To cross a stream, road or valley (wherever the delay brought on by a flight of locks at possibly side could well be unacceptable) the valley is usually spanned by a navigable aqueduct – a famous example in Wales will be the Pontcysyllte Aqueduct (now a UNESCO Environment Heritage https://travisjtydh.madmouseblog.com/17715538/little-known-facts-about-musica-infantil