The initial channel was 40 feet wide, but only 4 feet (1.2 meter) deep, with canal-boats having a draft of 3.5 feet -- leaving 6 inches of clearance between those and the canal bottom. Given the speed of travel -- about 3-5 mph (4.8 - 8 km/h) behind a horse or donkey tow -- bottoming out would like not have been disastrous, but would still have been at the very least, a nuisance.
Considering canals to alternatives, I also realised that one of these was that the surface was uniform, effectively flat, and immune to the hazards and treacheries of road-based travel, most especially mud, ruts, and wash-outs. A canal is the original self-healing substrate.
Even at 5 mph, the constant and smooth travel, as well as the size of the boat relative to the tow (1-3 horses, boats of up to 78 ft (24 meter) in length), travel time was cut in half and costs by an order of magnitude. From a note on the Wikpedia entry:
"Using Clark's Works of Man figures, a mule can draw 60,000 lbs but carry only 250 lbs, which need men to load and unload daily, have a need to carry grain as well (parasitic weight), and for same tonnages, required far more men as a labor force, drastically increasing running costs. A 95% reduction is probably conservative, 250#/30t is 0.4% the expenses, so reduction to 5% costs still indicates someone is taking a lot of profits."
https://en.wikipedia.org/wiki/Erie_Canal
The Erie Canal was eventually enlarged. But in its day, the initial configuration was an absolute revolution in transport for the United States.