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Is Johnson City prepared to handle a changing climate?

Jonathan Roberts • Jan 1, 2020 at 8:00 AM

It was a once-in-a-half-century storm, and the Skillville Community Workshop in downtown Johnson City took the brunt of the impact.

On Aug. 6, 2018, parts of downtown Johnson City saw more than two inches of rain fall in less than 15 minutes, flooding downtown streets — and inundating Skillville with two-to-three inches of water. And though it didn’t suffer any lasting damage, one of Skillville’s co-owners, Seth Thomas, isn’t sure how prepared they are if a similar storm hits again, though he isn’t worried about future storms.

“We’ve not had any issues (since), but I don’t think we’ve had the rain events like we had those two times that week so I don't know if it’s really been tested completely — but it does seem to work,” Thomas said. “It seems that the engineering is working in our favor there, and I think the infrastructure works for the most part unless it gets bombarded like that.”

Built on a floodplain, Johnson City has struggled with flooding issues “since Henry Johnson set up a depot here,” city manager Pete Peterson says, but that hasn’t stopped the city from investing millions of dollars trying to lessen the impact and threat of flooding in the city.

The city’s two biggest flood mitigation projects — Founders Park and King Commons — cost around $6 million and took years to complete. In addition to the two parks, the city spent millions more on other infrastructure improvements, and is looking at about $6 million to $9 million worth of additional projects to address flooding concerns in the coming years.

“We’ve seen a reduction in the number of storm events (that cause flooding) and we’ve certainly seen an improvement in the severity of the storm events with flooding,” Peterson said.

“Is it a cure? No, we have not eliminated flooding in Johnson City by any means, but we have certainly made the likelihood of flooding less, and lessened the severity of any potential flooding.”

Johnson City Public Works Director Phil Pindzola said that, generally, the city’s stormwater drainage systems can handle two inches of rain, but that intensity and duration of a storm are “critical,” as two inches over a one- or two-hour period would likely cause flooding. Peterson said some parts of the city can struggle with as little as a half-inch of rain, but that the rate at which it falls is key.

“Once it gets above two inches, that’s when we start seeing the problems occur,” Pindzola said.

And while the city has done well to mitigate the impacts of flooding and severe storms, the frequency of significant rainfall events is increasing — even if it doesn’t result in widespread flooding. Though Pindzola and Peterson are confident the city is equipped to handle most isolated severe rainfall events, constant rainfall over weeks and months has the city facing a new problem — the over-saturation of the ground.

“In a lot of places, it’s not that it can’t accept the water, it’s that when the caverns (underneath the city) are full then there is no place for the water to go,” Pindzola said. “It takes a while for the caverns to fill up, but if you had a series of rain events over a number of months, it doesn’t take long for them to show issues — even in smaller rain events — if the caverns are full.”

Since 2010, not only has the frequency of heavy rainfall events has increased, but the average annual rainfall total has as well — with the 2010s being the Tri-Cities’ wettest decade on record.

Annual average rainfall from 1940 to 1979 was 41.85 inches before bottoming out at just 38.11 inches per year in the 1980s. From 1990-2019, average yearly rainfall is about 43.14 inches, with 2010-19 seeing an average of 44.97 inches. This decade has also seen a 24% increase in the number of days where at least one inch of rain fell over a 24-hour period, and the region has seen a 38.4% increase in the number of days with at least two inches of rainfall since 2000.

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“The stuff we’re seeing is just the beginning of what’s happening, but hopefully we can take some action before it gets worse,” said Luke Carter, who leads the Northeast Tennessee chapter of the Citizens Climate Lobby, a group that advocates for bipartisan legislation to combat climate change. “And if we don’t start doing something I think we’re going to see much worse effects.”

Though severe storms are some of the most visible manifestations of climate change, rising temperatures are at the core of it.

As the planet warms — roughly 1.8° Fahrenheit since the beginning of the industrial revolution — sea ice and glaciers will continue to shrink and disappear, leading to rising water levels and more flooding; severe weather will become more frequent; and global temperatures will continue to rise, leading to prolonged and extreme heat waves and drought. In the Tri-Cities, the effects of climate change are being felt more and more as the region’s temperatures continue to rise.

Since 2009, the Tri-Cities’ average temperature has risen by 1.6°F, while the average maximum temperature has jumped a staggering 4.1°F over the same time period.

The average number of days above 90°F and nights above 68°F have also risen sharply, almost doubling from last decade. Data from the National Oceanic and Atmospheric Administration shows that heat and drought (which NOAA groups together) are one of the most dangerous natural events in America, having killed more Americans since 1980 than any other natural disaster aside from hurricanes.

And though Johnson City isn’t likely to see a sudden influx of deadly heatwaves, rising temperatures in the region will come with a cost.

“If we keep seeing these increases in temperature, people are going to depend more on cooling, and that’s going to take more of their monthly budgets,” said East Tennessee State University climatologist and meteorologist David Jennings. “I don’t think it’ll (cause) any major loss of life or anything like that, obviously, but I think the people it’ll hit the most are the poor and the elderly — they’re going to have the most problems with, literally, just living a more comfortable life.”

“I think people should be very concerned,” Jennings added. “It’s almost insidious that it happens so imperceptibly to us.”

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Increased temperatures don’t have much of an effect on the city’s day-to-day operations, though Johnson City has spent significant resources improving the energy efficiency of its buildings and street lights — lessening the city’s carbon footprint while saving money. Peterson estimates the city has spent millions of dollars on improvements in “almost all of our public buildings.”

“We feel like we are prepared for weather events and are committed to continuing our efforts to be environmentally conscious,” Peterson said. 

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