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I I I I I I I I I I I I I I I I I I I l2 INFLOW Hydrologic Characteristics After Implementation of the Master 1500 14 Plan: A pipe system with the capacity to convey the lO-year flood is proposed for North Dry Gulch. This would effectively reduce the surface flow in a lOO-year flood / "- 1200 I \ l~ , l 1100 \ \ , \ 10 J \ 0 I z , 0 I{ \ tJ 900 UJ 1/ \ VI Cd 0: 800 00'" 0 UJ 0..... J \ Il. -I I- ~ V \ UJ 700 , UJ u. J '0 \ tJ J \ QI 600 ::I I \ tJ I z 500 \ ~ \ 0 .J 400 u. 300 200 so that no overflow into Colfax Gulch would occur. The pipe system will carry considerably more flow along the North Dry Gulch route than would be presently conveyed on the surface. It should be noted that Colfax Gulch, after the improvements, will not be exposed to flooding from North Dry Gulch in floods of lOQ-year magnitude and smaller. This, however, does not mean that Colfax Gulch is relieved from its own flood hazard, since it also conveys flow from its own sub-basin. This Section has illustrated that the flow rates after construc- tion of the recommended facilities may be greater, in some instances, than those which would presently occur. These in- creased flow rates have been considered in the design of the proposed facilities. Thus, the flood hazard which will remain after construction will not be greater than the hazard which presently exists. In the majority of cases, the proposed faci- 100 o o \020 lities will carry the ten-year flow underground, thereby reducing the flood hazard created by surface flows to considerably less 40 60 80 100 120 140 160 \80 200 TIME, MIN., FROM BEGINNING OF STORM than the present hazard. FIGURE m-4 INFLOW AND OUTFLOW HYDROGRAPHS AT PROPOSED DETENTION POND AFTER CONSTRUCTION OF RECOMMENDED FACILITIES