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CLoSSERY or TERMS '. flood. An overflow of lends, not normally oovered by water, that are used or usable by man. floods have two assential character- istics: tha inundation of lend ia tempor..ry; end thll land ie ad- jecent to end inundated by overflow from a river or stream, or en ocean, leke, or other body of et..nding water. Normally, a "flood" is considered as ..nrternporary rise in streamflow or etege, but not the ponding of surface water, that results in eignificant adverse effecte in the vicinity. Ad_ VerSe effects mey inclu~e damages from overflow of land araae, temporary backw..ter effects in sewers end local drainage channele, creation of unsanitary conditions or other unfavorable situations, by deposition of materiels in stream chennels during flood recee_ sions, rise of ground water COincident with increased streamflow, and other problems. flood Crest. The maximum stage or elevation reached by ths wa- ters of a flood at a given location. flood Peek. The maximum instantaneous discharge of a flood at e given location. It usually occurs at or nSer the time of the flooocrest. flood Plain. The relatively flat area Or lowlands adjoining the channel of a river, strsam or watercourse, Dr ocean, lake, or other body_of standing weter, which has been or may be covered by floodwater. rlood Profila. A graph showing the relationship of water eurfaoe elevation to location, tha latter generally expressed as distenca abovsmo"uthforastreamofwatGrf1owinginanopenchennal. It is generally drawn to show surf~co elevation for the crest of a speoific flood, but may be prepared for conditions at a given Ume or stege. flood Steee. The stage or elevation at which overflow of the natural banks of e streem or body of water begins in the reach or area in which the elevation i" ",~asurlld. . . . " Head Loss. The effect of obstructions, euch as nerrow bridge open- inge Or buildings thet limit the area through which water must flow, reising the aurface of the water upstream from the obetruction., Intermediate Reoional flood. A flood having en everags frequenoy of occurrence in the order of once in 100 yeare although the flood mey occur in eny yeer. It is besed on statietioal analyees of streamflow records aveilable for the watershed and analyses of rain- fall and runoff charaoteristice in the Mgeneral ragion of the water_ ehsd.M Left or Richt Bank. The bank on the left or right aida of a river, stream, or watercourse, looking downatream. Low Steel.. The lowest point of a bridge or other etructure oVer or aCrOSS a river, stream, or w~tercourBe that limite the opening through which W8ter flews. Ste~~d Project flood. The flood that may be expected from the most severe combination of meteorological end hydrologicel con_ ditions that is oonsidered re~sonably characteri~tic of the geo- graphical area in which the drainage bsain is loceted, exoluding extremely rara combinations. Peak discharges for these floods ere generally about 40% to 6~ of the probable maXimum floods for the sama basins. Such floods, as ussd by the Corps of Enginears, are intended as practicable expressions of the degree of protection that should be sought in the design of flood oontrol works, the feilure of which might be dieastrous.' "