NPDP Dam Dictionary

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Term AKA Definition
Flowline The path that a particle of water follows in its course of seepage under laminar flow conditions.
Flownet A graphical representation of flowlines and equipotential (piezometric) lines used in the study of seepage phenomena.
Flume Shaped, open-channel flow sections that force flow to accelerate. Acceleration is produced by converging the sidewalls, raising the bottom, or a combination of both. An artificial channel, often elevated above ground, used to carry fast flowing water. See long- throated flume, Parshall flume, and short-throated flume.
Fluvial Pertains to streams and stream processes.
Fly ash A by-product of coal-fired powerplants which reacts with water and the free lime in cement while generating only half the heat of an equal amount of cement.
Food chain A succession of organisms in a community in which food energy is transferred from one organism to another as each consumes a lower member and in turn is consumed by a higher member.
Foot Twelve inches. One of a number of projections on a cylindrical drum of a tamping roller.
Foot-Pound Unit of work equal to the force in pounds multiplied by the distance in feet through which it acts. When a 1 pound force is exerted through a 1 foot distance, 1 foot pound of work is done
Footing A sill under a foundation. Ground, in relation to its load bearing and friction qualities.
Forage Vegetation used for animal consumption.
Forage fish Small fish that produce prolifically and are consumed by predator fish.
Forb A weed or a broad-leafed plant.
Forced outage Nonscheduled shut down of a generating unit or other facility for an emergency or other unforeseen reason.
Ford A place where a road crosses a stream under water.
Forebay Headrace Impoundment immediately upstream from a dam or hydroelectric plant intake structure. The term is applicable to all types of hydroelectric developments (storage, run-of-river, and pumped- storage).
Forepole A plank driven ahead of a tunnel face to support the roof or wall during excavation. See horsehead.
Foreshore That part of the shore between the ordinary high-and low-watermarks and generally crossed by the tide each day.
Formation Any sedimentary, igneous, or metamorphic material represented as a unit in geology; generally called rock, but not necessarily meeting the definition of rock.
Fossorial insects Insects that live in the soil.
Foundation Lower part of a structure which transmits the load to the earth.
Foundation drains ile or pipe for collecting seepage within a foundation.
Foundation material Foundation soil The upper part of the earth mass carrying the load of the structure.
Foundation surface The surface of the upper part of the earth mass carrying the load of the structure.
Foundation trench A trench built at and into the foundation of a dam and filled with clay or other impermeable substances to prevent water from seeping beneath the dam. See cutoff trench.
Foundation type The base on which the dam is founded. In the database the foundation type is denoted as Rock, Rock & Soil, Soil, or Unlisted/Unknown.
Freeboard The difference in elevation between the maximum water surface and the dam crest. The vertical distance between a stated water level and the top of a dam. Thus net freeboard dry freeboard or flood freeboard" is the vertical distance between the maximum water surface and the top of the dam. "Gross freeboard" or "total freeboard" is the vertical distance between the normal water surface and the top of the dam. That part of the "gross freeboard" attributable to the depth of flood surcharge is sometimes referred to as the "wet freeboard but this term is not recommended as it is preferable that freeboard be stated with reference to the top of dam.
Freeze-thaw damage Damage to concrete caused by extreme temperature variations as noted by random pattern cracking. Damage is accelerated by the presence of water and commonly more severe on the south-facing side of structures.
Freezeout Deeply frozen over for long periods of time.
French drain A covered ditch containing a layer of fitted or loose stone or other pervious material
Friction Resistance to motion when one body is sliding or tending to slide over another.