Tuesday, January 19, 2010
Waves from the south sweep into Canada's Boundary Bay, eroding bluffs and creating spits on both ends of the bay. On the west side, Point Roberts gradually gets reconstituted into Maple Beach, Centennial Beach, and Beach Grove. On the east side, the equivalent landform is Crescent Beach. This appears to have been a large spit (maybe a series of spits) extending northward into the corner of the bay.
Now much of the historic spit and back barrier wetlands have been converted to homes and streets, but the basic feature is still discernible in the aerial view (click the title of the post). Blackie Spit - next post - is about all that remains in a relatively natural state. The berm and backshore along the main part of Crescent Beach has been built up into a dike, in places armored with rock, that protects the low-lying community from storms and high tides.
Crescent Beach is a case study in groins. Larger and smaller, older and newer. Some of wood, some of rock. I guess the basic rationale is that there's a limited amount of sediment moving north along this shoreline and the groins offer a way to slow it up, maintaining beaches that would otherwise go elsewhere. At least for a while - and then they are gone.