The Portage Diversion ( 49°56′48″N98°20′06″W / 49.94667°N 98.33500°W ) (also known as the Assiniboine River Floodway) 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.
During flood years such as the 2011 Assiniboine River flood, inlet flows to the Portage Diversion control structure were measured at over 54,000 cu ft/s (1,500 m3/s). This amount of water would have disastrous effects if left to flood southern Manitoba. During the flood of spring 2011, the Portage Diversion handled roughly half the flow of Niagara Falls.
The Assiniboine River and diking system can handle flows up to approx 10,000 cubic feet per second (280 m3/s) without a serious breach. [1] However, many properties between Portage la Praire and Winnipeg are flooded once the flows exceed 10,500 cfs, including commercial establishments such as the KOA campground in St Francois Xavier. Over the past few years as high river flows have occurred east of Portage la Prairie, residents have noted significant bank erosion and stands of trees decades old are dying off. In recent years government policy has allowed 12,000 + cfs down the lower assiniboine towards Winnipeg causing major property and environmental damage.
The diversion was originally designed to carry a volume of 25,000 cubic feet per second (710 m3/s). Under a state of emergency in early May 2011, Manitoba authorities did extensive work by raising the dikes and were preparing to send up to 34,000 cu ft/s (960 m3/s) down the diversion channel with bridges downstream being the determining factor in flow rate.,
The diversion was built at a cost of $20.5 million in 1970. The diversion control dam is 35 feet (11 m) high and 1,400 feet (430 m) long and allows 14,600 acre-foot (18,000,000 m3) storage.
Below are data from years of operation of the Portage Diversion when its use resulted in a 0.5 foot or more rise in Lake Manitoba:
Year | Peak Flow (cfs) | Volume Diverted (acre-feet) |
---|---|---|
2011 | 34,804 [2] | 4,770,000 |
2014 | 34,100 [3] | 2,244,000 |
1976 | 26,000 [4] | 1,420,460 [5] |
2017 | 24,700 [6] | > 1,000,000 |
1995 | 13,800 | 1,120,000 |
2009 | 22,088 [7] | 932,000 |
1999 | 10,500 | 914,000 |
The Red River 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.
Lake Manitoba is the 14th largest lake in Canada and the 33rd largest lake in the world with a total area of 4,624 km2 (1,785 sq mi). It is located within the Canadian province of Manitoba about 75 km (47 mi) northwest of the province's capital, Winnipeg, at 50°59′N98°48′W.
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).
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.
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.
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The 1950 Red River flood was a devastating flood that took place along the Red River in The Dakotas and Manitoba from April 15 to June 12, 1950. Damage was particularly severe in the city of Winnipeg and its environs, which were inundated on May 5, also known as Black Friday to some residents.
Winnipeg lies at the bottom of the Red River Valley, a low-lying flood plain with an extremely flat topography. This valley was formed by the ancient glacial Lake Agassiz which has rich deposits of black soil. Winnipeg is on the eastern edge of the Canadian Prairies in Western Canada; it is known as the 'Gateway to the West'. It is relatively close to many large Canadian Shield lakes and parks, as well as Lake Winnipeg. Winnipeg is bordered by tallgrass prairie to the west and south and the aspen parkland to the northeast.
Delta Marsh consists of an extensive open marsh located near the south shore of Lake Manitoba, approximately 24 km north of the town of Portage la Prairie, Manitoba. The marsh extends for nearly 30 km along the shore of the lake, and has a breadth of up to 4 km. The marsh consists of a network of interconnected shallow bays separated from Lake Manitoba by a wooded barrier dune ridge of 300m to 600m width.
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.
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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.
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