NPDP Dam Dictionary

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Term AKA Definition
Flexible pipe Pipe designed to transmit the backfill load to the soil at the sides of the pipe. Flexible pipe must be supported on both the bottom and on the sides of the pipe.
Floatable days The number of days during the recreation season on which it is safe to allow floating activities on recreation facilities
Floatable flows River flows which make rafting and other floating recreation possible.
Floc Loose, open-structured mass formed in a suspension by the aggregation of minute particles.
Flood A temporary rise in water levels resulting in inundation of areas not normally covered by water. May be expressed in terms of probability of exceedance per year such as 1-percent chance flood or expressed as a fraction of the probable maximum flood or other reference flood.
Flood control capacity Reservoir capacity assigned to the sole purpose of regulating flood inflows to reduce flood damage downstream. See exclusive flood control capacity.
Flood control pool Reservoir volume above active conservation capacity and joint use capacity that is reserved for flood runoff and then evacuated as soon as possible to keep that volume in readiness for the next flood.
Flood plain Nearly level land, susceptible to floods, that forms the bottom of a valley.
Flood pool index Computed as the ratio of the flood control pool depth to the depth below the pool, multiplied by the percent of time the reservoir water surface will be within the flood control pool.
Flora All plant life associated with a given habitat, country, or period. Bacteria are considered flora.
Flow Volume of water that passes a given point within a given period of time. See base flow, discharge, enhancement flow, interstitial flow, minimum flow, peak flow, and return flow.
Flow augmentation The release of water stored in a reservoir or other impoundment to increase the natural flow of a stream.
Flowage Water that floods onto adjacent land.
Flowage easement The right or easement to overflow, submerge, or flood certain lands; a right to prohibit building on certain floodways
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.