Flood Hazard Determination
Flood Hazard areas are determined using statistical analysis of records of river flow, storm tides, and rainfall; information obtained through consultation with the community; floodplain topographic surveys; hydrologic and hydraulic analyses. The detailed flood insurance study (FIS) covers those areas subject to flooding from rivers and streams, along coastal areas and lake shores, or in shallow flooding areas, but does not include area of less than one square mile. For more information about Flood Hazard, please visit FEMA website
Flood Hazard Zones and What They Mean
Flood Zone X100 (100-year):
Refers to a flood level with a 1 percent or greater chance of being equaled or exceeded in any given year. Flood insurance is not mandatory.
Flood Zone .2 Percent (Formerly X100):
Outside the 100-year flood zone. Refers to a flood level with a .2 percent or greater chance of being equaled or exceeded in any given year. Flood insurance is NOT mandatory.
Flood Zone X500 (500-year):
Termed "minimal flood hazard areas". Flood insurance is NOT mandatory
Flood Zone X (Formerly X500):
Outside the 500-year flood zone. Termed "minimal flood hazard areas". Flood insurance is NOT mandatory.
Flood Zone VE:
Coastal flooding with a velocity hazard (wave action). The base flood elevations are determined.
Flood Zone A:
SFHAs subject to inundation by the 100-year flood. Detailed hydraulic analyses have not been performed, therefore no base flood elevation or depths are shown. Mandatory flood insurance requirements apply.
Flood Zone AE:
SFHAs subject to inundation by the 100-year flood determined by the Flood Insurance Study, utilizing detailed methods. Base flood elevations are shown. Mandatory flood insurance requirements apply. Zone AE is used on new and revised maps in place of Zones A1-30.
Flood Zone AH:
SFHAs subject to inundation by the 100-year shallow flooding (usually areas of ponding) where average depths are between one and three feet. Base flood elevations derived from detailed hydraulic analyses are shown. Mandatory flood insurance requirements apply.
Flood Zone AO:
SFHAs subject to inundation by the 100-year shallow flooding (usually sheet flow on sloping terrain) where average depths are between one and three feet. Average flood depth derived from detailed hydraulic analyses is within this zone. Mandatory flood insurance requirements apply.
AICUZ refers to Air Installation Compatible Use Zone Map. AICUZ contains Noise Zones and Accident Potential Zones for the areas surrounding Oceana Naval Air Station and Fentress Air Field. For more information, please visit NAS Oceana AICUZ Web site
Accident Potential Zone (APZ)
An area beyond the airfield runway where an aircraft mishap is most likely to occur if one occurs. It does not indicate a probability of an accident occurring, but is to be used for planning purposes. Based on historical data, aircraft accidents are most likely to occur near the airfield runway during aircraft takeoff and landing. An APZ is calculated for aircraft flight tracks to and from the airfield runway based on the number of aircraft operations.
The AICUZ map defines three APZs - the clear zone, APZ1, and APZ2.
The Clear zone extends 3000 feet beyond the runway and has the highest potential for accidents.
The APZ1 extends 5,000 feet beyond the Clear Zone.
The APZ2 extends 7,000 feet beyond APZ1.
If an accident is to occur, it is more likely to occur in APZ 1 than in APZ 2 and more likely to occur in the Clear Zone than in either APZ1 or APZ 2.
Ldn (day-night average sound level)
A standard noise measurement that takes into account the noise levels of all individual events that occur during a 24-hour period and the number of times those events occur. This measure includes a 10-decibel (dB) adjustment for the added intrusiveness of noise that occurs during normal sleeping hours, when people are more sensitive to noise.
Noise Contour: A line connecting points of similar day-night average sound levels measured from a specific noise source. At Naval air facilities, the primary noise sources are aircraft operations and aircraft engine maintenance operations. The LDN contours reflect the noise exposure in the surrounding communities and the fact that noise impacts diminish with distance from airfield operations. The Ldn contours on the AICUZ maps range from greater than 75 ldn nearest the air station to less than 65 ldn.