1) The 2008 Spring Green flooding was caused by record snowfall and rainfall over wet ground in late 2007 and early 2008, with no outlet for flood waters. This led to over 4,400 acres flooded and damage to homes, businesses, and infrastructure. 2) Modeling showed that constructing drainage basins and outlets could reduce the depth, area, and duration of future flooding, but would require overcoming numerous permitting challenges and coordinating with various stakeholders. 3) Allowing temporary flooding of agricultural fields for a few days was found to be important to implementing a feasible drainage system with multiple constructed outlets to the Wisconsin River.

1. Spring Green 2008 Flooding
and Flood Control Options
Jon Lefers, PE
Montgomery Associates: Resource Solutions, LLC
WAFSCM 2010 Conference
November 4, 2010

2. Introduction
• Why did the flood occur?
• What happened?
• Can something be done about future
damages from flooding?

3. Acknowledgments
• Jewell Engineering
• Town of Spring Green
• Wisconsin Geologic and Natural History
Survey
• Fred Iausly

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. Source: USGS, Professional Paper 1775

6. Mid-May
Through
Mid-June 2008
Precipitation

7. June 7-8 and June 12 Events
• Total of 10.1
inches fell
over 5 days

8. Current Runoff Pattern

9. Wisconsin River Valley Topography
Source: Sauk Co./F. Iausly/WGS

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. Flooding Extents
Source: F. Iausly

15. 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

16. Hydrologic Analysis
• Runoff Volumes
– SCS Curve
Number
Methodology
• Soils runoff
potential
• Land use runoff
potential
– Antecedent
moisture conditions
accounted for

17. Runoff Volumes (Acre-Feet)
100 year
June 7-8 June 12 Storm Current
Big Hollow 1,013 1,740 1,442
Runoff
Central Basin 560 546 725
Pattern
East Basin 360 350 479
West Basin 1,182 1,153 1,516
Total Volume 3,116 3,790 4,162

18. Model Water Table Map
Groundwater moves from high to low elevations
Wisconsin River
Source: WGNHS model

19. Modeled Increase in Water Table (ft) when
Recharge is Increased by 1 inch
1.5 ft
1.0 ft

20. Sample Scenario

21. Central Basin
6000
Before Basin
After Basin
5000
4000
Flow (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

22. Sample Scenario - Flooded Area
June 13

23. Sample Scenario - Flooded Area
June 15

24. Sample Scenario - Flooded Area
June 17

25. Other Flooded Areas
Source: F. Iausly

26. 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)

27. 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