With Hurricane Helene finally out of the picture, the true extent of the devastation and loss of life in Asheville, North Carolina has only just become apparent.
At least 35 people are dead in Buncombe County, with 41 total across the western part of the state as of noon Monday. With many still missing or out of power, the true death toll will remain uncertain for some time. Large swaths of Asheville, including Biltmore Village and the iconic River Arts District were submerged under nearly 25 feet of water after the French Broad River overflowed.
But why did this happen? This “100-year flood” is no expression — the flood of 1916 in Asheville crested at 21 feet, a record that has now been smashed by Helene. It’s partially due to a rare weather event, some back luck, and potentially climate change.
Why was there so much rainfall in Asheville, Western North Carolina?
Helene produced such a large amount of rainfall due in part to a predecessor event, small (relative to a hurricane) regions of heavy rainfall produced ahead of a hurricane. These rainfalls produce a band of “deep tropical moisture” which, when mixed with a hurricane, cause significant rainfall.
Those predecessor rainfalls hit Western North Carolina on Wednesday and Thursday. According to USA TODAY, 10 inches of rain fell on Asheville, 8 inches on Tryon and 6 inches in Bristol-Johnson, Tennessee before Helene even reached the area.
Did climate change play a part in North Carolina flooding?
Climate change is partially to blame as well. A recent study from Princeton University found more hurricanes are undergoing rapid intensification, where wind speeds increase at least 35 miles per hour within a day and produce “significantly higher rainfall hazard levels.” In North America, this occurs when the hurricane soaks up moisture from the Gulf of Mexico.
Princeton University researchers predict RI events will increase 10-30% for each degree of global temperature increase. “The changing climate will likely lead to more rapidly intensified cyclones and greater flooding potential in the coming years,” the study states.
Is this an example of the Fujiwhara effect?
While it appeared early in Helene’s life that mass amounts of rainfall would be created via the Fujiwhara effect, that is not what caused such high amounts of rain.
The phenomenon known as the Fujiwhara effect occurs when two storms with low pressure interact with and are pulled toward each other, causing them to rotate around a central point, and sometimes combine. This often produces heavy rainfall. KATV meteorologist James Bryant posted on X predictions of what would have happened to Helene if the Fujiwara effect occurred, showing the two storms combining into one over Arkansas.
In reality, Helene combined with the previously mentioned low pressure band of moisture to the north, causing catastrophic rainfall regardless.
Did any dams near Asheville burst?
Despite rumors that multiple dams in East Tennessee and Western North Carolina have burst, dams across the region are holding after the significant rainfall from Helene.
Lake Lure Dam in Rutherford County, North Carolina previously had water flowing over and around the dam, disrupting roadways and causing fear of failure. Local officials previously issued an evacuation warning on Friday, but as of Saturday, the flow rate has since been controlled and traffic is allowed in the area.
Despite a warning from Cocke County Mayor Rob Mathis that the Waterville Dam suffered a “catastrophic failure”, the Tennessee Emergency Management Agency confirmed that the dam was holding.
The Nolichucky Dam in Green County crested Saturday, reaching eight feet over the record elevation, but did not burst. Officials with the TVA confirmed the dam was stable Saturday afternoon.
And in Haywood County, Walters Dam was confirmed to have held through Helene after major flooding in the area.
Jacob Wilt is a reporter for The Commercial Appeal and contributing to Citizen-Times’ coverage. You can reach him at jacob.wilt@commercialappeal.com.