City of Cedar Rapids
Interim Flood Response Plan

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Frequently Asked Questions

The City of Cedar Rapids has developed answers for frequently asked questions (FAQs) about the Interim Flood Response measures being deployed in our community. The following FAQs are not comprehensive but should answer most questions as they may arise especially in light of the potential flooding in cities like Fargo and Morehead, South Dakota.

MARCH 25, 2009

1. What is an Interim Flood Response Plan?
   
   This is a plan to address major floods until a permanent system of river walls and levees is constructed.  This plan incorporates sand and water-filled barriers combined with the City’s existing walls, levees, and other measures that worked in past floods.
   
   
   
2. What is the flooding history of the Cedar River?
   
   The flood stage begins at 12 feet.  This happens more or less annually during spring thaw.  Most floods have occurred between March and June.  From 1851 to June 2008, 20-feet was the maximum flood stage ever measured.  The June 2008 flood crested at 31.1-feet, or 11.1 feet higher than all other flood crests in the past 157 years. 
   
   
   
3. What flood level did past plans meet?
   
   The City has been successfully protected to 20-feet in past flood events.  Because of the response plan and City crew experience, most annual floods are barely noticed by the public. 
   
   
   
4. Will the new plan protect some areas higher than 20 feet?
   
   The temporary barriers can add up to four feet of protection to reduce the risk of flood damage.  City crews and contractors will install nearly three miles of barriers between 3-feet and 8-feet tall (sand-filled barriers are stackable) in four main locations when the river level is forecasted to 20 feet. 
   
   
   
5. Where will the barriers be installed?
   
   The four main locations are the Time Check Area, Downtown East and West, and Czech Village.  See the maps below.
   
   
   

   
   
   
   
   
   

   
   
   
   

6. Will the temporary barriers protect the City against a record flood like in June 2008?
   
   The temporary barriers are not tall enough to protect against another flood similar to the June 2008 event.  Only permanent levees and walls as constructed with a Corps of Engineers project can protect Cedar Rapids at or near the record flood level. 
   
   
   
7. How reliable are these barriers?
   
   The barriers will reduce the risk of flood damage, but will not prevent all flood damage.  These barriers will at best have low reliability during a major flood warning.  The main reasons are limited availability of contractors and materials, limited experience protecting past a 20-foot flood, poor access due to flooded streets, and short warning time to install all measures.  Neighborhood evacuations will begin before temporary barriers are installed.  
   
   
   
8. How does the City define reliability and what is the reliability of the City’s flood response?
   
   Reliability is defined as the probability of achieving successful flood protection. Overall the City can protect to the 20-foot flood level with a high reliability because the City is very experienced with this flood level. The City can protect to higher flood levels with a much lower reliability because of uncertainties in the availability of:
• Experienced staff and contractor resources
• Materials
• Adequate response time
• Topographic constraints
  
  
  
9. Why isn’t my neighborhood protected with barriers?
   
   There will be a low probability that current staff and contractor resources can temporarily protect the four locations with two to three days notice.  The probability is even lower that additional locations can be protected with the same resources and time frame.  Semi-permanent measures, such as earth levees would have to be designed and constructed well in advance to protect other locations.  Like permanent levees, semi-permanent levees would involve permanent road closures, utility relocations, and property acquisition.  This work could take several years to complete.  Neighborhoods without temporary barriers will still be protected to a 20-foot flood with relatively high reliability. 
   
   
   
10. Why are flood barriers not provided on the east side south of 8th Avenue?
    
    The area on the east side of the Cedar River south of 8th Avenue will still receive interim protection to a 20-foot flood level. The City cannot provide temporary flood barriers in this area for the following reasons:
• Large diameter storm sewer pipes in the area exceed pumping capacity and exceed the plug sizes of readily available equipment.
• The area topographically is one of the lowest and flattest portions of the floodplain.
• This is the worst area affected by groundwater seepage. Flood barriers cannot prevent water from springing up behind the barrier.
  
  
  
11. Are there any improvements to flood warning?
    
    Cedar Rapids and other jurisdictions have partnered with the US Geological Survey (USGS) to install two new river gauges near Palo and Vinton.  The new gauges combined with existing gauges in Cedar Rapids and Waterloo will improve system reliability – more gauges mean that measurements will continue even if one or two gauges fail.  Flood forecasting accuracy will improve because more data will be collected.  The river gauge in Cedar Rapids was replaced with new equipment which gives early warning of a potential backup power failure.  This will help USGS keep the gauge running as long as it’s accessible.
    
    
    
12. What would happen if the City tried to protect additional areas with flood barriers as some have requested? 
    
    

    The City does not have sufficient internal workforce or contractor resources to protect all areas as requested with any confidence of success within a typical flood warning time. The reliability to protect four areas is already low. It will be even lower if other areas are added, making successful protection of any area very difficult. 
    
    

13. What are some limitations of an interim flood response plan? What can go wrong?
    
    

    There are many risks when fighting a major flood, including but not limited to:

    • Interim flood protection must be installed in a timely manner according to flood forecasts by the National Weather Service. This prediction window can be only a couple of hours in the case of an ice jam or up to two of three days for a major flood. Predictions can change rapidly, and in the case of 2008, may stop altogether.
    • Flood barriers installed by contractors provide roughly two to four feet of additional protection to an approximate 24-foot flood in some areas. With the flat topography of the City, a flood level greater than 24 feet will cause widespread flooding.
    • The plan does not prevent sewer back flows. Plugs and storm sewer wells have to withstand an additional two feet of pressure. If the river rises fast, plugs and wells have a greater probability of failure.
    • Heavy rainfall may flood behind the protection if pumps can’t keep up. 
    • Groundwater may seep through sandy soil to the surface behind flood protection measures in place.  This has been known to occur in areas south of downtown on both sides of the Cedar River.
    • Murphy’s Law - if something can go wrong, it will. A flood might cut off access to equipment and materials. If several towns are flooding at the same time we may receive less help. In a major flood, things may have already gone wrong and could get worse.
    
    
    
14. Are there any improvements to flood warning?
    
    

    Yes. Cedar Rapids and other jurisdictions have partnered with the US Geological Survey (USGS) to install two new river gauges near Palo and Vinton. The new gauges combined with existing gauges in Cedar Rapids and Waterloo will improve system reliability – more gauges mean that measurements will continue even if one or two gauges fail. Flood forecasting accuracy will improve because more data will be collected. The river gauge in Cedar Rapids was replaced with new equipment which gives early warning of a potential backup power failure. This will help USGS keep the gauge running as long as it’s accessible.
    
    

15. What precautions should I take to reduce the risk of flood damage on my property?
    
    All residents in flood-affected neighborhoods are recommended to purchase flood insurance regardless of interim protection.  The National Flood Insurance Program website www.floodsmart.gov is an excellent resource for flood proofing and flood insurance questions.
    
    
    
16. What is the City’s timeline for construction of permanent flood management?
    
    The City’s permanent flood management strategy – which includes levees, floodwalls and a greenway – has been submitted to the Army Corps of Engineers for its analysis and study process which is expected to last up to 24 months. When that is completed, Congressional authorization and funding will be needed before construction can begin. Construction is estimated to take 10 to 15 years.