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<br />SECTION IV <br /> <br />HYDRAULICS <br /> <br />The follm,.;ring Table IV-I Has prepared ~..:o il1ust:ra-~:e tbe r,lagni tuc.e of th.::: <br />IOO-year storm runoff rate in comparisoIl to the more frequent storm runoff <br />:cates at specific street crossings. The size and capacity of tbe existing <br />pipe under the street is provided. <br /> <br />Under high runoff rates the streets act as weirs as the runoff flows <br />over the streets unccntrolled. In most instances the culverts or cat~:h basins <br />\vould be plugged Hi tb debris '\vhich would increase this weir .f 1m.,;'. <br /> <br />TABLE IV-I <br /> <br />PEAK RUNOFF RATES AT DESIGN POINTS <br /> <br />Design Point <br /> <br />Storm <br />2-yr. <br /> <br />Frequency R~noEf <br />5-yr. 10-yr . <br /> <br />~.te (ds) <br />laO-yr. <br /> <br />Ex~~_ti'~~0ul.::::ert <br />Size Capacity(cfs) <br /> <br />Confluence with <br />Lena Gulch <br /> <br />89 <br /> <br />292 <br /> <br />619 <br /> <br />958 <br /> <br />}'1oss Street <br /> <br />81 <br /> <br />266 <br /> <br />561;. <br /> <br />873 48" CSP 90 <br />---------~~--_._~-----~---,------ <br /> <br />Nile Street <br /> <br />80 <br /> <br />263 <br /> <br />558 863 36" CSP 34 <br />_._._--------_.._----._-+~--------_._- ---..-----.-- <br /> <br />Orchard Street <br /> <br />76 <br /> <br />249 <br /> <br />5213 817 <br /> <br />43"x2711CSPA <br /> <br />43 <br /> <br />Pike Street <br /> <br />46 <br /> <br />149 <br /> <br />316 <br /> <br />__2..~_._.i:l"x2 7"CSP A <br />8>/0 <br />-3e-6- <br /> <br />39 <br />--~--------- <br /> <br />guaker Street <br /> <br />24 <br /> <br />42 <br /> <br />177 <br /> <br />36" CSP 25 <br />--~~-~---_.~---------- <br /> <br />A. FLOODING PROBLDIS CAUSED BY A 100-YEAR FLOOD <br /> <br />In studying the Flood Limi.ts Map in Figure III-3 there are several problems <br />~rhich are readily visible and are discussed as foLLow-s: <br /> <br />REACH 1: Lena Gulch to Moss Street <br /> <br />a. <br />acts <br />this <br /> <br />The chain link fence at the West <br />as a debris rack. As reflected <br />fence "ollld be washed out. <br /> <br />property line of Camp George West <br />in the flood limits bOllndary, <br /> <br />REACH 2: Hoss Street to Nile Street <br /> <br />a. There are two houses \Vhich are likely to receive some flooci damage. <br /> <br />b. The inadequa~y of the culvert uDder Nile Street causes the rlllloff <br />to sheet flm, over the street and "i.ll flood the house immedi.at,oly <br />belm" Nile Street. <br /> <br />c. The increasei. "idth of the flood l~nits is cacsed by the backwater <br />as a result of a~ inadequate culvert under the Jrive1;vay and the increased <br />roughness coeffi2ient caused by debris in the channel. <br /> <br />/5 <br />