Hurricane Helene not sole cause of Asheville’s severe flooding
Prior rainfall and topography worsened Asheville flooding after Hurricane Helene
Hurricane Helene was not the sole cause of the severe flooding that affected Asheville, North Carolina. Experts pointed to several other conditions, including prior rainfall and the area’s topography, which contributed to the deadly flash floods.
Helene hit Florida’s Big Bend on 26 September as a Category 4 hurricane, with 140 mph winds and a 15-foot storm surge affecting the Gulf Coast. The hurricane demonstrated that storms can have far-reaching effects, affecting regions hundreds of miles inland. After landfall, Helene moved north, causing tornadoes in five states and dropping more than 30 inches of rain in parts of North Carolina within a few days.
Following Hurricane Helene, a five-day special coverage titled “Southeast Strong: Help After Helene” (#SoutheastStrongABC) will air, focusing on the impacted southeastern communities and recovery efforts.
Hurricane Helene unleashed catastrophic flooding and mudslides that devastated western North Carolina. Roads and buildings in Asheville's historic Biltmore Village were severely damaged and covered in mud. https://t.co/C7fL3ejITK pic.twitter.com/VLp2gdy9CK
— The New York Times (@nytimes) October 2, 2024
Large hurricanes in the Gulf often lead to a precursor rain event inland. Art DeGaetano from the NOAA Northeast Regional Climate Center explained that the storm’s large rain shield interacts with a cold front, causing this phenomenon.
Before Helene struck, Asheville had already experienced heavy rainfall, with over a foot of rain in some areas, as reported by the North Carolina State Climate Office. By the time Helene arrived, the soil was saturated, and rivers and streams were full. The French Broad River and its tributaries overflowed, flooding nearby neighbourhoods quickly.
Though rare, similar events have occurred before. The “Great Flood of 1916” in Asheville resulted in 80 deaths. Marshall Shepherd from the University of Georgia noted that the storm’s size led to prolonged rainfall. The mountainous topography of the area also significantly influenced the flooding, according to Yuh-Lang Lin from North Carolina Agricultural and Technical State University.
Orographic lifting, where mountains force air to rise and cool, caused additional precipitation when combined with Helene’s system. Heavy moisture was then rapidly released over Asheville, funnelling into valleys, rivers, and streams, as DeGaetano described.
Jennifer Francis from the Woodwell Climate Research Center noted that such regions often see extreme flooding. DeGaetano also highlighted that climate change likely influenced Helene’s behaviour. The Gulf of Mexico’s warm waters enabled the storm to absorb more moisture and intensify, leading to heavy rainfall along its path.
Researchers are investigating whether an atmospheric river added to the precipitation. Shepherd mentioned the combined effects of the hurricane, orographic lifting, and an atmospheric river bringing moisture from the tropics.
Climate change is making extreme rainfall events more frequent and intense, according to the Fifth National Climate Assessment released in November 2023. Rising global temperatures are intensifying the water cycle, increasing rainfall and flood risks across the U.S. These extreme events are overwhelming existing infrastructure.
The East Coast has seen an overall increase in rainfall due to climate change. In the Southeast, extreme precipitation events have risen by about 37% in recent decades, as per the National Climate Assessment.
Frequently Asked Questions
Here are some common questions asked about this news
What caused the severe flooding in Asheville after Hurricane Helene?
A precursor rain event, saturated soil, and the region’s topography contributed to the severe flooding.
How much rain did parts of North Carolina receive from Hurricane Helene?
Parts of North Carolina received over 30 inches of rain from Hurricane Helene.
What is orographic lifting and how did it affect Asheville?
Orographic lifting occurs when mountains force air to rise and cool, causing additional precipitation.
How has climate change impacted rainfall in the Southeast?
Climate change has increased extreme precipitation events by about 37% in recent decades in the Southeast.
What was the ‘Great Flood of 1916’ in Asheville?
The ‘Great Flood of 1916’ was a similar flooding event in Asheville where 80 people died.
