Stormwater Management Standards Manual - Toledo Metropolitan ...

• Category 1 - wetlands are considered low quality, support minimal wildlife habitat, and
minimal hydrological and recreational functions.
• Category 2 - wetlands are of moderate quality, supporting moderate wildlife habitat, or
hydrological or recreational functions.
• Category 3 - wetlands are of high quality, support superior habitat, or hydrological and
recreational functions. The different categories require differing levels of review and
mitigation.
Category 1 wetlands require 1) avoidance and minimization, 2) stormwater quality controls, and 3)
compensatory mitigation. Category 2 wetlands have the added requirement of 4) social and economic
impact justification. Category 3 wetlands add the additional requirement of 5) public needs
demonstration.
Wetlands are a combination of three components that must all be present to meet the test of being a
wetland; hydric soils, hydric plants, and wetland hydrology.
Ohio administrative code describes wetlands as “areas where the water table is at, near, or above the
land surface long enough each year to support the growth of water-dependent vegetation and to result in
the formation of characteristic wet soil types. These include marshes, swamps, bogs and similar areas.”
Michigan's wetland statute, Part 303, Wetlands Protection, of the Natural Resources and Environmental
Protection Act, 1994 PA 451, as amended, defines a wetland as “land characterized by the presence of
water at a frequency and duration sufficient to support, and that under normal circumstances does
support, wetland vegetation or aquatic life, and is commonly referred to as a “bog,” “swamp,” or “marsh.”
The definition applies to public and private lands regardless of zoning or ownership.
The U.S. Department of Agriculture (USDA), US Natural Resources Conservation Service (NRCS),
describes hydric soils in their soil survey reports. Lists of hydric soils are available upon request from the
County Soil and Water Conservation Districts or NRCS offices. County soil surveys indicate where the
soils occur. In general, hydric soils have a dark surface color with higher organic matter contents than
surrounding upland soils. Contact the NRCS office for additional information.
Plants that grow in predominantly wet soil conditions are considered hydric vegetation. Lists of all
commonly occurring hydric plants are available for Ohio and Michigan in the publication, “National List of
Plant Species that Occur in Wetlands”, U.S. Fish and Wildlife Service.
Wetland hydrology is the driving force behind wetland formation. Of the three technical criteria for
wetland determination, wetland hydrology is often the least exact and most difficult to identify in the field.
Because of the difficulty of establishing wetland hydrology, the emphasis on delineating wetlands is
often placed on hydrophytic vegetation and hydric soils in the absence of significant hydrologic
modifications. Even so, wetland hydrology should always be considered.
Wetland hydrology means permanent or periodic inundation, or soil saturation for a significant period of
the growing season. Thus, all wetlands are at least periodically wet. The degree of wetness of an area is
influenced by precipitation, stratification of the soil, topography, permeability, and plant cover. The
frequency and duration of soil saturation can distinguish wetlands from non-wetlands with duration
having the stronger influence. The duration can be affected by the condition of outlet channel: log jams,
siltation reducing low water flows, and smoothness of the channel banks.
Hydrology varies annually, seasonally, and daily; consideration should be given to the time of year that
the hydrologic determination is being made, especially when considering the presence/absence of field
Third Edition Stormwater Standards Manual September 2008 Page 130