BALANCING NEW DEVELOPMENT REQUIREMENTS AND RETROFIT OF EXISTING DEVELOPMENT IN URBAN WATERSHED MANAGEMENT
Abstract:Gwinnett County's Watershed Protection Plan represents the culmination of a two-year watershed assessment and modeling project. As part of the project, an integrated assessment of the habitat, biological community, water quality, and pollutant loadings in the streams was used to assess both the current and the future impacts on the streams and their uses. The BASINS modeling framework was used to model the watersheds under existing and future land use conditions. The integrated assessment of these impacts was the key to developing an effective, efficient watershed protection and improvement strategy.
The Watershed Protection Plan incorporated a three-pronged approach to protecting and improving the county's watersheds:
New development requirements are implemented to protect watersheds from degradation.
Improving previously affected areas will allow aquatic integrity to improve.
Related activities that improve the effectiveness and scope of watershed improvement (such as conservation zoning, stream buffers, maximum limits on parking spaces, etc.) are recommended.
The focus of this paper is on balancing new development requirements and improvement of previously developed areas.
In areas where water quality criteria provide little practical guidance for developing watershed protection plans, statistical relationships between biotic integrity (benthos, fish, and habitat scores) and pollutant loadings for key parameters in kg/ha/yr (lb/ac/yr) were used to develop watershed improvement guidelines. An automated spreadsheet analysis tool (WISE) was used to facilitate this analysis and allow interactive evaluation with the county and citizens' group.
There are three basic strategies available for new development requirements: voluntary, proscriptive, and performance-based. Because performance-based strategies provide needed protection as well as maximum flexibility for the development community, the focus of this strategy is performance-based. An approach is presented that is simple to use and encourages site design that takes advantage of the natural site amenities and minimizes impervious surfaces. Options are provided for implementing BMPs on the site and delineating the tributary drainage area to each BMP. The form automatically graphs and compares the uncontrolled and controlled loading rates to the performance criterion. This tool can be used iteratively in the site design process.
The approach to retrofit of existing development is based on prioritization of impacted areas, reconnaissance to identify options and opportunities, evaluation of options, and implementation of improvements.
Document Type: Research Article
Publication date: January 1, 2000
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