FEMA has established certain requirements for the development and implementation of pre-disaster mitigation plans.  One of the elements of a quality plan is for emergency services experts to be able to easily update the data that drives the findings and strategies. 

Stakeholders in this plan are encouraged to submit documentation (maps, datasets, reports) that supports the information provided in the plan.  Users of the plan will be able to search these reference materials from this page.

Glossary of Terms

Abutment (dam)

The valley-side against which a dam is constructed.

Acre‐foot of Water

Approximately 326,000 gallons of water, or approximately a football field covered by one foot of water.

Active Faults

An active fault is defined as a fault displaying evidence of displacement along one or more of its traces during Holocene time (about the last 11,000 years).


Earthquakes during the seconds, hours, days to months following a larger earthquake (main shock) in the same general region.

Alluvial Fan

A cone‐shaped deposit of stream sediments, generally deposited at the base of a mountain where a stream encounters flatter terrain.

Amplitude (seismic waves)

The maximum height of a wave crest or depth of a trough. Amount the ground moves as a seismic wave passes, as measured from a seismogram.

Avalanche Path

The area in which a snow avalanche runs; generally divided into starting zone, track, and runout zone.

Basin and Range Physiographic Province

Consists of north‐south‐trending mountain ranges separated by valleys, bounded by the Rocky Mountains and the Colorado Plateau to the east and the Sierra‐ Cascade Mountains to the west (includes western Utah).

Bearing Capacity

The load per unit area, which the ground can safely support without excessive yield.


Solid in‐place rock, sometimes exposed and sometimes concealed beneath the soil.

Block Faulting

see normal fault

Collapsible Soil (hydrocompaction)

Loose, dry, low‐density soil that decreases in volume or collapses when saturated for the first time following deposition.

Critical Areas

Environmentally sensitive areas which include wetlands fish and wildlife habitat conservation areas; geologically hazardous areas; areas with a critical recharging effect on aquifers used for potable water; and frequently flooded areas. Critical areas have measurable characteristics which, when combined, create a value for or potential risk to public health, safety and welfare.

Critical/Essential Facilities

Structures meeting one or more of the following criteria: 

  • Fire stations, police stations, storage facilities for vehicles/equipment needed after a hazard event, and emergency operation centers.
  • Hospitals, nursing homes, and housing which is likely to contain occupants who may not be sufficiently mobile to avoid injury or death as a result of a hazardous event.
  • Public and private utility facilities, which are vital to maintaining or restoring normal services to, damaged areas after a hazardous event. 
  • Structures or facilities that produce, store, or use highly flammable, explosive, volatile, toxic and/or water-reactive materials.

Debris Flow

Involves the relatively rapid, viscous flow of surficial material that is predominantly coarse grained.

Debris Slide

Involves predominantly coarse‐grained material moving mainly along a planar surface.

Drought (Agricultural)

Lack of water for crop production in a given area.

Drought (Hydrologic)

Lack of water in the entire water supply for a given area.

Drought (Meteorological)

Lack of precipitation compared to an area’s normal.

Drought (Socioeconomic)

Lack of water sufficient to support an area’s population.

Earth Flow

Involves fine‐grained material that slumps away from the top or upper part of a slope, leaving a scarp, and flows down to form a bulging toe.


A sudden motion or trembling in the earth as fracture and movement of rocks along a fault release stored elastic energy.

Earthquake Fault Zone

Earthquake fault zones are regulatory zones around active faults. The zones are used to prohibit the location of critical facilities and structures designed for human occupancy from being built astride an active fault. Earthquake Fault Zones are plotted on topographic maps at a scale of 1‐inch equals 2,000 feet. The zones vary in width, but average about one‐quarter mile wide.

Earthquake‐induced Seiche

 Earthquake generated water waves causing inundation around shores or lakes and reservoirs.


The point on the earth’s surface directly above the focus of an earthquake.


Geologic time unit lasting more than an age but shorter than a period (Epoch 2008).


The removal of earth or rock material by many types of processes, for example, water, wind, or ice action.

Expansive Soil and Rock

Soil and rock which contain clay minerals that expand and contract with changes in moisture content.


A break in the earth along which movement occurs.

Fault Segment

Section of a fault that behaves independently from adjacent sections.

Fault Zone

An area containing numerous faults.

Federal Emergency Management Agency (FEMA)

Authorized under Section 404 of the Stanford Act. Provides funding for hazard mitigation projects that are cost‐effective and comply with existing post-disaster mitigation programs and activities. These projects cannot be funded through other programs to be eligible.


Material used to raise the surface of the land generally in a low area.

Fire‐resistant Vegetation

Plants that do not readily ignite and burn when subjected to fire because of inherent physiological characteristics of the species such as moisture content, fuel loading, and fuel arrangement.


An area adjoining a body of water or natural stream that has been or may be covered by floodwater.

Floodplain (100‐year/500‐year)

Floodplains that have the potential to flood once every 100 or 500 years or that has a 1% (100‐year) or 0.2% (500‐year) chance of flooding equal to or in excess of that in any given year.


An area of land immediately adjacent to a stream or river channel that, in times of flooding, becomes an enlarged stream or river channel and carries the floodwater with the highest velocity.


Concerning or pertaining to rivers or streams.


The point of origin of an earthquake within the earth, and the origin of the earthquake’s seismic waves.

Formation (geologic)

A mappable rock unit consisting of distinctive features/rock types separate from units above and below.

Frequency (seismic waves)

The number of complete cycles of a seismic wave passing a point during one second.

Fuel (fire)

Vegetation, building material, debris, and other substances that will support combustion.

Fuel Break

A change in fuel continuity, type of fuel, or degree of flammability of fuel in a strategically-located strip of land to reduce or hinder the rate of fire spread.

Fuel Type

A category of vegetation used to indicate the predominate cover of an area.

Glacial Moraine

Debris (sand to boulders) transported and deposited by glacial ice along a glacier’s sides or terminus.


A block of earth dropped between two faults.

Gradient (slope)

A measure of the slope of the land surface.

Ground Failure

A general term referring to any type of ground cracking or subsidence, including landslides and liquefaction‐induced cracks.

Ground Shaking

The shaking or vibration of the ground during an earthquake.

Ground Water

That portion of subsurface water which is in the zone of saturation.

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