FLOODGATE

Floodgates of the Wanapum Dam on the Columbia River, Washington gate for shutting out or releasing the flow of water over spillways, in connection with the operation of a dam. Vertical lift, or radial, gates rise to permit flow under the gate but over the spillway crest. Drum gates rotate backward, lowering their tops and permitting a measured flow over the top of the gate. Drum gates present the fewest problems in the passage of ice or drift over the spillway.