Depending the time of year and where on the Allegheny River you are at,it is 9 feet deep on average due to the 8 locks and dams to make the river navigable by commercial craft from East Brady ,PA all the way to Pittsburgh, PA where it meets the Monongahela to form the Ohio, but the reservoir at Kinzua dam is 100+ feet deep and in several places the river can be only a few feet deep between the dam and East Brady,PA where commercial navigation is not possible but small watercraft and canoes can go thru quite easily .
In the spring thaw the river can rise as much as several feet which is why it was a major commercial route for decades.