Comparison of Constructed Wetlands to a Preservation Wetland in the Nashville Basin, Tennessee (USA)
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WETLANDS RESTORATION
Comparison of Constructed Wetlands to a Preservation Wetland in the Nashville Basin, Tennessee (USA) Cole Liggett 1 & Thorsten Knappenberger 2
&
Joey N. Shaw 2 & Eve Brantley 2 & Audrey V. Gamble 2
Received: 17 May 2019 / Accepted: 30 October 2019 # Society of Wetland Scientists 2019
Abstract Wetland restoration projects are monitored to verify wetland function. Two constructed wetlands were compared with an onsite preservation wetland in the Nashville Basin, TN (U.S.) based on shallow groundwater wells, wetland determination forms, and Indicator of Reduction in Soil (IRIS) tubes data collected from 2013-2017. Results from Multiple Factor Analysis indicate that the constructed wetlands become more similar to the preservation wetland over the course of five years after construction. Shallow groundwater wells reported similar data in 42, 67, 63, and 55% of the growing season in 2013, 2014, 2015, and 2017, respectively. IRIS tubes documented the successful creation of aquic and hydric soil conditions in the created wetlands in 2016 and 2017. IRIS tube and groundwater monitoring well data indicate the duration of saturation required for developing reducing conditions decreases from 20 to 7 days as the growing season progresses. Hydrophytic vegetation was present during the course of this study. After five years of monitoring, the constructed wetlands are more similar to the preservation wetland, although the constructed wetlands still lacked the tree strata. Keywords Constructed wetlands . IRIS tubes . Soil development . Reducing conditions . Wetland mitigation
Introduction Wetlands were historically regarded as swampy lands that bred diseases, restricted overland travel, impeded the production of food and fiber, and generally were not useful for frontier survival (Dahl and Allord 1982). Settlers, commercial interests, and governments agreed that wetlands presented obstacles to development and that wetlands should be eliminated and the land reclaimed for other purposes (Dahl and Allord 1982). This led to the mass draining and filling of wetlands across the United States. By the mid-1980s, it is estimated that over half (54%) of U.S. wetlands had been drained or filled for agriculture or development (USDA-NRCS, 2014). To reduce further wetland losses, section ยง404 of the Clean Water Act of 1972
* Thorsten Knappenberger [email protected] 1
Civil & Environmental Consultants, Inc., Franklin, TN, USA
2
Department of Crop, Soil and Environmental Sciences, Auburn University, 201 Funchess Hall, Auburn, AL 36849, USA
provided the Army Corps of Engineers the authority to issue permits for the discharge of dredged or fill material into waters of the United States, including wetlands (Vepraskas 2016). To enforce Section 404 of the Clean Water Act, the Corps of Engineers published the Wetland Delineation Manual in 1987 (USACE 1987) to enable identification and delineation of wetlands. The Manual recognized a three-parameter approach consisting of wetland hydrology, vegetation, and soil. Regional supp
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