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<br />pr"flle Is generally drawn to silo,", .urface "1,,vatlcrI for the cr~"t of "-
<br />specHic flood but ..ay also!J.., pr"par,',l for ccmditions at II given time
<br />oTseage.
<br />
<br />Orthoplloeo Mapping
<br />Mapping ",hich ""perimpese. " coneour map On an aerial photograph
<br />of the aame 8cale.
<br />
<br />Flood Reconstitution
<br />- In hydrologlc--;;tudl"a, thla Is an ,HtClllpt to reproduee.~ histodc
<br />flood's discharge" "sIng" hydrologic rllOd"l >In.d known hht'Hk rainfall
<br />and w"tershod data. In hydra"Hc BtudleB, th!.i is nn attempt to
<br />recrcatcap".tflood'a"'at"r levelsus1ng recorded discharges.
<br />
<br />l'eakDlscharge
<br />Themaxl..,,0\1n.tantane<>usdlachargeofafloodataglvenloca-
<br />tion. It ullually occurs at or near the t1"", of ehe floodcre..t. In
<br />the graph1cal rel'r(l"(lnt..tlon of U"" V(lr"u~ U..e, which, 1.. known aa a
<br />flood hydrograph, the peak d1acharge occurs betw"en the ascension limb
<br />end the reeess10n limb.
<br />
<br />Frequency
<br />(Se,,"Prob<<bl1lty")
<br />
<br />l'hotograllllll('trlc
<br />~\aking topograpblc ...,.."..rernent.. by ehe use of aerial' phoeographs.
<br />
<br />Furur" Conditions
<br />In ehl" report, this r"f"r~ to th" potentlal fue"r" exeent of
<br />urMn developme"e in ~he Shc"p Dr.... basin. Aho <lnd"r thls condition,
<br />ehe irrigattonc""als and the slOOll irrign.ttnn da"swcreas8urned to be
<br />te1llOved. Ihe roadway~ were aa8LJrn,'d to re...>I.. 1n pl"ee.
<br />
<br />!lydrologicAnalyale
<br />'rhis refers to th., detenll.lnado" or dlacharge-pH,bal>llley
<br />reJationshipa"tvariouslocatlo\l8,
<br />
<br />Probability
<br />'rile annual chance of occurrence of apeel!ic hydrologic evene..,
<br />such ss rainfall, over'a specified area or. peak. discharge ae a
<br />apecitied locatIon expressed in p~rcent.. e.g_, 5 percene representing 1
<br />chanee in 20 of the evcnt occurr1ng in any year. The l~; 50-, tOO-,
<br />and 500-ye..r floods are floods having a 10-, 2-, 1-, or .2-pereene
<br />probability, reapectively, otoccutrence tn any yeat or an av"r ag..
<br />recurrence Interval 1n the order of onc.. in 10, 50, 100, or 500 y..ars,
<br />r..speee1"..ly, It may be bssed on atatistleal 80alY8.... of streamflow
<br />recorda and/or analyse.. of rninfall and runoff chnract..ri..tics 1n ehe
<br />g..neral r~gion of the wat..rshed.
<br />
<br />llyduul1c Analyds
<br />Thin refers to the determination af 8tt~arn water surface ele"..-
<br />tlons ulling diseharg~s of spe~if1ed rrn~~btlleien, ~rOs8 ""ctions,
<br />chAnn,,} 'l"d overbank roughn"ss, snd t~~ t,.),..,try of obsttuctions,
<br />
<br />IOIperviousness
<br />Th" degree to which an 'IT"''' .1111 shed ",,,t..r .'nd Mt "-11",,, r.inf.~ll
<br />to p",,,..trate. For ex","p1.., paved "reas atc cII~cnt1n.lly impcrvlou..,
<br />while aandy ateas sre very pervious.
<br />
<br />Rainfall Distribueion
<br />To ~re renllstically define eainfal1 and ""tlmat.. runoff, the
<br />total ra1nfall from ..n assumed seorOl of a cert..1n duration may be
<br />subd1vided 1neo rain falling in shorter ri.... incrementa, T~ rainfall
<br />....ynotbethesn<le1nalleilllCincrelllCnta.
<br />
<br />Inf11tut10n
<br />PrectpHaUon s03l<ing 1nto the ground. ,.or exa..ple," s"ndy soil
<br />may ab"orb s grene deal of ra1nfall without lcaving an exc..ss for sur-
<br />face runoff. 'rhis....y be "xpr"""ed as th", total proportion of rainfall
<br />..b~orb..d or a.. an infiltrat Ion rate In inches per huur (see "RUnoff").
<br />
<br />Recurr..nce Interval
<br />(See "Probnblllty")
<br />
<br />Reference Number
<br />A n"..ber"d point ..tong. a ..tr""'" channel'1dent1fyiI18'-""spec1t1c
<br />locatiunfo:r-eorr..latingthedataahownin"a:r-ioullfor..."through'oue..
<br />report.
<br />
<br />Mann1ng'.."n"
<br />- A ,"""sur" of the redst,,"ce to flow off~r..d by" chnnnel or flood
<br />plain. II low v"lue Indicates l<1s.. r,,~lst"nc" to the p;>asage of "'''ter.
<br />For example, cl"an, straight, concr..te or earth channeh mlght ha"" "u"
<br />v~lues ~f 0.Ol3 and 0,025, re~pcct1v..ly. A "hallow, weedy channel
<br />might have an "n" valu.. in "J("e~a of 0.100. FIl"tor. other than
<br />roughn""~ Infl\len"-"_ ",," \"~l,,.... S,,,,,,, other factors Include vcgct"-t lon,
<br />ch~nno'.l bends, ."<Il,,,,'nt, ~nd ~tn".. slop".
<br />
<br />Runoff.
<br />The quantIty of rainfall which flows uver the 8urfac" to enter the
<br />IItream as diecharge volu~e. Th" dtfference 1n quantity between
<br />ralnfall and runoff repr..s"nta 10"~"H to lnfiltratlon, detent 1""
<br />IIt~rage. and evapo-tran~ptrat10n.
<br />
<br />Str"amCag"
<br />A dev1ce t~ lndic~te the ",at~r d"pth of a ~Iream al a g~ge ..Ile.
<br />th~ diacharge at thl~ lO<l..tlun ,,;an be Jeter;olned by using the >toge of
<br />
<br />,-'
<br />. ,
<br />
<br />,\-4
<br />
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