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<br />Probabilit~ - The annual chance of occurrence of specific
<br />hydrologic events, such as rainfall over a specified
<br />area or peak discharge at a specified location ex-
<br />pressed in percent, e.g., 5% representing one chance
<br />in 20 of the event occurring in any year or an average
<br />recurrence of once in 20 years.
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<br />Fleod C:-c';l - The r:\axji~UIT. st<lgc or elt:."",tion reached by the
<br />waters of a flood at a given location.
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<br />Reach - Reach means a longitudial segment of a stream or
<br />river. A reach will generally include the segment of
<br />the flood hazard area where flood heights arc influ-
<br />enced by a man-made or natural obstruction. In an
<br />urban area, the segment of a stream or river between
<br />two consecutive briayc crossings would typically con-
<br />stitute a reach.
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<br />flood frequency - (See ProbabLlity)
<br />interval of specific discharges
<br />cause flooding.
<br />Flood Peak - The maximum instantaneous discharge of a flood
<br />at a given location. It ususally occurs at or near the
<br />tim", of th,' flood crest.
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<br />The aV0.rage recurrence
<br />or water stages which
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<br />Reference Point - A numbered point identifying a specific
<br />locatlon for correlating the data shown in various
<br />forms throughout the report.
<br />Runoff - The quantity of rainfall which flows over the sur-
<br />face to enter the stream as discharge VOlUMe. The dif-
<br />ference in quantity between rainfall and runoff repre-
<br />sents losses to infiltration and interception.
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<br />flood 1'l,1in - An area in and adjacent to a stream, which
<br /><lrc,1-1s subject to floodinq as the I:csult of the oc-
<br />c'n:-encc of a 100 year flood .:iod Which area thus is so
<br />adverse to past, current, or fore~eeablc construction
<br />or land use as to constitute a significant hazard to
<br />public health a~d safety or to property.
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<br />Stream - Any natural channel or depression through which
<br />water flows either continuously, intermittently or
<br />periodically, inCluding any artificial modification
<br />of the natural channel or depression.
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<br />Flo;)d Profile - A graph sho"-'ing the relationship of water
<br />surface elevation to location, the latter generally ex-
<br />pressed as distance above mouth for a stream of water
<br />flowing in an open channel. It is generally drawn to
<br />show su:-face elevation for the crest of a specific flood,
<br />but may be pl:epal:cd for conditions at a given time or
<br />stage.
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<br />flood Stage - The ~tace or elevation at which overflow of
<br />th", natural bankS of a stream or body of water begins
<br />in the reach n~ area in which the elevation is measured.
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<br />Watershed - The drainage area situated above a specified
<br />point on a stream including the area drainage by trib-
<br />utary streams which enter the main strea~ above this
<br />point.
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<br />Jr,tcrrn"diate Ik<Jional r'lood - ^ type of flood, including the
<br />wiltcr surface elov,1tlon ilnd territoriill occupation, thcn,-
<br />or. "':hich carl b" CXf.Occted to occur ilt i'lny tim..., in a 'Jivl'Jl
<br />.-,r0<< [",sed U[JOn L'ecord\"j historical pn"cipit.atirin and
<br />0th'2.l valiJ data, bll\ ,....ith iill <IV\.","l" statistic,...l 0Ilc"
<br />t,el~'0!Lt chLlrtce 'J[ being equalled or exceeded during any
<br />o:,e .i~.ar. The term is "sed int",.-"h,-.ngpi'lbly with a one
<br />::Jet"(cnt flood or 100 year flood. (See definition for
<br />100 y.car flu0dJ.
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<br />Cbstrllc',lor. - ;\nv d.,~', WillI, wharf, embankment, levee, dike,
<br />pi,,{], llbutm;'''t, ['rojection, excav,-.tion, channel,
<br />"cctific~tio~, bridge, conduit, culvert, building,
<br />W.lre, fone", , rock, gravel, refuse, fill, structure or
<br />~attc" in, ~lo~g, ~erOSB, or projecting into any chan-
<br />nel, watercoursR, or regulatory flood hazal:d a"e~
<br />wl;~('h may in';c>e<.k. I:etard or change the direction of
<br />U"., [low of w~te]C either in inself or by C<ltching or
<br />,,,,llpcting dRbri" cilrri.ed by such walol:, 01: th"t is
<br />pJ ;;wed '....here the f 10..... ot the Wat"" miyht c~rry the
<br />5ar1(~ dO'....:1f>tr<','r1 to t.h(' daloage vf life or property.
<br />!\~ "rtificial obstruction shall m<."iln any obstruction
<br />whie!,l", not ~ ni'ltural obstruction. A natural ob-
<br />srnlction sh,'11 Clean any rock. t:-,-,c., <j:-ClV<.' 1 , or other
<br />:natt.,:- th'lt ha5 been localed hy non-human cause.
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