Floodflow characteristics at proposed bridge site for State Highway 99, Kansas River at Wamego, Kansas
The Kansas Department of Transportation has proposed replacing a bridge over the Kansas River on State Highway 99, at Wamego, Kansas. The ability of the main channel along with the existing agricultural levee to contain the flow of the Kansas River, the effect of overflow structures under the highway south of the bridge, and the effect of an island upstream from the proposed bridge are discussed. The design of the proposed new bridge is adequate for passage of a 100-yr flood of 155,000 cu ft/sec; however, the existing levee along the right bank of the river upstream of the proposed bridge will not confine the flow to the main channel because parts of the levee have been broken or removed. The present overflow structures would allow a discharge of 26,000 cu ft/sec to occur in the bypass reach with a maximum depth of flow over the highway of 1.3 ft. If the structures were removed but the highway grade maintained, the discharge would increase to about 30,000 cu ft/sec with a depth of flow over the highway of 1.5 ft. If the overflow structures were removed and the elevated sections of the highway grade leveled, the discharge would increase to about 31,500 cu ft/sec, with a maximum depth of flow over the highway of 1.3 ft. The velocity of flow through four 30-in diameter concrete culverts located at overflow structure sites would be 8.6 ft/sec. Foreseeable changes in the island upstream from the proposed bridge would not interfere with the flow capacity of the new bridge. (Author 's abstract)