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<br />POTENTIAL FLOODS <br /> <br />This sactlon discusses the Intermediate Regional and <br />StilndilrdProjectFloodsand thelreffocts. The I nternwd iate Regional <br />Flood represents a flood with an average fre~uency of occurrence of <br />lIbOl.Jtonce In 100 years t1nd Is Incraasinglybeingtlcceptedbyth\l <br />public asa minimum limit for application of local regulations. The <br />Standard ProJect Flood isof gre<lterlMgnltudeand represents a <br />reasonable upper Ilmltof expocted floodIng. However, It Is not the <br />largest flood that could occur. It Is emphasized here that floods, <br />whiCh aro smaller than the Intermediate Regional Flood would be more <br />frequent. Although these lesser floods would Inundato small\lr areas <br />thoy would also cause damaRe, hardship and Inconveniences. <br /> <br />Standard Project Fiood proportions. Damages and routlngs for the <br />StandardProjectFloodarealsolntabies7andil,respectively. <br /> <br />Intermediate Regional Flood <br />Since discharge m\lasurOO\lnts are not available speclfi- <br />cally for the streams studied In this report, thefrequeocy-dlscharge <br />ralatlonshlps were developad from II correlation of data for sImilar <br />streams where records aro avaIlable. Table 7 - p~ge 30 - shews the <br />I ntermed iato Reglon~ I Flood d Iscn~rges at specific locations a long <br />aden str~dm. The di~eharges betwoen tho designated points yary In <br />proportion to distance between points. The water storage reservoirs <br />on R~lston Cr~Ak, Leyden Creek and Lena Gulch have a retarding effect <br /> <br /> <br />Damage to Independence Street crossing over <br />Lena Gulcn due to minor flooding in May 1969. <br /> <br />Standard Project Flood <br />TheStandardProjectFloo<.llspresented In this report <br />i'lS the practici'll upper IlmitoffIOOdi"'l' Stormsthatwouldpro<.luce <br />thIs flood are uncorrrnon, and itisdifticulttoasslgnfrcquoncles <br />of occurrence with any reasonable degree of accuracy. As already <br />e~plalned, portions of the June 1965 fiood at Castle ROCk wore of <br /> <br />Greater Floods <br />Floods eyen larger than the Standard Project Flood <br />arc possl~le, but the combination of factors to pro<.luce such floods <br />Io'outdbeextremalyrara. Suchfloodsarenotfurtherdlscussad In <br />this report, although they should not be overlOOked where a~SQluto <br />safety from flooding is a requirement. <br /> <br />0' '" flood flows passing through ,"0 dalPls. no floodS considered <br />'" '", repor_twere routed through each reservoir. Results of '" <br />routlngs are prosented '" table 8 -page3i. <br /> <br />" <br /> <br />29 <br />