Laserfiche WebLink
<br />e <br /> <br />e <br /> <br />I - <br />;e <br /> <br />(3) Maximum Probable (or "Muimum Possible)" Flood Estimates <br />representiJlg flood discharge that m:y be expected trca the IIIOst seY'tlre coa- <br />binat,ion of critic&1 meteorologic and hydrolo8ic ccmd1tiOl18 that are rea- <br />sonably possible in the region. <br /> <br />c. Statistic&1 Flood Studiee 01' aeveral types have proven uae- <br />tuJ. in eng1l1eering investigationa, the IIIOst preV&lent conahUng of nood- <br />frequency eatiJllatea. Flood-frequency dete%lll1Jlationa are used pr1mar:l.ly ae <br />a baeis for est1matiJlg the Ran lIIUlU&l benefits that IM1 be expected trca <br />the control or reduction of floodJl 01' relatively ClllllllDD OCcurreDce. <br /> <br />d. Standard Project Flood estiJllate .el"V'lt. the tollov1Jlg }lrima1'7 <br /> <br />purposea: <br /> <br />(1) llepresents a "standard" against which the degree 01' <br />protection finally selected tor a project may be judged and compared with <br />protection provided at s1m1lar projects in ather 10c&1itiea. The SPF <br />estimate must reflect a geDerali~ed analysis of flood potentialities in <br />a region, as contrasted to an analysia 01' flood recorda at the specific <br />locality that may be misleading because 01' the inadequacies 01' recorda <br />or abnormal sequences of hydrologic eventa dur1Ilg the period 01' stream <br />flow observation. <br /> <br />(2) Represent the flood discharge that should be selected <br />as the design flood for the project, or approached aa nearly as practicable <br />in consideration of economic or other gove1'D1Dg 11m1tatiOl18, where so. <br />IllIl&l.l degree of risk can be accepted but an UIlUSually high degree 01' pro- <br />tection is justified by ha~ards to lite and high property V&lues with1l1 <br />the area to be protected. Est1JDates completed to date indicate that SPF <br />flood discharges are generally equal to 40 to 60 pereent 01' -"1...... <br />probable" floods for the same basins. <br /> <br />e. Maximum Probable (or Max1mum Posaible) Flood estimatea are <br />applicable to projects where consideration 18 to be given to virtually <br />complete security against potenti&1 flood8. Applications 01' such est1JDate. <br />are usually confined'to thedete1'lll1nation 01' spillway requi_--=oLa tor <br />high dams, but in unusual casea may conatitute the deaign flood tor local <br />protection worka where an exceptionally high degree 01' protection i. <br />advisable and economically ob'tBinable. <br /> <br />1-07. DESIGN FLOOD <br /> <br />a. The term "design flood" rete1'll to the flood hydrograph <br />or pe~ discharge V&lue finally adopted as the basis for design of a <br />particular ;>roject or section thereof a1'ter t'ull consideration has been <br />b1ven to fl~od characteristics, frequenciea, and potentialities, and the <br />economic and other practical considerations entering into selection 01' <br />the design discharge criteria. The term "design flood" is synonymous <br />Vi th "project design flood", although use 01' the latter tem haa been <br />generally discontinued in order to avoid poadble coDfUsion with the te1'lll <br />"standard project flood". For convenience in reference, such terms as <br />"8,ii.:"""a:r 1es1gn flood" f "levee design flood", "chacnel design flood", etc., <br />are 'Jsed ".'here appropriate" <br /> <br />5 <br />