APPLICATION OF A GIS DECISION SUPPORT TOOL TO URBAN WATERSHED MANAGEMENT IN FULTON COUNTY, GEORGIA

The authors are responsible for developing stormwater and water quality master plans for Sandy Springs, a highly developed suburban area northwest of Atlanta. The high density of development reduces opportunities for new, areawide BMPs such as large detention ponds and suggests instead a retrofit program using multiple on-site or local BMPs (e.g. residential cisterns, instream flow control structures). We have developed an ArcView GIS application named LORELEI to rapidly develop and compare management alternatives for catchments with hundreds of BMPs. LORELEI provides decision support through four main activities:Data management. LORELEI is used to store data about potential BMP locations and associated drainage area, costs, types, and effectiveness along with “standard” geographic information such as natural features, watershed delineations, parcel maps, etc. The data structure supports the “BMP train” concept by including parent-child relationships, allowing the development and evaluation of complex series of BMPs to prevent or mitigate stormwater impacts.Scenario development. LORELEI provides a convenient environment for developing scenarios with different combinations of BMPs. The program allows the rapid selection of both individual projects and entire categories of BMPs. “BMP trains” can be used to build scenarios starting with low cost, high yield BMPs and testing program performance at each step along the train-building process. Citizen preferences can be built in to the train-building process and the cost-impact of these preferences quickly determined.Scenario evaluation. LORELEI estimates and compares scenario costs and benefits. Sensitivities can be quickly determined by adjusting expected performance or cost.Enhanced involvement and understanding. LORELEI uses the geographical context provided by GIS to give stakeholders and decision makers the opportunity to participate directly in development of scenarios, and to provide a clear picture of issues, components, and cost and benefit implications of different management scenarios. Its straightforward data handling and GIS linkages allow real-time finetuning of proposed scenarios during public meetings to determine the cost or performance impact of participants' suggestions.