What does the slope monitoring toolbox look like in 2025?

The options for slope monitoring continue to expand with advances in technology. The plethora of monitoring options and the large amount of data that can be generated are both an opportunity and a risk. The concept of a toolbox of methods is a useful one – the methods are tools to assist geoprofessionals to understand the behaviour of slopes, so that they can assess risks and present sound risk mitigation options / recommendations. Also, the challenge is to choose the right tools for the job, based on the understanding of expected and potential failure mechanisms. The use of UAVs has been a gamechanger in being able to both safely inspect and survey landslides. Installed instruments such as tilt sensors, extensometers, GNSS/GPS, rain gauges and CCTV cameras, as well as remote techniques from various types of spatial scanning, provide data on water content and deformation that can inform decisions on risk and the resultant actions. Trigger Action Response Plans (TARPs) are used to facilitate the decision process. This paper provides examples from monitoring of slope movements related to transport corridors in Victoria and New Zealand. Covered are the Bogong landslide which closed access to the Falls Creek Alpine Resort in Victoria, landslides threatening the North Island Main Trunk railway north of Wellington (Kapiti slope) and a rural road in the Wairarapa (Hinekura Road) and repeat multiple slope failures affecting SH1 road access to Northland, NZ (Mangamuka Gorge and Brynderwyns sites). A trial of InSAR for deformation of Northland roads is also presented. Examples of what went well and what didn’t are discussed to assist others with similar challenges. The importance of using multiple methods and having well trained staff involved in the choice of tools and data review is stressed.