Meet the Environmental Assessment Team
The Environmental Assessment: Our Role
The Environmental Assessment Process
Baseline Assessment Information
introduction / existing floodway / need for project / options considered / range of alternatives / proposed floodway expansion / separate project components / winnipeg flood improvements / recreational facilities
A word from the Environmental Assessment Study Team regarding Project Description for the Floodway Expansion Proposal
This Project Description is not considered complete at this stage of the environmental assessment and engineering design. A major effort of the Study Team will focus on building a detailed Project Description for this Proposal. The refinement of the design of Project components is currently ongoing and will be influenced by:
- Environmental Assessment Studies
- Socio-Economic Assessment
- Public Opinions derived from Public Consultations,
- Other Public Meetings, and;
- Engineering design and performance optimizations.
The Project Description is expected to evolve as the engineering design evolves in response to information resulting from ongoing assessments and consultations. Additional details regarding Project Description will be provided as they beccome available.
Introduction
The Government of Manitoba has established the Manitoba Floodway Expansion Authority (MFEA) charged with the responsibility of executing a proposed expansion of the existing Red River Floodway (Floodway) that exists to protect the City of Winnipeg from catastrophic damage in the event of extreme flooding events. The Red River Flood of 1997 resulted in water levels that took the existing Floodway to the limits of its existing design. Following the 1997 event, various levels of government initiated a series of meetings and commissioned engineering studies to assess vulnerabilities to flood damage and preferred options for providing a major increase in flood protection for the City of Winnipeg.
introduction / existing floodway / need for project / options considered / range of alternatives / proposed floodway expansion / separate project components / winnipeg flood improvements / recreational facilities
Existing Floodway
The existing Red River Floodway Control Structureand Channel during the 1997 Red River Flood.
The existing Floodway is a flood diversion channel that was constructed between 1962 and 1968 as a major element of a coordinated flood-defence response to massive damage incurred by the City of Winnipeg during the 1950 flood. After the 1950 flood, the Greater Winnipeg Diking Board was established and began construction of a system of dykes to provide a measure of protection against flooding within the City of Winnipeg. This initial effort resulted in the construction of boulevard dykes and installation of pumping stations to lift runoff into the rivers and outside the dykes in low-lying areas. A series of “borrow” sites were also established so material could be readily accessed to raise dykes in the event of future flooding emergencies.
In 1958, a Royal Commission on Flood-Cost Benefit reported its recommendations
based upon a major study to assess structural solutions to flooding problems
on the Red and Assiniboine Rivers. As a result of this Commission’s recommendations,
three projects were built within the period between 1962 and 1972:
- Red River Floodway to divert 1700 cubic metres per second from the Red River south of Winnipeg to the east of the city, discharging this flow back into the Red River at Lockport (project completed in 1968);
- a 700 cubic metre per second capacity diversion channel to convey floodwaters from the Assiniboine River immediately upstream of Portage la Prairie northward to Lake Manitoba (completed in 1970);
- the Shellmouth Dam in the upper reaches of the Assiniboine River just north of Russell (completed in 1972) to store floodwaters and reduce flow peaks downstream.
The existing Red River Floodway is a system consisting of four components: the floodway channel, the inlet control system, the dykes, and the outlet structure. The floodway channel is 48 kilometres long and drops in elevation 5 metres over the distance between the inlet and outlet. The designed depth of flow within the channel is 8 metres. The width at the top of the channel varies from 213 metres to 305 metres. Material excavated from the channel was deposited along the side of the channel to form embankment 6 metres high.
The entrance to the floodway is located in the eastern bank of the
Red River near St. Norbert. An earth-fill weir at the entrance
ensures that
flows below flood level continue down the Red River, and ensures that
ice floes do not enter the floodway channel.
The inlet control structure is located on the Red River just downstream
from the floodway inlet. The purpose of the control structure is to
regulate the flow between the natural channel of the Red River and
the floodway
channel, during the period of high water levels. The gates of the control
structure are normally in a submerged position with about 1.8 metres
of water over them in the summer months.
To prevent floodwaters from bypassing the inlet control structure,
dykes have been constructed on either side. On the east side of the
Red River,
the dyke is incorporated into the floodway embankment. To the west
of the Red River, the dyke extends for 34 kilometres from the inlet
control
structure to a point where the natural ground is above the design
flood elevation. During the 1997 flood, the dyke was raised and extended
an additional 25 km to prevent floodwaters from bypassing the structure
and entering the city.
The drop over the entire reach of the floodway is 5 metres, but the
corresponding drop of the Red River is 10 metres. The purpose of
the outlet structure
is to dissipate the energy in the water at its point of re-entry
to the Red River near Lockport, thereby preventing damage and erosion
in the
river.
introduction / existing floodway / need for project / options considered / range of alternatives / proposed floodway expansion / separate project components / winnipeg flood improvements / recreational facilities
The Need for Improved Flood Protection for the City of Winnipeg
The Floodway was designed 45 years ago to provide Winnipeg with protection up to an estimated flood magnitude that would be exceeded once in 160 years, based on statistical data on river floods that existed at that time. Recent recalculation of flood frequencies considering the past 40 years of flood data, a period that experienced a series of relatively large floods (in 1966,1974,1979,1996 and 1997) reveal that the design flood established in the 1960’s actually would represent only a 1 in 90 year flood event. Analyses of the historical record reveal that large flood events can occur more frequently than were calculated using the old (pre-1960’s) data.
The Floodway Channel under 1997 Flood conditions.
Flood control works on the Red and Assiniboine Rivers have been extensively
used since their completion. Floods occurred on the Red River in 1969,
1970, 1974, 1979, 1987 and 1997. The 1979 flood was similar in magnitude
to the devastating flood of 1950, which was the catalyst for the construction
of these works. In 1997, a flood surpassed only by the 1826 flood of
record occurred on the Red River. This event served to demonstrate
yet again the enormous value of the flood control works to the
City of Winnipeg
and, at the same time, to emphasize the likelihood that a flood of
even greater magnitude could occur. Costs incurred by damages
to the City
of Winnipeg under the “do-nothing” scenario in the event
of a flood event larger than the 1997 flood would dwarf the cost of
expanding the existing floodway system. The City of Winnipeg has benefited
enormously from the establishment of the Red River Floodway and the
overall flood protection system, where serious flooding has been avoided
since
control works went into operation. Potential damages prevented during
the 1969 to 1991 period are in excess of $1.1 billion (in 1998 dollars)
in Winnipeg alone. The damages prevented in 1997 are significant. In
the absence of these works, a large area of the City would have been
inundated, hundreds of thousands of people would have been evacuated,
and the economic centre of Manitoba would have been completely paralyzed.
The cost of the Red River Floodway, Portage Diversion and Shellmouth
Reservoir totaled $94 million when constructed, or about $416.6 million
in 1998 dollars. It is clear that these flood control works have been
extremely cost effective.
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Options Considered for Improved Flood Protection
Chronology
Following the 1997 Red River Flood, President Bill Clinton and Prime Minister Jean Chretien asked the International Joint Commission (IJC) to study the flood and its impacts. In June of 1997, the Canadian and American governments charged the IJC with examining and reporting on the causes and effects of damaging flood events in the Red River, and to make recommendations on means to reduce, mitigate and prevent harm from future flooding in the Red River Basin. In September of 1997, the IJC established the International Red River Basin Task Force to examine a range of alternatives to prevent future flood damage. This Task Force undertook and commissioned a series of studies and in 1999 commissioned a study on flood risks in Winnipeg and possible means to reduce those risks. Reports from the study were submitted to the IJC Task Force in 1999 and in 2000.
Reports to International Joint Commission (IJC)
The reports submitted to IJC contained several major findings:
- Winnipeg is at risk to major floods of the magnitude of the 1997 flood, or larger
- Many vulnerabilities exist that should be improved
- Potential damages to Winnipeg due to floods exceeding the 1997 Flood event would be as much as $17 Billion for a 1 in 1000 year flood.
- The preferred options to provide a major increase in flood protection were the St. Agathe Detention Structure or the Floodway Expansion.
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Range of Alternatives Considered
While the Reports to IJC in 1999 and 2000 led to the identification of two preferred options for improved flood protection, a wide range of alternatives were explored. These alternatives included:
- Channel improvements in the Red River in Winnipeg and in the river reach north of Winnipeg to increase discharge capacity of the river.
Diversion of the eastern tributaries of the Red River (including the Roseau River, Rat River, Joubert Creek, Cook’s Creek, etc.) around the city to re-enter the Red River north of the existing Floodway outlet.
A detention structure on the Red River upstream of Winnipeg near St. Agathe where some of the flood waters of the Red River would be detained temporarily during an extreme flood to reduce the outflow through the Winnipeg area, at the cost of incremental flooding upstream.
Raising of the primary dykes in Winnipeg on a permanent basis to permit more flow to safely pass through the river during a flood.
Installation of a massive pumping plants at the inlet to the floodway to mobilise the large discharge capacity of the Floodway at high water levels, without actually having to raise the water level upstream of the Floodway inlet above the ”State of Nature” level.
Increase the freeboard on the West Dike and modify the operation rules of the Floodway to permit more frequent and higher water levels upstream of the Floodway inlet.
Remove a portion of the East Embankment of the Floodway to permit more efficient entrance of floodwater into the Floodway, thereby increasing its discharge capacity.
Removal of the Outlet Control structure on the Floodway.
Removal of the entrance weir at the inlet to the Floodway.
Raise the bridges along the Floodway channel to increase the hydraulic capacity at high water levels.
Construct a “twin” floodway adjacent to the existing channel to increase the discharge capacity of the diversion. The possibility of extending this channel north of the current outlet location was also considered.
Construct a separate Floodway Channel to the west of Winnipeg.
Increase the capacity of the Portage Diversion, thereby reducing the potential for the Assiniboine River to intensify flood levels in Winnipeg.
Increase the height of the Shellmouth Dam to develop more storage capacity that could further reduce the contribution of flood from the Assiniboine River.
Expand the existing Floodway to increase its discharge capacity, and continue with the existing operation rules.
While all these alternatives were considered, not all options were analysed rigorously because cursory review was adequate to show that some option were clearly uneconomic, had only minor hydraulic benefits, or had environmental impacts that would be unmanageable or almost certainly unacceptable. At the request of the IJC, the consideration of alternatives did not consider the option of developing storage reservoirs upstream in the Red River watershed, as the IJC Task Force was evaluating this option in a separate process. In Novermber, 2000, the IJC concluded in its own process that it would be both economically and environmentally infeasible to produce enough acceptable large reservoir storage that alone would reduce substantially the flood peaks for major floods.
Subsequent to the release of the 1999 and 2000 reports, the Province
of Manitoba retained KGS Group to carry out further study of the two
preferred options that had emerged from the studies commissioned by
the IJC. The Report generated from this study was released in
November, 2001.
The Report described the costs and impacts of both schemes, without
selecting a preferred option. The selection between the two options
was deemed
by the consultant to be of major social significance to Manitoba, and
opted to yield a decision on selecting a preferred option to the provincial
government on behalf of the citizens of Manitoba. The Province of Manitoba
selected the Floodway Expansion option as the preferred option.
introduction / existing floodway / need for project / options considered / range of alternatives / proposed floodway expansion / separate project components / winnipeg flood improvements / recreational facilities
The Proposed Floodway Expansion
A finalised version of the project description for the proposed Floodway Expansion project does not yet exist. The concept continues to undergo refinement as results from ongoing studies become available. Consequently the designs will continue to evolve and undergo optimization as additional information is acquired. Studies currently underway to define the project in more detail include environmental impact assessments, re-engineering of bridge and utility crossings, drainage works and other engineering components not yet in the final design stage. In fact, the design of the Floodway Expansion itself is expected to evolve in response to issues identified in both the environmental assessment and public consultation processes which are currently underway. While complete engineering design is not yet finalised, sufficient detail does exist to offer conceptual detail of the main components of the proposed Floodway Expansion Project.
Project Components
The existing floodway diverts a limited volume of flow from Red River floodwaters around the City of Winnipeg using a system comprised of a gate control structure and the Floodway Channel. Spring runoff flood events are controlled by raising the control gates at the gate control structure, limiting Red River flow through the channel passing through the City of Winnipeg. Flow is diverted upstream of the control structure to the entrance of the Floodway Channel, where the flow is routed around the City of Winnipeg. Flow from the Floodway Channel re-enters the Red River via an engineered outlet structure located north of Lockport.
While the current Floodway configuration provides protection to the
City of Winnipeg from floods with a 1 in 90 years probability
of reoccurrence,
this level of protection was determined to be barely adequate for a
larger magnitude flood such as the Flood of 1997, which was a
1 in 100 year
flood event. The Proposed Floodway Expansion will increase protection
for the City of Winnipeg from a 1 in 90 year flood to a 1 in 700 year
flood event, primarily through deepening and widening of the existing
Floodway channel.
The Proposed Manitoba Red River Floodway Expansion Project consists
of upgrades and enhancements to several components of the existing
flood
control works and Floodway diversion system. Detailed information
about each of these enhancements will be provided during this
assessment
process once designs become more fully evolved. At this juncture,
a general description
of the enhancements and upgrades includes the following:
- Modifications to 13 existing railway and highway bridges, five transmission lines, other crossings, seven drainage structures, and the excavation of approximately 35 million cubic metres of soil for Floodway channel widening and deepening.
- Upgrades to the inlet control structure, including a fire protection system, installation of additional riprap and erosion control measures to protect the embankments of the control structure.
- Increases in elevation of the west dike and raising a portion of the Floodway channel adjacent to the inlet control structure
- Widening of the outlet structure and the discharge channel to the Red River. River bank stability and erosion in the Red River north of the Floodway outlet will also be addressed in this upgrade.
- Enlargement of the Floodway Channel by varying amounts along its 46 km (29 miles) length, with width increases up to approximately 110 m (360 ft), and depth increases up to 2 m (6.5 ft), subject to final design optimization. The total volume of excavation is estimated to be 34 million cubic metres (45 million cubic yards). The new design capacity will be 3960 m3/s (140,000 cfs), compared to the original design capacity of 1700 m3/s (60,000 cfs) used in the 1960’s.
Hydro transmission line crossings are one of several services crossing the Floodway Channel.
Specifically, separate upgrades are anticipated to consist of the following:
- Increase in the freeboard
at the existing West Dike that extends over 70 km (44
Miles) from the Floodway Inlet Control Structure in a generally south
westerly direction to tie into high ground at the west side
of the Red River Valley. The dike will be increased
in height by varying amounts estimated to be up to 1.2 m (4 ft) and
the west end will be
extended beyond the current location. The dike is currently considered
to provide
acceptable safety against wind effects on the floodwaters of the Red
River for water levels up to El 236 m (El 774 ft) at the Floodway
Inlet Control Structure. In its improved
condition, it is intended to be capable of safely protecting against
water levels up to El
237 m (El 778 ft) at that location. - Modification of the bridges over the Floodway Channel. This will
consist of a
combination of outright replacement of some of the bridges, and retrofitting of others to resist hydraulic loading due to overtopping. Considerable additional engineering will be required to define the modifications in their final form. - Enlargement of the Outlet Structure by extending the ogee crest and the stilling basin by an estimated 66 m (218 ft) towards the east, so that it will be capable of passing a flow of 1700 m3/s (140,000 cfs). This will be accompanied by enlargement and re- shaping of the Outlet Channel to permit the increased Floodway flow to re-enter the Red River with minimum impact on the riverbanks. The Outlet Channel construction will be the only component of the Floodway Expansion that will require work on an existing riverbank and will require measures to minimize the release of excavated sediment into the river flow.
- Riverbank fortification and protection at and downstream of the Floodway Outlet, where appropriate and justifiable.
Floodway Outlet north of Lockport on the Red River.
- Replacement of drainage structures where necessary along the east bank of the Floodway to accommodate the enlarged channel cross section. Adjustment to the capacity of these drainage structures will be possible if analysis of their performance since their original construction warrants it.
- Replacement of the Inlet and Outlet structures at the Seine River Inverted Siphon that carries riparian flows under the Floodway and release them into the Seine River on the west side of the Floodway. The current plan is to retain the existing conduit under the channel and to extend it as required to reach the new locations of the Inlet and Outlet Structures.
- Replacement of the Aqueduct under the Floodway to permit the deepening and widening of the Floodway that is planned at that location.
- Extension of a number of transmission lines that cross the Floodway.
- Replacement of a number of miscellaneous crossings, including gas pipelines, oil pipelines and underground pipelines.
- Improvements
at the existing Floodway Inlet Control structure will be carried
out.
The full extent of the improvements that are required
will be addressed in the planning
phase, and may include:
- Placement of additional riprap on the downstream slopes of the
embankments adjacent to the concrete structure to protect it from erosive
damage during the passage of large flows through the structure.
- Possible improvement of the riprap on the upstream face of the
embankments adjacent to the concrete structure to protect it from erosive
damage during extreme events that require raising the upstream water
level to as high as El 237 m (El 778 ft).
- Possible installation
of backup gates that could serve to control flow into
the Red River in Winnipeg during flood events if the existing gates were to malfunction. The justification for this will be examined in detail in the
planning phase.
- Placement of additional riprap on the downstream slopes of the
introduction / existing floodway / need for project / options considered / range of alternatives / proposed floodway expansion / separate project components / winnipeg flood improvements / recreational facilities
Ancilliary Project Components (Under Separate Process)
City of Winnipeg Flood Improvements
The concept for the Floodway Expansion also includes a series of improvements to the flood protection infrastructure within Winnipeg. The City of Winnipeg has plans to fund improvements over the next several years to several areas of its overall Flood Protection Works. This work will be carried out by the City of Winnipeg with funding and timing details that have yet to be announced. The City of Winnipeg Flood Improvements are not considered as part of this assessment process.
introduction / existing floodway / need for project / options considered / range of alternatives / proposed floodway expansion / separate project components / winnipeg flood improvements / recreational facilities
The proponent’s Project Description, issued in July 2003 has indicated a desire to incorporate recreational facilities to the maximum extent practical. Options that may be considered range from enhancement of existing ski-hill facilities near Bird’s Hill to hiking/biking/skiing trails along the expanded Floodway channel. Recreational use groups will be invited to present proposals and business plans for establishment and ongoing operation of potential new recreational facilities.
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