Tom Ravens and graduate student Garrett Yager completed a study (funded by the North Pacific Research Board) addressing the hydrodynamic and sediment transport impacts of the Endicott causeway on the North Slope of Alaska. Solid-filled causeways have been used along the Beaufort Sea coastline to support oil and gas drilling operations and to provide maritime access on a shallow coast. However, in some cases, these causeways also alter the nearshore hydrodynamics and sediment transport leading to excessive sedimentation. 

The Endicott causeway, located in the Sagavanirktok River delta on Alaska’s North Slope, caused increased sedimentation in the lagoon area landward of the causeway within a few years of its construction in the mid 1980’s. Past studies raised concern that infilling of the lagoon may eventually alter fish migration. 

The main objectives of this project is to determine if the lagoon has continued to infill and if the pattern of infilling has been related to the alterations imposed by the causeway. Key elements of the research include numerical modeling of the hydrodynamics with and without the causeway as well as bathymetry(the measurement of water depth at various places in a body of water) surveying of the lagoon area. 

Impact of an Arctic Causeway on Hydrodynamics and Sedimentation (2010-2012)
Geographic setting of the Sagavanirktok River Delta and the Endicott Causeway
Impact of an Arctic Causeway on Hydrodynamics and Sedimentation (2010-2012) 2
Contour plot of observed change in bathymetry between 1989 and 2009/10.

The results indicated that sediment has continued to deposit in the lagoon and the deposition has been related to the placement of the causeway. The depositing sediments were observed to be significantly finer than the native sediments. Our analysis indicates that the rate of sediment deposition in the lagoon has been decreasing and will likely continue to decrease in the future. The figure below shows the geographic setting of the project and the net deposition in the vicinity of the causeway in a 20 year period.


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