Whitehorse Trail Channel Migration Zone Assessment

NW Fish Passage performed a channel migration zone assessment for locations of concern along the Whitehorse Trail, a trail that follows the North Fork Stillaguamish River. Using historic imagery, LiDAR, and field assessment we delineated the historic migration zone, avulsion hazard area, and predicted erosion hazard area to find the locations where the North Fork Stillaguamish poses a risk to future channel migration. We predicted the erosion hazard area at our sites using a combination of channel migration trends and anticipated slope stability angle. This analysis will be used to inform the county on how far the trail needs to be moved to mitigate landslide risk within the next 30 years.