Post on 31-Jul-2020
Living Shorelines as an Erosion Mitigation Strategy
Living Shorelines as an
Erosion Mitigation Strategy
Evidence from the Guana Tolomato Matanzas
National Estuarine Research Reserve
Monica Quintiliani
Living Shorelines as an Erosion Mitigation Strategy
Page | ii
Table of Contents
Tables ................................................................................................................................................... ii
Figures ................................................................................................................................................. iii
Abstract ................................................................................................................................................ 1
Introduction .......................................................................................................................................... 2
Case Studies ......................................................................................................................................... 7
Grand Isle and St. Bernard Oyster Reef, Louisiana ......................................................................... 8
Saw Grass Point Salt Marsh, Dauphin Island, Alabama ................................................................ 10
Winyah Bay South Island Living Shoreline, Yawkey Wildlife Preserve, South Carolina ............ 12
Johns Point Landing, Virginia ........................................................................................................ 14
Gandy’s Beach/Money Island, Downe, New Jersey ...................................................................... 16
Summary ......................................................................................................................................... 18
Study Site ........................................................................................................................................... 20
Methods .............................................................................................................................................. 23
Results ................................................................................................................................................ 25
Beach Width ................................................................................................................................... 25
Marsh Area ..................................................................................................................................... 26
Discussion .......................................................................................................................................... 28
Conclusions ........................................................................................................................................ 33
Project Limitations ......................................................................................................................... 33
Future Research Recommendations ............................................................................................... 34
References .......................................................................................................................................... 36
Tables
Table 1. Summary of Case Study Findings ........................................................................................ 18
Table 2. Beach width over time.......................................................................................................... 25
Table 3. Marsh area over time. ........................................................................................................... 27
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Figures
Figure 1. Seawall .................................................................................................................................. 3
Figure 2. Groins .................................................................................................................................... 3
Figure 3. Living Shoreline design ........................................................................................................ 5
Figure 4. Grand Isle Living Shoreline, LA .......................................................................................... 8
Figure 5. Grand Isle, LA oyster substrate ............................................................................................ 9
Figure 6. Saw Grass Point Living Shoreline, AL ............................................................................... 10
Figure 7. Coastal Haven System, Dauphin Island, AL .................................................................... 11
Figure 8. Winyah Bay, SC Living Shoreline ..................................................................................... 12
Figure 9. Castle Blocks, Winyah Bay, SC ......................................................................................... 13
Figure 10. Johns Point Landing Living Shoreline .............................................................................. 14
Figure 11. Oyster shell bags as oyster substrate ................................................................................. 15
Figure 12. Gandy's Beach/Money Island, NJ ..................................................................................... 16
Figure 13. Coir fiber logs ................................................................................................................... 17
Figure 14. GTMNERR and Wright's Landing ................................................................................... 21
Figure 15. Wright's Landing Living Shoreline................................................................................... 22
Figure 16. Measurement Sites, Upper Peninsula ............................................................................... 23
Figure 17. Measurement Sites, Lower Peninsula ............................................................................... 24
Figure 18. Beach width over time ...................................................................................................... 26
Figure 19. Marsh area over time ........................................................................................................ 27
Figure 20. Hurricane Mathew damage, Ponte Verde Beach, FL ....................................................... 28
Figure 21. Hurricane Irma damage, St. Johns County ....................................................................... 29
Figure 22. Destroyed bulkhead .......................................................................................................... 30
Living Shorelines as an Erosion Mitigation Strategy
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Abstract
Erosion is a principal problem in coastal areas exacerbated by heavy residential and infrastructure
development. Traditionally, communities have used structures such as seawalls and groins to protect
their shorelines, yet new research suggests these structures increase erosion on site. Many land
managers are now turning to the Living Shoreline technique which uses ecosystem engineers to create
a more naturally protected shoreline. Five case studies were examined to determine whether clear
trends leading to living shoreline success existed. Satellite images of the Guana Tolomato Matanzas
National Estuarine Research Reserve (GTMNERR) from 2005, 2008, 2011, 2013, 20015, and 2017
were also analyzed to determine whether the living shoreline installed in 2012 has had any large
impacts on the shoreline over time.
Analysis of the GTMNERR site revealed little to no change in beach width or marsh area despite
heavy hurricane activity. These findings suggest the living shoreline installation may be protecting
the shoreline although no detectable accretion or erosion exists. A similar result was seen in the
Dauphin Island, AL case study. Other case studies revealed a possible benefit to marine concrete as
an oyster substrate and that these projects may need more time to establish before large impacts to
the shorelines will be seen. Proper planning, site selection, and monitoring are key to successful
living shorelines.
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Introduction
Coastal areas continue to be developed due to high economic opportunity and aesthetic value,
resulting in communities facing the important problem of erosion. To combat this, communities often
invest heavily in traditional forms of shoreline armoring (e.g. seawalls, groins, see Figures 1 & 2).
Conservative estimates as recent as 2015 have determined that the continental United States’ coasts
are roughly 14% armored (Dethier 2016). However, these traditional armoring techniques have been
found to intensify erosive forces instead of reducing them as intended (Cheong 2013) (Scyphers
2011). Furthermore, these armoring measures have been found to reduce the retention of wrack, or
organic beach debris (e.g. seaweed, drift wood) usually forming a “wrack line” at the high tide extent,
on the beach and the invertebrate populations residing within it. This reduces the diversity of mobile
macroinvertebrates, reduces high shore habitat for beach-spawning forage fish, and increases beach
temperatures resulting in increased fish egg mortality (Dethier 2016). Armored shorelines are often
found to be much narrower than unarmored shorelines (Pilkey 1988), likely due to the prevention of
the upper beach migrating inland as it naturally would (Dethier 2016).
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Figure 1. Seawall
Figure 2. Groins
Source: https://www.nccoast.org/protect-the-coast/advocate/terminal-groins/
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While negative effects of traditional armoring techniques are generally localized when a few, small
installations exist on a shoreline, ecosystem scale impacts can materialize when installations become
larger and more frequent. Benthic infaunal organisms, those which live burrowed into sediment,
experience decreased densities, likely due to a loss of nutrients from marsh detritus that these
organisms would usually consume. Reduced benthic infauna densities can affect higher levels of the
food chain as less prey species will be available to the predator species (National Oceanic and
Atmospheric Administration 2015). Considering these findings, academics and public servants alike
have been searching for better alternatives for shoreline protection.
Living shorelines is a new approach to shoreline protection gaining attention for its nature-based or
biophilic design. Living shoreline designs (Figure 3) emphasize positive interactions that generate
synergies (Cheong 2013) by using ecosystem engineers. Ecosystem engineers are species that either
reduce constraining variables or provide limiting resources to other species in response to their
changing environment (Crain 2006). Such species typically provide ecosystem services and influence
ecosystem function greatly (Crain 2006). Research has shown that by incorporating several abiotic
and biotic features into a living shoreline design (e.g. oyster reefs, saltmarsh, coir fiber logs, etc.),
community recovery and stability can be increased by orders of magnitude. The living shoreline
approach allows for multiple use design integrating recreation and ecosystem services, coastal
defense, and climate-adaptive and disaster coastal management (Cheong 2013).
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Figure 3. Living Shoreline design
Traditional armoring techniques are usually considered “easier” to implement as they are the status
quo in shoreline protection and tend to have little issue gaining funding and public support. Fewer
experts are needed to successfully accomplish these installations and time has allowed for refined
design and installation practices. However, as discussed above, these techniques do not typically
provide the desired goal of long-term shoreline protection health. While living shorelines can be
more expensive and require more experts to install, monitor, and maintain, the living shoreline
technique can protect shorelines from storm surges and sea level rise much more effectively than
traditional armoring techniques. Improved wildlife habitat, ecosystem services, and more
aesthetically pleasing shoreline protection are also benefits of this new approach (National Oceanic
and Atmospheric Administration 2015).
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Constructed oyster reefs, used as natural breakwaters, are a common feature among living shoreline
projects and can be a self-sustaining armoring technique used to prevent erosion in estuaries as long
as adequate recruitment and survival rates are maintained on the reef (Scyphers 2011). Reef success
is highly dependent on proper site selection, most significantly appropriate salinity regimes, tidal
exposure indices, and wave energy impacts (La Peyre 2015). While researchers are still working to
understand the needs of successful oyster reefs, environmental benefits from oyster presence has been
well defined. Oyster reefs have been found to have significant influence on water quality, primary
production, turbidity, suspended organic material, and bacteria (Cheong 2013). Oysters participate
in bioturbation and bioirrigation, processes in which sediment and water are filtered causing
disturbances which affect bulk density, oxygen availability, and nutrient fluxes resulting in increased
soft-sediment habitat heterogeneity. In turn, these interactions affect both ecological function and
biodiversity (Norkko 2011). Examples of these impacts include improved demersal, or benthic, fish
populations (Scyphers 2011) and positive effects on nutrient dynamics, commercial fisheries, and
saltmarsh retreat (La Peyre 2015).
With these benefits in mind, many land managers are beginning to integrate these promising natural
breakwaters into their coastal defense systems. However, there has been little research into how
constructed oyster reefs impact shorelines over time. The purpose of this study was to analyze and
identify the shoreline change of the Guana Tolomato Matanzas National Estuarine Research Reserve
(GTMNERR)’s western shore before and after the addition of the Wright’s Landing Living Shoreline
restoration project. Case study reviews of five other living shoreline projects along the East and Gulf
coasts of the United States were also included to analyze trends of successful projects. This research
will contribute to the understanding of living shoreline impacts across time and at a larger scale,
potentially leading to better implementation and management.
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Case Studies
Five living shoreline projects were reviewed to gain insight into the factors that contribute to
successful living shorelines on the East and Gulf coasts of the United States. Living shoreline projects
were discovered predominantly through the Living Shorelines Academy databases (Living Shorelines
Academy n.d.) and were evaluated based on the following metrics: accretion, saltmarsh advance,
oyster recruitment, oyster substrate used, land area intended to be restored, land type (urban or
protected land), and reported success. Results were then compared to determine if clear trends for
successful living shorelines exist.
Several different techniques were used in the following case studies to reestablish oyster reefs and
saltmarsh areas. Because oyster larvae, known as spat, will only attach to and complete its life cycle
on other oyster shells, each design incorporates oyster shell in some fashion.
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Grand Isle and St. Bernard Oyster Reef, Louisiana
The Grand Isle and St. Bernard Oyster Reef project, located on one of Louisiana’s southwestern
peninsulas (Figure 4), was constructed from 2010 to 2013 by The Nature Conservancy and partners
with over $4 million of funding from National Oceanic and Atmospheric Administration (NOAA)
through the Recovery Act (The Nature Conservancy 2017).
Figure 4. Grand Isle Living Shoreline, LA
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The project was installed with the intention of restoring 5.47177 km of oyster reefs (The Nature
Conservancy 2017), improving habitat, and promoting the use of living shorelines as a sustainable
option for storm protection and erosion prevention. This project also aimed to create both temporary
and permanent jobs for local people, investing in both the local and state economies (The Nature
Conservancy n.d.). Coastal Environments, Inc., a local business, was employed to construct the
triangular steal structures used to attach the oyster substrate to (Figure 5).
Figure 5. Grand Isle, LA oyster substrate
Bags of oyster shell, collected through an oyster shell recycling program in which oyster shell from
local restaurants are rerouted from the landfill to restoration projects, were then attached to the steel
structures and were used to recruit spat. Two years of monitoring was completed for this project by
Louisiana State University, concluding that this project was a success based on the following factors:
claimed reef establishment, nondescript shoreline changes, and improved habitat (The Nature
Conservancy 2017).
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Saw Grass Point Salt Marsh, Dauphin Island, Alabama
The Saw Grass Point Salt Marsh Living Shoreline, constructed in April 2005 by the Mississippi-
Alabama Sea Grant Consortium and partners, is located at the mouth of Mobile Bay (Figure 6) and is
the only inhabited barrier island in Alabama.
Figure 6. Saw Grass Point Living Shoreline, AL
The goal of this project was to control erosion caused by the prevention of saltmarsh naturally
migrating inland by both a major highway and residential development as well as periodic harbor and
channel dredging reducing sand over-wash necessary to sustain the beach. The Coastal Haven
system, pyramids of marine concrete with triangular openings in the sides to reduce pressure inside
the structure (Figure 7), was used as oyster substrate for this project. Marine concrete is a 100%
natural building material, the exact contents of which are protected by the manufacturing company
and not shared with the public (Allied Concrete Co. 2010).
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Figure 7. Coastal Haven System, Dauphin Island, AL
182 Coastal Haven units were positioned in two rows, creating 62m of structure. Despite the very
active storm season of 2005, measurements in November 2006 revealed an increase in oyster density
from less than one oyster/m2 before the installation to 205 oysters/m2 after installation and a 15cm
accretion along the protected 14.1hc of shoreline. This project both proved and raised public
awareness of the ability of living shorelines to protect private and public property from coastal storms
(Swann 2008).
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Winyah Bay South Island Living Shoreline, Yawkey Wildlife Preserve, South
Carolina
The Winyah Bay South Island Living Shoreline pilot project is located in northern South Carolina
(Figure 8).
Figure 8. Winyah Bay, SC Living Shoreline
This living shoreline was constructed in September 2010 by the South Carolina Department of Natural
Resources, Horry-Georgetown Technical College, the US Fish and Wildlife Service and other
partners to restore habitat, enhance environmental benefits, and improve human wellbeing and quality
of life. Because there were oysters already established in other parts of Winyah Bay, the research
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team felt this would be an appropriate site for their living shoreline installation. Manufactured marine
concrete blocks, known as castle bocks (Figure 9), were used as oyster substrate for this project.
Figure 9. Castle Blocks, Winyah Bay, SC
Approximately 1,000 castle blocks were used as oyster substrate and saltmarsh was transplanted in
October 2010 behind each castle group. This project was considered unsuccessful after the site
suffered further loss of saltmarsh and slow oyster colonization. Project managers suspect that project
failure was due to the high energy tidal flow washing away oyster spat and newly planted saltmarsh
(McColl 2011).
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Johns Point Landing, Virginia
The Johns Point Landing Living Shoreline project was constructed in 2013 and is located on a
Virginia peninsula extending into the Chesapeake Bay (Figure 10).
Figure 10. Johns Point Landing Living Shoreline
Bagged oyster shell was used as oyster substrate in this project, a common approach to reef
construction. With this approach, the natural fibers of the bags biodegrade over time, leaving nothing
but the newly recruited reef (Figure 11). Saltmarsh was also transplanted on site.
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Figure 11. Oyster shell bags as oyster substrate
One month after reef construction, oyster spat maturation and recruitment were observed. Saltmarsh
advance and seeding was also documented within the first growing season (April to August 2014).
Mussels benefited from the installation as well, their population tripling at the site. The species
diversity of benthic macroinvertebrates did not change post installation, but species composition did.
Only a select few species were present both before and after reef construction, suggesting that the
introduction of constructed reefs may alter the larger habitat. This living shoreline has restored 535m2
of saltmarsh habitat and was considered a success (Bilkovic 2014).
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Gandy’s Beach/Money Island, Downe, New Jersey
The Gandy’s Beach/Money Island Living Shoreline Project is located in southern New Jersey (Figure
12). Construction begun in 2014 by the US Fish and Wildlife Service, the Nature Conservancy, and
partners in response to the damage seen during Hurricane Sandy in 2012. The goal of this project
was to stabilize the surrounding creek banks and improve habitat and natural coastal defense and
stability.
Figure 12. Gandy's Beach/Money Island, NJ
Coir fiber logs made of coconut fibers (Figure 13), castle blocks with oyster shell bags, and
transplanted saltmarsh were all used in this living shoreline design.
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Figure 13. Coir fiber logs
When completed, this project will have restored 136.379 ha of coastline. The success of this project
has yet to be determined as it is still considered in progress. At this time, project managers claim to
have observed sediment accretion (US Fish and Wildlife Service 2016) and, as of October 2016, have
reported that the structures reduced wave action on the marsh by 15% throughout a full tidal cycle.
During low and mid tides, the installation has been recorded to reduce wave action by 50% (Brunetti
2016).
Source: http://floridalivingshorelines.com/project/escambia-bay-2/
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Summary
Table 1 provides a summary of the case study findings.
Table 1. Summary of Case Study Findings
U = Unknown
Project
Installation
Date
Last
Monitoring
Report
Accretion
Saltmarsh
Advance
Oyster
Recruitment
Oyster
Substrate
Restored
Area
Land
Type
Success
Grand
Isle, LA
2010-2013 2015 U U Yes
Triangular
frames
5.47177
km
Protected Yes
Dauphin
Island,
AL
2005 2008 Yes No Yes
Coastal
Haven
14.1 ha Protected Yes
Winyah
Bay, SC
2010 2011 No No No
Castle
blocks
U Protected No
Johns
Point,
VA
2013 2014 U Yes Yes Shell bags
0.0535
ha
Protected Yes
Gandy’s
Beach,
NJ
2014-
present
2016 Yes U U
Castle
blocks &
Shell bags
136.379
ha
Protected U
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Information on the current status of these projects proved difficult to find. Many projects are
considered successful, but do not explain the metrics used to determine success. Projects are often
built ambitiously, but then forgotten about once public interest subsides. Project monitoring is poorly
maintained, generally due to lack of funding and labor.
However, monitoring is critical for effective adaptive management. Without data describing the
conditions and health of the living shoreline, project managers do not know when intervention is
needed to sustain the project and its benefits. Because living shorelines appear very natural and are
intended to be self-sustaining, it may not be obvious when possible maintenance is required and
failure may only be evident when it is too late to correct.
The living shorelines analyzed here have all been installed on protected lands, typical of living
shorelines implemented to date. Yet project designers are beginning to explore the possibilities of
implementing living shorelines on more urban coasts. Examples of this include but are not limited to
Pensacola Bay, Florida scheduled to begin construction in October of 2018 (The City of Pensacola
n.d.) and Staten Island, New York City, New York in 2018 (McKee 2017). Time will tell whether
the trends seen on protected lands will translate to urban shorelines.
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Study Site
The Guana Tolomato Matanzas National Estuarine Research Reserve (GTMNERR) is a 74,000 acre
peninsular conservation area managed collaboratively by the Florida Department of Environmental
Protection and the National Oceanic and Atmospheric Administration (NOAA) as part of the National
Estuarine Research Reserve (NERR) system (Guana Tolomato Matanzas National Estaurine Research
Reserve 2017a). NERRs are federally designated conservation areas used for estuarine protection
and research. Established through the Coastal Zone Management Act, NERRs are operated as a
partnership between the federal and state governments in which NOAA provides funding and
guidance while a lead state agency or university manages the land with input from public partnerships.
Nationally, 1.3 million acres of estuarine land is protected through the NERR system (National
Oceanic and Atmospheric Administration 2017b).
A restoration project was undertaken in 2012 at GTMNERR’s Wright’s Landing site bordering the
Tolomato River on the western side of the peninsula (Figure 14). The restoration project was
developed by the Northeast Florida Aquatic Preserves Program, part of the Florida Department of
Environmental Protection’s Florida Coastal Office, with the goal of constructing a living shoreline to
reduce erosion and prevent further saltmarsh retreat at the site. Oyster reefs were constructed with
bagged oyster shell from a local oyster shell recycling program placed along coir fiber logs (Figure
15) and smooth cordgrass (Spartina alterniflora) was transplanted from a GTMNERR propagation
Living Shorelines as an Erosion Mitigation Strategy
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program to facilitate oyster and vegetation reestablishment (Guana Tolomato Matanzas National
Estuarine Research Reserve 2017b).
Figure 14. GTMNERR and Wright's Landing
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Figure 15. Wright's Landing Living Shoreline
Since installation, the Wright’s Landing living shoreline has not been consistently monitored.
GTMNERR self-reports that the living shoreline has resulted in increased biodiversity and successful
oyster recruitment (Guana Tolomato Matanzas National Estuarine Research Reserve 2017b), but does
not reveal the methods or metrics used to determine this.
http://www.gtmnerr.org/oceanwise-and-stewardship/
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Methods
To determine whether the living shoreline installation has had large scale impacts on the site, satellite
images of the Wright’s Landing restoration site at the GTMNERR were obtained from Google Earth
from the years 2005, 2008, 2011, 2013, 2015, and 2017. All images were taken in the fall and winter
months (October through January), providing seasonal consistency among measurements. Beach
width and saltmarsh area were then measured to capture shoreline changes over time. Beach width
was measured by taking the measurement from the center of the channel to the line of established
vegetation at six points along the GTMNERR peninsula: at the Wright’s Landing reef site, roughly
350m north and south of the reef site, and at three points along Guana Point. The area of coverage of
three saltmarsh sections 200 m2 each were also measured. All measurements were taken using Google
Earth’s measurement tools. Measurement points are illustrated in Figures 16 and 17.
Figure 16. Measurement Sites, Upper Peninsula
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Figure 17. Measurement Sites, Lower Peninsula
All beach width and saltmarsh measurements were compared to reveal shoreline changes. Major
shoreline changes were compared to two extreme weather events experienced at the site to account
for large shoreline changes from natural processes. Proximity, strength, and photographic evidence
of severe storm damage from Hurricanes Mathew (2016) and Irma (2017) were considered.
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Results
Beach Width
Beach width remained almost constant from 2005 to 2017, as illustrated in Table 2 and Figure 18.
Table 2. Beach width over time
Date
North
Beach (m)
Wright's
Landing (m)
South
Beach (m)
Guana
Beach (m)
Point 3 (m)
Guana
Point (m)
Mar-05 298 291 201 204 243 127
Jan-08 295 287 196 203 244 126
Dec-11 294 291 200 204 244 125
Jan-13 296 284 198 204 247 128
Nov-15 299 288 200 203 248 131
Sep-17 294 288 200 205 250 133
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Figure 18. Beach width over time
Marsh Area
Marsh area also did not experience large change. The most variable marsh area was C and Marsh A
did see some decline in coverage. Marsh B reached full coverage by 2008, maintaining this level of
coverage to September 2017. These results are illustrated in Table 3 and Figure 19.
298 295 294 296 299 294291 287 291 284 288 288
201 196 200 198 200 200204 203 204 204 203 205
243 244 244 247 248 250
127 126 125 128 131 133
0
50
100
150
200
250
300
350
Mar-05 Jan-08 Dec-11 Jan-13 Nov-15 Sep-17
Bea
ch W
idth
(m
)
Axis Title
Beach Width Change Over Time
North Beach (m) Wright's Landing (m) South Beach (m)
Guana Beach (m) Point 3 (m) Guana Point (m)
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Date Marsh A (m2) Marsh B (m2) Marsh C (m2)
Mar-05 124 150 30.4
Jan-08 111 200 53.4
Dec-11 101 200 33
Jan-13 97.2 200 41
Nov-15 85 200 62.4
Sep-17 68.7 194 21.78
Table 3. Marsh area over time.
Figure 19. Marsh area over time
124111
101 97.285
68.7
150
200 200 200 200 194
30.4
53.4
3341
62.4
21.78
0
50
100
150
200
250
Mar-05 Jan-08 Dec-11 Jan-13 Nov-15 Sep-17
Mar
sh A
rea
(m2 )
Date
Marsh Area Change Over Time
Marsh A (m2) Marsh B (m2) Marsh C (m2)
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Discussion
Although there were no drastic changes of GTMNERR’s Wright’s Landing shoreline from 2005 to
2017 and accretion was not measured by this study, this living shoreline installation may have
protected the site from the extensive damage caused by Hurricane Mathew in October 2016 and
Hurricane Irma in September of 2017. Figures 20 and 21 showcase the resulting damage from each
of these storms, at Ponte Verde Beach and in St. Johns County respectively.
Figure 20. Hurricane Mathew damage, Ponte Verde Beach, FL
Source: http://abcnews.go.com/US/florida-images-show-destruction-hurricane-matthew/story?id=42664304
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Figure 21. Hurricane Irma damage, St. Johns County, FL
Despite the damage at sites near the GTMNERR depicted above, GTMNERR’s Wright’s Landing
experienced minimal damage and no detectable erosion. While estuaries naturally benefit from some
inland protection and usually see less damage as the beach fronts shown in Figures 20 and 21, erosion
and other damages often still occur. These results are similar to those found at the living shoreline
project on Dauphin Island, AL. After being installed in April of 2005, Dauphin Island was subjected
to Tropical Storm Arlene in June, Hurricanes Cindy and Denis in July, and Hurricane Katrina in
August of 2005. Minimal damage was found at the site and measurements from November 2006
revealed a 15cm accretion at 55 locations along the living shoreline installation and no erosion at
three nearby reference sites. According to the research team on site, the Dauphin Island Living
Shoreline not only prevented private property damage on the island, but also raised public awareness
of this possibility (Swann 2008).
Source: https://www.accuweather.com/en/weather-news/reports-irma-leaves-over-6-million-without-power-across-florida/70002687
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Living shoreline installations along the coast of North Carolina’s outer banks also proved to provide
better protection than traditional armoring techniques during storm events. After Hurricane Irene in
2011, shorelines protected by living shorelines experienced sediment accretion whereas 75% of
bulkheads surveyed in the same region failed and were damaged (Figure 22). Similarly, 58% of
bulkheads near Charleston, South Carolina were destroyed in 1989 during Hurricane Hugo (National
Oceanic and Atmospheric Administration 2015).
Figure 22. Destroyed bulkhead
Not only do living shorelines appear to protect property during heavy storm activity, they may also
provide sea level rise mitigation. From 1993 to 2014 NOAA recorded a global sea level rise of 2.6
inches, with an expected 1/8th of an inch rise per year (National Oceanic and Atmospheric
Administration 2017a). Sea level rise experienced locally can be more subtle or more extreme based
on factors including but not limited to: upstream flood control, erosion, land subsidence,
topographical differences, and regional ocean currents (National Oceanic and Atmospheric
http://brick.shorebeat.com/2017/03/storm-blew-hole-in-manasquan-inlet-bulkhead-fishing-off-limits/
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Administration 2017a). Healthy living shorelines maintain a wide beach front and may prevent
further erosion of its protected shore, reducing the loss of available land from sea level rise.
Lack of long term monitoring appeared to be the greatest downfall of the reviewed living shoreline
projects. Many projects were considered successful, but were not descriptive on what metrics were
used to determine success. As with other restoration projects, living shoreline monitoring is often
poorly maintained, frequently due to lack of funding and labor. However, proper monitoring is
critical for effective adaptive management. If not improved, project managers will not know the
status of their work or be able to intervene to sustain projects when necessary.
It is important to note that, ecologically speaking, the living shoreline projects reviewed here are still
very young and may still need many years to fully establish themselves. Accretion is not always
detected in these projects. However, further erosion is usually not either. This may indicate that the
living shorelines may only hold the existing shoreline in place. While some would like to see
accretion, preventing or ending erosion at a site can be just as beneficial. Marine concrete used to
construct castle blocks and the Coastal Haven system may be the best oyster substrate, but further
research is needed on the material to determine this definitively. In order to better understand the
factors which make living shorelines successful, a meta-analysis of existing living shoreline projects
would be beneficial. Meta-analyses involve taking data from many different projects to analyze
trends in regard to factors that may determine outcomes or responses, which in this case is either
project success or failure based on factors such as shoreline wave energy, slope, salinity, materials
used, spatial configuration of design, and other project design factors (Biostat, Inc. 2017). Large
scale experimentation may also provide valuable insights, such as using different materials and spatial
designs at the same site to compare success.
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Because the primary material used to construct living shorelines are living organisms, it is essential
that proper planning, site selection, and monitoring are conducted throughout the entirety of the
project. While many communities wish to take action immediately, project failure can be disastrous
when tax payers’ money is used to fund a multimillion dollar living shoreline project such as the
planned $10.8 million Pensacola Bay (The City of Pensacola n.d.) and $60 million Staten Island
(Rebuild by Design n.d.) living shorelines. Project failure may lead to miseducation or mistrust of
the benefits of living shorelines as the public begins to doubt the technology’s ability to produce
desired outcomes, resulting in increased difficulty gaining necessary funding for future living
shoreline projects and other green infrastructure installations.
As an advocate for successful living shorelines, NOAA recommends that land managers and city
planners encourage living shoreline and green infrastructure design in disaster planning. To
accomplish this goal, NOAA offers partnership, along with other federal agencies and non-
governmental organizations, providing technical assistance and funding for living shoreline research
and design. NOAA has also provided several guiding principles to land managers considering
restoration efforts. Most importantly, NOAA stresses that shorelines should be left to erode as they
naturally would unless infrastructure is being threatened. Planting of Spartina spp. can reduce wave
energy by 50% and planted wetland vegetation significantly reduces damages to coastal communities
as well as provides fish habitat and nitrogen removal (National Oceanic and Atmospheric
Administration 2015).
NOAA also developed the Conceptual Framework for Considering Living Shorelines in 2015. The
framework consists of twelve guiding questions for land managers to consider when determining the
most appropriate shoreline stabilization approach for a particular site. The framework stresses proper
site selection and planning for sea level rise as well as acknowledges that the best solution at a site is
Living Shorelines as an Erosion Mitigation Strategy
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likely a balance between living shoreline and traditional techniques. This document also outlines the
available grants and other support, including design guidance and policy considerations, NOAA and
other federal agencies have available to aid in successful execution of these projects (National
Oceanic and Atmospheric Administration 2015).
Conclusions
Project Limitations
The living shoreline projects included in this study are still relatively young thus limiting the
conclusions that can be drawn. Large shoreline impacts and changes may be detectable once these
living shorelines further mature and stabilize. Conversely, older living shoreline projects may reveal
that such installations only halt the erosive process, not cause accretion.
Case study analysis was limited by lack of public information. Information gathered by this study
was obtained largely from websites explaining the plan to the public which only stated that monitoring
had been or would be completed. Few monitoring reports were available to the public. Those that
were available did not always incorporate sufficient data or explain their methods and metrics well.
Long term monitoring is rarely conducted at these sites resulting in large knowledge gaps as to the
status and success of these living shoreline installations. Most projects complete two years of
monitoring after which efforts are usually terminated due to lack of funding. It is likely that other
sites are informally monitored by management staff when time allows as done by the GTMNERR,
but formal reports with empirical data are lacking. Such data would give further insights into living
shoreline success and impacts and should be considered highly valuable by policy and budget
planners.
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The GTMNERR living shoreline is a small study site with limited available data. If monitoring
records were better maintained, it is possible that more insight into the success of this installation may
be discovered. Because of the landscape-level analysis of this study, accretion may not be detectable.
Satellite images used may not have been taken at a fine enough scale to reveal what may be minute
accretion at this time as illustrated by the 15cm accretion recorded at the Dauphin Island living
shorelines. However, there is an opportunity to increase the monitoring of this site as it continues to
mature so that greater knowledge can be obtained about the viability of this type of design and
ecosystem.
Future Research Recommendations
The development of a standardized assessment of living shoreline project health and success may be
helpful in determining the value and effectiveness of existing and future projects. A similar approach
taken to site selection could also be very beneficial. This could include more systematic identification
of sites at the regional landscape scale that may be the best locations for achieving success and
providing the most benefit. In addition, more research into the basic biology, habitat needs, and
preferences of living shoreline species is needed to properly inform such a rubric.
Determining the best measuring technique for shoreline change would result in more accurate records
of living shoreline success and impacts. On site measurements at consistent tidal phases from a fixed
point may prove a much better measure of shoreline accretion or erosion than measurements made
from satellite images. However, the retrospective benefit of historical satellite images is an advantage
that may be better capitalized by methods different from those used in this study.
Research focusing on how long living shorelines will take to fully establish and mature may reveal a
more accurate timeline for land managers to begin to expect to see shoreline impacts. With this
Living Shorelines as an Erosion Mitigation Strategy
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timeline in mind, better evaluations of living shoreline status and success may be possible. Similar
research may also definitively determine whether living shorelines truly are preventing erosion or
causing accretion on site and/or down site from the installation.
An important issue in establishing living shorelines is the “energy level” a shoreline receives from
wave action. High energy shorelines with frequent significant wave action are unlikely to harbor
successful living shoreline installations due to species’ intolerance, whereas low energy shorelines
provide a much greater opportunity for success. However, one of the potentially key future research
findings would be to determine what techniques might work in moderate to higher energy shoreline
ecosystems to provide the benefits of these projects in places that would currently be difficult or
impossible to implement successfully.
As living shorelines gain more popularity and begin to be implemented in the urban setting, extensive
research will be necessary to determine if the benefits of these installations do in fact extend to urban
shorelines and what, if any, adaptations or special considerations need to be made to the existing
technology to ensure success. Because these settings often deal with more intense ecological
degradation, living shorelines may not be as easily established in these areas and may require site
conditioning before installation occurs.
The living shorelines depicted here use species and designs adapted to the Gulf and East coasts of the
United States which are generally considered lower energy systems. Research focuses on determining
energy thresholds for different species and techniques would be extremely valuable to the
advancement of living shoreline technology. With these thresholds determined, alternative
techniques for higher energy systems will soon follow, as will adaptations to different areas of the
world.
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