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<br />pr"flle Is gencrally drawn to silo,", surface elevatlorI for the cr~"t of "-
<br />..p"cHic flood but ..ay also!J.., pr"par,',l for ccmditions at II givcn time
<br />orseage.
<br />
<br />Orthoplloeo Mapping
<br />Mapping which aupeTimposea " coneour map On an aerial photograph
<br />of the aame scale.
<br />
<br />Flood Reconstitution
<br />- In hydrologlc--;;t"dl"a, thla I. an ,HtClllpt to reproduce .~ historic
<br />flood's discharge" "sIng" hydrologic rllOd"l >In.d known hht'Hic rainfall
<br />and w..tershed data. In hydra"Hc studies, th!.i is nn attempt to
<br />recreetcap"stflood'a"'at"r levclsus1ng recordad discharge..
<br />
<br />l'eakDlscharge
<br />Themaxl..,,0\1nstantaneousdlachargeofafloodataglvenloca-
<br />tion. It uaually occurs at or near the ti"", of the floodcre"t. In
<br />the graph1cal rel'resentstlon of U"", v"rsu~ U..e, whiCh,1a known.... ..
<br />flood hydrogrsph, the peak d1scharge occurs between the ascension limb
<br />end the recess10n limb.
<br />
<br />Frequency
<br />(Se,,"Prob<<bl1tty")
<br />
<br />l'hotogrsllllll('trlc
<br />~\aking topographlc m.".surements by the use of aerial' photographs.
<br />
<br />Fatur" CondJtlons
<br />In thls report, this r"f,,~~ to th" potential futur" extent of
<br />urban develop,",,"t in ~he Shc"p Dra.. basin. Aho <lnd"r this condition,
<br />the irrigattonca"als and the "10011 irrisn.tt...n da"swcreasaurned to be
<br />re1llOved. The rosdway~ were aaaLJm,'d to reil\;>I.. 1n plaee.
<br />
<br />!lydrOlogicAnalysis
<br />'rhia refers to th., detenll.lnado" or dlsd".rge-ptobal>lllty
<br />relstionships 3.t vadous locatIons,
<br />
<br />Probability
<br />The annual chanee of occurrence of speclflc hydrologic events,
<br />such ss rainfsll, over'a specified areA or' peak. discharge at a
<br />specitied locatlon expressed in p~reent" e.g_, 5 percent representing 1
<br />chane.. in 20 of the evcnt occurr1ng in any year. The 1~; 50-, tOO-,
<br />and 500-yesr floods are floods having a 10-, 2-, 1-, or .2-percent
<br />probsbility, respectively, otoccurre"ce ln any year or an a""r ag..
<br />recurrence Interval 1n the order of once in 10, SO, 100, or 500 years,
<br />r....pect1ve1y. It may be bosed on atatistlcal analyse" of streamflow
<br />recorda and/or anslyaes of rainfall and runoff characteristics in the
<br />general region of the watershed.
<br />
<br />llydraulJc Analyda
<br />This refers to the determination of stteam water surface eleva-
<br />tions using discharges of spe~if1ed rrQ~~blllt1c8, ~ross scctions,
<br />chAnn"t "nd overbank roughn".s, And t~~ t,.),..,try of obstructions,
<br />
<br />IOIperviousness
<br />The degree to which an ar"," .1111 shed ..."t..r ..nd Mt "11",,, r.inf.~ll
<br />to p~n~trate. For ~xa,"pl.., pav~d "reas arc cs~cnt1ally 1mpervio<1s,
<br />while sandy Areas arc very pervLoua.
<br />
<br />Rainfall Distribution
<br />To ~re reallstically def1ne rainfall and estlmate runoff, the
<br />total ra1nfall from an assumed StOrOl of A certn1n durstion may be
<br />subdivided into rain falling in shorter time incrementa, T~ rainfall
<br />",aynotbethes;'''le1nalltilllClncrelllCnta.
<br />
<br />Infiltration
<br />Precipitation SO"king 1nto the ground. ,'or "xa..ple," s..ndy soli
<br />may ab"orb A greut doal of ra1nfall without loaving an exc..sa for .ur-
<br />face runoff. This.....y b.. ",xpr""""d as lh", total proportion of rainfall
<br />ab~orb..d or as an infilttnt Ion rate In inchos per hour (see "RUnoff").
<br />
<br />R..curr..nce Interval
<br />(See "Ptobabllity")
<br />
<br />Reference Number
<br />A numbered point .olong,a atre.... channel'1dentifyi"8'-""speeH1c
<br />10eationfol"corr..laUogthedat..sho'o'I\invariouafor..."through'out a
<br />report.
<br />
<br />Monn1ng',,"n"
<br />- Am""sur" of the res1st""ee tof!owoffet"d byachnnnel or flood
<br />plain. A low v..lue I"dtcat~s loss r"..lstance to the ]><lasage of w"ter.
<br />Forexa",pl", clean,stralght,coucreteore"rthchannelamlghtha",,"n"
<br />v~\ues ~f 0.0\3 and 0,025, te~pcct1vely. A .hallow, ~c~dy channel
<br />might hav" an "0" vslu" in eJ("e~s of 0.100. Fllctor. other than
<br />roughness Influen,,-,,_ "nn \,,~lue.. S,,,,,,, other factors Include v~gctat lon.
<br />"h~nnd be<ld., ."<I1,,,,'nt, ~nd ~tnam slop...
<br />
<br />Runoff.
<br />The quantity of rainfall which flows over the surface to enter the
<br />stream as diecharge volume. Th" dlfference 1n quan~lty between
<br />rslnfall and runoff represents 10"~"H to lnflltratlou, detent lOll
<br />storage, ~nd evapo-tran.ptratto.....
<br />
<br />StreamCag"
<br />A dev1ce to lndi<:~(e the w"ter depth of a .'ream lit a g~ge ~Ile.
<br />the discharge at thl~ lO<l..tlon ,,,an be Jet.,r;olned by uaing tbe :itagc at"
<br />
<br />,--
<br />. -
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