2011 Assiniboine River flood

Last updated

2011 Assiniboine River flood
DateApril 2011 – June 2011
Location Manitoba
Deaths1 [1]
Property damage>$1 billion [2]

The 2011 Assiniboine River flood was caused by above average precipitation in Western Manitoba and Saskatchewan. This was a 1 in 300 year flood that affected much of Western Manitoba. The flooding in Manitoba was expected to mostly involve the 2011 Red River Flood but instead the more severe flooding was found on the Assiniboine in the west.

Contents

Early signs

The 2011 flood first began in the fall of 2010 with several major rainfall events and generally wet conditions. Initially, it was predicted that the flood along the Assiniboine River would be similar to the flood of 1995. [3] During the winter of 2010–2011 the Shellmouth Reservoir was emptied in preparation, to store water for the coming spring flood. With more and more precipitation, the estimates on the flood were revised upwards.

The first major settlement to experience the floodwater was St. Lazare, Manitoba which was located near the confluence of the Assiniboine River and Qu'Appelle River. Dikes were built up to protect against the rising floodwater, but unfortunately some residences were not spared as their protective dikes were overwhelmed. The flood continued downstream, spilling over its banks and flooding campgrounds and fields in the flood plain. Brandon, Manitoba's second largest city, prepared well in advance of the anticipated flood building up both earthen dikes as well as sandbag/Hesco bastion dikes. After a heavy snowfall on April 29 and 30 over much of the Assiniboine River watershed the crest forecast for Brandon was revised upward well above the flood of 1976. The river peaked at about 36,700 cu ft/s (1,040 m3/s),60% higher than the previous highest recorded peak of 23,000 cu ft/s (650 m3/s) in 1923. The 2011 event is estimated to be a 1 in 300-year flood. [4]

Assiniboine River at Brandon Peaks Brandon peaks.png
Assiniboine River at Brandon Peaks

Shortly thereafter a state of emergency was declared in Brandon as well as other municipalities across Manitoba. [5] [6] [7] Premier Greg Selinger requested from Prime Minister Stephen Harper troops from the Canadian military to help with the flood fighting efforts. The last time the military was called in to help fight a flood in Manitoba was the 1997 Red River flood.

Downstream of Brandon, the Manitoba Government forecast that between 54000-56000 cu ft/s of water would enter into the Portage Diversion reservoir near Portage la Prairie. [8] The capacity for the Portage Diversion channel, which drains into Lake Manitoba, is only approximately 25,000 cu ft/s (710 m3/s), which would mean that between 29000-31000 cu ft/s of water would flow toward communities such as Poplar Point, St. Francois Xavier, and Headingley, before joining with the Red River at The Forks. [9] This amount of water would overwhelm the dikes downstream, along the Assiniboine River, which were only built to allow for a channel capacity of about 10,000-11,000 cu ft/s before spilling over. Otherwise breaching of dikes would occur. [8]

On June 22, 2011 the city of Minot in North Dakota issued an evacuation of 12,000 residents due to the swollen Souris River that flows through the city. The Souris River starts in Saskatchewan and makes its way south across the border and then back north into Manitoba. The Souris River then eventually joins up with the Assiniboine River past Brandon which could again raise water levels on the Assiniboine due to the swollen Souris and the possibility of Lake Manitoba raising up again. Preparations are under way for the communities along the Souris to raise dikes and evacuations have begun. The province has said it will push the limits of the flood protection again.

Intentional breach and flooding

It was determined by the Manitoba government that the capacity could be increased to 32000-34000 cu ft/s by building up the banks of the Portage Diversion, depending on hydraulic resistance on bridges along the channel. [8] This would reduce the flows on the Assiniboine River somewhat, but still not enough for the dikes to hold. It was also determined that a controlled release of water from the Assiniboine in the range of 2000–6000 cu ft/s should be created downstream of the Portage Diversion in order to reduce flows on the river, and divert the water into the La Salle River watershed, [10] resulting in more manageable river levels along the Assiniboine River. The exact location decided on was at the Hoop and Holler Bend.

The controlled breach of the dike was estimated to flood approximately 225 square kilometres (87 sq mi). This option was chosen as opposed to risking an uncontrolled breach, which could release as much as 500 square kilometres (190 sq mi) with flows of up to 15,000 cu ft/s (420 m3/s), while over 800 homes would be affected by the waters. [10] Military personnel were assigned to build flood protection in Brandon, on the Assiniboine River west of Portage la Prairie, and for residences that were at risk of flooding due to the controlled breach.

The intentional breach and overland flooding began on Saturday May, 14. [11] The resultant flooding was very slow moving and was expected to take several days to reach the La Salle River. The waters intentionally spilled from the Assiniboine were expected to cover 185 square kilometres (71 sq mi) and flood a possible 150 homes. [12] The Expected crest at the Portage Reservoir was then downgraded to around 52,000 cu ft/s (1,500 m3/s), leading some engineers to question the necessity of the breach at Hoop & Holler Bend as between the Portage Diversion (34,000 cu ft/s (960 m3/s)) and the Assiniboine River Channel (up to 20,000 cu ft/s (570 m3/s)) could have handled the floodwater. [13] The controlled breach has carried no more than 400 cu ft/s (11 m3/s) and flooding was modest.

Effects on Lake Manitoba

With the diversion of water from the Assiniboine using the Portage Diversion into Lake Manitoba, the water level on the lake increased. Increasing the capacity of the Diversion put surrounding residences in danger of being flooded, also prompting an evacuation of Delta Beach on Lake Manitoba. Due to the increased capacity of the diversion and the duration of its use, it increased water levels on Lake Manitoba significantly, more than the 1976 Assiniboine River Flood, which resulted in approximately 1,420,000 acre-feet (1.75 km3) of water being diverted. [14] In 2011 a total of 4,768,000 acre-feet (5.881 km3) [15] was diverted into the lake. The Manitoba Government's projections indicated that excluding the outflows of Lake Manitoba through the Fairford River resulted in an increase of 1.22 feet (0.37 m) in the level of the lake Archived May 28, 2016, at the Wayback Machine . The Flood of 2011 surpassed these totals, causing flooding to Lake Manitoba and peaked at 817.2 feet (249.1 m) above sea level, 5 feet (1.5 m) above the normal operating range . This led to flood fighting efforts shifting from the Assiniboine River to Lake Manitoba. [10] [16] [17] A technical review of the 2011 flood completed in October, 2013 concluded that the net effect of artificial works (Fairford River improvements and the Portage Diversion) was a rise of 0.3 feet (0.091 m) on the lake. [18] However, the rise occurred in weeks, rather than years as would occur in natural conditions.

Related Research Articles

<span class="mw-page-title-main">Lake Agassiz</span> Large lake in central North America at the end of the last glacial period

Lake Agassiz was a large proglacial lake that existed in central North America during the late Pleistocene, fed by meltwater from the retreating Laurentide Ice Sheet at the end of the last glacial period. At its peak, the lake's area was larger than all of the modern Great Lakes combined. It eventually drained into what is now Hudson Bay, leaving behind Lake Winnipeg, Lake Winnipegosis, Lake Manitoba, and Lake of the Woods.

<span class="mw-page-title-main">Red River of the North</span> River in the United States and Canada

The Red River, also called the Red River of the North to differentiate it from the Red River in the south of the continent, is a river in the north-central United States and central Canada. Originating at the confluence of the Bois de Sioux and Otter Tail rivers between the U.S. states of Minnesota and North Dakota, it flows northward through the Red River Valley, forming most of the border of Minnesota and North Dakota and continuing into Manitoba. It empties into Lake Winnipeg, whose waters join the Nelson River and ultimately flow into Hudson Bay.

<span class="mw-page-title-main">Lake Manitoba</span> Lake in Manitoba, Canada

Lake Manitoba is the 14th largest lake in Canada and the 33rd largest lake in the world with a total area of 4,624 square kilometres (1,785 sq mi). It is located within the Canadian province of Manitoba about 75 kilometres (47 mi) northwest of the province's capital, Winnipeg, at 50°59′N98°48′W.

<span class="mw-page-title-main">Red River Floodway</span> Artificial flood control channel in Manitoba, Canada

The Red River Floodway is an artificial flood control waterway in Western Canada. It is a 47 km (29 mi) long channel which, during flood periods, takes part of the Red River's flow around the city of Winnipeg, Manitoba to the east and discharges it back into the Red River below the dam at Lockport. It can carry floodwater at a rate of up to 140,000 cubic feet per second (4,000 m3/s), expanded in the 2000s from its original channel capacity of 90,000 cubic feet per second (2,500 m3/s).

<span class="mw-page-title-main">Assiniboine River</span> River in Western Canada

The Assiniboine River is a 1,070-kilometre (660 mi) river that runs through the prairies of Western Canada in Saskatchewan and Manitoba. It is a tributary of the Red River. The Assiniboine is a typical meandering river with a single main channel embanked within a flat, shallow valley in some places and a steep valley in others. Its main tributaries are the Qu'Appelle, Souris, and Whitesand Rivers. For early history and exploration see Assiniboine River fur trade.

<span class="mw-page-title-main">1997 Red River flood</span> Major flood on the Red River of the North

The Red River flood of 1997 was a major flood that occurred in April and May 1997 along the Red River of the North in Minnesota, North Dakota, and southern Manitoba. It was the most severe flood of the river since 1826. The flood reached throughout the Red River Valley, affecting the cities of Fargo and Winnipeg, but none so greatly as Grand Forks and East Grand Forks, where floodwaters reached more than 3 miles (4.8 km) inland. They inundated virtually everything in the twin communities. Total damages for the Red River region were US$3.5 billion. The flood was the result of abundant snowfall and extreme temperatures.

<span class="mw-page-title-main">Souris River</span> River in Canada and the United States

The Souris River or Mouse River is a river in central North America. Approximately 435 miles (700 km) in length, it drains about 23,600 square miles (61,100 km2) in Canada and the United States.

<span class="mw-page-title-main">Devils Lake (North Dakota)</span> Lake in North Dakota, United States

Devils Lake is a lake in the U.S. state of North Dakota. It is the largest natural body of water and the second-largest body of water in North Dakota after Lake Sakakawea. It can reach a level of 1,458 ft (444 m) before naturally flowing into the Sheyenne River via the Tolna Coulee. On June 27, 2011, it reached an unofficial historical high elevation of 1,454.3 ft (443.3 m). The cities of Devils Lake and Minnewaukan take their name from the lake as does the Spirit Lake Reservation, which is located on the lake's southern shores.

<span class="mw-page-title-main">Souris, Manitoba</span> Community in Manitoba

Souris is an unincorporated urban community in the Municipality of Souris-Glenwood within the Canadian province of Manitoba that held town status prior to the Manitoba municipal amalgamations on January 1, 2015. It is located within the municipality at the confluence of Plum Creek and Souris River, from which it takes its name. Before 1882, the town was called Plum Creek.

<span class="mw-page-title-main">Shellmouth Reservoir</span> Reservoir in Western Canada

The Shellmouth Reservoir is a man-made reservoir on the Assiniboine River in Manitoba and Saskatchewan, Canada.

<span class="mw-page-title-main">Portage Diversion</span> Spillway in Manitoba, Canada

The Portage Diversion is a water control structure on the Assiniboine River near Portage la Prairie, Manitoba, Canada. The project was made as part of a larger attempt to prevent flooding in the Red River Valley. The Portage Diversion consists of two separate gates which divert some of the flow of water in the Assiniboine River to a 29 km long diversion channel that empties into Lake Manitoba near Delta Beach. This helps prevent flooding on the Assiniboine down river from the diversion, including in Winnipeg, where the Assiniboine River meets the Red River.

<span class="mw-page-title-main">Morganza Spillway</span> Flood-control structure in Louisiana, U.S.

The Morganza Spillway or Morganza Control Structure is a flood-control structure in the U.S. state of Louisiana. It is located along the western bank of the Lower Mississippi River at river mile 280, near Morganza in Pointe Coupee Parish. The spillway stands between the Mississippi and the Morganza Floodway, which leads to the Atchafalaya Basin and the Atchafalaya River in south-central Louisiana. Its purpose is to divert water from the Mississippi River during major flood events by flooding the Atchafalaya Basin, including the Atchafalaya River and the Atchafalaya Swamp. The spillway and adjacent levees also help prevent the Mississippi from changing its present course through the major port cities of Baton Rouge and New Orleans to a new course down the Atchafalaya River to the Gulf of Mexico. The Morganza Spillway, operated by the U.S. Army Corps of Engineers, was opened during the 1973 and 2011 Mississippi River floods.

The history of flooding in Canada includes floods caused by snowmelt runoff or freshet flooding, storm-rainfall and "flash flooding", ice jams during ice formation and spring break-up, natural dams, coastal flooding on ocean or lake coasts from storm surges, hurricanes and tsunamis. Urban flooding can be caused by stormwater runoff, riverine flooding and structural failure when engineered flood management structures, including dams and levees, prove inadequate to manage the quantities and force of flood waters. Floods can also occur when groundwater levels rise entering buildings cracks in foundation, floors and basements. Flooding is part of the natural environmental process. Flooding along large river systems is more frequent in spring where peak flows are often governed by runoff volume due to rainfall and snowmelt, but can take place in summer with flash floods in urban systems that respond to short-duration, heavy rainfall. Flooding due to hurricanes, or downgraded severe storms, is a concern from August to October when tropical storms can affect Eastern North America. Flood events have had a significant effect on various regions of the country. Flooding is the costliest natural disaster for Canadians. Most home insurance claims in Canada deal with water damage due to sewer back-up, not fire.

<span class="mw-page-title-main">2009 Red River flood</span>

The 2009 Red River flood along the Red River of the North in North Dakota and Minnesota in the United States and Manitoba in Canada brought record flood levels to the Fargo-Moorhead area. The flood was a result of saturated and frozen ground, spring snowmelt exacerbated by additional rain and snow storms, and virtually flat terrain. Communities along the Red River prepared for more than a week as the U.S. National Weather Service continuously updated the predictions for the city of Fargo, North Dakota, with an increasingly higher projected river crest. Originally predicted to reach a level of near 43 feet (13 m) at Fargo by March 29, the river in fact crested at 40.84 feet (12.45 m) at 12:15 a.m. March 28, and started a slow decline. The river continued to rise to the north as the crest moved downstream.

<span class="mw-page-title-main">Rio Grande Project</span>

The Rio Grande Project is a United States Bureau of Reclamation irrigation, hydroelectricity, flood control, and interbasin water transfer project serving the upper Rio Grande basin in the southwestern United States. The project irrigates 193,000 acres (780 km2) along the river in the states of New Mexico and Texas. Approximately 60 percent of this land is in New Mexico. Some water is also allotted to Mexico to irrigate some 25,000 acres (100 km2) on the south side of the river. The project was authorized in 1905, but its final features were not implemented until the early 1950s.

<span class="mw-page-title-main">Twin Lakes Beach, Manitoba</span>

Twin Lakes Beach, also known locally by many as simply Twin Beaches, is a beach and community in the Canadian province of Manitoba. On Lake Manitoba, it is about 100 kilometres (62 mi) north-west of the provincial capital, Winnipeg. Twin Lakes Beach is in both the Rural Municipality of St. Laurent and the Rural Municipality of Woodlands, and it is in the town of St. Laurent.

<span class="mw-page-title-main">2011 Mississippi River floods</span> 2011 major floods in the United States

Major floods along the Mississippi River in April and May 2011 were among the largest and most damaging recorded along the U.S. waterway in the past century, comparable in extent to the Great Mississippi Flood of 1927 and Great Flood of 1993. In April 2011, two large storm systems deposited record levels of rainfall on the Mississippi River drainage basin. When that additional water combined with the springtime snowmelt, the river and many of its tributaries began to swell to record levels by the beginning of May. Flooding occurred in Illinois, Missouri, Kentucky, Tennessee, Arkansas, Mississippi, and Louisiana.

<span class="mw-page-title-main">2011 Souris River flood</span> 2011 flood affecting Canada and USA

The 2011 Souris/Mouse River flood in Canada and the United States occurred in June and was greater than a hundred-year flooding event for the river. The US Army Corps of Engineers estimated the flood to have a recurrence interval of two to five centuries.

<span class="mw-page-title-main">2014 Assiniboine River flood</span> 2014 disaster in Manitoba and Saskatchewan, Canada

The 2014 Assiniboine River flood was caused by above average precipitation in western Manitoba and Saskatchewan. Unlike most prior floods, this flood was not due to spring runoff, but rather significant rainfall. Flooding and high water involved both the main stem of the Assiniboine River and many of its tributaries including the Qu'Appelle River and the Souris River. The flood came just 3 years after the 2011 Assiniboine River Flood which was considered a 1 in 300 year event. Peak flows along the river for the first crest were generally slightly less than in 2011. However, the second peak on the river has exceeded 2011 levels starting near St. Lazare, Manitoba up to Brandon, Manitoba so far.

<span class="mw-page-title-main">Lake St. Martin</span> Lake in Manitoba, Canada

Lake St. Martin is a lake in the Interlake region of Manitoba, Canada. The lake is situated between Lake Manitoba and Lake Winnipeg. Lake St. Martin is downstream from the Fairford River with its Fairford River Control Structure. The Fairford River is the only outlet for Lake Manitoba. With the artificially increased flow and limited outflow, Lake St. Martin was turned into a reservoir. The outflow for Lake St. Martin exits through Dauphin River and into Lake Winnipeg, at a lower rate than the water comes in.

References

  1. ↑ Kevin Rollason (May 14, 2011). "Man rescued from Assiniboine, another presumed drowned". Winnipeg Free Press .
  2. ↑ Unattributed (May 15, 2011). "Manitoba breach flooding downsized". United Press International. Retrieved May 16, 2011.
  3. ↑ "Media Bulletin – 25 March" (PDF). RM of Macdonald. March 25, 2011. Archived from the original (PDF) on October 4, 2011. Retrieved May 14, 2011.
  4. ↑ "Brandon residents cope with state of emergency due to flooding". CTV Winnipeg . May 12, 2011.
  5. ↑ "Evacuees wait to return home as Brandon faces one-in-300-year flood". CTV Winnipeg. May 10, 2011.
  6. ↑ St-Arnaud, Pierre (May 10, 2011). "Quebec government poised to increase funding for flood-hit people and businesses". Canadian Press .[ dead link ]
  7. ↑ "Provincial State of Emergency Declared". CJOB . May 9, 2011. Archived from the original on March 31, 2012.
  8. 1 2 3 "Flood Bulletin #43". Government of Manitoba. May 11, 2011.
  9. ↑ "Flood Bulletin #40". Government of Manitoba. May 9, 2011. Archived from the original on March 4, 2016. Retrieved August 23, 2017.
  10. 1 2 3 "Flood Bulletin #41". Government of Manitoba. May 10, 2011.
  11. ↑ "Water flows through Manitoba dike breach". CBC News . May 14, 2011.
  12. ↑ "Controlled spill slows river's rise". CBC News. May 15, 2011.
  13. ↑ Bill Redekop (May 18, 2011). "Province miscalculated flooding: engineer". Winnipeg Free Press .
  14. ↑ "Water Stewardship Report" (PDF). Archived from the original (PDF) on May 28, 2016. Retrieved August 23, 2017.
  15. ↑ Calculated from Water Survey of Canada Data
  16. ↑ "Daily Water Levels and Forecasts – Manitoba Lakes" (PDF). Government of Manitoba. May 10, 2011.[ permanent dead link ]
  17. ↑ "Daily Water Levels and Forecasts for Manitoba Lakes" (PDF). Manitoba Water Stewardship. July 1, 2011.[ permanent dead link ]
  18. ↑ 2011 Flood:Technical Review of Lake Manitoba, Lake St. Martin and Assiniboine River https://www.gov.mb.ca/mit/floodinfo/floodproofing/reports/pdf/assiniboine_lakemb_lsm_report_nov2013.pdf

49°36′N99°30′W / 49.6°N 99.5°W / 49.6; -99.5

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.