To cross a stream, street or valley (the place the delay attributable to a flight of locks at either side could well be unacceptable) the valley may be spanned by a navigable aqueduct – a well-known case in point in Wales would be the Pontcysyllte Aqueduct (now a UNESCO https://edgarihyph.verybigblog.com/36173618/details-fiction-and-canal-infantil