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I ~ GLOSSARY OF TE~ Flood Staqe The stage o~ elevation at which overflow of the natural banks of a stream or body of water begins In the reach or area in which the elevation is measured. Flood An overflow an lands not normally cavered bYI</ater lInd thllt are used or usable by man. Floods have ho essential characterIstics: The inundation of land is temporary; and the Idnd is adjacent to and Inundated by overt I ow from II river or stream or an ocean, lake, or other body of standing water. Normally II flood is consldered as any temporary rise In streamflow or stage, but not the pondlng of surface water, that results in significant adverse effects In the vicinity. Adverse eftectsmaylncludBdamagesfromoverflowof land <Ireas. temporary backwater effects in sewers and local draInage channels, creatIon ot unsanitary conditions or other unfavorable situations by deposItIon of materIals in stream channels during flood recessions, rIse of ground water colncldent with Increased streamflow, and other problems. Head loss The effect of obstructions, such as narrow bridge open- Ingsor buildings that limIt the area through....hlch water must flow, raising the surtace of the ....ater upstream from the obstruc- tion. leHBank The bank on the left side of a river, strearn, or water- course,looklngdo....nstream. Flood Crest The ~~imum stage or elevation reached by the waters of a tloodataglven location. Rloht Bllnk The bank on the right side of a rIver, stream, or water- course, looking downstream. Flood Plain IO-Year, 50-Year, IOO-Year. 500-Yellr Flood A II<Vld h~vlng a 10, 2, I, an<:! .2 percent probabilIty, respectively, of occurrence In any year or an average frequancy of occurrence In tha order of once In IO,50,IOO,and500yellrs, respectively. The flOQdmay occur In any year. It Is based On statistical analysis of streamflow records and IInalysls of raln- fall and runoffcharacterlst1cs In the general region of the \o"atershed. Tho relatIvely flat area or lo\o"lands adjoInIng the channel of a river, stream, watercourse or ocean, lake, or otner body of standing water, whlcM Mas been or may be covered by floodwater. Flood Proli Ie A graph showIng the relationshIp of ~ater surface elevation to location, the latter generally expressod as distance ahove mouth tor a stream of water flowIng In an open channel. It Is generally drawn to show surface elevatlnn fnr the ~rest 01 a specific flood, but may be prepared for oonditlons at a given time or stage. " 19 ,