Parent Layer: Beachfront Armor

Name: Armored

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Description: This dataset represents beach armor after Hurricane Sandy. These data are part of a broader project Inventory of Habitat Modifications to Tidal Inlets and Sandy Oceanfront Beaches in the U.S. Atlantic Coast Breeding Range of the Piping Plover (Charadrius melodus) as of 2015: Maine to North Carolina.The total length of oceanfront shoreline between Georgetown, ME, and the North Carolina-South Carolina boundary that has been armored is at least 476.81 miles (767.35 km; 27% of the total shoreline length). This assessment is a minimum number because some structures are buried and not visible in aerial imagery; in addition, historical records or inventories of hard stabilization structures may be incomplete or unavailable to indicate where buried structures may exist. The Massachusetts coast has the greatest length of armored oceanfront beach by far, with 157.24 miles (253.05 km; 31%) of sandy shoreline modified by beachfront armor. The North Carolina and Maryland coasts are the least armored, with only 3% (9.05 miles or 14.56 km) and 5% (1.62 miles or 2.61 km) of their oceanfront shorelines, respectively, having beachfront armor as of 2015.Massachusetts has the highest number of armor structures by far, with a total of 2,894 armor structures identified on sandy shoreline within the state in 2015 – 35% of all the armor structures identified from Maine to North Carolina. As of 2015, there were 1,615 groins, 90 jetties, 21 breakwaters and 1,168 contiguous sections of seawalls, revetments and/or bulkheads along the sandy shoreline of Massachusetts. Connecticut and the Peconic Estuary shoreline of New York each have over 1,400 armor structures, both dominated by groins (944 in CT and 1,036 on the Peconic Estuary). Maryland (14) and Delaware (31) have the least number of armor structures, but they also have shorter shorelines. Altogether there were up to 5,144 groins, 235 jetties, 96 breakwaters, and 2,886 contiguous sections of seawalls, bulkheads and/or revetments along the sandy shoreline within the U.S. Atlantic Coast breeding range of the piping plover in 2015.Only ocean-facing shorelines or those directly exposed to Long Island Sound or the Peconic Estuary were included in this project area; inner harbors and bays were excluded, for a total length of sandy beaches of 1,742 miles from Maine to North Carolina. An assessment to estimate the length of each state’s sandy oceanfront beach that has been armored with hard structures was measured by identifying and digitizing structures visible in Google Earth imagery in historic and current aerial photography. Armoring structures include shore-parallel seawalls, bulkheads, revetments, riprap, geotube and sandbag revetments, groins, offshore breakwaters, and jetties.Where existing datasets were available delineating beachfront armor, those datasets were incorporated in this assessment. Existing datasets include those of MA DCR (2009) and Fontenault et al. (2013) in Massachusetts, a 2008 inventory by the North Carolina Division of Coastal Management of sandbag revetments in NC, and coastal engineering inventories conducted for some National Park Service lands (e.g., Dallas et al. 2013). Where existing datasets were not available, beachfront armor was digitized using a heads-up approach and colored fuchsia in a Google Earth data layer. All identifiable armoring structures were included, even if some are periodically buried, failing, in disrepair or remnant structures. Stormwater outfalls and docks were included if they were armored (typically with stone) and functioning like groins (i.e., the shoreline was offset on either side of the structure); their dual functions were noted in their labels.The armor structures were labelled with the community name followed by the type of structure and ending with a number for that type of structure representing its geographic order (from north to south or east to west). For example, “Rehoboth Beach groin 4” is the fourth groin in Rehoboth Beach, Delaware (DE), counted from north to south. “Dewey Beach bulkhead 1” is the first bulkhead in Dewey Beach, DE, counted from north to south. Note that some dates of aerial imagery within Google Earth are slightly offset from each other; the position of each armor structure was delineated from the same date of imagery used to identify the presence or absence of sandy beach habitat (i.e., 2015 or early 2016) and could appear offset in other imagery dates. Proposed armor structures were delineated in sky blue and prefaced with “PROPOSED” in their labels. Stormwater outfalls that were not visibly armored were delineated in light blue and labelled, in numerical order from north to south, by community (e.g., Ocean City outfall 1, Ocean City outfall 2).The length of shoreline modified by armoring was measured using the methodology of Coburn et al. (2010), Dallas et al (2013) and Schupp and Coburn (2015) in their recent coastal engineering inventories for the NPS, which utilized aerial imagery to identify and digitize shore protection structures within individual coastal parks. “The structure length used in calculating the percentage of shoreline armored for individual shore parallel structures was merely the length of the structure. For groin fields … the length of stabilized shore was set as the length of the groin field” (Dallas et al. 2013, p. 5). Where Dallas et al. (2013) defined a groin field as three or more groins, in this assessment a groin field was defined as two or more groins in close proximity to each other. An armoring “project was considered distinct if there was any discernible, physical separation between it and an adjacent coastal engineering project. A series of bulkheads constructed by individual interests, for example, would be classified as one structure as long as no identifiable gaps were observed between them” (Dallas et al. 2013, p. 5). The overall length of a contiguous section of seawalls, bulkheads and/or revetments was then measured and recorded as the length of shoreline armored in a given area. This length is not equivalent to total structure length since a series of connected seawalls, bulkheads, and/or revetments may have sections that are not constructed parallel to the beach. Digitization of the armoring structures within Google Earth allowed for overlapping armoring structures (i.e., a section of seawall with a groin field seaward of the wall) to be identified and the overall length of shoreline modified by the armoring to be measured without double counting. The lengths of sandy beach habitat modified by beach armoring were recorded in Microsoft Excel. All digitizing was completed by a single GIS analyst.The lengths of shoreline affected by armoring included in this report should be considered a minimum because of the difficulty in identifying structures that still may be hidden by vegetation, dunes, or beach fill. A number of armor structures that were not visible prior to Hurricane Sandy were exposed by the storm or during the three years after the storm, for example; these structures were not included in the 2012 armor inventories of Rice (2015b, 2015c), but were newly identified and included in this 2015 update. Wherever available, published sources on hard stabilization structures armoring the coast were used to verify the types of armoring and the lengths of shoreline armored in a given area. In addition, solitary shore perpendicular structures such as jetties or solitary groins were noted but not included in the lengths of shoreline armored. Although the adjacent shoreline is impacted by the solitary structure, the length of shoreline impacted is unique to the given setting and cannot be uniformly measured. Therefore the lengths of shoreline modified with armoring identified in this assessment are minimum values.

Copyright Text: Tracy Monegan Rice, Terwilliger Consulting, Inc.

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