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<br />1~,~' <br />))" <br />l{ ! <br />" <br /> <br />1:,!~' <br />\\: <br />W <br />i"~ - <br />Is <br />L <br />l!~ <br />IL. <br />.~ <br />Ii <br />ff~ <br />P' <br />-I <br />llL. <br />i1'... <br />'r <br /> <br /> <br />~", <br />il <br />, <br /> <br />hi <br /> <br />I' <br />II rill <br />! <br />j. <br />If"LJIi <br />'r-- <br />!J~ <br />I~L. <br />,;li .. <br /> <br />!~'1I <br />~ <br />L,.L. <br />l~-' <br />~.~ <br />II <br />I,'. <br />l~ . <br />I <br /> <br />I, \i, <br />,~ <br />l~ " <br />!)iI~ <br />i~ <br />1,.,11,' . <br />.,] <br />~~ <br />,. <br />111.__- <br /> <br />-- <br /> <br />Discharge <br /> <br />The quantity of water passing a given stream cross <br />section per. unit of time. Rate of flow in a stream <br />is usually expressed in cubic feet per s,econd. <br /> <br />Drainage Basin <br /> <br />A part of the surface of the earth that is occupied by <br />a drainage system, which consist!; of a surface stream <br />or a body of impounded surface water together with all <br />tributary surface streams and bodies of impounded sur- <br />face water. <br /> <br />Flood <br /> <br />An overflO1' on lands not normally covered by water <br />which are IJsed or usable by man. Floods have two <br />essential characteristics: (1) The inundation of <br />land is temporary. (2) The land is adjacent to and <br />inundated by overflow from a river or stream or an <br />ocean. lake or other body of standing water. <br /> <br />Normally. a flood is considered ,~s any temporary <br />rise in streamflow or stage, but not the ponding of <br />surface water which resul ts in significant adverse <br />effects in the vicinity. Adverse effects may include <br />damages from overflow of land areas, temporary back- <br />water effects in sewers and local drainage channels, <br />creation of unsanitary conditions or other unfavor- <br />able situations by deposition of materials in stream <br />channels during flood rece,ssions, use of ground <br />water coincident with inct'eased streamflow and other <br />problems~ <br /> <br />Flood, 1% Chance <br /> <br />A type of flood, includin~; the ..ater surface elevat:ion <br />and territorial occupation thereof, which can be <br />expected to occur at any time in a given area based <br />upon recorded historical precipitation and other valid <br />data, but with an average statistical one percent <br />chance of being equal1ed or exceeded during anyone <br />year. The term is used interchangeably with 100-yeai' <br />flood or Intermediate Regional Flood. <br /> <br />Floodway <br /> <br />The floodway is the channel of a stream, pIus any ad,- <br />jacent floodplain areas, that must be kept free of <br />encroachment in order that the 100-year flood may be <br />carried without substantial increases in flood heights. <br /> <br />Flood Frequency <br /> <br />(See Probability) The average recurrence interval oE <br />specific discharges or water stages which case flooding. <br /> <br />Flood Peak <br /> <br />The maximum instantaneous discharge of a flood at a <br />given location, It usually occurS at or near the time <br />of the flood crest. <br /> <br />'O)~ - <br />/ '\ <br /> <br />11_ <br /> <br />-- <br />