Spillway Approach Hydraulics
“Spillway approach configuration will influence the abutment contraction coefficient, the nappe profile, and possibly the flow characteristics throughout the spillway chute and stilling basin.” [1]
“Crest piers, abutments, and approach configurations of a variety of shapes and sizes have been used in conjunction with spillways... Not all of the designs have produced the intended results. Improper designs have led to cavitation damage, drastic reduction in the discharge capacity, unacceptable waves in the spillway chute, and harmonic surges in the spillway bays upstream from the gates. Maintaining the high efficiency of a spillway requires careful design of the spillway crest, the approach configuration, and the piers and abutments. For this reason, when design considerations require departure from established design data, model studies of the spillway system should be accomplished.” [1]
“Another factor influencing the discharge coefficient of a spillway crest is the depth in the approach channel relative to the design head... As the depth of the approach channel … decreases relative to the design head, the effect of approach velocity becomes more significant. The slope of the upstream spillway face also influences the coefficient of discharge… the flatter upstream face slopes tend to produce an increase in the discharge coefficient. [1]
Best Practices Resources
Hydraulic Design of Spillways (EM 1110-2-1603) (U.S. Army Corps of Engineers)
Citations:
Revision ID: 4011
Revision Date: 10/21/2022