Flash Flood — Transylvania, North Carolina

2024-09-26 to 2024-09-27 · near Rosman, Transylvania, North Carolina

Event narrative

Stream gauges and county comms reported major flash flooding developed along the headwaters of the French Broad basin after 15-22 inches of rain fell across much of the county over three days. Flash flooding first developed along the French Broad River near Rosman, where Depot St, a portion of Highway 178 near Chestnut St, and Hannah Ford Rd between Rosman and Brevard were inundated. Dozens of homes were damaged in Rosman alone, with some structures destroyed after bring inundated with several feet of water. The stream gauge on the French Broad at Rosman crested at 15.5 feet, which exceeded the record by more than a half foot (October 1964). Flooding later developed along the Davidson River toward daybreak, which damaged multiple campgrounds, low water crossings, and some structures in the Davidson River area of Pisgah National Forest, while also inundating and entering structures along portions of Davidson River Rd, Old Hendersonville Rd, Deavor Rd, and Wilson Rd in the Pisgah Forest area. Dozens of water rescues occurred in this area. Due to a combination of very heavy rainfall and backwater effects from the French Broad, the Little River inundated and damaged roads and campgrounds in Dupont State Forest and the Cedar Mountain area.

Wider weather episode

Tropical Cyclone Helene began organizing over the western Caribbean on the 23rd and 24th of September before rapidly intensifying as it moved north through the eastern Gulf of Mexico on the 25th and 26th. A plume of moisture extending from the intensifying storm interacted with a slow-moving cold front to produce a band of widespread heavy rain showers and embedded scattered thunderstorms over the southern Appalachians and vicinity on the 25th and 26th, resulting in a predecessor heavy rainfall and flash flooding event over these areas. Helene made landfall in the Florida Big Bend and moved quickly N/NE through Georgia before turning toward the N/NW once the remnant center reached northeast Georgia. Tropical rainbands around the center of Helene swept over areas with already-saturated soils over the mountains and foothills during the early morning of the 27th, resulting in extreme rainfall and record, catastrophic flash flooding across multiple basins with headwaters near the Blue Ridge escarpment. Due to its quick movement, Helene was still a strong tropical storm when the wind field reached the western Carolinas and northeast Georgia. Frequent wind gusts of 55 to 70 mph, with occasional gusts of 80 mph...and likely as high as 100 mph across the higher elevations combined with saturated soils to produce widespread damage to trees and electrical infrastructure. Across the mountains, some east and southeast-facing slopes above 3000 feet saw canopy-loss of 80% or more. Hundreds of trees fell on houses, vehicles, and power lines throughout the area, resulting in several fatalities. Almost all customers in several counties lost power for at least a brief period. Most people were without power for at least a couple of days, while thousands were without power for a week or more.

View location on OpenStreetMap → (35.1450, -82.8310)

Source: NOAA Storm Events Database, event_id 1218181. Narrative written by the NWS forecast office that issued the report.