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<br />Oak Gulch and Lemon Gulch
<br />Flood Hazard Area Delineation Study
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<br />Contents
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<br />Section Page
<br />
<br />1.0 In trod uction ................................................................................................................. 1
<br />1.1 Authorization ....,..,..., ..........,...................................,......................................... I
<br />1.2 Purpose .......,.. ...........,......,.... ,"'...................... ,......"'...........................,............. I
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<br />3.7 Results..................,.....,.....,............................,.... ........................................... .... 5
<br />3.7.1 Peak Flows,.............,.......,..,....,.....................,................,...................... 5
<br />, p' S d' 5
<br />3,7.2 Companson to revlOUS tu les .... "'.....,..,............................ "',..........,
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<br />2.0 Study Area Description ...........................,.................................................................. 1
<br />2.1 Topography and Physiography....,......,"'........................,....................,............ I
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<br />2.2 Soils. ......... ..... ................ ......"'............... ..."'............... .............................. ......... I
<br />2.3 Surface Water Resources ..,.....,...........,..,...................,"'...........,..........,....,......' I
<br />2.3.1 Stream Characteristics ..,.......,.....................................,......................... I
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<br />2.3.2 Reservoirs ..."........................,.................................................,............. 2
<br />2.3.3 Diversions .........,......,....,..,....:.........................,...................,.......,...,..... 2
<br />2.3.4 Flood History ..........................,.......,"'..........................,.............."',....' 2
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<br />2.4 Vegetation ........,..,...,........"',......"'..............,"'....................................,............' 2
<br />2.5 Watershed Imperviousness .....................................,.............."',....................... 2
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<br />4.0 Hydraulic Analysis...................................................................................................... 6
<br />4.1 Methodology ......,.....,"'..."'................,..,..,........,'....'.............,........................... 6
<br />4.2 Results .............,...............................,............"'.....,...,..................................... 7
<br />4.3 Generai'Overview of Flood Impacts........,....................,...................,..,..,..,...... 7
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<br />5.0 References ............................................................................................................. 8
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<br />Tables
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<br />Number
<br />
<br />Page
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<br />3.0 Hydrology Analysis ..................................................................................................... 3
<br />3.1 Subwatersheds..." .....,... ............. ............. ........" ..... ,.... ......"'......................... ..,.. 3
<br />3.2 Streams. .....,.., ...... ..,..........,........,.... .....,...... ...............,................... ...., ............... 3
<br />3.3 Hydrologic Models .."..................................,.............,.....................................' 3
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<br />3.4 Rainfall........,. ..,......... "'.. ..,................. .......,... ....... ............ .......,...... ..,................ 3
<br />3.4, I Criteria ....................."'...................................,.......,....,..,..,...........,....... 3
<br />3.4.2 Rainfall Depths .......,..,........'...........,..................................................... 3
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<br />3.4.3 Hyetographs ......................................,....................,..,........................... 4
<br />3.5 CUHP Modeling ..............,...................................,...........................................' 4
<br />3,5.1 Delineation of Sub watersheds"....,....."....,........................................... . 4
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<br />3,5.2 Imperviousness ....,..................,.........."..."'...........,....,............,....,..."'.' 4
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<br />3.5.3 Slope ,...."....."......"..........".....,................,"'....................................,....4
<br />3.5.4 Time of Concentration ..,................................,...................................... 4
<br />3.5.5 Retention Storage Losses........,..................."''''......................,............, 5
<br />3.5,5 Infiltration Losses .................,........................,..............................,..,.... 5
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<br />3.6 UDSWM2 Modeling...................................,.......................,............................. 5
<br />3.6.1 Conveyance Element Identification Number ..........,..............,........,....' 5
<br />3,6.2 Stream Geometry..................,"'.......................,....,....,...............,.., 5
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<br />3,6.3 Roughness ....""....'........"..,.....,.......,..'.',.....,......................",.........'."..' 5
<br />. C . ' 5
<br />3.6.4 Routmg onnectlvlty ....,'..,..,..............,.....,....................'.,.."..,.'..........'
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<br />3-1 Summary of Area Adjustments............,.........,........,....,............,.........................,......... 3
<br />3-2 Summary of Unadjusted Rainfall Depths ........................,................"',...........,.....un,.. 3
<br />3-3 Composite Future Imperviousness Values........,....,.........,......,..................................... 4
<br />3-4 100- Year Peak Discharges at Selected Locations................,"'...,....,............................ 5
<br />3-5 Comparison of I DO-Year Discharges to Other Studies..,................,..............,..,......,.... 6
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<br />Appendices
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<br />Appendix A: Subwatersheds Map (1 sheet)
<br />Appendix B: Soils Map (1 sheet)
<br />Appendix C: Future Imperviousness Map (1 sheet)
<br />Appendix D: Streams Map (1 sheet)
<br />Appendix E: Subwatershed Characteristics Table (1 sheet)
<br />Appendix F: Stream Characteristics Table (1 sheet)
<br />Appendix G: UDSWM2 Connectivity Diagrams (2 sheets)
<br />Appendix H: Peak Discharges Table (I sheet)
<br />Appendix I: Floodplain and Floodway Table (8 sheets)
<br />Appendix J: Floodplain Drawings (50 sheets)
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