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Proactive disclosure Print version   | |  Geomorphic effects and impacts from July 1996 severe flooding in the Saguenay area, Quebec
In 1996, major flooding occurred along a number of rivers in British Columbia, Alberta, Saskatchewan and Manitoba. The most disastrous flooding, however, occurred in the Lac Saint Jean-Saguenay area, southern Québec (Fig. 1), due to a major rainstorm during July 18-21, 1996. The Saguenay floods caused severe inundation and extensive erosion along some river reaches resulting in major channel widening and bank erosion, breaching of dams and dykes, and damage to bridges and roads. Commercial and industrial areas located along or dependent the rivers were severely affected. The flooding resulted in the evacuation of 16 000 people and the destruction or damage of approximately 1350 homes. Miraculously, only two people were killed locally (due to a small landslide triggered by the rainfall rather than by flood waters) out of a total of ten killed in southern Québec during the storm. The overall cost of damage in southern Québec attributed to the July 18-21 rainfall and related flooding is estimated to be at least 800 million dollars, making this one of Canada's most costly natural disasters. Flooding in the Saguenay area was caused by a major storm system that stalled over the mouth of the St. Lawrence River between July 18-21, 1996, and which dropped record amounts of rainfall. The largest zone of accumulation occurred just south of the Jonquière-Chicoutimi-La Baie area of the Saguenay Valley, where in excess of 200 mm of rain fell, most within a 36-hour period beginning at about 08:00 on July 19 and continuing until approximately 20:00 July 20. The intense rainfall from the July 18-21 storm, in combination with the near-saturated ground conditions produced by the antecedent July rainfall and the generally thin, discontinuous overburden blanketing the bedrock of the Laurentian Highlands produced widespread flooding throughout the northshore of the St. Lawrence River southern Quebec. The most severe flooding occurred along rivers flowing northwards into the Saguenay Valley and whose headwater areas were located within the greater than 200 mm rainfall accumulation zone. In particular, there was extensive flooding along Rivière aux Ecorces, Rivière Pikauba, and Rivière Cyriac which flow into Lac Kénogami (and therefore are tributaries of Rivière aux Sables and Rivière Chicoutimi), and Rivière du Moulin, Rivière à Mars and Rivière des Ha!Ha! (Fig. 1). Other rivers both in the Saguenay area and elsewhere in southern Québec also experienced major flooding during this storm. The selected photographs depict some of the geomorphic effects and impacts caused by the flooding. Photographs / Location Map Figure 1 Author: Greg Brooks
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