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<br />One is the abrupt drops in discharge, most notably at Hollywooo
<br />~rivc. These abrupt drops are due to either natural or manmade
<br />detention Or retention areas, Another characteristic is the
<br />abrupt increases in discharge. These are caused by concentra-
<br />tions of runoff froM local subbasins contributing at a given
<br />point. The final characteristic is the gradual decrease ~n
<br />discharge from approximately 'raft Hill Road to West Vine Drive.
<br />This gradual decrease is caused by the significant amounts of
<br />channel storage throughout this reach created by lack of defined
<br />channels and relatively flat slopes. Peak runoff rates for the
<br />various design storms for existing as well as future develop-
<br />ment are further delineated in Table 2, The outflow hydrographs
<br />for the drainage basin at the Colorado and Southern Railroad
<br />for all of the design storms for existing and future development
<br />exhibit double peaks, These double peaks for the 2 and 100
<br />year developed design storms arc illustratcd graphically as
<br />shown on Figure 4, The do~ble peaks are caused by the fact that
<br />a large amount of Channel storage, caused by lack of defined
<br />channels and ~Q~e ex~~t~ng detention and retention pccurs
<br />_throughout the qrainag~ basin. This delays the upstrea", flo'"
<br />causing the late second peak, Peak rates of runoff from local
<br />si.l.bbac:!.:-:::; ',~n.i;;;h cQntri)::;:.lte more or less dirOlcLiy to the c ~ ,5
<br />R,R. occur much closer to the beginning of the design storm causing
<br />the first peak, Channel storage combined with quick response
<br />time of local subbasins in the lower reaches created lower peaks
<br />at the Ilanna SUbdivision theITI at N. Frey Drive ,1S illustrated
<br />~n Table 2. This further illustrCltes the affects of channel
<br />5torClge and subsequ"nt pea.k a.ttenuation.
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<br />When <lrainage improvements, i,e. channels or storm sewers
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<br />th", un.in"'],, basin, any chann..lization significantly increase"
<br />downstream peak rates 0: runof~ for the various design storms for
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<br />2
<br />
<br />HYDROLOGIC
<br />
<br />SUMMARY
<br />
<br />-22-
<br />
<br />-23-
<br />
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