Causes of the current in Little current channel of Lake Huron

A current is observed to flow most of the time through Little Current Channel, between North Channel of Lake Huron and Georgian Bay. The current varies considerably in its speed, and frequently reverses its direction. Inconvenience is experienced by ships wishing to pass through the narrow and shallow channel at Little Current, as they must await an opportunity to do so at slack water or on an opposing current. A field survey was carried out during the summer of 1959 in the vicinity of Little Current, Ontario, to determine the causes of this current and to ascertain whether or not predictions for the state of the current might be made sufficiently in advance to be of assistance to shipping in the area. The field survey is described herein, and the analysis of the data is discussed in detail. The current in Little Current Channel is shown to be essentially a hydraulic flow, driven by differences in water level at the two ends of the channel. The differences in water level are attributed to the action of wind, atmospheric pressure, seiches, and lunar tides, in North Channel and Georgian Bay. The actions in North Channel are considered to be greater than those in Georgian Bay, and are most fully treated. It is concluded that the only contribution to the current at Little Current that could be predicted more than a day in advance is that due to the lunar tide, and that to predict this would be of little value, since on many occasions the other influences would distort and even conceal completely the tidal contribution. It is recommended, however, that a discussion of the causes of the current be incorporated into the Canadian Hydrographic Service's publication, Great Lakes Pilot, as a matter of local interest, and as an aid to mariners wishing to make their own short-term forecast of the current.