Mike Nowatzki, Published June 21 2009
Protection and price tags: Variety of flood control concepts are under studyThe saying goes that no two floods are the same.
The same could be said for flooding solutions.
A diversion that worked in Winnipeg may not be cost-effective in Fargo-Moorhead.
A system of levees and floodwalls like the one that guards Grand Forks and East Grand Forks would cost more in Fargo-Moorhead but possibly provide less protection.
And widespread water retention projects such as building new dams on rivers and holding more water in farm fields bring their own set of challenges.
But officials on both sides of the Red River agree on this: As the Army Corps of Engineers continues to study flood control options for the southern part of the Red River Valley, everything is being considered.
Several options popped up last month in a preliminary report laying out the scope of the corps’ Fargo-Moorhead Metropolitan Feasibility Study.
So far, only two have made it to the conceptual design phase: A
$909 million diversion on the Minnesota side and a $625 million levee system.
Those and other concepts are explored here with guidance from Craig Evans, a corps project manager based in St. Paul.
The corps hopes to have all of the alternatives fleshed out enough by December to start comparing them, he said.
Construction would start in April 2012 at the earliest, Evans said.
‘No action’ gets look
Under federal law, the corps must study the option of doing nothing.
As part of that study, the corps has calculated expected annual flood damages if no action is taken.
The price tag: more than $64 million annually.
That’s based on the probability of several factors, such as whether levees will fail and how often flooding will occur. The Red River in Fargo-Moorhead has exceeded its flood action stage of 17 feet in 51 of the past 107 years and every year from 1993 to 2009.
The model also assumes that emergency flood fights will continue to happen.
“But we don’t assume that they have a high probability of winning,” Evans said.
A catastrophic failure of flood protection carries much higher estimates: $2.1 billion in a 100-year flood, $5 billion in a 250-year flood and $6.6 billion in a 500-year flood.
This is another plan the corps must develop by law.
Nonstructural measures for flood-risk management include buying out flood-prone homes, flood-proofing by moving utilities and other items out of basements, elevating homes, controlling draining and flood insurance.
“It would typically be part of a plan rather than the whole plan,” Evans said.
Levees likely component
Early analysis indicates levees and floodwalls have a better chance of meeting the corps’ cost-benefit analysis than a diversion.
The corps’ estimate for a preliminary levee plan is $625 million, which includes Fargo’s
$161 million Southside Flood Protection Project. It would provide protection from a 100-year flood, which the corps considers a Red River level of 39.9 feet – almost a foot lower than this spring’s river crest.
But the levees would have 4 feet of freeboard – the distance from the water level to the top of the levee – putting the top of the structures at 43.9 feet.
“That’s going to get you close to a 500-year (flood) level,” Fargo City Engineer Mark Bittner said.
A corps official said last month that the levee system was rated 1.0 in a preliminary benefit-cost analysis. Projects scoring higher than 1.0 can be funded under federal rules.
Fargo and Moorhead don’t have to settle for what the corps decides is most cost beneficial. The cities can propose a larger or smaller project, known as a locally preferred plan, but it must be approved by the assistant secretary of the Army for Civil Works.
Diversion is costly
The corps is in the very early stages of studying the costs and feasibility of a Red River diversion around the metro area.
On the Minnesota side, a 30-mile, $909 million diversion would begin where the Red and Wild Rice rivers converge and run north between Dilworth and Glyndon before emptying back into the Red River northwest of Kragnes.
The 20-foot-deep floodway would be massive in scale, spanning 500 feet across the bottom and requiring 2,000 feet of right of way. It would cross four railway and 17 highway bridges.
However, it wouldn’t have to cross any major waterways, which Evans said would be a major challenge for a diversion west of the Red River.
The diversion plan for the North Dakota side is “nothing more than a line at this point,” he said.
The line starts about 10 miles south of Interstate 94 and goes west around Horace and West Fargo before veering back toward the east and emptying into the Red River north of Harwood, he said.
Any diversion through North Dakota would have to cross the Sheyenne, Maple and Rush rivers and likely the Wild Rice River, as well as some smaller drains, Evans said. It also would traverse Interstate 29 twice and I-94 once, along with at least four railroads.
“Whereas on the Minnesota side it’s much simpler,” Evans said.
The North Dakota diversion also would cost considerably more, but the corps doesn’t have an estimate yet, nor a proposed length, he said.
Based on early study, the chances of a federally funded diversion are slim.
Still, there is another diversion option: Using the I-29 corridor as a diversion channel.
The idea, first pitched by several North Dakota State University professors after the 1997 flood, is to rebuild I-29 at a lower elevation, creating a channel for Red River overflow to run through Fargo during severe floods. The highway would operate as normal during most years.
Donald Schwert, distinguished professor of geology at NDSU, said the option has advantages, most importantly that the public already owns the land. He also noted that I-29 north of Fargo closes during severe floods anyway.
Schwert acknowledged it would take “considerable creative engineering” to make the project happen and keep a sunken I-29 from becoming a snow trap, but added, “It’s worth consideration.”
Retention will play role
It sounds simple enough: Store more water upstream and curb the flows coming through Fargo-Moorhead during floods.
But corps and local watershed officials say environmental concerns are making it increasingly difficult to build dams on major waterways.
For example, the Maple River Dam completed in 2007 near Enderlin, N.D., took more than 20 years to get built. It holds back 60,000 acre-feet of water.
A 2005 corps study estimated the upper and lower ends of potential storage upstream of Fargo-Moorhead at 400,000 and 200,000 acre-feet, which would lower the 100-year flood level by 1.6 feet and 1.1 feet, respectively.
Assuming a cost of $800 to $1,000 per acre-foot of storage, the corps roughly figured storage costs at $160 million to $400 million.
Creating smaller impoundments by restoring wetlands and using farm fields to store water may be a more realistic approach than trying to build dams, Evans said.
The North Ottawa Impoundment Project in Minnesota’s Grant County will be able to hold 18,000 acre-feet of water on 75 square miles of farmland purchased by the Bois de Sioux Watershed District. That water eventually flows into the Red.
“We need a number of these projects scattered throughout the valley upstream of Fargo-Moorhead to really get a good handle on (flooding),” said Jon Roeschlein, district administrator.
It won’t be cheap: The flood control portion of the North Ottawa project cost about $15 million.
A different approach that would rely on storage throughout the Red River basin is the “Waffle Plan” developed by the University of North Dakota’s Energy and Environmental Research Center.
The plan calls for upgrading existing roads with new culvert gates and standpipes to hold water in farm fields for a few days to a couple of weeks to slow flows into the Red River and its tributaries.
The EERC estimates that had the Waffle Plan been in place in 1997, it would have reduced the Red River crest by 3.5 feet in Fargo and 5 feet in Grand Forks.
Center Director Gerald Groenewold said that, contrary to some criticism, EERC tests show the plan wouldn’t hurt crop production and in fact may enhance it by recharging aquifers and soil moisture.
The plan would cost
$50 million to implement and up to $600 million to operate over 50 years, though that’s a high estimate, said Bethany Kurz, EERC project manager. It could be in place in a year, she said.
“It’s essentially holding precipitation where it falls,” she said. “It’s not asking anybody to hold anybody else’s water.”
Readers can reach Forum reporter Mike Nowatzki at (701) 241-5528