•••efFecT 0f t!dEs•••

Navigation Skills

Tides & Currents

Page 4 of 15

Tides are the vertical rise and fall of the water. Tidal currents are the horizontal movement of the water caused by the tides. In our area we have two almost even high and low tides, and the corresponding floods and ebbs each day. In some areas (parts of the Gulf of Mexico) there is only one high and low tide each day. On the Pacific coast they get one higher and one lower high tide each day. Our tides change about every 6 hours, 13 minutes, with a full tidal cycle is about 12 and a half hours. Each day the tide is about an hour later. Click for Rules of 12 Chart.

All bodies of water have tides. Most people don't think lakes have tides, because the tides are so small. In the open ocean the tides are relatively small (about 2 or 3 feet). When the ocean meets land, the tides become larger, especially in bays and harbors. Tides in New York Harbor are around 5 to 6 feet, in Boston Harbor tides are about 11 feet and in the Bay of Fundy the tides can be over 50 feet.

To determine when it is high/low tide and when the flood/ebb starts, use a tide or current table. We use the Eldridge Tide And Pilot Book. Eldridge lists the tides for over 350 points, and currents for over 300 areas of the east coast for a full year. The tables are updated each year, so you need to buy the new Eldridge annually. Click to view sample Eldridge Tide and Current pages in PDF format. The tides and currents can also be found on the internet. Check our Navigation Links pages for more information.

Should you look up tides or currents? It depends on where you plan to paddle. The currents on open water will affect you more than tides. Functionally, there is a two knot difference between a one knot current moving with you versus a one knot current moving against you. Since many beginners only paddle at about two knots, this might make the difference between a good day and a frustrating one. Clearly, you can travel further if you plan your route to coincide with the currents. Tides are more significant when depth may be a factor. Some marsh areas, small bays and inlets will run out of water at low tides and you can get stuck for hours. In areas with big tides (e.g., Maine, or the Bay of Fundy)a landing at low tide will require a long walk with a loaded kayak to the high water mark and a safe campsite. For these areas look up the tides. Remember that weather (rain, wind, barometric pressure, etc.) can change the tides and currents. Low barometric pressure will cause higher high tides and lower low tides. High pressure will cause the opposite effect. It is not uncommon for the tide and current to change an hour earlier or later because of the weather.

The moon has the greatest effect on the tides. The sun has the second greatest effect and all the planets also affect the tides. The more these celestial bodies align the greater the gravitational pull and the higher the tides and the greater the currents.

The sun is 26 million times larger than the moon, but also 390 times further away. The moon has about 2.17 times greater effect than the sun.

The tides and currents are greatest during spring tides (full & new moon) and smallest during neap tides (first & third quarter). Tide height and current speed can increase by about 50% during spring tides. During a full moon the night high tide will be higher than the day high tide, while during a new moon the day high tide will be greater than the night high tide. Eldridge also gives the estimated tide height and speed of the water for each day.

The orbit of the moon is elliptical, with the moon at 252,000 miles at apogee and at 221,000 miles at perigee. The tides are much greater at perigee than at apogee.

Current Charts

Current charts show how fast and what direction the various currents are flowing for each hour of the tidal cycle. Eldridge has sets (12 charts/one for each hour) of current charts for New York Harbor, Long Island Sound/Block Island Sound, and Buzzards Bay/Nantucket Sound. These are very useful, but small. You can also buy current charts published by the government in a much larger format from many boat stores. These are more useful than the small charts in Eldridge and very inexpensive. These charts don't change from year to year, so it is a one time purchase.

.

A current chart shows each hour of the current cycle. The left chart is for "Slack Flood Begins" (SFB). The right chart is for "Slack Flood Begins + three hour" (SFB+3). Four other charts would also show the current for the other hours of flood. Six other charts would show the ebb current cycle for a total of 12 charts.

Use the current charts to plan your route. Know what the current will be doing. How fast is the current? In what direction is it flowing? At what time does the current change? Does your itinerary fit the conditions? Are there any eddies to take advantage of or to watch out for? Current charts will tell you all of that. There will be many smaller currents that don't show up on current charts, but will affect kayaks.

An eddy is water moving in the opposite direction from the main flow. By using the eddies you can paddle against the current using less energy. Also, by knowing where eddies are you will know where not to go when heading with the current.

The shortest route is not always the best route. When paddling against the current or wind it may take less energy to paddle a longer route and take advantage of eddies and lee shores. Current charts don't show the small eddies, but by looking at your chart, you can figure out where they are.