Compensating for Wetland Losses Under the Clean Water Act (2001) / Chapter Skim
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Appendix A: Survey of Studies: Comparison of Mitigation and Natural Wetlands
Appendix A: Survey of Studies: Comparison of Mitigation and Natural Wetlands
Pages 187-198
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Appendixes
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From page 188... ...
. Restoration of 2.17 acres Creation of 40 acres Creation of 2.8 acres and enhancement of 1.1 acres Restoration of 850 linear feet of stream banks Creation of 8 acres Creation of 1 1.8 acres forested wetlands and 10.1 acres herbaceous wetlands Creation of 5.09 acres palustnne forested wetlands and 0.66 acre palustnne emergent and scnJ~shrub wetlands
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Appendix A Survey of Studies: Comparison of Mitigation and Natural Wetlands
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190 APPENDIX A TABLE A-1 Survey of Studies: Comparison of Mitigation and Natural Wetlands Region Time Period # Sites Scope Massachusetts 1983 to 1994 114 Portland, Oregon 1987 to 1993 95 Orange County, California Vegetation (% cover) Size Hydrology If project was built Freshwater emergent and open-water wetlands, soil organic matter (SOM)
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Compliance but not similarity between replicated and impacted plant communities increased with greater completeness of the replication plan and Order of Conditions. Mean SOM concentrations were higher in naturally occurring wetlands (NOWs)
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and composition of natural and mitigation wetlands Relationships between floristic characteristics and variables describing land use, site conditions, and mitigation activities Susquehannah 1993 River watershed, Pennsylvania Iowa, Minnesota, 1989 to 1991 62 South Dakota 20 reference; Soil organic matter, matrix 44 created chrome, bulk density, total nitrogen, pH Restored prairie potholes Basin morphometry, hydrology, and vegetation zone development
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Current wetland management practices are replacing natural marsh and wet meadow systems with ponds, changing composition of plant species assemblages. Compared to reference wetlands, wetland creation projects contained less SOM at 5 cm and unlike reference sites, SOM content was uniform between 5 and 20 cm.
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194 TABLE A-1 Continued APPENDIX A Region Time Period # Sites Scope Florida 1990 40 projects Surface hydrology, vegetation Central Florida 1993 10 natural, Dipterans in freshwater 10 created herbaceous wetlands Galveston Bay, Fall 1990, 10 created, Densities of nekton and Texas spring 1991 5 natural infauna in salt marshes
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Densities of daggerblade grass shrimp were not significantly different among marshes, but the size of these shrimp was significantly smaller than in natural marshes. Densities of the marsh grass shrimp and of three commercially important crustaceans were significantly lower in created marshes than in natural marshes.
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196 TABLE A-1 Continued APPENDIX A Region Time Period # Sites Scope Ohio 1994 to 1995 5 replacement Hydrology, soils, vegetation, wildife, water quality Texas 10 Invertebrates, fish North Carolina 6 Sediment/soil, invertebrates North Carolina 5 Sediment/soil North Carolina Marshes established 1971 to 1974 and monitored for 2 natural 25 years marshes 2 constructed marshes Above-ground biomass, soil, benthic infauna, carbon, total nitrogen South Carolina 2 Sediment/soil, plants, invertebrates, fish Texas 3 Plants, invertebrates, fish California 2 Sediment/soil, plants, fish, topography North Carolina Multiple Plants, invertebrates
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Soil bulk density decreased and organic carbon and total nitrogen increased over time in constructed marshes. Nitrogen accumulation was much higher in constructed marshes than in natural marshes.
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in the Dutchman Creek, Oak Island, Snow's Marsh, and Walden Creek Marshes, Brunswick County, North Carolina, 1975-1976. 3rd Annual Report to Carolina Power and Light.
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