This database contains summary information on 168 Canadian flood disasters that occurred between 1900 and June 1997. The database originates from the Emergency Preparedness Canada disaster database (Office of the Senior Scientific Advisor, written communication, November 1997) that was modified by Brooks et al. (2001), a hard-copy listing of the flood database is contained in the latter reference. The database is not, by any means, a complete list of flood 'events' in Canada since the vast majority of the floods did not cause 'disasters' *. All mentions of damage costs have not been corrected for inflation. The database also is biased towards the more densely populated areas of Canada where floods are more likely to impact humans. Despite these limitations, the database provides an indication of the significance, impact, and location of damaging floods in Canada.

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Overview of the Database

Based on Brooks et al. (2001), the twelve provinces and territories (Nunavut is included within the Northwest Territories) have experienced 168 known flood disasters between 1900 and June, 1997 (Figure 1). In eastern Canada, the flood disasters have occurred predominately in the south where the population is concentrated (Figure 2). The distribution of disasters is much more scattered in western Canada, although there is notable clustering in southern Manitoba, and southwestern and northwestern British Columbia (Figure 2). About 62% of the disasters have occurred in four provinces; Ontario (37 events), New Brunswick (26 events), Québec (23 events) and Manitoba (18 events) (Figure 1). Specific areas that have experienced recurrent flood disasters are the Saint John River basin, New Brunswick, (16 disasters) and the Red River basin, Manitoba (15 disasters, including the Assiniboine River; (Figure 2). The relatively few disasters in the N.W.T. (5 events), and Yukon (3 events), which represent about 40% of the area of Canada, reflects the very sparse population in the north.

Flooding in Canada has resulted directly and indirectly in the deaths of at least 198 people and over several billion dollars of damage during the 20th century. This figure of 198 deaths must be considered a minimum because damaging floods not included in the database have almost certainly claimed additional lives. In terms of loss of life, the greatest Canadian flood disaster, by far, was caused by Hurricane Hazel, which struck southern Ontario in October 1954, killing 81 people. The most costly flood in Canada was the may 1950 flood disaster in the Red River valley, southern Manitoba, with costs estimated to be $1093 M in 1999 dollars (data from Emergency Preparedness Canada).

Although the brief summaries of the flood disasters in the database are in some cases too vague to identify the flood mechanisms conclusively, the database does reveals that over 65% of the flood disasters are the result of snowmelt runoff, storm rainfall or rain-on-snow (combinations of snowmelt runoff and storm rainfall are inferred to be rain-on-snow). Of secondary importance are hurricanes, ice jams, storm-rainfall/snowmelt-runoff/ice-jam combinations and snowmelt-runoff/ice-jam combinations. Hurricanes (or their remnants) are a significant flood mechanism in the Maritime provinces. Only one flood in the disaster database is the result of a natural dam failure (Kicking Horse Pass, BC; September 7, 1978).

Although flood disasters occur in every month of the year, about 40% happen in April and May, which coincides with the snowmelt period throughout much of southern Canada (Figure 3). This period is also when several common flood mechanisms (snowmelt runoff, storm rainfall and ice jams) are likely to occur concurrently, thereby increasing the likelihood of high flows. Many of the flood disasters during the January to March period are the result of rain-on-snow during winter mild spells, while floods during the June to November period are the result of rainstorm-runoff. 11 of the 20 flood disasters in eastern Canada (Ontario to Newfoundland) in the months of August, September and October were caused by hurricanes or their remnants. The smallest number of flood disasters has occurred in the months of November and December.

The database suggests that the number of flood disasters has increased through the 20th century with about 70% occurring after 1959 (Figure 4). This trend likely reflects several factors. Ashmore and Church (2001) indicate that there has been a general increase in the magnitude of flood events in the second half of the 20th century relative to the first half, along many Canadian rivers, which is thought to reflect a shift in climate. Also, over the 20th century there has been increased development on flood prone lands as Canada's population has grown. Finally, there is better reporting of flood disasters over the past several decades. Relating to the second point, smaller pre-1960 flood disasters probably are under-represented in the database because they were mainly reported in small, local papers and the details provided may be scant causing the events to be overlooked as 'disasters'.

For additional information concerning flood disasters in Canada, please contact: Greg Brooks.

* Emergency Preparedness Canada defines a disaster as "an interruption in time and space of normal processes causing death, injury or homelessness, economic or property lose, and/or significant environmental damage. The interruption is beyond the coping capacity of the community and/or is beyond the assumed risks of human activity. Assumed risk is inherent in most human activity such as transportation and handling of dangerous goods. The interruption precludes war."

References

Ashmore, P. and Church, M.: The impact of climate change on rivers and river processes in Canada, Geological Survey of Canada Bulletin 555, Ottawa, 58 p.

Brooks, G.R., Evans, S.G. and Clague, J.J.: 2001, Flooding, In G.R. Brooks (ed), A Synthesis of Natural Geological Hazards in Canada, Geological Survey of Canada Bulletin 548, Ottawa, pp, 101-143.