I kind of doubt it. The problem isn't just the dirt and debris dub up, there's also gasoline, pesticides, toxic chemicals, etc from flooded factories, etc. I'm not aware of any commercially available filters that can take heavy metals and petrochemicals out of the water (although activated charcoal is supposed to reduce them somewhat).

No, those filters are designed for basically clean water. They exchange calcium ions and iron ions and remove some organic chemicals to some degree. If you couldn´t drink the water before filtering, you coundn´t drink it after filtering either.
Even dedicated filters for outdoors use might be of limited effect for storm water. The descriptions of those filters clearly state the limits.

I would stay away from ground water due to chemical contamination possibility. Take containers and rain water collection stuff, then filter that with a typical backpacking filter. Or boil it.
That's probably as safe as you're going to get after a massive flood disaster.

Just be aware that boiling won't automatically make water safe if it's been contaminated with chemicals. Some of them are hydrophilic and have a boiling point close enough to that of water that they aren't separated out by boiling.

When all else fails, beer can be trusted (in reasonable amounts)....

Does anyone know of a personal sized or BOV transportable sized water filtration system that would remove chemical and biological contamination?

There are several that make the claim to be able to do both, but I have not been able to test any with a lab. Most can effectively remove biological contaminants, as can boiling the water. Some chemicals might be removed by boiling as well, if they are more volatile than the water. Others might be removed (heavier metals and chemicals) by setting up a still of sorts, so the water steams away and then is condensed back into liquid. In an emergency situation I would probably try about anything I could if I needed water that badly.

The key to the ability to remove heavy metals and chemicals is an activated carbon filter component.

You can minimize the quantity of chemicals if you draw your water from a clean (or cleaner) source. Pay attention to the sources of contamination, direction of flow and the original source.

For potential water purification needs, I always carry a metal cup or pot to boil water in.

I have never used these but the Berkey filters look good. They are gravity filters that require no electricity, and are available in several sizes. They remove bacteria, viruses, and lots of chemical contaminants.

As one might expect, they are not cheap.

I have no affiliation with them.

http://www.getberkey.com/

I wonder if anyone,anywhere thought to collect rain water?

Rain water can contain contaminants from dust but in any situation short of a bad chemical plant fire or nuclear event one would think rain would be at least easy to sanitize. In a pinch I would try it before drinking urban flood water.

This is probably obvious enough that I almost shouldn't need to say it but the time to worry about water is before the flood! Water is so cheap that it's almost ridiculous, especially given the importance of clean water and how hard it is to come by in many parts of the world. It's sad how many people run thousands of gallons down the drain without in thought in normal times yet have nothing but what's in the toilet tank or water heater when trouble strikes.