COMPARING CHANGES IN THE NOLICHUCKY RIVER’S NATURAL COURSE IN NORTHEAST TENNESSEE BEFORE AND AFTER TROPICAL STORM HELENE USING AERIAL IMAGERY AND LIDAR

In late September 2024, the Nolichucky River in Northeast Tennessee suffered massive flooding due to nearly 20 inches of rain at its headwaters caused by Tropical Storm Helene. This flooding shattered the previous discharge record at the Nolichucky Dam and destroyed the USGS Embreeville stream gauge. Downstream communities were devastated, and as large amounts of sediment were eroded along the banks, the river’s course was permanently altered. Local counties and cities who use data about waterways for zoning and floodplain management need updated information on how they have changed following major disasters to ensure the safety of the people living there. This study uses aerial LiDAR and color-infrared imagery to delineate polygons of the river’s course before and after the record-breaking floods. These polygons were then intersected and differenced with each other to determine areas of the river where flow occurred only before Helene, only after Helene, or where flow remained unchanged. The results of this study reveal patterns of river morphology change, including areas where meanders were reshaped and the river channel widened or moved laterally.