Combining InSAR and UAV data to analyze the stability of coastal cliffs

The study of coastal areas represents a real challenge for the research community, due to the numerous drivers that can control coastal processes (subaerial, marine or endogenous). In particular, the analysis of cliffs is fundamental for the assessment and management of coastal landslide hazard and risk.

In cliff stability studies, the integration of multiple data sources, including satellite imagery, aerial photography and LIDAR, represents an important development and advancement. The integration of various data sources can significantly improve our understanding of geological phenomena, as well as the accuracy of monitoring data and forecasting systems.

The aim of this work is to integrate the PS-InSAR technique and UAV LIDAR and photogrammetric surveys to improve cliff stability evaluations. UAV LIDAR/photogrammetry and PS-InSAR are remote sensing techniques that allow to improve information about slope geometry, even in hard-to-reach areas. LIDAR acquisitions in this study have been undertaken through a DJI Matrice 350 + Zenmuse L2 LIDAR system and are processed in high-resolution DTMs (in this work the cell resolution is ca 20 cm). With regard to PS-InSAR, Sentinel 1 Single Look Complex radar images have been processed through Sarproz software to extract Persistent Scatter points. The time series of the Persistent Scatter points are then used to monitor surface displacements in selected coastal cliffs. The combination of UAV and PS-InSAR data were then utilized to create detailed 3D slope models and validate the results of cliff stability simulations, verifying the main drivers controlling cliff stability and retrogression. Stability numerical cliff simulations could be in future a very powerful tool to potentially predict the future processes in relation to climate variations.

The combination of these advanced methodologies offers a comprehensive approach that improves the quality of cliff monitoring and the precision of the forecasting systems. By leveraging the strengths of both PS-InSAR and UAV data, detailed insights into reef dynamics can be obtained, ultimately leading to more informed decisions for coastal management and risk mitigation.