Natural Resources Canada
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Storm Surges
Storm surges can occur on both marine and lake shorelines and can cause significant coastal flooding. A storm surge is defined as the difference between predicted tide (or, for lakes, the typical lake level) and the measured high water level. Predicted tide is also known as astronomical tide because it is caused by the relative motions of the Sun, Moon and Earth, among other factors. Water level measured using a tide gauge incorporates both astronomical tide (or lake level) and meteorological impacts on water level, such as wind speed and direction, and air pressure. A storm surge is said to occur when water level exceeds the predicted tide or lake level. As the name implies, storm surges occur during storms when strong winds blow onshore, pushing water against the coast. Another factor is that low air pressure during storms further raises water levels at the coast. The underwater slope of the coast also influences how high a surge can grow locally (for example, surges are higher on gently sloping coasts than on steep coasts).
Storm Surges Map(s)
