Stream and Floodplain Restoration Lessons Learned Following 2024 Helene Flooding in Western North Carolina
Greg Jennings, PhD, PE
Jennings Environmental, PLLC
Asheville, NC
Extreme flooding occurred in September 2024 throughout Western North Carolina when Hurricane Helene produced unprecedented rainfall. Impacts to streams and rivers included erosion, deposition, loss of forest buffers, channel morphology changes, and pollution. This presentation describes post-flood observations of 40 ecosystem restoration projects implemented over the past decade in a variety of watershed settings. All projects included natural restoration techniques designed to enhance flood resilience through floodplain connectivity, native riparian vegetation, and in-stream wood and rock structures. Channel sizes range from 1 to 30 m in width and 0.2 to 3 m in depth. Flood inundation depths estimated based on visual indicators and nearby gages ranged from 1 to 6 m above top of bank. Floodplain widths ranged from 2 to 22 times the bankfull channel width of the restored stream channel. Post-flood site conditions were rated as successful, partially successful, or failing to meet flood resilience objectives in terms of maintaining natural channel forms and riparian vegetation. Of the 40 restoration projects assessed, 31 were successful, 7 were partially successful, and 2 were failing to maintain resilience. In general, successful projects were older and had wider floodplains with dense riparian forest buffers. Damaged projects were in more urbanized areas with local infrastructure such as bridges and had less available floodplain width for energy dissipation. Lessons learned from assessing restoration projects exposed to extreme flooding e should be integrated into plans for future projects to optimize flood resilience and ecosystem functions.
About Greg Jennings, PhD, PE
Greg Jennings, PhD., PE, has 35 years of experience in water resources engineering, specializing in stream and floodplain restoration. He leads a team of expert consultants providing restoration planning, design, permitting, and implementation services for local governments, non-profit organizations, and landowners in North Carolina and surrounding states.