A delicate balance is playing out as Keystone Lake is projected to bulge to its overflow limit by lunchtime Tuesday and then begin receding hours before more storms may roll in.
The Tulsa District of the U.S. Army Corps of Engineers expected the lake’s inflow and outflow to mercifully equalize Monday night — meaning water flowing into the lake would match the amount of water flowing out. The lake’s intake is predicted to be 250,000 cubic feet per second by lunchtime Tuesday, allowing for a modicum of storage capacity as the dam’s release was set to remain at 275,000 cfs through Thursday.
Engineers think the lake won’t overflow the floodgates and create a catastrophic situation; but there’s a looming issue: More rain is in the forecast Tuesday and Wednesday.
“Any significant rainfall on the lower basin or reservoir is problematic,” said David Williams, Tulsa District chief of hydrology and hydraulics engineering. “We just don’t have capacity. So if the inflow once again increases due to additional storms, we would have to adjust the outflow, because we do lack the capacity in the pool.”
Thunderstorms are forecast to develop west of Tulsa on Tuesday afternoon, then move into the area mainly along and north of Interstate 44 into the early evening hours. Another round is forecast to come through Wednesday afternoon along and south of I-44.
Williams feels “pretty comfortable” with projections but is hoping for scattered showers, which likely wouldn’t have much affect compared to widespread storms.
“This is the culmination of a flood that is now in its fourth week,” Williams said. “I know that it seems like only a weeklong event or so, but we’ve had excessive rainfall in the basin for a month now.”
The dam’s outflow of 275,000 cfs began at 7 a.m. Monday, up from 255,000 cfs. The highest release rate from Keystone Dam was 307,000 cfs in 1986, when the river reached a record level of 25.21 feet in Tulsa.
The river, which had been at about 21 to 22 feet in Tulsa since Thursday, had inched up to 22.75 feet as of 3:30 p.m. Monday.
With the increased dam output, floodwaters claimed more territory in River Parks and on Riverside Drive.
Floodwaters affected the west side of the Gathering Place, which closed its Sports Courts and Skate Park.
The River Parks trails were closed after erosion formed sinkholes, and Riverside Drive was partially closed Monday from Southwest Boulevard to Denver Avenue and from 21st Street to 31st Street.
East 38th Place, 39th Street, 26th Street, and Cincinnati Avenue were barricaded near Riverside Drive.
Luke and Ashley Emert could be seen moving into their home with the help of family near 39th Street and Cincinnati Avenue as floodwaters covered the intersection.
“We must look pretty silly,” Ashley Emert said.
She said they recently began moving into the home, which they had been renovating, and were welcomed with tornado warnings and flooding.
Luke Emert said he didn’t think the water would come as far as it did, which was licking the curb of their corner. But the pair wasn’t too concerned about it reaching their home.
Mike Stone, Ashley Emert’s father, said the family is trying to keep a positive attitude.
“Best time to move is when you’ve got a flood,” he joked, adding that they prayed over the move.
If God can part the Red Sea, then the Arkansas River should be a piece of cake, he said.
It will be a more difficult challenge for humans.
The inflow into Lake Keystone hasn’t been consistently below 250,000 cfs since 11 p.m. Wednesday. Williams thinks it will decline to that level by lunchtime Tuesday.
That may be only hours before more storms arrive.
Robert Darby, a National Weather Service meteorologist, said the Tulsa metro area is in a vulnerable position.
Darby said wind, hail and isolated tornadoes are possible with each system. But Wednesday harbors the highest likelihood for substantial rains — up to 2 to 3 inches — that would trigger flash flooding in the metro area.
“This is an historic event, so we don’t know exactly how the drainage systems will work with the Arkansas this high,” Darby said, adding that lakes, rivers and creeks are at their capacities.