Amends the National Flood Insurance Act of 1968 to provide that an increase in the risk premium rate charged for covered properties mapped into a higher-risk flood zone as the result of an update to a Flood Insurance Rate Map (post-FIRM properties) shall be limited to an annual increase for 5 years of 20% per year of the difference between: (1) the risk premium rate otherwise chargeable pursuant to such update; and (2) the chargeable risk premium rate for such property that existed before such update.