Glossary Of Terms


Beach – Shoreline zone comprised of unconsolidated sandy material upon which there is a mutual interaction of the forces of erosion, sediment transport and deposition that extends from the low water line landward to where there is a marked change in either material composition or physiographic form or to the line of woody vegetation (usually the effective limit of stormwaves), or the nearest impermeable man-made structure, such as a bulkhead, revetment, or paved road.


Chesapeake Bay Preservation Ordinance - Chapter 118 of the Code of Fairfax County was adopted by the Fairfax County Board of Supervisors on March 22, 1993, to meet the requirements established by the Code of Virginia, Section 10.1-2100, Chapter 21, known as the Chesapeake Bay Preservation Act.  The ordinance was adopted for the purposes of encouraging and promoting the protection of state waters and to preserve the habitat, which those waters provide, as well as to reduce existing pollution in the state waters and to prevent further pollution.


Erosion control – Measures used to prevent movement of sediment onto neighboring properties or into state waters; such movement of sediment is usually caused by excavation, clearing, grading and is exacerbated by the natural forces of wind and rain.


Fairfax County Wetlands Board – Seven members and one alternate member appointed by the Fairfax County Board of Supervisors and created on October 17, 1983, to meet the provisions of Title 28.2, Chapter 13, Section 28.2-1300 of the Code of Virginia, Chapter 116 of the Code of Fairfax County, known as the Wetlands Zoning Ordinance .  The Wetlands Board also administers Title 28.2, Chapter 14, Section 28.2 – 1400 of the Code of Virginia and Chapter 123 of the Code of Fairfax County, the Coastal Primary Sand Dune (Beach) Zoning Ordinance.

Floodplain – Those land areas in and adjacent to streams and watercourses subject to continuous or periodic inundation from flood events with a one (1) percent chance of occurrence in any given year (i.e. the 100-year flood frequency event) and having a drainage area greater than 70 acres.


Living Shoreline – A shoreline management practice that provides erosion control and water quality benefits; protects, restores or enhances shoreline habitat; and maintains coastal processes through the strategic placement of plants, stone, sand fill, and other structural and organic materials. (Virginia Marine Resources Commission)


Mean high water (MHW) – The average of all the high water heights observed over a 19-year period. (Virginia Institute of Marine Science)

Mean high water line (MHWL) – The contour line on a drawing that shows the average upland limit of an average high tide.

Mean low water line (MLWL) – A contour line on a drawing that shows the channelward limits of an average low tide.

Mean tide range – Mean high water and mean low water are defined as the average vertical elevation of all high water tides and low water tides, respectively that have occurred during the 19 year lunar cycle.


National Tidal Datum Epoch – The specific l9-year period adopted by the National Ocean Service as the official time segment over which tide observations are taken and reduced to obtain mean values (e.g., mean lower low water, etc.) for tidal datums.  (National Oceanic and Atmospheric Administration)

Non-vegetated wetlands – Unvegetated lands lying contiguous to mean low water and between mean low water and mean high water.


Resource Protection Area (RPA) – That component of the Chesapeake Bay Preservation Area comprised of lands at or near the shoreline or water’s edge that have an intrinsic water quality value due to the ecological and biological processes they perform or are sensitive to impacts which may result in significant degradation of the quality of state waters.  In their natural condition, these lands provide for the removal, reduction or assimilation of sediments and nutrients and potentially harmful or toxic substances from runoff entering the Bay and its tributaries.

Riprap Revetment – Rock strategically placed on the shoreline or at the water’s edge to slow erosion caused by wave action.


Tidal datum – A vertical reference based on some phase of the tide.  (Virginia Institute of Marine Science)

Tidal wetlands – Lands lying between and contiguous to mean low water and between mean low water and mean high water subject to flooding by normal tides and wind tides.

Tide – The periodic rise and fall of water (in oceans, bays, gulfs, inlets and tidal regions of rivers) resulting from the gravitational interactions between the sun, moon, and earth.


U.S. Army Corps of Engineers – This federal agency, which traces its origins back to the Continental Congress in 1775, has played a major role in civil and public works projects over the years.  The Corps oversees the federal regulatory role in the implementation and administration of The Clean Water Act.


Vegetated wetlands – Lands lying between and contiguous to mean low water and an elevation above mean low water equal to the factor on and one-half times the mean tide range.  Vegetated wetlands are lands, which are inundated, and saturated by surface and groundwater at a frequency and duration sufficient to support vegetation adapted to life in saturated soil.

Virginia Department of Environmental Quality – Department of the Commonwealth of Virginia formed in 1993 under the authority of the executive branch involved in regulating and permitting related to water, air and waste.

Virginia Marine Resources Commission (VMRC) – Agency of the commonwealth that is responsible for marine management, which seeks to protect the living resources and the habitat of those resources.  VMRC was originally established in 1875 as the Virginia Fish Commission and it was re-named by an act of the Virginia General Assembly in 1968.  In addition, the VMRC maintains responsibility for permitting encroachments in or over State-owned submerged lands and oversees the administration of the following laws:

  • The Virginia Wetlands Act, 1972;
  • The Coastal Primary Sand Dune Protection Act, 1980;
  • The Virginia Wetlands Act, 1982 revised to include non-vegetated wetlands;  
  • Fisheries Management Division, made a distinct division with strengthened authority, 1984.


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