Hurricane Helene Impacts to Northeast Tennessee

On September 23, Hurricane Helene began to develop in the Gulf of Mexico. By September 27, it had intensified into a Category 4 hurricane and made landfall near Perry, Florida. Moving at a speed of 20 to 30 mph, the storm traversed Florida's Big Bend region and continued into central Georgia. As it advanced, Helene downgraded to tropical storm status while moving into North Carolina and Tennessee, yet it still produced substantial and historic rainfall, resulting in record-breaking river flooding that caused severe damage to communities and infrastructure. Tennessee experienced the following impacts:

• Over 100,000 reports of power outages
• 4 wastewater treatment plants impacted
• 20 drinking water facilities impacted
• 5 counties issued boil water advisories
• 17 weather-related casualties*

 TEMA Flash Reports 

(*) As of October 21st, 2024

The river systems in East Tennessee began to rise significantly due to the intense rainfall. Prior to the storm, many regions were experiencing streamflow rates that were normal to well below average. However, as heavy precipitation from a stalled frontal boundary moved through the area on September 25, streamflow rates began to increase. On September 23, only 5% of streamflow gauges across the state indicated above-average streamflow; by September 28, this figure surged to 93%. The Doe, Nolichucky, Upper French Broad, and Pigeon Rivers were among the most severely affected by the storm, as these rivers drain watersheds that extend into the mountainous regions of western North Carolina. Notably, some of the highest rainfall totals in North Carolina (15-20-inches and even a few pockets of more than 20-inches) were recorded within these watersheds, causing these river systems to flood far worse than based on local rainfall in East Tennessee.

On September 25, the USGS Nolichucky River stream gauge at Embreeville recorded normal streamflow rates of approximately 700 cubic feet per second (cfs). However, this discharge rate experienced a dramatic increase over the following two days, reaching over 50,000 cfs before an equipment malfunction occurred. This escalation corresponds to river levels rising at a rate of two feet per hour. The Nolichucky Dam, situated in Greene County, recorded unprecedented flow rates and triggered a “Condition Red Alert,” indicating a risk of imminent failure. Water crested over the 94-foot-tall dam at up to a staggering rate of approximately 1.3 million gallons per second, nearly double the peak daily flow rate of Niagara Falls. Despite the water levels exceeding the previous record by more than twofold, the dam remained stable.

As of October 11th, at least 200 confirmed fatalities have been attributed to the impacts of Hurricane Helene across six states, with 17 confirmed deaths in Tennessee. Additionally, over 600 reports of missing persons have been received. The saturated soil conditions and high wind gusts downed trees and power lines throughout the area, resulting in widespread road closures and power outages. On Tuesday, October 1st, there were still 9,600 reports of power outages statewide. Further damage to road infrastructure occurred as rapidly moving floodwaters filled with debris eroded road beds and wiped out bridges, leading to critical failures. Major highways, including I-40 and I-26, were submerged under several feet of water, debris, and sediment. The storm caused extensive damage to thousands of commercial and residential properties. In response to the devastation, major disaster declarations have been authorized for Carter, Cocke, Greene, Hamblen, Hawkins, Johnson, Unicoi, and Washington counties.