FLOOD06381

• County: Otero
• Community: La Junta
• Stream Name: Arkansas River & Tributaries
• Basin: Arkansas
• Title: La Junta, Colorado Local Protection Project Phase I GDM Sediment Investigation
• Date: 9/1/1985
• Prepared For: US Army Corps of Engineers
• Prepared By: The Hydrologic Engineering Center
• Floodplain - Doc Type: Project

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Table of Contents

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5. Estimate of Channel Changes For a Single Event Flood 48
5.1 Development of Geometric Data for HEC-6 Single-Event Simulation 48
5.1.1 Existing Conditions 48
5.1.2 Project Conditions 48

5.2 Development of Sediment Data 48
5.2.1 Bed Material 50
5.2.2 Inflowing Load 50
5.2.3 Total Load Gradation 50

5.3 Development of Flood Hydrographs 50

5.4 Model Performance and Calibration 55

5.5 Simulation Results 55
5.5.1 Existing Conditions 55
5.5.2 Project Conditions 56
5.5.3 Evaluation of Scour Potential Using Hand Computation
Methods 57
5.5.4 Hand Computation Results 59

5.6 Interpretation of Simulation Results 60

6. Impacts of Irrigation Diversions (4)

67

7. Armoring Potential (6)

69

8. Equilibrium Slope Analysis (7)
8.1 Determination of Critical Shear Stress
8.2 Determination of Actual Shear Stress
8.3 Conclusions

70
70
73
73

9. Reach Classification (3)

74

10. Impacts of Vegetation and Land Use (6)
10.1 Vegetation
10.2 Land Use

75
75
75

11. Response of System to Operation of Pueblo Dam

76

12. Recommendations on Project Designs

77

APPENDICES

APPENDIX A:
APPENDIX B:
APPENDIX C:
APPENDIX D:
APPENDIX E:
APPENDIX F:

References
Scope of Work
Arkansas River Cross Sections, "Existing" Conditions
Arkansas River Cross Sections, "Project" Conditions
River Bed Profiles Computed By HEC-6 For A Single Flood Event
Deposition vs. Time at Each Cross Section For A Single Flood Event

ii