skip to main |
skip to sidebar
The remains of the old bulkhead (there wasn't much left) were pulled out several years ago and when I last visited in 2014, the site was doing remarkably well in its absence. Two subsequent winters have taken their toll and not surprisingly, the bank is continuing to erode. The vegetation is gone and it may get sloppy since there appears to be riprap and geofabric buried beneath the eroding fill.
Previous Visit: Possession: June 2014
This site consists of fill, so it is particularly susceptible to rapid erosion. The ocean had taken centuries to get to where it was before and now it's eager to get back there again. It will still take many years for the bank to retreat back to the original toe of the bluff, but by the time it does, the rate will be more typical of the normal slow erosion rates we see elsewhere on the Sound.
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.
It's getting harder and harder to imagine what this site looked like just six years ago - when 400' of timber bulkhead marked the shoreline and the channelized creek flowed over the bulkhead in a flume. The small estuary that was created behind the old bulkhead line is smaller than it started, since a lot of sediment came down the stream in the first couple of years, but it still represents new wetland, brackish marsh, and low gradient stream habitat. Salt marsh is establishing near the creek mouth and the forest is rapidly taking over the rest of the site.
AERIAL VIEW
The beach still seems to be naturally starved of sediment to me, and the restored spit has a strange appearance (look at the aerial), but all the pieces are in place and with time they will sort themselves into something that looks like it always belonged.
This is my fourth visit - you've got to go back to the 2009 post to see what it looked like before:
Nellita Creek: October 2011
Nellita: January 2010
S. of Frenchman's Cove: May 2009
By the way, this is part of the Stavis NRCA (WDNR's Natural Resource Conservation Area), since I realized I had never used that name in these posts. I'm still not even sure that Nellita Creek is really the correct name - or if it is, that I've spelled it right!
I'm not really sure what happened, but this is the first post in three months. The first since that beautiful day on Whidbey right after Thanksgiving. It's not that I haven't been to the beach, although those few trips have tended to be pretty gray and uninspiring. And it's not that there haven't been some interesting stories, but maybe the narrative and the photos weren't lining up. Or maybe I've been preoccupied with other stuff and let things slide! The next few posts will be a ragged attempt to get back on track.
We'll start here in Belfair, at the far tip of Hood Canal, way back in mid-December. The site isn't even a beach - too little sand and gravel, too few waves. But it's a neat salt marsh restoration project and has been in the on-deck pile ever since.
The large marsh complex at the mouth of the Union River is not unlike others found at the heads of inlets (Discovery Bay, Totten Inlet, and so forth). I guess on the delta ternary, it's mainly "tide", with a little "river," and almost no "waves." Like many historically drained ("pasturized?") marshes, this was an opportunity to pull out some dikes and allow the tides and the salt water back in. As elsewhere, there were challenges in deciding how much dike to remove, whether new dikes have to be built landward, how to maintain public access (there's a wonderful trail and boardwalk system here), and whether to recreate channels or let them figure themselves out. The current Google Maps aerial below shows the site under construction - a more recent image would show a remarkable network of s-shaped channels.
AERIAL VIEW
One thing that makes this marsh interesting to me is that its been subject to significant elevation changes - possibly rapid uplift associated with earthquakes, followed by more gradual subsidence. The story has been best worked out here in the marshes of Lynch Cove, but I suspect the story also helps explain the terraced appearance of much of the south arm of Hood Canal.
Here's the third of my Ebey's Landing posts from Black Friday, a week and a half ago.
The 3 1/2 mile loop from Ebey's around Perego's Lagoon is the best coastal hike on Puget Sound. Yes, there are other nice ones, but this is more special than the rest. Especially on a day like this one! Most people hike the loop counterclockwise, hiking up along the edge of the bluff and then returning along the beach.
The last time I hiked the whole loop was also right after Thanksgiving, but on a very foggy day!
Perego's Lagoon: 2008 (or for a different perspective on the same trip, see hshipman)
Perego's Lagoon is formed behind a narrow barrier beach - a looped barrier is one term I've heard to describe this kind of feature, a closed spit might be another. The general pattern of longshore transport is from north to south, although it's probably not quite that simple along here.
AERIAL VIEW
In the previous post I mentioned the perched dunes on the top of the bluff, which you traverse as you walk the crest of the slope to the north, with the grassy angle-of-repose bluff falling off to your left and the forest to your right. The bluff trail provides great views down at the lagoon and the spit, including some very nice overwash fans (I believe washover fans also works). The backside of the barrier is marked by several of these features, which mark occasions when waves overtopped the berm during a high tide storm and spread sand and gravel into the lagoon.
The northernmost is interesting for several reasons. First, it is fairly recent. It appeared sometime between the 1970s and the early 1990s. I'd put my money on the 1979 storm, which walloped this part of the Sound, but am in the process of seeing if I can find out more. Second, it completely crosses the lagoon, isolating a small portion to the north. I don't know whether these fans represent an event contained within a single storm and tide cycle, or whether they may have remained open for longer. I've also wondered how this feature would record a tsunami coming down the Strait!
Ebey's Landing lies below a low spot on the bluff on the west edge of Ebey's Prairie, a little west of Coupeville. The road drops down to a stretch of broad backshore terrace where the original pier had been built (it's a pretty exposed location for a pier). It's now a popular taking off spot for beach hikes, including the classic loop to the north.
I've posted about Ebey's Landing before on Gravel Beach, but here's one from my other blog (hshipman).
AERIAL VIEW
I mentioned in the previous post that the beach along this reach often diverges from the bluff. Here, the beach has filled in a curve in the coastline, creating a fairly wide low area. A little farther north of here, the beach takes an even wider excursion seaward of the original bluff line, creating mile-long Perego's Lagoon (next post).
Ebey's Prairie is a good place to think about the last stages of the Vashon glacier. Glacial marine drift, exposed in the upper portions of bluffs near here, records sediment deposited immediately after the ice left and marine water reoccupied the area. What you don't see without LIDAR or perhaps, really good low-light conditions, is the old strandlines that follow contours around Ebey's Prairie, marking the rapid retreat of the sea as glacial rebound returned Whidbey to its preglacial elevations. Imagery shows dozens of faint shoreline traces on the gradual slopes of the prairie.
Something you can definitely see, looking north along the top of the bluffs, is the dunes perched above the bluff itself. They are stable and largely forested now, but indicate conditions when wind blowing over the Strait carried fine sand up the bluffs and deposited it above the crest. Not surprisingly, these bluff-top dunes are called perched dunes and can be found elsewhere on the northwest side of Whidbey (West Beach 2012), on Protection Island farther west along the Strait, and on Lake Superior (Grand Sable Dunes 2010), among other places.
This is the first of three posts from the area around Ebey's Landing, all visited on the Friday after Thanksgiving. I'll try to keep this pretty short, since I've had too many long posts recently and the next couple are also likely to drag on.
The whole stretch north and south of Ebey's is backed by bluffs, but one of the many things that makes the reach interesting is that while in some places the beach runs right up to the base of the slope, in others the beach has built much farther seaward, isolating the bluff toe from wave action. It's interesting on the air photos to compare the line of the bluffs with the line of the beach and speculate about why they diverge.
AERIAL VIEW
The photos in this post are from the beach south of Ebey's Landing, which consists of high bluffs all the way to Camp Casey, two miles farther south. Although the width of the berm varies - and this is reflected in the amount of erosion at the bluff toe - the bluffs in this southern reach generally rise pretty directly from the beach.
Typical of Puget Sound's glacial stratigraphy, there is a great deal of lateral variability in the exposed units. Till is a relatively minor component of the bluff above (difficult to distinguish in the above photo, it lies below the glacial marine drift that caps the sequence and above the thick sandy unit mid-bluff), but dominates the upper portion of the bluffs farther south (below).
Keystone Spit is one of the larger barrier beaches in the central Sound, maybe even the largest, depending on how you measure these things. It's a south facing beach that forms a long crescent separating Crockett Lake from the rest of Puget Sound. The lake itself is actually a freshwater (maybe a little brackish in places) lagoon.
AERIAL VIEW
The well-sorted gravel results in a very steep beach. Breaking waves disappear into the permeable gravel with a whoosh, followed by the rattle of gravel rolling back down the beachface. Storms pile gravel into high storm berms. And as should be expected of any large south-facing beach on Puget Sound, this one collects logs, lots and lots of them, along with plastic and styrofoam and anything else that floats.
Keystone Spit is a beneficiary of large amounts of sediment converge from two different directions -- and that then have no where else to go. Sand and gravel deposited by landslides in the Ledgewood area (Ledgewood 2013) probably ends up here. And sediment from farther north on the island (see subsequent posts from Ebey's Landing) is transported southward around Admiralty Head. This material is held up briefly by Keystone Harbor at the west end of the spit, but is eventually bypassed (Keystone 2012) and gets blended on this beach with the gravel from the south.
A couple of ponds mark borrow pits form when gravel was removed from the spit decades ago. The two concrete posts were associated with a small building (Navy, I think) that was removed in the last couple of years, but I'm not sure just how they functioned.
Another beach restoration project, not far from the last one (Ala Spit). But what an entirely different flavor of beach! Bowman is a pocket beach, facing the Strait. Waves action can be significant, but its incidence is highly constrained by the rocky headlands that frame the entrance of the bay, so we get the typical crescent form of a swash-aligned beach, broken only by the offset against the boat ramp in the middle.
Here's a previous post: Bowman Bay: March 2012
AERIAL VIEW
The old ramp remains and the base of the pier still needed to be protected, but the revetment that had been here for decades was removed a few weeks ago. The basic idea was pretty simple, pull out the rock and excavate the old fill that was too high and too far waterward. On so many of these sites, the erosion problem is entirely one of our making - simply because we pushed the land seaward, crossing a well-defended border - and therefore the solution is simply to pull back to friendlier territory.
Ideally, we want to remove all of the fill and restore the entire profile to something similar to what existed prior to the fill. Any fill or extra elevation that gets left behind will remain subject to unnaturally high rates of erosion and often a scarp will develop.
In this case, there were constraints on how much of the old fill could be removed, which left a higher profile than might have been preferred. That, combined with a strong high tide storm a week after the project was wrapped up, resulted in a significant scarp at the top of the beach. What's missing from the restored beach is the natural berms that mark the unaltered beach north of the boat ramp. With time, this should remedy itself and a broad berm (or series of stepped berms) should form. A few good high tide storms might actually speed this recovery.
When the backshore is left too high, we essentially create a low eroding bluff (Keystone 2012). But natural berms are actually depositional features, so where it's possible, it may be be best to design to a lower profile, and then let nature build the berm where it wants to. This may require more excavation, the placement of more sediment lower on the profile (to supply that berm rebuilding process), and a tolerance of possible overwashing of the initial berm before it gets established.
Conceptually, the restoration at Bowman was pretty simple, but it provides a nice illustration that even simple projects can be difficult. Fortunately, restored beaches are inherently more malleable than what they replaced, so given time and some room, nature can sort things out. It may just take a little longer than we might have hoped.
You would think from many of my recent posts that taking rocks and concrete off of beaches has become pretty popular on Puget Sound!
Here's my most recent update from Ala Spit from a visit a week and a half ago.
In 2011, rock was pulled from the neck of the spit and the berm was reshaped, with hopes of restoring both the original spit and the processes that maintained it (see link to previous posts below). But once those processes were restored, they went to work reshaping the spit in ways that weren't exactly planned. A few quick storms eroded through the restored berm, spreading gravel into a broad deposit on the back side and leaving the berm crest low enough that high tides regularly washed over it. Unfortunately, the geometry of the site and the volume of available sediment have been inadequate to allow the berm to rebuild in the intervening years.
AERIAL VIEW
Earlier this fall, the County took another swing at it. The groin to the south has been partly dismantled. Essentially, the central portion of the groin was removed, a compromise that restores some sediment movement while also trying to maintain the wider beach that had built up on the southern (updrift) side of the structure. I suspect some of the structure may also have been left simply because a few of the rocks were enormous and would have been very difficult to remove.
The concrete bulkhead that ran from the groin to base of the spit is also gone, except for a short section in front of the parking lot. Whether erosion will be a problem at all in this area remains to be seen, but if nothing else, the remnant wall will provide a reference against which to compare future changes.
The big change is that the berm along the neck has been rebuilt. Right now it's still a little raw and looks more like a gravel causeway than a spit, but hopefully time and vegetation will help the site heal. My guess is that there is more than sufficient height and volume to make overwash unlikely. Ironically, one of the original processes to be restored was overwash, but finding a balance between too much and not enough is difficult.
It's been hard to write about Ala Spit, since there are strong opinions and much at stake. And because the more I watch it, the more I realize I don't understand. I'm one of those folks who thinks if the answer is simple or elegant, it is probably wrong!
Previous posts mentioning Ala Spit - most from Ala, but some from other places, too.
My attraction to Ala Spit has been that it illustrates some of the challenges of restoring dynamic geomorphic environments (not that we shouldn't keep trying). For example, different processes play out at different timescales. High tides and waves can wash over a berm in a single storm. The movement of sediment from updrift (south) occurs over seasons or years. And significant changes to the shallow bars offshore of the spit may take many decades.
Ala Spit may have been changing rapidly, even in the absence of 20th-century human modifications. The morphology of the spit is probably influenced by the building or shifting of those bars offshore, which influence sediment availability to the spit itself and which modify the wave environment along the base of the spit. And just to complicate things, Skagit Bay is subject to changes in currents as the Skagit Delta presses towards North Whidbey Island and is subject to potential elevation changes related to nearby faults with Holocene activity, both of which would have ramifications for the morphology of Ala Spit over longer time scales.
Tarboo Bay is located at the northernmost end of much larger Dabob Bay, sheltered behind an elegant series of spits.
AERIAL VIEW
This small site at the very head of the bay was recently restored by the Northwest Watershed Institute, the local organization that has spearheaded so much restoration work in this area. A year ago, there was a building built on piles over the water and an old timber bulkhead, but the structures have since been removed and the bank and the old driveway have been replanted with native trees and shrubs. In a few years, it will blend perfectly with the adjacent landscape.
The now unprotected bank is eroding, supplying coarse gravel to build a small beach and sand that is reshaping a tiny beach nearby. It will be interesting to see how long it takes for the marsh to recolonize the beach surface - wave energy is sufficiently low here that vegetation is the natural end point rather than a beach, something seen by looking at the adjacent shoreline to the north where marsh grass obscures the gravel beach beneath.
Another beach restoration project, not far from the last one (Ala Spit). But what an entirely different flavor of beach! Bowman is a pocket beach, facing the Strait. Waves action can be significant, but its incidence is highly constrained by the rocky headlands that frame the entrance of the bay, so we get the typical crescent form of a swash-aligned beach, broken only by the offset against the boat ramp in the middle.
In this case, there were constraints on how much of the old fill could be removed, which left a higher profile than might have been preferred. That, combined with a strong high tide storm a week after the project was wrapped up, resulted in a significant scarp at the top of the beach. What's missing from the restored beach is the natural berms that mark the unaltered beach north of the boat ramp. With time, this should remedy itself and a broad berm (or series of stepped berms) should form. A few good high tide storms might actually speed this recovery.
