Site Summary Flint Creek near Kansas, Oklahoma

On the morning of October 18, the team went downstream into Oklahoma where Flint Creek swings near Kansas, Oklahoma. The 110 square mile watershed above US Highway 412 receives an average of 44.5 inches precipitation annually. The annual runoff is just under 15 inches.

A Pebble Count was taken; 40 times in the riffle section just downstream from the surveyed cross section 2,242 feet upstream from the gage, working right to left and then another 40 samples in the same area working left to right. The median size of the particle’s secondary axis is 17 mm. Based upon tractive stress, the hydraulics of the channel will transport particles 24 mm minimum during bankfull flows.

The bankfull discharge is predicted to be 2,720 cubic feet per second (cfs). This rating was obtained by projecting the average reach slope of 0.00174 ft/ft from the top of the flat depositional feature in the cross section at station 2,316 back to the gage at station 74. The recurrence interval, based upon the Weibull Extreme Value plotting positions of 40 peak annual discharges, is 1.62 years. This can also be expressed by saying that the stream has a 62% chance of exceeding 2,720 cfs within a consecutive 12-month period.

Bankfull Stage at gage is 8.37 feet; gage datum is 854.59 feet above mean sea level. The bankfull stage in the cross section at station 2,316 is ~12.3 feet gage height, 5.9 feet above the bed. Water is flowing at a mean velocity of 4.8 feet per second through the riffle section. Manning’s roughness is 0.034, according to all of the assumptions of steady uniform flow. The cross sectional flow area is 566 square feet, bankfull top width is 130 feet, and the mean or hydraulic depth is 4.3 feet.

According to Rosgen’s criteria for stream classification, Flint Creek near Kansas, OK above the gage is a transitional B4c reach. It is moderately entrenched, (Entrenchment Ratio =1.8) as it only expands to a width of 240 feet as the depth doubles. Sinuosity is ~1.33 and the width to depth ratio is 30.

The B4c classification agrees with Russell Dutnell's determination, who independently came to this conclusion. Mr. Dutnell's estimates of the bankfull properties are as follows: Bankfull discharge of 2,692 cfs, 1.55-year return interval, 310 square feet cross-sectional bankfull area, 133 feet top width, 2.3 feet mean depth, width to depth ratio of 57, 1.6 entrenchment ratio. Bankfull slope is 0.00056 feet per feet.

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