The maps are being updated because the majority of the maps are based on analyses that were performed over 25 years ago. Watershed conditions such as topography have changed and there has been significant added development. Furthermore, analysis tools and historical data collection have improved over time and will increase map accuracy.
Flood hazard mapping is an important part of the National Flood Insurance Program (NFIP), as it is the basis of NFIP regulations and flood insurance requirements. The Federal Emergency Management Agency (FEMA) maintains and updates data through Flood Insurance Rate Maps (FIRMs) and risk assessments.