Not all wetlands are as obvious as a stand of cattails in a concave depression. For wetland ecologists, farmed wetlands can be some of the most challenging areas to identify and delineate. Farmed wetlands are regulated by federal and state laws the same as any other wetland type, so it is important that they are delineated accurately. These types of wetlands often lack a natural plant community and soils can be frequently disturbed due to plowing, particularly during dry years. Hydrology is often seasonal and these wetland areas can sustain a healthy crop during drier years.
As required by the U.S. Army Corps of Engineers and the Wisconsin Department of Natural Resources (WDNR), wetland ecologists must first evaluate the potential for farmed wetlands by conducting off-site determinations using methods found in the 1998 USDA National Food Security Act Manual (Section 513.30c – Wisconsin Wetland Mapping Conventions). In addition to analyzing NRCS and WDNR wetland inventory maps, soils maps, topographic maps and spring aerial photography, annual crop slides obtained from the County Farm Service Agency (FSA) office are also reviewed. These aerial slides are typically taken during the month of July after crops have been planted. They are evaluated for “wetland signatures” and compared to historical climatological data to determine if antecedent conditions were considered “wet,” “normal” or “dry” prior to the dates of the aerial slides.
Wetland signatures can appear on the aerial crop slides as distinctive black or white areas indicating the presence of surface water, as bare soil or mudflats indicating a drowned-out crop, as different shades of green indicating hydrophytic vegetation, as yellow indicating crop stress, or as patches of greener color in “dry” years. The signatures can also be seen as differences in color due to different planting dates or isolated areas not farmed within the rest of the field. Hydrology requirements are met if greater than 50% of the aerial slides show wetness signatures in a specific location. Once it has been determined where farmed wetlands are likely to occur, these areas are formally verified in the field following methods in the 1987 Corps Wetland Delineation Manual.
If you have any questions related to farmed wetland determination/delineation procedures or if you need a wetland delineation conducted on your property, please contact one of raSmith’s professional wetland ecologists: Tina Myers at (262) 317-3389 or Theran Stautz at (608) 421-5317.