Aufeis - When new ice continues to form on top of older ice. Ice-forming situations occur wherever there are continuous sources of water and freezing temperatures.
BFE - Base Flood Elevation. The water surface elevation of a flood that has a 1 percent chance of being equaled or exceeded in any given year. The BFE is commonly referred to as the 100-year flood level.
BLM - Bureau of Land Management
Buildings - All public and residential buildings excluding smokehouses, small storage sheds, saunas and others.
FEMA - Federal Emergency Management Agency. The federal agency under which the National Flood Insurance Program is administered.
FIRM - Flood Insurance Rate Map. An official map of a community, prepared by FEMA, which has delineated both the special hazard areas and the actuarial (rate premium) insurance zones applicable to the community.
FIS - Flood Insurance Study. An engineering study performed by FEMA to identify flood-prone areas, insurance risk zones and other flood data within a community.
Flood Gauge - A 1 foot by 8 foot staff gauge. Typically placed in a prominent place within the community and meant to function during severe floods. It often has attached plaques that indicate the elevation of community buildings, the flood of record and the recommended building elevation.
Flood of Record - The greatest flood recorded for a location usually referred to as the "maximum flood of record." The term is also sometimes used to mean any flood for which there is a measurement of height or other systematic or reliable record useful for technical analysis.
Flood Plain - The lowlands adjoining the channel of a river, stream, or watercourse, or ocean, lake, or other body of standing water, which have been or may be inundated by flood water. The channel of a stream or watercourse is part of the floodplain.
HWE - High Water Elevation. The water level of the highest recorded flood. The flood level is marked by a 5-inch by 8-inch white aluminum sign with black lettering that reads "High Water Elevation." The sign also has a symbol for water, which is placed at the flood level. The HWE may or may not be at the level of the 100-year flood.
HWM - High Water Mark. A 1.5-inch-diameter metal washer attached with a lag bolt to a building or a utility pole, placed at the water level of the highest recorded flood. The washer is stamped COE-HWM and painted fluorescent red at the time of installation. A HWM may or may not be at the level of the 100-year flood.
Jokulhlaup Flood - Term used internationally to describe the flood resulting from a rapid release of water from lakes formed in or under glaciers. Any glacier may produce an outburst flood.
MHW - Mean High Water. The average height of the high waters over a 19-year period. All high water heights are included in the average where the type of the tide is either semidiurnal or mixed.
MHHW - Mean Higher High Water. The average height of the higher high waters over a 19-year period.
MLW - Mean Low Water. The average height of the low waters over a 19-year period. All low water heights are included in the average where the type of the tide is either semidiurnal or mixed.
MLLW - Mean Lower Low Water. The average height of the lower low waters over a 19-year period.
MSL - Mean Sea Level. The average height of the sea for all stages of the tide over a 19-year period, usually determined from hourly height readings.
NFIP - National Flood Insurance Program. The federal program under which flood-prone areas are identified and flood insurance is made available in participating communities.
National Geodetic Vertical Datum (NGVD) - A measure of land elevation essentially the same as Mean Sea Level (MSL). NGVD is always given with the date of the datum.
NWS - National Weather Service
100-Year Flood - This is a flood of such magnitude that it occurs on the average of once every 100 years, when measured over a very long period of time. This is a statistical average; it is possible to have more than one 100-year flood within a few years. The level of the 100-year flood is the Base Flood Elevation.
Participating Communities - Those communities which participate in the National Flood Insurance Program.
Recommended Building Elevation - The recommended elevation of the bottom of the first floor of a building. This is a recommendation by the U.S. Army Corps of Engineers-Alaska District. The Corps does not regulate the floodplain. Participating communities may have different requirements.
Storm Surge - A rise in water surface level above the normal level on a lake or ocean coast, produced by wind, differences in atmospheric pressure during a storm or both.
USGS - U. S. Geological Survey
Zero Damage Elevation - The highest flood elevation which can occur without harming buildings or their contents.