Laserfiche WebLink
<br />The lowest embankment crossing of the ephemeral drainageway <br />(near the east line of Section 20) has a maximum ponding depth of <br /> <br />approximately 20 feet. This embankment also has two unequal size pipe <br />culverts (one 28 inch diameter, the other 30 inch diameter). The <br />available topography for this area has been used to develop'the area- <br />capacity data for the detention ponding. The maximum detention storage <br />for this temporary pond is 825 acre-feet. <br />In summary, the detention storage provided by the railroad embankment <br />and the culvert pipe sizes reduces the storm runoff flows from the <br />ephemeral drainageway down to values of approximately 70 cfs and a ponding <br />i <br />depth of approximately 5 feet above the pipe invert for the 100 year <br /> <br />recurrence interval event. <br /> <br />It can be seen that the railroad embankment creates a major influence <br /> <br />on the storm, water discharges from this drainage basin and actually <br /> <br />provides flood peak flow protection for the northern portion of the Town <br /> <br />of Yuma that lies, adjacent to this drainageway. Under no reasonable <br /> <br />condition or storm will the flood discharges create a ponding situation <br /> <br />behind the embankment that would divert the water from the drainageway <br /> <br />into the center section of Town. <br /> <br />B. Urban Drainage Basin <br />Character <br /> <br />The basin tributary to the existing urbanized areas are relatively <br />small with the agricultural portions of the basin exhibiting depressions <br />and high infiltration capability similar to the major ephemeral drainageway. <br /> <br />-6- <br /> <br />.' <br />