2025 Geologic implications of the Helene Weather Event in the southern Appalachians (56 mins.)

Recorded September 23, 2025 Level: Intermediate to advanced, though extensive conceptual illustration will make the presentation understandable to a general audience. Impacts of tropical or post-tropical weather systems on the southern Appalachians have been significant during recorded history in the region, but documentation of these events prior to the availability of digital topography—and photography—has been difficult. Region-scale impacts of the Helene weather event were documented in detail by on-the-ground observers, post-event aerial photography, and an increasing amount of post-event lidar imagery, allowing a comprehensive evaluation of the geomorphic implications of the storm across an entire region. Lidar is particularly valuable in establishing patterns of sediment transport from slopes into channels, with lidar change evaluation indicating large-scale fluvial transport of mobilized debris in many instances. The detailed record of this storm serves to inform understanding of the interplay between geology and climate in the region while also representing a valuable record of what low recurrence interval storm impacts look like in the region.