Predictability of long runout landslide motion: implications from granular flow mechanics

Straub, Steffen

doi:10.1007/s005310050150

Cited by 48 publications

(22 citation statements)

References 48 publications

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“…Kilburn and Sorensen (1998) note that, in sturtzstroms, the distance of runout lengths are proportional to the square root of their volume. This is mainly due to the fact that there is a negative correlation between the friction coefficient of the mass movement and its volume (Straub, 1997). Hsü (1975) concludes that there is a minimum volume of 50 000 m 3 for long runout distances, what explains the short distances travelled by debris flows in the Flysch Sector where they do not exceed 500 m 3 .…”

Section: Discussionmentioning

confidence: 99%

Debris flow characteristics and relationships in the Central Spanish Pyrenees

Lorente

Beguerı́a

Bathurst

et al. 2003

Nat. Hazards Earth Syst. Sci.

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Abstract. Unconfined debris flows (i.e. not in incised channels) are one of the most active geomorphic processes in mountainous areas. Since they can threaten settlements and infrastructure, statistical and physically based procedures have been developed to assess the potential for landslide erosion. In this study, information on debris flow characteristics was obtained in the field to define the debris flow runout distance and to establish relationships between debris flow parameters. Such relationships are needed for building models which allow us to improve the spatial prediction of debris flow hazards. In general, unconfined debris flows triggered in the Flysch Sector of the Central Spanish Pyrenees are of the same order of magnitude as others reported in the literature. The deposition of sediment started at 17.8 • , and the runout distance represented 60% of the difference in height between the head of the landslide and the point at which deposition started. The runout distance was relatively well correlated with the volume of sediment.

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Section: Discussionmentioning

confidence: 99%

Debris flow characteristics and relationships in the Central Spanish Pyrenees

Lorente

Beguerı́a

Bathurst

et al. 2003

Nat. Hazards Earth Syst. Sci.

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“…Despite their apparent simplicity, granular materials, such as sand or glass beads, exhibit non-trivial behaviors bringing new insights in the problem of debris flows dynamics [Savage, 1989;Campbell, 1990;Straub, 1997;Davies and McSaveney, 1999;Lube et al, 2004;Lajeunesse et al, 2004Lajeunesse et al, , 2005Lajeunesse et al, , 2006. Discrete numerical simulations of ideally simple granular flows have proven able to reproduce a realistic ability to flow, deform and spread, with a minimum number of assumptions on the flow rheology [Cleary and Campbell, 1993;Campbell et al, 1995;LinaresGuerrero et al, 2007;Staron, 2008].…”

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confidence: 99%

Understanding how volume affects the mobility of dry debris flows

Staron¹,

Lajeunesse²

2009

Geophysical Research Letters

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[1] The prediction of the runout length L of large dry debris flows has long been the subject of a considerable research effort, primarily due to the obvious concern caused by their destructive power. One seemingly well established feature is the increase of the mobility M of a rock avalanche, defined as the ratio of the runout distance to the fall height, with its volume V. The physical nature of this lubrication mechanism remains however controversial. In this paper, we analyse field data and discrete numerical simulations of granular flows and demonstrate the geometrical origin of the apparent enhancement of the mobility with the volume. We evidence the intertwined role of volume and topography and show the existence of two contributions in the runout, defining two flow regimes: one dominated by sliding, in which the runout is independent of V, and another dominated by spreading, in which the runout is strongly dependent on V. In the light of these results, the search of a volume dependent lubrication mechanism appears to be an ill-posed problem. Citation: Staron, L., [Howard, 1973]. Beside an obvious concern for hazard assessment, rock avalanches are also efficient agents of erosion in active orogens, capable of moving large masses of material over kilometre-scale distances instantaneously [Hovius and Stark, 2006;Korup et al., 2007]. In spite of the sustained interest these dramatic natural events have raised in the scientific community, they still escape physical understanding [Iverson, 1997[Iverson, , 2003.[3] Among the various issues raised by these flows, the prediction of their runout length L (see Figure 2a, insert) keeps a first rank position, primarily due to the obvious concern caused by their destructive power. Surprisingly, they can travel over distances several times larger than the height H of the source topography [Dade and Huppert, 1998]. One seemingly established feature is the increase of the mobility M = L/H with the volume V of rock mobilized by the avalanche (Figure 2a). This positive correlation was first noted by Heim [1932]. Yet, the identification of lubrication mechanisms enhanced by volume remains a persisting and challenging issue [Legros, 2002, and references therein]. In this paper, we analyse both field data and discrete numerical simulations of granular flows, and show that the increase of M with V reflects a purely geometrical correlation. In the light of these results, the search for a volume dependent lubrication mechanism appears to be an ill-posed problem.[4] The conventional analysis of the dissipative properties of geological granular flows relies on the hypothesis, first put forward by Heim [1932] and prompted by an analogy with solid friction, that the whole of the initial potential energy of the mass is dissipated by the work of friction forces along the topography. Neglecting centripetal acceleration induced by the topography, and any other energy transfers in the system, we obtain:where m e is an effective friction coefficient quantifying the average macroscopic d...

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“…Recent computer simulations of short-lived, wave-like granular avalanches show that the churning mass shears pervasively throughout its thickness (Campbell et al 1995). The simulations involve up to a million particles and are probably more realistic than previous ones, which describe the behavior of just a small volume of the flow (e.g., Campbell 1989;Cleary and Campbell 1993;Straub 1996Straub , 1997. In the simulations of Campbell et al (1995), velocity gradients are greatest at the base of the flow and decrease upward.…”

Section: Implications For Emplacement Dynamicsmentioning

confidence: 96%

“…Such pyroclastic flows have been assumed to travel as plug flows in which the bulk of the load travels as a non-or slowly deforming mass on a thin basal shear zone (Sparks 1976;Wright and Walker 1981;Valentine and Fisher 1986;Battaglia 1993). This is supported by numerical simulations and experimental studies of granular avalanches, which reveal the existence of a thin basal shear zone typically ten grain diameters thick (Savage 1984;Cleary and Campbell 1993;Campbell 1989;Straub 1996Straub , 1997.…”

Section: Implications For Emplacement Dynamicsmentioning

confidence: 98%

Particle fabric in a small, type-2 ignimbrite flow unit (Laacher See, Germany) and implications for emplacement dynamics

Hughes

Druitt

1998

Bull Volcanol

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Ignimbrites of the 13-ka Upper Laacher See Tephra were deposited from small, highly concentrated, moderately fluidized pyroclastic flows. Their unconsolidated nature, and the prominence of accidental Devonian slate fragments, make these ignimbrites ideal for clast fabric studies. The upper flow unit of ignimbrite M14 has characteristics typical of a type-2 ignimbrite. Layer 2a and the lower part of layer 2b of the flow unit have strong, upstream-inclined a[p] fabrics (a[p] means long particle axes parallel to flow direction). Only clasts with a/b axial ratios of 2.5 or greater preserve good a[p] fabrics, whereas the a-b planes of flat fragments dip upstream irrespective of axial ratio. The a-axis fabric becomes weaker, flatter, and more girdle-like in the upper half of layer 2b. At one locality the a-axis fabric appears to rotate 407 up through the flow unit, suggesting either shear decoupling of different levels in the moving flow or unsteadiness effects in a flow depositing progressively at its base. The existence of similarly strong a[p] fabrics in layer 2a and the lower half of layer 2b appears inconsistent with the common interpretation that ignimbrite flow units are emplaced as a plug of essentially non-shearing material (layer 2b) on a thin shear layer (layer 2a), and that the entire flow freezes en masse to form the deposit. The data suggest that, if the flow froze en masse, it was shearing pervasively through at least half its thickness. Another possibility is that the flow unit aggraded progressively from the base up, and that the fabrics record the integrated history of shear directions and intensities immediately above the bed throughout the duration of deposition.

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Predictability of long runout landslide motion: implications from granular flow mechanics

Cited by 48 publications

References 48 publications

Debris flow characteristics and relationships in the Central Spanish Pyrenees

Debris flow characteristics and relationships in the Central Spanish Pyrenees

Understanding how volume affects the mobility of dry debris flows

Particle fabric in a small, type-2 ignimbrite flow unit (Laacher See, Germany) and implications for emplacement dynamics

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