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Wind Tide

By Tom Neale - Published November 15, 2007 - Viewed 1147 times


Wind Tide reveals debris seldom seen
We had some friends who had a sailboat with a mast that was just short enough to get under the fixed high rise bridges in the ICW, but only by a small margin. They’d come down the coast successfully and were in the Indian River basin in Florida. This is a large body of water which has very limited access to the ocean and therefore almost no regular tides. They came upon a set of double high rise bridges. There are quite a few of these in the area, and they had already passed through many of them. This time it was different.

They passed under the first of the two bridges and the instruments on the top of their mast scraped badly. They slowed to a crawl and approached the second very carefully, having another boat sight to check for clearance. You really can’t do this from the deck of your own boat because the angle of vision gives the optical illusion that you’re going to hit even if you have many feet to spare. The verdict was clear. “No way you’re going to get under that second bridge.”

The two bridges were about 500 yards apart. Our friends turned around to try to get back under the bridge they’d just passed under and guess what: They couldn’t make it. They were trapped between the two bridges.

Now normally you’d think they could pull off out of the channel and anchor and wait a few hours for the tide to go down. But this was a place where there was very little tide. And the plot thickens. This was also one of those many places in Florida where some politicians had passed a “law” saying that you couldn’t anchor.

Of course, they anchored anyway, and started trying to figure out what to do. Some sailboats get through low bridge situations by swinging weights out on their booms and heeling the boat over enough to slide under. But this isn’t always a safe or good thing to do and sometimes you can’t get enough weight to cause the boat to heel enough to get under anyway. And as they sat and watched, they noticed that, as best as they could tell, the water was getting higher. Surely it was just their imagination—but passing hours proved it to be true.


About Wind Tides

1. Wind tides are likely to occur in large, relatively shallow and wide bodies of water with limited access to the sea. Surrounding flat land which allows the wind to readily push the waters may contribute. However the phenomenon can occur, to one degree or another, in many other areas.

2. Even deep bays with high hills or cliffs can develop wind tides, particularly if they are long and the wind blows up or down them, or if they open to an area, such as a coastal convex curve, which is subject to wind tides.

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Of course, it didn’t take long for the marine police to show up, advising them they’d have to leave. And it didn’t take long for the skipper to tell the marine police he’d love to leave if the long arm of the law would just tell them how to do it. I suppose this could have all turned nasty, but the marine police apparently reported the dilemma to other local authorities and a special exception was allowed for the sailboat (not that there was much choice) until a solution could be found. In the meantime, the trapped sailors were offered rides to the grocery store and made to feel most welcome by the good local folks. You might wonder if they’re still sitting there, but a day or so later they were on their way. Because the winds changed.

There had been unusually persistent and strong winds in the area at the time and the winds had simply piled up the waters. The folks on the boat between the bridges happened to be on the top of the pile at the wrong time and the wrong place. When the winds died the water leveled out and getting under the second bridge was “no problem, Mon.” Lest you think this is an isolated example that pertains only to sailboats, read on.


Wind Tide lowers water mark

We were once following a large tug boat heading north, running up the ICW. We’d passed through the Coinjock Cut in North Carolina, bucking a strong current, and were heading out into the broad shallows of Currituck Sound. I’d talked with the tug’s captain on VHF to establish his expected speed as I tried to decide whether I should pass. I’d concluded that I shouldn’t. The channel was narrow and shallow. I could tell that he’d been doing the trip for a long time. As we cleared the cut, he came back on VHF 13 and told me to look to my left. I was already looking, and I was amazed. So was he.

“I’ve been doing this trip probably 30 years and I’ve never seen what I’m seeing over there now,” he said. I’d been doing the trip over 20 years and I hadn’t either. There had always been the stone and cement ruins of an old factory or mill of some sort on the bank, but this day we could see stumps and tree knees and parts of the ancient foundation that we’d never seen.

And then the tug began to slow down. “Cap,” he called back, “I’m pushing mud where I’ve never pushed it before and I don’t know how fast you want to go or what you draw but you’d better not follow too close ‘cause I’m liable to come to a screeching halt up here.” I had no intention of following close, it’s seldom a good idea, but I thanked him for his help and held far back, barely able to maintain steering at my speed, as he slowly pushed his way through the mud down at the bottom in the middle of the channel. The tug ground its way north for hours, throwing up an occasional stump or log that had lain rotting on the bottom for decades. The wind? Well, it had been blowing hard from the north for days.


Debris from prop was is a danger here

Wind tides are more common than many think and play a greater role with navigation than many think. We’re all familiar with storm surges in hurricanes and extreme tides from other storms such as nor’easters. But there are maritime areas when prolonged winds, such as those produced by a strong stationary high pressure system, a low, a squeeze play between the two or various other phenomena, push water and, essentially pile it up. Typical areas where this occurs are those like the Indian River Basin. Lake Okeechobee, a place without tides, has suffered this phenomenon drastically in prolonged high winds, with great loss of life along the shore in some hurricanes. Currituck Sound and the other sounds behind the outer banks of North Carolina are subject to wind tides as is the Chesapeake Bay. Long bays and wide rivers in New England can see this phenomenon in the right conditions, as can areas on the West Coast and Great Lakes. Sometimes the effect is only inches; sometimes the effect can be much more than inches.


Much of this is normally under water

Wind tides not only cause unexpected water levels, they also cause unexpected currents. For example, when a strong northerly is blowing water toward the southern end of the sounds of North Carolina, Currituck Sound not only becomes more shallow but it develops a lot of current heading southward. And the dredged cut through Coinjock which provides a connection between the large Currituck Sound with the North River and Albemarle Sound and other sounds to the south can develop an exceptionally strong current running from north to south. If the wind suddenly stops, as it often does, or reverses, the current will normally reverse and flow strongly in the opposite direction as the water levels reach an equilibrium.

Sure this can really be a drag, in more ways than one. But look at it another way. It’s just one more example of how Mother Nature can throw a curve ball out on the water. It’s one more interesting maritime phenomenon to learn about, and hopefully to deal with. And I enjoyed my chat with the tug captain. And my friends sure enjoy telling about their experience between the bridges. Once you accept that nature is in charge, not you, it gets easier and better.

Copyright 2004-2008 Tom Neale





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