High-risk flood zones designated by FEMA where there is at least a 1% chance of flooding in any given year (also known as the 100-year floodplain). Properties located in SFHAs and secured by federally backed mortgages are required by law to carry flood insurance. These areas are shown on Flood Insurance Rate Maps (FIRMs) and include Zone A (riverine flooding) and Zone V (coastal flooding with wave action). Buildings in SFHAs face significantly higher flood insurance premiums than those in moderate or low-risk zones.