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.. CH2MHIlL ....... Page 2 February 25, 2000 145886 February 25, 2000 Job No,: 145886 Me Bill DeGroot Urban Draina~e and Flood Control District 2480 West 26 Avenue, Suite'S Denver, CO 80211 The channels in the study area are erodible and may undergo changes in shape, width, and direction during flood events, Therefore, flood hazards may exist outside the floodplain limits indicated in this report Subject Flood Hazard Area Delineation of Oak Gulch and Lemon Gulch UDFCD Agreement No, 97,12.03 We would like to acknowledge the staff of UDFCD, Douglas County, and Town of Parker for their work on the Project Advisory Committee and their contributions to the FHAD report It has been a pleasure to work with the project sponsors and Advisory Committee throughout the development of the FHAD report Sincerely, Dear Bill: CH2M HILL y~~ CH2M HILL is proud to submit the attached Flood Hazard Area Delineation of Oak Gulch and Lemon Gulch, dated February, 2000. The FHAD report includes floodplain information for approximately 5 miles of Oak Gulch and its tributaries, 2,7 miles of an unnamed stream and its tributary, and 9,5 miles of Lemon Gulch and its tributaries, The delineated reaches extend from their confluence with Cherry Creek to their upper, most subwatersheds, Derek Johns, PE Task Lead,Hydrology The picture on the cover shows the typically dry, sandy Lemon Gulch channel. The 100'year floodplain is generally confined to the outside channel banks of mainstem Lemon Gulch; however, the other streams analyzed in this study are typically shallow and overbank flooding is predicted in a number of areas, /;//~ This FHAD report provides a tool to the sponsoring agencies to manage development activities adjacent to floodplains in the study area, through their planning and development approval processes, Kyle Hamilton Project Engineer cf::;~~:~ Project Manager The report provides drawings showing the 1 OO'year floodplain, 10, and 1 OO'year water surface profiles, representative channel cross sections, and major road crossings, Tabular information is included showing floodplain data and floodway information based on both a 0,5,foot and 1.0,foot maximum rise in energy grade line. Floodway limits have been adjusted to provide for relatively consistent flow widths and stable water surface results, In some steep, narrow channels, floodway limits were adjusted to match the floodplain boundaries to preclude increasing velocity and erosion problems that would result from channel filling. Me Bill DeGroot