Point Defiance Drift Cell
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The Point Defiance Drift Cell (SPU 4026) is a beach system that runs from the Urban shorline near Ruston, westward to a convergence with SPU 8201 at Point Defiance.
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 4026 is a 7.1 km long beach system containing 236 meters of barrier beach (3%) and 5 creek mouths, one of 145 beach sites located in the South Central Sub-basin. Based on these attributes it ranks 66 out of 100 in terms of size and complexity among all Puget Sound Beach systems. Over five generations of beach development, 77 percent of beach length now has some indicator of sediment supply degradation, and 48 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 1818 meters. Based on these metrics, this site ranks 59 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 D15, a very large group of 247 sites with very high levels of sediment supply degradation and average to above average levels of shoreline development. Based on this grouping we recommend this site for a enhancement-based strategy, 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. The site faces a high 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 0.26 km, encompassing 0.6 hectares of tidal wetlands. This system is one among 88 barrier embayment complexes in the South Central Sub-basin. Based on these metrics this site ranks 22 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 P2, a very large group of 232 sites where very small embayments occuring at a typical density.
- Site 4026 currently has 0 embayment--1 less than under historical conditions. This has been accompanied by a 100 percent loss of wetland area and a 100 percent loss of embayment length, based on comparison to historic maps. None 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 69 out of 100 and placed this site in Degradation Group D7, a medium group of 30 barrier embayment systems where there has been an extremely high loss of embayment length, along with very high levels of sediment supply degradation. 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.
