In response to COVID-19, and in attempt to continue offering opportunities for discussion and to promote advancement of the Maryland stream restoration industry, MSRA is excited to announce a series of webinars featuring leading industry researchers and partners. Stay tuned through our website and social media channels for the series schedule. Continuing Education Credits will be offered for these events. We hope you will join us:
When: Tuesday, November 16, 2021
Time: 12:00 p.m. - 1:00 p.m.
Following your registration, and prior to the event, you will receive a webinar link from GoToWebinar which will give you access to the webinar.
Will you be attending?
Cost: Free for members, $10 for non-members
Theresa (Tess) Wynn Thompson is an Associate Professor and Turner Faculty Fellow in the Department of Biological Systems Engineering at Virginia Tech. She teaches courses in Fluvial Geomorphology, Stream Restoration, and Transport Processes. Her research program focuses broadly on the restoration of stream and wetland systems, with particular emphasis on determining the fundamental processes involved in the erosion of cohesive streambanks; developing more accurate tools for the design of wetland systems; and, developing management practices to minimize the impact of urbanization on stream ecosystems.
Instream structures are used to reinforce channel margins, redirect flows, and create habitat, but there is limited published design information and post-construction evaluation. In this study, 536 instream structures in the state of Maryland were assessed to evaluate the effect of structure-, project-, and watershed-scale factors on performance. Structures were assessed using a 19 point scoring system based on structural stability, sediment transport, and overall function. Structure-scale variables related to the construction, geometry, and placement of structures, and differed for six structure families: bank protection (BP), full and partial span vanes (FSV), constructed riffles (RF), regenerative stream conveyances, and step pools. Project- and watershed-scale variables related to flow, erosion resistance, and design approach. Relationships between structure scores and explanatory variables were evaluated using regression analysis. Results indicated structure performance was strongly influenced by the individual project, suggesting that design quality, construction, and maintenance are as important as specific design features. Structure durability decreased if there was additional urban development within the project watershed following construction. Results also indicated that when structures were used in series, there was a “protective effect” on other nearby structures. For rock BP, imbricated rock walls performed better than stone toe, likely due to increased structure height and boulder size. Rock FSVs that were keyed into the bank at angles between 35° and 90° were more durable, while RFs performed best when constructed using downstream grade control and increased substrate depth. Study results provide initial insights into design and project features that contribute to structure success.