Shoreline Projects Research Articles

Seven Years of Monitoring the Development of an Oyster Reef Living Shoreline

The implementation of nature-based solutions (NbS), including living shorelines, to mitigate estuarine habitat loss is increasing at a pace exceeding the evaluation of their long-term success. Constructed oyster reefs (CORs) made of shell, concrete, stone, and other materials are one living shoreline tactic that is widely utilized, yet few studies have been conducted to understand the development of CORs within the context of both physical and ecological parameters over longer time scales (4 + years). A COR-based living shoreline project at the Gandy’s Beach Preserve (GBP) in Delaware Bay, NJ, USA, had dual goals of coastal protection and habitat provisioning, which prompted the development of a goal-driven monitoring framework to track project objectives. Methods were developed to quantify the following multi-disciplinary metrics over 7 years: elevations of CORs, waves (height, period, and direction), shoreline elevations, change in extent of vegetation patches, oyster density and size, nekton richness and community composition, and horseshoe crab impingement. The CORs met most of their habitat provisioning objectives as they were colonized by a multi-generational population of shellfish and created habitat for nekton, while posing negligible hazards to horseshoe crabs. However, none of the coastal protection objectives was fully achieved including material stability, wave attenuation, and sediment elevation increase. Results highlight the value of longer-term monitoring to understand performance and the need to match the scale and type of NbS tactic(s) with both the scale of the landscape and the site-specific hydrodynamic conditions to meet project goals.

Future Shorelines: A Living Shoreline Site Selection and Design Decision Support Tool that Incorporates Future Conditions Induced by Sea Level Rise

Most living shoreline site selection and design decision support tools are based upon existing environmental conditions. We developed a web-based, geospatial tool called Future Shorelines that integrates high-resolution landscape elevation data and a matrix of locally derived NOAA Interagency Sea Level Rise Scenarios to characterize future conditions of submergence and shoreline translation induced by sea level rise. Once the practitioner selects a location of interest, sea level rise scenario (e.g., high), and target year (e.g., 2050), the tool will generate plan view and cross-sectional informational graphics specific to their choices. This information can then be paired with other menu options, like parcel ownership, to facilitate the planning and construction of nature-based shoreline stabilization solutions that (1) are located where opportunities for horizontal migration are optimized, (2) remain accessible for monitoring and maintenance, and (3) perform as intended over the design life of the installation. The tool’s menu options and the user interface were informed by project partner input solicited during numerous workshops convened over the duration of the 2-year project. This coproduction created a product that was familiar to the end user and therefore increased the likelihood that it would be utilized by them during the planning and design of living shoreline projects. Although developed for use in the Indian River Lagoon, located along the east-central Florida coast, it can be seamlessly replicated for application in other coastal regions of the USA where the requisite data are available.

Influence of structure characteristics on wave transmission and shoreline response at a low-crested segmented breakwater in Little Egg Harbor Township, NJ

Graveling Point Beach, a public beach within Little Egg Harbor Township, New Jer- sey, has been experiencing long-term erosion. To address the issue, a living shoreline project consisting of four low-crested rubble-mound breakwaters and a beach nour- ishment was constructed beginning in fall 2022 (structures) and finishing in spring 2023 (beach nourishment). A variety of field methods were used to investigate the influence of the breakwater system on wave transmission and beach fill evolution. The observations are then compared to common empirical estimations. A median wave transmission coefficient of 0.4 was measured for incident waves with a median height and peak period of 9 cm and 2 sec, respectively. The observed transmission coefficient was higher than that predicted by models such as Briganti et al. (2003) and Van der Meer and Daemen (1994) suggesting other processes such as diffraction may be influencing the results. Structure from Motion (SfM) was used to generate a series of Digital Elevation Models (DEMs) which show salients forming behind the structures. The resulting salient growth was compared to the model of Suh and Dalrymple (1987), which was shown to overpredict the amplitude of the salient at Graveling Point. However, the expected relationship of breakwaters with increased offshore distance having shorter salient lengths was generally observed. The equation was refit using the field data at Graveling Point and laboratory data with similar wave heights and periods from Suh and Dalrymple to derive a modified model that may be more appropriate in low-energy environments

The Utility of Ribbed Mussels Guekensia demissa for Marsh Grass Restoration on Living Shoreline Projects in the Southeast US: Potential and Pitfalls

The Utility of Ribbed Mussels Guekensia demissa for Marsh Grass Restoration on Living Shoreline Projects in the Southeast US: Potential and Pitfalls

Current extent and future opportunities for living shorelines in Australia

Living shorelines aim to enhance the resilience of coastlines to hazards while simultaneously delivering co-benefits such as carbon sequestration. Despite the potential ecological and socio-economic benefits of living shorelines over conventional engineered coastal protection structures, application is limited globally. Australia has a long and diverse coastline that provides prime opportunities for living shorelines using beaches and dunes, vegetation, and biogenic reefs, which may be either natural (‘soft’ approach) or with an engineered structural component (‘hybrid’ approach). Published scientific studies, however, have indicated limited use of living shorelines for coastal protection in Australia. In response, we combined a national survey and interviews of coastal practitioners and a grey and peer-reviewed literature search to (1) identify barriers to living shoreline implementation; and (2) create a database of living shoreline projects in Australia based on sources other than scientific literature. Projects included were those that had either a primary or secondary goal of protection of coastal assets from erosion and/or flooding. We identified 138 living shoreline projects in Australia through the means sampled starting in 1970; with the number of projects increasing through time particularly since 2000. Over half of the total projects (59 %) were considered to be successful according to their initial stated objective (i.e., reducing hazard risk) and 18 % of projects could not be assessed for their success based on the information available. Seventy percent of projects received formal or informal monitoring. Even in the absence of peer-reviewed support for living shoreline construction in Australia, we discovered local and regional increases in their use. This suggests that coastal practitioners are learning on-the-ground, however more generally it was stated that few examples of living shorelines are being made available, suggesting a barrier in information sharing among agencies at a broader scale. A database of living shoreline projects can increase knowledge among practitioners globally to develop best practice that informs technical guidelines for different approaches and helps focus attention on areas for further research.

Short-Term Recovery of Pilot Living Shoreline Projects for Salt Marsh Habitat in New Hampshire

Short-Term Recovery of Pilot Living Shoreline Projects for Salt Marsh Habitat in New Hampshire

“Whose carbon is it?” Understanding municipalities role in blue carbon ecosystems management in Canada

Blue carbon ecosystems are marine vegetated ecosystems, such as mangroves, salt marshes, kelp forests and seagrass meadows, that naturally sequester and store atmospheric carbon in their deep sediments and biomass. Their ecosystem services extend from carbon capture and storage to coastline protection and flood mitigation, making their management and protection a form of nature-based solution (NbS) for climate change adaptation. However, these ecosystems are subject to degradation and destruction from coastal development and land use change, releasing sequestered carbon into the atmosphere. In Canada, although home to the largest coastline of any country in the world, neither federal nor provincial policy explicitly address the management or protection of blue carbon ecosystems, leaving them susceptible to these threats. Coastal municipalities, however, may play an important role in the current management and protection of blue carbon. Land-use planning decisions on the local level offer an opportunity to protect and conserve coastal ecosystems and the co-benefits these ecosystems provide offer a NbS to address many climate threats faced by coastal communities. This study examines the current and potential role of municipalities in the management, protection and/or restoration of blue carbon ecosystems for sustainable land-use planning practices and carbon pollution mitigation by interviewing municipal staff from coastal municipalities across Canada. Study results demonstrated municipal interest in blue carbon ecosystems for their tangible co-benefits, not carbon sequestration and storage capacity, and that restoring blue carbon ecosystems for living shoreline projects was the most common active management strategy at the local level. However, institutional capacity, a lack of jurisdictional clarity and uncertainty surrounding blue carbon were identified as barriers that hindered municipal engagement in active management strategies, largely restricting them to play a supportive role to blue carbon projects led by local environmental non-governmental organizations.

Shoreline Management and Coastal Resilience in Virginia: Analysis of the Roles of Environmental Nonprofit Organizations in Encouraging Living Shorelines

Coastal erosion and shoreline retreat can be offset by responsible shoreline management through nature-based solutions such as living shorelines. This study describes five roles played by environmental nonprofit organizations in shoreline management and coastal resilience in Virginia by illustrating how these nonprofits support and encourage living shorelines. The five key roles played by environmental nonprofits are: (1) public education about living shorelines, (2) advocacy for living shorelines, (3) technical assistance to design and install living shoreline projects, (4) training for professionals to increase capacity for living shoreline projects, and (5) access to funding. The government regulatory framework primarily addresses the permitting process, leaving it to nonprofit organizations to fulfill various roles beyond the actual permitting process. The implications of greater involvement by the nonprofit sector in shoreline management that encourages and supports living shorelines are discussed.

Do small-scale saltmarsh planting living shoreline projects enhance coastal functionality? A case study in the Northern Gulf of Mexico

Human coastal occupation often leads to the degradation of the structural properties and environmental functions of natural coastlines. . Much research has been done on the cost-effectiveness of various living shorelines designs, however more work is needed for simple, small-scale designs that are typically adopted in waterfront residential or recreational properties. To contribute to this gap, we planted small-scale plots of black needlerush (Juncus roemerianus) in two sites, one in a residential property and another one in a recreational property in the Northern Gulf of Mexico that experienced significant wave energy. Plots were planted at two different densities (50% or 100% initial cover) or left unplanted (controls) and, along with monitoring the evolution of the planted salt marsh, we measured a number of functional metrics including soil slope, abundance of nekton within and in front of the plots, and cover of submerged aquatic vegetation (SAV) in front of the plots monthly over two years. In one of the sites plant cover decreased precipitously, and in the other site we did not observe any significant changes in plant cover over time (i.e. the initial 50% and 100% plantings remained at that level throughout the experiment) despite protecting the planted salt marsh with coir logs. We did not find any changes in soil slope or nekton abundance between planted and control plots. SAV growth was restrained in front of planted plots in relation to control plots, possibly due to deleterious impacts by the coir logs. Overall, the results suggest the protection against wave energy attained in this experiment is insufficient for adequate saltmarsh establishment and growth, thereby encountering decreasing or stationary plant density and no significant differences in soil slope or nekton abundance between planted and non-planted plots. Our results indicate the adoption of small-scale saltmarsh planting to reduce erosion and enhance coastal functionality needs to ensure that wave energy is sufficiently dampened for adequate saltmarsh growth and, concomitantly, the conceived saltmarsh protection mechanism does not negatively impact adjacent SAV.

Observations of Wave Height Amplification Behind an Oyster Castle Breakwater System in a High-Energy Environment: Gandys Beach, NJ

This study reports findings of an analysis of modifications to the incident wave field caused by constructed Oyster Castle® breakwater systems at Gandys Beach Preserve in Downe Township, NJ. The Nature Conservancy’s (TNC) Gandys Beach Preserve is a one-mile stretch of beach located along with intertidal mud flats, sandy beaches, tidal creeks, and salt marshes. Gandys Beach can be classified as a high-energy environment, with open water fetches exceeding 30 miles, and a tidal range on the order of 2 m. The Gandys Beach living shoreline project was designed and constructed by TNC in partnership with the United States Fish and Wildlife Service (USFWS) to investigate the effectiveness of various natural and nature-based features (NNBFs) in protecting and enhancing salt marshes and beaches in high (er) energy environments. Many of the NNBF techniques used at Gandys Beach, such as Oyster Castle® block breakwaters (Oyster Castles), had only been implemented at smaller scales in New Jersey prior to the project. Stevens was contracted by USFWS/TNC to evaluate the impact of the breakwater systems on incident waves. Four breakwater sections along the beach were selected to monitor wave attenuation. Month-long deployments of wave staffs and pressure sensors occurred in the summer and winter of 2019. Analysis of the data indicates that when crests of the Oyster Castles are exposed the breakwater system effectively attenuates waves. However, when the structures are submerged, wave height attenuation decreases, and under certain conditions wave heights behind Oyster Castles can be amplified more than 80%. These results are troubling, especially in areas experiencing sea level rise where the frequency of submergence will likely increase in the future. Due to the complex nature of Gandys Beach, exact mechanisms causing this amplification remain uncertain. Furthermore, transmission coefficients (Kt) above 1 are not typically modeled in existing empirical equations. Seabrook and Hall (Coast. Eng. Proc., 1998, 1 (26), 2000) is the only studied empirical formula that indicated an amplification of the Hs as observed during these field deployments and therefore was used to model Kt. However, poor agreement between the modeled and observed Kt was found and a better predictive tool is needed.

Assessing Wave Attenuation With Rising Sea Levels for Sustainable Oyster Reef-Based Living Shorelines

In densely populated coastal areas with sea-level rise (SLR), protecting the shorelines against erosion due to the wave impact is crucial. Along with many engineered structures like seawalls and breakwaters, there are also green structures like constructed oyster reefs (CORs) that can not only attenuate the incident waves but also grow and maintain pace with SLR. However, there is a lack of data and understanding of the long-term wave attenuation capacity of the living shoreline structures under SLR. In this study, we used the phase-resolving Boussinesq model, FUNWAVE-TVD, to examine the hydrodynamics including wave height and wave-induced currents around the CORs in the Gandys Beach living shoreline project area in the upper Delaware Bay, United States. Waves were measured at six locations (offshore to onshore, with and without CORs) in the Gandys Beach living shoreline project area for two winter months, during which four nor’easters occurred. We selected three cases that represent prevailing wind, wave, and tide conditions to examine the fine spatial and temporal changes in wave height and current velocity by the construction of the reefs. Wave heights and wave energy spectra generated from FUNWAVE-TVD were then validated with field observations. It is found that FUNWAVE-TVD is capable of simulating waves and associated hydrodynamic processes that interact with CORs. The model results show that wave attenuation rates vary with the incident wave properties and water depth, and wave-induced circulation patterns are affected by the CORs. The wave attenuation capacity of CORs over the next 100 years was simulated with the incorporation of the oyster reef optimal growth zone. Our study found that sustainable wave attenuation capacity can only be achieved when suitable habitat for COR is provided, thus it can vertically grow with SLR. Suitable habitat includes optimal intertidal inundation duration, current velocity for larval transport and settlement, on-reef oyster survival and growth, and other environmental conditions including salinity, temperature, and nutrient availability. Furthermore, the model results suggest that it would take CORs approximately 9 years after construction to reach and maintain the maximum wave attenuation capacity in sustainable living shorelines.

Data-driven modeling of wind waves in upper Delaware Bay with living shorelines

Living shoreline projects have been built to preserve coastal ecosystems under future climate change and sea level rise. To quantify the wave power variation across living shorelines, the wave characteristics around the constructed oyster reefs (CORs) in upper Delaware Bay were investigated in this study. Wave parameters seaward and shoreward of CORs were recorded by wave gauges in early 2018. Four winter storms happened in this period and induced strong winds and coastal flooding at the study site. To estimate the wind wave characteristics across the CORs on a yearly basis, soft computing-based models combining fully connected neural networks and long short-term memory were developed to extend the two-month energetic wave measurements. The results show that when CORs were emergent or slightly submerged, the averaged wave height attenuation was about 39.8% from the offshore gauge to the nearshore gauge (behind CORs) during 2018–2020, owing to the combined effect of nearshore bathymetric changes and CORs. Furthermore, it was found that the annually averaged wave power reduction from offshore to nearshore at the study site was about 30.0% in 2018, 2019, and 2020. This study provides a novel framework to predict long-term wave characteristics based on short-term wave measurements using soft computing-based models.

Years of Planning for the South San Francisco Bay Shoreline Project: Now It's Time to Build! Rapidly but Gently!

When a complicated project is completed, and you ask the engineers, “What was the most challenging part of this project?” a couple of difficulties usually come to mind. We've all heard war stories ...

Stabilizing the Edge: Southeastern and Mid-Atlantic Shorescapes Facing Sea-Level Rise

Adapting to sea-level rise will require measures that improve federal, state, and local governance mechanisms, management practices, and property owner behavior affecting the coastal zone. This Article arises out of an interdisciplinary research project funded by the National Science Foundation entitled Sustainability in Chesapeake Shorescapes: Climate Change, Management Decisions, and Ecological Functions, led by the Virginia Institute of Marine Science at William & Mary. As legal experts involved with the project, we have analyzed ocean-facing and estuarine protection laws from Florida to Delaware. To the authors’ knowledge, no such comprehensive overview or comparison of these shorescape protection, setback, and stabilization laws exists, and necessary adaptation will require a comprehensive understanding of these frameworks. Our analysis revealed important distinctions between how we manage ocean-facing and estuarine-facing shorelines as well as a wide variety of values and interests driving them. The Article found, for example, that the majority of ocean-facing shore protection laws in the study area have established jurisdictional lines designed based on erosion rates, but a trend towards “freezing” the most oceanward jurisdictional baselines is occurring, suggesting that rising sea-levels and increased flooding may create pressure to “hold the line” when more dynamic and adaptive responses are needed. Meanwhile, the estuarine protection laws analyzed define jurisdictional lines that measure pre-determined buffer widths from natural features. More dynamic boundary determinations for these areas using erosion rates and sea-level rise projections will be required, however, as some estuarine areas are more at risk from sea-level rise than ocean-facing areas. The Article also found that armored shorelines (e.g., seawalls and bulkheads) are almost always held to a lesser standard throughout our study area than nature-based living shorelines, even though living shoreline projects are more adaptive. In the same vein, while shoreline armoring is often cited as a management concern, the importance of uniformity is woven also throughout shore protection law and policy in the study area, with “gap-filling” and “shoreline alignment” policies furthering shoreline hardening. Finally, incorporating information into the regulatory framework is an important way to improve coastal decision-making, advance cooperative federalism, and further a more holistic, “shorescape” approach to shoreline management. Integrating the jurisdictional boundaries described in this Article with science-based modeling efforts – efforts that incorporate factors such as shoreline characteristics, shoreline change, sea-level rise projections, marsh migration projections, population projections, and demographics – would greatly further understanding of how existing regulatory frameworks may need to adapt to protect habitat, property, and human life. The Article discusses how such an approach is possible, and how the Coastal Zone Management Act (CZMA) is a promising vehicle to build upon in order to implement a shorescape approach. A shorescape approach informed by spatial analysis and modeling also would advance more dynamic cooperative federalism, as it would allow for improved communication among different levels of jurisdictions, interjurisdictional coordination, and future scenarios planning to inform a more robust discussion of trade-offs and examination of competing goals. Ultimately, the Article fills an important research gap in the existing climate change and coastal management literature, as it sets the stage for incorporating interdisciplinary findings from coastal science and social science research with legal and policy mechanisms to inform coastal zone management.

A Homeowner’s Guide to the Living Shoreline Permit Exemption Part 1: Florida Department of Environmental Protection

“Living shoreline” is a term that describes coastal shoreline stabilization interventions that rely on natural elements such as native vegetation and oyster reefs to protect property. Living shorelines typically involve construction or placement of materials within state waters (public lands that occur waterward of the mean high tide line). The Florida Department of Environmental Protection and other entities regulate the placement of living shorelines through a permitting process to ensure project activities do not conflict with the public interest. To streamline the approval process for environmentally beneficial projects such as living shorelines, the DEP has defined an exemption for small-scale living shoreline projects that meet certain criteria. This 17-page fact sheet written by Savanna Barry, Sara Martin, and Eric Sparks and published by the UF/IFAS Florida Sea Grant College Program provides a guide to completing the exemption forms. http://edis.ifas.ufl.edu/sg187
 Updated August 2020 to include information about updated Department of Environmental Protection form.

DESIGN AND CONSTRUCTION OF A LIVING SHORELINE PROJECT ALONG THE GULF COAST

The Hancock County Marsh Living Shoreline Project (project) was developed as an NRDA Early Restoration project. NRDA Early Restoration projects are intended to accelerate meaningful restoration of injured natural resources, and their services, resulting from the Deepwater Horizon oil spill. The Mississippi Department of Environmental Quality and National Oceanic and Atmospheric Administration (the federal and co-implementing trustee) worked cooperatively to develop a project along the Hancock County, Mississippi, shoreline. This project would partially offset injuries by preserving and protecting existing marsh and providing for increased secondary productivity. Currently, it is the largest restoration project to be designed and constructed in Mississippi.

COMPARISON OF SILL AND REVETMENT IN REDUCING SHORE EROSION AND WAVE OVERTOPPING

Sills (low–crested rubble mounds) are constructed to protect eroding bluffs and planted marshes in living shoreline projects (http://mycopri.org). Revetments are conventionally used to protect eroding shores and reduce wave overtopping and damage to backshore areas. However, revetment construction may result in loss of buffering wetlands. On the other hand, no established method exists to design the sill geometry (crest height, width and side slopes) and its distance from the eroding shore. This study compares the efficacies of the two different rubble structures with the same number of stones in order to clarify their similarity and difference for the purpose in reducing shore erosion and wave overtopping.

Effectiveness of Living Shorelines as an Erosion Control Method in North Carolina

Living shorelines are a shoreline stabilization strategy encompassing a range of vegetative to structural materials and serve as an alternative approach to the use of structures like bulkheads, which are known to aggravate erosion. Living shorelines are often installed with little to no long-term monitoring for effectiveness; specifically, there is a lack of quantitative data regarding their performance as a shoreline stabilization strategy. This study sought to assess the performance of living shorelines with sills, with respect to shoreline protection, by determining shoreline change rates (SCR) using geospatial analysis. Shoreline surveys were conducted using a real-time kinematic (RTK)-GPS unit at a total of 17 living shoreline projects and nine control segments at 12 sites along the coast of North Carolina. Current shoreline position was compared to historic (pre-installation) shoreline positions obtained from aerial imagery, dating to 1993. The average SCR among northern sites before installation was − 0.45 ± 0.49 m year−1, and in southern sites, it was − 0.21 ± 0.52 m year−1. After installation, average SCR was significantly less erosive at northern and southern sites with living shorelines, 0.17 ± 0.47 and − 0.01 ± 0.51 m year−1, respectively. Of the 17 living shoreline project segments, 12 exhibited a reduction in the rate of erosion; of those 12, six were observed to be accreting. This study supports the convention that living shorelines can reduce the rate of erosion and potentially restore lost shore zone habitat.

Streamlining Resiliency: Regulatory Considerations in Permitting Small Scale Living Shorelines

Living shorelines offer a valuable and environmentally friendly means of stabilizing shorelines while restoring and enhancing estuarine habitats. Because living shorelines are considered environmentally beneficial, several agencies have coordinated efforts to reduce the regulatory burden required to construct them. This 8-page fact sheet written by Thomas T. Ankersen, Alexandra Barshel, and Valerie Chesnut and published by the Florida Sea Grant College Program, UF/IFAS Extension, describes how to ensure that a living shoreline project will be successful and not run into any permitting difficulties. http://edis.ifas.ufl.edu/sg155

Monitoring the impact of coastal erosion on archaeological sites: the Cyprus Ancient Shoreline Project

Coastal erosion of archaeological sites has long been a problem for archaeologists seeking to understand maritime interactions in the past. A new model, using ArcGIS to collate various sources of data relating to processes of erosion over time along the south coast of Cyprus, is showcased here, with the hope that it can be expanded and adapted for use elsewhere in prioritising sites according to rates of destruction.