Saturday, February 06, 2010

Double Bluff

The end of Double Bluff Road was packed with cars, but I found a space and joined the crowd. Fortunately, it thinned out pretty quickly as I headed across the new spits and made my way to Double Bluff itself - arguably the biggest and best bluff on Puget Sound.

I will save more of my beach observations for a longer visit with better light. I'm sure I will be back.

What a great way to end the day - before racing off to catch the 6PM ferry back to the big city.

Sound Waters is a great excuse to visit Whidbey Island on a Saturday in February. If you search the blog for the label "Whidbey", you will find that several of the posts sprung from these trips. (Wow - 29 entries come up for Whidbey - I must spend way too much time up here!)

Mutiny Bay

I spent the day at Sound Waters but headed out while I still had some daylight left. There was no way I was going to spend a beautiful Saturday on Whidbey without actually going to a few beaches! As usual, the event was well packed and well run. As usual, congratulations to Beach Watchers and all the volunteers that make it happen.

The end of Robinson Road is a good way to experience the sandy beaches of Mutiny Bay. Every year a few thousand cubic yards of sand (that's a guess) heads past here on its long trip from Double Bluff to Bush Point. The abundant sand wreaks havoc with the boat ramp and with the outfall that drains the area behind the beach. I've never seen the beach - any beach - looking quite like this one did today. Intertidal lumps - it looked like a big pile of wet sand had been shaken. I honestly have no idea what happened here, but it sure looked cool!

Historically, Mutiny Bay consisted of a beautiful series of slender spits stretched out around the bay with large wetlands behind and occasional tidal inlets. Hard to tell now, beneath all the big houses. The lagoons are pastures or lawns and the only tidal inlets left are the drain outfalls.

Lowell Point

I hadn't walked this southernmost part of Camano Island State Park in many years. I'm often down here at very high tides when the waves leave little room to walk along the toe of the bluff - which makes walking the spit just north a more attractive option (
Lowell Point).

Wolf Bauer coined the term "feeder bluff" decades ago for the eroding bluffs that contribute sand and gravel to Puget Sound beaches and the term has stuck. We still use it in regulations and technical reports and interpretive signs. It's a great functional term that describes what these bluffs do. Sometimes I avoid the term - it lacks the scientific credentials and precision of wordier phrases - but in the end, it works.

This particular feeder bluff has been working well recently. The culprits include early season rains, some good freezes (which can contribute to certain kinds of failures), and the recent very high tides. A 13.9 foot tide, like those of two weeks ago, probably brings water right up to the toe of the bluff itself - even without waves.

Discovery Park

I was just down here in November (
West Point) but the tide had been too high to let me visit the big landslide on the south side of the park. Today, the water was lower and we were able to get a good look at this complicated stretch of shoreline.

There's been plenty of recent sliding - maybe a combination of early fall rains and the recent high tides. The beach was littered with scraps of wood and there was little logic or pattern to the sediment on the upper beach - suggesting lots of fresh material, lots of sorting still to happen.
The large central portion of the slide was dumping large amounts of sand onto the beach and a raised band of deformed clay 20-30 feet out on the beach marked the toe of the active slide. The lower beach at the south end of the park is marked by a confused series of ridges or berms. They did not appear to be normal bars - maybe they reflect irregularity in the topography of the platform due to historic deep-seated sliding or otherwise messed up geology.

There was little mobile sediment in this southern area. Maybe it's an an indication of a sediment-starved beach. The historic source of material is the two miles of updrift, and unstable, shoreline now called
Perkins Lane (2007) - which has been largely armored for most of a century.