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<br />.. <br /> <br />.- <br /> <br />. <br /> <br />Six Streams Group I Hydrology, Second Creek & Third Creek <br />April 1, 1975 <br />Page 2 <br /> <br />Table 1, Sub-Basin Data, provides the basin areas for each <br />of the sub-basins, designated in the Second and Third Creek <br />Basins. Table 3, Design Point Flows, provides the accumulated <br />area at each design point. The area at each design point re- <br />flects the total basin area above the design point as no flow <br />was considered to be intercepted by any upstream irrigation <br />ditches. <br /> <br />SECTION B - BASIN PARAMETERS <br /> <br />Each sub-basin was physically described in terms of the tribu- <br />tary area, basin length, length to basin centroid, degree of <br />perviousness throughout the basin and the selection of other <br />representative coefficients typical to the basin. This infor- <br />mation was determined for each sub-basin and shown on Table 1, <br />Sub-Basin Data. The projected development factors were estimated <br />from Adams County and Brighton Master Planning Maps. Table 4, <br />Land Use and Percent Pervious, shows the land uses within each <br />sUb-basin, the size of the use within the sub-basin and the <br />overall basin perviousness. <br /> <br />The coefficients used in the computation of the unit hydrograph, <br />Ct and Cp, have been determined from information published in <br />the Urban Storm Drainage Criteria Manual. Our analysis of these <br />coefficients for each of the sub-basins under developed condi- <br />tions gave an average value of Ct of .36 and an average value <br />of Cp of .51 for the total Second Creek Basin. For the Third <br />Creek Basin, the average Ct was .38 and average Cp was .51. <br />These compared to an average existing Ct of .40 and Cp of .54 <br />computed for the basin for the project REUSE study, and reflect <br />a projected basin development rather than the existing conditions <br />considered in project REUSE. <br /> <br />SECTION C - DESIGN RAINFALL <br /> <br />The Second and Third Creek basins are located in Townships 1, <br />2 and 3 South and Ranges 65 and 66 West of the 6th Principal <br />Meridian. The Design Rainfall was taken from the Rainfall/ <br />Runoff Information Report published under Project REUSE for <br />the respective townships and ranges. The 100-year rainfall <br />depths are given in Table 2. <br /> <br />_1 <br /> <br />For this study, the 100-year event was assumed to occur over <br />the entire basin concurrently. A 2-hour duration was selected <br />'as a critical storm duration. More critical storm conditions <br />--COU~d occur in this and other areas which could lead to much <br />