The challenges here will be different, and Sasuke's abilities and the fact that we could ward the area were important in protecting early construction.

A Trench is also a fortification as well as a way to irrigate, with that in mind Ditch seems the most suitable of your suggestions. If we divert a river we could call it Moat.

[D says it so calmly and and seriously there's no indication on if he's joking or not.]