Geological characterization and failure analysis of a catastrophic landslide in volcaniclastic soils: the Banjarnegara–Jemblung Landslide (Indonesia)

Abstract

The Banjarnegara–Jemblung Landslide was triggered on 12 December 2014 near the village of Jemblung in Central Java (Indonesia). The disaster occurred on the northern slope of Gunung Telagalele and caused more than 100 fatalities, making it the most disastrous landslide to have occurred in Indonesia in the past few decades. The event was characterized by multiple slope failures forming two landslide events A and B, with two connected scarps but two separated runout paths. According to eyewitnesses, landslide A was mobilized only a few minutes after the initial failure of B. Initially, both landslides began as earth slides that developed subsequently into very to extremely rapid earth flows. Although the failure volume was moderate, both slide flows reached very high velocities of several metres per second and travelled long distances, leading to remarkably low travel angles of 14° and 15°. Field investigations confirmed that slope failure was exacerbated by its geological predisposition based on a slope-parallel layering of volcaniclastic sediments of different origin and age, as well as intensive tropical weathering that generated clay-rich soils. Temporal relationships, as well as stability analysis, indicate that antecedent rainfall over 2 months and heavy rainfall the day before triggered the slope failure. Thematic collection: This article is part of the Leading to Innovative Engineering Geology Practices collection available at: https://www.lyellcollection.org/topic/collections/leading-to-innovative-engineering-geology-practices