In the days leading up to June 19, 2013, parts of southern and central Alberta, Canada experienced heavy rainfall that triggered catastrophic flooding described by the provincial government as the worst in Alberta's history. Areas along the Bow, Elbow, Highwood, Red Deer, Sheep, Little Bow, and South Saskatchewan rivers and their tributaries were particularly affected. A total of 32 states of local emergency were declared and 28 emergency operations centres were activated as water levels rose and numerous communities were placed under evacuation orders.
Five people were confirmed dead as a direct result of the flooding and over 100,000 people were displaced throughout the region. Some 2,200 Canadian Forces (CF) troops were deployed to help in flooded areas in addition to the Royal Canadian Mounted Police and Alberta Sheriffs Branch response. Total damage estimates exceeded C$5 billion and in terms of insurable damages, made the 2013 Alberta floods the costliest disaster in Canadian history at $1.7 billion, until the occurrence of the 2016 Fort McMurray wildfire. Receding waters gave way to a mammoth cleanup of affected areas, aided by a spontaneous volunteer campaign in which many homeowners were assisted by complete strangers.
Meteorology
Situated east of the Canadian Rockies, southern Alberta is a semi-arid region that does not usually receive high amounts of rainfall. A high-pressure system in northern Alberta blocked the passage to a low-pressure area to the south, 19-21 June. This blocked circulation and easterly winds pumped humidity on the rising slopes of the Rocky Mountains foothills, causing heavy rain into the province with rainfall amounts of over to fall in less than two days in many regions of the province, particularly west and southwest of Calgary. In Canmore, a town in Alberta's Rockies, over fell in just 36 hours, nearly half of the town's annual average rainfall. In the town of High River, rainfall amounts at one weather station recorded 325 millimetres (12.8 in) in less than 48 hours. The rain falling on already saturated ground, coupled with the steep watershed and heavy snow loads remaining in the front ranges of the Rocky Mountains, resulted in a rapid increase in the size and flow of several rivers.
At the peak of the flooding, the Bow and Elbow rivers were flowing through Calgary at three times their peak levels from a 2005 flood that caused C$400 million in damages. Within 48 hours, by 8 a.m. MDT on June 21, the flow rate on the Bow River had reached 1,458 cubic metres (51,489 cubic ft.) per second (m3/s), five times its normal rate for this time of the year. The Elbow and Highwood rivers reached flow rates of 544 m3/s (inside Calgary) and 734 m3/s respectively, ten times their averages for this time of year. According to data tracked by Alberta's Ministry of Environment and Sustainable Resource Development, "in the space of a day or two, the flows of the three rivers rocketed up five to 10 times their normal rates."
Impact
Government officials called the flooding the worst in Alberta's history.
By June 24, 2013, some 2,200 Canadian Forces (CF) troops had been deployed to help in flooded areas. Land Force Western Area brought in Coyote reconnaissance vehicles, Bison armoured vehicles, G-Wagen Jeeps, and other military vehicles.
As communities began to flood and people became displaced, area residents mobilized to offer support and assistance to evacuees and emergency response personnel. Some volunteers and several police officers worked up to 20 hours to help evacuation efforts despite knowing their own homes had been damaged or completely washed away. While coverage of the flooding spread throughout social media sites, many people and businesses also took to Facebook and Twitter to open their homes up to neighbours and strangers who did not have other places to stay or offer whatever support they could.
Calgary
In Calgary, Alberta's largest city, 26 neighbourhoods in the vicinity of the Bow and Elbow rivers were placed under a mandatory evacuation order on June 20 and 21 as the rivers spilled over their banks and flooded communities. Affecting 75,000 people, it was the largest evacuation order in the city's history. The city's downtown core was among the areas evacuated, as officials called for a "Neighbour Day" on June 21 and requested people to stay home, particularly the 350,000 people who work downtown. All schools in both the public and Catholic school districts were closed and officials urged residents to avoid unnecessary travel.
On June 21, the Bow River had reached a record high water level of . That same day, the river also reached a record high flow rate of .