Navigating Olympic’s Beaches with a Tide Chart

Without a map and a tide chart you run the risk of literally walking into a dangerous situation that could be life threatening. Do you know how to read them?

Going to the Pacific coast bordering Olympic National Park’s western side requires two important things: a topographic map and a tide chart. Without these, you run the risk of literally walking into a dangerous situation that could be life threatening.

Blame it on the tides. At low tide, you can walk down Olympic’s beaches, safely rounding some of its headlands and exploring tidal pools. What you may not realize is that high tide can make some of these headlands impassable, such as at Point of Arches on Shi Shi Beach or Hole in the Wall on Rialto Beach. If you are unaware of when the tides are coming up or down, you could get trapped in between steep cliffs and the water, leaving you no escape. People have died in the park because of the tides.

Pick Up a Topographical Map and Tide Chart

At Olympic, sometimes there is only one low tide on a day, so it is extremely important that you understand how to read a tide chart and have a topographic map with you, as well. Don’t ever assume there will be two low tides in one day. And don’t assume tides will be the same every day because they are different. Stop by any Olympic National Park visitor center or coastal ranger station to get both a topographic map and tide chart. For advance planning, you can download a tide chart for La Push from the National Park Service website (www.nps.gov/olym/planyourvisit/tides-and-your-safety.htm), but note that conditions can change.

A topographic map will let you know what headlands become impassable at high tide, which ones should not be passed regardless of the tides and what areas to use caution when exploring the beaches of Olympic. One source for topographic maps is Discover Your Northwest at www.discovernw.org.

According to the Olympic National Park website, words on maps like ” ‘danger’ usually means that a headland cannot be rounded at any time by walking on the beach. ‘Caution’ usually suggests a low tide height below which it may be safe to round headlands.” On the general overview map of the national park, an X means impassable headland; ALWAYS use overland trail and a red circle means to wait for low tide or use overland trail if available.

Tide warnings on the general overview map of Olympic National Park
Tide warnings on the general overview map of Olympic National Park (Photo: National Park Service)

On a tide chart, you can learn several critical things. First, you can see how high and low the tides will be, as well as at what time they will rise and fall. You also can see when the full moon is (the white colored moon) and the new moon (black-colored moon).

How to Read a Tide Chart

When you pick up your tide chart, you’ll notice there are a lot of numbers on it. Don’t be intimidated. Instead, start to look for specific things.

Example tide chart
Example tide chartNPS

1. Verify your chart is for the correct week and year

At the top of your chart, you will see the date and year that the chart is covering. Never use a tide chart from a different year or week than you plan on visiting Olympic National Park. Tides change based on where the moon is in relation to the Earth. This means that each day the tides will roll in and out at different times and at different heights. Make sure you have the right chart for your visit to the park.

2. Know what chart datum is

To read a tide chart, you should know what chart datum is. Chart datum is the average low water mark. If you downloaded your chart from the Olympic National Park website, you can find chart datum because it is the horizontal line that is labeled “0.” The height of a high tide is based on how how many feet above the chart datum the tide will be at its highest point.

Likewise, the height of a low tide is based on how far it falls below or close to the chart datum. When the low tide falls below the chart datum, you often will see the low tide height preceded by a negative sign like -1.3 feet. But there are times when low tide is still above the chart datum. In these cases, you won’t see a negative sign before the number, but you will see it is a low number like 1.4 feet as opposed to high tide that may be at 7.2 feet at its peak.

3. Locate the time

Each high and low tide will correspond to a specific time. Your chart may list an “a” next to the time for “a.m.” or “p” for “p.m. Or it could use military time, which utilizes a 24-hour clock rather than a day split in two by two groups of 12. If your chart is operating on military time, 13:00 is equivalent to 1 p.m., 14:00 is equivalent to 2 p.m. and so on until you reach 24:00, which is midnight.

4. Be aware of weather

If there are strong winds or a storm is under way or on its way, the tides will change more rapidly than your chart will indicate. This means you must be really aware of weather conditions along the coast in addition to following your chart.

Olympic National Park officials recommend rounding headlands on the coast within one to two hours before low tide. Trying to pass a headland as the tide is coming up can be extremely dangerous, especially if it is windy out or a storm is coming in.

Talk to an Olympic National Park ranger

Even if you have a tide chart and topographic map, it’s hard to visit a place and know all the hazards, safety tips and highlights. Check in with an Olympic National Park visitor center or coastal ranger station to get a weather and conditions update before you hike on the coast. You also can verify with a ranger that you are reading your chart correctly and are aware of all the potential hazards.