Currents around Saturna Island

Saturna’s Currents Decoded

Here a link in case you missed our article titled “Saturna’s Tides Decoded”  which connects with this article.

The general direction of flood (feathered arrow) and ebb tidal streams around Saturna Island are shown in the image. Ebb and flood currents between Saturna and Pender Islands are generally less strong, and direction varies. For detailed information it is helpful to refer to the Current Atlas (Juan de Fuca Strait to Strait of Georgia) by Fisheries and Oceans. This spiral bound publication has 93 scenarios of current direction and rate for our wider area. The corresponding Murray’s Table (purchase printed or download for free (correct link when last checked September 2018)) connects each hour with the applicable page. Note that currents at Boat Passage and similar cannot be properly identified this way. Thick, fat arrows indicate strong currents of 2.5 knots and above! Be very cautious in the surrounding area.

Kayakers often travel close to shore and passing through back eddies that are circular currents running in reverse direction of the main current and are not necessarily indicated in the Current Atlas. I often look at bull kelp as I paddle to help me identify the direction of such currents.

Tumbo Channel currents always run toward East Point due to an eddie forming at Tumbo and Cabbage Islands. The only time the surface water does not move that way is when winds are stronger and force the surface water the other direction. Other than that, plan your sea kayaking trip taking advantage of the tidal stream whenever it is safe to do so (i.e. travel counter clockwise around Tumbo Island).

 

Boat Passage at Flood Current

Boat Passage at Flood Current

Visit Boat Passage once a while from shore and view it at different flow rates. You may see a still pond and an hour later a raging river. With currents as strong as 6 knots, it can run twice as fast as the speed of an average skilled paddler. At high speeds expect turbulent water with whirlpools also. If not understood, Boat Passage can become a one-way trip ending in a rescue scenario or at best a very long wait for a turn of tidal stream flow. You can however cross many narrow passages by sea kayak during a predictable window of opportunity when tidal horizonal movement turns, called slack tide. To work out how much time you have to get through a passage, you need to know slack time as well as the maximum ebb or flood of the current before and after slack (typically around 3 hours before and after). I am going to pick an example here around a new moon when tidal ranges are great. Let’s say that you want to get through Boat Passage on October 7th, 2018 and wonder when it is safe to do so. There is no current station measuring speeds and times here; data is derived from surrounding current stations. We find the numbers close to what happens. Look up maximum ebb (into Winter Cove), slack time and maximum flood currents (toward Vancouver) and click through to currents at Boat Passage (and choose the date):

Max Ebb: 4.3 knots

Slack: 9:21am

Max Flood: 5 knots

 

Apply the Slack Water Rule:

Period of Slack Water (minutes) = 60/Speed of Max Current (knots)

Period of Slack Water = 60/4.3 = 14 minutes (before slack)

Period of Slack Water = 60/5 = 12 minutes (after slack)

Total Period of Slack Water = 14+12 = 26 minutes (starting 14 minutes before slack water at 9:21, so at 9:07am)

 

This formula calculates how much time there is to safely get through a passage by sea kayak. Always arrive early, so that you can allow for variables and be flexible if conditions are beyond your skill level. If you are not sure it is safe, apply common sense and don’t cross till you have gained more skills as well as better judgement. Always be aware of your surroundings and other boats passing through, some of which are unable to move out of the way, if you move into theirs. Boat Passage is a very short passage and therefore travelling through it under the right conditions is fast. If you wanted to get through Active Pass, you want to be aware of the much longer distance and time needed to travel through it. If your paddling speed is 3 knots, just one knot of current against you, will slow you down to 2 knots. One nautical mile will take you 30 minutes instead of 20. While not the whole stretch of Active Pass encounters the strong currents, certain areas are extremely fast flowing with whirlpools and in addition ferry traffic and waves to look out for.

Great, now that you can figure out when to get through Boat Passage safely, think about the rest of your trip. Will you go to a destination beach and return in around six hours with the next slack time? Or will you carry on your journey to a different destination. If you are planning on going around Samuel Island, beware that the passage between Samuel and Mayne Island also has currents that can be significant for a paddler.

Tide, weather and current information relevant to Saturna Island can be found at the same link. Use this information for the Go-No-Go decision making process that we use in planning and launching a trip, considering various environmental factors.

In a future article I will share some insights on currents at Boiling Reef / East Point. Paddlers that were unfamiliar with the currents have gotten into trouble, needed to be rescued as well as capsized empty kayaks have floated across to US waters from here.

KayakingSkills.com provide Paddle Canada Sea Kayaking skills and instructor courses at various levels. We are planning a series of courses that will go in more detail with local weather, tides and currents, rescues and stroke clinics. Let us know what you are interested to learn more about.

Saturna’s Tides Decoded

The following information, observations and conclusions are from the perspective of a Saturna Island based Sea Kayaker and Paddle Canada certified Sea Kayaking Instructor and compiled to the best of her knowledge and experience over the past five years.

Tides move up and down, currents move side to side. Tides are actually long-period waves that roll around the planet as the ocean is “pulled” back and forth as the moon and sun interact with earth. The moon orbits earth and earth spins around the sun. The moon and sun both have a gravitational pull, strongly effecting large bodies of water. There is a repeating cycle as the moon orbits earth. The moon causes the majority of the gravitational pull. When sun, moon and earth align during full moon and new moon, the gravitational pull is amplified. Around two days later we experience the largest tides, called spring tides (think of “springing up and down”). This means that more water moves between low and high tides. During the first and third quarter moons, the gravitational pull is reduced, and we have smaller tidal ranges, called neap tides. Currents, also called tidal streams, are the horizontal effect of the tidal movement. While tides are biggest at spring tides, currents are also stronger as more water volume is pulled around earth. Due to the varied coastline and the many small islands in our area, slack water (when there is little to no current at the change of direction of tidal flow) does not necessarily occur simultaneously with high and low tide times, despite their correlation. The West coast of North America mostly experiences two high and two low tides of different heights each lunar day. This tidal pattern is called a mixed semi diurnal tide.

Which tidal station do I look up when paddling off Saturna Island? Primary tide stations that are relevant for Saturna Island are at Fulford Harbour on Salt Spring Island and Point Atkinson between Horseshoe Bay and West Vancouver. Saturna Island has two secondary tide stations: Tumbo Channel and Narvaez Bay and there is also Hope Bay on Pender Island nearby. I once wrote down tide predictions for Hope Bay, Tumbo Channel and Narvaez Bay, Fulford Harbour and Point Atkinson. I converted all the information into a graph and noticed that the difference and potential error margin for our purpose is too small to really fuss about (see graph). Especially when looking at Tumbo Channel, Hope Bay and Fulford Harbour: the graph looked almost identical for those three. Who knows, maybe I just picked a particularly good day to compare them 🙂

 

Keep predicted tide heights and possible variance due to wind and barometric pressure in mind when leaving your boat at the beach while going for walks or overnighting. Always secure your kayak with a rope too. High pressure systems can contribute to very low tides while low pressure systems can increase the height of a predicted high tide.

The Department of Fisheries and Oceans publishes tabulated printed data annually. You can buy Volume 5 for tidal stations of Juan de Fuca Strait & Strait of Georgia or get Tide information at Fisheries and Oceans. Tabulated data is easy to write down while a graph puts numbers visually into perspective and considers that tide heights increase fastest in the middle two hours between low and high tide (roughly six hours apart); both are useful tools.

Ensure that tide times are in PDT (Pacific Daylight Time) or PST (Pacific Standard Time, which you need to adjust during daylight savings in summer). In Canada, tides are measured in metres. Many websites work in feet and generate graphs which I find easy to relate to my needs. What interests us as when launching and landing a sea kayak in Lyall Harbour, is when the tide is going to be over four to five feet (by Fulford Harbour tide station). We prefer to avoid the otherwise inevitable mud battle. Intertidal zones are illustrated in green colour on nautical charts. Looking at a nautical chart for the area, you will notice how much intertidal zone there is at different beaches (look at Cabbage Island for example). Consider this when choosing launching and landing sites, especially when packing gear for overnight camping trips and dealing with low tides.

Kayaking along rocks with a large visible intertidal zone is particularly beautiful and interesting. Sea stars, sea urchins and other sea creatures, normally hidden, become visible at low tide. Take care when crossing fragile intertidal zones, seaweeds and eelgrass that provide fundamental ecosystems for the Salish Sea.

We have summarised sources of information for tide, weather and currents relevant to Saturna Island.

Use this information for the Go/No-Go decision making process that we use in planning and executing a trip, considering various environmental factors.

Ok, so we have figured out the relevant tide stations. And we understand that greater tide ranges happen at spring tides and smaller tidal ranges during neap tides. If you are looking for less currents, go kayaking during neap tides. If you are looking for more currents to play in, look for spring tides. All this is especially relevant when navigating through small passages like Boat Passage or around Boiling Reef off East Point. Our next article will decode currents around Saturna Island.

KayakingSkills.com offer Paddle Canada Sea Kayaking skills and instructor courses at various levels. We teach essential and relevant sea- man/woman -ship. We promise to educate and entertain you. You will get hands on experience with tides and currents in our courses when planning a sea kayaking trip. We help you identify hazards to avoid and risks to mitigate for your sea kayaking adventures. Our intermediate courses include current clinics in areas such as Boiling Reef, Tumbo Island and Boat Passage.

Happy Paddling!