Critical Area Commission for the Chesapeake and Atlantic Coastal Bays

Development in the Critical Area

Overview

All land within the Critical Area, except for land owned by the federal government, is assigned one of three land classifications based on the predominant land use and the intensity of development at the time it was mapped. The classification system allows jurisdictions to use local zoning to effectively implement Critical Area programs through land use and development regulations and performance standards. The use of land classifications:

  1. promotes the location of new growth and development near or within existing developed areas;
  2. provides for infill development of similar uses and intensity; and
  3. facilitates the designation of areas for natural resource conservation and related resource utilization activities, such as agriculture, forestry, and aquaculture. Each of the three land classifications includes use and intensity restrictions, as well as development performance standards for proposed development and redevelopment.

These provisions are used to ensure that land within the Critical Area is managed, used, and developed in a manner that will achieve the goals of the Critical Area Program.

Illustration of Critical Area Land Use Classifications

Land Classifications

Intensely Developed Areas (IDAs)

Intensely Developed Areas (IDAs) are defined as areas of twenty of more adjacent acres where residential, commercial, institutional or industrial land uses predominate. IDAs are areas of concentrated development where little natural habitat occurs. In IDAs, the main focus of the Critical Area Program is on improving water quality. The Law requires that new development and redevelopment include techniques to reduce pollutant loadings associated with stormwater runoff. These techniques include site design, infiltration practices, and structural stormwater treatment practices such as sand filters and swales.

State and local Critical Area regulations specify that these techniques must be capable of reducing pollutant loads generated from a developed site to a level at least 10% below the loads generated at the same site prior to development. This requirement is commonly referred to as the "10% Rule". On some development sites, compliance with the 10% Rule may not be possible because of site constraints such as a high water table or poor soils. For these projects, local jurisdictions may allow alternatives to meeting the requirement on the project site. The alternatives include providing stormwater treatment off-site, implementing an offset program by which equivalent water quality benefits are achieved off-site but within the jurisdiction, and the collection of fees-in-lieu. Fees-in-lieu can be collected from multiple projects and used to finance larger stormwater retrofit projects.

The Critical Area regulations for IDAs require that designated Habitat Protection Areas be identified and conserved and promote the use of clustering of development to reduce the amount of impervious surfaces and increase the area of natural vegetation. There are no clearing limits and no lot coverage limits within IDAs; however urban forestry programs that minimize the destruction of forest and woodland vegetation and benefit water quality by controlling sediment, reducing runoff and removing nutrients are encouraged.

Limited Development Areas (LDAs)

Limited Development Areas (LDAs) are areas characterized by low or moderate intensity development, but that also contain areas of natural plant and animal habitats. Generally, the quality of runoff from these areas has not been substantially altered or impaired. In order for an area to be classified as LDA at the time it was mapped, it had to have housing density between one dwelling unit per five acres and four dwelling units per acre; have public water or public sewer or both; or have IDA characteristics but consist of fewer than 20 acres.

Within LDAs, the Critical Area regulations permit development and redevelopment that is consistent with the prevailing character of land use as determined by the jurisdiction. Local zoning regulations specify what uses and residential densities are permitted. The Critical Area regulations specify that development and redevelopment activities must maintain or improve water quality and conserve existing areas of natural habitat. These objectives are met through performance standards that address lot coverage, forest and developed woodland retention and replacement, construction on steep slopes, and stormwater management.

Lot coverage is defined as the percentage of a lot or parcel that is occupied by structures, parking areas, roads, walkways, pavers, gravel, or any man-made material. (Decks through which water passes freely do not count towards lot coverage calculations.) Generally, lot coverage is limited to 15 % of the parcel or lot, or of the subdivision or development project as a whole. For lots under one-half acre that were created prior to the effective date of the Critical Area regulations, lot coverage is limited to 25 % of the parcel or lot. (There are provisions that allow for additional lot coverage on small grandfathered lots subject to limits based on lot size and appropriate mitigation. The local government can provide specific information regarding theses allowances.)

Within LDAs, the retention and increase of forested areas is extremely important to the health of the Chesapeake Bay, Atlantic Coastal Bays, and all of their tributaries. Maintaining and increasing forest cover provides significant benefits including habitat enhancement, stormwater infiltration, shoreline stabilization, nutrient absorption, and water temperature mediation. The Critical Area regulations require that all development projects include the replacement of cleared forest cover in ratios ranging from 1:1 to 3:1, depending on the percentage of forest acreage cleared. When it is impossible to replace forest cover on the project site, local jurisdictions collect fees-in-lieu that are used to reforest other areas in the Critical Area or other locations beneficial to the Critical Area. In areas of new development or redevelopment, where no forest coverage existed prior to development, for example when a subdivision is platted on agricultural lands, 15% of the area must be planted with trees.

In order to protect water quality in LDAs by managing runoff and controlling erosion in LDAs, local Critical Area regulations prohibit development and disturbance in areas where slopes exceed 15%. In addition, stormwater treatment is required for most development projects in the LDA. Treatment measures may include infiltration, grassed swales, rain gardens, ponds, wetlands, and filtering devices.

Resource Conservation Areas (RCAs)

RCAs make up approximately 80% of the Critical Area and are characterized by natural environments or areas where resource-utilization activities are taking place. Resource-utilization activities include agriculture, forestry, fisheries activities, and aquaculture, which are considered “protective” land uses. In order for an area to be classified as RCA at the time it was mapped, the area would have been developed at a residential density less than one dwelling unit per five acres or be dominated by agricultural uses, wetlands, forests, barren land, surface water, or open space.

Because RCAs make up most of the Critical Area and provide the greatest opportunity for meeting the goals of the Critical Area Program, the land use regulations are the most restrictive. Within RCAs, new development is limited to residential uses and uses associated with resource utilization activities. In general, new commercial, industrial, and institutional uses are not permitted. Residential density is limited to one dwelling unit per 20 acres because studies have indicated that higher densities create patterns of development that are not compatible with maintaining habitat and protecting water quality. The regulations do not require 20-acre lots, and clustering of development is encouraged. Well-designed development at the 1-per-20 density is intended to ensure that RCAs maintain a natural character, allowing the continuation of resource related land uses while avoiding fragmentation of important areas of wildlife and plant habitat.

In order to conserve, protect, and enhance the ecological value of the land and water resources within the RCA and to protect biological productivity and diversity, there are performance standards for development. These performance standards address lot coverage, forest and developed woodland retention and replacement, construction on steep slopes, and stormwater management.

Lot coverage is defined as the percentage of a lot or parcel that is occupied by structures, parking areas, roads, walkways, pavers, gravel, or any man-made material. (Decks through which water passes freely do not count towards lot coverage calculations.) Generally, lot coverage is limited to 15% of the parcel or lot, or of the subdivision or development project as a whole. For lots under one-half acre that were created prior to the effective date of the Critical Area regulations, lot coverage is limited to 25% of the parcel or lot. (There are provisions that allow for additional lot coverage on small grandfathered lots subject to limits based on lot size and appropriate mitigation. The local government can provide specific information regarding theses allowances.)

Within the RCA, the retention and increase of forested areas is extremely important to the health of the Chesapeake Bay, Atlantic Coastal Bays, and all of their tributaries. Maintaining and increasing forest cover provides significant benefits including habitat enhancement, stormwater infiltration, shoreline stabilization, nutrient absorption, and water temperature mediation. The Critical Area regulations require that all development projects include the replacement of cleared forest cover in ratios ranging from 1:1 to 3:1, depending on the percentage of forest acreage cleared. When it is impossible to replace forest cover on the project site, local jurisdictions collect fees-in-lieu that are used to reforest other areas in the Critical Area or other locations beneficial to the Critical Area. In areas of new development or redevelopment, where no forest coverage existed prior to development, for example when a subdivision is platted on agricultural lands, 15% of the area must be planted with trees.

In order to protect water quality in RCAs by managing runoff and controlling erosion in RCAs, local Critical Area regulations prohibit development and disturbance in areas where slopes exceed 15%. In addition, stormwater treatment is required for most development projects in the RCA. Treatment measures may include infiltration, grassed swales, rain gardens, ponds, wetlands, and filtering devices.

The Critical Area Program also requires local governments to address agriculture, forestry, fisheries, and aquaculture uses through interagency coordination and the use of Soil Conservation and Water Quality Plans for farms, Timber Harvest and Forest Management Plans for forestry uses, and Water-Dependent Facilities regulations for fisheries and aquaculture.