Montreal Flood of 1987
Encyclopedia
The Montreal Flood of 1987 happened on July 14 of that year when a series of strong thunderstorm
s crossed the island of Montreal
, Canada, between the noon hour and 2:30 p.m. Over 100 mm of rain fell during this very short period of time. The sewer
systems were overwhelmed by the deluge and the city was paralyzed by the flooded roads. Autoroute 15, a sunken highway also known as the Decarie Expressway, soon filled with water trapping motorists. Some 350,000 houses lost electricity, and tens of thousands had flooded basements. Two people died, one in a submerged car and another who was electrocuted
.
had been affecting the province of Quebec, Canada, for over a week. Temperatures in the air mass
were reaching 35 °C (95 °F) and the dew point
s were around 25 °C (77 °F), both exceptionally high for Southern Quebec. During the evening of July 13, a northeast to southwest cold front
approached the Montreal region from Ontario and triggered isolated severe thunderstorms.
Evaluation of the nearby upper air station tephigram
showed a very strong convective available potential energy
(CAPE) and the hodograph had a strong wind shear
in the first 4 kilometres (13,123.4 ft) above ground, conducive to rotation in the convective clouds, hail
, heavy rain downpours, and downburst
s. There was a thick layer of clouds northwest of Montreal, near the frontal zone, but only a thin layer of low clouds further southeast. The analysis of the upper air data led to the prediction of a maximum temperature again above 30 °C (86 °F) and dew points of 23 °C (73.4 °F).
showed the following conditions at 11 a.m.: temperature of 28.5 °C (83.3 °F), relative humidity
of 73%, wind speed
of 9 km/h, and weather conditions hazy
. By noon, conditions deteriorated quickly to thunderstorms and heavy rain showers.
The weather radar loop on the right shows that a series of four thunderstorms, noted A to D, crossed the Island of Montreal from Valleyfield
to Sorel
. These affected roughly the same area from 1620 GMT (12:20 pm local) to 1830 GMT (2:30 pm local). The intensities on the 1.5 km height CAPPI
are over 47 dBZ which represents rain rates of 40 millimetres (1.6 in) per hour or more. Three times, these intensities reached above 7 kilometres (22,965.9 ft), indicating the possibility of severe downbursts and hail. Trees were uprooted and large hail reported. But these phenomena were dwarfed by the amount of rain the thunderstorms left.
and downtown areas. The largest official amount has been 103 millimetres (4.1 in) at Parc Lafontaine
but a non official total of 181 millimetres (7.1 in) was recorded by a City of Montreal station in the downtown core. The city of Laval, Quebec
that occupy Île Jésus
just to the North received a large amount of rain too, up to 72.4 millimetres (2.9 in). However, the region just across the Saint Lawrence River
from Montreal was spared the worst as only 10 millimetre (0.393700787401575 in) is recorded at Saint-Hubert airport and 20 millimetre (0.78740157480315 in) in Laprairie according to Environment Canada
.
Montreal's sewer system was designed to handle only 36 millimetres (1.4 in) per hour, according to Gaston Moreau assistant director of public works, which is a 10 year occurrence. The flood is estimated to be at least a 50 years return period
. Lightning and wind caused widespread power outages which in turn stopped the pumping system from evacuating the excess water from low lying roads and underpasses. Décarie expressway, a sunken highway, rapidly filled with water descending from access roads and soon became a river. Thousands of motorists were trapped and had to be rescued by firefighters and truckers with higher vehicles. An 80-year-old man died from drowning and another person died of electrocution.
Nearly households lost electrical power, to houses and businesses were flooded causing an estimated CAD$220 million (of 1987) in damages. Traffic was paralyzed for hours as most streets and roads had flooded areas. Montreal Metro
, buses and suburban trains service were stopped. The basement of an old-age hospital in the Saint-Henri neighbourhood
was flooded and 240 patients were left without electricity, food, and health services for a while.
.
In 1988, all the cities on the Island of Montreal, regrouped into the Montreal Urban Community
, set up a common Emergencies Coordination Bureau (Bureau des mesures d'urgence). In 1997, the bureau was renamed Centre de sécurité civile. Following the Municipal reorganization in Quebec
in 2002, most of the cities were regrouped into the greater Montreal and the center became the Centre de sécurité civile de Montréal.
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...
s crossed the island of Montreal
Island of Montreal
The Island of Montreal , in extreme southwestern Quebec, Canada, is located at the confluence of the Saint Lawrence and Ottawa Rivers. It is separated from Île Jésus by the Rivière des Prairies....
, Canada, between the noon hour and 2:30 p.m. Over 100 mm of rain fell during this very short period of time. The sewer
Sewer
Sewer may refer to:* Part of sewerage, the infrastructure that conveys sewage*Effluent sewer, a collection system that transports only the liquid portion of wastewater through small-diameter pipes laid at contour...
systems were overwhelmed by the deluge and the city was paralyzed by the flooded roads. Autoroute 15, a sunken highway also known as the Decarie Expressway, soon filled with water trapping motorists. Some 350,000 houses lost electricity, and tens of thousands had flooded basements. Two people died, one in a submerged car and another who was electrocuted
Electrocution
Electrocution is a type of electric shock that, as determined by a stopped heart, can end life. Electrocution is frequently used to refer to any electric shock received but is technically incorrect; the choice of definition varies from dictionary to dictionary...
.
Meteorological situation
A heat waveHeat wave
A heat wave is a prolonged period of excessively hot weather, which may be accompanied by high humidity. There is no universal definition of a heat wave; the term is relative to the usual weather in the area...
had been affecting the province of Quebec, Canada, for over a week. Temperatures in the air mass
Air mass
In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. They are classified according to latitude and their continental or maritime...
were reaching 35 °C (95 °F) and the dew point
Dew point
The dew point is the temperature to which a given parcel of humid air must be cooled, at constant barometric pressure, for water vapor to condense into liquid water. The condensed water is called dew when it forms on a solid surface. The dew point is a saturation temperature.The dew point is...
s were around 25 °C (77 °F), both exceptionally high for Southern Quebec. During the evening of July 13, a northeast to southwest cold front
Cold front
A cold front is defined as the leading edge of a cooler mass of air, replacing a warmer mass of air.-Development of cold front:The cooler and denser air wedges under the less-dense warmer air, lifting it...
approached the Montreal region from Ontario and triggered isolated severe thunderstorms.
Initial analysis
The map on the left shows the meteorological situation at 1200 GMT of the morning of July 14, 1987 (0800 local). The cold front at the border between Ontario and Quebec is supported by an intensifying barometric trough at 500 mb, and a low pressure is developing at the surface, just southwest of Ottawa, Ontario. Cumulonimbus with high tops were easily forming in the moist, humid and unstable air mass near the ground while drier air was cooling the air in the mid-tropospheric levels. A wind divergence at the upper level and a convergence near the surface, due to the low pressure, was helping to organize the deep convection.Evaluation of the nearby upper air station tephigram
Tephigram
A tephigram is one of four thermodynamic diagrams commonly used in weather analysis and forecasting. The name evolved from the original name "T-\phi-gram" to describe the axes of temperature and entropy used to create the plot...
showed a very strong convective available potential energy
Convective available potential energy
In meteorology, convective available potential energy , sometimes, simply, available potential energy , is the amount of energy a parcel of air would have if lifted a certain distance vertically through the atmosphere...
(CAPE) and the hodograph had a strong wind shear
Wind shear
Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and direction over a relatively short distance in the atmosphere...
in the first 4 kilometres (13,123.4 ft) above ground, conducive to rotation in the convective clouds, hail
Hail
Hail is a form of solid precipitation. It consists of balls or irregular lumps of ice, each of which is referred to as a hail stone. Hail stones on Earth consist mostly of water ice and measure between and in diameter, with the larger stones coming from severe thunderstorms...
, heavy rain downpours, and downburst
Downburst
A downburst is created by an area of significantly rain-cooled air that, after reaching ground level, spreads out in all directions producing strong winds. Unlike winds in a tornado, winds in a downburst are directed outwards from the point where it hits land or water...
s. There was a thick layer of clouds northwest of Montreal, near the frontal zone, but only a thin layer of low clouds further southeast. The analysis of the upper air data led to the prediction of a maximum temperature again above 30 °C (86 °F) and dew points of 23 °C (73.4 °F).
Development
The surface low deepened as the day progressed and moved very slowly. Rising temperatures and breaking of the low clouds meant that cumulonimbus developed along the clouds’ edge when the dry air at the upper level reached extreme southwestern Quebec. The Montreal-Dorval weather stationWeather station
A weather station is a facility, either on land or sea, with instruments and equipment for observing atmospheric conditions to provide information for weather forecasts and to study the weather and climate. The measurements taken include temperature, barometric pressure, humidity, wind speed, wind...
showed the following conditions at 11 a.m.: temperature of 28.5 °C (83.3 °F), relative humidity
Relative humidity
Relative humidity is a term used to describe the amount of water vapor in a mixture of air and water vapor. It is defined as the partial pressure of water vapor in the air-water mixture, given as a percentage of the saturated vapor pressure under those conditions...
of 73%, wind speed
Wind speed
Wind speed, or wind velocity, is a fundamental atmospheric rate.Wind speed affects weather forecasting, aircraft and maritime operations, construction projects, growth and metabolism rate of many plant species, and countless other implications....
of 9 km/h, and weather conditions hazy
Haze
Haze is traditionally an atmospheric phenomenon where dust, smoke and other dry particles obscure the clarity of the sky. The World Meteorological Organization manual of codes includes a classification of horizontal obscuration into categories of fog, ice fog, steam fog, mist, haze, smoke, volcanic...
. By noon, conditions deteriorated quickly to thunderstorms and heavy rain showers.
The weather radar loop on the right shows that a series of four thunderstorms, noted A to D, crossed the Island of Montreal from Valleyfield
Valleyfield
Valleyfield may refer to:* Valleyfield, Fife, Scotland* Valleyfield, Newfoundland and Labrador, Canada...
to Sorel
Sorel
Sorel is a line of winter boots, currently a subsidiary of Columbia Sportswear. The boot has long been popular in Canada for its high quality and warmth. The Sorel line was introduced in 1962 by Kitchener, Ontario-based Kaufman Rubber Co. , and became the world's best-selling cold weather boot...
. These affected roughly the same area from 1620 GMT (12:20 pm local) to 1830 GMT (2:30 pm local). The intensities on the 1.5 km height CAPPI
Constant Altitude Plan Position Indicator
The Constant Altitude Plan Position Indicator, better known as CAPPI, is a radar display which gives a horizontal cross-section of data at constant altitude...
are over 47 dBZ which represents rain rates of 40 millimetres (1.6 in) per hour or more. Three times, these intensities reached above 7 kilometres (22,965.9 ft), indicating the possibility of severe downbursts and hail. Trees were uprooted and large hail reported. But these phenomena were dwarfed by the amount of rain the thunderstorms left.
Impact
Heavy rain affected all of the Island of Montreal. There was 57.8 millimetres (2.3 in) recorded at Montreal Pierre-Elliot Trudeau International Airport on the West end and 56 millimetres (2.2 in) at Rivière-des-Prairies on the East end. However the highest amounts were recorded around the Mont-RoyalMount Royal
Mount Royal is a mountain in the city of Montreal, immediately west of downtown Montreal, Quebec, Canada, the city to which it gave its name.The mountain is part of the Monteregian Hills situated between the Laurentians and the Appalachians...
and downtown areas. The largest official amount has been 103 millimetres (4.1 in) at Parc Lafontaine
Parc Lafontaine
Parc La Fontaine is a 36-hectare urban park located in Montreal's Plateau Mont-Royal district. Named in honour of Louis-Hippolyte Lafontaine, features include two linked ponds with a fountain and waterfalls; the Théâtre de Verdure open-air venue; the Calixa-Lavallée cultural centre, a monument to...
but a non official total of 181 millimetres (7.1 in) was recorded by a City of Montreal station in the downtown core. The city of Laval, Quebec
Laval, Quebec
Laval is a Canadian city and a region in southwestern Quebec. It is the largest suburb of Montreal, the third largest municipality in the province of Quebec, and the 14th largest city in Canada with a population of 368,709 in 2006...
that occupy Île Jésus
Île Jésus
Île Jésus is an island in southwestern Quebec, separated from the mainland to the north by the Rivière des Mille Îles, and from the Island of Montreal to the south by the Rivière des Prairies....
just to the North received a large amount of rain too, up to 72.4 millimetres (2.9 in). However, the region just across the Saint Lawrence River
Saint Lawrence River
The Saint Lawrence is a large river flowing approximately from southwest to northeast in the middle latitudes of North America, connecting the Great Lakes with the Atlantic Ocean. It is the primary drainage conveyor of the Great Lakes Basin...
from Montreal was spared the worst as only 10 millimetre (0.393700787401575 in) is recorded at Saint-Hubert airport and 20 millimetre (0.78740157480315 in) in Laprairie according to Environment Canada
Environment Canada
Environment Canada , legally incorporated as the Department of the Environment under the Department of the Environment Act Environment Canada (EC) (French: Environnement Canada), legally incorporated as the Department of the Environment under the Department of the Environment Act Environment...
.
Montreal's sewer system was designed to handle only 36 millimetres (1.4 in) per hour, according to Gaston Moreau assistant director of public works, which is a 10 year occurrence. The flood is estimated to be at least a 50 years return period
Return period
A return period also known as a recurrence interval is an estimate of the interval of time between events like an earthquake, flood or river discharge flow of a certain intensity or size. It is a statistical measurement denoting the average recurrence interval over an extended period of time, and...
. Lightning and wind caused widespread power outages which in turn stopped the pumping system from evacuating the excess water from low lying roads and underpasses. Décarie expressway, a sunken highway, rapidly filled with water descending from access roads and soon became a river. Thousands of motorists were trapped and had to be rescued by firefighters and truckers with higher vehicles. An 80-year-old man died from drowning and another person died of electrocution.
Nearly households lost electrical power, to houses and businesses were flooded causing an estimated CAD$220 million (of 1987) in damages. Traffic was paralyzed for hours as most streets and roads had flooded areas. Montreal Metro
Montreal Metro
The Montreal Metro is a rubber-tired metro system, and the main form of public transportation underground in the city of Montreal, Quebec, Canada....
, buses and suburban trains service were stopped. The basement of an old-age hospital in the Saint-Henri neighbourhood
Saint-Henri
Saint-Henri is a neighbourhood in southwestern Montreal, Quebec, Canada, in the borough of Le Sud-Ouest.Saint-Henri is usually considered to be bounded to the east by avenue Atwater, to the west by Autoroute 15, to the north by Autoroute 720, and to the south by the Lachine Canal.- Description...
was flooded and 240 patients were left without electricity, food, and health services for a while.
Long-term impact
Most home insurance claims were declined unless the insured was specifically covered by a clause concerning flood. However, the car owners were covered. The Quebec government promised monetary help but only 20 to 40% of the expected CAD$40 million was ever distributed. Court cases against the municipal authorities, including a class action, were rejected as the flood was considered an Act of GodAct of God
Act of God is a legal term for events outside of human control, such as sudden floods or other natural disasters, for which no one can be held responsible.- Contract law :...
.
In 1988, all the cities on the Island of Montreal, regrouped into the Montreal Urban Community
Montreal Urban Community
The Montreal Urban Community was a regional government that covered all municipalities that later merged into the megacity of Montreal.- History :...
, set up a common Emergencies Coordination Bureau (Bureau des mesures d'urgence). In 1997, the bureau was renamed Centre de sécurité civile. Following the Municipal reorganization in Quebec
Municipal reorganization in Quebec
The most recent episode of municipal reorganization in Quebec, Canada, was undertaken in 2002 by the Parti Québécois Government of Quebec, headed by Premier Lucien Bouchard and his successor Bernard Landry....
in 2002, most of the cities were regrouped into the greater Montreal and the center became the Centre de sécurité civile de Montréal.