The formation of collapse holes, locally known as ‘tomos’ is very common in the Rotorua-Taupo area. These form due to internal erosion in the soft pumice based soils, where water seeping into the ground is washing finer particles away creating a subsurface cavity and path for water to flow in. This regressive erosion of particles from downstream works upstream towards the surface until a continuous pipe is formed and collapse of the ground surface into the cavity occurs.…
Reported landslides occurring during May 2016.
Friday 6 May
A landslide blocked one lane of SH60 from Riwaka to Takaka, 3km north of the intersection with Riwaka Valley Road.
In East Cape, several landslides affected East Cape Road, from approximately 1.0km from start of road.
Monday 16 May
Haast Pass Highway between Haast and Makarora was reduced to one lane by a landslide. SH8 through Lindis Pass was reduced to one lane in several places due to landslides.…