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FLOOD HAZARD AREA DELINEATION Flood Frequency and Discharge Flood Plain and Floodway Data I ] I Floods of the same and greater magnitude than those that have occurred in the past, will occur in the future. With development in the basin, flooding will occur more frequently. The discharges reported on Figures 4 through 9 for the 10, 50, and 100-year flood frequencies, represent the extent and impact of each flood event. The discharge information is usable not only for flood plain regulation, but also for planning and engineering of flood plain improvements, The 100-year flood plain limits and water surface profiles for each of the streams are shown on the Flood Hazard Area Delineation drawings, and computed 100-year flood elevations at each reference point are tabulated in Tables 4 through 8. A brief description of the floodin3 for each of the streams follows. The 100-year flood event can be expected to occur at any time in a given area. Based upon recorded historical precipitation and other valid data, there is a one percent chance that the 100-year storm will be equalled or exceeded in anyone year. The risk of failure of structural flood plain improvements is lower for the 100-year storm that for the 10-year or 50-year storm events. The 100-year flood is considered by the Urban Drainage and Flood Control Oistrict, the Colorado Water Conservation Board, and the Federal Insurance Administration, as the flood magnitude for which flood plains should be designated for regulatory and improvement purposes. In Colorado, the 100-year flood plain is an area of state interest as defined in H. B. 1041. Happy Canyon Creek - The 100-year flood plain and water surface profiles for Happy Canyon Creek are shown on the Flood Hazard Area Oelineation Maps, sheets 4 through 26. Happy Canyon Creek joins Cherry Creek approximately 2,600 feet northeast of Jordan Road. The original channel between the confluence and Jordan Road has been relocated and is currently a sod farm. The new channel is undefined and the entire area is very flat. The flood plain at the confluence of Cherry Creek is influenced by the 100-year flood plain of Cherry Creek which is wide and not well defined. The 10 and 50-year recurrence flood magnitudes have also been calculated at various design points along each creek. These flood magnitudes represent events which can cause damage but would not inundate the area as would the 100-year event. Peak flows for these events should be used in determining the feasibility of improvements because of the higher risk of damage or failure and where the hazard to life and property.is lower or non-existent. There are three road crossings in the Grand View Estate subdivision reach which are overtopped by the 100-year flood, creating higher stages and wider flood plains as shown on sheets 15 through 18. Existing development is outside of the flood plain and no major flood damage is anticipated. Badger Gulch - There are two road crossings in the entire reach which are overtopped by the 100-year flood, causing higher stages and wider flood plains upstream as shown on sheets 27 and 28. Flood magnitudes greater than the 100-year flood magnitude can and will occur. Plans for land improvement adjacent to the 100-year flood plain should consider the probability of flood damage. Newlin Gulch - The 100-year flood plain and water surface profiles for Newlin Gulch are shown on the Flood Hazard Area Delineation Maps, sheets 30 through 39. The reach from the confluence with Cherry Creek to Jordan Road is farming area and no development exists in the flood plain. The area upstream from the confluence is very flat, the flood plain is wide and the channel is undefined. The flood plain at the confluence is influenced by the Cherry Creek 100-year flood plain. 7