ABSTRACT
Wetlands are hydrologic buffers by virtue of their locations within landscapes and may serve a variety of buffer roles, including that of a water quality filter strip. Water quality buffer effectiveness (with respect to storm runoff from adjacent land) depends on the ability or propensity to (1) delay flow or reduce flow velocities through the buffer; (2) reduce or minimize the stream power of overland flow; (3) produce surface runoff; and (4) maintain particular biogeochemical conditions which are pollutant specific. In addition, for riparian buffers the relative proportion of water supplied from runoff from adjacent hillslopes vs. overbank flooding is a critical consideration. In general, wetlands are inferior to nonwetlands with respect to delaying flow and producing surface runoff. Wetlands are often superior for reducing stream power and may be more or less effective than nonwetlands with respect to specific biogeochemical conditions, depending on whether aerobic or anaerobic processes are required. This is demonstrated by comparing buffer effectiveness indices of hydric and nonhydric soils for 161 soil series of the Tar River basin, North Carolina. The water quality buffer values of wetlands derive primarily from their landscape setting and vegetated status, not from their hydrologic properties. Because wetlands may be poor buffers and are themselves often critical resources, wetlands themselves should be buffered in many cases.
