Elwha Watershed Information Resource

The Elwha nearshore is a critical part of the watershed ecosystem providing a feeding area, refuge, and migration corridor for many species, including threatened salmon and char (Shaffer and others 2006). Wind and currents through the Strait of Juan de Fuca help mix the water in the nearshore area and contribute to its rich nutrients. Historically, the Elwha River was home to some of the biggest and most diverse salmon runs in Washington state. In the last century, dams have blocked sediment transport and bulkhead structures constructed along the river have significantly eroded the nearshore area. However, the nearshore still supports a variety of plants, fish, shellfish, and wildlife.

Physical Processes

Beach seining off the Elwha bluffs. Anne Shaffer, Washington Dept. of Fish and Wildlife

Physical processes (such as wind and tidal currents) significantly impact the Elwha nearshore area, helping to bring many nutrients and other resources to this historically plentiful area. For example, strong seasonal storms move pulses of freshwater and sediment into the Strait of Juan de Fuca forming large areas (lenses) of very low salinity and very high turbidity within the nearshore (Shaffer and others 2006). Strong winds and currents continue to mix nutrients from rivers in with the deep ocean water, resulting in a nearshore area where the water is well-mixed, cold, and nutrient-rich year round (Mackas and Harrison 1997). In the nearshore area, wind is the dominant process, but it is highly variable. Currents in the nearshore often change dramatically within hours as a result of both regional and larger-scale oceanic winds (Hickey 1996; Strickland 1983).

Sedimentation

Sedimentation also plays a significant role in shaping the Elwha nearshore (Downing 1983). Sedimentation is the natural method whereby minerals and organic matter (such as silt and rocks) are deposited along the Elwha River nearshore region, which builds it up. Historically, more than 70 percent of the nearshore shoreline material came from natural coastal bluff erosion and the rest was provided by the river (Schwartz 1994; USCoE 1971). In a healthy nearshore environment, ocean currents will continue to wash some of the accumulated sediment away--but ultimately the lost sediment will be replaced with new material from the bluffs and the river and this cycle sustains the nearshore area.

Since the early 1900s, the natural replenishment of sediment has been disrupted by restrictions to both sediment flow and sediment sources--resulting in a sediment starved nearshore area (Shaffer and others 2006). The natural flow of sediment down the river is blocked by the Elwha and Glines Canyon Dams (constructed in 1914 and 1927, respectively). In the last ninety years, a little over 17 million cubic yards of large and fine grained sediment has built up behind the dams. The sediment problem was further compounded when a 9,000-foot bulkhead was built in the late 1950s. The bulkhead prevents the coastal bluff from eroding, which has deprived the nearshore of its largest historic sediment contributor (Shaffer and others 2006). Together, these structures have contributed to significant long-term erosion of the Elwha nearshore area (USCoE 1971; Downing 1983; Harring 1999; Schwartz 1972).

Erosion caused by human activities (such as tidgegates, dikes, and bulkheads) has altered the nearshore marine habitat (Clallam County Marine Resources Committee 2001). Bulkheading the shoreline increases wave energy, which in turn decreases spawning and migration habitat and creates coarse substrate that is unsuitable for forage fish. Human alterations of the nearshore area have also caused loss of wetlands, eel grass, and clam habitat.

Nearshore Habitats

Even with the erosion, the diverse Elwha nearshore provides many species with critical habitat. In the nearshore area, these species (which include three federally listed salmon and char--the Puget Sound Chinook, the Strait of Juan de Fuca/Hood Canal Summer Chum, and the coastal/Puget Sound bull trout) can find food and take refuge from predators; this area is also an important part of the Strait of Juan de Fuca migration corridor (Shaffer and others 2006). For example, forage fish (including eulachon, surf smelt, sand lance, and herring) spawn, feed, and migrate in the nearshore area (Shaffer and others 2006).

Vegetated habitats--that is, areas with significant quantities of plants--predominate in the nearshore, covering 60 percent or more of the shoreline (Shaffer and others 2006). These vegetated habitats help provide the cover so essential to many of the species in the area for refuge and spawning. Nearshore vegetated habitats include:

• Kelp beds
• Eelgrass beds
• Drift algae
• Rocky/cobble shorelines with seaweed cover

The Strait of Juan de Fuca kelp beds account for 78 percent of Washington's kelp, and these coastal kelp resources can be found along at least 40 percent of the Elwha nearshore (Shaffer and others 2006). There are three dominant species: Macrocystis integrifolia (giant kelp), Nereocystis luetkeana (bull kelp), and Pterygophora californica (an understory kelp). After the kelp beds, the next largest vegetated habitat in the area are eelgrass beds. Zostera marina (eelgrass) covers at least 20 percent of the Strait of Juan de Fuca shoreline (Thom and Hallum 1990; VanWagenen 1998).

Many species inhabit the nearshore area. Some examples of area shellfish and wildlife are listed below.

Elwha nearshore shellfish include:

• Crab
• Shrimp
• Geoduck
• Abalone
• Scallops
• Native and Pacific oysters
• Urchins
• Sea cucumbers

Elwha nearshore wildlife includes:

• Alcids (marbled murrelets, tufted puffins, rhinoceros auklets, and others)
• Sea otters
• Dahl’s porpoise
• Harbor porpoise
• Orca and Gray whales

Reference

Clallam County Marine Resources Committee. 2001. Interactive public workshop series.

Downing, J. 1983. The coast of Puget Sound: Its processes and development. Washington SeaGrant, University of Washington Press, Seattle, Washington. 

Haring, D. 1999. Salmon and steelhead habitat limiting factors, WRIA 18. Washington Conservation Commission Final Report, Olympia, Washington.

Hickey, Barbara. 1996. "Physical Oceanography of the Olympic Coast." Olympic Coast Marine Research Workshop Proceedings. Occasional Paper OCNMS 96001.Olympic Coast National Marine Sanctuary. Port Angeles, Washington.

Mackas, D.L. and P.J. Harrison. 1997. "Nitrogenous nutrient sources and sinks in the Juan de Fuca/Strait of Georgia/Puget Sound Estuarine System: Assessing Potential for Eutrophication." Estuarine, Coastal, and Shelf Science. Volume 44. Pages 1 to 21.

Schwartz, M. 1994. Beach geomorphology at the Elwha river delta in connection with removal of the Elwha and Glines canyon dams. A report to the Lower Elwha Tribal Council, Coastal Geologic Consultants, Inc. Bellingham, WA.

Schwartz, M. 1972. Spits and bars. Dowden, Hutchinson, and Ross, Publishers. Stroudsburg, Pennsylvania.

Shaffer, J.A. and others. Nearshore of the Central Strait of Juan de Fuca and Removal of the Elwha and Glines Canyon Dams: An Overview. March 2006.

Strickland, R. 1983. The fertile fjord. Seagrant Publications, University of Washington Press. Seattle, Washington.

Thom, R. and L. Hallum. 1990. Long term changes in the areal extent of tidal marshes, eelgrass meadows, and kelp forests of Puget Sound. Fisheries Research Institute, University of Washington. FRI-UW-9008. Seattle, Washington.

United States Army Corps of Engineers. 1971. Report on survey of Ediz Hook for beach erosion and related purposes. Part II. Seattle District Army Corps of Engineers. Seattle, Washington.

VanWagenen, R.F. 1998. Washington coastal kelp resources: Port Townsend to the Columbia River. A report to the Washington Department of Natural Resources. Olympia, Washington.