Stormwater flows of approximately 2-inches or more will unlock and open the Watergate. During these periods of increased flow and heavy rain, the screen unlocks to allow runoff into the storm drain to prevent flooding. When the water flow subsides, the screen will return to the closed and locked position. Patented Positive Force Closing reduces the possibility of debris becoming trapped under the screen. The Integral Control Arm prevents opening beyond operational limits. If the screen is clogged with debris, the top overflow design directs flow onto the actuator, which helps the unit open.