Leveraging historical aerial photographs and digital photogrammetry techniques for landslide investigation-a practical perspective

Aerial photography has been extensively used for civil engineering applications for more than a century. The availability of digital photogrammetry tools has allowed for aircraft, UAV, and ground-based digital photogrammetry to become a reliable and standard tool for landslide management. Digital photographs and digitized historic aerial photos can be used to develop digital surface elevation models. This technical note presents a recent example of the use of historical aerial photographs in combination with modern remote sensing techniques and digital photogrammetry tools. The note provides valuable insights into landslide kinematics and evolution of the Chin Coulee landslide in southern Alberta, Canada. Conventional aerial photo interpretation allowed for a qualitative understanding of landslide feature evolution as a response to external factors (road construction and reservoir infilling at the toe of the landslide). More importantly, topographic changes were quantified through change detection techniques between topographic surfaces derived from historical photographs and a ground-based laser scanner. The results from change detection allowed to confirm the kinematics of the Chin Coulee landslide as a compound slide, an assumption which was previously based on limited deformation measurements. Furthermore, the results helped define the boundary between the active wedge of the landslide moving downslope as it pushes the passive wedge into the reservoir. Although challenges remain regarding the aggregation of datasets with different resolutions, this note demonstrates the valid practical application of this approach for landslide assessment and management.