Use of small unmanned aerial vehicles and related digital data in geotechnical and natural hazard impact assessment

Unmanned Aerial Vehicles (UAVs or drones) facilitate data collection that allows rapid and enhanced geotechnical assessment of the risks associated with landslides, slopes and structures during normal conditions and following natural hazard events.

WSP Opus has used UAVs over the past 10 years in New Zealand, and more recently in Australia, to assist engineering assessments for highways, railways, and infrastructure for local authorities, government departments and private clients. The early uses were mainly for occasional geotechnical slope and site mapping purposes. However, since 2011 UAVs have been systematically used for surveying and geotechnical applications. Examples are presented in this paper of the use of UAVs for assessment of slopes and existing landslides, as well as for post disaster assessments.

UAVs were utilized following the damaging February 2011 (M6.3) Christchurch Earthquake, the 2011-2015 storm events in central New Zealand, and the November 2016 (M7.8) Kaikoura Earthquake to inspect and provide damage records of sections of highways, slopes, and river stopbanks (levees), and to facilitate rapid development of remedial options.

The data gathered from UAVs have been used with post processing of imagery to create 3D terrain models. Comparison of periodic UAV derived models or comparison with previous LiDAR models enabled the detection and monitoring of slope change in areas affected by slope failures along transportation corridors. UAVs were also used to inspect and obtain geological data to assist with the assessment of rock slope stability. In the Blue Mountains Rail Corridor (NSW) in Australia, the use of UAVs provided a much safer alternative than having staff carry out observations directly (for example by rope access), given the hazardous nature of these locations. A comparison of geological and other data obtained from UAV inspections with those gained from conventional methods showed good correlation.

In addition to the safety benefits, the use of UAVs has enabled better and early decisions to be made to manage the risks associated with hazardous sites, and the rapid development of remedial solutions.