Fox Island

The old dock at the southeast end of the island wasn't in very good shape when the state picked it up 20 years ago - but now it's a nice little piece of public shore on an island with very little of it. The dock is now a fishing pier. There wasn't much beach given the high tide - it disappears under the trees to the south - and under a private bulkhead to the north.

Rosario Beach

Rosario is a pocket beach, trapped in a small cove just north of Rosario Head. It's a steep, gravel beach with a series of high storm berms, topped with big logs, separating the ocean from a small back barrier wetland. The southern part of the beach is in Deception Pass State Park, while the northern part is private.

The beach has a "classic" log spiral form (I suspect any curved beach can be made to fit a log spiral if one tweaks the coefficients correctly, but the point is that the curvature of the beach is tightly wound at the south end, but then relaxes to the north). This results from the southwesterly waves wrapping (refracting and diffracting) around Rosario Head. Click on the title of this post to see the aerial image in Google Maps.

Weaverling Spit

This little point in southern Fidalgo Bay is a little hard to decipher, but I suspect it is basically a rocky island separated from the rest of Fidalgo Island by a tombolo. The tombolo, which probably once harbored tidal wetlands and a native community, is now covered in fill and RVs and an old railroad grade (which is now a bike trail). There are small pocket beaches on the north side (not really pockets, since drift can get past at low tide) of the rocky point and a small spit at the eastern end (aerial photo - courtesy Google).

The railroad used Weaverling to launch it's trestle across the bay and the resulting causeway has altered the southern shore of the point. The causeway and trestle has probably had several effects. It must have altered tidal circulation at the south end of the bay and may have reduced the exposure of the southern end of the bay from the rare northerly storms. It protects the little spit at the tip of the point from southerly wave action - there was never much due to the limited fetch, but now there's none. This might be expected to lead to small shifts in the configuration of the feature over many decades - but since change would be driven by those rare northerlies, it might take many decades for much change to occur. The causeway has also created a long skinny, rock-lined lagoon on the south side of the point.

Fernwood

Saltspring is a pretty rocky island and beaches are scarce. This year I tried to get to the tombolo at Walker's Hook, but gave up in the face of mud and private property (yes, these Canadians are just as proprietary about their beaches as us Americans). Clearly, I need a boat.

Fernwood is on the northwest shore of the island, not far from St. Mary Lake where we stay every year and across the road from the Raven Street Market where we occasionally come for pizza. And now there' a coffee place, too, so I have another excuse to come down to the beach early in the morning before everyone else gets up.

The beach is a thin gravel one, anchored by outcrops of steeply dipping metamorphosed sediments and scattered glacial boulders.

Beach Grove

The beach at Centennial Park runs out of steam as it heads north and is eventually replaced by a dike. But where the dike turns west (at 12th Avenue), a spit has formed and created a small lagoon and marsh. North of the lagoon, behind the houses on Beach Grove Road, seawalls line the narrow beach. Maybe next year I'll come back with more time and my bike - there's a trail that follows the dike eastward along Boundary Bay.

Centennial Beach

Lily Point, at the southeast corner of Point Roberts, has been feeding sediment to the beach for millenia and waves have been sending it north to form the beaches that extend from Maple Beach on the American side into Beach Grove on the Canadian side. Yes, several thousand cubic yards of American dirt going to Canada every year -- no charge, no duty, no intention to return. The sediment has accumulated in a series of prograding spits in the northwest corner of Boundary Bay, where they created the large marsh behind and beneath Beach Grove - now diked and managed to accommodate the growth of suburban Vancouver (this is all part of Tssawwassen).

The long history of accretion means there's a broad sandy backshore, and even some semblance of low dunes. The upper foreshore is a narrow band of gravelly sand, running along the edge of the broad flats of Boundary Bay. The transition between the upper foreshore and the flats occurs at mid-tide or above. The lower beach appeared to be a lag surface of small gravel.

What I found intiriguing was the strong southeast-northwest fabric to the lower beach - a pattern seen both in gravel ridges (amplitude of ten cms or so and wavelength of several meters) and in the sand between them (amplitude of mms and wavelength of several cms). Strange. These did not look like ripples or cusps or any sort of depositional feature - they looked more like erosional features (I'm not sure why I felt that). And their orientation was parallel to the large fetch from the southeast - where I might have expected just the opposite. It looked like a surface that had been scoured by strong southeast winds and waves. As with every beach, there is a story here. I just don't have much clue as to what it is.

Elwha

The story of the beach between the mouth of the Elwha River and Port Angeles is well known – or at least often told. Dams, riprap, and a spit starved of sediment. Simple stories are easy to tell. There’s a longer, more complicated story, and one that I won’t try to tell here, in part because there are others working hard on figuring it out, but here’s snippet.

Years ago, I noticed in older aerial photos that the character of the beach between the delta and Dry Creek seemed to change significantly on a decadal scale. Photos from the 1970s show a wide gravel berm and a heavily vegetated bluff, while photos from the 1990s showed a narrow berm and a bare, eroding bluff. By the beginning of this decade, the beach was widening again in locations and the bluff seemed to be responding by growing trees. When I walked this stretch in 2005, the beach showed evidence of the building seaward in sections, but for the most part the berm farther east was relatively narrow (beach level photos).

Last week, I flew over this stretch of shoreline and took this aerial of the same stretch. Wow! Whatever the mechanics – longshore drift, onshore transport – that’s a lot of gravel!

In the spirit of multiple working hypotheses…. The Elwha probably releases sediment to the beach in pulses, maybe associated with avulsion of the spits that regluarly form across its mouth, and one would expect these to travel downdrift in a somewhat coherent fashion. Or alternatively, there are oceanographic or meteorological factors that lead to long-term cycles of accretion and erosion. Or maybe, longshore gravel transport in highly oblique wave environments is influenced by nonlinearities that give rise to emergent landforms (I’ve probably butchered the jargon). Or maybe all three.

Bridge Canyon

We reached the high water mark of Lake Mead around Gneiss Rapid in Bridge Canyon. But we didn't reach the actual lake until the middle of the next day - more than 60 miles downstream. Its been a bad few years for the reservoir (see my posts from our January trip to Vegas) and it just keeps dropping. During its better years, and particularly in the decades between 1937 and 1963 before Glen Canyon Dam was built, the Colorado dumped its load in this section of the canyon. The tributaries built their alluvial fans to match the reservoir level. So the river now flows between banks eroded into these mid-20th century river deposits. And flows tens or even hundreds of feet above the rapids that used to be found on this stretch of river, which are now buried in silt.

Time to wrap up the Grand Canyon stuff. Between this blog and the other two, I've posted way too much material, much of it redundant, and its time to go back to the shorelines this blog was originally meant to address!

National Canyon

More beach details. A small sandy berm, and not too far away, a small eroding scarp.

The river rises and falls about once a day in the canyon -- a remarkably regular diurnal tide. But it's tied to the sun, not to the moon. When the sun shines on Phoenix and other southwestern cities, the air conditioners turn on and the power grid demands electricity. More water is allowed though the penstocks at Glen Canyon Dam and the flow in the Colorado downstream goes up. When it cools in the late evening, power demand falls, and so does the river. The resulting tide is generated at Glen Canyon, but it takes a day and half for the wave to travel down the river to Lake Mead.

Blacktail Canyon

Blacktail Canyon is on river right at Mile 120. Unlike so many other side canyons, it does not end in a spectacular pool or a waterfall. What it does have is a sand and gravel beach, although not one most folks would recognize right away.

It is the base of the Tapeats Sandstone, lying on top of the schist at head level as we head up the canyon. This is the Great Unconformity - a boundary in the rock layers that represents a gap between incredibly old rocks and rocks that are merely ancient. The top of the underlying schist, perhaps 1.8 billion years old, is the eroded surface of a rocky coastal landscape caught in time half a billion years ago. As the ocean gradually rose, the waves planed off this surface, breaking off chunks of the metamorphic rock and spreading it in layers on the advancing beach. What we see now on the wall of Blacktail Canyon are multiple layers of sand separated by bands of coarse, angular gravel derived from the schist (there are quartz veins in the underlying rock and quartz clasts in the overlying beach deposits).

I suppose for each of the layers we see preserved, many more were formed and then erased. I wonder if each of these layers records a storm or a series of spring tides? Maybe on closer examination we would find thinner layers that represented the sediment moved by individual waves?

Imagine a rocky shoreline on the New England coast. The rocks are Paleozoic schists and phyllites, intruded by slightly less ancient granites. The Atlantic is at your feet, but the coast is gradually subsiding and the beaches advancing farther onto the land. With time, these rocks are buried by more layers of beach sand and then later, as the water deepens, with silt and mud and eventually limestone. Half a billion years later, the land has been uplifted, a river has carved a deep canyon, and some strange creature in a rubber raft discovers your fossilized cellphone (the size and basic skeletal structure of a 3" trilobite) on the unconformity that separates the schist from the beach.

The Tapeats was my favorite rock formation in the Canyon - partly because it told this wonderful story of ancient shorelines and partly because it was a distinctive and beautiful feature of the canyon. Downstream from Blacktail we float through Conquistador Aisle, with beautiful ledges of Tapeast Sandstone lining the river.