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Critical Area Commission
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Annapolis, MD 21401


Glossary To Key Terms and Definitions


Wrecks facing the shore by Jim D'Intino

Afforestation The establishment of a tree crop on an area from which it has always or very long been absent, or the planting of open areas which are not presently in forest cover.

Agriculture All methods of production and management of livestock, crops, vegetation, and soil. This includes, but is not limited to, the related activities of tillage, fertilization, pest control, harvesting and marketing. It also includes, but is not limited to, the activities of feeding, housing, and maintaining of animals such as cattle, dairy cows, sheep, goats, hogs, horses, and poultry and handling their by-products.

Agricultural Easement A non-possessory interest in a parcel of land which restricts the conversion of the use of the land, preventing non-agricultural uses.

Anadromous fish Fish that travel upstream (from their primary habitat in the ocean) to fresh waters in order to spawn.

Anadromous fish propagation waters Those streams that are tributary to the Chesapeake Bay where spawning of anadromous species of fish (e.g., rockfish, yellow perch, white perch, shad, and river herring ) occurs or has occurred.

Aquaculture The farming or culturing of finfish, shellfish, other aquatic plants or animals, or both in lakes, streams, inlets, estuaries, and other natural or artificial water bodies or impoundments.

Atmospheric deposition A process whereby pollutants are transported from a ground-based source and through atmospheric processes are deposited on a distant land or water surface.

Barren Land Unmanaged land having sparse vegetation.

Best Management Practices (BMPs) Conservation practices or systems of practices and management measures that control soil loss and reduce water quality degradation caused by nutrients, animal wastes, toxics, and sediment. Agricultural BMPs include strip cropping, terracing, contour stripping, grass waterways, animal waste structures, ponds, minimal tillage, grass and naturally vegetated filter strips, and proper nutrient application measures.

Board of Appeals The local jurisdiction body, created by ordinance, whose responsibility is to hear appeals from decisions of the local zoning administrative official and to consider requests for variances and special exceptions (special use permits, conditional use permits) permissible under terms of that jurisdiction's zoning ordinance and Critical Area program.

Buffer A naturally vegetated area established or managed to protect aquatic, wetland, shoreline, and terrestrial environments from man made disturbances.

Clearcutting The removal of an entire stand of trees in one cutting with tree reproduction obtained by natural seeding from adjacent stands or from trees that were cut, from advanced regeneration or stump sprouts, or from planting of seeds or seedlings by man.

Cluster Development A development pattern - for residential, commercial, industrial, institutional, or combination of uses, in which the uses are grouped or "clustered", through a density transfer, rather than spread evenly throughout the parcel as in conventional lot-by-lot development. A local jurisdiction's Critical Area Program may authorize such development by permitting smaller lot sizes if a specified portion of the land is kept in permanent open space to provide natural habitat or open space uses through public or private dedication.

Colonial nesting water birds These birds include : Herons, egrets, terns, and glossy ibis. For purposes of nesting, these birds congregate (colonize) in relatively few areas, at which time, the regional populations of these species are highly susceptible to local disturbances.

Commercial harvesting A commercial operation that would alter the existing composition or profile, or both, of a forest, including all commercial cutting operations done by companies and private individuals for economic gain.

Community piers Boat docking facilities associated with subdivisions and similar residential areas, and with condominium, apartment, and other multiple-family dwelling units. Private piers are not included in this definition.

Conservation easements A non-possessory interest in land which restricts the manner in which the land may be developed in an effort to reserve natural resources for future use.

Critical Area All lands and waters defined in Section 8-1807 of the Natural Resources Article, Annotated Code of Maryland. They include:

  • all waters of, and lands under the Chesapeake Bay and its tributaries to the head of tide as indicated on the State Wetlands maps, and all State and private wetlands designated under Title 9 of the Natural Resources Article, Annotated Code of Maryland;
  • all land and water areas within 1000 feet beyond the landward boundaries of State and Private wetlands and the heads of tides designated under Title 9 of the Natural Resources Article, Annotated Code of Maryland.

Critical Area Commission The 29-member Critical Area Commission was created by the 1984 Chesapeake Bay Protection Act. Initially, the Commission was tasked with developing the Critical Area Criteria, which are the basis of the 64 local Critical Area programs. The members of the Commission are appointed by the Governor and represent the Critical Area jurisdictions, affected interest groups, and State agencies. The Commission meets monthly and must review and approve all changes to local jurisdictions’ Critical Area programs, including changes resulting from the required six-year comprehensive update. The Commission also reviews and approves all development projects in the Critical Area on State land.

Crustaceans A group of predominately aquatic animals including crabs, shrimps, and barnacles, having hard outer skeletons or shells, and paired, jointed, limbs.

Density The average number of families, persons, or housing units per unit of land; usually density is expressed "per acre". The control of density is one of the principal strategies implemented in the Resource Conservation Area (RCA).

Developed woodlands Areas which predominately contain trees and natural vegetation but which also include residential, commercial, or industrial structures and uses.

Development activities The construction or substantial alteration of residential, commercial, industrial, institutional, or transportation facilities or structures.

Easement A right given by the owner of land to another party for specific limited use of that land such as wildlife conservation or creation of natural habitat.

Ecosystem A more or less self-contained biological community together with the physical environment in which the community's organisms occur.

Endangered species Any species of fish, wildlife, or plants which have been designated as such by regulation by the Secretary of the Department of Natural Resources. Designation occurs when the continued existence of these species as viable components of the State's resources is determined to be in jeopardy. This includes any species determined to be an "endangered" species pursuant to the federal Endangered Species Act.

Estuaries A somewhat restricted body of water where the flow of freshwater mixes with saltier water transported, by tide, from the ocean. Estuaries are the most productive water bodies in the world.

Eutrophication A process by which an excess of plant nutrients (e.g., nitrogen and phosphorous) reduces the oxygen dissolved within a body of water, producing an environment that does not readily support aquatic life.

Excess stormwater runoff Any increase in stormwater resulting from: an increase in the imperviousness of a site, including all additions to buildings, roads, and parking lots; changes in permeability caused by compaction during construction or modifications in contours, including the filling or drainage of small depression areas; the alteration of drainageways, or regrading of slopes; the destruction of forest; or the installation of collection systems to intercept street flows or to replace swales or other drainageways.

Finding A determination or conclusion based on the evidence presented and prepared by a hearings body in support of its decision. Local jurisdiction Boards of Appeal are required by the Critical Area Law to hold a public hearing to hear evidence when they receive a petition for a variance, special exception, rezoning, or appeal of a planning official's decision. When it presents its decision the body is required to demonstrate, in writing, that the facts presented in evidence support its decision in conformance with the law. The Critical Area Law requires findings of hardship, that the proposed development activity will not adversely affect water quality or adversely impact fish, wildlife, or plant habitat within the critical area, and be in harmony with the general spirit and intent of the Critical Area Law before the Board of Appeal can grant of a variance to Critical Area regulations.

Forest A biological community dominated by trees and other woody plants.

Forest interior-dwelling birds Species of birds which require relatively large forested tracts in order to breed successfully (various species of flycatchers, warblers, vireos, and woodpeckers, for example).

Forest management The protection, manipulation, and utilization of the forest to provide multiple benefits, such as timber harvesting, water transpiration, wildlife habitat, etc.

Forest practice The alteration of the forest either through tree removal or replacement in order to improve the timber, wildlife, recreational, or water quality values.


Growth Allocation Growth allocation is a process whereby local jurisdictions are allowed to approve additional growth and development in certain parts of the Critical Area by changing the Critical Area classification from RCA to either LDA or IDA or from LDA to IDA. Growth allocation is used to accommodate more intense land uses and development than what would have been permitted based on the existing classification. Each county is allotted a finite number of acres that can be used to reclassify land. Requests to use growth allocation must go through a rigorous review and approval process at the local level and must be approved by the local governing body. Following local approval, growth allocation requests must be submitted to the Critical Area Commission for review and approval.

Grandfathering A “grandfathered lot” is a lot or parcel that existed in its current configuration prior to adoption of the local Critical Area program. Grandfathered lots are not exempt from the Critical Area regulations. However, each local government adopted grandfathering provisions, which allow pre-existing uses to continue even though they may be inconsistent with the local program. Local governments also have grandfathering provisions that include limited flexibility for compliance with the Critical Area regulations and allow a property owner to request a variance from the strict application of the regulations. It is important to check with your local planning and zoning office when you are planning to develop or build on your grandfathered lot to ensure that your project complies with the applicable standards for your property.


Habitat Protection Areas Those areas, including buffers, non-tidal wetlands, habitat of threatened, endangered, and species in Need of Conservation, Plant and Wildlife Habitat, and Anadromous Fish Propagation Waters that are protected under the Critical Area legislation.

Highly erodible soils Soils with a slope greater than 15%; or those soils with a K value greater than .35 and with slopes greater than 5%.

Hydric soils Soils that are wet frequently enough to periodically produce anaerobic conditions, thereby influencing the species composition or growth, or both, of plants on those soils.

Hydrophytic vegetation Plants that grow in water or on a substrate that is at least periodically deficient in oxygen as a result of excessive water content (plants typically found in water habitats).

Impervious surface An area covered with solid material or that is compacted to the point where water can not infiltrate underlying soils (e.g. parking lots, roads, houses, patios, swimming pools, tennis courts, etc.). Stormwater runoff velocity and volume can increase in areas covered by impervious surfaces.

Mallows Bay by Stephen Badger



Land clearing Any activity that removes the vegetative ground cover.

Lot coverage Lot coverage is the percentage of a lot or parcel that is developed with a structure, parking area, driveway, walkway, or roadway. Lot coverage includes areas covered with gravel, stone, shell, impermeable decking, pavers, permeable pavement, or any other man-made material. Lot coverage does not include: 1) a fence or wall that is less than one-foot wide and is constructed without footer, 2) a walkway in the Buffer that provides access to a pier, 3) a wood mulch pathway, or 4) a deck with gaps to allow water to pass feely.

If your property is classified as RCA or LDA, there are limits on the amount of total lot coverage permitted on a parcel. Generally, lot coverage is limited to 15% of the total land area of the lot. There are some exceptions. If your parcel is one-half acre or smaller, and was in residential use before December 1, 1985, then the maximum lot coverage is 25% of the parcel or lot. (The date is June 1, 2002 for lots in the Atlantic Coastal Bays Critical Area.) Subject to certain requirements, a local government may allow you to exceed the lot coverage limit by 500 square feet or more, up to 31.25% of the lot. If your lot is greater than one-half acre and less than one acre, then lot coverage may exceed the 15% limit up to 5,445 square feet.

In some cases, lots within a subdivision may have different lot coverage limits; however, total lot coverage for the subdivision must remain at or below 15%.

Map, Critical Area Legal documents, adopted by the governing body of a local jurisdiction, and approved by the Chesapeake Bay Critical Area Commission, that exhibit those lands within the 1000 foot Critical Area boundary and the land use classification (RCA, LDA, IDA), according to land use as of December 1, 1985, assigned to each parcel. These maps can be amended only if a mistake in the original designation can be demonstrated by the applicant and with the approval of the local governing body and the Chesapeake Bay Critical Area Commission. These maps are available for public inspection at each jurisdiction's Office of Planning and Zoning.

Marina Any facility for the mooring, berthing, storing, or securing of watercraft, but not including community piers and other non-commercial boat docking and storage facilities.

Mean high water line (MHW) The average level of high tides at a given location.

Natural Heritage Area Any communities of plants or animals which are considered to be among the best Statewide examples of their kind.

Natural vegetation Plant communities that develop in the absence of human activities.

Non-point source pollution Pollution generated by diffuse land use activities rather than from an identifiable or discrete facility. It is conveyed to waterways through natural processes, such as rainfall, storm runoff, or groundwater seepage rather than by deliberate discharge. Non-point source pollution is not generally corrected by "end-of-pipe" treatment, but rather, by changes in land management practices.

Non-renewable resources Resources that are not naturally regenerated or renewed.

Non-tidal wetlands Those lands, in the Critical Area, excluding tidal wetlands, where the water table is at, or near, the surface or lands where the soil or substrate is covered by shallow water at some time during the growing season. These lands are usually characterized by one or both of the following: At least periodically, the lands support predominately hydrophytic vegetation; the substrate is predominately undrained hydric soil.

Nonconforming Use A lot or parcel, the area, width, or other physical characteristic of which fails to meet the requirements of the critical area land use classification in which it is located and which was conforming ( "of record") prior to the enactment of the Critical Area Law.

Nutrient A group of chemicals that nourish growth. In the Chesapeake Bay system, nitrogen and phosphorus are the nutrients contributing to excessive plant (e.g., Algal) growth and eutrophication.

Open Space Land and water areas retained in an essentially undeveloped state.

Parcel A lot, or contiguous group of lots in single ownership or under single control, and usually considered a unit for purposes of development.

Permeable surfaces Areas characterized by materials that allow stormwater to infiltrate the underlying soils (e.g., soil covered or vegetated areas)

Plant habitat A community of plants commonly identifiable by the composition of its vegetation and its physiographic characteristics.

Political subdivision Any political entity, such as a Town, City, or County, governed by its own legislative body and exercising planning and zoning authority. Sixty political subdivisions, including 16 counties and 44 municipalities surrounding Maryland's portion of the Chesapeake Bay are within the jurisdiction of the Critical Area Law.

Pollutants A waste material that contaminates air, soil, or water. Sediment, nutrients, and toxic chemicals are considered the major groups of pollutants contributing to the deterioration of the Chesapeake Bay ecosystem.

Private harvesting The cutting and removal of trees for personal use.

Project approvals The approval of development, other than development by a State or local government agency, in the Chesapeake Bay Critical Area by the appropriate local approval authority. The term includes approval of subdivision plats and site plans; inclusion of areas within floating zones; issuance of variances, special exceptions, and conditional use permits; and issuance of zoning permits. The term does not include building permits.


Reclamation The reasonable rehabilitation of disturbed land for useful purposes, and the protection of natural resources of adjacent areas, including waterbodies.

Redevelopment The process of developing land which is, or has been, developed.

Reforestation The establishment of a forest through artificial reproduction or natural regeneration.

Renewable resource A resource that can renew or replace itself and, therefore, with proper management, can be harvested indefinitely.

Riparian habitat A habitat that is strongly influenced by water and which occurs adjacent to streams, shorelines, and wetlands.

Selection The removal of single, scattered, mature trees or other trees from uneven-aged stands by frequent and periodic cutting operations.

Sediment Control Plan A written plan with appropriate maps and cross-sections which describes how erosion and transportation of sediment is to be controlled on a development site, and the time or schedule of the controlled activities.

Site Plan A plan, to scale, showing uses and structures proposed for a parcel of land as required by the Critical Area regulations involved. It includes lot lines, streets, building sites, buildings, other impervious surfaces, other areas of human disturbance, and major landscape features. Site plans are reviewed by the local jurisdiction and the Critical Area Commission staff.

Soil Conservation and Water Quality (SCWQ) Plans Land-use plans for farms that show farmers how to make the best possible use of their soil and water resources while protecting and conserving those resources for the future.

Steep slopes Slopes of 15 percent or greater incline.

Stewardship The concept of land as a resource, our responsibility to wisely manage that resource, and our responsibility to future generations for the condition of that resource when we leave it.

Structure Anything constructed or erected on the ground or which is attached to something located on the ground. Structures include, but are not limited to, buildings, radio and TV towers, sheds, swimming pools, tennis courts, gazebos, decks, boathouses.

Subdivision The process (and the result) of dividing a parcel of raw land into smaller buildable sites, streets, open spaces, and public areas, and the designation of utilities and other improvements. Critical Area regulations govern the density and design of new subdivisions.

Thinning Forest practices used to accelerate tree growth of quality trees in the shortest interval of time.

Threatened species Any species of fish, wildlife, or plants designated as such by the Secretary of the Department of Natural Resources which appear likely, within the foreseeable future, to become endangered, including any species of wildlife or plant determined to be a "threatened" species pursuant to the Federal endangered Species Act.

Transitional Habitat A plant community whose species are adapted to the diverse and varying environmental conditions that occur along the boundary that separates aquatic and terrestrial areas.

Tidal wetlands Those vegetated, or unvegetated, lands bordering, or lying beneath, tidal waters which are subject to regular or periodic tidal action.

Turbidity Exhibiting suspended or stirred up particles of sediment.

Use The purpose or activity for which a piece of land or its buildings is designed, arranged, or intended, or for which it is occupied or maintained. Land use planning and control - through zoning and other devices such as the Critical Area Law - is a primary concern of the public and planners; with depletion of natural resources and the degrading of environmental quality, land use is increasingly being recognized as a major national issue.

Variance A device which grants a property owner relief from certain provisions of the Critical Area ordinances when, because of the particular physical surroundings, shape, or topographical condition of the property, compliance would result in a particular hardship upon the owner, as distinguished from a mere inconvenience or a desire to benefit economically. Authority to decide variances is vested in the local jurisdiction's Board of Appeals or, in certain jurisdictions, a special hearing examiner. All variances granted by Boards of Appeal or hearing examiners within the Critical Area are reviewed by Critical Area Commission staff for consistency with State regulations.

Waterfowl Birds which frequent and often swim in water, nest and raise their young near water, and drive at least part of their food from aquatic plants and animals.

Watershed A large region of uplands where the slope of the topography contributes stormwater runoff to an adjacent waterbody or network of waterbodies. The watershed of the Chesapeake Bay encompasses some 16 million acres.

Wildlife corridors A strip of land having vegetation that provides habitat and a safe passageway for wildlife.

Wildlife habitat Those plant communities and physiographic features that provide food, water, and cover, nesting and foraging or feeding conditions necessary to maintain populations of animals in the Critical Area.



Zoning Permit An official finding that a planned use of a property, as indicated by an application, complies with the requirements of the jurisdiction's zoning ordinance and Critical Area Program or meets special conditions of a variance or special permit.

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