It's worth remembering that massive flooding doesn't just mean high water and destruction. It's what's in the water, too (from AP):
"Flooded rivers from Florence’s drenching rains have swamped coal ash dumps and low-lying hog farms, raising pollution concerns as the swollen waterways approach their crests Monday.Add to that raw sewage and waste treatment plant flooding, all kinds of animal carcasses, snakes and other vermin carried along with the flood waters. It's a toxic stew flowing everywhere. Terrible.
North Carolina environmental regulators say several open-air manure pits at hog farms have failed, spilling pollution. State officials also were monitoring the ongoing threat from the breach of a Duke Energy coal ash landfill near Wilmington."