Date: 2021-09-07 09:00:00
CRUSO – Mountain storms like the one that inundated this small community along the East Fork of the Pigeon River are notorious for their destructive power — and speed.
Part of that relates to mountain terrain and hydrology, while another key element is the intensity of the storms we’re seeing now.
In Haywood County on Aug. 17, the two factors combined to create a deadly situation, a “wall of water” effect that cleared out trees and swept trailers downstream. Six people died in the flooding, mostly in the Cruso area, but the flooding extended all the way into Canton, where the Pigeon River caused extensive damage.
“The rain gauge at Cruso Fire Department, in the (Aug. 17) event, they had received about 8.7 inches of rain,” said the National Weather Service’s Josh Palmer, a service hydrologist. “That was the highest total that we officially recorded.”
A couple of gauges above Cruso nearer to the Balsam Ridge near the Blue Ridge Parkway recorded 7-7.5 inches.
And that was the culmination of three days of rain. By Aug. 17, the ground was absolutely saturated when the remnants of Tropical Depression Fred parked over Haywood and Transylvania counties.
“One of the issues with the flooding is that parts of the area had almost 6 inches in the three days before Fred, so the ground was pretty saturated and streams already full, then along came Fred resulting in huge runoff,” said David Easterling, director of the National Climate Assessment Technical Support Unit, part of NOAA’s National Centers for Environmental Information in Asheville. “For the seven-day period ending with Fred, some parts of Transylvania and Haywood counties got more than 12-15 inches.”
That, Palmer said, is “what made this event so scary.
“We saw two historic rainfall events almost back to back,” he said. “That was especially true in Haywood County.”
‘Like a sponge’ getting wrung out
The mountain ridges of Western North Carolina can act like a dam for storm systems. As the storm system moves into the area, it hits the mountain ridges and stalls.
And then keeps raining.
“It’s like a sponge – it gets wrung out these peaks,” Palmer said. “The Balsam Ridge is a notorious location for this, where you’ve got a good southernly flow and you’ve got a good tropical moisture fetch, so you’re bringing in deep tropical moisture.”
Even an unnamed storm can result in huge downpours, Palmer said.
“It gets wrung at these ridges, and it falls at the tops of the ridges and it travels down the mountain slope at a pretty swift pace,” Palmer said. “You get significant runoff, and that’s why you see something like a debris flow happen in a situation like that, where the soil just gives way from all that heavy rain.”
The Balsam Ridge, near the Haywood-Transylvania line, sits above Cruso at 5,000 feet or more. Cruso’s elevation is 2,936 feet and Canton’s 2,615.
From where the East Fork of the Pigeon River starts, by Greasy Cove Prong, it’s about 6 miles as the crow flies to Cruso Fire & Rescue, near some of the worst damage. But the river winds its way down the mountain in anything but a straight line.
That’s an enormous amount of water moving several miles downhill and gathering speed, all in a matter of a few hours.
Pigeon was 10 feet out of banks
Palmer said he visited the hard-hit Mundy Field Road area several days after the storm. It’s about 5 miles from the Cruso fire station.
“There were a couple of high-water marks on some of the trees that were adjacent to the river bank that were a good 10 feet above the ground level,” Palmer said. “So, when you talk about a wall of water, I think any time the water is 7 to 10 feet above ground level, that’s a pretty good wall of water right there.”
At 10:15 a.m. on Aug. 17, the water level gauge on the East Fork of the Pigeon River, located near the junction of N.C. 110 and U.S. 276, measured 1.9 feet, about normal. Flood stage is 8.5 feet.
By 2 p.m., it measured 4.6 feet. By 3:15 p.m., it has risen to 6.5 feet. Just 45 minutes later, it hit 9.5 feet, a foot above flood stage, and it would keep rising until it peaked at 5:45 p.m. at 16.2 feet.
That amount of water sweeps away trees, trailers, propane tanks, cars, sheds, even homes.
One landslide occurred north of the Cruso Fire Department on U.S. 276 and “definitely left a pretty big scar on the mountain,” Palmer said, estimating its width at the road level at 200-300 feet.
Dams of debris commonplace in mountain floods
In other areas, the uprooted, broken trees and other debris got jammed up. Some people in Cruso reported dammed up areas that cause water to pool, then burst free.
That’s entirely possible, Palmer said.
“There were definitely situations where those trees, those logs got wedged up against the bridges,” Palmer said. “That happens often in the mountains. I mean, you’re almost always we’re going to have that damming effect.”
The water can even uproot and flush down sizable trees, with a 12-18-inch diameter, Palmer said.
These debris flows end up in the river, pushed downstream at a rapid rate because of the flow of the water. They hit bridges and cause log and debris jams.
“I had heard reports of kind of a ‘wall of water’ effect where you’ve got that damming effect against a bridge,” Palmer said. “And that forces the water up and over the bridge in sort of like a wall kind of fashion.”
In some cases, recreational vehicles were pushed up against trees, bridges and buildings, and that adds to the damming effect.
Scott McCracken, who lost numerous outbuildings and vehicles to the flood, lives on Chinquapin Road, not far from Mount Pisgah and less than a mile from the Cruso Fire Department. The river is his area is about 1,000 feet away, but it expanded so far it caused serious damage.
Shortly after the flooding, he talked to neighbors who live above him.
“This is something hard to get your head around — we’re at 3,000 feet, but at the bottom of the river basin,” McCracken said. “The people we know at 3,800 feet, there was an 8-foot deep lake separating them from getting out of their house.”
Palmer said they had not pinpointed specific dams, but the effect could have occurred in multiple areas.
More of these events likely
“I don’t doubt the reports from some residents of hearing interesting sounds and a wall of water kind of effect,” Palmer said. “The rate at which the river rose, and the speed at which it did so was going to create some pretty crazy responses. There no question that that happened in some respect.”
They have not traced a specific, large dam break, though.
These types of rain events likely will increase as climate change continues, Easterling said. Tropical hurricanes and storms “won’t necessarily increase in numbers, but those that do occur will likely be stronger — wetter and stronger winds.
“There also is evidence that these storms are moving slower, thus dropping more rain like what happened with Hurricanes Harvey and Florence,” Easterling said.
In short, “anyone living in a flood plain is in danger of being flooded out.”
“Honestly, anytime there is a flash flood warning from National Weather Service, anyone near a stream should leave for higher ground,” Easterling said. “You can turn on weather alerts on your cell phone and receive severe weather and flash flood warnings from the National Weather Service. Keep in mind it may not be raining that hard where you are, but if you get heavy event upstream it can lead to flash flooding where you are.”
Many mountain gorges, from Hickory Nut in Chimney Rock to the Pigeon River, are prone to these high-speed floods, debris flows and damming effects, Palmer said.
“It’s not just the East Fork of the Pigeon,” Palmer said. “I think anybody who lives in these narrow valleys in the mountains, (along) these smaller streams, are going to run the risk of these kinds of intense rainfalls causing a significant floodway, unfortunately.”
“It’s not so much how much rain you receive,” Palmer added. “It’s a combination of how much rain you receive and over what period that you receive it.”
Piedmont areas such as those in the Carolinas can accept more rainfall because it spreads out over the flatter land. It causes flooding, but generally not with the forcefulness of mountain deluges like the one that hit Cruso.
“You take that volume of water and you channel it over small watershed like that, and there’s nowhere for the water to go,” Palmer said. “There’s literally nowhere for the water to go, except the path of least resistance in that watershed, and unfortunately that’s where people are living next to a stream like that, in the flood plains.”