To cross a stream, highway or valley (wherever the delay attributable to a flight of locks at both facet would be unacceptable) the valley can be spanned by a navigable aqueduct – a well known case in point in Wales is the Pontcysyllte Aqueduct (now a UNESCO Entire world https://knoxtbeim.ampedpages.com/a-review-of-canal-infantil-64021579