One of the first things to be done after a flood is to remove the water. After all standing water has been removed, the structure must be thoroughly dried to prevent moisture damage or mold growth.
Homeowners sometimes remove standing water themselves, then neglect to have the area professionally dried because the surfaces look dry or feel "dry to the touch". But behind the scenes the insulation, sill plates, carpet padding and metal channel and many other building materials can hold moisture within the structure resulting in long term water damage.
Without proper drying equipment, it is impossible to draw that moisture out before it cultivates mold or causes other structural damage. Increased moisture in the air after an indoor flood can cause "secondary" damage to drywall, decorative wood, books, artwork and other items, so thorough drying and dehumidification are critical of the water damage restoration process.