Originally posted by Kindred™ ©:

trolls cross moats fyi

If you have 1 inch of water, in a 20 foot deep trench...no troll is going to get through that.

Getting down to water level is for aesthetics, really. Like it has been mentioned the key is depth to the trench. Water is an after thought.

But my opinion is that Moats/trenches are over powered and render the raids mostly pointless. Same goes for earthen walls.