FLOOD03253

• County: Boulder
• Community: Boulder
• Stream Name: South Boulder Creek
• Basin: South Platte
• Title: South Boulder Creek Draft Hydrology Study Phase III
• Date: 2/10/2000
• Prepared For: UDFCD
• Prepared By: Taggart Engineering Associates, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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TABLE OF CONTENTS

SECTION I - SUMMARY .........................,...........,. 1-'

Watershed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-'
Prior Hydrology Studies ....................................... 1-4
Objectives of this Study ....................................... 1-5
Simplified Scope ...............................,............ 1-5
Modifications or Departures from Scope ............................ '-6

Consultations .............................................. 1-7
UDSWMM Model . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8
Summary Flow Results and Comparison ............................ 1-9
Model Reasonableness and Refinement . , . . . . . . . . . . . , . . . . . . . . . . . . . . 1-'3
General Conclusions . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . 1-14
Recommendations ...............,.......................... 1-' 5

SECTION II - SOUTH BOULDER CREEK WATERSHED. . . . . . . . . . . . . . . . .. 11-'
General Features ................,.......................... 11-'
Irrigation Ditch Diversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11-2
Key Flood Control Features ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11-3
Historical Floods and Hydrology Comparison ........................ 11-9
Example Flood Events. . . . . . . , , . . _ . . . _ . . _ . . . . . . . . . . . . , . . . . . .. 11-'0
Geomorphology . . . . . . . . , . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., 11-' 2

SECTION III - PRECIPITATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111-'

Overview ...'............................................ 111-1
Rainfall Specifics ........................................... 111-2
Agency Review ............................................ 111-7

SECTION IV - SURFACE RUNOFF. , . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . IV-'
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-'
Infiltration , . . . . , . . , . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . IV-'
Impervious Land Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-4
Depression Losses ..................................,...... IV-"
Surface Runoff Hydraulic Parameters ............................ IV-"
Overland Flow Lengths and Slopes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-"
Overall Results. . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-'2

SECTION V - HYDROLOGY MODEL .................,............ V-'
Model Overview. . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. V-,

Limitations ..................,............................ V-'
Representative'OO.Year Flood Hydrographs .. . . . . . . . . . . . . . . . . . . . . .. V-2
Reasonableness Checks ..........................,.......... V-'7

Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . .. V-20