Tuesday, August 25, 2015

St Mary Lake

This relatively small lake on Saltspring Island has neither the waves nor the sediment to form natural beaches and is fringed by reeds everywhere except where the bedrock plunges too steeply to provide any shallow water where vegetation can take hold. And like most lakes in the great northwest, the original shoreline was probably once a tangle of fallen trees.

This beach is artificial, probably created many decades ago by cutting the vegetation, building two small rock groins, and dumping a few truckloads of coarse sand. I suppose they may have added a little sediment since, but in the 18 years I've been visiting it, I've seen very little change. 


Like all pocket beaches, it is swash-aligned, facing the dominant wind waves coming up the lake (corresponding to the maximum fetch). There's not a lot of action on this beach. There are no tides, although there is some seasonal fluctuation in the lake level. On windy days, waves can create small (tiny) berms, but mainly they just leave a line of froth. The only significant morphological change is the result of junior engineers building boat basins and sand castles.

I thought I'd added this beach to my collection years ago, but apparently this is its first appearance in this blog.  Ironic, given I've probably spent more time contemplating this beach than any other. It does show up regularly every August in my hshipman blog (here are posts from 2010, 2011, and 2012).

No comments: