Categories
Built Projects

Mordecai Island (Barnegat Bay, New Jersey)

Figure 1. Photo of Mordecai Island in 2019.

Background

Mordecai is an undeveloped back barrier island that runs parallel to the Barnegat Bay shoreline of Beach Haven, New Jersey (Figure 1). In addition to providing habitat for a wide range of estuarine organisms and nesting shorebirds, the island serves as a wave-break, protecting the adjacent developed shoreline of Beach Haven from the erosive action of waves generated in Barnegat Bay.

Over the past century, persistent wave action has taken a toll on Mordecai Island, resulting in a loss of roughly 50 percent of its total area and leading to a breach that effectively separated the island into two lobes (Figure 2). Continuing erosion threatens the existence of Mordecai Island, its biological communities and habitat, and the vital role that it plays in protecting the Beach Haven shoreline.

Figure 2. Photos of Mordecai Island A) in 2014 before sediment placement and, B) in 2018 after placement.

Project Description

In 2015, the US Army Corps of Engineers (USACE) Philadelphia District used sediment dredged from the New Jersey Intracoastal Waterway (NJ ICW) to fill the erosional gap that separated the two remaining parts of Mordecai Island. The project design involved the use of ~30,000 cubic yards of sediment to create a central high-elevation mound intended to provide habitat for shorebird nesting. The placement area was later planted with native salt marsh and transitional and upland vegetation (Figure 3).

Figure 3. A close up photo of the Mordecai Island placement area in 2019, planting occurred in 2016. The stakes visible are leftover from the goose exclusion fencing installed during planting.

Monitoring

To determine the effectiveness of dredged material placement and other shoreline modifications in stabilizing the island and to quantify the success of ongoing restoration efforts, the Philadelphia District partnered with the National Oceanic and Atmospheric Administration (NOAA)’s National Centers for Coastal Ocean Science (NCCOS) and the Mordecai Land Trust to track changes in surface elevation and shoreline position over time and monitor changes in biological communities. NOAA NCCOS is also evaluating potential ecological impacts of these activities by monitoring changes in saltmarsh vegetation, seagrass cover, and the abundance and diversity of nearshore benthic invertebrates. An understanding of how each of these groups responds to the shoreline modifications occurring on Mordecai Island is crucial to determining the broader ecological impacts of sediment placement and shoreline protection strategies and can be the basis for change detection.

Figure 4. Aerial photo of Mordecai overlaid with the polygon data layers showing shoreline retreat on the western edge. Since 1970, the western shoreline retreated at an annual rate of 0.8m, a cumulative loss of 40 m (130 feet).

Study Results

To better understand the amount of erosion occurring along the western side of the island that experiences high boat wakes, NCCOS developed digital elevation models from drone aerial photography and conducted shoreline change analyses using a combination of historical aerial imagery and on-the-ground surveys. An analysis of elevation change between 2017 and 2019 showed a redistribution of sediments within the placement region, that without additional sediment and stabilization by planting, is likely to result in the formation of a channel and, ultimately, lead to the island being separated once again into two lobes. Similarly, analyses of historical shoreline positions indicate that between 1970 and 2019, the western shoreline of Mordecai Island retreated at an average rate of 0.83 meters per year leading to a cumulative loss of roughly 15 acres of land. However, there is also evidence that the shoreline stabilization structures along the southwestern shoreline have minimized erosion on the adjacent shoreline (Figure 4). In addition, results of this study revealed that there were no long-term changes to the benthic intertidal community which has been a concern for in-water sediment placement activities such as the Seven Mile Living Laboratory (SMILL).

Project Significance

Shoreline erosion is a major source of the sediments that end up clogging navigation channels and leading to the need for maintenance dredging; it is also a cause of habitat loss for marsh islands like Mordecai. Beneficial use of sediments to restore these habitats can be a part of the solution. Monitoring and continued data collection will inform adaptive management strategies and further document the rate of ecosystem service provision and protective capacity of Mordecai Island. Research to capture appropriate ecosystem variables at demonstration sites like this will play a pivotal role in determining the efficacy and optimal use of such applications.

Points of Contact

Jenny Davis, NOAA NCCOS – jenny.davis@noaa.gov

Monica Chasten, USACE Philadelphia District – monica.a.chasten@usace.army.mil

Len Balthis, NOAA NCCOS – len.balthis@noaa.gov

More Information and Related Links

https://coastalscience.noaa.gov/news/new-report-evaluates-benefits-of-using-dredged-sediments-to-enhance-coastal-ecosystems/

https://coastalscience.noaa.gov/project/assessment-of-the-beneficial-use-of-dredged-sediment-to-restore-mordecai-island-new-jersey/

Mordecai Island Story Map

EWN Swan Island

References

Davis,J.L., Balthis, W.L., Greene, M.D., Giannelli, R.A. 2020. Ecological Assessment of the Beneficial Use of Dredged Sediments for Island Restoration: Mordecai Island, Barnegat Bay, NJ. NOAA Technical Memorandum NOS NCCOS 287, Silver Spring, MD. 52pp.doi:10.25923/gja6-a224

Categories
Built Projects

Horseshoe Bend Island

Background

During the 1990s, placement of shoal material dredged from Horseshoe Bend of the lower Atchafalaya River occurred at wetland development sites located along the river’s banklines adjacent to the channel. Capacity of these placement sites was nearly exhausted by 1999. Thus, to meet the anticipated disposal requirements for future channel maintenance, the USACE New Orleans District (MVN) evaluated three placement alternatives: (1) convert the wetland development sites into upland disposal areas; (2) open water placement of dredged material via a long-distance pipeline into the open waters of Atchafalaya Bay; and (3) mounding of material at mid-river open water placement sites within a 350-acre area immediately adjacent to the navigation channel and upriver of a small naturally forming island. The third alternative was selected on a demonstration basis to investigate the impacts of mid-river placement on shoaling trends downriver of the site. Beginning in 2002, strategic placement of the sediment dredged from Horseshoe Bend occurred at the mid-river open water placement area. Placement of between 0.5 to 1.8 million cubic yards of sediment was conducted every 1 to 3 years which influenced and contributed to the development of an approximately 35 ha island mid-river (Figure 1). Sediment dredged from the adjacent Federal navigation channel during routine maintenance was strategically placed in mounds upriver of the island over a period of 12 years. The mounded material was dispersed by the river’s currents to self-design the unconfined island over time. While the strategic placement of dredged sediments upriver of a naturally-occurring island was initially conducted to reduce dredging costs and promote the island’s growth, additional environmental, navigation, and climate change benefits were realized using this innovative placement practice.

Figure 1. Behind the dredge California, the river island at Horseshoe Bend on the lower Atchafalaya River, Louisiana is being self-designed by dredged sediment strategically placed upriver (lower right), allowing the river’s energy to disperse the sediment. The dispersed sediment contributes to the island’s growth, thus creating environmental and other benefits. (Photography by Wings of Anglers, courtesy of Great Lakes Dredge and Dock)

Project Description

A USACE MVN and USACE Engineer Research and Development Center (ERDC) project team was formed to generate data and other information regarding ecosystem classification and mapping, floral and faunal composition of the island. To help understand how and why the island was formed over the last 12 years, the USACE conducted studies to better understand the hydrology of the river used to transfer the mounded material onto the island. Information regarding ecosystem classification and mapping and floral and faunal composition of the island were conducted to document environmental and other benefits being realized. In addition, multiple moderate and high-resolution aerial photographs available from prior to 2002 to the present clearly documented the growth of the island (Figure 2). To address this goal, project objective focused on demonstrating how dredged material can be used beneficially to nourish a naturally forming river island. Biology, ecology, and hydrodynamics were examined to catalog the island’s maturation for determining the effectiveness of this individual project in terms of restoring, creating, enhancing, and protecting the coastal Louisiana landscape.

Figure 2. Imagery displaying island location prior to dredged material (DM) placement and subsequent formation (1992 and 1998 images), establishment, and growth since strategic dredged sediment placement began in 2002. (Imagery provided by USACE New Orleans District)

Monitoring

The study used a multi-factor ecological assessment including: 1) landscape geomorphology, 2) ecosystem classification, 3) floral communities, 4) avian communities, 5) aquatic invertebrates, 6) soils and biogeochemical activity, and 7) hydrodynamic and sediment modeling. Ecological components comprising primary producers, microbial communities, invertebrates that form the basis of aquatic food webs, and higher organisms were studied, providing a comprehensive assessment of dredged material supported wetlands. This framework can be used in future studies examining the ecological, societal, and economic value of the strategic placement of dredged material applied in this manner. Results demonstrated that each of the factors examined at Horseshoe Bend Island proved comparable or exceeded the other study areas examined, including the naturally formed riverine island and a traditionally created dredged material supported island. This innovative beneficial use of dredged material for creating Horseshoe Bend Island can be applied in other riverine project scenarios to demonstrate the success and potential benefits of this application of the EWN practice of utilizing natural process for improving wetland creation and restoration outcomes.

Study Results

Our results indicated that Horseshoe Bend Island is providing four distinct habitat types supporting complex communities of vegetation, invertebrates, soil microbes, and higher organisms such as birds. Horseshoe Bend Island contains a wide variety of vegetation including >85% native species, with species richness values exceeding observations from both traditional dredged material supported and natural reference areas. The design utilized at Horseshoe Bend Island resulted in landscape and landform characteristics (e.g., distance from shore, flooding regime) that support a large, successful wading bird rookery. Horseshoe Bend Island also supports more invertebrate abundance and diversity than natural islands in the region that lack the emergent aquatic bed landforms resulting from the strategic placement of dredged materials.

Previous studies only provided qualitative documentation of the fauna, flora, and geomorphology of the island. Completed quantitative surveys of the plant communities that have developed on the island indicated that Horseshoe Bend Island provides habitat and biogeochemical functions at rates comparable or exceeding observations made at a traditional dredged material supported island and a natural reference island in the area. Wetland classification and analysis of geomorphic features demonstrated that Horseshoe Bend Island provides a variety of habitat types supporting complex communities of vegetation, invertebrates, soil microbes, and higher organisms (i.e., avian species; Figure 3). The distribution of forested, shrub-scrub, emergent, and emergent aquatic bed habitat types corresponds to the natural distribution reported throughout the study area. Horseshoe Bend Island contains a wide variety of vegetation including >85% native species, with species richness values exceeding observations from both traditional dredged material supported and natural reference areas. The EWN design utilized at Horseshoe Bend Island resulted in landscape and landform characteristics (e.g., distance from shore, flooding regime) that support a large, successful wading bird rookery (Figure 3). Horseshoe Bend Island also supports more invertebrate abundance and diversity than natural islands in the region that lack the emergent aquatic bed landforms resulting from the strategic placement of dredged materials. Finally, the soils at the Horseshoe Bend Island display a capacity to sequester nutrients and other compounds and perform water quality functions at levels comparable to natural wetlands in the region.

Figure 3: A diverse assemblage of native plant and animal life has colonized the island, including the native American lotus (Nelumbo lutea; upper left), various amphibians (lower left), and juvenile glossy ibis (Plegadis falcinellus; right) observed during nesting season.

Project Significance

The project uses natural processes to maximum benefits, thereby reducing demands on limited resources, minimizing the environmental footprint of the project, and enhancing the quality of project benefits. Economic benefits are being realized as the enlarging island has reduced the overall cross-sectional area of the river, increasing the river’s flow through the navigation channel to velocities that were sufficient to reduce shoaling and maintenance dredging requirements. Costs were lower than the conventional approach because all other placement alternatives required additional equipment and land-rights to convey dredged material over long distances. Signs of human activity were also noted on the island, as the presence of shotgun shells signified that the island was being used for hunting. Intentionally aligning natural processes in the river with engineering processes via strategically mounding dredged material is realizing tangible environmental, social, and economic benefits. To this day, the island continues to provide multiple benefits and offers a means of beneficially using dredged sediments from the adjacent federal navigation channel to sustain and grow the island over time (Figure 4).

Figure 4. Aerial image of the northern end of Horseshoe Bend Island after placement of 500,000 cy of dredged sediments were placed there in late January 2020. The energy from the lower Atchafalaya River will disperse the sediment to shore up the western portions of the island. Periodic strategic placement is a sustainable beneficial use of sediments dredged from the adjacent federal navigation channel. (Photo courtesy USACE New Orleans District)

Investigations quantifying the multiple environmental and other benefits of using dredged material to create such riverine islands will provide a more complete understanding of the formation of the island so this concept can be integrated into other dredging projects in coastal Louisiana and elsewhere, thereby providing substantial environmental, social, and economic benefits as part of ongoing USACE maintenance dredging activities. To this end, the USACE is currently applying these practices and lessons learned at other locations along the Louisiana gulf coast and within the Philadelphia District, among others.

Points of Contact

Jeff Corbino, USACE New Orleans District: Jeffrey.M.Corbino@usace.army.mil

Burton Suedel, USACE Engineer Research and Development Center

More Information

Please see publications below for more in-depth information about the Horseshoe Bend project.

References

Foran, C.M., Burks-Copes, K.A., Berkowitz, J., Corbino, J., and Suedel, B.C. 2018. Quantifying Wildlife and Navigation Benefits of a Dredging Beneficial Use Project in the Lower Atchafalaya River: A Demonstration of Engineering With Nature®. Integr. Environ. Assess. Manage. 14(6):759-768. DOI: 10.1002/ieam.4084.

Berkowitz, J.F., Green, L., VanZomeren, C.M. and White, J.R. 2016. Evaluating soil properties and potential nitrate removal in wetlands created using an Engineering With Nature based dredged material placement technique. Ecological Engineering. 97:381-388.

Categories
Built Projects

Peanut Island (Lake Worth Lagoon, Florida)

Background

Peanut Island, located in the Lake Worth Lagoon (LWL) within Palm Beach County, Florida, was originally created in 1918 using the material excavated when the Lake Worth Inlet was created (Figure 1). First called Inlet Island, the island was renamed Peanut Island for a planned peanut oil-shipping operation which failed in 1946. The island originally encompassed only ten acres (4.0 hectares). By 1923 the Port was using the island as a spoil storage site for the maintenance of the inlet and the Port shipping channel. In 1991 the Port sold the northern half of the island to the Florida Inland Navigation District (FIND) as a spoil storage site for Intracoastal Waterway maintenance dredging.

Today, as a result of continued sediment deposition from maintenance dredging, Peanut Island comprises approximately 86 acres (34.8 hectares). The primary use of the island will continue as a spoil storage site, but the Port Authority and FIND have made the perimeter of the island available to the public as a park through a long-term arrangement with Palm Beach County. The park hosts facilities for passive and active recreational use that includes beaches, swimming/ snorkel areas, picnic and camping areas, docking facilities, a fishing pier, sidewalks, trails throughout the island and environmental enhancement areas.

Figure 1. Aerial photo of Peanut Island and Lake Worth Inlet.

Project Description

In 1996 a public park at the northeast corner of the island, a 10-foot wide concrete hiking trail around the island perimeter, a snorkeling area, a barge docking facility with proposed bulkhead and spoil access road, an observation deck and restroom facilities were authorized. In addition, the proposed park itself consisted of a campground, picnic areas, ranger station and maintenance building, restroom with shower, a boat dock and fishing pier.

In 1998, Palm Beach County Environmental Resources Management (ERM) began planning a habitat enhancement project at the Lake Worth Golf Course of which the Peanut Island makeover project included offloading 1.2 million cubic yards of spoil to Snook Islands.

In 2002 the addition of two floating ADA compliant docking structures were authorized as well as flushing channels to restore existing mangroves where realigned to further minimize mangrove impacts and modification of the mangrove boardwalk.

Reef Sites: Peanut Island has four separate reef sites. The fishing pier and east dock sites contain concrete tetrahedrons, modules and caprock deployed in 2000 and 2011. Major enhancements occurred on the Island in 2005, including creation of the 10’ deep snorkel reef which is protected by limestone and granite boulders. Between 2006 and 2012, 6 breakwaters were added on the east and south sides of the island. These multiple structures encompass 1.7 acres in depths ranging from 2 to 4 feet.

Breakwater Reefs (2008): Limestone rock (500 tons) was used to construct three breakwaters on Peanut Island’s shoreline. One breakwater was constructed on the east side of the island and two smaller structures were installed on the southeastern shoreline. The structures not only slow beach erosion and provide shoreline protection, they also provide reef habitat. The breakwater reefs are very popular with snorkelers and provide a variety of restored habitats for fish, invertebrates, and birds.

Lagoon/ Shoreline Restoration (2009): Sand was dredged from the Peanut Island boat docks and fishing pier and reused onsite to stabilize the beach and prevent further erosion of the walking path. The sand was also used to recontour the snorkeling lagoon and create 0.4 acres of intertidal Spartina (salt marsh cordgrass) habitat which stabilizes the shoreline, increases nutrient uptake, and provides important wildlife habitat.

Figure 2. Aerial photo showing the breakwaters and reef improvements and the snorkeling lagoon created on the east and south side of Peanut Island.

Breakwaters and Reef Improvements (2012): The project was designed to improve the tidal flow within the snorkeling reef system and provide increased shoreline protection and reef habitat on the island’s east shore (Figure 2). The existing rock infrastructure was modified due to the area experiencing ongoing problems with poor water quality and minimal tidal flushing, so the removal of 720 tons of granite rock that was placed in a Y-shape groin and additional 1,300 tons of granite rock along the southwest lagoon side occurred. The rock was relocated to create a breakwater structure to reduce wave energy and protect a walkway along the eastern shoreline. Additionally, 890 tons of granite was placed behind two breakwaters to enhance the areas. These breakwaters provide shoreline protection as well as artificial reef habitat in an area that is void of natural resources. The reef system is utilized by snorkelers due to the clear oceanic water, fish, coral, and other reef resources that it provides as it is located adjacent to the Lake Worth Inlet.

Additional enhancement activities were permitted in 2013 for the installation of two 110-foot long emergent reef structures for shoreline protection and reduction in wave energy as well as providing artificial reef habitat for both marine life and recreational snorkeling. Also permitted was the placement of limestone rocks in discrete piles to create an artificial snorkel reef trail within two separate areas on the eastern side of the island.

Monitoring & Study Results

The snorkel reef was monitored in 2007, 2008, and 2012. A total of 26 families and 63 species of fish were recorded. Haemulidae (grunt) and Scaridae (parrotfish) were represented by the most species with 11 and 10 species respectively. Unusual sightings included a black grouper (Mycteroperca bonaci) juvenile.

During the 2007 site visit only two years after the limerock boulders were installed, five hard coral species and a gorgonian were observed. Unusual sightings included spaghetti worms (Eupolymnia crassicornis) and an unidentified octopus. The site visit in September 2012 documented 12 different species of corals. Several of these corals have attained larger sizes, such as 30 cm for boulder brain coral (Colpophyllia natans) and 20 cm for symmetrical brain coral (Diploria strigosa). Other species of note were several sponges, urchins, clams, and tunicates. Due to the proximity to the inlet, this area is bathed semidiurnally by clear Gulf Stream waters, which make this a unique and diverse reef.

Project Significance

The projects at Peanut Island have improved tidal flushing to northern LWL, providing needed habitat and recreational opportunities. Peanut island also provides a buffer to the city of Riviera Beach reducing shoreline erosion.

USACE has the authority, provided by Section 1135 and Section 206 of the Water Resources Development Act of 1986, as amended, to plan, design and construct fish and wildlife habitat restoration measures. The Corps has partnered with Palm Beach County to construct many restoration projects within the LWL through the Section 1135 program including, Munyon Island, Snook Islands and John’s Island Restoration Projects.

Point of Contact

Kelly Egan, USACE Jacksonville District- Kelly.A.Egan@usace.army.mil

More Information

https://discover.pbcgov.org/parks/Pages/PeanutIsland.aspx
https://discover.pbcgov.org/erm/Pages/Lake-Worth-Lagoon.aspx

References

Proceedings of the 34th Annual Conference on Ecosystems Restoration and Creation 2007. Institute of Florida Studies.

Peanut Island, Lake Worth Florida

Categories
Built Projects

Swan Island (Chesapeake Bay, Maryland)

Background

Coastal islands and marshes of the Chesapeake Bay are disappearing along with the critical ecosystem services and shoreline protection benefits they provide. At Swan Island, Maryland, a 25 acre island within the Martin National Wildlife Refuge in Tangier Sound, Chesapeake Bay, high rates of shoreline erosion and subsidence have deteriorated the island’s natural habitat and reduced its ability to shelter the nearby town of Ewell, Maryland from wave energy. To counter such losses, the U.S. Army Corps of Engineers Baltimore District used dredged sediments from a nearby navigation dredging project to enhance Swan Island’s natural habitats. Ultimately, this project will increase the long-term resilience of Swan Island and its capacity to defend adjacent shorelines from wave energy.

Project Description

In October 2018, the Baltimore District of the U.S. Army Corps of Engineers began dredging the navigation channel that runs between Swan and Smith Islands in Chesapeake Bay. Approximately 60,000 cubic yards of the dredged sediments were used to restore the footprint of Swan Island. The restoration plan included creation of low dunes and high and low intertidal marsh. The island was transformed from one characterized by low and highly fragmented marsh to one with a wider range of habitats that sit higher in the tidal frame (Figure 1. Figure 2. Swan Island post placement 2019.jpg Figure 3. Swan Island 2020.jpg,).

Figure 1. Swan Island in 2017 pre-construction. (photo credit. USFWS)
Figure 2. Swan Island 2 months post-construction and planting in 2019. (photo credit NOAA)
Figure 3. Swan Island approximately 1 year post-construction. (photo credit NOAA)

Monitoring and Adaptive Management

The Swan Island restoration presents an opportunity to evaluate the efficacy of managing coastal islands to protect and enhance their long-term resilience to storms and sea level rise. Project success is being measured through the collaborative efforts of a multi-disciplinary project team with members from USACEs Engineer Research and Development Center (ERDC), USACE Baltimore District, NOAA National Centers for Coastal Ocean Science (NCCOS), US Fish and Wildlife Service and the Maryland Department of Natural Resources. Initially, the project team came together in a series of iterative group-mediated workshops to develop project goals and a conceptual model describing interactions between the island’s physical properties and biological communities. The outcome was a refining of the team’s project goals, a conceptual model (Figure 3), a monitoring program, and the development of a Monitoring and Adaptive Management Plan.

Figure 4. Simplified Resilience Conceptual Model for Swan Island. These hydrodynamic, ecological, topographic (elevations) and sediment parameters are required to understand the performance of Swan Island in reducing wave energy and erosion to nearby shorelines.

The overarching project goal is to quantify coastal resilience performance of Swan Island in terms of reducing wave energy and erosion to nearby shorelines and habitats. Researchers are collecting pre and post-restoration data such as sediment (total suspended solids, accretion), hydrodynamic (waves, currents, water level), ecological (vegetation) and topographic (elevations) parameters. These data will be used to develop and evaluate integrated hydrodynamic and ecological models that will answer questions such as: How resilient is the island and its habitats against rising sea level and periodic storm events? Or how much wave attenuation does Swan Island provide the Town of Ewell?

Figure 5. One of 4 platforms installed around Swan Island, each has an Acoustic Doppler velocimeter (ADV), CTD and ISCO sampler attached. These instruments allow researchers to capture waves, currents and sediment to better understand sediment movement and erosion processes.

The Monitoring and Adaptive Management Plan (MAMP) tracks progress and serves as a blueprint for the project team for all aspects of the monitoring (e.g. What, How, and How often data is collected) and the adaptive management approach. This includes reporting, data management, roles and responsibilities, performance metrics and decision thresholds for adaptive management.

Figure 6. Scientists collecting RTK GPS data to document island elevations. (photo credit NOAA)

Study Results

Two years of post-restoration monitoring has been completed. As of September 2020, the high marsh was characterized by vigorous ingrowth of planted Spartina patens with 50 percent cover in elevations from 0.5 – 0.9 meters NAVD88. However, below 0.4 meters NAVD the low marsh experienced significant mortality, triggering the adaptive management threshold for percent cover determined in the MAMP (Figure 3). Accordingly, the team intends to replant 25,000 low marsh (S. alterniflora) plants in Spring 2021. Shoreline erosion, elevation change, and trends in the aerial extent of the Island’s various vegetative communities are also being measured and tracked over time, using georeferenced drone-based imagery products such as Digital Elevation Models and habitat classification maps (Figure 7. Figure 8.). Trends in these data will be evaluated with respect to water movement (waves, tides and currents) through the model development process which is ongoing. Ultimately, the resulting simulation model will be used to quantify the relationships between physical and ecological changes in Swan Island and the impact of these changes on its long-term resilience.

Figure 7. Elevation change in meters NAVD88 between Sept 2019 and Sept 2020. The greater than 3 meter increase shown in dark blue on the western side of the island is due to high marsh growth. (photo credit NOAA)
Figure 8. Habitat classification map developed from drone-based imagery from Sept 2020. Products like this will allow researchers to track habitat and vegetation changes over time. (photo credit NOAA)
Figure 9. Swan Island high marsh habitat looking north in 2020. (photo credit NOAA)

Project Significance

The products developed through this project will inform the design and placement of future island restoration activities and will be used by regulatory agencies involved in permitting island restoration projects. Monitoring data collected for this project is being used to develop and evaluate an integrated hydrodynamic and ecological model to address how the island and its ecological communities will respond to physical forcings, like storms and sea level rise. The results of these modeling efforts will also address current information gaps on the impacts of island restoration activities on nearby ecosystems, and the protective benefits provided by these islands. The results will inform how restoring these islands, by leveraging natural and engineered processes, can achieve EWN ‘triple win’ benefits to address the uncertainties identified as barriers to implementation.

Points of Contact

Danielle Szimanski, USACE Baltimore District
Jenny Davis, NOAA NCCOS – jenny.davis@noaa.gov

Additional Information and Related Links

NCCOS Swan Island Project Page

Swan Island Restoration Begins Video

Presentation to the International Conference for Coastal Engineering – “Island Restoration to Meet “Triple-Win” Engineering With Nature® Outcomes”

Mordecai Island EWN web site

Publications

Herman BD, Whitfield PE, Davis J, Tritinger AS, Golden BR, Dillon SC, Szimanski DM, Swannack TM, Gailani JZ, King JK. (2023) Swan Island resilience model development; Phase I : conceptual model. ERDC TR-23-1. Engineer Research and Development Center (U.S.) Available at https://hdl.handle.net/11681/46402 [Verified 27 January 2023]

References

Erwin ME, Brinker DF, Watts BD, Costanzo GR, Morton DD. 2011. Islands at bay: rising seas, eroding islands, and waterbird habitat loss in Chesapeake Bay (USA). J Coast Conserv doi: 10.1007/s11852-010-0119-y.

Grant WE, Swannack TM 2008 Ecological Modeling: A Common-Sense Approach to Theory and Practice. Blackwell Publishing, Oxford UK. 155 Pp.

Herman B, Swannack TM, King JK, Whitfield PE, Davis J, Szimanski D, Bryant D, Gailani, J, (2020) Proceedings from the US Army Corps of Engineers and the National Oceanic and Atmospheric Administration – National Ocean Service, Ecological Modeling Workshop. April 11-12, 2019

Kearney MS, Stevenson JT, (1991) Island Land Loss and Marsh Vertical Accretion Rate Evidence for Historical Sea-Level Changes in Chesapeake Bay. J. Coastal Research. 7(2):403-415pp

Perini Management Services. 2014. Study Report, Smith Island, Martin National Wildlife Refuge, Hurricane Sandy Resiliency Project #31, Fog Point Living Shoreline Restoration.

Whitfield, Davis, Tritinger et al. (forthcoming) Draft Monitoring and Adaptive Management Plan for Swan Island, to be published as an ERDC Technical Report

Categories
Built Projects

Baptiste Collette Bayou Bird Islands

Background

Dating to the late 1860’s, Baptiste Collette Bayou was a small canal that extended between the Mississippi River and the historic Breton Island Sound. In a series of storm-related events and USACE dredging authorizations beginning in the early 1900’s, a sub-delta that had developed covering as much as 20 square miles by 1959 had begun to deteriorate due to considerable subsidence and ponding. The inception of the channel occurred in 1968 from a Congressional Authority to enlarge the waterway. Work began with emergency dredging events in 1972 and 1973 to provide relief to barge traffic on the Gulf Intracoastal Waterway while the Inner Harbor Navigation Canal lock was closed. The first bird island was born of this emergency maintenance.

Construction of the bird islands began in 1978 when the New Orleans District (CEMVN) began to regularly maintain Baptiste Collette (Figure 1). They focused their efforts on creating island habitat that could serve as nesting habitat for a wide variety of shorebirds. Yet the Baptiste Collette Bird Islands created by the beneficial use of dredged sediment are subject to storms and wave energy from the open Gulf of Mexico. The aerial image below shows the bayou as it existed in 1978 soon after beneficial use activities began in 1977. Sediment placement to create habitat on the west side of the jetty channel began in 1988.

Figure 1. Aerial photograph of Baptiste Collette Bayou in 1978 showing the recently placed dredged sediment (white areas denote bare ground of placed sediment) that began the prior year. North is at the top of the photo.

Project Description

Sediment beneficial use from maintenance of the Baptiste Collette Bayou channel occurs on an annual basis with the placement of dredged sediment in shallow open water either on the east or west side of the channel. The unconfined placement is designed to create wetland habitat adjacent to the waterway’s jettied entrance and islands seaward of the jetties that are suitable for colonial nesting seabirds. Use of dredged sediment to create or restore coastal habitat considered innovative in the late 1970’s has become current state-of-the-practice. Following creation of an island, CEMVN periodically places sediment from subsequent maintenance activities to prevent vegetative succession, keeping the island relatively vegetation-free for colonial nesting seabirds that prefer bare sand for nesting. In cases where pelican nesting has been observed, vegetation is left undisturbed to encourage return during future nesting seasons. The most recently constructed “Gunn Island” was established in 2014 to accommodate shoaling further out in the bar channel and to avoid enlarging the existing islands while maintaining sufficient spacing between them. Recent examples of beneficial use activities on Gunn Island include placement of 836,00 cubic yards of sediment in 2018 to achieve a +6.0 feet MLG elevation, creating roughly 12 acres of bird nesting habitat. In 2019, 943,000 cubic yards of dredged sediment was placed on Gunn Island, creating an additional 56 acres of bird nesting habitat. Figure 2 shows the bird islands as of 2019.

Figure 2. Aerial photograph of Baptiste Collette Bayou in 2019 showing the beneficial use wetland habitat and islands created over time, including Gunn Island that was established in 2014.

Monitoring

Nesting surveys were performed regularly prior to 2000 to develop data and other supporting evidence to promote the recognition of the islands as beneficial by the resource agencies. Surveys have relied on ground observations to estimate numbers of birds utilizing the island habitat for nesting and other purposes. Created habitats include marsh, scrub-shrub, bare land, and beach. Seventy-six species of salt and freshwater plants have been documented on these sites. Additional monitoring is recommended to more completely understand the effectiveness of dredged sediment placement for creating the islands and to quantify the successes of ongoing efforts. An understanding of how the seabirds respond to the placement activities in Baptiste Collette Bayou is needed to determine the broader ecological and other benefits of sediment placement strategies so these best practices can be optimally applied here and elsewhere.

STUDY RESULTS

The results compiled on the Baptiste Collette Bayou Bird Islands indicated that the islands created using dredged sediment have been providing meaningful nesting habitat for a variety of seabirds since observations began in 1986. That year, several thousand birds were observed nesting on Plover Island (Figure 2), including Caspian Terns, Royal Terns, Black Skimmers, Gull-billed Terns, and Sandwich Terns. The island was designed to use sediment beneficially specifically for the purpose of utilization by seabirds for nesting and other purposes. In August 2020, the Louisiana Department of Wildlife and Fisheries recently observed over 50,000 seabirds nesting on Gunn Island (Figure 2) composed of approximately 75% Royal Terns, 15% Caspian Terns, and the remaining 10% were comprised of Black Skimmers, Gull-billed Terns, and Sandwich Terns (Figure 3). Contributions to the success of the islands to serve as nesting habitat are attributed to a combination of remoteness to discourage terrestrial predators, small size to limit the spread of avian disease, presence of bare sand, and elevation sufficient to prevent tidal and storm inundation.

Figure 3. Photograph of tern nestlings hatched on Gunn Island in August 2020. (Photo courtesy P.J. Hahn)
Figure 4. Photograph of Bird Islands skimmers.

Using an adaptive management approach to design and construct additional islands has proved largely successful to the present day. One such example is to maintain at least a 1,200-foot gap between the islands to reduce the likelihood of predators reaching the outer islands. The islands’ exposure to the open waters of the Gulf of Mexico result in degradation of the islands over time, yet the availability of sediment dredged from the channel offers a reliable and sustainable supply of clean sediment for maintaining the islands structure and multiple environmental and other benefits.

Project Significance

In 2020, as part of the Baptiste Collette Bayou Bird Island chain, Gunn Island hosted the state of Louisiana’s largest nesting tern colony that was believed to have been displaced from the low-lying Breton Island by tropical storm overwash. Since the initial construction of the Baptiste Collette navigation channel, over 1,000 acres of coastal habitat have been created by placement of dredged material during routine maintenance dredging events. The bird nesting islands have been identified as a U.S. Important Bird Area because of the essential habitat they provide to significant numbers of breeding Caspian and gull-billed terns and roosting pelicans. Five species of terns have been recorded as breeding on these islands. Research to document ecosystem services at sites like these will play a meaningful role in determining the efficacy and optimal use of such beneficial use applications in the future.

Points of Contact

Jeff Corbino, USACE New Orleans District: Jeffrey.M.Corbino@usace.army.mil
Burton Suedel, USACE Engineer Research and Development Center

More Information

Please see link below to a story that Fox TV Station WVUE New Orleans/Baton Rouge ran on 14 August 2020 related to the bird colony on Gunn Island.

https://www.fox8live.com/2020/08/14/birds-nest-brand-new-louisiana-island/?fbclid=IwAR3MgzgdmUz4d4hjHgEiv71ts5gvCzGJXBuiaVTwsBOrOa45i38o1tTl0NI

Categories
Built Projects

Snook Islands

Background

The Snook Islands project site is located adjacent to the Lake Worth Golf Course (LWGC) in the Lake Worth Lagoon (LWL) in central Palm Beach County, Florida. The LWL is a 22 mile (35.5 km) long coastal lagoon with two oceanic inlets (Figure 1).

In the late 1800’s developers began dredging and filling the wetland edges of Lake Worth Lagoon, an activity that would continue into the 1970s. Inter- and shallow sub-tidal resources were decimated. Marinas and hundreds of private docks are scattered along the shoreline. Approximately 81% of the lagoon shoreline is bulkheaded, while only about 19% of the shoreline remains fringed by mangroves.

The Lake Worth Golf Course (LWGC) has approximately 1.2 linear miles (1.9 km) of shoreline along the western shore of central Lake Worth Lagoon. The existing upland portions of the LWGC were created through the dredging and filling of inter- and sub-tidal wetland resources and associated bulkhead construction. These dredge and fill activities along the shoreline resulted in a steep littoral profile, with elevations dropping quickly from +4.0 feet referenced to the National Geodetic Vertical Datum of 1929 (NGVD) at the shoreline to -7.0 feet NGVD just offshore. This steep grade minimized the area suitable for development of inter- and shallow sub-tidal resources such as mangroves, seagrasses, and oyster reefs. In addition, open water dredge holes as deep as -23.0 NGVD existed prior to construction prior to Snook Islands construction, and depths below -10.0 NGVD were common. Prior to construction of Snook Islands, over one-half of the existing shoreline was fringed with three species of mangroves (red: Rhizophora mangle, black: Avicennia germinans, and white: Laguncularia racemosa), inter-mixed with exotic Australian pine (Casuarina sp.) and Brazilian pepper (Schinus terebinthifolius). The bulkhead along the LWGC failed over time, leading to erosion of the shoreline from wind and wake-generated wave energy (Figure 2).

Figure 1. Aerial photograph of Snook Islands, Lake Worth Florida in 2016.
Figure 2. Failed shoreline armoring that was replaced with vegetative habitat.

Project Description

In 1998, Palm Beach County Environmental Resources Management (ERM) began planning a habitat enhancement project at the LWGC. Given that dredging and the bulkheading of the shoreline to create the golf course, eliminated areas suitable for re-establishment of inter- and shallow sub-tidal biotic communities the only viable option to remediate the loss of habitat was to place fill in the water to reconstruct sediment topography and depths appropriate for establishment of inter- and shallow sub-tidal vegetation. Peanut Island, a spoil storage site for the maintenance of Lake Worth Inlet and the Port of Palm Beach shipping channel, was a ready source of dredge spoil as the island’s spoil storage was at capacity; and an island makeover was in the final planning stages for Peanut Island. Approximately 1.2 million cubic yards of spoil was transport 10 miles from Peanut Island to the Snook Islands. This amounted to over 1,560 barge loads of sediment resulting in the creation of 10 acres of red mangroves, 2.8 acres of Spartina marsh, 2.3 acres of oyster reef, and approximately 50 acres of seagrass recruitment area. Approximately 28,000 tons (25, 401 metric tons) of 1-3 ft (0.3-0.9 m) diameter limestone boulder riprap was used to create the oyster reefs and mangrove planting breakwaters (Figure 3).

In addition exotic vegetation from approximately 5 acres (2 hectares) of the LWGC shoreline was removed and approximately 1,800 ft shoreline armor (rip rap, concrete rubble, and collapsed seawall) was removed, except in areas where the seawall was still intact and buried in situ.

Figure 3. Updated image of Snook Islands low tide (2016).

Monitoring & Study Results

The project was completed in June 2005 and resulted in creation of 10 acres of red mangroves, 2.8 acres of Spartina marsh, 2.3 acres of oyster reef, and approximately 50 acres of seagrass recruitment area. Project construction eliminated the original shoreline armor along the golf course, and replaced it with a soft, vegetated shoreline. The offshore islands and oyster reefs provided protection from wind and wave energy, stabilizing the formerly eroding shoreline. In 2004, Hurricanes Frances and Jeanne made landfall near the project site. Because the project was well underway, no damage was sustained to the project or to the LWGC shoreline.

Red mangroves

The planted red mangroves achieved a survival rate of approximately 80% after two years. The mangroves were collected as propagules by volunteers and raised in a nursery to the 6 to 8 leaf stage. They were then planted on 10 different occasions by volunteers as construction of the islands and shoreline planters was completed.

Spartina

The Spartina was planted by the contractor as each section of shoreline was completed. The plantings coalesced in approximately two years.

Oysters

Oysters (Crossastrea virginica) have colonized the oyster reefs and base of the mangrove planting wave breaks. The fill used for project construction had 30% by volume of rock rubble intermixed. Oysters have also colonized the shoreline areas where the rubble is exposed. No oyster counts have been completed as yet, but visual observations suggest significant coverage.

Seagrass

Three species of seagrass occur in the project vicinity: Halophila decipiensHalophila johnsonii, and Halodule wrightiiH. johnsonii, listed as a threatened species, is the most abundant on site as it is throughout the LWL. H. johnsonii was observed recruiting to the newly placed fill even as construction and associated turbidity continued.

The first post-construction seagrass inventory was conducted during summer 2006. The survey method involved visiting the site at the lowest of low tides and wading the shoreline to a depth where the bottom was no longer visible. Wire survey flags were placed around the edges of the observed grass beds, which were mapped using GPS to sub-meter accuracy. This method proved effective for one-third to one-half of the potential seagrass areas. The results of the 2006 survey show that H. johnsonii has become established along the entire 1.2 mile length of the project, covering a total of 1.2 acres (0.5 hectares). Only a few small beds of H. decipiens were observed. Densities of both species were high wherever they occurred.

A second survey was performed during summer 2007. Seagrass coverage had increased by more than 10 times to 14.1 acres (5.7 hecrtares). H. wrightii was observed in at least two locations, and cover of H. decipiens was increasing. H. johnsonii still represented roughly 90%-95% of the seagrass present. From 2008 to 2010 seagrass acreage increased from 1.2 to 44.5 acres. (Figure 4).

Figure 4. 2006-2010 Seagrass cover (excerpted from the Snooks Island seagrass monitoring report 2006-2010.

Wildlife

Fish and wildlife usage of the project site increased dramatically after construction. Prior to construction, there was a seawall with an immediate drop into an anoxic dredged hole. Construction created a gradually sloping inter-tidal wetland shelf, and shallow submerged areas recruiting seagrass. Wading birds, shorebirds, and ospreys regularly use the site as feeding and resting areas. Schools of juvenile fish are swimming in the shallows and around the Spartina at high tide. Manatees have also been observed feeding on the Spartina. A pair of American oystercatchers (Haematopus palliatus), listed a Species of Special Concern in Florida, appeared in 2004 and have been nesting each year on top of the mangrove riprap wavebreak. They successfully fledged a chick in the summer of 2007. American oystercatchers have since continued to successfully nest and fledge multiple chicks yearly. Currently there are 4 nesting pairs of oystercatchers utilizing the spoil islands. Recent counts within the LWL have averaged with a 81 percent overall fledge success and number of total fledged chick of 29 (Figure 5).

Figure 5. American oystercatchers (Haematopus palliatus) began nesting on top of the mangrove riprap wavebreak in 2007.

Project Significance

This project provided an opportunity to add almost 100 acres of inter-tidal and shallow sub-tidal resources to the Lake Worth Lagoon. Projects such as this are necessary to offset the historic loss of natural resources. Living shorelines provide an alternative to seawalls and armoring by reducing shoreline erosion. Constructing the offshore mangrove islands and oyster reefs provided an increased buffer against waves and boat wakes precluding the need to construct a new seawall, as well as restoring valuable fish and wildlife habitat. Public use amenities, including a boardwalk, fishing pier and kiosks, educate the public on the importance of living shorelines, while the day-use docks provide boater access to downtown Lake Worth, generating revenue for local businesses.

In 2012 the Snook Islands Natural Ara Public Use Facilities were created to allow visitors to view wildlife, fish, and explore the lagoon waters. Public-use components includes a boardwalk with observation platform, fishing pier, kayak launch structure, day-use docks, boat trailer parking, bike racks, benches, and informational kiosks.

Snook Islands Wetlands Restoration Phase II begun in 2013 which included the construction of two mangrove islands and oyster reefs. The additional habitat created included 0.45 acres of oyster reef, 0.74 acres of red mangroves and 7.17 acres of additional seagrass habitat. The additional open areas were created to improve bird use of the shoreline and mudflats, as well as increase utilization for fish and other wildlife.

Points of Contact

David C. Carson, Palm Beach County ERM-DCarson@pbcgov.org
Kelly Egan, USACE Jacksonville District- Kelly.A.Egan@usace.army.mil

More Information

https://discover.pbcgov.org/erm/NaturalAreas/Snook-Islands.aspx
https://discover.pbcgov.org/erm/Pages/Lake-Worth-Lagoon.aspx

References

FIND SINA Wetland Mitigation Fourth Annual Monitoring Report 2019. Palm Beach County Department of Environmental Resources Management.

Proceedings of the 34th Annual Conference on Ecosystems Restoration and Creation 2007. Institute of Florida Studies.

Snook Islands Seagrass monitoring 2006-2010.