FLOOD10207

• Designation Number: 503
• County: Jefferson
• Community: Unincorporated Jefferson County
• Stream Name: Woman Creek, Walnut, Upper Big Dry and Rock Creek
• Basin: South Platte
• Title: Drainage & Flood Control Master Plan - Rocky Flats Plant
• Date: 4/1/1992
• Designation Date: 9/1/1999
• Floodplain - Doc Type: Floodplain Report/Masterplan

TABLE OF CONTENTS

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SECTION I

EXECUTIVE SUMMARY

OVERVIEW ...................................... I-I
STUDY AREA................ ...... . .............. I-I
FLOOD HYDROLOGY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
WA1ER RIGHTS AND DITCHES.. ...................1-2
CHANNELHYDRAUUCSANDFLOODPUUN
DEUNEATIONS ............... ...................1-2
CORE AREA DRAINAGE ........................... 1-2

WA1ER QUALITY.............. ..... ..............1-3
MANAGEMENT OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

SECTION IV

SECTION II

INTRODUCTION

STUDY AREA BACKGROUND. . . . . . . . . . . . . . . . . . . . .. II-I
MAS1ER PlAN PRIMARY & SECONDARY OBJECTIVES 11-2

PlANNING AREA ................................ 11-2
ANALYTICAL PROCEDURES . . . . . . . . . . . . . . . . . . . . . .. 11-2
FWOD HYDROLOGY. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11-3
FLOODPUUN DEUNEA TION . . . . . . . . . . . . . . . . . . . . . .. 11-3

DE1ENTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11-3
FUTURE BASIN DEVELOPMENT ................... 11-4
QUALIFICATIONS AND UMITATIONS ............... 11-4

APPENDIX II-A - REVIEW LETfERS . . . . . . . . . . . . . . . .. 11-5

SECTION III

STUDY AREA DESCRIPTION

TOPOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. I1I-2
RAINFALL/RUNOFF PARAME1ERS . . . . . . . . . . . . . . .. I1I-2
DRAINAGE BASIN DESCRIPTIONS ................. I1I-3

Walnut Creek. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. I1I-4
Woman Creek .............................. I1I-4
Upper Big Dry Creek . . . . . . . . . . . . . . . . . . . . . . . .. I1I-4

Ponds .................................... 111-5
DRAINAGE BASIN DESIGNATIONS ................ I1I-?
Great Western Reservoir Drainage Basin .......... 1I1-?
Standley Lake Drainage Basin .................. I1I-S

Rock Creek ................................ 111-9
SOILS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 111-9
GEOLOGY .................. . . . . . . . . . . . . . . . . .. 111-9
GROUNDWA1ER........ ..... ....... .......... .. I1I-lD

SECTION V

TABLE OF CONTENTS (cont'd)

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FLOOD HYDROLOGY

PREVIOUS STUDIES ............................. IV-2
PRECIPITATION DATA. . . . . . . . . . . . . . . . . . . . . . . . . .. IV-3
DESCRIPTION OF MODELS ....................... IV-3
CUHP Model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. IV-5
SWMM Model........... ................ ... IV-6
Implementation of Rocky Flats Plan
CUHP /SWMM Models ...................... IV-6

Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-IO
Calibration & Verification of CUHP/SWMM ....... IV-IS
FUTURE BASIN HYDROLOGY .................... IV-I?
INFLOW TO STANDLEY LAKE/GREAT WES1ERN . . . . IV-I?
LONG-1ERM STORMS ........................... IV-IS

SNOWMELT .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-19

APPENDIX IV-A - SUMMARIES OF PAST DRAINAGE

STUDIES. .. . . . .. . . . . .. . . . . . . . . . . . . . . . . . . . IV-20

APPENDIX IV-B - PEAK FLOW, RUNOFF VOLUME,
PEAK FLOW, RUNOFF VOLUME, PEAK FLOW
PER UNIT AND UNIT RUNOFF FOR 6-HOUR

STORM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-3?

APPENDIX IV-C - HYDROGRAPHS FOR VARIOUS
POINTS ON WALNUT CREEK, WOMAN CREEK
AND UPPER BIG DRY CREEK ............... IV-4?

WATER RIGHTS AND DITCHES

DITCH FLOOD P01ENTIAL . . . . . . . . . . . . . . . . . . . . . . .. V-2
KINNEAR DITCH RELOCATION .................... V-3
SOUTH BOULDER DIVERSION CANAL .............. V-3
DITCH ADMINISTRATION ......................... V-3
DITCH DIVERSIONS .............................. V-3

SUMMARY ..................................... V-4

APPENDIX V-A - SEDIMENT REPORT ON COAL CREEK
IN VICINITY OF HEADGA1ES TO UPPER
CHURCH AND KINNEAR DITCHES ............ V-5