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<br />b. The tenn "design flood" or "reservoir des18D flood" ~ <br />be applied to the most severe flood that a particular reservoir may be <br />capable of controlling under an adopted plan ot operation but such usage <br />ba8 little value except vllere the reservoir 1& provided pr1JDar1ly for <br />protection ot damage centers near the dam. Usually selection of the flood <br />control allocation in a reservoir is governed by consideration of flood <br />control e~ects at several locations dovostream, involving the analysis <br />of a number ot flood situations. Aecord1:llgly, application ot the te:nn <br />"design flood" or "reservoir des18D flood" should be l1m1ted to those <br />cases in vllich the te:nn is actually indicative ot the basis tor a flood <br />control storage allocation, more detaUed criteria beiDg specitied tor <br />other cases. <br /> <br />. <br /> <br />1-08. RELATION OF SPF TO DESIGN FUlOD <br /> <br />a. In the design of flood control projects it would ot course <br />be desirable to provide protection against the maximum probable flood, if <br />this were feasible within acceptable l.1m1ts 01' cost. However, it is seld.olll <br />practicable to provide absolute flood protection by means 01' local protec- <br />tion projects or reservoirs: - usually the costs are too high, and in many <br />cases the acquisition of adequate rights-01'-way tor the purpose would <br />involve un~asonably dest~ction or modi1'ications 01' properties along the <br />1'loodway. As a rule, some risk must be accepted in the selection of des18D <br />flood discharges. A decision as to how lIIUch risk should be accepted in <br />each case is of utmost importance and should be based on caret'ul consider- <br />ation of flood characteristics and potentialities in the basin, the class <br />01' area to be protected, and economic l1m1tations. <br /> <br />. <br /> <br />b. The "design flood" for a particular project JIlAY be either <br />greater or less than the st811dard project flood, dependiJIg to an 1mportant <br />extent upon economic factors and other practical considerations govem1Jl& <br />the selection of design capacity in a specitic case. However, selections <br />should not be gove1"lled by estimates 01' average annual benetits ot a tlll:lgible <br />nature alone, nor should const~ction di~iculties that JIlAY prove trouble- <br />some but not insurmountable be allowed to dictate the des18D flood selection, <br />particularly where protection 01' high class urban or agricultural areas <br />is involved. Intangible benefits, resultiDg 1'rom provision ot a high degree <br />of security against floods 01' a disastrous magnitude, including the pro- <br />tection 01' human lite, mu~t be considered in addition to tlll:lgible bene tits <br />that may be estimated in monetary tenDS. <br /> <br />c. The Standard Project nood is intended as a practicable <br />expression of the degree of protection that should be sought as a general <br />rule in the design 01' tlood control vorka tor c_it1e. where protect1on <br />01' hUlll&A lite Uld unu.U&lly h1gh-valued property 18 1Dwlwd. IDaaIllUCIl.. <br />SPF estilllates are to be based on generalhed studies 01' meteoro.logic and <br />hydrologic conditions in a region, the SPF e.timate. provides a basis tor <br />comparing the degree 01' protection provided b:y flood control projects in <br />difterent localities, thus promotiDg a lION cond.tent pollcy with respect <br />to selection of design 1'100d giving a cCllllP&1"&ble degree 01' protection tor <br />similAr c1.aases 01' property. <br /> <br />6 <br /> <br />e <br />