Osage Plains wetland and Stream mitigation Bank
Cass County, Missouri
Swallowtail designed, built, and monitored the first private wetland and stream mitigation bank in western Missouri. The primary restoration activities on this roughly 40-acre property included the widening of the riparian buffer of the East Branch of the South Grand River to 300 feet on one side for more than a half mile and the restoration and enhancement of about 20 acres of wetlands in a diversity of habitats and landscape positions. These improvements to water quality and wildlife habitat are used for compensatory mitigation for impacts to waters of the United States in the Central Plains / Osage / South Grand Ecological Drainage Unit which encompasses the upper portion of the Osage River watershed in Missouri.
Swallowtail recognized that the site, which had been in row crop production for decades, had a significant amount of local topographic variability and a favorable position in the landscape for wetland development. The enhancement of the site’s intricate topography has led to a wide variety of microhabitats along a hydrologic gradient which allowed for the establishment of a high amount of botanical diversity because of Swallowtail’s extensive planting of a wide diversity of appropriate native plant species to match the unique topography, soil, and hydrologic conditions of the site.
The site receives almost 400 acres of local runoff from adjacent agricultural properties via several small streams that flow across the property into the East Branch of the South Grand River. By detaining much of that runoff in the site’s restored and enhanced floodplain wetlands, Swallowtail was able to decrease the amount of nutrients, sediment, and agricultural pollution that flows into the East Branch of the South Grand River and downstream waters, including Truman Lake and Lake of the Ozarks. In addition, the East Branch of the South Grand River floods the site at least annually so the development of a significant amount of floodplain wetlands on the site also provides some level of water quality improvement of those flood waters. Moreover, the excavation of the eastern floodplain areas and the creation of floodplain pools in the western half of the site has significantly increased the flood storage capacity of the property.
Wildlife has responded very favorably to the restoration of the site’s riparian, wetland, and upland buffer habitats. A variety of frogs and salamanders now inhabit the site along with a diversity of waterfowl, wading birds, turtles, and other species adapted to the shallow marsh habitat that is the site’s dominant feature. The Bank has completed its final year of formal monitoring and provided compensatory mitigation for 14 local projects.