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Title: Sweetwater River Channel Improvement Project, San Diego County, California : hydraulic model investigation
Authors: United States. Army. Corps of Engineers. Los Angeles District.
Turner, Herman O.
Keywords: Curved channel
Drop structure
Curvilinear flow
Sediment wedge
Sweetwater River
San Diego
Stream channelization
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-88-3.
Description: Technical Report
Abstract: The Sweetwater River is located in San Diego County, California. In the area of proposed improvement, the Sweetwater River is a poorly defined channel varying from 1,200 to 2,000 ft wide in a relatively broad floodplain. An entrenched trapezoidal channel with a base width of 320 ft has been excavated ending just upstream of a freeway bridge. This channel has a radius of 1,000 ft and turns approximately 80 deg in relation to the proposed channel alignment through the freeway bridge. A drop structure is to be located in the radius of the curve at the beginning of the project. A study of the proposed project was conducted using a fixed-bed model constructed at a scale of 1:40 to study the effect of downstream waves and disturbances caused by the curvilinear flow conditions. The main objectives of the model study were to obtain quantitative information on flow patterns, flow distribution, waves, and disturbances throughout the curved reach of channel, as well as to determine the effects of sediment buildup on water-surface elevations. Testing of the project began with the upstream approach and proceeded downstream to the other areas. The model study revealed that certain refinements are needed to the Sweetwater River project to eliminate potential problems. The upstream approach as designed created an uneven distribution of flow which affected the energy dissipation of the drop structure. A levee installed on the left overbank area resulted in improved upstream flow conditions at discharges which would ordinarily have created flow over the left bank area. The slope of the grouted stone drop structure should be changed from IV on 3H to IV on 2H. The testing program revealed that better energy dissipation and downstream flow conditions will result if the steeper slope is used. The side channel overflow spillway did not create any adverse flow conditions. This was due to low discharges coming over the spillway relative to the much larger discharge which would occur simultaneously in the Sweetwater River. Whenever the natural deposition of bed material forms the sediment buildup in the main channel, higher water-surface elevations will result. These higher water-surface elevations will cause flooding along the right side of the main channel in the overflow spillway and bridge pier areas. Higher levee heights are recommended for these areas.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Report

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