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<br />I <br />I <br />. <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />4. Property line swales <br /> <br />5. Parks <br /> <br />6. Road embankments <br /> <br />An example of detention pond calculations is shown graphically <br /> <br />in Chart No. III of this report. This figure shows the cumu- <br /> <br />lative runoff in both five year and ten year frequencies, along <br /> <br />with the outflow from the outlet structure. Quantities are <br /> <br />thousands of cubic feet versus time in minutes. Table No. V <br /> <br />provides the detention storage data for the City of Yuma, listing <br /> <br />each one of the storage ponds along with the outlet structure <br /> <br />sizes and existing storage calculations. <br /> <br />B. DITCH DESIGN <br /> <br />The open ditches as discussed in the improvement section and <br /> <br />shown in Exhibit No. II of this report were designed based on <br /> <br />a Mannings "N" value of .03. Variations can be provided in <br /> <br />many instances. For example on the airport, the ditches should <br /> <br />possibly have a 10:1 slope providing no general sharp drop <br /> <br />for an aircraft which might miss the runway. In minor green belts, <br /> <br />the ditches can be designed and shaped to conform to any adja- <br /> <br />cent area for esthetic qualities. Proposed ditch data is shown <br /> <br />in Table IV on the following page. <br /> <br />41 <br />