Runout Characteristics and Grain Size Distribution of Large-scale Debris Flows Triggered by Deep Catastrophic Landslides

Abstract

Deep catastrophic landslides (DCLs) sometimes lead to large-scale debris flows with serious impacts on human life and infrastructure. However, no adequate information about DCL-triggered debris flows, such as the topography of eroded and deposited areas or the grain size distribution, exist. We compiled published data and obtained additional new data for the topographic characteristics and grain size distributions of 10 recent DCL-triggered debris flows in Japan. We compared these data with previously published data of small-scale debris flows, steep-slope failures, and large-scale debris flows. We examined the effects of topography and DCL volume on erosion and deposition due to debris flow as well as on grain size distribution. The longitudinal gradient of the lower end of the deposited area decreased with increasing landslide volume, and about half of DCL-triggered debris flows deposited material where the longitudinal gradient of the lower end of the deposited area was less than 2°. However, the minimum longitudinal gradient of the eroded section due to debris flow was not affected by the landslide or the debris flow volume. We found that the travel distance of debris flow, including DCL-triggered debris flow, might also be a function of landslide and/or debris flow volume and that the grain size of debris flows triggered by DCLs spanned more than eight orders of magnitude.

New Numerical Simulation Procedure for Large-scale Debris Flows (Kanako-LS)

“…In steep mountainous regions, both soils and weathered bedrock are known to slide, often simultaneously [e.g., Uchida et al, 2011]. These landslides sometimes move rapidly and trigger debris flows [e.g., Nishiguchi et al, 2012], and can have serious impacts on human lives and infrastructure [e.g., Evans et al, 2007;Jitousono et al, 2008;Shieh et al, 2009]. It has been proposed that the development of early warning systems and the construction of countermeasures for these deep-seated rapid (catastrophic) landslides could be important tools for disaster risk reduction.…”

Laboratory Landquakes: Insights From Experiments Into the High‐Frequency Seismic Signal Generated by Geophysical Granular Flows

“…According to these models, a flow identical to those in our experiments, except with particles of radius 1 m, should produce a seismic force signal with power spectral density per unit flow area ˆ( ) / F P f A, of order (10 2 -10 6 ) N 2 m −2 s below a corner frequency f c of order 100 Hz. A more difficult adjustment is required to account for the wide particle polydispersity typical of geophysical flows (Nishiguchi et al, 2012;Takahashi, 1981), which makes d hard to define and necessitates consideration of the segregation of particles by size that is well-documented within granular flows (e.g., Garve, 1925;Gray, 2018). Farin, Tsai, et al (2019) proposes a promising approach for each given model, of dividing the flow into a coarse-grained front and a fine-grained tail and calculating for each a percentile of the particle size distribution that will be representative, but this proposal requires validation.…”

Collapsed material movement of deep-seated landslides caused by Typhoon Talas 2011 on the Kii Peninsula, Japan

“…widely used as an indicator of travel distance [Dahl et al ., 2010;Finlay et al ., 1999;Hsu, 1975;Nishiguchi et al ., 2012;Okura et al ., 2003;Rickenmann, 2005;Scheidegger, 1973;Usuki et al ., 2006], and is greatly influenced by topographic factors [Hattanji and Moriwaki, 2009;Okura et al ., 2003]. ECF (= Σ H /Σ L) is the ratio between relative height (Σ H ) and total travel length (Σ L) from the top of the failure zone to the end of the deposition zone (Fig.…”

“…Historical documents and topography reveal the formation of many landslide dams, some of which broke and caused major damage in Japan [Tabata et al ., 2002]. Debris flow from deep-seated landslides can have serious impacts on human life and infrastructure [Nishiguchi et al ., 2012]. However, landslide dams holds further threats: back-flooding threatens upstream areas, and when the dam breaks, commonly owing to overflow of backed-up water, large surge and debris flows threaten downstream areas [e.g., Ermini and Casagli, 2003;.…”