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Title:	Side-channel Spillway and Outlet Works for San Antonio Dam : Hydraulic Model Investigation
Authors:	Barela, Dave A.
Keywords:	Los Angeles County (Calif.) San Bernadino (Calif.) Dams Hydraulic models
Publisher:	United States. Army. Corps of Engineers. Los Angeles District.
Abstract:	Model studies of the proposed uncontrolled side-channel spillway and outlet works for San Antonio Dam were conducted to develop, by means of 1:36- and 1:48-scale models of the spillway and a 1:20-scale model of the outlet works, satisfactory and economical designs for these elements. Particular attention was given to flow characteristics in the side channel, spillway chute, and flip bucket for the side-channel spillway and to performance of the intake structure, outlet conduit, and diversion structure for the outlet works. Although the spillway crest functioned satisfactorily as originally designed, excessive ride-up and turbulence in the side channel during the maximum design flow of 54,000 cfs indicated the need for improved performance of the channel. The addition of baffle blocks on the side-channel invert provided adequate control of the flow and reduced the excessive ride-up occurring in the channel. The flow in the spillway chute was more stable and less turbulent. A flip bucket with a radius of 75 ft and a terminal slope of 20 degrees above the horizontal is provided at the end of the chute. The bucket proved to be satisfactory and produced a favorable hydraulic action. At a spillway flow of 54,000 cfs, the bucket diffused the spillway jet quite well over the surface of the water and resulted in a lesser degree of erosion well removed from the end of the structure. Design wall heights were determined from water-surface profiles measured in the model. Tests of the intake structure and outlet circular conduit disclosed that the flow conditions were acceptable. The slide gates were calibrated, and the outlet conduit discharge capacity curve was determined. Open-channel flow on the rising stage existed up to a discharge of 9,000 cfs; at discharges greater than 9,000 cfs, and with a falling stage down to 8,000 cfs, the conduit flowed full. The diversion structure at the downstream end of the conduit was designed to accommodate an ultimate flow of 1,000 cfs through the diversion chamber and to divert 700 cfs to the left part of the spreading grounds which is in San Bernardino County and 300 cfs to the right part which is in Los Angeles County. Flow conditions were investigated for discharges from 1,000 cfs to 11,000 cfs flowing in the conduit, and the gate openings were varied for certain discharges in order to observe flow characteristics in the diversion chamber. Results of the investigations revealed that for a discharge of 1,000 cfs, the performance of the diversion structure was satisfactory. The measured discharge to each part of the spreading grounds agreed with the design assumptions. As the flow in the outlet conduit was increased, however, the disturbance at the entrance to the chamber became more pronounced. For higher discharges, the impact flow on the downstream edge of the slot caused the water to spray over a large area. A spray shield was proposed to prevent water from splashing over the channel walls.
Description:	Technical Report
Rights:	Approved for Public Release; Distribution is Unlimited
URI:	https://hdl.handle.net/11681/43680
Size:	59 pages / 17.15 MB
Types of Materials:	PDF/A
Appears in Collections:	Technical Reports