Restoration and Enhancement of Aquatic Habitats

The Corps of Engineers has a central role in restoring aquatic ecosystems. Under the authority of the 1986 Water Resource Development Act and subsequent amendments, the Corps can modify or construct projects to restore fish and wildlife habitat, as well as assist states and other non-Federal agencies with ecosystem and watershed planning (Table 1). Mitigation of larger water resource projects is required under the National Environmental Policy Act. Thus, the Corps uses a variety of techniques to accomplish restoration and mitigation goals, but the biological merits of each have not been comprehensively evaluated. Restoration measures, implemented by environmental engineering, change physical habitat and subsequently effect changes in biotic communities. As part of the EMRRP, success criteria for restoration projects are being developed by modeling fish communities. Species within a fish community exhibit broad ranges of sensitivity to environmental disturbance (intolerant to tolerant), reproductive strategies (brooders to explosive breeders), lifespans, (1-10+ years), and trophic position (herbivores to piscivores). Consequently, community indices (percent composition, diversity, biotic integrity) are ideally suited to represent ecosystem function and health because they are not subjectively biased by any single species. Empirical measures of such indices are readily correlated with physical (e.g., water depth, substrate type) and landscape (e.g., percent forested lands) variables. These measures can be used to identify and predict restoration benefits for engineering solutions to habitat degradation.