Sunday, August 21, 2016

Jackson Rock

Fulford Harbor, like pretty much everything else on Saltspring Island, is oriented NW-SE, reflecting the underlying geologic structure of the islands sedimentary rocks. Last week, during our annual trip to the island, I paddled from the head of the harbor out to Wen,Na,Nec (August 2013) and Jackson Rock, then back on the other side.


The northeast side of the harbor (the Fulford/Reginald Hill side) is steep and rocky and there are few beaches. The southwest side (from Drummond Park out toward Isabella Point) is a little more gradual and includes both more erodible glacial? sediments and a stream mouth or two, so the beaches are a little better developed.

Here on Jackson Rock, the only material available to build the tiny beaches is broken shell. And the orientation of the beaches and bars is a messy function of the islets' irregular configuration and bathymetry.

Sunset Beach

Sunset Beach is actually several beaches, held in place against three large rock groins just west of the Burrard Bridge on the north side of the entrance of False Creek. The inner shorelines of English Bay are oblique to the dominant wave action, which arrives from the west (roughly), so beaches don't stay put unless there's a natural promontory or an artificial structure of some sort for them to pile up against.


Looking at English Bay from the air is useful, since it shows the westward orientation of the beaches not just on Sunset Beach, but also the larger beach farther west on English Bay (December 2014) and the beaches in Kitsilano (May 2016) on the south side of the bay.

This last photo shows the seawall and path just west of Sunset Beach - I guess it illustrates the challenge of creating and maintaining beaches where the orientation is wrong (especially where there is also no sediment).

Friday, August 19, 2016

Clam Bay

There are enough constructed beaches on Puget Sound, and Puget sound is large enough, so that it's easy to lose track of some of them. Including some of the nicest ones. Particularly when they're located a little off the track. This one, which I last visited in October 2010, is located in Manchester, pretty much in front of the Manchester Environmental Lab (EPA and Ecology). It is a secured area, so professional interest is tolerated, but a lunch stop with the kids would be frowned on.


The "Shore Protection System" (some might call it a gravel beach) was built in 1999-2000? as part of cleaning up and capping the old Navy dump site (nothing like a little lagoon behind a spit in which to dump stuff, then burn it for fire training exercises). The Corps is responsible for occasionally checking on how it's doing, but I don't know if there has been any tweaking of the original beach work. Frankly, it looks like it's doing just fine.

This is a really neat beach. It has a slightly engineered look, particularly the coarse gravel storm berm, but what a great alternative to the rock revetment that might have been built otherwise. Remind me someday to figure out how to draw more attention to these projects!

Manchester State Park

This is the second of three posts from Manchester in south Kitsap County. Each from a very different kind of beach! Here on Puget Sound, we don't go for that notion of miles and miles of unchanging beach - we'd rather keep people guessing.


The State Park is located just inside the mouth of Rich Passage. It's located near the trace(s) of the east-west Seattle Fault and the upland consists of the terrace raised by movement on the fault. The shore here is basically a small pocket beach, fed by erosion of the low terrace on both sides. The erosion on the west side had begun to threaten the roadway (now a path) and within the last few years an effort was made to protect the low scarp by using anchored logs backfilled by gravel.

It looks to me like there have been some problems - waves have scoured behind the root wads and the path is still vulnerable (just the edge, nothing's going away very fast). This is a tricky site - the wave energy isn't terribly high, but there's little protective beach on this obliquely-oriented, sediment-starved reach, so eroded sediment is rapidly swept farther into the cove.


Pomeroy Park, in downtown Manchester (not to be confused with the grittier versions in England and New Hampshire), is a nice centerpiece to the small community's waterfront. Which contrasts nicely with the distant Seattle skyline.


I noted this site and the elevated boat ramp several years ago: Manchester: October 2010

Kitsap County recently completed an innovative stormwater project in town and the new outfall was integrated into the base of the pier. This is an interesting design and personally, I like the idea of allowing stormwater (relatively clean stormwater, at least) to run out across the beach much like a natural stream.

This does pose some coastal design issues, though, since the stream can erode sand and gravel on the upper beach and transport it to the lower beach. During heavy flows at low tide, this may result in a channel of sorts and this in turn can lead to localized erosion on adjacent banks. This has been addressed in part with a series of tiered logs backfilled with gravel. Fortunately, this type of erosion can be fairly ephemeral, and as long as there is adequate sediment on the beach, can recover quickly.

Traditionally, one approach to reducing erosion below an outfall would have been to construct an apron of angular rock across the beach. The irony is that this would have protected the beach from erosion by burying it under rock. I'm glad they didn't do that here - or at least if they did, it's below beach grade.