Helene made landfall in Florida's Big Bend area on Sept. 27, 2024 as a category 4 hurricane--the strongest tropical cyclone to strike that region on record. In the southern Appalachians, far to the north, the cyclone's impacts were magnified by the area's topography, leading to historic flooding, a record number of landslides and extensive forest blowdowns. By 10 days after the storm, high resolution remote sensing was available from NOAA, WorldView-2 and 10m Sentinel-2 imagery.  The very high resolution imagery available was and remains spotty, while 10m Sentinel-2 change detection using HiForm provides our best all-lands insight into how this historical storm impacted the entire region's landscape.

During the fall season, change detection can be challenging because foliage is undergoing its normal transition, and leaf-stripping from wind readily occurred in deciduous forests without any structural damage to trees. Thus, change detection alone was not enough to understand the highly complex impacts that occurred across this region. This highlight reflects both the rapid change detection analysis using HiForm and the results of early assessment efforts that involved documentation from field observations and very high resolution imagery, where available. The map products can be viewed in ArcGIS Online using the links provided in the attached document. Impacts to five landscapes are described in detail. These are Roan Mountain, the Big Ivy area, Elk Mountains, Asheville's urban forest, the Pisgah Ranger District, and Linville Gorge.