Flood zones and evacuation zones measure different conditions that may not occur at the same time. The flood zones and evacuation zones are determined by different methods and have different purposes. A home may be located in a non-evacuation zone yet still be located in a flood zone because of a nearby stream or pond. Residents must check both zones. Flood zones are areas mapped by FEMA for use in the National Flood Insurance Program. Each flood zone designation, represented by a letter or letters, tells homeowners what the risk is for flooding at their property over a period of years, regardless of the cause. Evacuation zonesare based on hurricane storm surge zones determined by the National Hurricane Center using ground elevation and the area's vulnerability to storm surge from a hurricane. The evacuation zones are marked from A through E, plus non-evacuation zones.