Wednesday, November 28, 2018

Fort Worden

A week and half ago, I got to spend two days at Fort Worden, a (very) little of which actually got spent on the beach. This is a familiar site (searching the blog for Fort Worden or Point Wilson turns up some related posts) and one I often use to illustrate how structures can impede littoral drift and how shorelines respond.

AERIAL VIEW


The Port Townsend Marine Science Center now occupies the end of the pier, but the structure itself has a long military history associated the Fort. At some point, planks were placed between the pier's pilings, most likely to reduce sedimentation in the small boat basin tucked in behind it. This resulted in a wide beach accumulating on the south side (sediment arrives from Port Townsend and the Chetzamoka Bluffs from this direction), and a substantial offset in the shoreline to the northeast (towards Point Wilson itself).

Every decade or so, people start wondering whether something can be done to alleviate some of the inconvenient geomorphic ramifications of the pier (and the associated boat basin and launch ramp). Trouble is, some things are hard to undo without creating other problems.







Port Gamble

There is a neat little beach hidden at the bottom of Teekalet Bluff in Port Gamble. People often stop to take in the view from the top, since it's a great place to monitor everything coming in and out of Hood Canal -- war canoes, sailing ships, nuclear submarines. But not so many people visit this little beach. I've known it was here for a long time, but this was the first time I'd actually checked it out.

AERIAL VIEW

When the northern shoreline of Port Gamble was developed, fill was extended out over the beach and protected with large rock (and other junk). This projection blocks the eastward drift and over time, a small wedge of beach has built out in front of the forested toe of the bluff.

I doubt there's much sediment being transported along this shoreline. It's at the end of a long littoral cell that begins farther south on Hood Canal, but I suspect the transport rates are higher where the southerly waves can act more effectively. Much of the sediment probably stalls out in the vicinity of Salsbury Point (a mile west of here), since there isn't much wave action to urge it along this north-facing shoreline (something similar happens between Point Elliott in Mukilteo and the Port of Everett, so I suppose this beach is a bit analogous to Pigeon Creek Beach), though none of this probably makes sense unless you look at the map).

It's possible that some of the sediment on this beach now makes itself around the riprap, but the fill extends into relatively deep water and I'd expect any excess material gets lost offshore. There is a small accidental beach tucked into the northwest side of the jetty a little farther east (bottom photo), but it doesn't show much evidence of continuing to accumulate sediment.

Here's another post from Port Gamble from a few years ago:
Teekalet: August 2014








Thursday, September 13, 2018

Devil's Lake

Devil's Lake lies in a steep sided gorge that cuts through the southern Baraboo Range about an hour north of Madison. The billion and a half-year old Baraboo Quartzite forms steep cliffs along the edge of the valley and erosion has left an assortment of stones standing alone or leaning against each other. The stones that didn't remain on top are piled in a talus slope along the base of the slopes.

AERIAL VIEW

The lake itself is formed between two moraines - left at the western edge of the ice during the last ice age. We're right at the eastern edge of the driftless area, which extends west into Minnesota. Given it's shape and location, I had sort of expected that the gorge was a glacial margin outwash channel, but apparently it's much older and may mark an earlier route of the Wisconsin River. The quartzite is awfully resistant stuff and it makes sense that this gorge was not formed easily or quickly.

I assume the reddish sand beaches are derived from these same rocks. This was one of those sites where you could see primary ripple marks on the quartzite blocks, and then find modern ripples of the same sand on the edge of the lake.





Wednesday, August 08, 2018

Pigeon Creek Beach

Here's a nice example of a small beach project that almost no one knows about. It's an artificial gravel beach at a hard-to-find public access on Everett's industrial waterfront. The initial project was done in conjunction with an outfall in the very early 2000s and then was revisited a few years ago.

AERIAL VIEW

The beach lies in a corner created by the railroad grade and the large projecting fill associated with the Port of Everett. While the orientation is favorable to maintain some sort of beach, they've had problems here maintaining a sustainable profile. I suspect they need smaller gravel and more room - the latter of which may simply not be possible on this site. It's not just the geometry of the upland, but also the proximity of Pigeon Creek, which would be a constant sink for sediment were the beach to extend much farther west.

I actually think there's a nice location for another beach just around the corner to the north - maybe toss in a few thousand cubic yards of sandy gravel and let it sort itself out.


Marine View Drive

The Dick Gilmur Shoreline Access point is located along Marine View Drive on the north side of Commencement Bay, on the way out towards Browns Point. It's a relatively recent soft shore project intended to restore a more natural beach while also allowing for a small parking area and kayak launch.

AERIAL VIEW

One of the questions that keeps coming up for me is how to catalog and disseminate information about the large number of soft shore and beach restoration projects going on around Puget Sound. Overall, it's a remarkably positive story that needs to be told. It would provide people with design ideas and inspiration to do more projects and to do them better. It might provide an inventory from which people could choose sites for monitoring, for documentation, or simply for visiting.

But this has proven difficult. The number of projects is large, but they vary enormously and there is much disagreement about what types of projects should be included and how to assess performance. Many are poorly known and poorly documented. There is sensitivity among funders and landowners and contractors about possible problems and this makes it difficult to discuss the less successful projects (or more commonly, successful projects with unsuccessful elements), even if those are the ones we would all learn the most from.





West of Twin Rivers

The shore platform along parts of the western Strait of Juan de Fuca is etched with large arcuate features often 100's of meters across. I recall first seeing these in air photos decades ago and a number of colleagues have mentioned them over the years. This was my first chance to get out and see some of the better examples at a good low tide.

AERIAL VIEW

This happens to be a coastline marked by numerous large, deep-seated landslides and these arcs seem to be consistent with the offshore extension of many of these. The features consist of narrow ridges of boulders that curve out from the shoreline across a very broad, flat, and often fine grained erosional surface.

Boulder arcs have been described or show up in photos of coastal landslides in other parts of the world and I can think of one smaller example on Hood Canal (Termination Point), but I haven't seen a good discussion of the mechanism by which they form. Particle segregation can occur in large slides and debris flows. The slide may bulldoze large boulders as it moves. And there could be additional ways in which a boulder lag like this might be concentrated in this way.

This would be a fun topic to discuss further, but I've got neither the time nor the knowledge to do with this well. But it was great to actually see them up close and it was fun to participate in a discussion of how they might have been created and whether they might have been used, or even modified, by Native Americans.


Dungeness

Dungeness Spit is built from sand and gravel that has been delivered to its base by waves for millennia. That sediment had to come from somewhere and that happens to be a long reach of high, eroding bluffs to the west.

But bluff erosion has implications. Erosion results in the gradual, though jerky, retreat of the top edge of the bluff. We talk of retreating from eroding shorelines, and we should, but this is just a reminder that retreating is one thing if you have wheels or legs, but not quite so easy if you have a foundation or otherwise lack mobility. In which case, we often abandon instead of retreat.

In the case of a small gravel parking lot and a wooden fence, this may not be a big deal, but if it's houses and hotels and highways, it is both a societal and a practical mess. This is not a new challenge - but it's a challenge that may overwhelm us in the next century.


Burfoot Park


Having finally caught up on our early summer Scandinavian trip, I find I've got a backlog of more local beaches from July. I'm going to try to crank out several short posts and see if I can catch up before heading off for B.C. this weekend.

This is a nice example of how easy it is to bury a beach under fill - and hints at how easy it might be to restore some beaches. It also underscores the point that on a lot of sites, it's the fill as much as the armor that is the problem. We focus on removing armor, or softening it, but ignore the culprit, which is that we buried the beach to create a lawn or a parking lot. Sometimes those things are necessary; sometimes they are not. But if you don't need the fill, you often don't need the armor.

AERIAL VIEW

Here, I suspect the existing beach access (a road down the bluff that doesn't show well in the photos) could be maintained with a very small landing, a ramp, and maybe some steps.



Tuesday, August 07, 2018

Tropical Beach

Really, that's what this beach in Helsingborg is called, although it's also referred to as Parapeten (which I believe is what they call the breakwater that forms this part of the harbor). Tropical Beach reflects the beach cafe, the thatched roof, and maybe some wishful thinking. But on a sunny evening (I found it very early on a gray morning), I imagine it's quite popular.

I had gone for a walk - contemplating the reality of being back in Seattle by the end of the day - down to the waterfront. A constant stream of ferries were heading in and out, making the relatively short trip across to Denmark.

AERIAL VIEW

Tropical Beach is tucked into a corner, adjacent to the northern jetty. I wondered if it could have been built out of sediment dredged from the harbor mouth, but it sounds like it may represent a natural accumulation of material against the jetty (given the orientation, it seems that waves would tend to move sediment in this direction).

According to the internet (where else but Wikipedia?), while the beach may have begun forming when the Parapeten was constructed in the late 1800s, the Tropical Beach theme dates back to a 1999 exposition of some sort.

If you search for information about Tropical Beach online, you discover that some people have no sense of humor. Suggesting that this place misrepresents itself seems to miss the whole point. I thought it was a great last beach on our Scandinavian adventure (if you don't count a couple in Iceland we saw from the airplane later the same day).


Mellbystrand

This long stretch of beach lies along Laholm Bay (and the Kattegat), around the mouth of the Lagan River. It's more of your classic sandy beach. Glacial and bedrock influences were much less evident than on most of the beaches we'd visited in the past few weeks. And the beach was much more extensive (it runs at least 10-15 miles along the shore).


AERIAL VIEW


The beach is backed by a broad swath of low dunes and the development looks much like modest residential beach communities elsewhere. We only visited one beach access point, but at least here, the homes all seemed to be well back from the shore. I have no idea if this is planned or fortuitous.

The strandline was marked by windrows of seagrass(?) and seashells.

I thought this might be the last beach of our trip, but as it turned out, I discovered another the next morning (next post).


Monday, August 06, 2018

Fjällbacka

We spent about 24 hours in Sweden, which was just enough time for a few stops along its west coast. The first was Fjallbacka, where we hiked up to the overlook above town. No beaches - just an undulating granitic (or something similar) landscape emerging from the sea.



Aerial imagery show some small pocket beaches in the general area, although you have to look pretty hard to find them. As ever, for beaches, you need both sediment and a place to keep it. In a glaciated landscape like this, any grus weathered or scraped from the granite was probably carried away by the ice - save for small patches where topography and waves conspire to retain it.


Farstad

I'd added this beach to my list months ago. It had sort of jumped off the map when I was exploring trip options on Google, perhaps because there simply weren't that many beaches to choose from. We were staying in Kristiansund for two days and I knew we'd be checking out the Atlantic Road (Atlanterhavsveien). Farstad was just a few more kilometers farther down the coast and seemed like a good lunch stop before turning around and heading back.


AERIAL VIEW

The beach is a crescent-shaped kilometer of sand, bracketed by a stream mouth at one end and a boulder moraine at the other. I suspect the stream is the source of the sand, since it drains a fairly substantial valley and once it hits the ocean, there's not much place for the sediment to go besides onto the beach and into the small dune field.

The presence of a few large boulders on the beach indicate that the original glacial surface doesn't lie far beneath the sand. These boulders are unlikely to have been moved here by waves (if they were, I wouldn't want to have been nearby). They were most likely already here and the beach simply built around them.

According to the sign, this is the "world's northernmost sand dune region of the southern variety." I'll take their word for it, even if I'm not quite sure what that means.

This was my favorite beach of the trip.

There are a lot more pictures from our Norway trip on my hshipman blog. Here's the link to Farstad, but if you want the whole trip (60 posts!), you can try:
hshipman: Scandinavia 2018