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
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.