Flood Controls and Protection

As a means of celebrating the role of engineering and geosciences for the 90th year of APEGM’s history, the Heritage Committee began a series of articles in 2010, under the general theme of “Liquid Assets” that link water to the economic and social development of the province. This is a follow-up article in light of the spring and summer of 2011, when the liability side of water’s balance sheet affected the lives of Manitobans and the contribution of engineering and geoscience to the flood control and protection system have been both recognized and questioned. From the experience of 2011 Manitobans, and Winnipeggers when they gaze beyond the perimeter highway, now have an enhanced awareness of the realities of living in the bottom of a former glacial lake.

Awareness of vulnerability to flooding has been with Manitobans since before the Province’s entry into confederation. The spring of 1826 brought the greatest flood to inundate the valley and Red River Settlement, estimated by engineers on the basis of journals and eye-witness recollection to have risen to an elevation of 764.87 ft. above sea level. The 1852 flood crested two feet lower than in 1826, but it caused more damage in the settlement due to urban growth and rapid rise due to a number of large ice jams. In May of 1950 the Red River crested at 757.87 ft. at James Avenue, creating a lake seven miles wide at Winnipeg's southern limits.

One of the earlier engineering papers on the mitigation of flooding was authored by D.L. McLean, who had previously been a design engineer on the Greater Winnipeg Water District aqueduct. It was published in 1920. Since then engineers have continued to be instrumental in implementing the Province’s system of flood control and protection. That contribution has been acknowledged throughout the system’s development, and was recognized by the association (APEGM at the time) during the Centennial of Engineering in Canada in 1987. The physical reminder is a plaque dedicated by the Lieutenant-Governor of Manitoba at the 1987 annual meeting.

The wording of the dedication of the plaque was:

“On the occasion of the Centennial of The Engineering Profession in Canada and to recognize the Profession’s service to the citizens of the Province and its contribution to the development of the Province, the association of Professional Engineers of Manitoba has chosen to honour the engineering undertaking which exemplifies that contribution over the past 100 years.

By Reducing damage and the threat to lives and property from recurring floods in many parts of the Province, the Manitoba Flood Control and Protection System has greatly contributed to the peace of mind and the social and economic well-being of a vast number of the citizens of our Province. The works, the operational procedures and the emergency response mechanisms which comprise the system are deemed to epitomize the obligation of Professional Engineers to ensure the safety and comfort of people in all engineering undertakings.

October 19, 1987

Dedicated by The Honourable George Johnson, Lieutenant Governor of Manitoba”

Other wording on the plaque describes features of the system as it was in 1987. It included; the Red River Floodway, Shellmouth Dam, Assiniboine [Portage] Diversion, Seine River Diversion, Fairford Control Works, Diking Systems, and Flood Forecasting. The wording can be accessed at the Heritage Committee section of the APEGM website www.apegm.mb.ca/Heritage/index.html. A copy of the 1920 paper by D.L. Mclean is also available in that section.

Since 1987

The descriptions on the 1987 plaque provided an overview of the system at that time. Most of them have since become familiar to Manitobans. Since then we have experienced the 1997 “Flood of the Century” and are aware that the Red River Floodway has been expanded. In 1987 eight communities in the Red River Valley were protected by ring dikes. After the 1997 flood twelve additional communities were protected and 1 800 homes, businesses and farms in the valley were either raised onto pads or protected with individual ring dikes. The effectiveness of the flood control works in the Red River Valley was evident during the spring of 2011 when very little flood damage occurred even though the flood was larger than the historic 1950 flood.

But there have been other projects outside of the Red River Valley that have not garnered as much attention. The first two below were mentioned in the 1987 plaque:

Seine River Diversion The first major flood water diversion constructed in Manitoba, the SeineRiver Diversion, diverts excess Seine River flows of up to 4 270 cfs from a point upstream of Ste. Anne to the Red River near St. Adolphe. The diversion was constructed in 1962 at a cost of $1.8 million to provide flood control along the Seine River through and below Ste. Anne.

Fairford Control Works Located at the outlet of Lake Manitoba on the Fairford River, the Fairford Control Works together with upstream and downstream channel improvements were constructed in 1961 to control Lake Manitoba levels within a much narrower range than that which occurred historically. The control structure doubles as the PTH #6 highway bridge. Stop logs are installed or removed to control the flow.

Carman Diversion A diversion of the Boyne River around the Town of Carman was completed in 1991. Before the diversion was constructed Carman experienced flooding in 1893,1923, 1970, 1974, and 1979. The 1979 flood caused damages of over $3 million. The$6 million diversion diverts flood water from the Boyne River west of Carman through a 9.8 km channel that exits into the Norquay Channel. It has been very effective in flood prevention.

Ste. Rose du Lac Following a 1975 flood from the Turtle River in Ste. Rose du Lac a diking system was constructed through the town. A flood in 1986 overtopped these dikes.The dikes have since been upgraded to provide protection against a one in 100 year flood event. The dikes were raised and sandbagging was necessary to protect Ste. Rose du Lac in 2011

The Pas Area A series of dikes along the Saskatchewan River and Carrot River in the vicinity of The Pas has been constructed to protect agricultural and residential areas. The Carrot River is located south of the Saskatchewan River flowing easterly. It is generally about 10 km south of the Saskatchewan and joins that river just before it reaches The Pas. The Carrot River has approximately 39 km of dikes. The Salt Channel which protects the western boundary of the Carrot valley area has 34 km of dikes. Together with the Pasquia River dikes they protect 57 000 hectares of farm and residential land.

Rock Lake, Pelican Lake Controls Completed in 1991, the Pelican Lake Controls include a diversion channel from the Pembina River to Pelican Lake and control structures. The diversion channel brings water to the lake to raise low lake levels and drains water from the lake to prevent high water levels, providing improved regulation of water levels. At Rock Lake a weir and an outlet channel to the Pembina River have been built, along with dikes on the west side of the lake to protect farmland.

Assiniboine River Diking Systems Downstream of the Shellmouth Dam (the reservoir formed by the dam, the Lake of the Prairies, extends into Saskatchewan) the Assiniboine River meanders in the bottom of the deep river valley that was formed by the melting glaciers approximately 10 000 years ago. The valley is subject to flooding when the Assiniboine River spills over its banks as happened in 1976 and in 1995. The Town of St. Lazare, 60 km downstream of the dam, has been protected by a ringdike.

Further downstream at Brandon the Assiniboine flows in the deep valley on the north side of the City. While most of the City is located on the higher elevations above the valley floodplain, industrial, commercial, residential and recreational properties and facilities exist in the floodplain. Most notable is the Brandon Flats area located on the south side of the river between First Street and 26th Street. Prior to 2011, flood prone properties were protected to varying degrees, but generally not against a 100 year flood.

East of Brandon the Assiniboine River breaks out of the glacial valley into the Assiniboine River delta east of the Manitoba escarpment and enters the flat remnants of Glacial Lake Agassiz. East of the Portage Diversion and the City of Portage la Prairie to just east of Baie St. Paul (near St. Francois Xavier) there are 67 km of diked channel for a total of 134 km of dikes. The dikes were first constructed in 1912. They were reinforced in 1950 and again following the 1997 flood. They protect farmland, farms, and rural residences aswell as the communities of Elie, La Salle, Sanford and Starbuck.

Souris River The Souris River begins in Saskatchewan, runs south into North Dakota, and returns to Manitoba, joining the Assiniboine River near Treesbank. In North Dakota the River passes through the City of Minot and many smaller centres. In Manitoba the Souris passes through the towns of Melita, Souris, and Wawanesa. Those Manitoba communities had dikes along the Souris before 2011.

The “Perfect Storm” of 2011

Despite the pre and post 1987 measures, with the events of 2011 we have come to realize that Manitoba is vulnerable to the impact of major flood events. While the system performed well for the Red River Valley, unusually high runoff on the Assiniboine and Souris Rivers, exceptional rainfall in Saskatchewan, and high water levels in Lake Manitoba and Lake St. Martin converged to require emergency measures and caused devastation – particularly on Lake Manitoba and Lake St. Martin.

At Brandon, to address the predictions made in February, the City raised approximately 5 km of dike by about 0.6m, thought to be 0.3m above the predictions for the 2011 spring flood. But it far exceeded all expectations and required an enormous additional diking effort including the assistance of the Canadian Army. The Assiniboine had several crests; the largest had a flow of 37,100 cfs representing a 300 year flood. While the dikes protected the low lying areas, the risk of a breach required evacuation of the Flats area for several weeks and traffic was disrupted on the major access roads to the city.

East of Portage la Prairie where the design capacity was a flow of 18 500 cfs, the dikes were at considerable risk and the Canadian Army was called upon to assist with strengthening and inspection. Because of the softened condition of dikes due to persistent wet weather some sections were reinforced with sandbags delivered by helicopter. Because the flow in the Assiniboine at Portage la Prairie was 52 400 cfs (34 500 beyond the downstream capacity) the Portage Diversion was upgraded to divert a peak of 34,000 cfs to Lake Manitoba, much beyond its 25 000 cfs design capacity. The emergency over capacity flow required evacuations along the diversion for safety.

As another emergency measure to prevent overtopping of the dikes a breach in the south dike was made at the Hoop and Holler bend to release water toward the LaSalle River.While only approximately 400 cfs were released, the deliberate release and flooding of lands south of the river illustrate the grave concern along the Assiniboine between Portage la Prairie and Baie St. Paul.

There were three crests on the Souris River, the first on April 9, 2011. Each time dikes were raised and reinforced. The last crest was caused by a major rainstorm in Saskatchewan near the middle of June. The flood devastated the City of Minot where 11,000 people were displaced and 4 200 residences were inundated, many to roof level.

In Manitoba, dikes were raised by as much as two metres above the already raised and reinforced levels and once again the Army was called upon at the last minute to assist. The peak flow exceeded 30 000 cfs, in the range of a 300 year flood. The temporary dikes held and averted a disaster similar to what occurred in Minot. Extensive damage was caused to roads, bridges, and other infrastructure. Most notable was the loss of the famous Souris swinging bridge.As the crest approached it was feared the bridge would be ripped from its moorings which could have damaged the dikes on each side of the river. One endof the bridge was severed as a precaution.

The diversion of water to Lake Manitoba, along with high flows in the Waterhen River from Lake Winnipegosis and in the Whitemud River has caused an enormous flood all around Lake Manitoba and Lake St Martin. At this time, July 21, 2011,Lake Manitoba is above 817 feet above sea level. Many stakeholders around Lake Manitoba, including farmers, ranchers and cottagers feel the ideal level is 810.5 – 812.5 feet. That range was adopted by the Lake Manitoba Regulation Advisory Committee in 2003. That leaves the July 2011 level at 5.5 - 7 feet above optimum.

To compound the situation a fierce wind storm from the northwest on May 31, 2011 caused widespread destruction even as protective measures were being undertaken prior to the rise in lake level. Winds were 75 kilometres per hour with gusts to 100 kilometres per hour. The destruction to the farms and ranches and the cottage communities from Twin Lakes in the south to Laurentia Beach and Johnson Beach in the north was devastating and still has not been fully assessed as access for roughly two thirds of the cottages, including permanent residents,was only restored in mid July. Delta Beach at the south end of the lake was devastated.

Diking against the high water and potential wind storms continues for the many homes and communities all around the lake. While three weeks of dry and hot weather in July have assisted and Lake Manitoba levels have stabilized for several days,the predicted peak of 817.5 has not yet been assured. The flood resulting from high lake levels and wind has been described as a once in 2000 year event.

Lake Manitoba drains through the Fairford Control Structure described above, into Lake St. Martin and the Dauphin River to Lake Winnipeg. With Lake Manitoba at high levels the flow through the Fairford Control Structure is at 20 800 cfs compared to a normal flood flow of 6 000 cfs in summer and 3 500 cfs in winter. Lake St. Martin and the Dauphin River have also been flooded. Four First Nation Communities; Fairford First Nation; Little Saskatchewan First Nation; Lake St.Martin First Nation; and Dauphin River First Nation have been evacuated for up to three months with no end in sight. Lake St. Martin is at elevation 806, three feet above the historic 1955 peak of 803 and 6-8 feet above the desirable range of 798-800.

The Lakes are predicted to remain at flood levels well into winter and approximately 2000 residents and cottagers are not permitted into most areas except for day visits to retrieve belongings. Thousands of cattle have been moved to higher ground or out of the area for feed as the hay crops are flooded.

Moving Forward

The experience of the many necessary emergency actions and the devastation from the outcomes of the 2011 flooding in Manitoba tells us that the job of effective flood control and protection is not yet finished. After the 1950 flood the focus of flood protection was on protecting Winnipeg from future floods. After the 1997 Red River flood the focus was on increasing flood protection for Winnipeg and the whole Red River Valley. Both of these efforts have proved very successful. With the 2011 flood the focus has turned towards increasing flood protection along the Assiniboine and Souris Rivers and on Lakes Manitoba and St. Martin.

A major study on an up to 9 000 cfs channel parallel to the Dauphin River from Lake St.Martin to Lake Winnipeg has been completed and released in late July. It includes a seemingly optimistic construction completion date of November 1, 2011. The 8 km long channel from Lake St. Martin to Big Buffalo Lake, from which the water would flow through existing streams and return to the Dauphin River near Lake Winnipeg is estimated to cost $100 million. The channel would go through very wet bog and the location is only accessible for equipment by crossing Lake St. Martin by barge. If emergency approval and funding from the federal government is obtained, environmental impact studies would have to be made during construction to meet the November date. Opposition has already been expressed by the Dauphin River First Nation and the community of Dauphin River over increased flows and the effect of river levels on access, the Dauphin River, ice conditions and the fishery.

The Fairford Control structure is operating at maximum capacity and the new channel will only help to reduce water levels by making it possible to operate the control structure at a higher capacity during the winter when the flow normally has to be reduced to prevent flooding along PR 513 and at Dauphin River due to ice conditions in the Dauphin River. It is predicted the lake could be drawn down to elevation 813.1 by spring, rising to near 814 with spring runoff, still several feet above optimum with possible use of the Portage Diversion looming.

A second phase would see a new bypass channel from Lake Manitoba to Lake St. Martin estimated to cost $60 million. The channel would increase the flow capacity from Lake Manitoba to Lake St. Martin. A third phase is to increase the capacity of the bypass channel. These necessary works are only in the concept stage. Providing effective controlled drainage of the Lake Manitoba system, and by extension the Lake Winnipeg and Nelson River system, will be necessary if Manitobans are to preserve and maximize the asset of our water supply.

One of the earlier engineering papers on the mitigation of flooding was authored by D.L. McLean, who had previously been a design engineer on the Greater Winnipeg Water District aqueduct. It was published in 1920. Since then engineers have continued to be instrumental in implementing the Province’s system of flood control and protection. That contribution has been acknowledged throughout the system’s development, and was recognized by the association (APEGM at the time) during the Centennial of Engineering in Canada in 1987. The physical reminder is a plaque dedicated by the Lieutenant-Governor of Manitoba at the 1987 annual meeting.

The wording of the dedication of the plaque was:

“On the occasion of the Centennial of The Engineering Profession in Canada and to recognize the Profession’s service to the citizens of the Province and its contribution to the development of the Province, the association of Professional Engineers of Manitoba has chosen to honour the engineering undertaking which exemplifies that contribution over the past 100 years.

By Reducing damage and the threat to lives and property from recurring floods in many parts of the Province, the Manitoba Flood Control and Protection System has greatly contributed to the peace of mind and the social and economic well-being of a vast number of the citizens of our Province. The works, the operational procedures and the emergency response mechanisms which comprise the system are deemed to epitomize the obligation of Professional Engineers to ensure the safety and comfort of people in all engineering undertakings.

October 19, 1987

Dedicated by The Honourable George Johnson, Lieutenant Governor of Manitoba”

Other wording on the plaque describes features of the system as it was in 1987. It included; the Red River Floodway, Shellmouth Dam, Assiniboine [Portage] Diversion, Seine River Diversion, Fairford Control Works, Diking Systems, and Flood Forecasting. The wording can be accessed at the Heritage Committee section of the APEGM website www.apegm.mb.ca/Heritage/index.html. A copy of the 1920 paper by D.L. Mclean is also available in that section.