Landslide and debris flow susceptibility zonation using TRIGRS for the 2011 Seoul landslide event

Abstract

Abstract. This paper presents the results from the application of a regional, physically based stability model: Transient Rainfall Infiltration and Grid-based Regional Slope-stability analysis (TRIGRS) for a region on Woomyeon Mountain, Seoul, South Korea. This model couples an infinite-slope stability analysis with a one-dimensional analytical solution to predict the transient pore pressure response to the infiltration of rainfall. TRIGRS also adopts the geographic information system (GIS) framework for determining the whole behaviour of a slope. In this paper, we suggest an index for evaluating the results produced by the model. Particular attention is devoted to the prediction of routes of debris flow, using a runoff module.In this context, the paper compares observed landslide and debris flow events with those predicted by the TRIGRS model. The TRIGRS model, originally developed to predict shallow landslides, has been extended in this study for application to debris flows. The results predicted by the TRIGRS model are presented as safety factor (FS) maps corresponding to transient rainfall events, and in terms of debris flow paths using methods proposed by several researchers in hydrology.In order to quantify the effectiveness of the model, we proposed an index called LR class (landslide ratio for each predicted FS class). The LR class index is mainly applied in regions where the landslide scar area is not well defined (or is unknown), in order to avoid overestimation of the model results. The use of the TRIGRS routing module was proposed to predict the paths of debris flow, especially in areas where the rheological properties and erosion rates of the materials are difficult to obtain. Although an improvement in accuracy is needed, this module is very useful for preliminary spatio-temporal assessment over wide areas. In summary, the TRIGRS model is a powerful tool of use to decision makers for susceptibility mapping, particularly when linked with various advanced applications using GIS spatial functions.

Sensitivity analysis and calibration of a dynamic physically based slope stability model

“…The details of the infiltration models have been presented in previous studies (e.g. Baum et al, 2010;Iverson, 2000;Kim et al, 2013;Park et al, 2013;Salciarini et al, 2006). The result of both infiltration models is the evolution of pore pressures with depth and time as a response to the infiltration of timevarying precipitation.…”

“…Regolith depth maps are prepared as a function of the slope angle (Salciarini et al, 2006), using a geomorphologically indexed model (Zizioli et al, 2013), using a spline interpolation of direct measurements (Kim et al, 2013) and with spatially constant values (Park et al, 2013;Vieira et al, 2010). The initial depth of the water table d wi (positive in downward direction) is assumed to be either at the regolith-bedrock interface (Kim et al, 2013;Park et al, 2013;Vieira et al, 2010) or at a depth relative to it (Salciarini et al, 2006;Zizioli et al, 2013). For the background infiltration rate describing a steady-state infiltration component, constant values (e.g.…”

Developing an Accessible Landslide Susceptibility Model Using Open-Source Resources

“…Some modules within TRIGRS are based on Iverson's linearized methods of Richards' equation and extensions [23,36]. Moreover, TRIGRS also employs a number of Heaviside step functions for rainfall intensity and time-varying sequences for duration [37]. However, because predicting landslide risks is a highly rational process, and requires significant quantities of data to overcome uncertainty, a number of environmental variables need to be taken into account [38,39].…”

Potential Impact of Landslide and Debris Flow on Climate Extreme – A Case Study of Xindian Watershed in Taiwan

“…The TRIGRS is an inventory of shallow landslide simulation program developed by USGS , and it has been widely used in several case studies of shallow landslide (Salciarini et al, 2006;Godt et al, 2008;Park et al, 2013;Shih et al, 2015). As TRIGRS is a shallow landslide simulation program, the deep-seated landslide is not available in our discussion.…”