Indiana Wetland Mitigation Monitoring


Since 1986 the Indiana Department of Environmental Management (IDEM) has reviewed approximately 3,000 projects requiring Section 401 Water Quality Certification. The projects have involved a variety of activities, purposes, applicants, size and level of impacts to the state of Indiana's aquatic resources. Hand in hand with the diversity of projects has been the diversity of plans for the establishment of replacement wetlands. Construction of replacement wetlands has involved enhancement of existing wetlands, restoration of drained wetlands and creation of wetlands where no wetlands existed before. Types of replacement wetlands constructed include isolated wetlands, wetlands adjacent to lakes and streams, emergent wetlands, and forested wetlands.

Techniques used to establish the three basic parameters (vegetation, hydrology, and soils) have varied considerably. Many variables in a variety of wetland replacement plans have been altered in many ways in an attempt to establish viable replacement wetland.

A survey of replacement wetlands in other states has shown that for the majority of projects requiring wetland replacement, the replacement wetland was not constructed or was not constructed correctly, and, if constructed correctly many were not successful. In Indiana wetland replacement is a major factor in determining whether or not a project receives Section 401 Water Quality Certification.

Indiana Wetland Compensatory Mitigation: Area Analysis (June 2001)

The purpose of this study was to gauge the performance of compensatory mitigation efforts in Indiana by measuring the area of wetland established as a result of these efforts. This study used Global Positioning System (GPS) techniques to map the total area of wetland, and the area of each wetland vegetation community, established at 31 randomly selected wetland compensatory mitigation sites in Indiana. The Indiana Department of Environmental Management (IDEM) required 34.31 ha (84.7 ac) in compensation for the 13.72 ha (33.9 ac) of state waters lost through the permit actions associated with these sites. The mapping effort demonstrated that a total of 15.21 ha (37.6 ac) of wetland and other waters had established at these sites, a net gain of 1.49 ha (3.7 ac).

Mapping of each vegetation community at these sites revealed that forested areas, which had a failure rate of 71%, and wet meadow areas (87% failure) were harder to establish than shallow emergent areas (17% failure) and open water areas (4% failure). Compensation for this risk of failure would require minimum mitigation ratios of 3.4:1 for forested, 7.6:1 for wet meadow, 1.2:1 for shallow emergent, and 1:1 for open water. Additional mitigation may be needed to offset the effects of temporal loss of wetland function. Although there was a net gain in area over all, forested wetlands experienced a net loss of 4.15 ha (10.3 ac) raising concerns that forested areas are being replaced with shallow emergent and open water community types.

Indiana Wetland Compensatory Mitigation: Area Analysis Report [PDF]

Indiana Wetland Compensatory Mitigation: Inventory (May 2000)

Amid questions about the efficacy of wetland compensatory mitigation, the Indiana Department of Environmental Management (IDEM) sponsored an effort to objectively study Indiana's mitigation sites. The first part of this program, the current study, sought to inventory Indiana's mitigation sites. Between 1986 and 1996 IDEM, through its Water Quality Certification program (Section 401 of the Clean Water Act), required 345 mitigation sites that met the criteria for inclusion in this study. The author visited each of these sites during 1998 and spring of 1999. Applicants had constructed 214 (62.03%) of the sites. Another 70 (20.29%) were incomplete.

No attempt had been made to construct the mitigation on 49 (14.24%) of the sites. The author could not evaluate another 12 (3.48%) of the certifications due to a lack of information in the certification files. These sites were not distributed evenly across Indiana, but were in general clustered in the northern half of the state. The sites were especially dense around the Lake Michigan area, Fort Wayne and Indianapolis. Watersheds that feed Lake Erie and Lake Michigan contained 37% of the 345 sites. The watershed directly abutting Lake Michigan holds nearly 20% of the mitigation sites, raising cumulative impact concerns.

Indiana Wetland Compensatory Mitigation: Inventory Report [PDF]