Edmonton yesterday gave its residents access to home-specific flood history and predictions for overland flooding—a first for any Canadian city.
The city was forced by Postmedia’s Freedom of Information request to disclose the flood maps, based on non-riverine (flooding not caused by overflowing rivers) patterns. Postmedia had asked for the maps last spring, insisting that residents have a right to know their risk. When the city declined, the media company appealed to the province and won.
Edmonton Journal reported that along with the flood maps, city officials also added a complete set of flood reports for each upland home dating back to 1946. Sewers expected to reach capacity in the event of a one-in-100-year flash flood were also identified in the maps.
The maps are available at Edmonton’s official website.
Branch manager Chris Ward reassured the public that despite the severe flooding the maps suggest, the simulated models only depict what would happen should the mother of all storms hits.
“Don’t panic. This is a worst-case scenario,” Ward said.
The maps were prepared using high-resolution topographic maps of the flat table-lands above the region’s valley. The maps were matched with sewer data, then run through computer simulations of one-in-100-year flash flood events.
Most of the at-risk flood areas were located where prairie sloughs once lay.
“You will see this very clearly on the flood map,” Ward explained to the
Edmonton Journal. “These are locations where we built residential neighbourhoods in the bottom of a lake bed without filling it in.”
The flood maps cover over 100 neighborhoods built before 1989, excluding Mill Woods, where flood mitigation work has already begun based on 2004 and 2012 data. New areas were also excluded from the maps, particularly in areas where the road network is designed to carry water to a safe storage place.
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