Why would it need to be 1.2 miles deep? at that point, the floor no longer 26 feet below sea level, but 1.2 miles below.
The builders may not account for the curve, but if they are digging relative to sea level., then they never have to. If throughout the whole stretch of the canal the depth is 26 feet, then the base of it actually is curved without them even intending it to be.
Sea level is relative to the center of the earth though, not the surface of the land. So sea level actually does have a curve
Why would it need to be 1.2 miles deep? at that point, the floor no longer 26 feet below sea level, but 1.2 miles below.
The builders may not account for the curve, but if they are digging relative to sea level., then they never have to. If throughout the whole stretch of the canal the depth is 26 feet, then the base of it actually is curved without them even intending it to be.
26 feet is deep enough, so 1.2 miles would be plenty deep for a canal.
Gravity acts on everything, including canals. I'm not sure what your point is...
The whole water "bending" part is a little misleading. Water is a fluid. It's not bending at all. It's filling a container.