Analysis: Cost of flood diversion vs. damage

Diverting part of the Red River to lessen the risk of flooding in Fargo and Moorhead could cost $1.3 billion, and it's still not clear where the money would come from.

While the price tag might leave some wondering if it's even worth it, city and state officials point to a variety of expenses that add up in a flood fight: filling and delivering sandbags, constructing clay levees and paying for extra law enforcement -- not to mention the damage to homes, roads and other infrastructure if floodwaters can't be held back.

Frequent flooding can make those expenses add up quickly over time. Minnesota and North Dakota spent a combined $200 million on flood fights throughout the two states in 2009.

But no one can truly predict how many times a given river will flood in the future, so government officials and engineers must determine by looking at past floods whether it makes sense to divert a river, build a permanent levee or take other action to mitigate flooding.

"You have to look at what the risk is and ask how much are you willing to pay to avoid that risk," said Kent Lokkesmoe, director of waters for the Minnesota Department of Natural Resources.

Lokkesmoe said several flood mitigation projects in Minnesota have proven to be cost effective.

For example, a project in Oslo, a town located about 24 miles north of Grand Forks, N.D., that cost $2 million in the 1970s has prevented an estimated $50 million in damages since then.

The DNR and U.S. Army Corps of Engineers consider the Oslo project one of the best uses of flood prevention money in the state.

Lokkesmoe said flood mitigation projects in Breckenridge, Crookston, Mankato, Grand Forks and East Grand Forks have also helped avoid millions of dollars worth of damage over the years.

"It's cost effective," he said. "Plus, you take away the worry, you take away all the stress and the risk of fighting floods."

Farther south in the western Minnesota town of Browns Valley, a half-finished diversion channel that was a response to a major flood in 2007 was credited for keeping homes and businesses dry this year. Despite a leak in the project that damaged a bridge and road on Monday, officials said Main Street would have been under a foot of water this year without the project.

"We have more water now than in 2007," Browns Valley Mayor Jeff Backer told MPR's Morning Edition earlier this week. "This channel is doing what it's supposed to and that's protecting the citizens."

Besides diverting rivers, flood mitigation can include building levees and buying property in the flood plain, including moving or demolishing houses. Fargo and Moorhead have bought dozens of homes in flood-prone areas.

Funding for flood mitigation is made up of a combination of federal, state and local money. The state money often comes from bonding, such as the $63.5 million for flood hazard mitigation that's part of this year's bill signed by Gov. Tim Pawlenty. The DNR has received $150 million worth of requests, Lokkesmoe said.

"The requests always exceed the available money," he said. "I think a lot of (the projects) are ready to go, but not everybody is going to get what they want."

The city of Moorhead is likely to get some of that money to equip storm drains with a special valve that can close the drains so that officials aren't forced to manually block them each time there's a flood.

Lokkesmoe said state and federal officials scrutinize each project not only for its predicted cost-benefit relationship, but also to make sure the solution isn't creating more problems elsewhere.

"Are you just passing the problem around? Because if you do a levee or (diversion), you may raise flood levels downstream or upstream," he said. "So vacating the flood plain and letting the floodwaters go where they historically went is often the best solution."

(MPR reporter Dan Gunderson contributed to this report.)

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