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

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

doi:10.1038/ngeo1040

Cited by 500 publications

(502 citation statements)

References 41 publications

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“…Instead they found high entrainment rates to be caused by high-frequency pore-pressure fluctuations near the surface when the bed sediment was saturated. This agrees with the results of Iverson et al [18] who found that entrainment of bed sediment was predominantly controlled by sediment saturation as excess pore pressure was generated in the fluid matrix. …”

Section: State Of Current Entrainment Researchsupporting

confidence: 83%

Visualization of the internal flow properties and the material exchange interface in an entraining viscous Newtonian gravity current

2013

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In order to simulate a simple entraining geophysical flow, a viscous Newtonian gravity current is released from a reservoir by a dam-break and flows along a rigid horizontal bed until it meets a layer of entrainable material of finite depth, identical to the current. The goal is to examine the entrainment mechanisms by observing the interaction between the incoming flow and the loose bed. The sole parameter varied is the initial volume of the gravity current, thus altering its height and velocity. The gravity current plunges or spills into the entrainable bed and the velocity of the flow front becomes linear with time. The bed material is directly affected: motion is generated in the fluid far downstream of, and in that lying beneath the encroaching front. Shear bands are identified, separating horizontal flow downstream from flow with a strong vertical component close to the step. Downstream of the step the flow is horizontal and stratified, with no slip on the bottom boundary and very low shear near the surface. Between these two regions may lie transitional zones with linear velocity profiles, separated by horizontal bands of high shear; the number of transitional zones in the cross-section varies with the initial volume of the dam-break.

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Section: State Of Current Entrainment Researchsupporting

confidence: 83%

Visualization of the internal flow properties and the material exchange interface in an entraining viscous Newtonian gravity current

2013

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“…These studies point out that the main factors affecting (E/D) rates are the amount of rainfall and volume of sediments available, the hydrologic characteristics of the streambottom deposits, the flow depth, and the morphology of the channel (Mizuyama and Kobashi, 1996;Fagents and Baloga, 2006;Berger et al, 2011;Okano et al, 2012;Thouret et al, 2014). Moreover, a number of studies address the issue of identifying governing factors of debris flow entrainment, and most of them have been carried out in laboratory (Mangeney et al, 2010;Iverson et al, 2011) or mountain environments (e.g., Chen et al, 2005;Hungr et al, 2005;Guthrie et al, 2010;Berger et al, 2011;McCoy et al, 2012;Abancó and Hürlimann, 2014;Theule et al, 2015). These latter studies show large scattered results, which suggests that mechanisms governing the entrainment are complex and depend on site and flow characteristics.…”

Section: Introductionmentioning

confidence: 99%

Factors controlling erosion/deposition phenomena related to lahars at Volcán de Colima, Mexico

Vázquez

Capra

Coviello

2016

Nat. Hazards Earth Syst. Sci.

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Abstract. One of the most common phenomena at Volcán de Colima is the annual development of lahars that runs mainly through the southern ravines of the edifice. Since 2011 the study and the monitoring of these flows and of the associated rainfall has been achieved by means of an instrumented station located along the Montegrande ravine, together with the systematic surveying of cross-topographic profiles of the main channel. From these, we present the comparison of the morphological changes experimented by this ravine during the 2013, 2014 and 2015 rainy seasons. The erosion/deposition effects of 11 lahars that occurred during this period of time were quantified by means of the topographic profiles taken at the beginning and at the end of the rainy seasons and before and after the major lahar event of 11 June 2013. We identified (i) an erosive zone between 2100 and 1950 m a.s.l., 8 • in slope, with an annual erosional rate of 10.3 % mainly due to the narrowness of the channel and to its high slope angle and (ii) an erosive-depositional zone, between 1900 and 1700 m a.s.l., (∼ 8 % erosion and ∼ 16 % deposition), characterized by a wider channel that decreases in slope angle (4 • ). Based on these observations, the major factors controlling the erosion/deposition rates in the Montegrande ravine are the morphology of the gully (i.e., channel bed slope and the cross section width) and the joint effect of sediment availability and accumulated rainfall. On the distal reach of the ravine, the erosion/deposition processes tend to be promoted preferentially one over the other, mostly depending on the width of the active channel. Only for extraordinary rainfall events are the largest lahars mostly erosive all along the ravine up to the distal fan where the deposition takes place. In addition, as well as the morphological characteristics of the ravine, the flow depth is a critical factor in controlling erosion, as deeper flows will promote erosion against deposition. Finally, by comparing rainfalls associated with lahars that originated after the last main eruptive episode that occurred in 2004-2005, we observed that higher accumulated rainfall was needed to trigger lahars in the 2013 and 2014 seasons, which points to a progressive stabilization of the volcano slope during a post-eruptive period. These results can be used as a tool to foresee the channel response to future volcanic activity, to improve the input parameters for lahar modeling and to better constrain the hazard zonation at Volcán de Colima.

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“…Only such a reduction of T x can enhance landslide momentum in conjunction with entrainment (Iverson et al, 2011). The equation @z=@t ¼ T jump =rv x further implies that entrainment rates must decrease as basal landslide velocities increase À assuming that all other factors, such as slope angle, remain constant.…”

mentioning

confidence: 99%

DISCUSSION: Numerical study on the entrainment of bed material into rapid landslides. M. PIRULLI and M. PASTOR (2012). Géotechnique 62, No. 11, 959–972, http://dx.doi.org/10.1680/geot.10.P.074

Iverson¹

2013

Géotechnique

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

Cited by 500 publications

References 41 publications

Visualization of the internal flow properties and the material exchange interface in an entraining viscous Newtonian gravity current

Visualization of the internal flow properties and the material exchange interface in an entraining viscous Newtonian gravity current

Factors controlling erosion/deposition phenomena related to lahars at Volcán de Colima, Mexico

DISCUSSION: Numerical study on the entrainment of bed material into rapid landslides. M. PIRULLI and M. PASTOR (2012). Géotechnique 62, No. 11, 959–972, http://dx.doi.org/10.1680/geot.10.P.074

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