---

Home definition functions History losses alterations Restoration Decisions: (and theory) design type site reference sites HGM vs. IBI Case Studies hydrology vegetation soil landscape State of the Science success criteria floristic quality References Created by: Abby Rokosch Jessen Book Siobhan Fennessy

Definitions of the methods used to design and site the mitigation wetlands. (Adapted from Gwin et al., 1999). Mitigation Method Definition Creation Construction of a wetland in an area that was not a wetland in the recent past (within the last 100-200 years) (Kruczynski, 1990; Lewis, 1990) and that is isolated from existing wetlands (i.e. not directly adjacent). Typically, a wetland is created by excavation of upland soils to elevations that will support the growth of wetland species through the establishment of an appropriate hydroperiod (Kruczynski, 1990; Lewis, 1990). Restoration Return of an ecosystem to a close approximation of its condition prior to disturbance (NRC, 1992). Restoration requires knowledge of the wetland type prior to disturbance and has the goal of returning the wetland to that type. Restoration also may occur when an altered wetland is returned to a previous, although altered condition (Lewis, 1990). Enhancement Modification of specific structural features of an existing wetland to increase one or more functions based on management objectives, typically done by modifying site elevations or the proportion of open water. Although this term implies gain or improvement, a positive change in one wetland function may negatively affect other wetland functions (Kruczynski, 1990; Lewis, 1990). Exchange Enhancement taken to the extreme (Kruczynski, 1990), with most or all of the wetland converted from one type of wetland to a different type. For example, resource managers may intend to enhance habitat value for waterfowl by excavating an area of open water within an existing emergent marsh. However, if the open water replaces the emergent wetland or a large proportion of it, wetland types have been exchanged. Expansion Enlargement of an existing wetland through the creation (see above) of new wetland area adjacent to an existing wetland. Usually, area of the same wetland type is added to the existing wetland.

---