Thursday, December 15, 2011

At the Locks

Posted: October 14, 8:27 am | (permalink) | (0 comments)

A lock is a kind of elevator for boats, to get from an area of one water level to a one with a higher level, and the principle is the same whether it’s elevating giant tankers on the Panama Canal, or pleasure yachts on the Great Lakes, or barges on the ICW. A lock is a section of canal with a gate on either end, making a kind of water-filled chamber. Open the gate at the downstream end and motor the boat in. Then close the gate behind the boat, and add water to the lock. As the lock fills, the boat floats higher until it reaches the level of the upper water body, then the gate at the upstream end is opened and the boat can float out. At least, that’s the way an ordinary lock works.

There is one lock on the ICW by the route we took, and we went through it last week. This lock, at Great Bridge, VA (near Norfolk) is not “ordinary.” It is located on a canal that connects Currituck Sound, NC with the Elizabeth River, VA, which ultimately connects to the mouth of the Chesapeake Bay and Atlantic Ocean. Because the ocean has 3-foot tides in this area, and the sound does not, sometimes the ocean is higher, and sometimes the sound is higher, so unlike most locks, this particular lock was made to be reversible. When you come in by boat, you never know in advance whether you’ll be going up, or down, or staying almost level. When we went through, we were almost level, and passage was quick and easy.

Once on the other side, we tied the boat to the side of the canal, and took a rest day, to watch the world float by.

writing the log great bridge

Sitting in the cockpit, writing the ship's log, while tied up to the side of the canal. Startling to see grass alongside the boat, instead of water!


A collection of tugs and barges bringing equipment into the lock. I was chatting with the skipper of one of them while he was waiting for the lock to cycle. "If it floats on the water, I'll move it," he proclaimed. This load started in Jacksonville, FL and was headed for Cape May, NJ.

By the way, remember I said in my last post, that the ICW is a series of natural bays and rivers, linked by manmade canals? Well, this particular canal that we just traversed, theAlbemarle/Chesapeake Canal, was conceived before the Revolutionary War, built in the mid-1800s, and caused environmental problems that were recognized as far back as the 1930s, a generation before the EPA was ever invented. Sometimes, during mid-tide when the water level in the ocean was the same as the level in the sound, the gates were left open to allow easy passage. That’s where the trouble started, because Currituck Sound was fresh water, and of course the Atlantic is saltwater, and when the canal gates were left open, the salt water got into the freshwater bay and created havoc with the ecology there. The locks are now kept closed unless a boat is actually transiting, and they serve as much a water-quality protection function as a marine navigation one.

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