Sunday, October 10, 2010

Elwha Delta

This is a little out of order - I managed to skip over it when posting other entries last week. These shots go back about two weeks.

The Elwha River drains the northern interior of the Olympic Mountains, arriving at the coast in a gravelly delta a few miles west of Port Angeles. The river mouth shifts around, although maybe not as much as it did before the levees were built in the lower valley - including one immediately west of the mouth that has recently been raised. The mouth is a complex set of coarse gravel spits, bars, and islands and a number of small lakes and lagoons.

The delta projects well out into the Strait of Juan de Fuca where it is influenced both by waves and swell from the west, as well as storm waves from the northeast. The beach on the western side, facing Freshwater Bay, is a broad crescent and longshore transport may be fairly balanced (aerial view). On the eastern side, however, the beach that fronts the delta is eroding rapidly and sediment is moved eastward down the coast towards Ediz Hook in Port Angeles (previous posts on this stretch of shoreline).

The Elwha's two high dams are supposed to start coming out next year. It may be some time before the gravel behind the dams shows up at the coast, but maybe the delta will see more immediate changes due to differences in flood events or the release of fine sediment. This is going to be a neat place to watch over the next decade.

No comments: