duration curve — A curve which expresses the relation of all the units of 

 some item such as head and flow, arranged in order of magnitude along 

 the ordinate, and time, frequently expressed in percentage, along the 

 abscissa; a graphical representation of the number of times given 

 quantities are equaled or exceeded during a certain period of record. 



erosion, stream bed — The scouring of material from the water channel and 

 the cutting of the banks by running water. The cutting of the banks 

 is also known as stream bank erosion. 



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. 



flood — Any flow which 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, 



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