One year ago, during the late hours of April 30 and the morning of May 1, 17 tornadoes struck Oklahoma.
The storm carried with it 5 to 6 inches of rainfall that flooded homes and ripped rooftops off others across the northeast corridor of the state.
Gov. Kevin Stitt later declared a state of emergency for 52 counties.
That turned out to be only the beginning.
Oklahoma’s second-wettest May on record followed and a long summer of flood disaster and prolonged recovery ensued.
This year, with repeated heavy rains in late February and March and flash flooding last week, Oklahomans are justified in feeling a little worried as another May begins.
Odds are the water won’t be lapping at their porches again.
The National Weather Service Climate Prediction Center’s outlook calls for increased odds of precipitation, which is typical for this time of year. The saturated ground does exacerbate the possibility of flash floods, especially, and widespread flooding as well. But a pattern with widespread rainfall is not in the picture like it was in 2019, and western Oklahoma is actually in a drought, according to State Climatologist Gary McManus.
Still, experts always keep an eye on the rivers this time of year.
“The ground still remembers all that rainfall so it’s still in pretty good shape for flooding. It’s saturated, so more of what falls runs off into the streams,” he said.
At the end of April 2019, Tulsa was enjoying a relatively normal rainfall year, just a tad wetter than normal, he said. A year later, the ground still has hardly had a break from 2019’s record-smashing wettest year on record for the northeast region.
So far in 2020 Tulsa is experiencing its eighth wettest year on record, he said.
Tulsa’s rainfall total through May 1 is 16.87 inches. Last year at this time, the area was just slightly wetter than normal with 11.06 inches.
“We just haven’t had that long stretch without rainfall so flooding would be a concern, especially in northeast Oklahoma. May and the first half of June usually means a lot of rainfall,” he said.
“In this part of the state we’re pretty much always on alert at this time of year,” said James Paul, service coordination hydrologist with the National Weather Service Arkansas Red River Basin Forecast Office in Tulsa.
Last week’s storms brought “1 and 2 inches of rain that ran off pretty quickly into smaller streams, but we have enough greening of vegetation now it slows it down some. We saw some minor rises but no flooding in the mainstream rivers,” he said.
Since heavy rains in early March swelled some reservoirs to occupy 30% to 50% of their flood pool retention, the U.S. Army Corps of Engineers has been working to return reservoirs to normal levels. The Grand River system lakes had another dousing early this week and are about 10% into their flood pools now. Oologah, Eufaula, and Tenkiller each are 5% to 7% filled, just a few feet above normal.
“Most are pretty well down now and they’ve done a pretty good job at that,” Paul said. “The (Arkansas River) channel has been running pretty full but it’s going down.”
Tulsa County District 12 Levee Commissioner Todd Kilpatrick said he’s resting easier this year, but added with a chuckle that his office is still surrounded by thousands of sandbags he doesn’t plan to move for some time yet. “Maybe in August after everything is burned off,” he said.
The levee system is ready should the waters happen to rise again. A $3 million grant came through for work on pumps at two levee stations and the feasibility report for permanent repairs was completed in April on an expedited schedule, a 3-year process completed in 16 months, he said.
“If we ever have to go to battle like that again let’s hope it’s when we’ve got some better components in place,” he said.
Raised reservoirs and soaked grounds raise a particular question often posed to U.S. Army Corps of Engineers hydrologist David Williams by Tulsa and Sand Springs residents: “Will you draw down the lake to a lower level?”
“I talked to a guy whose house flooded last year and it was a horrible situation,” Williams said. “I get why people are nervous and we want people to be able to sleep soundly at night.”
But the lakes will always come down toward their target “conservation pool” levels, he said.
Taking them below that level is against federal law and would offer very little advantage in terms of available flood storage volume or flood management, he said.
The conservation pool at Keystone Lake is 723 feet. Last year on the last day of April the level in Keystone Lake was 725.07 feet and dropping. On Friday the level was 725.22 and dropping.
Keystone will continue to drop toward 723 feet, but it will come down slowly with priorities now on reducing levels on the Grand River system, he said.
“Every year is different,” Williams said. “The reservoirs do have a large volumes associated with them and we have had some heavy rainfalls that cover large areas but there’s a difference between covering 10 or 20 miles and when it is occurring of 1,000 or 2,000 square miles and it’s happening over and over again like it did last year.”
That 2019 weather pattern is just not very common, he said.