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<br />"
<br />
<br />profile is geocrslly drawn to ~how surface elevation ror the crest of a
<br />specHic flood but may "Iso "" prep.~red for conditio"" at a ~ivcn time
<br />O["t"II'"
<br />
<br />Orthophora Mapping
<br />Mapping which superimposes a contour map on an acrial photograph
<br />of the s,,"'"",ca1e.
<br />
<br />Flood Reconstitution
<br />--Inhydrologi"studles, thhhanstt""'ptt<> reproduce a hhtork
<br />flood's discharges uslnll a hydrologic model and known historic rainfall
<br />and ",..rershed data. In hydrsnHc "tudies, this is a" attempt to
<br />recreate a past flood's water levols using recorded discharges.
<br />
<br />Peak Dhcharlle
<br />The ma~illlum instantaneous discharge of a flood at a gtven loca-
<br />tion. It uaually OCcuts at or ne"r the tilllCof the flood crcH. In
<br />the graphical representation of flow versos time, which is known a.a a
<br />flood hydrograph, the peak discharge occurs between tbe aacenaton Itmb
<br />lI.nd the receasionlimb.
<br />
<br />Frequency
<br />(Sec"probability")
<br />
<br />Future Conditions
<br />In this report, thts refer~ to the potential future extent of
<br />urban dcvclop~nt In the Sheep Draw basIn. Also undcr this condition,
<br />theirdgll.tion c1l.o"lsand the smatl irrigatlon dams were assumed to be
<br />removed. The rO>ldways were assu..ed to remai.. in place.
<br />
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<br />I
<br />
<br />Photogralllllletric
<br />Making topographic ~aaurement. by the use of aerial photographs.
<br />
<br />Hydrologic Analysts
<br />Thtsufers to thedctcTllIinatl",' ofdiacharge-prnbability
<br />relat!olllihips at various locations.
<br />
<br />Probability
<br />The annu"l chance of occurrence of specific hydrologic events,
<br />such as rainfall, over a specified area or peak discharge at a
<br />spectfied location expreased tn percent, e.g.. 5 percent representing I
<br />chance in 20 of the event occurring in any year. The 10-, 50-, 100-.
<br />and SOO-year floods are floods having a 10-, 2-, 1-, or .2-pereent
<br />probability. respectively, of occurrence tn any year or an average
<br />recurrence interval in the order of once tn 10, 50, 100, or 500 years,
<br />respeetively. It may be ba$ed on $tatistteal analyses of $treamflow
<br />reeorda and/or analyaes of rainfall and runoff characteristics 1n the
<br />lleneral region of the watershed.
<br />
<br />~ydra~lic Analysis
<br />This refers to the determlnation of sere.... water surface er.'va-
<br />tions using diacharges of specified ~robubilities, crnss sections,
<br />channel and nverbank roughness, and th~ &:Jmetry of obstruct tons.
<br />
<br />IlIperviousness
<br />The degr~e to which "n area will shed water ~nd not sllow fainfall
<br />to penetrate. For e~..ple. paved areas are essentially impervious,
<br />"bile aandyar.,,,s are very pervlou..
<br />
<br />Rainfall Distribution
<br />To more realtstically define rainfatl and est1mate runoff, rhe
<br />total rainfall from an aaBumed storm of a certain duration may be
<br />aubdivided into raIn fatling in shorter time increments. The rainfall
<br />""'y not be the aame ina11 time increments.
<br />
<br />Illflltration
<br />Precipitation .oaking into the ground. For example, a sandy 11.011
<br />~'y abaorb a great deal of raInfall without leaving an exceas for BUr-
<br />face runoff. Thia may be c~pressed as the total proportion of rainfall
<br />absorbed or as an infUtrat!on rate in inches per bour (see "ll.un"ff~).
<br />
<br />Recurrence Interval
<br />(See "Probability")
<br />
<br />Reference Number
<br />A numbered point along a atream channel identifying a apecttic
<br />location for correlating tbe data shown in variOl'" forma throughout 11.
<br />report.
<br />
<br />ManninR's"n"
<br />A messure of the resIstance to flow offered by a channet or flood
<br />plain. A low value indicatcs leas resistance to the passaRe of "ater.
<br />Por"""..ple, cle<ln, straIght, c,,ocreteor e<lrth channels might hav co"n"
<br />vnln"," of 0.013 and 0.025, resfl<'ctive1y. Aah"llo", ""'"dychann"l
<br />OIlgbt have an "n" value 1n e~c"ss of 0.100. Pactors other than
<br />roughness influence "n" values. S01:le otber hctors include vegetation,
<br />chaOll..1 he'lda, ,,(!diment, Hndatrealls1op".
<br />
<br />Runoff.
<br />The Quantity of rainfall which flows over the surface to enter the
<br />stream as discharge volu~. The difference in quantity between
<br />rainfsll and runoff represents losses to infiltration, detention
<br />storage, and evapo-transpiration.
<br />
<br />Stream Gage
<br />A device to indi~ste the ~.ter depth of a stream at a gaR" site.
<br />The dlschsrge at this 10<;attonc3n be d..terrained by using the ata8" or
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