Flood of Saguenay

The flood of Saguenay is a series of Inondation S which struck the Saguenay-Lake-Saint-Jean, in the center of the Canadian province of the Quebec, from July 19th to 21st 1996. Those occurred when an important depression passed on the south of Quebec, responsible for moisture coming from the Atlantic east coast. This system gave from 50 to 100 Millimètre S of rain on the majority of the areas of the valley of the St. Lawrence, but even more in the mountainous region which surrounds Saguenay. One owes him ten deaths and more than 1,5 billion CAN in damage.

Weather situation

After one spring and a beginning of fresh summer and rainy, especially the two weeks before the flood, the ground made up of Graben was already saturated with water. Moreover, in the most affected areas, the many basins Barrage S hydroelectric (of which several had Digue S secondaries out of ground and rocks) were full.

The synoptic weather situation observed from July 18th to 21st 1996 was thus not very common in full summer period on the east of Canada. A major depression passed from the Big lakes towards Montreal, then went up slowly along the the Appalachian Mountains, towards the Golfe of the St. Lawrence. The explosive intensification of the system on the south of Quebec, then on the State of Maine, was typical development of a winter storm.

The main features and the thermodynamic features of this depression were, according to Environnement Canada:

a trajectory having swept the south of Quebec
an intensification marked of the storm on Quebec
an important deceleration on the State of Maine
a stagnation of the zones of Precipitation S on the center and is of Quebec
a thermal contrast which was not particularly intense at the beginning, but which intensified on Quebec
a Humidité available important
a release of Latent heat which was the main motor of the development
an activity Orage uses overlapping and a Orographie which were the principal components of the space variability of the levels of rain recorded.

This system gave from 50 to 100 Millimètre S of rain on all the south-west of Quebec. The quantities however reached up to 275 mm on the areas bordering Saguenay. These quantities correspond roughly so that the area receives on the whole in normal July. Secondary axes of precipitations of less intensity were also observed in Abitibi and Estrie. According to Canada Environment: “The analyzes of recurrence of maximum precipitations, for this event, show local periods of return of more than 100 years for several sites for which the total of precipitations exceeded 120 mm in 48 hours. From a Canadian historical point of view, the pouring rain from July 18th to 21st 1996 is found among the most important events of measured abundant rains. ”.

The sudden surge of rain overloaded the basins of the stoppings. Even if the valves of the latter were opened, the surplus of water created breaches in certain dams around Chicoutimi. The areas of the Coast-North also received significant amounts of rain and sudden of the floods.

Too bad

Nearly two meters of water broke in the towns of Chicoutimi and the Bay, killing seven people (two with the Bay and five on the Coast-North) and causing the evacuation of 16.000 others. The material damage was estimated at 1,5 billion Canadian dollars.

The river of the ha! Ha!, to the south of Chicoutimi, also left its regular course to trace new while cutting the roads, isolating a good part of the area from low Saguenay and back-country.

Elsewhere, several culverts yielded along the road 138 between Tadoussac and Seven-Islands. Three other people lost the life in these areas.

Board of inquiry

Following the events, a board of inquiry, chaired by the engineer Roger Nicolet, was established. All the speakers came to testify: the Weather service of Canada (SMC) of Environment Canada, owners of the Stopping S (Alcan, Hydro-Quebec), governmental authorities and local elections, experts in disasters, researchers in Hydrologie (like those of the INRS-water) as well as citizens.

Among the recommendations of the commission, it was marked that the Québécois company was to obtain more strict standards on the level of the construction and the monitoring of the stoppings. Indeed, the stoppings of the Saguenay dated of more than 50 years and some of the Vanne S of the crest gates of Crue S were not functional calculuses. Moreover, even if a warning weather of abundant rain had been emitted, the operators did not react quickly. The report/ratio also recommended the town and country planning of the floodplains and those at the risk, as well as the respect by the municipalities of the public administration of these zones.

There exists approximately: 11000 stoppings with the Quebec. Among those: 2200 are considered with strong capacity of water according to their height and the volume of water selected. Quebec also has: 2600 vestiges of stoppings, which requires a global level in the event of critical situation.

Another of the recommendations was to envisage an emergency plan for each municipality of Quebec for any possibility, not only the Inondation S. These plans started to be defined when, in January 1998, the south-west of the province underwent a massive glaze. That made it possible to better manage the crisis.

Anecdotes and other effects

The image of left shows the flood with Chicoutimi. One sees water passing above the Digue and breaking in cascades. All these buildings were carried later, except the white small house (with the extreme right-hand side on the photograph) and the church (with the extreme left), which miraculeusement were miraculeusement saved. The house became, later, a symbol for the area and a Musée on the flood.

The rivers Saguenay and ha! Ha! saw their Sédiment S strongly polluted covered by a new layer with sediments. Thus the flood will have had this ecologically beneficial effect (at least, in the short run), although unexpected.

External bonds

University of Sherbrooke: assessment
Assessment by [[Laval university|the Laval university]]
Photographs of witnesses

Random links: