One of the first things to remember is that you need to assume that A: All flood water is contaminated and B: Protect yourself accordingly.
The first step when recovering from a flood is removing any remaining water with a wet/dry-vacuum or water pump that is specifically designed to suck up water. Most cities or town have drainage systems in place, so make sure that the drains in your building are free from debris and that the water in and around your foundation has a clear path to the city sewage systems. Similarly, keep street gutters clear to help water recede quickly.
Once all of the standing water has receded or been removed, you can start the drying out process. Have indoor dehumidifiers and fans in the spaces that need drying. It is ok to open up doors and windows to speed the drying process (as long as it isn’t raining).
Completely removing all trapped moisture will prevent mold and decay from causing serious problems down the road. You need to remove baseboards, shower trays, and anything that has space beneath or behind it. Remove the mud you find and begin drying these areas immediately. Before replacing the fixtures, make sure those spaces are completely dry.
If trapped moisture is allowed to linger, this can compromise a building's structural integrity - which is a high cost to repair. Remember that locked in moisture can cause wood to rot, weakening its ability to hold up the weight of your structure.
Mold only needs moisture to grow, and it could grow in areas that are not visible to you. This can in turn, induce illness, create hazardous living conditions, and severely depreciate the property value.
For more information, check with the government agencies listed below.