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<br />5. Perform hydraulic computations to verify the adequacy of the <br />proposed improvements. <br /> <br />6. Prepare cost estimate of reemill"ended layoutsc <br /> <br />7. Incorporate changes ill the scoJle of- ilnprovements as sllgg{~sted <br /> <br /> <br />in the Distri.et's letter of December cO, 1976c <br /> <br />Ily_<?!~~l()J;), <br /> <br />The hydrology of First Creek bas,n is desc<ibed in detail in Chap- <br /> <br /> <br />ter III of Phase A report. Basically, the hydrologic studies described <br /> <br />in Phase B incorporate most of the inforrnation presented in Phase A. In <br /> <br /> <br />addilion, the impact of implementing t.he modified Plan A of the routed <br /> <br /> <br />flows is presented in this study. <br /> <br />Basin Characteristics <br /> <br />The drainage basin characteri~;1~ic5 for the First Creek basin <br /> <br /> <br />are given in ~rable II-I. The total basitl is divided into First Creek <br /> <br />prop'::'r designated !IF" and a major tributary designated "Tll. First. Creek <br /> <br /> <br />basi:l was furhter divided into smaller sllb.~-)asin'S. These sub-basins <br /> <br />were based on the drainage and outflow char.)cteristics of each area to <br /> <br /> <br />ensure that each sub-basin would behave as uniformly as possible during <br /> <br /> <br />a st1lrm, and to enable the routing and 1_~lgging c'omplltations to be as <br /> <br /> <br />accu,~ate as tile basic data will permit. <br /> <br />First Creek was divided into " l0~al of 34 sub-basinsc These <br /> <br />sub-llasins, sllown in Drawings No.3 and l, of Vol.ume II, are designated <br /> <br /> <br />F-I through Fn23, for the main stem, and T.-l t.hrough T-1I for the tribu- <br /> <br />tary areas. The areas, lengths, distancE: t(l cCfltroids, percentages of <br /> <br />perV:LOus and impervious areas, <br />and the infiltration rates are <br /> <br />uniL hydr'c'gJ"ilph c'oefficients C and C , <br />t P <br />shown for each sub-basin. The breakdown <br /> <br />of the basin into such small arf'3S was rH:'C('~:;sary to make a reasonable <br /> <br />estinate of the runoff at each drainage ~t:nlctllre and crit:lcal section. <br /> <br />[[.-2 <br />