The Time-Dependent Hydraulic Flow and Dissipation over the Still of Observatory Inlet

Abstract

The time-dependent hydraulic flow over the sill of a tidally energetic fjord, Observatory Inlet, British Columbia, is studied. Acoustic observations of streamlines and velocity were made near the sill crest during the summer of 1982, a time when freshwater runoff into the inlet had created a distinct surface layer. While the tide is accelerating, a simple, three-layer, hydraulic model accurately simulates the flow near the sill crest. However once the tide begins decelerating the observed flow undergoes a transition which the three-layer model cannot explain. It is estimated that during the period of observation the hydraulic flow utilized only about 5% of all the energy removed from the barotropic tide. This suggests that other processes, such as the internal tide, are removing most of the energy from the barotropic tide.