Identifying Rockfall Hazards in White Canyon, British Columbia: An Approach to the Development and Analysis of Dense Point Clouds from Different Remote Sensors

Abstract

Due to the numerous extensive rock cuts required through steep topography, rockfalls are a common risk to which the Canadian National Railway (CN) and Canadian Pacific Railway (CP) rail corridors in Western Canada are exposed. Rockfall hazards on railway corridors create risk of derailment which can result in damage to property or the environment and cause injury or loss of life. There is interest in understanding the location and severity of such hazards so that management strategies can be implemented. Previous studies at White Canyon near Lytton, British Columbia have demonstrated how remote sensing data collection such as terrestrial laser scanning (TLS) and photogrammetry has increased knowledge of the magnitude and frequency distribution of rockfalls. However, there are some data limitations preventing analysis of all sectors of the canyon, largely due to complex geometry of the slope which includes vertical spires of rock protruding from the slope. This study aims to improve the understanding of rockfalls through the integration of TLS and UAV-SfM point clouds. In addition, new terrestrial monitoring methods using particle tracking on sequential photographs generates results at higher temporal resolution with less computational expense for the near real-time evaluation of slopes. The research presented herein has several objectives: (1) Generate dense point clouds from different patterns in the flight plans of a UAV to collect data in remote areas; (2) Combine point clouds from TLS and UAV-SfM to obtain a complete model of the complex geomorphology of the spires in White Canyon; (3) Perform change detection calculations in integrated UAV-SfM and TLS point clouds and filter the change detected; and (4) Implement low-cost, near real-time frequency terrestrial photomonitoring to collect data from the slope and spires.