FLOOD01787

• County: Boulder
• Stream Name: South Boulder Creek
• Title: South Boulder Creek/ Flatirons
• Date: 12/5/1997
• Prepared For: Boulder
• Prepared By: Consultants
• Floodplain - Doc Type: Community File

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TABLE OF CONTENTS

SECTION I - SUMMARY ................................... 1-'
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-'

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
Data Obtained and Reviewed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

Findings .............................................. 1-3
Limitation and Recommendations for Future Study and Investigation .... 1-5

SECTION II - FEATURES AFFECTING LOCAL DRAINAGE AND
SOUTH BOULDER CREEK OVERFLOWS FROM HIGHWAY 36
TO THE AREA OF THE WELLMAN DITCH. . . . . . . . . . . . . . . . . . . . .. 11-'
General Features ....................................... 11-'
Key Features Affecting Local Drainage and South Boulder Creek
Overflows - Highway 36 to the Wellman Ditch .................. 11-3

SECTION III - PAST HYDROLOGY MODELING REVIEW. . . . . . . . . . . . . 111-'
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111-'
Basin and Subbasin Delineation and Comparison ................. 111-'

Rainfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111-3
Corps' Modeling Calibration and Sensitivity Tests ................ 111-5
Review of Corps' SWMM Hydrology Calibration . . . . . . . . . . . . . . . . . . 111-8

SECTION IV - INITIAL HYDROLOGY MODELING OF THE WEST
OVERFLOW AREA OF SOUTH BOULDER CREEK BELOW HIGHWAY 36 .IV-'
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-'
Initial Flow Estimates and Methodology ....................... IV-'
Field Work. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-2
Comparisons with MWE Modeling of Areas Tributary to 55th and
Wellman Ditch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-2
Limitations ........................................... IV-2
Specific Notes and Assumptions ............................ IV-3

SECTION V - RECOMMENDATIONS. . . . . . . . . . . . . . . . . . . . . . . . . . V-'

Summary ............................................ V-,
Detailed Study and Analysis Recommendations .................. V-2