U.S. Geological Survey and U.S. Fish & Wildlife Service
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U.S. Fish & Wildlife Service
U.S. Geological Survey and U.S. Fish & Wildlife Service
Report: Impacts of Sediment Removal from and Placement in
Coastal Barrier Island Systems
Frequently Asked Questions
Q: Who prepared this report and why
was it created?
On June 2, 2021, the U.S. Geological
Survey (USGS) published an Open
File Report on the impacts of sediment
removal from and placement in coastal
barrier island systems (OFR
2021-1062). The report was prepared
jointly by the USGS and the U.S. Fish
and Wildlife Service (FWS) in response
U.S. Army Corps of Engineers
to a June 2019 request from the House
Committee on Natural Resources that
the two agencies evaluate the short-
and long-term impacts of sediment
removal on areas in and adjacent to the
Coastal Barrier Resources System
(CBRS). The agencies assembled a
team of scientists and landscape
managers who reviewed and
summarized the scientific literature on The U.S. Army Corps of Engineers Philadelphia District pumps sand onto Brant
how sediment-supply alterations affect Beach, NJ in June of 2013
physical and ecological processes of
coastal barriers and, in turn, how actions for any particular CBRS units tion about CBRA is available at: https://
specific species, habitats, and coastal or other site-specifc areas were be- www.fws.gov/cbra.
resilience are impacted. The report can yond the scope of this report.
be accessed at: https://doi.org/10.3133/ Q: What are coastal barrier island
ofr20211062. Q: What is the Coastal Barrier Resourc- systems?
es Act? Barrier islands, and the environments
Q: What is the scope of the report? The Coastal Barrier Resources Act therein, are dynamic systems, re-
This report contains a comprehensive (CBRA) of 1982 originally established sponding to wave and tidal processes,
summary of the scientific literature on the CBRS which now encompasses sediment supply and disruption, and
the physical, biological, and ecological about 3.5 million acres along the Atlan- sea-level change. These islands sup-
effects of sediment removal and place- tic, Gulf of Mexico, Great Lakes, U.S. port a great diversity of plants and
ment in coastal barrier island systems. Virgin Islands, and Puerto Rico coasts. animals, including many threatened
Specifically, the report presents the The purpose of the law is to protect and endangered species. Historically,
consensus findings and relevant knowl- natural resources, save taxpayer mon- coastal barrier island systems were
edge gaps associated with the impacts ey, and keep people out of harm’s way largely sustained by natural sediment
of sediment removal and placement on: by removing the federal incentive to de- exchanges between the inner conti-
physical barrier island processes and velop ecologically-sensitive and storm- nental shelf, shoreface, beach, dunes,
sediment supplies; benthic habitats; fish prone coastal barriers. CBRA prohibits marsh, and estuary. Today, humans also
and other marine species; subaerial most new federal expenditures and alter these systems through sediment
beach habitats; and coastal resiliency. fnancial assistance for projects and management, which refers to the re-
activities within the CBRS, including moval of sediment from one part of the
The report identifies the physical and projects to prevent the erosion of, or to system (e.g., dredging) for placement in
biological data required for assessing otherwise stabilize, any inlet, shoreline, another part of the system (e.g., nour-
and monitoring impacts of sediment or inshore area (16 U.S.C. 3504(a)(3)). ishment). These practices are used for
management actions in coastal barrier The law does not restrict the use of either hazard mitigation (e.g., erosion
island systems and provides a table of private, state, or local funds or limit the and food control) or coastal resto-
existing USGS data resources for five issuance of federal permits within the ration (e.g., expansion or restoration
CBRS areas of interest as identified by CBRS. FWS is responsible for main- of beach, dune, and/or marsh habitats).
FWS (Hereford Inlet, NJ, Carolina taining the maps that depict the CBRS In instances where barrier systems are
Beach, NC, Masonboro Inlet, NC, New and consulting with other federal altered through human intervention,
River Inlet, NC, and Folly Beach, SC). agencies that propose spending funds naturally occurring coastal processes
Assessments of sediment management within the CBRS. Additional informa- can be modifed, enhanced, or impeded.
manatees and sea turtles, include direct and back-barrier environments. For
Q: What are the key fndings of this entanglement in or physical strikes example, removal of sediment from any
report? from dredging equipment. part of the submerged barrier system
An extensive review of the literature may alter the position of barrier island
for this report found that sediment The report also highlights some posi- shorelines. Over time, placed sediment
management actions can have both tive impacts of sediment management. may be dispersed to other barrier is-
benefcial and detrimental impacts on For instance, sediment placement can land environments and may cause both
coastal species and the physical and increase feeding areas, viable nesting physical and ecological benefts, such as
ecological resiliency of barrier island habitat, and increase nesting success increased sediment supply to downdrift
systems, depending on where and how for some coastal wildlife like shore- beaches and increasing habitat extent.
they are applied. birds and turtles. However, the timing Placement may also result in adverse
of nourishment is important, since impacts, such as the alteration of nat-
The key fndings in the report illus- the addition of sediments to beaches, ural sediment exchanges between bar-
trate how some sediment management dunes and marshes could interfere with rier island environments that decrease
practices can have negative impacts on breeding seasons of certain species. habitat suitability.
seafoor habitats, fsh and other ma- Though beach nourishment can tem-
rine species, beach and dune habitats, porarily protect coastal infrastructure This review revealed a need for more
and the coastal sediment supply that and habitats from storm inundation and research and monitoring on the follow-
maintains barrier island resiliency. For erosion, it may lead to negative affects ing topics in order to better estimate
instance, when sediment is removed at other locations. Beach nourishment both benefcial and adverse physical
from one barrier island system and can cause detrimental sedimentation impacts of sediment removal and
used in a separate system it reduces on sensitive seafoor habitats and placement on coastal systems: (1) prior
the amount of sediment for the orig- the dredging required to acquire the to sediment removal, it is important to
inal island. This may lead to coastal sediments needed for nourishment establish the range of natural shoreline
erosion near the removal location or can reduce sediment supply to barrier variability so that after sediment re-
could cause longer-term impacts to the islands, which reduces their ability to moval, variability in shoreline position
supply of sediments to neighboring keep pace with sea-level rise. can be attributed to sediment supply
barrier islands, all of which may alter disruptions; (2) substantial uncertainty
the islands’ ability to withstand future Five topics addressed in the report and surrounds forecasts of the impacts of
storms and increases in sea level. This associated fndings (and knowledge sediment removal or placement due to
process of removing sediments from gaps) are: the episodic nature of the storms that
an area can also directly and indirectly drive many of the changes and the dif-
alter the quality of nearshore seafoor 1. Physical Impacts of Sediment fculty in predicting exact magnitudes
habitats like seagrass beds and fsh Removal and Placement on Coastal of storm-related sediment transport;
nurseries that are critical for support- Sediment Supplies (3) effects of sediment placement on
ing economic and ecologically import- Sediment removal and placement estuarine or back-barrier beaches is
ant species. Organisms that live in or reshapes barrier islands and their adja- less studied than effects on ocean-fac-
on the seafoor, which often serve as cent environments by altering: a) wave ing beaches; and (4) more
food sources for many threatened and and current impacts at the shoreline, understanding is needed of the barrier-
endangered coastal and marine spe- b) the volume of sediment exchanged system as a whole, including effects of
cies, may be directly excavated during via inlets, c) alongshore sediment sediment removal from inlet-associated
dredging activities. Additional impacts transport, and/or d) the frequency of shoals, tidal fats, and channels on inlet
to surface-dwelling species, such as sediment exchanges between beaches shore-lines and downdrift sediment
supply and physical and ecological
feedbacks from sediment placement.
2. Impacts of Sediment Removal and
Placement on Benthic Habitats and
Their Importance
Benthic habitats, and the organisms
that live in and on the seabed, are
directly and immediately impacted
by sediment removal and placement.
U.S. Army Corps of Engineers
Changes to water depth, sediment
composition, and the hydrodynamic
conditions at the seafoor can impact
habitat quality for benthic organisms,
which are important food resources
for shore and waterbirds and other
marine species. The physical removal of
sediments causes immediate mortality
and reduced abundances of benthic
organisms. Sediment placement also
A mixture of sand and water is pumped onto Rockaway Beach, Queens, NY, has immediate impacts to benthic
June 26, 2014, from an offshore borrow site. organisms. Whether on the beach or
underwater, those buried by placed
sediments die, reducing the food supply
for shorebirds and surf fsh. Further, in-
creased suspended sediment associated
with removal or placement can impact
nearby sensitive seafoor habitats, such
as seagrasses, corals, and hard bot-
toms. Importantly, recovery of benthic
communities is highly variable. In
contrast, thin layers of placed sediment
have been found to increase vegetation
cover and number of benthic organisms
in degraded marshes.
The primary knowledge gaps for
U.S. Fish and Wildlife Service
benthic communities include improving
understanding of: (1) how sediment
removal and placement affect ben-
thic ecosystem functioning; (2) how
effciently and quickly resident taxa
repopulate affected areas, and how
less-mobile members of the benthic
community repopulate affected areas;
and (3) the long-term effects of sedi-
ment removal and placement or those Loggerhead sea turtle hatchlings at Back Bay National Wildlife Refuge in Vir-
that might persist beyond the typical ginia
1-2 year monitoring period, particularly
when actions are repeated. placement, particularly that which ex- ecosystem services, including habitat
pands the area of estuarine tidal fats, for federally- and state-listed plants
3. Impacts of Sediment Removal and can increase viable habitat for fsh and and animals, which may be directly or
Placement on Fish and Other Marine other estuarine/marine species more so indirectly impacted by sand placement
Species than other “hard engineering” solu- on beaches. Beach nourishment can
Although sediment removal and place- tions, such as armoring or bulkheading. lead to improved sea turtle and shore/
ment occur at specifc sites, threats to However, it is unknown whether the waterbird use by widening severely
fsh and other marine species emerge beneft of habitat expansion outweighs eroded beaches. However, if sediment
from direct entrainment and entangle- the burial of benthic food sources on placement occurs during the shore/
ment of organisms, suspended/settled/ those tidal fats on which fshes and waterbird breeding season, there is
contaminated sediment, noise, and net other species depend. potential harm to reproductive suc-
bathymetric change that occur at those cess by increasing human disturbance,
sites or beyond. Species vulnerability to Uncertainties in the sand removal crushing or burying eggs or unfedged
sediment management effects depends and placement impacts to fsh and chicks, reducing prey species, and
on an organism’s mobility relative to other marine species are due to lack impeding access to back-barrier
the spatial extent and frequency of the of species population information and foraging habitats. The removal of
sediment removal or placement activity. lack of understanding of the interaction sediment from shoals, mudfats, and
Vulnerability is particularly acute when of those populations with sediment sandbars can affect habitats that are
sediment removal and increased sus- management activities. Given the wide vital to overwintering and migrating
pended sediment overlaps spatially or variation in known responses among shore- and waterbirds. Losses in the
temporally with sensitive habitats (e.g., fsh species and life stages, prevalence abundance and diversity of seagrass,
coral reefs), migration paths or forag- of laboratory studies versus feld macroinvertebrate, and benthic species
ing areas in which individuals congre- studies, and existing knowledge gaps, during both the removal and placement
gate, or spawning, nursery, or overwin- additional research is necessary to: (1) phases of nourishment projects can
tering habitats. In addition to changes characterize population, species, and propagate up through the food web
to the physical environment, vulnera- community-level impacts of sediment to shore- and waterbirds, resulting in
bility can result from direct interaction removal in situ; (2) quantify fne-scale reduced shore- and waterbird popula-
with equipment and vessels. Direct activity patterns on free-ranging tions on nourished beaches throughout
dredging impacts include species animals using new tools; and (3) assess the annual cycle. Detrimental effects
entanglement in buoys or lines marking contaminants in marine sediment de- to shore- and waterbirds through the
projects and physical injury if struck posits to determine the extent to which food web can persist for months to
by transiting vessels or impacted by disturbed sediments release toxins into several years. However, the placement
vessel noise. In particular, sea turtles, the environment and food chain. of dredged materials can also provide
manatee, and sturgeon are susceptible entirely new foraging grounds for these
to vessel collisions, propeller strikes, 4. Impacts of Sediment Removal birds where such habitats were lacking
and/or crushing because they may and Placement on Subaerial Beach due to shoreline erosion.
spend a considerable amount of time Habitats
at or near the water surface. Sediment Sandy beaches provide important This review found only a limited num-
ber of studies that evaluated the direct marsh accretion. Connectivity through shoreface and profile nourishment in
effects of beach nourishment on coastal these short- and long-term exchanges the context of storm protection and
taxa, and most of these studies focused of inorganic sediments and organic short-term coastal resilience; (3)
on sea turtles and shorebirds. The materials across the barrier island are evaluation of the long-term effects of
following additional areas of research critical for maintaining the form and sediment removal from ebb deltas or
and monitoring are warranted: (1) function of its ecosystems. As such, it is channel dredging on sediment
the impacts of beach nourishment on this natural physical and ecological re- pathways and erosion and deposition
plants, insects, and other species; (2) silience that has allowed barrier islands patterns along adjacent shorelines;
statistically rigorous before-and-after to successfully support coastal commu- and (4) analysis of beach nourishment
monitoring studies on species’ popula- nities and their economies. Sediment and frequent complementary activities
tion dynamics; (3) evaluation of the im- removal and placement can impact (e.g., berm construction, sand fencing)
pacts of repeated nourishment cycles; short- and long-term coastal resil- on ecosystem connectivity over short
(4) evaluation of the biological effects ience. Sediment placement is often, by and long timescales.
of construction, disturbance, and other design, a short-term strategy that can
related practices; and (5) evaluation help protect coastal infrastructure and Q: What are the next steps with this
of other beach nourishment-related critical habitats from storm inundation. report?
impacts on sea turtles. However, sediment removal at one This report provides a comprehensive
location may cause downdrift shoreline summary of the science that can help
5. Impacts of Sediment Removal and erosion and reduced sediment supply federal agencies evaluate the possible
Placement on Coastal Resiliency at other locations. These impacts may outcomes of sediment management ac-
Coastal resiliency is defned as the abil- be exacerbated by sea-level rise. A few tions within and adjacent to the CBRS.
ity of a coastal system to withstand and studies suggest that nourishment may It can also be used to help inform proj-
adapt to perturbations, natural or oth- be helpful in reducing erosion under ect stakeholders and state and commu-
erwise. In their natural states, barrier future sea-level rise; however, artifcial- nity coastal planners on the impacts of
islands are inherently resilient to short- ly high nourished dunes may reduce dredging and beach nourishment on
and long-term drivers such as storms overwash and deprive back-barrier coastal species, habitats, and barrier
and sea-level rise, respectively. During environments of deposition needed to island resiliency. FWS and USGS plan
storms, sediment is exchanged be- keep pace with sea-level rise. to review the existing knowledge gaps
tween the dunes, beach and shoreface in the report to help prioritize future
to reduce wave energy. During post- Based on the literature reviewed research, modeling, and monitoring
storm periods of recovery, waves and for this report, a number of current efforts. Furthermore, efforts will be
currents return sediment to the beach knowledge gaps exist on the effects made to identify best management
to increase elevation and width, while of sand removal and placement on practices that may ameliorate some of
winds transport beach sediment to the short- and long-term coastal resilience. the identified negative impacts
dunes so that they grow and revege- Observations and modeling can be associated with sediment removal and
tate. Over longer time scales, barrier applied to: (1) studies to assess how placement in coastal barrier systems.
islands migrate landward or seaward in past and present nourishment of beach, Any future studies and collaborations
response to changes in sea level, con- dune, and shoreface can improve long- will depend upon availability of re-
stantly changing elevations and widths term barrier island resilience, sources for such efforts.
in balance with sea level through dune especially under future sea-level rise;
overwash, alongshore transport, and (2) studies that evaluate the effects of
U.S. Geological Survey U.S. Fish & Wildlife Service
St. Petersburg Coastal and Marine Ecological Services
Science Center 5275 Leesburg Pike
600 4th Street South Falls Church, VA 22041
St. Petersburg, FL 33701 703-358-2171
727-502-8000 cbra@fws.gov
https://www.usgs.gov/centers/spcmsc https://www.fws.gov/cbra
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