To cross a stream, street or valley (the place the delay brought on by a flight of locks at either facet might be unacceptable) the valley is usually spanned by a navigable aqueduct – a well known illustration in Wales would be the Pontcysyllte Aqueduct (now a UNESCO Planet https://connerirxbf.theobloggers.com/43548163/facts-about-urso-fofo-revealed