Real-time measurements of ice draft and velocity in the St. Lawrence River

The Canadian Coast Guard monitors winter ice conditions in the St. Lawrence River as part of its responsibilities to prevent and break ice jams in order to minimize the risks of flooding and maintain safe navigation conditions on the St. Lawrence River throughout the winter months. Near real-time information about the coverage, thickness and motion of the ice cover in the navigation channel are required to coordinate icebreaking for maintaining the shipping route, and to prevent and identify ice jams as they develop. Aerial and satellite surveillance provides ice coverage data, but not thickness. This work describes a test installation in the St. Lawrence that provides real-time ice thickness, ice motion, current velocity and meteorological data from a remote site. The IPS (Ice Profiling Sonar) and ADCP Data Display System (IADDS) consists of two submerged instruments (IPS and ADCP), connected by cable to a nearby lighthouse that is equipped with a computer, weather station, appropriate display software and data transmission capability to shore and the Fisheries and Oceans Department's network. The principles and operation of the IPS and the use of an ADCP to measure ice velocity are described. The IPS and ADCP are installed at 13 m depth in the navigation channel in Lac St. Pierre in the St. Lawrence River. Real-time data from the instruments and the weather station are collected at the lighthouse site, and then formatted and transmitted to the Coast Guard headquarters in Quebec City, approximately 200 km away. Web-compatible graphs of the data are then produced for display on the Coast Guard Intranet. The structure of the control, data transmission and storage software is described, and examples are given of the data and its use for managing navigation and detecting ice jams. The results of on-site validation measurements made in the winter of 2002-2003 are also described.