Comprehensive Stream Physical Assessment and GIS Data Management Tools Support Fairfax County's Watershed Management Program

Fairfax County is currently undertaking a number of studies and projects related to watershed protection and restoration. These include the Stream Protection Strategy (SPS) program, a wetlands assessment and monitoring program, a perennial streams mapping project, and the development of comprehensive management plans for the County's watersheds. The SPS program is an ongoing biological monitoring effort with the overall goal of identifying and assessing trends in stream conditions County-wide. The baseline SPS study, completed in January 2001, documented current conditions throughout the County's streams on the basis of biological indicators and provided a foundation for prioritizing and implementing sound watershed management strategies.Building on the biological assessment in the SPS study, a physical habitat assessment of streams was conducted on 801 miles of streams County-wide. This abstract documents the physical habitat assessment data collection protocols and procedures used in the field, the GIS data management tools developed, and data summaries and analysis. As the data were compiled, the County has gained a thorough understanding of each stream and watershed, and will be able to integrate the data to anticipate, prevent, mitigate, and correct stormwater impacts in coordination with the County's land use goals. The addition of habitat information to the Stream Evaluation program will allow a more comprehensive assessment of the stream conditions. Stream aquatic integrity in urban settings is directly affected by physical changes in the watershed, some of which result in the degradation of the chemical and/or physical condition of the stream. Habitat information is extremely important for discriminating between physical and chemical effects. The habitat information can be integrated with the historic and ongoing biological and chemical data collected by Fairfax County to develop comprehensive tools that predict the effects of watershed changes on stream features and integrity.The following assessment protocols were developed and field teams assessed the conditon of about 806 miles of streams in the fall and winter of 2002:Characterizing stream and riparian zone habitat conditionsIdentifying erosion and pollution problems associated with infrastructure and other factorsMaking visual observations about general water quality conditionsClassifying stream shape based on geomorphic conditions, using the Channel Evolution ModelCollecting the data in uniform and standard process so they are accurate and reproducible This paper presents an overview of protocols used in the field, the QA/QC program applied to the data collection, and the GIS-based data management tool used to store and visualize the data. In addition, data summaries are presented, along with a preliminary assessment of results for the County's streams and correlations with watershed indicators and biological indicators.