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2.3.2 Reservoirs There are no reservoirs within the study area, other than a number of small farm ponds, The Happy Canyon Development is a residential development that was recently proposed within the buffer zone. The density proposed was more of a single family type density with a composite imperviousness of 32 percent, which is a higher density than recommended in the Douglas County Master Plan. Douglas County has rejected the proposal, but the developer may be submitting a revised proposal in the future, Because of the potential for some sort of development occurring, it was decided to use 32 percent imperviousness for the area in the hydrology analysis. The UDFCD, Town of Parker, and Douglas County sponsors believe that this is conservative, but appropriate for delineating regulatory floodplains. 2.3.3 Diversions There are no significant surface water diversions in the watershed. 2.3.4 Flood History No published information related to past flooding in the three tributaries was found, One resident rancher, Mr. Stevens, who lives along the main channel of Lemon Gulch, attested that over the past 52 years he has seen floodwaters in Lemon Gulch spill out of its banks (depths of up to 15 feet) approximately 15 times. Mr. Steven's ranch is located on Lemon Gulch at Station 165+00. The Castle Park Ranch was assumed to have a future imperviousness of2% since it is platted with 35 acre lots. The Agricultural One area was assumed to have a 20 percent imperviousness. Even though this area is to remain undeveloped according to the Douglas County Master Plan, the project sponsors decided that 20 percent imperviousness would be appropriate in case some development did occur. UDFCD used 20 percent imperviousness for a similar situation on a recent hydrologic analysis of Willow Creek in western Douglas County. 2.4 Vegetation Future imperviousness for Stroh Ranch, located near the Town of Parker, and Maher Ranch, located near Castle Rock, was based on preliminary development plans. The Secondary Urban Service area shown on the future imperviousness map is an area designated in the Douglas County Master Plan. Future imperviousness for the Secondary Urban Service area was assumed to the same as for the Stroh Ranch single family area. Vegetation in the Oak Gulch and Unnamed Tributary watersheds consists generally of short native grasses and scattered areas of scrub oak and yucca. The Lemon Gulch watershed is vegetated with short native grasses and scattered areas of scrub oak, cottonwood and pine trees, and yucca. In general, the Lemon Gulch watershed is more densely vegetated with shrubs and trees than the Oak Gulch and Unnamed Tributary watersheds. 2.5 Watershed Imperviousness Existing development is sparse and consists primarily of ranches and one large-lot rural subdivision called Castle Park Ranch. Imperviousness representative offuture development conditions in the study area is shown in Appendix C. Future imperviousness for long,term full build,out conditions was based on input by the project sponsors, existing zoning maps, several preliminary development plans, and the Douglas County Master Plan. According to the Douglas County Master Plan, the middle portion of the study area is to remain undeveloped for the purpose of providing a buffer zone between the communities of Castle Rock and the Town of Parker. The purpose for this undeveloped buffer zone, according to the Master Plan, is to keep the communities separate (not linked together with development) and preserve their separate identities. For the hydrology study, the buffer zone was divided into three separate areas: an Agricultural One area, the Castle Park Ranch area (platted at 35 acres per lot), and the proposed Happy Canyon Development area. 2 Oak Gulch and Lemon Gulch FHAD.DOC