Rainfall-triggered landslides in Auckland, New Zealand: engineering properties, failure processes and InSAR analysis

Synopsis

With ~1.7m people, Auckland is New Zealand’s most populous region, and much of the region is prone to landslides. The geology of the region is varied, with most of the region covered in residual soils formed on Miocene age sedimentary or volcanic rocks. In addition, the remnants of 53 volcanoes of the Quaternary Auckland Volcanic Field (AVF) dominate the topography of the city and suburbs. While the slopes of many of these scoria cones are free-draining, landslides have occurred in recent years. On the west coast of Auckland, Pio-Pleistocene Awhitu Group sands are present, and failure of slopes formed on these materials has had disastrous consequences for houses downslope. These dune sands are largely uncemented and permeable, but include discrete (<1 m thick) beds of weathered distal tephra from the Taupo Volcanic Zone (TVZ). These beds act as aquicludes during heavy rainfall, destabilising the overlying uncemented sands, which can…