Elwha Drift Cell
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The Elwha Drift Cell (SPU 1400) is a long beach system which originates at the Elwha Delta and forms Ediz Hook, a long spit that forms the northern edge of Port Angeles Harbor.
Notes
- A industrial water supply line along the downdrift portion of this system has been armored, and prevents bluff erosion. Some level of residential development has occured above this armoring.
- A municipal landfill at roughly the midpoint of this drift cell has been exposed by bluff recession, and has been armored.
- Removal of Elwha River dams has resulted in increased sediment input at the Elwha Delta, increasing sediment supply after almost 100 years of sediment starvation.
- Washington State Department of Ecology's Mapping beach change to inform sediment management strategies effort has completed baseline boat-based LiDAR mapping of beaches and bluffs along this shoreline.
Nearshore Strategies Data Report
Cereghino et al 2012 completed a soundwide analysis to identify and describe beach sites in Puget Sounds as part of a nearshore ecosystem restoration strategy (using remote sensing data c. 2000-2006). The following narrative was developed to support distribution and use of analysis results:
- Beach Site 1400 is a 17.09 km long beach system containing 11599 meters of barrier beach (68%) and 3 creek mouths, one of 29 beach sites located in the Juan de Fuca Sub-basin. Based on these attributes it ranks 91 out of 100 in terms of size and complexity among all Puget Sound Beach systems. Over five generations of beach development, 45 percent of beach length now has some indicator of sediment supply degradation, and 26 percent of the nearshore zone has estimated impervious levels higher than 10 percent. Property boundaries now legally segment the shoreline with an average of one property every 190 meters. Based on these metrics, this site ranks 49 out of 100 in terms of estimated degradation among all beach sites in Puget Sound. The PSNERP Strategy Analysis places this site in Degradation Group D7, a group of 33 sites with large parcels and low intensity of shoreline development, but with average levels of sediment supply degradation. Based on this grouping we recommend this site for a restoration-based strategy, where there may be the opportunity through a combination of protection and restoration efforts to recover the full operation of ecosystem processes thereby recovering ecosystem services that are either degraded or at risk. The site faces a moderate risk from jetty development impounding sediment, has no impacts from active shoreline railroad, and faces a slight risk from predicted future population growth.
- This site is among 518 littoral cells that contained barrier-type embayments. Historically this system contained 1 barrier-type embayment, with an embayment shoreline of 2.94 km, encompassing 23.6 hectares of tidal wetlands. This system is one among 23 barrier embayment complexes in the Juan de Fuca Sub-basin. Based on these metrics this site ranks 65 out of 100 in terms of size and complexity among all Puget Sound barrier embayment systems. The PSNERP Strategy Analysis placed this site in Potential Group P9, a large group of 69 sites with large embayments and wetlands at a typical density, identified as noteworthy sites for their high potential to provide ecosystem services.
- Site 1400 currently has 1 embayment--the same as under historical conditions. This has been accompanied by a 55 percent loss of wetland area and a 45 percent loss of embayment length, based on comparison to historic maps. 100 percent of the remaining embayment shoreline length has evidence of shoreline modification. Based on these metrics, and the general development status of the drift cell, the PSNERP Strategy Analysis ranked this system 74 out of 100 and placed this site in Degradation Group D8, a small group of five barrier embayment systems where remaining shortened embayments have extremely developed shorelines, with moderate urbanization and loss of sediment supply across the driftcell. Based on this grouping, the site is recommended for a enhancement-based approach, where due to extensive development and degradation, the likelihood of restoring ecosystem processes is low, and efforts should focus first on mitigating development impacts, and strategically protecting and restoration critical habitat functions for key species.
