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The Taihape landslide covers approximately 45 hectares and contains over 200 households a primary school
and a hospital. The Waikorora landslide covers approximately 6 hectares and is traversed by the Maui gas
pipeline, which provides New Zealand with 80% of its gas requirements. Both landslides are currently active
and are being monitored using a combination of field mapping, sub-surface investigation and near real-time
monitoring of rainfall, ground-shaking intensity, groundwater levels and surface movement. Data from the
landslides are being used to correlate different rates of surface movement to the triggering factors enabling
movement triggering thresholds to be established. Until 2006, monitoring was carried out manually, with the
monitoring frequency ranging from twice a year to once every five years. New monitoring equipment
operating in a near real-time framework was installed in 2006. A key component are the surface movement
monitoring systems which, at Taihape, comprises a laser survey network that automatically tracks, at defined
(hourly) intervals, the positions of reflectors placed on the landslide; and at Waikorora, a series of
continuous GPS receivers installed on the active landslide. These movement data, along with data from
piezometers, rain gauges and strong motion accelerographs installed on the landslides are transmitted by
radio and internet to a central hub where they can be viewed in near real-time. The greater temporal and
spatial resolution of the monitoring networks allow movement triggering intensity/duration thresholds to be
developed, which will allow alert levels, based on landslide movement to be set, once a better understanding
of the movement patterns have been established.
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Petley, D.N., Mantovani, F., Bulmer, M.N. and Zannoni, A. (2004) The use of surface monitoring data for the
interpretation of landslide movement patterns. Geomorphology. 66 (1-4) pp. 133-147.
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North Island, New Zealand. PhD Thesis, University of Auckland.
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active toe area. Unpublished report for Earthquake Commission, NZ.
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Rock Slope Stability
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