May 12th, 2017

Canada Flood Events, May 6 - 11

Posted at 7:06 AM ET

canadaflood-5-11-map-smA slow-moving upper-level weather pattern with an embedded frontal system has brought periods of heavy rainfall to areas of eastern Canada to include the Saint Lawrence, Ottawa and Rideau Rivers and surrounding watersheds. The heavy rainfall together with melting snow has caused significant flooding for areas of southern Québec and eastern Ontario to include areas of Montréal and the National Capital Region. Flood control measures in north Montréal were also compromised, causing the flood threat to amplify. At least 4,141 homes have been flooded in Québec. More heavy rainfall is expected over the coming days.

A separate frontal system has also brought heavy rainfall to the British Columbia Interior. This heavy rainfall together with melting snow has brought flooding to areas including the Okanagan and Kelowna. Additional heavy rainfall with another weather system is forecast for the area, and resulting flood impacts are expected to be severe.

canadaflood-5-11-map-lg

Ontario and Québec Flood Event. SOURCE: CatIQ.

canadaflood-72-hour-precip-lg72 Hour Forecast Precipitation Amounts (inches, through 8 a.m. EDT/12 UTC Sunday). SOURCE: NOAA/WPC

canadaflood-120-hour-precip-lg

120 Hour Forecast Precipitation Amounts (inches, through 8 a.m. EDT/12 UTC Tuesday). SOURCE: NOAA/WPC

Hazard data illustrated in the CAT-i map was taken from GC AdvantagePoint®, Guy Carpenter’s web-based risk management platform. GC AdvantagePoint users can view impacted areas on any map as well as see how their portfolios were affected. Please contact your broker or cat modeling analyst for further information.

Meteorological/Hydrological Summary

Periods of active weather during the month of April have brought historic precipitation to areas of eastern Canada, with especially severe impacts in the Ottawa, Rideau and Saint Lawrence Rivers and surrounding watersheds. Since April 1, the Senior Climatologist at Environment Canada reports that Montréal received 232 millimeters (mm) (about 9 inches) of precipitation, compared to an average of 86 mm (about 3.4 inches), and the prior record of 162 mm (about 6.4 inches). Areas of eastern Canada have received anywhere between two to three times the normal amount of precipitation.

In recent days, a potent and slow-moving frontal system embedded in a highly-amplified and slow-moving upper-air pattern crossed the area. The system brought additional heavy rainfall to the area in combination with melting snow to cause severe flooding. The flooding in the north Montréal area was amplified when flood-control measures were compromised in the Pierrefonds-Roxboro neighborhood. Water levels are reported to be in decline since the peak flooding of recent days.

Another weather system is expected to develop and affect the Saint Lawrence and Ottawa Valley areas over the next several days. Forecast five-day rainfall amounts could exceed 25 mm (one inch) over a large area, with local amounts possibly to exceed 50 to 75 mm (2 to 3 inches), according to precipitation forecasts from the NOAA Weather Prediction Center.

Further west, a separate weather system in a highly-amplified, slow-moving upper-air pattern brought periods of heavy rainfall together with melting snow to cause flooding for areas of the British Columbia interior including the Okanagan and Kelowna areas. Further rounds of precipitation are expected to affect the area over the coming days as another frontal system crosses the area. Rainfall amounts could exceed 25 mm (one inch) through Sunday morning for certain areas according to precipitation forecasts from the NOAA Weather Prediction Center. Environment Canada has posted rainfall warnings, severe thunderstorm watches and special weather statements for areas under threat. This heavy rainfall, together with melting snow is expected to amplify the flood threat for affected areas. The British Columbia River Forecast Centre maintains flood watches for areas under threat. Officials indicate that water levels are expected to peak through tomorrow morning, according to media reports.

Impacts

Eastern Canada

In Québec, media reports indicate that police are searching for two people who were swept away after their car entered a river. Flood inundation has affected at least 173 municipalities around Québec, including 21 in the Mauricie region where at least 300 homes have flooded. At least 4,141 homes have flooded across the province, and at least 3,033 people have had to evacuate as a result. Over 427 roads have flooded. Numerous schools have been closed.

At least 10 cities or towns have declared a state of emergency, including the largest city of Montréal, Yamachiche, Laval, Rigaud and Deux-Montagnes, according to media reports. Montréal officials are considering extending that state of emergency for another five days. At least 1,650 Canadian soldiers and support personnel have been deployed to support response efforts including sandbagging homes. Media reports indicate that more Canadian troops are being deployed to Québec.

In western Québec and eastern Ontario, water levels on the Ottawa River continue to drop where flood impacts have caused inundation in the National Capital Region. Officials in Ottawa and Gatineau have asked the federal government for additional supplies to help deal with the deluge after having run out of sandbags. Federal civil servants were told to stay home on Monday to help keep roads clear for emergency vehicles. Federal government offices located in Gatineau were closed on Monday. Canadian government officials noted on Monday that the general situation appeared to be stabilizing although local circumstances were still unstable, according to media reports.

British Columbia

In British Columbia, rescue crews are searching for two men who went missing late Friday, according to media reports. Flooding and washouts caused problems in the Shuswap and around Kamloops and Merritt. A reported mudslide has affected Tappen and caused a house to slide off its foundation. A state of emergency was declared in the District of Lake Country, Kelowna, West Kelowna, the Fintry Delta and the Regional District of Central Okanagan. Water quality was affected for Vernon, Kimberly, Nelson and parts of the Westbank First Nation. Localized flooding affected areas of the Central Okanagan Regional District where evacuation orders were necessary. Evacuation alerts were also issued for the Fintry Delta and areas of Kelowna. A precautionary evacuation alert was issued for areas south of Logan Lake over concerns of possible damage to the Mamit Lake dam spillway.

Okanagan residents are being urged to prepare for further flooding Thursday when more heavy rainfall is expected in the area. The Central Okanagan Regional District has issued another round of evacuation alerts for nearly 600 properties at the south end of Wood Lake, near Kelowna.

Sources: Environment Canada, BBC, CBC, NOAA Weather Prediction Center, Weather Underground, Times-Colonist British Columbia.

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Guy Carpenter publishes CAT-i reports for major natural catastrophes worldwide. These reports cover catastrophes including worldwide tropical cyclones, earthquakes, major UK and European floods and any other natural event that is likely to incur a significant loss to the (re)insurance industry. Please email CAT.i@guycarp.com if you wish to be added to the free email distribution list.

Guy Carpenter compiles RISK-i reports for major technological or man-made events worldwide. These reports cover risks to property, transport and life including explosions, fires, crashes, engineering disasters and terrorist attacks that are likely to incur a significant loss to the (re)insurance industry. Please email RISK.i@guycarp.com if you wish to be added to the free email distribution list.

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