FLOOD00385

• County: Boulder
• Community: Boulder
• Stream Name: Boulder Creek
• Title: South Boulder Creek Interim Hydrology Study
• Date: 7/1/2000
• Prepared For: Boulder County
• Prepared By: Taggart Engineering Associates, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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TABLE OF CONTENTS

SECTION I - SUMMARY ....................................... 1-1

Watershed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
Prior Hydrology Studies ....................................... 1-4
Objectives of this Study ....................................... 1-5
Simplified Scope ............................................ 1-5
Modification or Departures from Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
Consultations .............................................. 1-7

UDSWMM Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . '. . . . . . . 1-9
Summary Flow Results and Comparison with Previous Hydrology .......... 1-9
Discharge Profiles .......................................... 1-14
Model Reasonableness and Refinement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-14
General Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-18
Recommendations .......................................... 1-19

SECTION II - SOUTH BOULDER CREEK WATERSHED. . . . . . . . . . . . . . . . .. 11-1
General Features ........................................... 11-1
Irrigation Ditch Diversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11-2
Key Flood Control Features .................................... 11-4
Summary Control Features .................................... 11-8
Historical Floods and Hydrology Comparison ....................... 11-10
Example Flood Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11-11
Geomorphology .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11-1 3

SECTION III - PRECIPITATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111-1

Overview ................................................ 111-1
Rainfall Specifics ........................................... 111-2

Agency Review ............................................ 111-9
May 1969 Storm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111-12

SECTION IV - SURFACE RUNOFF. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-1
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-1

Infiltration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-1
Impervious Land Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-4
Depression Losses ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-11
Surface Runoff Hydraulic Parameters ............................ IV-11
Overland Flow Lengths and Slopes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-11
Overall Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV -12