The Effect of Design and Site Characteristics on the Success of Instream Structures in Maryland
Benjamin Smith
Stantec Consulting
Roanoke, Virginia
Authors: Benjamin S. Smith, Tess Wynn-Thompson
Instream structures are utilized as part of stream restoration projects to redirect flows, protect banks, provide grade control, and increase habitat diversity. Often instream structures are used as less invasive, more environmentally friendly alternatives to traditional channel stabilization techniques such as concrete-channelization and riprapping. This study examines the effect of design characteristics and site conditions on the success of instream structures in Maryland, USA, including cross vanes, j-hook vanes, single arm vanes, sills/ weirs, toe protection, rock walls, constructed riffles, and step-pool channels. Structure design variables include material type and size, footer depth, vane-arm bank angle, and key-in distance. Site condition variables include specific watershed area, average watershed slope, land use, structure density, riparian vegetation, and soil erodibility (K). Statistical analysis will be used to correlate site and structure characteristics to the success of a structure type in three categories: structural integrity, impacts on sediment, and overall function. Structural integrity is the degree to which a structure remains in-place as constructed. Impacts on sediment include whether a structure has caused unintended bed or bank scour or aggradation. Finally, overall function describes whether a structure is functioning as intended (i.e. is a cross vane holding grade and creating a riffle upstream and a pool downstream?). The results of this study will provide additional guidance on the siting and design of common in-stream structures.
About Benjamin Smith
Ben is a former Biological Systems Engineering Master's student from Virginia Tech, whose research focused on in-stream structures. Currently, Ben works as an Environmental Engineer in Training at Stantec as part of the water resources engineering and the nature-based climate solutions teams. He has been involved in environmental engineering work for the Commonwealth of Virginia's power and transportation infrastructure, performed carbon and greenhouse gas inventories for natural systems, and is involved in the development of a tool for estimating carbon offsets.