Monday, February 18, 2013
As readers may have noted from posts over the past year or two, we're seeing more and more examples of beaches being restored - often these are relatively small projects where an old structure or a bulkhead has been removed or where historic fill has been pulled back.
This was an old log dump used, as I understand it, for getting logs from trucks into the water. At least as of now, the Google Maps image still shows the old looped dock. But that's all gone now, replaced by a curving beach, a revegetated backshore, and an awful lot of large wood.
I'm sure wood has always been a common component of Salish Sea beaches and there's plenty of evidence that suggests it can influence patterns of erosion and accretion - to a point. But from looking at many of the projects going in these days, you'd think beaches were all about wood, not about sediment! I'm excited about all these neat projects. I just hope the wood doesn't get in the way of the beach doing it's thing. Fortunately, in most cases, the wood doesn't seem to be having too much effect on the beach doing it's thing.
Dry Creek emerges from a small canyon midway along the otherwise unbroken line of bluffs between the Elwha Delta and Ediz Hook in Port Angeles. I've posted from here before (Dry Creek March 2008; October 2009) and this entry is sort of an update, along with a way of capturing photos from last week's visit.
To the west of Dry Creek lies more than a mile of beautiful cliffs - no stairways, no seawalls. During the last few years, a broad foreland has developed along this stretch (see Elwha: August 2009). There's a good view of this feature from the top of the landfill. In the 1970s, a broad beach protected the bluffs along the same shoreline but in the 1990s, it was gone. Now it's back again. This is a huge amount of sand and gravel and suggests a far more complicated picture of sediment transport between the river and the spit than is typically told. Fortunately, thanks to the Elwha Restoration, there are plenty of folks watching these beaches and maybe in another decade we'll understand more than we do now. I suppose this feature may be gone by then - I wonder to where?
To the east of Dry Creek is the Port Angeles landfill. A large seawall was built several years ago to protect the western portion of the landfill, where trash had historically been dumped over the edge. But the cliff to the east continues to erode, threatening a more recent part of the landfill that was constructed immediately landward of the retreating bluff (nope - doesn't make sense to me either). There's no easy or cheap fix, but moving the garbage out of the way is probably the more practical and forward thinking option - it was nice to see it getting serious consideration.
Wednesday, February 06, 2013
Another State Park -- another deep-seated landslide. I used Camano Island State Park to illustrate this symbiotic relationship in November (Gravel Beach: Camano Island SP), but much the same applies to this park on the west side of Whidbey Island.
The trail down to the beach at South Whidbey SP traverses the headscarp of the main slide, then winds through hummocks and around sag ponds, before arriving at the lower bluff, which is where the recent movement has been and which has taken some of the trail along with it.
This is a wonderful stretch of beach. Bush Point lies to the south, Lagoon Point to the north (Gravel Beach: last year, same afternoon). Other than the stairs at the park and a few drain pipes coming down the high bluff south of the park boundary, it's a pretty wild beach.
There are a couple of waterfalls that plunge directly to the beach and both were running full, their streams cutting through the thin sand layer deposited by the previous high tide. And there is a large glacial erratic. My petrology is rusty, but I was told once that this was a block of dunite, most likely from Twin Sisters near Mount Baker (anyone want to confirm or refute?)
There are some spectacular landslides - historic ones and new ones - on the bluffs between here and Bush Point. The sun was going down or I would have checked them out on this hike. Maybe later this spring.
Side note: This is my 60th post from Whidbey Island since this little adventure began back at the end of 2005. 'Whidbey' is the most common label on the blog after 'Washington' and 'Puget Sound.'
Sound Waters is held every year on the first Saturday of February and whether I stay for the afternoon classes or skip out after lunch to go to the beach, it's always a good day. This year they moved the venue from Langley to Oak Harbor High School, so I started near the north end of the island and worked my way south.
West Beach was calmer than on my last visit - back on December 17th when a storm coincided with a record high tide and caused a lot of damage to both homes and bulkheads.
Gravel Beach: 17 December 2012
This community is a poster child for imprudent development. It certainly isn't sustainable in the long run, particularly with rising sea levels. At least not without a great deal of expense and heavy duty fortification.
It's a wonderful place at low tide on a sunny July afternoon, but events like December's storm are exactly what built this ephemeral spit of land and what will wallop it again and again. Peat ledges on the foreshore are evidence of the beach's landward retreat. Tsunami warnings are reminders of the beach's lack of elevation and proximity to shifting plate boundaries. The old failed seawalls at the south end are a fitting monument.
The big slide we posted about last year (search on the label 'camano') was quiet all summer and early fall, but has gotten more active this winter. Water was flowing over the top during this visit and was eroding the sandy unit below the till. This appears to undercut the till which then fails in larger blocks, although nothing too dramatic has happened yet this year. Most of the colluvium in the gully still looked like the trodden and rained-on remains of last year's debris. I would expect more failures as long as the water is flowing, but I wouldn't pretend to guess how large.
One reason for my visit was reports of a new slide south of the one I just described. Sure enough, there had been a fairly large debris avalanche on the lower half of the slope, in line with a substantial gully that probably corresponds to an earlier slide. Water was flowing from somewhere mid-slope. This new slide is immediately north of one that occurred in the late 1990s. There is plenty of tree debris on the beach, and a fair amount of dirt, but nothing like the other slide. There's a steep bare headwall at the very top of the slope, but the upper slope doesn't appear to have failed in this event. I suppose the recent slide could make that more likely, at least if conditions stay wet.
There was also a small slide - a small earthflow more precisely - on the slope nearer the resort, above where the old bungalows were. When the park was redeveloped, a decision was made to remove several of the old bungalows at the north end, at least in part due to their vulnerability to slides. Probably a very good idea.