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|Title:||South Ellenville flood control project, Rondout Creek basin, New York : hydraulic model investigation|
|Authors:||United States. Army. Corps of Engineers. New York District.|
Melsheimer, Edwin S.
South Ellenville Flood Control Project
Rondout Creek Basin
|Publisher:||Hydraulics Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Technical report (U.S. Army Engineer Waterways Experiment Station) ; H-74-2.|
Abstract: Model investigations of the proposed channel improvements for flood control on North Gully and Sandburg Creek at South Ellenville, New York, were conducted to supplement and verify hydraulic computations for the original design and to develop alterations effecting improved hydraulic performance and reduced construction costs. A 1:20-scale model was used to verify and improve design features including the chute entrance, chute alignment, superelevation in bends, effect of large materials in the chute on inflow disturbances in the chute, hydraulic performance of stilling basin, wall heights, and elevation of bridges, and to determine the need for riprap protection below the stilling basin. The model reproduced portions of the overall project including proposed improvements along the lower 2200 ft of North Gully and approximately 600 ft of Sandburg Creek below the junction with North Gully. Tests of the original design indicated flow conditions within the proposed chute to be generally satisfactory. However, unsatisfactory flow conditions were observed at the entrance to the high-velocity chute in North Gully, where discharges of 1200 cfs or more in Nor th Gully overtopped the left chute wall 30 to 40 ft downstream of the chute entrance. At low flows (300 to 1500 cfs) a cross-wave disturbance at sta 4+55.36 resulted in unequal distribution of flow enter ing the stilling basin. This unequal flow distribution coupled with the submergence effect of the end sill at low discharges resulted in eddy action in the stilling basin. Debris entering the high-velocity chute tended to choke the stilling basin and create a damming effect in Sandburg Creek immediately below the stilling basin. Improvements in flow conditions at these locations were effected by : (A.) installing a 7-25-ft-high weir at the entrance to high-velocity chute, (B.) flattening the slope of the transition section upstream of the basin and modifying the parabolic drop entering the basin to provide a more vertical drop, and (C.) increasing the height of the debris barrier to prevent passage of debris into the chute. Design wall heights were determined from the profiles of the water surface obtained in the model along each wall with the design discharge (3750 cfs). The exit area below the stilling basin in Sandburg Creek will require a concrete splash pad and adjacent riprap protection for about 260 ft to ensure prevention of scour. The 2-ft-high and 4-in.-wide concrete wearing surface along the bottom of the chute walls had little apparent effect on flow characteristics in the chute.
|Rights:||Approved for public release; distribution is unlimited.|
|Appears in Collections:||Technical Report|
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