Physical Model of Knik Arm and the Port of Anchorage, Alaska

A large physical model replicating approximately 19 miles of Cook Inlet was constructed at ERDC with a horizontal length scale of 800-to-1 and a vertical length scale of 200-to-1. The model included the Knik Arm, a portion of Eagle Bay, and a region south of Point Woronzof. The Port of Anchorage is located in the Knik Arm, and tidal flows at the Port generated by the +30-ft tide range are highly influenced by a large gyre that forms to the south of Cairn Point during ebb tide. The purpose of the physical model was to evaluate changes to tidal flows caused by a large, multi-phased Port expansion that might impact the Alaska District's navigation mission at the Port. Model validation consisted of reasonable reproduction of field-measured tidal velocities collected at three locations near the Port over the spring tide cycle. Velocity measurements over a tide cycle were acquired in the model at strategic locations near the Port berthing areas for each phase of the Port expansion. Comparisons between the different expansion phases quantified expected changes to the flow regime. Potential sedimentation problems were identified using both measurements and flow visualization techniques coupled with time-lapse video.