Many homeowners do not know that their regular homeowners’ insurance does not cover damaging from flooding. For that you must purchase separate flood insurance. In many areas, only about 10% of homeowners have flood insurance on their properties, resulting in massive uninsured losses. You also need to have purchased flood insurance at least 30 days before you are eligible to make a claim, which prevents people that are under imminent threat of flooding from purchasing flood insurance at the last moment. Learn more about this insurance, which costs a few hundred dollars a year for most people, from Clark Howard here.
If you are interested in the history of the flood insurance program, this Washington Post article describes how it was formed and its current shaky financial state.