Best Practices

Communities are beginning to implement best practices that allow them to grow and develop with less impact to water quality and quantity. These best practices are based on model development principles compiled by the Center for Watershed Protection. These principles are described below. Links to examples of how communities are implementing these principles are included, too.

The Center for Watershed Protection convened a group of national experts to develop the model development principles. These experts came to consensus on twenty-two principles. The principles provide design guidance for economically viable, yet environmentally sensitive development. They provide a benchmark for planners, developers, and local officials who want to investigate where existing ordinances may be modified to reduce impervious cover, conserve natural areas, and prevent storm water pollution. These principles are not national design standards. Instead, they identify areas where changes to existing codes and standards can better protect streams, lakes and wetlands at the local level. Each principle is presented as a simplified design objective.

These principles are summarized in the Center for Watershed Protection’s, "Consensus Agreement on Model Development Principles to Protect Our Streams, Lakes and Wetlands" and are described in more detail in the "Better Site Design Handbook". Participants in the Site Planning Roundtable Management Training receive the Handbook and Consensus Agreement.

Communities are beginning to implement these principles, and through their development rules requiring their use. Go to the Communities’ Progress page on this website to see which communities are leading the way to implement best practices.

Site Planning Model Development Principles

The Center for Watershed Protection convened a group of nation experts. These experts came to consensus on twenty-two model development principles. These principles provide design guidance for economically viable, yet environmentally sensitive development. They provide a benchmark for planners, developers, and local officials who want to investigate where existing ordinances may be modified to reduce impervious cover, conserve natural areas, and prevent storm water pollution. These development principles are not national design standards. Instead, they identify areas where changes to existing codes and standards can better protect streams, lakes and wetlands at the local level. Each principle is presented as a simplified design objective.

These principles are summarized in the Center for Watershed Protection’s Consensus Agreement on Model Development Principles to Protect Our Streams, Lakes and Wetlands and described in more detail in their Better Site Design Handbook. Participants in the Site Planning Roundtable Management Training receive the Handbook and Consensus Agreement.

Communities are implementing these principles, and through their development rules requiring their use. Examples from communities are provided the following groups of best practices:

Street Design
The following set of model development principles reduce the amount of impervious cover associated with the road network in a community. They also encourage the treatment of runoff from streets using non-structural best practices.

Model Principle 1. Street Width
Design residential streets for the minimum required pavement width needed to support travel lanes; on-street parking; and emergency, maintenance, and service vehicle access. Base these widths on traffic volume.

Model Principle 2. Street Length
Reduce the total length of residential streets by examining alternative street layouts to determine the best option for increasing the number of homes per unit length.

Model Principle 3. Right-of-Way Width
Wherever possible, residential street right-of-way widths should reflect the minimum required to accommodate the travel-way, the sidewalk, and vegetated open channels. Utilities and storm drains should be located within the pavement section of the right-of-way wherever feasible.

Model Principle 4. Cul-de-sacs
Minimize the number of residential street cul-de-sacs and incorporate landscaped areas to reduce their impervious cover. The radius of cul-de-sacs should be the minimum required to accommodate emergency and maintenance vehicles. Consider alternative turnarounds.

Model Principle 5. Vegetated Open Channels
Where density, topography, soils, and slope permit, use vegetated open channels in the street right-of-way to convey and treat storm water runoff.

Parking Design
The following set of model development principles reduce the amount of impervious cover associated with parking in a community. They also encourage the treatment of runoff from parking areas using non-structural best practices.

Model Principle 6. Parking Ratios
Enforce the required parking ratio governing a particular land use or activity as both a maximum and a minimum in order to curb excess parking space construction. Review existing parking ratios for conformance taking into account local and national experience to see if lower ratios are warranted and feasible.

Model Principle 7. Parking Codes
Revise parking codes to lower parking requirements where mass transit is available or enforceable-shared parking arrangements are made.

Model Principle 8. Parking Lot Design
Reduce the overall imperviousness associated with parking lots by providing compact car spaces, minimizing stall dimensions, incorporating efficient parking lanes, and using pervious materials in spillover parking areas where possible.

Model Principle 9. Structured Parking
Provide meaningful incentives to encourage structured and shared parking to make it more economically viable.

Model Principle 10. Parking Lot Runoff
Wherever possible, provide storm water treatment for parking lot runoff using bioretention areas, filter strips, and/or other practices that are part of required landscaping areas and traffic islands.
 

Lot Design and Open Space
The following set of model development principles encourage denser development patterns and the preservation of open space. They reduce the amount of impervious cover in a development.

Model Principle 11. Open Space Developments
Advocate open space design development incorporating smaller lot sizes to minimize total impervious area, reduce total construction costs, conserve natural areas, provide community recreational space, and promote watershed protection .

Model Principle 12. Setbacks and Frontages
Relax side yard setbacks and allow narrower frontages to reduce total road length in the community and overall site imperviousness. Relax front setback requirements to minimize driveway lengths and reduce overall lot imperviousness.

Model Principle 13. Sidewalks
Promote more flexible design standards for residential subdivision sidewalks. Where practical, consider locating sidewalks on only one side of the street and providing common walkways linking pedestrian areas.

Model Principle 14. Driveways
Reduce overall lot imperviousness by promoting alternative driveway surfaces and shared driveways that connect two or more homes together.

Model Principle 15. Open Space Management
Clearly specify how community open space will be managed and designate a sustainable legal entity responsible for managing both natural and recreational open space.

Rooftop Runoff - Examples
Model Principle 16. Rooftop Runoff
Direct rooftop runoff to pervious areas such as yards, open channels, or vegetated areas and avoid routing rooftop runoff to the roadway and the storm water conveyance system.

Buffers - Examples
Model Principle 17. Aquatic Buffers
Create a variable width, naturally vegetated buffer system along all perennial streams that also encompasses critical environmental features such as the 100-year floodplain, steep slopes and freshwater wetlands.

Model Principle 18. Buffer Maintenance
The riparian stream buffer should be preserved or restored with native vegetation. Maintain the buffer system through the plan review delineation, construction, and post-development stages.


Tree and Natural Vegetation Conservation
Model Principle 19. Clearing and Grading
Clearing and grading of forests and native vegetation at a site should be limited to the minimum amount needed to build lots, allow access, and provide fire protection. Manage fixed portion of any community open space as protected green space in a consolidated manner.

Model Principle 20. Tree Conservation
Conserve trees and other vegetation at each site by planting additional vegetation, clustering tree areas, and promoting the use of native plants. Wherever practical, manage community open space, street rights-of-way, parking lot islands, and other landscaped areas.Incentives

Model Principle 21. Conservation Incentives
Incentives and flexibility in the form of density compensation, buffer averaging, property tax reduction, storm water credits, and by-right open space development should be encouraged to promote conservation of stream buffers, forests, meadows, and other areas of environmental value. In addition, off-site mitigation consistent with locally adopted watershed plans should be encouraged.Storm Water Outfalls

Model Principle 22. Storm Water Outfalls
New storm water outfalls should not discharge unmanaged storm water into jurisdictional wetlands, sole-source aquifers, or sensitive areas.his workshop is currently being developed.