The Waaiersluis, for closing against flow

The Waaiersluis is a device that uses the pressure of a flow of water to close a gate against flow. Invented in 1808 by Jan Blanken of The Netherlands, it was important in military water movement before air warcraft.

The quarter-circle pool in which the movable structure normally sits at repose can be fed and drained by pipes coming from and going to the canal upstream and downstream.

"Waaiersluis" op Wikipedia NL...

The length of the dam wall on the pool side of the right-angle lock doors is just longer than that on the canal side, the one that will block passage. The pressure of the downstream flow fed in upon the larger surface of the longer wall is just enough greater that the oparators may close the shorter side against the flow of water assisted by slight additional force.