Cross-border flooding makes waves in the Prairies

- Pembina River Basin, Manitoba

Advanced computer modeling helps to part the waters

To keep North Dakota's spring thaw waters from flooding into Canada, Canadian farmers from Manitoba's Pembina River Basin constructed a 29 km dike just 10 metres north of the U.S.-Canada border. Built in the 1940s, the dike has proved an effective method in stemming the flow onto Canadian soil, but flood waters now inundate farmlands south of the border.

To counteract the flooding, American farmers have attempted to install large pipes and have dug new channels to help divert the water flow. But while these efforts have seen some success, they have not been effective in times of extreme flooding. Further aggravating the situation is heavier and more frequent rainfall in the region, as well as reduced recovery time between flood cycles.

Facing a source of contention on both sides of the border, the Canada-U.S. International Joint Commission (IJC) decided to pursue a more advanced and long-term flood management solution. As a first step, it reached out to the National Research Council (NRC) and its 2D flood modeling experts to dive deep into the Pembina basin's water issues.

Getting their feet wet

Knowing that aerial photographs would only provide a snapshot of water conditions, NRC relied on Telemac, a sophisticated 2D modeling tool that can simulate river flows and related processes with uncanny realism. Using carefully prepared simulations combined with real-world data, the advanced tool proved essential in providing accurate visual depictions of water levels, flow directions and flood extent over the entire Pembina basin.

To build the 2D model of the Pembina basin, Thierry Faure, NRC Project Lead, reviewed historical reports and gathered data from farmers, government representatives and other sources on both sides of the border. NRC and IJC staff also spent considerable time making sure that members of the public understood the facts about the basin, the watershed, the model and their progress. "This was critical to our success, since stakeholders needed to believe in the model and make it their own," adds Faure.

Also critical was making the jump from the traditional one-dimensional modeling normally used in flood-prone areas to the 2D simulations, which provide much more detailed and reliable information about the basin’s water issues.

Assessing the landscape

Following a four-year period studying a series of possible solutions to minimize the flooding, including building more dikes and adding canals, the project team acknowledged that finding a permanent solution that would satisfy everyone would be a challenge. This was due mainly to the unpredictable weather conditions in the area and the complex interactions between the precipitation, the snowmelt, the low-relief agricultural landscape and the wet-dry cycles that are typical in the prairies.

IJC was nonetheless impressed with the progress made and with the agility of the team in meeting its objectives. "We depend on NRC as a credible, authoritative partner," says Glenn Benoy, Senior Water Quality and Ecosystem Adviser, IJC Canadian Section. "The synergy between the two organizations has helped us build capacity for ongoing studies of this kind."

Benoy believes that establishing a co-operative arrangement along the dike could address issues at a local level and minimize flooding across farms and towns, and he is confident that the creation of a binational task force will help address the basin's water-related issues on a broader and longer-term basis. Doing so will save time and resources and help to tame the flood waters and keep farmers dry.

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