I was actually a bit curious about this, as at one point I was going to have to drive through there for a wedding. Went to look around a bit, and it sounds like
part of the reason we had such high levels in that province this year was due to the amount and timing of snowfalls.
In any case, floods of these sizes are not rare. There's been
massive floods for the entire period that we've been keeping records, with the top end from way back in the 1800s.
Indeed, the one with the
highest magnitude was in the 19th century, and there is extensive evidence of them going back 400 or so years. The risk of flooding is always present in these river valleys and is Manitoba's most prevelant natural disaster issue, if I remember correctly. Several times, as seen from the above links, have they come a few years in the same decade.
I think it's a bit quick to state that it is due to climate, at least not alone. While I am not going to get into that climate change debate, I find all too often it's an excuse for other things -- deforestation making flooding easier, for example (this is happening predominantly in farmland, I remind you). Dams, bridges and roads restricting flow or available space for the river to expand too elsewhere in it's course. Reservoirs taking in water, and the amount which is expelled back in and where. I don't think it's prudent to overlook other potential ways which flooding in that valley can be made worse.
Just my opinion.