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<br />StOl~m Hydrograph <br /> <br />storm hydro graphs for each slJbal:ea '"Iere developed from ,:o.e <br />effective rainfall and unit l1ydrograph according to the manua,l. <br />A rainfall duration of three hours 'Na,S used because 1:he incre- <br />menl:al rainfalls beyond three hours. axe relatively smaL. and <br />may be neglected. Since the drainaqe boundaries of most of the <br />subareas were redefined, the storm hydro1'raph for each subarea <br />had to be recalculated. For mOBt of ':he' subareas which were <br />divided from an original suba.rea in the Pha.se A study, l:he <br />storm hydrographs '....ere obtai!'led by uS:.ner straight arE!a proportion. <br /> <br />Drainage An~a No. 5 was divided into l:h:i:'1~e subareas (Nos. 5A, '3B, <br />and SC) because th,~ flood flow from these three subareaE; drain:; <br />into three different drainaqc areas.. Hydrographs for D.A. Nos. <br />SA, SB, and SC were de1:ermil:,cd by s.t: ~aic,'ht area proportion. <br /> <br />D.A. No.6 "as subdivided int:o fo"~r ;3ubilJ:eas (Nos. 6A, 6B, 6C, <br />and 6D). Storm hydrographs of D.}\' l'Ios. 61\ and 6B w'~re reestab- <br />lished through the procedUre'; of UI:\1.I: hydrograph, effective rain- <br />fall and storm hydrographs for the t~.., 10-, lOO..year storm events <br />and 'the SPF as weLL as the p]vlF'. The carame ters used .to establish <br />the storm hydrographs for 0..1\,. Nos. Ii:", and 6B were listed in <br />'rabl,~ 2. <br /> <br />st.Or:n hydrog-raphs for D.A. Nos. 6C, :';IJ, and B were established by <br />combining these three subareaS int:o one drainage area, 8A" The <br />drai:1a'1e basin parameters were lLs.ted in Table 2. St:orm }lydro- <br />graphs of D.A. No. 8A for 1:he 2-, 10"", lOO-year st.orm events and <br />the :31'1" were established through 1::h€! same procedUJees as described <br />in the last paragra.ph. Storm hydroqraphoJ for D .A. Nos. 6C, 6D, <br />and :3 were then det,ermined by st::cai'lU: area proportion. <br /> <br />Flood Routing, <br /> <br />FlOOd routing was performed bY using P'w BEC-l computer program <br />with modified PuIs method to deb,rmi:ne t:he flood runoff and storage <br />volumes required for the proposed improvements. 'L'he st01-'age-sta'le- <br />outflow relations were estab:tished for the existing and proposed <br />detention ponds before flood rou'::ing was started. The si:orage- <br />stage-outflol" relations for detention ponds were t.hen modified to <br />accommodate the design requirement s. Peak runoffs at vaJ:ious <br />locat:ions we:re det,ermined from the final flood rou.tinq results. <br />Five frequenoies (2-, 10-, 100-year SPF and PI.iP) were' rotl.ted <br />from Pond D 1:0 Kelly Pond to provide the hydrologic data required <br />for the Corps of En':rineers too de~d'ln flood control facilities <br />wi thin Lowry Air Force Base. There w'=re only two frequencies <br />(lO-year and lOO-year) routE,d between Kelly Road Heservoir and <br />Sand Creek t:o determine the desiqn di.3chaxges and the stage re- <br />duction of the lOO-year flood after improvements. Improvements <br />to channels for the lO.'year flood were recomm'~nded by 'the Corps <br />of Engineers after the cost-benefit analysis was conducted. The <br />recommendation of lO-year charmel .i.mVcovements will be discussed <br />.in a later section. <br /> <br />-12.- <br />