Monday, April 28, 2014
The shoreline of Point Defiance offers some interesting contrasts - as this and the next post will show. On the east side, Owen Beach is a broad gravel beach that shows little evidence of long-term erosion or accretion. Southeasterly winds blowing out of Commencement Bay probably wrap into this beach with enough energy to drive sediment northwestward. Northerlies coming down Colvos Passage do the opposite. The net result appears to be a fairly stable beach. Some new sediment may get here from the bluffs towards the Point, but I suspect most of that goes north and is lost over the edge (see next post).
The beach to the south is backed by a long seawall that supports the promenade that connects with the southern end of the park. At the northwest end, in front of the parking area, the wall ends and the sidewalk is stepped back far enough so that a modest berm and backshore remains, along with the normal drift logs. Again, it looks like a pretty stable beach, although I suppose on exceptionally high tides, waves can push debris back onto the lawn. But that's flooding, not erosion.
Farther north, concrete debris has been used to stabilize some old fill (on which a trail is built), and this is eroding (slowly) - but that's because the fill extended waterward of the natural beach profile. It would be easy to just pull it out.