FEMA will provide some assistance, but it comes with a lot of red tape. So people cannot return to their homes for some time. Usually the poorest and most disadvantaged get the worst of it since their homes tend to get damaged more, and they don't have any money to get it rebuilt without FEMA's assistance.
Many people don't even know that their home owner's insurance do not cover flood. Flood insurance is expensive. Private insurance companies do not offer it (or what they offer is extremely expensive), so you have to get it from National Flood Insurance Program, which is run by FEMA. The maps for which they mandate buying flood insurance are inacurate and outdated, so many people don't even know they are at risk.