TIDES AND TIDAL CURRENTS ON THE MAINE COAST
FOR the cruising sailor accustomed to a tidal range of one or two feet in Chesapeake Bay, Florida, or the Caribbeanor even Long Island Sounds 7 feetthe rise and fall of 11 feet in Penobscot Bay or 20 or more feet in Passamaquoddy Bay and beyond presents a new and sometimes intimidating challenge to navigating and piloting. Remember, though, that sailors and fishermen have been dealing with these tides for hundreds of years. Once you know what to expect, its just a matter of gaining a little experience.
Spring Tides and Neap Tides. As every schoolchild learns, tides are caused by the gravitational influence of the sun, the earth, and, primarily, the moon. Tides of increased range, called spring tides, occur twice a month when the moon and sun are in conjunction or opposition (a day or two after a new moon or a full moon). Tides of decreased range, called neap tides, occur twice a month when the sun and moon partially counteract each other (first or third-quarter moon).
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Tidal Range. The tidal range increases as you sail from west to east along the coast of Maine and New Brunswick, Canada. Starting with a range of 9 feet or so in Kittery, it reaches about 19 feet in Eastport, and 25 feet in Saint John, New Brunswick.
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To understand these great tidal ranges and why they increase as you move east, imagine the Atlantic Ocean as a large basin of water being sloshed back and forth. The motion of the water in the middle of the basin is relatively small, but when it enters the narrow confines of the Bay of Fundy, the tidal range reaches an extraordinary 50 feet or more, culminating in a dramatic tidal bore at Moncton, New Brunswick.
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Anchoring with Large Tides. The large tidal range requires caution when anchoring. Many a cruising sailor has anchored in a large open bay only to find in the night that the water has drained away, leaving him high and dry on an unsuspected ledge or wallowing in the mud. Study the chart carefully before anchoring. Try to visualize the anchorage at low tide and anticipate where you will lie if the wind or current shifts. In crowded harbors, be suspicious of any large areas free of moored boatsthere is probably a reason for their absence, and it is probably lurking under water.
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When anchoring, scope needs to be calculated for the highest tide, especially when the tidal range is great or the depth is shallow. For example, at Mount Desert, where the tidal range is 12 feet, you could anchor in 16 feet at low and put out 96 feet of scope for a respectable scope-to-depth ratio of six to one. But at high tide, the 16 feet of water will become 28, and your ratio will shrink to an inadequate 3.4 to 1. If you had been in Passamaquoddy Bay, with a tidal range of 20 feet, your ratio would be even worse. The specifics of anchoring and tying up way Down East are discussed in detail in Region 7. Meanwhile, use plenty of scope wherever you cruise in Maine.
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Large tides have their advantages, too. Certain anchorages have dangers unseen at high tide which reveal themselves at low. An approach that can be a game of guesswork at high tide can be straightforward at midtide or less when the dangers are visible.
Drain Tides. During the time of spring (large) tides each month, the extreme lows are called drain tides. Where the tidal range is small, these are of little importance. In Maine, however, you must pay attention to drain tides, shown in the tide tables as negative numbers. This means that the tides fall below the mean water level on which the chart soundings are based. For example, the depth in Kennebunkport at an average low tide is around 6 feet. Thats fine if you draw 6 feet or less. But on days of drain tides, the water may be as much as a foot or two below that level, and your keel will be deep in the mud. If the charted depth in a harbor is close to your draft, be sure to consult your tide tables. Canadian charts use lower datum to indicate soundings, so negative tides are rarer and smaller.
In this guide, whenever we mention the depth in an anchorage or alongside a float, we are referring to an average low tide. There will be less water during drain tides.
Rivers. Tides in big rivers such as the Kennebec and the Penobscot vary considerably as you go upstream. At the mouth of the Kennebec, for example, the maximum range of tide is 9.7 feet. By the time you reach Bath, upstream, the maximum range is only 7.4 feet, and farther upstream at Richmond, it is only 6 feet. On the Penobscot River, the reverse is true. The range of tide increases as you go upstream, from about 11.8 feet at the mouth to a maximum of 15.5 feet at Bangor. The massive tides at Saint John, New Brunswick are hardly felt once you are above the reversing falls on the Saint John River.
Tide Tables. Have a current copy of the U.S. Tide Tables aboard (Atlantic Coast of North America). If there is a chance you will approach Canadian waters, you will also need the Canadian Tide and Current Tables (Vol. 1, Atlantic Coast and Bay of Fundy).
Many commercial firms print complimentary tide tables for specific locations such as Boston, Portland, Rockland, and Bar Harbor. They are convenient and can save time looking up the tides in the tables. Errors are not uncommon, however, so they should be used with caution and double-checked periodically with official tables, the tidal information broadcast on NOAA Weather Radio, by computer, or by your own observations.
For estimating how much the sea level rises or falls at different stages of the tide, remember the Rule of Twelfths:
For example, if the tidal range is 12 feet, the tide will rise about one foot the first hour after low slack, 2 more feet the second hour, 3 more feet the third hour, etc.
The state of the tide is so important to your planning when cruising Down East that most people find it handy to look up the times of high and low tides each day and post them somewhere aboard for easy reference.
Tidal Currents. Large tidal ranges create strong currents, and strong currents get stronger where they are constricted by coastal geography. The U.S. government does not publish tidal current charts for the coast of Maine, but general information can be obtained in the Coast Pilot, the Tidal Current Tables for the United States (a separate publication from the Tide Tables), or the Canadian Tide and Current Tables. Canada also publishes a broad but interesting Atlas of Tidal CurrentsBay of Fundy and Gulf of Maine.
Generally, all along the coast of Maine, the tide floods to the north and east and ebbs to the south and west. Along the coast and in the wider bays, the current seldom exceeds 2 knots. In narrower passages, though, such as Upper and Lower Hell Gate, Oven Mouth (see Midcoast), and the constricted portions of the rivers, it will run much harder.
As you approach Canadian waters and the Bay of Fundy, currents get stronger as the tidal range gets larger. In Grand Manan Channel, Down East, the maximum tidal current runs 3 knots. In Head Harbour Passage, Letete Passage, and Lubec Narrows, the tidal current runs 8 knots or more, with boils, eddies and whirlpools (see Passamaquoddy Bay). At Saint John, New Brunswick, the current literally cascades upriver at the reversing falls.
The direction of the ebb and flood varies in passages tending east and west. In Fox Island Thorofare, the flood comes in from both directions, meeting at Iron Point, and it also ebbs in both directions. In Eggemoggin Reach, the current floods northwest and ebbs southeast (see Penobscot Bay). In Deer Island Thorofare and Merchant Row, the current floods east and ebbs west, but strong winds can reverse the flow (see Mount Desert Island region). In Casco Passage and Moosabec Reach, the current floods east and ebbs west. At Bass Harbor Bar, the current floods west.
In making a passage east or west, especially Down East where currents are stronger, plan to use the current as much as possible. Fighting 2 or 3 knots of current from Mount Desert to Roque Island or Grand Manan is frustratingly slow. With the current pushing you along, the headlands slip by effortlessly, and you arrive with daylight to spare.
In limited visibility, an estimate of current is critical for good dead reckoning, especially crossing a big bay such as the Penobscot with the current on the beam. Watching the current on lobster buoys helps. Remember, the current may be influenced by a strong wind blowing for a period of time.
River Currents. In the rivers of Maine, the ebb is usually much stronger than the flood, since the strength of the river is added to the tidal current. You can expect stronger currents in narrow stretches of river. Consult the Coast Pilot and Tidal Current Tables for details.
When you are picking up a mooring or approaching a dock in a river, the current is usually a more important consideration than the wind except at slack water. In the Piscataqua or the Kennebec, for example, you would normally head into the current regardless of wind direction.
Wind against Current. In certain places such as the mouth of the Kennebec River, Bass Harbor Bar, and Petit Manan Bar, the river or tidal current running against a strong wind will produce a vicious chop that is dangerous to small craft and highly uncomfortable even to 40-footers.
See also Tide and tidal current information for kayakers.