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 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 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 Army Corps of Engineers managers who reviewed and U.S. summarized the scientific literature on The U.S. Army Corps of Engineers Philadelphia District pumps onto Brant how sediment-supply alterations affect , 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 , 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, of Mexico, Great Lakes, U.S. port a great diversity of plants and ment in coastal barrier island systems. Virgin Islands, and Puerto Rico . 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, , sediment supplies; benthic habitats; fish prone coastal barriers. CBRA prohibits marsh, and . 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 of, or to system (e.g., dredging) for placement in biological data required for assessing otherwise stabilize, any , 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, , 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 - 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 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 . 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 ; 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 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 , c) alongshore sediment sediment removal from inlet-associated dredging activities. Additional impacts transport, and/or d) the frequency of , 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 , are directly and immediately impacted by sediment removal and placement. 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 Army Corps of Engineers sediments causes immediate mortality

U.S. 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 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; Service Fish and Wildlife

and (3) the long-term effects of sedi- U.S. ment removal and placement or those Loggerhead sea turtle hatchlings at Back 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 dredging on sediment the impacts of beach nourishment on this natural physical and ecological re- pathways and erosion and 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., 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 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 [email protected] https://www.usgs.gov/centers/spcmsc https://www.fws.gov/cbra

June 2021