(Courtesy of Applied Physics Group, Johns Hopkins University)

Every year, a few large storms batter Atlantic Canada. The greatest fear in low-lying coastal areas is flooding. This happens where low pressure and strong onshore winds raise the water level up a metre or more above normal forming a STORM SURGE.

This is the storm surge of January 2000, as modelled on a computer at Dalhousie University. Record water levels flooded parts of Charlettetoen, P.E.I. (High-water levels are red).

(Source: Dalhousie Storm Surge Forecast System)

Carrier Waves

Extreme water levels are achieved when a storm surge happens during a very high tide. Storm waves that accompany the surge can then wreak great damage. The tide is the CARRIER WAVE for the surge; the surge is the CARRIER WAVE for the storm waves.

What can we do to protect our communities and farms from storm surge flooding?

Greater floods to come!

If floods have happened many times in the past, why worry about the future? The answer is that sea level will rise dramatically in Atlantic Canada over the next century. Storm surges will flood areas NEVER BEFORE FLOODED.

An example of the CARRIER WAVE idea is the notorious SAXBY TIDE, which flooded the lowlands at the head of the Bay of Fundy on Otober 5, 1869 (right). The storm surge generated by a hurricane moving into New Brunswick coincided with the high tide to give extreme water levels that overtopped the dykes.

Threatened areas: some examples

(Photograph courtesy of G. Parkes)

Placentia, Newfoundland was flooded by storm surges until a dyke and a sea wall were built. With rising sea level, the defences will have to be strengthened.

(Photograph courtesy of K. Oxner, The Yarmouth Vanguard)

When a storm hit Yarmouth in February 1976, much of the town was flooded, leaving cars and buses stranded; many buildings were destroyed. Yarmouth, like many other communities on Atlantic Canada, faces worse flooding in the future.

(Photograph courtesy of E. Desplanque)

A freight train runs along the dyke near Sackville, N.B. The tide is only a few feet below the crest of the dyke. A storm surge at highest tide would reach half way up the side of the freight cars. As time goes by, this situation will get worse. Dykes will have to be heightened or abandoned.

(Courtesy of D.R. Parrott)

(Courtesy of D.R. Parrott)

Today, the town of Truro, Nova Scotia (above bottom) would be flooded (above right) by a storm surge similar to the Saxby Tide of 1869; however, sea level has risen 44 cm since 1869, and will increase by 70 cm by 2100 A.D. As time goes by, Truro will be flooded more frequently and the floods will become more severe.