Provincial Engineering & Geoscience Week

6 | W I N N I P E G F R E E P R E S S P R O V I N C I A L E N G I N E E R I N G & G E O S C I E N C E W E E K By Geoff Kirbyson for the Free Press T he Red River Floodway is kind of like health insurance — you hope you never have to use it but if disaster strikes, you're glad you've got it. But just like you probably don't know what the fine print of your policy says, you likely don't understand how the city's intricate flood protection system works, either. Just open up the gates, right? Wrong. It's much more complicated than that. Sure, Chris Propp, Hydrologic Services Engineer with Manitoba Infrastructure, admits that opening the gates is part of the process, but without the proper strategy and infrastructure both upstream and downstream, Winnipeg would be in for a world of wet every April and May. In a typical spring flood, the goal is to maintain natural water levels at the inlet, which is the level that would have occurred if all of the flood control infrastructure along the Assiniboine and Red rivers and the Portage Diversion weren't in place. Combined, they reduce the peaks coming into the city. (The Portage Diversion consists of two separate gates which divert some of the water in the Assiniboine into a 29-kilometre channel that empties into Lake Winnipeg near Delta Beach.) "When people picture the floodway gates, they think of a door that you open to let water in and you close it when you're done. In fact, they're large drum gates that come out of the bed of the river and raise the river level up so more water can spill over the floodway inlet into the floodway," he said. "If everything is working right, people don't ask too many questions." The natural water level is constantly changing and Propp and his team need to continually monitor the flows through every tributary coming into the city — this includes little creeks and streams. "It's a dynamic system — that's where the engineering comes in. To balance all that water, we're constantly calculating our natural water level and making short-term forecasts based on the water you see coming into the system," he said. The relatively low levels of snow in Manitoba, Saskatchewan and North Dakota this winter have not put any flood experts on high alert. Yet. "Things can always change. It just takes one big event. Currently it looks pretty promising but there's still lots of time left," he said. Predicting the exact timing and magnitude of future floods is nearly as difficult as dynamic system Keeping tabs on a "It's a dynamic system — that's where the engineering comes in. To balance all that water, we're constantly calculating our natural water level and making short-term forecasts based on the water you see coming into the system." The floodway gates at the Red River Floodway control structure south of the city of Winnipeg. Wayne Glowacki / Winnipeg Free Press Files

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