Final Baseline Hydrology Report - October 2012 - Urban Drainage ...

Sanderson Gulch Major Drainageway Plan
Baseline Hydrology Report October 2012
TABLE OF CONTENTS
1.0 INTRODUCTION...................................................................................................................................... 1
1.1 Authorization ................................................................................................................................... 1
1.2 Purpose and Scope ........................................................................................................................ 1
1.3 Planning Process ............................................................................................................................ 1
1.4 Mapping and Surveys ..................................................................................................................... 1
1.5 Data Collection ............................................................................................................................... 2
1.6 Acknowledgements ........................................................................................................................ 2
APPENDICES
Appendix A – Project Correspondence
Appendix B – Hydrologic Analysis
Appendix E – Wetland and Riparian Inventory
2.0 STUDY AREA DESCRIPTION ............................................................................................................. 3
2.1 Project Area .................................................................................................................................... 3
2.2 Land Use......................................................................................................................................... 3
2.3 Reach Descriptions ........................................................................................................................ 3
2.4 Irrigation Ditches ........................................................................................................................... 14
2.4.1 Agricultural Ditch ........................................................................................................................... 14
2.4.2 Ward Canal ................................................................................................................................... 14
2.5 Flood History ................................................................................................................................. 17
2.6 Environmental Assessment .......................................................................................................... 18
3.0 HYDROLOGIC ANALYSES ............................................................................................................... 27
3.1 Overview and Methodology .......................................................................................................... 27
3.2 Duplicate Hydrologic Model .......................................................................................................... 27
3.2.1 Subwatershed Delineation ............................................................................................................ 27
3.2.2 Basin Parameters ......................................................................................................................... 28
3.2.3 Detention Pond Routing ............................................................................................................... 28
3.2.4 Results Before Calibration ............................................................................................................ 28
3.2.5 Calibration of Duplicate Hydrologic Model ................................................................................... 28
3.3 Corrected (Baseline) Hydrologic Model ........................................................................................ 28
3.3.1 Design Rainfall .............................................................................................................................. 28
3.3.2 Watershed Imperviousness .......................................................................................................... 29
3.3.3 Depression Losses ....................................................................................................................... 29
3.3.4 Infiltration ...................................................................................................................................... 29
3.3.5 Detention Ponds ........................................................................................................................... 29
3.3.6 Hydrograph Routing ..................................................................................................................... 30
3.4 Mississippi Gulch Major Storm Hydrology .................................................................................... 30
3.5 Results – Corrected (Baseline) Hydrology Model ........................................................................ 31
3.6 Comparison to Previous Studies .................................................................................................. 32
4.0 REFERENCES.................................................................................................................................... 33