THE GROUND IS MOVING ALL AROUND US: REGIONAL LIDAR CHANGE DETECTION IN WESTERN WASHINGTON

Understanding the location and movement history of recently active landslides allows engineers, planners, and scientists to make informed decisions related to development, conservation, and geohazard risk. High resolution topography data is a key resource in identifying landslides and their activity levels. In 2015, state legislation mandated the Washington Geological Survey, under the Washington Department of Natural Resources (WDNR), to collect, analyze, and publicly distribute aerial lidar data in Washington State. Throughout the collection campaigns, multi-temporal data have been acquired, particularly in populated areas and areas known for the presence of active landslides (e.g., river valleys). The multi-temporal datasets contain a wealth of information on landslide deformation and sediment transport processes through time. However, unlocking this insight was until recently a challenging, time-intensive task. Processing thousands of square kilometers of lidar to compute changes required significant computational resources and was compounded by issues related to datasets of varying quality and resolution. BGC Engineering recently supported WDNR in computing point-based change detection for approximately 6,000 km² of overlapping high-resolution lidar datasets. BGC performed the change detection in six weeks by using an industry-leading workflow including GPU hardware acceleration, and interactively displayed results in our internally developed Cambio geohazard risk management platform. Using this process has allowed for the rapid identification of landslides in northwest Washington with movement of greater than 1-3 ft in the last 20 years.