Monday, May 12, 2008
Chambers Creek arrives at Puget Sound from beneath a railroad bridge. The stream mouth began as a barrier estuary with a couple of spits at its mouth, still evident in the aerial (click on title of post) and in these photos, though they've been partially lost beneath boat storage sheds and fill. This poor little estuary has suffered more than just the loss of its spits. Its watershed is paved, there is a weir at the head of the small bay that turns the upper estuary into a lake. And the thick forest that once lined its banks is long gone. Industries along its shores have died, only to be replaced by big homes climbing up the surrounding slopes.'
The shoreline for a mile north of the creek used to be high gravel bluffs. What's left of the bluff is now 1/4 mile or more inland and all that gravel is the aggregate in Puget Sound's highways and skyscrapers. But the mining is all done and I understand the new golf course is almost done, too. One of these days I've got to check out the narrow strip of beach left on the west side of the railroad tracks.
The original beach was back at the base of the bluff, under what has been the railroad tracks for the past 100 years. This rounded point is originally the byproduct of a gravel loading operation and has had a varied history, including being a sewage treatment plant, before finally becoming a park. Trouble is, big piles of gravel pushed onto the beach tend to wash away. This place ended up with a timber seawall. And two attempts to nourish the beach with sand from the nearby Chambers Creek pit. That washed away, too. But in the mid 1990s the City of Steilacoom removed the old seawall and reconfigured the shoreline. It's been doing remarkably well ever since, although some fine tuning (maintenance, adaptive management) is probably in order.
It's basically an artificial gravel beach, but in one segment demands to protect a fairly high upland area and some popular trees forced a steeper slope than nature could sustain. Wolf Bauer proposed this intriguing double bulkhead approach. I guess it's a variation on a perched beach. The lower bulkhead is perforated, to allow drainage of the upper tier during high water events. The beach may have dropped a little in the last decade, but not very much. I should chase down the measurements I made back then. This is by no means an approach we would recommend widely. I doubt it provides the ecological value of a natural beach - it certainly disconnects the back beach from everything else- but it is a nice alternative to the very high wall that would have been required otherwise. I have never seen anything else like it on the Sound - though I did once see something described on Lake Michigan that looked remotely like this.
Saturday, May 03, 2008
Unfortunately, the early 1990s photo linked to the title of this post predates the major work done at Seattle's Southwest Harbor container facility and the creation of this great, but poorly publicized, "industrial" public access site along the shoreline. A wonderful trail links several great overlooks of Elliott Bay port operations and the Seattle skyline. It's easy to get find - the turn off is just south of Salty's on Harbor Avenue.
Within the last couple of years, a couple of gravel pocket beaches were created along this shoreline. Until recently, I hadn't been aware of them. I like the concept of building beaches on industrial shorelines, but I'm puzzled by these. They both have a high gravel berm that rolls back onto a much lower backshore. Maybe they were built exactly like this, but it looks like maybe they were built with a lower berm crest and a flatter slope and nature has simply pushed them up into their current form. Orientation is a key design element (well, it should be) on artificial pocket beaches. The western beach (top photo) is at an angle to the primary wave action, as best as I can tell, so I expect material will shift southward with time. The angle on the eastern beach (lower photo) makes more sense, but I'm not sure what would keep the gravel from spilling out of the far end.
Regardless of their geology, I hope keeping them fenced off isn't part of the long term plan.
Piner Point, at the south end of Maury Island, is a beautiful stretch of undeveloped shoreline, with gradually eroding bluffs and trees hanging across the beach. Just around the corner to the northeast, the beach briefly widens to form a sandy backshore (in front of a seawall). This is a pattern observed in many places on the Sound and is probably related to the fact the change in shoreline orientation results in a decrease in the potential rate of longshore transport and accretion occurs. The beach then continues north along a shoreline characterized by high bluffs and lots of gravel (a point important to both the industrial history and the modern politics of this island).
One of the more interesting recent seawalls on Puget Sound can be seen in the lower picture - a wall designed to allow sediment to be artificially fed to the beach.
Another shoreline with a complex 19th and 20th century history, mainly involving boats and boatyards, the remains of which can be found on this beach and on to the northwest. This appears to have originally been a small stream mouth, marsh, and low-energy beach. Wave energy is low, but sufficient to maintain a beach of medium gravel among the riprap, historic artifacts, and remnant marsh exposed on the shore (the presence of marsh on the beach face is due to the low wave energy, the presence of eroded marsh soil at beach grade, and probably the abundance of freshwater seepage). This may have begun as a small barrier beach with a back-barrier marsh, or more likely, a low, freshwater wetland, with a narrow beach across it's eroding front. Or a combination of both.
The park itself consists of a parking lot and boat ramp, along with a concrete seawall behind the minimal remaining beach. In the 1970s, we pumped state money into building parking lots on the beach - the better to sit in your car and watch the birds with your engine running. The stream itself emerges from a pipe near low tide. To the west, there's a chance to remove fill and riprap, rebuild a wetland and barrier beach, capture the upland drainage and create a stream mouth, and add some historic interpretation and recreational benefits as well.
This small estuary was originally separated from the north end of Quartermaster Harbor by a spit, with a tidal inlet at the east end. Early on, a road was built across the spit and the entrance changed, first to the west end (where old box springs now help to plug the gap) and then to the center, where a decaying wier now maintains a minimum elevation to the lagoon. The geometry of the artificial channel creates currents that have scoured out the area just inside the entrance. The beach itself has been largely buried by fill and the rubble placed to keep it from eroding away.
The name shows the hand of early inhabitants with grand visions. Located at a small stream mouth on the west side of Camano Island, between two points formed of glacial till (or something similar) and marked by large boulders, this site has been a town, a mosquito fleet port, and a tourist camp - it is now an assortment of old and new homes, some built to conform with property boundaries constrained by the geologic and the human history of the site.
The construction is largely wrapped up and the park will open in June (Cama Beach State Park, see also hshipman).
The shoreline just north of the point has always been the most dynamic section of the beach in terms of the formation and subsequent erosion of storms berms. I suspect it is particularly sensitive to the different effects of wave action from south and north. Many beaches are exposed to waves from two directions, but those near the tips of points, where shoreline orientation changes rapidly, seem more likely to exhibit profile changes in response to different wave conditions. It helps when there is sufficient sediment to provide a response.
It is often easy to see where the natural beach wants to be, even on a heavily intruded shoreline. The beach contours, including the distinct gravel berms, curve into the seawall as if the structure wasn't even there. Maybe this is a reminder that we too often focus on the potential complex interactions of seawalls and waves and beaches, rather than looking at the obvious - the fact that the beach has simply been buried - or as in this case, the beach has continued to shift landward, despite the presence of the concrete wall. The wall has "moved" seaward over the past several decades as the beach has shifted position around/beneath it.
This beach is remarkable in the large proportion of clam shell - much of it intact. I suppose it changes the overall density and particle mobility of sediment and may contribute to the propensity of this beach to build steep, narrow berms. Once the park opens, I wonder if the foot traffic will affect the preservation of these beautiful whole-shell berms?
English Boom, on the northern end of Camano Island, and facing across Skagit Bay, lies on what I guess I call the delta fringe. In an unengineered world, this beach would be destined to become part of the southern Skagit Delta, as the river gradually captures northern Camano. Although exposure to the north is significant, wave action is muted by the broad tidal flats and the lower shoreface is dominated by fine-grained (probably fluvial) sediment. There is salt marsh vegetation growing in patches on the beach. Rockweed grows among the marsh patches and on the iron and wood relics of the historic log booming operation. Despite the delta's heavy influence, this is still a sand and gravel barrier, with a large salt marsh (covered with drift logs) between it and the heavily forested bluff.
Blogs require honesty only in posting dates (all else is suspect). This one is out of order - I forgot it earlier - and belongs back on Camano on Tuesday, not in the midst of Vashon/Maury beaches from Thursday. But I can't go back and insert it where it belongs. (Never mind - now it's back in the proper order. See comments below)