North Loup Flood Reduction Study Lower Loup NRD May 2020 THIS PAGE LEFT INTENTIONALLY BLANK North Loup Flood Reduction Study Lower Loup Natural Resources District Table of Contents Table of Figures ............................................................................................................................................ iii Table of Tables ............................................................................................................................................. iv Table of Appendices ..................................................................................................................................... iv Executive Summary ....................................................................................................................................... v Chapter 1. Introduction .......................................................................................................................... 1 1.01 Project Purpose ............................................................................................................................. 1 1.02 Project Area .................................................................................................................................. 1 1.03 Scope Of Work .............................................................................................................................. 2 Chapter 2. Background ........................................................................................................................... 3 2.01 Watershed Characteristics ............................................................................................................ 3 2.02 Historic Flooding ........................................................................................................................... 5 2.03 Interior Drainage ........................................................................................................................... 6 2.04 Existing Studies and Plans ........................................................................................................... 10 Chapter 3. Hydrology and Hydrogeologic Assessment ......................................................................... 11 3.01 Surface Water Hydrology ............................................................................................................ 11 3.02 Surface Water Hydraulics ............................................................................................................ 11 3.03 Study Area Geology ..................................................................................................................... 12 3.04 Groundwater Assessment ........................................................................................................... 12 Chapter 4. Hydrologic Alternative Identification .................................................................................. 13 4.01 Initial Alternatives ....................................................................................................................... 13 4.02 Alternative Summaries ................................................................................................................ 13 No Action ............................................................................................................................................ 13 Channel Cleanout ................................................................................................................................ 15 Berm on South Side of Mira Creek ...................................................................................................... 15 Watershed Flood Control Structures .................................................................................................. 16 Mira Creek Bypass Channel ................................................................................................................. 18 Detention Basin ................................................................................................................................... 19 Ord – North Loup Canal Bypass .......................................................................................................... 20 Interior Drainage, Drainage Structures/Improvements...................................................................... 21 4.03 Groundwater Recharge ............................................................................................................... 21 Chapter 5. Alternative Summary .......................................................................................................... 23 JEO CONSULTING GROUP INC i North Loup Flood Reduction Study Lower Loup Natural Resources District 5.01 Alternative Performance ............................................................................................................. 23 5.02 Permitting Discussion .................................................................................................................. 23 5.03 Opinion of Cost ........................................................................................................................... 24 Chapter 6. Preferred Alternative and Recommendations .................................................................... 25 6.01 Recommendations ...................................................................................................................... 25 Channel Cleanout ................................................................................................................................ 25 Large Dam ........................................................................................................................................... 25 Berm .................................................................................................................................................... 26 Combination ........................................................................................................................................ 26 6.02 Interior Drainage Improvements ................................................................................................ 30 6.03 Groundwater Data Gaps ............................................................................................................. 31 6.04 Funding Options .......................................................................................................................... 31 6.05 Action Items ................................................................................................................................ 34 6.06 Disclaimer .................................................................................................................................... 35 Chapter 7. Community Engagement..................................................................................................... 36 Chapter 8. References .......................................................................................................................... 38 Appendix A: Mira Creek Hydrogeologic Assessment .................................................................................. 39 LRE Water Memorandum - April 13th, 2020........................................................................................ 39 Appendix B: Detailed Cost Opinions ........................................................................................................... 40 Small Dam 2 ........................................................................................................................................ 40 Small Dam 5 ........................................................................................................................................ 40 Small Dam 6 ........................................................................................................................................ 40 Large Dam 1 ........................................................................................................................................ 40 Large Dam 2 ........................................................................................................................................ 40 Mira Creek Berm ................................................................................................................................. 40 Small Bypass Channel .......................................................................................................................... 40 Large Bypass Channel.......................................................................................................................... 40 Detention Basin ................................................................................................................................... 40 Appendix C: Public Outreach Materials ...................................................................................................... 41 Meeting Items ..................................................................................................................................... 41 Project Handouts ................................................................................................................................ 41 JEO CONSULTING GROUP INC ii North Loup Flood Reduction Study Lower Loup Natural Resources District TABLE OF FIGURES Figure 1: Project Area Location ..................................................................................................................... 2 Figure 2: Mira Creek