Working with Tidal Currents – an Example

posted Apr 10, 2013, 2:44 PM by Richard Sevenich   [ updated Apr 10, 2013, 3:28 PM ]

My wife and I have planned a September 2013 kayak vacation, using Discovery Islands Lodge as our base for day trips (yes, we're non camping wimps most of the time). Our stay at this delightful lodge, is scheduled for 5 nights with September 18 being the first of those. I decided that one of my day trips (weather permitting) would be to circumnavigate Maurelle Island. There are 2 channels on this route where significant currents can be encountered, Surge Narrows and Hole in the Wall (HitW). At my skill level, traversing these two sections with potentially frenzied water should be done near slack current.

I decided that a clockwise circumnavigation would be optimal. Then the potentially challenging sections would occur early in the day when time uncertainties were most controllable. Current tables are readily accessible via the Internet and a close inspection suggested that September 21 was as good a day as was available during our stay. In particular,

  • Surge Narrows has a slack turning to ebb at 6:13 AM [max ebb would be ~ 8.8 kt at 9:24 AM, so we can expect low current for about 12 to 15 minutes]

  • the ebb would be a help rather than a hindrance as we continued toward HitW

  • the next available slack at HitW would be at 12:38 PM, turning to flood so we would need to hang out somewhere like Francisco Island once we got close to HitW ... and wait

  • the early minutes of the flood would be a help going through HitW [max flood would be ~ 8.4 kt at 3:27 PM, so we can expect low current for about 12 to 15 minutes]

So the plan is as follows (with selected distances from start):

  • leave the lodge about 5:45 AM i.e. be on the water at that time

  • enter Surge Narrows at slack (6:18 AM) or very shortly after

  • maybe stop for breakfast at Yeatman Bay [at ~ 2.3 nm]

  • subsequently set off for Francisco Island, where we'll wait and maybe have lunch [at ~ 6 nm]

  • enter HitW at slack (12:38 PM) or very shortly after

  • hang a right once we reach Calm Channel [at ~10.3 nm]

  • and eventually another right at Whiterock Passage [at ~14.4 nm]

  • head for the lodge [at ~19 nm]

I have previously traversed Surge Narrows a number of times, but am unfamiliar with HitW. The entire channel comprises an approximately 4 nautical mile stretch. The chart suggests that the rapids are concentrated at the west end i.e. our entrance to the channel. Aided somewhat as HitW turns to flood, I could expect to traverse the rapids well before the peak, expected to be 8.4 kt. So if we hit the entrance spot at slack, we'll be fine. Nevertheless, to be sure I needed local knowledge, so I queried the West Coast Paddlers Forum and received a reply that this plan should work.

Plans of this sort are prone to errors. For example, are the slack times correct? In fact, one table gave times in PDT, the other in PST - better catch that! Missing slack time by an hour makes the plan worthless. One must also double check that the data are for the right day of the right year etc. Once the plan is debugged and solid, the weather can still destroy all your careful work. The day of circumnavigation can easily become a day to stay off the water and read a book. Nevertheless, whether the plan goes smoothly or goes awry, the planning process itself is a valuable learning experience which will pay future dividends.