Wednesday, March 22, 2017

Lincoln Park

Lincoln Park is one of the better documented beaches on Puget Sound, although much of what was written is now 25 years old. And apparently, this is the first time I've included it in the blog. A good reminder that there are just too many beaches.

The glacial landscape of West Seattle juts out into Puget Sound on the north side of Fauntleroy Cove. As commonly occurs on promontories on Puget Sound, a very small depositional landform - a cuspate foreland - has formed at its tip (this is in contrast to Brace Point, to the south, which is a much larger cuspate foreland). You may have learned in Beaches 101 that headlands get eroded and bays get filled in until the whole coast is straight, which may be true if you're on a coast where large waves approach straight on. But here on Puget Sound, where waves approach at a strong angle to the coast, it seems that sometimes sediment is attracted to the points, not removed from them. Or at least that's sure what it looks like to me.


The photos show both the more heavily visited south beach and the somewhat less explored north beach. And the riprap that protects the point itself. Note that this landform was perfectly happy without riprap, despite its exposed position, for hundreds of years. The riprap probably reflects the need to protect the walkway, which was likely built over the original backshore. Colman Pool (saltwater) replaces whatever little lagoon probably once occupied the same place on this landscape.

The south beach is the main story here. During the 1930s, the WPA built the stone bulkhead (now largely buried) and the promenade. Over the next few decades, the beach eroded and dropped in elevation and by the 1970s the wall had been repaired many times. Old photos show the beach far below the top of the wall. When Seattle approached the Corps of Engineers for help, the Corps proposed beach nourishment. Resource agencies pushed back - the idea of burying the beach under fill was unthinkable (they preferred the idea of a riprap apron at the toe of the wall).

Fortunately, nourishment won out over riprap. The initial placement in 1988 was large - something like 80,000 cubic yards - but the few subsequent renourishments have been much smaller. And despite some wrinkles along the way, I think the overall project remains a big success story. I think it was critical in reshaping the opinions of the agencies about the potential value of nourishment. This was also because monitoring, required of the original project, led to some good early work on Puget Sound beach biota and their response to seawalls and nourishment.

Wolf Bauer, who had been advocating and building gravel beaches on Puget Sound for more than a decade before the work at Lincoln Park, was a bit skeptical of the design. He had some valid gripes (the berm was too high, for one, so it immediately developed a large scarp), but I suppose he also just sort of enjoyed poking the Corps (don't we all?).

Most folks walking the beach last Sunday (the last day of winter), probably had no idea of the beach's history. I don't recall if the park has any interpretive signs showing the 1930s construction or the engineers standing below the towering bulkhead in the 1970s.

There's more about Lincoln Park - it's relationship with the sandier Fauntleroy Cove to the south, the asymmetry of the north and south beaches, and the heavily developed shoreline to the north of the Park along Beach Drive (which is also the story of the uplifted terrace of the Seattle Fault). Maybe another time.

Tuesday, March 21, 2017

Sculpture Park

Some beaches change all the time. Or at least you can be pretty sure that if you haven't been there in while, it will be different when you come back. This beach isn't one of those. It has few degrees of freedom - admittedly, that was a key point of its design. It's the beach equivalent of putting a wide-ranging predator in a small enclosure in an old-fashioned zoo. Not very authentic, but much easier to manage.


The sediment is all nicely sorted gravel. Which means the beachface remains the same in both shape and texture. The coarse gravel also tends to stay high on the beach - it has less tendency to want to get lost offshore (ignoring stone-throwing children). The two rock groins assure that no material escapes and therefore the beach volume and position don't change. The groins also constrain the small opening of the beach to Elliott Bay which assures that the wave regime is limited and the beach can't shift back and forth too much in its cage.

I love this little beach and wish we could incorporate beaches into our urban shorelines more often. But I also think it is a good reminder that we shouldn't confuse domesticated beaches for wild ones. On the surface, they may look similar, but the domestic ones are more predictable and as a result, may have a little less character.