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<br />e <br /> <br />e <br /> <br />I <br />e <br /> <br />n. GE!mlALIZZIl SPS ZS~ FOR SMALL IlIlAl1UDB llASDE <br /> <br />2 -0 1. (l nIERA1. <br /> <br />a. The crit.eria prellented 1n th1e lIectiou apply epec1r1ca.ll7 <br />to dr8.1nage areu east ot 1050 longitude aAd pn-rlly to bu1lla le... <br />thaA appro:dJDately 1000 IIquare 1Il11ee 1n area. The raiu.tall criteria are <br />b....1ned pr1Jll&r11y on lm&.1.Y'II1II ot _Jor IItorme ot record that have <br />occurred 1n the IIprillg, II.-r aDd tall lIeuoulI, dur1Jlg Which COJlwcti ft <br />activity ill pl'Olldnent. The criteria.-e not geueral.ly applicable to 11_ <br />se....onll without llpecial a4,julrtments. Ina8lllUch.... reco~ 1JId1cate that <br />the moet lIevere (but uot necellllarily the lllOst trequent) fioo.s. 1n draiAag. <br />e.re.... ot lUll thaA a tev thoullaDd IIquare llilell, witlnn the area coftred <br />by the genera.l1zed charta, ullUAl.ly resu.1.t traa iDteuee ra1Jltall during the <br />non-llnov eeason, the criteria preeented hereiD&f'ter are considered applic- <br />able 1n the cCIIIpUtation ot SPF est1JDatell tor IDOllt baa1lla. Where thia <br />conclusion is not considered applicable by the reporting lIIIg1neer, .s.wlOll- <br />ment ot the SPS ellt1JDate ahau.ld be baaed on a apecial atudy ot tl.ood <br />producing tactora aN'ecting the particular b..iD. It 111 aAticipated that <br />such exceptiona will appl,y only Were runoff trom _ IIllIlt, vith or with- <br />out coincident rainfall, ia a major tact or in the production ot UDIIa11&l <br />tloods. <br /> <br />b. Various approa.ches to the IItaDdArdbatiou ot methods lUld <br />crite::1.a related to the car>p\.ltation ot SPS and SPI' eet1JDatea have been <br />studied during the pa8t tvo JI1'ars. :Because ot the var1abil1ty ot hcton <br />involved, l1m1tations in basic data, and th nature ot the problem, <br />certain arbitrary assumptions aDd s1mplit1catioall ot criteria have beea <br />necessary to c,bta1n results suitable tor practical uae. Although IUly <br />standardization at criteria must involve certa1n approX1lllati0U8, it h&II <br />beeu concluded that adoption at generalized rail:ll'al.l criteria subllt&lltiaJ.1Jr <br />as presented herein ie advisable tor the purpolle ot 1UI11ur1J1g c0U8iateDc;r <br />betwen SPF ellt1JDates prepared by var10us office., .. vell 1UI to ......4..,,&. <br />vork required in the preparat1.ou ot est~tell. <br /> <br />c. The development ot geuer&.1.i&ed SPS ra1Jltall criteria tor <br />drainage areu lellll than approxiJDatel;r 1000 IIquare 1II11es, l.oeated eut ot <br />1050 longitude, 1a revealed geuerally by the explaDatiou ot plate. iD <br />the tollov1ng p&railraph. <br /> <br />2-02. EX?I.ANATION OF PIMl'S <br /> <br />a. Plate 1. Gener&.1.ized Eat1JDatell, !ofaYi"",," Possible h'eci- <br />;: itation. ~e illohJl1'ta on thill chart reprellent tb; lllI',.it..,," probable <br />24-hour rtUlU'all over 200 aquare llilell area, U ellt1lll&ted. by the 1I7dro- <br />meteorological Section ot the U. S. Weather Bureau ad. explA1Ded 1n ID6 <br />R~rt No. 23. <br /> <br />, ~ <br />, <br />