Saturday, March 31, 2007
The historic maps (1800s) show Maxwelton Creek entering Useless Bay behind a very long spit extending north along this shoreline, but the spit is no longer. The once large estuary is now pasture and ditches; the tidal inlet is a pipe, a tide gate, and a brand new house; and the spit has been replaced by the broad beach and the homes along Mill Road (which refers to the mill that sat on this spot in the early 1900s). The photos show what's left of an old series of timber groins and the concrete outlet of the creek.
This will be the first of two posts from Maxwelton. Mackie Park lies on the broad foreland south of the old estuary, sandwiched betweeen beach homes. The boat ramp temporarily captures northward drift on its way to Sunlight Beach. Recently, erosion has increased just north of the ramp, possibly due to a rapid buildup of bars (the beginnings of a new spit?) farther south, which may be limiting sediment to this section of beach.
The shoreline from Possession Head at the south end of Whidbey north past the ferry terminal at Clinton is a mix of high bluffs and low spits that longshore drift has stretched north along the east side of the island. Possession Beach and Columbia Beach are built on long barriers out in front of the toe of the bluff, while Glendale was built on the mouth of a small creek (probably began as a barrier estuary with the stream mouth spit deflecting the creek northward - but that was long, long ago). There are a couple stretches of relatively natural shoreline left, including a beautiful segment just south of Columbia Beach where a little of the spit remains almost undisturbed with forested bluff rising behind (the hydrology is probably completely altered thanks to the development to the north (see air photo - click on title of this post), but it looks good from a distance).
Tuesday, March 13, 2007
The railroad around the south end of Discovery Bay headed right across the spit in front of this little pocket marsh. The original inlet at the distal (southwestern) end of the spit was blocked and a pipe or tidegate installed. Now the railroad is gone and there's an opportunity to exhume the spit and reconnect the salt marsh to the bay.
Back to the south end of San Juan Island with a new class of Beach Watchers. The slopes of Mount Finlayson face south over the Strait toward the Olympics. Old post-glacial shorelines can be seen as benches cut into the hillside. The bluffs are eroding (that's why they are bluffs) and it looks like they may be relocating the road (the section in the distance where it is closest to the edge) in the not-to-distant future. Sand and gravel eroded from the bluffs feeds a broad beach to the west and a series of dunes that march up the hill.
Salsbury Point has suffered several insults over the decades. The eastern portion of the spit and back barrier lagoon, including the historic tidal inlet, were replaced with houses. The western part was filled for the boat launch and the park. I understand the fill material was from the excavation of the approaches to the Hood Canal Bridge.
The bridge itself appears to have had a profound effect in this beach. Littoral drift (net) was originally north up Hood Canal and east around the point (it's why there was a recurved spit here in the first place), but the bridge acts like a big breakwater, effectively reducing fetch from the south and increasing the influence of northerly storms. I believe the bridge has reversed the net drift pattern, so that sediment eroded from the park now moves south and cannot be replaced. (In an earlier post, I noted that the west side of Point Roberts is another place where net drift may have been reversed).
Erosion had been met for years with haphazard dumping of large rocks, but in October, 1995, Kitsap County Parks replaced the rock and some of the fill with a gravel beach. 11 years later, it is doing great, except that it continues to spill gravel arond the corner toward the bridge. The beach at the eastern end has dropped at least a foot. What this beach really needs is an infusion of a few truckloads of sandy gravel every few years! Otherwise, someone will panic some November night and bury the beach under riprap again.
This shoreline at the south end of Deception Pass State Park has the best developed dunes of any site on the Sound. The beach is at the northern end of the large littoral cell that extends from Point Partridge. It's a barrier beach that separates Cranberry Lake from the Strait of Juan de Fuca. The gravel continues north, falling off into the deep currents of Deception Pass, but some of the sand is blown inland to form these dunes. Coarse gravel can be found among the dunes, maybe evidence of past overwash by storms or the erosion of the dunes to expose earlier beach deposits. I don't think the wind bloew it there.
Offshore bars are common along West Beach, presumably in part due to the exposure to long-period waves coming down the Strait (muted Pacific swell?). The beach from the park south has experienced significant erosion recently - the logs have been cast up onto the eroding dunes. There is some suggestion that this erosional zone has been moving north over the past several years. West Beach appears susceptible to long periods of erosion and accretion which may be related to plugs of sand and gravel moving north.
Washington's loudest beach! Just off the runway of Whidbey Naval Air Station, the planes do touch and gos for hours on end. The old prop P-3's are quiet (I grew up with them, a couple miles from the Brunswick Naval Air Station), but these A-6s have got to be the noisiest planes ever made. But it doesn't seem to phase the bald eagles. The air field was probably built over dunes and back barrier wetlands and the base's shoreline is now "protected" with concrete debris, but the main effect here on the north side is due to the presence of rock groins and a stream mouth. They modified the groin a few years ago and that may, or may not, play a role in the recent beach changes from here north.