Multiple Watershed Scales Approach for Placement of Best Management Practices in SUSTAIN

Since 2003, the U.S. Environmental Protection Agency has been developing a decision support system for placement of best management practices (BMPs) at strategic locations in urban watersheds. This system is called the System for Urban Stormwater Treatment and Analysis INtegration (SUSTAIN). One dominant technical requirement for SUSTAIN is the ability to place management practices at multiple scales. To manage the complexity of larger watershed scale applications, SUSTAIN uses a tiered approach to evaluate both individual and multiple nested watersheds. In addition, for distributed BMPs in residential parcels of a new development or an existing neighborhood, SUSTAIN uses an optional lumped approach to aggregate BMPs by two generic BMPs, representing infiltration and storage processes. This paper describes the procedures for performing a tiered evaluation of BMPs at various spatial scales and aggregation of distributed BMPs. It illustrates framework features and performances through selected examples that are typical of the conditions and scenarios of watershed stormwater management. The tiered optimization implemented in SUSTAIN provides an efficient and manageable means for large watershed scale decision makings and allows users the flexibility in placing assessment points throughout a watershed where flow and pollutant load reduction goals are to be met.