary approach, consisting of geomorphological, dendro-chronological and geodetic methods, in order to map the river bed and reconstruct the history of the extreme flooding and debris flow events. Geodetic studies included several approaches, using the classical and satellite based methods. The former consisted of angle and distance measurements between the Geodolite 502 total station and the reflecting prisms placed on top of the control points located within the riverbed. These type of measurements are precise, although present several disadvantages such as the lack of absolute coordinates that makes the geo-referencing difficult, as well as a relatively time-consuming process that involves two persons. For this reason, we have also measured the same control points using the differential GNSS system, in order to evaluate the feasibility of replacing the total station measurements with the GNSS. The latter measuring method is fast and can be conducted by one person. However, the fact that the study area is within the riverbed, often below the trees

  4. Bed Stability and Debris Flow Erosion: A Dynamic "Shields Criterion" Associated with Bed Structure

    NASA Astrophysics Data System (ADS)

    Longjas, A.; Hill, K. M.

    2015-12-01

    Debris flows are mass movements that play an important role in transporting sediment from steep uplands to rivers at lower slopes. As the debris flow moves downstream, it entrains materials such as loose boulders, gravel, sand and mud deposited locally by shorter flows such as slides and rockfalls. To capture the conditions under which debris flows entrain bed sediment, some models use something akin to the Shields' criterion and an excess shear stress of the flow. However, these models typically neglect granular-scale effects in the bed which can modify the conditions under which a debris flow is erosional or depositional. For example, it is well known that repeated shearing causes denser packing in loose dry soils, which undoubtedly changes their resistance to shear. Here, we present laboratory flume experiments showing that the conditions for entrainment by debris flows is significantly dependent on the aging of an erodible bed even for narrowly distributed spherical particles. We investigate this quantitatively using particle tracking measurements to quantify instantaneous erosion rates and the evolving bed structure or "fabric". With progressive experiments we find a signature that emerges in the bed fabric that is correlated with an increasing apparent "fragility" of the bed. Specifically, a system that is originally depositional may become erosional after repeated debris flow events, and an erodible bed becomes increasingly erodible with repeated flows. We hypothesize that related effects of bed aging at the field scale may be partly responsible for the increasing destructiveness of secondary flows of landslides and debris flows.

  5. Sedimentology, Behavior, and Hazards of Debris Flows at Mount Rainier, Washington

    USGS Publications Warehouse

    Scott, K.M.; Vallance, J.W.; Pringle, P.T.

    1995-01-01

    Mount Rainier is potentially the most dangerous volcano in the Cascade Range because of its great height, frequent earthquakes, active hydrothermal system, and extensive glacier mantle. Many debris flows and their distal phases have inundated areas far from the volcano during postglacial time. Two types of debris flows, cohesive and noncohesive, have radically different origins and behavior that relate empirically to clay content. The two types are the major subpopulations of debris flows at Mount Rainier. The behavior of cohesive flows is affected by the cohesion and adhesion of particles; noncohesive flows are dominated by particle collisions to the extent that particle cataclasis becomes common during near-boundary shear. Cohesive debris flows contain more than 3 to 5 percent of clay-size sediment. The composition of these flows changed little as they traveled more than 100 kilometers from Mount Rainier to inundate parts of the now-populated Puget Sound lowland. They originate as deep-seated failures of sectors of the volcanic edifice, and such failures are sufficiently frequent that they are the major destructional process of Mount Rainier's morphologic evolution. In several deposits of large cohesive flows, a lateral, megaclast-bearing facies (with a mounded or hummocky surface) contrasts with a more clay-rich facies in the center of valleys and downstream. Cohesive flows at Mount Rainier do not correlate strongly with volcanic activity and thus can recur without warning, possibly triggered by non-magmatic earthquakes or by changes in the hydrothermal system. Noncohesive debris flows contain less than 3 to 5 percent clay-size sediment. They form most commonly by bulking of sediment in water surges, but some originate directly or indirectly from shallow slope failures that do not penetrate the hydrothermally altered core of the volcano. In contrast with cohesive flows, most noncohesive flows transform both from and to other flow types and are, therefore, the

  6. Spatial estimation of debris flows-triggering rainfall and its dependence on rainfall severity

    NASA Astrophysics Data System (ADS)

    Destro, Elisa; Marra, Francesco; Nikolopoulos, Efthymios; Zoccatelli, Davide; Creutin, Jean-Dominique; Borga, Marco

    2016-04-01

    Forecasting the occurrence of landslides and debris flows (collectively termed 'debris flows' hereinafter) is fundamental for issuing hazard warnings, and focuses largely on rainfall as a triggering agent. Debris flow forecasting relies very often on the identification of combinations of depth and duration of rainfall - rainfall thresholds - that trigger widespread debris flows. Rainfall estimation errors related to the sparse nature of raingauge data are enhanced in case of convective rainfall events characterized by limited spatial extent. Such errors have been shown to cause underestimation of the rainfall thresholds and, thus, less efficient forecasts of debris flows occurrence. This work examines the spatial organization of debris flows-triggering rainfall around the debris flow initiation points using high-resolution, carefully corrected radar data for a set of short duration (<30 h) storm events occurred in the eastern Italian Alps. The set includes eleven debris-flow triggering rainfall events that occurred in the study area between 2005 and 2014. The selected events are among the most severe in the region during this period and triggered a total of 99 debris flows that caused significant damage to people and infrastructures. We show that the spatial rainfall organisation depends on the severity (measured via the estimated return time-RT) of the debris flow-triggering rainfall. For more frequent events (RT<20 yrs) the rainfall spatial pattern systematically shows that debris flow location coincides with a local minimum, whereas for less frequent events (RT>20 yrs) the triggering rainfall presents a local peak corresponding to the debris flow initiation point. Dependence of these features on rainfall duration is quite limited. The characteristics of the spatial rainfall organisation are exploited to understand the performances and results of three different rainfall interpolation techniques: nearest neighbour (NN), inverse distance weighting (IDW) and

  7. Quantifying sources of fine sediment supplied to post-fire debris flows using fallout radionuclide tracers

    NASA Astrophysics Data System (ADS)

    Smith, H. G.; Sheridan, G. J.; Nyman, P.; Child, D.; Lane, P. N.; Hotchkis, M.

    2011-12-01

    The supply of fine sediment and ash has been identified as an important factor contributing to the initiation of runoff-generated debris flows after fire. However, despite the significance of fines for post-fire debris flow generation, no investigations have sought to quantify sources of this material in debris flow affected catchments. In this study, we employ fallout radionuclides (Cs-137, excess Pb-210 and Pu-239,240) as tracers to measure proportional contributions of fine sediment (<10 μm) from hillslope surface and channel bank sources to levee and terminal fan deposits formed by post-fire debris flows in two forest catchments in southeastern Australia. While Cs-137 and excess Pb-210 have been widely used in sediment tracing studies, application of Pu as a tracer represents a recent development and was limited to only one catchment. The estimated range in proportional hillslope surface contributions of fine sediment to individual debris flow deposits in each catchment was 22-69% and 32-74%. No systematic change in the proportional source contributions to debris flow deposits was observed with distance downstream from channel initiation points. Instead, spatial variability in source contributions was largely influenced by the pattern of debris flow surges forming the deposits. Linking the tracing analysis with interpretation of depositional evidence allowed reconstruction of temporal sequences in sediment source contributions to debris flow surges. Hillslope source inputs dominated most elevated channel deposits such as marginal levees that were formed under peak flow conditions. This indicated the importance of hillslope runoff and fine sediment supply for debris flow generation in both catchments. In contrast, material stored within channels that was deposited during subsequent surges was predominantly channel-derived. The results demonstrate that fallout radionuclide tracers may provide unique information on the changing source contributions of fine

  8. Debris flows resulting from glacial-lake outburst floods in tibet, China

    USGS Publications Warehouse

    Cui, P.; Dang, C.; Cheng, Z.; Scott, K.

    2010-01-01

    During the last 70 years of general climatic amelioration, 18 glacial-lake outburst floods (GLOFs) and related debris flows have occurred from 15 moraine-dammed lakes in Tibet, China. Catastrophic loss of life and property has occurred because of the following factors: the large volumes of water discharged, the steep gradients of the U-shaped channels, and the amount and texture of the downstream channel bed and bank material. The peak discharge of each GLOF exceeded 1000 m3/s. These flood discharges transformed to non-cohesive debris flows if the channels contained sufficient loose sediment for entrainment (bulking) and if their gradients were >1%. We focus on this key element, transformation, and suggest that it be included in evaluating future GLOF-related risk, the probability of transformation to debris flow and hyperconcentrated flow. The general, sequential evolution of the flows can be described as from proximal GLOFs, to sedimentladen streamflow, to hyperconcentrated flow, to non-cohesive debris flow (viscous or cohesive debris flow only if sufficient fine sediment is present), and then, distally, back to hyperconcentrated flow and sediment-laden streamflow as sediment is progressively deposited. Most of the Tibet examples transformed only to non-cohesive debris flows. The important lesson for future hazard assessment and mitigation planning is that, as a GLOF entrains (bulks) enough sediment to become a debris flow, the flow volume must increase by at least three times (the "bulking factor"). In fact, the transforming flow waves overrun and mix with downstream streamflow, in addition to adding the entrained sediment (and thus enabling addition of yet more sediment and a bulking factor in excess of three times). To effectively reduce the risk of GLOF debris flows, reducing the level of a potentially dangerous lake with a siphon or excavated spillway or installing gabions in combination with a downstream debris dam are the primary approaches.

  9. Thirty-one years of debris-flow observation and monitoring near La Honda, California, USA

    USGS Publications Warehouse

    Wieczorek, G.F.; Wilson, R.C.; Ellen, S.D.; Reid, M.E.; Jayko, A.S.

    2007-01-01

    From 1975 until 2006,18 intense storms triggered at least 248 debris flows within 10 km2 northwest of the town of La Honda within the Santa Cruz Mountains, California. In addition to mapping debris flows and other types of landslides, studies included soil sampling and geologic mapping, piezometric and tensiometer monitoring, and rainfall measurement and recording. From 1985 until 1995, a system with radio telemetered rain gages and piezometers within the La Honda region was used for issuing six debris-flow warnings within the San Francisco Bay region through the NOAA ALERT system. Depending upon the relative intensity of rainfall during storms, debris flows were generated from deep slumps, shallow slumps, shallow slides in colluvium and shallow slides over bedrock. Analysis shows the storms with abundant antecedent rainfall followed by several days of steady heavy intense rainfall triggered the most abundant debris flows. ?? 2007 millpress.

  10. Analysis of Debris Flow Behavior Using Airborne LIDAR and Image Data

    NASA Astrophysics Data System (ADS)

    Kim, G.; Yune, C. Y.; Paik, J.; Lee, S. W.

    2016-06-01

    The frequency of debris flow events caused by severe rainstorms has increased in Korea. LiDAR provides high-resolution topographical data that can represent the land surface more effectively than other methods. This study describes the analysis of geomorphologic changes using digital surface models derived from airborne LiDAR and aerial image data acquired before and after a debris flow event in the southern part of Seoul, South Korea in July 2011. During this event, 30 houses were buried, 116 houses were damaged, and 22 human casualties were reported. Longitudinal and cross-sectional profiles of the debris flow path reconstructed from digital surface models were used to analyze debris flow behaviors such as landslide initiation, transport, erosion, and deposition. LiDAR technology integrated with GIS is a very useful tool for understanding debris flow behavior.

  11. The debris flows risk in south Baikal region of Russia - high losses or low risk

    NASA Astrophysics Data System (ADS)

    Shnyparkov, Aleksandr; Baburin, Vyacheslav; Sokratov, Sergey; Khismatullin, Timur

    2016-04-01

    Debris flows were previously not considered as frequent and disastrous natural hazards in the south Baikal region of Russia. The historical records list only two events resulting in reported serious economical losses in here (1903 and 1962). However, an event of June 2014 (Arshan settlement destruction) raised discussion on the debris flow danger and necessity of expensive mitigation measures in the regions. That is why debris flow risk was estimated for the region as a whole with the purpose to calculate the necessary investments into the debris flows protection. The presented results suggests that the degree of debris flows danger is still at least twice lower than is such regions as the North Caucasus in Russia and single events should not be considered as a main basis for regional land use planning.

  12. Debris flows from small catchments of the Ma Ha Tuak Range, metropolitan Phoenix, Arizona

    NASA Astrophysics Data System (ADS)

    Dorn, Ronald I.

    2010-08-01

    Debris flows debauch from tiny but steep mountain catchments throughout metropolitan Phoenix, Arizona, USA. Urban growth in the past half-decade has led to home construction directly underneath hundreds of debris-flow channels, but debris flows are not recognized as a potential hazard at present. One of the first steps in a hazard assessment is to determine occurrence rates. The north flank of the Ma Ha Tuak Range, just 10 km from downtown Phoenix, was selected to determine the feasibility of using the varnish microlaminations (VML) method to date every debris-flow levee from 127 catchment areas. Only 152 of the 780 debris-flow levees yielded VML ages in a first round of sampling; this high failure rate is due to erosion of VML by microcolonial fungi. The temporal pattern of preserved debris-flow levees indicates anomalously high production of debris flows at about 8.1 ka and about 2.8 ka, corresponding to Northern Hemisphere climatic anomalies. Because many prior debris flows are obliterated by newer events, the minimum overall occurrence rates of 1.3 debris flows per century for the last 60 ka, 2.2 flows/century for the latest Pleistocene, and 5 flows/century for the last 8.1 ka has little meaning in assessment of a contemporary hazard. This is because newer debris flows have obliterated an unknown number of past deposits. More meaningful to a hazards analysis is the estimate that 56 flows have occurred in the last 100 years on the north side of the range, an estimate that is consistent with direct observations of three small debris flows resulting events from a January 18-22, 2010 storm producing 70 mm of precipitation in the Ma Ha Tuak Range, and a 500 m long debris flow in a northern metropolitan Phoenix location that received over 150 mm of precipitation in this same storm. These findings support the need for a more extensive hazard assessment of debris flows in metropolitan Phoenix.

  13. Development of a remotely controlled debris flow monitoring system in the Dolomites (Acquabona, Italy)

    NASA Astrophysics Data System (ADS)

    Tecca, Pia R.; Galgaro, Antonio; Genevois, Rinaldo; Deganutti, Andrea M.

    2003-06-01

    Direct measurements of the hydrological conditions for the occurrence of debris flows and of flow behaviour are of the outmost importance for developing effective flow prevention techniques. An automated and remotely controlled monitoring system was installed in Acquabona Creek in the Dolomites, Italian Eastern Alps, where debris flows occur every year. Its present configuration consists of three on-site stations, located in the debris-flow initiation area, in the lower channel and in the retention basin. The monitoring system is equipped with sensors for measuring rainfall, pore-water pressure in the mobile channel bottom, ground vibrations, debris flow depth, total normal stress and fluid pore-pressure at the base of the flow. Three video cameras take motion pictures of the events at the initiation zone, in the lower channel and in the deposition area. Data from the on-site stations are radio-transmitted to an off-site station and stored in a host PC, from where they are telemetrically downloaded and used by the Padova University for the study of debris flows. The efficiency of the sensors and of the whole monitoring system has been verified by the analysis of data collected so far. Examples of these data are presented and briefly discussed. If implemented at the numerous debris-flow sites in the Dolomitic Region, the technology used, derived from the development of this system, will provide civil defence and warn residents of impending debris flows.

  14. Elements of an improved model of debris-flow motion

    USGS Publications Warehouse

    Iverson, R.M.

    2009-01-01

    A new depth-averaged model of debris-flow motion describes simultaneous evolution of flow velocity and depth, solid and fluid volume fractions, and pore-fluid pressure. Non-hydrostatic pore-fluid pressure is produced by dilatancy, a state-dependent property that links the depth-averaged shear rate and volumetric strain rate of the granular phase. Pore-pressure changes caused by shearing allow the model to exhibit rate-dependent flow resistance, despite the fact that the basal shear traction involves only rate-independent Coulomb friction. An analytical solution of simplified model equations shows that the onset of downslope motion can be accelerated or retarded by pore-pressure change, contingent on whether dilatancy is positive or negative. A different analytical solution shows that such effects will likely be muted if downslope motion continues long enough, because dilatancy then evolves toward zero, and volume fractions and pore pressure concurrently evolve toward steady states. ?? 2009 American Institute of Physics.

  15. Triggering conditions and mobility of debris flows associated to complex earthflows

    NASA Astrophysics Data System (ADS)

    Malet, J.-P.; Laigle, D.; Remaître, A.; Maquaire, O.

    2005-03-01

    Landslides on black marl slopes of the French Alps are, in most cases, complex catastrophic failures in which the initial structural slides transform into slow-moving earthflows. Under specific hydrological conditions, these earthflows can transform into debris flows. Due to their sediment volume and their high mobility, debris flow induced by landslides are far much dangerous than these resulting from continuous erosive processes. A fundamental point to correctly delineate the area exposed to debris flows on the alluvial fans is therefore to understand why and how some earthflows transform into debris flow while most of them stabilize. In this paper, a case of transformation from earthflow to debris flow is presented and analysed. An approach combining geomorphology, hydrology, geotechnics and rheology is adopted to model the debris flow initiation (failure stage) and its runout (postfailure stage). Using the Super-Sauze earthflow (Alpes-de-Haute-Provence, France) as a case study, the objective is to characterize the hydrological and mechanical conditions leading to debris flow initiation in such cohesive material. Results show a very good agreement between the observed runout distances and these calculated using the debris flow modeling code Cemagref 1-D. The deposit thickness in the depositional area and the velocities of the debris flows are also well reproduced. Furthermore, a dynamic slope stability analysis shows that conditions in the debris source area under average pore water pressures and moisture contents are close to failure. A small excess of water can therefore initiate failure. Seepage analysis is used to estimate the volume of debris that can be released for several hydroclimatic conditions. The failed volumes are then introduced in the Cemagref 1-D runout code to propose debris flow hazard scenarios. Results show that clayey earthflow can transform under 5-year return period rainfall conditions into 1-km runout debris flow of volumes ranging

  16. Hazard Analysis for Post-Fire Debris-Flow Potential in Arizona

    NASA Astrophysics Data System (ADS)

    Youberg, A.; Koestner, K. A.; Schiefer, E.; Neary, D. G.

    2011-12-01

    Several large, devastating wildfires occurred in Arizona during the past 2 years, after a 4-year period without any large wildfires. In June, 2010, the human-caused Schultz Fire near Flagstaff burned 6,100 ha of mostly steep terrain. Subsequent rains from the 4th wettest monsoon on record produced numerous debris flows, significant erosion, and substantial flooding of the downslope residential areas. In May and June of 2011, 3 very large human-caused wildfires (Wallow, Horseshoe 2, and Monument Fires) burned over 320,000 ha, posing serious threats to communities below burned slopes. The Burned Area Emergency Response (BAER) teams, in need of a rapid method to assess the potential for post-fire debris flows, turned to models developed by the USGS for this purpose [Cannon and others, 2010, GSA Bull, 122(1-2), 127-144]. These models, while providing quick results, have not been evaluated for use in Arizona's varied physiographic provinces. Here we use data from the Schultz Fire to compare basin responses with those predicted by the USGS post-fire debris-flow models. Data from the Schultz Fire includes detailed field documentation of debris-flow occurrence and runout distances, 1:12,000 stereo aerial photographs, high-resolution digital elevation models (DEMs) and tipping-bucket rainfall data. These data document debris-flow producing storms, basin response, and the extent of debris-flow runout, and provide estimates of debris-flow volumes. The hydrologic responses from 30 small, steep, upper basins burned by the Schultz Fire were assessed for debris or flood flow occurrences. Nineteen basins produced debris flows during a July 20th storm that had a peak 10-minute intensity of 24 mm. A second storm on August 16th, with a peak 10-minute intensity of 15 mm, produced additional debris flows in several of the same basins. Of the 30 basins assessed, 19 were completely burned; four at high severity and 12 at moderate to high severity. The basin with the smallest burned area

  17. Calibration of numerical models for small debris flows in Yosemite Valley, California, USA

    USGS Publications Warehouse

    Bertolo, P.; Wieczorek, G.F.

    2005-01-01

    This study compares documented debris flow runout distances with numerical simulations in the Yosemite Valley of California, USA, where about 15% of historical events of slope instability can be classified as debris flows and debris slides (Wieczorek and Snyder, 2004). To model debris flows in the Yosemite Valley, we selected six streams with evidence of historical debris flows; three of the debris flow deposits have single channels, and the other three split their pattern in the fan area into two or more channels. From field observations all of the debris flows involved coarse material, with only very small clay content. We applied the one dimensional DAN (Dynamic ANalysis) model (Hungr, 1995) and the two-dimensional FLO2D model (O'Brien et al., 1993) to predict and compare the runout distance and the velocity of the debris flows observed in the study area. As a first step, we calibrated the parameters for the two softwares through the back analysis of three debris- flows channels using a trial-and-error procedure starting with values suggested in the literature. In the second step we applied the selected values to the other channels, in order to evaluate their predictive capabilities. After parameter calibration using three debris flows we obtained results similar to field observations We also obtained a good agreement between the two models for velocities. Both models are strongly influenced by topography: we used the 30 m cell size DTM available for the study area, that is probably not accurate enough for a highly detailed analysis, but it can be sufficient for a first screening. European Geosciences Union ?? 2005 Author(s). This work is licensed under a Creative Commons License.

  18. Debris-flow hazards caused by hydrologic events at Mount Rainier, Washington

    USGS Publications Warehouse

    Vallance, James W.; Cunico, Michelle L.; Schilling, Steve P.

    2003-01-01

    At 4393 m, ice-clad Mount Rainier has great potential for debris flows owing to its precipitous slopes and incised steep valleys, the large volume of water stored in its glaciers, and a mantle of loose debris on its slopes. In the past 10,000 years, more than sixty Holocene lahars have occurred at Mount Rainier (Scott et al., 1985), and, in addition more than thirty debris flows not related to volcanism have occurred in historical time (Walder and Driedger, 1984). Lahars at Mount Rainier can be classed in 3 groups according to their genesis: (1) flank collapse of hydrothermally altered, water-saturated rock; (2) eruption-related release of water and loose debris; and (3) hydrologic release of water and debris (Scott et al., 1985). Lahars in the first two categories are commonly voluminous and are generally related to unrest and explosions that occur during eruptive episodes. Lahars in the third category, distinguished here as debris flows, are less voluminous than the others but occur frequently at Mount Rainier, often with little or no warning. Historically at Mount Rainier, glacial outburst floods, torrential rains, and stream capture have caused small- to moderate-size debris flows (Walder and Driedger, 1984). Such debris flows are most likely to occur in drainages that have large glaciers in them. Less commonly, a drainage diversion has triggered a debris flow in an unglaciated drainage basin. For example, the diversion of Kautz Glacier meltwater into Van Trump basin triggered debris flows on the south side of Rainier in August 2001. On the basis of historical accounts, debris flows having hydrologic origins are likely to be unheralded, and have occurred as seldom as once in 8 years and as often as four times per year at Mount Rainier (Walder and Driedger, 1984). Such debris flows are most likely to occur during periods of hot dry weather or during periods of intense rainfall, and therefore must occur during the summer and fall. They are likely to begin at or

  19. Resistance formulas in hydraulics-based models for routing debris flows

    USGS Publications Warehouse

    Chen, Cheng-lung; Ling, Chi-Hai

    1997-01-01

    The one-dimensional, cross-section-averaged flow equations formulated for routing debris flows down a narrow valley are identical to those for clear-water flow, except for the differences in the values of the flow parameters, such as the momentum (or energy) correction factor, resistance coefficient, and friction slope. Though these flow parameters for debris flow in channels with cross-sections of arbitrary geometric shape can only be determined empirically, the theoretical values of such parameters for debris flow in wide channels exist. This paper aims to derive the theoretical resistance coefficient and friction slope for debris flow in wide channels using a rheological model for highly-concentrated, rapidly-sheared granular flows, such as the generalized viscoplastic fluid (GVF) model. Formulating such resistance coefficient or friction slope is equivalent to developing a generally applicable resistance formula for routing debris flows. Inclusion of a nonuniform term in the expression of the resistance formula proves useful in removing the customary assumption that the spatially varied resistance at any section is equal to what would take place with the same rate of flow passing the same section under conditions of uniformity. This in effect implies an improvement in the accuracy of unsteady debris-flow computation.

  20. Can Wet Rocky Granular Flows Become Debris Flows Due to Fine Sediment Production by Abrasion?

    NASA Astrophysics Data System (ADS)

    Arabnia, O.; Sklar, L. S.; Bianchi, G.; Mclaughlin, M. K.

    2015-12-01

    Debris flows are rapid mass movements in which elevated pore pressures are sustained by a viscous fluid matrix with high concentrations of fine sediments. Debris flows may form from coarse-grained wet granular flows as fine sediments are entrained from hillslope and channel material. Here we investigate whether abrasion of the rocks within a granular flow can produce sufficient fine sediments to create debris flows. To test this hypothesis experimentally, we used a set of 4 rotating drums ranging from 0.2 to 4.0 m diameter. Each drum has vanes along the boundary ensure shearing within the flow. Shear rate was varied by changing drum rotational velocity to maintain a constant Froude Number across drums. Initial runs used angular clasts of granodiorite with a tensile strength of 7.6 MPa, with well-sorted coarse particle size distributions linearly scaled with drum radius. The fluid was initially clear water, which rapidly acquired fine-grained wear products. After each 250 m tangential distance, we measured the particle size distributions, and then returned all water and sediment to the drums for subsequent runs. We calculate particle wear rates using statistics of size and mass distributions, and by fitting the Sternberg equation to the rate of mass loss from the size fraction > 2mm. Abundant fine sediments were produced in the experiments, but very little change in the median grain size was detected. This appears to be due to clast rounding, as evidenced by a decrease in the number of stable equilibrium resting points. We find that the growth in the fine sediment concentration in the fluid scales with unit drum power. This relationship can be used to estimate fine sediment production rates in the field. We explore this approach at Inyo Creek, a steep catchment in the Sierra Nevada, California. There, a significant debris flow occurred in July 2013, which originated as a coarse-grained wet granular flow. We use surveys to estimate flow depth and velocity where super

  1. Effects of Different Rainfalls on Run-out Distances and Affected Areas of Debris Flow

    NASA Astrophysics Data System (ADS)

    Lin, Meei-Ling; Chen, Ter-Wei; Lin, Yu-Chung; Chen, Tien-chien; Wang, Kuo-Lung; Huang, Hsiao-Yue; Chen, Mei-Jeng

    2013-04-01

    Taiwan locates at the junction of plate tectonic boundaries with active geologically condition, which results in steep terrains and fragile geological conditions. The heavy rainfall carried by typhoons often causes severe hazard of landslide and debris flow. After Typhoon Morakot, 2009, it was found that the volume of debris transported by the triggered debris flow and its effects on the affected area were much more significant compared to previous case history due to the very large amount of rainfall carried by the Typhoon. In this study, field investigations of 21 debris flow torrents with events triggered by Typhoon Morakot, 2009, were conducted, and the database of debris deposition volume and run-out distance was established. Additional dataset of debris deposition volume and run out distance of debris flow triggered by different typhoons were also collected. Comparisons of the debris deposition volumes by Typhoon Morakot and other typhoons suggested that the high precipitation of Typhoon Morakot caused larger volume of debris transportation. Statistical analysis was performed to determine the correlation of run-out distance and watershed properties. The results suggest that the correlation based on Typhoon Morakot would tend to over-estimate the possible run-out distance of the affected area in most other precipitation condition. Based on the regression analysis of dataset, regression formula of Typhoon Morakot with 50% and 70% of data distribution coverage can be used for determining run-out distance for delineating the affected area, which corresponds to medium and heavy precipitation conditions, respectively. The proposed delineation procedures for the debris flow affected area provide helpful tool for developing delineation map of potential debris flow torrent under effects of different predicted rainfall.

  2. Procedures for the documentation of historical debris flows: application to the Chieppena Torrent (Italian alps).

    PubMed

    Marchi, Lorenzo; Cavalli, Marco

    2007-09-01

    The reconstruction of triggering conditions, geomorphic effects, and damage produced by historical floods and debris flows significantly contributes to hazard assessment, allowing improved risk mitigation measures to be defined. Methods for the analysis of historical floods and debris flows vary greatly according to the type and quality of available data, which in turn are influenced by the time the events occurred. For floods and debris flows occurring in the Alps a few decades ago (between about 1950 and 1980), the documentation is usually better than for previous periods but, unlike events of most recent years, quantitative data are usually scanty and the description of the events does not aim to identify processes according to current terminology and classifications. The potential, and also the limitations of historical information available for the reconstruction of historical debris flows in the Alps have been explored by analyzing a high-magnitude debris flow that occurred on November 4, 1966 in the Chieppena Torrent (northeastern Italy). Reconstruction of the event was based on the use of written documentation, terrestrial and aerial photographs, and geomorphological maps. The analysis aimed to define the temporal development of phenomena, recognizing the type of flow processes and assessing some basic flow variables, such as volume, channel-debris yield rate, erosion depth, total distance traveled, and runout distance on the alluvial fan. The historical development of torrent hydraulic works, both before and after the debris flow of November 1966, was also analyzed with regard to the technical solutions adopted and their performance. PMID:17602256

  3. Fragmentation as a new hypothesis on the origin of granulometric bimodality of debris flow deposits

    NASA Astrophysics Data System (ADS)

    Soto, E.; Caballero, L.; Sarocchi, D.; Borselli, L.

    2013-12-01

    Debris flows are mixtures of water with high concentrations of sediments. Their dynamic behavior is governed by mechanisms that involve clast interaction and fluid matrix characteristics among others. Both mechanisms are studied by means of analogical experiments using a rotating drum named Los Angeles abrasion machine. Four mixtures with compositions resembling cohesive and noncohesive debris flows were prepared. A detailed textural analysis of the mixtures based on granulometry, clast morphology and rheologic properties of the fluid matrix were performed. The results show that the fragmentation process occurs inside debris flows and is reflected in the final textural characteristics of the mixtures. The mode of particle breakage is related to particle size. Clast collisions between particles produce comminution of the coarsest fractions while finer particles fracture along their entire surface. Both modes produce fine sand and silt that continuously feed the fluid matrix during transport, producing bimodal distributions of the mixtures. Granulometric bimodality is a common characteristic in debris flows deposits and has often been explained by bulking or debulking processes related to external flow conditions. In this study, the experimental evidence suggests that this characteristic could also be explained only by internal processes. Fragmentation has a major influence on debris flow dynamics. It modifies rheologic behavior increasing yield stress and viscosity over time. The results show good agreement between real debris flow characteristics and analogic experiments. The proposed hypothesis has important implications to understand the rheological behavior of debris flows and could constitute a basis for new approaches to modeling these phenomena.

  4. Debris flow impact on mitigation barriers: a new method for particle-fluid-structure interactions

    NASA Astrophysics Data System (ADS)

    Marchelli, Maddalena; Pirulli, Marina; Pudasaini, Shiva P.

    2016-04-01

    Channelized debris-flows are a type of mass movements that involve water-charged, predominantly coarse-grained inorganic and organic material flowing rapidly down steep confined pre-existing channels (Van Dine, 1985). Due to their rapid movements and destructive power, structural mitigation measures have become an integral part of counter measures against these phenomena, to mitigate and prevent damages resulting from debris-flow impact on urbanized areas. In particular, debris barriers and storage basins, with some form of debris-straining structures incorporated into the barrier constructed across the path of a debris-flow, have a dual role to play: (1) to stimulate deposition by presenting a physical obstruction against flow, and (2) to guarantee that during normal conditions stream water and bedload can pass through the structure; while, during and after an extreme event, the water that is in the flow and some of the fine-grained sediment can escape. A new method to investigate the dynamic interactions between the flowing mass and the debris barrier is presented, with particular emphasis on the effect of the barrier in controlling the water and sediment content of the escaping mass. This aspect is achieved by implementing a new mechanical model into an enhanced two-phase dynamical mass flow model (Pudasaini, 2012), in which solid particles mixture and viscous fluid are taken into account. The complex mechanical model is defined as a function of the energy lost during impact, the physical and geometrical properties of the debris barrier, separate but strongly interacting dynamics of boulder and fluid flows during the impact, particle concentration distribution, and the slope characteristics. The particle-filtering-process results in a large variation in the rheological properties of the fluid-dominated escaping mass, including the substantial reduction in the bulk density, and the inertial forces of the debris-flows. Consequently, the destructive power and run

  5. Monitoring debris flow induced channel morphodynamics with terrestrial laser scanning, Chalk Cliffs, CO (Invited)

    NASA Astrophysics Data System (ADS)

    Wasklewicz, T. A.; Staley, D. M.

    2010-12-01

    Debris flows are important geomorphic agents in alpine drainages. They have been linked with channel initiation in headwater streams, connectivity of organic material and sediment through drainage basins, and as hazards to human development in and adjacent to steep watersheds. Debris flows also significantly alter channel morphometry at a variety of spatial scales. Of particular interest are topographic changes associated with multiple surge fronts within a debris flow as well as between several debris flows. An unnamed tributary stream to Chalk Creek, CO has over the last decade experienced one to four debris flow events annually. Four field sampling campaigns were conducted in the summer and fall of 2009. A Leica ScanStation 2, in conjunction with a robust local control network, were used to capture channel morphodynamics along five stream reaches prior to the debris flow season and after three debris flows. Point cloud data from the scanner permit the generation of two centimeter planimetric resolution digital terrain models (DTM). DTM-of-difference analyses and measures of slope, roughness, sediment transport volumes and channel dimensions were employed to detect spatial and temporal morphometric changes. The first debris flow occurred on unsaturated bed material and resulted in aggradation along 3 of the 5 reaches. One reach, a bedrock step, remained relatively unchanged, while the final reach saw significant erosion along boulder steps in the channel and an associated mass failure adjacent to the stream bank through this section. The second debris flow resulted in net aggradation along all of the reaches. The third and largest debris flow took place on saturated bed materials. The flow produced net erosion along all reaches. Significant channel changes were associated with the headward erosion of debris flow snouts and bank failures associated with undercutting of angle-of-repose slopes during debris flow erosion. Analysis of the potential relationships

  6. Case study of severe debris flow hazard caused by typhoon Morakot, 2009

    NASA Astrophysics Data System (ADS)

    Lin, Meei-Ling; Wang, Kuo-Lung; Chen, Tien-Chien; Lin, Sheng-Chi

    2010-05-01

    Typhoon Morakot struck southern Taiwan on August, 8, 2009 with high rainfall intensity and accumulated rainfall as high as 2860 mm for 72 hours. The rainfall concentrated in the mountain area of southern Taiwan, especially at Alishan and affected downstream watersheds. Severe landslide and debris flow hazards were induced in watersheds described above. The debris flow causing severe impacts to local communities were selected for case study. Field investigation and analysis were conducted. The investigation shows that the debris flow located at Sanshia group formation in the west part of Central mountain and Lushan slate formation in the east part of Central mountain. The debris flow cases selected in this research are Nanshalu, Maya, and Dakanuwa villages of Namasha township, Shinkai and Shinfa areas of Liugui township, Kaohsiung county, and Chianghuangkern of Nanhua township, Tainan county. It was found that the locations of the severe debris flow were consistent with the aspect facing storm, and the triggering areas were located at the steeper up-slope areas. Moreover, the comparison of debris flows after Chi-Chi earthquake was conducted to discuss the trend and variation of debris flow hazard 10 years after the earthquake.

  7. Spatial and temporal patterns of debris flow deposition in the Oregon Coast Range, USA

    USGS Publications Warehouse

    May, Christine L.; Gresswell, Robert E.

    2004-01-01

    Patterns of debris-flow occurrence were investigated in 125 headwater basins in the Oregon Coast Range. Time since the previous debris-flows was established using dendrochronology, and recurrence interval estimates ranged from 98 to 357 years. Tributary basins with larger drainage areas had a greater abundance of potential landslide source areas and a greater frequency of scouring events compared to smaller basins. The flux rate of material delivered to the confluence with a larger river influenced the development of small-scale debris-flow fans. Fans at the mouths of tributary basins with smaller drainage areas had a higher likelihood of being eroded by the mainstem river in the interval between debris-flows, compared to bigger basins that had larger, more persistent fans. Valley floor width of the receiving channel also influenced fan development because it limited the space available to accommodate fan formation. Of 63 recent debris-flows, 52% delivered sediment and wood directly to the mainstem river, 30% were deposited on an existing fan before reaching the mainstem, and 18% were deposited within the confines of the tributary valley before reaching the confluence. Spatial variation in the location of past and present depositional surfaces indicated that sequential debris-flow deposits did not consistently form in the same place. Instead of being spatially deterministic, results of this study suggest that temporally variable and stochastic factors may be important for predicting the runout length of debris-flows.

  8. Debris-flow origin for the Simud/Tiu deposit on Mars

    USGS Publications Warehouse

    Tanaka, K.L.

    1999-01-01

    A late Hesperian smooth plains deposit on Mars interpreted as a debris flow extends more than 2000 km from Hydraotes Chaos, through Simud and Tiu Valles, and into Chryse Planitia. The Simud/Tiu deposit widens out to >1000 km and embays streamlined landforms and knobs made up of sedimentary and perhaps volcanic deposits that were carved by earlier channeling activity. Morphologic features of the Simud/Tiu deposit observed in Viking and Pathfinder images are generally consistent with a debris-flow origin, but some of the deposit's salient features are not readily explained by catastrophic flooding or ice flow. Internal depressions appear to be bounded by linear scarps along flow margins where differential shearing may have occurred and in areas where flow spreading may have produced zones of extensional breakup and thinning within the flow. Possible flow lobes within the deposit may have formed by successive flow surges within the flow unit. The Pathfinder landing site is on the Simud/Tiu deposit, and the observations there are consistent with debris flow. The low, longitudinal ridges at the site may have formed by clast interactions as the flow ground to a halt. Imbricated, planar rocks on the ridges, such as in the Rock Garden, also may have been emplaced by debris or ice flow. However, stream energy calculations at Ares Vallis and channel geology indicate that flooding probably was incapable of emplacing the meter-size boulders observed at the Pathfinder site. Dewatering of pressurized zones in the debris flow or underlying material may be responsible for mud eruptions that formed a couple of patches of low pancakelike shields up to 5 km in diameter and for probable water flows that formed two small rille channels a few kilometers long. Local irregular grooves may be cracks that resulted from later desiccation and contraction of the flow material. The debris-flow unit apparently coalesced from outflows of water-fluidized debris originating from beneath chaotic and

  9. Alpine debris flows triggered by a 28 July 1999 thunderstorm in the central Front Range, Colorado

    NASA Astrophysics Data System (ADS)

    Godt, Jonathan W.; Coe, Jeffrey A.

    2007-02-01

    On 28 July 1999, about 480 alpine debris flows were triggered by an afternoon thunderstorm along the Continental Divide in Clear Creek and Summit counties in the central Front Range of Colorado. The thunderstorm produced about 43 mm of rain in 4 h, 35 mm of which fell in the first 2 h. Several debris flows triggered by the storm impacted Interstate Highway 70, U.S. Highway 6, and the Arapahoe Basin ski area. We mapped the debris flows from color aerial photography and inspected many of them in the field. Three processes initiated debris flows. The first process initiated 11% of the debris flows and involved the mobilization of shallow landslides in thick, often well vegetated, colluvium. The second process, which was responsible for 79% of the flows, was the transport of material eroded from steep unvegetated hillslopes via a system of coalescing rills. The third, which has been termed the "firehose effect," initiated 10% of the debris flows and occurred where overland flow became concentrated in steep bedrock channels and scoured debris from talus deposits and the heads of debris fans. These three processes initiated high on steep hillsides (> 30°) in catchments with small contributing areas (< 8000 m 2), however, shallow landslides occurred on slopes that were significantly less steep than either overland flow process. Based on field observations and examination of soils mapping of the northern part of the study area, we identified a relation between the degree of soil development and the process type that generated debris flows. In general, areas with greater soil development were less likely to generate runoff and therefore less likely to generate debris flows by the firehose effect or by rilling. The character of the surficial cover and the spatially variable hydrologic response to intense rainfall, rather than a threshold of contributing area and topographic slope, appears to control the initiation process in the high alpine of the Front Range. Because

  10. Alpine debris flows triggered by a 28 July 1999 thunderstorm in the central Front Range, Colorado

    USGS Publications Warehouse

    Godt, J.W.; Coe, J.A.

    2007-01-01

    On 28 July 1999, about 480 alpine debris flows were triggered by an afternoon thunderstorm along the Continental Divide in Clear Creek and Summit counties in the central Front Range of Colorado. The thunderstorm produced about 43??mm of rain in 4??h, 35??mm of which fell in the first 2??h. Several debris flows triggered by the storm impacted Interstate Highway 70, U.S. Highway 6, and the Arapahoe Basin ski area. We mapped the debris flows from color aerial photography and inspected many of them in the field. Three processes initiated debris flows. The first process initiated 11% of the debris flows and involved the mobilization of shallow landslides in thick, often well vegetated, colluvium. The second process, which was responsible for 79% of the flows, was the transport of material eroded from steep unvegetated hillslopes via a system of coalescing rills. The third, which has been termed the "firehose effect," initiated 10% of the debris flows and occurred where overland flow became concentrated in steep bedrock channels and scoured debris from talus deposits and the heads of debris fans. These three processes initiated high on steep hillsides (> 30??) in catchments with small contributing areas (< 8000??m2), however, shallow landslides occurred on slopes that were significantly less steep than either overland flow process. Based on field observations and examination of soils mapping of the northern part of the study area, we identified a relation between the degree of soil development and the process type that generated debris flows. In general, areas with greater soil development were less likely to generate runoff and therefore less likely to generate debris flows by the firehose effect or by rilling. The character of the surficial cover and the spatially variable hydrologic response to intense rainfall, rather than a threshold of contributing area and topographic slope, appears to control the initiation process in the high alpine of the Front Range. Because

  11. Debris Flow Damage Incurred to Buildings: An In-Situ Back Analysis

    NASA Astrophysics Data System (ADS)

    Jalayer, Fatemeh; Aronica, Giuseppe T.; Recupero, Antonino; Carozza, Stefano; Manfredi, Gaetano

    2016-04-01

    The flash-flood debris event of the October 1st 2009 in the area of Messina, Sicily, Italy has led to loss of life and significant damage to the constructed environment. Focusing the attention on an eighteenth masonry building (damaged and upgraded after the Messina-Reggio Calabria Earthquake of 1906) located in the village of Scaletta Zanclea, we have strived to reconstruct analytically the damages incurred to this building due to the debris flow event of 2009. In order to re-construct the damages incurred to the building due to the flash flood/debris flow event, hydrostatic and hydrodynamic force envelopes, calculated via a 2D hydrodynamic finite element model specifically designed for debris flow spatial propagation, have been applied to the building in question (assuming perfect coherence between static and dynamic maxima). The hydrograph for the solid discharge is then estimated by scaling up the liquid volume to the estimated debris volume. The hydrodynamic model used for the debris flow propagation proved to be well suited for these specific applications. The debris flow diffusion is simulated by solving the differential equations for a single-phase 2D flow employing triangular mesh elements, taking into account also the channeling of the flow through the building. The damage to the building is modeled, based on the maximum hydraulic actions caused by the debris flow, using 2D finite shell elements, modeling the boundary conditions provided by the openings, floor slab, orthogonal wall panels and the foundation. The finite element approach showed its capability in describing the complex geometries of the urban environments as the distributed nature of the 2D code allows to derive a reliable spatial distribution of debris flow actions. The reconstruction of the event and the damages to the case-study building confirms the location of the damages induced by the event.

  12. Numerical modelling study of gully recharge and debris flows in Haida Gwaii, British Columbia

    NASA Astrophysics Data System (ADS)

    Martin, Yvonne; Johnson, Edward; Chaikina, Olga

    2015-04-01

    In high mountains, debris flows are a major process responsible for transferring sediment to more downstream fluvial reaches. This sediment transfer begins on mountain hillslopes where various mass wasting processes move sediment from hillslopes to uppermost reaches of the channel system (these reaches are herein referred to as gullies and only experience water flow during high intensity precipitation events). Sediment recharge into gullies, which has received minimal attention in the scientific literature, refers to the transfer of sediment and other debris from surrounding hillslopes into gullies (Jakob and Oden, 2005). Debris flow occurrence and debris flow volumes depend on some precipitation threshold as well as volumes of material contained in the particular gully. For example, if one debris flow has removed all of the accumulated material from the gully, then any subsequent debris flow will be smaller if enough time has not yet passed for notable sediment recharge. Herein, we utilize the numerical model of landscape development, LandMod (Martin, 1998; Dadson and Church, 2005; Martin, 2007), to explore connections between hillslope processes, gully recharge rates, and transfer of sediment to downstream channel reaches in the Haida Gwaii, British Columbia. Hillslope processes in the model include shallow landsliding, bedrock failures and weathering. The updated debris flow algorithm is based on extensive field data available for debris flows in Haida Gwaii (e.g., Rood, 1984; Oden, 1994; Jakob and Oden, 2005), as well as theoretical considerations based on debris flow studies. The most significant model extension is the calculation of gully recharge rates; for each gully, the total accumulated sediment in gullies at each time step is determined using a power-law relation for area-normalized recharge rate versus elapsed time since the last debris flow. Thus, when the stochastic driver for debris flow occurrence triggers an event, the amount of stored material is

  13. Three occurred debris flows in North-Eastern Italian Alps: documentation and modeling

    NASA Astrophysics Data System (ADS)

    Boreggio, Mauro; Gregoretti, Carlo; Degetto, Massimo; Bernard, Martino

    2015-04-01

    Three occurred events of debris flows are documented and modeled by back-analysis. The three debris flows events are those occurred at Rio Lazer on the 4th of November 1966, at Fiames on the 5th of July 2006 and at Rovina di Cancia on the 18th of July 2009. All the three sites are located in the North-Eastern Italian Alps. In all the events, runoff entrained sediments present on natural channels and formed a solid-liquid wave that routed downstream. The first event concerns the routing of debris flow on an inhabited fan. Map of deposition pattern of sediments are built by using post-events photos through stereoscopy techniques. The second event concerns the routing of debris flow along the main channel descending from Pomagagnon Fork. Due to the obstruction of the cross-section debris flow deviated from the original path on the left side and routed downstream by cutting a new channel on the fan. It dispersed in multiple paths when met the wooden area. Map of erosion and deposition depths are built after using a combination of Lidar and GPS data. The third event concerns the routing of debris flow in the Rovina di Cancia channel that filled the reservoir built at the end of the channel and locally overtopped the retaining wall on the left side. A wave of mud and debris inundated the area downstream the overtopping point. Map of erosion and deposition depths are obtained by subtracting two GPS surveys, pre and post event. All the three occurred debris flows are simulated by modeling runoff that entrained debris flow for determining the solid-liquid hydrograph downstream the triggering areas. The routing of the solid-liquid hydrograph was simulated by a bi-phase cell model based on the kinematic approach. The comparison between simulated and measured erosion and deposition depths is satisfactory. The same parameters for computing erosion and deposition were used for the three occurred events.

  14. On the application of kinematic models to simulate the diffusive processes of debris flows

    NASA Astrophysics Data System (ADS)

    Arattano, M.; Franzi, L.

    2010-08-01

    Debris flows generally propagate along steep mountain torrents with dynamics primarily governed by gravitational and frictional forces. Thus, debris flows modelling can be successfully performed through the application of kinematic models, which consider only the effects of slope and friction and neglect the remaining terms of the momentum equation. However, the diffusion processes that can be observed in the field, such as the spreading of the debris flow wave as it flows downstream, can not be theoretically predicted by kinematic models, since diffusion is a second-order process neglected in the kinematic approximation. In this paper, this issue is discussed and an application for both a generalized diffusion wave model and a kinematic model is proposed of a debris flow which occurred in an Italian instrumented torrent to identify, in a real case scenario, the effective value of the neglected terms in the kinematic approximation.

  15. The enormous Chillos Valley Lahar: An ash-flow-generated debris flow from Cotopaxi Volcano, Ecuador

    USGS Publications Warehouse

    Mothes, P.A.; Hall, M.L.; Janda, R.J.

    1998-01-01

    The Chillos Valley Lahar (CVL), the largest Holocene debris flow in area and volume as yet recognized in the northern Andes, formed on Cotopaxi volcano's north and northeast slopes and descended river systems that took it 326 km north-northwest to the Pacific Ocean and 130+ km east into the Amazon basin. In the Chillos Valley, 40 km downstream from the volcano, depths of 80-160 m and valley cross sections up to 337000m2 are observed, implying peak flow discharges of 2.6-6.0 million m3/s. The overall volume of the CVL is estimated to be ???3.8 km3. The CVL was generated approximately 4500 years BP by a rhyolitic ash flow that followed a small sector collapse on the north and northeast sides of Cotopaxi, which melted part of the volcano's icecap and transformed rapidly into the debris flow. The ash flow and resulting CVL have identical components, except for foreign fragments picked up along the flow path. Juvenile materials, including vitric ash, crystals, and pumice, comprise 80-90% of the lahar's deposit, whereas rhyolitic, dacitic, and andesitic lithics make up the remainder. The sand-size fraction and the 2- to 10-mm fraction together dominate the deposit, constituting ???63 and ???15 wt.% of the matrix, respectively, whereas the silt-size fraction averages less than ???10 wt.% and the clay-size fraction less than 0.5 wt.%. Along the 326-km runout, these particle-size fractions vary little, as does the sorting coefficient (average = 2.6). There is no tendency toward grading or improved sorting. Limited bulking is recognized. The CVL was an enormous non-cohesive debris flow, notable for its ash-flow origin and immense volume and peak discharge which gave it characteristics and a behavior akin to large cohesive mudflows. Significantly, then, ash-flow-generated debris flows can also achieve large volumes and cover great areas; thus, they can conceivably affect large populated regions far from their source. Especially dangerous, therefore, are snowclad volcanoes

  16. Characteristics of debris flows of noneruptive origin on Mount Shasta, northern California

    USGS Publications Warehouse

    Blodgett, James C.; Poeschel, Karen R.; Osterkamp, Waite R.

    1996-01-01

    Studies of Mount Shasta indicate that eruptive activity has occurred, on the average, once every 800 years. Debris flows and deposits of non- eruptive origin, in addition to those associated with eruptive activity (lava flows, pyroclastic flows, and ash fall), inundate the fans and channels and can endanger people or property on the flanks of the mountain. This study evaluates the source and characteristics of historical noneruptive debris flows in the vicinity of Mount Shasta. At least 70 debris flows of noneruptive origin that occurred during the last 1,000 years have been identified in various stream channels on Mount Shasta. Of the four areas around the mountain, the most active are the McCloud River and The Whaleback-Ash Creek Butte depression; the Sacramento River area is the least active. Between 1900 and 1985, 37 debris flows occurred on different streams, with an average interval of 2.3 years between flows. Since 1900, Mud Creek (nine flows) and Whitney Creek (six flows) have been the most active channels. The path followed by a debris flow is not always at the lowest point in the channel, and the extent of downstream movement depends on the size of the flow. Former channels are inundated by the new flows and deposits, and new channels are eroded. In time, most of the entire channel between valley walls is subject to reworking. Most debris-flow deposits ranged in thickness from 0.4 to 2.5 meters. Thickness tends to decrease in a downstream direction. The deposits are generally of a convex shape, highest in the middle and lowest near the original valley wall. The ratio of water to solids in the slurry- sediment mixture of debris flows averages 68 percent by volume.

  17. Predicting spatial distribution of postfire debris flows and potential consequences for native trout in headwater streams

    USGS Publications Warehouse

    Sedell, Edwin R; Gresswell, Bob; McMahon, Thomas E.

    2015-01-01

    Habitat fragmentation and degradation and invasion of nonnative species have restricted the distribution of native trout. Many trout populations are limited to headwater streams where negative effects of predicted climate change, including reduced stream flow and increased risk of catastrophic fires, may further jeopardize their persistence. Headwater streams in steep terrain are especially susceptible to disturbance associated with postfire debris flows, which have led to local extirpation of trout populations in some systems. We conducted a reach-scale spatial analysis of debris-flow risk among 11 high-elevation watersheds of the Colorado Rocky Mountains occupied by isolated populations of Colorado River Cutthroat Trout (Oncorhynchus clarkii pleuriticus). Stream reaches at high risk of disturbance by postfire debris flow were identified with the aid of a qualitative model based on 4 primary initiating and transport factors (hillslope gradient, flow accumulation pathways, channel gradient, and valley confinement). This model was coupled with a spatially continuous survey of trout distributions in these stream networks to assess the predicted extent of trout population disturbances related to debris flows. In the study systems, debris-flow potential was highest in the lower and middle reaches of most watersheds. Colorado River Cutthroat Trout occurred in areas of high postfire debris-flow risk, but they were never restricted to those areas. Postfire debris flows could extirpate trout from local reaches in these watersheds, but trout populations occupy refugia that should allow recolonization of interconnected, downstream reaches. Specific results of our study may not be universally applicable, but our risk assessment approach can be applied to assess postfire debris-flow risk for stream reaches in other watersheds.

  18. Wildfire impacts on the processes that generate debris flows in burned watersheds

    USGS Publications Warehouse

    Parise, M.; Cannon, S.H.

    2012-01-01

    Every year, and in many countries worldwide, wildfires cause significant damage and economic losses due to both the direct effects of the fires and the subsequent accelerated runoff, erosion, and debris flow. Wildfires can have profound effects on the hydrologic response of watersheds by changing the infiltration characteristics and erodibility of the soil, which leads to decreased rainfall infiltration, significantly increased overland flow and runoff in channels, and movement of soil. Debris-flow activity is among the most destructive consequences of these changes, often causing extensive damage to human infrastructure. Data from the Mediterranean area and Western United States of America help identify the primary processes that result in debris flows in recently burned areas. Two primary processes for the initiation of fire-related debris flows have been so far identified: (1) runoff-dominated erosion by surface overland flow; and (2) infiltration-triggered failure and mobilization of a discrete landslide mass. The first process is frequently documented immediately post-fire and leads to the generation of debris flows through progressive bulking of storm runoff with sediment eroded from the hillslopes and channels. As sediment is incorporated into water, runoff can convert to debris flow. The conversion to debris flow may be observed at a position within a drainage network that appears to be controlled by threshold values of upslope contributing area and its gradient. At these locations, sufficient eroded material has been incorporated, relative to the volume of contributing surface runoff, to generate debris flows. Debris flows have also been generated from burned basins in response to increased runoff by water cascading over a steep, bedrock cliff, and incorporating material from readily erodible colluvium or channel bed. Post-fire debris flows have also been generated by infiltration-triggered landslide failures which then mobilize into debris flows. However

  19. Cosmogenic 3He ages and frequency of late Holocene debris flows from Prospect Canyon, Grand Canyon, USA

    USGS Publications Warehouse

    Cerling, T.E.; Webb, R.H.; Poreda, R.J.; Rigby, A.D.; Melis, T.S.

    1999-01-01

    Lava Falls Rapid, which was created and is maintained by debris flows from Prospect Canyon, is the most formidable reach of whitewater on the Colorado River in Grand Canyon and is one of the most famous rapids in the world. Debris flows enter the Colorado River at tributary junctures, creating rapids. The frequency of debris flows is an important consideration when management of regulated rivers involves maintenance of channel morphology. We used cosmogenic 3He, 14C, and historical photographs to date 12 late Holocene and historic debris flows from Prospect Canyon. The highest and oldest deposits from debris flows on the debris fan yielded a 3He date of about 3 ka, which indicates predominately late Holocene aggradation of one of the largest debris fans in Grand Canyon. The deposit, which has a 25-m escarpment caused by river reworking, crossed the Colorado River and raised its base level by 30 m for an indeterminate although likely short period. We mapped depositional surfaces of 11 debris flows that occurred after 3 ka. Two deposits inset against the highest deposit yielded 3He ages of about 2.2 ka, and at least two others followed shortly afterwards. At least one of these debris flows also dammed the Colorado River. The most recent prehistoric debris flow occurred no more than 0.5 ka. The largest historic debris flow, which constricted the river by 80%, occurred in 1939. Five other debris flows occurred after 1939; these debris flows constricted the Colorado River by 35-80%. Assuming the depositional volumes of late Holocene debris flows can be modeled using a lognormal distribution, we calculated recurrence intervals of 15 to more than 2000 years for debris flows from Prospect Canyon.

  20. GIS-based modeling of debris flow processes in an Alpine catchment, Antholz valley, Italy

    NASA Astrophysics Data System (ADS)

    Sandmeier, Christine; Damm, Bodo; Terhorst, Birgit

    2010-05-01

    Debris flows are frequent natural hazards in mountain regions, which seriously can threat human lives and economic values. In the European Alps the occurrence of debris flows might even increase with respect to climate change, including permafrost degradation, glacier retreat and variable precipitation patterns. Thus, detailed understanding of process parameters and spatial distribution of debris flows is necessary to take appropriate protection measures for risk assessment. In this context, numerical models have been developed and applied successfully for simulation and prediction of debris-flow hazards and related process areas. In our study a GIS-based model is applied in an alpine catchment to address the following questions: Where are potential initiating areas of debris flows? How much material can be mobilized? What is the influence of topography and precipitation? The study area is located in the Antholz valley in the eastern Alps of Northern Italy. The investigated catchment of the Klammbach creek comprises 6.5 km² and is divided into two sub-catchments. Geologically it is dominated by metamorphic rock and altitudes range between 1310 and 3270 m. In summer 2005 a debris flow of more than 100000 m³ took place, originating from a steep, sparsely vegetated debris cone in the western part of the catchment. According to a regional study, the lower permafrost boundary in this area has risen by 250 m. In a first step, during a field survey, geomorphological mapping was performed, several channel cross-sections were measured and sediment samples were taken. Using mapping results and aerial images, a geomorphological map was created. In further steps, results from the field work, the geomorphological map and existing digital data sets, including a digital elevation model with 2.5 m resolution, are used to derive input data for the modeling of debris flow processes. The model framework ‘r.debrisflow' based on GRASS GIS is applied (Mergili, 2008*), as it is

  1. The effects of groundwater abstraction on low flows

    NASA Astrophysics Data System (ADS)

    de Graaf, I. E. M.; van Beek, L. P. H.; Wada, Y.; Bierkens, M. F. P.

    2012-04-01

    In regions with frequent water stress and large aquifer systems, groundwater often constitutes an essential source of water. If groundwater abstraction exceeds groundwater recharge over a long time and over large areas persistent groundwater depletion can occur. The resulting lowering of groundwater levels can have negative effects on agricultural productivity but also on natural streamflow and associated wetlands and ecosystems, in particular during low-flow events when the groundwater contribution through baseflow is relatively large. In this study we focus on the effects of global groundwater abstraction on low-flow magnitude, frequency and duration for the major rivers of the world for the period 1960-2000. As a basis, we use the large-scale hydrological model PCR-GLOBWB that calculates all major water balance terms on a daily time step at a 0.5ox0.5o resolution. Currently, PCR-GLOBWB represents groundwater and the associated baseflow by means of a linear reservoir that is parameterized using global lithological data and drainage density. It simulates renewable groundwater storage within each 0.5o cell. Lateral flow between cells is not considered. The specific runoff from the model is subsequently transformed into discharge by means of a kinematic wave routing scheme. In this study we perform a sensitivity analysis in which we evaluate the effects of total water demand for the period 1960-2000 (Wada et al., 2011: doi:10.5194/hess-15-3785-2011). This demand is preferentially met by renewable groundwater storage, secondly by surface water. Any remainder is assumed to stem from non- renewable (i.e. fossil) groundwater resources. Thus, groundwater abstractions act as a direct sink of (renewable) groundwater storage, whereas surface water abstractions act as a direct sink of streamflow. The resulting response is non-trivial as abstractions are variably taken from both groundwater and surface water, where return-flows contribute to a single source: return flow from

  2. Evidence of debris flow occurrence after wildfire in upland catchments of south-east Australia

    NASA Astrophysics Data System (ADS)

    Nyman, Petter; Sheridan, Gary J.; Smith, Hugh G.; Lane, Patrick N. J.

    2011-02-01

    Numerous reports of "flash floods", "mud torrents" and "landslides" in burnt landscapes of south-east Australia were only recently linked to debris flows and recognised as a significant process that warrant more detailed investigation. This paper provides a systematic documentation of high-magnitude erosion events after wildfire in south-east Australia, focusing on small (< 5 km 2), upland catchments in eastern Victoria that were burnt by wildfire between 2003 and 2009. The aims of the study were to i) collect and show evidence of debris flow occurrence after wildfire; ii) quantify erosion rates from debris flows and; iii) identify rainfall thresholds and key hydrological properties. The result showed that 13 out of the 16 recorded high-magnitude erosion events were runoff generated debris flows. These occurred in dry eucalypt forests burnt at high or very high severity in steep headwater catchments throughout the eastern uplands of Victoria. The debris flows were triggered by intense, short duration rainfall events ( I30 35-59 mm h -1) with annual exceedance probability in the order of 20%. This is the first paper to document the occurrence of post-fire runoff generated debris flows in Australia, so the discussion draws on literature from the western USA, where a large body of research has been dedicated to evaluating the risk posed by post-fire debris flows and their role in landscape processes. Typical features common to both systems include low infiltration capacity of burnt catchments; widespread sheet erosion and levee lined rills on steep upper hillslopes; and severe channel erosion initiated in response to convergent flow in previously un-scoured drainage lines. The depth of sheet erosion on surveyed slopes in the upper catchments (4.6 ± 0.96 mm to 18.4 ± 2.7 mm) indicates that hillslope material provides an important source of sediment. The average channel entrainment rate of three debris flows ranged from 0.6 to 1.4 m 3 m -1. Runoff generated debris

  3. Implementation of the RAMMS DEBRIS FLOW to Italian case studies

    NASA Astrophysics Data System (ADS)

    Vennari, Carmela; Mc Ardell, Brian; Parise, Mario; Santangelo, Nicoletta; Santo, Antonio

    2016-04-01

    RAMMS (RApid Mass MovementS) Debris Flow runout model solves 2D shallow-water equation using the Voellmy friction law. The model has been developed by the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), and the Swiss Federal Institute for Snow and Avalanche Research (SLF). It requires as input the following data: topography, release area or hydrograph, and the friction parameters μ and ξ. Deposition height, velocity, pressure and momentum are the most important outcomes, also in terms of Max values. The model was applied primarily in Alpine catchments to simulate debris flow runout. Beside the Alps, alluvial events are very common even in torrential catchments of the Southern Apennines of Italy, and contribute to build alluvial fans mainly located at the foothill of carbonate and volcanic mountains. During the last decades several events occurred in these areas, often highly populated, and caused serious damage to society and to people. Several case studies have been selected from a database on alluvial events in torrential catchments of Campania region, aimed at applying the RAMMS model to back-analyze the documented events, and to simulate future similar scenarios in different triggering conditions. In order to better understand the obtained data and choose the best results, field data are mandatories. For this reason we focused our attention on torrential events for which field data concerning deposition area and deposition height were available. We simulated different scenarios, with variable peak discharge and friction parameters, reproducing also the influence of anthropogenic structures. To choose the best results, observed data and predicted data were compared in an objective way, by means of a quantitative analysis. Predicted and observed deposition areas were compared in a GIS environment, and the best test was evaluated by computing several statistics accuracy derived from the confusion matrix, including the sensitivity, that

  4. The perfect debris flow? Aggregated results from 28 large-scale experiments

    USGS Publications Warehouse

    Iverson, Richard M.; Logan, Matthew; LaHusen, Richard G.; Berti, Matteo

    2010-01-01

    Aggregation of data collected in 28 controlled experiments reveals reproducible debris-flow behavior that provides a clear target for model tests. In each experiment ∼10 m3 of unsorted, water-saturated sediment composed mostly of sand and gravel discharged from behind a gate, descended a steep, 95-m flume, and formed a deposit on a nearly horizontal runout surface. Experiment subsets were distinguished by differing basal boundary conditions (1 versus 16 mm roughness heights) and sediment mud contents (1 versus 7 percent dry weight). Sensor measurements of evolving flow thicknesses, basal normal stresses, and basal pore fluid pressures demonstrate that debris flows in all subsets developed dilated, coarse-grained, high-friction snouts, followed by bodies of nearly liquefied, finer-grained debris. Mud enhanced flow mobility by maintaining high pore pressures in flow bodies, and bed roughness reduced flow speeds but not distances of flow runout. Roughness had these effects because it promoted debris agitation and grain-size segregation, and thereby aided growth of lateral levees that channelized flow. Grain-size segregation also contributed to development of ubiquitous roll waves, which had diverse amplitudes exhibiting fractal number-size distributions. Despite the influence of these waves and other sources of dispersion, the aggregated data have well-defined patterns that help constrain individual terms in a depth-averaged debris-flow model. The patterns imply that local flow resistance evolved together with global flow dynamics, contradicting the hypothesis that any consistent rheology applied. We infer that new evolution equations, not new rheologies, are needed to explain how characteristic debris-flow behavior emerges from the interactions of debris constituents.

  5. Soil volume estimation in debris flow areas using lidar data in the 2014 Hiroshima, Japan rainstorm

    NASA Astrophysics Data System (ADS)

    Miura, H.

    2015-10-01

    Debris flows triggered by the rainstorm in Hiroshima, Japan on August 20th, 2014 produced extensive damage to the built-up areas in the northern part of Hiroshima city. In order to consider various emergency response activities and early-stage recovery planning, it is important to evaluate the distribution of the soil volumes in the debris flow areas immediately after the disaster. In this study, automated nonlinear mapping technique is applied to light detection and ranging (LiDAR)-derived digital elevation models (DEMs) observed before and after the disaster to quickly and accurately correct geometric locational errors of the data. The soil volumes generated from the debris flows are estimated by subtracting the pre- and post-event DEMs. The geomorphologic characteristics in the debris flow areas are discussed from the distribution of the estimated soil volumes.

  6. Wildfire-related debris-flow initiation processes, Storm King Mountain, Colorado

    USGS Publications Warehouse

    Cannon, S.H.; Kirkham, R.M.; Parise, M.

    2001-01-01

    A torrential rainstorm on September 1, 1994 at the recently burned hillslopes of Storm King Mountain, CO, resulted in the generation of debris flows from every burned drainage basin. Maps (1:5000 scale) of bedrock and surficial materials and of the debris-flow paths, coupled with a 10-m Digital Elevation Model (DEM) of topography, are used to evaluate the processes that generated fire-related debris flows in this setting. These evaluations form the basis for a descriptive model for fire-related debris-flow initiation. The prominent paths left by the debris flows originated in 0- and 1st-order hollows or channels. Discrete soil-slip scars do not occur at the heads of these paths. Although 58 soil-slip scars were mapped on hillslopes in the burned basins, material derived from these soil slips accounted for only about 7% of the total volume of material deposited at canyon mouths. This fact, combined with observations of significant erosion of hillslope materials, suggests that a runoff-dominated process of progressive sediment entrainment by surface runoff, rather than infiltration-triggered failure of discrete soil slips, was the primary mechanism of debris-flow initiation. A paucity of channel incision, along with observations of extensive hillslope erosion, indicates that a significant proportion of material in the debris flows was derived from the hillslopes, with a smaller contribution from the channels. Because of the importance of runoff-dominated rather than infiltration-dominated processes in the generation of these fire-related debris flows, the runoff-contributing area that extends upslope from the point of debris-flow initiation to the drainage divide, and its gradient, becomes a critical constraint in debris-flow initiation. Slope-area thresholds for fire-related debris-flow initiation from Storm King Mountain are defined by functions of the form Acr(tan ??)3 = S, where Acr is the critical area extending upslope from the initiation location to the

  7. The Time-Frequency Signatures of Advanced Seismic Signals Generated by Debris Flows

    NASA Astrophysics Data System (ADS)

    Chu, C. R.; Huang, C. J.; Lin, C. R.; Wang, C. C.; Kuo, B. Y.; Yin, H. Y.

    2014-12-01

    The seismic monitoring is expected to reveal the process of debris flow from the initial area to alluvial fan, because other field monitoring techniques, such as the video camera and the ultrasonic sensor, are limited by detection range. For this reason, seismic approaches have been used as the detection system of debris flows over the past few decades. The analysis of the signatures of the seismic signals in time and frequency domain can be used to identify the different phases of debris flow. This study dedicates to investigate the different stages of seismic signals due to debris flow, including the advanced signal, the main front, and the decaying tail. Moreover, the characteristics of the advanced signals forward to the approach of main front were discussed for the warning purpose. This study presents a permanent system, composed by two seismometers, deployed along the bank of Ai-Yu-Zi Creek in Nantou County, which is one of the active streams with debris flow in Taiwan. The three axes seismometer with frequency response of 7 sec - 200 Hz was developed by the Institute of Earth Sciences (IES), Academia Sinica for the purpose to detect debris flow. The original idea of replacing the geophone system with the seismometer technique was for catching the advanced signals propagating from the upper reach of the stream before debris flow arrival because of the high sensitivity. Besides, the low frequency seismic waves could be also early detected because of the low attenuation. However, for avoiding other unnecessary ambient vibrations, the sensitivity of seismometer should be lower than the general seismometer for detecting teleseism. Three debris flows with different mean velocities were detected in 2013 and 2014. The typical triangular shape was obviously demonstrated in time series data and the spectrograms of the seismic signals from three events. The frequency analysis showed that enormous debris flow bearing huge boulders would induce low frequency seismic

  8. Mobility statistics and automated hazard mapping for debris flows and rock avalanches

    USGS Publications Warehouse

    Griswold, Julia P.; Iverson, Richard M.

    2008-01-01

    Power-law equations that are physically motivated and statistically tested and calibrated provide a basis for forecasting areas likely to be inundated by debris flows, rock avalanches, and lahars with diverse volumes. The equations A=α1V2/3 and B=α2V2/3 are based on the postulate that the maximum valley cross-sectional area (A) and total valley planimetric area (B) likely to be inundated by a flow depend only on its volume (V) and the topography of the flow path. Testing of these equations involves determining whether or not they fit data for documented flows satisfactorily, and calibration entails determining best-fit values of the coefficients α1 and α2 for debris flows, rock avalanches, and lahars. This report describes statistical testing and calibration of the equations by using field data compiled from many sources, and it describes application of the equations to delineation of debris-flow hazard zones. Statistical results show that for each type of flow (debris flows, rock avalanches, and lahars), the dependence of A and B on V is described well by power laws with exponents equal to 2/3. This value of the exponent produces fits that are effectively indistinguishable from the best fits obtained by using adjustable power-law exponents. Statistically calibrated values of the coefficients α1 and α2 provide scale-invariant indices of the relative mobilities of rock avalanches (α1 = 0.2, α2 = 20), nonvolcanic debris flows (α1 = 0.1, α2 = 20), and lahars (α1 = 0.05, α2 = 200). These values show, for example, that a lahar of specified volume can be expected to inundate a planimetric area ten times larger than that inundated by a rock avalanche or nonvolcanic debris flow of the same volume. The utility of the calibrated debris-flow inundation equations A=0.1V2/3 and B=20V2/3 is demonstrated by using them within the GIS program LAHARZ to delineate nested hazard zones for future debris flows in an area bordering the Umpqua River in the south-central Oregon

  9. Catastrophic debris flows transformed from landslides in volcanic terrains : mobility, hazard assessment and mitigation strategies

    USGS Publications Warehouse

    Scott, Kevin M.; Macias, Jose Luis; Naranjo, Jose Antonio; Rodriguez, Sergio; McGeehin, John P.

    2001-01-01

    Communities in lowlands near volcanoes are vulnerable to significant volcanic flow hazards in addition to those associated directly with eruptions. The largest such risk is from debris flows beginning as volcanic landslides, with the potential to travel over 100 kilometers. Stratovolcanic edifices commonly are hydrothermal aquifers composed of unstable, altered rock forming steep slopes at high altitudes, and the terrain surrounding them is commonly mantled by readily mobilized, weathered airfall and ashflow deposits. We propose that volcano hazard assessments integrate the potential for unanticipated debris flows with, at active volcanoes, the greater but more predictable potential of magmatically triggered flows. This proposal reinforces the already powerful arguments for minimizing populations in potential flow pathways below both active and selected inactive volcanoes. It also addresses the potential for volcano flank collapse to occur with instability early in a magmatic episode, as well as the 'false-alarm problem'-the difficulty in evacuating the potential paths of these large mobile flows. Debris flows that transform from volcanic landslides, characterized by cohesive (muddy) deposits, create risk comparable to that of their syneruptive counterparts of snow and ice-melt origin, which yield noncohesive (granular) deposits, because: (1) Volcano collapses and the failures of airfall- and ashflow-mantled slopes commonly yield highly mobile debris flows as well as debris avalanches with limited runout potential. Runout potential of debris flows may increase several fold as their volumes enlarge beyond volcanoes through bulking (entrainment) of sediment. Through this mechanism, the runouts of even relatively small collapses at Cascade Range volcanoes, in the range of 0.1 to 0.2 cubic kilometers, can extend to populated lowlands. (2) Collapse is caused by a variety of triggers: tectonic and volcanic earthquakes, gravitational failure, hydrovolcanism, and

  10. Application of the Empirical Thresholds of Precipitation to the Debris Flows in Mexico

    NASA Astrophysics Data System (ADS)

    Cardoso-Landa, G.

    2013-05-01

    The debris flows are particularly dangerous for the life and the properties due to its high speeds and great destructive force, destroying houses, ways, bridges, trees and cultures, currents and ecosystems throughout its trajectory. The extraordinary precipitation events are one of the predominant physical processes that produce the genesis of the debris flows. The empirical thresholds of precipitation are based on the historical analyses of the occurrence relation precipitation/debris flow, for example statistical analyses. At the present time a limited number of this type of empirical thresholds exists and have been used different diagrams to represent them, depending on the combinations of precipitation parameters more commonly used: antecedent precipitation, duration, accumulated intensity and rain, and the most commons are that obtained by Caine and Aleotti. An analytical presentation of the concept of threshold of precipitation of a debris flow was recently introduced by Iritanno et al. (1998), who introduced the called function of mobilization Y(t), indirectly describing all the factors that contribute to trigger a process of landslides and that is dependent, in every moment of time t, the amount of water infiltrate on the ground before the time t. In the full article was applied the Iritanno's function of mobilization to the records of precipitation that produced the debris flows in the north of Puebla State, in the country of México, obtaining relationships intensity of rain-duration for these debris flows are greater from 3.43 to 2.1 times over empirical thresholds of precipitation generators of debris flows proposed by Caine and Aleotti in other regions of the world. .Intensity of precipitation for the debris flows in Mexicot;

  11. A Detailed Study of Debris Flow Source Areas in the Northern Colorado Front Range.

    NASA Astrophysics Data System (ADS)

    Arana-Morales, A.; Baum, R. L.; Godt, J.

    2014-12-01

    Nearly continuous, heavy rainfall occurred during 9-13 September 2013 causing flooding and widespread landslides and debris flows in the northern Colorado Front Range. Whereas many recent studies have identified erosion as the most common process leading to debris flows in the mountains of Colorado, nearly all of the debris flows mapped in this event began as small, shallow landslides. We mapped the boundaries of 415 September 2013 debris flows in the Eldorado Springs and Boulder 7.5-minute quadrangles using 0.5-m-resolution satellite imagery. We characterized the landslide source areas of six debris flows in the field as part of an effort to identify what factors controlled their locations. Four were on a dip slope in sedimentary rocks in the Pinebrook Hills area, near Boulder, and the other two were in granitic rocks near Gross Reservoir. Although we observed no obvious geomorphic differences between the source areas and surrounding non-landslide areas, we noted several characteristics that the source areas all had in common. Slopes of the source areas ranged from 28° to 35° and most occurred on planar or slightly concave slopes that were vegetated with grass, small shrubs, and sparse trees. The source areas were shallow, irregularly shaped, and elongated downslope: widths ranged from 4 to 9 m, lengths from 6 to 40 m and depths ranged from 0.7 to 1.2 m. Colluvium was the source material for all of the debris flows and bedrock was exposed in the basal surface of all of the source areas. We observed no evidence for concentrated surface runoff upslope from the sources. Local curvature and roughness of bedrock and surface topography, and depth distribution and heterogeneity of the colluvium appear to have controlled the specific locations of these shallow debris-flow source areas. The observed distribution and characteristics of the source areas help guide ongoing efforts to model initiation of the debris flows.

  12. Analysis of Geomorphic and Hydrologic Characteristics of Mount Jefferson Debris Flow, Oregon, November 6, 2006

    USGS Publications Warehouse

    Sobieszczyk, Steven; Uhrich, Mark A.; Piatt, David R.; Bragg, Heather M.

    2008-01-01

    On November 6, 2006, a rocky debris flow surged off the western slopes of Mount Jefferson into the drainage basins of Milk and Pamelia Creeks in Oregon. This debris flow was not a singular event, but rather a series of surges of both debris and flooding throughout the day. The event began during a severe storm that brought warm temperatures and heavy rainfall to the Pacific Northwest. Precipitation measurements near Mount Jefferson at Marion Forks and Santiam Junction showed that more than 16.1 centimeters of precipitation fell the week leading up to the event, including an additional 20.1 centimeters falling during the 2 days afterward. The flooding associated with the debris flow sent an estimated 15,500 to 21,000 metric tons, or 9,800 to 13,000 cubic meters, of suspended sediment downstream, increasing turbidity in the North Santiam River above Detroit Lake to an estimated 35,000 to 55,000 Formazin Nephelometric Units. The debris flow started small as rock and ice calved off an upper valley snowfield, but added volume as it eroded weakly consolidated deposits from previous debris flows, pyroclastic flows, and glacial moraines. Mud run-up markings on trees indicated that the flood stage of this event reached depths of at least 2.4 meters. Velocity calculations indicate that different surges of debris flow and flooding reached 3.9 meters per second. The debris flow reworked and deposited material ranging in size from sand to coarse boulders over a 0.1 square kilometer area, while flooding and scouring as much as 0.45 square kilometer. Based on cross-sectional transect measurements recreating pre-event topography and other field measurements, the total volume of the deposit ranged from 100,000 to 240,000 cubic meters.

  13. Modeling four occurred debris flow events in the Dolomites area (North-Eastern Italian Alps)

    NASA Astrophysics Data System (ADS)

    Boreggio, Mauro; Gregoretti, Carlo; Degetto, Massimo; Bernard, Martino

    2016-04-01

    Four occurred debris flows in the Dolomites area (North-Eastern Italian Alps) are modeled by back-analysis. The four debris flows events are those occurred at Rio Lazer (Trento) on the 4th of November 1966, at Fiames (Belluno) on the 5th of July 2006, at Rovina di Cancia (Belluno) on the 18th of July 2009 and at Rio Val Molinara (Trento) on the 15th of August 2010. In all the events, runoff entrained sediments present on natural channels and formed a solid-liquid wave that routed downstream. The first event concerns the routing of debris flow on an inhabited fan. The second event the deviation of debris flow from the usual path due to an obstruction with the excavation of a channel in the scree and the downstream spreading in a wood. The third event concerns the routing of debris flow in a channel with an ending the reservoir, its overtopping and final spreading in the inhabited area. The fourth event concerns the routing of debris flow along the main channel downstream the initiation area until spreading just upstream a village. All the four occurred debris flows are simulated by modeling runoff that entrained debris flow for determining the solid-liquid hydrograph. The routing of the solid-liquid hydrograph is simulated by a bi-phase cell model based on the kinematic approach. The comparison between simulated and measured erosion and deposition depths is satisfactory. Nearly the same parameters for computing erosion and deposition were used for all the four occurred events. The maps of erosion and deposition depths are obtained by comparing the results of post-event surveys with the pre-event DEM. The post-event surveys were conducted by using different instruments (LiDAR and GPS) or the combination photos-single points depth measurements (in this last case it is possible obtaining the deposition/erosion depths by means of stereoscopy techniques).

  14. Probabilistic rainfall thresholds for triggering debris flows in a human-modified landscape

    NASA Astrophysics Data System (ADS)

    Giannecchini, Roberto; Galanti, Yuri; D'Amato Avanzi, Giacomo; Barsanti, Michele

    2016-03-01

    In the Carrara Marble Basin (CMB; Apuan Alps, Italy) quarrying has accumulated widespread and thick quarry waste, lying on steep slopes and invading valley bottoms. The Apuan Alps are one of the rainiest areas in Italy and rainstorms often cause landslides and debris flows. The stability conditions of quarry waste are difficult to assess, owing to its textural, geotechnical and hydrogeological variability. Therefore, empirical rainfall thresholds may be effective in forecasting the possible occurrence of debris flows in the CMB. Three types of thresholds were defined for three rain gauges of the CMB and for the whole area: rainfall intensity-rainfall duration (ID), cumulated event rainfall-rainfall duration (ED), and cumulated event rainfall normalized by the mean annual precipitation-rainfall intensity (EMAPI). The rainfall events recorded from 1950 to 2005 was analyzed and compared with the occurrence of debris flows involving the quarry waste. They were classified in events that triggered one or more debris flows and events that did not trigger debris flows. This dataset was fitted using the logistic regression method that allows us to define a set of thresholds, corresponding to different probabilities of failure (from 10% to 90%) and therefore to different warning levels. The performance of the logistic regression in defining probabilistic thresholds was evaluated by means of contingency tables, skill scores and receiver operating characteristic (ROC) analysis. These analyses indicate that the predictive capability of the three types of threshold is acceptable for each rain gauge and for the whole CMB. The best compromise between the number of correct debris flow predictions and the number of wrong predictions is obtained for the 40% probability thresholds. The results obtained can be tested in an experimental debris flows forecasting system based on rainfall thresholds, and could have implications for the debris flow hazard and risk assessment in the CMB.

  15. Development of the Assessment Items of Debris Flow Using the Delphi Method

    NASA Astrophysics Data System (ADS)

    Byun, Yosep; Seong, Joohyun; Kim, Mingi; Park, Kyunghan; Yoon, Hyungkoo

    2016-04-01

    In recent years in Korea, Typhoon and the localized extreme rainfall caused by the abnormal climate has increased. Accordingly, debris flow is becoming one of the most dangerous natural disaster. This study aimed to develop the assessment items which can be used for conducting damage investigation of debris flow. Delphi method was applied to classify the realms of assessment items. As a result, 29 assessment items which can be classified into 6 groups were determined.

  16. Debris flow boundary stresses and bedrock erosion: large scale laboratory experiments

    NASA Astrophysics Data System (ADS)

    Hsu, L.; Dietrich, W. E.

    2008-12-01

    Field observations indicate that debris flows can cause erosional wear of bedrock channels. On steep slopes, where debris flows are dominant, this wear may be the primary means of long-term channel incision. However, we presently lack a large-scale, experimentally tested theory to predict bedrock erosion by debris flows. Here, we hypothesize that impact erosion by particles colliding with the bed removes more bedrock than sliding erosion from the bulk weight of the flow. To develop and test a process-based theory for bedrock incision by debris flows, we study the erosional processes of granular flows in a 4-meter diameter, 80-cm wide vertically rotating drum. Debris flow slurries are created with mixtures of natural sediment from clay-sized to 20-cm diameter combined with varying amounts of water. During the experimental runs, the normal force on the bed is directly measured by a 225-cm2 load plate and the corresponding longitudinal profile and plan-view velocity field of the debris slurry is measured with a laser profiler and video camera, respectively. The erosion volume is obtained by repeated topographic measurement of 60 cm by 60 cm synthetic and natural rock samples embedded in the floor of the drum. By varying the grain size distribution, water content, and flow volume, we created both impact-dominated and sliding-dominated erosion conditions. The erosion of the bedrock, instead of scaling with the mean bulk stress of the flow, scaled with the stress deviations from the mean, which are caused by impacts of individual grains on the bed. This result supports the hypothesis that for bedrock erosion, dynamic stresses caused by individual clasts are more important than mean stress at the bed of the flow. Stress deviations from the mean depend on grain size distribution and particle trajectories, and therefore these properties should be measured in natural debris flows and included in modeling efforts of dynamics and erosion.

  17. The fluidity of boulder debris flows is affected by fine sediment in the pore water

    NASA Astrophysics Data System (ADS)

    Hotta, Norifumi; Kaneko, Takahiro; Iwata, Tomoyuki; Nishimoto, Haruo

    2013-04-01

    Basic equations for debris flows are frequently derived using the simple assumption of monogranular particles. However, actual debris flows include a great diversity of grain sizes, resulting in inherent features such as inverse grading, particle size segregation, and liquefaction of fine sediment. The liquefaction of fine sediment affects the fluidity of debris flows, although the behavior and influence of fine sediment in debris flows have not been examined sufficiently. This study used flume tests to detect the effect of fine sediment on the characteristics of laboratory debris flows consisting of particles with two diameters: one diameter was fixed at a large particle size, while the small diameters were varied with the experimental conditions. From the experiments, the greatest sediment concentration and flow depth were observed in the debris flows mixed with finer sediment, indicating increased flow resistance. Then, the experimental friction coefficient was compared with the theoretical friction coefficient derived by substituting the experimental values into the constitutive equations for debris flow. The theoretical friction coefficient was obtained from two models with different fine-sediment treatments: one assuming that all of the fine sediments were solid particles and the other that the particles consisted of a fluid phase involving pore water liquefaction. A discriminant index was introduced to clarify which contribution from the two models could better explain the experimental results. The comparison of the friction coefficients detected a fully liquefied state for the finest particle mixture with sediment. However, even with the same particle size, the debris flows could be regarded as a liquefied state, a solid state, or a partially liquefied transition state depending on the experimental conditions other than the sediment particle size. These results infer that the liquefaction of fine sediment in debris flows was induced not only by the

  18. Setting up the critical rainfall line for debris flows via support vector machines

    NASA Astrophysics Data System (ADS)

    Tsai, Y. F.; Chan, C. H.; Chang, C. H.

    2015-10-01

    The Chi-Chi earthquake in 1999 caused tremendous landslides which triggered many debris flows and resulted in significant loss of public lives and property. To prevent the disaster of debris flow, setting a critical rainfall line for each debris-flow stream is necessary. Firstly, 8 predisposing factors of debris flow were used to cluster 377 streams which have similar rainfall lines into 7 groups via the genetic algorithm. Then, support vector machines (SVM) were applied to setup the critical rainfall line for debris flows. SVM is a machine learning approach proposed based on statistical learning theory and has been widely used on pattern recognition and regression. This theory raises the generalized ability of learning mechanisms according to the minimum structural risk. Therefore, the advantage of using SVM can obtain results of minimized error rates without many training samples. Finally, the experimental results confirm that SVM method performs well in setting a critical rainfall line for each group of debris-flow streams.

  19. Probability and volume of potential postwildfire debris flows in the 2011 Wallow burn area, eastern Arizona

    USGS Publications Warehouse

    Ruddy, Barbara C.

    2011-01-01

    This report presents a preliminary emergency assessment of the debris-flow hazards from drainage basins burned in 2011 by the Wallow wildfire in eastern Arizona. Empirical models derived from statistical evaluation of data collected from recently burned drainage basins throughout the intermountain western United States were used to estimate the probability of debris-flow occurrence and debris-flow volumes for selected drainage basins. Input for the models include measures of burn severity, topographic characteristics, soil properties, and rainfall total and intensity for a (1) 10-year-recurrence, 1-hour-duration rainfall and (2) 25-year-recurrence, 1-hour-duration rainfall. Estimated debris-flow probabilities in the drainage basins of interest ranged from less than 1 percent in response to both the 10-year-recurrence, 1-hour-duration rainfall and the 25-year-recurrence, 1-hour-duration rainfall to a high of 41 percent in response to the 25-year-recurrence, 1-hour-duration rainfall. The low probabilities in all modeled drainage basins are likely due to extensive low-gradient hillslopes, burned at low severities, and large drainage-basin areas (greater than 25 square kilometers). Estimated debris-flow volumes ranged from a low of 24 cubic meters to a high of greater than 100,000 cubic meters, indicating a considerable hazard should debris flows occur

  20. Processing the ground vibration signal produced by debris flows: the methods of amplitude and impulses compared

    NASA Astrophysics Data System (ADS)

    Arattano, M.; Abancó, C.; Coviello, V.; Hürlimann, M.

    2014-12-01

    Ground vibration sensors have been increasingly used and tested, during the last few years, as devices to monitor debris flows and they have also been proposed as one of the more reliable devices for the design of debris flow warning systems. The need to process the output of ground vibration sensors, to diminish the amount of data to be recorded, is usually due to the reduced storing capabilities and the limited power supply, normally provided by solar panels, available in the high mountain environment. There are different methods that can be found in literature to process the ground vibration signal produced by debris flows. In this paper we will discuss the two most commonly employed: the method of impulses and the method of amplitude. These two methods of data processing are analyzed describing their origin and their use, presenting examples of applications and their main advantages and shortcomings. The two methods are then applied to process the ground vibration raw data produced by a debris flow occurred in the Rebaixader Torrent (Spanish Pyrenees) in 2012. The results of this work will provide means for decision to researchers and technicians who find themselves facing the task of designing a debris flow monitoring installation or a debris flow warning equipment based on the use of ground vibration detectors.

  1. Debris flow susceptibility mapping using a qualitative heuristic method and Flow-R along the Yukon Alaska Highway Corridor, Canada

    NASA Astrophysics Data System (ADS)

    Blais-Stevens, A.; Behnia, P.

    2016-02-01

    This research activity aimed at reducing risk to infrastructure, such as a proposed pipeline route roughly parallel to the Yukon Alaska Highway Corridor (YAHC), by filling geoscience knowledge gaps in geohazards. Hence, the Geological Survey of Canada compiled an inventory of landslides including debris flow deposits, which were subsequently used to validate two different debris flow susceptibility models. A qualitative heuristic debris flow susceptibility model was produced for the northern region of the YAHC, from Kluane Lake to the Alaska border, by integrating data layers with assigned weights and class ratings. These were slope angle, slope aspect, surficial geology, plan curvature, and proximity to drainage system. Validation of the model was carried out by calculating a success rate curve which revealed a good correlation with the susceptibility model and the debris flow deposit inventory compiled from air photos, high-resolution satellite imagery, and field verification. In addition, the quantitative Flow-R method was tested in order to define the potential source and debris flow susceptibility for the southern region of Kluane Lake, an area where documented debris flow events have blocked the highway in the past (e.g. 1988). Trial and error calculations were required for this method because there was not detailed information on the debris flows for the YAHC to allow us to define threshold values for some parameters when calculating source areas, spreading, and runout distance. Nevertheless, correlation with known documented events helped define these parameters and produce a map that captures most of the known events and displays debris flow susceptibility in other, usually smaller, steep channels that had not been previously documented.

  2. Debris flow susceptibility mapping using a qualitative heuristic method and Flow-R along the Yukon Alaska Highway Corridor, Canada

    NASA Astrophysics Data System (ADS)

    Blais-Stevens, A.; Behnia, P.

    2015-05-01

    This research activity aimed at reducing risk to infrastructure, such as a proposed pipeline route roughly parallel to the Yukon Alaska Highway Corridor (YAHC) by filling geoscience knowledge gaps in geohazards. Hence, the Geological Survey of Canada compiled an inventory of landslides including debris flow deposits, which were subsequently used to validate two different debris flow susceptibility models. A qualitative heuristic debris flow susceptibility model was produced for the northern region of the YAHC, from Kluane Lake to the Alaska border, by integrating data layers with assigned weights and class ratings. These were slope angle, slope aspect (derived from a 5 m × 5 m DEM), surficial geology, permafrost distribution, and proximity to drainage system. Validation of the model was carried out by calculating a success rate curve which revealed a good correlation with the susceptibility model and the debris flow deposit inventory compiled from air photos, high resolution satellite imagery, and field verification. In addition, the quantitative Flow-R method was tested in order to define the potential source and debris flow susceptibility for the southern region of Kluane Lake, an area where documented debris flow events have blocked the highway in the past (e.g., 1988). Trial and error calculations were required for this method because there was not detailed information on the debris flows for the YAHC to allow us to define threshold values for some parameters when calculating source areas, spreading, and runout distance. Nevertheless, correlation with known documented events helped define these parameters and produce a map that captures most of the known events and displays debris flow susceptibility in other, usually smaller, steep channels that had not been previously documented.

  3. Model simulations of flood and debris flow timing in steep catchments after wildfire

    USGS Publications Warehouse

    Rengers, Francis; Mcguire, Luke; Kean, Jason W.; Staley, Dennis M.; Hobley, D.E.J

    2016-01-01

    Debris flows are a typical hazard on steep slopes after wildfire, but unlike debris flows that mobilize from landslides, most post-wildfire debris flows are generated from water runoff. The majority of existing debris-flow modeling has focused on landslide-triggered debris flows. In this study we explore the potential for using process-based rainfall-runoff models to simulate the timing of water flow and runoff-generated debris flows in recently burned areas. Two different spatially distributed hydrologic models with differing levels of complexity were used: the full shallow water equations and the kinematic wave approximation. Model parameter values were calibrated in two different watersheds, spanning two orders of magnitude in drainage area. These watersheds were affected by the 2009 Station Fire in the San Gabriel Mountains, CA, USA. Input data for the numerical models were constrained by time series of soil moisture, flow stage, and rainfall collected at field sites, as well as high-resolution lidar-derived digital elevation models. The calibrated parameters were used to model a third watershed in the burn area, and the results show a good match with observed timing of flow peaks. The calibrated roughness parameter (Manning's $n$) was generally higher when using the kinematic wave approximation relative to the shallow water equations, and decreased with increasing spatial scale. The calibrated effective watershed hydraulic conductivity was low for both models, even for storms occurring several months after the fire, suggesting that wildfire-induced changes to soil-water infiltration were retained throughout that time. Overall the two model simulations were quite similar suggesting that a kinematic wave model, which is simpler and more computationally efficient, is a suitable approach for predicting flood and debris flow timing in steep, burned watersheds.

  4. Effects of Debris Flows on Stream Ecosystems of the Klamath Mountains, Northern California

    NASA Astrophysics Data System (ADS)

    Cover, M. R.; Delafuente, J. A.; Resh, V. H.

    2006-12-01

    We examined the long-term effects of debris flows on channel characteristics and aquatic food webs in steep (0.04-0.06 slope), small (4-6 m wide) streams. A large rain-on-snow storm event in January 1997 resulted in numerous landslides and debris flows throughout many basins in the Klamath Mountains of northern California. Debris floods resulted in extensive impacts throughout entire drainage networks, including mobilization of valley floor deposits and removal of vegetation. Comparing 5 streams scoured by debris flows in 1997 and 5 streams that had not been scoured as recently, we determined that debris-flows decreased channel complexity by reducing alluvial step frequency and large woody debris volumes. Unscoured streams had more diverse riparian vegetation, whereas scoured streams were dominated by dense, even-aged stands of white alder (Alnus rhombiflia). Benthic invertebrate shredders, especially nemourid and peltoperlid stoneflies, were more abundant and diverse in unscoured streams, reflecting the more diverse allochthonous resources. Debris flows resulted in increased variability in canopy cover, depending on degree of alder recolonization. Periphyton biomass was higher in unscoured streams, but primary production was greater in the recently scoured streams, suggesting that invertebrate grazers kept algal assemblages in an early successional state. Glossosomatid caddisflies were predominant scrapers in scoured streams; heptageniid mayflies were abundant in unscoured streams. Rainbow trout (Oncorhynchus mykiss) were of similar abundance in scoured and unscoured streams, but scoured streams were dominated by young-of-the-year fish while older juveniles were more abundant in unscoured streams. Differences in the presence of cold-water (Doroneuria) versus warm-water (Calineuria) perlid stoneflies suggest that debris flows have altered stream temperatures. Debris flows have long-lasting impacts on stream communities, primarily through the cascading effects of

  5. Probabilistic forecasts of debris-flow hazard at the regional scale with a combination of models.

    NASA Astrophysics Data System (ADS)

    Malet, Jean-Philippe; Remaître, Alexandre

    2015-04-01

    Debris flows are one of the many active slope-forming processes in the French Alps, where rugged and steep slopes mantled by various slope deposits offer a great potential for triggering hazardous events. A quantitative assessment of debris-flow hazard requires the estimation, in a probabilistic framework, of the spatial probability of occurrence of source areas, the spatial probability of runout areas, the temporal frequency of events, and their intensity. The main objective of this research is to propose a pipeline for the estimation of these quantities at the region scale using a chain of debris-flow models. The work uses the experimental site of the Barcelonnette Basin (South French Alps), where 26 active torrents have produced more than 150 debris-flow events since 1850 to develop and validate the methodology. First, a susceptibility assessment is performed to identify the debris-flow prone source areas. The most frequently used approach is the combination of environmental factors with GIS procedures and statistical techniques, integrating or not, detailed event inventories. Based on a 5m-DEM and derivatives, and information on slope lithology, engineering soils and landcover, the possible source areas are identified with a statistical logistic regression model. The performance of the statistical model is evaluated with the observed distribution of debris-flow events recorded after 1850 in the study area. The source areas in the three most active torrents (Riou-Bourdoux, Faucon, Sanières) are well identified by the model. Results are less convincing for three other active torrents (Bourget, La Valette and Riou-Chanal); this could be related to the type of debris-flow triggering mechanism as the model seems to better spot the open slope debris-flow source areas (e.g. scree slopes), but appears to be less efficient for the identification of landslide-induced debris flows. Second, a susceptibility assessment is performed to estimate the possible runout distance

  6. Debris Flow Hazard Map Simulation using FLO-2D For Selected Areas in the Philippines

    NASA Astrophysics Data System (ADS)

    Khallil Ferrer, Peter; Llanes, Francesca; dela Resma, Marvee; Realino, Victoriano, II; Obrique, Julius; Ortiz, Iris Jill; Aquino, Dakila; Narod Eco, Rodrigo; Mahar Francisco Lagmay, Alfredo

    2014-05-01

    On December 4, 2012, Super Typhoon Bopha wreaked havoc in the southern region of Mindanao, leaving 1,067 people dead and causing USD 800 million worth of damage. Classified as a Category 5 typhoon by the Joint Typhoon Warning Center (JTWC), Bopha brought intense rainfall and strong winds that triggered landslides and debris flows, particularly in Barangay (village) Andap, New Bataan municipality, in the southern Philippine province of Compostela Valley. The debris flow destroyed school buildings and covered courts and an evacuation center. Compostela Valley also suffered the most casualties of any province: 612 out of a total of 1,067. In light of the disaster in Compostela, measures were immediately devised to improve available geohazard maps to raise public awareness about landslides and debris flows. A debris flow is a very rapid to extremely rapid flow of saturated non-plastic debris in a steep channel. They are generated when heavy rainfall saturates sediments, causing them to flow down river channels within an alluvial fan situated at the base of the slope of a mountain drainage network. Many rural communities in the Philippines, such as Barangay Andap, are situated at the apex of alluvial fans and in the path of potential debris flows. In this study, we conducted simulations of debris flows to assess the risks in inhabited areas throughout the Philippines and validated the results in the field, focusing on the provinces of Pangasinan and Aurora as primary examples. Watersheds that drain in an alluvial fan using a 10-m resolution Synthetic Aperture Radar (SAR)-derived Digital Elevation Model (DEM) was first delineated, and then a 1 in 100-year rain return rainfall scenario for the watershed was used to simulate debris flows using FLO-2D, a flood-routing software. The resulting simulations were used to generate debris flow hazard maps which are consistent with danger zones in alluvial fans delineated previously from satellite imagery and available DEMs. The

  7. A process for fire-related debris flow initiation, Cerro Grande fire, New Mexico

    USGS Publications Warehouse

    Cannon, S.H.; Bigio, E.R.; Mine, E.

    2001-01-01

    In this study we examine factors that pertain to the generation of debris flows from a basin recently burned by wildfire. Throughout the summer 2000 thunderstorm season, we monitored rain gauges, channel cross-sections, hillslope transects, and nine sediment-runoff traps deployed in a steep, 0??15 km2 basin burned by the May 2000 Cerro Grande fire in New Mexico. Debris flows were triggered in the monitored basin during a rainstorm on July 16, 2000, in response to a maximum 30 min rainfall intensity of 31 mm h-1 (return period of approximately 2 years). Eleven other storms occurred before and after the July storm; these storms resulted in significant runoff, but did not generate debris flows. The debris flows generated by the July 16 storm initiated on a broad, open hillslope as levee-lined rills. The levees were composed of gravel- and cobble-sized material supported by an abundant fine-grained matrix. Debris-flow deposits were observed only on the hillslopes and in the first and second-order drainages of the monitored basin. No significant amounts of channel incision were measured following the passage of the debris flows, indicating that most of the material in the flows originated from the hillslopes. Sediment-runoff concentrations of between 0??23 and 0??81 kg 1-1 (with a mean of 0-42 kg 1-1) were measured from the hillslope traps following the debris-flow-producing storm. These concentrations, however, were not unique to the July 16 storm. The materials entrained by the July 16 storm contained a higher proportion of silt- plus clay-sized materials in the <2 mm fraction than the materials collected from storms that produced comparable sediment-runoff concentrations but not debris flows. The difference in materials demonstrates the critical role of the availability of fine-grained wood ash mantling the hillslopes in the runoff-dominated generation of post-wildfire debris flows. The highest sediment-runoff concentrations, again not unique to debris-flow

  8. Debris flows on Belding Creek, Salmonberry River basin, northern Oregon Coast Range

    SciTech Connect

    Burris, L.M. . Dept. of Geology)

    1993-04-01

    Belding Creek, a tributary of the Salmonberry River, has experienced repeated debris flow episodes. The Salmonberry River flows through Paleocene Tillamook Basalt and is located at longitude 45[degree]43 minutes in the Northern Oregon Coast Range. On January 9, 1990, a debris flow initiated on a first order tributary of Belding Creek during a heavy precipitation event. A month later another debris flow initiated on a different first order stream under similar conditions. Both debris flows traveled for a distance of approximately 2.1 km and poured into the main Belding Creek channel washing out Belding Road which crosses the stream. Numerical data was obtained from the youngest flow deposit. The debris flow material density is 2.5 g/cm[sup 3]. It traveled at an average velocity of 2.9 m/s with a shear strength of 2.5 [times] 10[sup 4] dn/cm[sup 2], a friction angle of 4[degree], and a cohesion value of 1.4 [times] 10[sup 4] dn/cm[sup 3]. Less than 3% of the fine sediments deposited are clay and silt. Deposits from previous, older debris flow events are in and adjacent to the Belding Creek stream channel. Similar processes are evident in other major tributaries of the Salmonberry River, although these other stream channels have not shown recent activity. Each stream in the area that has experienced past debris flows similar to Belding Creek has a landslide feature at the top and follows regional lineation patterns.

  9. Evidence for debris flow gully formation initiated by shallow subsurface water on Mars

    USGS Publications Warehouse

    Lanza, N.L.; Meyer, G.A.; Okubo, C.H.; Newsom, Horton E.; Wiens, R.C.

    2010-01-01

    The morphologies of some martian gullies appear similar to terrestrial features associated with debris flow initiation, erosion, and deposition. On Earth, debris flows are often triggered by shallow subsurface throughflow of liquid water in slope-mantling colluvium. This flow causes increased levels of pore pressure and thus decreased shear strength, which can lead to slide failure of slope materials and subsequent debris flow. The threshold for pore pressure-induced failure creates a distinct relationship between the contributing area supplying the subsurface flow and the slope gradient. To provide initial tests of a similar debris flow initiation hypothesis for martian gullies, measurements of the contributing areas and slope gradients were made at the channel heads of martian gullies seen in three HiRISE stereo pairs. These gullies exhibit morphologies suggestive of debris flows such as leveed channels and lobate debris fans, and have well-defined channel heads and limited evidence for multiple flows. Our results show an area-slope relationship for these martian gullies that is consistent with that observed for terrestrial gullies formed by debris flow, supporting the hypothesis that these gullies formed as the result of saturation of near-surface regolith by a liquid. This model favors a source of liquid that is broadly distributed within the source area and shallow; we suggest that such liquid could be generated by melting of broadly distributed icy materials such as snow or permafrost. This interpretation is strengthened by observations of polygonal and mantled terrain in the study areas, which are both suggestive of near-surface ice. ?? 2009 Elsevier Inc.

  10. New debris flow mitigation measures in southern Gansu, China: a case study of the Zhouqu Region

    NASA Astrophysics Data System (ADS)

    Xiong, Muqi; Meng, Xingmin; Li, Yajun

    2014-05-01

    A devastating debris flow occurred in Zhouqu of Gansu Province, China, on 8th August 2010, resulting in a catastrophic disaster, with 1463 people being perished. The debris flow valleys, as other numerous debris valleys in the mountainous region, had preventive engineering constructions, such as check dames, properly designed based on common engineering practices for safe guiding the town located right on the debris flow fan. However, failures of such preventive measures often cause even heavier disasters than those that have no human interactions, as the mitigations give a false safety impression. Given such a weird situation and in order to explore a much more effective disaster prevention strategy against debris flows in the mountainous region, this paper makes a comparative study based on two cases in the area of which one had preventive structures and one hasn't. The result shows that inappropriate mitigation measures that have commonly been applying in the disaster reduction practices in the region are of questionable. It is concluded that going with the nature and following with the natural rules are the best strategy for disaster reduction in the region. Key words: debris flow disasters, disaster reduction strategy, preventive measures

  11. Debris flows from failures Neoglacial-age moraine dams in the Three Sisters and Mount Jefferson wilderness areas, Oregon

    USGS Publications Warehouse

    O'Connor, J. E.; Hardison, J.H.; Costa, J.E.

    2001-01-01

    The highest concentration of lakes dammed by Neoglacial moraines in the conterminous United States is in the Mount Jefferson and Three Sisters Wilderness Areas in central Oregon. Between 1930 and 1980, breakouts of these lakes have resulted in 11 debris flows. The settings and sequences of events leading to breaching and the downstream flow behavior of the resulting debris flows provide guidance on the likelihood and magnitude of future lake breakouts and debris flows.

  12. Estimation of Rheological Properties of Viscous Debris Flow Using a Belt Conveyor

    NASA Astrophysics Data System (ADS)

    Hübl, J.; Steinwendtner, H.

    2000-09-01

    Rheological parameters of viscous debris flows are influenced by a great amount of factors and are therefore extremely difficult to estimate. Because of this uncertainties a belt conveyor (conveyor channel) was constructed to measure flow behaviour and rheological properties of natural debris flow material. The upward movement of the smooth rubberised belt between fixed lateral plastic walls causes a stationary wave relative to these bends. This special experimental design enables to study behaviour of viscous ebris flow material with maximum grain diameters up to 20 mm within several minutes and to hold measuring equipment very simple. The conveyor channel was calibrated first with Xanthan, a natural polysaccharide used as thickener in food technology, whose rheological properties are similar to viscous debris flow material. In a second step natural debris flow material was investigated. Velocities and rheological parameters were measured with varying solid concentration and slope of the channel. In cases where concentration of coarse particles exceed around 15% by volume the conveyor channel obtains an alternative to expensive commercial viscometers for determination of rheological parameters of viscous debris flows.

  13. Debris Flow Monitoring in the Acquabona Watershed on the Dolomites (Italian Alps)

    NASA Astrophysics Data System (ADS)

    Berti, M.; Genevois, R.; LaHusen, R.; Simoni, A.; Tecca, P. R.

    2000-09-01

    In 1997 a field monitoring system was installed in Acquabona Creek in the Dolomites (Eastern Italian Alps) to observe the hydrologic conditions for debris flow occurrence and some dynamic properties of debris flow. The monitoring system consists of three remote stations: an upper one located at the head of a deeply-incised channel and two others located downstream. The system is equipped with sensors for measuring rainfall, pore pressures in the mobile channel bottom, ground vibrations, debris flow depth, total normal stress and fluid pore-pressure at the base of the flow. Two video cameras record events at the upper channel station and one video is installed at the lowermost station. During summer 1998, three debris flows (volumes from less than 1000 m3 up to 9000 m3) occurred at Acquabona. The following results were obtained from a preliminary analysis of the data: 1) All of the flows were triggered by rainfalls of less than 1 hour duration, with peak rainfall intensities ranging from 4.8 to 14.7 mm / 10 minute. 2) Debris flows initiated in several reaches of the channel, including the head of the talus slope. 3) The initial surges of the mature flows had a higher solid concentration and a lower velocity (up to 4 m/s) than succeeding, more dilute surges (more than 7 m/s). 4) Total normal stress and pore fluid pressures measured at the base of the flow. (mean depth about 1.1 m) were similar (about 15 kPa), indicating a completely liquefied flow. 5) Peak flows entrained debris at a rate of about 6 m 3/m of channel length and channel bed scouring was proportional to the local slope gradient and was still evident in the lower channel where the slope was 7°.

  14. Debris flow monitoring in the Acquabona watershed on the Dolomites (Italian Alps)

    USGS Publications Warehouse

    Berti, M.; Genevois, R.; LaHusen, R.; Simoni, A.; Tecca, P.R.

    2000-01-01

    In 1997 a field monitoring system was installed in Acquabona Creek in the Dolomites (Eastern Italian Alps) to observe the hydrologic conditions for debris flow occurrence and some dynamic properties of debris flow. The monitoring system consists of three remote stations: an upper one located at the head of a deeply-incised channel and two others located downstream. The system is equipped with sensors for measuring rainfall, pore pressures in the mobile channel bottom, ground vibrations, debris flow depth, total normal stress and fluid pore-pressure at the base of the flow. Two video cameras record events at the upper channel station and one video is installed at the lowermost station. During summer 1998, three debris flows (volumes from less than 1000 m3 up to 9000 m3) occurred at Acquabona. The following results were obtained from a preliminary analysis of the data: 1) All of the flows were triggered by rainfalls of less than 1 hour duration, with peak rainfall intensities ranging from 4.8 to 14.7 mm / 10 minute. 2) Debris flows initiated in several reaches of the channel, including the head of the talus slope. 3) The initial surges of the mature flows had a higher solid concentration and a lower velocity (up to 4 m/s) than succeeding, more dilute surges (more than 7 m/s). 4) Total normal stress and pore fluid pressures measured at the base of the flow (mean depth about 1.1 m) were similar (about 15 kPa), indicating a completely liquefied flow. 5) Peak flows entrained debris at a rate of about 6 m3/m of channel length and channel bed scouring was proportional to the local slope gradient and was still evident in the lower channel where the slope was 7??. ?? 2000 Elsevier Science Ltd. All rights reserved.

  15. Peculiar debris-flow event of June 2013 in Livingstone mountain range (Alberta, Canada)

    NASA Astrophysics Data System (ADS)

    Franz, Martin; Rudaz, Benjamin; Humair, Florian; Jaboyedoff, Michel; Froese, Corey

    2014-05-01

    Heavy precipitations occurred in western Alberta in mid-June 2013, which lead to several floods. In particular, this event produced a lot of debris-flow in the area of Mount Livingstone Alberta, Canada (N50° 8' 24.20", W114° 24' 19.69"). The area is mainly composed of folded Devonian to Jurassic carbonates. The peculiarity of the event is that the initiations of the debris-flows were located high in scree slopes, with reduced contributing area. No debris-flow deposits anterior to that event are visible, which contrasts with the number of simultaneous events (~30) triggered by this specific precipitation period (up to 220 mm in 36 hours). Fieldwork was carried out in July, less than one month after this event. Extensive photographic and Terrestrial Laser Scanner (TLS) data was acquired. In-line grain-size distribution, fine matrix sampling and cross-sections of the debris flow channel were performed at the initiation zone, the propagation zone and deposition area. Samples are analyzed by sieving as well as using laser diffraction methods for fine materials. Morphologic characterization is performed through pre-event HR-DEM (1m cell size) and TLS point-cloud comparison, along with cross-sections. Volumes can thus be calculated. The pristine debris-flow lobes, levees and source areas allowed the dynamic of the different debris-flow pulses to be reconstructed. Comparison between 2012 and 2013 field photographs emphasize the radical morphologic change caused by this single event on an apparently dormant erosion context. The conditions of initiation of the debris flows are compared with literature values, in term of slope, contributing area and saturation of the scree material. Preliminary analysis indicates that these debris-flows started at unusually low slopes in regard to the contributing area. This reinforces the extreme character of this event, attributed to two identified causes: the accumulation and weathering of rock debris in the scree slopes over time and

  16. Predicting debris flow occurrence in Eastern Italian Alps based on hydrological and geomorphological modelling

    NASA Astrophysics Data System (ADS)

    Nikolopoulos, Efthymios I.; Borga, Marco; Destro, Elisa; Marchi, Lorenzo

    2015-04-01

    Most of the work so far on the prediction of debris flow occurrence is focused on the identification of critical rainfall conditions. However, findings in the literature have shown that critical rainfall thresholds cannot always accurately identify debris flow occurrence, leading to false detections (positive or negative). One of the main reasons for this limitation is attributed to the fact that critical rainfall thresholds do not account for the characteristics of underlying land surface (e.g. geomorphology, moisture conditions, sediment availability, etc), which are strongly related to debris flow triggering. In addition, in areas where debris flows occur predominantly as a result of channel bed failure (as in many Alpine basins), the triggering factor is runoff, which suggests that identification of critical runoff conditions for debris flow prediction is more pertinent than critical rainfall. The primary objective of this study is to investigate the potential of a triggering index (TI), which combines variables related to runoff generation and channel morphology, for predicting debris flows occurrence. TI is based on a threshold criterion developed on past works (Tognacca et al., 2000; Berti and Simoni, 2005; Gregoretti and Dalla Fontana, 2008) and combines information on unit width peak flow, local channel slope and mean grain size. Estimation of peak discharge is based on the application of a distributed hydrologic model, while local channel slope is derived from a high-resolution (5m) DEM. Scaling functions of peak flows and channel width with drainage area are adopted since it is not possible to measure channel width or simulate peak flow at all channel nodes. TI values are mapped over the channel network thus allowing spatially distributed prediction but instead of identifying debris flow occurrence on single points, we identify their occurrence with reference to the tributary catchment involved. Evaluation of TI is carried out for five different basins

  17. Evolution of a natural debris flow: In situ measurements of flow dynamics, video imagery, and terrestrial laser scanning

    USGS Publications Warehouse

    McCoy, S.W.; Kean, J.W.; Coe, J.A.; Staley, D.M.; Wasklewicz, T.A.; Tucker, G.E.

    2010-01-01

    Many theoretical and laboratory studies have been undertaken to understand debris-flow processes and their associated hazards. However, complete and quantitative data sets from natural debris flows needed for confirmation of these results are limited. We used a novel combination of in situ measurements of debris-flow dynamics, video imagery, and pre- and postflow 2-cm-resolution digital terrain models to study a natural debris-flow event. Our field data constrain the initial and final reach morphology and key flow dynamics. The observed event consisted of multiple surges, each with clear variation of flow properties along the length of the surge. Steep, highly resistant, surge fronts of coarse-grained material without measurable pore-fluid pressure were pushed along by relatively fine-grained and water-rich tails that had a wide range of pore-fluid pressures (some two times greater than hydrostatic). Surges with larger nonequilibrium pore-fluid pressures had longer travel distances. A wide range of travel distances from different surges of similar size indicates that dynamic flow properties are of equal or greater importance than channel properties in determining where a particular surge will stop. Progressive vertical accretion of multiple surges generated the total thickness of mapped debris-flow deposits; nevertheless, deposits had massive, vertically unstratified sedimentological textures. ?? 2010 Geological Society of America.

  18. Physical Limits on the Predictability of Erosion and Sediment Transport by Landslides and Debris Flows

    NASA Astrophysics Data System (ADS)

    Iverson, R. M.

    2015-12-01

    Episodic landslides and debris flows play a key role in sculpting many steep landscapes, and they also pose significant natural hazards. Field evidence, laboratory experiments, and theoretical analyses show that variations in the quantity, speed, and distance of sediment transport by landslides and debris flows can depend strongly on nuanced differences in initial conditions. Moreover, initial conditions themselves can be strongly dependent on the geological legacy of prior events. The scope of these dependencies is revealed by the results of landslide dynamics experiments [Iverson et al., Science, 2000], debris-flow erosion experiments [Iverson et al., Nature Geosci., 2011], and numerical simulations of the highly destructive 2014 Oso, Washington, landslide [Iverson et al., Earth Planet. Sci. Let., 2015]. In each of these cases, feedbacks between basal sediment deformation and pore-pressure generation cause the speed and distance of sediment transport to be very sensitive to subtle differences in the ambient sediment porosity and water content. On the other hand, the onset of most landslides and debris flows depends largely on pore-water pressure distributions and only indirectly on sediment porosity and water content. Thus, even if perfect predictions of the locations and timing of landslides and debris flows were available, the dynamics of the events - and their consequent hazards and sediment transport - would be difficult to predict. This difficulty is a manifestation of the nonlinear physics involved, rather than of poor understanding of those physics. Consequently, physically based models for assessing the hazards and sediment transport due to landslides and debris flows must take into account both evolving nonlinear dynamics and inherent uncertainties about initial conditions. By contrast, landscape evolution models that use prescribed algebraic formulas to represent sediment transport by landslides and debris flows lack a sound physical basis.

  19. Reconstructing spatio-temporal patterns of debris-flow activity using dendrogeomorphological methods

    NASA Astrophysics Data System (ADS)

    Bollschweiler, Michelle; Stoffel, Markus; Ehmisch, Melanie; Monbaron, Michel

    2007-07-01

    Debris flows are a major threat in many parts of the Alps, where they repeatedly cause severe damage to infrastructure and transportation corridors or even loss of life. Nonetheless, the spatial behavior of past debris-flow activity and the analysis of areas affected during particular events have been widely neglected in reconstructions so far. It was therefore the purpose of this study to reconstruct spatio-temporal patterns of past debris flows on a forested cone in the Swiss Alps (Bruchji torrent, Blatten, Valais). The analysis of past events was based on a detailed geomorphic map (1:1000) of all forms related to debris flows as well as on tree-ring series from 401 heavily affected trees ( Larix decidua Mill. and Picea abies (L.) Karst.) growing in or next to deposits. The samples were analyzed and growth disturbances related to debris-flow activity assessed, such as tangential rows of traumatic resin ducts, the onset of reaction wood or abrupt growth suppression or release. In total, 960 growth disturbances were identified in the samples, belonging to 40 different event years between A.D. 1867 and 2005. In addition, the coupling of tree-ring data with the geomorphic map allowed reconstruction of eleven formerly active channels and spatial representation of individual events. Based on our results we believe that before 1935, debris flows preferentially used those channels located in the western part of the cone, whereas the eastern part of the cone remained widely unaffected. The spatial representation of the 40 events also allowed identification of five different spatial patterns for debris flows at the study site.

  20. Quick Analysis Method for Estimating Debris Flow Prone Area Caused by Overflow from Landslide dam

    NASA Astrophysics Data System (ADS)

    Shimizu, T.; Uchida, T.; Yamakoshi, T.; Yoshino, K.; Kisa, H.; Ishizuka, T.; Kaji, A.

    2012-04-01

    When earthquake or torrential rainfall cause deep catastrophic landslides, landslide dams can be formed in mountainous region. If water overflows from the landslide dams, large scale debris flow can occurs and possibly causes serious disasters in the downward region. Debris flow caused by the overflow from landslide dam is possible to affect the larger area than normal debris flow and flash flood. It is important for both a decision maker and resident in the area to recognize the disaster prone area as early as possible. For that reason, it is important to establish a quick analysis method for estimating debris flow prone area caused by overflow from landslide dams under the emergency situation. This situation requires the method to have both accuracy and speed for release. Nonetheless these two factors have trade-off relationship. We recently developed the quick analysis method to estimate debris flow disaster prone area caused by overflow from landslide dams. The method including the ways of efficient survey and numerical simulation programs called QUAD-L (QUick Analysis system for Debris flow caused by Landslide dam overflow). Our quick analysis system was actually applied to show the area for evacuation against debris flow caused by overflow from landslide dam formed by the 2011 Typhoon Talas which hit mainly the central region of Japan on September 2-4th, 2011. In addition to background of this application, since May 1st, 2011, Erosion and Sediment Control (SABO) Department of the Ministry of Land, Infrastructure, Transport and Tourism, Japan (MLIT) launched a new scheme using above-mentioned quick analysis method.

  1. Sediment budgets and channel scouring of two alpine debris-flow torrents (SE France)

    NASA Astrophysics Data System (ADS)

    Theule, J. I.; Liébault, F.; Loye, A.; Jaboyedoff, M.; Laigle, D.

    2011-12-01

    Steep mountain catchments typically experience sediment pulses from hillslopes which are stored in headwater channels and flushed out by debris-flows. Event-based sediment budget monitoring in two active debris-flow torrents in the French Alps (Manival and Réal) during a two-year period gave insights about catchment-scale sediment routing during rainfall forcings of moderate intensity. This study allowed for further investigation on channel scour relationships with gradient. The monitoring was based on intensive topographic resurveys of low- and high-order channels using different techniques (cross-section surveys with total station and high-resolution channel surveys with terrestrial and airborne laser scanning). For the Manival Torrent, sediment outputs from the main channel were obtained by a sediment trap. Two debris-flows were observed in the Manival and three in the Réal, as well as several bedload transport flow events. Sediment budget reconstitution of the five debris-flows revealed that most of the debris-flow volumes were supplied by channel scouring (always more than 92%). Bedload transport during autumn contributed to the sediment recharge of high-order channels by the deposition of large gravel wedges. This process is recognized as being fundamental for debris-flow occurrence during the subsequent spring and summer. A time shift of scour-and-fill sequences was observed between low- and high-order channels, revealing the discontinuous sediment transfer in the catchment during common flow events. A conceptual model of sediment routing for different event magnitude was proposed. Significant channel scouring by debris-flows took place in alluvial reaches. Throughout the torrent channel, the upstream channel gradient (from a local reach) is identified to play a role in debris-flow scour. Maximum scours normally occur between slopes ranging from 0.18 to 0.20 (depending on sediment availability at the time of occurrence). It is found that above this

  2. In situ measurements of post-fire debris flows in southern California: Comparisons of the timing and magnitude of 24 debris-flow events with rainfall and soil moisture conditions

    USGS Publications Warehouse

    Kean, J.W.; Staley, D.M.; Cannon, S.H.

    2011-01-01

    Debris flows often occur in burned steeplands of southern California, sometimes causing property damage and loss of life. In an effort to better understand the hydrologic controls on post-fire debris-flow initiation, timing and magnitude, we measured the flow stage, rainfall, channel bed pore fluid pressure and hillslope soil-moisture accompanying 24 debris flows recorded in five different watersheds burned in the 2009 Station and Jesusita Fires (San Gabriel and Santa Ynez Mountains). The measurements show substantial differences in debris-flow dynamics between sites and between sequential events at the same site. Despite these differences, the timing and magnitude of all events were consistently associated with local peaks in short duration (< = 30 min) rainfall intensity. Overall, debris-flow stage was best cross-correlated with time series of 5-min rainfall intensity, and lagged the rainfall by an average of just 5 min. An index of debris-flow volume was also best correlated with short-duration rainfall intensity, but found to be poorly correlated with storm cumulative rainfall and hillslope soil water content. Post-event observations of erosion and slope stability modeling suggest that the debris flows initiated primarily by processes related to surface water runoff, rather than shallow landslides. By identifying the storm characteristics most closely associated with post-fire debris flows, these measurements provide valuable guidance for warning operations and important constraints for developing and testing models of post-fire debris flows. copyright. 2011 by the American Geophysical Union.

  3. In situ measurements of post-fire debris flows in southern California: Comparisons of the timing and magnitude of 24 debris-flow events with rainfall and soil moisture conditions

    NASA Astrophysics Data System (ADS)

    Kean, Jason W.; Staley, Dennis M.; Cannon, Susan H.

    2011-12-01

    Debris flows often occur in burned steeplands of southern California, sometimes causing property damage and loss of life. In an effort to better understand the hydrologic controls on post-fire debris-flow initiation, timing and magnitude, we measured the flow stage, rainfall, channel bed pore fluid pressure and hillslope soil-moisture accompanying 24 debris flows recorded in five different watersheds burned in the 2009 Station and Jesusita Fires (San Gabriel and Santa Ynez Mountains). The measurements show substantial differences in debris-flow dynamics between sites and between sequential events at the same site. Despite these differences, the timing and magnitude of all events were consistently associated with local peaks in short duration (< = 30 min) rainfall intensity. Overall, debris-flow stage was best cross-correlated with time series of 5-min rainfall intensity, and lagged the rainfall by an average of just 5 min. An index of debris-flow volume was also best correlated with short-duration rainfall intensity, but found to be poorly correlated with storm cumulative rainfall and hillslope soil water content. Post-event observations of erosion and slope stability modeling suggest that the debris flows initiated primarily by processes related to surface water runoff, rather than shallow landslides. By identifying the storm characteristics most closely associated with post-fire debris flows, these measurements provide valuable guidance for warning operations and important constraints for developing and testing models of post-fire debris flows.

  4. Emergency Assessment of Postfire Debris-Flow Hazards for the 2009 Station Fire, San Gabriel Mountains, Southern California

    USGS Publications Warehouse

    Cannon, Susan H.; Gartner, Joseph E.; Rupert, Michael G.; Michael, John A.; Staley, Dennis M.; Worstell, Bruce B.

    2009-01-01

    This report presents an emergency assessment of potential debris-flow hazards from basins burned by the 2009 Station fire in Los Angeles County, southern California. Statistical-empirical models developed for postfire debris flows are used to estimate the probability and volume of debris-flow production from 678 drainage basins within the burned area and to generate maps of areas that may be inundated along the San Gabriel mountain front by the estimated volume of material. Debris-flow probabilities and volumes are estimated as combined functions of different measures of basin burned extent, gradient, and material properties in response to both a 3-hour-duration, 1-year-recurrence thunderstorm and to a 12-hour-duration, 2-year recurrence storm. Debris-flow inundation areas are mapped for scenarios where all sediment-retention basins are empty and where the basins are all completely full. This assessment provides critical information for issuing warnings, locating and designing mitigation measures, and planning evacuation timing and routes within the first two winters following the fire. Tributary basins that drain into Pacoima Canyon, Big Tujunga Canyon, Arroyo Seco, West Fork of the San Gabriel River, and Devils Canyon were identified as having probabilities of debris-flow occurrence greater than 80 percent, the potential to produce debris flows with volumes greater than 100,000 m3, and the highest Combined Relative Debris-Flow Hazard Ranking in response to both storms. The predicted high probability and large magnitude of the response to such short-recurrence storms indicates the potential for significant debris-flow impacts to any buildings, roads, bridges, culverts, and reservoirs located both within these drainages and downstream from the burned area. These areas will require appropriate debris-flow mitigation and warning efforts. Probabilities of debris-flow occurrence greater than 80 percent, debris-flow volumes between 10,000 and 100,000 m3, and high

  5. Onset of submarine debris flow deposition far from original giant landslide.

    PubMed

    Talling, P J; Wynn, R B; Masson, D G; Frenz, M; Cronin, B T; Schiebel, R; Akhmetzhanov, A M; Dallmeier-Tiessen, S; Benetti, S; Weaver, P P E; Georgiopoulou, A; Zühlsdorff, C; Amy, L A

    2007-11-22

    Submarine landslides can generate sediment-laden flows whose scale is impressive. Individual flow deposits have been mapped that extend for 1,500 km offshore from northwest Africa. These are the longest run-out sediment density flow deposits yet documented on Earth. This contribution analyses one of these deposits, which contains ten times the mass of sediment transported annually by all of the world's rivers. Understanding how this type of submarine flow evolves is a significant problem, because they are extremely difficult to monitor directly. Previous work has shown how progressive disintegration of landslide blocks can generate debris flow, the deposit of which extends downslope from the original landslide. We provide evidence that submarine flows can produce giant debris flow deposits that start several hundred kilometres from the original landslide, encased within deposits of a more dilute flow type called turbidity current. Very little sediment was deposited across the intervening large expanse of sea floor, where the flow was locally very erosive. Sediment deposition was finally triggered by a remarkably small but abrupt decrease in sea-floor gradient from 0.05 degrees to 0.01 degrees. This debris flow was probably generated by flow transformation from the decelerating turbidity current. The alternative is that non-channelized debris flow left almost no trace of its passage across one hundred kilometres of flat (0.2 degrees to 0.05 degrees) sea floor. Our work shows that initially well-mixed and highly erosive submarine flows can produce extensive debris flow deposits beyond subtle slope breaks located far out in the deep ocean. PMID:18033295

  6. Onset of submarine debris flow deposition far from original giant landslide.

    PubMed

    Talling, P J; Wynn, R B; Masson, D G; Frenz, M; Cronin, B T; Schiebel, R; Akhmetzhanov, A M; Dallmeier-Tiessen, S; Benetti, S; Weaver, P P E; Georgiopoulou, A; Zühlsdorff, C; Amy, L A

    2007-11-22

    Submarine landslides can generate sediment-laden flows whose scale is impressive. Individual flow deposits have been mapped that extend for 1,500 km offshore from northwest Africa. These are the longest run-out sediment density flow deposits yet documented on Earth. This contribution analyses one of these deposits, which contains ten times the mass of sediment transported annually by all of the world's rivers. Understanding how this type of submarine flow evolves is a significant problem, because they are extremely difficult to monitor directly. Previous work has shown how progressive disintegration of landslide blocks can generate debris flow, the deposit of which extends downslope from the original landslide. We provide evidence that submarine flows can produce giant debris flow deposits that start several hundred kilometres from the original landslide, encased within deposits of a more dilute flow type called turbidity current. Very little sediment was deposited across the intervening large expanse of sea floor, where the flow was locally very erosive. Sediment deposition was finally triggered by a remarkably small but abrupt decrease in sea-floor gradient from 0.05 degrees to 0.01 degrees. This debris flow was probably generated by flow transformation from the decelerating turbidity current. The alternative is that non-channelized debris flow left almost no trace of its passage across one hundred kilometres of flat (0.2 degrees to 0.05 degrees) sea floor. Our work shows that initially well-mixed and highly erosive submarine flows can produce extensive debris flow deposits beyond subtle slope breaks located far out in the deep ocean.

  7. Water fact sheet, history of landslides and debris flows at Mount Rainier

    USGS Publications Warehouse

    Scott, K.M.; Vallance, J.W.

    1993-01-01

    Many landslides and debris flows have originated from Mount Rainier since the retreat of glaciers from Puget Sound about 10,000 years ago. The recurrent instability is due to several factors--height of the steep-sided volcanic cone, frequent volcanic activity, continuous weakening of rock by steam and hot, chemical-laden water, and exposure of unstable areas as the mountains glaciers have receded. The landslide scars and deposits tell a fascinating story of the changing shape of the volcano. Landslides occur when part of the volcano "collapses" or fails and slides away from the rest of the volcano. The failed mass rapidly breaks up into a jumble of disaggregated pieces that flow at high velocity like a fluid. Clay and water in the debris cause further change to a liquid slurry known as a debris flow or mudflow. Volcanic debris flows are also widely known by the Indonesian term "lahar." Although the largest debris flows at Rainier form from landslides, many smaller flows are caused by volcanic eruptions, intense rainfall, and glacial-outburst floods.

  8. Micromorphology of a debris flow deposit: evidence of basal shearing, hydrofracturing, liquefaction and rotational deformation during emplacement

    NASA Astrophysics Data System (ADS)

    Phillips, Emrys

    2006-04-01

    Micromorphological analysis has been applied to a very coarse debris flow deposit and associated sand-dominated glaciofluvial sediments exposed in Westend Wood Quarry, Carstairs, Central Scotland. The microstructures present (folds, faults, plasmic fabrics) within this diamicton and underlying predominantly sandy sediments are interpreted in terms of sedimentary processes active during emplacement of the debris flow. These processes include the formation of a basal shear zone, the deformation and mixing of fine-grained sediments incorporated into the base of overriding debris flow. Features associated with liquefaction, sediment remobilisation and water escape are also present and developed in response to increasing overburden pressure during debris flow emplacement. These microstructures have also been recorded elsewhere within subglacial diamictons, and an evaluation is made between microstructures in palaeo-debris flow deposits and those found in modern debris flows.

  9. Abstracts of the symposium on unsaturated flow and transport modeling

    SciTech Connect

    Not Available

    1982-03-01

    Abstract titles are: Recent developments in modeling variably saturated flow and transport; Unsaturated flow modeling as applied to field problems; Coupled heat and moisture transport in unsaturated soils; Influence of climatic parameters on movement of radionuclides in a multilayered saturated-unsaturated media; Modeling water and solute transport in soil containing roots; Simulation of consolidation in partially saturated soil materials; modeling of water and solute transport in unsaturated heterogeneous fields; Fluid dynamics and mass transfer in variably-saturated porous media; Solute transport through soils; One-dimensional analytical transport modeling; Convective transport of ideal tracers in unsaturated soils; Chemical transport in macropore-mesopore media under partially saturated conditions; Influence of the tension-saturated zone on contaminant migration in shallow water regimes; Influence of the spatial distribution of velocities in porous media on the form of solute transport; Stochastic vs deterministic models for solute movement in the field; and Stochastic analysis of flow and solute transport. (DMC)

  10. Positive feedback and momentum growth during debris-flow entrainment of wet bed sediment

    USGS Publications Warehouse

    Iverson, R.M.; Reid, M.E.; Logan, M.; LaHusen, R.G.; Godt, J.W.; Griswold, J.P.

    2011-01-01

    Debris flows typically occur when intense rainfall or snowmelt triggers landslides or extensive erosion on steep, debris-mantled slopes. The flows can then grow dramatically in size and speed as they entrain material from their beds and banks, but the mechanism of this growth is unclear. Indeed, momentum conservation implies that entrainment of static material should retard the motion of the flows if friction remains unchanged. Here we use data from large-scale experiments to assess the entrainment of bed material by debris flows. We find that entrainment is accompanied by increased flow momentum and speed only if large positive pore pressures develop in wet bed sediments as the sediments are overridden by debris flows. The increased pore pressure facilitates progressive scour of the bed, reduces basal friction and instigates positive feedback that causes flow speed, mass and momentum to increase. If dryer bed sediment is entrained, however, the feedback becomes negative and flow momentum declines. We infer that analogous feedbacks could operate in other types of gravity-driven mass flow that interact with erodible beds. ?? 2011 Macmillan Publishers Limited. All rights reserved.

  11. Removing the impact of water abstractions on flow duration curves

    NASA Astrophysics Data System (ADS)

    Masoero, Alessandro; Ganora, Daniele; Galeati, Giorgio; Laio, Francesco; Claps, Pierluigi

    2015-04-01

    Changes and interactions between human system and water cycle are getting increased attention in the scientific community. Commonly discharge data needed for water resources studies were collected close to urban or industrial settlements, thus in environments where the interest for surveying was not merely scientific, but also for socio-economical purposes. Working in non-natural environments we must take into account human impacts, like the one due to water intakes for irrigation or hydropower generation, while assessing the actual water availability and variability in a river. This can became an issue in alpine areas, where hydropower exploitation is heavy and it is common to have water abstraction before a gauge station. To have a gauge station downstream a water intake can be useful to survey the environmental flow release and to record the maximum flood values, which should not be affected by the water abstraction. Nevertheless with this configuration we are unable to define properly the water volumes available in the river, information crucial to assess low flows and investigate drought risk. This situation leads to a substantial difference between observed data (affected by the human impact) and natural data (as would have been without abstraction). A main issue is how to correct these impacts and restore the natural streamflow values. The most obvious and reliable solution would be to ask for abstraction data to water users, but these data are hard to collect. Usually they are not available, because not public or not even collected by the water exploiters. A solution could be to develop a rainfall-run-off model of the basin upstream the gauge station, but this approach needs a great number of data and parameters Working in a regional framework and not on single case studies, our goal is to provide a consistent estimate of the non-impacted statistics of the river (i.e. mean value, L-moments of variation and skewness). We proposed a parsimonious method, based

  12. A new hierarchical Bayesian approach to analyse environmental and climatic influences on debris flow occurrence

    NASA Astrophysics Data System (ADS)

    Jomelli, Vincent; Pavlova, Irina; Eckert, Nicolas; Grancher, Delphine; Brunstein, Daniel

    2015-12-01

    How can debris flow occurrences be modelled at regional scale and take both environmental and climatic conditions into account? And, of the two, which has the most influence on debris flow activity? In this paper, we try to answer these questions with an innovative Bayesian hierarchical probabilistic model that simultaneously accounts for how debris flows respond to environmental and climatic variables. In it, full decomposition of space and time effects in occurrence probabilities is assumed, revealing an environmental and a climatic trend shared by all years/catchments, respectively, clearly distinguished from residual "random" effects. The resulting regional and annual occurrence probabilities evaluated as functions of the covariates make it possible to weight the respective contribution of the different terms and, more generally, to check the model performances at different spatio-temporal scales. After suitable validation, the model can be used to make predictions at undocumented sites and could be used in further studies for predictions under future climate conditions. Also, the Bayesian paradigm easily copes with missing data, thus making it possible to account for events that may have been missed during surveys. As a case study, we extract 124 debris flow event triggered between 1970 and 2005 in 27 catchments located in the French Alps from the French national natural hazard survey and model their variability of occurrence considering environmental and climatic predictors at the same time. We document the environmental characteristics of each debris flow catchment (morphometry, lithology, land cover, and the presence of permafrost). We also compute 15 climate variables including mean temperature and precipitation between May and October and the number of rainy days with daily cumulative rainfall greater than 10/15/20/25/30/40 mm day- 1. Application of our model shows that the combination of environmental and climatic predictors explained 77% of the overall

  13. Evaluating the use of high-resolution numerical weather forecast for debris flow prediction.

    NASA Astrophysics Data System (ADS)

    Nikolopoulos, Efthymios I.; Bartsotas, Nikolaos S.; Borga, Marco; Kallos, George

    2015-04-01

    The sudden occurrence combined with the high destructive power of debris flows pose a significant threat to human life and infrastructures. Therefore, developing early warning procedures for the mitigation of debris flows risk is of great economical and societal importance. Given that rainfall is the predominant factor controlling debris flow triggering, it is indisputable that development of effective debris flows warning procedures requires accurate knowledge of the properties (e.g. duration, intensity) of the triggering rainfall. Moreover, efficient and timely response of emergency operations depends highly on the lead-time provided by the warning systems. Currently, the majority of early warning systems for debris flows are based on nowcasting procedures. While the latter may be successful in predicting the hazard, they provide warnings with a relatively short lead-time (~6h). Increasing the lead-time is necessary in order to improve the pre-incident operations and communication of the emergency, thus coupling warning systems with weather forecasting is essential for advancing early warning procedures. In this work we evaluate the potential of using high-resolution (1km) rainfall fields forecasted with a state-of-the-art numerical weather prediction model (RAMS/ICLAMS), in order to predict the occurrence of debris flows. Analysis is focused over the Upper Adige region, Northeast Italy, an area where debris flows are frequent. Seven storm events that generated a large number (>80) of debris flows during the period 2007-2012 are analyzed. Radar-based rainfall estimates, available from the operational C-band radar located at Mt Macaion, are used as the reference to evaluate the forecasted rainfall fields. Evaluation is mainly focused on assessing the error in forecasted rainfall properties (magnitude, duration) and the correlation in space and time with the reference field. Results show that the forecasted rainfall fields captured very well the magnitude and

  14. Evaluation of a debris-flow entrainment model on field cases from the Swiss Alps

    NASA Astrophysics Data System (ADS)

    Frank, Florian; McArdell, Brian; Huggel, Christian; Vieli, Andreas

    2015-04-01

    Debris-flow erosion is an important process for shaping the landscape and highly relevant in terms of hazard due to the potential of substantially increasing the flow magnitude. Here we describe the development and testing of a model for the erosion of sediment deposits by entrainment. The model is based on a generalization of field data from the Illgraben torrent channel in Switzerland, where the slope of the channel on the fan varies between 8% and 10%. The entrainment model predicts the maximum depth of erosion as a function of basal shear stress (Schürch et al., 2011), and limits the rate of erosion to be less than the maximum erosion rate observed at the Illgraben by Berger et al. (2010, 2011). The entrainment model is a module implemented in the RAMMS debris-flow runout model which solves the 2D shallow water equations of motion for granular flows and includes the Voellmy friction relation (Christen et al., 2012). The intention of the model is to provide a tool to researchers and practitioners to estimate and investigate the influence of debris-flow erosion on the runout of debris flows, at least until new physically-based models are available. After calibration of the friction coefficients without considering entrainment, the model was systematically tested at two field sites where both the sequence of debris flows is known and where differential terrain elevation models have been used to identify the spatial pattern of erosion. Tests at the field site Spreitgraben (Canton Berne), where the channel slope on the fan is approximately 30%, indicate that the new model is better at predicting the flow pattern in comparison with model results without entrainment. Additionally, when sediment erosion is included in model, the shape of the debris-flow wave (flow depth as a function of time) has a generally steep debris-flow front, which is typical of field observations of debris flows. The model as also evaluated at the field site Meretschibach catchment (Canton

  15. Field Reconnaissance of Debris Flows Triggered by a July 21, 2007, Thunderstorm in Alpine, Colorado, and Vicinity

    USGS Publications Warehouse

    Coe, Jeffrey A.; Godt, Jonathan W.; Wait, T.C.; Kean, Jason W.

    2007-01-01

    On the evening of July 21, 2007, a slow-moving thunderstorm triggered about 45 debris flows on steep mountainsides near the community of Alpine, Colorado. Most of the debris flows were initiated by surface-water runoff that eroded and entrained loose sediment in previously existing channels. About 12 of the debris-flow channels were located in the lower half of Weldon Gulch upslope from Alpine, which is on a debris fan at the mouth of the Gulch. Most of these channels were deeply incised by the flows, and many of the resulting oversteepened channel banks are now failing and beginning to refill the channels with sediment. Debris flows that emerged from the mouth of Weldon Gulch primarily flowed onto the eastern half of the debris fan and closed roads and damaged vehicles and structures. Debris-flow deposits on the fan generally become finer grained and thinner with distance from the head of the fan. Given the existing conditions in Weldon Gulch, it is estimated that the debris-flow hazard on the fan has neither decreased nor increased as a result of the July 21 debris flows. Preventive measures that need to be considered by Alpine residents and government officials concerned with safety on the fan include: (1) establishing a channel and(or) catchment/diversion structure on the fan that routes future water and debris flows in a manner that protects existing roads and structures, and (2) maintaining vigilance during rainstorms by watching and listening for unusual flows of water or debris that may indicate debris-flow activity upstream, particularly during the summer months when thunderstorms are common in the area.

  16. SCDAP/RELAP5 modeling of heat transfer and flow losses in lower head porous debris. Revision 1

    SciTech Connect

    Siefken, L.J.; Coryell, E.W.; Paik, S.; Kuo, H.

    1999-05-01

    Designs are described for implementing models for calculating the heat transfer and flow losses in porous debris in the lower head of a reactor vessel. The COUPLE model in SCDAP/RELAP5 represents both the porous and nonporous debris that results from core material slumping into the lower head. Currently, the COUPLE model has the capability to model convective and radiative heat transfer from the surfaces of nonporous debris in a detailed manner and to model only in a simplistic manner the heat transfer from porous debris. In order to advance beyond the simplistic modeling for porous debris, designs are developed for detailed calculations of heat transfer and flow losses in porous debris. Correlations are identified for convective heat transfer in porous debris for the following modes of heat transfer; (1) forced convection to liquid, (2) forced convection to gas, (3) nucleate boiling, (4) transition boiling, and (5) film boiling. Interphase heat transfer is modeled in an approximate ma nner. Designs are described for models to calculate the flow losses and interphase drag of fluid flowing through the interstices of the porous debris, and to apply these variables in the momentum equations in the RELAP5 part of the code. Since the models for heat transfer and flow losses in porous debris in the lower head are designed for general application, a design is also described for implementation of these models to the analysis of porous debris in the core region. A test matrix is proposed for assessing the capability of the implemented models to calculate the heat transfer and flow losses in porous debris. The implementation of the models described in this report is expected to improve the COUPLE code calculation of the temperature distribution in porous debris and in the lower head that supports the debris. The implementation of these models is also expected to improve the calculation of the temperature and flow distribution in porous debris in the core region.

  17. Debris-flow hazards on tributary junction fans, Chitral, Hindu Kush Range, northern Pakistan

    NASA Astrophysics Data System (ADS)

    Khan, M. Asif; Haneef, M.; Khan, Anwar S.; Tahirkheli, Tazeem

    2013-01-01

    The Chitral district of northern Pakistan lies in the eastern Hindu Kush Range. The population in this high-relief mountainous terrain is restricted to tributary-junction fans in the Chitral valley. Proximity to steep valley slopes renders these fans prone to hydrogeomorphic hazards, including landslides, floods and debris flows. This paper focuses on debris-flow hazards on tributary-junction fans in Chitral. Using field observations, satellite-image analyses and a preliminary morphometry, the tributary-junction fans in the Chitral valley are classified into (1) discrete and (2) composite. The discrete fans are modern-day active landforms and include debris cones associated with ephemeral gullies, debris fans associated with ephemeral channels and alluvial fans formed by perennial streams. The composite fans are a collage of sediment deposits of widely different ages and formed by diverse alluvial-fan forming processes. These include fans formed predominantly during MIS-2/Holocene interglacial stages superimposed by modern-day alluvial and debris fans. Composite fans are turned into relict fans when entrenched by modern-day perennial streams. These deeply incised channels discharge their sediment load directly into the trunk river without significant spread on fan surface. In comparison, when associated with ephemeral streams, active debris fans develop directly at composite-fan surfaces. Major settlements in Chitral are located on composite fans, as they provide large tracts of leveled land with easy accesses to water from the tributary streams. These fan surfaces are relatively more stable, especially when they are entrenched by perennial streams (e.g., Chitral, Ayun, and Reshun). When associated with ephemeral streams (e.g., Snowghar) or a combination of ephemeral and perennial streams (e.g., Drosh), these fans are subject to frequent debris-flow hazards. Fans associated with ephemeral streams are prone to high-frequency (˜10 years return period) debris-flow

  18. Debris-flow Dynamics Inferred From Aggregated Results of 28 Large-scale Experiments

    NASA Astrophysics Data System (ADS)

    Iverson, R. M.; Logan, M.; Lahusen, R. G.; Berti, M.

    2008-12-01

    Key features of debris-flow dynamics are revealed by identifying reproducible trends in data collected during 28 large-scale experiments with closely controlled initial and boundary conditions. In each experiment, 10 m3 of water-saturated sediment consisting mostly of sand and gravel discharges abruptly from behind a vertical headgate, descends a ~90 m concrete flume inclined 31 degrees, and forms a deposit on a nearly horizontal runout surface. The experiments are grouped into three sets of 8 to 11 replicates distinguished by differing mud contents (1% vs. 7% by dry weight) and basal boundary roughnesses (1 mm vs. 20 mm characteristic amplitude). Aggregation of sensor data from each set of replicates reveals universal patterns, as well as variances, in evolution of flow velocities, depths, basal normal stresses, and basal pore pressures. The patterns show that debris flows consistently develop blunt, coarse-grained, high-friction flow fronts pushed from behind by nearly liquefied, finer-grained debris. This flow architecture yields lobate deposits bounded by coarse-grained snouts and lateral levees. The aggregated data also show that imposed differences in basal boundary conditions and debris compositions produce systematic -- and sometimes surprising -- differences in flow dynamics and deposits. For example, flows on rough beds run out further than flows on smooth beds, despite the fact that flows on smooth beds attain greater velocities. This counterintuitive behavior results from enhanced grain-size segregation in the presence of a rough bed; segregation accentuates development of lateral levees that channelize flow and retard depletion of downstream momentum by lateral spreading. Another consistent finding is that flows with significant mud content are more mobile (attain greater velocities and runouts) than flows lacking much mud. This behavior is evident despite the fact that mud measurably increases the viscosity and yield strength of the fluid component

  19. Map showing alpine debris flows triggered by a July 28, 1999 thunderstorm in the central Front Range of Colorado

    USGS Publications Warehouse

    Godt, Jonathan W.; Coe, Jeffrey A.

    2003-01-01

    This 1:24,000-scale map shows an inventory of debris flows that were triggered above timberline by a thunderstorm in the central Front Range of Colorado. We have classified the debris flows into two categories based on the style of initiation processes in the debris-flow source areas: 1) soil slip, and 2) non-soil slip erosive processes. This map and associated digital data are part of a larger study of the debris-flow event, results of which we plan to present in a forthcoming paper.

  20. Estimation of the annual flow and stock of marine debris in South Korea for management purposes.

    PubMed

    Jang, Yong Chang; Lee, Jongmyoung; Hong, Sunwook; Mok, Jin Yong; Kim, Kyoung Shin; Lee, Yun Jeong; Choi, Hyun-Woo; Kang, Hongmook; Lee, Sukhui

    2014-09-15

    The annual flow and stock of marine debris in the Sea of Korea was estimated by summarizing previous survey results and integrating them with other relevant information to underpin the national marine debris management plan. The annual inflow of marine debris was estimated to be 91,195 tons [32,825 tons (36% of the total) from sources on land and 58,370 tons (64%) from ocean sources]. As of the end of 2012, the total stock of marine debris on all South Korean coasts (12,029 tons), the seabed (137,761 tons), and in the water column (2451 tons) was estimated to be 152,241 tons. In 2012, 42,595 tons of marine debris was collected from coasts, seabeds, and the water column. This is a very rare case study that estimated the amount of marine debris at a national level, the results of which provide essential information for the development of efficient marine debris management policies.

  1. Estimation of the annual flow and stock of marine debris in South Korea for management purposes.

    PubMed

    Jang, Yong Chang; Lee, Jongmyoung; Hong, Sunwook; Mok, Jin Yong; Kim, Kyoung Shin; Lee, Yun Jeong; Choi, Hyun-Woo; Kang, Hongmook; Lee, Sukhui

    2014-09-15

    The annual flow and stock of marine debris in the Sea of Korea was estimated by summarizing previous survey results and integrating them with other relevant information to underpin the national marine debris management plan. The annual inflow of marine debris was estimated to be 91,195 tons [32,825 tons (36% of the total) from sources on land and 58,370 tons (64%) from ocean sources]. As of the end of 2012, the total stock of marine debris on all South Korean coasts (12,029 tons), the seabed (137,761 tons), and in the water column (2451 tons) was estimated to be 152,241 tons. In 2012, 42,595 tons of marine debris was collected from coasts, seabeds, and the water column. This is a very rare case study that estimated the amount of marine debris at a national level, the results of which provide essential information for the development of efficient marine debris management policies. PMID:25038983

  2. The application of numerical debris flow modelling for the generation of physical vulnerability curves

    NASA Astrophysics Data System (ADS)

    Luna, B. Quan; Blahut, J.; van Westen, C. J.; Sterlacchini, S.; van Asch, T. W. J.; Akbas, S. O.

    2011-07-01

    For a quantitative assessment of debris flow risk, it is essential to consider not only the hazardous process itself but also to perform an analysis of its consequences. This should include the estimation of the expected monetary losses as the product of the hazard with a given magnitude and the vulnerability of the elements exposed. A quantifiable integrated approach of both hazard and vulnerability is becoming a required practice in risk reduction management. This study aims at developing physical vulnerability curves for debris flows through the use of a dynamic run-out model. Dynamic run-out models for debris flows are able to calculate physical outputs (extension, depths, velocities, impact pressures) and to determine the zones where the elements at risk could suffer an impact. These results can then be applied to consequence analyses and risk calculations. On 13 July 2008, after more than two days of intense rainfall, several debris and mud flows were released in the central part of the Valtellina Valley (Lombardy Region, Northern Italy). One of the largest debris flows events occurred in a village called Selvetta. The debris flow event was reconstructed after extensive field work and interviews with local inhabitants and civil protection teams. The Selvetta event was modelled with the FLO-2D program, an Eulerian formulation with a finite differences numerical scheme that requires the specification of an input hydrograph. The internal stresses are isotropic and the basal shear stresses are calculated using a quadratic model. The behaviour and run-out of the flow was reconstructed. The significance of calculated values of the flow depth, velocity, and pressure were investigated in terms of the resulting damage to the affected buildings. The physical damage was quantified for each affected structure within the context of physical vulnerability, which was calculated as the ratio between the monetary loss and the reconstruction value. Three different empirical

  3. Particle size reduction in debris flows: Laboratory experiments compared with field data from Inyo Creek, California

    NASA Astrophysics Data System (ADS)

    Arabnia, O.; Sklar, L. S.; Mclaughlin, M. K.

    2014-12-01

    Rock particles in debris flows are reduced in size through abrasion and fracture. Wear of coarse sediments results in production of finer particles, which alter the bulk material rheology and influence flow dynamics and runout distance. Particle wear also affects the size distribution of coarse particles, transforming the initial sediment size distribution produced on hillslopes into that delivered to the fluvial channel network. A better understanding of the controls on particle wear in debris flows would aid in the inferring flow conditions from debris flow deposits, in estimating the initial size of sediments entrained in the flow, and in modeling debris flow dynamics and mapping hazards. The rate of particle size reduction with distance traveled should depend on the intensity of particle interactions with other particles and the flow boundary, and on rock resistance to wear. We seek a geomorphic transport law to predict rate of particle wear with debris flow travel distance as a function of particle size distribution, flow depth, channel slope, fluid composition and rock strength. Here we use four rotating drums to create laboratory debris flows across a range of scales. Drum diameters range from 0.2 to 4.0 m, with the largest drum able to accommodate up to 2 Mg of material, including boulders. Each drum has vanes along the boundary to prevent sliding. Initial experiments use angular clasts of durable granodiorite; later experiments will use less resistant rock types. Shear rate is varied by changing drum rotational velocity. We begin experiments with well-sorted coarse particle size distributions, which are allowed to evolve through particle wear. The fluid is initially clear water, which rapidly acquires fine-grained wear products. After each travel increment all coarse particles (mass > 0.4 g) are weighed individually. We quantify particle wear rates using statistics of size and mass distributions, and by fitting various comminution functions to the data

  4. Friction in debris flows: inferences from large-scale flume experiments

    USGS Publications Warehouse

    Iverson, Richard M.; LaHusen, Richard G.; ,

    1993-01-01

    A recently constructed flume, 95 m long and 2 m wide, permits systematic experimentation with unsteady, nonuniform flows of poorly sorted geological debris. Preliminary experiments with water-saturated mixtures of sand and gravel show that they flow in a manner consistent with Coulomb frictional behavior. The Coulomb flow model of Savage and Hutter (1989, 1991), modified to include quasi-static pore-pressure effects, predicts flow-front velocities and flow depths reasonably well. Moreover, simple scaling analyses show that grain friction, rather than liquid viscosity or grain collisions, probably dominates shear resistance and momentum transport in the experimental flows. The same scaling indicates that grain friction is also important in many natural debris flows.

  5. Empirical assessment of debris flow risk on a regional scale in Yunnan province, southwestern China.

    PubMed

    Liu, Xilin; Yue, Zhong Qi; Tham, Lesliw George; Lee, Chack Fan

    2002-08-01

    Adopting the definition suggested by the United Nations, a risk model for regional debris flow assessment is presented. Risk is defined as the product of hazard and vulnerability, both of which are necessary for evaluation. A Multiple-Factor Composite Assessment Model is developed for quantifying regional debris flow hazard by taking into account eight variables that contribute to debris flow magnitude and its frequency of occurrence. Vulnerability is a measure of the potential total losses. On a regional scale, it can be measured by the fixed asset, gross domestic product, land resources, population density, as well as the age, education, and wealth of the inhabitants. A nonlinear power-function assessment model that accounts for these indexes is developed. As a case study, the model is applied to compute the hazard, vulnerability and risk for each prefecture of the Yunnan province in southwestern China. PMID:12105765

  6. Debris-flow deposits and watershed erosion rates near southern Death Valley, CA, United States

    USGS Publications Warehouse

    Schmidt, K.M.; Menges, C.M.; ,

    2003-01-01

    Debris flows from the steep, granitic hillslopes of the Kingston Range, CA are commensurate in age with nearby fluvial deposits. Quaternary chronostratigraphic differentiation of debris-flow deposits is based upon time-dependent characteristics such as relative boulder strength, derived from Schmidt Hammer measurements, degree of surface desert varnish, pedogenesis, and vertical separation. Rock strength is highest for Holocene-aged boulders and decreases for Pleistocene-aged boulders weathering to grus. Volumes of age-stratified debris-flow deposits, constrained by deposit thickness above bedrock, GPS surveys, and geologic mapping, are greatest for Pleistocene deposits. Shallow landslide susceptibility, derived from a topographically based GIS model, in conjunction with deposit volumes produces watershed-scale erosion rates of ???2-47 mm ka-1, with time-averaged Holocene rates exceeding Pleistocene rates. ?? 2003 Millpress.

  7. Experimental Investigation of Entrainment Rate by Debris Flows: from Shear Stress to Granular Temperature

    NASA Astrophysics Data System (ADS)

    Hill, K. M.; Longjas, A.; Moberly, D.

    2015-12-01

    Debris flows - flows of boulders, gravel, sand, fine particles, and fluids - erode sediment from steep hillsides and deposit them at lower slopes. Current model frameworks for erosion by debris flow vary significantly and include those that consider macroscopic fields such as excess shear stresses, similar to traditional models of bedload transport, to those that consider the "granular" physics, from force chains (related to bed fabric) to granular temperatures (related to random kinetic energy of the flow). We perform experiments to investigate the underlying mechanics associated with entrainment of bed materials by overlying flows in an instrumented laboratory debris flow flume. In particular, we investigate how the erosion rate of a flowing mass impinging on an erodible bed of particles depends on boundary conditions, dynamics of the flow, and the state of the bed. Using high speed imaging to capture average and instantaneous particle dynamics simultaneously with bed stress measurements, we investigate the effectiveness of a variety of model frameworks for capturing the relationships between flow dynamics and erosion rates. We find no correlation between the bed shear stress associated with the mass of the flow and erosion rate. Similarly, we found no correlation between the erosion rate and a Reynolds stress, that is, the stress associated with correlations between downstream and vertical velocity fluctuations. On the other hand, we found that granular temperature is well-correlated with entrainment rate during particular phases of our experimental debris flow. In particular, we found the instantaneous entrainment rate ɛ is linearly dependent on the ratio of the granular temperature Tg to the kinetic energy associated with the average flow velocity u: ɛ ~ (Tg / ρm u2) where ρm is the local instantaneous density of the flow. We present these results and discuss how they vary with the state of the flow, boundary conditions, and particle mixtures.

  8. Propagation of a channelized debris-flow: experimental investigation and parameters identification for numerical modelling

    NASA Astrophysics Data System (ADS)

    Termini, Donatella

    2013-04-01

    Recent catastrophic events due to intense rainfalls have mobilized large amount of sediments causing extensive damages in vast areas. These events have highlighted how debris-flows runout estimations are of crucial importance to delineate the potentially hazardous areas and to make reliable assessment of the level of risk of the territory. Especially in recent years, several researches have been conducted in order to define predicitive models. But, existing runout estimation methods need input parameters that can be difficult to estimate. Recent experimental researches have also allowed the assessment of the physics of the debris flows. But, the major part of the experimental studies analyze the basic kinematic conditions which determine the phenomenon evolution. Experimental program has been recently conducted at the Hydraulic laboratory of the Department of Civil, Environmental, Aerospatial and of Materials (DICAM) - University of Palermo (Italy). The experiments, carried out in a laboratory flume appositely constructed, were planned in order to evaluate the influence of different geometrical parameters (such as the slope and the geometrical characteristics of the confluences to the main channel) on the propagation phenomenon of the debris flow and its deposition. Thus, the aim of the present work is to give a contribution to defining input parameters in runout estimation by numerical modeling. The propagation phenomenon is analyzed for different concentrations of solid materials. Particular attention is devoted to the identification of the stopping distance of the debris flow and of the involved parameters (volume, angle of depositions, type of material) in the empirical predictive equations available in literature (Rickenmanm, 1999; Bethurst et al. 1997). Bethurst J.C., Burton A., Ward T.J. 1997. Debris flow run-out and landslide sediment delivery model tests. Journal of hydraulic Engineering, ASCE, 123(5), 419-429 Rickenmann D. 1999. Empirical relationships

  9. Debris Flows and Record Floods from Extreme Mesoscale Convective Thunderstorms over the Santa Catalina Mountains, Arizona

    USGS Publications Warehouse

    Magirl, Christopher S.; Shoemaker, Craig; Webb, Robert H.; Schaffner, Mike; Griffiths, Peter G.; Pytlak, Erik

    2007-01-01

    Ample geologic evidence indicates early Holocene and Pleistocene debris flows from the south side of the Santa Catalina Mountains north of Tucson, Arizona, but few records document historical events. On July 31, 2006, an unusual set of atmospheric conditions aligned to produce record floods and an unprecedented number of debris flows in the Santa Catalinas. During the week prior to the event, an upper-level area of low pressure centered near Albuquerque, New Mexico generated widespread heavy rainfall in southern Arizona. After midnight on July 31, a strong complex of thunderstorms developed over central Arizona in a deformation zone that formed on the back side of the upper-level low. High atmospheric moisture (2.00' of precipitable water) coupled with cooling aloft spawned a mesoscale thunderstorm complex that moved southeast into the Tucson basin. A 15-20 knot low-level southwesterly wind developed with a significant upslope component over the south face of the Santa Catalina Mountains advecting moist and unstable air into the merging storms. National Weather Service radar indicated that a swath of 3-6' of rainfall occurred over the lower and middle elevations of the southern Santa Catalina Mountains. This intense rain falling on saturated soil triggered over 250 hillslope failures and debris flows throughout the mountain range. Sabino Canyon, a heavily used recreation area administered by the U.S. Forest Service, was the epicenter of mass wasting, where at least 18 debris flows removed structures, destroyed the roadway in multiple locations, and closed public access for months. The debris flows were followed by streamflow floods which eclipsed the record discharge in the 75-year gaging record of Sabino Creek. In five canyons adjacent to Sabino Canyon, debris flows approached or excited the mountain front, compromising floow conveyance structures and flooding some homes.

  10. Conditions for generation of fire-related debris flows, Capulin Canyon, New Mexico

    USGS Publications Warehouse

    Cannon, S.H.; Reneau, S.L.

    2000-01-01

    Comparison of the responses of three drainage basins burned by the Dome fire of 1996 in New Mexico is used to identify the hillslope, channel and fire characteristics that indicate a susceptibility specifically to wildfire-related debris flow. Summer thunderstorms generated three distinct erosive responses from each of three basins. The Capulin Canyon basin showed widespread erosive sheetwash and rilling from hillslopes, and severe flooding occurred in the channel; the North Tributary basin exhibited extensive erosion of the mineral soil to a depth of 5 cm and downslope movement of up to boulder-sized material, and at least one debris flow occurred in the channel; negligible surface runoff was observed in the South Tributary basin. The negligible surface runoff observed in the South Tributary basin is attributed to the limited extent and severity of the fire in that basin. The factors that best distinguish between debris-flow producing and flood-producing drainages are drainage basin morphology and lithology. A rugged drainage basin morphology, an average 12 per cent channel gradient, and steep, rough hillslopes coupled with colluvium and soil weathered from volcaniclastic and volcanic rocks promoted the generation of debris flows. A less rugged basin morphology, an average gradient of 5 per cent, and long, smooth slopes mantled with pumice promoted flooding. Flood and debris-flow responses were produced without the presence of water-repellent soils. The continuity and severity of the burn mosaic, the condition of the riparian vegetation, the condition of the fibrous root mat, accumulations of dry ravel and colluvial material in the channel and on hillslopes, and past debris-flow activity, appeared to have little bearing on the distinctive responses of the basins. Published in 2000 by John Wiley and Sons, Ltd.

  11. Debris-flow runout predictions based on the average channel slope (ACS)

    USGS Publications Warehouse

    Prochaska, A.B.; Santi, P.M.; Higgins, J.D.; Cannon, S.H.

    2008-01-01

    Prediction of the runout distance of a debris flow is an important element in the delineation of potentially hazardous areas on alluvial fans and for the siting of mitigation structures. Existing runout estimation methods rely on input parameters that are often difficult to estimate, including volume, velocity, and frictional factors. In order to provide a simple method for preliminary estimates of debris-flow runout distances, we developed a model that provides runout predictions based on the average channel slope (ACS model) for non-volcanic debris flows that emanate from confined channels and deposit on well-defined alluvial fans. This model was developed from 20 debris-flow events in the western United States and British Columbia. Based on a runout estimation method developed for snow avalanches, this model predicts debris-flow runout as an angle of reach from a fixed point in the drainage channel to the end of the runout zone. The best fixed point was found to be the mid-point elevation of the drainage channel, measured from the apex of the alluvial fan to the top of the drainage basin. Predicted runout lengths were more consistent than those obtained from existing angle-of-reach estimation methods. Results of the model compared well with those of laboratory flume tests performed using the same range of channel slopes. The robustness of this model was tested by applying it to three debris-flow events not used in its development: predicted runout ranged from 82 to 131% of the actual runout for these three events. Prediction interval multipliers were also developed so that the user may calculate predicted runout within specified confidence limits. ?? 2008 Elsevier B.V. All rights reserved.

  12. Predicting the probability and volume of postwildfire debris flows in the intermountain western United States

    USGS Publications Warehouse

    Cannon, S.H.; Gartner, J.E.; Rupert, M.G.; Michael, J.A.; Rea, A.H.; Parrett, C.

    2010-01-01

    Empirical models to estimate the probability of occurrence and volume of postwildfire debris flows can be quickly implemented in a geographic information system (GIS) to generate debris-flow hazard maps either before or immediately following wildfires. Models that can be used to calculate the probability of debris-flow production from individual drainage basins in response to a given storm were developed using logistic regression analyses of a database from 388 basins located in 15 burned areas located throughout the U.S. Intermountain West. The models describe debris-flow probability as a function of readily obtained measures of areal burned extent, soil properties, basin morphology, and rainfall from short-duration and low-recurrence-interval convective rainstorms. A model for estimating the volume of material that may issue from a basin mouth in response to a given storm was developed using multiple linear regression analysis of a database from 56 basins burned by eight fires. This model describes debris-flow volume as a function of the basin gradient, aerial burned extent, and storm rainfall. Applications of a probability model and the volume model for hazard assessments are illustrated using information from the 2003 Hot Creek fire in central Idaho. The predictive strength of the approach in this setting is evaluated using information on the response of this fire to a localized thunderstorm in August 2003. The mapping approach presented here identifies those basins that are most prone to the largest debris-flow events and thus provides information necessary to prioritize areas for postfire erosion mitigation, warnings, and prefire management efforts throughout the Intermountain West.

  13. Precipitation thresholds and debris flow warning: comparing gauge versus weather radar detection

    NASA Astrophysics Data System (ADS)

    Marra, Francesco; Borga, Marco; Creutin, Jean-Dominique

    2013-04-01

    Methods relying on rainfall thresholds for debris-flow warning have a long tradition in geomorphology. Usually, the precipitation thresholds are developed based on rain gauge and debris flows data. However, it is well known that extreme rainfall sampling errors over rugged topography may lead to biased precipitation thresholds. At least two reasons contribute to such sampling errors: i) the regions of complex topography have low rain gauge densities; ii) orography may enhance intense precipitation at very localized places. We studied six storm events that triggered several debris flows each over the Trentino-Alto Adige Region, in the central Italian Alps, between 2005 and 2010. The region is monitored by i) a rain gauge network with an average density of 1/100 km2 and ii) a C-band radar instrument. Radar data have been accurately corrected for errors due to ground clutter contamination, beam blockages, vertical profile of reflectivity, attenuation and wet radome in order to obtain a high quality set of radar-based rainfall fields. We characterized the variability of each rainfall event using space (horizontal) and time variograms and we investigated the altitude (vertical) distribution of rainfall using hypsometric rainfall moments. We also defined the local severity of the rainfall accumulations over the debris flow areas for different time accumulations. We used the radar precipitation fields to represent space-time rainfall variability and we simulated gauge sampling with a stochastic model accounting for sub-grid variability of precipitation and for gauge measurement errors. We show that rain gauges systematically underestimate the local severity over the proven debris flow triggering locations. This leads to biased precipitation thresholds. In this respect gauge spatial sampling appears inappropriate both in the horizontal and in the vertical dimensions while the usual gauge time sampling looks appropriate. Moreover, this shows the potential of rainfall

  14. Debris flow occurrence future changes in high populated mountains (French Alps).

    NASA Astrophysics Data System (ADS)

    Pavlova, I.; Jomelli, V.; Brunstein, D.; Grancher, D.

    2010-03-01

    The growth of tourism in recent decades, the dense population and more than 100 large ski areas create a high potential for damage to people, settlements and associated infrastructures in the French Alps. Increasing demographic pressures in mountainous regions and recent catastrophic events have renewed interest in various gravitational hazards predetermination in European countries. Results of the models considering the A2 hypothesis (IPCC 2007) showed that the most significant climatic trends for the end of the century will be a decrease in intense rainy events and an increase in temperature. As it is known that debris flows are often triggered by intense rainy events, a change in global climate in the future could have an impact on the frequency of this process. Our approach is to link the current (1960ies-2000ies) or future climate and the occurrence of debris flows based on statistical modeling. Regional climatic scenarios were computed from the ARPEGE model developed by the Centre National de Recherches Météorologiques of Météo-France. We developed new models using the simulated current climatic data with debris flows. Then we compared the probabilities of the occurrence of debris flows in the current period and in the coming century. Probabilistic models for the end of the twenty-first century were computed by interchanging meteorological parameters used in the statistical models established for the current period by meteorological data simulated for the future period. The future changes should have impacts on the occurrence of debris flows. We expect a decrease in about 10-30% of debris flows occurrence probabilities. From a spatial point of view, the increase in temperature should result in a shift of the 0°C isotherm to a higher elevation which, in turn, should result in a 20% reduction of the number of slopes affected by the process compared to the current period.

  15. Modelling the feedbacks between mass balance, ice flow and debris transport to predict the response to climate change of debris-covered glaciers in the Himalaya

    NASA Astrophysics Data System (ADS)

    Rowan, Ann V.; Egholm, David L.; Quincey, Duncan J.; Glasser, Neil F.

    2015-11-01

    Many Himalayan glaciers are characterised in their lower reaches by a rock debris layer. This debris insulates the glacier surface from atmospheric warming and complicates the response to climate change compared to glaciers with clean-ice surfaces. Debris-covered glaciers can persist well below the altitude that would be sustainable for clean-ice glaciers, resulting in much longer timescales of mass loss and meltwater production. The properties and evolution of supraglacial debris present a considerable challenge to understanding future glacier change. Existing approaches to predicting variations in glacier volume and meltwater production rely on numerical models that represent the processes governing glaciers with clean-ice surfaces, and yield conflicting results. We developed a numerical model that couples the flow of ice and debris and includes important feedbacks between debris accumulation and glacier mass balance. To investigate the impact of debris transport on the response of a glacier to recent and future climate change, we applied this model to a large debris-covered Himalayan glacier-Khumbu Glacier in Nepal. Our results demonstrate that supraglacial debris prolongs the response of the glacier to warming and causes lowering of the glacier surface in situ, concealing the magnitude of mass loss when compared with estimates based on glacierised area. Since the Little Ice Age, Khumbu Glacier has lost 34% of its volume while its area has reduced by only 6%. We predict a decrease in glacier volume of 8-10% by AD2100, accompanied by dynamic and physical detachment of the debris-covered tongue from the active glacier within the next 150 yr. This detachment will accelerate rates of glacier decay, and similar changes are likely for other debris-covered glaciers in the Himalaya.

  16. Downstream dilution of a lahar: transition from debris flow to hyperconcentrated streamflow.

    USGS Publications Warehouse

    Pierson, T.C.; Scott, K.M.

    1985-01-01

    Nearly instantaneous melting of snow and ice by the March 19, 1982, eruption of Mount St. Helens, released a 4 X 106 m3 flood of water from the crater that was converted to a lahar (volcanic debris flow) through erosion and incorporation of sediment by the time it reached the base of the volcano. Over the next 81 km that it traveled down the Toutle River, the flood wave was progressively diluted through several mechanisms. A transformation from debris flow to hyperconcentrated streamflow began to occur about 27 km downstream from the crater, when the total sediment concentration had decreased to about 78% by weight (57% by volume).-from Authors

  17. Special challenges in assessing and mapping flood risk following a flood-debris flow event

    NASA Astrophysics Data System (ADS)

    Aggett, Graeme

    2016-04-01

    Severe rainfall along the Colorado front range in 2013 delivered flood and debris flows to many mountain communities, causing millions of dollars of damage as well as taking several lives. Phase changes in clear-hyperconcentrated-debris flows during the event created challenges in recreating the hydrology post-flood and in estimating and mapping new regulatory floodplains to support ongoing flood recovery efforts. This presentation highlights approaches used to overcome these challenges and to adequately represent the different processes and their uncertainties in updated flood hazard and risk assessments. It also considers the need to educate and involve the community in this process.

  18. Case study: Mapping tsunami hazards associated with debris flow into a reservoir

    USGS Publications Warehouse

    Walder, J.S.; Watts, P.; Waythomas, C.F.

    2006-01-01

    Debris-flow generated impulse waves (tsunamis) pose hazards in lakes, especially those used for hydropower or recreation. We describe a method for assessing tsunami-related hazards for the case in which inundation by coherent water waves, rather than chaotic splashing, is of primary concern. The method involves an experimentally based initial condition (tsunami source) and a Boussinesq model for tsunami propagation and inundation. Model results are used to create hazard maps that offer guidance for emergency planners and responders. An example application explores tsunami hazards associated with potential debris flows entering Baker Lake, a reservoir on the flanks of the Mount Baker volcano in the northwestern United States. ?? 2006 ASCE.

  19. Debris Flow Control on Fluvial Hanging Valley Formation in the South Fork Eel River, CA

    NASA Astrophysics Data System (ADS)

    Deshpande, N.; Perkins, J.; Finnegan, N. J.

    2012-12-01

    An understanding of how base level signals are transmitted into landscapes is fundamental to interpreting river long profiles in tectonically active settings. Fluvial hanging valleys, locations where waves of incision have apparently arrested at tributary junctions, suggest that base level propagation is an unsteady process in many settings. A recent hypothesis (Wobus et al., 2006) explains the formation of fluvial hanging valleys via an instability in the saltation abrasion model of Sklar and Dietrich (2004). At locations where small steep tributaries join trunk streams, tributary incision rates can actually decrease with increasing channel slope when subjected to downstream base-level fall. However, we note that in mountainous river networks steep tributaries also commonly convey debris flows into trunk channels. Since these tributary junctions mark the upstream limit of channels whose beds are mobilized on a regular basis during flood events, here we hypothesize that transitions from fluvial to debris flow channels control the location of fluvial hanging valleys. To test our hypothesis, we exploit a natural experiment in base level fall and landscape evolution along the South Fork Eel River, which is argued to be responding to an increase in rock uplift rate associated with the passage of the Mendocino Triple Junction. In order to separate debris flow channels from fluvial channels, we use airborne laser swath mapping (ALSM) to quantify channel slopes and concavities. In our analysis, concavity data are noisy and represent a poor metric for determination of debris flow channels. In lieu of this, we choose a more straightforward metric of channel slope to discriminate where debris flows occur on the landscape. We find that, on average, fluvial hanging valleys are only present in tributaries with average gradients above 0.10, consistent with empirical determinations of the gradient at which debris flow channels transition to fluvial channels (0.03-0.10). Field

  20. Debris-Flow Hazards within the Appalachian Mountains of the Eastern United States

    USGS Publications Warehouse

    Wieczorek, Gerald F.; Morgan, Benjamin A.

    2008-01-01

    Tropical storms, including hurricanes, often inflict major damage to property and disrupt the lives of people living in coastal areas of the Eastern United States. These storms also are capable of generating catastrophic landslides within the steep slopes of the Appalachian Mountains. Heavy rainfall from hurricanes, cloudbursts, and thunderstorms can generate rapidly moving debris flows that are among the most dangerous and damaging type of landslides. This fact sheet explores the nature and occurrence of debris flows in the central and southern Appalachian Mountains, which extend from central Pennsylvania to northern Alabama.

  1. Historical Account to the State of the Art in Debris Flow Modeling

    NASA Astrophysics Data System (ADS)

    Pudasaini, Shiva P.

    2013-04-01

    In this contribution, I present a historical account of debris flow modelling leading to the state of the art in simulations and applications. A generalized two-phase model is presented that unifies existing avalanche and debris flow theories. The new model (Pudasaini, 2012) covers both the single-phase and two-phase scenarios and includes many essential and observable physical phenomena. In this model, the solid-phase stress is closed by Mohr-Coulomb plasticity, while the fluid stress is modeled as a non-Newtonian viscous stress that is enhanced by the solid-volume-fraction gradient. A generalized interfacial momentum transfer includes viscous drag, buoyancy and virtual mass forces, and a new generalized drag force is introduced to cover both solid-like and fluid-like drags. Strong couplings between solid and fluid momentum transfer are observed. The two-phase model is further extended to describe the dynamics of rock-ice avalanches with new mechanical models. This model explains dynamic strength weakening and includes internal fluidization, basal lubrication, and exchanges of mass and momentum. The advantages of the two-phase model over classical (effectively single-phase) models are discussed. Advection and diffusion of the fluid through the solid are associated with non-linear fluxes. Several exact solutions are constructed, including the non-linear advection-diffusion of fluid, kinematic waves of debris flow front and deposition, phase-wave speeds, and velocity distribution through the flow depth and through the channel length. The new model is employed to study two-phase subaerial and submarine debris flows, the tsunami generated by the debris impact at lakes/oceans, and rock-ice avalanches. Simulation results show that buoyancy enhances flow mobility. The virtual mass force alters flow dynamics by increasing the kinetic energy of the fluid. Newtonian viscous stress substantially reduces flow deformation, whereas non-Newtonian viscous stress may change the

  2. Debris flow monitoring experience in the Cancia basin (Dolomites, Northeast Italian Alps).

    NASA Astrophysics Data System (ADS)

    Stancanelli, Laura; Bernard, Martino; Gregoretti, Carlo; Berti, Matteo; Simoni, Alessandro; Lanzoni, Stefano

    2016-04-01

    The monitoring campaign presented here aims to understand the dynamics of sediment transport processes in small head-water catchments of the Italian Alps and to evaluate the rainfall thresholds for debris flow triggering. The monitored basin of Cancia is located on the Eastern Italian Dolomites, in the Belluno Province. In particular, it is situated on the left side on the Boite river valley, next to the Borca di Cadore village, and is delimited by the western slope of the Mt. Antelao. The drainage area is 1.8 km2 while the elevation ranges from 2451 m a.s.l. to 880 m a.s.l., with a slope varying from 30-40° in the upper part to 10-15° in the lower part (fan area). The basin is characterized by a lithology very common in the Italian Alps, which consist of high permeability, poorly sorted rock debris, containing boulders up to 3-4 m in diameter, and include heterogeneous scree, alluvium and old debris flow deposits. The spatial distribution of sediment is characterized by: an upper part where prevails the presence of rocks, a medium part characterized by poorly sorted rock debris and fine sediment material, and a downstream part plenty of sediment material The Cancia basin is prone to stony debris flows, owing to the plenty availability of loose and coarse sediments and frequent convective events. In particular, the smaller grain sized material is provided by the erosion of lateral slope, while gravel, pebbles and cobbles are provided by the upper part of the basin, characterized by rocky material. The precipitation regime is marked by rainfalls of short duration and high intensity, usually occurring in the summer period. The debris flow channel has began to be surveyed in August 2009 to identify the debris flow generation area. At the beginning of July 2013 topographical surveys of the channel downstream the triggering area began in order to investigate the morphological evolution of the debris flow channel from 2013 until 2015. Moreover, at the beginning of

  3. Merging field survey and LiDAR technology for the analysis of debris-flow erosion

    NASA Astrophysics Data System (ADS)

    Bertoldi, G.; Reginato, M.; D'Agostino, V.

    2012-04-01

    Hazardous debris flows are usually triggered by rainfall or snowmelt on steep mountainside and might increase due to an erosive self-feeding from channel bed and banks. While trigger and deposition mechanisms might be more directly investigated in terms of sediment volumes in play, channel network erosions are quantitatively more complex particularly if a continuous detailed trend of the phenomenon is researched. In fact, data on debris-flow channel erosion are quite rare and often contradictory. In the last decade the increase of remotely sensed technologies such laser scanners has improved the quality and the detail of terrain information, thus providing a suitable tool for earth surface processes analysis. In this work the topic of debris-flow erosion has been analyzed through intensive field surveys and high resolution topography (before and after event) of two adjacent catchments, where an extreme rainfall event was recorded. Debris flows occurred on the 15th of August 2010 in the 'Rio Val Molinara' and 'Rio Val del Lago' torrents (Baselga di Pinè, Trento, Italy) seriously damaging the village of Campolongo. Event magnitudes were estimated equal to 40.000 and 10.000 m3 respectively and were almost completely generated by channel and bank erosion. The two catchments have a drainage area of about 1 km2 and are characterized by porphyritic lithology and a dominant cover of conifer forest. Both basins were considered as sediment supply limited before the event and this evaluation was corroborated by more than 150 years of inactivity resulting from historical sources. Field surveys have been carried out in summer 2011, providing geomorphic estimation of type of process (debris flow/debris flood), removed volumes, post-event sediment availability, local peak discharges and flow velocities of 150 homogeneous reaches subdivided into 200 cross sections. Field data were then compared with pre and post-event using high resolution DTMs (1 m grid cell size) derived from

  4. Debris Flow Risk Management Framework and Risk Analysis in Taiwan, A Preliminary Study

    NASA Astrophysics Data System (ADS)

    Tsao, Ting-Chi; Hsu, Wen-Ko; Chiou, Lin-Bin; Cheng, Chin-Tung; Lo, Wen-Chun; Chen, Chen-Yu; Lai, Cheng-Nong; Ju, Jiun-Ping

    2010-05-01

    Taiwan is located on a seismically active mountain belt between the Philippine Sea plate and Eurasian plate. After 1999's Chi-Chi earthquake (Mw=7.6), landslide and debris flow occurred frequently. In Aug. 2009, Typhoon Morakot struck Taiwan and numerous landslides and debris flow events, some with tremendous fatalities, were observed. With limited resources, authorities should establish a disaster management system to cope with slope disaster risks more effectively. Since 2006, Taiwan's authority in charge of debris flow management, the Soil and Water Conservation Bureau (SWCB), completed the basic investigation and data collection of 1,503 potential debris flow creeks around Taiwan. During 2008 and 2009, a debris flow quantitative risk analysis (QRA) framework, based on landslide risk management framework of Australia, was proposed and conducted on 106 creeks of the 30 villages with debris flow hazard history. Information and value of several types of elements at risk (bridge, road, building and crop) were gathered and integrated into a GIS layer, with the vulnerability model of each elements at risk applied. Through studying the historical hazard events of the 30 villages, numerical simulations of debris flow hazards with different magnitudes (5, 10, 25, 50, 100 and 200 years return period) were conducted, the economic losses and fatalities of each scenario were calculated for each creek. When taking annual exceeding probability into account, the annual total risk of each creek was calculated, and the results displayed on a debris flow risk map. The number of fatalities and frequency were calculated, and the F-N curves of 106 creeks were provided. For F-N curves, the individual risk to life per year of 1.0E-04 and slope of 1, which matched with international standards, were considered to be an acceptable risk. Applying the results of the 106 creeks onto the F-N curve, they were divided into 3 categories: Unacceptable, ALARP (As Low As Reasonable Practicable) and

  5. Estimating construction and demolition debris generation using a materials flow analysis approach.

    PubMed

    Cochran, K M; Townsend, T G

    2010-11-01

    The magnitude and composition of a region's construction and demolition (C&D) debris should be understood when developing rules, policies and strategies for managing this segment of the solid waste stream. In the US, several national estimates have been conducted using a weight-per-construction-area approximation; national estimates using alternative procedures such as those used for other segments of the solid waste stream have not been reported for C&D debris. This paper presents an evaluation of a materials flow analysis (MFA) approach for estimating C&D debris generation and composition for a large region (the US). The consumption of construction materials in the US and typical waste factors used for construction materials purchasing were used to estimate the mass of solid waste generated as a result of construction activities. Debris from demolition activities was predicted from various historical construction materials consumption data and estimates of average service lives of the materials. The MFA approach estimated that approximately 610-78 × 10(6)Mg of C&D debris was generated in 2002. This predicted mass exceeds previous estimates using other C&D debris predictive methodologies and reflects the large waste stream that exists.

  6. A new approach for empirical runout prediction of alpine debris flows

    NASA Astrophysics Data System (ADS)

    Scheidl, C.; Rickenmann, D.

    2009-04-01

    A new technique to forecast the runout of a debris flow event is introduced. First, processes of recorded, past torrential alpine events in Austria, Switzerland and Northern Italy are identified, using common classification techniques. Similarly to previous studies, we apply an empirical equation based on the planimetric area and volume to our dataset, and we compare it's the obtained mobility coefficients with published results based on other data. We present a new empirical approach to determine the mobility coefficient which is a key parameter to predict the runout behaviour of debris flows. It is based on geomorphologic catchment parameters. The predictive equation is implemented in a GIS based simulation program and combined with a simple flow routing algorithm, in order to determine the potential runout area covered by debris-flow deposits. The simulation uses the ARC-Objects environment of ESRI© and is adapted to run with high resolution (2.5m x 2.5 m grid) elevation models, generated from LiDAR data. The program called TopRunDF is tested with debris flow events of 1987 and 2005 in Switzerland for areas where LiDAR generated elevation models are available.

  7. 1D numerical model of muddy subaqueous and subaerial debris flows

    USGS Publications Warehouse

    Imran, J.; Parker, G.; Locat, J.; Lee, H.

    2001-01-01

    A 1D numerical model of the downslope flow and deposition of muddy subaerial and subaqueous debris flows is presented. The model incorporates the Herschel-Bulkley and bilinear rheologies of viscoplastic fluid. The more familiar Bingham model is integrated into the Herschel-Bulkley rheological model. The conservation equations of mass and momentum of single-phase laminar debris flow are layer-integrated using the slender flow approximation. They are then expressed in a Lagrangian framework and solved numerically using an explicit finite difference scheme. Starting from a given initial shape, a debris flow is allowed to collapse and propagate over a specified topography. Comparison between the model predictions and laboratory experiments shows reasonable agreement. The model is used to study the effect of the ambient fluid density, initial shape of the failed mass, and rheological model on the simulated propagation of the front and runout characteristics of muddy debris flows. It is found that initial failure shape influence the front velocity but has little bearing on the final deposit shape. In the Bingham model, the excess of shear stress above the yield strength is proportional to the strain rate to the first power. This exponent is free to vary in the Herschel-Bulkley model. When it is set at a value lower than unity, the resulting final deposits are thicker and shorter than in the case of the Bingham rheology. The final deposit resulting from the bilinear model is longer and thinner than that from the Bingham model due to the fact that the debris flow is allowed to act as a Newtonian fluid at low shear rate in the bilinear model.

  8. Emergency assessment of post-fire debris-flow hazards for the 2013 Powerhouse fire, southern California

    USGS Publications Warehouse

    Staley, Dennis M.; Smoczyk, Gregory M.; Reeves, Ryan R.

    2013-01-01

    Wildfire dramatically alters the hydrologic response of a watershed such that even modest rainstorms can produce dangerous flash floods and debris flows. Existing empirical models were used to predict the probability and magnitude of debris-flow occurrence in response to a 10-year recurrence interval rainstorm for the 2013 Powerhouse fire near Lancaster, California. Overall, the models predict a relatively low probability for debris-flow occurrence in response to the design storm. However, volumetric predictions suggest that debris flows that occur may entrain a significant volume of material, with 44 of the 73 basins identified as having potential debris-flow volumes between 10,000 and 100,000 cubic meters. These results suggest that even though the likelihood of debris flow is relatively low, the consequences of post-fire debris-flow initiation within the burn area may be significant for downstream populations, infrastructure, and wildlife and water resources. Given these findings, we recommend that residents, emergency managers, and public works departments pay close attention to weather forecasts and National-Weather-Service-issued Debris Flow and Flash Flood Outlooks, Watches, and Warnings and that residents adhere to any evacuation orders.

  9. Emergency assessment of post-fire debris-flow hazards for the 2013 Springs Fire, Ventura County, California

    USGS Publications Warehouse

    Staley, Dennis M.

    2014-01-01

    Wildfire can significantly alter the hydrologic response of a watershed to the extent that even modest rainstorms can produce dangerous flash floods and debris flows. In this report, empirical models are used to predict the probability and magnitude of debris-flow occurrence in response to a 10-year rainstorm for the 2013 Springs fire in Ventura County, California. Overall, the models predict a relatively high probability (60–80 percent) of debris flow for 9 of the 99 drainage basins in the burn area in response to a 10-year recurrence interval design storm. Predictions of debris-flow volume suggest that debris flows may entrain a significant volume of material, with 28 of the 99 basins identified as having potential debris-flow volumes greater than 10,000 cubic meters. These results of the relative combined hazard analysis suggest there is a moderate likelihood of significant debris-flow hazard within and downstream of the burn area for nearby populations, infrastructure, wildlife, and water resources. Given these findings, we recommend that residents, emergency managers, and public works departments pay close attention to weather forecasts and National Weather Service-issued Debris Flow and Flash Flood Outlooks, Watches, and Warnings, and that residents adhere to any evacuation orders.

  10. Distribution of Amphipods (Gammarus nipponensis Ueno) Among Mountain Headwater Streams with Different Legacies of Debris Flow Occurrence

    EPA Science Inventory

    To understand the impacts of debris flows on the distribution of an amphipod with limited dispersal ability in the context of stream networks, we surveyed the presence of Gammarus nipponensis in 87 headwater streams with different legacies of debris flow occurrence within an 8.5-...

  11. Debris-flow deposits of Early Miocene age, Deadman Stream, Marlborough, New Zealand.

    USGS Publications Warehouse

    Lewis, D.W.; Laird, M.G.; Powell, R.D.

    1980-01-01

    Detailed analysis is presented of a conformable succession of conglomerates and sandstones lying between massive marine mudstones. The coarse sediments reflect deposition by a spectrum of subaqueous debris-flow mechanisms during an early pulse of tectonism that ultimately resulted in Plio-Pleistocene eversion of the Kaikoura Mountains. Sparse pebbly mudstones and rare sandy conglomerates show disoriented clasts and reflect high-viscosity flows and slurry- creep flow mechanisms. Other deposits have little mud matrix, hence appear to reflect low-viscosity flow processes. Common sorted sandstones and some conglomeratic sandstones show diffuse parallel lamination. Other conglomeratic sandstones show trough cross-bedding which we attribute to entrained bedload movement during intersurge episodes of debris flow. - from Authors

  12. Estimated Probability of Post-Wildfire Debris-Flow Occurrence and Estimated Volume of Debris Flows from a Pre-Fire Analysis in the Three Lakes Watershed, Grand County, Colorado

    USGS Publications Warehouse

    Stevens, Michael R.; Bossong, Clifford R.; Litke, David W.; Viger, Roland J.; Rupert, Michael G.; Char, Stephen J.

    2008-01-01

    Debris flows pose substantial threats to life, property, infrastructure, and water resources. Post-wildfire debris flows may be of catastrophic proportions compared to debris flows occurring in unburned areas. During 2006, the U.S. Geological Survey (USGS), in cooperation with the Northern Colorado Water Conservancy District, initiated a pre-wildfire study to determine the potential for post-wildfire debris flows in the Three Lakes watershed, Grand County, Colorado. The objective was to estimate the probability of post-wildfire debris flows and to estimate the approximate volumes of debris flows from 109 subbasins in the Three Lakes watershed in order to provide the Northern Colorado Water Conservancy District with a relative measure of which subbasins might constitute the most serious debris flow hazards. This report describes the results of the study and provides estimated probabilities of debris-flow occurrence and the estimated volumes of debris flow that could be produced in 109 subbasins of the watershed under an assumed moderate- to high-burn severity of all forested areas. The estimates are needed because the Three Lakes watershed includes communities and substantial water-resources and water-supply infrastructure that are important to residents both east and west of the Continental Divide. Using information provided in this report, land and water-supply managers can consider where to concentrate pre-wildfire planning, pre-wildfire preparedness, and pre-wildfire mitigation in advance of wildfires. Also, in the event of a large wildfire, this information will help managers identify the watersheds with the greatest post-wildfire debris-flow hazards.

  13. The Debris Flow of September 20, 2014, in Mud Creek, Mount Shasta Volcano, Northern California

    NASA Astrophysics Data System (ADS)

    De La Fuente, J. A.; Bachmann, S.; Courtney, A.; Meyers, N.; Mikulovsky, R.; Rust, B.; Coots, F.; Veich, D.

    2015-12-01

    The debris flow in Mud Creek on September 20, 2014 occurred during a warm spell at the end of an unusually long and hot summer. No precipitation was recorded during or immediately before the event, and it appears to have resulted from rapid glacial melt. It initiated on the toe of the Konwakiton Glacier, and immediately below it. The flow track was small in the upper parts (40 feet wide), but between 8,000 and 10,000 feet in elevation, it entrained a large volume of debris from the walls and bed of the deeply incised gorge and transported it down to the apex of the Mud Creek alluvial fan (4,800'). At that point, it overflowed the channel and deposited debris on top of older (1924) debris flow deposits, and the debris plugged a road culvert 24 feet wide and 12 feet high. A small fraction of the flow was diverted to a pre-existing overflow channel which parallels Mud Creek, about 1,000 feet to the west. The main debris flow traveled down Mud Creek, confined to the pre-existing channel, but locally got to within a foot or so of overflowing the banks. At elevation 3920', video was taken during the event by a private citizen and placed on YouTube. The video revealed that the flow matrix consisted of a slurry of water/clay/silt/sand/gravel, transporting boulders 1-6 feet in diameter along with the flow. Cobble-sized rock appears to be absent. Sieve analysis of the debris flow matrix material revealed a fining of particles in a downstream direction, as expected. The thickness of deposits on the fan generally decreased in a downstream direction. Deposits were 5-6 feet deep above the Mud Creek dam, which is at 4,800' elevation, and 4-5 feet deep at the dam itself. Further downstream, thicknesses decreased as follows: 3920'aqueduct crossing, 3-4 feet; 3620' Pilgrim Creek Road crossing, 2-3 feet; 3,520', 1-2 feet; 3,440' abandoned railroad grade, 1 foot. This event damaged roads, and future events could threaten life and property. There is a need to better understand local

  14. Climatological and meteorological conditions associated with rain-induced periglacial debris flows in the Cascade Range, USA

    NASA Astrophysics Data System (ADS)

    Parker, L.; Nolin, A. W.

    2009-04-01

    Title: Climatological and meteorological conditions associated with rain-induced periglacial debris flows in the Cascade Range, USA Authors: L. Parker, A.W. Nolin Affiliation: Department of Geosciences, Oregon State University, Corvallis, Oregon, USA In November of 2006 an intense rainstorm of tropical origin, known colloquially as "Pineapple Express," inundated the Pacific Northwest region of the United States, initiating numerous periglacial debris flows on several of the stratovolcanoes in the Cascade Range of Oregon and Washington. Rain-induced periglacial debris flows are the result of the over-saturation and subsequent collapse of steep moraine in formerly glaciated valleys. These debris flows rapidly aggrade channels, deposit thick sediments in their path, and severely damage infrastructure. Here we focus on Mount Hood, Oregon and Mount Rainier, Washington in the investigation of meteorological and climatological conditions surrounding rain-induced periglacial debris flow events and their variability over time. Both anecdotal and observational evidence suggest that the Pineapple Express storms are a likely triggering mechanism for these rain-induced debris flows on the stratovolcanoes. Dates for the debris flow events for each mountain were linked with corresponding Pineapple Express storm events. Preliminary analysis suggests that one or more particular climatological or meteorological conditions may be central to the initiation of debris flows, though these conditions may not always be present during Pineapple Express storms. Antecedent snowpack conditions are also hypothesized to play an important role in periglacial rain-induced debris flow initiation as the presence of snow cover on the moraines and glaciers is thought to reduce the likelihood of a debris flow. Radiosonde and precipitation data from Salem, Oregon (KSLE) and Quillayute, Washington (KUIL) data are used to determine if freezing levels and precipitation amounts have changed over time for

  15. Updated logistic regression equations for the calculation of post-fire debris-flow likelihood in the western United States

    USGS Publications Warehouse

    Staley, Dennis M.; Negri, Jacquelyn A.; Kean, Jason W.; Laber, Jayme L.; Tillery, Anne C.; Youberg, Ann M.

    2016-01-01

    Wildfire can significantly alter the hydrologic response of a watershed to the extent that even modest rainstorms can generate dangerous flash floods and debris flows. To reduce public exposure to hazard, the U.S. Geological Survey produces post-fire debris-flow hazard assessments for select fires in the western United States. We use publicly available geospatial data describing basin morphology, burn severity, soil properties, and rainfall characteristics to estimate the statistical likelihood that debris flows will occur in response to a storm of a given rainfall intensity. Using an empirical database and refined geospatial analysis methods, we defined new equations for the prediction of debris-flow likelihood using logistic regression methods. We showed that the new logistic regression model outperformed previous models used to predict debris-flow likelihood.

  16. Updated logistic regression equations for the calculation of post-fire debris-flow likelihood in the western United States

    USGS Publications Warehouse

    Staley, Dennis M.; Negri, Jacquelyn A.; Kean, Jason W.; Laber, Jayme L.; Tillery, Anne C.; Youberg, Ann M.

    2016-06-30

    Wildfire can significantly alter the hydrologic response of a watershed to the extent that even modest rainstorms can generate dangerous flash floods and debris flows. To reduce public exposure to hazard, the U.S. Geological Survey produces post-fire debris-flow hazard assessments for select fires in the western United States. We use publicly available geospatial data describing basin morphology, burn severity, soil properties, and rainfall characteristics to estimate the statistical likelihood that debris flows will occur in response to a storm of a given rainfall intensity. Using an empirical database and refined geospatial analysis methods, we defined new equations for the prediction of debris-flow likelihood using logistic regression methods. We showed that the new logistic regression model outperformed previous models used to predict debris-flow likelihood.

  17. High-resolution modeling of overland flow and sediment transport following wildfire: Insights into initiation mechanisms and sediment sources for runoff-generated debris flows

    NASA Astrophysics Data System (ADS)

    McGuire, L.; Kean, J. W.; Staley, D. M.; Rengers, F. K.

    2015-12-01

    Sediment transport in steep landscapes may be facilitated by both water-dominated flows and debris-flow processes. Given the differences in erosion potential and mobility possessed by runoff and debris flows, knowledge of the conditions that determine the runoff-to-debris-flow transition has important implications for hazard assessment as well as our understanding of the long-term evolution of steep bedrock channels. Debris flows in alpine areas and burned steeplands are frequently triggered by runoff following high-intensity rainfall, but the mechanics by which runoff generates a debris flow are not well understood. To examine the connections between runoff and debris flow initiation, we developed a numerical model that couples overland flow with sediment transport and debris-flow processes. We applied the model to study erosion and debris-flow initiation that occurred during a rainfall event that produced numerous debris flows within a burned drainage basin in the San Gabriel Mountains, CA, USA. Input data for the numerical model was constrained by rain gauges, stage measurements at the basin outlet, soil-moisture sensors, and high-resolution topographic data obtained using a terrestrial laser scanner (TLS). Numerical model predictions, which compare well with TLS-derived measurements of topographic change, indicate that hillslope erosion at our study site was primarily the result of raindrop-induced sediment transport. Further, results indicate that the majority of sediment eroded from the hillslopes was deposited within the channel system during the storm with only minor amounts being transported out of the basin in suspension. Based on model results, we hypothesize that numerous debris flows were generated from the mass failure of sediment dams that built up within the channel system throughout the storm. This study adds to our understanding of sediment transport in steep landscapes and provides insight into the topographic and hydrologic factors that

  18. Analysis of the relationship of occurrence between precipitation and debris flows in Mexico

    NASA Astrophysics Data System (ADS)

    Cardoso-Landa, Guillermo

    2010-05-01

    The debris flows are the fast earth landslide movements, caused by hyperconcentrated flows of water and sediments, which happen in a great variety of environment throughout everybody. They are formed of a mixture of fine material (sand and clay), heavy material (gravel and rocks) and a variable amount of water, that a mud forms, which moves down towards slope, in swelling generally induced by the action of the gravity and the sudden collapse of the material in the bank. They are particularly dangerous for the life and the properties due to its high speeds and great destructive force, lowering natural houses, ways, bridges, trees and farmings, currents and ecosystems throughout its trajectory. Empirical thresholds are based on the historical analysis of the relationship of occurrence precipitation and debris flow (e.g., statistical analyses). There is now a limited number of this type of empirical thresholds and have been employed different diagrams to represent them, depending on rainfall parameters commonly used combinations: antecedent precipitation, duration, intensity and accumulated rain, to be the most famous obtained by Caine and Aleotti. In this article it was applied the function of mobilization of Iritanno and the propose relations of empirical thresholds by Caine and Aleotti to the precipitation registries that originated, among other factors, the debris flows happened in Teziutlán, México, being appraised that the relations intensity of rain-duration for this debris flow are greater from 3,43 to 2,1 times with respect to generating the empirical precipitation thresholds of debris flows proposed by Caine and Aleotti.

  19. Coupled prediction of flash flood response and debris flow occurrence in an alpine basin

    NASA Astrophysics Data System (ADS)

    Amponsah, William

    2015-04-01

    Coupled prediction of flash flood response and debris flow occurrence in an alpine basin Author(s): William Amponsah1, E.I. Nikolopoulos2, Lorenzo Marchi1, Roberto Dinale4, Francesco Marra3,Davide Zoccatelli2 , Marco Borga2 Affiliation(s): 1CNR - IRPI, Corso Stati Uniti 4, 35127, Padova, ITALY, 2Department of Land, Environment, Agriculture and Forestry, University of Padova,VialeDell'Università 16, 35020, Legnaro PD, ITALY 3Department of Geography, Hebrew University of Jerusalem, ISRAEL 4Ufficio Idrografico, Provincia Autonoma di Bolzano, Bolzano, Italy This contribution examines the main hydrologic and morphologic metrics responsible for widespread triggering of debris-flows associated with flash flood occurrences in headwater alpine catchments.To achieve this objective, we investigate the precipitation forcing, hydrologic responses and landslides and debris-flow occurrences that prevailed during the August 4-5, 2012 extreme flash flood on the 140 km2 Vizze basin in the Eastern Alps of Italy. An intensive post-event survey was carried out a few days after the flood. This included the surveys of cross-sectional geometry and flood marks for the estimation of the peak discharges at multiple river sections and of the initiation and deposition areas of several debris flows. Rainfall estimates are based on careful analysis of weather radar observations and raingauge data. These data and observations permitted the implementation and calibration of a spatially distributed hydrological model, which was used to derive simulated flood hydrographs in 58 tributaries of the Vizze basin. Of these, 33 generated debris-flows, with area ranging from 0.02 km2 to 10 km2, with an average of 1.5 km2. With 130 mm peak event rainfall and a duration of 4 hours (with a max intensity of 90 mm h-1 for 10 min), model-simulated unit peak discharges range from 4 m3 s-1 km-2for elementary catchments up to 10 km2 to 2 m3 s-1 km-2 for catchments in the range of 50 - 100 km2. These are very high

  20. Role of debris flows in long-term landscape denudation in the central Appalachians of Virginia

    USGS Publications Warehouse

    Eaton, L.S.; Morgan, B.A.; Kochel, R.C.; Howard, A.D.

    2003-01-01

    Four major storms that triggered debris flows in the Virginia-West Virginia Appalachians provide new insights into the role of high-magnitude, low-frequency floods in long-term denudation and landscape evolution in mountainous terrain. Storm denudation in the Blue Ridge Mountain drainage basins in approximately an order of magnitude greater compared to basins located in the mountains of the Valley and Ridge province. This difference is probably the result of higher storm rainfall from the Blue Ridge storms. Radiocarbon dating of debris-flow deposits in the Blue Ridge indicates a debris-flow return interval of not more than 2-4 k.y, in mountainous river basins. This finding, combined with measurements of basin denudation, suggests that approximately half of the long-term denudation from mechanical load occurs episodically by debris-flow processes. Although floods of moderate magnitude are largely responsible for mobilizing sediment in low-gradient streams, our data suggest that high-magnitude, low-frequency events are the most significant component in delivering coarse-grained regolith from mountainous hollows and channels to the lowland floodplains.

  1. Loss estimation of debris flow events in mountain areas - An integrated tool for local authorities

    NASA Astrophysics Data System (ADS)

    Papathoma-Koehle, M.; Zischg, A.; Fuchs, S.; Keiler, M.; Glade, T.

    2012-04-01

    Torrents prone to debris flows regularly cause extensive destruction of the built environment, loss of life stock, agricultural land and loss of life in mountain areas. Climate change may increase the frequency and intensity of such events. On the other hand, extensive development of mountain areas is expected to change the spatial pattern of elements at risk exposed and their vulnerability. Consequently, the costs of debris flow events are likely to increase in the coming years. Local authorities responsible for disaster risk reduction are in need of tools that may enable them to assess the future consequences of debris flow events, in particular with respect to the vulnerability of elements at risk. An integrated tool for loss estimation is presented here which is based on a newly developed vulnerability curve and which is applied in test sites in the Province of South Tyrol, Italy. The tool has a dual function: 1) continuous updating of the database regarding damages and process intensities that will eventually improve the existing vulnerability curve and 2) loss estimation of future events and hypothetical events or built environment scenarios by using the existing curve. The tool integrates the vulnerability curve together with new user friendly forms of damage documentation. The integrated tool presented here can be used by local authorities not only for the recording of damage caused by debris flows and the allocation of compensation to the owners of damaged buildings but also for land use planning, cost benefit analysis of structural protection measures and emergency planning.

  2. Transformation of ground vibration signal for debris-flow monitoring and detection in alarm systems.

    PubMed

    Abancó, Clàudia; Hürlimann, Marcel; Fritschi, Bruno; Graf, Christoph; Moya, José

    2012-01-01

    Debris flows are fast mass movements formed by a mix of water and solid materials, which occur in steep torrents, and are a source of high risks for human settlements. Geophones are widely used to detect the ground vibration induced by passing debris flows. However, the recording of geophone signals usually requires storing a huge amount of data, which leads to problems in storage capacity and power consumption. This paper presents a method to transform and simplify the signals measured by geophones. The key input parameter is the ground velocity threshold, which removes the seismic noise that is not related to debris flows. A signal conditioner was developed to implement the transformation and the ground velocity threshold was set by electrical resistors. The signal conditioner was installed at various European monitoring sites to test the method. Results show that data amount and power consumption can be greatly reduced without losing much information on the main features of the debris flows. However, the outcome stresses the importance of choosing a ground vibration threshold, which must be accurately calibrated. The transformation is also suitable to detect other rapid mass movements and to distinguish among different processes, which points to a possible implementation in alarm systems.

  3. Recognizing the importance of tropical forests in limiting rainfall-induced debris flows

    EPA Science Inventory

    Worldwide concern for continuing loss of montane forest cover in the tropics usually focuses on adverse ecological consequences. Less recognized, but equally important to inhabitants of these affected regions, is an increasing susceptibility to rainfall-induced debris flows and t...

  4. Probability and volume of potential postwildfire debris flows in the 2011 Monument burn area, southeastern Arizona

    USGS Publications Warehouse

    Ruddy, Barbara C.; Verdin, Kristine L.

    2011-01-01

    This report presents a preliminary emergency assessment of the debris-flow hazards from drainage basins burned by the Monument wildfire in southeastern Arizona, in 2011. Empirical models derived from statistical evaluation of data collected from recently burned drainage basins throughout the intermountain Western United States were used to estimate the probability of debris-flow occurrence and volumes of debris flows for selected drainage basins. Input for the models include measures of burn severity, topographic characteristics, soil properties, and rainfall total and intensity for a (1) 2-year-recurrence, 30-minute-duration rainfall, (2) 5-year-recurrence, 30-minute-duration rainfall, and (3) 10-year-recurrence, 30-minute-duration rainfall. Estimated debris-flow probabilities in the drainage basins of interest ranged from a low of 26 percent in response to the 2-year-recurrence, 30-minute-duration rainfall to 100 percent in response to the 10-year-recurrence, 30-minute-duration rainfall. The high probabilities in all modeled drainage basins are likely due to the abundance of steep hillslopes and the extensive areas burned at moderately to high severities. The estimated volumes ranged from a low of about 2,000 cubic meters to a high of greater than 200,000 cubic meters.

  5. Transient hazard model using radar data for predicting debris flows in Madison County, Virginia

    USGS Publications Warehouse

    Morrissey, M.M.; Wieczorek, G.F.; Morgan, B.A.

    2004-01-01

    During the rainstorm of June 27, 1995, roughly 330-750 mm of rain fell within a 16-hour period, initiating floods and over 600 debris flows in a small area (130 km2) of Madison County, VA. We developed a distributed version of Iverson's transient response model for regional slope stability analysis for the Madison County debris flows. This version of the model evaluates pore-pressure head response and factor of safety on a regional scale in areas prone to rainfall-induced shallow (<2-3 m) landslides. These calculations used soil properties of shear strength and hydraulic conductivity from laboratory measurements of soil samples collected from field sites where debris flows initiated. Rainfall data collected by radar every 6 minutes provided a basis for calculating the temporal variation of slope stability during the storm. The results demonstrate that the spatial and temporal variation of the factor of safety correlates with the movement of the storm cell. When the rainstorm was treated as two separate rainfall events and a larger hydraulic conductivity and friction angle than the laboratory values were used, the timing and location of landslides predicted by the model were in closer agreement with eyewitness observations of debris flows. Application of spatially variable initial pre-storm water table depth and soil properties may improve both the spatial and temporal prediction of instability.

  6. An integrated approach to the study of catastrophic debris-flows: geological hazard and human influence

    NASA Astrophysics Data System (ADS)

    Del Ventisette, C.; Garfagnoli, F.; Ciampalini, A.; Battistini, A.; Gigli, G.; Moretti, S.; Casagli, N.

    2012-09-01

    On 1 October 2009, a prolonged and intense rainstorm triggered hundreds of landslides (predominantly debris flows) in an area of about 50 km2 in the north-eastern sector of Sicily (Italy). Debris flows swept the highest parts of many villages and passed over the SS114 state highway and the Messina-Catania railway, causing more than 30 fatalities. This region has a high relief, due to recent uplift. The peculiar geological and geomorphological framework represents one of the most common predisposing causes of rainstorm-triggered debris flows. This paper deals with the geological and hydro-geomorphological studies performed as a part of the post-disaster activities operated in collaboration with Civil Protection Authority, with the aim at examining landslides effects and mechanisms. The data were elaborated into a GIS platform, to evaluate the influence of urbanisation on the drainage pattern, and were correlated with the lithological and structural framework of the area. Our study points at the evaluation of the volume involved, the detection of triggering mechanisms and the precise reconstruction of the influence of urbanisation as fundamental tools for understanding the dynamics of catastrophic landslides. This kind of analysis, including all the desirable approaches for the correct management of debris flow should be the starting point for robust urban planning.

  7. On the hyperbolicity of a two-fluid model for debris flows

    NASA Astrophysics Data System (ADS)

    Mineo, C.; Torrisi, M.

    2010-05-01

    We consider the system of partial differential equations associated with the mathematical model for debris flows proposed by E.B. Pitman and L. Le (Phil. Trans. R. Soc. A, 363, 1573-1601, 2005) and analyze the problem of the hyperbolicity of the model.

  8. Forecasting inundation from debris flows that grow volumetrically during travel, with application to the Oregon Coast Range, USA

    NASA Astrophysics Data System (ADS)

    Reid, Mark E.; Coe, Jeffrey A.; Brien, Dianne L.

    2016-11-01

    Many debris flows increase in volume as they travel downstream, enhancing their mobility and hazard. Volumetric growth can result from diverse physical processes, such as channel sediment entrainment, stream bank collapse, adjacent landsliding, hillslope erosion and rilling, and coalescence of multiple debris flows; incorporating these varied phenomena into physics-based debris-flow models is challenging. As an alternative, we embedded effects of debris-flow growth into an empirical/statistical approach to forecast potential inundation areas within digital landscapes in a GIS framework. Our approach used an empirical debris-growth function to account for the effects of growth phenomena. We applied this methodology to a debris-flow-prone area in the Oregon Coast Range, USA, where detailed mapping revealed areas of erosion and deposition along paths of debris flows that occurred during a large storm in 1996. Erosion was predominant in stream channels with slopes > 5°. Using pre- and post-event aerial photography, we derived upslope contributing area and channel-length growth factors. Our method reproduced the observed inundation patterns produced by individual debris flows; it also generated reproducible, objective potential inundation maps for entire drainage networks. These maps better matched observations than those using previous methods that focus on proximal or distal regions of a drainage network.

  9. Objective definition of rainfall intensity-duration thresholds for the initiation of post-fire debris flows in southern California

    USGS Publications Warehouse

    Staley, Dennis; Kean, Jason W.; Cannon, Susan H.; Schmidt, Kevin M.; Laber, Jayme L.

    2012-01-01

    Rainfall intensity–duration (ID) thresholds are commonly used to predict the temporal occurrence of debris flows and shallow landslides. Typically, thresholds are subjectively defined as the upper limit of peak rainstorm intensities that do not produce debris flows and landslides, or as the lower limit of peak rainstorm intensities that initiate debris flows and landslides. In addition, peak rainstorm intensities are often used to define thresholds, as data regarding the precise timing of debris flows and associated rainfall intensities are usually not available, and rainfall characteristics are often estimated from distant gauging locations. Here, we attempt to improve the performance of existing threshold-based predictions of post-fire debris-flow occurrence by utilizing data on the precise timing of debris flows relative to rainfall intensity, and develop an objective method to define the threshold intensities. We objectively defined the thresholds by maximizing the number of correct predictions of debris flow occurrence while minimizing the rate of both Type I (false positive) and Type II (false negative) errors. We identified that (1) there were statistically significant differences between peak storm and triggering intensities, (2) the objectively defined threshold model presents a better balance between predictive success, false alarms and failed alarms than previous subjectively defined thresholds, (3) thresholds based on measurements of rainfall intensity over shorter duration (≤60 min) are better predictors of post-fire debris-flow initiation than longer duration thresholds, and (4) the objectively defined thresholds were exceeded prior to the recorded time of debris flow at frequencies similar to or better than subjective thresholds. Our findings highlight the need to better constrain the timing and processes of initiation of landslides and debris flows for future threshold studies. In addition, the methods used to define rainfall thresholds in this

  10. Sediment delivery in debris-flow torrents: two case studies in the Italian Alps

    NASA Astrophysics Data System (ADS)

    Bertoldi, Gabriele; Vincenzo, D'Agostino

    2013-04-01

    Flood-risk mitigation strategy is moving from fixed, structural and costly mitigation measures to more effective proactive solutions. This change is driven both by Flood Directive 2007/60/EC and limitations of financial resources and it requires a deep knowledge of the involved processes. In mountain catchments debris flow and debris floods are the most important sources of hazard and their impact on the fan areas is heavily conditioned by the sediment dynamics along the 'transport' reaches of the torrents. Last advances show how many cases of erosion and deposition within the transport reach greatly affect the total volume that is delivered to the fan as well the overall dynamics of the debris flow/flood event. Due to logistic and practical constraints this intermediate phase of the process has been scarcely investigated and the complex behavior of the sediment budgeting in torrent-streams is emerging. The objective of this work consists of collecting information on the evolution of the debris-flow sediment budget along Alpine torrents in order to provide novel data about erosive, depositional and recharging processes under different geological conditions. Two high frequency debris-flow catchments have been selected: the Rio Rudan basin in the geological setting of the Dolomites (near Cortina d'Ampezzo, Veneto Region, Italy) and the metamorphic dominated catchment of the Rio Gadria (near Lasa, Trentino Alto Adige, Italy), which has been recently instrumented (EU project Monitor II). Periodical field monitoring has been carried out since summer 2011. 25 cross sections have been observed in the Rio Rudan catchment along a 480 m torrent reach (slope of 36%) where additional sediment entrainment after debris-flow initiation takes place. 20 cross sections have been selected in the upper Rio Gadria basin and more precisely in two reaches close to debris-flow triggerring areas. Other 31 cross sections have been also monitored of the Rio Gadria main channel covering a

  11. Progress of a sediment wave along the Lillooet River, British Columbia following a large debris flow

    NASA Astrophysics Data System (ADS)

    De Rego, K. G.; Eaton, B. C.; Hassan, M. A.; Lauer, J. W.

    2014-12-01

    We report field data and preliminary numerical modeling results documenting the transit of a sediment wave along the Lillooet River following a large debris flow in 2010. The Lillooet drains a midsize ( 4000 km2) glacially-influenced alpine catchment. Our study reach lies 70 km between the Mt. Meager Volcanic Complex (MMVC) and Lillooet Lake, which traps over 90% of incoming sediment. The channel transitions from braided and cobble-bedded to straight and sand-bedded, and the downstream half is dyked. Sediment supply is dominated by frequent debris flows originating in the MMVC. In 2010, a landslide on the MMVC released 48.5 x 106 m3 of material and triggered a debris flow that extended 2.5 km down the Lillooet Valley, briefly damming the river and causing an outburst flood. 1500 valley residents were evacuated temporarily, and the event led to $10 M CAD of damage to commercial forests and roads. The subsequent sediment wave is expected to lead to channel aggradation, putting pressure on the Lillooet's dyking system. We conducted bulk sampling and Wolman pebble counts along the river in 2014. Grainsize distributions from channel bars along the reach are compared to those of cutbanks to track the extent of the wave and the mobility of individual grainsize classes. We use the Morphodynamics and Sediment Tracers in 1-Dimension (MAST-1D) model to simulate the Lillooet's response to the debris flow on decadal timescales and to predict its recovery time. Sediment from the debris flow is traced in the model to estimate the proportion of the sediment wave that will remain in permanent storage within the valley fill. Future work will focus on quantifying the role of floodplain-channel interactions on sediment wave evolution for decadal and longer timescales.

  12. Debris flow sensitivity to glacial-interglacial climate change - supply vs transport

    NASA Astrophysics Data System (ADS)

    D'Arcy, Mitch; Roda Boluda, Duna C.; Whittaker, Alexander C.

    2016-04-01

    Numerical models suggest that small mountain catchment-alluvial fan systems might be sensitive to climate changes over glacial-interglacial cycles, and record these palaeoclimate signals in the sedimentology of their deposits. However, these models are still largely untested, and the propagation of climate signals through simple sediment routing systems remains contentious. Here, we present detailed sedimentological records from 8 debris flow fan systems in Owens Valley, California, that capture the past ~ 120 ka of deposition. We identify a strong and sustained relationship between deposit grain size and palaeoclimate records over a full glacial-interglacial cycle, with significantly coarser-grained deposits found in warm and dry periods. Our data show that these systems are highly sensitive to climate with a rapid response timescale of < 10ka, which we attribute to rapid transfer from source to sink. This sensitive record might be explained by changes in sediment supply and/or changes in sediment mobilisation, and we evaluate these mechanisms quantitatively. We find little evidence that changes in catchment hypsometry, weathering patterns, past glaciation or sediment production can explain the grain size changes we observe on the fans. However we do find that grain size has increased exponentially with rising temperatures, at a rate that matches the intensification of storms with warming. As these debris flows are triggered by surface runoff during intense storms, we interpret that enhanced runoff rates in warm and stormy conditions are responsible for entraining larger clasts during debris flow initiation. This implies that debris flow fans might record signals of past storm intensity. Our study utilises field sedimentology and focuses on short transport distances (~ 10 km) and climate changes over ~ 1-100 ka timespans, but could additionally have important implications for how eroding landscapes might respond to future warming scenarios. We address the

  13. Debris-flow hazards in areas affected by the June 27, 1995, storm in Madison County, Virginia

    USGS Publications Warehouse

    Morgan, B.A.; Wieczorek, G.F.; Campbell, R.H.; Gori, P.L.

    1997-01-01

    A severe storm on June 27, 1995 triggered hundreds of rock, debris and soil slides from the steep hillsides of Madison County, Virginia. Most of these transformed into debris flows that inundated areas downslope causing damage to structures, roads, utilities, livestock and crops. This report contains an analysis of areas susceptible to debris flows including an examination of source areas, channels and areas of deposition. These analyses are used to develop a methodology for identifying areas subject to debris-flow hazards in Madison County. The report concludes with a discussion of strategies for reducing debris-flow hazards and the long term risk of these hazards in Madison County as well as for similar areas along the eastern flank of the Blue Ridge.

  14. Effects of Recent Debris Flows on Stream Ecosystems and Food Webs in Small Watersheds in the Central Klamath Mountains, NW California

    NASA Astrophysics Data System (ADS)

    Cover, M. R.; de La Fuente, J.

    2008-12-01

    Debris flows are common erosional processes in steep mountain areas throughout the world, but little is known about the long-term ecological effects of debris flows on stream ecosystems. Based on debris flow histories that were developed for each of ten tributary basins, we classified channels as having experienced recent (1997) or older (pre-1997) debris flows. Of the streams classified as older debris flow streams, three streams experienced debris flows during floods in 1964 or 1974, while two streams showed little or no evidence of debris flow activity in the 20th century. White alder (Alnus rhombifolia) was the dominant pioneer tree species in recent debris flow streams, forming localized dense patches of canopy cover. Maximum temperatures and daily temperature ranges were significantly higher in recent debris flow streams than in older debris flow streams. Debris flows resulted in a shift in food webs from allochthonous to autochthonous energy sources. Primary productivity, as measured by oxygen change during the day, was greater in recent debris flow streams, resulting in increased abundances of grazers such as the armored caddisfly Glossosoma spp. Detritivorous stoneflies were virtually absent in recent debris flow streams because of the lack of year-round, diverse sources of leaf litter. Rainbow trout (Oncorhynchus mykiss) were abundant in four of the recent debris flow streams. Poor recolonizers, such as the Pacific giant salamander (Dicamptodon tenebrosus), coastal tailed frog (Ascaphus truei), and signal crayfish (Pacifistacus leniusculus), were virtually absent in recent debris flow streams. Forest and watershed managers should consider the role of forest disturbances, such as road networks, on debris flow frequency and intensity, and the resulting ecological effects on stream ecosystems.

  15. Trace projection transformation: A new method for measurement of debris flow surface velocity fields

    NASA Astrophysics Data System (ADS)

    Yan, Yan; Cui, Peng; Guo, Xiaojun; Ge, Yonggang

    2016-09-01

    Spatiotemporal variation of velocity is important for debris flow dynamics. This paper presents a new method, the trace projection transformation, for accurate, non-contact measurement of a debris-flow surface velocity field based on a combination of dense optical flow and perspective projection transformation. The algorithm for interpreting and processing is implemented in C ++ and realized in Visual Studio 2012. The method allows quantitative analysis of flow motion through videos from various angles (camera positioned at the opposite direction of fluid motion). It yields the spatiotemporal distribution of surface velocity field at pixel level and thus provides a quantitative description of the surface processes. The trace projection transformation is superior to conventional measurement methods in that it obtains the full surface velocity field by computing the optical flow of all pixels. The result achieves a 90% accuracy of when comparing with the observed values. As a case study, the method is applied to the quantitative analysis of surface velocity field of a specific debris flow.

  16. Vadose zone process that control landslide initiation and debris flow propagation

    NASA Astrophysics Data System (ADS)

    Sidle, Roy C.

    2015-04-01

    Advances in the areas of geotechnical engineering, hydrology, mineralogy, geomorphology, geology, and biology have individually advanced our understanding of factors affecting slope stability; however, the interactions among these processes and attributes as they affect the initiation and propagation of landslides and debris flows are not well understood. Here the importance of interactive vadose zone processes is emphasized related to the mechanisms, initiation, mode, and timing of rainfall-initiated landslides that are triggered by positive pore water accretion, loss of soil suction and increase in overburden weight, and long-term cumulative rain water infiltration. Both large- and small-scale preferential flow pathways can both contribute to and mitigate instability, by respectively concentrating and dispersing subsurface flow. These mechanisms are influenced by soil structure, lithology, landforms, and biota. Conditions conducive to landslide initiation by infiltration versus exfiltration are discussed relative to bedrock structure and joints. The effects of rhizosphere processes on slope stability are examined, including root reinforcement of soil mantles, evapotranspiration, and how root structures affect preferential flow paths. At a larger scale, the nexus between hillslope landslides and in-channel debris flows is examined with emphasis on understanding the timing of debris flows relative to chronic and episodic infilling processes, as well as the episodic nature of large rainfall and related stormflow generation in headwater streams. The hydrogeomorphic processes and conditions that determine whether or not landslides immediately mobilize into debris flows is important for predicting the timing and extent of devastating debris flow runout in steep terrain. Given the spatial footprint of individual landslides, it is necessary to assess vadose zone processes at appropriate scales to ascertain impacts on mass wasting phenomena. Articulating the appropriate

  17. High frequency seismic monitoring of debris flows at Chalk Cliffs (CO), USA

    NASA Astrophysics Data System (ADS)

    Coviello, Velio; Kean, Jason; Smith, Joel; Coe, Jeffrey; Arattano, Massimo; McCoy, Scott

    2015-04-01

    A growing number of studies adopt passive seismic monitoring techniques to investigate slope instabilities and landslide processes. These techniques are attractive and convenient because large areas can be monitored from a safe distance. This is particularly true when the phenomena under investigation are rapid and infrequent mass movements like debris flows. Different types of devices are used to monitor debris flow processes, but among them ground vibration detectors (GVDs) present several, specific advantages that encourage their use. These advantages include: (i) the possibility to be installed outside the channel bed, (ii) the high adaptability to different and harsh field conditions, and (iii) the capability to detect the debris flow front arrival tens of seconds earlier than contact and stage sensors. Ground vibration data can provide relevant information on the dynamics of debris flows such as timing and velocity of the main surges. However, the processing of the raw seismic signal is usually needed, both to obtain a more effective representation of waveforms and to decrease the amount of data that need to be recorded and analyzed. With this objective, the methods of Amplitude and Impulses are commonly adopted to transform the raw signal to a 1-Hz signal that allows for a more useful representation of the phenomenon. In that way, peaks and other features become more visible and comparable with data obtained from other monitoring devices. In this work, we present the first debris flows seismic recordings gathered in the Chalk Cliffs instrumented basin, central Colorado, USA. In May 2014, two 4.5-Hz, three-axial geophones were installed in the upper part of the catchment. Seismic data are sampled at 333 Hz and then recorded by a standalone recording unit. One geophone is directly installed on bedrock, the other one mounted on a 1-m boulder partially buried in colluvium. This latter sensor integrates a heavily instrumented cross-section consisting of a 225 cm2

  18. Using AVIRIS hyperspectral imagery to study the role of clay mineralogy in Colorado Plateau debris-flow initiation

    NASA Astrophysics Data System (ADS)

    Rudd, Lawrence Parker

    2005-11-01

    The debris-flow initiation variable of clay mineralogy is examined for Holocene age debris-flow deposits across the Colorado Plateau. A Kolmogorov-Smirnov two-sample test between 25 debris-flow producing shale units and 23 shale units rated as not producing debris-flows found a highly significant difference between shale unit kaolinite-illite and montmorillonite clay content. Debris-flow producers tend to have abundant kaolinite and illite (61.5% of clays) and small amounts of montmorillonite (10.4%). Clay sample soluble cation (Na, Ca, K, and Mg) content could not be used to accurately divide the data set into debris-flow producers and debris-flow non-producers by either cluster analysis or a Kolmogorov-Smirnov two-sample test. AVIRIS hyperspectral data reveal that debris-flow deposits, colluvium, and some shale units in Cataract Canyon, Utah display the double-absorption feature characteristic of kaolinite at 2.2 mum. Lab-based reflection spectra and semi-quantitative x-ray diffraction results show that Cataract Canyon debris-flow matrix clays are dominated by kaolinite and illite and lacking in montmorillonite. A surface material map showing the spectral stratigraphy of the study area was created from AVIRIS data classified using an artificial neural network and compares favorably to existing geologic data for Cataract Canyon. A debris-flow initiation potential map created from a GIS-based analysis of surface materials, slope steepness, slope aspect, and fault maps shows the greatest debris-flow initiation potential in the study area to coincide with outcrops of the Moenkopi Formation on steep (>20%), southwest-facing slopes. Small areas of extreme debris-flow initiation potential are located where kaolinite and illite clay-rich colluvial wedges are located on southwest-facing walls of Colorado River tributary canyons. The surface materials map shows formations clearly when they remain relatively consistent in composition and exposure throughout the study area

  19. Radar-based observatiions of variable thickness debris cover on martian ice masses: evidence of debris transfer by flowing ice on Mars

    NASA Astrophysics Data System (ADS)

    Souness, Colin; Brough, Stephen; Woodward, John; Hubbard, Bryn; Davis, Joel; Grindrod, Peter

    2016-04-01

    The mid-latitudes of Mars host a wide range of ice-based landforms, many of which display surface morphologies indicative of viscous flow of that ice. Despite being shrouded beneath a layer of rocky debris, these viscous flow features (VFFs) are thought to have similarities with terrestrial glaciers. Until recently most studies that focussed on the origin, structure and role of these martian VFFs were restricted to observations made from satellite imagery. Little data have been available to gain a clearer picture of VFF internal structure, which has impeded our collective ability to infer many particulars of VFF growth and flow, including the extent to which these ice flows have interacted with, and potentially helped shape, the martian landscape. However, the Shallow Radar (SHARAD) system mounted on the Mars Reconnaissance Orbiter (MRO) can, in some cases, provide a valuable insight into what lies beneath the surface of these ice masses. We present a SHARAD-based study of glacial systems on Mars which reveals pronounced heterogeneity in the thickness of their observed superficial debris covers. The surface debris layers in question appear to thicken in a down-slope direction. Radar data indicates that in the lower reaches of each studied glacial catchment, ice surface debris cover exceeds 10 m in thickness. The observed flow-parallel a-symmetry in debris thickness atop these martian glaciers is similar to that recorded on many terrestrial glaciers, indicating that cumulative down-flow debris mass transfer such as occurs within glacierised catchments on Earth may also currently operate, or have operated, on Mars. This suggests that glaciers on Mars have played a substantial role in redistributing lithic material from mountainous catchments to lower-lying areas, potentially throughout the glacial regions of Mars' mid-latitudes, thus making an important processual contribution to the evolution of Mars' contemporary landscape.

  20. Effective mitigation of debris flows at Lemon Dam, La Plata County, Colorado

    USGS Publications Warehouse

    deWolfe, V.G.; Santi, P.M.; Ey, J.; Gartner, J.E.

    2008-01-01

    To reduce the hazards from debris flows in drainage basins burned by wildfire, erosion control measures such as construction of check dams, installation of log erosion barriers (LEBs), and spreading of straw mulch and seed are common practice. After the 2002 Missionary Ridge Fire in southwest Colorado, these measures were implemented at Knight Canyon above Lemon Dam to protect the intake structures of the dam from being filled with sediment. Hillslope erosion protection measures included LEBs at concentrations of 220-620/ha (200-600% of typical densities), straw mulch was hand spread at concentrations up to 5.6??metric tons/hectare (125% of typical densities), and seeds were hand spread at 67-84??kg/ha (150% of typical values). The mulch was carefully crimped into the soil to keep it in place. In addition, 13 check dams and 3 debris racks were installed in the main drainage channel of the basin. The technical literature shows that each mitigation method working alone, or improperly constructed or applied, was inconsistent in its ability to reduce erosion and sedimentation. At Lemon Dam, however, these methods were effective in virtually eliminating sedimentation into the reservoir, which can be attributed to a number of factors: the density of application of each mitigation method, the enhancement of methods working in concert, the quality of installation, and rehabilitation of mitigation features to extend their useful life. The check dams effectively trapped the sediment mobilized during rainstorms, and only a few cubic meters of debris traveled downchannel, where it was intercepted by debris racks. Using a debris volume-prediction model developed for use in burned basins in the Western U.S., recorded rainfall events following the Missionary Ridge Fire should have produced a debris flow of approximately 10,000??m3 at Knight Canyon. The mitigation measures, therefore, reduced the debris volume by several orders of magnitude. For comparison, rainstorm

  1. Effective mitigation of debris flows at Lemon Dam, La Plata County, Colorado

    NASA Astrophysics Data System (ADS)

    deWolfe, Victor G.; Santi, Paul M.; Ey, J.; Gartner, Joseph E.

    2008-04-01

    To reduce the hazards from debris flows in drainage basins burned by wildfire, erosion control measures such as construction of check dams, installation of log erosion barriers (LEBs), and spreading of straw mulch and seed are common practice. After the 2002 Missionary Ridge Fire in southwest Colorado, these measures were implemented at Knight Canyon above Lemon Dam to protect the intake structures of the dam from being filled with sediment. Hillslope erosion protection measures included LEBs at concentrations of 220-620/ha (200-600% of typical densities), straw mulch was hand spread at concentrations up to 5.6 metric tons/hectare (125% of typical densities), and seeds were hand spread at 67-84 kg/ha (150% of typical values). The mulch was carefully crimped into the soil to keep it in place. In addition, 13 check dams and 3 debris racks were installed in the main drainage channel of the basin. The technical literature shows that each mitigation method working alone, or improperly constructed or applied, was inconsistent in its ability to reduce erosion and sedimentation. At Lemon Dam, however, these methods were effective in virtually eliminating sedimentation into the reservoir, which can be attributed to a number of factors: the density of application of each mitigation method, the enhancement of methods working in concert, the quality of installation, and rehabilitation of mitigation features to extend their useful life. The check dams effectively trapped the sediment mobilized during rainstorms, and only a few cubic meters of debris traveled downchannel, where it was intercepted by debris racks. Using a debris volume-prediction model developed for use in burned basins in the Western U.S., recorded rainfall events following the Missionary Ridge Fire should have produced a debris flow of approximately 10,000 m 3 at Knight Canyon. The mitigation measures, therefore, reduced the debris volume by several orders of magnitude. For comparison, rainstorm-induced debris

  2. Development of a debris-flow monitoring system in the Réal Torrent (Southern French Alps)

    NASA Astrophysics Data System (ADS)

    Navratil, O.; Liébault, F.; Travaglini, E.; Bellot, H.; Theule, J. I.; Ravanat, X.; Ousset, F.; Laigle, D.; Segel, V.; Ficquet, M.

    2011-12-01

    Small upland catchments in degraded terrains are prone to debris-flows which may endanger the safety of life and infrastructure in the vicinity of torrent channels. These flows mobilise high sediment loads and they are often responsible for most of the sediment yield from upland headwaters. Despite their importance in terms of natural hazard prevention and sediment management in upland catchments, our understanding of the mechanisms that control debris-flow initiation, propagation and deposition is still largely insufficient. This is partly explained by the paucity of field observation programs dedicated to channelized debris-flows. Such programs need to overcome several difficulties related to the nature of the phenomena: debris-flows are rapid, short-lasting, rare and destructive events that need a sophisticated and robust monitoring strategy to guarantee a performing reconstitution of natural processes. Over the last 20 years, increasing efforts have been undertaken in Europe, United States and Asia to develop high-frequency debris-flow monitoring stations. In France, despite the presence of very active debris-flow torrents and a long historical legacy of torrent-control works, there is not any instrumented torrent dedicated to the study of debris-flow. Moreover, monitoring programs generally focus on station location flow properties (velocity, stage, shear strength) mainly located in the vicinity of hillslope sources; but they rarely emphasized the downstream changing nature of a debris-flow and its interactions with the torrent channel morphology. To address this issue, a very active debris-flow torrent located in Southern French Alps, the Réal Torrent (2.3 km2), have been equipped with 3 monitoring stations in late 2010. In this contribution, we present the research aims, the main characteristics of the torrent and the first results. A detailed presentation of the deployed equipments and monitoring system is proposed. Debris-flow monitoring systems are based

  3. Hydrologic and Geomorphologic Assessment of Debris Flow Events for Mount Hood Highway

    NASA Astrophysics Data System (ADS)

    Armstrong, A.

    2003-04-01

    A hydrologic and geomorphologic assessment was performed for past debris flows events for Mount Hood Highway. This highway is located on the eastern and southern flank of the Mount Hood, a dormant volcano that is part of Cascade Range in Oregon State in western United States. There are at least twelve glaciers or named snowfields located on Mount Hood containing approximately 0.35 cubic kilometers of ice. Various streams crossing this highway have glacial origin and the glacial-melt provides majority of discharge. The highway crossings, bridges or culverts, on these streams have routinely suffered severe damage due to debris flows. This paper presents assessment for two stream drainages, White River and Pollalie Creek. The primary objective of this assessment was to select a design alternative with least total life cycle cost. A range of alternatives, including relocation of the highway, were considered. Glacial outbursts and associated lahar events on Mount Hood can generate peak discharges that are one to two orders of magnitude larger than seasonal peak flow discharge. Additionally, debris flows associated with these events have the potential to permanently alter the channel morphologies of streams that emanate from the upper reaches of the mountain. A number of triggering mechanisms, including glacial, geothermal, and meteorological, have been suggested as the cause of these events; however, a strong correlation between cause and effect has not been identified. Major streams such as White River, Newton Creek, and Clark Creek, whose headwaters are located at glacier termini, can become laden with debris flow material and inflict severe damage to highway structures located downstream. These structures are typically designed to pass a specific calculated peak discharge for rain-on-snow events and are not hardened or sized to withstand the forces of these extreme debris flows. During this assessment it was evident that conventional hydrologic methods, regression

  4. Influence of topography on debris flow development in Ichino-sawa subwatershed of Ohya-kuzure landslide, Japan

    NASA Astrophysics Data System (ADS)

    Tsunetaka, H.; Hotta, N.; Imaizumi, F.; Hayakawa, Y. S.

    2015-12-01

    Large sediment movements, such as deep-seated landslides, produce unstable sediment over the long term. Most of the unstable sediment in a mountain torrent is discharged via the development of debris flows through entrainment. Consequently, after a large sediment movement, debris flows have long-term effects on the watershed regime. However, the development of debris flows in mountain torrents is poorly understood, since the topography is more complicated than downstream. We compared temporal changes in topography to examine how topography affects the development of flows. The study site was the Ichino-sawa subwatershed in the Ohya-kuzure landslide, Japan. Unstable sediment has been produced continuously since the landslide occurred in 1707. Several topographic surveys using a terrestrial laser scanner (TLS) and aerial shoots by an unmanned aerial vehicle (UAV) were performed between November 2011 (TLS) or November 2014 (UAV) and August 2015. High-resolution digital elevation models were created from the TLS and UAV results to detect temporal topographic changes. Debris flow occurrences and rainfall were also monitored using interval cameras and rain gauges. Downstream, the deposit depth decreased after the debris flows. Upstream, more complex changes were detected due to surges in the debris flows, which not only induced entrainment, but were also deposited in the valley floor. Furthermore, sediment was supplied from the stream bank during the debris flows. Consequently, several debris flows of different magnitudes were observed, although the rainfall conditions did not differ significantly. The results imply that the magnitude of the debris flows was affected by successive sediment movement resulting from the changing of the topographic conditions.

  5. Andic soil features and debris flows in Italy. New perspective towards prediction

    NASA Astrophysics Data System (ADS)

    Scognamiglio, Solange; Calcaterra, Domenico; Iamarino, Michela; Langella, Giuliano; Orefice, Nadia; Vingiani, Simona; Terribile, Fabio

    2016-04-01

    Debris flows are dangerous hazards causing fatalities and damage. Previous works have demonstrated that the materials involved by debris flows in Campania (southern Italy) are soils classified as Andosols. These soils have peculiar chemical and physical properties which make them fertile but also vulnerable to landslide. In Italy, andic soil properties are found both in volcanic and non-volcanic mountain ecosystems (VME and NVME). Here, we focused on the assessment of the main chemical and physical properties of the soils in the detachment areas of eight debris flows occurred in NVME of Italy in the last 70 years. Such landslides were selected by consulting the official Italian geodatabase (IFFI Project). Andic properties (by means of ammonium oxalate extractable Fe, Si and Al forms for the calculation of Alo+1/2Feo) were also evaluated and a comparison with soils of VME was performed to assess possible common features. Landslide source areas were characterised by slope gradient ranging from 25° to 50° and lithological heterogeneity of the bedrock. The soils showed similar, i.e. all were very deep, had a moderately thick topsoil with a high organic carbon (OC) content decreasing regularly with depth. The cation exchange capacity trend was generally consistent with the OC and the pH varied from extremely to slightly acid, but increased with depth. Furthermore, the soils had high water retention values both at saturation (0.63 to 0.78 cm3 cm‑3) and in the dryer part of the water retention curve, and displayed a prevalent loamy texture. Such properties denote the chemical and physical fertility of the investigated ecosystems. The values of Alo+1/2Feoindicated that the soils had vitric or andic features and can be classified as Andosols. The comparison between NVME soils and those of VME showed similar depth, thickness of soil horizons, and family texture, whereas soil pH, degree of development of andic properties and allophane content were higher for VME soils

  6. Andic soil features and debris flows in Italy. New perspective towards prediction

    NASA Astrophysics Data System (ADS)

    Scognamiglio, Solange; Calcaterra, Domenico; Iamarino, Michela; Langella, Giuliano; Orefice, Nadia; Vingiani, Simona; Terribile, Fabio

    2016-04-01

    Debris flows are dangerous hazards causing fatalities and damage. Previous works have demonstrated that the materials involved by debris flows in Campania (southern Italy) are soils classified as Andosols. These soils have peculiar chemical and physical properties which make them fertile but also vulnerable to landslide. In Italy, andic soil properties are found both in volcanic and non-volcanic mountain ecosystems (VME and NVME). Here, we focused on the assessment of the main chemical and physical properties of the soils in the detachment areas of eight debris flows occurred in NVME of Italy in the last 70 years. Such landslides were selected by consulting the official Italian geodatabase (IFFI Project). Andic properties (by means of ammonium oxalate extractable Fe, Si and Al forms for the calculation of Alo+1/2Feo) were also evaluated and a comparison with soils of VME was performed to assess possible common features. Landslide source areas were characterised by slope gradient ranging from 25° to 50° and lithological heterogeneity of the bedrock. The soils showed similar, i.e. all were very deep, had a moderately thick topsoil with a high organic carbon (OC) content decreasing regularly with depth. The cation exchange capacity trend was generally consistent with the OC and the pH varied from extremely to slightly acid, but increased with depth. Furthermore, the soils had high water retention values both at saturation (0.63 to 0.78 cm3 cm-3) and in the dryer part of the water retention curve, and displayed a prevalent loamy texture. Such properties denote the chemical and physical fertility of the investigated ecosystems. The values of Alo+1/2Feoindicated that the soils had vitric or andic features and can be classified as Andosols. The comparison between NVME soils and those of VME showed similar depth, thickness of soil horizons, and family texture, whereas soil pH, degree of development of andic properties and allophane content were higher for VME soils. Such

  7. The Montesbelos mass-flow (southern Amazonian craton, Brazil): a Paleoproterozoic volcanic debris avalanche deposit?

    NASA Astrophysics Data System (ADS)

    Roverato, M.

    2016-07-01

    The present contribution documents the extremely well-preserved Paleoproterozoic architecture of the Montesbelos breccia (named here for the first time), which is interpreted as a rare example of a subaerial paleoproterozoic (>1.85 Ga) granular-dominated mass-flow deposit, few of which are recorded in the literature. Montesbelos deposit is part of the andesitic Sobreiro Formation located in the São Felix do Xingu region, southern Amazonian craton, northern Brazil. The large volume, high variability of textural features, presence of broken clasts, angular low sphericity fragments, mono- to heterolithic character, and the size of the outcrops point to a volcanic debris avalanche flow. Fluviatile sandy material and debris flows are associated with the deposit as a result of post-depositional reworking processes.

  8. Emergency assessment of post-fire debris-flow hazards for the 2013 Mountain fire, southern California

    USGS Publications Warehouse

    Staley, Dennis M.; Gartner, Joseph E.; Smoczyk, Greg M.; Reeves, Ryan R.

    2013-01-01

    Wildfire dramatically alters the hydrologic response of a watershed such that even modest rainstorms can produce dangerous flash floods and debris flows. We use empirical models to predict the probability and magnitude of debris flow occurrence in response to a 10-year rainstorm for the 2013 Mountain fire near Palm Springs, California. Overall, the models predict a relatively high probability (60–100 percent) of debris flow for six of the drainage basins in the burn area in response to a 10-year recurrence interval design storm. Volumetric predictions suggest that debris flows that occur may entrain a significant volume of material, with 8 of the 14 basins identified as having potential debris-flow volumes greater than 100,000 cubic meters. These results suggest there is a high likelihood of significant debris-flow hazard within and downstream of the burn area for nearby populations, infrastructure, and wildlife and water resources. Given these findings, we recommend that residents, emergency managers, and public works departments pay close attention to weather forecasts and National Weather Service–issued Debris Flow and Flash Flood Outlooks, Watches and Warnings and that residents adhere to any evacuation orders.

  9. Emergency Assessment of Debris-Flow Hazards from Basins Burned by the Padua Fire of 2003, Southern California

    USGS Publications Warehouse

    Cannon, Susan H.; Gartner, Joseph E.; Rupert, Michael G.; Michael, John A.

    2004-01-01

    Results of a present preliminary assessment of the probability of debris-flow activity and estimates of peak discharges that can potentially be generated by debris flows issuing from basins burned by the Padua Fire of October 2003 in southern California in response to 25-year, 10-year, and 2-year recurrence, 1-hour duration rain storms are presented. The resulting probability maps are based on the application of a logistic multiple-regression model (Cannon and others, 2004) that describes the percent chance of debris-flow production from an individual basin as a function of burned extent, soil properties, basin gradients, and storm rainfall. The resulting peak discharge maps are based on application of a multiple-regression model (Cannon and others, 2004) that can be used to estimate debris-flow peak discharge at a basin outlet as a function of basin gradient, burn extent, and storm rainfall. Probabilities of debris-flow occurrence for the Padua Fire range between 0 and 99% and estimates of debris-flow peak discharges range between 1211 and 6,096 ft3/s (34 to 173 m3/s). These maps are intended to identify those basins that are most prone to the largest debris-flow events and provide information for the preliminary design of mitigation measures and for the planning of evacuation timing and routes.

  10. Instrumental record of debris flow initiation during natural rainfall: Implications for modeling slope stability

    USGS Publications Warehouse

    Montgomery, D.R.; Schmidt, K.M.; Dietrich, W.E.; McKean, J.

    2009-01-01

    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 hydrologie 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 hydrologie conditions within incipient debris flows under natural conditions. Copyright 2009 by the American Geophysical Union.

  11. Regional debris flow susceptibility analysis in mountainous peri-urban areas through morphometric and land cover indicators

    NASA Astrophysics Data System (ADS)

    Rogelis, M. C.; Werner, M.

    2014-11-01

    A method for assessing regional debris flow susceptibility at the watershed scale, based on an index composed of a morphometric indicator and a land cover indicator, is proposed and applied in 106 peri-urban mountainous watersheds in Bogotá, Colombia. The indicator of debris flow susceptibility is obtained from readily available information common to most peri-urban mountainous areas and can be used to prioritise watersheds that can subsequently be subjected to detailed hazard analysis. Susceptibility is considered to increase with flashiness and the possibility of debris flows occurring. Morphological variables recognised in the literature to significantly influence flashiness and occurrence of debris flows are used to construct the morphometric indicator by applying principal component analysis. Subsequently, this indicator is compared with the results of debris flow propagation to assess its capacity in identifying the morphological conditions of a watershed that make it able to transport debris flows. Propagation of debris flows was carried out using the Modified Single Flow Direction algorithm, following identification of source areas by applying thresholds identified in the slope-area curve of the watersheds. Results show that the morphometric variables can be grouped into four indicators: size, shape, hypsometry and (potential) energy, with energy being the component that best explains the capability of a watershed to transport debris flows. However, the morphometric indicator was found to not sufficiently explain the records of past floods in the study area. Combining the morphometric indicator with land cover indicators improved the agreement and provided a more reliable assessment of debris flow susceptibility in the study area. The analysis shows that, even if morphometric parameters identify a high disposition to the occurrence of debris flow, improving land cover can reduce the susceptibility. However, if favourable morphometric conditions are present

  12. Debris-flow susceptibility and hazard assessment at a regional scale from GIS analysis

    NASA Astrophysics Data System (ADS)

    Bertrand, M.; Liébault, F.; Piégay, H.

    2012-12-01

    Small torrents of the Southern French Alps are prone to extreme events. Depending on the rainfall conditions, the sediment supply from hillslopes, and the gravitational energy, these events can occur under different forms, from floods to debris-flows. Debris-flows are recognized as the most dangerous phenomena and may have dramatic consequences for exposed people and infrastructures. As a first step of hazard assessment, we evaluated the debris-flow susceptibility, i.e. the likelihood that an event occurs in an area under particular physical conditions, not including the temporal dimension. The susceptibility is determined by (i) the morphometric controls of small upland catchments for debris-flows triggering and propagation, and by (ii) sediment supply conditions, i.e. erosion patterns feeding the channels. The morphometric controls are evaluated with indicators calculated from basic topographic variables. The sediment supply is evaluated by considering the cumulated surface of erosion area connected to the hydrographic network. We developed a statistical model to predict the geomorphic responses of the catchments (fluvial vs. debris-flow) and we apply this model within a GIS for regional-scale prediction. The model is based on two morphometric indicators, i.e. fan / channel slope and the Melton ruggedness index, and is based on a wide set of data including the Southern French Alps. We developed a GIS procedure to extract the indicators automatically using a 25m DEM and the hydrographic network as raw data. This model and its application have been validated with historical data. Sediment sources feeding debris-flow prone torrents are identified by first automatically mapping the erosion patches from the infrared orthophotos analysis then identifying the ones connected to the stream network. A classification method has been developed (segmentation into homogeneous objects classified with a neural network algorithm) and validated with expert interpretation on the

  13. Satellite-rainfall estimation for identification of rainfall thresholds used for landslide/debris flow prediction

    NASA Astrophysics Data System (ADS)

    Maggioni, Viviana; Nikolopoulos, Efthymios I.; Marra, Francesco; Destro, Elisa; Borga, Marco

    2016-04-01

    Rainfall-induced landslides and debris flows pose a significant and widespread hazard, resulting in a large number of casualties and enormous economic damages worldwide. Rainfall thresholds are often used to identify the local or regional rainfall conditions that, when reached or exceeded, are likely to result in landslides or debris flows. Rain gauge data are the typical source of information for the definition of these rainfall thresholds. However, in-situ observations over mountainous areas, where these hazards mainly occur, are very sparse or inexistent. Therefore identification and use of gauge-based rainfall thresholds is impossible in many landslide prone areas over the globe. The vast advancements in satellite-based precipitation estimation over the last couple of decades have lead to the creation of a number of global precipitation datasets at various spatiotemporal resolutions. Although several investigations have shown that these datasets can be associated with considerable uncertainty, they provide the only source of precipitation information over many areas around the globe. Therefore it is important to assess their performance in the context of landslide/debris flow prediction and investigate how we can potentially benefit from the information they provide. In this work, we evaluate the performance of three widely used quasi-global satellite precipitation products (3B42v7, PERSIANN and CMORPH) for the identification of rainfall threshold for landslide/debris flow triggering. Products are available at 0.25deg/3h resolution. The study region is focused over the Upper Adige river basin, northern Italy where a detailed database of more than 400 identified debris flows (during period 2000-2015) and a raingauge network of 95 stations, is available. Rain-gauge based rainfall thresholds are compared against satellite-based thresholds to evaluate strengths and limitations in using satellite precipitation estimates for defining rainfall thresholds. Analysis of

  14. Monitoring of debris flows and landslides by wired and wireless systems. Experiences from the Catalan Pyrenees.

    NASA Astrophysics Data System (ADS)

    Hürlimann, Marcel; Abancó, Clàudia; Moya, José; Vilajosana, Ignasi; Llosa, Jordi

    2013-04-01

    Sophisticated monitoring of landslides for research purpose has started in the 1990thies in the Catalan Pyrenees. Since then several types of mass movements (large landslides, debris flows, shallow landslides and rock falls) and multiples techniques have been applied. In this contribution, special attention will be given to the debris-flow monitoring system installed since summer 2009 in the Rebaixader catchment, Central Pyrenees. The monitoring system has continuously been improved during the last years and nowadays includes devices studying the three major aspects: 1) initiation, 2) flow dynamics, and 3) accumulation. While some parts of the monitoring network include a traditional wired system, the newer parts were installed using low-power wireless devices. Two major aspects will be discussed. First, results of the Rebaixader monitoring site will be presented. Second, experience regarding the monitoring will be evaluated focussing on technical aspects and the comparison between wired and wireless techniques. In the Rebaixader catchment, 6 debris flows and 11 debris floods were observed between August 2009 and October 2012. Surprisingly, also 4 major rock falls were recorded. The rainfall analysis shows that the debris flows were triggered by short, high-intensity rainstorms with a preliminary threshold of about 15 mm during 1 hour. In addition, there was observed a positive trend between event volume and rainfall amount or intensity. The analysis of the ground vibration signals shows significant differences between the time series recorded at the different geophones. These differences are associated with the geophone location in the channel (distance and material), the mounting or the data acquisition system. For instance, the most downstream geophone, installed in bedrock, shows the clearest debris-flows vibration time series, while the uppermost is the most reliable regarding the detection of rockfalls. An evaluation of wired versus wireless monitoring

  15. Sedimentology of Holocene debris flow-dominated alluvial fans, northwest Wyoming: Contributions to alluvial fan facies models

    SciTech Connect

    Cechovic, M.T.; Schmitt, J.G. . Dept. of Earth Sciences)

    1993-04-01

    Facies models for debris flow-dominated alluvial fans are based exclusively upon studies of relatively few fans in the arid American southwest. Detailed geomorphic, stratigraphic, and sedimentologic analyses of several highly-active, debris flow-dominated alluvial fans in northern Yellowstone National Park, WY (temperature, semi-arid) serve to diversify and increase the usefulness of alluvial fan facies models. These fans display an intricate distributary pattern of incised active (0--6 m deep; 700--900 m long) and abandoned channels (1--4 m deep; 400 m long) with levees/levee complexes (<3 m high; <20 m wide; <750 m long) and lobes constructed by pseudoplastic to plastic debris flows. The complex pattern of debris flow deposits is due to repeated channel back filling and overtopping by debris flows behind in-channel obstructions which subsequently lead to channel abandonment. Debris-flow deposition is dominant due to: (1) small, steep (up to 35 degrees) source area catchments, (2) extensive mud rock outcrops in the source area, and (3) episodic summer rainfall events. Proximal to distal fan surfaces exhibit sheetflood deposits several cm thick and up to 70 m in lateral extent. Vertical lithofacies profiles reveal: (1) massive, matrix- and clast-supported gravel units (1--2 m thick) deposited by clast-poor and clast-rich debris flows respectively, with reworked; scoured tops overlain by thin (<0.25 m) trough cross-bedded gravel and ripple cross-laminated sand intervals, and (2) volumetrically less significant 1--2 m thick intervals comprising fining-upward sequences of interbedded cm-scale trough cross-bedded pebbly gravel, massive sand, horizontally stratified sand, and mud rock deposited by hyperconcentrated flow and stream flow during decelerating sheetflood events. Organic rich layers record periods of non-deposition. Channelized stream flow is restricted to minor reworking of in-channel debris flow and hyperconcentrated flow deposits.

  16. Debris-flow deposits in an alluvial-plain succession: The upper Triassic Callide coal measures of Queensland, Australia

    SciTech Connect

    Jorgensen, P.J.; Fielding, C.R.

    1999-09-01

    The Carnian-Rhaetian Callide Coal Measures are preserved in a small (22.5 km by 8 km), partially fault-bounded basin remnant in east-central Queensland, Australia. The <150 m thick coal-measure succession is interpreted to have accumulated during a phase of mild crustal extension that formed a series of discrete, intermontane basins in eastern Australia. The succession fines upward from a conglomerate-rich lower part into a finer-grained and coal-bearing upper section (including coal seams <34 m thick), and is interpreted as the deposits of an alluvial-plain environment. Anomalous, matrix-rich diamictites, breccias, and conglomerates have been recognized within the succession at several localities, in many cases interbedded with coals. These are interpreted as the product of debris flows. Two debris-flow lithofacies are recognized: (1) mixtures of fine carbonaceous material, clay, silt, sand, gravel, and volcaniclastic debris, and (2) breccias consisting principally of coal clasts in a coaly matrix with minor clastic and volcaniclastic debris. The distribution of debris flows in the Callide Coal Measures shows a coincidence with mapped faults and interpreted structural lineaments. The debris flows may have been triggered by fault movements, which formed rupture topography on the flat alluvial plain, and caused destabilization of water-saturated clastic and organic sediments. Some debris-flow bodies may have been mounded, such that subsequent peat formation was restricted until those bodies were buried. The preservation of debris-flow units at different stratigraphic levels along mapped structures suggests multiple paleoseismic events or multiple debris-flow units at different stratigraphic levels along mapped structures suggests multiple paleoseismic events or multiple debris-flow events along those structures. The mixing of volcaniclastic debris into debris-flow facies suggests that seismic events were coincident with (or perhaps caused by) nearby, explosive

  17. Laboratory experiments investigating entrainment by debris flows and associated increased mobility

    NASA Astrophysics Data System (ADS)

    Moberly, D.; Maki, L.; Hill, K. M.

    2014-12-01

    As debris flows course down a steep hillside they entrain bed materials such as loose sediments. The entrainment of materials not only increases the size of the debris flows but the mobility as well. The mechanics underlying the particle entrainment and the associated increased mobility are not well-understood. Existing models for the entrainment process include those that explicitly consider stress ratios, the angle of inclination, and the particle fluxes relative to those achieved under steady conditions. Others include an explicit consideration of the physics of the granular state: the visco-elastic nature of particle flows and, alternatively, the role of macroscopic force chains. Understanding how well these different approaches account for entrainment and deposition rates is important for accurate debris flow modeling, both in terms of the rate of growth and also in terms of the increased mobility associated with the entrainment. We investigate how total and instantaneous entrainment and deposition vary with macroscopic stresses and particle-scale interactions for different particle sizes and different fluid contents using laboratory experiments in an instrumented experimental laboratory debris flow flume. The flume has separate, independent water supplies for the bed and "supply" (parent debris flow), and the bed is instrumented with pore pressure sensors and a basal stress transducer. We monitor flow velocities, local structure, and instantaneous entrainment and deposition rates using a high speed camera. We have found that systems with a mixture of particle sizes are less erosive and more depositional than systems of one particle size under otherwise the same conditions. For both mixtures and single-sized particle systems, we have observed a relatively linear relationship between total erosion and the slope angle for dry flows. Increasing fluid content typically increases entrainment. Measurements of instantaneous entrainment indicate similar dependencies

  18. Joint NOAA/NWS/USGS prototype debris flow warning system for recently burned areas in Southern California

    USGS Publications Warehouse

    Restrepo, P.; Jorgensen, D.P.; Cannon, S.H.; Costa, J.; Laber, J.; Major, J.; Martner, B.; Purpura, J.; Werner, K.

    2008-01-01

    Debris flows, also known as mudslides, are composed gravity-driven mixtures of sediment and water that travel through steep channels, over open hillslopes, and the like. Addressing this issue, US Geological Survey (USGS) and NOAA have established a debris-flow warning system that has the ability to monitor and forecast precipitation and issue timely weather hazard warning. In 2005, this joint NOAA-USGS prototype debris-flow warning system was issued in Southern California and as a result, it has provided valuable information to emergency managers in affected communities.

  19. Empirical models to predict the volumes of debris flows generated by recently burned basins in the western U.S.

    USGS Publications Warehouse

    Gartner, J.E.; Cannon, S.H.; Santi, P.M.; deWolfe, V.G.

    2008-01-01

    Recently burned basins frequently produce debris flows in response to moderate-to-severe rainfall. Post-fire hazard assessments of debris flows are most useful when they predict the volume of material that may flow out of a burned basin. This study develops a set of empirically-based models that predict potential volumes of wildfire-related debris flows in different regions and geologic settings. The models were developed using data from 53 recently burned basins in Colorado, Utah and California. The volumes of debris flows in these basins were determined by either measuring the volume of material eroded from the channels, or by estimating the amount of material removed from debris retention basins. For each basin, independent variables thought to affect the volume of the debris flow were determined. These variables include measures of basin morphology, basin areas burned at different severities, soil material properties, rock type, and rainfall amounts and intensities for storms triggering debris flows. Using these data, multiple regression analyses were used to create separate predictive models for volumes of debris flows generated by burned basins in six separate regions or settings, including the western U.S., southern California, the Rocky Mountain region, and basins underlain by sedimentary, metamorphic and granitic rocks. An evaluation of these models indicated that the best model (the Western U.S. model) explains 83% of the variability in the volumes of the debris flows, and includes variables that describe the basin area with slopes greater than or equal to 30%, the basin area burned at moderate and high severity, and total storm rainfall. This model was independently validated by comparing volumes of debris flows reported in the literature, to volumes estimated using the model. Eighty-seven percent of the reported volumes were within two residual standard errors of the volumes predicted using the model. This model is an improvement over previous models in

  20. Triggering conditions and depositional characteristics of a disastrous debris flow event in Zhouqu city, Gansu Province, northwestern China

    NASA Astrophysics Data System (ADS)

    Tang, C.; Rengers, N.; van Asch, Th. W. J.; Yang, Y. H.; Wang, G. F.

    2011-11-01

    On 7 August 2010, catastrophic debris flows were triggered by a rainstorm in the catchments of the Sanyanyu and Luojiayu torrents, Zhouqu County, Gansu Province northwestern China. These two debris flows originated shortly after a rainstorm with an intensity of 77.3 mm h-1 and transported a total volume of about 2.2 million m3, which was deposited on an existing debris fan and into a river. This catastrophic event killed 1765 people living on this densely urbanised fan. The poorly sorted sediment contains boulders up to 3-4 m in diameter. In this study, the geomorphological features of both debris flow catchment areas are analyzed based on the interpretation of high-resolution remote sensing imagery combined with field investigation. The characteristics of the triggering rainfall and the initiation of the debris flow occurrence are discussed. Using empirical equations, the peak velocities and discharges of the debris flows were estimated to be around 9.7 m s-1 and 1358 m3 s-1 for the Sanyanyu torrent and 11 m s-1 and 572 m3 s-1 for the Luojiayu torrent. The results of this study contribute to a better understanding of the conditions leading to catastrophic debris flow events.

  1. Debris Flow Vulnerability Assessment in Urban Area Associated with Landslide Hazard Map : Application to Busan, Korea

    NASA Astrophysics Data System (ADS)

    Okjeong, Lee; Yoonkyung, Park; Mookwang, Sung; Sangdan, Kim

    2016-04-01

    In this presentation, an urban debris flow disaster vulnerability assessment methodology is suggested with major focus on urban social and economic aspect. The proposed methodology is developed based on the landslide hazard maps that Korean Forest Service has utilized to identify landslide source areas. Frist, debris flows are propagated to urban areas from such source areas by Flow-R model, and then urban vulnerability is evaluated by two categories; physical and socio-economic aspect. The physical vulnerability is associated to buildings that can be broken down by a landslide event directly. This study considers two popular building structure types, reinforced concrete frame and non-reinforced concretes frame, to evaluate the physically-based vulnerability. The socio-economic vulnerability is measured as a function of the resistant levels of the exposed people, the intensity and magnitude of indirect or intangible losses, and preparedness level of the local government. An indicator-based model is established to evaluate the life and indirect loss under urban debris flow disasters as well as the resilience ability against disasters. To illuminate the validity of the suggested methodology, physical and socio-economic vulnerability levels are investigated for Daejeon, Korea using the proposed approach. The results reveal that the higher population density areas under a weaker fiscal condition that are located at the downstream of mountainous areas are more vulnerable than the areas in opposite conditions. Key words: Debris flow disasters, Physical vulnerability, Socio-economic Vulnerability, Urban Acknowledgement This research was supported by a grant(13SCIPS04) from Smart Civil Infrastructure Research Program funded by Ministry of Land, Infrastructure and Transport(MOLIT) of Korea government and Korea Agency for Infrastructure Technology Advancement(KAIA).

  2. Geomorphic effects of large debris flows and flash floods, northern Venezuela, 1999

    USGS Publications Warehouse

    Larsen, M.C.; Wieczorek, G.F.

    2006-01-01

    A rare, high-magnitude storm in northern Venezuela in December 1999 triggered debris flows and flash floods, and caused one of the worst natural disasters in the recorded history of the Americas. Some 15,000 people were killed. The debris flows and floods inundated coastal communities on alluvial fans at the mouths of a coastal mountain drainage network and destroyed property estimated at more than $2 billion. Landslides were abundant and widespread on steep slopes within areas underlain by schist and gneiss from near the coast to slightly over the crest of the mountain range. Some hillsides were entirely denuded by single or coalescing failures, which formed massive debris flows in river channels flowing out onto densely populated alluvial fans at the coast. The massive amount of sediment derived from 24 watersheds along 50 km of the coast during the storm and deposited on alluvial fans and beaches has been estimated at 15 to 20 million m3. Sediment yield for the 1999 storm from the approximately 200 km2 drainage area of watersheds upstream of the alluvial fans was as much as 100,000 m3/km2. Rapid economic development in this dynamic geomorphic environment close to the capital city of Caracas, in combination with a severe rain storm, resulted in the death of approximately 5% of the population (300,000 total prior to the storm) in the northern Venezuelan state of Vargas. ?? 2006 Gebru??der Borntraeger.

  3. Sediment Transportation Induced by Deep-Seated Landslides in a Debris Flow Basin in Taiwan

    NASA Astrophysics Data System (ADS)

    Lin, Meei Ling; Chen, Te Wei; Chen, Yong Sheng; Sin Jhuang, Han

    2016-04-01

    Typhoon Morakot brought huge amount of rainfall to the southern Taiwan in 2009 and caused severe landslides and debris flow hazard. After Typhoon Morakot, it was found that the volume of sediment transported by the debris flow and its effects on the affected area were much more significant compared to previous case history, which may due to the huge amount of rainfall causing significant deep-seated landslides in the basin. In this study, the effects and tendency of the sediment transportation in a river basin following deep-seated landslides caused by typhoon Morakot were evaluated. We used LiDAR, DEM, and aerial photo to identify characteristics of deep-seated landslides in a debris flow river basin, KSDF079 in Liuoguey District, Kaohsiung City, Taiwan. Eight deep-seated landslides were identified in the basin. To estimate the potential landslide volume associated with the deep-seated landslides, the stability analysis was conducted to locate the critical sliding surface, and the potential landside volume was estimated based on the estimation equation proposed by the International Geotechnical Societies' UNESCO Working Party on World Landslide Inventory (WP/WLI, 1990). The total potential landslide volume of the eight deep-seated landslides in KSDF079 basin was about 28,906,856 m3. Topographic analysis was performed by using DEM before and LiDAR derived DEM after typhoon Morakot to calculate the landslide volume transported. The result of erosion volume and deposition volume lead to a run out volume of 5,832,433 m3. The results appeared to consist well with the field condition and aerial photo. Comparing the potential landslide volume and run out volume of eight deep-seated landslides, it was found that the remaining potential landslide volume was about 80%. Field investigation and topographic analysis of the KSDF079 debris flow revealed that a significant amount of sediment deposition remained in the river channel ranging from the middle to the downstream

  4. Debris-flow and flooding hazards associated with the December 1999 storm in coastal Venezuela and strategies for mitigation

    USGS Publications Warehouse

    Wieczorek, G.F.; Larsen, M.C.; Eaton, L.S.; Morgan, B.A.; Blair, J.L.

    2001-01-01

    Heavy rainfall from the storm of December 14-16, 1999 triggered thousands of landslides on steep slopes of the Sierra de Avila north of Caracas, Venezuela. In addition to landslides, heavy rainfall caused flooding and massive debris flows that damaged coastal communities in the State of Vargas along the Caribbean Sea. Examination of the rainfall pattern obtained from the GOES-8 satellite showed that the pattern of damage was generally consistent with the area of heaviest rainfall. Field observations of the severely affected drainage basins and historical records indicate that previous flooding and massive debris-flow events of similar magnitude to that of December 1999 have occurred throughout this region. The volume of debris-flow deposits and the large boulders that the flows transported qualifies the 1999 event amongst the largest historical rainfall-induced debris flows documented worldwide.

  5. Particle-Scale Controls on Entrainment and Deposition due to Debris Flows

    NASA Astrophysics Data System (ADS)

    Hill, K. M.; Maki, L.; Kaitna, R.

    2013-12-01

    When a debris flow - a large flow of boulders, gravels, sands, and mud - course down mountains, it can entrain materials many times the initial mass of the debris flow. The material is deposited at lower slopes. The amount of material they entrain and deposit can influence both the potential damage they do to habitat and communities in their paths and the landscape along the way. There is little quantitative understanding of the controls of entrainment and deposition along a debris flow path. We present experiments in a novel laboratory flume developed at the University of Minnesota to study particle-scale controls on entrainment and deposition due to debris flows. We control particle size distribution and water content in the flow itself and in an erodible bed over which the mixture flows, independently. Particle velocities, pore pressures, and local particle size distributions can be monitored, as can total erosion and deposition. Here, we first demonstrate how subtle differences in the bed structure or 'fabric' induced by the bed preparation can have dramatic differences on the entrainment rate of bed particles by the flowing mixture. Then we demonstrate the dependence of entrainment on particle size distribution in the flow and in the bed itself as it varies with angle of inclination of the bed. In all cases, we find that the erosion increases (or at lower angles, deposition decreases) with increasing angle of inclination of the bed. When the particles in the flow are uniform and the same size as those in the bed, we find the dependence of erosion on angle of inclination is linear. We find that single-sized systems exhibit more erosion and less deposition under the same conditions as their mixed counterparts. When the flow has a larger or smaller average particle size than that in the bed, the dependence of erosion on angle is somewhat more complicated. We model the variability by considering granular temperature in the flow, average stress on the bed, and the

  6. Particle-Scale Controls on Entrainment and Deposition due to Debris Flows

    NASA Astrophysics Data System (ADS)

    Hurst, M. D.; Mudd, S. M.; Walcott, R.; Attal, M.; Yoo, K.; Weinman, B. A.

    2011-12-01

    When a debris flow - a large flow of boulders, gravels, sands, and mud - course down mountains, it can entrain materials many times the initial mass of the debris flow. The material is deposited at lower slopes. The amount of material they entrain and deposit can influence both the potential damage they do to habitat and communities in their paths and the landscape along the way. There is little quantitative understanding of the controls of entrainment and deposition along a debris flow path. We present experiments in a novel laboratory flume developed at the University of Minnesota to study particle-scale controls on entrainment and deposition due to debris flows. We control particle size distribution and water content in the flow itself and in an erodible bed over which the mixture flows, independently. Particle velocities, pore pressures, and local particle size distributions can be monitored, as can total erosion and deposition. Here, we first demonstrate how subtle differences in the bed structure or 'fabric' induced by the bed preparation can have dramatic differences on the entrainment rate of bed particles by the flowing mixture. Then we demonstrate the dependence of entrainment on particle size distribution in the flow and in the bed itself as it varies with angle of inclination of the bed. In all cases, we find that the erosion increases (or at lower angles, deposition decreases) with increasing angle of inclination of the bed. When the particles in the flow are uniform and the same size as those in the bed, we find the dependence of erosion on angle of inclination is linear. We find that single-sized systems exhibit more erosion and less deposition under the same conditions as their mixed counterparts. When the flow has a larger or smaller average particle size than that in the bed, the dependence of erosion on angle is somewhat more complicated. We model the variability by considering granular temperature in the flow, average stress on the bed, and the

  7. Pore fluid pressure and shear behavior in debris flows of different compositions

    NASA Astrophysics Data System (ADS)

    Kaitna, Roland; Palucis, Marisa; Yohannes, Bereket; Hill, Kimberly; Dietrich, William

    2016-04-01

    Debris flows are mixtures of sediment and water that can have a wide range of different grain size distributions and water contents. The composition of the material is expected to have a strong effect on the development of pore fluid pressures in excess to hydrostatic, which in turn might affect the internal deformation behavior. We present a set of large scale experiments with debris flow mixtures of different compositions in a 4-m diameter rotating drum. Longitudinal profiles of basal fluid pressure and normal stress were measured and a probe to determine fluid pressure at different depths within the flow was developed and tested. Additionally we determined vertical profiles of mean particle velocities in the flow interior by measuring small variations of conductivity of the passing material and calculating the time lag between signals from two independent measurements at a small, known distance apart. Mean values of basal pore fluid pressure range from hydrostatic pressure for gravel-water flows to nearly complete liquefaction for muddy mixtures having a wide grain size distribution. The data indicate that the presence of fines dampens fluctuations of normalized fluid pressure and normal stress and concentrates shear at the base. The mobility of grain-fluid flows is strongly enhanced by a combination of fines in suspension as part of the interstitial fluid and a wide grain size distribution. Excess fluid pressure may arise from fluid displacement by converging grains at the front of the flow and the slow settling of grains through a highly viscous non-Newtonian fluid. Our findings support the need for pore pressure evolution and diffusion equations in debris flow models as they depend on particle size distributions. This study contributes to the understanding of the production of excess fluid pressure in grain fluid mixtures and may guide the development of constitutive models that describe natural events.

  8. Mega debris flow deposits on the western Wilkes Land margin, East Antarctica

    USGS Publications Warehouse

    Donda, F.; O'Brien, P.E.; De Santis, L.; Rebesco, M.; Brancolini, Giuliano

    2007-01-01

    Multichannel seismic data collected off Western Wilkes Land (East Antarctica) reveal the occurrence of mega debris flow deposits on the lower slope and rise that were formed throughout the Miocene. Commonly, debris flow units are separated by thin deposits of well-stratified facies, interpreted as predominantly glaciomarine mixed contouritic and distal turbidite deposits. These units could act as weak layers and could have played a major role in the slope instability. High sedimentation rates, due to large amounts of sediment delivered from a temperate, wet-based ice sheet, constituted a key factor in the sediment failures. The main trigger mechanism would probably have been earthquakes enhanced by isostatic rebound following major ice sheet retreats.

  9. Brief Communication: A new testing field for debris flow warning systems and algorithms

    NASA Astrophysics Data System (ADS)

    Arattano, M.; Coviello, V.; Cavalli, M.; Comiti, F.; Macconi, P.; Marchi, L.; Theule, J.; Crema, S.

    2015-03-01

    Early warning systems (EWSs) are among the measures adopted for the mitigation of debris flow hazards. EWSs often employ algorithms that require careful and long testing to grant their effectiveness. A permanent installation has been so equipped in the Gadria basin (Eastern Italian Alps) for the systematic test of event-EWSs. The installation is conceived to produce didactic videos and host informative visits. The populace involvement and education is in fact an essential step in any hazard mitigation activity and it should envisaged in planning any research activity. The occurrence of a debris flow in the Gadria creek, in the summer of 2014, allowed a first test of the installation and the recording of an informative video on EWSs.

  10. Brief Communication: A new testing field for debris flow warning systems

    NASA Astrophysics Data System (ADS)

    Arattano, M.; Coviello, V.; Cavalli, M.; Comiti, F.; Macconi, P.; Theule, J.; Crema, S.

    2015-07-01

    A permanent field installation for the systematic test of debris flow warning systems and algorithms has been equipped on the eastern Italian Alps. The installation was also designed to produce didactic videos and it may host informative visits. The populace education is essential and should be envisaged in planning any research on hazard mitigation interventions: this new installation responds to this requirement and offers an example of integration between technical and informative needs. The occurrence of a debris flow in 2014 allowed the first tests of a new warning system under development and to record an informative video on its performances. This paper will provide a description of the installation and an account of the first technical and informative results obtained.

  11. Multi-scale roughness spectra of Mount St. Helens debris flows

    NASA Technical Reports Server (NTRS)

    Austin, Richard T.; England, Anthony W.

    1993-01-01

    A roughness spectrum allows surface structure to be interpreted as a sum of sinusoidal components with differing wavelengths. Knowledge of the roughness spectrum gives insight into the mechanisms responsible for electromagnetic scattering at a given wavelength. Measured spectra from 10-year-old primary debris flow surfaces at Mount St. Helens conform to a power-law spectral model, suggesting that these surfaces are scaling over the measured range of spatial frequencies. Measured spectra from water-deposited surfaces deviate from this model.

  12. Roads at risk: traffic detours from debris flows in southern Norway

    NASA Astrophysics Data System (ADS)

    Meyer, N. K.; Schwanghart, W.; Korup, O.; Nadim, F.

    2015-05-01

    Globalisation and interregional exchange of people, goods, and services has boosted the importance of and reliance on all kinds of transport networks. The linear structure of road networks is especially sensitive to natural hazards. In southern Norway, steep topography and extreme weather events promote frequent traffic disruption caused by debris flows. Topographic susceptibility and trigger frequency maps serve as input into a hazard appraisal at the scale of first-order catchments to quantify the impact of debris flows on the road network in terms of a failure likelihood of each link connecting two network vertices, e.g. road junctions. We compute total additional traffic loads as a function of traffic volume and excess distance, i.e. the extra length of an alternative path connecting two previously disrupted network vertices using a shortest-path algorithm. Our risk metric of link failure is the total additional annual traffic load, expressed as vehicle kilometres, because of debris-flow-related road closures. We present two scenarios demonstrating the impact of debris flows on the road network and quantify the associated path-failure likelihood between major cities in southern Norway. The scenarios indicate that major routes crossing the central and north-western part of the study area are associated with high link-failure risk. Yet options for detours on major routes are manifold and incur only little additional costs provided that drivers are sufficiently well informed about road closures. Our risk estimates may be of importance to road network managers and transport companies relying on speedy delivery of services and goods.

  13. The formation of granular fronts in debris flow - A combined experimental-numerical study

    NASA Astrophysics Data System (ADS)

    Leonardi, Alessandro; Cabrera, Miguel; Wittel, Falk K.; Kaitna, Roland; Mendoza, Miller; Wu, Wei; Herrmann, Hans J.

    2015-04-01

    Granular fronts are amongst the most spectacular features of debris flows, and are also one of the reasons why such events are associated with a strong destructive power. They are usually believed to be the result of the convective mechanism of the debris flow, combined with internal size segregation of the grains. However, the knowledge about the conditions leading to the formation of a granular front is not up to date. We present a combined study with experimental and numerical features that aims at providing insight into the phenomenon. A stationary, long-lived avalanche is created within a rotating drum. In order to mimic the composition of an actual debris flow, the material is composed by a mixture of a plastic fluid, obtained with water and kaolin powder, and a collection of monodisperse spherical particles heavier than the fluid. Tuning the material properties and the drum settings, we are able to reproduce and control the formation of a granular front. To gain insight into the internal mechanism, the same scenario is replicated in a numerical environment, using a coupling technique between a discrete solver for the particles, the Discrete Element Method, and a continuum solver for the plastic fluid, the Lattice-Boltzmann Method. The simulations compare well with the experiments, and show the internal reorganization of the material transport. The formation of a granular front is shown to be favored by a higher drum rotational speed, which in turn forces a higher shear rate on the particles, breaks their internal organization, and contrasts their natural tendency to settle. Starting from dimensional analysis, we generalize the obtained results and are able to draw implications for debris flow research.

  14. Glacial-Interglacial Climate Changes Recorded by Debris Flow Grain Size, Eastern Sierra Nevada, California

    NASA Astrophysics Data System (ADS)

    D'Arcy, M. K.; Whittaker, A. C.; Roda Boluda, D. C.

    2015-12-01

    Uncertainties remain about the sensitivity of eroding landscapes to climate changes over a range of frequencies and amplitudes. Numerical models suggest that simple catchment-fan systems should be responsive to glacial-interglacial climate cycles, recording them in both sediment flux and the grain size distribution of their deposits. However these models are largely untested and the propagation of climatic signals through simple sediment routing systems remains contentious. Here, we present detailed sedimentological data from 8 debris flow fans in Owens Valley, eastern California. These fans have an exceptionally well-constrained depositional record spanning the last 120 ka, which we use to examine how sediment export has varied as a function of high-amplitude climate changes. We find a strong and sustained relationship between debris flow grain size and paleoclimate proxies over an entire glacial-interglacial cycle, with significantly coarser-grained deposits correlated with warm and dry conditions. Our data suggest these systems are highly reactive to climate forcing, with a short response timescale of <10 ka and no evidence of signal buffering, which we interpret to be driven by rapid sediment transfer from source to sink. We demonstrate that debris flow grain size follows an exponential relationship with temperature, coarsening at a rate of ~10 % per °C. Using this observation, and a known relationship between temperature and storm intensity, we propose that the climate signal recorded in these fan deposits captures changing storm intensity during the last glacial-interglacial cycle. This study offers a direct test of existing models of catchment-fan systems, confirming that glacial-interglacial climate changes can be clearly expressed in their grain size records. Our results also suggest that these debris flow deposits contain a high-resolution, testable record of past storm intensity, and that storminess is the primary control on their sedimentological

  15. Soil morphology of a debris flow chronosequence in a coniferous forest, southern California, USA

    USGS Publications Warehouse

    Turk, J.K.; Goforth, B.R.; Graham, R.C.; Kendrick, K.J.

    2008-01-01

    Soils on a series of debris flow deposits, ranging from < 1 to 244??years old, were described and sampled in order to investigate the early stages of soil development. The parent material at the site is debris flow regolith, composed mainly of gneiss, the soil moisture regime is xeric, and the vegetation is mixed coniferous forest. Ages of the deposits were assessed using dendrochronology. Morphologic trends in the organic horizons included a thickening of the humus form over time, along with the development of Fm and Hr horizons. The humus forms underwent a progression from Mormodors (20??years old), to Hemimors (26-101??years old), and finally Lignomors (163??years old) and Resimors (184-244??years old). Changes in physical properties of the uppermost mineral horizons as a function of increasing age included a decrease in the volume of coarse fragments, a linear decrease in bulk density, and a darkening and reddening of the soil color. No significant soil development took place in the subsoil during the time span of this chronosequence. The soils described were classified as Typic Xerofluvents and Typic Xerorthents (Regosols and Leptosols). Buried A horizons were observed in many of the soils. Where the A horizons could be linked to dendrochronology to assess the age of the buried surface, we found that the properties of the buried A horizons do not serve as a good indicator of the age of the surface. This study suggests rapid development of the humus form profile (organic horizons and A horizon) following debris flow deposition and rapid degradation of these horizons when the debris flow surface is buried. ?? 2008 Elsevier B.V.

  16. Hydrogeomorphic response to extreme rainfall in headwater systems: Flash floods and debris flows

    NASA Astrophysics Data System (ADS)

    Borga, Marco; Stoffel, Markus; Marchi, Lorenzo; Marra, Francesco; Jakob, Matthias

    2014-10-01

    Flash floods and debris flows develop at space and time scales that conventional observation systems for rainfall, streamflow and sediment discharge are not able to monitor. Consequently, the atmospheric, hydrological and geomorphic controls on these hydrogeomorphic processes are poorly understood, leading to highly uncertain warning and risk management. On the other hand, remote sensing of precipitation and numerical weather predictions have become the basis of several flood forecasting systems, enabling increasingly accurate detection of hazardous events. The objective of this paper is to provide a review on current European and international research on early warning systems for flash floods and debris flows. We expand upon these themes by identifying: (a) the state of the art; (b) knowledge gaps; and (c) suggested research directions to advance warning capabilities for extreme hydrogeomorphic processes. We also suggest three areas in which advancements in science will have immediate and important practical consequence, namely development of rainfall estimation and nowcasting schemes suited to the specific space-time scales, consolidating physical, engineering and social datasets of flash floods and debris-flows, integration of methods for multiple hydrogeomorphic hazard warning.

  17. A regional reconstruction of debris-flow activity in the Northern Calcareous Alps, Austria

    NASA Astrophysics Data System (ADS)

    Procter, Emily; Bollschweiler, Michelle; Stoffel, Markus; Neumann, Mathias

    2011-09-01

    Dendrogeomorphic dating of historical debris-flow events is a highly valuable tool for improving historical records in the field of natural hazard management. Previous dendrogeomorphic investigations generally have focused on case studies of single torrents; however, regional investigations may offer a more accurate reconstruction of regional patterns of activity and therefore may have an advantage over individual cases. The aim of the study is to provide a regional reconstruction of debris-flow events for a site in the Northern Calcareous Alps of western Austria (Gamperdonatal, Vorarlberg) and to document spatial and temporal morphological changes in individual and neighboring torrents. Analysis of 442 trees (268 Pinus mugo ssp. uncinata, 164 Picea abies, and 10 Abies alba) allowed identification of 579 growth disturbances corresponding to 63 debris-flow events since A.D. 1839. The majority of growth disturbances were in the form of growth suppression or release (76%) owing to the nature of both the deposited material and the process characteristics. Regional patterns of event frequency indicated a paucity of activity in the early to mid-twentieth century and increased activity since A.D. 1948, whereby large events were followed by subsequent years of continued activity of smaller magnitude. Patterns of frequency could be attributed primarily to spatiotemporal changes in channel morphology, but may also be reflective of changes in transport conditions within the valley. This study provides the first regional investigation in the Austrian Alps and contributes to the documentation of tree responses to geomorphic disturbances in calcareous material.

  18. Succession of desert plants on debris flow terraces, Grand Canyon, Arizona, U.S.A.

    USGS Publications Warehouse

    Bowers, Janice E.; Webb, R.H.; Pierson, E.A.

    1997-01-01

    Vegetation sampling on 11 debris flow terraces in Grand Canyon National Park, Arizona, U.S.A., showed that plant assemblages changed as age of surface increased. The terraces ranged in age from about 5 to about 3100 years. There were distinct differences among sites in the life history characteristics of the dominant plants. Young terraces (5-55 years) were dominated by short-lived plants that had high reproductive potential. Older surfaces were dominated by species with longer life-spans and lower reproductive potential. Density and cover of long-lived species increased with age of surface; for short-lived plants, density was inversely related to surface age. Species composition was also correlated with site age; however, location, exposure, and other factors ensured that no two debris flows supported identical mixtures of species. Succession on recent Grand Canyon debris flows is driven in part by life-history strategies, particularly life-span and seed dispersal traits, and also by climatic factors, especially those that control germination and establishment of the long-lived dominants.

  19. High-Resolution Debris Flow Volume Mapping with Unmanned Aerial Systems (uas) and Photogrammetric Techniques

    NASA Astrophysics Data System (ADS)

    Adams, M. S.; Fromm, R.; Lechner, V.

    2016-06-01

    Debris flows cause an average € 30 million damages and 1-2 fatalities every year in Austria. Detailed documentation of their extent and magnitude is essential for understanding, preventing and mitigating these natural hazard events. The recent development of unmanned aerial systems (UAS) has provided a new possibility for on-demand high-resolution monitoring and mapping. Here, we present a study, where the spatial extent and volume of a large debris flow event were mapped with different UAS, fitted with commercial off-the-shelf sensors. Orthophotos and digital terrain models (DTM) were calculated using structure-from-motion photogrammetry software. Terrain height differences caused by the debris flow in the catchment and valley floor were derived by subtracting the pre-event airborne laser scanning (ALS) DTM from a post-event UAS-DTM. The analysis of the volumetric sediment budget showed, that approximately 265,000 m³ material was mobilised in the catchment, of which 45,000 m³ settled there; of the material, which reached the valley floor, 120,000 m³ was deposited, while another 10,000 m³ was eroded from there. The UAS-results were validated against ALS data and imagery from a traditional manned-aircraft photogrammetry campaign. In conclusion, the UAS-data can reach an accuracy and precision comparable to manned aircraft data, but with the added benefits of higher flexibility, easier repeatability, less operational constraints and higher spatial resolution.

  20. Laboratory simulation of debris flows over sand dunes: Insights into gully-formation (Mars)

    NASA Astrophysics Data System (ADS)

    Jouannic, Gwenaël; Gargani, Julien; Conway, Susan J.; Costard, François; Balme, Matthew R.; Patel, Manish R.; Massé, Marion; Marmo, Chiara; Jomelli, Vincent; Ori, Gian G.

    2015-02-01

    Gully morphology (often summarized as comprising an alcove, channel and debris apron) is one of the key elements used to support the argument for liquid water in the recent past on Mars. Nevertheless, the processes that create different gully morphologies, on both Mars and Earth, are not fully understood. One of the puzzling morphologic attributes of Martian dune gullies is their apparent lack of an apron, or terminal deposit, which has caused debate about their formation process. Several physical processes such as runoff, debris flows, granular flows, and sliding blocks falling downslope could explain the formation of these gullies. In this work, we focus on the role of liquid in the substrate as well as in the flow and choose to experimentally test the plausibility of this hypothesis. We performed a series of analogue experiments to investigate the formation of gullies on sand dune-like substrates. We used controlled flows of water over an inclined sand-box to produce gully-like forms. Ice-rich sedimentary substrates were used, including substrates that included a thin liquid water-saturated thawed layer (an 'active layer') above the ice-saturated zone to give an analogue for a 'periglacial' environment. We quantitatively demonstrate that debris flow processes in 'periglacial' experiments are conducive to the formation of narrow and long channels with small terminal deposits with perched channels. By re-analysis of Martian elevation data for dune-gullies on Mars, we have found good evidence that such terminal deposits could exist. Our experiments revealed that increased water content in the thawed layer above the frozen bed increases flow-length due to the subsequent reduction in infiltration capacity. Water is incorporated into the flow by erosion of the wet thawed layer (sand plus water) and by drainage of the thawed layer. Using a Mars environment simulation chamber, we found that atmospheric pressure conditions seem to have a limited influence on the

  1. Submarine debris flows and continental slople evolution in front of Quaternary ice sheets, Baffin Bay, Canadian Arctic

    SciTech Connect

    Hiscott, R.N.; Aksu, A.E. )

    1994-03-01

    Baffin Bay is a semi-enclosed extension of the Labrador Sea in the Canadian Arctic. The upper Pliocene and Quaternary successions beneath the continental slope contain important slumps and debris-flow deposits. New high-resolution single-channel seismic data have been acquired from a 500 to 600-m-deep transverse trough that indents that shelf in an area where glacial outflow was focused during the Pliocene and Pleistocene. Major shelf-edge progradation occurred both inside and on the flanks of the transverse trough. In the lower slope, several large debris flows carried proglacial deposits into the deep basin. The largest of these debris flows dramatically reshaped the sea floor by reducing bottom slopes both by proximal erosion and distal thickening of the debris-flow deposit. Subsequently, the lower slope was starved of terrigenous input, and the upper slope was steepened by accumulation of basinward thinning wedges of mass flow deposits. The processes of emplacement of large debris flows, slope reshaping, and out-of-phase accumulation identified in upper and lower slope areas of Baffin Bay are relevant to the interpretation of other line-source margins affected by major sea level falls or changes in sediment influx, including siliciclastic slope aprons and carbonate platform margins. On fans, muddy debris flows provide both a potential seal for hydrocarbons generated after burial and a potentially important mass of organic-rich mudstones that may act as source rocks in the subsurface. 32 refs., 14 figs., 1 tab.

  2. Coarse-grained debris-flow deposits in the Miocene fan deltas, SE Korea: a scaling analysis

    NASA Astrophysics Data System (ADS)

    Sohn, Y. K.

    2000-01-01

    The viscoplastic and inertial grain-flow models have been widely used as tools for description and interpretation of ancient debris-flow deposits, providing a basis to estimate yield strength, viscosity, cohesion, and internal friction angle. Recent studies suggest, however, that a debris flow is an intimate mixture of solid and fluid, in which a number of momentum-transfer mechanisms operate. It is therefore necessary to evaluate the relative importance of different momentum-transport processes to properly describe a debris flow. Scaling analysis may be useful to this end, using the Bagnold number (the ratio of inertial grain stress to viscous shear stress), Savage number (the ratio of inertial grain stress to shear stress borne by sustained grain contacts), friction number (the ratio of frictional shear stress to viscous shear stress), and Darcy number (the ratio of grain-fluid interaction stress to inertial grain stress). Scaling analyses of Miocene gravelly debris-flow deposits in Korea suggest that different types of debris flows can be better distinguished by the analyses, providing some implications for debris-flow processes.

  3. Methods for the Emergency Assessment of Debris-Flow Hazards from Basins Burned by the Fires of 2007, Southern California

    USGS Publications Warehouse

    Cannon, Susan H.; Gartner, Joseph E.; Michael, John A.

    2007-01-01

    This report describes the approach used to assess potential debris-flow hazards from basins burned by the Buckweed, Santiago, Canyon, Poomacha, Ranch, Harris, Witch, Rice, Ammo, Slide, Grass Valley and Cajon Fires of 2007 in southern California. The assessments will be presented as a series of maps showing a relative ranking of the predicted volume of debris flows that can issue from basin outlets in response to a 3-hour duration rainstorm with a 10-year return period. Potential volumes of debris flows are calculated using a multiple-regression model that describes debris-flow volume at a basin outlet as a function of measures of basin gradient, burn extent, and storm rainfall. This assessment provides critical information for issuing basin-specific warnings, locating and designing mitigation measures, and planning of evacuation timing and routes.

  4. IN SITU FLOW METERS AROUND A GROUNDWATER CIRCULATION WELL (ABSTRACT)

    EPA Science Inventory

    The primary benefit of groundwater circulation well (GCW) technology is the development of strong vertical flows surrounding the treatment well. The extent of significant vertical flow surrounding a circulation well is difficult to establish from traditional groundwater elevation...

  5. Regional based modeling approach for rainfall-induced debris flows in the continental-climatic Northern Tien Shan (SE Kazakhstan)

    NASA Astrophysics Data System (ADS)

    Fischer, Thomas; Küfmann, Carola; Haas, Florian; Baume, Otfried; Becht, Michael

    2013-04-01

    The high mountain systems of Central Asia (Hindukush, Pamir and Tien Shan) are dominated by continental-climatic conditions. Nevertheless, westerly maritime air circulation and convective rainfalls during the summer season result in high rainfall intensities. In combination with a high availability of unconsolidated material rainfall triggered debris flows are prominent and intensive geomorphologic processes in these mountain areas. The presented study aims to figure out a regional based modeling approach for rainfall-induced debris flow processes based on combination of a disposition model for debris flow starting zones with process-flow models. The investigation area has a size of about 700 square kilometers and is situated in the Northern Tien Shan mountains in SE Kazakhstan (investigation areas: valleys of Prochadnaja, Big Almatinka, Little Almatinka and Left Talgar). The area is characterized by mountain forest zone, alpine meadows and high-alpine glaciated areas with the highest peaks at 4500m. In a first step the disposition (point of process triggering) of actual debris flows was analyzed. Due to different triggering mechanisms, the processes were divided into channel-type and slope-type debris flows. Detailed mapping of actual debris flows initiation areas and a GIS-based geostatistical disposition analysis are used to identify the main geofactor-variables and geofactor combinations which enhance the triggering of rainfall-induced debris flows. It can be shown that both, longtime variable geofactors (such as local geomorphology and hydrology) plays a significant role for triggering debris flows, as well as mid- and short time variable geofactors. Especially actual permafrost distribution and degradation plus glacier retreat comes into the focus of interest. This is most notably for rainfall induced slope-type debris flows which primarily are triggered in the discontinuous and continuous permafrost areas eroding younger unconsolidated material from actual

  6. Probability and volume of potential postwildfire debris flows in the 2010 Fourmile burn area, Boulder County, Colorado

    USGS Publications Warehouse

    Ruddy, Barbara C.; Stevens, Michael R.; Verdin, Kristine

    2010-01-01

    This report presents a preliminary emergency assessment of the debris-flow hazards from drainage basins burned by the Fourmile Creek fire in Boulder County, Colorado, in 2010. Empirical models derived from statistical evaluation of data collected from recently burned basins throughout the intermountain western United States were used to estimate the probability of debris-flow occurrence and volumes of debris flows for selected drainage basins. Data for the models include burn severity, rainfall total and intensity for a 25-year-recurrence, 1-hour-duration rainstorm, and topographic and soil property characteristics. Several of the selected drainage basins in Fourmile Creek and Gold Run were identified as having probabilities of debris-flow occurrence greater than 60 percent, and many more with probabilities greater than 45 percent, in response to the 25-year recurrence, 1-hour rainfall. None of the Fourmile Canyon Creek drainage basins selected had probabilities greater than 45 percent. Throughout the Gold Run area and the Fourmile Creek area upstream from Gold Run, the higher probabilities tend to be in the basins with southerly aspects (southeast, south, and southwest slopes). Many basins along the perimeter of the fire area were identified as having low probability of occurrence of debris flow. Volume of debris flows predicted from drainage basins with probabilities of occurrence greater than 60 percent ranged from 1,200 to 9,400 m3. The predicted moderately high probabilities and some of the larger volumes responses predicted for the modeled storm indicate a potential for substantial debris-flow effects to buildings, roads, bridges, culverts, and reservoirs located both within these drainages and immediately downstream from the burned area. However, even small debris flows that affect structures at the basin outlets could cause considerable damage.

  7. Emergency Assessment of Debris-Flow Hazards from Basins Burned by the 2007 Ammo Fire, San Diego County, Southern California

    USGS Publications Warehouse

    Cannon, Susan H.; Gartner, Joseph E.; Michael, John A.; Bauer, Mark A.; Stitt, Susan C.; Knifong, Donna L.; McNamara, Bernard J.; Roque, Yvonne M.

    2007-01-01

    INTRODUCTION The objective of this report is to present a preliminary emergency assessment of the potential for debris-flow generation from basins burned by the Ammo Fire in San Diego County, southern California in 2007. Debris flows are among the most hazardous geologic phenomena; debris flows that followed wildfires in southern California in 2003 killed 16 people and caused tens of millions of dollars of property damage. A short period of even moderate rainfall on a burned watershed can lead to debris flows. Rainfall that is normally absorbed into hillslope soils can run off almost instantly after vegetation has been removed by wildfire. This causes much greater and more rapid runoff than is normal from creeks and drainage areas. Highly erodible soils in a burn scar allow flood waters to entrain large amounts of ash, mud, boulders, and unburned vegetation. Within the burned area and downstream, the force of rushing water, soil, and rock can destroy culverts, bridges, roadways, and buildings, potentially causing injury or death. This emergency debris-flow hazard assessment is presented as relative ranking of the predicted median volume of debris flows that can issue from basin outlets in response to 1.75 inches (44.45 mm) of rainfall over a 3-hour period. Such a storm has a 10-year return period. The calculation of debris flow volume is based on a multiple-regression statistical model that describes the median volume of material that can be expected from a recently burned basin as a function of the area burned at high and moderate severity, the basin area with slopes greater than or equal to 30 percent, and triggering storm rainfall. Cannon and others (2007) describe the methods used to generate the hazard maps. Identification of potential debris-flow hazards from burned drainage basins is necessary to issue warnings for specific basins, to make effective mitigation decisions, and to help plan evacuation timing and routes.

  8. Emergency Assessment of Debris-Flow Hazards from Basins Burned by the 2007 Rice Fire, San Diego County, Southern California

    USGS Publications Warehouse

    Cannon, Susan H.; Gartner, Joseph E.; Michael, John A.; Bauer, Mark A.; Stitt, Susan C.; Knifong, Donna L.; McNamara, Bernard J.; Roque, Yvonne M.

    2007-01-01

    INTRODUCTION The objective of this report is to present a preliminary emergency assessment of the potential for debris-flow generation from basins burned by the Rice Fire in San Diego County, southern California in 2007. Debris flows are among the most hazardous geologic phenomena; debris flows that followed wildfires in southern California in 2003 killed 16 people and caused tens of millions of dollars of property damage. A short period of even moderate rainfall on a burned watershed can lead to debris flows. Rainfall that is normally absorbed into hillslope soils can run off almost instantly after vegetation has been removed by wildfire. This causes much greater and more rapid runoff than is normal from creeks and drainage areas. Highly erodible soils in a burn scar allow flood waters to entrain large amounts of ash, mud, boulders, and unburned vegetation. Within the burned area and downstream, the force of rushing water, soil, and rock can destroy culverts, bridges, roadways, and buildings, potentially causing injury or death. This emergency debris-flow hazard assessment is presented as relative ranking of the predicted median volume of debris flows that can issue from basin outlets in response to 1.75 inches (44.45 mm) of rainfall over a 3-hour period. Such a storm has a 10-year return period. The calculation of debris flow volume is based on a multiple-regression statistical model that describes the median volume of material that can be expected from a recently burned basin as a function of the area burned at high and moderate severity, the basin area with slopes greater than or equal to 30 percent, and triggering storm rainfall. Cannon and others (2007) describe the methods used to generate the hazard maps. Identification of potential debris-flow hazards from burned drainage basins is necessary to issue warnings for specific basins, to make effective mitigation decisions, and to help plan evacuation timing and routes.

  9. Emergency Assessment of Debris-Flow Hazards from Basins Burned by the 2007 Poomacha Fire, San Diego County, Southern California

    USGS Publications Warehouse

    Cannon, Susan H.; Gartner, Joseph E.; Michael, John A.; Bauer, Mark A.; Stitt, Susan C.; Knifong, Donna L.; McNamara, Bernard J.; Roque, Yvonne M.

    2007-01-01

    INTRODUCTION The objective of this report is to present a preliminary emergency assessment of the potential for debris-flow generation from basins burned by the Poomacha Fire in San Diego County, southern California in 2007. Debris flows are among the most hazardous geologic phenomena; debris flows that followed wildfires in southern California in 2003 killed 16 people and caused tens of millions of dollars of property damage. A short period of even moderate rainfall on a burned watershed can lead to debris flows. Rainfall that is normally absorbed into hillslope soils can run off almost instantly after vegetation has been removed by wildfire. This causes much greater and more rapid runoff than is normal from creeks and drainage areas. Highly erodible soils in a burn scar allow flood waters to entrain large amounts of ash, mud, boulders, and unburned vegetation. Within the burned area and downstream, the force of rushing water, soil, and rock can destroy culverts, bridges, roadways, and buildings, potentially causing injury or death. This emergency debris-flow hazard assessment is presented as relative ranking of the predicted median volume of debris flows that can issue from basin outlets in response to 2.25 inches (57.15 mm) of rainfall over a 3-hour period. Such a storm has a 10-year return period. The calculation of debris flow volume is based on a multiple-regression statistical model that describes the median volume of material that can be expected from a recently burned basin as a function of the area burned at high and moderate severity, the basin area with slopes greater than or equal to 30 percent, and triggering storm rainfall. Cannon and others (2007) describe the methods used to generate the hazard maps. Identification of potential debris-flow hazards from burned drainage basins is necessary to issue warnings for specific basins, to make effective mitigation decisions, and to help plan evacuation timing and routes.

  10. Emergency Assessment of Debris-Flow Hazards from Basins Burned by the 2007 Buckweed Fire, Los Angeles County, Southern California

    USGS Publications Warehouse

    Cannon, Susan H.; Gartner, Joseph E.; Michael, John A.; Bauer, Mark A.; Stitt, Susan C.; Knifong, Donna L.; McNamara, Bernard J.; Roque, Yvonne M.

    2007-01-01

    INTRODUCTION The objective of this report is to present a preliminary emergency assessment of the potential for debris-flow generation from basins burned by the Buckweed Fire in Los Angeles County, southern California in 2007. Debris flows are among the most hazardous geologic phenomena; debris flows that followed wildfires in southern California in 2003 killed 16 people and caused tens of millions of dollars of property damage. A short period of even moderate rainfall on a burned watershed can lead to debris flows. Rainfall that is normally absorbed into hillslope soils can run off almost instantly after vegetation has been removed by wildfire. This causes much greater and more rapid runoff than is normal from creeks and drainage areas. Highly erodible soils in a burn scar allow flood waters to entrain large amounts of ash, mud, boulders, and unburned vegetation. Within the burned area and downstream, the force of rushing water, soil, and rock can destroy culverts, bridges, roadways, and buildings, potentially causing injury or death. This emergency debris-flow hazard assessment is presented as relative ranking of the predicted median volume of debris flows that can issue from basin outlets in response to 2.25 inches (57.15 mm) of rainfall over a 3-hour period. Such a storm has a 10-year return period. The calculation of debris flow volume is based on a multiple-regression statistical model that describes the median volume of material that can be expected from a recently burned basin as a function of the area burned at high and moderate severity, the basin area with slopes greater than or equal to 30 percent, and triggering storm rainfall. Cannon and others (2007) describe the methods used to generate the hazard maps. Identification of potential debris-flow hazards from burned drainage basins is necessary to issue warnings for specific basins, to make effective mitigation decisions, and to help plan evacuation timing and routes.

  11. Emergency Assessment of Debris-Flow Hazards from Basins Burned by the 2007 Santiago Fire, Orange County, Southern California

    USGS Publications Warehouse

    Cannon, Susan H.; Gartner, Joseph E.; Michael, John A.; Bauer, Mark A.; Stitt, Susan C.; Knifong, Donna L.; McNamara, Bernard J.; Roque, Yvonne M.

    2007-01-01

    INTRODUCTION The objective of this report is to present a preliminary emergency assessment of the potential for debris-flow generation from basins burned by the Santiago Fire in Orange County, southern California in 2007. Debris flows are among the most hazardous geologic phenomena; debris flows that followed wildfires in southern California in 2003 killed 16 people and caused tens of millions of dollars of property damage. A short period of even moderate rainfall on a burned watershed can lead to debris flows. Rainfall that is normally absorbed into hillslope soils can run off almost instantly after vegetation has been removed by wildfire. This causes much greater and more rapid runoff than is normal from creeks and drainage areas. Highly erodible soils in a burn scar allow flood waters to entrain large amounts of ash, mud, boulders, and unburned vegetation. Within the burned area and downstream, the force of rushing water, soil, and rock can destroy culverts, bridges, roadways, and buildings, potentially causing injury or death. This emergency debris-flow hazard assessment is presented as relative ranking of the predicted median volume of debris flows that can issue from basin outlets in response to 1.75 inches (44.45 mm) of rainfall over a 3-hour period. Such a storm has a 10-year return period. The calculation of debris flow volume is based on a multiple-regression statistical model that describes the median volume of material that can be expected from a recently burned basin as a function of the area burned at high and moderate severity, the basin area with slopes greater than or equal to 30 percent, and triggering storm rainfall. Cannon and others (2007) describe the methods used to generate the hazard maps. Identification of potential debris-flow hazards from burned drainage basins is necessary to issue warnings for specific basins, to make effective mitigation decisions, and to help plan evacuation timing and routes.

  12. Emergency Assessment of Debris-Flow Hazards from Basins Burned by the 2007 Witch Fire, San Diego County, Southern California

    USGS Publications Warehouse

    Cannon, Susan H.; Gartner, Joseph E.; Michael, John A.; Bauer, Mark A.; Stitt, Susan C.; Knifong, Donna L.; McNamara, Bernard J.; Roque, Yvonne M.

    2007-01-01

    INTRODUCTION The objective of this report is to present a preliminary emergency assessment of the potential for debris-flow generation from basins burned by the Witch Fire in San Diego County, southern California in 2007. Debris flows are among the most hazardous geologic phenomena; debris flows that followed wildfires in southern California in 2003 killed 16 people and caused tens of millions of dollars of property damage. A short period of even moderate rainfall on a burned watershed can lead to debris flows. Rainfall that is normally absorbed into hillslope soils can run off almost instantly after vegetation has been removed by wildfire. This causes much greater and more rapid runoff than is normal from creeks and drainage areas. Highly erodible soils in a burn scar allow flood waters to entrain large amounts of ash, mud, boulders, and unburned vegetation. Within the burned area and downstream, the force of rushing water, soil, and rock can destroy culverts, bridges, roadways, and buildings, potentially causing injury or death. This emergency debris-flow hazard assessment is presented as relative ranking of the predicted median volume of debris flows that can issue from basin outlets in response to 2.25 inches (57.15 mm) of rainfall over a 3-hour period. Such a storm has a 10-year return period. The calculation of debris flow volume is based on a multiple-regression statistical model that describes the median volume of material that can be expected from a recently burned basin as a function of the area burned at high and moderate severity, the basin area with slopes greater than or equal to 30 percent, and triggering storm rainfall. Cannon and others (2007) describe the methods used to generate the hazard maps. Identification of potential debris-flow hazards from burned drainage basins is necessary to issue warnings for specific basins, to make effective mitigation decisions, and to help plan evacuation timing and routes.

  13. Emergency Assessment of Debris-Flow Hazards from Basins Burned by the 2007 Canyon Fire, Los Angeles County, Southern California

    USGS Publications Warehouse

    Cannon, Susan H.; Gartner, Joseph E.; Michael, John A.; Bauer, Mark A.; Stitt, Susan C.; Knifong, Donna L.; McNamara, Bernard J.; Roque, Yvonne M.

    2007-01-01

    INTRODUCTION The objective of this report is to present a preliminary emergency assessment of the potential for debris-flow generation from basins burned by the Canyon Fire in Los Angeles County, southern California in 2007. Debris flows are among the most hazardous geologic phenomena; debris flows that followed wildfires in southern California in 2003 killed 16 people and caused tens of millions of dollars of property damage. A short period of even moderate rainfall on a burned watershed can lead to debris flows. Rainfall that is normally absorbed into hillslope soils can run off almost instantly after vegetation has been removed by wildfire. This causes much greater and more rapid runoff than is normal from creeks and drainage areas. Highly erodible soils in a burn scar allow flood waters to entrain large amounts of ash, mud, boulders, and unburned vegetation. Within the burned area and downstream, the force of rushing water, soil, and rock can destroy culverts, bridges, roadways, and buildings, potentially causing injury or death. This emergency debris-flow hazard assessment is presented as relative ranking of the predicted median volume of debris flows that can issue from basin outlets in response to 2.25 inches (57.15 mm) of rainfall over a 3-hour period. Such a storm has a 10-year return period. The calculation of debris flow volume is based on a multiple-regression statistical model that describes the median volume of material that can be expected from a recently burned basin as a function of the area burned at high and moderate severity, the basin area with slopes greater than or equal to 30 percent, and triggering storm rainfall. Cannon and others (2007) describe the methods used to generate the hazard maps. Identification of potential debris-flow hazards from burned drainage basins is necessary to issue warnings for specific basins, to make effective mitigation decisions, and to help plan evacuation timing and routes.

  14. Emergency Assessment of Debris-Flow Hazards from Basins Burned by the 2007 Harris Fire, San Diego County, Southern California

    USGS Publications Warehouse

    Cannon, Susan H.; Gartner, Joseph E.; Michael, John A.; Bauer, Mark A.; Stitt, Susan C.; Knifong, Donna L.; McNamara, Bernard J.; Roque, Yvonne M.

    2007-01-01

    INTRODUCTION The objective of this report is to present a preliminary emergency assessment of the potential for debris-flow generation from basins burned by the Harris Fire in San Diego County, southern California in 2007. Debris flows are among the most hazardous geologic phenomena; debris flows that followed wildfires in southern California in 2003 killed 16 people and caused tens of millions of dollars of property damage. A short period of even moderate rainfall on a burned watershed can lead to debris flows. Rainfall that is normally absorbed into hillslope soils can run off almost instantly after vegetation has been removed by wildfire. This causes much greater and more rapid runoff than is normal from creeks and drainage areas. Highly erodible soils in a burn scar allow flood waters to entrain large amounts of ash, mud, boulders, and unburned vegetation. Within the burned area and downstream, the force of rushing water, soil, and rock can destroy culverts, bridges, roadways, and buildings, potentially causing injury or death. This emergency debris-flow hazard assessment is presented as relative ranking of the predicted median volume of debris flows that can issue from basin outlets in response to 1.75 inches (44.45 mm) of rainfall over a 3-hour period. Such a storm has a 10-year return period. The calculation of debris flow volume is based on a multiple-regression statistical model that describes the median volume of material that can be expected from a recently burned basin as a function of the area burned at high and moderate severity, the basin area with slopes greater than or equal to 30 percent, and triggering storm rainfall. Cannon and others (2007) describe the methods used to generate the hazard maps. Identification of potential debris-flow hazards from burned drainage basins is necessary to issue warnings for specific basins, to make effective mitigation decisions, and to help plan evacuation timing and routes.

  15. Using patterns of debris flow erosion and deposition in the Icelandic Westfjords to delineate hazard zones.

    NASA Astrophysics Data System (ADS)

    Conway, S. J.; Decaulne, A.; Balme, M. R.; Murray, J. B.; Towner, M. C.

    2009-04-01

    Debris flows pose a significant risk to infrastructure and people; hence the aim of this study is to better understand the behaviour of debris flows by studying examples from above the town of Ísafjörður in north-western Iceland. Debris flow is a recognised hazard in the region [1], but above Ísafjörður occurs with particularly high regularity [2] and can involve large volumes of debris. We have used airborne laser altimeter (LiDAR) and differential GPS data to produce isopach maps of flows that occurred in 1999, 2007 and 2008 above Ísafjörður and in adjacent valleys. Compared to observations from the literature, e.g. [3-5], these flows start depositing at unusually high slope gradients (up to 45°). However the larger flows are also unusually mobile compared to typical hill-slope debris flows [4], but they are not as mobile as channelized flows [6]. This means that for a given volume their run-out distance is much greater than expected and hence more likely to reach the town. The volumes for the flows were calculated in two ways: firstly we were able to take the difference between the surfaces before (LiDAR) and after (dGPS) three small flows that occurred in 2008. Secondly, for flows prior to our 2008 LiDAR survey, we interpolated the pre-flow surface based on surrounding topography and measured differences from our post-flow surveys. The second method therefore has a tendency to over-estimate the flow volumes. The scheme for dGPS surveying involved obtaining numerous cross sections and taking long profiles along the channel and adjacent levees. Based on the volumes that we have calculated using these more accurate methods, we have increased the value of volume estimates for recorded historic debris flows reported by [2] and have revised the local denudation rate to 45 mm per 100 yr. Using the isopach maps and associated field observations we have found a relationship between slope and deposition volume, where the runout and pattern of deposition is a

  16. Dramatical Impact Of Low Amounts of Swelling Clays On The Rheology Of Alpine Debris Flows

    NASA Astrophysics Data System (ADS)

    Bardou, E.; Bowen, P.; Banfill, P. G.; Boivin, P.

    2004-12-01

    Field observations show that the role and amount of swelling clays in the complex hard suspensions of alpine debris flow type were underestimated (see Boivin et al., this session). This work aims at exploring to which extent the swelling clay content influences the global rheology of a flow of rock grains from which the size spectrum extends from clays to gravel. We made a sample from calibrated materials with a grain size distribution similar to that of a viscoplastic debris flow (Bardou et al., 2003). Four replicates were made with the same grading curve. The clay content of the samples was 2% dry weight only, and different 2:1 swelling clay to 1:1 clay ratio were used. The swelling clay ratio (SCR) was calculated as the percentage of 2:1 clay in the clay fraction of the bulk samples. The 1:1 clay was (industrial) kaolinite and the 2:1 clay was a natural soil smectite. The smectite content in the bulk sample ranged from 0% to 2% dry weight, corresponding to SCR ranging from 0 to 80%. The four prepared samples were sheared in the large-size apparatus fully described in Tattersall and Banfill (1983). This apparatus is based on the measure of the torque necessary to rotate an impeller immersed in the sample. The impeller has the form of an "H" and moves in a plane according to two parallel axes. The observed behaviour were very contrasted. The sample with SCR=0 was poorly sensitive to changes in the solid concentration, in contrast to the three samples with SCR>0. Moreover, a small change in the SCR of the clay fraction induced a dramatic change of the behaviour of the mixture. For SCR=0, only little changes in the rheological parameters of the bulk samples were observed with respect to changes in the solid concentration. On the contrary the rheological parameters of the bulk samples with SCR>0, apparently followed a power law according to solid concentration. These tests carried out in the laboratory accord with observations realised on natural debris flow material

  17. An Early Warning System from debris flows based on ground vibration monitoring data

    NASA Astrophysics Data System (ADS)

    Arattano, Massimo; Coviello, Velio

    2015-04-01

    Among the different countermeasures that can be adopted for the mitigation of landslide hazard, Early Warning Systems (EWSs) are receiving an increasing attention. EWSs are the set of capacities needed to generate and disseminate timely and meaningful warning information to enable individuals and communities threatened by a hazard to appropriately act, in sufficient time, to reduce the possibility of harm or loss (UNEP, 2012). An EWS from debris flows can be classified into two main categories: advance and event EWSs. Advance EWSs predict the occurrence of a debris flow by monitoring hydro-meteorological conditions that may lead to its initiation. Despite their widespread adoption, these latter systems are prone to false alarms because they are heavily affected by bias between regional rainfall threshold and local conditions. Event EWSs, on the contrary, detect the occurrence of a debris flow when the process is already in progress. They usually rely on the use of algorithms for processing in real time the monitoring data. Their effectiveness depends on the reliability of those algorithms, which require long development and testing phases. A specific testing field for event EWSs has been equipped in the Gadria instrumented basin, located in the Eastern Italian Alps. A specifically designed monitoring unit capable to record data from different type of sensors and to implement aboard warning algorithms has been installed along a straight reach of the torrent. A flashing light, installed on the bank of the torrent, has been wired to this unit. The flashing light is framed by a fixed video camera that also shoots the passage of debris flows in the torrent. This provides a visual verification of the efficacy of the algorithm under test, particularly useful to show to practitioners and administrators a clear demonstration of the warning outcome. In this work, we present the performance of a warning algorithm that has been experimented in the Gadria testing field in 2013

  18. The altitude effect on the climatic factors controlling debris flows activation: the Marderello Torrent case study

    NASA Astrophysics Data System (ADS)

    Palladino, Michela; Turconi, Laura; Savio, Gabriele; Tropeano, Domenico

    2015-04-01

    The left Cenischia valley includes some of the best known alpine basins prone to debris flow in Northwestern Italian Alps. In particular, in the Marderello catchment (6,6 km²), a left tributary of the Cenischia river, 31 important debris flood/flow events occurred during the last one hundred years. According to the chronicles of the last three centuries, events with significant volumes are on the average liable to take place every 3-4 years, whereas minor events may occur even twice per year. Due to the high frequency of activations, the site is of relevant interest for monitoring purposes. Since the early nineties, the CNR IRPI equipped the Marderello basin with meteorological monitoring devices. The rainfall monitoring network consists of four rain gauges, placed at different elevations, between 800 m a.s.l. and 2854 m a.s.l. Other meteorological data (air moisture and temperature, atmospheric pressure, wind speed and direction) are provided by three stations located at 3150, 2150 and 830 m a.s.l. The main objective of the monitoring is the investigation of the triggering conditions for debris flows initiation. In the scientific literature the prediction of debris flows is often tackled by the use of empirical methods, based on the analysis of past activation and related rainfall triggering conditions. The effectiveness of these methods strictly depends on the representativeness of the meteorological monitoring stations used to collect the data. In complex orography sites, as the Alpine catchments are, the remarkable elevation gaps between the source areas of debris flows and the rain gauges position make it difficult to identify the triggering rainfall. To attain more reliable results, the elevation effect must be considered. In fact, elevation influences the precipitation in terms of cumulative values and, as a result of the temperature gradient, it controls the nature of the precipitation (rain/snow). In the present study we use the rainfall and temperature

  19. "The Great Cataract" - Effects of Late Holocene Debris Flows on Lava Falls Rapid, Grand Canyon National National Park, Arizona

    USGS Publications Warehouse

    Webb, Robert H.; Melis, Theodore S.; Wise, Thomas W.; Elliott, John G.

    1996-01-01

    Lava Falls Rapid is the most formidable reach of whitewater on the Colorado River in Grand Canyon and is one of the most famous rapids in the world. Although the rapid was once thought to be controlled by the remnants of lava dams of Pleistocene age, Lava Falls was created and is maintained by frequent debris flows from Prospect Canyon. We used 232 historical photographs, of which 121 were replicated, and 14C and 3He dating methods to reconstruct the ages and, in some cases, the magnitudes of late Holocene debris flows. We quantified the interaction between Prospect Canyon debris flows and the Colorado River using image processing of the historical photographs. The highest and oldest debris-flow deposits on the debris fan yielded a 3He date of 2.9?0.6 ka (950 BC), which indicates predominately late Holocene aggradation of one of the largest debris fans in Grand Canyon. The deposit, which has a 25-m escarpment caused by river reworking, crossed the Colorado River and raised its base level by 30 m for an indeterminate, although probably short, period. We mapped depositional surfaces of 6 debris flows that occurred after 950 BC. The most recent prehistoric debris flow occurred no more than 500 years ago (AD 1434). From April 1872 to July 1939, no debris flows occurred in Prospect Canyon. Debris flows in 1939, 1954, 1955, 1963, 1966, and 1995 constricted the Colorado River between 35 and 80 percent and completely changed the pattern of flow through the rapid. The debris flows had discharges estimated between about 290 and 1,000 m3/s and transported boulders as heavy as 30 Mg. The recurrence interval of these debris flows, calculated from the volume of the aggraded debris fan, ranged from 35 to 200 yrs. The 1939 debris flow in Prospect Canyon appears to have been the largest debris flow in Grand Canyon during the last 125 years. Debris flows in Prospect Canyon are initiated by streamflow pouring over a 325-m waterfall onto unconsolidated colluvium, a process called the

  20. Detecting debris- and mud-flow propagation at a distance with a microseismic monitoring network

    NASA Astrophysics Data System (ADS)

    Coviello, Velio; Arattano, Massimo; Turconi, Laura

    2014-05-01

    Debris-flow (mixtures of water and sediment of diverse shapes and sizes, commonly ranging from clay particles to great boulders) and mud-flow (mixtures mostly composed of grains smaller than sand) are among the most dangerous natural phenomena that may occur in mountainous torrents. They can cause severe damages to human settlements and infrastructures that are built too close to the torrent channel or on the alluvial fan. Monitoring these phenomena in instrumented catchments allows the collection of field data that can provide an important comparison with the geomorphological and topographical surveys of erosion, sediment supply and channel evolution. Monitoring data and the inferred quantification of the transported sediment are also of crucial importance for hazard assessment, land-use planning and design of torrent control structures, including warning systems. The reduced boulder content of mud-flows may have an important influence on the results of the monitoring, which might be significantly different than those of debris-flows. This is particularly true if seismic devices were employed as detecting tools, since the lack of huge boulders and large particles might impede the generation of strong ground vibrations. The ground vibration signals produced by mud-flows might also have different frequency ranges and different peak frequencies. These different behaviors should be investigated, not only for scientific purposes but also because they might lead to the choice of different parameters and algorithms in case seismic sensors are used for warning purposes. For these reasons the CNR IRPI has undertaken an experimental investigation and equipped the left Cenischia valley (NW Italian Alps), an alpine catchment prone to debris- and mud-flows previously instrumented only with a rainfall monitoring network. Actually, the monitoring station consisting of four 10 Hz vertical geophones placed on the ground, an ultrasonic sensor and 3 videocameras, is installed along

  1. A database on post-fire erosion rates and debris flows in Mediterranean-Basin watersheds

    NASA Astrophysics Data System (ADS)

    Parise, M.; Cannon, S. H.

    2009-04-01

    Wildfires can affect many Mediterranean countries on a yearly bases, producing damage and economic losses, both as direct effect of the fires and as consequent events, including erosion and sedimentation in the recently burned areas. Even though most of the wildfires occur in Spain, Portugal, southern France, Italy and Greece, it can be stated that no one of the Mediterranean countries is completely immune by such hazards. In addition to destruction of the vegetation, and in addition to direct losses to the built-up environment, further effects may also be registered as a consequence of the fire, even weeks or months after its occurrence. Wildfire can have, in fact, profound effects on the hydrologic response of watersheds, and debris-flow activity is among the most destructive consequences of these effects, often causing extensive damage to human infrastructure. Wildfires are today continuously monitored by several European institutions, and forecasting of the conditions (weather, temperature, wind, etc.) more likely conducive to their occurrence is often available in real time. On the other hand, not much is known about the processes that occur as a consequence of the fire, including erosion and debris flows. These are often underestimated, and become object of study only after some catastrophic event has occurred. This is in strong contrast with all the established techniques of risk mitigation; as a result, no prevention action is generally considered, and the society relies only on the emergency phase following a disaster. Aimed at contributing to gather information about the occurrence of erosional and debris-flow activity in recently burned Mediterranean areas, and at making available these information to land planners and scientists, a specific database has been compiled and presented in this contribution. To date, scientific literature on the topic in Europe has never been catalogued, and was dispersed in a number of different journals and in conference

  2. Influence of deposition of fine plant debris in river floodplain shrubs on flood flow conditions - The Warta River case study

    NASA Astrophysics Data System (ADS)

    Mazur, Robert; Kałuża, Tomasz; Chmist, Joanna; Walczak, Natalia; Laks, Ireneusz; Strzeliński, Paweł

    2016-08-01

    This paper presents problems caused by organic material transported by flowing water. This material is usually referred to as plant debris or organic debris. Its composition depends on the characteristic of the watercourse. For lowland rivers, the share of the so-called small organic matter in plant debris is considerable. This includes both various parts of water plants and floodplain vegetation (leaves, stems, blades of grass, twigs, etc.). During floods, larger woody debris poses a significant risk to bridges or other water engineering structures. It may cause river jams and may lead to damming of the flowing water. This, in turn, affects flood safety and increases flood risk in river valleys, both directly and indirectly. The importance of fine plant debris for the phenomenon being studied comes down to the hydrodynamic aspect (plant elements carried by water end up on trees and shrubs, increase hydraulic flow resistance and contribute to the nature of flow through vegetated areas changed from micro-to macro-structural). The key part of the research problem under analysis was to determine qualitative and quantitative debris parameters and to establish the relationship between the type of debris and the type of land use of river valleys (crop fields, meadows and forested river sections). Another problem was to identify parameters of plant debris for various flow conditions (e.g. for low, medium and flood flows). The research also included an analysis of the materials deposited on the structure of shrubs under flood flow conditions during the 2010 flood on the Warta River.

  3. DebrisInterMixing-2.3: a Finite Volume solver for three dimensional debris flow simulations based on a single calibration parameter - Part 2: Model validation

    NASA Astrophysics Data System (ADS)

    von Boetticher, A.; Turowski, J. M.; McArdell, B. W.; Rickenmann, D.; Hürlimann, M.; Scheidl, C.; Kirchner, J. W.

    2015-08-01

    Here we present the validation of the fluid dynamic solver presented in part one of this work (von Boetticher et al., 2015), simulating laboratory-scale and large-scale debris-flow experiments. The material properties of the experiments, including water content, sand content, clay content and its mineral composition, and gravel content and its friction angle, were known. We show that given these measured properties, a single free model parameter is sufficient for calibration, and a range of experiments with different material compositions can be reproduced by the model without recalibration. The model validation focuses on different case studies illustrating the sensitivity of debris flows to water and clay content, channel curvature, channel roughness and the angle of repose of the gravel. We characterize the accuracy of the model using experimental observations of flow head positions, front velocities, run-out patterns and basal pressures.

  4. Application of different techniques to obtain spatial estimates of debris flows erosion and deposition depths

    NASA Astrophysics Data System (ADS)

    Boreggio, Mauro; Gregoretti, Carlo; Degetto, Massimo; Bernard, Martino

    2016-04-01

    In Alpine regions, debris flows endanger settlements and human life. Danger mitigation strategies based on the preparation of hazard maps are necessary tools for the current land planning. To date, hazard maps are obtained by using one- or two-dimensional numerical models that are able to forecast the potential inundated areas, after careful calibration of those input parameters that directly affect the flow motion and its interaction with the ground surface (sediments entrainment or deposition). In principle, the reliability of these numerical models can be tested by flume experiments in laboratory using, for example, particles and water mixtures. However, for more realistic materials including coarse particles, the scaling effects are still difficult to account for. In some cases, where there are enough data (for example, point measures of flow depths and velocities or spatial estimation of erosion and deposition depths), these models can be tested against field observations. As it regards the spatial estimates of debris flows erosion and deposition depths, different approaches can be followed to obtain them, mainly depending on both the type and accuracy of the available initial data. In this work, we explain the methods that have been employed to obtain the maps of erosion and deposition depths for three occurred debris flows in the Dolomites area (North-Eastern Italian Alps). The three events are those occurred at Rio Lazer (Trento) on the 4th of November 1966, at Fiames (Belluno) on the 5th of July 2006 and at Rio Val Molinara (Trento) on the 15th of August 2010. For each case study, we present the available initial data and the related problems, the techniques that have been used to overcome them and finally the results obtained.

  5. Resolved granular debris-flow simulations with a coupled SPH-DCDEM model

    NASA Astrophysics Data System (ADS)

    Birjukovs Canelas, Ricardo; Domínguez, José M.; Crespo, Alejandro J. C.; Gómez-Gesteira, Moncho; Ferreira, Rui M. L.

    2016-04-01

    Debris flows represent some of the most relevant phenomena in geomorphological events. Due to the potential destructiveness of such flows, they are the target of a vast amount of research (Takahashi, 2007 and references therein). A complete description of the internal processes of a debris-flow is however still an elusive achievement, explained by the difficulty of accurately measuring important quantities in these flows and developing a comprehensive, generalized theoretical framework capable of describing them. This work addresses the need for a numerical model applicable to granular-fluid mixtures featuring high spatial and temporal resolution, thus capable of resolving the motion of individual particles, including all interparticle contacts. This corresponds to a brute-force approach: by applying simple interaction laws at local scales the macro-scale properties of the flow should be recovered by upscaling. This methodology effectively bypasses the complexity of modelling the intermediate scales by resolving them directly. The only caveat is the need of high performance computing, a demanding but engaging research challenge. The DualSPHysics meshless numerical implementation, based on Smoothed Particle Hydrodynamics (SPH), is expanded with a Distributed Contact Discrete Element Method (DCDEM) in order to explicitly solve the fluid and the solid phase. The model numerically solves the Navier-Stokes and continuity equations for the liquid phase and Newton's motion equations for solid bodies. The interactions between solids are modelled with classical DEM approaches (Kruggel-Emden et al, 2007). Among other validation tests, an experimental set-up for stony debris flows in a slit check dam is reproduced numerically, where solid material is introduced trough a hopper assuring a constant solid discharge for the considered time interval. With each sediment particle undergoing tens of possible contacts, several thousand time-evolving contacts are efficiently treated

  6. Evidence for enhanced debris flow activity in the Northern Calcareous Alps since the 1980s (Plansee, Austria)

    NASA Astrophysics Data System (ADS)

    Dietrich, Andreas; Krautblatter, Michael

    2016-04-01

    From 1950 to 2011 almost 80.000 people lost their lives through the occurrence of debris flow events (Dowling and Santi, 2014). Debris flows occur in all alpine regions due to intensive rainstorms and mobilisable loose debris. Due to their susceptible lithology, the Northern Calcareous Alps are affected by a double digit number of major hazard events per year. Some authors hypothesised a relation between an increasing frequency of heavy rainstorms and an increasing occurrence of landslides in general (Beniston and Douglas, 1996) and debris flows in special (Pelfini and Santilli, 2008), but yet there is only limited evidence. The Plansee catchment in the Ammergauer Alps consists of intensely jointed Upper Triassic Hauptdolomit lithology and therefore shows extreme debris flow activity. To investigate this activity in the last decades, the temporal and spatial development of eight active debris flow fans is examined with GIS and field mapping. The annual rates since the late 1940s are inferred accurately by using aerial photos from 1947, 1952, 1971, 1979, 1987, 2000 and 2010. These rates are compared to the mean Holocene/Lateglacial debris flow volume derived from the most prominent cone. The contact with the underlying till is revealed by electrical resistivity tomography (ERT). It shows that the mean annual debris flow volume has increased there by a factor of 10 from 1947-1952 (0.23 ± 0.07 10³m³/yr) to 1987-2000 (2.41 ± 0.66 10³m³/yr). A similar trend can be seen on all eight fans: mean post-1980 rates exceed pre-1980 rates by a factor of more than three. This increasing debris flow activity coincides with an enhanced rainstorm (def. 35 mm/d) frequency recorded at the nearest meteorological station. Since 1921 the frequency of heavy rainstorms has increased there on average by 10% per decade. Recent debris flow rates are also 2-3 times higher compared to mean Holocene/Lateglacial rates. Furthermore, we state a strong correlation between the non

  7. Numerical simulation of the debris flow dynamics with an upwind scheme and specific friction treatment

    NASA Astrophysics Data System (ADS)

    Sánchez Burillo, Guillermo; Beguería, Santiago; Latorre, Borja; Burguete, Javier

    2014-05-01

    Debris flows, snow and rock avalanches, mud and earth flows are often modeled by means of a particular realization of the so called shallow water equations (SWE). Indeed, a number of simulation models have been already developed [1], [2], [3], [4], [5], [6], [7]. Debris flow equations differ from shallow water equations in two main aspects. These are (a) strong bed gradient and (b) rheology friction terms that differ from the traditional SWE. A systematic analysis of the numerical solution of the hyperbolic system of equations rising from the shallow water equations with different rheological laws has not been done. Despite great efforts have been done to deal with friction expressions common in hydraulics (such as Manning friction), landslide rheologies are characterized by more complicated expressions that may deal to unphysical solutions if not treated carefully. In this work, a software that solves the time evolution of sliding masses over complex bed configurations is presented. The set of non- linear equations is treated by means of a first order upwind explicit scheme, and the friction contribution to the dynamics is treated with a suited numerical scheme [8]. In addition, the software incorporates various rheological models to accommodate for different flow types, such as the Voellmy frictional model [9] for rock and debris avalanches, or the Herschley-Bulkley model for debris and mud flows. The aim of this contribution is to release this code as a free, open source tool for the simulation of mass movements, and to encourage the scientific community to make use of it. The code uses as input data the friction coefficients and two input files: the topography of the bed and the initial (pre-failure) position of the sliding mass. In addition, another file with the final (post-event) position of the sliding mass, if desired, can be introduced to be compared with the simulation obtained result. If the deposited mass is given, an error estimation is computed by

  8. Determining the physical vulnerability of roads to debris flow by means of an expert judgement approach

    NASA Astrophysics Data System (ADS)

    Winter, M. G.; Smith, J. T.; Fotopoulou, S.; Pitlakis, K.; Mavrouli, O.-C.; Corominas, J.; Argyroudis, S.

    2012-04-01

    The physical vulnerability of roads to debris flow is expressed through fragility functions that relate flow volume to damage probabilities. Fragility relationships are essential components of quantitative risk assessments (QRA) as they allow for the estimation of risk within a consequence-based framework. To the best of the Authors' knowledge this is the first time that fragility curves have been produced in order to provide the conditional probability for a road to be in, or to exceed, a certain damage state for a given debris flow volume. Preliminary assessments were undertaken by means of a detailed questionnaire. A total of 47 returns were received from experts in 17 countries: 32% academia, 51% the commercial sector and 17% governments. Fragility curves have been defined for three damage states (limited damage, serious damage and destroyed) for each of low speed and high speed roads in order to cover the typical characteristics of roads vulnerable to debris flow. The probability of any given damage state being met or exceeded by a debris flow of a given volume (10 to 100,000m3) was derived from the mean of the responses received. Inevitably there was a degree of scatter in the results and the treatment of such variation, or 'experimental errors', was crucial to understanding the data and to developing the fragility curves. Both qualitative and quantitative methods of arriving at these preliminary fragility curves were utilised. The nature of the data is such that unless all respondents return that value the average probability at the largest flow volume cannot reach unity; as a result the upper ends of each curve were forced to unity and in order to account for larger potential volumes manual extrapolation was undertaken to 1,000,000m3. In addition to an assessment of the probabilities of given damage states being exceeded respondents to the questionnaire were polled as to their level of experience and confidence in their ability to provide a valid and

  9. Space-time organization of debris flows-triggering rainfall: effects on the identification of the rainfall threshold relationships

    NASA Astrophysics Data System (ADS)

    Borga, Marco; Nikolopoulos, Efthymios; Creutin, Jean Dominique; Marra, Francesco

    2015-04-01

    Debris flow occurrence is generally forecasted by means of empirical rainfall depth-duration thresholds which are often derived based on rain gauge observations (Guzzetti et al., 2008). Rainfall sampling errors, related to the sparse nature of raingauge data, lead to underestimation of the intensity-duration thresholds (Nikolopoulos et al., 2014, Nikolopoulos et al., 2015). This underestimation may be large when debris flows are triggered by convective rainfall events, characterized by limited spatial extent, turning into less efficient forecasts of debris flow occurrence. This work investigates the spatial and temporal structure of rainfall patterns and its effects on the derived rainfall threshold relationships using high-resolution, carefully corrected radar data for 82 debris flows events occurred in the eastern Italian Alps. We analyze the spatial organization of rainfall depths relative to the rainfall occurred over the debris flows initiation point using the distance from it as the main coordinate observing that, on average, debris flows initiation points are characterized by a maximum in the rainfall depth field. We investigate the relationship between spatial organization and duration of rainfall pointing out that the rainfall underestimation is larger for the shorter durations and increases regularly as the distance between rainfall measurement location and debris flow initiation point increases. We introduce an analytical framework that explains how the combination of the mean rainfall depth spatial pattern and its relationship with rainfall duration causes the bias observed in the raingauge-based thresholds. The consistency of this analytical framework is proved by using a Monte Carlo sampling of radar rainfall fields. References Guzzetti, F., Peruccacci, S., Rossi, M., Stark, C.P., 2008. The rainfall intensity-duration control of shallow landslides and debris flows: an update. Landslides 5, 3-17, 10.1007/s10346-625 007-0112-1 Nikolopoulos, E.I., S

  10. Relative tectonics and debris flow hazards in the Beijing mountain area from DEM-derived geomorphic indices and drainage analysis

    NASA Astrophysics Data System (ADS)

    Cheng, Weiming; Wang, Nan; Zhao, Min; Zhao, Shangmin

    2016-03-01

    The geomorphic setting of the tectonically active area around Beijing is a result of complex interactions involving Yanshan neotectonic movements and processes of erosion and deposition. The Beijing Mountain study area contains the junction of two mountain ranges (the Yanshan Mountains and the Taihang Mountains). Tectonic activity has significantly influenced the drainage system and the geomorphic situation in the area, leading to a high probability of the development of debris flows, which is one of the major abrupt geological disasters in the region. Based on 30-m-resolution ASTER GDEM data, a total of 752 drainage basins were extracted using ArcGIS software. A total of 705 debris flow valleys were visually interpreted from ALOS satellite images and published documents. Seven geomorphic indices were calculated for each basin including the relief amplitude, the hypsometric integral, the stream length gradient, the basin shape indices, the fractal dimension, the asymmetry factor, and the ratio of the valley floor width to the height. These geomorphic indices were divided into five classes and the ratio of the number of the debris flow valleys to the number of the drainage basins for each geomorphic index was computed and analyzed for every class. Average class values of the seven indices were used to derive an index of relative active tectonics (IRAT). The ratio of the number of the debris flow valleys to the number of the drainage basins was computed for every class of IRAT. The degree of probable risk level was then defined from the IRAT classes. Finally, the debris flow hazard was evaluated for each drainage basin based on the combined effect of probable risk level and occurrence frequency of the debris flows. The result showed a good correspondence between IRAT classes and the ratio of the number of the debris flow valleys to the number of the drainage basins. Approximately 65% of the drainage basins with occurred debris flow valleys are at a high risk level

  11. Detailed study of a catchment prone to debris flows along the International Road n° 7, Mendoza Province, Argentina

    NASA Astrophysics Data System (ADS)

    Wick, E.; Baumann, V.; Favre-Bulle, G.; Jaboyedoff, M.; Loye, A.; Marengo, H.; Rosas, M.

    2009-04-01

    The International Road 7 crosses Argentina from East to West, linking Buenos Aires to the Chile border. Crossing the Andes Cordillera, it is exposed to numerous natural hazards, such as avalanches, rockfalls and debris flows. This study focuses on a catchment prone to debris flows above the International Road n° 7 between Potrerillos and Uspallata (Mendoza Province, Argentina) and is part of a regional study that assesses the hazard along the mountainous section of this road. The catchment measures 4.7 km2 and is constituted of three main torrents that unite a few meters above the International Road. Heavy rainfalls triggered debris flows in each of these torrents during the evening of 11 January 2005, reaching the road apparently at a very short interval of time. A car was hit by one of these debris flows and two people were injured. The study has been realized from Quickbird satellite imagery and field data principally. The conditions that triggered the debris flows in this catchment were established from meteorological data, as well as particle size and mineralogy of the material. Satellite imagery and a digital elevation model showed that the debris flows initiated mainly at the top of the catchment. Erosion of a highly altered granite produced abundant sandy material. The debris flows were classified as granular matrix with a collisional-frictional behavior. Various calculations of volumes, peak discharges and velocities (~ 7 m/s) were realized using different approaches. It appears that important volumes could be mobilized, especially in the longest torrent. A new event could imply more than 65'000 m3 of material. A detailed geomorphologic study shows the effect of mitigation works on the debris flows hazard. Indeed, the torrents were deviated towards a more adequate place for the construction of a road bridge. Three propagation scenarios show the limited efficiency of these works. The road bridge is under-dimensioned and deposits of the 2005 event have not

  12. Non-local rheology of stony debris flow propagating over a cohesionless sediment bed

    NASA Astrophysics Data System (ADS)

    Lanzoni, Stefano; Gregoretti, Carlo

    2016-04-01

    Velocity profiles of gravel-water mixtures observed in flume experiments often exhibit a double-slope behavior, with a lower narrower region where the velocity increases slowly, and an upper wider region often exhibiting a nearly linear behavior. Even though the flow can be classified within the grain-inertia regime, the overall profile seems to not conform to the power law (with exponent 1.5) distribution obtained by integrating along the normal to the flow the dispersive stresses envisaged by Bagnold (1954) in his pioneer work. Note that this formulation neglects the contribution to the velocity profile of the quasi-static (frictional) stresses that tend to dominate close to an erodible sediment bottom. The present work investigates the possibility to find out a uniformly valid distribution of shear stress from the bottom to the flow surface. To this aim we follow a heuristic coherence length approach (GDR-MIDI, 2004) similar to the mixing length procedure commonly used to study the atmospheric boundary layer over canopy (see, e.g., Harmann and Finnegan, 2007). A database built on 64 systematic debris flow experiments is used to disclose the general features of velocity profiles that establish within the body of almost steady water-sediment flows and the dependence of transport sediment volumetric concentration on the relevant parameters. The almost steady water-sediment flows considered in the study were generated by releasing a prescribed water discharge on a saturated layer of sediment (specifically, 3 mm gravel, 6 mm gravel, and 3 mm glass spheres) initially placed in a 10 m long and 0.2 m wide laboratory flume. The analysis clearly indicates that stony debris flow conditions characterized the experiments. The mixing length does not result constant, as required by a Bagnold-like profile, but varies gradually, from zero at the flow surface, to a finite value near the erodible bottom. We discuss this structure in terms of shear stress distribution along the

  13. Numerical simulation of the debris flow dynamics with an upwind scheme and specific friction treatment

    NASA Astrophysics Data System (ADS)

    Sánchez Burillo, Guillermo; Beguería, Santiago; Latorre, Borja; Burguete, Javier

    2014-05-01

    Debris flows, snow and rock avalanches, mud and earth flows are often modeled by means of a particular realization of the so called shallow water equations (SWE). Indeed, a number of simulation models have been already developed [1], [2], [3], [4], [5], [6], [7]. Debris flow equations differ from shallow water equations in two main aspects. These are (a) strong bed gradient and (b) rheology friction terms that differ from the traditional SWE. A systematic analysis of the numerical solution of the hyperbolic system of equations rising from the shallow water equations with different rheological laws has not been done. Despite great efforts have been done to deal with friction expressions common in hydraulics (such as Manning friction), landslide rheologies are characterized by more complicated expressions that may deal to unphysical solutions if not treated carefully. In this work, a software that solves the time evolution of sliding masses over complex bed configurations is presented. The set of non- linear equations is treated by means of a first order upwind explicit scheme, and the friction contribution to the dynamics is treated with a suited numerical scheme [8]. In addition, the software incorporates various rheological models to accommodate for different flow types, such as the Voellmy frictional model [9] for rock and debris avalanches, or the Herschley-Bulkley model for debris and mud flows. The aim of this contribution is to release this code as a free, open source tool for the simulation of mass movements, and to encourage the scientific community to make use of it. The code uses as input data the friction coefficients and two input files: the topography of the bed and the initial (pre-failure) position of the sliding mass. In addition, another file with the final (post-event) position of the sliding mass, if desired, can be introduced to be compared with the simulation obtained result. If the deposited mass is given, an error estimation is computed by

  14. On the use of the calibration-based approach for debris-flow forward-analyses

    NASA Astrophysics Data System (ADS)

    Pirulli, M.

    2010-05-01

    In the present paper the problem of modeling the propagation of potential debris flows is tackled resorting to a numerical approach. In particular, numerical analyses are carried out with the RASH3D code, based on a single-phase depth-averaged continuum mechanics approach. Since each numerical analysis requires the selection of a rheology and the setting of the rheological input parameters, a calibration-based approach, where the rheological parameters are constrained by systematic adjustment during trial-and-error back-analysis of full-scale events, has been assumed. The back-analysis of a 1000 m3 debris flow, located at Tate's Cairn, Hong Kong, and the forward-analysis of a 10 000 m3 potential debris flow, located in the same basin have been used to investigate the transferability of back-calculated rheological parameters from one case to another. Three different rheologies have been tested: Frictional, Voellmy and Quadratic. From obtained results it emerges that 1) the back-calculation of a past event with different rheologies can help in selecting the rheology that better reproduces the runout of the analysed event and, on the basis of that selection, can give some indication about the dynamics of the investigated flow, 2) the use of back-calculated parameters for forward purposes requires that past and potential events have similar characteristics, some of which are a function of the assumed rheology. Among tested rheologies, it is observed that the Quadratic rheology is more influenced by volume size than Frictional and Voellmy rheologies and consequently its application requires that events are also similar in volume.

  15. Reconstruction of Val Molinara 2010 debris flow and validation of the hazard mapping methodology

    NASA Astrophysics Data System (ADS)

    Zorzi, Nadia; Begnudelli, Lorenzo; Rosatti, Giorgio

    2013-04-01

    In this work, a real debris flow over an urbanized conoid is studied and reconstructed using the bidimensional finite-volume mathematical model Trent2D (Armanini et. al, Computer & Geosciences 2009). The event occurred in August 2010 in the village of Campolongo (Province of Trento, Italy) as a result of torrential rains and is particularly well documented thanks to the availability of aerial pictures, ground surveys, sediment deposition measurements, and data of two nearby rain gauges as well of radar. The 2D mathematical model adopted in the study is based on a two-phase description of the debris flow with immediate adaptation of the transport to the local flow conditions. It adopts a rheological closure valid in the grain-inertia regime. The equations are solved on a structured quadrilateral grid using a Godunov-type scheme, where inter-cell fluxes are evaluated using a MUSCL-Hancock approach with second order spatial and temporal accuracy. In order to reconstruct the event, the following tasks have been carried out: a) computation of liquid discharge through a rainfall-runoff model; b) evaluation of the debris flow discharge (and therefore of the discharge of solid mass); c) estimation of the model's parameters; d) execution of simulation and comparison with available data. Model's predictions are compared with surveys in order to show its capabilities as well as understand its possible limitations arising from the hypothesis the model is based on. Moreover, the sensitivity of model to variations of parameters and boundary conditions (i.e. discharge) is tested showing interesting results. Finally, the hazard map for the area is generated adopting the standard procedure as required by national and local regulations in order to study how predictive simulations compare to the results of a back analysis process.

  16. High Detailed Debris Flows Hazard Maps by a Cellular Automata Approach

    NASA Astrophysics Data System (ADS)

    Lupiano, V.; Lucà, F.; Robustelli, G.; Rongo, R.; D'Ambrosio, D.; Spataro, W.; Avolio, M. V.

    2012-04-01

    The individuation of areas that are more likely to be interested by new debris flows in regions that are particularly exposed to such kind of phenomena is of fundamental relevance for mitigating possible consequences, both in terms of loss of human lives and material properties. Here we show the adaption of a recent methodology, already successfully applied to lava flows, for defining flexible high-detailed and reliable hazard maps. The methodology relies on both an adequate knowledge of the study area, assessed by an accurate analysis of its past behavior, together with a reliable numerical model for simulating debris flows on present topographic data (the Cellular Automata model SCIDDICA, in the present case). Furthermore, High Performance Parallel Computing is employed for increasing computational efficiency, due to the great number of simulations of hypothetical events that are required for characterizing the susceptibility to flow invasion of the study area. The application of the presented methodology to the case of Gragnano (Italy) pointed out the goodness of the proposed approach, suggesting its appropriateness for land use planning and Civil Defense applications.

  17. Circulation patterns related to debris-flow triggering in the Zermatt valley in current and future climates

    NASA Astrophysics Data System (ADS)

    van den Heuvel, Floor; Goyette, Stéphane; Rahman, Kazi; Stoffel, Markus

    2016-11-01

    The principal objective of this study was to investigate the types of large-scale meteorological situations that are conducive to the precipitation and temperature conditions most likely to trigger debris flows in the Zermatt valley, Switzerland, under current and future climates. A two-dimensional Bayesian probability calculation was applied to take account of uncertainties in debris-flow triggering. Precipitation quantities exceeding the 95th percentile of daily precipitation amounts were found to have a significantly higher probability to coincide with observed debris flows. A different relationship exists for extreme temperatures, however. Southerly air flows, weak horizontal pressure gradients over Europe, and westerly flows are mostly associated with observed debris flows and 95th precipitation percentile exceedances. These principal flow directions are well represented in the regional climate model (RCM) HIRHAM control simulations for events exceeding the 95th precipitation percentile and the 30th temperature percentile. Under the IPCC A2 emission scenario, westerly and southerly flows are mostly responsible for these precipitation and temperature conditions under the hypothesis of slow adaptation to climate change (HS1/HC1). Under the hypothesis of rapid adaptation to climate change (HS1/HS1), southerly flows and weak horizontal pressure gradients are likely to gain in importance. In both scenarios for the future, southeasterly flows are among the principal flow directions responsible for the joint exceedance of the 95th precipitation percentile and the 30th temperature percentile, while these were absent in observations and the control simulation.

  18. Postwildfire debris-flow hazard assessment of the area burned by the 2013 West Fork Fire Complex, southwestern Colorado

    USGS Publications Warehouse

    Verdin, Kristine L.; Dupree, Jean A.; Stevens, Michael R.

    2013-01-01

    This report presents a preliminary emergency assessment of the debris-flow hazards from drainage basins burned by the 2013 West Fork Fire Complex near South Fork in southwestern Colorado. Empirical models derived from statistical evaluation of data collected from recently burned basins throughout the intermountain western United States were used to estimate the probability of debris-flow occurrence, potential volume of debris flows, and the combined debris-flow hazard ranking along the drainage network within and just downstream from the burned area, and to estimate the same for 54 drainage basins of interest within the perimeter of the burned area. Input data for the debris-flow models included topographic variables, soil characteristics, burn severity, and rainfall totals and intensities for a (1) 2-year-recurrence, 1-hour-duration rainfall, referred to as a 2-year storm; (2) 10-year-recurrence, 1-hour-duration rainfall, referred to as a 10-year storm; and (3) 25-year-recurrence, 1-hour-duration rainfall, referred to as a 25-year storm. Estimated debris-flow probabilities at the pour points of the 54 drainage basins of interest ranged from less than 1 to 65 percent in response to the 2-year storm; from 1 to 77 percent in response to the 10-year storm; and from 1 to 83 percent in response to the 25-year storm. Twelve of the 54 drainage basins of interest have a 30-percent probability or greater of producing a debris flow in response to the 25-year storm. Estimated debris-flow volumes for all rainfalls modeled range from a low of 2,400 cubic meters to a high of greater than 100,000 cubic meters. Estimated debris-flow volumes increase with basin size and distance along the drainage network, but some smaller drainages also were predicted to produce substantial debris flows. One of the 54 drainage basins of interest had the highest combined hazard ranking, while 9 other basins had the second highest combined hazard ranking. Of these 10 basins with the 2 highest

  19. Multiple-pulsed debris avalanche emplacement at Mount St. Helens in 1980: Evidence from numerical continuum flow simulations

    NASA Astrophysics Data System (ADS)

    Sousa, James; Voight, Barry

    1995-07-01

    The complex 1980 Mount St. Helens debris avalanche is modeled numerically as a transient biviscous fluid flow. Several approaches are considered, including two-step rheologically-distinct models for avalanche I and combined avalanches II/III, and a composite flow model consisting of retrogressive slides of identical rheology successively accreted to the main avalanche flow. For the two-step situation, flow rheologies are evaluated separately for the initial avalanche, comprising the debris avalanche block facies, and an ensuing explosive-influenced flow. Strengths (normalized by density) as high as 250 m 2/s 2 and apparent Newtonian viscosities as much as 275 m 2/s were established for the block facies. These parameters for the explosively-influenced flow are an order of magnitude lower. The distribution of stratigraphic units within flowing model debris, compared with field distributions, suggests that the higher-strength emplacement models are appropriate for debris deposited on Johnston Ridge and in the upper parts and flanks of the North Fork Toutle River valley. In general, models for which constant rheology is assumed throughout the flow process provide lower-bound emplacement times, and excessive early velocities, as compared to the prototype event. Because model calibration is based on matching runout by trial and error, it is therefore biased toward the rheologic parameters essential to achieving that runout. These values characterize the flow in its latter stages, whereas the actual strength and viscosity may have substantially decreased as a function of displacement. Two-dimensional models predict debris accumulation about twice as thick as that observed at the foot of Mount St. Helens, where flow divergence was significant. This discrepancy is lessened with a quasi-three-dimensional modification of the flow model. Accretionary composite flow models with homogeneous rheology simulate the overriding of early avalanche debris by later debris pulses. The

  20. Relationship Analysis of Debris Flow-inducing Factors in Typhoon Morakot Affected Area By Using Data Mining Techniques

    NASA Astrophysics Data System (ADS)

    Shen, Che-Wei; Hsiao, Cheng-Yang; Ku, Bing-Huan; Tsao, Ting-Chi; Cheng, Chin-Tung; Lo, Wen-Chun; Chen, Chen-Yu

    2013-04-01

    Typhoon Morakot lashed Taiwan during Aug. 7 to 9, 2009. It dumped heavy rainfall in southern Taiwan, especially around the Central Mountain Range in Pingtung, Chia-Yi, and Kaohsiung County. In view of this, Comprehensive field investigation was carried out by government and private organizations after Typhoon Morakot, useful information of debris flow was gathered. Besides, after Typhoon Morakot, the debris flow-inducing factors become more challenging in Taiwan, many aspects had to be considered. The scope of this study was mainly discussed in debris flow-inducing factors in serious damaged areas which including Nantou, Chia-Yi, Tainan, Kaohsiung, Pingtung, Taitung County. Totally 218 torrents were included. Field investigation data and disaster records of Typhoon Morakot were utilized to analyze debris flow-inducing factors in three aspects: terrain, rainfall and sediment source. First, by using Principle Component Analysis(PCA) and Pearson Product Moment Correlation Analysis(CA) to select significant factors, 101 factors were reduced to the most important 18. Then through descriptive statistics and scatter diagram were selected to discuss the correlation among "Average slope gradient of watershed", "Landslide rate along the stream within 50m buffer zone" as well as the "rainfall intensity during Typhoon Morakot". The above charts were used to summarize the range of factor value which tend to occur phenomenon of debris flow in Typhoon Morakot. Besides, Random Forest Algorithm (RF) was utilized to research the relationship toward multi-variables. The significant factors which tend to affect the debris flow-inducing factor were "effective accumulated rainfall", "hourly rainfall", "landslide rate along the stream within 50m buffer zone", "average elevation value of effective watershed area higher than 10 degree", sequentially. By the results, the most significant factor is the rainfall factor during Typhoon Morakot. The results can be utilized in improving debris

  1. A method for assessing regional debris flow risk: an application in Zhaotong of Yunnan province (SW China)

    NASA Astrophysics Data System (ADS)

    Liu, Xilin; Lei, Junzhong

    2003-06-01

    Based on the definitions of the United Nations, the assessment of risk involves the evaluation of both hazard and vulnerability. This forms the basis of a generalized assessment model of debris flow risk. Hazard is a measure of the threatening degree of an extreme event and is expressed theoretically as a function of event magnitude and frequency of occurrence. Mathematically, it is the definite integral area under the magnitude-frequency curve. Based on the need for a model applicable in regions that lack data, a new method that incorporates theoretical concepts with empirical analysis is presented to calculate the regional hazardousness of debris flows. Debris flow hazard can be estimated from gully density, mean annual rainfall and percentage of cultivated land on steep slope. Vulnerability is defined as the potential total maximum losses due to a potential damaging phenomenon for a specified area and during a reference period. On a regional scale, it is dependent on the fixed assets, gross domestic product, land resources and population density, as well as age, education and wealth of the inhabitants. A nonlinear, power-function model to compute the vulnerability degree is presented. An application of the proposed method to Zhaotong prefecture of Yunnan province, SW China, provides high accuracy and reasonable risk estimates. The highest risk of debris flow is in Zhaotong county with a value of 0.48; the lowest risk of debris flow is in Yanjin county with a value of 0.16. The other counties have debris flow risks ranging from 0.22 to 0.46. This provides an approach for assessing the regional debris flow risk and a basis for the formulation of a regional risk management policy in Zhaotong prefecture.

  2. Improving the early-warning of a mud-debris flow using radar rainfall data

    NASA Astrophysics Data System (ADS)

    Jun, Hwandon; Kim, Soojun; Lee, Jiho

    2016-04-01

    The timely and accurate warning of mud-debris flows including landslide hazards is very important to protect life and property. The rainfall estimation uncertainty makes it difficult to issue accurate warning. Traditionally rain gauges have been the main source of surface rainfall measurements. The rain gauges provide an accurate point rainfall estimates, but their spatial resolution is limited by the low-density of a gauge network. The errors associated with interpolation schemes to fill in the missing data over the ungauged sites can introduce significant error due to the long distance between the rain gauge stations and the hazard site (ungauged sites), particularly over rough terrain. The radar system can provide rainfall information at higher temporal and spatial resolutions than was previously possible from rain gauge measurements. While radar provides accurate spatial and temporal resolution of the rainfall field at significant heights above the surface of the earth, numerous measurement errors can result in an inaccurate rainfall depth at the ground. This study attempts to improve mud-debris flow early-warnings through accurate rainfall depth estimation by applying an innovative artificial neural network method. The first scenario uses the nearest rainfall observing site from an ungauged hazard site. The second uses the radar rainfall data and improves the rainfall estimation compared to the first scenario. The third scenario integrates the above two scenarios using both radar and observed rainfall at the sites around the ungauged hazard site, and improves the rainfall estimation by the largest margin. This methodology is applied to the Seoul metropolitan area. The proposed methodology can be applied to improve the confidence in the early-warning of the mud-debris flow hazard in other areas. Acknowledgment This research was supported by a grant (13SCIPS04) from Smart Civil Infrastructure Research Program funded by Ministry of Land, Infrastructure and

  3. Video-Seismic coupling for debris flow study at Merapi Volcano, Indonesia

    NASA Astrophysics Data System (ADS)

    Budi Wibowo, Sandy; Lavigne, Franck; Mourot, Philippe; Sukatja, Bambang

    2016-04-01

    Previous lahar disasters caused at least 44.252 death toll worldwide from 1600 to 2010 of which 52 % was due to a single event in the late 20th century. The need of a better understanding of lahar flow behavior makes general public and stakeholders much more curious than before. However, the dynamics of lahar in motion is still poorly understood because data acquisition of active flows is difficult. This research presents debris-flow-type lahar on February 28, 2014 at Merapi volcano in Indonesia. The lahar dynamics was studied in the frame of the SEDIMER Project (Sediment-related Disasters following the 2010 centennial eruption of Merapi Volcano, Java, Indonesia) based on coupling between video and seismic data analysis. We installed a seismic station at Gendol river (1090 meters asl, 4.6 km south from the summit) consisting of two geophones placed 76 meters apart parallel to the river, a high definition camera on the edge of the river and two raingauges at east and west side of the river. The results showed that the behavior of this lahar changed continuously during the event. The lahar front moved at an average speed of 4.1 m/s at the observation site. Its maximum velocity reached 14.5 m/s with a peak discharge of 473 m3/s. The maximum depth of the flow reached 7 m. Almost 600 blocks of more than 1 m main axis were identified on the surface of the lahar during 36 minutes, which represents an average block discharge of 17 blocks per minute. Seismic frequency ranged from 10 to 150 Hz. However, there was a clear difference between upstream and downstream seismic characteristics. The interpretation related to this difference could be improved by the results of analysis of video recordings, especially to differentiate the debris flow and hyperconcentrated flow phase. The lahar video is accessible online to the broader community (https://www.youtube.com/watch?v=wlVssRoaPbw). Keywords: lahar, video, seismic signal, debris flow, hyperconcentrated flow, Merapi, Indonesia.

  4. Idealized debris flow in flume with bed driven by a conveyor belt

    USGS Publications Warehouse

    Ling, Chi-Hai; Chen, Cheng-lung

    1989-01-01

    The generalized viscoplastic fluid (GVF) model is used to derive the theoretical expressions of two-dimensional velocities and surface profile for debris flow established in a flume with bed driven by a conveyor belt. The rheological parameters of the GVF model are evaluated through the comparison of theoretical results with measured data. A slip velocity of the established (steady) nonuniform flow on the moving bed (i.e., the conveyor belt) is observed, and a relation between the slip velocity and the velocity gradient at the bed is derived. Two belts, one rough and the other smooth, were tested. The flow profile in the flume is found to be linear and dependent on the roughness of the belt, but not much on its speed.

  5. Simulations of Debris-Flow Dominated Margins with Relevance to Morphologic Evolution of Trough-Mouth Fans

    NASA Astrophysics Data System (ADS)

    O'Grady, D. B.; Syvitski, J. P.

    2001-12-01

    Large-scale morphology of glacier-fed continental slopes is influenced by the rate and method of sediment delivery to the slope through time. Slopes fed by fast flowing ice streams (i.e. at trough-mouth fans) and dominated by debris flow deposition exhibit a morphology that is inherently different from other types of glacial margins. Empirical analyses suggest that the average gradient of a trough mouth fan is related to the width of the adjacent continental shelf and, correlatively, to the amount of sediment delivered to the margin by the ice stream. This gradient relationship is not observed for other polar margins. A process-based stratigraphic model (SedFlux) is used to examine the evolution of debris-flow dominated continental slopes under differing boundary conditions and flow properties. Margins are simulated as building from initial bathymetry of a simple shelf-slope-rise configuration. The angle of the continental slope varies between simulations ranging from 1 to 10 degrees. In addition to boundary conditions, the kinematic viscosity (0.0001 m2/s to 0.1 m2/s) and yield strength (1 pa to 500 pa) of the debris flows varies between model runs. The changing morphology of the margin is tracked by measuring the gradient of the margin profile throughout the simulation. Also tracked are the runout distances of the flows and their deposit thickness. Hydroplaning debris flows are not explicitly modeled but are approximated by implementing very low viscosities. Results show that basin depth influences the runout length of debris flows and subsequently the length of the margin slope. The rate of sediment input influences the number and frequency of slope failures leading to debris flows although the overall morphology does not change in response to sediment input rate. All simulations show an evolution of profile morphology as the margin progrades outward, with the continental slope becoming less steep through time. This morphologic evolution is coupled with a

  6. The comparison between two airborne LiDAR datasets to analyse debris flow initiation in north-western Iceland

    NASA Astrophysics Data System (ADS)

    Morino, Costanza; Conway, Susan J.; Balme, Matthew R.; Jordan, Colm; Hillier, John; Sæmundsson, Þorsteinn; Argles, Tom

    2015-04-01

    A debris flow is a very rapid to extremely rapid flow (e.g., 0.8-28 ms-1) [1], that occurs when coarse and poorly-sorted debris, mixed with water and/or air, move down hill slopes in response to gravity [2]. Both the fluid and the solid have a strong influence on the movement of debris flows. They can be extremely destructive, due to their capability of transporting metre-size boulders [e.g., 3, 4]. There are two main ways in which a debris flow can be initiated: by slope failure or by the "fire hose" effect. The slope failure type is particularly common in alpine regions, where landslides can evolve into debris flows [5], triggered by the coalescence of different slope failures. Steep slope gradients, high pore-water pressures, heavy rainfall and/or snowmelt favour this process. The "fire hose" effect occurs when there is a high concentration of debris accumulated within a pre-existing channel; a surge of water through the channel can then develop into a debris flow by incorporating this debris [e.g. 5-7]. In this study, we examine the triggering style of debris flows above the town of Ísafjörður in the Westfjords of Iceland. The slope above the town is characterised by a large topographic bench upon which 20-35 m of glacial till is perched. The sediments are unstable at the bench margin and thus generate frequent, large, hillslope debris flows [8, 9]. In our new analysis, we report on the comparison between the two airborne LiDAR elevation models (collected in 2007 and 2013 by the UK Natural Environment Research Council Airborne Research and Survey Facility), which display several new debris flows and also related mass movements. From these analyses, we find that debris flows in the region are triggered by simple failure of the glacial till, as recognised before [8, 9]. However, debris flows may also be regenerated by the "fire hose" effect, when debris that has collapsed into chutes is remobilised by a later snowmelt or precipitation event. Comparing

  7. r.avaflow, the GIS simulation model for avalanche and debris flows: new developments and challenges

    NASA Astrophysics Data System (ADS)

    Mergili, Martin; Queiroz de Oliveira, Gustavo; Fischer, Jan-Thomas; Krenn, Julia; Kulisch, Helmut; Malcherek, Andreas; Pudasaini, Shiva P.

    2016-04-01

    We present the latest developments and discuss some of the key challenges with regard to the novel and unified computational tool r.avaflow, representing an advanced, comprehensive, GIS-based open source simulation environment for two-phase geophysical mass flows such as avalanches of snow or rock, flows of debris or mud, and related process chains. r.avaflow is freely available and adoptable as a raster module of the GRASS GIS software (http://www.avaflow.org). We focus on the following issues: (1) We back-calculate a laboratory-scale debris flow experiment with r.avaflow and thereby show that different types of drag may govern the evolving flow dynamics, depending on the initial flow configuratiuon. In particular, it appears necessary to consider viscous ambient drag in order to achieve simulation results in line with experimentally measurements. (2) We employ a set of well-documented rock avalanche events to illustrate the use of a built-in functionality for parameter sensitivity analysis and optimization. To do so, we demonstrate possible strategies going beyond the deficient one-at-a-time simulation approach. They allow us to test three or more parameters at once with a limited number of model runs. Computational times are kept at an acceptable level by multi-core processing strategies and use of the Vienna Scientific Cluster. We further discuss a number of key issues with regard to (i) arbitrary mountain topography; and (ii) entrainment and deposition of material. Most tests indicate a good model performance when the affected areas predicted for a late stage of the flow simulation are compared with observed affected areas. However, we note that such a validation is not fully justified without the implementation of a physically correct model for the deposition process. Acknowledgement: The work was conducted as part of the international cooperation project "A GIS simulation model for avalanche and debris flows (avaflow)" supported by the Austrian Science Fund

  8. Probability and volume of potential postwildfire debris flows in the 2012 Waldo Canyon Burn Area near Colorado Springs, Colorado

    USGS Publications Warehouse

    Verdin, Kristine L.; Dupree, Jean A.; Elliott, John G.

    2012-01-01

    This report presents a preliminary emergency assessment of the debris-flow hazards from drainage basins burned by the 2012 Waldo Canyon fire near Colorado Springs in El Paso County, Colorado. Empirical models derived from statistical evaluation of data collected from recently burned basins throughout the intermountain western United States were used to estimate the probability of debris-flow occurrence and potential volume of debris flows along the drainage network of the burned area and to estimate the same for 22 selected drainage basins along U.S. Highway 24 and the perimeter of the burned area. Input data for the models included topographic parameters, soil characteristics, burn severity, and rainfall totals and intensities for a (1) 2-year-recurrence, 1-hour-duration rainfall, referred to as a 2-year storm (29 millimeters); (2) 10-year-recurrence, 1-hour-duration rainfall, referred to as a 10-year storm (42 millimeters); and (3) 25-year-recurrence, 1-hour-duration rainfall, referred to as a 25-year storm (48 millimeters). Estimated debris-flow probabilities at the pour points of the the drainage basins of interest ranged from less than 1 to 54 percent in response to the 2-year storm; from less than 1 to 74 percent in response to the 10-year storm; and from less than 1 to 82 percent in response to the 25-year storm. Basins and drainage networks with the highest probabilities tended to be those on the southern and southeastern edge of the burn area where soils have relatively high clay contents and gradients are steep. Nine of the 22 drainage basins of interest have greater than a 40-percent probability of producing a debris flow in response to the 10-year storm. Estimated debris-flow volumes for all rainfalls modeled range from a low of 1,500 cubic meters to a high of greater than 100,000 cubic meters. Estimated debris-flow volumes increase with basin size and distance along the drainage network, but some smaller drainages were also predicted to produce

  9. Probability and volume of potential postwildfire debris flows in the 2011 Horseshoe II burn area, southeastern Arizona

    USGS Publications Warehouse

    Ruddy, Barbara C.

    2011-01-01

    This report presents a preliminary emergency assessment of the debris-flow hazards from drainage basins burned in 2011 by the Horseshoe II wildfire in southeastern Arizona. Empirical models derived from statistical evaluation of data collected from recently burned drainage basins throughout the intermountain western United States were used to estimate the probability of debris-flow occurrence and debris-flows volumes for selected drainage basins. Input for the models include measures of burn severity, topographic characteristics, soil properties, and rainfall total and intensity for a (1) 2-year-recurrence, 30-minute-duration rainfall, (2) 5-year-recurrence, 30-minute-duration rainfall, and (3) 10-year-recurrence, 30-minute-duration rainfall. Estimated debris-flow probabilities in the drainage basins of interest ranged from less than 1 percent in response to the 2-year-recurrence, 30-minute-duration rainfall to a high of 100 percent in response to the 10-year-recurrence, 30-minute-duration rainfall. The high probabilities in all modeled drainage basins are likely due to the abundance of steep hillslopes and the extensive areas burned at moderate to high severities. The estimated debris-flow volumes ranged from a low of 20 cubic meters to a high of greater than 100,000 cubic meters.

  10. Exhumation By Landslide-Initiated Debris Flows in the 2013 Colorado Front Range Storm

    NASA Astrophysics Data System (ADS)

    Anderson, R. S.; Anderson, S. W.; Anderson, S. P.; Schellhase, D. A.

    2014-12-01

    What is the role of rare events in the exhumation of steep landscapes? We use the "millennial" storm that hit the Front Range, Colorado, USA, in September 2013 to explore this question in a semi-arid landscape. More than 250 mm of rain fell over a ~100 km swath of the Front Range in a 5 day period; totals in some areas exceeded average annual precipitation. The storm triggered over 1300 landslides and debris flows in four major Front Range watersheds (Coe et al., 2014). We created a DEM of difference in the 102 km2 area of overlap using aerial LiDAR surveys, acquired in August 2010 by the Boulder Creek CZO and in November 2013 by FEMA. The study region covers the Boulder Creek watershed from the middle of the Rocky Mountain Surface to the western edge of the Plains, and encompasses Boulder Canyon, Fourmile Canyon, and the 26-km2 2010 Fourmile Canyon Fire. Precambrian crystalline rocks underlie most of the area, although the eastern margin includes sedimentary rocks in hogbacks along the mountain front. We computed site characteristics and volumes for 120 failures. Within the crystalline terrain, most failures occurred at or near the bedrock interface at 0.5-1 m depth, often near the ridgelines downslope of bedrock outcrops. Failures occurred on slopes of 25-40°, and show no slope aspect bias. Failures evolved into debris flows that scoured chutes from the initiation site down to the master stream, traveling at up to 10 m/s. We saw little evidence of deposition; most debris was entrained in the flooding master streams and exited the mountain front. Evacuated sediment volumes represent several hundred years of exhumation within the source basins, based on published long-term erosion rates calculated from 10Be concentrations. We infer that, even in this semi-arid environment, debris flows initiated by rare shallow landslides are a dominant process for evacuating sediment from steep channels and delivering it to the plains.

  11. Debris-Covered Glaciers in Antarctica: Analogs for Viscous-Flow Features on Mars

    NASA Astrophysics Data System (ADS)

    Marchant, D. R.; Phillips, W. M.; Schaefer, J.; Fastook, J.; Landis, G.

    2007-12-01

    The McMurdo Dry Valleys (MDV) are generally classified as a hyper-arid, cold-polar desert. Subtle variations in climate parameters throughout the region result in considerable differences in the distribution, origin, and morphology of buried ice. In the coastal thaw zone, near-surface buried ice experiences seasonal melt and may have formed where pore water from surface snowmelt freezes underground (segregation ice). Characteristic landforms associated with this type of buried ice include thermokarst, shallow planar slides, and solifluction. In contrast, in the coldest and driest regions of the MDV, the stable upland zone, there is insufficient meltwater to produce extensive segregation ice. Rather, widespread buried ice in this zone is typically glacier ice. Temperature data indicate that ice remains frozen in this zone if buried beneath ~15 cm of debris. The Mullins-valley debris-covered glacier, which lies within the stable upland zone, contains ancient glacier ice beneath a thin layer of sublimation till. Four independent dating techniques confirm that the glacier age ranges from ~10 ka near the valley head, to >8 Ma at its diffuse terminus in central Beacon Valley. The dating methods include cosmogenic-nuclide analyses of surface boulders; horizontal ice-flow velocities as determined from synthetic aperture radar interferometry; 40Ar/39Ar analyses of in-situ ash fall in relict polygon troughs at the till surface; and numerical ice-flow models. Age results so derived are in accord with measured variations in ancient community DNA extracted from pristine ice samples along the length of the glacier. Multi- channel seismic and ground-penetrating radar surveys demonstrate that the ice is relatively clean and that it averages from ~45 m to ~150 m thick. Morphologic comparisons of the Mullins Valley debris-covered glacier are used to shed light on the origin and modification of near-surface ice on Mars.

  12. A finite volume solver for three dimensional debris flow simulations based on a single calibration parameter

    NASA Astrophysics Data System (ADS)

    von Boetticher, Albrecht; Turowski, Jens M.; McArdell, Brian; Rickenmann, Dieter

    2016-04-01

    Debris flows are frequent natural hazards that cause massive damage. A wide range of debris flow models try to cover the complex flow behavior that arises from the inhomogeneous material mixture of water with clay, silt, sand, and gravel. The energy dissipation between moving grains depends on grain collisions and tangential friction, and the viscosity of the interstitial fine material suspension depends on the shear gradient. Thus a rheology description needs to be sensitive to the local pressure and shear rate, making the three-dimensional flow structure a key issue for flows in complex terrain. Furthermore, the momentum exchange between the granular and fluid phases should account for the presence of larger particles. We model the fine material suspension with a Herschel-Bulkley rheology law, and represent the gravel with the Coulomb-viscoplastic rheology of Domnik & Pudasaini (Domnik et al. 2013). Both composites are described by two phases that can mix; a third phase accounting for the air is kept separate to account for the free surface. The fluid dynamics are solved in three dimensions using the finite volume open-source code OpenFOAM. Computational costs are kept reasonable by using the Volume of Fluid method to solve only one phase-averaged system of Navier-Stokes equations. The Herschel-Bulkley parameters are modeled as a function of water content, volumetric solid concentration of the mixture, clay content and its mineral composition (Coussot et al. 1989, Yu et al. 2013). The gravel phase properties needed for the Coulomb-viscoplastic rheology are defined by the angle of repose of the gravel. In addition to this basic setup, larger grains and the corresponding grain collisions can be introduced by a coupled Lagrangian particle simulation. Based on the local Savage number a diffusive term in the gravel phase can activate phase separation. The resulting model can reproduce the sensitivity of the debris flow to water content and channel bed roughness, as

  13. The 1980 Polallie Creek debris flow and subsequent dam-break flood, East Fork Hood River basin, Oregon

    USGS Publications Warehouse

    Gallino, Gary L.; Pierson, Thomas C.

    1984-01-01

    At approximately 9 p.m. on December 25, 1980, intense rainfall and extremely wet antecedent conditions combined to trigger a landslide of approximately 5,000 cubic yards at the head of Polallie Creek Canyon on the northeast flank of Mount Hood. The landslide was transformed rapidly into a debris flow, which surged down the channel at velocities between about 40 and 50 ft/s, eroding and incorporating large volumes of channel fill and uprooted vegetation. When it reached the debris fan at the confluence with the East Fork Hood River, the debris flow deposited approximately 100,000 cubic yards of saturated, poorly sorted debris to a maximum thickness of 35 ft, forming a 750-ft-long temporary dam across the channel. Within approximately 12 minutes, a lake of 85 acre-feet formed behind the blockage, breached the dam, and sent a flood wave down the East Fork Hood River. The combined debris flow and flood resulted in one fatality and over $13 million in damage to a highway, bridges, parks, and a water-supply pipeline. Application of simple momentum- and energy-balance equations, and uniform flow equations resulted in debris flow peak discharges ranging from 50,000 ft3/s to 300,000 ft3/s at different locations in the Polallie Creek Canyon. This wide range is attributed to temporary damming at the boulder- and log-rich flow front in narrow, curving reaches of the channel. When the volume of the solid debris was subtracted out, assuming a minimum peak debris-flow discharge of 100,000 ft3/s at the canyon mouth, a minimum peak-water discharge of 40,000 ft3/s was obtained. A computer dam-break model simulated peak flow for the outbreak flood on the East Fork Hood River in the range of 20,000 to 30,000 ft3/s using various breach shapes and durations of breach between 5 and 15 minutes. A slope conveyance computation 0.25 mi downstream from the dam gave a peak water discharge (solids subtracted out) for the debris-laden flood of 12,000 to 20,000 ft3/s, depending on the channel

  14. A hacker's guide to catching a debris flow: Lessons learned from four years of chasing mud in Colorado and southern California

    NASA Astrophysics Data System (ADS)

    Kean, J. W.; McCoy, S. W.; Staley, D. M.; Coe, J.; Leeper, R.; Tucker, G. E.

    2012-12-01

    Direct measurements of natural debris flows provide valuable insights into debris-flow processes and hazards. Yet debris flows are difficult to "catch" because they live in rugged terrain, appear infrequently, and have an appetite for destroying monitoring equipment. We present an overview of some successful (and failed) techniques we have used over the past four years to obtain direct measurements of 40+ debris flows in Colorado and southern California. Following the "MacGyver" theme of the session, we focus on the improvised equipment and methods we use in our hunt for quality data. These include an inexpensive erosion sensor to measure rates of debris-flow entrainment, a custom load cell enclosure for measuring debris-flow normal force, tracer rocks implanted with passive integrated transponders, basic pressure transducers to measure debris-flow timing, and standard digital cameras adapted to obtain high-resolution (1936 x 1288 pixels) video footage of debris flows. These techniques are also suitable for catching data on elusive flash floods. In addition, we also share some practical solutions to the logistical problems associated with installing monitoring equipment in rugged debris-flow terrain, such as suspension of non-contact stage gages high above channels.

  15. Numerical simulation of the inundation area for landslides induced debris flow -a case study of Hong-shui-xian gully in southern Taiwan

    NASA Astrophysics Data System (ADS)

    Chen, Jinn-Chyi; Chuang, Meng-Ru; Jeng, Ching-Jiang; Wang, Ji-Shang

    2013-04-01

    Typhoon Morakot (2009) caused serious landslides and debris flows in southern Taiwan due to intensive rainfall with long duration. The case study area of the Hong-shui-xian gully, located in Liouguei District, Kaohsiung city, is one of the debris flows caused by this typhoon. The watershed of the Hong-shui-xian gully has area of 34.1 ha. The majority of the landslide debris (landslides covered 33.7% of the watershed area) entered the main stream of the gully, where it mixed with water and became a debris flow. Eroding the sidewalls of the stream, the debris flow entrained additional material and traveled downstream into village and Laonong River. In this study, a two-dimensional commercial model FLO-2D was used to simulate debris-flow inundated area. Because the debris-flow event is highly related to landslides, how to consider the sediment concentration due to landslides in inflow hydrograph, and to select resistant parameters is important in the simulation work. The inflow hydrograph that considered sediment concentration caused by flood, landslide, and debris flow were proposed in this study. Rheological property of the debris-flow deposited sediment was analyzed by laboratory experiment, and the rheological equations were determined. The influence of inflow hydrograph, sediment concentration, and roughness coefficient on the simulated results was discussed. The sediment concentration and the roughness coefficient were calibrated by the comparison with the debris-flow inundated area and deposited depth in field survey. The simulated results showed that the average sediment concentration by volume of debris flow was 0.50. The maximum deposited depth in the debris-flow inundated area was up to 6 m, maximum velocity 5 m/s, and the deposited volume 780,000 m3. The simulated deposited depth and inundation area showed a reasonable match to field investigation.

  16. Hydroplaning of subaqueous debris flows and glide blocks: Analytical solutions and discussion

    NASA Astrophysics Data System (ADS)

    Harbitz, Carl B.; Parker, Gary; ElverhøI, Anders; Marr, Jeffrey G.; Mohrig, David; Harff, Peter A.

    2003-07-01

    Subaqueous debris flows often attain significantly higher velocities and longer run-out distances than their subaerial counterparts in spite of increased viscous drag and reduced effective gravity due to buoyancy. Recent experimental research suggests that a basal lubricating layer of water associated with hydroplaning decouples the sediments from the bed, resulting in a dramatic reduction of the basal shear stress. Hydroplaning thus provides an explanation for these observations. The conditions for onset of hydroplaning are discussed in terms of critical densimetric Froude number. The stress reduction due to a lubricating layer of water or mud slurry is studied via equilibrium solutions for a two-layer Couette flow. The calculations reveal that the stresses in both the low-viscosity lubricating layer and the high-viscosity deforming deposits below it are substantially reduced. The principles of laminar boundary layers are used to develop an equilibrium solution for the steady motion of a hydroplaning debris glide block. This adjusted version of lubrication theory properly accounts for hydroplaning associated with a dynamic pressure generated at the head of the block. Example calculations at both laboratory and field scale support the experimental results of reduced bed friction, limited erosion, sediment rheology independence, and high velocities. The results also reveal the possibility for a net up-slope discharge in the lubricating layer.

  17. Emergency assessment of potential debris-flow peak discharges, Missionary Ridge fire, Colorado

    USGS Publications Warehouse

    Cannon, Susan H.; Rea, Alan H.; Gleason, J. Andrew; Garcia, Stephen P.

    2002-01-01

    These maps present the results of assessments of peak discharges that can potentially be generated by debris flows issuing from the basins burned by the Missionary Ridge fire of June 9 through July 14, 2002, near Durango, Colorado. The maps are based on a regression model for debris-flow peak discharge normalized by average storm intensity as a function of basin gradient and burned extent, and limited field checking. A range of potential peak discharges that could be produced from each of the burned basins between 1 ft3/s (0.03 m3/s) and 6,446 ft3/s (183 m3/s) is calculated for the 5-year, 1-hour st