The historic deluge of rain and flooding from Hurricane Helene in September 2024 did more than just devastate the surface landscape of western North Carolina; it triggered significant, rapid changes to the region’s groundwater. A team of university researchers, capitalizing on a pre-existing hydrological monitoring network, captured a rare before-and-after snapshot of the storm’s impact, providing critical new data on how extreme weather alters the chemistry and safety of subterranean water resources.
These findings carry urgent implications for the many residents in the Southern Appalachian region who rely on private wells and springs for their drinking water. Following the storm, which saw entire towns washed away, officials immediately warned of widespread contamination risks from bacteria, sewage, and chemical pollutants swept into the groundwater systems. The new scientific analysis offers a detailed view of the mechanics behind this contamination, informing how communities can better prepare for and respond to the growing threat of similar weather events predicted to become more common with climate change.
An Unprecedented Natural Experiment
Scientists at Western Carolina University were uniquely positioned to study the hurricane’s effects on the subsurface environment. Prior to Helene’s arrival, the researchers had already established a well-instrumented hydrological research station in the Cullowhee Creek watershed. This network provided a comprehensive baseline of the area’s water systems during a period of drought, which set the stage for a dramatic contrast when the hurricane arrived. The research infrastructure included more than 40 groundwater wells, four stream gauges, five soil moisture sites, and a weather station, all of which collected data before, during, and after the storm.
This existing setup transformed Hurricane Helene into a large-scale natural experiment. While catastrophic for the region, the event afforded an unparalleled opportunity to document the precise hydrologic responses across different terrains and scales. The goal of the research is to produce a full analysis of the hurricane’s impact on the Cullowhee Creek watershed and three of its nested sub-basins, which range in size from 0.06 to 22.6 square miles. Such detailed data from an extreme event is rare and essential for building more accurate models of future storm impacts.
Tracing the Storm’s Hydrologic Fingerprint
The storm’s intensity was exceptional for the mountainous region. The research station in Cullowhee, home to Western Carolina University, recorded about 10 inches of rain over a 48-hour period. This amount of precipitation in such a short time frame is considered a 1-in-200-year event. While the town was spared the worst of the record-setting floods that devastated other parts of the Southern Appalachians, the massive influx of water sent a shock through the local watershed that was captured by the monitoring equipment.
Preliminary analysis of the data focused on several key areas. Researchers are exploring the rate of groundwater recovery after being abruptly pulled from drought conditions by the hurricane’s deluge. They also observed that headwater catchments of different sizes and geographies varied significantly in their discharge response to the extreme rainfall. A central focus of the ongoing research is understanding how soil moisture levels, which were low due to the preceding drought, influenced the pathways the rainwater took and how that ultimately affected the response of local streams.
Widespread Contamination Risks
The scientific data provides a framework for understanding the widespread public health crisis that unfolded in Helene’s wake. Experts warned that the high-velocity floodwaters, which were powerful enough to snap iron pipes in half, would overwhelm private wells and public water systems alike. These systems, common in western North Carolina, are highly vulnerable to being inundated with surface water carrying a cocktail of dangerous contaminants. This includes biological threats like E. coli from overflowing sewage systems and chemical pollutants from industrial sites, paper mills, and fertilizer factories that were in the storm’s path.
Health officials and water quality specialists drew on lessons from past storms, such as Hurricane Florence in 2018, which led to a documented increase in E. coli contamination rates in affected wells. Based on these experiences, authorities expected similar contamination from Helene and strongly advised residents to disinfect and clean their wells before using them for drinking or cooking. The state’s Department of Health and Human Services issued advisories urging citizens to have their water tested, acknowledging the invisible threat lurking in the floodwaters.
A Region Grappling with Recovery
The challenge of ensuring safe drinking water became a critical part of the storm recovery effort. Many residents in the mountain communities had never experienced flooding of this magnitude and were unfamiliar with the necessary safety protocols for dealing with contaminated wells. To address the overwhelming need for testing, the U.S. Environmental Protection Agency deployed a mobile water testing laboratory to Asheville to support local health departments and utilities. This federal assistance was crucial for communities where local infrastructure, including water and wastewater utilities, had been damaged or destroyed, impairing their ability to provide safe water.
The recovery process is complicated by the sheer scale of the disaster and the geography of the region. The hurricane caused not only water damage but also extensive topsoil and vegetation loss, increasing the future risk of landslides and mudslides during heavy rains. This environmental degradation could set back the recovery process and poses a long-term threat to the stability and safety of the watershed.
Preparing for a Future of Extremes
Both the scientific researchers and public health experts agree that Hurricane Helene is a preview of future challenges in a warming climate. Events like Helene are predicted to become more prevalent, making the data collected by the Western Carolina University team vital for future preparedness. This research can help scientists understand how geologically similar watersheds throughout the Southern Appalachian region may react to the next major natural disaster.
By analyzing the hydrologic response in detail, from groundwater recharge rates to stream discharge patterns, researchers can help build better predictive models. This knowledge is essential for developing mitigation strategies, improving infrastructure resilience, and creating more effective public health responses. Understanding the precise vulnerabilities of groundwater systems is the first step toward protecting these vital resources from the inevitable storms of the future.