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I I . , , " I I I I I Head Lose. The effect of obstruction~, such ~g narro~ bripge openings or buildings that limit the area through which water ~uot flow, r~ising ths surf~ee of the water wp~tr8~rn from the ~bstruction. !ntcrm~diate Recional flood. ~ flood having an average frequency of occurrence in ths order of once in 100 years although the flood ~ay occur in any year. It is based on statistical analyaes of stree~flow :ecords available for the watarahod and analyse" of rainfall and r~n"ff characteristics in the "general region of the watsI:shed." CLOSSARYOf TERM5 flood. An overflow of laoda, not normally covered ty w~ter, tMat e~e used Or w5able by man, Floods h~ve tWQ ecsential character- istics: the inundation of land is te~po~ary; and the land is ~dja~ent to and inundated by overflo~ from a river or strea~, or an o~ean, lake, or other body of standing ~ater. Normally, a ~flood" is ~onsidered es any te'nporery rise in streamflo~ or stage, bwt not the ponding of surf~C6 water, that results in sigoificant adverse effects in tha vicinity. Adverso effects may inolude d~ages from overflow of lend area~, temporary backwater effacts in sewers and local drainage channels, croatian of unsanit~ry condition~ or other unfavor~bl~ situations by deposition of materials in etre~ channels d~ring flood reces- sions, rise of gro~nd watet coincident with increased "treamflo~, and other problems. Flood Cra~t. The wa~imum stage or elevation reached by tha woters of a flood at a given location. flood Plain. The relatively flat are~ or lo~ land5 adjoining the channel of a river, stream or watercourse. or ocean, lake, or other body of ~tanding water. ~hich hoo be~n or may b~ covered by fl<lod~.ater. Flood Profile. A graph showing the relationShip of water ourface elevation to location, the l~tter generally expressed a~ di~tance ~bove mouth far a etraa~ of watar flowing in ~n open cMann~l. !t is generally drawn to show eurfaco clavation for tho cr~rrt of a specific flood, but may bsprepe.red for conditions et a given time or staga. flood 5to~~. T~~ st~gn or elnvation et ahich ovo~flo~ of the n8tLIral banks of a strea'" or body of water begins in th~ rea~h or erS8 in which the slev~tion is ~e3surad. I I ( L9ft or Rioht Bank, TMe bank On the left or right side of a river, strea~, or watercourse, looking downstroom. Standard Proiect flood. The fl<lod that may be expected from the most severe combination of meteorological and hydrologioal con_ ditions that is considered reasonably charactoristic of the geo_ graphical area in whi~h the drainage basin is loosted. exclLIding extremely rore co~bination". Peak discMarges for thsse floods ore generally abo~t 4:% to 50% of the probabl~ ~oximurn floods for the se~e basing. Such floods, as used by the Corps of [nginBers, orG intended as practicsble expressions of the degree of protection that ohould te sought in the design of flood control works, the failure of which might ba disestrous. Under clearance. The lo~e6t point of s bridge or other str~cture over or scross s river, stream, or ~atercourse that limits the opening through which ..at~r flows. This is referred to "s "lo~ steel" in some r~gions. ;0 ~1 ,