The following was written by Scott Forbes, a feelance journalist, UofW prof and resident of Twin Lakes Beaches:
“I have reading commentaries on various articles posted on the Free Press / CBC etc. of late, and see that there is still a great deal of misunderstanding about the origins of the flood — i.e., the notion that this was natural. This also seems to be creeping into comments of our public officials again as they gear for the lawsuits.
To satisfy my curiosity, I performed a simple modelling analysis to project water levels on Lake Manitoba last year WITHOUT if the Portage Diversion had not been opened. As you know, some Assiniboine water would have made it into Lake Manitoba even without the Diversion. This is based upon the published work of my colleague Bill Rannie, a hydrologist at the U of Winnipeg, who estimates that about 20% of the Assiniboine flow would have ended up in Lake Manitoba naturally. Using Bill’s estimate I projected how much the lake would have risen if the Diversion had remained closed, and just the natural flow had reached the lake on top of the other natural inputs to the lake.
The results are pretty clear. First, the lake’s peak level reaches just over 814.5 feet on the 7th of July – a minor flood overall, with some damage certainly to low elevation properties, but nothing like the disaster we experienced.
Second, the lake on May 31st is BELOW the flood level of 814 feet (and my numbers are deliberately conservative – it probably wouldn’t have been even that high). Again, we would have avoided nearly all of the damage on the 31st of May. There would have been continued shoreline erosion, perhaps a handful of low elevation structures damaged, but nearly everyone would have escaped major damage. The wind setup, estimated to have reached 5 feet on 31 May, would not have been as high (perhaps 4 feet?).
The conclusion is that we would have experienced a relatively minor flood, worse than the weather bomb in the fall of 2010, yes, but not anywhere near the scale we observed in 2011. It was very much an artificial flood.”
