Laserfiche WebLink
<br />-3- <br /> <br />- \ -..\ <br />" <br />'-, ": <br /> <br />local jurisdiction, Upstream from the "major" drainageway cutoff <br />point, the drainageways is considered to b(~ part of the local <br />drainage system and designed for a(:cordingly. The 100-year flows <br />are most often conveyed via a ~;torm sewer/street system. <br /> <br />C ~I <br />,," \ <br /> <br />:: ..... <br />- ! " I With a tributary area of 250 acres, tht~ peak nmoff rate would be <br />~~ "-<!- <br />>. ). 'f~ -i. approximately 500 cfs., Wil:h these flows and an existing ground <br />~,t r.,"^' "l slope of 5 to lO percent, the peak 100--year runoff can be conveyed <br />,/' "1') in a 60-inch RCP, maximum, Thus, a storm sewer/street system <br />.", ~ . ~'1 would convey the flows and be considered plllt of the local drain-.._ <br />(<:'-' t age system. )':.' <br />.j <br /> <br />;.. '. <br /> <br />3. Appendix B contains photographs of typical channel sections for <br />these drainageways. ][n many instances, there is no defined chan- _~__, V <br />...------ net The drainageway!; identified by the FIRMs often simply convey " <br />irrigation water during the summer season. <br /> <br />4, These drainageways have been integrated into the BMP Master Plan <br />for the storm runoff. Pertinent portions of the Master Plan are <br />given in Appendix C, <br /> <br />Modification of 100-year Floodplain <br />The drainageways to remain on the FIRMs are shown on Figure 6 with the mod- <br />ified naming nomenclature. A LOMR is also requested for these drainageways <br />within the BMP PUD boundaries for the delineation of the lOO-year flood- <br />plain. <br /> <br />The I DO-year floodplain for drainageways to remain on the FIRMs given on <br />Figure 7 were determined using normal depth calculations with a typical <br />channel cross section for each channd segment, and the peak runoff rates <br />calculated with HEC-l. The hydraulic calculations are contained in Appen- <br />dix D, Using the SOD-foot scale, 5-foot contour interval mapping, the <br />approximate lOO-year floodplains are delineated on Drawing ], <br /> <br />C. .: <br /><.:1 !\ <br />0' <br />J.:.. ''::''',''(''''.''/ <br /> <br />~ --' <br />