Thursday, May 17, 2018

Yellow Island

Yellow Island sits in San Juan Channel, one of the small Wasp Islands between Orcas and San Juan Island. Like all of these islands, it consists primarily of metamorphic bedrock and most of the shoreline is marked by rocky cliffs. But also like on many of them, there may be patchy deposits of glacial drift, which form an erodible substrate that forms small bluffs in the few places it reaches to the water.


At each end of the island, small spits extend out to rocky ledges, creating tombolos, with small gravel beaches on both sides of each. In addition, there is also a pocket beach below a low bluff on the south shore of the island. 

On some rocky islands, the dearth of erodible sediment and the abundance of shellfish and barnacles on the resistant substrate gives rise to beaches consisting primarily of shell  debris. But as far as I can see, the beaches here are primarily gravel, presumably derived from the glacial deposits -- although there's not an obvious active source of this material, aside from occasional erosion of the toe of the bank associated with particularly major storm events. Of course, what we don't know is whether there might be a source, or at least a reservoir, of sand and gravel in shallow water offshore.

According to Phil, who has been watching this place carefully for a long time, the eastern tombolo is subject to significant changes from year to year. In particular, the cobble on the south beach is sometimes exposed (as on this trip), but may be covered in gravel some years. The fact that the beach changes significantly from year to year is not surprising, but understanding what drives this is more challenging. On a low tombolo like this, there may be large transfers of gravel back and forth across the berm during high tide storms from one direction or the other.

For more on the Preserve:
Yellow Island: The Nature Conservancy

And for a first hand account of life on Yellow Island:
Island Time on Yellow

Weaverling Spit

The new beach at Weaverling Spit has progressed in three phases, the most recent of which was completed this past fall.


Each phase was designed a bit differently, reflecting slightly different site conditions, objectives, and perhaps lessons along the way. Of course, I suspect budgets and permit requirements were slightly different on each phase, too. All three involved beach nourishment, combined with planting of the bank/backshore and the use of anchored logs as small sills or groins.

Phase 1, farthest west, is 9(?) years old now and looks great.

Phase 2, in the middle, was done a few years later. The nature of the anchored log sills was different - the root masses were oriented differently and they were placed fairly high compared to the adjacent beach grade.

Phase 3 is still fresh and I assume plantings are planned. The folks who rent out those RV spots probably don't want trees and thick brush, but there are a lot of good options. The berm is much larger, although I suspect this is a function of the backshore being lower here than on the earlier phases.

Note the log placed perpendicular to the beach immediately west of the boat ramp at the easternmost end of the project. I assume this was to limit the movement of the added sediment onto the ramp - which might be expected since the new nourished beach is slightly higher (and there's a slight tendency for eastward drift of material along here anyway). I'll be curious to see how well this works.

There's more on this project at:
CGS: Weaverling Spit

And here's a link to all of my posts from here:
Gravel Beach: Weaverling Spit

Friday, May 11, 2018

Kukutali Preserve


I love this little tombolo between Kiket Island and Flagstaff Point, particularly the arcuate fine gravel pocket beach on the north side, which sort of underscores the challenges of simplistic beach classifications. While the overall landform is a tombolo, a type of barrier beach, this particular beach acts in most ways like a pocket beach - not an unusual situation. The one complication might be that under the right conditions, sediment might get carried to this beach by overwash from the south side, slightly confusing the otherwise simple picture of a pocket beach as an isolated sediment cell with negligible import or export of sediment.

The south beach gets more wave action and collects logs (south winds push them onto the berm on high tides). The north beach is more protected and logs don't accumulate, since south winds blow them off the beach (if they ever make it there in the first place).

Visitors are discouraged from tromping across Flagstaff Point in order to protect the vegetation community on the relatively rare rocky bald (I think that's the right name). Around the edges, we could see the Camas coming up and the rock outcrops were covered with sedums.

For shots from previous visits, check out Kukutali 2016 and Kiket Island 2009. And for a nice view of Kukutali from the air, check out the drone footage at:'

Wednesday, May 09, 2018

Hidden Beach

Hidden Beach is hard to find. It's tucked in at the base of a high bluff along Saratoga Passage, at the bottom of a steep road that most folks on the main road don't even know exists. Even when you get to it, the beach is still sort of hard to find. It's buried beneath rocks and fill and old concrete and the occasional auto part. A row of piles out on the beach testifies to the original intentions, but this stretch at the north end was never developed, or if it was, little is left of it now. 


Years (decades) ago, I came down here and walked north to check out the wonderful high fluted till bluffs and some large glacial boulders just offshore. I don't think I've been back since, although I often look across at this shoreline from Cama Beach (on Camano Island), just across the water. 

The Hidden Beach community to the south is a great example of a type of development that is pretty common on Whidbey Island (elsewhere, too). Or was - most of the initial earthwork occurred in the 1950s and 1960s - you could never fill on top of the shoreline like this today.

Here's what it looks like on Ecology's Coastal Atlas: Aerial Photos

I've heard different versions of how these places were built, but basically the developer built a seawall out on the beach and then filled behind the bulkhead, burying the beach and creating building lots where logs once floated and fish once swam. They added just enough fill to raise the building sites above (most of) the highest tides. The fill material typically came from the bluff itself. Sometimes they used equipment, sometimes they used hoses, and sometimes they used dynamite.

The result was small, isolated beach communities that were wonderful escapes in the summer but that were squeezed beneath landslides from above and storm waves from the Sound in the winter. And an access road that would become impassable just when folks most needed to get out.