Aethien wrote:
I wonder if part of the problem, too, is that flood water is no longer nice and clean the way the Nile might have been. Probably a lot of toxic crap, heavy metals, etc. in the silt that's gonna get laid down by this.
Not really. The concentrations we'd be talking about during a flood are not very significant.
In a town, OMG yes they are (sewage, household chems, warehouse and industry chems, automotive chems, etc), but not really in main channel flood waters, or rural areas.
So, when you see people wading through flood waters in a city, keep in mind that the sewers have backed up, the industrial areas have all been flooded, etc.