Placement of Riparian Forest Buffers to Improve Water Quality

Riparian forest buffers can improve stream water quality, provided they intercept and remove contaminants from surface runoff and/or shallow groundwater. Soils, topography, hydrology, and surficial geology determine the capability of forest buffers to intercept and treat these flows. This paper describes landscape analysis techniques for identifying and mapping locations where forest buffers can effectively improve water quality. One technique employs soil survey and climate information to rate soil map units for how effectively a buffer would treat runoff. Results can be used to compare map units for relative effectiveness of buffer installations to improve water quality and, accordingly, to prioritize locations to support buffer establishment. Within watersheds, another technique uses topographic and stream-flow information to help identify specific locations where buffers are more likely to intercept water moving towards streams. For example, a wetness index, an indicator of potential soil saturation based on terrain, identifies where buffers can readily intercept surface runoff and/or shallow groundwater flows. Maps based on this index can be useful for site-specific buffer placement at farm and small-watershed scales. A case study utilizing this technique shows that riparian forests likely have the greatest potential to improve water quality along first-order streams, rather than larger streams. Some locations are better than others for improving water quality using riparian forest buffers. These landscape analysis techniques use public data and produce results that are broadly applicable to identify priority areas for riparian buffers. The information can guide projects and programs at scales ranging from farm-scale planning to regional policy implementation.