re: The view from the bridge
That would be a little scary...don't rock the boat! With only 6" to keep your boat from going overboard V hulls probably a no no. I'll bet it was challenging at gale force winds. ;-)
You can be sure those mules had blinders on.
Iron does make a lot of sense (constuction/leakage).
I imagine around 1 meter in depth although I can't imagine those boats drafting more than 1/2 meter.
The second photo showing the structure gives way to me asking if these concepts are derived from the ancient Roman elevated aqueducts.
Very interesting, Thanks,
SteveS