Maximum Runout Distance Research Articles

Engineering geological investigation into rockfall problem: A case study of the Seated Seokgayeorae Image carved on a rock face at the UNESCO World Heritage site in Korea

This paper considers the rockfall problems around the Seated Seokgayeorae Image at the UNESCO World Heritage site in Korea. Using the Barton-Bandis (BB) model in Universal Distinct Element Code (UDEC), quantitative information on the detachment of the loose boulders was obtained. Based on the result of the field survey and laboratory tests, key parameters for rockfall simulation were determined, and then back analysis was performed to calibrate the parameters for the study site. The maximum run-out distances, bounce heights, kinetic energies and translational velocities of falling boulders were simulated using RocFall 4.0 to assess the rockfall hazard around the Seated Seokgayeorae Image to ensure both the stability of the bas-relief and the safety of tourists. The results of the analyses showed that about 80% of falling boulders in a range of 100–150 kg pass the altar with an average speed of 8.4 m/s and that the maximum kinetic energy of the falling boulders is 12.5 kJ if the boulders hit the head of the statue. Therefore, the removal of loose blocks and trees on the upper outcrop and limited rock bolting were suggested for the reduction of rockfall risk.

Static and flowing regions in granular collapses down channels

Through laboratory experiments we investigate inertial granular flows created by the instantaneous release of particulate columns into wide, rectangular channels. These flows are characterized by their unsteady motion, large changes of the free surface with time, and the propagation towards the free surface of an internal interface separating static and flowing regions. We present data for the time-dependent geometry of the internal interface and the upper, free surface for aspect ratios, a, in the range from 3 to 9.5 (where a=hi∕di is the ratio of the initial height to basal width of the column). The data were analyzed by two different approaches. First, by integrating under the entire internal interface we obtained data for the static area, AD, as a function of time for different a. Second, in order to characterize vertical deposition rates, we measured the thicknesses of the flowing region, hF(x,t), and the static region, hD(x,t), at fixed horizontal positions, x, and time, t, since the initiation of the experiment. We also determined detailed velocity profiles with depth at distances scaled to the final maximum runout distance to analyze the kinematic behavior of the flowing layer. In the initial free-fall phase, the temporal variation of the static area is independent of hi and scales as gdit. During the subsequent lateral spreading phase, AD(t) varies linearly with time and the nondimensional deposition rate (dAD∕dt)∕(gdi3)1∕2 is a linear function of a. The thickness of the interface hD(x,t) at constant x depends on a and varies linearly with time. The local deposition rate ∂hD∕∂t is not constant along the flow length. Data show that for the major part of the flow length ∂2hD∕∂t∂x is constant. In the lateral spreading phase, the velocity profiles are characteristically linear with a basal exponential region, a few grains in thickness, which separates static from moving regions. The shear rate is a constant dependent on a modified initial height h̃i as (g∕h̃i)1∕2, where h̃i is a characteristic length scale in the system describing the fraction of the granular column actually involved in the flowing region.

Computer simulation of stone falls and rockfalls

The paper gives an overview of the literature on available computer (simulation) models of stone falls and rockfalls, divided into 2D and 3D models. 2D models consider single blocks in the rock-fall mass as lumped mass or a rigid body, and are used to assess the single rockfall runout distance. Opposed to the 2D models, 3D models are composed not only of a dispositional model (depicting rockfall source areas) and friction model (determination of deposition areas and maximum runout distances), but also from a trajectory model (determination of travel areas).

Computing extreme avalanches

Increasing the reliability and accuracy of avalanche zoning method is of primary importance in heavily populated areas of the Alps. This usually involves computing the characteristics of large return-period avalanches. Current tools (avalanche-dynamics or statistical models) cannot achieve this objective properly. A new generation of models has emerged, which, by combining statistical and deterministic viewpoints, can reduce a number of shortcomings in the original tools. This paper explores the possibility of updating the Salm–Burkard–Gubler method by adding a probabilistic procedure for fitting parameters to field data and using it in Monte Carlo simulations. The resulting model is intended to provide more accurate results of extreme avalanches. It has been applied to a series of close avalanche paths in the French Alps. Despite their similarities, these paths reveal some differences in their avalanche activity in terms of frequency and maximum run-out distance. Therefore, in order to provide a fair description of the intensity/frequency relationship, the model parameters must be fitted for each path, which leads to thinking that not all the important physical processes have been taken into account in this model.

An equation for spreading length, center of mass and maximum run-out shortenings of dense avalanche flows by vertical obstacles

In this paper, we consider dense snow avalanches interacting with a defense structure. The maximum run-out distance of dense snow avalanches is the sum of the center of mass run-out and the spreading length. We make the simplifying assumptions that the center of mass run-out is mainly dependent on the velocity of the avalanche flow and the spreading length is mainly linked to the volume of the deposit. The obstacle reduces momentum of the avalanche by (i) velocity reduction and (ii) mass reduction by deposition upstream of the obstacle. The first effect leads to the shortening of the center of mass run-out and the second one explains the spreading length decrease. Therefore, the maximum run-out reduction is a function of both velocity and volume reductions. An equation is proposed to predict the maximum run-out reduction. This equation is tested on small-scale granular avalanches. For laboratory experiments with confined granular avalanches interacting with a thin vertical dam, velocity and volume reductions are expressed as simple functions of the vertical dam height. The equation for the maximum run-out shortening is then calibrated on experimental data and used to predict the velocity reduction and the critical height for which the granular avalanche is entirely stopped by the vertical dam.

Pyroclastic flow deposits of the 1991 eruption of Volc�n de Colima, Mexico

The April 16, 1991, eruption of Volcan de Colima represents a classical example of partial dome collapse with the generation of progressively longer-runout, Merapi-type pyroclastic flows that traveled up to 4 km along the El Cordoban gullies (East, Central and West). The flows filled the gullies with block-and-ash flow deposits up to 10 m thick, of which, after 7 years of erosion, only remnants remained in the El Cordoban West and East gullies. The El Cordoban Central gully, however, provided a well-preserved and incised longitudinal section of the 1991 deposits. The deposits were emplaced as proximal and distal facies, separated by a change in slope angle from >30° to <20°. The proximal facies consists of massive, clast-supported flow units (up to 1 m thick) with andesite blocks locally supported by a matrix of coarse ash and devoid of segregation structures or grading. The distal facies consists of a massive, matrix-supported deposit up to 8 m thick, which contains dispersed andesite blocks in a fine ash matrix. In the distal facies, a train of blocks marks flow-unit upper boundaries and, although sorting is poor, some grading is present. Thin, finely stratified, or dune-bedded layers of fine ash material are locally present above or below units of both facies. Sedimentologic parameters show that the size or fraction of large pyroclasts (larger than −1 φ) decreases from proximal to distal facies, as the percentage of matrix (0 to 4 φ) increases, especially immediately beyond the break in slope. We propose that the propagation of the Colima pyroclastic flows is critically dependent on local slope angle, the presence of erodible slope debris, and the decrease in grain size with distance from the vent. The progressive fining is probably caused by some combination of erosion, clast breakup and deposition of larger pyroclasts, and is itself influenced by the slope angle. In the proximal region, the flows moved as granular avalanches, in which interacting grains ground each other and erosion occurred to produce an overriding dilute ash cloud. The maximum runout distance of the avalanches was controlled by the angle of repose of the material, and the volume and grain size of source and eroded material. Because the slope angle is close to the repose angle for this debris, granular avalanches were not able to propagate far beyond the change in slope. If, however, an avalanche had enough mass in finer grain size fractions, at least part of the flow continued beyond the break in slope and across the volcano apron, propagating in a turbulent state and depositing surge layers, or in an otherwise settling-modified state and depositing block-and-ash flow layers.

Remote sensing based assessment of hazards from glacier lake outbursts: a case study in the Swiss Alps

Glacier lakes are a common phenomenon in high mountain areas. Outbursts from glacier lakes have repeatedly caused the loss of human lives as well as severe damage to local infrastructure. In several high mountain ranges around the world, a grave uncertainty about the hazard potential of glacier lakes still exists, especially with respect to the effects of accelerating rates of glacier retreat as a consequence of atmospheric warming. Area-wide detection and modeling of glacier lake hazard potentials is, therefore, a major challenge. In this study, an approach integrating three scale levels allows for the progressive focus on critical glacier lakes. Remote sensing methods for application in glacier lake hazard assessment are presented, and include channel indexing, data fusion, and change detection. Each method matches the requirements of a certain scale level. For estimating potential disaster amplitudes, assessments must be made of maximum discharge and runout distance of outbursts floods and debris flows. Existing empirical relations are evaluated and complementary ones as derived from available data are proposed. Tests with observations from a recent outburst event from a moraine-dammed lake in the Swiss Alps show the basic applicability of the proposed techniques and the usefulness of empirical relations for first hazard assessments. In particular, the observed runout distance of the debris flow resulting from the outburst does not exceed the empirically estimated maximum runout distance. A list of decision criteria and related remote sensing techniques are discussed in conclusion. Such a list is an essential tool for evaluating the hazard potential of a lake. A systematic application of remote sensing based methods for glacier lake hazard assessment is recommended.Key words: glacier lake outburst, hazard potential, remote sensing, empirical parameters.

Statistical prediction of maximum avalanche run-out distances from topographic data in the western Catalan Pyrenees (northeast Spain)

We present regression models to estimate maximum avalanche run-out distances in the western Catalan Pyrenees (northeast Spain). The regression equations have been calculated from topographic parameters of 216 well-known avalanche paths, mapped on avalanche location maps at a scale of 1: 50 000. Historical information about avalanche maximum run-out zones has been available for some avalanche paths hut most of them have been delimited by vegetation and geomorphological indices.The avalanche profiles, which are representative of avalanche paths, have been classified on the basis of avalanche run-out zone morphology, because this has a considerable influence on avalanche behaviour and run-out. Three classes have been defined and regression equations obtained for each class and also for the total. Finally, some examples have been calculated in order to appreciate the applicability of the models to improving avalanche mapping.

Statistical prediction of maximum avalanche run-out distances from topographic data in the western Catalan Pyrenees (northeast Spain)

We present regression models to estimate maximum avalanche run-out distances in the western Catalan Pyrenees (northeast Spain). The regression equations have been calculated from topographic parameters of 216 well-known avalanche paths, mapped on avalanche location maps at a scale of 1: 50 000. Historical information about avalanche maximum run-out zones has been available for some avalanche paths hut most of them have been delimited by vegetation and geomorphological indices.The avalanche profiles, which are representative of avalanche paths, have been classified on the basis of avalanche run-out zone morphology, because this has a considerable influence on avalanche behaviour and run-out. Three classes have been defined and regression equations obtained for each class and also for the total. Finally, some examples have been calculated in order to appreciate the applicability of the models to improving avalanche mapping.

A statistical model for maximum avalanche run-out distances in southwest Montana

An extreme value (Gumbel) distribution was evaluated as a model of maximum run-out distances of avalanches in southwest Montana defined in terms of dimensionless ratios. The run-out ratios are defined relative to an arbitrarily defined reference point. The development and analysis of the statistical model were based on data taken from surveys of 24 avalanche paths. The technique bears promise as a user-friendly tool; however, due to the small vertical drop of avalanches in southwest Montana, the model appears to be quite sensitive to measurement errors in the field. This sensitivity also seems to depend on the definition of the reference point. Comparison with models developed for other mountain ranges indicates that models developed for one range cannot be used to estimate accurately maximum avalanche run-out distances in other mountain ranges until influencing factors are better understood.

A statistical model for maximum avalanche run-out distances in southwest Montana

An extreme value (Gumbel) distribution was evaluated as a model of maximum run-out distances of avalanches in southwest Montana defined in terms of dimensionless ratios. The run-out ratios are defined relative to an arbitrarily defined reference point. The development and analysis of the statistical model were based on data taken from surveys of 24 avalanche paths. The technique bears promise as a user-friendly tool; however, due to the small vertical drop of avalanches in southwest Montana, the model appears to be quite sensitive to measurement errors in the field. This sensitivity also seems to depend on the definition of the reference point. Comparison with models developed for other mountain ranges indicates that models developed for one range cannot be used to estimate accurately maximum avalanche run-out distances in other mountain ranges until influencing factors are better understood.

Morphology and emplacement of an unusual debris-avalanche deposit at Jocotitl�n volcano, Central Mexico

A pre-historic collapse of the northeastern flank of Jocotitlan Volcano (3950 m), located in the central part of the Trans Mexican Volcanic Belt, produced a debris-avalanche deposit characterized by surficial hummocks of exceptional size and conical shape. The avalanche covered an area of 80 km2, had an apparent coefficient of friction (H/L)_of 0.11, a maximum runout distance of 12 km, and an estimated volume of 2.8 km3. The most remarkable features of the Jocotitlan debris avalanche deposit are: the several steep (29–32°) conical proximal hummocks (up to 165 m high), large tansverse ridges (up to 205 m high and 2.7 km long) situated at the base of the volcano, and the steep 15–50 m thick terminal scarp. Proximal conical hummocks and parallel ridges that can be visually fitted back to their pre-collapse position on the mountain resulted from a sliding mode of emplacement. Steep primary slopes developed as a result of the accumulation of coarse angular clasts at the angle of repose around core clasts that are decameters in size. Distal hummocks are commonly smaller, less conical, and clustered with more diffuse outlines. Field evidence indicates that the leading distal edge of the avalanche spilled around certain topographic barriers and that the distal moving mass had a yield strength prior to stopping. In the NE sector, the avalanche was suddenly confined by topographically higher lacustrine and volcaniclastic deposits which as a result were intensely thrust-faulted, folded, and impacted by large clasts that separated from the avalanche front. Post-emplacement loading also induced normal faulting of these soft, locally water-rich sediments. The regional tectonic pattern, N-NE direction of flank failure, and the presence of a major normal fault which intersects the volcano and is parallel to the orientation of the Acambay graben located 10 km to the N suggest a genetic relationship between the extensional tectonic stress regime and triggering of catastrophic slope failure. The presence of a 3-m-thick sequence of pumice and obsidian-rich pyroclastic surge and fall tephra directly overlying the debris-avalanche deposit indicates that magma must have been present within the edifice just prior to the catastrophic flank failure. The breached crater left by the avalanche has mostly been filled by dacitic domes and lava flows. The youngest pryroclastic surge deposits on the upper flanks of the volcano have an historical C14 age of 680±80 yearsBp (Ad 1270±80). Thus Jocotitlan volcano, formerly believed to be extinct, should be considered potentially active. Because of its close proximity to Mexico-City (60 km), the most populous city in the world, reactivation could engender severe hazards.

Calculation of Maximum Snow-Avalanche Run-Out Distance by use of Digital Terrain Models

Digital maps and terrain models are used to calculate maximum snow-avalanche run-out distance based on topographic parameters. Maps of 1:50 000 scale are found to be accurate enough for the purpose. 113 well-known avalanches are discussed in this paper. A computer system is used to calculate terrain parameters such as rupture area (A), avalanche-path length (L), avalanche-track lengths (L1L2), and run-out lengths (L3). Maximum run-out angle (α), avalanche-track angle (β). and average angle of rupture zone (γ) are also found by computer. The use of computer and terrain model reduces subjective judgement of parameters to a minimum. Run-out distance was found to be best expressed by the regression equation:α = 0.91β + 0.08γ–3.5°. R2 = 0.94, S = 1.4°.L = 0.93L1 + 0.97L2 + 0.61A + 182 m. R2 = 0.96, S = 137 m.

Calculation of Maximum Snow-Avalanche Run-Out Distance by use of Digital Terrain Models

Digital maps and terrain models are used to calculate maximum snow-avalanche run-out distance based on topographic parameters. Maps of 1:50 000 scale are found to be accurate enough for the purpose. 113 well-known avalanches are discussed in this paper. A computer system is used to calculate terrain parameters such as rupture area (A), avalanche-path length (L), avalanche-track lengths (L 1 L 2), and run-out lengths (L 3). Maximum run-out angle (α), avalanche-track angle (β). and average angle of rupture zone (γ) are also found by computer. The use of computer and terrain model reduces subjective judgement of parameters to a minimum. Run-out distance was found to be best expressed by the regression equation: α = 0.91β + 0.08γ–3.5°. R 2 = 0.94, S = 1.4°. L = 0.93L 1 + 0.97L 2 + 0.61A + 182 m. R 2 = 0.96, S = 137 m.

Characterization of debris avalanche deposits in Japan

Seventy-one debris avalanche deposits are identified from 52 Japanese Quaternary volcanoes. The structures of these volcanoes are mostly stratovolcanoes and lava domes. No avalanche deposit is found in calderas, pyroclastic cones or maar volcanoes. Debris avalanche deposits are found in 18% of all Quaternary volcanoes or 25% of Quaternary stratovolcanoes and lava domes. The ratio rises to 49% when considering only active stratovolcanoes and lava domes. At least five debris avalanche deposits have formed since 9th century. The maximum height difference of sliding ( H) for each debris avalanche ranges from 200 to 2400 meters and the maximum runout distance of sliding ( L) ranges from 1.6 to 32 km. The ratio H/ L ranges from 0.2 to 0.06, and becomes smaller in larger debris avalanches. They are more mobile than landslides in non-volcanic areas. Volume is within a range of 0.03 and 9 km 3. There is no relation between the direction of sliding and the regional horizontal compressional stress axis at the site of a volcano. Two-dimensional computer simulations of avalanches using a simplified physical model are made. The maximum velocity is mainly controlled by the length of steep slope.

Calculation of Snow Avalanche Runout Distance

Distance of maximum avalanche runout is calculated by four topographical factors. An empirical equation found by regression analysis of 206 avalanches is used to predict the maximum runout distance in terms of average gradient of the avalanche path (angle α). The correlation coefficient R = 0.92, and the standard deviation of the residuals SD = 2.3°.The avalanche paths are further classified into different categories depending on confinement of the path, average inclination of the track 6, curvature of the path y", vertical displacement Y, and inclination of rupture zone Q. The degree of confinement is found to have no significant effect on the runout distance expressed by a. Best prediction of runout distance is found by a classification based on 5 and Y. For avalanches with β &amp;lt;30° and Y &amp;gt; 900 m, R = 0.90 and SD = 1.02°.The population of avalanches is applied to a numerical/dynamical model presented by Perla and others (1980). Different values for the friction constantsvand M/DY are computed, based on the observed extent of the avalanches. The computations are supplied by velocity measurements v from a test avalanche where Y = 1 000 m, and vmax= 60 m s−1. The best fitted values are μ = 0.25 and M/DY = 0.5, which gives R = 0.83 and SD = 3.5°.

Calculation of Snow Avalanche Runout Distance

Distance of maximum avalanche runout is calculated by four topographical factors. An empirical equation found by regression analysis of 206 avalanches is used to predict the maximum runout distance in terms of average gradient of the avalanche path (angle α). The correlation coefficient R = 0.92, and the standard deviation of the residuals SD = 2.3°.The avalanche paths are further classified into different categories depending on confinement of the path, average inclination of the track 6, curvature of the path y", vertical displacement Y, and inclination of rupture zone Q. The degree of confinement is found to have no significant effect on the runout distance expressed by a. Best prediction of runout distance is found by a classification based on 5 and Y. For avalanches with β &lt;30° and Y &gt; 900 m, R = 0.90 and SD = 1.02°.The population of avalanches is applied to a numerical/dynamical model presented by Perla and others (1980). Different values for the friction constants v and M/DY are computed, based on the observed extent of the avalanches. The computations are supplied by velocity measurements v from a test avalanche where Y = 1 000 m, and vmax = 60 m s−1. The best fitted values are μ = 0.25 and M/DY = 0.5, which gives R = 0.83 and SD = 3.5°.

Observed Maximum Run-Out Distance of Snow Avalanches and the Determination of the Friction Coefficients µ and ξ

AbstractTo fix the limits of different hazards in the avalanche-hazard maps one uses criteria pertaining to avalanche dynamics. These criteria are at present the velocity and the run-out distance of a given avalanche for a given place. In 1955 A. Voellmy published his theory of avalanche dynamics which has widely been used in practical map preparation. Since 1962 his equations have also been used by the Eidg. Institut für Schnee- und Lawinenforschung (EISLF) to calculate avalanche pressures and run-out distances. Furthermore B. Salm (EISLF) developed another equation for the calculation of run-out distances in 1978. Both the equations of Voellmy and of Salm contain two friction coefficients, µ and ξ. Little is known about them and opinions, even among specialists, differ on what values should be given to them.This paper presents field observations on very long run-out distances. These observations are used to calculate values for pairs of µ and ξ. For avalanche zoning, only extreme values are of interest, i.e. very low values for µ and very high values for ξ. For the calibration of those coefficients, ten avalanches from the winters 1915–16, 1967–68, 1974–75, and 1977–78 have been used. Those avalanches occurred during heavy and intense snowfalls. For those avalanches, the pair µ= 0.155, ξ = 1 120 m/s2 was found for the Voellmy equation and the pair µ = 0.157, ξ =1 067 m/s2 for the Salm equation. These values only partially agree with those used up to date by EISLF. It is recommended for example that for extreme flowing avalanches (newly fallen snow, soft slabs) the pair µ = 0.16,ξ = 1 360 m/s2 be used.

Observed Maximum Run-Out Distance of Snow Avalanches and the Determination of the Friction Coefficients µ and ξ

AbstractTo fix the limits of different hazards in the avalanche-hazard maps one uses criteria pertaining to avalanche dynamics. These criteria are at present the velocity and the run-out distance of a given avalanche for a given place. In 1955 A. Voellmy published his theory of avalanche dynamics which has widely been used in practical map preparation. Since 1962 his equations have also been used by the Eidg. Institut für Schnee- und Lawinenforschung (EISLF) to calculate avalanche pressures and run-out distances. Furthermore B. Salm (EISLF) developed another equation for the calculation of run-out distances in 1978. Both the equations of Voellmy and of Salm contain two friction coefficients,µandξ. Little is known about them and opinions, even among specialists, differ on what values should be given to them.This paper presents field observations on very long run-out distances. These observations are used to calculate values for pairs ofµandξ. For avalanche zoning, only extreme values are of interest, i.e. very low values forµand very high values forξ. For the calibration of those coefficients, ten avalanches from the winters 1915–16, 1967–68, 1974–75, and 1977–78 have been used. Those avalanches occurred during heavy and intense snowfalls. For those avalanches, the pairµ= 0.155,ξ= 1 120 m/s2was found for the Voellmy equation and the pairµ= 0.157,ξ=1 067 m/s2for the Salm equation. These values only partially agree with those used up to date by EISLF. It is recommended for example that for extreme flowing avalanches (newly fallen snow, soft slabs) the pairµ= 0.16,ξ= 1 360 m/s2be used.