Theses and Dissertations at Montana State University (MSU)
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Item Assessment of service and ecological function of constructed wetlands for stormwater management in delaware county, ohio(Montana State University, 2020) Binger, David John; Chairperson, Graduate Committee: William KleindlI conducted a case study in Delaware County, Ohio to assess the service and function of constructed stormwater ponds and their contribution to maintaining wetland functions and values. As a result of population expansion around the City of Columbus, natural wetland cover decreased from 2,471 to 2,250 acres from 1994 to 2019. To manage the excess surface runoff, increasing numbers of stormwater ponds are being constructed to substitute for the absence of wetlands. Stormwater pond land cover was found to have increased from 1,145 to 2,482 acres from 1994 to 2019. When considering the status and trends of the wetlands, the functions and service of constructed systems such as stormwater ponds are not considered. Using the Ohio Rapid Assessment Method (ORAM), nine detention and seven retention ponds were scored providing a numeric representative of the condition of the system's structure necessary to perform functions and were factored into the Delaware County wetland budget. The average ORAM score for the constructed stormwater ponds was 15.06 in comparison to reference wetlands which was 80. If the 221 acres of wetland lost from 1994 to 2019 had the same average ORAM score as the three-reference wetland, it would be a 17,680 loss of wetland "value and function" as defined by ORAM. If the 1,337 acres of stormwater ponds added from 1994 to 2019 had the same average ORAM score as the observed stormwater ponds, it would be a 20,135 gain of "value and function" as defined by ORAM. Overall, this would suggest that even though there has been a loss in total wetland area, wetland functions and values have been maintained by the construction of stormwater ponds. Even with the addition of 1,116 acres of aquatic ecosystem from 1994 to 2019, the representative score of wetland structure remained nearly the same. This estimate of the preservation of wetland functions and values demonstrates both the benefits but shortcomings of stormwater ponds in replacing wetland values such as diverse ecological habitats. By evaluating the differences in metric scores between the stormwater ponds and reference wetlands, I recommended design improvements for future stormwater pond construction to provide the same services, but with improved ecological benefits.