State of the Beach/State Reports/NC/Beach Erosion
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First, it's useful to define what beach erosion is and how it's measured. This discussion is from Greg Rudolph of the Carteret County Shore Protection Office.
15% of North Carolina's shoreline is critically eroding, according to the report "State Coastal Program Effectiveness in Protecting Natural Beaches, Dunes, Bluffs, and Rock Shores" (T. Bernd-Cohen and M. Gordon), Coastal Management 27:187-217. 1999. Shoreline erosion maps released in 2003, which incorporated the results of a 1998 survey, indicate that about 18% of the shoreline is "severely" eroding, which is defined as areas that are eroding at a rate greater than 4.5 feet per year.
Using current and historical aerial photography and sophisticated computer software, the Division of Coastal Management evaluates erosion rates about every five years. Their Erosion Rate Maps indicate that average annual shoreline change rates (1942-1998) ranged from 0 to more than 40 feet/year (on the southern end of Ocracoke Island). There are a few places that accreted over the 50-year period, such as Sunset Beach. However, most beaches showed some erosion. Chronically eroding areas include Masonboro Island, Ocracoke Island, Onslow Beach near New River Inlet, Shackelford Banks at Cape Lookout National Seashore, and much of the Outer Banks. The 50-year average does not necessarily reflect short-term erosion. The Erosion Rate Maps for all 64 coastal segments through 1998 are available from the NCDCM Website in Adobe Acrobat format.
During 2004, DCM incorporated updated long-term average annual erosion rates into the state’s oceanfront development rules. The new erosion rate maps provide the most accurate depiction of shoreline change that the state has ever had.
New with this round of erosion rate updates is an interactive GIS based mapping tool. This mapping tool (note: this may take a while to download) will let you zoom in on portions of the coast and find out the latest long-term average annual erosion rate. http://dcm3.enr.state.nc.us/website/ncshore/viewer.htm
In their book, "Drowning the North Carolina Coast: Sea-Level Rise and Estuarine Dynamics", Stan Riggs and Dorothea Ames of East Carolina University estimate the shoreline in northeastern North Carolina is receding at an average rate of about 2.7 feet per year.
Coastal mapping done by the Federal Emergency Management Agency in 1999 determined that the 65% of the Southern Shores of North Carolina were eroding with the highest rates being 11.5 ft/year. The study concluded that 26% of North Carolina’s shoreline was accreting and 74% was eroding.
The Geological Society of America Special Paper Eye of a human hurricane: Pea Island, Oregon Inlet, and Bodie Island, northern Outer Banks, North Carolina by Riggs, et. al. provides a very informative history of both the natural and human-caused changes to these barrier islands. The paper's abstract concludes:
As the coastal system responds to ongoing processes of rising sea level and storm dynamics, efforts to engineer fixes are increasing and now constitute a “human hurricane” that pits conventional utilization of the barriers against the natural coastal system dynamics that maintain barrier-island integrity over the long term.
In 1996, Hurricane Fran caused more than $2 billion in damage to homes and businesses in the state. The hurricane wiped out most of the dunes on Topsail Island.
In September 2003, Hurricane Isabel tore a 1,700-foot gap in Hatteras Island, cutting N.C. 12 in half. The new inlet was 24 feet deep in some spots.
A more recent illustration of beach erosion was reported in the February 20, 2003 edition of the Charlotte Observer. Andy Coburn, assistant director of Duke University's program for the study of developed shorelines, Brad Murray, professor of geomorphology and coastal processes and two dozen of their students visited private Figure Eight Island to see how erosion on the island's north side has left more than a dozen million-dollar homes relying on sandbags to keep from toppling into the ocean. This area was renourished two years prior, but the sand lasted only a few months before the beach, dunes, and back yards were lost again to the encroaching waves.
In September 2005, Hurricane Ophelia caused erosion along North Carolina's Outer Banks. Topsail Island appeared to sustain the most damage in the region, with parts of Surf City losing 25 feet of beach. According to a state damage assessment report, 90 percent of the beach stair accesses in Topsail Beach were damaged or destroyed.
Storm damage at Cape Lookout National Seashore included a new channel cut across Cape Lookout Point, a new inlet 1.5 miles south of New Drum Inlet, and a significant widening of Old Drum Inlet. Hurricane Ophelia also did more than $1 million damage to Camp Lejeune - half of that to Riseley Pier, which lost half its length.
An early tropical storm in May 2007 caused substantial erosion in several areas along the North Carolina Coast, wiping out the gains in beach width from some recent beach fill projects.
Hurricane Irene passed over the North Carolina coast in late August 2011. A report Bogue Banks Beach and Nearshore Mapping Program Hurricane Irene Post-Storm Impact Evaluation was published in late September 2011. Storm impacts were evaluated by comparing the results of a pre-storm monitoring survey (beach profiles) completed during June 2011 with a post-storm survey completed between August 29 and September 2, 2011, immediately following the passage of Hurricane Irene.
Hurricane Irene also caused damage and increased erosion elsewhere along the coast. At North Topsail Beach, the owners of the Topsail Reef condo complex spent about $1,000,000 in April 2012 to install a wall of sandbags in front of the ocean front buildings. This is intended to provide protection until a river inlet channel relocation project, scheduled to start in November 2012, can generate 544,000 cubic yards of sand, which is supposed to go 1.7 miles, which will go past the Topsail Reef area.
NCDCM staff estimates that approximately 5 miles of beach (1 to 2% of the coastline) has no dry sand at high tide. They also estimate that about 240 miles of beach, or 75% of the coastline, is eroding, with the balance of the coastline accreting.
A report Survey Report 2005, Bogue Banks, North Carolina was prepared for Carteret County Shore Protection Office by Coastal Science & Engineering in November 2005. This report provides results of beach monitoring surveys covering the period June 1999 through May 2005, completed as part of the Bogue Banks Beach and Nearshore Mapping Program (BBBNMP) sponsored by Carteret County, North Carolina. The report documents changes in the condition of the beach over a six-year period which encompassed the following major events:
- Hurricanes Dennis and Floyd (September 1999)
- Phase 1 beach restoration project (Pine Knoll Shores and Indian Beach, December 2001–April 2002)
- Morehead City navigation project inner harbor material (nourishment disposal) to Fort Macon State Park (February 2002)
- Phase 2 beach restoration project (Emerald Isle, January–March 2003)
- US Army Corps of Engineers (USACE) Section 933 beach nourishment (Indian Beach and western Pine Knoll Shores, February to March 2003)
- Hurricane Isabel (September 2003)
- Post-Isabel FEMA beach renourishment (Emerald Isle, March 2004)
- Phase 3 beach restoration (Emerald Isle, February–April 2005)
- New inlet dredging at Bogue Inlet (January–April 2005)
- Hurricane Ophelia (September 2005)
- Brandt Island pumpout and disposal along Atlantic Beach and Fort Macon State Park (November 2004–February 2005)
- USACE Morehead City Harbor dredge disposal along Atlantic Beach and Fort Macon State Park (February–April 2005)
UPDATE: The monitoring section of the Protect the Beach Website now contains Annual Monitoring Reports from 2002-2003 through 2012, as well as 2007 Shoreline Maps of Bogue Banks.
Some of the main conclusions derived from monitoring along Bogue Banks and adjacent islands from 1999 to 2007 are as follows:
- There has been a 7.7 million cubic yard increase in sand volume along the entire oceanfront between June 1999 and May 2007. This volume was measured to –11 ft NGVD.
- Nearly 1.36 million cubic yards of the increase occurred between May 2006 and May 2007.
- The county project, which does not include the highly variable section of oceanfront beach at the western end of Emerald Isle, has gained 5.82 million cubic yards of sand (66.1 cy/ft) since June 1999.
- The rest of the oceanfront outside of the “county project” has gained 1.55 million cubic yards (38.4 cy/ft) over the same time period.
- Over the past monitoring period between May 2006 and May 2007, the “county project” has gained 1.41 million cubic yards of sand (16.0 cy/ft) but the rest of the oceanfront not included in the county project has lost nearly 56,000 cy over a 40,293 ft (“entire oceanfront” minus “county project”) length of beach (approximately –1.38 cy/ft). These volumes are measured to –11 ft NGVD.
- Seventy-two percent of the gain in sand volume in the “county project” reaches is on the recreational beach above low-tide wading depth (–4 ft NGVD). Along the rest of the island outside the “county project” reaches, only 40 percent of the sand volume measured to –11 ft is above low-tide wading depth.
The Bogue Banks 2009 State of the Beach Report (no connection to this report) discusses "major beach losses", "major beach gains", and "beach monitoring" from Beaufort Inlet to Bogue Inlet.
In working on its proposed budget for 2006-2007, the Carteret County Beach Commission gave County Shore Protection Manager Greg Rudolph the go ahead to look into creating a virtual beach mapping Website similar to those created by the county tax office. The site would take all of Carteret's historic shoreline data, its property parcels, aerial photos, dredged material disposal areas and borrow sites and even sea turtle nesting information, and put that information together in such a way that visitors to the site could pull up facts particular to their interests.
Carteret County launched its Coastal Mapping Portal in late April 2008. The mapping portal is a public geographic-information-system (GIS) Website enabling users to select, manipulate, and manage coastal data of their choosing. Information concerning beach nourishment, shoreline positions over time, parking & access locations, artificial reefs and shipwrecks, and even historical hurricane tracks are available to be accessed utilizing a familiar “folder drop-down” menu format. In 2012 the Coastal Mapping Portal was migrated from the ArcIMS to the ArcServer platform.
A substantial amount of data and information on coastal erosion, tides, currents, winds and waves in Duck, North Carolina and elsewhere along the North Carolina coast can be obtained from the Website of the U.S. Army Corps of Engineers Field Research Facility (FRF), an internationally recognized coastal observatory. Instruments at the facility constantly record the changing waves, winds, tides, and currents. Central to the facility is a 560m (1840 ft) long pier and specialized equipment like the CRAB, LARC, and SIS. The latest technology utilized by FRF is a Coastal Lidar and Radar Imaging System, or "Claris." Essentially a Sno-Cat fitted with radar and lidar sensors, it travels along the beach as its radar makes precise measurements of the speed, frequency and size of waves. Meanwhile, the lidar instrument (lidar stands for light detection and ranging) produces highly accurate maps of beach topography, above the water and beneath it. Researchers used Claris to observe beaches on the Outer Banks before and after Hurricane Irene struck in August 2011. Researchers at the facility have relied on the CRAB (coastal research amphibious buggy), a 30-foot tripod with a tiny cabin and sensors, powered by a Volkswagen engine. Moving laboriously out into the surf and then back to shore, it can measure changes in the bottom of less than an inch. But the CRAB cannot work in heavy surf, and it takes days to measure even a mile of beach. Claris thrives on heavy surf — in fact, it relies on measurements of wave heights to calculate the shape of the bottom.
Beachgoers in Brunswick County now have up-to-the-hour data on surf conditions and rip tides, thanks to researchers who have installed offshore instruments that provide information on everything from how fast the water is flowing to which direction it's traveling and how warm it is. Information about conditions are available online at http://www.cormp.org. Cape Fear Community College students used the research vessel Martech to submerge the instruments off the Ocean Crest Pier in Oak Island. They're the first in the county to monitor surf conditions. The $95,000 subsurface equipment sits about 800 feet off the pier and is connected to the pier by an underwater cable. A meteorological station also will be installed on the pier to measure wind speed and direction, air temperature and humidity.
A similar instrument installed by CORMP off Wrightsville Beach and a new weather station at Johnnie Mercers Pier are also up and running. Monitoring the water in Brunswick County will provide more accurate readings because those beaches face south rather than east as Wrightsville Beach does. Currently, the weather service relies on reports from emergency management and people on and around the beach. Another benefit is that the instruments will track how sand moves around the beaches - a useful tool for the Army Corps of Engineers for when it tries to replenish beaches. With CORMP set to lose federal funding, the Brunswick instrument and a separate monitoring buoy to be placed about 25 miles off the coast near Jacksonville will be the last pieces of equipment installed for the time being. The buoy installment is planned for January 2006. Funding from the National Oceanic and Atmospheric Administration is being slashed from $2.5 million to $500,000.
A National Park Service boundary survey project at Cape Hatteras National Seashore was started in December 2005. Two survey teams will be working from the southern end of Ocracoke Island north to Whalebone Junction and along village boundaries to survey and remark Seashore boundary lines. Work is anticipated to be completed in the spring of 2006.
An image gallery of several North Carolina Beaches is available on the Website of Western Carolina University's Program for the Study of Developed Shorelines.
The USGS Woods Hole Science Center is conducting a North Carolina Coastal Change project. The objective of this task is to improve the capabilities of coastal change models to predict large-scale shoreline change on open-ocean sandy coasts, with specific application to the Northern Outer Banks of North Carolina. Numerical models will be tested and developed using high-resolution observations of geological framework and shoreline change in North Carolina, with the objective of first simulating past changes (hindcasting) and then developing a forecasting capability.
The coastal change observations collected under the North Carolina Regional Coastal Erosion Study provide unprecedented resolution, revealing patterns of shoreline change along 130 km of coast at an interannual (several year) time scale. Geologic framework observations reveal bathymetric features and near-surface sediment distribution patterns that appear to be tied to the observed shoreline variability. Along one 5-km section of coast, a strong pattern of interannual erosion and accretion appears to be associated with a set of shore-oblique bars on the shoreface (in 4 -15 m water depths). This location will be evaluated using several modeling systems.
The Coastal and Marine Geology Program of the U.S. Geological Survey has generated a comprehensive database of digital vector shorelines and shoreline change rates for the U.S. Southeast Atlantic Coast (Florida, Georgia, South Carolina, North Carolina). These data were compiled as part of the U.S. Geological Survey's National Assessment of Shoreline Change Project. http://pubs.usgs.gov/of/2005/1326/
The Heinz Center's Evaluation of Erosion Hazards report mentioned below discusses information related to the Cape Hatteras Lighthouse. When constructed in 1870, the lighthouse was 1,500 feet from the shore. Protective measures to reduce the rate of beach erosion in front of the lighthouse provided a temporary solution, but by late 1987 the lighthouse stood only 160 feet from the sea and was in danger of collapsing. In 1999, after several years of debate and lawsuits aimed at blocking relocation, the National Park Service successfully moved the lighthouse back 2,900 feet at a cost of $9.8 million. The report states that average erosion rates are 2-3 ft/year in Dare, NC.
Another link about beach erosion in North Carolina which focuses on the Cape Hatteras Lighthouse is http://whyfiles.org/091beach/index.html. There also links to other pages that give a nice overview of beach erosion-related issues.
Surfrider Foundation published an article in their Making Waves newsletter summarizing the decision to move the Cape Hatteras Lighthouse, a victory for both the coast and the lighthouse. The lighthouse was moved at a cost of $9.8 million, in response to a shoreline that had eroded 1,340 feet over 117 years.
North Carolina Sea Grant (NCSG) is another source of information on beach erosion-related issues. Their Website identifies an extensive list of NCSG publications. http://www.ncseagrant.org/
The Heinz Center's Evaluation of Erosion Hazards, conducted for the Federal Emergency Management Agency (FEMA), studied the causes of coastal erosion hazards and proposed a variety of national and regional responses. The study, published in April 2000, concentrates on the economic impacts of erosion response policies as well as the cost of erosion itself to homeowners, businesses, and governmental entities.
A NOAA website that has graphs of sea level data for many coastal locations around the country over the last 40 to 50 years and projections into the future is http://tidesandcurrents.noaa.gov/sltrends/sltrends.shtml
NOAA Shoreline Website is a comprehensive guide to national shoreline data and terms and is the first site to allow vector shoreline data from NOAA and other federal agencies to be conveniently accessed and compared in one place. Supporting context is also included via frequently asked questions, common uses of shoreline data, shoreline terms, and references. Many NOAA branches and offices have a stake in developing shoreline data, but this is the first-ever NOAA Website to provide access to all NOAA shorelines, plus data from other federal agencies. The site is a culmination of efforts of NOAA and several offices within NOS (including NOAA’s Coastal Services Center, National Geodetic Survey, Office of Coast Survey, Special Projects Office, and Office of Ocean and Coastal Resource Management) and other federal agencies to provide coastal resource managers with accurate and useful shoreline data.
A related site launched in 2008 is NOAA Coastal Services Center's Digital Coast, which can be used to address timely coastal issues, including land use, coastal conservation, hazards, marine spatial planning, and climate change. One of the goals behind the creation of the Digital Coast was to unify groups that might not otherwise work together. This partnership network is building not only a website, but also a strong collaboration of coastal professionals intent on addressing coastal resource management needs. Website content is provided by numerous organizations, but all must meet the site’s quality and applicability standards. More recently, NOAA Coastal Services Center has developed a Sea Level Rise and Coastal Flooding Impacts Viewer as part of its Digital Coast website. Being able to visualize potential impacts from sea level rise is a powerful teaching and planning tool, and the Sea Level Rise Viewer brings this capability to coastal communities. A slider bar is used to show how various levels of sea level rise will impact coastal communities. Completed areas include Mississippi, Alabama, Texas, Florida, and Georgia, with additional coastal counties to be added in the near future. Visuals and the accompanying data and information cover sea level rise inundation, uncertainty, flood frequency, marsh impacts, and socioeconomics.
Erosion Contact Info
Division of Coastal Management
Coastal Hazards Specialist
1638 Mail Service Center
Raleigh, NC 27699-1638
Phone: 919-733-2293, ext. 241
- ↑ North Carolina Division of Coastal Management, "Long Term Average Annual Shoreline Change Rates Updated Through 1992 (Map)."
- ↑ "North Carolina's Disappearing Coast", by Jack Betts. The Charlotte Observer, May 9, 2004.
- ↑ John Sutherland, NC Division of Water Resources. Surfrider State of the Beach survey response, January 2003
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