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Title: RIPRAP DESIGN FOR PIPE SPILLWAYS AT -1.0 </= TW/DO </= 0.7

Author
item Rice, Charles
item Kadavy, Kem

Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: Pipe spillways are used as farm pond and upstream flood-control spillways. Erosion at the exit of pipe spillway outlets may result in scour holes of such size that damage will occur to the pipe spillway and possibly the dam itself. Properly sized and placed rock riprap will provide protection against this scour. Since information was not available to adequately design the rock riprap, tests were conducted and mathematical relationship developed to determine the size and placement of riprap downstream of pipe spillway outlets to ensure the stability of the pipe spillway and the dam. This design information is used by the USDA Natural Resources Conservation Service, other government entities, and private consultants who have responsibilities for the design, construction, and maintenance of farm pond and upstream flood-control reservoirs.

Technical Abstract: This study resulted in criteria to determine the geometry of riprap-lined plunge pools downstream of pipe spillways with tailwater elevations in the range of 1.0 pipe diameter below to 0.7 pipe diameter above the outlet invert elevation. Dimensionless relationships were developed to determine dimensions of plunge pool and riprap size required for stability using a laboratory scaled physical model. The variables studied are: pipe diameter; tailwater elevation; riprap size; downstream channel bed elevations; and discharge. Example problems are presented to illustrate use of the recommended design procedure. The design equations will result in stable riprap-lined plunge pools downstream of pipe spillways with tailwater elevations in the range of 1.0 pipe diameter below to 0.7 pipe diameter above the outlet invert elevation over a wide range of flow conditions.