AUTC project number: 309009
Horacio Toniolo (UAF)
Messing with Mother Nature takes knowledge and work, and she is hard to outfox, especially when it comes to redirecting rivers. To protect infrastructure, however, sometimes river flow must be altered. This study focuses on two erosion-control projects built in Alaska using different design criteria. One was constructed by ADOT&PF at the Sagavanirktok River to protect the Dalton Highway, the other was built by Alyeska Pipeline Service Company at Hess Creek to protect the trans-Alaska pipeline. Though bank erosion along river bends is a natural process, lateral erosion, which causes streams to shift laterally, can expose infrastructure to serious risk. To avoid damaging or destroying the transportation system, researchers and engineers have developed several types of strategies to prevent streambank erosion, including watercourse realignment, that is, moving water away from the bank. Project researchers gathered hydraulic data, including continuous velocity measurements, at selected points in both streams. Results from a turbulence analysis suggest that Hess Creek was in equilibrium at the time of surveying it, while the condition at the Sagavanirktok River is unclear. The project took an unexpected turn when the research team decided to include a hydraulic numerical model. This model is capable of simulating different flow conditions, calculates shear stress, velocity and Froude number, among other hydraulic parameters. Different scenarios were simulated by the model, showing how the river might behave under different flow conditions at different seasons. ADOT&PF personnel and the research team are looking for opportunities to implement the model in different settings, particularly where ADOT&PF is planning river training structures. This numerical model will improve the design process for future structures by helping designers plan appropriate structures for actual river conditions. Graduate student Paul Duvoy, who is working on a Master of Science in civil engineering, has done much of the work on this model.