If you’ll be paddling in areas that are influenced by the tides, it’s vital that you know how to read a tide chart. In some of the world’s most coveted paddling locations, the tide can change 20 feet (or even more) in six hours.
Knowing how these tides work can help you anticipate challenging waters, catch a free ride on a flooding tide, and ensure your gear won’t float away if you’re camping.
What Are Tides and What Causes Them
Tides are caused by the gravitational influence of the moon and sun, but the moon provides the majority of this influence. Despite the moon being smaller than the sun, its closer proximity to earth allows it to have a greater gravitational pull.
This gravitational force is felt on both water and land, but is barely noticeable on land without finely tuned instruments. However, on large bodies of water, it causes the surface to bulge in the direction of the gravitational pull, causing the water to be drawn towards the moon.
Most places on earth have two high tides every day. How can that be if the moon only makes one circuit every day? The second high tide is caused by inertia. The inertia on the water on the far side resists the weaker gravitational pull of the moon and bulges.
But not all tides are created equal. For example, tidal fluctuations are more extreme around the new and full moon, approximately every two weeks. In these situations, the sun and moon are aligned, escalating the gravitational pull and inertia on the globe, causing higher high tides and lower low tides.
These bigger tides are referred to as spring tides, though they occur year-round. The smaller tides around the quarter and third quarter moons are known as neap tides.
What Is a Tide Chart
Tide charts provide us with accurate high and low tide levels and what time they’ll occur each day. The info is readily available in booklets, sheets provided by local park services, or online. Tide charts can often provide the high and low tide levels down to the exact foot and inch.
Looking at a tide chart can be a marvel with all the lunar and solar influences on the tidal fluctuations. How can we mortal humans distill all of this into a tide chart that is accurate to a tenth of a foot?
The answer is maths and a lot of computer work. In the old days, scientists used pens attached to gauges to record the changing tide intervals on pieces of paper.
Today the process is much more intricate. GPS, satellites, and radars are all utilized to collect data and feed them into computer programs. This allows tide books to be published with every high and low tide up to a year in advance.
Local geography is also taken into account. For example, narrow bays, contours on the seafloor, and even wind and air pressure can all be factors that need to be measured for accurate tidal readings.
How to Read a Tide Chart
Tide charts can look like a random assortment of dates and numbers the first time you pick one up. But once you understand the language, they’re intuitive and easy to understand.
A generic tide chart may read something like this.
Bartlett Cove, AK: 05/14/2022
H: 12:22 am 15.57 ft
L: 6:49 am -1.36 ft
H: 1:03 pm 13.83 ft
L: 6:55 pm 1.10 ft
That height in feet refers to how high or low the water is to the mean water level at the equator at the given time. It’s not unusual to see places consistently over the mean water height at the equator, so don’t panic about that. More important is understanding how it relates to your kayaking that day.
One day of tide information doesn’t provide much long-term information. But understanding where you are in the tide cycle and what a high tide for the area is can help you anticipate rough or tidally influenced water, months before you depart.
Take the above example. Between 6:49 am and 1:03 pm, the depth of the water will change 14-feet! That’s a decent amount of water moving, especially if it’s traveling through a bottleneck area like the narrow mouth of a bay or a shallow inlet.
The tide is rising or falling at its fastest halfway between the high and low tide. So, again, our above example means that the water will be rising at its most rapid rate around 10 am, probably when you want to be on the water.
Does this mean you need to sit on the beach all morning or get up at the break of dawn? No. But it does mean that 10 am would be an inconvenient, even dangerous time to try paddling through a narrow waterway where tidal rips or strong currents can make your journey hazardous.
Step 1: Find the Daily Tide Information for Your Location
This can be found in various places, with online and hard copies available for most areas. In addition, many websites aggregate tidal information several months in advance.
In national parks, state parks, and other federal or state-run sites, tide charts are common on bulletin boards at their respective visitor centers, with extra copies available, usually free of charge.
Small tide books are a mainstay of most boating, hardware, and similar stores along the coast. These little books can fit in your back pocket and hold tide charts for the calendar year. Usually, they cover a large geographic area. For example, in southeast Alaska, these small books have the tide tables from Skagway to Ketchikan (several hundred miles).
But what do you do if you are paddling in an area without designated tidal information? The tide table for Glacier Bay, Alaska is accurate for the lower portion of the bay, but doesn’t do much good for the upper reaches 65 miles away.
If the area is near a national or state park, a ranger or staff member can probably give you an estimate. Most pocket-sized tide books also come with handy adjustments for a range of locations listed after each region; these are denoted like so:
H: -0:05, L: +0.23.
In this example, the high tide for Alert Bay is five minutes before the listed time, and the low tide will arrive twenty-three minutes later.
Step 2: Look Up the Dates You’ll be Kayaking
The time of the high and low tide changes every day. The changing increments aren’t large, usually less than 45-minutes. Still, if you’re out kayaking for several days, you’ll notice the steady march of the tidal fluctuations. Especially if you’re loading and unloading your kayak again and again.
It’s essential to carry a copy of the tide chart while you paddle. Ideally, you should have it laminated so that you can have it strapped to the deck of your kayak without fear of it getting wet. If this isn’t an option, keep it secure in a Ziploc or a waterproof bag.
Step 3: Understand Chart Datum
Chart Datum refers to the lowest astronomical tide level, essentially how low the tide can get. This is usually denoted by a dotted line on nautical charts along the shoreline. Between this line and the shore will be a scattering of dots representing the intertidal area.
Having a grasp of this chart datum can help you identify ideal camping spots. For example, shorelines with a long, gradual beach often have flat ground above the high tide line, which is ideal for camping.
Step 4: Make a Note of High & Low Tide Times
This can be the difference between a relaxing evening and having to swim for your kayak. Make sure you know what time the high tide is in the middle of the night, and ensure that your kayak is far up the beach. Always tie your kayak to a living tree or something else that won’t float away.
In many areas during the summer months, the higher of the day’s two high tides comes in the middle of the night, so don’t use the high tide during the day as a barometer for where the tide will reach during the evening or early morning.
Step 5: Understand Wave Height & Interval
Of course, tides also factor into the equation while you’re on the water. One part of this juggling act is anticipating bottlenecks and where the tide will be stronger. But the other is how it can alter the overall water conditions.
Most important is watching for situations when the tide and wind move in opposite directions. In these circumstances, waves have a tendency to stack up.
When this happens, wave height can increase dramatically, and the interval between waves can shorten drastically. This can make, at the minimum, difficult paddling conditions, and it can quickly change your day from uncomfortable to dangerous.
Having an accurate weather forecast and understanding what the water will do in a given area during the flood and the ebb can be the difference between a memorable paddle and a life-threatening one. These conditions can be dramatically different depending on your location.
If you’re unfamiliar with the region and know that tides play a significant role, finding someone with local knowledge of the area is essential.
Step 6: Factor in the Weather
This ties in with step five. Winds under 10 knots (often described in marine forecasts as light and variable) probably won’t have much impact on the tide. But once you approach estimates of 15 knots or more, they should be taken seriously.
Again, watch for forecasts where the tide and wind will be working against each other. For example, say you’ll be paddling north in a bay that runs north to south, and the forecast is calling for a south wind of 15 knots. If you were planning on riding a flooding tide into the bay, look out for stacking waves as these two powerful elements work against each other. When in doubt, go to shore and wait.
While not as violent, waves and tides working together can also be dicey. You may not get the tight interval of the previously mentioned scenario, but wave height can increase dramatically. It will probably be inconvenient or frustrating if you’re paddling into this weather.
But if you’re trying to paddle across or with it, those bigger waves can be a challenge to navigate. Riding broadside to these big rollers can put your bracing skills to the test. While paddling with them makes it tough to anticipate when you’ll hit the next big wave since it’s coming from behind you.
How to Use Tide Chart Information for Kayaking
It’s not possible to explain exactly how the tide will affect your next kayaking trip. A lot will depend not just on the moon’s cycle, but the time of year and your exact location. I’ve paddled in flat, calm areas, but the water sounds like a rushing river a quarter-mile away as the tide funnels through.
Misinterpreting how water will pass through tight areas or the day’s weather forecast can make a calm day a raging nightmare. While proper planning and anticipating tidal changes can give you a sweet 5-knot boost that sends you rocketing up the strait faster than you could have believed.
When you can, travel with the tides for increased paddling efficiency. But if you’re unfamiliar with the region, consult someone who knows your paddle path and ask them how the water tends to behave during the flood and the ebb.
Common Terms Used to Describe Tides
Flood – The period when the tide is rising.
Ebb – The period when the tide is falling.
Slack – The short time frame around high or low tide where the water is relatively calm. This can be an hour or more, a matter of minutes, or in tightly congested areas, still result in tidal rips and whirlpools.
Semi-Diurnal – An area that has two high and two low tides every day.
Diurnal – One tide cycle every day. These are rarer than semi-diurnal, but occur in the Gulf of Mexico, some parts of southeast Asia, and western Alaska.
Neap Tide – Periods of lower tidal fluctuation, occurring around the quarter and third quarter moon.
Spring Tide – Periods of higher tidal fluctuation, occurring around the full and new moon.
Vanishing Tide – When the tidal change between the “high low tide” and “low high tide” are indistinguishable.
Perigean Tide – A tide of increased range due to the moon being closer to earth than usual.