Brother Meredith
Baron
That was my 2nd port of call.WFRP 'River life of the Empire' had a pull out section called 'River folk of the Empire' with nice plans & sections, albiet riverboats and patrol boat. Page 11 also had a stuff on locks with nice picture of an actual lock gate(!) and barge in action. In real life Dutch barges were able to navigate older canals in the UK (especially up from the Thames) just not the later industrial narrow boat ones I guess.

4th Ed WFRP has a similar section in the Enemy Within Companion.
The tunnel is https://warhammerfantasy.fandom.com/wiki/River_of_Echoes but there also another near Ubersreik.