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.


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.


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.


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.


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.

Thursday, July 09, 2015

Grimes Point

It's a little difficult to make out the old shorelines of Lake Lahontan in this photo. I'm sure it would have been better earlier or later in the day when the sun was lower and the shadows more distinct.

Lahontan was a large lake formed during the cooler period that followed the last glaciation and it filled much of the area between the mountains in western Nevada 10,000 years ago.  It lingered at lower levels much later than that and the petroglyphs at Grimes Point are carved into boulders that would have been scattered around the edges of of a shallower lake several thousand years later. Or at least that's how I understand the story.

Gilbert did some classic work on the spits and other landforms that formed on the shores of Lake Bonneville, but I haven't done my homework and don't know how much has been done on the shorelines of Lake Lahontan (although I'm pretty sure shorelines features and beach ridges have been described).

Nevada Beach

Nevada Beach is a long strand of coarse red sand, very different than the landscape at Sand Harbor. It's located at the southeast corner of the lake and appears to be the result of sand moved eastward, possibly from stream sources along the south shore shore of the lake. The backshore is wide and suggests a very long period of sand accumulation (or a lot of human intervention that I'm missing). From the shape of the beach, I assume the dominant wind and waves impacting this stretch are westerlies - it just seems like this shoreline would look very different if northerly wave action was a significant factor.


As usual, my observations are based on awfully limited experience and virtually no research, so I apologize if I've got the story wrong. All my searches for information on Lake Tahoe beaches went to tourist sites and vacation rentals, not shoreline geomorphology, although I can't imagine that some geologist hasn't found an excuse to spend a summer or two studying these beaches.

Sand Harbor

100 years ago, Sand Harbor was a place to load logs onto boats headed for the mill. Now it's the primary beach access for Nevada's Lake Tahoe State Park. The small bay is actually a pocket beach tucked into the north side of a bouldery point. There is a much broader beach on the south side of the point.  The orientation of the beaches at this northeast corner of the lake - here and just north in Incline Village - matches the large fetch across the 22-mile long lake.

I love the juxtaposition of the rounded boulders with the deep blue water. The beaches on the lake seem to range from white to pink - which I suppose reflects the variation in the granitic rocks from which they were eroded.

I made a mental note to come back sometime and spend a lot more time exploring the beaches around the rest of the lake. On this trip, I had to stick to a fairly tight schedule and to the east side.

Wednesday, July 08, 2015

Lake Almanor

Lake Almanor is a broad, shallow reservoir south of Mount Lassen, located on the north fork of the Feather River. Lake levels rise and fall through 10-20 feet seasonally depending on the year. The shoreline includes a diversity of landforms, including marshes, low bluffs, and beaches.  On my fairly quick drive down the eastern shore, I caught a few of these.

This post, along with the next several, are from a very nonlinear road trip in June. No route between Seattle and Madison, no matter how contrived, contains all that many beaches (although on some previous trips I've looked pretty hard), so some of the following sites are a little bit of a stretch. But I've noted before that this blog, despite it's title (and subtitle), allows for some flexibility. The common theme is that posts should be based on a relatively specific place and have some relevance to shorelines and/or geology. Which I think these all will.

While this trip only generated a small number of posts here, it did (or soon will) result in two dozen posts on my other blog. For readers of Gravel Beach that are also interested in extended road trips, obscure (and not so obscure) National Parks, state high points, geographic trivia, roadside geology, and glimpses into the peculiar things that float my boat (besides beaches), you might check out hshipman: Road Trip 2015 (in progress - it will be a few days before I catch up over there, too).

Monday, July 06, 2015

Mission Beach

Mission Beach, on the Tulalip Reservation, is a heavily developed stretch of shoreline, with homes built out over the beach and perched on top of the bank. It's a continuous (albeit colorful) line of stairways, boat lifts, and timber bulkheads.

I visited several years ago (see photo and link below) and this stretch at the south end was a long row of homes tucked into the toe of an unstable bluff. Storm waves could be tossing logs against the front windows while mud from the hillslope flowed in the back door.


These properties were all leased from the tribe and the tribe decided a long time ago that when the leases ran out, they would reclaim the beach. And in 2013, that's exactly what happened. I'm sure that no amount of warning makes someone feel good about dismantling something that's been part of their family's lives for decades, but it's also a neat reminder that nothing is forever (or at least that some things, like beach houses below unstable slopes, should be forever). It would be nice if the remaining pile bulkhead could be pulled - it provides little, if any, benefit and prevents complete restoration of the beach.

Everett Herald: February 2013

Here's what this same stretch looked like in 2009 (from Mission Beach 2009)

Barker Creek

Two years ago, Kitsap County pulled out the old bulkhead at Anna Smith Park on Dyes Inlet (October 2012). This year, a bulkhead was pulled out on private property a short distance away and it's already hard to imagine that there was a structure here at all.

Yes, erosion will occur - as matter of fact, that is part of the point. But erosion is awfully slow and poses no risk to the upland development - and will not for many, many decades (longer than that, actually). There is still a way for residents to get to their beach and there is actually more beach for them to get to. The slope has been planted and will quickly blend in with natural shorelines in the vicinity.

It's amazing to see the progress being made by local groups in pulling out unneeded structures and in restoring beaches and shorelines. These will be the core of a growing menu of examples that help convince a lot of reluctant property owners that a natural shoreline can also be a desirable one. It's not the answer everywhere, but Puget Sound is an enormous place (2500 miles of shoreline) and there is plenty of room for both urban development and natural shorelines. But it would be nice if we could maintain or restore more of the natural in these rural and suburban areas.

The spit at the mouth of Barker Creek

Weaverling Spit

Late in May, I had a chance to visit Weaverling Spit again. It remains a very accessible and a very nice example of a relatively low energy gravel nourishment project. The second phase of the project - less than two years old - is blending in much better with the adjacent beaches than it did a year ago.


Dan met up with us and helped us identify the recent spawning in the upper intertidal gravel - although I think even a geologist might have found the eggs on this particular occasion! It's been reassuring to find that smelt and sand lance will spawn on nourished beaches, although there is still some question in my mind about whether this beach really would benefit from more sandy material.

Previous posts: Weaverling Spit

Barnum Point

Thousands of years of wave action has carved off the southeasterly face of this glacial ridge, creating a beautiful high bluff. A thick till drapes the ridge, with outwash sand and gravel below. The relatively straight line of the bluff faces directly down Port Susan, or pretty close to it, making this a nice example of a swash-aligned bluff (something we also see in other places around the Sound). 


Eroding till inevitably leaves behind cobble and boulders. Some is on the beach, but there were also clearly some very large rocks far offshore (some just barely breaking the surface during the paddle and creating some wonderful little rips where the current was fast).

The eagles were out in force - although they seemed to be too intent on watching me than to actually be catching any fish. There were at least four - and there may have been more but they all looked the same to me and I wasn't sure I was double counting.

Increasing recognition of the importance of eroding bluffs in the overall formation of beaches and spits on Puget Sound has resulted in some significant conservation purchases in the last few years. In the past, coastal conservation acquisitions were mainly focused on salt marsh and estuarine habitat, so it's neat to see beaches and even bluffs getting attention. Not only are these bluffs geologically and ecologically significant, they are iconic Puget Sound landscapes.

Barnum Point is one of the more recent examples of this:
Barnum Point (Nature Conservancy)

For another example, check out Lily Point on Point Roberts.