Print Page   |   Sign In   |   Register
Community Search
VI Mid-Island 2020 - Tides and Currents via Zoom
Tell a Friend About This EventTell a Friend
VI Mid-Island 2020 - Tides and Currents via Zoom

Open to all BCA members! This is a 2-night must-do for your summer cruising so you can confidently tackle the tides and currents of our coastal waters.

2020-06-25 to 2020-06-30
When: June 25 (Thurs) and 30 (Tues)
Where: Online Zoom Meeting
Contact: Kate Swangard

Online registration is closed.
« Go to Upcoming Event List  

Course Information

Through this course you will realize that there is a lot more to learn about tides and currents than just reading the basic information on your tide table book or smart phone.  You will find out the most reliable sources of information and why they are the best.  Learn how to predict tides and currents when no daily predictions are available.  Learn about tide and current effects from the North Coast to the Strait of Juan de Fuca.


Day 1

7:00 PM to 9:30 PM (2 hr presentation with ½ hr for questions)


The forces that raise tides

·       Tidal forces drive currents

·       Types of tides

o   Spring Tides, Neap Tides

o   Large tides, small tides

o   Diurnal tides; semi-diurnal tides; mixed, mainly semi-diurnal tides

·       Meteorological modification of tides. Effects of:

o   Low pressure, high pressure

o   Onshore and offshore winds

Tide prediction and current prediction

·       Constituents and how they affect  predictions

o   Quality of predictions is based on quality of constituents

o   Knowing where your tide data comes from and why it matters

·       Different sources, different quality of information

o   Various tidal data sources and rating their quality

·       Reference stations and secondary stations

o   Calculating tides and currents at secondary locations for which daily predictions are not provided

·       Estimating intermediate tidal heights

·       Estimating intermediate current speeds

The nature of tidal currents: Why and how they form and how they affect the boater

·       Tidal waves (not tsunamis) and how they generate currents

o   Tidal currents in landlocked systems

o   Tidal channels between two tidal basins

o   Tidal currents in estuarine (river) systems

o   Laminar vs turbulent flow

·       Tidal Rapids

o   Anatomy of tidal rapids

o   Challenging tidal rapids

o   Characteristics of Tidal Rapids


Day 2

7:00 PM to 9:30 PM (2 hr presentation with ½ hr for questions)


Wind, waves, currents, and their interactions.

·       The effect of wind opposing currents

o   Standing waves

·       Shallow Water effects

o   River Bars

Local tide and current effects

·       Juan de Fuca

o   Deception Pass, Admiralty Inlet

o   San Juan Islands

o   Puget Sound Current Atlas

·       Georgia Strait

o   Areas of greatest fetch (Cape Mudge, Sand Heads)

o   Gulf Islands

o   Strait of Georgia Current Atlas

·       Johnstone Strait system

o   Current Atlas of Johnstone Strait system

o   The very real effects of Coriolis force, Johnstone Strait sill, back-eddies

o   Johnstone Strait as an estuarine system

o   Why there are times when Johnstone Strait does not have a flood current for several days at a time

o   The surface flood current is suppressed as far as Pine Island

o   Strategies for transiting Johnstone Strait and conflicting weather conditions

o   Transiting Yuculta Rapids/Gillard Passage/Dent Rapids

o   Transiting Greene Point Rapids/Whirlpool Rapids

o   Transiting Seymour Narrows

·       Queen Charlotte Strait

o   Slingsby Channel

o   Nawhitti Bar

·       Central Coast

o   Hakai Pass

o   Jackson Narrows

o   Kildidt Lagoon

o   Myers Narrows

o   Higgins Passage

·       North Coast

o   Headland effects

o   Wright Sound—Sailing Directions

o   Grenville Channel

Note that a PDF of the power point presentation will be provided.


Prerequisites and Materials



About the Instructor

Kevin Monahan is a retired Canadian Coast Guard officer with more than 20 years navigating the British Columbia coast as a patrol vessel captain. He has also worked on fishing boats, ferries, and coastal transports. Kevin was Superintendent of the Canadian Coast Guard’s Office of Boating Safety (Pacific Region) from 2001 to 2005 before joining Transport Canada Marine Safety National Headquarters. Retiring from public service in 2012, Kevin now splits his time between publishing (Ports and Passes, The Radar Book, etc.) and teaching nautical subjects to commercial and recreational mariners. In 2013 he was awarded the Queen Elizabeth Diamond Jubilee Medal.



Thurs June 25 and Tues June 30, 2020



1900h to 2130h



Zoom Meeting

(Note: You do not require a subscription to Zoom to participate. Register, and we will send you an email with the link a couple days before the course.)



BCA Members:

$40 ($25 for one spouse/partner if registered at the same time)


$50 pp ($35 for one spouse/partner if registered at the same time)


Maximum Class Size




$15 non-refundable until June 23 @ 5:00 pm.  After that there will be no refunds.


On your honour

  • Do not share the Zoom link and password with anyone.
  • For copyright and privacy reasons, we ask that you don't record the session. (You will receive a PDF of the PowerPoint presentation.)
  • No eavesdropping please. If more than one person is attending online then please pay accordingly. Course fees are how we pay instructors, admin, and overhead. This is how we are able to continue offering quality courses to all our members at such affordable prices.


Sign In