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Water: Best Management Practices


Minimum Measure: Post-Construction Stormwater Management in New Development and Redevelopment

Subcategory: Municipal Program Elements

Zoning is a classification scheme for land use planning. Zoning can serve numerous functions.  It can help mitigate stormwater runoff problems by facilitating better site designs. By applying the right zoning technique, development can be targeted at specific areas, limiting development in and providing protection for the most important land conservation areas.

There are numerous types of zoning techniques for better site design.  They include watershed-based zoning, overlay zoning, floating zones, incentive zoning, performance zoning, urban growth boundaries, large lot zoning, infill/community redevelopment, transfer of development rights, and limiting infrastructure extensions. Table 1 describes each of these zoning techniques and its utility.

Table 1. Zoning techniques (Source: Caraco et al., 1998)

Land Use Planning Technique


Utility as a Watershed Protection Technique

Watershed-Based Zoning

Watershed and subwatershed boundaries are the foundation for land use planning.

Protects receiving water quality on the subwatershed scale by relocating development outside of particular subwatersheds.

Overlay Zoning

Superimposes additional regulations or specific development criteria within specific mapped districts.

Requires development restrictions or allows alternative site design techniques in specific areas.

Impervious Overlay Zoning

Specific overlay zoning that limits total impervious cover within mapped districts.

Protects receiving water quality at both the subwatershed and site level.

Floating Zones

Applies a special zoning district without identifying the exact location until land owner specifically requests the zone.

Obtains proffers or other watershed protective measures that accompany specific land uses within the district.

Incentive Zoning

Applies bonuses or incentives to encourage creation of amenities or environmental protection.

Encourages development within a particular subwatershed or to obtain open space in exchange for a density bonus at the site level.

Performance Zoning

Specifies a performance requirement that accompanies a zoning district.

Requires additional levels of performance within a subwatershed or at the site level.

Urban Growth Boundaries

Establishes a dividing line that defines where a growth limit is to occur and where agricultural or rural land is to be preserved.

Used in conjunction with natural watershed or subwatershed boundaries to protect specific waterbodies.

Large Lot Zoning

Zones land at very low densities.

Decreases impervious cover at the site or subwatershed level, but may have an adverse impact on regional or watershed imperviousness.

Infill/Community Redevelopment

Encourages new development and redevelopment within existing developed areas.

Used in conjunction with watershed-based zoning or other zoning tools to restrict development in sensitive areas and foster development in areas with existing infrastructure.

Transfer of Development Rights (TDRs)

Transfers potential development from a designated "sending area" to a designated "receiving area."

Used in conjunction with watershed-based zoning to restrict development in sensitive areas and encourage development in areas capable of accommodating increased densities.

Limiting Infrastructure Extensions

A conscious decision is made to limit or deny extending infrastructure (such as public sewer, water, or roads) to designated areas to avoid increased development in these areas.

A temporary method to control growth in a targeted watershed or subwatershed. Usually delays development until the economic or political climate changes.


The type of zoning to apply will depend on management goals. If water or land quality is a primary goal of the zoning technique, then watershed-based zoning can provide a comprehensive approach. At the same time, incentive zoning, performance zoning, and transfer of development rights can be used as protection measures for specific conservation areas.


Watershed-Based Zoning: Watershed-based zoning can employ a mixture of land use and zoning options to achieve desired results. A watershed-based zoning approach should include the following nine steps:

  • Conduct a comprehensive stream inventory.

  • Measure current levels of impervious cover.

  • Verify impervious cover/stream quality relationships.

  • Project future levels of impervious cover.

  • Classify subwatersheds-based on stream management "templates" and current impervious cover.

  • Modify master plans/zoning to correspond to subwatershed impervious cover targets and other management strategies identified in Subwatershed Management Templates.

  • Incorporate management priorities from larger watershed management units such as river basins or larger watersheds (see discussion later in this fact sheet).

  • Adopt specific watershed protection strategies for each subwatershed.

  • Conduct long-term monitoring over a prescribed cycle to assess watershed status.

Overlay Zoning: The advantage of overlay zones is that specific criteria can be applied to isolated areas without the threat of being considered spot zoning. Overlay districts are not necessarily restricted by the limits of the underlying base zoning. An overlay zone may take up only a part of an underlying zone or may even encompass several underlying zones. Often the utilization of an overlay zone is optional.

Impervious Overlay Zoning: This type of overlay zoning limits future impervious areas. The environmental impacts of future impervious cover are estimated and a limit is set on the maximum imperviousness within a given planning area. Site development proposals are then reviewed in the context of an imperviousness cap. Subdivision layout options must then conform to the total impervious limit of the planning area.

Floating Zones: Normally, a parcel of land will not qualify for the application of the floating zone district unless it is large enough to allow the buffering of its development from the surrounding area. It is important to note that the existence of a floating zone district does not automatically grant rezoning to each landowner whose property complies with the prescribed conditions. Each property owner must have his or her application for rezoning reviewed and approved by the local governing body to determine if it is consistent with a comprehensive development plan.

Incentive Zoning: This planning technique relies on bonuses or incentives for developers to encourage the creation of certain amenities or land use designs. A developer is granted the right to build more intensively on a property or given some other bonus in exchange for an amenity or a design that the community considers beneficial. Developers stand to gain an increase in profits from the more intensive use of the property, while a community might use incentive zoning to promote more compact development, encourage open space designs, or generate other desired amenities such as trails, parks, or totlots.

Performance Zoning: Performance zoning is a flexible approach that has been employed in a variety of fashions in several different communities across the country. Some performance factors include traffic or noise generation limits, lighting requirements, stormwater runoff quality and quantity criteria, protection of wildlife and vegetation, and even architectural style criteria.

Urban Growth Boundaries: Urban growth boundaries are sometimes called development service districts and include areas where public services are already provided (e.g., sewer, water, roads, police, fire, and schools). The delineation of the boundary is very important. Several important issues to consider in establishing an urban growth boundary include the following:

  • Public facilities and services must be nearby and/or can be provided at reasonable cost and in a specific time frame.

  • A sufficient amount of land to meet projected growth over the planning period must be provided.

  • A mix of land uses must be provided.

  • The potential impact of growth within the boundary on existing natural resources should be analyzed.

  • The criteria for defining the boundary needs to be fair and should consider natural features (versus man-made features) wherever possible. The use of watershed boundaries as the urban growth boundary is one such natural feature.

Large Lot Zoning: Although large lot zoning tends to reduce impervious cover and therefore the amount of stormwater runoff at a particular location, it also spreads development over vast areas. The road networks required to connect these large lots can actually increase the total amount of imperviousness created for each dwelling unit (Schueler, 1995). In addition, large lot zoning contributes to regional sprawl. Sprawl-like development increases the expense of providing community services such as fire protection, water and sewer systems, and school transportation.

Infill/Community Redevelopment: Infill and redevelopment can be employed both in large or small projects. Impediments to more widespread implementation of these types of projects include the existing condition of a potential redevelopment site in terms of environmental constraints, land use regulations, and pressing social and economic issues. Local governments may need to modify local zoning or building codes to make infill and redevelopment more attractive to developers. In addition, citizen involvement has been demonstrated to be a vital catalyst for leveraging funding or revising codes. Furthermore, lending institutions must be progressive in their view of funding infill and redevelopment projects. One possibility is to partner with local governments or community organizations.

Transfer of Development Rights (TDRs): The principle of TDRs is based on the premise that land ownership entails certain property rights. While some of these rights may be restricted by zoning, building codes, and environmental constraints, landowners are "entitled" to use their land for the "highest and best use." TDRs are based on a market-driven incentive program where it is possible to sell development potential (zoned density) without buying or selling land. Landowners in preservation areas are compensated for lost development potential , while conventional down-zoning deprives landowners of this potential value.


Some zoning techniques may be limited by economic and political acceptance and should be evaluated on these criteria as well as stormwater management goals.

Maintenance Considerations

Some maintenance issues to consider for the long term are the following:

  • What are the most economically and politically acceptable zoning technique(s) that can be used to shift or reduce impervious cover among the subwatersheds?

  • How accurate are the estimates of the amount and location of future impervious cover in the watershed? Are better projections needed?

  • Will future increases in impervious cover create unacceptable changes to a watershed and/or subwatershed?

  • Which subwatersheds appear capable of absorbing future growth in impervious cover?

There are numerous case studies of performance-based zoning used in different communities. Some of these examples are summarized in Table 2.

Table 2. Case examples of performance-based zoning (Source: Porter et al., 1991)


Performance Zoning Provisions


Fort Collins, Colorado

Planned Unit Development (PUD) options are applied to all parcels in city. Developers may choose conventional zoning or the optional PUD. PUD proposals must meet a point value for an absolute criterion and a relative criterion.

Applications are discussed at a conceptual stage, when suggestions are made to improve scores. The local planning board uses its considerable discretion to require special conditions.

Largo, Florida

The Land Use Plan defines uses and densities. Four overlay "policy" districts (environmental conservation, management, redevelopment, and downtown) define general standards and prohibited uses. Each land use within a policy district falls into a one of three classes (allowable, allowable with special mitigating measures, or prohibited).

A variety of uses are permitted within the 4 policy districts when applying the special mitigating measures. The city also has a five-tiered system of review and approval that facilitates fast reviews for many common applications and a more involved process for projects that require mitigation.

Hardin County, Kentucky

The land development ordinance allows agricultural and single family uses by right. All other uses must be evaluated in a three-step process. In the first step, the agricultural and development potential is evaluated using a point system. If the site scores a minimum threshold value, it moves onto the second step, a compatibility assessment. The final step involves typical review of subdivision standards and requirements.

The program places a special emphasis on preserving agricultural uses. The process involves a unique feature that calls on citizen consensus for each step. This decision making process might be considered highly discretionary, but with a widespread interest by most Hardin County citizens in seeing development proceed, there have been few complaints.

Bath Charter Township, Michigan

The township's ordinance provides five zoning districts: two traditional districts for rural, low-density residential; and three applied to existing settlements or expected development corridor. These three districts allow a range of uses either "by right" or with special permits for certain uses.

The ordinance is a compromise between complex, inflexible zoning and no zoning at all. The process allows for extensive review and individual decisions for individual controversial cases.

Buckingham Township, Pennsylvania

The ordinance contains typical zoning districts but provides cluster and performance standard development provisions. It aims to preserve natural resources by clustering housing on the least environmentally sensitive areas.

Development of cluster and performance standards are "by rights," and as such do not require public hearings. The sensitivity of natural areas makes the zoning more flexible in unrestricted areas but less flexible than most conventional zoning in placing restrictions for protecting natural areas.

Duxbury, Massachusetts

Two new categories of development (planned developments and cluster) were created in addition to existing traditional zoning. Both types are allowed in different portions of the town under a special permit process.

Termed "impact zoning," the ordinance aimed to create incentives for developers to build more diverse and environmentally sensitive housing. Developers are choosing standard subdivisions over the optional techniques to avoid lengthy and complex reviews.

Cost Considerations

Subwatershed planning for better site design zoning involves many costs. Mapping, photography, delineations, and public involvment are some of the items typically found in such a budget (Table 3).

Table 3. Unit prices for subwatershed planning (Adapted from CWP, 1998)

Budget Item

Estimated Unit Cost


Aerial Photography

$500 per photo

Includes aerial flyover and developing of one color photographs.

Base Mapping


For Subwatershed Management Map using USGS 7.5 minute Quad. Sheet. Includes, subwatershed delineation, overlaying land use, monitoring stations, and transportation routes.

Base Mapping


For Aquatic Corridor Management Map, using aerial topography at 2' contour interval. Includes, aerial topography at 1" = 200', locating existing utilities, floodplain, wetlands, and riparian cover from existing maps (no field walk and no topo. survey control).

Floodplain Delineation


Detailed analysis beyond FEMA, cross-sections plotted at 1000 ft on-center, topo spot-checked, road crossings evaluated, includes report, assumes flow data are available.

Geographic Information System (GIS)start-up


High end work station and software (e.g., ARC/INFO), includes approx. 2 weeks of training for operator. Does not include data layers

GIS Obtain or Digitize Data Layers


Data layers include impervious cover, topography (5' C.I.), zoning, utilities, vegetative cover (broad categories)

Impervious Cover Measurement Actual


Uses digital orthophotography, impervious layer clipped at subwatershed boundary, algorithm to calculate impervious area

Impervious Cover Estimation Land Use


Uses land use designations or zoning and measured areas compared against tables, requires review of aerial photo (not included) to estimate build-out.

Impervious Cover Projection Based on Future Land Use


Uses zoning or master plan and measured areas compared against tables, requires assessment of future build-out

Public Attitude Survey

$15,000 per survey

1000 homes contacted by telephone, includes survey questionnaire preparation and data analysis.

Stakeholder Involvement Program


Plan and hold four public and four community meetings, direct mail to 20,000 people, staff time and direct expenses included.


Caraco, D.S., R.A. Claytor, P.M. Hinkle, H.Y. Kwon, T.R. Schueler, C.P. Swann, S. Vysotsky, and J. Zielinski. 1998. Rapid Watershed Planning Handbook: A Comprehensive Guide for Managing Urbanizing Watersheds. Center for Watershed Protection, Inc., Ellicott City, MD.

Porter, D.R., P.L. Phillips, T.J. Lassar. 1991. Flexible Zoning: How it Works. Urban Land Institute, Washington, DC.

Schueler, T.  1995.  Site Planning for Urban Stream Protection.  Metropolitan Washington Council of Governments, Washington, DC. 

Information Resources

Easley, G. 1992. Staying Inside the Lines: Urban Growth Boundaries. American Planning Association, Chicago, IL.

Kendig, L., S. Connor, C. Byrd, and J. Heyman. 1973. Performance Zoning. American Planning Association, Chicago, IL.

Lerable, C. 1995. Preparing a Conventional Zoning Ordinance. Planning Advisory Service, Chicago, IL.

Meshenberg, M.J. 1976. The Administration of Flexible Zoning Techniques. American Planning Association, Chicago, IL.

Murphy, M. and J. Stinson. 1997. Incentive Zoning. Pace University School of Law, White Plains, NY.

Northeastern Illinois Planning Commission. 1988. Model Stream and Wetland Protection Ordinance for the Creation of a Lowland Conservancy Overlay District. Northeastern Illinois Planning Commission, Chicago, IL.

Planning Commissioner Service. 1996. Innovative Controls for Land Use Regulation. American Planning Association, Chicago, IL.

Rahenkamp Sachs Wells and Associates, Inc. and the American Society of Planning Officials. 1977. Innovative Zoning: A Local Official's Guidebook. U.S. Department of Housing and Urban Development, Office of Policy Development and Research, Washington, DC.

Simons, R.A. 1998. Turning Brownfields into Greenbacks. Urban Land Institute, Washington, DC.

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