Lock is different than dam. It is a gate.

Dams stop water. Yes. Stop water. They hold the water behind them. Damming the water. Correct.

The concept of a dam is not that of a gate. Dams stop water. Gates allow a toll and watercraft through in your example. Yes locks need maintaining like dams need maintaining because they erode if they aren't maintained.

Hydro dams release water, the overflow, and the dammed, stored water, to power turbines generating an electrical charge.

If water flow over dam. Look. It burst. It is not a dam. It's a river. God damn it. Retard.