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Title: Little Sioux control structure, Little Sioux River, Iowa : hydraulic model investigation
Authors: United States. Army. Corps of Engineers. Omaha District
Hite, John E.
Keywords: Control structures
Hydraulic models
Hydraulic structures
Little Sioux River
Water regulation
Flow regulation
Publisher: Hydraulics Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Technical report (U.S. Army Engineer Waterways Experiment Station) ; HL-86-5.
Description: Technical Report
Abstract: The Little Sioux Project, located in Woodbury, Monona, and Harrison Counties, Iowa, consisted of remedial work on the channel of the Little Sioux River, three existing sills at the mouth of the river, and the construction of a channel control structure about 5.75 miles above the mouth. A model study of the original channel control structure was conducted to develop a satisfactory design for discharges up to 10,000 cfs. Since the construction of the original control structure, the channel has degraded 11 ft and flows exceeding 10,000 cfs have occurred regularly. Flows exceeding the berm height scoured the side slopes causing the riprap to fail, and convergence of the concentrated flows from the right and left bank berm sections caused the development of a severe scour hole downstream of the stilling basin. High flows during the spring of 1983 caused the structure to fail so another model investigation was necessary to develop a design for the replacement structure and to determine methods to stabilize the area downstream of the structure and the channel side slopes. Tests on a 1:25-scale hydraulic model of the replacement structure were conducted to develop the design. The model reproduced about 650 ft of topography upstream from the structure, the control structure, and 1,150 ft of topography downstream from the structure. Modifications to the original design were made to produce a structure that provided an acceptable headwater rating curve, and one with adequate energy dissipation in the stilling basin. A notched weir was developed that provided a desired range of headwater elevations for the expected discharges. The weir also produced velocities upstream and downstream from the low-flow notch for discharges less than 1,000 cfs that were considered appropriate for upstream fish migration. Stable riprap designs were determined for the channel bottom downstream from the stilling basin and the channel side slopes.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Report

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