My observation regarding rainwater in Toronto (I walk several miles everyday) is that the ground is absorbing it nicely. The soil is very porous. Were it frozen at any depth, it would be a different matter altogether.
Naturally there will be the usual flood-prone places (like the lower Don) but to somehow suggest this is on a par with hurricane Katrina is ludicrous. In fact, our trees will benefit mightily from it all; and when the weather warms up, we can look forward to some glorious weeks, maybe months, all on account of the rain.