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NDSU researchers use computer models to answer if Red River diversion dam will harm farmers

Donald J. Solberg of West Fargo looks over a field Monday, Aug. 10, 2015, he leases out near Oxbow, N.D. It is still unclear to him how a plan to reimburse diversion impacts would affect him. Michael Vosburg / Forum News Service

FARGO -- The question was simple: How would a flood-control dam on the Red River affect farmers working the land on the wet side?

The dam is expected to be built as part of the proposed $1.8 billion Fargo-Moorhead flood diversion and, for North Dakota State University researchers using computer models to answer that question, the answer has been anything but simple.

"We joke that the lights dim when we hit the enter key," said Dean Bangsund, who leads the effort as part of a contract with the Fargo-Moorhead Flood Diversion Board of Authority.

After modeling for the intensity of flooding, the land elevation, the common kinds of crops raised in the area and thousands of the most likely combinations of these factors, and then comparing how they all change when the dam is built, Bangsund said the computer will spit out 39.2 million data points.

But Bangsund said the modeling isn't that hard. The biggest challenge, he said, is explaining the results so that a layman can understand them.

The study is an important part of the diversion project because it addresses a key complaint about the dam: Farmers will be harmed because the dam, when in operation, will flood prime farmland.

Donald Solberg, who owns about 260 acres southeast of Oxbow, said he's worried the dam will harm his earnings because the farmer who rents from him will suffer crop losses. The water may drain after the flood ends, he said, but it will delay planting and harm crops.

Mark Brodshaug, a retired Horace farmer who serves on the Diversion Authority, said the group plans to insure the crops of affected farmers, and the NDSU study will reveal just how big such an insurance program would be.

Farmers would still buy regular crop insurance, which will protect against hail or drought but not against what's essentially man-made flooding, he said. The Diversion Authority's insurance would go into effect "the second that we operate the project, where the gates are shut and water backs up on the land."

The NDSU study, which must still be reviewed by experts, is expected to be completed in about a month, Bangsund said.

Flooding

A flood is what happens when the volume of water is too big for existing channels to drain. The purpose of the dam is to reduce the volume going into the diversion channel and the Red River during major floods to avoid harming downstream communities.

The area that the dam would flood, called the "staging area," totals 60 square miles. How much is flooded in any year depends on the size of the flood.

Given the current understanding of flooding, the U.S. Army Corps of Engineers projects that the dam will go into operation during what's called a "10-year flood," which means there's a 10 percent chance of such a flood every year, not that it happens like clockwork once a decade. In such an event, it's likely the dam would flood a small portion of the staging area.

The storage capacity of the dam maxes out during a 100-year flood, meaning a flood with a 1 percent chance of happening each year. This is when the whole staging area could be flooded. Several communities inside would be protected by ring dikes, but not the farmlands.

Bangsund's team is trying to find out how much that dam will affect farmers' ability to begin planting on time, which affects the yield.

"We're not measuring the difference between a no-flood year and a flood year," Bangsund said. "We're measuring the difference between what the diversion would create versus the conditions without the diversion."

That is, a dam might be built and a farmer's field might be flooded, but that doesn't always mean the dam is to blame. Bangsund gave as an example a low-lying field that already floods and continues to be flooded for the same number of days when the dam is built. In this case, the dam is not harmful.

Another example is if a dam is built and causes a longer delay in planting. If the weather is warm enough that everyone outside the staging area can plant but those inside can't, then the dam is harmful. But if the weather is so cool that no one outside or inside can plant, then the dam is not harmful.

Simulation

Bangsund and three other NDSU researchers began their work for the Diversion Authority in October, and have spent most of their time since then gathering data and developing a computer model.

From the Corps of Engineers and the Diversion Authority, they gathered information about the probability of water flooding different tracts and how long that water will stick around. From agronomy experts, they gathered information about when common crops are planted and how delays usually affect those crops, checking the numbers with area farmers.

There are millions of possible combinations of these factors for any single piece of land, from the exact days the water is on the land to the day it dries out enough for farmers to get in the field to the exact change in yield-loss for crops.

To reduce the computational workload, the NDSU team took a random sample of 10,000 of the combinations, with weight given to the most probable combinations. They weeded out snow in September and snowmelt in January. Instead of every flood, the team looked at five, from a 10-year flood to a 500-year flood. Instead of every crop, the team looked at corn, soybeans, sugar beets and wheat.

The job of the computer is to simulate how long farmers on each of the tracts will have to wait to plant during each of the five floods in any of the 10,000 combinations. Then it simulates how each of the four crops would be affected by delayed planting. Finally, it compares all of these scenarios with their counterparts if a dam is built.

Bangsund said the team could use more combinations, but analysis suggests 10,000 is enough to provide a realistic simulation.

End product

What farmers will be able to take away is how much longer they'd have to wait to start planting under different floods if the dam is built. What the Diversion Authority will take away is how much the metro area may have to pay farmers to compensate for their sacrifices in the name of flood protection.

"It kind of helps identify a lot of the key issues that a lot of people are struggling with right now," Bangsund said. "Is this a multimillion-dollar problem? Is this something that's not particularly damaging? Nobody has attempted to estimate that to this point."

But the harder step is convincing farmers and landowners that crop insurance will eliminate the risk the dam presents to their income. Part of that is an inherent skepticism.

Greg Hanson, who owns land south of Oxbow that he farms, said he keeps asking the Diversion Authority and anyone affiliated with the project what they'll do for the farmers, but nobody has any details. He just doesn't trust that anything will be done, he said.

Solberg said his land hasn't flooded since the 1960s when his father drained the potholes and made those acres productive, so it's hard for him to accept someone building a dam and deliberately flooding it. At this point, he said he is "101 percent" opposed to the diversion project and it would take "one heck of a plan or guarantee" to convince him otherwise.

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