Spring Green 2008 Flooding and Flood Control Options

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Spring Green 2008 Flooding and Flood Control Options - Jon Lefers, Montgomery Associates

Nov 2008

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Spring Green 2008 Flooding and Flood Control Options

  1. 1. Spring Green 2008 Flooding and Flood Control Options Jon Lefers, PEMontgomery Associates: Resource Solutions, LLC WAFSCM 2010 Conference November 4, 2010
  2. 2. Introduction• Why did the flood occur?• What happened?• Can something be done about future damages from flooding?
  3. 3. Acknowledgments• Jewell Engineering• Town of Spring Green• Wisconsin Geologic and Natural History Survey• Fred Iausly
  4. 4. Why did the flood occur?• Wetter than normal late summer/fall in 2007• Record winter snowfall• June 7-8 and June 12 storms• No outlet for flood waters
  5. 5. Source: USGS, Professional Paper 1775
  6. 6. Mid-May ThroughMid-June 2008 Precipitation
  7. 7. June 7-8 and June 12 Events• Total of 10.1 inches fell over 5 days
  8. 8. Current Runoff Pattern
  9. 9. Wisconsin River Valley Topography Source: Sauk Co./F. Iausly/WGS
  10. 10. What happened?• 4,400 acres flooded• Crops destroyed • Sanitary sewer failures• Homes and businesses • Culvert failures damaged or destroyed • Roads flooded• Families evacuated & • Health and safety displaced from homes problems
  11. 11. Flooding Extents Source: F. Iausly
  12. 12. Can something be done about future damages from flooding?FEMA Buyouts• 28 substantially damaged homes were acquired and demolished or removed from flood hazard areas at a total cost of $5.4 million.Flooding Reduction• Developed a rainfall-runoff-routing model• Evaluated several scenarios for performance – Key factors: Depth, area, and duration of flooding• Evaluated impacts and costs for various solutions
  13. 13. Hydrologic Analysis• Runoff Volumes – SCS Curve Number Methodology • Soils runoff potential • Land use runoff potential – Antecedent moisture conditions accounted for
  14. 14. Runoff Volumes (Acre-Feet) 100 year June 7-8 June 12 Storm Current Big Hollow 1,013 1,740 1,442 RunoffCentral Basin 560 546 725 Pattern East Basin 360 350 479 West Basin 1,182 1,153 1,516Total Volume 3,116 3,790 4,162
  15. 15. Model Water Table MapGroundwater moves from high to low elevations Wisconsin River Source: WGNHS model
  16. 16. Modeled Increase in Water Table (ft) when Recharge is Increased by 1 inch 1.5 ft 1.0 ft
  17. 17. Sample Scenario
  18. 18. Central Basin 6000 Before Basin After Basin 5000 4000Flow (cfs) 3000 2000 1000 0 6/7/2008 0:00 6/8/2008 0:00 6/9/2008 0:00 6/10/2008 6/11/2008 6/12/2008 6/13/2008 6/14/2008 6/15/2008 6/16/2008 0:00 0:00 0:00 0:00 0:00 0:00 0:00
  19. 19. Sample Scenario - Flooded Area June 13
  20. 20. Sample Scenario - Flooded Area June 15
  21. 21. Sample Scenario - Flooded Area June 17
  22. 22. Other Flooded Areas Source: F. Iausly
  23. 23. Permits, Coordination, & Design Standards• DNR• US Army Corps• Lower Wisconsin State Riverway Board• DOT (Highways and railroad)• Wisconsin & Southern RR• DATCP & NRCS• Town of Spring Green• Sauk County• Above and below ground utilities• Local landowners (irrigation and land impacts)
  24. 24. Conclusions• Flooding in Spring Green was a combination of flash flooding and groundwater-driven extended flooding• Allowing for flooding of agricultural fields lasting a few days is critical to implementing a feasible drainage system.• Several drainage outlets would need to be constructed.• Multiple permitting and design challenges exist for constructing drainage outlets to the Wisconsin River

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