Flooding events in Canada: Atlantic Provinces

New Brunswick

The Province of New Brunswick has a long history of flooding, with incidents of varying severity being reported frequently since 1696. Snowmelt, ice jams and heavy rainfall are the principal causes. As illustrated, a large proportion of flood events involve various combinations of these factors. Most of the major reported floods, such as those of 1887, 1923, 1936, 1970, 1973, 1976, 1979, and 1987, fall into this category.


Lincoln-Baker Brook, Highway 7 - Fredericton, NB (May 1, 1973)

Lincoln-Baker Brook, Highway 7 - Fredericton, NB (May 1, 1973)

Flooding due to snowmelt may result from spells of warm weather following a winter of heavy snowfall. These conditions existed during the floods of early May 1961, April 1977, and April-May 1982. More often, serious floods involving snowmelt occur when a heavy rainfall accompanies the annual spring runoff, as was the case in the major flood of April-May 1973. As well, this combination often contributes to the formation of ice jams. Although snowmelt was the sole cause of only 7% of the reported floods, it was factor in 40% of the province's documented flood events. Severe flood conditions associated with ice jamming generally occur in spring breakup, and occasionally in midwinter thaws during January to March. A more detailed description of ice jam flooding of the Saint John River is provided later.

Floods involving ice jams tend to be more destructive than open water events, particularly in regard to bridges. For example, during the February 1970 flood, which featured a series of ice jams in six rivers, 32 bridges were destroyed and 124 others damaged. In approximately 42% of the province's reported floods, ice jams have been a factor.

Hurricanes have been responsible for several disastrous floods in New Brunswick. Flooding accompanied Hurricane Edna in 1954, Hurricane Gladys in 1968, and Hurricane Belle in 1976. In September 1979, Tropical Storm David reportedly caused an estimated $500 000 ($881 600 in 1998 dollars) in damages in the Moncton area. Extensive rainfall over long periods from cyclonic storms has also produced destructive floods. For example during late-May 1961, significant damage were reported in the Saint John, Nashwaak, Miramichi and Tobique River basins. Convective storms can generate localized flooding conditions in small drainage basins such a Marsh Creek near Saint John. Overall, heavy rainfall has been the cause of 43% of the flood events in New Brunswick.

This chart illustrates the causes of flooding in New Brunswick: 


Source: Flooding in New Brunswick - An Overview 1969-1984, Environment Canada.

Causes of flooding in New Brunswick

The Saint John River

The Saint John River in Atlantic Canada is characterized by repeated ice jam flooding. Ice jams occur primarily during an early breakup of the ice cover. The breakup is generally started by a sudden increase in temperature melting the snow, in combination with a heavy rainfall. Runoff from the snowmelt and rainfall raises the water levels and exerts pressure on the ice cover, forcing it to break up. As the ice moves downstream it lodges on bars, islands, and at bridge piers.

Flood records exist for the Saint John River since 1696. However, it is difficult to distinguish from early reports which ones were related to ice jams.

1902

In March 1902, an unusually early breakup and downstream movement of the ice cover due to heavy rains and warm temperatures raised water levels. Floods resulting from the 15 ice jams that developed in the Saint John River basin were some of the most serious this century. Two deaths were recorded. Extensive damage, including washouts, was inflicted on bridges, roads and railways. The lumber industry was particularly hard hit, with damage to mills and loss of stock. Province-wide damage estimates, from various accounts, amounted to $25 000 (about $881 600 in 1998 dollars).

1936

Weather conditions in March of 1936 were similar to those of 1902, resulting again in an early breakup of the ice cover. Twenty-two ice jams were recorded in the basin, some extending 10 kilometres upstream. Damages included partial or complete destruction of 15 bridges; inundation of roads and railways; flooding and destruction of homes, businesses and barns; loss of lumber mill stock; and loss of livestock. Province-wide damage estimates totalled $1.9 million, or about $33.9 million in 1998 dollars.


Looking east toward Maugerville United Baptist Church (May 2, 1973)

Photo - Looking east toward Maugerville United Baptist Church (May 2, 1973)

Perth-Andover, 1976 and 1987

Severe ice jam flooding events have occurred at the same location, Perth-Andover, on the Saint John River in 1976 and 1987. In 1976, the main point of lodgement was 6.4 kilometres below the railway bridge near the community of Perth-Andover. Floodwaters backed up by the jam inundated regional highways and municipal streets and formed massive ponds in some residential areas. A State of Emergency was declared when it became necessary to evacuate the Hotel Dieu Hospital. About 200 homes, several businesses, a seniors home, and the junior high school were submerged. Approximately 400 people required evacuation. Concern mounted that the railway bridge might collapse. To prevent the bridge from being pushed off its piers, 17 cars loaded with wood chips were rolled onto the bridge to add weight. The bridge held.

Although the 1987 ice jam at the Perth-Andover railway bridge was a secondary jam (the result of a jam near Upper Guisiguit Brook), the damages were considerably higher than in 1976.

The flood happened quickly. Despite a major drawdown on the river, initiated by the New Brunswick Electric Power Commission very early in the morning of April 2, water continued to rise at Perth-Andover. By 6:00 a.m., ice flowing downstream was accumulating behind the railway bridge. As in 1976, loaded railway cars were moved onto the bridge. Unlike 1976, the bridge could not withstand the pressure and collapsed around 9:00 a.m. A railway car carried by the ice and surging water was later found 1.1 kilometres downstream. On its way downstream it had passed unobstructed under a highway bridge. The level of the 1987 flooding exceeded the 1976 event by about 1 metre. Again, a State of Emergency was declared, the hospital was evacuated, and hundreds of people were forced from their homes.


Looking east across the St. John River upstream of the CNR bridge (May 1, 1973)

Photo - Looking east across the St. John River upstream of the CNR bridge (May 1, 1973)

Nova Scotia

Although snowmelt itself has not caused flooding events in Nova Scotia, it has been a contributing factor in 65 instances since the first flood recorded in 1759. Flooding conditions associated with snowmelt often occur during winter rainstorms in December, January and February. Spells of warm weather accompanied by rain are not uncommon in Nova Scotia during these months. In fact, such conditions led to all 48 flood events recorded in the province during these three months, 36 of which involved snowmelt. Prolonged warm spells during this period can be particularly disastrous. For instance, the flooding in the aftermath of what was known as the longest January thaw, from January 3 to 18, 1956, caused province-wide damage.

Floods involving snowmelt also occur when a heavy rainfall accompanies the annual spring runoff. This was the case for most of the 35 floods recorded in March and April. The most serious floods of this type happen following a winter of heavy snowfall. The event of April 2-10, 1962, which affected almost the entire province, was caused by heavy rain during the spring snowmelt. Also, during this event, the ice cover broke up and jammed, exacerbating the situation.

As in the other Atlantic provinces, ice jams have contributed destructively during winter thaws and the spring freshet. For example, during the January thaw of 1956, ice jams destroyed more than 100 bridges across the province.

Tropical or hurricane-type storms also have caused extensive flooding in the province. About $5.1 million ($20.4 million in 1998 dollars) in damages were sustained in August 1971 during Hurricane Beth. Other major tropical storms resulting in floods were Hurricane Ethel in 1964, Hurricane Gladys in 1968, and the hurricane-like storms of September 1936 and August 1950.

Cyclonic storms have also produced heavy rainfall with serious flooding throughout the province, such as occurred during the flood of October 10-11, 1967.

Unusually high tides have damaged the coastline, but the most destructive coastline flooding has been a consequence of storm surges accompanying hurricane and cyclonic storms. The "Groundhog Day Storm" of February 2-3, 1976, battered all coastal areas of the province. Although only one river basin was reported to have been affected, the original estimates of storm damage exceeded $10 million ($24.9 million in 1998 dollars).

Convective storms often result in heavy rainfall and are the single most common cause of flooding in Nova Scotia. They seldom cause significant area-wide floods.

This chart illustrates the causes of flooding in Nova Scotia: 


Source: Flooding in Nova Scotia - An Overview 1759-1986, Environment Canada.

Causes of flooding in Nova Scotia

Newfoundland and Labrador

As in the other Atlantic provinces, the moderating effect of the ocean is evident in the flood regime. For central and southern drainage basins, floods may occur any time of the year as a result of snowmelt, rainfall, ice jams, or rainfall from major storms. Midwinter thaws accompanied by rainfall may cause breakup of the ice cover, leading to ice jams. Toward the northern part of the Island, especially the Northern Peninsula, the snow usually remains through the winter, and floods result from the spring freshet. In the southeastern part of the province, the Avalon Peninsula frequently experiences coastal flooding. For example, flooding has been recorded in the town of Placentia since 1904 and, in recent times has occurred in 1977, 1982 (twice), 1983 (twice) and 1989.

A major winter storm in January 1983 led to severe flooding in the Exploits and Gander River basins. Rainfall, warm temperatures and snowmelt over a three-day period were the causes. There was extensive damage to public and private property, including the partial destruction of the dam and power house at Bishop's Falls. The damage along the Exploits and Gander rivers was estimated to be about $34 million ($41.8 million in 1998 dollars).

Newfoundland is in the path of storms often originating in the tropical Atlantic Ocean. However, in most cases, the storms have lost their tropical characteristics and much of their wind force before they reach the Island. Historical records indicate that few floods have been caused by hurricanes.

Tsunami strikes East Coast

Tsunamis are such uncommon events on the East Coast that the term itself is rarely used. Yet on November 18, 1929, the unthinkable occurred. A large-scale earthquake rocked the eastern coast of North America at 5:00 p.m. In St. John's, Newfoundland, although no serious damage was sustained, the quake shook buildings, broke dishes, and upset furniture. Most people were unacquainted with earthquakes and thought it was an explosion of some sort.

There ensued a debate as to the location of the epicentre of the quake. Numerous broken underwater cables eventually led researchers to believe the epicentre was located 560 kilometres south of St. John's, in the Atlantic Ocean.

At this time, the communication network in Newfoundland was sparse. Radio was in its infancy, there were few telephones, and because of the earthquake, many of the telegraph cables were down. Therefore, while the rest of the East Coast residents had settled back into their daily routines, they were unaware of the tragedy that had struck Newfoundland's Burin Peninsula.

The fact that a tsunami had struck the area was not known by the outside world until three days after the quake when the steamship Portia arrived in Burin on a regularly scheduled call. A radio message from the ship alerted the world to what had happened.

The story emerged that the Peninsula had been struck by an enormous wave hours after the earthquake. The wave had drowned 27 people. Scores of homes, businesses, wharves, and fishing boats were smashed or swept away, along with the fish harvest, food, and fuel oil supplies.

As elsewhere along the coast, the earthquake was felt at 5:00 p.m. and damage was minimal. With nothing unusual occurring following the quake most residents returned to their activities.

Sometime after the quake, many people noticed the water draining out of the coves and harbours. In St. Lawrence, the harbour bottom, which on average is 10 metres deep, was visible in places. Not understanding what was happening, many residents moved to higher ground, probably saving many lives.

Two and one-half hours after the earthquake, the wave arrived. It was unclear from witnesses whether there were two or three waves involved, but all agreed that the first wave was the most destructive. The wave height was reported to have been between 15 and 30 metres. The shape and width of the wave depended on the configuration of the coastline and the sea floor. The greatest impact of the wave was felt where the water was forced into a confined area, such as the coves and harbours.

The herculean wave either carried buildings inland and deposited them, or swept them into the harbours or out to sea when it receded. In St. Lawrence, 31 buildings were carried away. The wave entered and circled around the harbour, carrying buildings from one side to the other. Burin, a collection of a dozen or so communities, was also seriously affected, with many lives lost.

Several stories emerged about that night. Many people thought the towns were sinking as the water levels quickly rose.

While the wave smashed and destroyed many buildings, it simply lifted others off their foundations and floated them away. One store, 9 x 17 metres, was moved 60 metres inland and deposited in a meadow, with all its stock left intact.

People took to the remaining boats in search of people hanging to debris or trapped in floating homes. A kerosene lamp burning in the second floor window of one floating house led rescuers to a sleeping baby, whose family had been drowned on the first floor. A man, swept to sea, swam to another floating house only to find it was his own. The house was later towed back to shore and replaced on its foundation.

During the night a gale blew up, dropping temperatures and adding sleet and snow to the survivors' misery.

The ferocity of the wave was not restricted to the land; it also tore up the seabed. This destruction of the seabed was believed by many to be the dominant factor in poor fish catches during much of the Great Depression.

Most of the energy of the wave was spent on the southern coast of the Burin Peninsula. The nearby communities of Fortune and Grand Bank, in the shelter of Fortune Bay, only experienced minor disruption. In Nova Scotia, the wave also struck Cape Breton, where one person was reported to have drowned.

Prince Edward Island

The smaller size of Prince Edward Island's rivers makes it relatively flood-free. The Island is not exempt, however, as demonstrated by the major flood in early April of 1962, when a frontal storm on the south coast quickly deposited about 180 millimetres of rain over heavy snow. Extensive washouts and damage to paved highways occurred in many areas of the province.

Steel arrived in the province yesterday for the construction of the St. Peter's bridge, one of a number of bridges washed out over the weekend as torrential rain and melting snow caused an estimated $300 000 damage.

- The Guardian, April 4, 1962

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