Back to C Session Agenda

Passive Wetland Restoration Through Stream Restoration

Laura W. Kelm
GreenVest, LLC
Bowie, Maryland

MDOT SHA - Maryland Department of Transportation State Highway Administration contracted with GreenVest, LLC (GV) to design, build, and maintain the Bacon Ridge Branch Stream Restoration Project (Project) in the South River Watershed to provide stream restoration for use in meeting Total Maximum Daily Load (“TMDL”) reductions for the SHA’s MS4 permit requirements. In the pre-construction condition, two main perennial stream channels with sand beds were deeply incised from approximately 3 to 8 feet with vertical, bare, and eroding banks. The channel incision and bank erosion reduced bedform diversity, in-stream habitat, and floodplain function. The stream valley understory was dominated by Japanese stiltgrass (microstegium vimineum). The primary method of stream restoration was the construction of engineered log jam structures to raise the stream water surface elevation and hydrologically reconnect the stream to its disconnected floodplain. An associated goal of the restoration was to explore the potential hydrologic rehabilitation of remnant floodplain wetlands through stream restoration. Project construction, completed in Spring 2020, resulted in just under 18,000 linear feet of stream restoration. Groundwater monitoring wells were installed along three transects from the stream bank, across the floodplain, to the valley wall; up to 300 feet away from the top of the stream bank. The results of groundwater monitoring before and after construction show that the increase in groundwater elevation in response to the stream restoration was immediate and persistent. In addition to stream and floodplain restoration and reconnection, this project has restored and enhanced the hydrology of approximately 50 acres of forested floodplain wetlands and led to widespread changes in the vegetation communities observed throughout the site while maintaining sufficient canopy cover for continued use of the site by forest interior dwelling species (FIDS). Data will be presented to show the changes that have occurred within the floodplain between pre-construction conditions and three growing seasons since the completion of construction. We hope to stimulate more projects of this type, where appropriate, by helping the design and construction community build capacity for this type of truly sustainable ecological restoration.