Abstract

SEQUEIRA-ARGUEDAS, José María. Geology, geomorphology and landslide occurrence in the upper Virilla River basin, Costa Rica. Rev. Geog. Amer. Central [online]. 2021, n.66, pp.313-339. ISSN 2215-2563.  http://dx.doi.org/10.15359/rgac.66-1.12.

The Cerro de Pico de Piedra (translated as Mount Pico de Piedra) is a collapsed volcanic structure of the Irazú Volcanic Group associated with Paraíso Member’s volcanism and constitutes part of the upper basin of the Virilla River. Data interpretation gathered by remote sensing, bibliographical compilation, geomorphological survey and field visits allowed the identification of intensive erosion processes, slope instability and hazard (damage) susceptibility of the La Holanda transport corridor (road) that connects milk and tuber-producing farms with the town of San Isidro de Coronado. Landslide occurrence and transport corridor susceptibility were assessed according to modified Mora-Vahrson and probabilistic infinite slope analysis (PISA) methodologies by modeling various degrees of soil water saturation in volcanic soils under two conditional seismic scenarios referenced to the Patillos (1952) and Cinchona (2009) Costa Rican earthquakes. Integrated geological zoning of the upper basin suggests the need to preserve the current forest coverage, minimize erosion rates and maintain appropriate buffering allowance distances of anthropogenic activities from fluvial bodies. Current agricultural areas are located within the legally established regulated territorial zoning attributed as being the most stable in relation to their geomorphological conditions.

Keywords : Landslides; Volcanic soils; Boulder drag; Seismic hazard; Geomorphology..

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