Thursday, August 27, 2015

Thunder Mountain Lake



Upper Thunder Mountain Lake lies at roughly 6400', just east of the Cascade crest, and therefore drains towards Icicle Creek and Leavenworth. Most of its modest shoreline consists of granitic slabs or large granitic boulders that have arrived from the surrounding slopes. The steep, rocky shores don't lend themselves to beaches, because there is little sand or gravel size sediment and even if there were, it would be lost rapidly to the bottom of the lake.


But at the north end, where the bottom is more gradual, a beach has formed. More accurately, a small stream delta has formed, but there is sufficient wave action to have reworked it into a beach. A series of berms mark the progressive fall of the lake over the summer.

AERIAL VIEW

The source of the sediment is a small basin that yields grus (the granular remains of weathered granite) that the seasonal stream can easily carry to the lake. Most of the action probably happens in the early summer by water flowing from the melting snowpack or perhaps in occasional heavy rains. I suspect that lighter rains probably soak pretty fast into the porous soil and yield little surface flow to transport material, but this is not exactly a system I'm familiar with.




Tuesday, August 25, 2015

Quarry Beach



Tafoni weathering in sandstone
There can't be many publicly accessible beaches on Salt Spring that I haven't visited at this point, but each year I try to find something new. And fortunately, I think people on the island have done a pretty good job of generating new access points to keep me amused.


This is what most folks would probably call a rocky beach. It's not far from Vesuvius Bay (August 2013), where the geology is similar, but where at least there's a small cove to trap a nice little beach. Here, there's just not much beach, which makes it easier to admire the steeply tilted sedimentary layers of the Nanaimo Formation.


AERIAL VIEW
Could almost be a Seahawk



Yeo Point





Yeo Point itself is not a beach, but a rocky promontory at the north end of Ruckle Park on the southeastern corner of Saltspring Island. But it shelters a small, gravelly pocket beach on its south side. Nothing remarkable, but wonderfully quiet and secluded early on a weekday morning. More photos at hshipman.
AERIAL VIEW



On the north side of the point, there is an even smaller beach - probably not a beach at all by normal folks' standards. It's basically an accumulation of sand and gravel-size shell fragments (it's the only sediment available) pushed up onto the rocky ledges.


St Mary Lake



This relatively small lake on Saltspring Island has neither the waves nor the sediment to form natural beaches and is fringed by reeds everywhere except where the bedrock plunges too steeply to provide any shallow water where vegetation can take hold. And like most lakes in the great northwest, the original shoreline was probably once a tangle of fallen trees.

This beach is artificial, probably created many decades ago by cutting the vegetation, building two small rock groins, and dumping a few truckloads of coarse sand. I suppose they may have added a little sediment since, but in the 18 years I've been visiting it, I've seen very little change. 

AERIAL VIEW

Like all pocket beaches, it is swash-aligned, facing the dominant wind waves coming up the lake (corresponding to the maximum fetch). There's not a lot of action on this beach. There are no tides, although there is some seasonal fluctuation in the lake level. On windy days, waves can create small (tiny) berms, but mainly they just leave a line of froth. The only significant morphological change is the result of junior engineers building boat basins and sand castles.

I thought I'd added this beach to my collection years ago, but apparently this is its first appearance in this blog.  Ironic, given I've probably spent more time contemplating this beach than any other. It does show up regularly every August in my hshipman blog (here are posts from 2010, 2011, and 2012).








Sunday, August 02, 2015

Mission Creek


Mission Creek is another small stream mouth with a long history. The old road cut across the mouth of the estuary on a small causeway but in the last couple of years, local groups have worked together to remove the armor and the fill and the creek now flows freely.

AERIAL VIEW

This site is at the south end of Olympia's Priest Point Park and within sight of the Capitol Building and the city's Port Peninsula. There's not much wave energy here on Budd Inlet. The shoreline in the park north of this site consists of a small promontory of Pleistocene gravel that would probably be long gone if the waves were bigger and a salt marsh that has formed without the need for a protective spit.

One the challenges of restoring these small stream mouths - besides the occasional railroad (see previous post) - is their cultural history. These places were probably always important Native American sites. They were low-lying areas with fresh water and easy access to the Sound. And later they were the obvious places for settlers to homestead or to build fishing camps and shingle mills. That means that although restoration may sound good to everyone, it is very difficult to do it without disturbing something of importance to someone.






Lund's Gulch


Meadowdale is one of the several small parks that sit on stream mouths along the railroad between Seattle and Everett. I like to call this stretch the Great Northern Beach, after the railroad that shaped this coastline for so much of the 20th century and which continues today as the BNSF.


Spits are common at the mouths of coastal streams and the one here has been growing the last few years, extending north and then pushing the stream outlet into a narrow channel. These spits tend to grow for a few years, get cut off by the erosion associated with a big stream flood or a big coastal storm, and then do it all over again.

AERIAL VIEW

The creek that flows through Lund's Gulch is one of thousands of small streams that empty into Puget Sound. Very few remain in their natural condition and even in remote parts of the Sound we find that their lower sections have been rechanneled, their estuaries filled, and their mouths funneled through culverts beneath roads and railroads.

This stream drains a small watershed surrounded by dense residential development. The valley itself seems to be in pretty good shape, but generates a lot of sediment, all of which must find its way to the mouth. Unfortunately, the stream's last leg is through a small concrete box culvert that must pass high flows, sediment, fish, and pedestrians - and it can't do these all at the same time.

There is no simple way to enlarge the opening beneath the rails. This problem is shared with many other stream mouths around the Sound and I've always wished their was some strategic approach that could be applied to a suite of these sites - an approach that would fix the stream mouths, improve conditions for fish, and also help improve safe public access to the beach along this dense urban corridor.

Some other stream mouths along the Great Northern Beach:
Carkeek Park (2009)
Boeing Creek (2013)
Picnic Point (2007)
Merrill and Ring (2009)
Howarth Park (2011)

And elsewhere:
Sequalitchew Creek (2010) (on another section of the railroad)
Nellita Creek (2010, 2011)
Seahurst (2009)
Glendale (2009)
Eglon (2007)

Brand new sand bar right at the stream mouth













Monday, July 13, 2015

Baker Beach




Whereas Crissy Field lies just inside the Golden Gate, Baker Beach lies just outside. And as a result, it was about 20 degrees colder! Whereas Crissy Field is an estuarine barrier beach, Baker Beach is more of a pocket beach, tucked in below steep bluffs of serpentinite.

The upscale Sea Cliff neighborhood is perched on the rocky cliffs above the southwest end of the beach - the closest homes isolated from the public by walls and chainlink fence.

AERIAL VIEW


The USGS has produced some beautiful sonar maps of the sea bottom off the Golden Gate, including an amazing field of sand waves in the deeper water offshore of this beach.

Under the Golden Gate Bridge, Dartnell and others, 2006.


This is the last post from my June road trip, which also means I've finally caught up. I've also caught up on my other blog. The road trip generated almost 30 entries on hshipman ("roadtrip2015") - and while there is a little bit of overlap with this one, most of the entries over there aren't beaches.

Crissy Field



Crissy Field is located in San Francisco, just inside the Golden Gate. It's seen major restoration work in the last couple of decades (mainly around 1999-2000, I believe) and has now become an amazing recreational destination. It offers great views of both the bay and the city (and of course, the Golden Gate Bridge) and on a Saturday afternoon in June it was crawling, rolling, jogging, and just plain crowded with visitors, both local and from far away.

AERIAL VIEW

The restoration work included not just the tidal lagoon and marsh, but also the beach and the dunes. For more on the history and restoration of Crissy Field, see this description at the Golden Gate National Recreation Area website.



Saturday, July 11, 2015

Bonneville Salt Flats


Here's yet another post from a place where the notion of beaches is a little fuzzy. The Bonneville Salt Flats are the floor of prehistoric Lake Bonneville. They are higher than the current extent of Great Salt Lake, but much lower than the prehistoric levels of Lake Bonneville. This is a pretty typical dry season view, but in wet periods the flats can flood with a very shallow layer of water, which may qualify the edge of the highway shoulder as a shoreline of some sort. Maybe with wave action, the gravelly shoulder of the road is actually a beach.

AERIAL VIEW

If you look carefully at this photo, you can find a distinct Lake Bonneville shoreline on the mountain slope in the background.

For another shot of Lake Bonneville's shorelines, you might check this post on Gravel Beach:
Lake Bonneville: July 2007

And for more about Lake Bonneville's history and geography, look at this one over on hshipman:
Bear Lake: June 2012

Medano Creek


Shorelines and geomorphology, but instead of coastal processes, the story here is the interaction of fluvial and aeolian processes. The broad San Luis Valley gathers sediment eroded off the surrounding mountain ranges, particularly the San Juan range to the west. Like so many western valleys, this one was once (probably more than once?) filled with a large lake and sand and silt accumulated on its bottom. When the lake dried up, southwesterly winds remobilized the sandy material and blew it across the valley, piling it up against the base of the Sangre de Christo Mountains and creating this large dune field. Storm winds coming down the hill from the east further shapes the dunes, creating the landscape we see today.

AERIAL VIEW

Medano Creek flows out of the Sangre de Christosand is deflected southward when it encounters the dune field. In spring, when it is flowing, it erodes the forward edge of the dunes and carries sand southward into the valley, where it is probably picked up again by the wind when the creek dries up.

The braided nature of the broad shallow creek is a result of its being maxed out with sandy sediment. It was fun to see the channels and riffles shifting around, even over short periods of time, and to watch the rapids surge as the flow fluctuated.