Conserving Relict Floodplain Soils during Stream Restoration to Promote Soil Health and Floodplain Nutrient Cycling
Tyler Jones, EIT
Brian Tetrick, PE
WSP USA
Baltimore, MD
Authors: Jones, Tyler, EIT; Genito, Dennis; Inamdar, Shreeram, PhD
Floodplain health is recognized as an important component in stream restoration. Functioning floodplains can provide not only physical hydraulic benefits, but also water quality and ecological benefits through their biogeochemistry. Many stream valleys in the East Coast contain major deposits of upland soils that flooded into the valleys during the era of forest clearing following European colonization (“legacy sediment”), burying wetland soils which had established over thousands of years. While these relict hydric still exist, little is known about the ecological function and water quality services (e.g., denitrification) they may provide once reconnected to hydrology and the root zones of riparian vegetation. Denitrifying functions are reflected in Protocol 2 of the Maryland Expert Panel Consensus Recommendations on Stream Restoration Crediting.
The Baltimore County Department of Environmental Protection and Sustainability (DEPS) identified Roches Run at Hammershire Road in Reisterstown, MD as a priority restoration project. The project involves restoration of approximately 3,000 linear feet of mainstem and tributary channels. WSP identified the project site as containing potential relict floodplain soils and coordinated a collaboration between DEPS and the University of Delaware (UD) Department of Plant and Soil Sciences.
In collaboration with DEPS and UD scientists, WSP identified the extents of relict hydric floodplain soils. Where feasible, floodplain elevations of the restored stream valley were designed to intersect these soil horizons; in other locations the construction plans called for separate stockpiling of excavated relict soils for placement at the constructed floodplain surface. WSP worked with the project contractor, Environmental Quality Resources (EQR) to field verify the locations of relict soils and to confirm their exposure or relocation in dedicated areas of the restoration project.
Sampling transects have been designed for consistent long-term monitoring of relict soil reconnection areas relative to areas of clean fill or excavated legacy sediment. DEPS and WSP will apply the findings of recent UD soil health research to select appropriate soil health metrics. The results of this monitoring will be presented in the future. This project forged a collaboration between municipality, academics, and consulting engineers study the feasibility and performance of incorporating relict hydric soils into reconnected floodplains.
About Tyler Jones, EIT
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About Brian Tetrick, PE
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