Thursday, September 24, 2015

Seiche 'Tide' on Dorcas Bay

While further exploring the west shore of the Bruce Peninsula, on another evening we drove up to Dorcas Bay, part of the Bruce Peninsula National Park.  It's probably the best beach with public access on the northern peninsula.  And my pictures revealed a 'seiche'!

Dorcas Bay is probably the flattest beach I've ever seen.  Can you spot the people on the far distant left, not even up to their knees in the water?  It's an amazing place to take young kids wading!

It was evening and I hoped we might get a nice sunset, but this was about the nicest it got.  One reason I had been looking for public access points on the west shore was to take sunset photos.

But take a careful look at these two pictures.  I took the one above, and stood there for 10 minutes hoping for the sunset to change.  Then I suddenly realized the sand around my feet was getting drier, and the open water was further away.

So I took a comparison shot, not perfect, but almost the same shot.  You can see how much sand is exposed compared to the photo above.  This very small oscillation in water levels on large bodies of water like the Great Lakes, is called a 'seiche', and it's very like the tide coming in, but on a very small scale, only a change of a few inches.  It happens regularly,  just because the vast amount of water in Lake Huron is not perfectly flat, but sloshing back and forth ever so slightly.

Behind us on the beach there were lots of interesting plants too, though the evening light didn't capture them well.  These are one of the Ladies'-Tresses, probably Nodding Ladies'-Tresses.

These are the flowers of Grass of Parnassus, which as you can see isn't a grass at all, but a member of the Saxifrage Family.

It loves the wet sand habitat, and shows up as little white lights all over the low sands here.

And there were more Fringed Gentians, though they were mostly closed blooms in the evening.

And beyond the low sand ridge and small parking lot, is a large 'fen', a shallow wetland that is very unusual for this far south, and botanically very diverse.  But that's another story.

Dorcas Bay has a very interesting history, which I've played a small part in, as I first came here in 1962!  It was rescued from cottage development by Ontario Nature (then the Federation of Ontario Naturalists) in that year, and managed as a nature reserve for many years.  I was Chair of the committee that cared for it for a few years, and brought students here numerous times.  It was eventually sold to Parks Canada when the national park was established.  Perhaps I'll tell the story in more detail next year when I can get more pictures.


  1. Wonderful scenery, location, blooms. I had to Google this park to find out its exact location.

  2. I'd heard about Seiche tides, but never seen evidence of the effect before, so I find these very interesting as well as beautiful photos. In some ways it reminds me of The Wash, the huge expanse of mudflats and sandbanks on the East coast of England; there you can see birds far out from the beach and the water doesn't even come up to their knees!

  3. Like the water sunset. Been many years since I've been to the Dorcas Bay area but we did hit a few areas along the Lake Huron shoreline a couple summers ago when we spent a few day with our RV just south of there Totally love that whole Bruce Peninsula region.

  4. As soon as I saw the title, I remembered learning the name of a seiche tide, but I didn't know what it is. Now I do, and your pictures made it so I won't forget any time soon. :-)

  5. A nice peaceful area. Bringing up the word fen reminds me of a conversation with a British visitor recently who mentioned the area they come from is referred to as the Fens.

  6. Swampy areas are few and far between in Iowa. I can just feel it when I see it but I don't experience those areas unless I go to Minnesota. I like seeing all the plants that grow there.

  7. Very fine! The second shot is my favorite.

  8. LOVE the one shot of the sunset in the water reflection! awesome. The shallow water on Round Lake is one of the main reasons we camp there every summer. All of my children have learned to swim in that water, and it makes for great water Frisbee!! :)