Application of Numerical Models to Evaluate Performance of Two Stream Bank Stabilization Techniques - Paul Duvoy , Civil & Environmental Engineering, University of Alaska Fairbanks (co-authors: Alex Lai/Alyeska, Horacio Toniolo/UAF)

ABSTRACT

Bank erosion along river bends is a natural process. As a result of lateral erosion, streams tend to shift laterally and this displacement can impose serious risks to infrastructure. To avoid damage or destruction to the transportation system, researchers and engineers developed several types of strategies to prevent streambank erosion, including water course realignment, which moves it away from the bank.

The Dalton 414 Erosion Control Project was constructed in 2006 to prevent further displacement of the Sagavanirktok River near the road. Eight bendaway weirs (stream barbs) oriented upstream were installed in the reach. The goal of this project was to transfer erosive velocities away from the stream bank through the interruption of helicoidal currents and cross-stream flow that develop within the meander flow.

The Trans-Alaska Pipeline crosses Hess Creek on a 180 foot steel plate girder bridge. Erosion altered the stream pattern with formation of a meander bend upstream of the bridge. To prevent additional erosion along the river bank ten riprap directional flow vanes 10-98 ft long, and up to 6 ft wide and 6 ft deep were installed orienting downstream along the 800 ft meander bend. The vanes manipulated flow direction, nudging the stream into a shallower curvature prior to entering the pipeline bridge opening. Spacing and length of the vanes increased from upstream to downstream in the meander bend.

Numerical modeling using an existing software, CCHE2D, was performed to reproduce flow conditions at both sites before and after the installation of river training structures. The numerical model is a 2D hydrodynamic model that accounts for unsteady and steady flow conditions. Model results were compared with post-construction monitoring to properly assess model verification and validation, and to determine actual and future evolution of the channel realignment under different flow scenarios. Additional Info: To be presented after "An assessment of stream bank stabilization techniques using upstream and downstream pointed vane structures" oral presentation by Alex Lai.

Topic: Alaska Hydrology