Thursday, April 21, 2016

Kitsilano Beach



Most of Vancouver's shorelines are oriented obliquely to the large western fetch across Georgia Strait, which means that beaches (natural or constructed) tend to do best when the orientation of shoreline allows west-facing swash aligned beaches to form. This is best seen by looking at aerial views of West Vancouver, Third Beach in Stanley Park, English Bay, and Kitsilano.

AERIAL VIEW

The main beach at Kitsilano, on the south side of English Bay, is controlled by a bouldery headland that makes the swash-aligned beach possible. I suspect sediment has been added periodically to maintain the broad recreational beach, but other than a couple of small rock groins, this beach doesn't depend on larger groins like we've seen at Ambleside or on the north shore of English Bay.


There's a second beach at Kitsilano, just around the corner northeast of the main beach. But it appears to have been created by the construction of a rock jetty at the entrance to False Creek (see aerial). It's oriented a little differently than the main beach, suggesting (to me, at least) that waves may refract around the headland between the beaches and approach this one at a slightly sharper angle.

I've always been intrigued by these rippled patterns on Salish Sea beaches. They're often pretty subtle, but they raise questions about their formation. These are not the same as ripples you might see in other types of beach environments. They typically form perpendicular to the beach and may extend through a significant tidal range. They tend to have wavelengths of 30-60 cms, but sometimes more. It seems like they would have to form on a falling tide to be preserved. But once the pattern is established at high tide, it is propagated down the beach as the tide falls. They may be somehow related to larger scale horns and cusps on other beaches, where the emergent bedform influences subsequent swash patterns, further reinforcing the original undulations. If that makes any sense at all! This phenomenon is probably well documented by others, but I've never seen it described. There is an abundant literature on cusps (still controversial) and on ripples, but I think this is something a little different. Or maybe in between.


Wednesday, April 20, 2016

Point Grey Foreshore - Part Four


Okay, one more post from this short stretch of beach. The seawall immediately west of Volunteer Park is very new and has gotten a lot of attention, in part because it is so unique and so visible.

As sculpture, or architecture, I thought it was pretty cool. If seawalls are going to get built, it would be nice to see them designed to be beautiful as well as functional. So many are ugly or boring or uninspired or cookie cutter. Sort of like strip malls and eastern-bloc apartment buildings. This is different.

The seawall is constructed from Corten (COR-TEN) Steel, an alloy intended to oxidize rapidly, creating a rust coating that doesn't require painting. It's been around for a long time and has become a favorite of some architects and artists who like its raw look and functionality. 

For more on this seawall, including about its designers and builders, check out:
ShapedScape 2014

Houzz: Metamorphous

When this was first brought to my attention earlier this year, one of the claims was that it would naturally degrade over time. I understood this to mean that it was really just a temporary structure - which is sort of a neat idea with seawalls, as long as they don't just get replaced by something else later on. Given that the recommendations for Corten Steel suggest not using it near saltwater (because it will corrode even faster), I guess this adds weight to the argument that this is a "temporary" installation. But what happens as it breaks down over a few decades? Does the steel begin to develop ragged holes as the rust stains gradually spread down the beach? Or is the whole process completely benign?

For the time being, the wall is sufficiently far back that only the highest tides will reach it. But if this shoreline is eroding - and we must assume that it is - there will be less and less beach in front of the wall over time. The boulders placed on the beach (we saw this approach used in West Vancouver a few posts back) may trap some sediment, but they don't really change the underlying processes of rising sea level and chronic erosion.





Point Grey Foreshore - Part Three



While the foreshore is natural, the terrestrial edge is definitely not. This shoreline is almost entirely walled off. The walls reduce erosion, but probably their greatest benefit to the residences above is that they allow the terraces and patios to be extended right to the bluff edge, something the ragged natural edge would make difficult. Many of the walls had glass railings bolted to their top edge. The walls also discourage invasive brambles and human trespassers.  


Seawalls are often very mundane, utilitarian structures -- unpainted concrete, rock, or timber surfaces that are rarely seen by the people who live above them. But seawalls, particularly high walls like these, are great surfaces for artistic expression, and while this does nothing to address the environmental impacts, it sure makes the walls more interesting to folks on the beach.







Point Grey Foreshore - Part Two


As I often do, I've done some homework on this shoreline, trying to find background material, interesting footnotes, and corroboration for some of my observations. One thing I found fascinating was that this was described as the last natural shoreline in Vancouver. I guess it depends on where you stand, and what direction you look. If you stand at the base of the bluff and look towards the green residential towers of downtown and the West End, the shore does indeed look natural. But if you stand on the foreshore and look landward, you see some of Vancouver's most expensive homes, some amazing seawalls, and none of the original forest.


Calling it natural makes more sense if you contrast it with much of Vancouver's other shoreline, which consists of a wonderful public promenade, built atop a spectacular seawall. You can walk or ride a bike from Canada Place on Burrard Inlet all the way to Kitsilano, following 11 km of paved trail around Coal Harbor, Stanley Park, English Bay, False Creek, and past Granville Island (Vancouver Seawall). The Seawall ends in Kitsilano and the path then follows an inland route west to Jericho Beach and UBC.

Stanley Park 2008
Yaletown 2011

There have been proposals to extend the seawall (the one with the promenade) west from Kitsilano to Jericho Beach along this northern shore of Point Grey, but these have been opposed by folks who want to see this shoreline remain as it is (Georgia Strait: July 2012).

For another perspective on the natural shoreline, and for those who like to mix interpretive dance with their coastal geology, Rewilding Vancouver is a reminder that nature is defined by humans, and we may all define it a little differently.


Point Grey Foreshore - Part One




This short stretch of shoreline just west of Volunteer Park, between Kitsilano and Jericho Beach, is a fascinating collision of public beach, geology, seawalls, and art. I really had trouble figuring out how to separate these things.  My posts get confusing (or simply never get done) when I try to cover too many different topics in a single entry, so I'm going to break this 45-minute beach walk into three four separate posts. That also makes it easier to use more photos.

The Point Grey Foreshore is carved into a low bluff of Eocene sandstone. As we'll see in the next couple of posts, the cliff itself is now largely hidden behind high walls, but the sandstone makes extensive appearances on the foreshore as southerly dipping ledges. These can be seen in both the photos and in the aerial imagery.


AERIAL VIEW

There's not a lot of sand or gravel on the platform, although there are sporadic patches of beach associated with irregularities in the uneven shoreface. Much of the sediment is actually shell hash, suggesting that the sandstone erodes slowly enough to allow crustaceans to establish and not fast enough to generate much mineral sediment. What sand and gravel does exist is probably moved rapidly eastward by westerly wave action - to end up at Kitsilano Beach in another few posts.

Point Grey seems a pretty appropriate name for these photos, given the drab afternoon - but the next couple of posts will at least try to add some local color.  By the way, I believe Point Grey refers to the entire peninsula, which extends out to Wreck Beach (a prime future post) at UBC, but "Point Grey Foreshore" typically refers to this northern shore.






Sunday, April 17, 2016

Dundarave



I've got better pictures of this shoreline from my last visit, but the tide was lower this last week and revealed more of the beach. This was just a quick stop before dinner and we didn't stay long.

Dundarave: October 2011

The groin (or mole) here at the end of 25th Street probably started as a pier, but was eventually filled in, and a nice pocket beach has formed on its western (updrift) side. A smaller, lower energy beach has formed in the lee of the structure as well. But there isn't much mobile sediment on these beaches once you get away from the structure.


AERIAL VIEW

The shoreline farther east (in the distance) is heavily armored and gets hammered during high tide storms. But there probably aren't many people strolling along the trail on those days - just work crews clearing logs and gravel off the walkway.







Lawson Creek



I visited this shoreline four and a half years ago (also at the end of a long day at the Salish Sea Conference) and made a note to come back at a lower tide. I've been hearing about this project from a number of directions and wanted to see it for myself. I dragged a few other folks along, too.

Previous Post: West Vancouver 2011

West Vancouver's shoreline is subject to highly oblique wave action from the west, which moves whatever sediment is available eastward. Prior to development, most of this material probably ended up stacked against the delta of the Capilano River (under the Lion's Gate Bridge), in a more natural version of today's engineered Ambleside Beach (Ambleside 2011). Now much of it is trapped against groins or other obstructions at Dundarave and Ambleside.


I don't know this area well, but I suspect most of the sediment comes from the streams that flow to the beach off the hills above West Vancouver. And I don't know how that budget has changed with development - is it increased, or is it trapped in detention ponds? The problem is keeping it on the steep foreshore when it gets there.

At Lawson Creek just west of Ambleside, there have been efforts to add large boulders to the beach face in order to retain, or trap, sand and gravel. The result is a beach covered with (almost) randomly placed clusters of rocks. I suppose there were already scattered glacial boulders on the beach, but the result here was one of the weirder beaches I've seen. This approach has also been tried, or is planned, at other West Vancouver creek mouths.

(Now that I've looked at the aerials again, I'm wishing we'd gone a little farther west to see the next creek, where this basic idea has been taken to a another level)

AERIAL VIEW

I admit to being a little skeptical about this approach. It's not that it may not work locally, but it seems like it depends on how much sediment is really available. And whether the volumes are sufficient to make a substantial difference in the profile on these steep, narrow beaches.

Engineers have been proposing placing objects of some sort on the foreshore to trap sediment and prevent erosion forever (only a minor exaggeration). Groins, artificial seagrass, submerged sills and breakwaters, and a whole series of patented concrete devices sold for their promise of building back a beach where one has been lost. They may work, in some places, for a while, but they often do not. When sediment is successfully retained, the consequence can adversely impact down-drift beaches (much as with traditional groins). This may not be an issue here where the beach sediment is already largely confined to the big pockets against the projecting groins and piers.



Blaine



Marine Park in Blaine, just south of the Canadian border, is located on the northwestern edge of a large peninsula built out of fill when they dredged their port and marina. The shoreline edge is pretty ragged and was composed of rocky headlands formed from old concrete and rock debris and a few scattered, somewhat accidental beaches. I visited it six years ago when the City was contemplating improvements to the park's shoreline (Blaine 2010).

AERIAL VIEW

One segment of the shoreline has recently been fixed up. The concrete has been replaced with better constructed and more attractive riprap promontories and the pocket beach has been enhanced. The idea of taking advantage of the existing headlands is a good one and it facilitates the creation of stable pocket beaches. There's probably more that they could do along here, but this is a great start.

There were signs of some erosion of the bank just north of the large log and root wad (see pictures). This isn't anything serious, although it bears watching. I wonder if it's a result of last months high tide storm interacting with the large log that's been placed on the bank. This log, which includes a big root wad, seems too high to have just floated in, so I assume it's an installation. As we've seen on other sites, there's some risk associated with placing big wood high on a steep profile - - it may eventually get undermined. But then it roll down to a more natural place on the beach.


Chicago


We were in Chicago a little less than three weeks ago, winding up our brief trip back to the midwest. My only foray to the beach was on the morning we left, when I dodged rain squalls on my way to meeting M for breakfast at Tempo.

I've got much better shots of these beaches from an earlier trip:  Chicago: July 2010

The first three photos are from Oak Street; the bottom one is from Ohio Street Beach.

But rain or not, I still love these public beaches against the backdrop of Chicago's skyline. There's nothing terribly natural about them - nourished and groomed pocket beaches have replaced the spits and marshes that once marked the mouth of the Chicago River - but it shows that we can still provide ways for people to interact directly with the water, even in our most urban settings.

There are a lot more photos from this trip, mainly of skyscrapers, over on the other blog (hshipman: Chicago).




Saturday, April 16, 2016

Wind Point






Much of the southeastern shore of Lake Michigan, from Wisconsin south through Chicago towards the Indiana Dunes at the south end of the Lake, consists of eroding bluffs. But there are a number of locations where the bluff is absent, either because a lower river valley intersects the shore or because the beaches have accreted out into the lake.


AERIAL VIEW

I don't know the explanation for Wind Point, just north of Racine, but it extends out into the lake. It's low, but doesn't appear depositional. I suspect there may be bedrock control - a more resistant layer at modern lake level - but would need to do considerably more homework for this to be anything more than speculation. 

Sediment transport is pretty strongly from north to south on this shore of the lake, reflecting the strong north wave action (winds and long fetch). The presence of both sand and gravel, like on Puget Sound, is mainly a function of glacial sediment sources.
These small trees being eroded away just south of the lighthouse tell a story, but it's not a story I learned during my short visit!