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I GLOSSARY OF TERMS flOOd Flood Staqe The st~ge or elevation at which overflow of the natural banks 01 a stream or bOdy of wator begins In the reach or aroa In whICh the elevation is measured. An overflow On lands not normally covered by water and that are used or usable by rTIIIn, Ffoodsn"vetwoessentialchar. ac-terlstlcs: The inundation of !llnd is temporary; and the IMd Is adjacent to and inundated by overflow from a river or stream 0.. "n OC9"'''', lake,orotherbodyofstandlngwilItcr, Nonnallya flOOd Is conslderOd "5 any temporary rise in stream flow or stage, but not the pondlng of surface water, that results In significant adverse effects In the vicinity. Adverse effects may include damages from overflow of land areas, temporary baCkwater effects In sewers ~nd 10c~1 dr~lnage ch~nnels. creation of unsanitary conditions or other unfavorable situations by deposi- tion of m~terlaJs in stre~m channelS durlng flOOd recessions, rise of ground water coincident with Increased stream flow, and other problems. Head loss The effect of obstructions, such as narrow bridge open- Ings or buildings that limit the area through which water must ftow, ralSlng the surface of the water upstream from tho obstruc- tion. Left Bank Tho bank on the left sldo of a river, stream, Or water course. looking downstream. flOOd Crest The maximum stage or elevation reaches by the waters of a flood '3t a given Incatlon, , , " I RlqhtEklnk Tho bank on tho right side of a river, ~troam, or water course looklng downstream, FlOOdPlain la-Year, 50-Year, loa-Year, 500-YeilrFlood A flood havln9 II 10,1, l,and.2percelltprobebllitv. respectively, of occurrence in any year or en average frequency Of occurrence 111 the order of once In 10, 50, IOO,andSOO-years, respectively_ The flood may occur In ~ny YOlar. It ls besed on statistical analysis of streamflow records end analysl~ of raln- f'3ll and runoff characterIstIcs Inthtlgonorlll reglono/the watershed. Tho reletivOly /Iat area Or low lands adjoining the channel or a rlver, stream, ..ater course or ocean, lake or other body of standing water, which has been or may be covered by f loodw~ter. Flood Profile A graph showinn the rel~tlonsh;p of water surface ele- vetiOllto locatlon. tho latter generally expn.ss..d..s distllnce above mouth fora streltmof water flo'oling In an open channel, It is generally dr~wn to ShOw Surface clovatlon for the crest 0/ a specific flood, but ~ay be prepared for conditions at ~ given tlmoorstaqe. " 19 I ,