Water: Best Management Practices
Subcategory: Innovative BMPs for Site Plans
Development districts (or in some cases special zoning districts) are zoning districts created for the purpose of permitting property development. Development districts are characterized by larger site areas (typically 5 or more acres), and their construction requires complex and coordinated rezoning, transportation, and planning efforts. Examples of special zoning districts include, but are not limited to:
- Transit Oriented Development districts (TOD),
- Business Improvement Districts (BIDs),
- Traditional Neighborhood Designs (TNDs),
- Brownfields redevelopment projects and
- Main Street Revitalization Districts.
A development district's stormwater handling performance is typically assessed at the site, neighborhood, and regional (or watershed) levels. While the construction of a development district may involve a higher percentage of imperviousness than surrounding or conventional patterns, satisfying development needs on a smaller footprint brings benefits. In addition, the coordinated planning effort can help identify strategic opportunities for infiltration, stormwater recapture, and treatment.
A city, county or township's Planning or Zoning Department usually develops plans for development districts. Stormwater managers may need to meet with planning counterparts to coordinate plans, since common, stand-alone elements found in stormwater management plans for individual site plans, such as site coverage limitations, infiltration requirements, and rules discouraging sidewalks can run counter to the urban design elements of successful development districts.
Development districts can be large redevelopment efforts, infill projects, or new "greenfields" projects. The regional applicability is strong since successful development districts coordinate multiple objectives, including environmental protection and stormwater control. These districts also tend to handle more development intensity and mix of uses on a smaller footprint, and thus they also have applicability for watershed planning and source water protection.
Although land constraints and large developable sites can be a challenge, certain types of development district planning, such as transit oriented development and business improvement districts are common in urban areas.
Since urban projects are mainly redevelopment projects, stormwater retrofits of both older "gray" infrastructure and urban "green" techniques can be included in redevelopment planning. For retrofits, cities should consider offering a flexible menu of approaches to meet the variety of unexpected site constraints found in highly developed urban areas.
Siting and Design Considerations
As noted above, development districts can be incorporated anywhere. One main consideration for rural areas might be a lack of zoning or other land use classification. Subdivision regulations or drainage district requirements may impede plans to establish a mix of uses or higher densities.
The design of a development district will determine its environmental performance. When considering a development proposal's stormwater and water-quality attributes, look for these themes:
Compact project and community design: A powerful strategy for reducing a development's footprint, and hence its stormwater impact, is to focus on compact development. Reducing an individual building's footprint can also be a strategy, though there are circumstances that call for greater lot coverage in districts where higher development intensity is needed (for example, near transit stations). Compact development also lends itself to more environmentally friendly transportation options, such as walking and biking, or shorter and less frequent automobile trips.
Street Design and Transportation Options: Well designed, compact communities are served by a highly connected street and trail system designed for multiple modes of transportation. The pattern need not be a grid; in some areas, topography and environmentally sensitive areas will influence where roads go. A compact district also provides for more efficient use (and reuse) of infrastructure.Mix of Uses: A community's transportation options increase when jobs, housing and commercial activities are located close together. Efficiencies for providing infrastructure emerge. Fewer auto trips reduce the need to accommodate standard parking requirements. Mixing daytime and nighttime uses increase the opportunities for businesses to share parking spaces.
As noted above, development districts can be sited almost anywhere. For urban areas, look for designs that re-use existing impervious surface and infrastructure, and provide opportunities to repair infrastructure or handle water on-site.
For conservation subdivisions or designs, look closely at the connections among transportation, community services, and jobs. The water benefits of conservation clustering can be negated if the new housing becomes part of a development pattern that includes dispersed uses, demands for upgrades to urban-level services and transportation, and a lack of connections among infrastructure elements.
During the site design process, pressures may develop to eliminate elements critical to a development district's environmental performance. For example, a successful development district will shorten, combine, or eliminate auto trips. However, if pressure mounts to increase parking or decrease connections among uses, a city or county may be unable to reduce the amount of impervious surfaces, diminishing transportation and water benefits.
If the stormwater regulations for redevelopment districts are more stringent than those for greenfields, then cities may find it difficult to attract developers. Rules for water protection and stormwater should be consistent watershed-wide.
Traditional community designs are more compact and connected than conventional community designs. Mixed uses provide for more walking trips instead of car trips, which reduce the need for additional traffic lanes and parking spaces. At the neighborhood or watershed scale, less impervious surface is created and more natural areas are left undeveloped. Conventional community designs generally consume more land per unit, are less connected, and separate land uses, thereby leading to more car trips and to more road and parking infrastructure. At the neighborhood or watershed scale, more impervious surface has been created even though at the site level, the percentage of imperviousness may be less. In addition, fewer natural areas have been protected.
Various design elements will direct a development district's maintenance plan, although it is likely to include a combination of BMPs. Comprehensive plans include common urban design elements like tree-lined streets, water features, and landscaping. Planners and stormwater professionals should look to these features to achieve urban design and water quality goals, and plan their maintenance procedures accordingly.
A development district's effectiveness can be viewed at the site, neighborhood, and watershed levels. Redevelopment can significantly reduce the demand for new development elsewhere in the watershed. Designs that repair existing infrastructure and treat stormwater on-site are particularly beneficial. Where urban redevelopment occurs on open lots that serve a stormwater handling function, the city and the developer will need to assess the impacts neighborhood-wide and mitigate accordingly.
Clustering, open space, and other "green" designs offer stormwater and water quality benefits to communities considering new housing developments. However, the site's design needs to be combined with watershed and regional planning designs that curb uncontrolled, large-scale growth. It's important to consider neighborhood and watershed outcomes. Will new conservation development spur unplanned development? Does conservation development compliment the community's overall conservation goals? How does the new development relate to jobs, schools, and services?
The costs of developing and implementing coordinated development districts vary. The primary drivers of these costs are: consultant and staff time to develop or align plans; repairing or establishing water, sewer, and transportation infrastructure; and any incentives a city, county, or township provides to developers or public/private partnerships.
For developers, costs can vary from a conventional site plan dependent upon the combinations of BMPs and the relative cost of a more complex site development plan. However, many redevelopment projects command a premium market price due to their location or enhanced desirability.
Combinations of Policies and Best Management Practices to Support Development Districts
A development district's environmental performance is supported by a combination of BMPs. These include traditional stormwater BMPs, emerging stormwater BMPs, and land development policies not traditionally viewed as stormwater BMPs. The following section is not meant to establish a rigid menu of BMPs, but rather offer examples of mutually supportive BMPs. The selection process will also depend on the pollutant control required, as well as other water quality and quantity imperatives such as TMDLs or downstream flooding. The Resources section provides links to detailed information on a range of BMPs.
Urban development and redevelopment projects are more likely to be served by heavier transit (i.e. subways and established bus lines), follow a traditional street pattern, and be governed by a complex set of existing land development requirements.
Municipalities can use a combination of policies to promote desired densities. Some of these policies include the following:
- Transfer of development rights receiving zones - A system in which a landowner in a "preservation area" or "sending zone" gets credits for foregoing development rights, credits that he can sell or have a 'bank' consolidate. Developers can buy and use these credits to gain permission for denser development in "receiving zones," which are areas targeted for denser development.
- Allow creation of bonus densities, which allow developers who agree to complete projects or project additions that meet specific goals to increase density
- Create mixed use zoning,
- Create form-based zoning codes,
- Modify parking policies that, for example, create a maximum number of parking spaces allowed and have better management of on-street parking,
- Create sidewalk improvement programs,
- Encourage micro-detention stormwater handling areas such as use of rain gardens or stormwater BMPs that serve multiple purposes (i.e., Green Roofs),
- Encourage street tree canopy programs,
- Create financial incentives (e.g., tax-increment financing, vacant property reform),
- Enact or promote programs to enhance transit use (customized information, employer assistance),
- Enact rehabilitation codes for older buildings, proprietary devices (e.g., in-pipe filtration devices),
Suburban development districts are likely to take advantage of existing development and infrastructure, and require connections among older developed areas. In addition to some of the policies in urban settings, planners and developers in suburban settings could consider the following BMPs and policies to aid in protecting water resources:
- Promote Grayfields programs to redevelop underperforming malls and strip malls,
- Create highway corridor redevelopment programs,
- Enhance retail and housing districts around park and ride lots,
- Adopt smart growth street design standards at local and state level,
- Establish infill policies,
- Adopt traditional neighborhood design manuals that integrate transportation,
Rural development districts are likely to occur on undeveloped or sparsely developed land. Successful rural development districts will complement or spur rural employment opportunities, such as agriculture, manufacturing, or warehousing and distribution. In order to protect water resources on a regional scale, planners should encourage conservation of rural settings to offset increased impervious areas in urban and suburban settings.
Several policies that encourage economic development while retaining rural character include:
- Create transfer of development rights sending zones,
- Establish water protection overlay zones,
- Connect housing with rural job and transportation centers,
- Create watershed-wide impervious surface trading programs,
- Create design manuals for rural housing or housing in environmentally sensitive areas,
- Encourage "Main Street" redevelopment programs in older downtowns.
Detailed information describing many of these policies can be found in Protecting Water Resources with Smart Growth (120 pp, 1.4MB, About PDF). An additional recommended resource describing these policies is Getting to Smart Growth: 100 Policies for Implementation (104 pp, 2MB, About PDF) .
Emeryville, California. 1997. Design Guidelines for Green, Dense Redevelopment. [http://www.ci.emeryville.ca.us/planning ]. Accessed April 25, 2006. (Emeryville California has developed design guidelines for highly urbanized areas with limited opportunities for infiltration.)
EPA. Brownfields Cleanup and Redevelopment. [http://www.epa.gov/swerosps/bf/index.html]. Last updated April 25, 2006. Accessed April 25, 2006.
EPA. Smart Growth. [http://www.epa.gov/smartgrowth]. Last updated March 31, 2006. Accessed April 25, 2006.
EPA. Protecting Water Resources with Smart Growth. [http://www.epa.gov/smartgrowth/water_resource.htm]. Last updated April 25, 2006. Accessed April 25, 2006.
Metropolitan Council. 2003. Urban Small Sites Best Management Practice Manual. [http://www.metrocouncil.org/environment/Water/BMP/manual.htm ]. Accessed April 25, 2006.
National Trust for Historic Preservation. 2006. Main Street: Revitalizing Your Commercial District. [http://www.mainstreet.org/ ]. Accessed April 25, 2006.
Planning Commissioners Journal. PlannersWeb: City & Regional Planning Resources. [http://www.plannersweb.com ]. Accessed April 25, 2006. (This site contains information on transfer of development rights programs, including examples, common challenges and resources.)
State of Oregon. Water Quality Model Code and Guidebook. [http://egov.oregon.gov/LCD/docs/publications/wqgb chapter4dsnstan.PDF (30 pp, 203K, About PDF) ]. Accessed April 25, 2006. (The state of Oregon has a created a design manual for development districts, which can serve as a base example for developing a joint smart growth and stormwater design manual.)