If you have just had a flood you should go out and get yourself a dehumidifier. This is something you need to do as soon as possible. Going out and buying one today is one of the smartest decisions you can make.
Floods can cause mold growth within the drywall of your walls. If you can get dehumidification in there as quickly as possible you might be able to save some of your walls from having to be replaced. However, a delay in dehumidification can be the difference between replacing drywall and keeping your drywall in tact.
After a flood, you need to get the best dehumidifier possible. Do not go out there and buy a $90 dehumidifier with a 20 gallon bucket. Try to go industrial strength if possible, but a 70 or 80 gallon bucket could work as well. The goal is to only have to empty the bucket once a day so that you can have it run as close to 100% of the time as possible.
Make sure to buy or rent an industrial size fan as well. A combination of a fan and dehumidifier is a very smart choice to prevent mold growth. That is still not to say that the carpet will not need to be replaced, but if you can prevent the mold growth within walls, couches, or anything else that the water touched then you need to do that right now.
There are companies out there that will rent industrial dehumidifiers especially if you are located in a flood zone. In some cases this is a smart idea, but if you think you might get flooded again and/or if it is your basement that got flooded then you very well might consider purchasing one. This way you can use the dehumidifier in the basement even when your basement is not flooded.
After a flood, dehumidification is essential to preventing a horrible smell. The smell of mold kicks in really quickly and without a dehumidifier it can linger for weeks.
Once you have had a flood, go out right away and buy a dehumidifier. It just might save you thousands of dollars in flood repair costs.