17.4.2. Ogee (Overflow) Spillway An ogee spillway has a control weir whose profile is as shown in Fig. 17.6. The upper part of the spillway surface matches closely with the profile of the lower nappe of a ventilated sheet of water falling freely from a sharp-crested weir. The lower part of the spillway surface is tangential to the upper curve and supports the falling sheet of water. The downstream end of the spillway is in the form of a reverse curve which turns the flow into the apron of a stilling basin or into the spillway discharge channel. An ogee spillway is generally used for concrete and masonry dams. It is ideally suited to wider valleys where sufficient crest length may be provided.
