Laserfiche WebLink
<br />11 <br /> <br />Peak Discharge Profile <br /> <br />Table 4 presents a la-year peak discharge profile along the Ditch <br />under future development. Without mitigation. larger overflows would occur <br />at Nodes 1 and 2; existing channel capacity would be exceeded between <br />Nodes 3 and 5, resulting in more severe flooding in developments such as <br />the Whitcomb Addition.than currently exists. <br /> <br />Runoff Vol umes <br /> <br />Table 5 summarizes weighted runoff curve numbers and runoff volumes <br />at each node under assumed future development. <br /> <br />NEAR-TERM DRAINAGE IMPROVEMENTS <br /> <br />Near-term improvements to the Pioneer Drainage Ditch will require: (a) <br />increasing the discharge capacity of crossings in upstream areas to <br />prevent overflows and, (b) providing detention storage downstream in order <br />to reduce peak discharges to safe levels between North Division Avenue <br />and Highway 138. It should be noted that increasing the discharge capacity <br />of crossings upstream without providing detention storage downstream <br />would shorten the time of concentration and significantly increase flood <br />peaks. Likewise, providing detention storage without eliminating the <br />bottlenecks would not effectively mitigate local flooding from overflows. <br /> <br />DENTENTIoN STORAGE <br /> <br />Leaf and RCI (1983) recommended that detention storage be provided at <br />Node 4. The area is topographically suited for this type of land use. <br />Moreover. detention storage at this location would significantly reduce <br />flood peaks, Currently, a la-Year rainfall event results in a water surface <br />elevation of 3.924.5 feet (m.s.1.). some 1.5 feet above the elevation of <br />the intersection at Coolidge and Logan streets in the Whitcomb Addition <br />(see Leaf and RCI. 1983). <br />