Saturday, October 11, 2014

Elwha Delta

The Elwha Delta continues to build outward in step with the delivery of sediment from the reservoirs behind the Elwha and Glines Canyon Dams. Both dams are gone, the river is running freely, and an amazing amount of sand has made it to the river mouth, although there is a lot more still to come. 

Gravel is beginning to appear on the new bars and spits at the river mouth, although I suspect it will take repeated cycles of river mouth movement and wave action to recycle and sort this material before more persistent coarse-grained features can form.

For a more thorough update on what's been going on, you might start with Ian's most recent post on the Elwha and then move backwards:
Coast Nerd Gazette: September 2014

One of the most interesting questions, at least to me, is how growth of the delta will eventually contribute to transport of gravel farther down the coast towards Port Angeles. This probably isn't a slow dribbling of material to downdrift beaches, but rather it may be driven by events that release larger plugs of material - a shift in the river mouth, a big storm, the growth of a new spit on the east side - who knows?  I'm glad folks are watching.

Previous posts on Gravel Beach:
Elwha Delta (October 2010)
Elwha Delta (March 2013)
Elwha Delta (July 2013)

There's a lot of great material online about the Elwha and the changes occurring on the coast. Besides The Coast Nerd Gazette, check the National Park Service, and the Coastal Watershed Institute. Lynda Mapes has written Elwha: A River Reborn and there is a documentary film, Return of the River out as well.

Hollywood Beach

Hollywood Beach in Port Angeles is one of those neat little pocket beaches that can form when sediment is trapped against an artificial headland - and which are pretty common in heavily modified shorelines. The beach is neither natural nor intentionally created. It just sort of happened and has evolved to become a neat recreational resource.

The original shoreline was located much farther to the south, nearer the base of the original bluff, but in the early 1900s the Port Angeles shoreline was filled outward and the original beach was buried, along with the remnants of the native village that once lay at the mouth of Ennis Creek.

Karl Wegman and others provide a very nice analysis of the original shoreline and its subsequent reconfiguration, with an emphasis on the archaeological implications at:
Also, Peninsula Daily News (May 2010)

Some lower portions of Hollywood Beach were marked off where, earlier this summer, depressions began to appear. There was much speculation about the mysterious sinkholes and I'm not quite sure where it all got left. Because the modern beach is located on top of many feet of fill, there could be any number of things underneath the beach that might give rise to this.  It sounds like one of the most likely explanations is that this is the result of old logs and wood rotting out.

The eastern part of the beach is covered in fine dark wood particles, although I don't know if this came from this location or floated in from elsewhere. Port Angeles Harbor has been in the wood products business for its' entire history and there are no shortage of possible sources of this kind of material.