The Utah Department of Transportation commissioned a study to determine whether or not shallow-flow rock structures could reliably be used at bridge abutments in place of riprap. Research was conducted in a two-phase effort beginning with numerical modeling and ending with field verification of model findings. As part of phase one, two finite element meshes were created in Surface-water Modeling Software (SMS) and analyzed with FESWMS-2DH. Second, field studies were conducted and a preliminary database was developed to track field studies conducted on 98 shallow-flow rock structures in Utah. Data organization in ArcGIS® and Microsoft Access® is presented followed by instructions on how to use the database. Both numerical model and field research results indicate that shallow-flow rock structures are not viable scour countermeasures at bridges.

Instream structures are used to reinforce channel margins, redirect flows, and create habitat, but there is little consensus about their design or whether they function as intended. In this study, 536 instream structures in the state of Maryland were assessed to determine 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, 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. 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 following construction. Results also indicated that restoration activities have a "protective effect" on nearby structures. For rock BP, imbricated rock walls performed better than stone toe, 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. The results of this study provide insight into design and project features that contribute to structure success. / Master of Science / Stream restoration aims to rehabilitate streams that have been impacted by humans, and log or rock structures in the channel are utilized to protect the bed and banks, redirect water away from the banks, and create habitat for aquatic organisms. However, there are few design standards for these structures. In this study, 536 instream structures in the state of Maryland were assessed to determine the effect of design and site characteristics on performance. Structures were scored for performance based on structural stability, sedimentation, erosion, and function. Design characteristics related to structure construction and placement, while site conditions related to the project and watershed characteristics. Statistical analyses were used to determine the relationship between structure performance and design and site characteristics. Structure performance was strongly influenced by the restoration project, indicating that design quality, construction, and maintenance are as important as specific design features. Structure durability decreased if there was additional urban development in the watershed following construction. Results also indicated that when structures were used in series, there was a "protective effect" on other nearby structures. Rock walls performed better as height increased, while rock weirs that were constructed into the streambank between 35° and 90° were more durable. These results provide insight into design and project features that contribute to structure success.

This report was sponsored by the Utah Department of Transportation (UDOT) to determine if stream restoration structures could be used as scour countermeasures near state highways and bridges. Scour countermeasures that are effective in preventing erosion exist but that are not so friendly for aquatic organisms. UDOT is interested in finding a countermeasure that is both effective in preventing erosion while not harming aquatic organisms. Stream restoration structures are friendly for aquatic organisms but are prone to failure when flows exceed the design levels. David Rosgen has developed restoration structures that are friendly for aquatic organisms and that have provided streambank protection. These structures are the J-Hook vane, Cross-Vane and W-Weir. Based research done in this report, Cross-Vanes and W-Weirs are best suited to protect bridges because they will protect both sides of a stream bank. For these restoration structures to be reliable at higher flows and shear stresses experienced at bridges, they must follow the design criteria specified in this report. One of the most important design requirements is that the structures designed by David Rosgen have an attached floodplain where the structure meets the streambank. The floodplain disperses the energy of the flow, reducing shear stress. In the vicinity of some bridges, a floodplain cannot be implemented. In such cases, culverts can be installed at the floodplain level, that pass under the bridge to help reduce shear stresses, mimicking a floodplain. Cross-Vanes and W-Weirs can be used to protect bridges and other infrastructure. Based on modeling and comparing restoration structures to a labyrinth weir, they still have an impact on higher flows. At higher than design flows, such as experienced at bridges, the structures help to reduce shear stresses. To further investigate their use as a scour countermeasure near bridges, it is recommended that a structure be installed near a bridge following this report's design criteria. This will be determined depending on available funding.