State Will Build Cummins Falls Flood Warning System ‘With All Possible Speed’ | Nashville Public Radio

State Will Build Cummins Falls Flood Warning System ‘With All Possible Speed’

Jun 12, 2019

When rangers were alerted to rising water at Cummins Falls State Park last weekend, they had about two minutes to evacuate visitors to safety. A 2-year-old boy was swept away during a flash flood at the base of the waterfall.

But a system of gauges that was proposed for the area around the park might have given them one to two hours of warning.

Now, the Tennessee Department of Environment and Conservation says it will install that system "with all possible speed." In the meantime, TDEC is closing the base of the waterfall to visitors.

Less Rainfall Still Causes Floods

The current protocol for Cummins Falls State Park makes the National Weather Service the first line of defense against flood problems. When NWS meteorologists see heavy rains in the basin that feeds into Cummins Falls, they call the park rangers.

Larry Vannozzi, who manages NWS's Nashville office, says they already know that Cummins Falls floods more easily because of its geography. It takes less rainfall to cause a flood there than in other parts of the state.

They learned this the hard way: In 2017, two women died in an unexpected flash flood. At that point, the waterfall had been a state park for only five years.

"The numbers that we came up with a few years ago were just something below typical flash flood guidance values," he said. "We knew that if we waited until the normal amount of rain that caused flash floods, it would already be a disaster within the falls."

But the flash flood this past weekend exposed a flaw in the current system. In that area of the state, NWS doesn't have access to many physical rain gauges, so it relies on radar estimates. The estimates showed that less than an inch of rain was coming down — which is not supposed to be enough to set off a flood, even there.

And yet, it did.

So what went wrong?

"To be honest right now, we're not sure," Vannozzi said.

'Here Comes The Flood'

But Evan Hart, an earth sciences professor at Tennessee Tech University, believes the problem is with relying on radar estimates of rainfall.

"Sometimes the radar doesn't show the small bursts of rain that we get in the summer afternoon thunderstorms," he said. "You get this big downpour, and then you drive over here and it's totally dry. And the radar sometimes in the summer cannot see down to that level of detail."

After the 2017 flood, Hart and some colleagues proposed a warning system that would give a more accurate picture of when waters in the park would rise. It would include a series of wireless gauges in the streams that flow into the park — essentially, a system of electronic sensors that would send a radio signal when the water rises too rapidly.

That way, Hart says, rangers could know to evacuate visitors up to two hours ahead of time. "The rain already happened. Here comes the flood down the stream, and it's coming."

Hart gave his proposal to the state nearly two years ago. Park officials lauded the collaboration and said it was a step toward making the park safer.

The Tennessee Department of Environment and Conservation, which oversees state parks, says it's "conducting a comprehensive investigation to determine why the implementation of the monitoring system has not occurred." 

"TDEC will keep the falls and gorge area of the park closed until this matter has been investigated," the agency said in a statement.

The agency says it's working on an after-action report and initiating "emergency procurement authorization" to purchase and install a water flow monitoring system.

It is also exploring a permit system to limit the number of visitors to the park. Visitors would have to first attend a safety program before going down into the gorge.

Lawmakers Pressure TDEC

Lawmakers are asking questions too.

Four of them, representing the area around Cummins Falls, sent a letter Wednesday to TDEC "asking why action has not been taken to install a warning system."

Rep. John Mark Windle, D-Livingston, tells WPLN he expected it to be finished by now. "I don't recall a specific timeline, but it was certainly my understanding that two years later it would be complete," he said.

Sen. Paul Bailey, R-Sparta, said he wants to figure out if there was a breakdown in communication between Tennessee Tech and the state, and if so, how long ago the breakdown took place.

"If there was a disagreement between Tennessee Tech and state parks, then state parks should have moved forward with the system regardless," he said.

Gov. Bill Lee told reporters that TDEC is releasing a plan of action Wednesday.

But even if the system is now fast-tracked, it will still take time to install. In the meantime, Vannozzi says the National Weather Service will probably re-evaluate when it's appropriate to issue a flood warning for Cummins Falls.

"We would certainly be open to changing that criteria, even lowering it further," Vannozzi said. "If we do, though, it would be getting down into the neighborhood of just an average thunderstorm."

Which could mean the waterfall might close to the public a lot more often until a better warning system is put in place.