The Kansas Turnpike Authority plans to reduce the risk of flooding on a 2-mile stretch of road where seven people have died during heavy rains since 2003.
Although the change will meet the minimum recommended design standard for interstates, the turnpike won’t be doing as much to protect motorists from flooding as some surrounding states.
The authority plans to expand or build additional drainage culverts, or large drainage pipes, to carry floodwater under the turnpike and reduce the risk of flowing water topping the roadway.
Whether the agency should build drainage culverts to a higher flood standard after the deaths “is a question a lot of people are asking,” Turnpike Authority spokeswoman Rachel Bell acknowledged.
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But going to a higher standard than is planned would be “overdesign,” she said. “We don’t feel overdesign is a sustainable practice.”
The turnpike is spending an estimated $3 million to expand culverts in a 20-mile stretch that includes where the flood deaths have occurred. It also will improve drainage a few miles north of the Matfield Green Service Area, which is at mile marker 97 between El Dorado and Emporia. If weather permits, the work should be done around the fall of 2016.
Planning for the expanded culverts to reduce flooding was underway when the latest death occurred July 10.
Zachary Clark’s Mustang ran into an estimated 10 inches of floodwater on the turnpike about 9 miles south of Emporia. The car spun into a submerged ditch at mile marker 118, where water was flowing to a culvert that couldn’t drain fast enough. The culvert, at an east fork of Jacob Creek, sits in a low spot that collects storm water from the Flint Hills.
Clark, a 21-year-old Texan, was on his way to an internship with the Catholic Diocese in Minnesota. His car was sucked underwater when a swirling whirlpool formed above the swamped culvert. The culvert, considered undersized by today’s engineering guidelines, has been in place since the turnpike opened in 1956.
In 2003, six people – a 33-year-old Missouri woman and her four small children and a Texas man trying to rescue people – died when a wall of floodwater swept cars off the turnpike. That was at mile marker 116, at Jacob Creek, 2 miles south of where Clark died. In both places, the creeks drain to culverts that run under the turnpike.
Now a seventh white cross, with “Zach” in blue letters, sits along the turnpike.
The project at mile marker 118, where Clark died, and 116, where the six died, will bring the drainage system from below the current national recommended guideline up to the minimum design for interstate culverts.
Even after the culverts are changed, there’s no guarantee the roadway won’t be overwhelmed with floodwaters again, turnpike CEO Steve Hewitt told The Eagle soon after the accident.
To help keep cars out of high water, the Turnpike Authority also is installing warning signs and considering a guardrail, Bell said.
When the 236-mile Kansas Turnpike opened 59 years ago, the culverts were designed to protect the roadway from flooding during a 25-year flood. That’s a flood that has a 4 percent chance of occurring in any given year.
A more protective 50-year flood design is now the minimum standard recommended by the American Association of State Highway and Transportation Officials to reduce flooding on roadways. That’s a flood that has a 2 percent chance of happening in any year.
That’s the standard the turnpike is using when it rebuilds the culverts near Jacob Creek and its east fork. The 50-year design also is required for federal interstates, the association says.
Oklahoma and Nebraska now use the 50-year-flood design on their interstates or turnpikes. Texas uses the 50-year flood as a minimum standard.
But Missouri and Colorado use a more protective design. When Missouri installs larger culverts on its interstates, it engineers them to handle a 100-year flood, said Llans Taylor, innovations engineer with the Missouri Department of Transportation. Colorado designs culverts so that the 100-year flood doesn’t top the interstate, said Josh Laipply, chief engineer with the Colorado Department of Transportation.
A 100-year flood is one with a 1 percent chance of happening in any given year.
The Kansas Turnpike Authority has no estimate of the cost of using the 100-year design where the deaths have occurred because the 50-year design is the correct engineering solution, Bell said.
Each state sets its own guideline, officials say, because soil characteristics, rainfall and topography vary.
A motorist’s view
Derby resident Mike Alumbaugh was just a few vehicles back when traffic came to a stop moments after Clark’s car lost control in the floodwater and spun off.
He has thought about that day since then and shared his concerns with his state representative and in a letter to The Eagle.
“I still think that for the safety of commuters along that line, when it has the history that it has, it would be better to opt for the higher bar” and use the 100-year standard instead of the 50-year standard, Alumbaugh said.
“When you have that combination of a severe situation and one that reoccurs … in my opinion you take the higher action, you take the more aggressive action, and you do the right thing – you engineer to the higher standard.”
He added: “I think Missouri and Colorado thought it was important enough to do, that we should be thinking the same thing.”
The 2003 flood that sent a wall of water over the turnpike at Jacob Creek was close to a 500-year flood event, Bell said. A 500-year flood, referred to as a “super flood” in the engineering world, is so rare and severe that it has only a 0.2 percent chance of happening in any given year.
When the 7-foot-wide, 7-foot-tall culvert at Jacob Creek was installed before the turnpike opened, the design criteria was for a 25-year-flood, Bell said.
When the Turnpike Authority replaces the current culvert at Jacob Creek with two 12-by-12 culverts to bolster drainage, it will raise the design to the 50-year flood level, she said.
At the spot where the latest death occurred, the turnpike will add two 8-by-10 culverts to the existing 8-by-8 culvert, also improving it from the 25-year to the 50-year design.
Elevating the road by building a bridge over the two creeks wouldn’t be viable because of the cost and because it would make the surface prone to freezing, causing a new hazard, Bell said.
In the next few months, Bell said, the turnpike will install four digital message signs that could be used for weather warnings, accidents and construction between El Dorado and Emporia, covering the area where the flooding deaths occurred.
Alumbaugh, the Derby man who saw the flooding on July 10, said, “I think the warning system is very important.” It would allow motorists to pull off and wait out a storm.
If travelers aren’t warned, they’re likely run into trouble, because so many are “flying through there” and are not tuned into local weather information, he said.
By Sept. 1, the Turnpike Authority hopes to determine what other features could be added, including permanent caution signs to warn of low-lying or flood-prone areas, Bell said.
Another safety feature under consideration is a guardrail, although that has to be weighed against the concern that it could pose a hazard, Bell said. It’s important that the decisions be made carefully, not hastily, she said.
The Turnpike Authority is aware of the concerns raised after the recent death, she said.
“We have heard. We are listening, and we are willing to continue listening … and do more.”
It is important “that our customers believe we are providing a safe road,” Bell said.
Computing flood volume, risk
On the Saturday before Labor Day in 2003, the amount of water that flowed down Jacob Creek and swept seven cars off I-35 was more than three times what the highway’s drainage system was able to handle, according to an estimate provided by the U.S. Geological Survey about a week after the flood.
After July 10, when Clark died at the east fork of Jacob Creek, the state didn’t request that the USGS measure the high-water marks used to compute flood volume. It’s probably too late to get an accurate measurement because the marks would have become altered since the flooding happened, said USGS hydrologist Brian Loving, based in Lawrence.
Loving said he didn’t want to imply that it was wrong for the state not to request the measurement this time; it wouldn’t necessarily be expected, he said.
Loving and Janet Salazar, service hydrologist with the National Weather Service in Wichita, said the Flint Hills that surround the turnpike where the deaths have occurred have been paved by nature with shallow, rocky soil that produces fast runoff because the soil doesn’t absorb well, and it flows to the lowest point. The hills’ slopes increase the runoff.
It’s a recipe for flash flooding.
Turnpike engineers do consider the soil and slope in their design, Bell said.
Although the July 10 flooding came after heavy rainfall, that amount of rainfall is not rare for that area, Salazar said. Radar estimates showed that 3 to 4 inches fell near the turnpike that day.
Economics, policy, custom and regulatory requirements all play a part in determining how much flooding risk is acceptable on roadways, the highway association says in its drainage guidelines.
“The alternative of accommodating the worst possible event that could happen is usually so costly that it may be justified only where consequences of failure are especially grave,” according to the association’s guidelines.
The association also gives this caution: “Even if the hydrologic analysis at a particular location suggests that the chance for recurrence of the maximum historical flood is very small, the possibility for designing the waterway opening to convey this flood still should not be overlooked.”
And this: “Because it is difficult to place a credible value on human life, potential flooding involving possible loss of life related to a highway must be given careful consideration.”
Reach Tim Potter at 316-268-6684 or email@example.com.
Turnpike weather safety tips
▪ Check the National Weather Service for flood warnings, tornado warnings and other severe weather alerts. The Wichita office will start including sections of the turnpike from Chase County south to the Oklahoma line in its weather alerts. The Topeka office includes sections of the turnpike from Lyon county north. Check www.noaa.gov and search for Topeka and Wichita. The National Weather Service also offers an app.
▪ Watch for electronic message boards. The Kansas Turnpike Authority is installing 16 new digital message signs along the turnpike, in addition to those already in use. On July 22, the authority began broadcasting customized weather advisories for the turnpike on those signs.
▪ Slow down.
▪ Pull over if it’s safe to do so.
▪ Tune to a local radio station for weather information.
▪ Maintain a safe following distance for the conditions.
▪ If you encounter severe weather, consider taking a break from driving while the storm passes.
▪ Rest stops along the turnpike and all toll areas offer tornado shelters.
Other things to consider are:
▪ Make sure tire tread is in good condition before you get on the road.
▪ Check the weather before you go – if adverse weather conditions are expected, consider delaying your trip.
▪ No matter what the weather, always buckle up.
Source: Kansas Turnpike Authority and the National Weather Service