On Tuesday February 6, 2001, Environment Canada issued a storm surge warning for New Brunswick, which read:
An intense low pressure system over the Bay of Fundy... will move northeastward today to lie near Port-aux-Basques Newfoundland this evening.
This system is expected to generate a storm surge this afternoon of around one metre along the New Brunswick Gulf of St. Lawrence coast and into the western Northumberland Strait.
This storm surge will coincide with a high run of astronomical tides this afternoon to produce unusually high water levels which will result in some flooding very close to the shoreline. There is ice all along the shoreline so there will be no ocean waves at the shoreline. However gale force northeast winds this afternoon will cause strong ice pressure close to the coast which will cause ice rafting and could result in some ice pile-up at the shoreline.
The threat will end as the storm surge diminishes and the astronomical tide lowers this evening.
What is a storm surge?
The United States National Hurricane Center defines storm surge as "the abnormal rise in water level caused by wind and pressure forces of a hurricane. It can be extremely devastating, and is in fact a major cause of damage from hurricanes. The storm surge itself is caused by the wind and pressure 'pushing' the water into the continental shelf and onto the coastline. The height of a surge is basically measured as a deviation from the mean sea level in the area, and in some historical storms, this value has reached over 20 feet (six metres)."
What causes a storm surge?
As the Environment Canada weather warning indicates, a storm surge is caused by a combination of factors.
The intensity and size of the surge depends on the strength of the winds. Most storm surges occur during hurricanes and usually the stronger the hurricane, the higher the storm surge.
Low pressure acts like a vacuum, creating higher waves and raising the sea level.
The direction of the wind is important, wind blowing on to the coastline pushes water inland, wind blowing along the coast (as is sometimes the case in a hurricane) pushes the water along the shore.
A lower elevation (as in Bangladesh which is often threatened by storm surge) means the storm can move water further inland.
The slope of the sea bottom can also magnify a storm surge under certain conditions.
Higher tides at the time of a storm surge – sometimes called storm tides – produce surges that can be 50 per cent higher than normal high tides.
How dangerous is a storm surge?
The U.S. National Ocean and Atmospheric Administration says the storm surge "is unquestionably the most dangerous part of a hurricane," adding the surge can "act like a giant bulldozer sweeping everything in its path." In tropical areas, a hurricane storm surge can sometimes cause nine of every 10 fatalities. The danger doesn't just come from wind and water. The surge smashes everything in its path, boats, trees, utility poles and buildings.
During Hurricane Camille in 1969, one of the highest storm surges on record – 25 feet or 7.6 metres – smashed into the town of Pass Christian, Mississippi.