Laserfiche WebLink
<br />e <br /> <br />e <br /> <br />I <br />,e <br /> <br />-J <br /> <br />d. ~le: SPF Series. The 4eriTation of a "SPF S.ri.." for <br />the ll,700 sq. m. drainage of tile CuIIlberlaDd R1.,..r buin above Old K1ckor'J'I <br />Tell:ll., cover1llg a 4 , lIlOn1;h period tro. 23 Dee to 7 May h cnztlu..4 below: <br /> <br />(1) Flovs for a three-lIll)nth period anteae4ent to tbe SPF <br />flood \/ere uSUlDed &II equaJ. to d&il,. discbarges recorded during tbe period <br />from 23 Dec 1932 to 22 Mar 1933. The purpose of including tbe "antecedent" <br />!lovs vas to >>rovi4e .. concrete bads of 4ete1"lll1ll1l:lg the statua 1A ex1ltillC <br />and anticipated reservoirs 1A the basill corresponding to rur.otr conditionl <br />considered relUlonably likely to prevail prior to the SPF. lllmotr durizIi <br />tbe three-montb period eelected vas approximately 25 percent ..bove the <br />..verage observed f'or the IIlOntbs of Je:tJUAZ"f. February a:ad M&rcb OTer a 29- <br />year period ot record from 1919 to 1947. The novs by IIlOnthll vere aJ.so dis- <br />tributed fairly unif'orm.ly a:ad V1L1"1ations \/ere f..irly representative of flood <br />se'l.uence observed during tbe period of record, excluding a fev years of extra- <br />ordinary flood occurrences. Altbougb the general criteria adopted for sel- <br />ection of the "s.ntecedent" flov data are ill tbis case arbitrary and subject <br />to appreciable V1L1"1ations on the be.ais of personal ju~nt, tbe procedure <br />vas adopted e.a s.n expedient in viev of tbe necessity of teJd..ng into account <br />the effects of a:atecedent conditions on rout1l:lg of tbe SPF. It is apparen1; <br />that tbe criteria follo~d vill require V1L1"1atioDll in other c1rcumata:ac.s, <br />but it il believed that reasonable results may be obta1lled by exerc1ee of <br />Jud<Pent on the part of hydraulic engint!8rs responsible for sucb studies. <br /> <br />(2) Flovs for the 15-day period fro. 23 Mar to 7 Apr ~re <br />computed from rainfall-excess estimates derived fro. tbe selected l2O-hour <br />sta:adard project storm vhich vas based on a transposition of the 23-27 Mar <br />1913 storm (OR 1-15) as discussed in paragraph 3-02 b. <br /> <br />(3) Flovs for a 30-day period subsequent to the SPF were <br />assu:ned as e'l.ual to daily discharge recorded during the period from 8 Apr to <br />7 May 1933. Tne 30-day period of flovs "subsequent" to the SPF vas inclu4e4 <br />to permit a calculation of the time required to drav do"ll the reservoirs <br />if runoff should equal approximately tbe average observed for correspond1zlg <br />period ove:.- the period of record. In general, the derivation of a SPF <br />Series is re<;.uired only vben runoff before or at'ter the SPF is likely to <br />infiuence conclusions reached by rout1l:lg the SPF hydrograph thN Itorage. <br /> <br />3-03. USE OF SPS GE!lERALIZED DEPl'H-AREA CURVES IN SELECTION OF STOlMl <br />FOR COMPARISON. The genera.llzed curves and data sbo"ll on Plates 5 to 9, <br />may be used in the selection of stOl'lll8 tor detailed compa:r1.son in prepar1n& <br />SPS es-t1lDates for draiDage basills up to 20,000 square mIea, in lieu ot the <br />procedure outlined in sub-paragraph 3-02!l. In tbis lDllmIer the number of <br />atol'mB r8CJ.'U.r1ng detailed atudy to determine c:r1.tical 1'l.o04 produc1zlg capa- <br />bilities _y be reduced to a IIIl&ll INllIDer. The roo....inder of the procedure <br />.bouJ.d 'be suba'taDt1ally as cnztl.1ned in parlI6rapba 3-02 b to 3-02 d. <br /> <br />:7 <br />