I”m not sure how we managed transiting the southern Gulf Islands in British Columbia without a Current Atlas, published by the Canadian Hydrographic Service. We always consult the tide guides and noticed that often our calculations seemed a bit off. While approaching the southern tip of an island on an ebb tide, we would encounter strong current against us, instead of with us. We credited this to seasonal variations or barometric pressure and thought nothing further of the discrepancies.
“Tides in these coastal waters are caused by the large scale tidal motions of the Pacific Ocean that are a response to the gravitational pulls of the moon and sun, and their changing character from day to day reflects the complex character of that response” (Current Atlas – Juan de Fuca Strait to Georgia Strait, pg 1). When the Pacific Ocean meets the coast of British Columbia on a flood tide, water is forced against land and weaves in and out around bays, channels and islands creating rip tides, large, swirling eddies and overfalls.
The Current Atlas along with the Current Atlas Table are invaluable resources to all mariners. The tides were studied and it was determined that there is a pattern to the movement of the water and that it is possible to predict what the water would be doing at any given point during the tide cycle. Therefore, the Current Atlas is always relevant – you simply purchase a new Table every year for $5.00 – 6.00.
The Atlas has a picture of every hour of the tide cycle and shows the movement of water around the islands, sometimes in the opposite direction of the tide. The direction of the tide is depicted by arrows of varying sizes; the larger the arrow, the stronger the tide. The tide in some areas can be twice that of a typical sailboat resulting in loss of steerage. The large, back eddies and tide rips are a serious hazard to smaller vessels.
The Current Atlas helps us plan the best route to our destination while using the movement of the water to our advantage. If we find ourselves having to travel against the tide, it helps us plan a course that will receive less current. Anything that makes our cruising time more enjoyable, makes sense to me.