MAINE'Stides are large. The tides themselves and their associated tidal currents are of vital importance to boaters on this coast. Average tidal ranges run from about 8.7 feet along the southern coast to 20 feet or more in Passamaquoddy Bay. The changing water depth can create a beautiful bay out of a mud flat or change an easy landing into an arduous trek over slippery rocks. COPYRIGHT 2002 DIAMOND PASS PUBLISHING Tidal currents generally flood in a northeasterly direction and ebb to the southwest, but coastal geography determines their ultimate direction. Currents in east-west passages vary in direction all along the coast. COPYRIGHT 2002 DIAMOND PASS PUBLISHING Tidal currents are subject to physical landmass influences similar to those of the wind. Constrictions tend to increase the force of the current; more expansive shorelines will slow them. And near points or headlands, the directions of the currents may change. Boaters can often use these currents to boost their speed or progress. Adverse currents can be avoided by keeping close to shore, where the shoreline slows the movement of the water or where the current actually reverses itself in a back-current that can help push the boat along. IF YOU ARE READING THIS, YOU HAVE VIOLATED The currents, however, can be dangerous, especially when wind opposes the current. This opposition can set up steep standing or breaking waves that can present real hazards to small boats. And since the currents are tidal, these waves may appear at certain points in the tide cycle yet be completely absent at other times. INTERNATIONAL COPYRIGHT LAW. Two rules help estimate the height of tide and its associated currents at different stages of the tide cycle. The “Rule of Twelfths” estimates tide heights between high and low water. Over the six-hour period between any high and low tide, 1/12 of the volume of water will move in the first hour, 2/12 will move in the second hour, 3/12 will move in the third hour, 3/12 will move in the fourth hour, 2/12 will move in the fifth hour, and the last 1/12 will move in the sixth hour. For example, if the tide rises 1.25 feet in the first hour after low tide, the water will be 2.5 feet deeper in the next hour and the total tide range will be about 15 feet. PLEASE RESPECT AND SUPPORT THE WORK THAT HAS The “50-90 rule” estimates current speeds between slack water and maximum flow. Divide the time between slack water and maximum ebb or flood into thirds. In the first third, the current will increase to 50% of its maximum. In the second third it will reach 90%. And in the last third, it only increases the last 10%. BROUGHT YOU THIS INFORMATION. BUY THE GUIDE! The complexities of Maine’s convoluted coast make charting its currents a daunting task. Current tables are available, but their information is often too general for the boater dealing with the eddies and counter currents close inshore. Wherever possible, we have included current information in our text. Maine is also blessed with a perfect way to estimate the strength and direction of tidal currents almost anywhere along the coast—lobster buoys. These ubiquitous floating telltales stream back in any current, and the ripples around them easily show the current’s strength. Click here for more about understanding and navigationg with lobster buoys. Remember, never haul a lobster trap, even out of curiosity—these are owned by the lobstermen who fish them, and few things are considered more sacred in Maine.