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Case Studies of Sea Level Rise Projections and Ecological Information in Coastal Restoration and Management

These nine case studies are place-based examples of implementation along the Atlantic and Gulf Coasts that demonstrate how numeric sea level rise projections and quantitative ecological information, including species and habitat thresholds and ecosystem services, can be used to inform decision making in coastal restoration and management.

1. Saltwater intrusion into coastal freshwater impoundments at Prime Hook National Wildlife Refuge, Delaware Bay
2. Valuing corporate  coastal hazard mitigation for The Dow Chemical Company Operations, Freeport, Texas
3.  Drowning marshes at Rhode Island's Sachuest Point National Wildlife Refuge and the use of thin-layer deposition
4. Measuring impacts of sea level rise and storms on piping plover habitat in a highly developed area, Suffolk County, New York
5. Landscape connectivity to combat sea level rise within the Guana Tolomato Matanzas National Estuarine Research Reserve, northeastern Florida
6. Valuing ecosystem services from restoration projects in Massachusetts
7. Coastal protection at a landscape scale: The acquisition of Powderhorn Ranch in Coastal Texas
8. Integrative adaptation planning by the State of Maine
9. Community coastal resilience planning as a toolbox for addressing coastal risk in the Town of Guilford, Connecticut 


1. Saltwater intrusion into coastal freshwater impoundments at Prime Hook National Wildlife Refuge, Delaware Bay

The U.S. Fish & Wildlife Service (USFWS) is undertaking a tidal marsh restoration project at Prime Hook National Wildlife Refuge, Delaware Bay to protect the refuge from continued habitat loss and degradation. This refuge provides critical resting, spawning, nesting, and feeding habitat for many federally and State-listed threatened and endangered species that use the refuge or surrounding area, including the American oystercatcher; black rail; least tern; piping plover; red knot; American black duck; Atlantic and shortnose sturgeons; and Kemp’s Ridley, leatherback, loggerhead, and green sea turtles (USFWS 2015a). Both natural and human processes have impacted the refuge and led to erosion and subsidence. The refuge had two freshwater impoundments for the benefit of waterfowl (USFWS 2012), but these areas were often breached during coastal storms, such as Hurricane Sandy, and were converting from non-tidal freshwater systems to saltwater.

The freshwater impoundments, along with dikes and tidal flow restrictions within the Delaware Estuary, removed sediment from the system and resulted in lowered marsh elevations. Accretion rates in the area are the lowest in the state and half of long-term local rates of SLR, which are approximately 3 to 3.5 mm per year. Between 1992 and 2009, SLR rates were nearly 5 mm per year in parts of Delaware Bay likely due to land subsidence (USFWS 2015a). Consequently, impounded areas were experiencing increasing sediment deficits and were frequently submerged. Additionally, shoreline erosion rates in the area show a continued rate of erosion of about 10 feet per year in recent years (USFWS 2015a).

Supported by funding from the Hurricane Sandy Disaster Relief Act, this marsh restoration project is restoring manmade impounded freshwater areas within the refuge back to brackish and salt marsh, as well as restoring sediment transport to build elevation. It is re-establishing the refuge’s beach berm and dune system and supplementing substrate elevations along the back barrier marsh to support the recolonization of Spartina-dominated salt marsh, along with tidal channels that will restore natural hydrologic circulation and support saltmarsh species (USFWS 2015a). Dredged material will help close breaches and create a back barrier marsh platform, planted with Spartina alterniflora, Spartina patens, and other vegetation. Tidal influx is expected to facilitate sediment transport back into these areas to reverse subsidence and enhance the rate of marsh development. Research suggests that if relative SLR stays under a rate of 12 mm per year in areas with high sediment loading, S. alterniflora growth is expected to sustain an equilibrium elevation and optimal depth of tidal flooding relative to water levels (USFWS 2015a; Morris et al. 2002). While species thresholds related to SLR have not yet been considered, project partners expect to research and monitor the impacts of climate change on the marsh to identify thresholds or guidelines that will help mitigate future habitat loss and, thus, benefit local species, such as by identifying when further action may be required to prevent marsh drowning such as through sediment augmentation or periodic restoration of the back barrier marsh platform.

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2. Valuing corporate coastal hazard mitigation for The Dow Chemical Company operations in Freeport, Texas

As losses from natural hazards increase, coastal communities are faced with a difficult question of whether to pursue green or grey coastal infrastructure protection to help mitigate losses to businesses and residents. In 2011, The Dow Chemical Company (Dow) and The Nature Conservancy (TNC) collaborated in a pilot project that is helping Dow to identify, value, and incorporate the benefits of biodiversity and ecosystem services into its decision making. One of the focal ecosystem services was mitigating coastal hazards with natural infrastructure for Dow’s operations in Freeport, Texas. The company’s operations in Freeport are located in a low-lying area along the Gulf of Mexico where the lower Brazos River and the Columbia Bottomlands meet. The facility is mostly between 3 and 8 feet above sea level and is highly vulnerable to hurricanes and SLR, which is projected to be 1.5 feet higher in this area by 2050 (TNC-Dow 2012). Fortunately, the facility is fronted by several miles of undeveloped land and coastal marshes that provide flood protection and habitat for fish and wildlife. 

The project compared three flood protection strategies: using coastal habitat to mitigate losses; constructing a levee along six miles of undeveloped land in Freeport; and a hybrid approach that combined the use of coastal habitat and a levee. Dow and TNC identified a levee design for the 100-year storm and modeled flood levels and damages associated with category 1-5 storms to estimate and compare avoided damages resulting from each strategy. In collaboration with the Natural Capital Project (2016), new ecological and economic models were further developed to consider how the costs of levee construction could be reduced if its design incorporated the wave attenuation or vertical elevation gain of marsh habitat and the projected impacts of SLR, which had not been incorporated in previous risk assessments at the Freeport site.

Based on conservative assessments of flood protection provided by each strategy at this site, the levee provides the greatest flood protection benefit. However, coastal wetlands offer additional benefits that include habitat for 12 fish species and more than 200 other species as well as long-term carbon sequestration. The analysis showed an estimated 2% reduction in levee costs due to incorporation of coastal habitat, which was deemed too small to affect design of the multi-million dollar levee project. However, storm damage protection provided by these coastal wetlands was estimated to be $23 million to Freeport and surrounding communities. In addition, the net value of these habitats for carbon sequestration over 30 years was estimated at $30 million, and the recreation value was estimated at $130 million (TNC-Dow 2012).

These results suggest that a hybrid approach that combines marshes with more conventional hardened infrastructure makes the most economic sense at this location by offering the greatest benefits to communities in terms of flood protection from large hurricanes combined with additional economic and ecological benefit (TNC-Dow 2012). Overall, the pilot study at Freeport reaffirms that natural infrastructure can help to protect coastal businesses and their assets from storms. Results of the study have culminated in a unique commitment among Dow to consider nature in all of its business decisions (TNC-Dow 2016). The collaboration has also led to the development of a new tool for quantifying the value of nature, called the Ecosystem Services Identity and Inventory tool, designed to provide metrics about ecosystem services provided by nature at a business site ( This tool is helping to address a lack of methods for measuring the value of ecosystem services and will help to promote natural infrastructure in business decision making.

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3. Drowning marshes at Rhode Island’s Sachuest Point National Wildlife Refuge and the use of thin layer deposition

Marshes gain elevation slowly in Rhode Island due to a lack of sediment supply, making relative rates of SLR a primary concern. SLR averaged 2.8 mm per year from 1930 to 2013 at the tide gauge at Newport, which is nearly double the average rate of accretion in the state (1.5 mm per year), and from 1993 to 2014 the Newport and Providence tide gauge stations showed an even higher rate of 4.1 mm per year (Boyd et al. 2015). Sea levels are expected to rise 0.3 m by 2035 and by as much as 2.1 m above 1990 levels by 2100 in certain parts of the region (CRMC 2015). According to the Rhode Island Coastal Resources Management Council, the state could lose roughly 52% of existing salt marsh with a SLR of 0.9 m and about 87% with a SLR of 1.5 m (CRMC 2015). Sachuest Point, Rhode Island is particularly vulnerable due to sediment deficits, degradation from storm surge and wave erosion, low elevation, and poor drainage, making it susceptible to long periods of inundation and flooding that threaten high-marsh vegetation which generally occurs above mean high water. Additionally, much of the marsh is surrounded by developed upland areas and does not have the ability to migrate naturally as sea levels rise.

As part of post-Sandy federal funding dedicated to restoring wetlands and increasing coastal resilience across the Northeast, the USFWS and The Nature Conservancy (TNC) partnered to restore an 11-acre salt marsh in the Sachuest Point National Wildlife Refuge using thin-layer deposition to add elevation to the marsh surface using wet sand in areas where the marsh is too low. The amount of wet sand being added will range from one inch to one foot in a single location, with a total of 11,000 cubic yards of sand being spread across the marsh in all, at a cost of $644,000 (USFWS 2016).

Refuge staff is monitoring marsh accretion rates against changing sea levels using surface elevation tables to determine the effectiveness of thin-layer deposition and whether restoration techniques need to be revisited to ensure the majority of the marsh surface remains at elevations that can support S. patens (USFWS 2015b). Previous experience suggests that a deposition thickness of less than 10 cm will allow for survival of existing S. patens and a greater thickness is needed to ensure marsh re-establishment, which may be needed for high marsh vegetation to support saltmarsh sparrow nesting and reproduction (USFWS 2015b). The target elevation of the marshes within the refuge is 2.2 to 2.3 NAVD88, which is based on the upper end of the elevation range for existing S. patens and selected to maximize the resilience of the restored habitat to SLR while minimizing potential for invasive species (USFWS 2015b).

Understanding the point at which the marsh is no longer able to keep up with SLR is critical to the near- and long-term sustainability of the refuge’s restoration plan, which emphasizes the maintenance of tidal marsh bird populations currently threatened by SLR. The pairing of quantitative tolerance thresholds and population viability estimates for the saltmarsh sparrow together with information on S. patens provides resource managers better benchmarks for restoration and long-term monitoring efforts.

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4. Measuring impacts of SLR and storms on piping plover habitat in a highly developed area of Suffolk County, New York

The federally threatened piping plover is a good indicator species for measuring the effects of SLR and other stressors like human development that degrade vital barrier island habitat used by shorebirds. While their population numbers have increased in recent decades, climate change introduces new risks that interact with other threats, such as interruption of natural barrier beach dynamics due to sand fill, inlet maintenance, beach stabilization, and recreational use.

Habitat response models have helped to identify important thresholds related to storms and SLR on piping plover habitat for barrier islands in Suffolk County, New York (Seavey et al. 2011). These models suggest that piping plover habitat could be severely reduced by storms in developed areas. Under a SLR scenario of 1.5 m over the next 100 years and including the influence of development, models show that a category 2 hurricane can flood 75% of potential plover nesting habitat, and a category 3 hurricane surge can flood over 95% of their habitat in this area (Seavey et al. 2011). Developed areas prevent important natural processes from occurring, particularly overwashing and breaching that help to maintain plover habitat and allow barrier islands to dynamically respond to SLR and storms (Schupp et al. 2013; Seavey et al. 2011). The best outcome for the resilience of barrier islands to SLR, and not coincidentally piping plover habitat, occurs under a dynamic response scenario (ability of barrier islands to migrate), which allowed potential plover habitat areas to increase with a SLR of up to 1.5 m (Seavey et al. 2011), although the authors concede this scenario is not very likely as it did not consider the influence of development.

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5. Landscape connectivity to combat SLR within the Guana Tolomato Matanzas National Estuarine Research Reserve, northeastern Florida

Flooding and erosion are ongoing problems in the Guana Tolomato Matanzas National Estuarine Research Reserve (GTM NERR), a natural estuary and important conservation area supporting diverse habitat and species in the Matanzas Basin of northeastern Florida. Sea levels in the region have risen 0.25 m on average over the last century, which has led to accelerated erosion, more frequent and severe flooding, saltwater intrusion into aquifers, ecosystem changes, and species migration (Frank et al. 2015). Future SLR in northeast Florida is projected to be between 0.5 and 1.5 m by 2100 (Frank et al. 2015). The majority of the GTM Research Reserve has an elevation between 0 and 3 m above sea level.

In 2012, the GTM NERR initiated a proactive 3-year adaptation planning project to conserve 264,000 acres of high biodiversity and cultural resources and increase the area’s resilience to future SLR. Titled “Planning for Sea Level Rise in the Matanzas Basin,” the project was a collaborative effort between the GTM NERR and the University of Florida, funded by the NERR System Science Collaborative. A species impact analysis measured the impacts of SLR on 37 species within the basin. Two SLR scenarios were considered using the sea level rise affecting marshes model (SLAMM): 1 m and 2.5 m by 2100, assuming no changes in existing developed land (Hoctor et al. 2015). The version of SLAMM used did not take into account existing or future flood protection measures or increased flooding that may result from poor stormwater drainage or rising groundwater, and it did not account for landscape responses such as the potential of saltmarsh to convert to mangrove ecosystems which has already been observed within the GTM reserve (Frank et al. 2015).

Under the 1 m SLR scenario, the black rail was projected to lose the greatest amount of its current habitat, up to 58%, and the seaside sparrow was projected to lose roughly 43% of its habitat (Hoctor et al. 2015). Furthermore, all sea turtles combined (loggerhead, green, Kemp’s Ridley, and leatherback) could lose 64% of their habitat within the GTM NERR. Under the high SLR scenario, 95% of estuarine habitats (salt marshes, mangroves, tidal flats, etc.) were projected to convert to open water and average habitat loss for all species increased from 6% to 12%, causing many species to lose most or all of their habitat. Some species that are dependent on wetlands and open water and that do not nest exclusively in high marsh areas could gain habitat with increasing SLR, with an extreme example being the American oystercatcher (see Table 2) (Hoctor et al. 2015).

The Reserve is using the results of this planning effort to identify new adaptation strategies, including the use of living shorelines, marsh restoration, habitat conservation through acquisitions and easements, and water conservation easements (Frank et al. 2015). Results revealed that the basin may need to consider conservation lands outside the reserve to mitigate habitat losses, and the planning team has identified priority habitat within a 1-mile radius of the reserve as possible new, unprotected lands that could be conserved as an adaptation strategy (Hoctor et al. 2015). The Reserve is working with the state to add over 8,000 acres of watershed for surface water protection and possibly for the future migration of salt marshes. The Reserve is also working with other conservation groups to create the “Matanzas to Ocala Conservation Corridor,” which is over 100,000 acres of conservation land connecting the Matanzas Basin to the Ocala National Forest that will protect habitat critical for native wildlife (Reynolds 2016). The information and data generated from the project will likely continue to influence and guide planning efforts and local decision making.

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6. Valuing ecosystem services from restoration projects in Massachusetts

Recognizing that restoration of degraded habitats can generate significant benefits for people and the environment, the Massachusetts Department of Fish and Game’s Division of Ecological Restoration (DER) conducted a 2-phase study from 2011-2013 to analyze the economic benefits of restoration projects in the state. The goal was to estimate the economic value and return on investment in dollar value estimates to help fill an information gap of understanding the benefits of ecological restoration in terms of monetary values and effects on the state’s economy.

In phase one of the analysis, DER worked with Industrial Economics, Inc. to conduct a valuation study using four representative projects: one dam removal (North Hoosic River Restoration in Clarksburg); one culvert replacement (Stony Brook Restoration in Brewster); and two multi-practice wetland restoration projects (the Broad Meadows Restoration in Quincy and the Eel River Headwaters Restoration in Plymouth). The analysis used the IMPLAN economic impact model, which has been used in similar studies by state agencies in Massachusetts and elsewhere in the U.S. (MA DER 2014). The results showed that these project investments led to indirect and induced economic activity that equaled or exceeded economic activity generated by other types of capital projects. In-state project costs ranged from $630,000 (North Hoosic River) to about $5.4 million (Broad Meadows) (MA DER 2012). The average economic output of the DER projects generated a 75% return on investment. In addition, they created or maintained 12.5 full-time jobs for every $1 million spent (MA DER 2014). Long term, the ecological benefits of the restoration projects are expected to produce additional positive economic effects, though these were not included in the assessment (MA DER 2012).

The DER worked with ICF International in the second phase of the study to analyze four types of ecosystem service enhancements that are improved by certain DER projects: flood protection; carbon sequestration; water quality; and landscape appeal. In particular, the Town of Salisbury incurred substantial losses and damages from major coastal flooding in the mid-2000s, which prompted a flood mitigation and salt marsh restoration. The project included the installation of two new culverts and tide gates in the dike at the mouth of the creek to enhance flood protection and tidal flow. Using the IMPLAN tool, the project will result in nearly $2.5 million in avoided flood losses of business assets (lost inventory and sales) over the next 30 years; project costs totaled $1.3 million (MA DER 2014). The DER further estimated extensive benefits to water quality and aquatic habitat from the restoration project but these were not quantified in economic terms.

The DER calculated the areal extents of different plant communities before and following marsh tidal flow restoration to estimate carbon sequestration benefits and determine changes resulting from restoration projects. Natural wetland soil-building processes generate dense, peat-based soils that can store tons of atmospheric carbon. Rates of carbon sequestration were assigned to the plant communities for two restoration projects. The first was a 20-acre restoration project in Damde Meadows, Hingham that removed two culverts to restore tidal flows to salt marsh, which showed a net increase in carbon sequestration of 76 metric tons of CO2 per year. The second was a 60-acre restoration project in Broad Meadows, Quincy. This project removed over four feet of wetland fill to restore salt marsh and grassland habitat, which led to a net increase in carbon sequestration of 101 metric tons of CO2 per year. Carbon sequestration values were measured using the Social Cost of Carbon method, which is a model to determine the economic damages associated with a small increase in carbon due to greenhouse gas emissions (Interagency Working Group on Social Cost of Carbon 2013). This tool provided an estimated net increase in carbon sequestered in the restored wetlands through the year 2050 to be equal to emissions from burning more than 800,000 gallons of gasoline from 2013 to 2050.

The combined results from this two-phase study show that ecological restoration projects can stimulate economic activity through design and construction expenditures and can improve ecosystem services and generate substantial economic value. Further, these projects’ dual objectives of ecological restoration with flood and climate mitigation translates into many other valuable benefits to the communities and local economies such as increased resilience to SLR and enhanced habitat for commercial and recreational fisheries (MA DER 2014).

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7. Coastal protection at a landscape scale: The acquisition of Powderhorn Ranch in coastal Texas

Texas has lost hundreds of thousands of acres of coastal wetlands since the 1950s (TPWD 2014). Growing human populations across the Gulf Coast coupled with rising sea levels and coastal storm surge are straining and fragmenting remaining vulnerable coastal wetlands. Powderhorn Ranch is among the largest remaining undisturbed areas of native coastal prairie habitat in Texas and has long been a conservation target for its diverse habitats that support many shorebirds, wading birds, and waterfowl along with other wildlife.

Through a partnership between The Nature Conservancy, the National Fish and Wildlife Foundation (NFWF), Texas Parks and Wildlife Foundation, Conservation Fund, and the Texas Parks and Wildlife Department, the 17,351-acre Powderhorn Ranch was purchased in 2014 for $50 million with funds from Deepwater Horizon oil spill through the NFWF’s Gulf Environmental Benefit Fund and Texas Parks and Wildlife Foundation.

The conservation of this vast landscape has clear benefit to both human and ecological populations. The area contains thousands of acres of freshwater wetlands and salt marshes that provide important fish and wildlife habitat, as well as important ecosystem services such as water filtering, recreation, and coastal flood protection (TPWD 2014). The ranch consists of diverse habitat that includes tallgrass prairies, freshwater pothole ponds, salt marshes, and 11 miles of tidal bay front that protects seagrass beds and mollusk reefs. Conservation of this area will enable marshes to migrate with changing sea levels and is also likely to provide future habitat to the federally endangered whooping crane, which currently winters just south of the ranch and is threatened by moderate to high scenarios of SLR (TPWD 2014).

The acquisition of Powderhorn Ranch provides an important example of landscape-scale conservation for the benefit of species and their habitats which was made possible through a public-private partnership. It highlights how recovery funds can be leveraged to support large-scale conservation in support of an ecologically connected network of protected lands for the benefit of ecological and human communities (TPWD 2014). Protection of the Powderhorn Ranch will help to ensure that coastal wetlands can keep pace with rising sea levels and provide important habitat for whooping cranes and many other wildlife species into the future.

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8. Integrative adaptation planning by the State of Maine

Following completion of a climate impact assessment conducted by the University of Maine to prepare for future climate change (Jacobson et al. 2009), the State’s Department of Environmental Protection (DEP) developed climate adaptation recommendations to address the impacts that climate change will have to its built, natural, coastal, and social environments. Recommendations included an increased focus on data and monitoring, especially of the regions that are most vulnerable to climate impacts including beaches, salt marshes, wetlands, barrier beaches, and shellfish harvest areas. To ensure that adaptation options are successfully implemented, the DEP further emphasized increased planning and coordination among local and state governments as well as stakeholder groups. Recommendations made were to: consider climate change impacts on wildlife and habitat in decision making and land use planning; invest in habitat restoration to improve connectivity and build resilience; and create a state policy on coastal areas that uses zoning, conservation, and/or land acquisition to allow the landward migration of vulnerable areas in response to changing rates of sea level rise and climate change (Gregg 2010a).

In addition, the Southern Maine Regional Planning Commission (SMRPC), a council of governments serving 39 municipalities that provides planning, economic development, and technical assistance, is facilitating local and regional responses to SLR and coastal storms through a partnership with the Maine Geological Survey. This partnership is helping local decision makers increase their resilience to the risks from these coastal hazards. They launched the Coastal Hazard Resiliency Tools Project in 2008 with four communities (Scarborough, Saco, Biddeford, and Old Orchard Beach) and have since added two more communities (Kennebunk and York) to develop adaptation strategies for SLR and storms and get communities to consider zoning and other policy and regulatory options for addressing these risks. Solutions have focused on nonstructural approaches that include accounting for SLR in comprehensive plans; elevating roads; relocating infrastructure; and acquiring land. In particular, the project is informing shoreline management issues by incorporating SLR projections into siting and construction of public and private infrastructure (Gregg 2010b).

The existing minimum standard in shoreline zoning in Maine is a 2-foot SLR over the next 100 years, but the partnership is encouraging communities to consider higher rates of SLR (Gregg 2010b). To help overcome existing economic restrictions and limited political and public support for more aggressive action, public meetings were held to present hazard and inundation maps showing the potential impacts from SLR on coastal infrastructure and habitats. In these meetings, participants discussed several nature-based approaches to encourage soft shoreline stabilization approaches and discourage hardened approaches. Adaptation options that were discussed included: discouraging investments in flood-prone areas; acquiring land in adjacent upland areas to allow shoreline migration; increasing the number of nature preserves to act as buffer zones to wetland migration; and considering the effects of SLR and storms in siting and design standards for public and private projects.

The communities of Scarborough, Saco, and Biddeford have established a Sea Level Adaptation Working Group to coordinate floodplain management and planning. Specifically, the working group is charged with identifying regional infrastructure vulnerabilities, facilitating coordinated responses, and seeking funding for the implementation of adaptation projects, which aim to balance retreat and similar nonstructural options with engineered solutions (SMRPC 2011).

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9. Community coastal resilience planning as a toolbox for addressing coastal risk in the Town of Guilford, Connecticut

The Town of Guilford, Connecticut developed a Community Coastal Resilience Plan as a toolbox for addressing current and future impacts of SLR, coastal storms, flooding, and erosion. This plan together with a 2012 Risk and Vulnerability Assessment Report and a 2013 Report of Options to Increase Coastal Resilience establishes a framework to increase the town’s social, economic, and ecological resilience to these hazards. The town expects to identify a municipal agency or commission to administer the plan and work with existing staff from planning, public works, and emergency management departments to set and coordinate priorities and implement the plan (Town of Guilford 2014).

The town’s coastal habitats are highly vulnerable to current and future projections of SLR and coastal storms. In the town’s 2012 Risk and Vulnerability Assessment, future flood scenarios were mapped using The Nature Conservancy’s Coastal Resilience Tool. Three scenarios were used for the decades of the 2020s, 2050s, and 2080s: no storm (only impacts of SLR); Category 2 hurricane; and Category 3 hurricane. These sets of conditions were paired with downscaled SLR projections using high, medium, and conservative projections (which ranged from a conservative 3.5 inches in the 2020s to a high scenario of 52 inches by the 2080s) based on IPCC emissions scenarios and combined with global climate change models, historic tide gauge data, and subsidence rates (Town of Guilford 2012).

Results of the assessment revealed that all tidal marshes in the region are vulnerable to SLR and will continue to undergo erosion as the duration and frequency of inundation increases and as other contributors to sudden marsh dieback continue (Town of Guilford 2012). Coastal squeezing is already occurring in areas where marshes are unable to migrate inland and the effects of squeezing could increase if future rates of SLR are too fast for marshes to accrete vertically to maintain the elevation range needed to persist. Some marsh systems are currently not keeping up with current rates of SLR and by 2020 the town suspects that many marshes will be submerged, and by 2050 upland areas will be wet, though some marshes may be able to advance into town‐owned and private property (Town of Guilford 2012). The report further suggests that existing seawalls and bulkheads and the properties they protect are vulnerable to increasing rates of SLR and storms due to increased risks of failure.

In 2013, The Nature Conservancy completed an assessment of salt marsh advancement zones across the town’s entire coastline projected out to the 2080s to help the community identify where salt marsh shorelines will move upslope as sea levels rise and inform stakeholders and mangers about future migration corridors and which parcels of land are most critical to securing advancement into suitable areas to ensure the persistence of the area’s natural resources (Town of Guilford 2014). The report assessed the future extent of marsh advancement across the town’s coastline by the 2080s to inform stakeholders and managers about future migration corridors, current land use, and which parcels are particularly critical to ensure the long term persistence of marshes for the benefit of species and the community. The town’s Coastal Resilience Plan recognizes that open space preservation plays an important role in future wetland extent and increased resilience and that this information is vital for land management, economic development, and planning. The plan further emphasizes that coastal land acquisitions should be pursued both for human recreational use and as well as for protecting species and habitats. Coastal lands identified as being ecologically significant, important for recreational use, or as having exceptional conservation value are recommended for evaluation for acquisition (Town of Guilford 2014).

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