fines — The finer grained particles of a mass of soil, sand, or gravel. The 

 material, in hydraulic sluicing, that settles last to the bottom of 

 a mass of water. 



f lood — Any flowwhich exceeds the bank-full capacity of a stream or chan- 

 nel and flows out on the floodplain; greater than bank-full discharge. 



floodplain — The relatively level land composed of primarily unconsolidated 

 river deposits that is located adjacent to a river and is subject to 

 flooding; it contains an active floodplain and sometimes contains an 

 inactive floodplain or terrace(s), or both. 



flood probability — The probability of a flood of a given size being 



equaled or exceeded in a given period; a probability of I percent would 

 be a 100-year flood, a probability of 10 percent would be a 10-year 

 f lood. 



flow — The movement of a stream of water or other mobile substances, or 

 both, from place to place; discharge; total quantity carried by a 

 stream. 



flow, base — That portion of the stream discharge which is derived from 



natural storage - i.e., groundwater outflow and the draining of large 

 lakes and swamps or other sources outside the net rainfall which 

 creates the surface runoff; discharge sustained in a stream channel, 

 not a result of direct runoff and without the effects of regulation, 

 diversion, or other works of man. Also called sustaining flow. 



flow, laminar — That type of flow in a stream of water in which each par- 

 ticle moves in a direction parallel to every other particle. 



flow, low — The lowest discharge recorded over a specified period of time. 



flow, low summer — The lowest flow during a typical open-water season. 



flow, uniform — A flow in which the velocities are the same in both magni- 

 tude and direction from point to point. Uniform flow is possible only 

 in a channel of constant cross section. 



flow, varied — Flow occurring in streams having a variable cross section 

 or slope. When the discharge is constant, the velocity changes with 

 each change of cross section and slope. 



fork length — The length of a fish measured from the tip of the nose to the 

 fork in the tail. 



freeze front — A surface that may be stationary, which has a temperature 

 of C and is warmer on one side of the surface and colder on the 

 other. 



frequency curve — A curve of the frequency of occurrence of specific 

 events. The event that occurs most frequently is termed the mode. 



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