Primary purpose
To rate freshwater wetlands when making decisions regarding 401 Water Quality Certifications. Also, described as a tool for evaluating wetland acquisition, restoration, and mitigation banks.
Expertise needed
Professional(s) who have schooling in environmental sciences.
Applicable habitat types
Freshwater wetlands in North Carolina (not applicable to stream channels).
Categories assessed
Six values are addressed: water storage; bank/shoreline stabilization; pollutant removal; wildlife habitat; aquatic life value; and recreation and education.
Procedure
The user(s) visits a wetland area and refers to flow charts that provide a series of choices leading to a single score or range of scores (scale 0 - 5) for each function. Each function rating is multiplied by a set weight (range 1-4) and summed to derive a total wetland score.
Key terminology
Ability: the characteristics of a wetland that determine whether it can provide a particular value.
Function: processes taking place within the wetland ecosystem irrespective of their effect on human society.
Opportunity: chance a wetland has to perform a function.
Value: ecosystem functions that are perceived to have a positive impact on people.
Output
Rating of the value of a wetland.
Estimated time to assess 1 acre site
Total 4 hours per site.
Time variable: Gather information (step 1)
4 hours per site: Apply flow charts (step 2) and record results (step 3).
Comparison of habitat types
Can directly compare freshwater wetlands within North Carolina.
Use as guide to design
NC Guidance should not be used as a guide to design; however, individual variables (factors) may provide useful information. It is not the intended purpose for the procedure; therefore, it contains properties that limit its application for this purpose. For example, the NC Guidance uses opportunity variables, but does not set upper limits on those opportunities that could potentially reduce function/values (e.g., an area with > 10% urban, agricultural, or otherwise disturbed with 1/2 mile upstream is considered a preferred condition for the pollutant removal function). In some circumstances, a wetland may not have the capacity to remove all pollutant input. An upper limit on the opportunity must be defined to insure that the existing or planned wetland can predictably have the capacity to provide a function. Also, NC Guidance does not provide validated threshold values for many variables. Some of the variables may provide useful information. Users can refer to the factors within the flow charts to determine which conditions increase or decrease function. This can be translated into design criteria with explicit measurements (e.g., design wetland 0-50 ft of main bank/shoreline). Finally, the design criteria for some variables may be unsuitable and the overall rating of function may be misleading for the reasons given above.
Contact person
John Dorney, NC Department of Environment and Natural Resources, Division of Water Quality, 4401 Reedy Creek Rd., Raleigh, NC 27607 phone: (919) 733-1786; fax: (919) 733-9959; e-mail: john_dorney@h20.enr.state.nc.us
Related procedures
None.
Extent of use/field testing
Used to evaluate a wide variety of projects (e.g., highways, commercial, residential) and enforcement actions . NC Guidance has been used approximately 200 times in the last two years by Division of Water Quality staff.
Proposed future revisions
Plans are to revise NC Guidance in 1998 by eliminating the recreation/education category and giving more equal weights to the other categories. Some of the choices in the flow charts may be updated and revised.
Key Reference
North Carolina Department of Environment and Natural Resources. 1995. Guidance for rating the values of wetlands in North Carolina. Raleigh, NC. 57 pp.