Wednesday, July 31, 2013

Waddell Bluffs

High hills reach the ocean just north of Waddell Creek, on the coastline between Santa Cruz and Ana Nuevo, forcing Highway 1 to follow to the beach.  The roadway is protected from El Nino storms by an impressive riprap revetment and from the still-collapsing bluff by a high fence of cable netting.

Google Maps:  AERIAL VIEW

There's an impressive ledge of exposed rock on the platform that appears to act like a big groin, influencing the shape of the local shoreline.  I suppose it makes it a little easier to protect the road to the north, a little more difficult to protect the road to the south.

Pleasure Point

Much of the shoreline between Capitola and Santa Cruz consists of bluffs cut into Tertiary siltstone and sandstone (and overlying more Pleistocene coastal deposits) of the eroding marine terrace. Pleasure Point and the Opal Cliffs have now been heavily armored to protect both homes and Cliff Drive. Rock or concrete protects the base. Sprayed and textured concrete protects the upper portion, lending to a Disneyland effect.

Google Maps: AERIAL VIEW


The village of Capitola is built at the mouth of Soquel Creek, which like many of the streams along this coastline sometimes flows to the ocean and sometimes runs out of steam before it gets there.  Compare my photo (the creek ends in a closed lagoon) with the Google Maps aerial photo below (the creek flows to the ocean).

Apparently there's sufficient connectivity in the nearshore that Capitola suffered from the construction of the jetties at the mouth of Santa Cruz harbor several miles to the west. These trapped large amounts of sand that otherwise would have been transported eastward past Capitola, leading to rapid erosion.  This in turn led to the construction of a large groin at the east end of Esplanade Beach, which saved the village beach, but further exacerbated erosion on the bluffs to the east.  I've seen pictures of this same bluff with apartments perched on the edge - apartments since removed.

go to Google Maps

Saturday, July 20, 2013

Carpenter Creek

Carpenter Creek empties through a small estuary into Apple Tree Cove, the small bay on which Kingston is located. The estuary's inlet is formed by two spits, parts of which are now obscured by development on both sides. The geometry of any bay like this means that longshore transport (assuming there is sufficient wave energy in the first place) will be into the bay, since that's the direction most of the wave energy comes from. The actual configuration of the spits is also influenced by tidal currents in the restricted inlet (which also favor growth in towards the estuary in most cases).  Here, a small secondary bar or spit has formed on the west side, perhaps in response to the ebb flow?

Historical development in these settings often involved building roads across the mouth of the estuaries, taking advantage of the spits and the short stream crossing.  What began as simple roadways and pile bridges turned into more substantial causeways and culverts.

Here, an undersized culvert had led to strong currents and scour on both the flood and ebb sides, impacting the use of the estuary by salmon and other fish. In 2011, the old culvert was replaced with a short bridge, a simple (but not necessarily cheap) measure to restore estuarine function.

Personally, I just think it makes this a nicer place.

Google Earth:  AERIAL VIEW
Ecology Coastal Atlas:  2006 AERIAL PHOTO

After several evenings of playing catch-up, I think I have actually caught up. I'm writing this exactly one week after my visit to Carpenter Creek last Saturday evening (returning from the Elwha field trip).  Unless I go to the beach tomorrow, my next post should be from Santa Cruz or Big Sur!

Elwha Delta

Back to the Elwha, again. And I'm sure I will be back again many more times over the next decade, watching the story play out as 100 years of sediment is released from the old reservoirs and allowed to move to the coast.

Elwha Delta:  March 2013

Our group arrived at a fairly low tide and we got to see the waves breaking on the sweeping bar that has formed offshore.  For the last couple of months, the river has been taking taking a sharp left as it reaches the Strait and flowing west along the beach, although I'm sure this won't last.

The amount of deposition offshore is impressive and suggests the scale of changes still to come.

For more information about the changes, see:
The Coast Nerd Gazette 

Google Maps: AERIAL VIEW
Ecology Coastal Atlas:  2006 AERIAL PHOTO

Lake Aldwell

This used to be Lake Aldwell, the lower of two reservoirs on the Elwha River.  The Elwha Dam has been gone now for much of a year - completely gone - and the river is rearranging the sediment that used to fill the upper portion of the reservoir.  An awful lot of the sand that was here is now down at the river mouth (next post), building a bigger delta.

National Park Service:  Elwha River Restoration

As the river cuts down through the reconfigured lake bed, it is exposing older sediment, layers of organic detritus, and the enormous stumps of trees that grew (and were cut) in the valley before the dam was built.

Google Maps: AERIAL VIEW
Ecology Coastal Atlas:  2007 Photos of Lower Elwha Dam, Lake Aldwell


I was lucky to visit Ledgewood the afternoon of the big landslide back on March 27th, and then again briefly one week later.  But I hadn't been able to get back until very late on the afternoon of July 10th (this blog is relatively sequential, but rarely live).

Ledgewood:  27 March 2013

My visit was brief, as the tide was rising and I didn't want to get squeezed too tightly between the water and the drift logs hanging over the edge of the old beach - 15' above my head.

The toe of the slide has eroded rapidly this spring and much of the uplifted beach has now been redistributed by waves to the adjacent beaches (see Ian's blog below). Most of the eroding scarp consists of a thick sandy unit.  In the top foot or two there are some gravel layers that are consistent with the upper surface being a raised beach.  The toe of the scarp consists of the deformed dark gray clay that I assume marks the slide surface.  I can't wait to see a more through geologic analysis of this thing -- the thick sand is intriguing and I'd like to hear if folks understand the origin of the clay or its role in the slide.

The scarp has not yet reached the displaced pre-March drift log line.  Maybe some time next fall, the retreating bluff will reach the back of the uplifted beach and begin to work its way into the forest. As this promontory gradually succumbs to waves over the years to come it will probably leave a beach underlain by hummocky clay and covered with fallen trees.

Ian Miller with Sea Grant has been following the slide and has posted observations and time-lapse video on his blog:

If anyone is aware of more geologic information available online, feel free to mention it in a comment.

Google Maps:  AERIAL VIEW

Thursday, July 18, 2013

San de Fuca

A couple of small spits converge on a lagoon (two, actually) here at the northwestern corner of Penn Cove below the community of San de Fuca. Sometimes the place is referred to as Coveland.

There's enough fetch from the east and southeast to maintain the gravel spits, but not enough wave energy to keep the pickleweed (salicornia) from colonizing the more protected parts of the beach.

I couldn't find too much detail online, but I confirmed what I'd been told many years ago that there had once been a small tide-powered saw mill on the site. They apparently built a dam or control structure of some sort at the mouth of the inner lagoon, and it looks like they turned a portion of the spit into more of a dike, but not much is left besides some rusted pipes and some of the foundation of the mill.

Google Maps:  AERIAL VIEW
Ecology Coastal Atlas:  2006 Aerial Photo

Cornet Bay

Last fall, WA State Parks, the NW Straits Foundation, the Island County Marine Resources Committee, and others collaborated to pull out the old creosoted timber bulkhead at Cornet Bay and restore a more natural beach.

When it was first built, I was concerned that the temporary erosion protection extended too low on the beach (see October 2012 post below), but ultimately the high tides of December (including the record one on the 17th) sorted out those details.  It did mean that there was some scrambling this spring to clean up a lot of the mulch that ended up accumulating on the lower beach.

Cornet Bay:  October 2012 Cornet Bay:  March 2008

The high tides were good, in that they helped clarify the upper edge of the new beach. It will take a while for the sediment and the logs to settle into more comfortable positions, but the basic concept is great and I'm looking forward to seeing this place in a few years.

There are some interesting details that bear watching. A lot of large wood has stacked up against the west side of the piers and may require some active management.The small drainage outfall in the middle of the eastern segment may lead to some local erosion of the upper beach and the formation of a small delta on the lower beach.  Invasive plants will try very hard to invade the backshore, testing the persistence of volunteer groups.

Ironically, I suspect the hard parts of the project will fare the poorest. Gravity, and probably children, are already causing a shift of the small rock down the beach.  The rounded cobbles are ahead, but the angular quarry spalls will follow. As the small rock and the beach itself shifts, the logs may be undermined, putting more wear on their metal hardware. The rocky areas around the anchored wood will probably attract the most aggressive of the weeds and will be hard to maintain (and remain hard to walk across).

But again, these are details.  Compare these shots to the ones from before the project.  And then compare them to the ones in a couple of years when the beach and the vegetation have become better established.  In 2004, a bunch of us stood on the old bulkhead and wondered what might be done -- this is better than we could have imagined!

Google Maps:  AERIAL VIEW
Ecology Coastal Atlas:  2006 Aerial Photo

Weaverling Spit

This is a revisit to the site of a small-scale nourishment project that was done several years ago on the north side of Weaverling Spit (which is really a heavily modified tombolo, I think) on southern Fidalgo Bay.  The original project has held up nicely and is still one of my favorite examples of a nicely conceived soft shoreline treatment - in an earlier era, this would have all been riprap.

Weaverling: September 2009

Last fall, the Samish Tribe extended the concept to the southeast. This project used a larger prism of material, but still used a few anchored logs as small groins as did the earlier effort.  The backshore has been planted and I suspect these sites will age very nicely, as long as the invasive plants don't take over.

Ultimately, these beaches are still coarser than they were reported to be several decades ago and lack sufficient sand to support the historic levels of spawning (surf smelt, I think). Some of this may take time. Some may require some adaptive management.  But regardless, it deserves some watching and waiting.

Google Maps:  AERIAL VIEW
Ecology Coastal Atlas:  2006 AERIAL PHOTO

Wednesday, July 17, 2013

Kinney Point

Kinney Point is the southern tip of Marrowstone Island and is actually a Washington State Park. It has no upland access, but it does host a Washington Water Trails campsite.  On my long walk around the south end of the island, this was the final turn before the home stretch back to the car.

Kinney Point is a double point, with a little notch in between.  As with so much of this end of the island, most of the upper bluff is glacial drift, but the bottom few feet is older sedimentary rock. I think the shape of the point reflects a change in the resistance of the toe to wave action.  A layer of sandstone anchors the eastern bump of the point, but it dips to the west and vanishes below beach level, exposing what appears to be a more erodible, finer grained unit (mudstone?) on the western bump.  At the same time, the amount of water seeping out over this unit increases significantly in the same direction and maybe that also affects erosion patterns.

Google Maps:  AERIAL VIEW
Ecology Coastal Atlas:  2006 AERIAL PHOTO

On the western side of the point, both the till and the older rocks seem pretty messed up, and my gut told me they were suggesting a more complicated story than the previous several miles of fairly predictable layer cake geology.

There are plenty of things that influence the shape of the coastline.  Around here, the primary factor is the basic form it inherited from the glacier.  But wave action, the resistance of the shoreline to erosion, and the width/height of the beach (which buffers the effect of wave action), are all important in controlling relative erosion rates and therefore the evolution of the shoreline. Here on the south end of Marrowstone, the overall shape reflects its glacial origins, but it seems like the geology of the bluff toe (largely influenced by the presence and type of harder pre-glacial sediments) is an important factor in some of the secondary bumps and wiggles.

Heading back northwest, the beach changes dramatically.  The bluff vanishes entirely at the campsite and there is even peat and wood exposed on the beach, probably the abandoned relic of the marshy swale still seen at the modern shoreline. Continuing north, the beach grows to become a barrier beach that extends 500 meters along the shoreline before reconnecting with the bluffs downdrift.

Google Maps:  AERIAL VIEW
Ecology Coastal Atlas:  2006 AERIAL PHOTO