Amends the National Flood Insurance Act of 1968 to state that, if a flood has commenced or is in progress before expiration of the 30-day waiting period before a new or modified flood insurance policy becomes effective, the insurance coverage shall take effect upon the expiration of such 30-day period. Allows coverage for damage occurring after expiration of the waiting period, however, only if the property has not suffered damage or loss as a result of such flood before the waiting period expires.