Willapa Bay Research Articles

Invasive European green crab (Carcinus maenas) predation in a Washington State estuary revealed with DNA metabarcoding.

Predation by invasive species can threaten local ecosystems and economies. The European green crab (Carcinus maenas), one of the most widespread marine invasive species, is an effective predator associated with clam and crab population declines outside of its native range. In the U.S. Pacific Northwest, green crab has recently increased in abundance and expanded its distribution, generating concern for estuarine ecosystems and associated aquaculture production. However, regionally-specific information on the trophic impacts of invasive green crab is very limited. We compared the stomach contents of green crabs collected on clam aquaculture beds versus intertidal sloughs in Willapa Bay, Washington, to provide the first in-depth description of European green crab diet at a particularly crucial time for regional management. We first identified putative prey items using DNA metabarcoding of stomach content samples. We compared diet composition across sites using prey presence/absence and an index of species-specific relative abundance. For eight prey species, we also calibrated metabarcoding data to quantitatively compare DNA abundance between prey taxa, and to describe an 'average' green crab diet at an intertidal slough versus a clam aquaculture bed. From the stomach contents of 61 green crabs, we identified 54 unique taxa belonging to nine phyla. The stomach contents of crabs collected from clam aquaculture beds were significantly different from the stomach contents of crabs collected at intertidal sloughs. Across all sites, arthropods were the most frequently detected prey, with the native hairy shore crab (Hemigrapsus oregonensis) the single most common prey item. Of the eight species calibrated with a quantitative model, two ecologically-important native species-the sand shrimp (Crangon franciscorum) and the Pacific staghorn sculpin (Leptocottus armatus)-had the highest average DNA abundance when detected in a stomach content sample. In addition to providing timely information on green crab diet, our research demonstrates the novel application of a recently developed model for more quantitative DNA metabarcoding. This represents another step in the ongoing evolution of DNA-based diet analysis towards producing the quantitative data necessary for modeling invasive species impacts.

Recruitment and Losses through the Life Cycle for Intertidal Clams in Willapa Bay, Washington

Recruitment and Losses through the Life Cycle for Intertidal Clams in Willapa Bay, Washington

No trade-off between growth and OsHV-1 tolerance in Pacific oysters (Crassostrea gigas) farmed on the West Coast, USA.

An important pathogen of concern for Pacific oyster growers in the USA is ostreid herpesvirus 1 (OsHV-1). Currently, oyster stocks exist that are tolerant to OsHV-1; however, it is uncertain if a trade-off exists between their tolerance to OsHV-1 and their growth in different environments. To investigate any potential trade-offs, Pacific oyster families with varying levels of OsHV-1 tolerance were grown in a bay where OsHV-1 is endemic (Tomales Bay, CA) and in a bay where OsHV-1 is absent (Willapa Bay, WA). In Tomales Bay, we found that oysters from OsHV-1 tolerant families grew faster than oysters from OsHV-1 susceptible families, while in Willapa Bay, no statistically significant difference in growth was found between oyster families with different levels of OsHV-1 tolerance observed in Tomales Bay. These findings indicate that Pacific oysters bred to be tolerant to OsHV-1 would not be expected to have a longer time-to-market regardless of the presence of OsHV-1 in the growing environment.

The signature of accumulated permanent uplift, northern Cascadia subduction zone

AbstractUplift of the overriding plate at a subduction zone denotes interseismic strain accumulation, which is subsequently released during a megathrust earthquake. Although most interseismic strain is thought to be released elastically, observations of uplifted coastal regions at subduction zones worldwide indicate that some strain may result in permanent uplift. The Grays Harbor and Willapa Bay (Washington, USA) coastal region of the Cascadia subduction zone hosts flights of marine terraces testifying to late Pleistocene rock uplift. Our new detailed mapping of the marine terraces recognizes nine new units, including estuarine and fluvial sediments. Luminescence dating, relative age based on soil maturity and terrace elevation, and an evaluation of previous ages from fossil shells collectively constrain the probable ages of three estuarine units to sea-level high stands during Marine Isotope Stages 5a, 5c, and 5e. We estimate an average uplift rate of 0.4 ± 0.1 mm/yr for the terraced estuarine units, consistent with other Pleistocene uplift and incision rates in Cascadia. When compared with observed interseismic vertical deformation, these rates suggest that about one-tenth of interseismic strain may become permanent. The values are permissible within the uncertainties of uplift based on regional estimates of interseismic vertical strain rates and of coseismic subsidence.

Multi-decade changes in the condition index of adult Pacific oysters (Crassostrea gigas) in response to climate in a US west coast estuary

Pacific oysters (Crassostrea gigas) were introduced to the US west coast in the early 1900's, but only regularly spawned in several discrete estuarine locations like Willapa Bay where conditions allowed for adult oyster gametogenesis as well as larval survival, retention, and settlement. Oyster industry participants have long recognized that the condition of marketable oysters was related to proximity of their growing areas to the ocean. This prompted resource managers to routinely collect data and identify trends in oyster condition index (CI) in this estuary. An analysis of this almost seven- decade long CI record revealed consistent trends across four sampling locations in Willapa Bay where 50–70% of the variability in CI was explained by a single component. This component of variability in CI was related most strongly to variability in the upwelling index (UI) which was positively correlated with CI during the summer upwelling season. A relationship with the Pacific Decadal Oscillation (PDO), a broader basin-scale index of temperature was also significant, but weaker and PDO was negatively correlated with CI. Shifts or breaks in the long-term CI record occurred in 1977/78 and 1999/2000 with another shift related to the second component of variation in CI that occurred in 1988/1989. The change in 1977/78 has previously been shown to correspond with a shift in the basin scale PDO, but more recent shifts appear to be correlated with local fluctuations in both temperature and upwelling intensity. Further investigation into shifts in the seasonal timing of temperature and phytoplankton as variables that control the oyster gametogenic cycle seem warranted.

Nekton use of co-occurring aquaculture and seagrass structure on tidal flats

On the extensive tidal flats of Willapa Bay (Pacific coast, USA), oyster culture, seagrass, and mudflats create a mosaic of intertidal habitats. Structured habitats are generally considered to increase abundance and diversity of associated species, but less attention has been paid to roles of different kinds of structure (seagrass meadows, reefs, farm infrastructure) or co-occurring structure in shaping nekton assemblage structure. Here, we investigated the effects of different oyster culture methods (suspended culture and bottom culture) on nekton communities and abundance across a gradient of seagrass habitats, during multiple seasons, and using both seine and video sampling methods. Of 23 major estuarine taxa, 2 were generally associated with vertical structure (eelgrass or suspended culture), 3 were seagrass specialists, and 3 primarily used habitats lacking vertical structure (mudflats and bottom culture). Where oyster culture was present, 5 taxa associated with on-bottom and 2 taxa associated with suspended culture. Assemblage structure responded to co-occurring structure as expected from responses to each structure type independently (i.e. additive effects of seagrass and oyster culture). In contrast to much empirical evidence in structured habitats, seagrass density was a poor predictor of overall fish abundance. These findings together suggest that maintaining a mosaic of available habitats is favorable for promoting diversity in Willapa Bay.

Differential Responses of Eelgrass and Macroalgae in Pacific Northwest Estuaries Following an Unprecedented NE Pacific Ocean Marine Heatwave

The 2013-2016 northeast Pacific Ocean marine heatwave (MHW) had myriad impacts on marine communities, but little is known about how this event affected coastal estuaries. We examined the extent to which elevated temperatures associated with the offshore MHW were observed in four estuaries (Willapa Bay, Washington and Netarts Bay, Yaquina Bay, and Coos Bay, Oregon) and the responses of macrophytes at marine dominated sites within these estuaries. Records of eelgrass (Zostera marina), ulvoid macroalgae (Ulva and Enteromorpha spp.), and environmental characteristics, including water temperature, were analyzed over three periods: before (2006-2010), during (2015-2016), and after (2017-2019) the MHW. During the MHW, all four estuaries experienced “estuarine heatwaves” (anomalous warm water events) at monitoring stations and there was an associated decline in macroalgae biomass. In northern estuaries (Willapa and Netarts bays) where water temperatures are normally higher and estuaries are shallower, aboveground eelgrass biomass declined and did not recover for at least three years after the MHW. In southern estuaries (Yaquina and Coos bays), where water temperatures are normally colder and estuaries are deeper, the MHW was associated with a neutral, or temporarily positive, change in aboveground eelgrass biomass. Our analysis supports the hypothesis that upwelling intensity and estuarine depth determined the severity of MHW impacts on macrophytes at marine dominated sites, and that the colder and deeper estuaries in the south may serve as refuges for eelgrass but not macroalgae. We suggest that estuary-specific responses were predictable given the drivers of macrophyte abundance at marine dominated sites, and that baseline ocean upwelling and estuarine temperature can be used to anticipate macrophyte responses at marine dominated sites to MHWs in the future.

Competition and coexistence in a rare Northeastern Pacific multispecies seagrass bed

Seagrass meadows with more than two species co-occurring at a small scale are unusual in temperate regions, and such multispecies seagrass beds are undocumented in the Northeastern Pacific. Seagrasses in multispecies beds may coexist through trait differentiation in body size, life history types and phenology, especially when competitive exclusion is interrupted by environmental variability. Here, we survey and manipulate a multispecies seagrass meadow in Willapa Bay, Washington (USA), containing Zostera marina, Zostera japonica and Ruppia maritima; our 13-month survey is the first formal documentation of multispecies seagrass bed occurrence in the Northeastern Pacific. Z. japonica, a non-native species, reached an end-of-summer biomass that was an order of magnitude greater than either native seagrass. To test competition, we experimentally removed Z. japonica and found competition occurred disproportionately on the smaller R maritima relative to larger Z. marina. R. maritima germinated later and senesced earlier than the two Zostera species, and the removal of Z. japonica positively affected R. maritima biomass, supporting previous studies that R. maritima is an opportunistic species. In addition to species-specific phenology and body size, all species presented annual life histories and thus began each annual cycle under high resource availability, such as light, space and nutrients, which may contribute to coexistence.

Diatoms of the intertidal environments of Willapa Bay, Washington, USA as a sea-level indicator

An understanding of the modern relationship between diatom species and elevation is a prerequisite for using fossil diatoms to reconstruct relative sea level (RSL). We described modern diatom distributions from seven transects covering unvegetated subtidal environments to forested uplands from four tidal wetland sites (Smith Creek, Bone River, Niawiakum River, and Naselle River) of Willapa Bay, Washington, USA. We compared our diatom dataset (320 species from 104 samples) to a series of environmental variables (elevation, grain-size, total organic carbon (TOCSOM), and porewater salinity) using hierarchical clustering and ordination. While no single variable consistently explains variations in diatom assemblages at every site, elevation, salinity, and substrate (mud fraction and TOCSOM) are variables affecting diatom distribution along our transects. Elevation was the major environmental control of diatom variability (explained 27–39% variance) at four transects (Bone River Transect 1, Niawiakum River Transect 2, Naselle River Transect 1 and 2). Salinity and substrate were the major environmental controls (explained 12–32% variance) of diatom variability at three transects (Niawiakum River Transect 1: salinity; Smith Creek Transect and Bone River Transect 2: TOCSOM). Analyses of a combined regional dataset of all transects suggest that elevation is the driver of regional diatom variability in Willapa Bay, with salinity and substrate co-varying along an elevation gradient. We identify species with narrow elevation tolerances that can serve as indicator species of specific environments. Despite the site-specific variability of our modern diatom distribution, the regional dataset provides an important dataset that can be used to reconstruct RSL in Willapa Bay.

A Comparison of the Juvenile Dungeness Crab Metacarcinus magister Habitat Provided by Contemporary Oyster Aquaculture Versus Historical Native Oysters in a U.S. West Coast Estuary

Oysters and seagrasses provide structurally complex estuarine habitat for fish and invertebrate species. On the U.S. West Coast, complex oyster habitat was historically provided by the native Olympia oyster Ostrea lurida but is now provided by the commercially cultured oyster Crassostrea gigas. Ostrea lurida is found in subtidal and low intertidal areas, whereas C. gigas is predominantly cultured at higher intertidal elevations, resulting in a potential shift in available habitat for other fish and invertebrates that use this intertidal habitat. This change in the available habitat and its use was examined for the juvenile Dungeness crab Metacarcinus magister, and results showed the following: (1) comparable crab densities in remnant and restored populations of O. lurida and cultured C. gigas in two estuaries, (2) generally higher crab densities in both of these shell habitats than those observed in eelgrass Zostera marina or open mud habitat, (3) contemporary juvenile crab density in intertidal areas of Willapa Bay was most influenced by distance from the estuary mouth (declining with increasing distance) but also declined with increasing tidal elevation, and (4) when extrapolated to the estuarine ecosystem scale using areal estimates of habitat coverage, historical habitat provided by O. lurida potentially produced three times more juvenile crabs than those currently produced in cultured C. gigas. Nonetheless, both intertidal oyster habitats contribute more to juvenile crab production than eelgrass or open unstructured mud, and the ecosystem services associated with the placement of native and commercial oyster beds should be considered when defining goals for and permitting both aquaculture and native oyster restoration in Willapa Bay and other U.S. West Coast estuaries. Managers should consider this shifting temporal baseline in intertidal habitat provision, but also conducting similar evaluations at this broader estuary scale when evaluating habitat value for other resources that use these habitats differently.

Estimating Long-term Trends in Populations of Two Ecosystem Engineering Burrowing Shrimps in Pacific Northwest (USA) Estuaries.

Temporal variation in the density and distribution of the burrowing shrimps, Neotrypaea californiensis and Upogebia pugettensis, were compared in two estuaries along the West coast of the United States (USA) where they are recognized as important ecosystem engineers. Since these shrimp construct deep burrows in the sediment, we quantified the relationship between burrow openings and shrimp density (1.5 and 1.7 burrow openings per shrimp for N. californiensis and U. pugettensis respectively) to permit population abundance estimates to be made over broad landscape scales. Neotrypaea californiensis populations estimated from burrow counts collected using a gridded survey design across representative tide flats declined by 25% between 2008-2010 in Yaquina Bay, Oregon and by 67% in Willapa Bay, Washington from 2006-2011, but increased again in Willapa Bay by 2014. Upogebia pugettensis had mostly disappeared from Willapa Bay by 2006 and declines were observed in Yaquina Bay, but the magnitude and long-term trajectory of U. pugettensis in this estuary was less clear. These species population fluctuations mirrored those observed in density collected at discrete sampling locations over the same period, equate to large changes in secondary production, and have likely resulted in substantial changes to estuarine habitat and food webs.

Factors limiting oyster growth in Willapa Bay (Washington, USA) evaluated with in situ feeding experiments

Natural and anthropogenic environmental changes in estuaries affect the growth and health of organisms living there, often along spatiotemporal gradients. Throughout the world's estuaries, aquaculture and wild oyster populations support food and cultural systems, so quantifying factors affecting growth may inspire interventions to prevent future losses of oyster productivity. In Willapa Bay (Washington, USA), an estuary that produces 10–20% of US oysters, oysters are primarily harvested for market from the lower estuary, putatively due to food limitation up-estuary. We present studies in which in situ experimental systems were designed to manipulate food availability in the upper, and in one case contrasting to the lower, estuary. Contrary to expectations, food addition did not improve survival, shell growth rate or tissue mass of post-metamorphosis juvenile Pacific oysters, Crassostrea gigas. Instead, the experiment did not recapitulate the impaired growth up-estuary that typifies on-bottom oyster outplants, and irrespective of food addition, growth rates in the upper estuary were equivalent to rapid summer growth (>10 mm month−1) in other regions of the bay. Multiple lines of evidence suggest that elevating oysters above the substrate in the experimental systems removed food limitation caused by reduced clearance rates, thus allowing oysters to grow rapidly, even when other environmental conditions such as carbonate chemistry were poor. This observation is consistent with experience of shellfish growers and a valuable observation for managers of wild and aquaculture shellfish in estuaries.

Collaborating for First Foods: Archaeological Investigations of Chinookan and Lower Chehalis Foodways in Willapa Bay, Washington

Collaborating for First Foods: Archaeological Investigations of Chinookan and Lower Chehalis Foodways in Willapa Bay, Washington

Changing Nature-Society Conditions and the Oyster Industry, Willapa Bay, Washington

Changing Nature-Society Conditions and the Oyster Industry, Willapa Bay, Washington

Editorial Notes

Editorial Notes Craig S. Revels It is with great pleasure that I welcome you to this, the eighty-third volume of the Yearbook of the Association of Pacific Coast Geographers. Last year's volume was published in a time of great uncertainty as the COVID-19 pandemic swept across the world, and this year's unfortunately arrives under similar conditions, slowly improving though they may be. The tragedies, disruptions, and general state of societal affairs during the pandemic will not soon be forgotten. The pandemic also generated uniquely historic circumstances for the Association. The most immediate of these was the cancellation of the 2020 annual meeting, one of only four such years (the other three being 1943–45, during WWII) that APCG had failed to hold a meeting since its founding in 1935. Additionally, the annual meeting is essential to the official workings of the Association, including leadership transitions. With the cancellation, the Executive Council made the decision to extend official council positions for an additional year and forgo the awards and accolades that are a key part of our meetings. One of the traditional functions of the Yearbook is to serve as an official record of the annual meetings held by the Association of Pacific Coast Geographers. With no 2020 meeting, these elements are of course missing from this year's volume, though they will reappear next year. Instead, volume eighty-three is comprised solely of original research and reviews that collectively suggest a theme of vibrancy and relevance for geographic inquiry in the wider world. Our first article takes us to the Pacific Northwest, where the delicate balance between rural livelihoods and the ecosystems upon which they rely is a recurring topic of debate. Lisa Butler Harrington and John Harrington consider the oyster industry of Willapa Bay, placing the evolution of local livelihoods in the context of broader questions concerning invasive species, ecosystem health, and external policy decisions that have historically influenced resource management and will continue to do so in the future. Many residents of the Pacific Northwest take for granted the hydro-electric landscapes that form the foundation of the region's economy and contemporary character. Katherine Heslop delves deeply into the broad societal currents and local impulses that led to the development of those landscapes. Thus, we see them as facets of early twentieth-century progressive [End Page 9] movements and the advent of federally based regional planning in Roosevelt's New Deal, juxtaposed with deeper regional processes that in many ways are still at work today. Geographers have been at the forefront of research into the spread of COVID-19 since the earliest days of the pandemic, and Steve Graves and Petra Nichols contribute an analytical perspective on infection rates in Los Angeles County. In particular, they statistically identify a causal relationship between infection and a range of key socioeconomic and demographic variables, a relationship influencing the location and rate of spread for the disease. They leave us to consider how those factors must be addressed in any preparations for future public health crises. Race and racism have once again returned to the national discourse, with a great deal of emphasis on its structural and institutional forms in areas such as housing policy, gentrification, and urban inequality. As Mallory Stermon and Chris Lukinbeal remind us, the legacy of redlining—essentially housing segregation arising from governmental lending policy—remains pervasive in the urban landscape. The authors analyze the persistence of redlining through the use of historical GIS and spatial analysis of neighborhood demographics through time. Examining the changing demographics of minority populations in Boston, Detroit, and Los Angeles, they demonstrate the potential of spatial analysis to help address one of the most challenging urban issues of the twenty-first century. The next articles illustrate two different ways in which students can be trained in the techniques of analysis and observation, contributing not only to our own research agendas but also developing valuable skills for their own future endeavors. Understanding local fire history is increasingly important in the western United States, and macroscopic charcoal analysis is the leading method for reconstructing them. However, several key methodological questions remain unanswered. Here, lead author Megan Walsh discusses...

NATURE-BASED DYNAMIC REVETMENT CONSTRUCTION AT NORTH COVE, WASHINGTON, USA

A dynamic revetment was constructed at North Cove, Washington, USA in December 2018 along a historically eroding 2-km shoreline reach of coastal barrier at the northern entrance to Willapa Bay. The revetment is composed of poorly sorted angular quarry rock ranging in size from pea gravel to small boulders as well as large wood debris and structures, a dune ridge, and native vegetation integrated with the revetment. The design, aim, and maintenance of the dynamic revetment is to simulate the functions of naturally forming cobble berms along composite beaches in the U.S. Pacific Northwest. The dynamic revetment continues to be adaptively constructed over time, enabling the testing of innovative design approaches and concepts that are rarely possible to do at full-scale in the field. The project provides a unique opportunity to explore nature-based engineering principles and design features.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/5w18tEjEePg

On the edge: assessing fish habitat use across the boundary between Pacific oyster aquaculture and eelgrass in Willapa Bay, Washington, USA

Estuaries are subject to diverse anthropogenic stressors, such as shellfish aquaculture, which involve extensive use of estuarine tidelands. Pacific oyster Crassostrea gigas aquaculture is a century-old practice in US West Coast estuaries that contributes significantly to the regional culture and economy. Native eelgrass Zostera marina also commonly occurs in intertidal areas where oyster aquaculture is practiced. Eelgrass is federally protected in the USA as ‘essential fish habitat’, restricting aquaculture activities within or near eelgrass. To contribute scientific information useful for management decisions, we sought to compare fish habitat use of oyster aquaculture and eelgrass, as well as the edges between these 2 habitats, in Willapa Bay, Washington, USA. Furthermore, given a recent shift towards off-bottom culture methods, in part to protect seagrasses, long-line and on-bottom oyster aquaculture habitats were compared. A combination of direct (underwater video, minnow traps) and indirect (predation tethering units, eelgrass surveys) methods were employed to characterize differences in fish habitat use. Eelgrass density declined within both aquaculture habitats but less so within long-line aquaculture. Most fish species in our study used long-line oyster aquaculture and eelgrass habitats similarly with minimal edge effects, and on-bottom aquaculture was used less than either of the other 2 habitat types. These results are consistent with previously observed positive relationships between fish abundance and vertical habitat structure, but also reveal species-specific behavior; larger mesopredators like Pacific staghorn sculpins were sighted more often in aquaculture than in interior eelgrass habitats.

Genetic divergence of selected and wild populations of Pacific oysters (Crassostrea gigas) on the West Coast of North America

The Molluscan Broodstock Program (MBP) has been selecting Pacific oysters Crassostrea gigas for improved yield for over two decades. Nevertheless, realized gain in yield, the percent difference in least-square mean yield between MBP and pooled control families made from “wild” stock, was reported to be zero in the fifth generation. Among the potential explanations for zero realized gain was that MBP-derived stock had spread or reproduced in bays with extensive oyster farming and contributed to the “wild” broodstock used for the control population. This “MBP = wild” hypothesis was tested by analyses of genetic data from four MBP cohorts and 11 wild populations, including founders of MBP cohorts. A new 2016 sample from Willapa Bay, the primary source of MBP's control families, was genotyped by high-resolution melting (HRM) of 45, SNP-containing PCR amplicons and compared to previous HRM data for a 1996 sample. Average temporal variance in allele frequencies for Willapa Bay implies a small, local, effective population size (Ne = 55, 95% CI, 32–159) with very high gene flow among Pacific Northwest populations (migration rate, m = 0.99, 95% CI, 0.25–1.0). These estimates, which are remarkably consistent with previous estimates, also based on 20-y intervals, for populations in Pipestem Inlet and Dabob Bay, support the general conclusion that the North American Pacific oyster metapopulation is evolving by genetic drift, likely owing to local sweepstakes reproductive processes, with high gene flow maintaining spatial similarity. Direct comparison of MBP and wild populations reveals 7× more genetic divergence between selected and wild populations than among wild populations. Evidence for genetic drift within the Willapa Bay wild population that is uncorrelated with genetic drift in Dabob Bay, together with evidence for genetic drift between MBP and all wild populations studied to date, falsifies the hypothesis that gene flow from MBP-derived commercial stocks to wild populations is responsible for a realized gain in yield of zero. Further analyses of parentage and relatedness in four MBP cohorts suggests that pedigree errors may have contributed to inaccuracies in the selective breeding program and resulted in the observed realized gain in yield of zero.

Preliminary analysis of bivalve prey available to spring migrant Red Knots at Grays Harbor and Willapa Bay, Washington, USA

Preliminary analysis of bivalve prey available to spring migrant Red Knots at Grays Harbor and Willapa Bay, Washington, USA

Late-Holocene shoreline responses to competing shelf, bay, and beach accommodation spaces under conditions of relative sea level change, and the potential for future catastrophic beach retreat in the Columbia River Littoral Cell, Washington and Oregon, USA

The Columbia River Littoral Cell (CRLC) (160 km in length) provides opportunities to compare competing accommodation space relations under different conditions of relative sea level change. The CRLC system includes abundant littoral sand supply from the large Columbia River, late-Holocene prograded beach plains and barrier spits (0.5–5 km in width), two large marine-dominated estuaries (Willapa Bay and Grays Harbor), and a high-wave-energy inner-shelf. Littoral sand accumulation rates in prograded beach plains and barrier deposits are based on paleo-shoreline positions that are dated by great-earthquake catastrophic beach retreat scarps (n = 10) from 0.3 to 5.0 ka. The retreat scarp timelines are mapped in across-shore GPR transects (n = 79), yielding timeline-bounded polygons (n = 247). The polygons are evaluated for littoral sand volume and bounding ages, yielding volume accretion rates (m3 ka−1), which are summed for the four CRLC subcells; Clatsop Plains (27.4 × 106 m3 ka−1), Long Beach (19.8 × 106 m3 ka−1), Grayland Plains (15.9 × 106 m3 ka−1), North Beaches (11.7 × 106 m3 ka−1). Major submarine sinks of littoral sand, including the inner-shelf and large marine-dominated estuaries, are evaluated for increased littoral sand accommodation space that could result from potential future sea level rise of 1, 2 and 3 m during the next century or two. The estimated beach and nearshore sand erosion needed to fill the increased submarine accommodation space from a 2.0 m rise in relative sea level would result in averaged beach retreat values of ~0.7 km (Clatsop Plains), ~1.2 km (Long Beach), and ~ 1.3 km (Grayland Plains), about 30–50% larger than previous estimates based on the Brunn method. These catastrophic shoreline retreat distances (0.7–1.3 km) represent 25–50% of the present widths of prograded barrier spits and beach plains. They serve as warnings about future catastrophic beach erosion resulting from potential future SLR in other similar barrier spit and beach plain shorelines worldwide.