trench

A trench is an excavated pathway or channel which is not filled with water. It must be dug into the earth below the mean ambient surface level; a gap blasted through an outcropping, hill, or mountain does not count as a trench. It must also be bounded by retained earth on both sides.

The excavation lies below the ambient terrain rather than merely cutting through a raised hill or outcrop. Earth remaining on both sides bounds the channel.

A canal is a constructed navigable water channel. The trench has the stated waterless form instead.