Wednesday, March 25, 2009
Birch Bay is a complicated story of beaches and coastal history and would take longer to tell clearly than I have time tonight. Maybe another time - either added to this post or in a new post. But meanwhile, here are groins, seawalls, and a mile of state park.
Tongue Point is the northern tip of Semiahmoo Spit - at least that's the easiest way for me to distinguish the two somewhat overlapping place names. This was the site of a large cannery, and a small town, for much of the earlier part of the last century and many of the old buildings and wharves remain.
The historic structures have divided this shoreline into three separate sections of beach, each with a different texture and composition. The western segment, under the old piers, is gravelly sand that made it past the bar (see the previous post). The central segment is all sand. The eastern crescent beach is sand and gravel with lots of broken shell.
What better location for a Canadian-U.S. workshop on sea level rise than a large resort built on the tip of a spit within a stone's throw of the international border and within a meter of high water.
Semiahmoo Spit is located at the distal end of a drift cell that begins about 5 miles south near Birch Point. For thousands of years, sand and gravel has traveled north, traversing the mouth of Drayton Harbor on this slender strip of land, and then disappeared under the bar. Seriously, the beach just sort of runs under Packers Lounge, then shows up on the other side as the slightly mellower beaches of Tongue Point (next post) at the tip of the spit. Packer's would be an appropriate location for some future meeting of coastal geomorphologists - the bar at the end of the beach.
The distal portion of Semiahmoo is large, particularly when compared to the narrow neck of the spit that you have to cross to get to it (see the aerial - click on the title of the post). Most of this land was built up with fill (dredged from the channel and the marina, I assume), so it has a couple foot headstart on anthropocene sea levels -- though it will become increasingly hard to get here, or to get away from here, during the big storms that will toss gravel and logs over the access road. Fortunately, most of the development on the spit has been kept away from the shoreline and except for the riprap that protects the neck, the beach is in good shape - except that in some places it is backed by an unnatural eroding bank of fill.
Sunday, March 22, 2009
I dropped the guys off at the South Park playfield for their Ultimate game on Saturday afternoon and then headed for the river (there are a few more pictures at hshipman). The Duwamish is a straight line here, long removed from its original meanders and heavily lined with concrete debris and riprap. Except at this little sandy beach at Duwamish Waterway Park, where a small cove has been created. The only waves here are from passing boats.
Just downstream, the Port of Seattle (or is it the City?) has just created a nice little public access at the end of 8th Avenue South, where until 1937 there was a bridge. I assume the wall of big anchored logs is to improve habitat and to provide protection from boat wakes for new plantings on the bank. There's a little gravel ramp for launching small boats or dipping one's foot in Seattle's poorly treated and long overlooked river.
The Duwamish has suffered from over a century of replumbing. It is basically the lower Green River, carrying whatever the Corps allows to flow past Howard Hanson Dam. The White River used to flow to the Sound this way, but long ago it was pointed south and now it flows out the Puyallup in Tacoma. And the Cedar used to flow this way, too, but then they lowered Lake Washington and built the ship canal and now all its water and its salmon flow out the Ballard Locks to Shilshole Bay. Good thing salmon are adaptable. Too bad there are so few left.
Friday, March 13, 2009
Onamac is one of several similar landforms along the west shore of Camano Island - and such a common type on Puget Sound that I suppose we really need a better name for them. Or a name at all. I might call it an assymetric looped barrier (in private) (title of post links to an aerial view). It's hard to call it a cuspate foreland, or a recurved spit, because those don't quite fit (though they are close) and the more generic names like accretion beach, depositional shoreform, constructional landform, or low point are too broad. We were visiting this private site last week because it's a dead ringer for Kayak Point, a few miles east on the eastern shore of Port Susan. And we needed an analog to explain to the Parks folks the rationale for proposed improvements at Kayak Point.
The high bluff north of Onamac is an impressive perch for a bunch of big homes with outstanding views and an abrupt edge to their lawn. This is also the only place I am aware of on the Sound where we have good evidence for a large landslide that involved both the bluff and the submarine slope. This huge headscarp is matched by an enormous slide block on the bottom of Saratoga Passage (see Whitaker's UW senior thesis). Must have been an exciting ride - and maybe a big splash, too. With better coastal bathymetry, maybe we could identify more of these things.
Wednesday, March 11, 2009
In previous years, we've brought this class to Kala Point, but this year we shifted things around and headed to Marrowstone Island and Fort Flagler instead. Marrowstone Point is a cuspate foreland at the northeastern tip of the island, fed by sediment from the eastern shore of the island and a short stretch of bluffs on the north. The north side has been turned into a dike and armored with riprap, the better to protect the point from whatever it is that it didn't need protection from for the previous two thousand years (and pretty much eliminating the high tide beach and the backshore). Right at the base of the point, where the bluff starts to rise, there's a big glacial boulder eroding out of the till, along with an old military pillbox or something of that sort. Someting to measure future erosion against.
The bluffs northwest of the point have been impressively collapsing for the last three years, dumping sandy sediment onto the beach (the pictures of the bluffs this trip were really dark, but there's a nice slightly outdated one at Fort Flagler, May, 2006) . I don't know of another 1/4 mile stretch of shoreline in the Sound where this much erosion has happened so quickly. Locals report a significant loss of kelp, which the heavy sediment loading might help explain, but the kelp started disappearing long before this recent episode of mass-wasting and has been disappearing in other places where erosion isn't a clear culprit. There's so much that we don't understand about this system!
Wednesday, March 04, 2009
Of the class of 40 or so people here to learn about climate change, only half a dozen or so probably wandered down the 200 yards to the overlook at the bluff. The classroom at the Reserve is nice, but the shore is always better. The tide was out, exposing not just the narrow gravelly beach, but miles of tidal flats and matted eelgrass waiting to be floated by the next tide.
A couple interesting things illustrated by the photos. If you look carefully, you can see a gravelly fan extending out across the flats - this is typical wherever a small stream reaches the beach along here and at lower tides spreads the sand and gravel seaward. The tree shows how you can use vegetation (big straight-growing conifers, at least) to infer the history of bank stability. This tree suggests two episodes of instability - one, many decades ago, when a young tree collapsed and a branch took over vertical growth, and then a more recent event that caused the vertical trunk to tilt landwards as the roots slid. Or something like that.
Tuesday, March 03, 2009
The Port of Olympia sits on a promontory of fill at the southern end of Budd Inlet, at the mouth of the Deschutes River. Its northern shoreline faces up the inlet and wave action is primarily from that direction. Not surprisingly, the artificially imposed shoreline erodes if not protected or otherwise managed. They've done a nice job of cleaning up and redeveloping this area and this shoreline is an improvement over the industrial mess of a few years ago, but it looks like maybe they still have some problems to work out.
I suspect the intentions were good. Maintain a softer shoreline and avoid simply riprapping the eroding bank (the way it would have been dealt with 60, or even 10, years ago). The problem is that there's nothing to prevent ongoing erosion of the gravelly beach face and it is going to gradually retreat and undercut the large line of boulders. A couple have already begun their march down the beach. I suspect that in order to maintain a soft shoreline here, it may be necessary to add some more gravel and some sort of sill at the west end (maybe under the restaurant?) to keep the gravel from getting away.
Priest Point Park, just up the inlet from here, is a nice leftover piece of original South Sound shoreline.
I probably should have titled this post "Capitol Lake," just to avoid controversy, but after all, it is the mouth of the Deschutes River and it would be an estuary were it not for the inconvenience of a small dam under 5th Avenue. I'm not sure it's fair to call this a beach since there isn't enough wave energy to move the gravel around very much. I suppose it would look a little different if the 15' tide was restored to this placid little reflecting pond.
The shoreline runs almost east-west between Elliott Point (Mukilteo) and Everett and the result is beaches with exposure from the north, but that are largely protected from the more common southerly storm waves. Drift still tends to be west to east (towards Everett), but the shoreline is largely swash-aligned and net transport rates are probably pretty low. The shoreline intersects several north-trending stream gullies - Japanese Gulch, Powder Mill, Merrill and Ring, Pigeon Creek, and others. Each stream emerges through a culvert under the railroad grade and spills across a small delta.
The protruding deltas may act a bit like groins, segmenting the shoreline into somewhat independent compartments. And the stream deltas probably greatly complicate cross-shore sediment behavior - gravel gets transported by waves higher on the beach, but then gets transported offshore by the streams during lower tides. Whether or not the streams are major sources of terrestrial sediment (debated), the stream deltas are probably signficiant sinks for coastal sediment.
Monday, March 02, 2009
The steep rocky coastline along Chuckanut Drive is built of 50-million year sandstone. It contains beautiful tropical fossils since it used to be warmer around here -- or at least these particular rocks were at a warmer latitude back then (sorry, no photos of them this trip). And the salt weathering at beach level leads to wonderful honeycomb patterns in the rocks. I'll have to spend more time up here when I have more time and when the sun makes for better pictures.
Clayton Beach is at the southern end of Larrabee State Park, a 10-minute walk down the old interurban line, which headed "out to sea" here, running on piles in the bay parallel to the shoreline all the way to the McElroy Mill (long gone) at the south end of Chuckanut (historic photo). The Great Northern had already used up what little space there was along the base of the cliffs in 1902, forcing the trolley to choose the marine route. The interurban stopped running at the beginning of the Great Depression (the First Great Depression?), but the piles are still sticking out of the beach and there is a strange rock and timber structure further offshore - maybe a breakwater?
I don't know the story behind the eroding sandy bluff behind the the beach. It's rich in clam shells, but I wasn't sure whether it was a natural deposit or some sort of fill associated with the construction of the railroad. Time to do some holework - or come back for longer. I liked the way the sand from the eroding bluff spread down across the upper beach to end in such a distinct line against the gravel.
Before it became Taylor Shellfish, this little point was the base for Rock Point Oysters. To get down here you follow the Taylor sign at the hairpin on Chuckanut and drop down Oyster Creek to the tracks. There's a small marsh at the creek mouth trapped behind the railroad grade (which was built around the turn of the century) and a few dilapidated buildings, remnants I suppose, of the camp that housed the convicts who built Chuckanut Drive in the 1920s.
The shoreline is typical of this southern section of Chuckanut - steep rocky slopes plunging into the deep mud of the bay. There's not much beach down here, since the railroad sits on top of whatever beach there might have once been. The beaches in these pictures are artificial pockets, created by human structures. That's not all that's anthropogenic. The stream mouth is kept from meandering across the oyster beds by a rock dike and the area around the oyster operation is a 20th-century shell midden (historic photo).
Little Mountain, just southeast of Mount Vernon, provides another great overview of the Skagit Flats. The Skagit flows through Mount Vernon in big sweeping, levee-lined bends, then splits into two distributaries (the south fork and the north fork) which create two sides of triangular Fir Island - the third side of which is Skagit Bay. As the river has grown out into the Sound, it has gradually engulfed islands which are now hills amidst the delta flats. In addition, as the delta reached Fidalgo and Samish Islands it created three separate bays - Skagit, Padilla, and Samish. The southern portion of the Skagit overlaps with the northern edge of the Stilliguamish Delta, although Camano Island now forms a fairly clear demarcation between the two.
Two posts from high points above the greater Skagit Delta. This one is from the Samish Overlook above Chuckanut Drive, which provides spectacular views of both the northern Skagit Delta (now adopted by the much smaller Samish River) and the San Juan Islands. Nice contrast of river delta and rocky coastline.
The Skagit River now flows out to the southern portion of this great flat piece of farmland, but the Skagit, Samish, and Padilla Bay areas are all basically part of the same system - and a bulk of the sediment is probably Cascade Mountain dirt delivered by the Skagit River. The foundation of this delta may be Fraser sediment, since as the ice receded, that much larger Canadian River may have dumped into this area, too, though not for long as it shifted north a dozen millenia ago.
The seaward edge of the delta along Samish Bay (seen here) has been heavily diked for a century or more. And it's been longer than that since the Skagit actually flowed into this northern bay - except perhaps in an occasional really big flood?
Big Lake is one of dozens of medium size lakes scattered across the Puget Lowland. Like most of them, it was probably once lined with thick forest and the shoreline was probably choked with fallen trees and drift wood. Now the trees have been cleared, the water levels altered, and the local watershed is filling up with suburbia.
Except on the largest lakes (like Lake Washington), there probably wasn't sufficient wave action to form beaches, and even where there may have been, they would have required sand and gravel and not too many fallen trees. At this little postage stamp of public shoreline on the west side of the lake, it looks like gravel was brought in from elsewhere to create a little beach next to the boat ramp. Without housekeeping, the reeds and the forest would eventually take this site back over.