1-Percent-Annual Chance Flood: The flood that has a 1 percent chance of being equaled or exceeded in any given year. Synonymous with 100-Year Flood and Base Flood.

Action Stage: The stage which, when reached by a rising stream, represents the level where the NWS or a partner/user needs to take some type of mitigation action in preparation for possible significant hydrologic activity.

American Red Cross (ARC): A humanitarian organization that provides emergency assistance, disaster relief, and disaster preparedness education in the United States.

Bankfull Stage: An established gage height at a given location along a river or stream, above which a rise in water surface will cause the river or stream to overflow the lowest natural stream bank somewhere in the corresponding reach.

Base Flood Depth (BFD): The depth of water above highest adjacent grade resulting from a flood that has 1-percent chance of being equaled or exceed in a given year. 

Base Flood Elevation (BFE): The elevation of a flood having a 1-percent chance of being equaled or exceeded in any given year.

Base Level Engineering: Engineering analysis techniques are used to determine the expected hydrologic (how much water) and hydraulic (how will the water be conveyed) conditions in the vicinity of streams and water courses during the 1% annual chance storm event.

Base Map: The map of the community that depicts cultural features (for example, roads, railroad, bridges, dams, culverts, drainage features, and corporate limits). 

Community Rating System (CRS): A FEMA initiative, established under the NFIP, to recognize and reward communities that have implemented floodplain management measures beyond the minimum required by NFIP regulations.

Crest: The level at which river peaks before going down. It is the rise above the normal level and happens during the flood. 

Crest-Stage Gage (CSG): Used to determine the elevation of a peak stage occurring at a specific location in a stream.

Cut Line: When the flow of water erodes a stream bank, a rapid water high-water mark called a cut line or scour line can form.

Debris Line: Debris lines are trails of twigs, grasses, and other small debris left on sloping ground at the edge of a river where calmer water, as it receded, deposits the material.

Digital Elevation Model (DEM): A 3D computer graphics representation of elevation data to represent terrain, commonly of a planet, moon, or asteroid.

Digital Terrain Model (DTM): A DEM in which terrain data has been further enhanced with break lines, creating greater accuracy as it contains additional information defining terrain in areas where Lidar data alone is unable to do the job effectively.

Estimated Base Flood Elevation (Est BFE): The estimated elevation of flood water during the 1% annual chance storm event. Structures below the estimated water surface elevation may experience flooding. 

Flash Flood Warning (FFW): An alert issued by national weather forecasting agencies to warn the public that a flash flood is imminent or occurring in the warned area.

Flood: A general and temporary condition of partial or complete inundation of normally dry land areas from the overflow of inland or tidal waters or the unusual and rapid accumulation or runoff of surface waters from any source.

Floodplain: A land area that is susceptible to being inundated by water from any source.

Flood Profile: A graph showing the relationship of water-surface elevation to location, with the latter generally expressed as distance above the mouth for a stream of water flowing in an open channel.

Flood-prone Community: Any community that is subject to inundation by the 1-percent-annual-chance (base or 100-year) flood.

Flood Stage: An established gage height for a given location above which a rise in water surface level begins to create a hazard to lives, property, or commerce. The issuance of flood advisories or warnings is linked to flood stage. Not necessarily the same as bankfull stage.

Flood Insurance Rate Map (FIRM): The insurance and floodplain management map produced by FEMA that identifies, based on detailed or approximate analyses, the areas subject to flooding during a 1-percent-annual-chance flood event in a community.

Floodplain Management: The operation of a program of corrective and preventative measures for reducing flood damage, including, but not limited to, emergency preparedness plans, flood control works, and floodplain management regulations.

Geodatabase: A database of geographical information such as countries, administrative divisions, cities and related information. 

Geographic Information Systems (GIS): A system of computer hardware, software, and procedures designed to support the capture, management, manipulation, analysis, modeling, and display of spatially referenced data for solving complex planning and management problems.

Global Forecast System (GFS): A weather forecast model produced by National Centers for Environmental Prediction (NCEP). This dataset contains dozens of atmospheric and land-soil variables. 

High Water Mark (HWM): A high water mark is a point that represents the maximum rise of a body of water over land.

Ice Ring: When floods recede during freezing periods, ice sheets may form at the water surface.

Memorandum of Agreement (MOA): A written document describing a cooperative relationship between two parties wishing to work together on a project or to meet an agreed-upon objective.

Memorandum of Understanding (MOU): Defines a “general area of understanding” within both parties’ authorities and no transfer of funds for services is anticipated. 

Minor Flooding: Minor Flooding is defined to have minimal or no property damage, but possibly some public threat.

Moderate Flooding: Moderate Flooding is defined to have some inundation of structures and roads near the stream. Some evacuations of people and/or transfer of property to higher elevations may be necessary.

Major Flooding: Major Flooding is defined to have extensive inundation of structures and roads. Significant evacuations of people and/or transfer of property to higher elevations are necessary.

Mud Line: When turbid water comes into contact with natural and man-made objects, the water can leave a film on the outside of nonporous surfaces called a mud line.

Rapid-Water High-Water Marks: In higher-velocity stream reaches, water often transports higher sediment loads and leaves behind high-water marks that are characteristic of high-energy flows.

River Gage or Stream Gage: It contains instruments that measure and record the amount of water flowing in a river or a steam. 

Seed Line: Seed lines form when fine materials float on top of tranquil water and remain on objects after the water recedes.

Special Flood Hazard Area (SFHA): An area identified by the US FEMA as an area with a special flood or mudflow, and/or flood related erosion hazard, as shown on a flood hazard boundary map or flood insurance rate map.

Stage: The level of the water surface of a river or stream above an established gage datum at a given location.

Tabletop Exercise (TTX): Discussion-based sessions where team members meet in an informal, classroom setting to discuss their roles during an emergency and their responses to a particular emergency situation. A facilitator guides participants through a discussion of one or more scenarios.

Texas Natural Resources Information System (TNRIS):  The principal state archive in Texas for natural resources data. TNRIS provides a central access point for Texas Natural Resources data, census data, digital and paper maps, and information about datasets collected by state agencies and other organizations.

Tranquil-Water High-Water Marks: Tranquil water presents a smooth horizontal surface. High-water marks left behind by tranquil water have a similarly smooth trend.

Vessel Traffic Service (VTS): VTS is a marine traffic monitoring system established by harbor or port authorities, similar to air traffic control for aircraft.

Voice Over Internet Protocol (VOIP): A method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol networks, such as the Internet.

Wash Line: Like cut lines, wash lines indicate the removal of loose material from the top of the ground surface without carving away significant amounts of soil, revealing a “cleaner” look than the adjacent non-flooded soil.

Wireless Emergency Alerts (WEA): A public safety system that allows customers who own compatible mobile devices to receive geographically targeted, text-like messages alerting them of imminent threats to safety in their area.