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(360) 461-0799The untold story of the Elwha nearshore, by A. Shaffer, Coastal Watershed Institute 13 March 2014
The Elwha nearshore is one of the unique features of the Pacific Northwest The Strait of Juan de Fuca is 294 km long, 20-28 km wide, and up to 250 m deep. Over 80% of the water from Puget Sound and Strait of Georgia flows through the Strait (Mackas and Harrison 1997) So what is nearshore? ‘Nearshore’ is defined as extending from the area of tidal influence in lower rivers, and includes the riparian zone (along both river and marine shorelines), and reaches offshore to a depth of 30 meters
mean low low water (MLLW). Sediment is what makes our nearshore, and ‘drift cells’ define the sediment movement that creates our nearshore. Drift cells have three main zones: Sediment source (river/bluff or both); Transport zone, where wave energy moves sediment along shore, and the Deposition zone (spit) that is the terminus of a drift cell.
The Elwha nearshore in a nutshell is around 12 miles long and includes five main sections: 1. Lower river (north to south) 0.3miles 2. Estuary ( total area): 90 acres 3. Embayed shoreline (Freshwater Bay):4 miles 4. Feeder bluffs 4 miles 5. Ediz Hook (spit) 3 miles
All provide critical habitat for the fish that are drivers for the dam removal project including Chinook, coho, chum, steelhead, bull trout, cutthroat, herring and eulachon (Shaffer et al 2008; Ward et al 2008). They simply can’t live without a functioning nearshore.
Two critically important species of forage fish, surf smelt, and sand lance depend on the nearshore with a fascinating life history. Most of their lives they are pelagic schooling fish but lay their eggs on high intertidal beaches. Each have very specific grain size requirements: surf smelt spawn on gravel sand mix; sand lance (in winter) on sand mix
(Penttila 2007). Sediment is a defining feature of Elwha nearshore-historically-prior to dam installation-260,000 m3/year total and over 85% of the sediment of the Elwha littoral system
was recruited from bluffs. This sediment formed, and maintained, Ediz Hook, which in turn forms Port Angeles Harbor. (USCoE 1971) Around dam installation, an industrial pipe line unwisely installed along approximately 2 miles of Elwha feeder bluffs- and then armored. This made the shoreline hard and a hydrodynamic washing machine. It kicked off a series of
horrible erosion-and more armoring events. So sediment delivery to Elwha nearshore after dam constructions was severely limited- to less than 10% of historic rates (Parks et al. in prep). Synopsis? Primarily shoreline armoring-added with dams-has resulted in significant and persistent sediment starvation and disruption of hydrodynamics of the Elwha
nearshore. As a result, much of the Elwha nearshore is a hostile lunar landscape because of the sediment starved beach topography and wave energy-a far cry from what it should look
like (Dungeness Bluffs) What does this mean for the nearshore ecosystem? Nothing says it better than forage fish spawning distribution. The Elwha drift supports surf smelt spawning along less than 11% of it’s beaches compared to 47% along the comparative-and intact -Dungeness drift cell. And less than 3% of the Elwha drift cell supports sand lance spawning, compared to 28 percent of the Dungeness drift cell beaches.
Sediment starvation and lower river alterations have also dramatically impacted Elwha estuary from once having two river mouths and stable complex lower river and estuary
To a channelized, coarsened and diked single river mouth that has a fraction of the complexity. But beginning in 2011, profound changes are underway.
The river mouth has transitioned from this…
To this:
Approximately 16,000,000 cubic meters of sediment behind the dams-an asstounding volume- is predicted to reach the nearshore after dam removal. Sediment will leave the river mouth, and much will travel east to those sediment starved bluffs and spit. Only 2,500, 000 cubic meters-16% – delivered to the nearshore as of Sept 2013 (Stevens et al 2013) so restoration opportunity just beginning. As of September 2013 the river mouth has extended out 100 meters and depths have changed by 10 (Draut and Ritchie 2013; Stevens et al 2013) The area that historically was estuary is now freshwater, and new estuary is forming (Draut
and Ritchie 2013) -literally before our eyes. And what are the fish doing?
Freshwater species-including red sided shiner and prickley sculpin are using the new freshwater habitat (that was formerly estuary), and Chinook, chum, coho, juvenile surf smelt, and eulachon are using the new estuary (Shaffer et
al unpublished data). We’ll be providing details (and numbers) at the upcoming Salish Sea Conference in Seattle in May 2014. The adage holds in the nearshore-if you build it they will come. None of us anticipated how quickly these changes and use would occur. Changes are starting to transform the other landforms of the Elwha nearshore-surf smelt are already spawning on previously inhospitable beaches along Freshwater
Bay (Shaffer et al unpublished data). And we expect to see similar changes in forage fish spawning habitat along the Elwha feeder bluffs. But the sediment’s not there yet…. But remember the restoration along the feeder bluffs and Ediz Hook due to dam removal sediment will only be temporary. Feeder bluff armoring structures will stay in place- with more installed every year. And the lower river will remain diked.
This CAN be changed and true long term ecosystem restoration achieved along these shorelines-but we have alot to do to make it happen. The Elwha nearshore is an untold story and a once in a lifetime restoration event and opportunity Sediment from dam removals will be delivered to the nearshore within five years of dam removal- we’re two years into it.
So if we’re going to optimize this once in a lifetime nearshore restoration opportunity…We’d better get busy. For more information on how you can join the team contact Anne Shaffer at anne.shaffer@coastalwatershedinstitute.org
Citations
Draut, A. E., and A. C. Ritchie 2013. Sedimentology of new fluvial deposits on the Elwha River, Washington, USA, formed during large-scale dam removal. River Research and Applications
Mackas, D. L., & Harrison, P. J. (1997). Nitrogenous nutrient sources and sinks in the Juan de Fuca Strait/Strait of Georgia/Puget Sound estuarine system: Assessing the potential for eutrophication. Estuarine, Coastal and Shelf Science, 44(1), 1-21.
Penttila, D. 2007. Marine Forage Fishes in Puget Sound. Puget Sound Nearshore Partnership Report No. 2007-03. Published by Seattle District, U.S. Army Corps of Engineers, Seattle, Washington.
Shaffer, J.A, P. Crain, B. Winter, M. McHenry, C. Lear and T. Randle. 2008. Nearshore Restoration of the Elwha River Through Removal of the Elwha and Glines Canyon Dams: An Overview. Northwest Science. 82:48-58.
Stevens, A., G.Gelfenbaum, J.Warrick, 2013.Morphological Monitoring on the Elwha River delta. USGS report., Menlow Park, California. U.S. Army Corps of Engineers (USCOE). 1971. Report on survey of Ediz Hook for beach erosion and related purposes. Part II. Seattle District Army Corps of Engineers, Seattle, WA.
Ward, L., P. Crain, B. Freymond, M. McHenry, D. Morrill, G. R. Pess, R. Peters, J. A. Shaffer, B. Winter, B. Wunderlich. 2008. Elwha River Fish Restoration Plan, developed pursuant to the Elwha River Ecosystem and Fisheries Restoration Act, Public Law 102-495. U.S. Dept. of Commerce, NOAA Tech. Memo., NMFS-NWFSC-90, 168 p