To cross a stream, street or valley (in which the delay attributable to a flight of locks at either side could well be unacceptable) the valley is usually spanned by a navigable aqueduct – a well known instance in Wales may be the Pontcysyllte Aqueduct (now a UNESCO Planet https://musicainfantil24332.theobloggers.com/43537856/facts-about-urso-fofo-revealed