Brief Communication: Monitoring slope acceleration and impending failure with very high spatial and temporal resolution space borne Synthetic Aperture Radars

Abstract. We demonstrate how high spatial and temporal resolution spaceborne synthetic aperture radar (SAR) imagery can be applied to improve slope deformation monitoring. We process ICEYE data acquired over the Brienz/Brinzauls slope instability in the Swiss Alps, where a catastrophic failure occurred on June 15th, 2023. The available images provided unprecedented viewing of the moving slope from satellite SAR, with revisit times ranging from less than 1 hour to a maximum of 4 days. We apply image correlation algorithms (i.e., pixel-offset analysis) on SAR backscattering to measure surface velocity before the failure event and compared the results against ground-based SAR data used for early-warning purposes. We also compare pre- and post-failure imagery to map areas invaded by debris and to compute volumetric changes associated with the down wasted materials, showing good agreement with digital surface models generated from photogrammetric drone flights. Our results demonstrate how weather independent, high resolution satellite SAR data can provide data in critical scenarios of slope deformation, suggesting that crucial information can be retrieved timely also in remote, poorly accessible regions where in-situ monitoring is not viable.