During a flood situation the water becomes very polluted within a day or so.
Initially as the water rushes in the flow is not all that polluted.
For instance the New Orleans levee breach had clean water flowing in from Lake Pontchartrain, but as it rushes in it picks up debris, garbage and waste.
As it gets higher it kills animals and humans, which begin to decay.
The flooding waters become polluted with chemicals and human waste.
All of these things can cause severe stomach pains, disease and death to those who drink the water.
There are a number of very good personal water filtration systems out there, but many of them will not kill the bacteria, which is in the water.
Some recommend using Clorox or chlorine to clean the water before you drink it.
But if you are on your roof you may not be able to get to your laundry cleaning supplies to get it.
If you swim down into your house underwater you might end up contaminating yourself with the very bacteria you are trying to prevent from getting into your body or you could die trying to swim in and swim out if you get stuck inside your house underwater and drown.
There are a few small personal devices, which can keep you alive and if you live under the water levels or behind a dam or levee you may wish to consider these.
Here is one example of such a device.
http://www.
alpinesurvival.
com/emergency-water-filters.
html If we were to give one of these units to all those on top of their houses with a care package, we could prevent deaths while we carefully take the elderly and children off the roofs of buildings first.
Likewise we would first remove those folks who are on buildings, which are less substantially built or barely sticking out of the water.
Think on this.