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. . . . I . I . . I I I I I I I I . I year flood causing a higher stage and a wider flood plain upstream. The area between Station 105 and 126 is flat and the flood plain is wide. In the reach from Jordan Road to the uPI'~t- are twO r~ad crossings which are overtopped by the]H~,*'%ii'~,\,;tl~.creating higher water surface elevations and a WTaer'~11,a'1Ir;"There is a split flow and a wide flood plain between St~~ib;;"lr6~~~'d West Parker Road. Tallman Gulch - The lOa-year flood plain limits and profiles are shown on sheets 64 through 66. I n the reach from its confl uence wi th Sui phur Gulch to the upper study limit, there are two road crossings in the Rowley Downs subdivision area. The crossings are adequate to pass the lOa-year flood. Baldwin Gulch - The laO-year flood plain and water surface profiles for Baldwin Gulch are shown on the Flood Hazard Area Delfneation Maps, sheets 40 through 48. In the reach from the confluence with Cherry Creek to the SCS flood control dam, there are..twe-rea<l-eres~ings. The gravel road at Station 101 is overtopped by the lOa-year flood, and a shallow flooded area exists between Station 72 and 94 as shown on sheets 43 and 44. Floodways have been computed for each stream. A floodway represents a part of the flood plain which is required to pass a 100.year flood event without raising the flood profile more than an acceptable amount and also represents that part of the flood plain most hazardous to personal safety and welfare. In this study, the floodway was defined as being the limit of encroachment into the flood plain where existing flood profiles are not increased more than 0.5 feet. Floodway widths, which represent the maximum limits of encroachment into the flood plain, are tabulated in Tables 4 through 8. From the SCS flood control dam to the upper study limit, there is presently no development in the flood plain. Antelope Trail is overtopped by the lOa-year flood. Sulphur Gulch - The flood plain limits and lOa-year water surface profiles for Sulphur Gulch are shown on the Flood Hazard Area Delineation Maps, sheets 49 through 63. Flood Velocities Average flow velocities, characteristic of a lOa-year flood event are shown on the profile portion of the Flood Hazard Area Delineation drawings. The lOa-year event flow velocities vary )n the channels as follows: In the reach from its confluence with Cherry Creek to Station 71, there are three road crossings. The private road crossing at Station 8+90 is a grade crossing, with no pipes or structures. The road, therefore, is inundated by regular flood events. Presentiy there is no development in the flood plain. Creek 2 to 1 to 2 to 1 to 1 to 4 to 12 FPS 9 FPS 10 FPS 9 FPS 12 FPS 8 FPS Happy Canyon Badger Gulch Newlin Gulch Baldwin Gulch Sulphur Gulch Tallman Gulch In the reach of Rowley Downs subdivision there is presently no development in the laO-year flood plain. The flood plai~ is not very wide and it is well defined. There are two road crossings and only the private road at Station 71+40 is overtopped by the lOa-year flood as shown on sheet 53. Water flowing at a rate greater than 6 to 8 feet per second will cause severe erosion of stream banks and is capable of transporting large rocks. Velocities in the range of 6 to 8 feet per second could erode fill around bridge abutments. Water flowing at about 2 feet per second or less will deposit debris and silt. From Station 100 to the upper study limit, there is no development in the flood plain. The road at Station 262+30 is overtopped by the 100- 8 ~ - - ~---~-