As COVID-19 tightens grip, flood potential increases in northeastern Oklahoma
May is approaching, which usually means a lot of moisture for Oklahoma.
In spring of 2019, the northeastern part of the state experienced one of the worst floods in history.
Heavy rainfall throughout the south-central region of the country paved the way for record-level flooding, as both Oklahoma and Arkansas declared Natural Disaster Emergencies to receive Federal help.
Following a wet start to the spring, heavy rains engulfed southern Kansas and northern Oklahoma May 19-21, which led to the historic flood that killed five people and caused $3 billion in damages.
Fast forward a year … the COVID-19 pandemic has taken over the world and most local and national leaders are paying close attention to the daily updates from the Coronavirus situation, when potential for another record-level flood is increasing as moisture begins to accumulate in northeastern Oklahoma.
Currently, the water-level readings in Keystone Lake are showing they are four feet above normal.
“We are watching the water levels very closely,” Jenks Mayor Robert Lee said. “We have not forgotten the lessons from last year. When we saw the levels go up about three weeks ago, our ears really perked up. We kind of just have to wait and see how much rain we get and how much the Corps of Engineers releases out of the Keystone Dam.”
Lee said the City of Jenks learned a lot about its water drainage system and what it can handle when it comes to floods.
“We hope we don’t have to do what we did last year,” Lee said. “We do have a better idea of what we are up against and a better idea of what our water ways are capable of to not be surprised this time. Following the 1986 historic flood, it was decided that all new developments in Jenks were to be built at least one foot above the 1986 flood line and that ended up passing the test for us last year.”
Jenks City Manager Chris Shrout said the City of Jenks is better prepared to handle another flood if it were to occur again this year.
“We have been monitoring the (Keystone) lake and flood storage levels every day with the police, fire and public works departments making sure we are prepared for a similar event to the one we saw a year ago,” Shrout said. “We are prepared from what we experienced last year, and we are confident in our ability to respond. We have a much better idea of what it means for the river when the Corps of Engineers says it is releasing a certain amount of water. We definitely learned a lot and are better for it.”
David Williams, Chief of Hydraulics and Hydrology Branch’s Engineering Section for the U.S. Army Corps of Engineers discussed several items regarding a potential flood for northeastern Oklahoma again in 2020.
“In 2019, rainfall during the winter resulted in above normal lake levels to begin the year, but these were drawn down to normal levels by March,” Williams said. “In 2020, rainfall in February and early March resulted in above normal lake levels that peaked at about 40% of the available flood-control storage in late March, but the reservoirs have been steadily drawn down since then, and most of the reservoirs are approaching their normal levels.”
Williams said that no two floods are the same and if there is a flood in 2020, it will be based on different variables than in 2019 and therefore evolve differently. He added that the Keystone Dam, which determines the water levels in the Arkansas River going through the Tulsa area and down into the eastern portion of the state and into Arkansas, is operated as part of a 30-reservoir system in the Arkansas River basin in Kansas and Oklahoma.
“All of these reservoirs are regulated in accordance with Congressionally-authorized water control plans,” Williams said. “During floods, these reservoirs are operated in conjunction with one another. Most of the volume available in Keystone Lake is reserved for flood control. It fills at the same percentage as the other reservoirs in the system and is then drawn down in the same manner. Major floods can exhaust the flood-control storage available in the reservoirs. When this occurs, large releases are made from Keystone Dam and the other reservoirs in the system. The two largest releases in the 55-year history of Keystone Dam occurred on Oct. 5, 1986 (307,000 cubic feet per second) and May 29, 2019 (275,000 cubic feet per second).”
Williams said without the Keystone Dam, the flooding last year would have been catastrophic for Tulsa and other communities downstream.
“While there is always an awareness about downstream impacts, flood-control dams mitigate the severity of floods,” Williams said. “For example, the peak release on May 29, 2019 was 275,000 cubic feet per second. Without Keystone Dam, the peak flow through Tulsa would have been 375,000 cubic feet per second. Keystone Dam, the Tulsa/West Tulsa Levees, and the Jenks Levee prevented $1.8 billion in damages in Tulsa County during this single flood event. It is important to remember that these are flood-control dams, not flood-prevention dams. Communication of this risk to downstream communities is a top priority of the Tulsa District.”
Williams said dams like the Keystone Dam and their stability and safety are a top priority for the U.S. Army Corps of Engineers.
“Dams are flood risk reduction structures and are not a guarantee of safety,” Williams said. “Dam safety is a paramount concern of the U.S. Army Corps of Engineers and our efforts conducting inspections and performing maintenance are for the purpose of preventing such an event. All the flood-control dams owned and operated by the Tulsa District (including Keystone) undergo regular, comprehensive assessments. Maintenance, repairs and improvements are necessary components of all infrastructure life cycles, including flood-control dams.”
Numerous low-water dams along the Arkansas River in northeastern Oklahoma have been discussed for several years. Williams said the ability to finance and maintain the low-water dams is a local community issue and as long as it is approved by the U.S. Corps of Engineers and does not affect the function of the Keystone Dam, he doesn’t mind them being built. He also said the COVID-19 situation has not slowed down the interest in potential flooding.
“Based on the number of questions that have been received from concerned citizens and their elected officials over the past several weeks, there is a heightened awareness and concern about flooding,” Williams said. “Any natural disaster coinciding with the ongoing pandemic would be especially stressful considering the economic impacts that are affecting everyone coupled with the strain on emergency responders.”
Williams said flood planning and preparation never stops for the U.S. Corps of Engineers and the Tulsa District has a highly skilled staff that studies floods, operates flood-control projects in real time, and responds to emergencies when they occur.
“Communication of flood risk to downstream communities is extremely important,” Williams said. “Although major floods are rare, they do occur. Large releases from Keystone Dam are no exception. Persons living downstream from flood-control dams should understand this risk and should carry flood insurance if they live within or close to the regulatory floodplain. In fact, flood insurance is required by law for houses within the regulatory floodplain that have Federally backed mortgages.”
At this time, the U.S. Army Corps of Engineers has a policy to not release any water from the Keystone Dam unless there is water on the ground. The Corps does not use forecasted rain data to release water from the dam prior to the rain falling.
State Representative Lonnie Sims (R-Jenks) disagrees with the U.S. Army Corps of Engineers’ policy.
“We don’t want to see flooding like we did last year,” Sims said. “I am very hopeful the Corps of Engineers has looked at its internal policies and has updated its preparedness plan. We found weak spots in the notification system along the river and the Corps of Engineers should help with that. They are working with water-release plans that were created when the dams were built, and since have only seen minimal changes.
“There is a huge miss on the Corps of Engineers’ part with not using the forecasting data we have now,” Sims said. “This needs to be an all hands-on deck and all technology-on deck situation, and we need to prepare our communities along the river in a much better way. Right now, the Corps of Engineers operates off an old plan and is not willing to use technologies we now have available and that is unacceptable.”
Williams addressed the U.S. Army Corps of Engineers’ decision-making process when deciding when and how much water to release out of dams, such as the Keystone Dam. He also discussed the models and technology that are used to make these decisions.
“Releases are based on the principle of ‘water on the ground.’ In other words, inflow forecasts are developed by using observed runoff at stream gages in the watershed upstream from the reservoir,” Williams said. “The basis for this policy is the uncertainty associated with weather forecasts. The release of water from a flood-control reservoir in anticipation of rainfall can actually increase the risk associated with downstream flooding if the forecast is either not realized at all or if the rainfall occurs in a different location. In Keystone Lake, the conservation pool accounts for about 20% of the total available volume, with the remainder reserved for flood control. During the 2019 flood, the total volume in the reservoir completely cycled six times. A pre-release would not have affected the outcome. Hydrologic data are retrieved on an hourly basis from a network of rainfall and stream flow gages within the basin. In real-time operations, this information is used in forecast models to develop inflow hydrographs for the Tulsa District reservoirs. During a flood, models are updated on a continual basis, resulting in revised inflow forecasts both day and night. These forecasts are used in conjunction with the Congressionally authorized water control plan to schedule releases.”