2) Standing water in areas like this are breeding grounds for all types of pestilence that we have not seen in our generation; e.g. typhoid.
Would it be wise to dump large quantities of chlorine in the flood water?
I think the only sure way to prevent disease-causing organisms from growing in the water is to get rid of the water. We're about to see the biggest emergency water pumping project in history.
If you get the people out, typhoid is not a problem
Salmonella typhosa.