Shallow landslide susceptibility assessment in a data-poor region of Guatemala (Comitancillo municipality)

Abstract

Although landslides are frequent natural phenomena in mountainous regions, the lack of data in emerging countries is a significant issue in the assessment of shallow landslide susceptibility. A key factor in risk-mitigation strategies is the evaluation of deterministic physical models for hazard assessment in these data-poor regions. Given the lack of physical information, input parameters to these data-intensive deterministic models have to be estimated, which has a negative impact on the reliability of the assessment. To address this problem, we examined shallow landslide hazard in Comitancillo municipality, Guatemala. Shallow landslides are here defined as small (less than two or three metre-deep) rotational or translational slides or earth flows. We based our hazard simulation on the stability index mapping model. The model's input parameters were estimated from a statistical analysis of factors affecting landslides in the municipality obtained from a geodatabase. The outputs from the model were analysed and compared to an inventory of small-scale landslides. The results of the comparison show the effectiveness of the method developed to estimate input parameters for a deterministic model, in regions where physical data related to the assessment of shallow landslide susceptibility is lacking. IntroductionVarious natural disasters in recent centuries in Central America have been caused by landslides and debris flows (Zaitchik and van Es, 2003;Petley et al., 2005;Devoli et al., 2007aDevoli et al., , 2007bMedina, 2007;Miner and Villagran de Leon, 2008;Devoli et al., 2009). For example, in early October 2005 at the end of the rainy season, a storm system led to heavy rainfall in Guatemala (UNEP, 2005) and resulted in several landslides that had a severe impact on communities. More than 1800 people died (Cepeda et al., 2010) and the landslides that hit the Sololà and San Marcos Departments wrecked entire villages (Medina, 2007). However, the municipality of Comitancillo (San Marcos Department) escaped the disaster. There were no large-scale land movements (MAGA, 2001), although several shallow landslides and/or earthflows were observed. Nevertheless, landslides are the most significant cause of denudation in watersheds with steep slopes (Wentworth, 1943;Scott and Street, 1976;Li, 1988;Terlien, 1997;Lan et al., 2004).Most landslides in Central and South America occur (or have the potential to occur) in mountainous regions of the Andes and steep slopes in volcanic regions. In rural zones of Guatemala, forested land has been degraded (Medina, 2007) or partially converted to subsistence agriculture (Bresci et al., 2013). Such changes in land use and land cover affect soil cohesion and critical pore water pressure, causing loss of root reinforcement and reduction of the canopy effect on interception and evapotranspiration (Kuriakose et al., 2009).In the municipality the factors affecting landslides have never been identified or analysed; they include lithology, soil texture, slope angle, elevation (Lan et al....

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