A case study of a hillside slope instability in South East Queensland

This paper describes the failure mechanism associated with multiple landslides over the east facing slopes MapletonMaleny Plateau around 80 km north of Brisbane, Queensland. High localised groundwater outflows have been observed during remedial works to these landslides which are believed to be unique to these east facing slopes as a consequence of the combination of basaltic cap and structural geology of this area. Landslides of varying scale have been noted in this area since early settlement mainly associated with colluvial soils contained within relic drainage lines that bisect the steep slopes. This case history will summarise investigative work undertaken in this area following a particularly severe period of landslide activity that followed heavy rains of January 2011 and aims to summarise observations with regard to their commonality and possibly connectivity.