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Functional Lift of a Headwater Stream-Wetland Complex Restoration Revealed By a Decade of Environmental and Ecological Monitoring

Jesse Robinson, PE
University of Louisville Stream Institute
Louisville, KY

Authors:
Jesse Robinson - Stream Institute, J.B. Speed School of Engineering, University of Louisville, Louisville, Kentucky
Michael Croasdaile - Stream Institute, J.B. Speed School of Engineering, University of Louisville, Louisville, Kentucky
Art Parola, PhD, PE - Stream Institute, J.B. Speed School of Engineering, University of Louisville, Louisville, Kentucky
Amy Braccia - Department of Biological Sciences, Eastern Kentucky University, Richmond, Kentucky
Jamie Lau - Biology Department, Radford University, Radford, Virginia
Emily Jones - Stream Institute, J.B. Speed School of Engineering, University of Louisville, Louisville, Kentucky

Dynamic stream restorations are a relatively recent approach to mitigation, and long-term studies of their effectiveness are lacking. Here we present a functional assessment from 10 years of monitoring of the Slabcamp Creek stream-wetland complex, a pioneering dynamic restoration project. Monitoring includes 5 years prior to and 5 years post-colonization by beaver.

Prior to restoration Slabcamp Creek, a 0.9 mi2 headwater in the Western Allegheny Plateau ecoregion, was a single thread, incised channel, with poor, frequently disturbed habitat and a hydraulically disconnected floodplain. The restoration approach included reconnecting the stream and floodplain to the historic valley aquifer, creating interconnected and diverse habitat, establishing a frequent flooding regime, and reducing flood velocities to retain wood and organic matter. The goal of the project was to recover as much of the functionality of the pre-settlement aquatic ecosystem as possible.

To support the functional assessment of this restoration approach, a decade of interdisciplinary environmental and ecological monitoring was initiated at construction completion in Slabcamp Creek and nearby unrestored sites. Monitoring was focused on the hydrologic, hydraulic, geomorphic, and ecological function of the site and its performance relative to the unrestored and pre-restoration condition.

After restoration, the channel was anabranched, perennially flowing, retentive, and dynamically stable. Macroinvertebrates in the restored channel showed significantly greater taxa richness, and greater density and biomass, with pools revealed as a hot spot for macroinvertebrates and organic matter accumulation. Floodplain environments were converted from dry terraces with upland vegetation to laterally connected, frequently flooded (>10 times annually) wetlands and pools. Beaver arrival expanded the diversity of habitat through continuous dam formation, maintenance, and abandonment. Fish showed greater biomass and density in all habitats, including in the backwater of beaver dams. Beaver arrival led to unexpected effects, including the arrival of otters to the headwater restoration.