The landslide stage of the Hsiaolin catastrophe: Simulation and validation

Abstract

[1] Typhoon Morakot struck southern Taiwan in the summer of 2009, causing the most severe flooding since the 1950s. In the early morning of August 9, rainfall triggered the Hsiaolin landslide, and the resulting debris avalanche covered the township of Hsiaolin Village, Kaohsiung. Around five hundred people were buried alive. Reconstruction of the runout of the debris avalanche would increase understanding of the large-scale avalanches for future hazard mitigation purposes. Simulation of the debris avalanche runout can provide valuable information for this purpose. A new continuum shallow-water model is applied to flow over general topography. The Coulomb friction law is adopted; the friction coefficient is initially determined by high pressure rotary-shearing tests and subsequently fine-tuned by an iterative procedure to minimize the difference between the simulation and the measurement. The friction coefficients measured by laboratory tests are found to be in reasonable agreement with the best-fit result of the simulation. In addition, Voellmy rheology is applied, but it is found that the role of the fluid viscous drag is insignificant. The simulation result in the village area is further corroborated by near-surface magnetic surveys. These indicate that the northern part of the village is dislocated, while the artifact structures of the southern part are buried near their original locations. By comparing the landslide front and the flow direction of the simulation, we are able to confirm, as also described by survivors, that the landslide swept the northern part of the village into the Cishan River, while the southern part was flooded subsequently by the debris from a dam breach about 20 min after the landslide.

Magnetic signature of Siaolin Village, southern Taiwan, after burial by a catastrophic landslide due to Typhoon Morakot

“…Furthermore, such a destruction frontier indicates a major flow direction along the NE to the SW for the sliding of materials into Siaolin Village. Such an inference based on the magnetic survey is supported by a very recent simulation of the Siaolin landslide by Kuo et al (2010). The magnetic observations in this study thus provide a relevant constraint for further numerical simulation (e.g., Crosta et al, 2004;Kuo et al, 2009) of the flow pattern of the Siaolin landslide event (Kuo et al, 2010).…”

Modelling shallow debris flows of the Coulomb-mixture type over temporally varying topography

“…Hui et al, 1999). For further details of the numerical implementation, the readers are referred to Tai and Lin (2008); Tai et al (2011).…”

“…Taking advantage of the introduction of the UC system and the concept of general topography in Bouchut and Westdickenberg (2004), Tai and Kuo (2008) proposed a singlephase model with a deformable coordinate system for twodimensional mountain slopes, where the coordinate ζ = 0 always coincides with the varying topographic surface. A single-phase model for a three-dimensional topography was proposed by Tai et al (2012), and it is capable of successfully resolving the real catastrophic Hsiaolin landslide (Taiwan), see Kuo et al (2011). The present study is a Coulombmixture extension of Tai et al (2012)'s work with temporally varying coordinates for the entrainment-deposition processes.…”

“…The momentum correction factor ̟ is set to be 1.0 in the present simulation for ease of comparison. The readers are referred to Tai et al (2011) for a more detailed discussion of the factor ̟ .…”

Reconstruction of the Kinematics of Landslide and Debris Flow Through Numerical Modeling Supported by Multidisciplinary Data: The 2009 Siaolin, Taiwan Landslide

“…The major slid mass on the east side of the Cishan River is www.intechopen.com best-fit algorithm to minimize the difference between the simulation and the field measurement, it is confirmed that the optimal value of the friction coefficient is 11.5 o , with just a minute offset from the straightforward estimation. Fuller theoretical and numerical details of the simulation have been reported in a designated paper (Kuo et al, 2011). Two snapshots at t = 32 and t = 60 seconds are shown in Figures 3A and 3B, respectively.…”