FEMA has a temporary program of a lower cost flood insurance for those homeowners who did not have flood insurance but are now in a flood zone. These rates may be temporarybut may give you some time to file for a LOMA (Letter of map amendment) if your house would qualify for one. Below are links to FEMA infomrational documents. You must discuss this with your insurance company.
Preferred Risk Extention FAQ's
Prefeered Risk Community Fact Sheet
Preferred Risk Talking Points
LOMA Process letter of map amendment
Letter of Map Amendment - Out as Shown
to be used if the house is clearly out of the flood zone
Interpreting Flood Insurance Rate Maps October 2015