Reported in the Gisborne Herald in New Zealand.
In the week before Christmas, members from the GNS Engineering Geology team (Brenda Rosser, Jason Farr, Andrew Boyes) travelled to Gisborne to survey the large landslide at Whareongaonga.
Using unmanned aerial vehicles (UAV), LiDAR (light detection and ranging) and 3D mapping they estimated the landslide involved the movement of more than 1 million cubic metres of earth — enough to fill 400 Olympic-sized swimming pools or 70,000 dump trucks.
The landslide and others adjacent to it undermined the already damaged Wairoa-to-Gisborne rail line and buried several wahi tapu sites, including a historic Ngāi Tāmanuhiri pā site, māra kai (food gardens) and taunga ika (fishing grounds).
“The team used our new LiDAR (Light Detection and Ranging) drone (UAV) to capture high-resolution topographic data of the landslides,” a GNS spokeswoman told The Herald.
“Lidar is a remote sensing method that uses light in the form of a pulsed laser to measure distances to the Earth surface and enables us to build a high resolution (1m) 3D model of the ground surface.
“The data will be used to determine the volume of material involved in the landslide — both the volume evacuated from the source area and deposited downslope and in the sea — and to interpret the processes involved in the landslide initiation and movement.
“The survey data will also be used as a baseline to map the landslide and tension cracks surrounding the slip, and to monitor changes in the landslide (and deposit) over time as the sea and future rain events erode the landslide and deposit.
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