FLOOD07509

• Designation Number: 150
• County: Adams
• Community: Thornton
• Stream Name: Direct Flow Area 0054
• Basin: South Platte
• Title: Flood Hazard Area Delineation - Direct Flow Area 0054 - Including Major Drainageway Planning DFA 0054 Phase A Report 11/79
• Date: 10/1/1979
• Designation Date: 1/1/1980
• Floodplain - Doc Type: Floodplain Report/Masterplan

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FLOOD HAZARD AREA DELlNEA TION
DIRECT FLOW AREA 0054

Table of Contents

Preface
List of Tables
List of Figures
Introduction
Study Area Description
Drainage Basin Characteristics
study Reach Description
Historic Flooding
Hydrologic Analysis
Derivation of Hydrographs
Rainfall Data
Land Use
Losses
Flood Hydrographs
Hydraulic Determinations
Flood Hazard Areas
Flooded Areas
Direct Flow Area 0054-1
Direct Flow Area 0054-2
Direct Flow Area 0054-3
References
Drawings

Page

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26
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28
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29

List of Tables
Page
1. Watershed Parameters 8
2. One Hour Rainfall Depth - Rainfall Hyetographs 9
3. Culvert Data 12
4. Floodplain and Floodway Reference Data -
Direct Flow Area 0054-1 21
5. Floodplain and Floodway Reference Data
Direct Flow Area 0054-2 23
6. Floodplain and Floodway Reference Data
Direct Flow Area 0054-3 24
List of Figures
Page
la. Holly Street Embankment Failure - July 21, 1977 5
lb. Holly Street Embankment Failure - July 21, 1977 5
2. Holly Street overtopping and erosion - May 2, 1979 6
3. Holly Street overtopping and erosion - May 2, 1979 6
4. Riverdale Road overtopping looking North - May 2, 1979 7
5. Reach 3 - Erosion of channel through residential
construction project - May 2, 1979 7
6. Colorado Agricultural Canal beneath Holly Street
May 2, 1979 7
7. Rainfall Hyetograph - 100 Year Storm 10
8. 100-Year Flood Hydrograph - Direct Flow Area 0054-1
at South Platte River and Riverdale Road 13
9. 100-Year Flood Hydrograph - Direct Flow Area 0054-1
a t Holly Street 14
10. 100-Year Flood Hydrograph - Direct Flow Area 0054-1
at 112th Avenue 15
11. 100-Year Flood Hydrograph - Direct Flow Area 0054-2
at South Platte River and Riverdale Road 16
12. 100-Year Flood Hydrograph - Direct Flow Area 0054-3
at South Platte River, and Southern and Northern
Branches at Riverdale Road 17
13. Peak Flood Discharges - Direct Flow Area 0054-1 18
14. Peak Flood Discharges - Direct Flow Area 0054-1
Middle and Northern Branches 19
15. Peak Flood Discharges - Direct Flow Area 0054-2 and
0054-3 20

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