Testing Wetland Delineation Indicators in New England Boulder Fields

Abstract : We evaluated the potential for regulating wet boulder fields as wetlands or other Waters of the US under Section 404 of the Clean Water Act. We monitored hydrology in two boulder fields in Maine during the 2011 growing season and documented the presence/absence of hydric soil, wetland hydrology, hydrophytic vegetation, and Ordinary High Water Mark (OHWM) indicators. The wetland hydrology criterion was statistically associated with the presence of primary hydrology indicator C4, hydric soils, FACU-dominated wetland, and a separation between the folist layer and the soil surface. The occurrence of hydrophytic vegetation and the combined use of primary and secondary hydrology indicators were not associated with the wetland hydrology criterion. Wet boulder fields should be delineated as wetland/nonwetland mosaics that contain problematic wetland types. We strongly suggest discontinuing the use of secondary hydrology indicators and primary indicator B8 (sparsely vegetated concave surface) in wet boulder fields. Alpha,alpha-dipyridyl paper strips are the most accurate method for determining if a primary hydrology indicator is present. We recommend applying this test several times over fourteen days. IRIS tubes and hydric soil indicators are reliable, but we suggest that alpha,alpha-dipyridyl paper strips be used to confirm a determination of nonhydric soil when a soil lacks a hydric soil indicator.