by Trudy Irvine, PaBIA Education Committee

Fine weather in Georgian Bay is always enjoyable, but most Pointe au Baril residents also thrill to the kind of storms that we had last Saturday night and Sunday morning. It is exciting to watch the rapid approach of slate blue skies and to feel the wind pick up. There is a rush to take down flags and close windows as the sky darkens and boats race home. (Somehow, we always forget to take the plugs out of the little boat, but the depth of the rainwater accumulated in the cockpit makes a handy measure of just how intense a storm has been.)

While the open skies of Pointe au Baril make for such good weather watching, the rise in water level created by the (usually) west wind makes for more intrigue. Or lately, angst. With some shore docks turned into splash pads and boathouses already in up to their knees, the surging water is more menace than marvel. Flatrock Island reported an overturned tinny drifting east down their channel Saturday evening, and a washed-out footbridge Sunday morning. By Sunday afternoon, the wind had dropped and the water flowing back west out the Station Channel was creating enormous turbulence in narrow areas like Brignall Banks. 

The elegant French word for this rise and fall of lake water with wind and atmospheric pressure is “seiche”, meaning “to sway back and forth”. Seiches can create standing waves large and small as water rocks back and forth between lake shores, much like the ripples created by sloshing in a bathtub.

It can be amazing to watch this sloshing and what I suppose are the smaller standing waves or oscillations resulting from it in smaller areas. The crevices between the east-west rock spines on Lookout Island are a good spot to look. Here I once observed water flowing quickly in one direction down a shallow channel, only to change a few minutes later and rush just as furiously in the other direction, again and again. 

Luckily, seiches in Georgian Bay are smaller and historically, less destructive than those in other Great Lakes. Click  here  more information.