State of the Beach/State Reports/MD/Beach Erosion
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According to MDNR information, approximately 69 percent of Maryland’s coast is currently eroding. The average rate of erosion along the coast has been calculated at 0.58 feet per year. Approximately 48 miles of shoreline are experiencing erosion rates greater than eight feet per year.
Nine percent of Maryland'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.
The Coastal and Environmental Geosciences Program at the Maryland Geological Survey periodically assesses shoreline change – erosion and accretion – for Maryland's tidal waters. These include the Chesapeake Bay and its tributaries, the Atlantic coast, and the Coastal Bays west of Fenwick and Assateague Islands. The Program has acquired or produced a sequence of digital shorelines for all 125 of the State's 7.5-minute coastal quadrangles. Shoreline dates cover a range from 1841 to 1995, with several intermediate years commonly available. However, the number of shorelines and the specific shoreline dates vary from quadrangle to quadrangle, depending on availability. Products of this work can be used to assess the historical changes in shoreline position over time.
Products of this effort are available in two basic formats:
Shoreline Change Maps are available for online viewing or for downloading in Adobe PDF format. These maps products display the shorelines over 1988-1995 digital orthophotographs. An example from a portion of the Tilghman Island Quadrangle is shown to the right. The pdf files were produced for plotting at a scale of 1:24,000 on a 36-inch wide paper plotter, and as a result are quite large – up to 45Mb each, and may take time to download depending on connection speed. Plotted colors may vary from those shown on-screen depending on the settings of individual plotters.
Shoreline Change Map Data for GIS. These are vector format maps. Unlike raster images, they can be rescaled without distortion. The maps were created in ArcGIS 8.3 and consist of polyline segments and polygons. The dates of these shorelines range from the mid 1800s to the 1990s. Three file formats are available: Autodesk's Drawing Exchange Format (.DXF), ESRI's Shapefile (.SHP) and Arc Export (.E00) formats. These are widely accepted vector data standards and are used by programs such as AutoCAD, ArcGIS, ArcInfo, CorelDraw, Adobe Illustrator, JASC's Paint Shop Pro, Bryce 3D, 3D Studio Max, and many Intergraph programs. The ESRI .SHP file format contains shoreline attribute data. These products can be used as input to a variety of commercially available GIS programs for further analysis. As noted above the historical shorelines available range from 1841 to 1995 and vary from quadrangle to quadrangle.
Several coastal erosion maps are available at: http://www.mgs.md.gov/esic/publications/internet.html
Additional erosion rate maps are available online at the Maryland Coastal Atlas. The map server provides average erosion rates generated from shoreline determined on orthophotographs from 1941 to 1995. To be able to read the erosion rates the maps must be zoomed in until you can see the transects.
A governor-appointed Shore Erosion Task Force was formed in 1999 to collect, review, and discuss current knowledge and concerns, and to make recommendations concerning shoreline erosion. The Task Force was charged with identifying shore erosion control needs by county in Maryland, clarifying local, state, and federal roles regarding shore erosion, establishing 5- and 10-year plans, and reviewing contributing factors to shore erosion.
According to the Shore Erosion Task Force Final Report, released January 2000, approximately 31% of Maryland's 4,360-mile coastline is currently experiencing some degree of erosion. All 16 coastal counties along the Chesapeake and coastal Bays watersheds are affected. Erosion rates among these counties vary from a high of 54% eroding shoreline in Dorchester County to 15% in Caroline County. Among the western coastal counties, Prince Georges County has the highest percentage of its shoreline eroding, 43%. The Shore Erosion Task Force Final Report can be downloaded at: http://www.mgs.md.gov/esic/publications/download/drnerostf.pdf
The Task Force published a set of nine recommendations to be implemented under the umbrella of a Comprehensive Shore Erosion Control Plan. The recommendations are:
- Establish an immediate response capability to provide the necessary planning and technical means to initiate development of a Comprehensive Shore Erosion Control Plan; emergency assistance for critical shore erosion control needs; and, interim financial assistance for structural shore erosion control measures.
- Identify and analyze areas subject to shore erosion, sea level rise, and environmental sensitivity to prioritize and target shore protection activities through the establishment of regional shore erosion control strategies.
- Develop project review and selection criteria to guide the implementation of regional shore erosion control strategies.
- Improve coordination of shore protection activities among various entities and individuals in order to encourage the implementation of cooperative regional projects.
- Conduct technical evaluations of new shore protection products and methods, evaluate the need for minimum engineering standards, and review industry practices.
- Encourage the beneficial use of dredged materials in both individual and regional scale projects.
- Conduct public outreach on technical matters, funding resources, and environmental issues related to shore erosion control.
- Pursue projects to fill identified data and information needs to support the development of a Comprehensive Shore Erosion Control Plan.
- Identify overall funding needs and potential funding resources, and develop a financial strategy to implement a Comprehensive Shore Erosion Control Plan.
As the name suggests, the Comprehensive Plan is designed to move Maryland from the current uncoordinated approach towards shore erosion control to an approach that quantifies regional shore erosion impacts and uses sound planning, based on best available data, to achieve the objectives outlined by the Governor's Task Force.
According to the 2001 Assessment, it is currently estimated that 376 miles of Chesapeake Bay shoreline are eroding at greater than 2 feet per year (up to 16 feet per year), with the development along the shoreline at greatest risk. Public facilities and infrastructure as well as vital coastal habitats are in danger of being degraded or completely destroyed. Coastal hazards in Chesapeake Bay are epitomized at Smith Island, where coastal inundation is endangering several island towns and impacting critical habitats for submerged aquatic vegetation and juvenile blue crabs.
The state is currently developing criteria for, and identifying, erosion "hotspots" within the state. Some areas have already been mapped and others are in progress.
Sea level rise is a significant factor contributing to shore erosion in Maryland. It contributes to coastal erosion by influencing and exacerbating ongoing coastal processes, making coastal areas more vulnerable to extreme events. Tide gauge measurements in Chesapeake Bay and the Mid-Atlantic show rates of sea level rise nearly twice the global average. The average rate of sea level rise on Maryland's coastline has been between 3-4 mm per year or approximately one foot per century. These rates are expected to accelerate due to global warming, resulting in a sea level rise of up to 2 to 3 feet per 100 years.
A 1985 EPA report Potential Impacts of Sea Level Rise on the Beach at Ocean City, Maryland concluded:
- Sea level rise could double the rate of erosion at Ocean City in the next forty years. If no additional erosion control measures are taken, the shore will erode 85-153 feet by 2025 assuming current sea level trends. An 11-inch global rise in sea level would increase expected erosion to between 180 and 238 feet, if no additional measures are taken; a 15-inch rise would increase expected erosion to between 216 and 273 feet.
- The projected rise in sea level would increase the quantity of sand necessary to maintain the current shoreline for the next forty years from 5-10 million cubic yards if current trends continue, to 11-15 million cubic yards for the two scenarios of accelerated sea level rise.
- Projected sea level rise would increase the priority of erosion control-measures under current policies of the Corps of Engineers. Current policies place a greater emphasis an flood protection than recreational benefits provided by proposed projects. Because of the substantial erosion that could occur from a rise in sea level, the need for flood protection will be greater if sea level rises.
- A significant rise in sea level would require a change in the technology used to control erosion at Ocean City. The current plan to construct groins was designed to curtail erosion caused by sand moving along the shore. However, groins do not prevent erosion caused by sea level rise. Placement of additional sand onto the beach would offset erosion caused by both sea level rise and alongshore transport.
- The cost of controlling erosion caused by sea level rise does not threaten the economic viability of Ocean City in the next forty years. Even the most pessimistic estimate of future erosion control implies a cost of less than fifty cents for every visitor that comes to Ocean City each year. Protecting the shore at Ocean City will continue to be economically justified.
- Understanding the likely impact of sea level rise on Ocean City in the next century will require identification of the most cost-effective and environmentally acceptable sources for up to fifty million cubic yards of sand to be placed on the beach.
- Better estimates of future sea level rise would enable decision makers to more adequately determine the most prudent strategy for controlling erosion at Ocean City.
- Although improved procedures for estimating erosion are desirable, current methods are sufficient to yield first-order estimates for use in long-term planning.
According to the 2001 Assessment, shoreline position maps for the entire state are being updated and digitized; updated shore erosion rates will then be calculated. LIDAR topographic data will be collected for small stretches of shoreline in three counties. The new shoreline positions will then be utilized to determine potential costs of the impact on public and private infrastructure and other valuable resources. This information will be used as a public education and outreach tool and to develop mitigation strategies.
Hurricane Isabel caused an estimated $273 million in damages to coastal properties in 2003. Much of this damage was to private property, since an estimated 96% of Maryland's coastline in privately owned. About 70 miles of shoreline was damaged.
An article in the Washington Post on October 25, 2010 by David Fahrenthold Last house on sinking Chesapeake Bay island collapses documents the demise of a house built around 1888 on Holland Island in Chesapeake Bay. The article claims that 580 acres of Maryland shoreline are lost each year from the combined effects of erosion, subsidence and sea level rise. The article also states:
It definitely won't, however, be the end of the Chesapeake's erosion problems. A few miles away, a watermen's community on Smith Island is just a few inches above the waves. And Maryland is contemplating how to, in one official's words, "facilitate abandonment and retreat" when faster-rising waters eventually threaten towns on the Eastern Shore's mainland.
Maryland Sea Grant is also another potential source of information on beach erosion.
A USGS report National Assessment of Shoreline Change: Historical Shoreline Change along the New England and Mid-Atlantic Coasts was released in February 2011. The New England and Mid-Atlantic shores were subdivided into a total of 10 analysis regions for the purpose of reporting regional trends in shoreline change rates. The average rate of long-term shoreline change for the New England and Mid-Atlantic coasts was -0.5 meters per year. The average rate of short-term shoreline change for the New England and Mid-Atlantic coasts was also erosional but the rate of erosion decreased in comparison to long-term rates. The net short-term rate as averaged along 17,045 transects was -0.3 meters per year.
General Erosion Data References
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 Sea Levels Online.
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
Coastal & Estuarine Geology Program
Maryland Geological Survey
2300 St. Paul St.
Baltimore, MD 21218
Hazard Avoidance Policies/Erosion Response
See the Erosion Response section.
- "Officials Put Isabel's Cost at $273 Million", The Baltimore Sun. January 24, 2004.
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