Kansas Turnpike Authority to reduce risk of flash flooding on highway

The Kansas Turnpike Authority will do more than originally planned to protect motorists on a two-mile stretch south of Emporia where seven people have died in flash flooding since 2003.

KTA on Tuesday announced the additional measures it is taking to keep water off the toll road.

The design is intended to keep water off the roadway during what is known as a 100-year storm, KTA said in a news release. The work is expected to be done in 2016. A 100-year storm is one with a 1 percent chance of happening in any given year.

KTA also will install a stream monitor at mile marker 118, where 21-year-old Zachary Clark of Texas died on July 10 when his Ford Mustang ran into an estimated 10 inches of floodwater on the turnpike. The car spun into a submerged ditch, where water flowed 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.

The monitor will be operating around mid-September, KTA said. Two other places on the turnpike have monitors – at mile marker 116, where six people died in 2003, and at mile marker 199 near Lawrence.

Internal discussions and review have led KTA to make “a notable change to its drainage structure designs,” the KTA statement said.

Current national guidelines call for culverts, which carry water underneath the interstate, to be big enough to handle water from a 50-year storm.

However, KTA is shifting its focus from the design of the culverts to the potential for flooding on the interstate.

That “ultimately is what’s important to travelers,” KTA said in a news release. “The new focus is to keep water off the roadway during a 100-year storm, regardless of how the structure is designed.”

Five of the six drainage structures to be installed in 2016 meet this goal. The sixth structure, at mile marker 116, will be redesigned.

It was there that a wall of floodwater swept cars off the turnpike in 2003, killing six people. At mile marker 116, the turnpike crosses over Jacob Creek, 2 miles south of where Clark died. In both places, creeks drain to culverts that run under the turnpike.

The turnpike is spending an estimated $3 million to expand culverts in a 20-mile stretch that includes where the flood deaths have occurred. The cost is expected to increase with the redesign at Jacob Creek, said Rachel Bell, KTA spokeswoman.

KTA said it also has chosen permanent signs to alert motorists to the potential for flash flooding. There will be six signs – four will have flashing lights when stream monitors at mile markers 116 and 118 show the culvert is half full. The signs, which will say “Watch for water when flashing” will be installed by mid-September.

The turnpike also is installing 16 additional digital messaging signs throughout the length of the highway to alert motorists to hazards and weather warnings such as flash flooding, high winds and tornadoes.

KTA and the engineers it consulted with considered installing guardrail to protect motorists from floodwater on or by the highway, but guardrail can also pose a hazard if a vehicle strikes it, Bell said.

KTA decided guardrail won’t be installed “to protect against potential flooding that is already being addressed with these drainage structure improvements,” the statement said.

This story was originally published September 1, 2015 at 11:22 AM with the headline "Kansas Turnpike Authority to reduce risk of flash flooding on highway."