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Ironies and issues float to surface after great flood

The Calgary Herald by Cathy Ryan and Jerry Osborn 1 May 2014

Just as floods are inevitable, so too is the pattern of the aftermath. Complaints against insurance companies, complaints against the government, folks wanting to be considered to be on the floodway (so they can get bought out), folks wanting to be considered to be off the floodway (so they can stay put), general resistance to floodplain regulation, pressure to solve problems with engineering solutions, accrual of political capital by quick action on highly visible projects — these stories have played out many times in North America.

In the Calgary case, a few ironies emerge:

* Some floodplain residents complained that the provincial government had not acted on the Groeneveld report recommendations after the 2005 flood. But when the government tried to enact some of the same recommendations in 2013, floodplain residents complained even louder.

* Many floodplain residents complained they were not aware of a flood hazard in Calgary. This is partly because some of their neighbours have tried to keep the flood hazard quiet, starting in 1973 after the first floodplain study by Montreal Engineering, so as to keep their property values intact. The cycle of designed ignorance continues. In August, the province indicated they would require inclusion of a note on flood-fringe land titles for information purposes, but then backed off due to intense pressure from flood plain residents.

* Much flood damage was caused by groundwater inundation rather than overland flow. This happens when river water enters its permeable gravel banks and high water tables propagate further back from the river. When water tables are higher than a basement floor, groundwater enters cracks in the foundation, or via the tub or toilet in the absence of an effective backflow preventer. Certainly some groundwater inundation was misdiagnosed as sewage backup.

* The first permanent residents of Calgary had no information about flood history, yet were more enlightened land-use planners than subsequent immigrants: the Mounties in 1875 built their fort next to, but on a hill comfortably above, the Bow and Elbow rivers.

Studies of possible mitigation measures are underway as mentioned in the Herald’s April 30 story, “Flood mitigation inches ahead.” The centrepiece of a proposed Elbow River scheme is a tunnel to divert water from the lower Elbow River into the Bow. The dollar cost almost certainly would be significantly higher than has been suggested; a giant tunnelling machine would have to be bought or leased, and big-project cost overruns are a dime a dozen.

For example, Seattle’s Big Bertha tunnelling machine as of December had used up 50 per cent of its budget digging 10 per cent of the highway tunnel it is trying to bore. It is presently stuck under Seattle, and requires a “rescue.”

Meanwhile in Calgary, the floodplain mapping done in 2012 shows a distinct demarcation between areas flooded by the Bow and Elbow. In particular, it shows that 100-year flood waters in eastern downtown come from the Bow, not the Elbow. The Elbow ran north and flooded East Village, but they were designed for it. It flooded the Stampede grounds, but they were insured for it.

We conclude that the main beneficiaries of the tunnel would be the small fraction of Calgarians living on the Elbow River floodplain. Losers in the tunnel scheme would be Bow River floodplain residents of southeast Calgary downstream of the tunnel outfall, who for any given storm would experience slightly higher Bow flood levels than they do now.

There are many complications. Expensive riverfront properties cost the city money, but they also contribute commensurately high property taxes. In general, floodplain residents have a pretty good deal, enjoying coveted riverside locations while the general taxpayer has helped many of them twice in the past decade, for their taking of risks so high that insurance companies back off.

Individual Calgarians have to pay for a lot of things they may never use, such as schools even when they have no children. There is a certain delicious irony, however, in the concept of the less-prosperous residents of northeast Calgary helping to subsidize the riverfront amenities of the mostly prosperous homeowners along the Elbow River.

Scientists cannot predict when and where the likes of Slave Lake fires or eastern ice storms will happen next. We do know well, however, where rivers will flood next, and with what average frequencies. It seems simple and rational to give the river room to do its thing — flood.

If one were to consider the most effective solution for Calgarians at large, it might be to gradually redevelop the parts of the Elbow River floodplain close to the channel into a long green strip for all to enjoy.

Politics, of course, have to be considered by politicians, but we think it is appropriate for Calgarians to make flood-related decisions informed by good science and good information.

Cathy Ryan is a hydrologist in the geoscience department at the University of Calgary and Jerry Osborn is a geologist.