160-8 A catchment-wide assessment of the impacts of Hurricane Helene on the Wilson Creek Drainage along the Blue Ridge Escarpment, North Carolina

Session: Advances in Fluvial Processes and Sediment Transport, Part I

Presenting Author:

Bradley Johnson

Authors:

Johnson, Bradley G¹, Marshall, Anna², Farmer, Anna³, Holmes, Mary⁴, Linton, Torin⁵, Ponder, Graham⁶, Rauscher, Neve⁷, Payne, Susanna⁸, Chi, Jingyan⁹, Tanner, Mena¹⁰, Cordon, Jazmine¹¹, Masteller, Claire¹², Mirus, Ben¹³, Hunter, Brooke¹⁴, Schneider, Katie¹⁵

(1) Environmental Studies, Davidson College, Davidson, NC, USA, (2) Geography and Sustainability, University of Tennessee Knoxville, Knoxville, TN, USA, (3) Environmental Studies, Davidson College, Davidson, NC, USA, (4) Environmental Studies, Davidson College, Davidson, NC, USA, (5) Environmental Studies, Davidson College, Davidson, NC, USA, (6) Environmental Studies, Davidson College, Davidson, NC, USA, (7) Environmental Studies, Davidson College, Davidson, NC, USA, (8) Environmental Studies, Davidson College, Davidson, NC, USA, (9) Environmental Studies, Davidson College, Davidson, NC, USA, (10) Environmental Studies, Davidson College, Davidson, NC, USA, (11) Environmental Studies, Davidson College, Davidson, NC, USA, (12) Department of Earth, Environmental, and Planetary Sciences, Washington University, St. Louis, MO, USA, (13) Geologic Hazards Science Center, United States Geological Survey, Golden, Colorado, USA, (14) Geological and Environmental Sciences, Appalachian State University, Boone, NC, USA, (15) Geosciences and Natural Resources Department, Western Carolina University, Cullowhee, NC, USA,

Abstract:

Hurricane Helene was a generational event in the Blue Ridge Mountains of North Carolina in terms of precipitation intensity and accumulation, flooding, catastrophic mass movements, and forest loss. Assessing the cumulative impacts of Helene on the landscape involves both quantifying the geomorphic work done during the storm and understanding the ways in which these direct consequences have now primed the geomorphic system for evolution over the coming decades. Here we present preliminary field data collected in the Wilson Creek drainage where basin-wide geomorphic mapping was completed immediately before Helene. Following Helene, we conducted preliminary landslide mapping, inventories of large woody debris for 1^st through 4^th order streams, discharge estimates for various sub-basins, qualitative descriptions of changes to the fluvial system, and detailed hillslope tree-throw surveys. This holistic approach across the continuum from landslide initiation zones to stream channels sheds light on the sources and sinks for both sediment and large wood across the hillslope and fluvial process domains. For example, we are able to estimate tree density within landslide tracks and approximate the number of trees recruited by the river for landslides of various sizes. We compare these recruitment estimates to actual logjam volumes to determine the relative degree of wood recruitment from landslides versus stream banks. We also present tree throw hole volume ranges to better understand soil displacement on hillslopes with large blowdown events.  Our field data and detailed observations provide an important ground truth for interpreting subsequent differencing of pre- and post-event lidar and vegetation change detection as we seek to better understand the geomorphic impacts of Helene across the Blue Ridge Mountains more broadly.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8744

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.