With or without water it can be used as a barrier, as an alternative for a fence.
A trench is a long narrow ditch.
Types and applications include:
... size is 3.04. In the town the population is spread out with 25.2% under the age of 18, 4.8% from 18 to 24, 27.3% from 25 to 44, 28.7% from 45 to 64, and 13.9% who are 65 ...