Research upstream detention

Byline: Clark Rieke

As the Army Corps of Engineers works on a feasibility study of the proposed levee for Cedar Rapids, we should ask it to consider upstream detention -- temporarily detaining storm water where it falls -- because upstream detention provides benefits throughout the Cedar River watershed and costs can be shared by all communities who benefit.

Those benefits include:

1. Flood protection for river communities, upstream and downstream

2. Localized protection from frequent flash floods

3. Reduction in nitrite fertilizer pollution runoff

4. Stabilization of our aquifer

5. Lower flood insurance costs in the long run

The projected cost of a levee and other improvements to protect Cedar Rapids alone is $1 billion. Dividing this amount by the number of square miles in the Cedar River watershed (6,510) gives us more than $150,000 per square mile to spend on flood protection. Once we estimate how much detention capacity we can buy, we can estimate how much smaller we can build the levee and at what cost.

Once we have an understanding that there is a trade-off -- that an increase in detention capacity allows for a decrease in levee height -- then we are ready to discuss the level of flood protection for the whole watershed.

The challenge of looking at the whole watershed is that we need a new hydrology model that addresses questions such as: Are levees in Cedar Falls and Waterloo high enough? If upstream detention was put in above Cedar Falls and Waterloo, what would be a fair allocation of costs and benefits between these two cities, Cedar Rapids and communities downstream?

Don Palmer has made us aware that the University of Iowa Hydrology Department has achieved significant advances already and state Sen. Rob Hogg, D-Cedar Rapids, led the successful legislative achievement to fund a new University of Iowa Flood Center. An example of technological advance that is ready for us to use is the new aerial LIDAR technology for maps with ground elevation much more accurate than current maps.

Evolving technologies enable hydrologists to better address the most cost-effective blend of flood-protection projects for the whole watershed rather than settling for how high to build a levee in any one city. Our challenge is to find the political will to invest enough in research and demonstration projects to capitalize on the technology.

I believe spending enough to learn the cost effectiveness of upstream detention would yield a good return on the investment.

Clark Rieke of Cedar Rapids is a real estate broker who, with retired engineer Don Palmer, has studied and promoted the use of detention basins to reduce flooding.