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. "Part 303 requires the department and local units of government to use the technical wetland delineation standards set forth in the United States Army Corps of Engineers January 1987 Wetland Delineation Manual, and appropriate regional supplements, in identifying wetland boundaries. Two regional supplements apply to Michigan: the Midwest supplement for portions of Southeast Michigan (portions of Hillsdale, Lenawee, Washtenaw, Livingston, Wayne, and Oakland Counties) and the Northcentral and Northeast Supplement, which covers the remainder of Michigan.
The 1987 U.S. Army Corps of Engineers Manual
Midwest Regional Supplement
Northcentral and Northeast Regional Supplement
Identification of wetlands using the federal delineation method primarily involves the determination of three factors: the predominance of wetland vegetation, hydric (wetland) soils, and signs of hydrology. The presence of water (the hydrology) is necessary at certain times of the year for the development of a wetland. The timing, frequency, and level of saturation each year influences the type of vegetation that can grow in an area and the type of chemical and physical reactions which occur in the soil.
Knowledge about the plants in an area is essential for delineating wetlands. Wetland plants have adaptations or responses that allow them to survive, grow, and reproduce with their roots in water or saturated soils for at least part of a year. Conversely, many plants cannot survive in saturated conditions and are commonly referred to as upland plants. Due to the need to identify plant species, it is recommended that any wetland identification occur during the growing season. The National Wetland Plant List provides information about how often a plant occurs in wetlands and other useful information.
A hydric soil is a soil that is saturated, flooded, or ponded long enough during the growing season to develop anaerobic conditions. This lack of oxygen in the soil can lead to the formation of certain observable characteristics in wetland soils, such as a thick layer of organic matter (non-decomposed plant materials) in the upper part of the soil column. Other observable features include oxidized root channels and redoximorphic features (concentrations and depletions of Iron and other elements). Field Indicators of Hydric Soils in the United States includes hydric soil indicators approved by the Natural Resources Conservation Service and the National Technical Committee for Hydric Soils (NTCHS) for use in identifying, delineating, and verifying hydric soils in the field. In addition, several Supplemental Hydric Soil Field Indicators for Michigan were approved by the National Hydric Soils Committee in 2012.
EGLE offers a fee-based Wetland Identification Program (WIP) to assist landowners in identifying wetland and non-wetland (upland) areas on their property.