Padilla Bay

Too many meetings; not enough beaches. Yesterday's meeting was at the Padilla Bay Reserve, however, so with sandwiches in hand a few of us walked down to the shore at lunch. Padilla Bay is an inactive portion of the much larger Skagit Delta - the Skagit River currently dumps all of its sediment into Skagit Bay between La Conner and Stanwood. Maybe because of the lack of fluvial sedimentation, the tidal flats of Padilla Bay are infested (maybe I should just say thick) with eelgrass (mainly zostera marina, some z. japonica). The bay is the largest single expanse of eelgrass in the Sound, although it is a bit unrepresentative of the narrow, fringing beds that characterize the steep, narrow platforms typical most everywhere else.

The gravel beaches along the edge of the bay are narrow and pretty low energy. As is typical of high-sediment areas around the margins of deltas, the transition from the steeper, gravelly foreshore to the fine-grained flats is pretty high - probably about mid-tide. On exposed beaches without big sediment loadings, the break is typically near MLLW. I suspect the original gravel beach probably extends down below the fine grained sediment and the eelgrass, though I haven’t actually checked. Presumably as the delta moved into the neighborhood, it basically buried the existing low tide terrace and lower intertidal gravel beach. If the river had stayed, or if it were to come back, the edge of the bay might all eventually turn to salt marsh as the delta front marched north.

This time of year, eelgrass can wash up in thick windrows along the beach – two distinct deposits were evident today, both hopping with amphipods and small flies.

49th Parallel

There is a nice overlook and a trail down to the beach where the big gas-pressurized electric cables cross to Vancouver Island - or so I learned from the sign. Then I walked south to the minimally marked border. I guess anyone who tries to sneak in to the States via Point Roberts is sort of foolish anyway -- it's basically a dead end. I didn't want to do anything to alarm the guys at Homeland Security, so I didn't stray to far into the U.S. Maybe a little, but it was for the sake of photos and geological observations, right?

This is a nice gravel beach with a very broad sandy low-tide terrace (it's basically the outer part of the Fraser Delta). If the causeways have reversed long-term net drift directions, it sure isn't obvious here. There's some evidence of erosion, mainly at the foot of old slides, but for the most part the bluffs looked pretty stable. There's a broad backbeach and large firs growing on the face of the slope. There is a large drainage outfall structure just on the Canadian side of the line with a small stream dribbling out onto the beach.

The Canadian side of the border has big homes hanging over the top of the bluff, but Monument Park on the American side looks like a wonderful forested shoreline. I'll have to visit it some day - but I'll come in from the American side!

Wheels

In general, I title my posts with place names, but I suppose historical artifacts are another option. If I can called one Bathtubs, I guess I can also call one Wheels. The tire doesn't appear to go with the hub, though they weren't too far away from one another. I wonder if they are Canadian, or they drifted north from the states? (I suspect the former).

English Bluff

English Bluff is the western side of the Point Roberts peninsula. The Canadian side is considerably more built up than the American side (it's basically suburban Vancouver). Homes line both the top and the bottom of the bluff. Amazing variety of bulkheads and foundations. It looks like they're on sewer at least, judging from the manhole covers in the beach.

Tsawwassen

Point Roberts began as an island in Georgia Strait, but thousands of years of sedimentation has subsequently attached it to North America as the Fraser Delta has engulfed its northern end. Now it's a Canadian peninsula that hangs down into the U.S. Last year I explored the American side (Lighthouse Park and Maple Beach). This year, I checked out the Canadian side.

Tsawwassen, which is an extension of aptly named Delta, B.C., is the site of two major causeways that extend out to the deep water at the edge of Roberts Bank. The first causeway connects to the Deltaport industrial complex, where coal and containers are loaded and unloaded. The second causeway serves the BC Ferry Terminal and extends southwest almost to the waterward extension of the U.S. border.

A gravel beach has formed on the south side of the ferry causeway, maybe from the fill material originally used to build the roadway? A pocket beach has built in the corner formed by the causeway and the original English Bluff shoreline, presumably as a result of northerly transport of material in the lee of this unintentional breakwater.

Lake Bonneville

Back when Puget Sound was covered with ice - the last time, at least - it was much wetter in Utah's Great Basin. The Great Basin was still a great basin, however, with no place for the water to get out. Lake Bonneville reached over 1000 feet in depth before spilling out it's north end into the Snake River valley. The Great Salt Lake is but a small remnant of this once much greater, and much fresher, body of water. The lake left several distinct shorelines and beaches at its margins - as seen in the benches on the hillslope in this picture (hazy due to brush fires).

Headwaters

Six weeks ago I was in New Orleans, not far from where the Mississippi enters the Gulf of Mexico. Almost 3900 miles upstream, in Yellowstone Park, the Firehole and Gibbon Rivers join to form the Madison River. The Madison joins the Jefferson and Gallatin Rivers in Three Forks, Montana, to form the Missouri River, which in turn joins the Mississippi at St. Louis. It's a long way from the hot springs of Yellowstone to the French Quarter.

Yellowstone Lake

Some of my favorite gravel beaches are these barriers on Yellowstone Lake. I saw them first by accident about a dozen years ago - although my recollection is that the lake level was considerably higher. I believe on that trip, the beaches at the north end were almost submerged, whereas they seemed just the opposite this year. I'll have to see if I have some pictures from back then.

Although the lake is ultimately volcanic in origin - it fills a large part of the Yellowstone Caldera - these beaches are built of glacial sediments. The pictures include the north end near Sedge's Creek, a beach south of Bridge Bay, and a site on the western shore north of West Thumb. Maps and online aerial imagery show many more elegant barriers around the lake, each probably jealously guarded by its own grizzly bear.

Samish Beach

This stretch of spit on Samish Bay has a complicated history, as does the shoreline to the west from which this spit is fed (see May 2006 post). Beach erosion was rapid in the 1980s and early 1990s, leading to bulkhead failures in 1996-1997. A gravel beach was reconstructed in 1998 as an alternative to building more massive walls or placing riprap. The beach continues to look good. Sediment has continued to be lost to the east, as was expected, although at relatively low rates. This past winter's storms (maybe December 14-15th, in particular) reportedly caused significant erosion at the west end and has prompted residents to begin thinking about whether some minor renourishment may be in order.

Bathtubs

Different sizes and shapes of particles behave in different ways on beaches and there are folks (mainly British, I suspect) who have spent their careers looking at ridges of disc-shaped cobbles and bands of spherical pebbles found on shingle (gravel) beaches.

Based on this limited sample of an unusual sediment type, I have found that cast-iron bathtubs on southwest facing gravel-sand beaches in central Puget Sound tend to wind up upside down and are left projecting a few inches above the beach surface. I am not sure if this is generalizable to other types of bathtubs or other types of beaches, but I am absolutely sure this is pretty much irrelevant to just about anything.