A Stream-Wetland-Riparian (SWR) Index for Assessing Condition of Aquatic Ecosystems in Small Watersheds along the Atlantic Slope of the Eastern U.S.

Robert P. Brooks 1, Mary McKenney-Easterling 1, Mark M. Brinson 2, Richard Rheinhardt 2, Kirk Havens 3, David O’Brien 3, Joseph A. Bishop 1, Jennifer M. Rubbo 1, Brian Armstrong 1 and Jeremy Hite 1

1 Penn State Cooperative Wetlands Center, Department of Geography, Pennsylvania State University, University Park, Pennsylvania
2 Department of Biology, East Carolina University, Greenville, North Carolina
3 Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, Virginia

As part of a regional study by the Atlantic Slope Consortium (ASC) to develop ecological and socioeconomic indicators of aquatic ecosystem condition, we developed and tested a protocol for rapidly assessing condition of the stream, wetland, and riparian components of freshwater aquatic ecosystems. Aspects of hydrology, vegetation, in-stream and wetland characteristics, and on-site stressors were measured in the field. The resulting metrics were used to develop an index of overall condition, termed the Stream-Wetland-Riparian (SWR) Index. Values of this Index were compared to existing biotic indices and chemical measures, and to a separate Landscape Index created using satellite-based land cover data and a geographic information system (GIS). Comparisons were made at several levels of spatial aggregation and resolution, from site to small watershed. The SWR Index and Landscape Index were shown to correlate highly with biological indicators of stream condition at the site level and for contributing subwatersheds. Aggregating these site-level values to the whole watershed should be interpreted with caution. We suggest a top-down approach that managers can use to sequentially apply these methods, to first prioritize watersheds based on the Landscape Index and then assess condition and diagnose stressors at the subwatershed and site level using the SWR Index.

Keywords: stream, riparian, wetland, watershed, indicators, Mid-Atlantic Region