Canals operate on the basic idea that a trench can be dug and water sent through it to create an artificial waterway. However, depending on where that trench is dug, it may cross over rivers and streams or even run uphill, which water is loathe to do.
Building the Canal
Many canals were built in sections with teams of men working on different areas. The work was done with hand tools, horses and later blasting powder.
The first job for the teams was to clear the area. Trees were cut. Stumps were pulled. The surface was scraped clear, according to the National Park Service in Chesapeake and Ohio Canal (Washington, D.C.: U.S. Department of the Interior, 1991).
Then the canal trench was dug and lined with waterproof clay, called puddling. In places where additional strength was needed, such as lock walls or areas of the berm that also served as retaining walls, rock walls were constructed.
Next the lock gates, feeder dams, weir and aqueducts were builts.
Some Parts of a Canal
Aqueducts carried the canal over streams and rivers. This kept canal boats, which were not easy to maneuver, from having to deal with cross currents or flood conditions. The aqueducts were essentially stone bridges that could simple or very elaborate.
Weirs were dams in the canal that helped control the water around the locks to keep water in the canal while the locks were closed.
Feeder dams were in the rivers to make sure the canals had plenty of water to operate with.
Raising Canal Boats
The most-common locks were used to raise or lower a boat. Canals were essentially built in level sections connected by locks. Locks were necessary if a canal traveled uphill. Going though a lock was called locking through.
The C&O Canal, for instance, used mitered gates that when closed formed a point that was aimed upriver. That way, the water pressure coming against the closed gates helped keep them closed, according to the National Park Service.
If the upriver gates were closed, then the downriver gates could be opened to allow a boat into the lock.
Boats were designed to fit snugly in the locks. This reduced the chance of a boat being knocked about into the walls of the lock as it was raised or lowered.
Once a boat was in the lock and the lock gates closed, sluice gates as the bottom of the upriver doors were opened. This allowed water to flow into the lock, which raised the canal boat inside. When the water level in the lock was level with the upriver canal water level, the sluice gates were closed and the upriver gates were opened.
The entire process took about 8 to 10 minutes.
Lowering a Boat
To lower a boat, the process was done in reverse. The boat came into the lock with the downriver gates closed. The upriver gates were closed and the sluice valves on the downriver doors were opened.
Water went out of the lock and the boat was lowered. When the level inside the lock matched that on the downriver side, the sluice gates were closed and the doors opened.
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