Monitoring 4D landslide displacement using very high resolution Pléiades satellite remote sensing.Case study of the La Valette landslide, French Alps

Slow-moving landslides may pose a substantial threat to communities and infrastructure, with annual creeping distances ranging from a few mm to 100 m. To protect local communities from the landslide motion, landslide displacement monitoring is necessary. However, traditional field investigations are time- and labor-consuming, which may limit the understanding of the landslide evolution and thereby mitigation. Here we propose a 4D landslide displacement framework using optical very high resolution (0.5m) Pléiades satellite constellation imagery. We use our method to monitor the annual movement of the ‘La Valette’ landslide, southern French Alps, between 2012 and 2022. During this period, the landslide moved most actively during the years 2012 and 2013, with average 3D displacement rates of 1.22 and 0.89 cm / day, respectively. Furthermore, we found a decelerating trend in movement rate from 2012 to 2022, which we attribute to warmer weather, decreasing precipitation rates, drier air conditions, and the implementation of a drainage installation. Our study demonstrates the great potential of very-high resolution satellite imagery for near-real time monitoring of 4D landslide displacement, which may benefit research and may contribute to the mitigation of damage and fatalities of slow-moving landslides.