Tuesday, March 22, 2016
A major windstorm coincided with high tide early on the morning of March 10th. The Seattle tide gauge pushed 14.3', a little less than 2' above the predicted 12.4'. In some places, the impacts were reported greater than the storm on February 4th, 2006 (ten years ago). In others, the effects were less. The differences may have been due to the relative role of high water versus waves, to local variability in wind intensity and orientation, and to small changes in beach conditions that can lead to big differences in how waves impact the landward area.
A week later, I was finally able to get to the beach - a quick series of stops on the way to an event in Langley. But it was enough to get some sense of the effects of the storm at a few places that I'm getting to know pretty well.
So here we are back at Ala Spit. The overtopped and eroded berm was rebuilt this fall (Ala Spit: November 2015) and this storm gave it a serious test. Pictures forwarded by others showed this portion of the spit pretty much submerged during the peak of the storm, but apparently not enough for the waves to wash the drift wood over the back into the lagoon - or at least not much of it.
But farther out the spit, beyond the area of the recent projects, the effects of the previous week's storm were much more evident. The spit had been overwashed, the logs largely floated off, much of the vegetation stripped or buried, and the previous berm spread out in a relatively uniform sheet of gravel back from the leading edge of the spit.
The gravelly overwash deposits contrast nicely with the sandier material farther inboard of the beach and also suggests some differences between the processes that shaped each. I suspect the gravel sheet is classic bedload transport by breaking waves, thus the abrupt landward edge and the fact that smaller overwash lobes were generally oriented northwesterly, perpendicular to the beachface. The ripples in the coarse sand suggest flowing water -- with currents flowing in a much more northerly direction (more parallel to the overall trend of the spit).
Overwash is typically accompanied by erosion of the upper beach face - it's where much of that gravel comes from. Here you can see how it stripped the the area of the previous berm right down to the underlying substrate (some organic, some anthropogenic, confirming a complex natural and human history).
The fact that the most significant overwash occurred here rather than at the rebuilt neck of the spit is interesting, but not necessarily surprising. The new berm had been built very high, probably higher than the natural berm in this area, and therefore was less prone to inundation (this in marked contrast to the circumstances five years ago during a lesser storm when an earlier attempt at a restored berm washed over into the lagoon (Ala Spit: December 2011). It's also possible that the orientation of the storm was a little different. But there's another possible twist, one that only really good morphological monitoring could confirm. This segment of beach may have been starved of sediment by the 2011-2012 washover events just updrift. In which case, this is exactly where you might expect the spit to be most vulnerable!
Saturday, March 05, 2016
This fall the rock revetment between the boat ramp and the pier was removed and that section of beach restored. I've included a picture of that beach at the bottom of this post, but this entry is really about a portion of the same beach another 100-200 meters to the south.
We think the wetland used to be much larger, extending to much of the area now occupied by lawn, but there's still a large marsh behind the beach at the south end of Bowman Bay. It collects runoff from a fairly large area, including Pass Lake up on the main road. It drains through a 12" culvert that exits on the lower beach. This keeps the normal water level of the wetland pretty low.
But this winter wasn't normal. It was wet. And the wetland was filling faster than it could drain through the pipe. A couple of weeks ago, the water level got so high it flowed over the berm creating a new outlet (or at least re-establishing the old outlet -- the history isn't well known). The trail crosses this spot on a bridge, so presumably there's been some history of a channel or of flow through this area before, although the structure normally seemed more like a boardwalk with hand rails.
As the rains diminish (really, I'm sure they will!), the water in the marsh will fall, and the new channel will dry up. Waves will push gravel into the gap and rebuild the berm across the outlet. But what's interesting is that there has been talk in the last few years of restoring a more natural connection between the wetland and the bay. The conditions of the past couple of weeks actually provide useful hints about how that might work. Maybe there is some simple replumbing that would allow the natural outlet to be the primary outlet, and relegate any pipes to more an overflow feature.
The photo below is of the main beach where the restoration work was done this fall. At the time, I posted about the site (Bowman Bay) and noted the steep scarp that had formed during a big storm that occurred right after the project was completed. This photo shows the scarp remaining, but it has been broken down by foot traffic and the beach in front has built back up, reducing the overall effect. Personally, I think this beach needs a few good high tide storms to cut that upper bank back another 10-15', dropping that big super-elevated log down a couple feet to a more natural position and creating a more natural berm for the dune grass to recolonize.
Wednesday, March 02, 2016
The northern half of Birch Bay's eastern shoreline is a long curving gravel barrier beach, separating the bay from extensive wetlands farther inland. Birch Bay Drive pretty much follows the original berm and there isn't much high tide beach left - what wasn't buried by the road has eroded away to a narrow strip, much of it covered in riprap or a concrete seawall. Dozens of small groins reflect an early, and not terribly successful, attempt to hold the beach together (Birch Bay - Part Two: March 2015).
Except for the groins and a few big storm drains, the beach is pretty much continuous and accessible, from the north end south to the mouth of Terrell Creek. South of the creek, things get sort of ugly, but that's another story (Birch Bay - Part One: March 2015). There is one other exception - a notable one.
M and I had a Sunday afternoon appointment in Blaine and stopped in here for lunch beforehand. It was quiet and our table was just a few feet above the beach - and considerably seaward of the high water line. This might be pretty exciting on a stormy day, but I guess that's why they have those shutters that can be pulled up to cover the lower portion of the windows. Keeps the gravel from breaking the glass, the salt water off the carpet, and the logs from landing on the tables.
There are major plans to rehabilitate the beach in next year or two, fulfilling portions of a vision Wolf Bauer laid out almost 40 years ago. He imagined a wonderful public beach stretching along this entire shoreline -- I guess they'll sort of have to build it around this place.
Tuesday, March 01, 2016
The beach along Saratoga Passage is classic Puget Sound - particularly on a gray day. A forested bluff collapsing in small pieces onto a mixed sand and gravel beach. This is a north-facing (northeast, actually) shoreline and avoids the more common southerly storm waves, although the rare sustained northerly can really stir things up given the large fetch.
There are scattered bulkheads along here, although they have limited value in preventing the steep slopes from sliding during wet winters. But this particular stretch is remarkably undeveloped, except for an occasional stairway. And this huge elevated rectangle of upland - built out across the beach in the 1960s. Back when such things, even if not entirely legal, were rarely noticed.
In many cases, including many on southern Whidbey Island, homes would have been built on the reclaimed land, at risk from slides and storms, increasingly expensive to maintain, and an unnecessary intrusion into what Wolf called the shore process corridor (more on Wolf in a subsequent post).
Here, there is an opportunity to make it right. The small private community improves its beach access and Saratoga Passage regains a beach. It will take a lot of work, but there is interest and willingness and leadership and perhaps even funding to make it happen. Hopefully, I can report back on this site in a year or two.
Previous Visit: Possession: June 2014
I trust that by the time the erosion gets back there, Parks will have reimagined the site. The old house doesn't make much sense and the marine campsite could be relocated to a more sustainable site. It's a wonderful place and as with so many of these undiscovered parks, the biggest challenge will be managing visitors with limited parking and facilities.