Kansas Turnpike Closure

[Phone_Harold]

The Kansas Turnpike is closed between Wellington to the Oklahoma state line.

https://www.kansas.com/news/weather/article230187749.html

[US71]

The Kansas Turnpike is closed between Wellington to the Oklahoma state line.

https://www.kansas.com/news/weather/article230187749.html

I saw that on Fakebook. Anyone get stranded in the flood itself?

[J N Winkler]

There have been no reports of casualties or stranded vehicles in this flooding incident, unlike the case with the ones in the Flint Hills discussed in the linked article, which describes the death of Zachary Clark but does not go into detail on an earlier 2003 incident that swept multiple vehicles off the road and (if memory serves) killed eight, including all but the father of a family from Kansas City.

In terms of rain and flooding, the Turnpike is the least resilient of Interstates in Kansas by a wide margin.  This is a result not just of dated hydrological design (implicated as a factor in the 2003 disaster) but also of very unconservative geometric design.  KDOT Interstates often have to close because of blowing snow, but I have never heard of a single instance of their having to close because of inundation.

[kphoger]

The KTA is my least favorite highway to drive on in rain or snow, for precisely the "dated hydrological design" JNW mentioned.

[CtrlAltDel]

This is a result not just of dated hydrological design (implicated as a factor in the 2003 disaster) but also of very unconservative geometric design.

I hate to just bombard you with questions, but:

How has hydrological design changed over time? And in what was is the Kansas Turnpike deficient?
What would a more conservative design have been? Does it have something to do with consisting mostly of straight lines?

[J N Winkler]

I hate to just bombard you with questions, but:

How has hydrological design changed over time? And in what ways is the Kansas Turnpike deficient?

No worries regarding questions!

*  The Turnpike was designed using hydrological data gathered through the early 1950's.  More data has accumulated since, with the result that a flood with a 1% chance of occurring in any given year ("100-year flood") corresponds to higher water levels and flow volumes now than in 1955.  The 2003 flood was in fact computed to be about a 500-year flood (0.2% recurrence) per the data available through 2003.

*  Hydrological design involves choosing a maximum chance of recurrence/a minimum recurrence interval.  When culvert expansions along the Flint Hills segment (site of the 2003 flood) were under consideration, KTA was heavily criticized for designing for a 50- to 75-year flood when state DOTs in neighboring states like Colorado were designing Interstates for 100-year floods.  KTA reportedly revised the design in response to this criticism.

*  When it is possible to cater locally for a longer flood interval at little added cost, it is prudent to do so since it brings the roadway as a whole closer to a higher level of climate resilience (and proofing against uncertainty in the underlying hydrological data) for a onetime spend of fixed costs such as traffic management, pavement replacement, reinforced concrete construction for an expanded culvert, etc.

What would a more conservative design have been? Does it have something to do with consisting mostly of straight lines?

From the standpoint of flood management, it is helpful to have alignment design that is conservative in the vertical plane.  This means vertical curves with high k-values, which in turn often means elevating the roadway on embankment significantly above low-lying ground (often with extensive use of box culverts or flood arches).  This in turn improves forward sight distance and makes it easier for vehicles to draw to a stop when the traveled way is inundated.

Especially through the Flint Hills, the Turnpike hugs hillsides as it goes down into and up out of valleys, which invites inundation of the roadway when flash flooding overloads culverts and also makes it harder for drivers to see water flowing fast over the road in time to avoid it.  This was a factor in the 2003 and 2014 disasters.  (There has been no underlying change in land use that makes these disasters more likely; the Flint Hills are locally prominent and have always been used as rangeland.)  I-70 west of Topeka also goes through the Flint Hills, but largely stays clear of valley floors and has no history of inundation.

[J N Winkler]

The Turnpike has reopened as of yesterday evening, and KTA has posted a YouTube video of the repairs.