Marni Radcliffe has lived at Edina’s Nine Mile Village townhouses for 20 years. She’s never had a problem with water or flooding.

That’s why she was flabbergasted to get a letter this spring notifying her that her house is now in a flood plain.

“It was a total surprise, because we have never been in a flood plain before,” she said. “It just doesn’t make sense.”

The city of Edina has questions, too. It’s hired an engineering firm to review data used by the Federal Emergency Management Agency (FEMA) to issue new flood plain maps. Barr Engineering is reviewing elevation data for three areas in the city that contain about 150 properties to see whether the flood plain designation should be appealed. The appeal deadline is July 4.

“Nobody wants to be in a flood plain,” said Laura Adler, Edina’s water resources coordinator. “It wouldn’t be surprising if the [flood plain areas] moved a little bit. It was the large areas that raised a red flag.”

If a house is in a flood zone, homeowners who still have a mortgage may be required by their bank to buy expensive flood insurance. Any federally backed loan will include that requirement. And a flood plain designation can complicate selling property and affect remodeling or expanding a home.

The new FEMA maps are part of a national effort to update and improve flood plain mapping, said Ceil Strauss, state flood plain coordinator for the Department of Natural Resources.

In Minnesota, she said, the effect of the update, which calculates runoff from a 100-year flood, varies by county. In Washington County, twice as many properties were removed from flood zones as went in. But in other counties, flood plains were added around lakes, affecting more property owners.

In Hennepin County, updated mapping provided more detail on elevation, changing the boundaries of flood plains along Minnehaha and Nine Mile creeks, Strauss said.

“There are winners and losers there from the perspective of homeowners,” she said.

‘Onus on homeowners’

When new flood plain maps come out, banks that finance mortgages hire third-party “determination companies” that check maps to figure whether homeowners are living on a lot that’s part of a flood plain. Usually, they don’t look at the elevation of the dwelling. So homeowners may be notified that they are required to get flood insurance even if the house is 20 feet higher than the creek.

“It puts the onus on homeowners to prove otherwise,” Strauss said.

Challenges to flood plain maps are usually done by individual property owners, who hire a surveyor to prove that buildings are outside the reach of a flood. Edina took the unusual move of hiring Barr Engineering on behalf of homeowners, at a cost not to exceed $30,500.

Adler said the city got involved because so many residents were affected and the technical nature of fighting the flood designation. Also, she said, some of the flood plain boundaries are different from work the city has done.

Data will be re-examined in:

• Rolling Green, just south of Meadowbrook Golf Course. About 80 homes in the area, some valued at more than $1 million, are now in a flood plain, apparently because of their proximity to Meadowbrook Lake and Minnehaha Creek.

• Nine Mile Village, just east of Bredesen Park and north of Crosstown Hwy. 62, where Mud Lake and Nine Mile Creek are nearby and water travels in a ditch along the Crosstown and could spill into the area. About 24 townhouses are affected.

• Morningside, where an area around a pond had long been defined as a flood plain. That area has been enlarged, and the city questions whether the border is correct. Sixteen properties could be removed from the flood plain if the border were redrawn.

‘Waiting to see what happens’

For homeowners in Edina, a change in flood plain zones could hit particularly hard, because the city is in the midst of a teardown frenzy. Edina has been tightening its standards for new housing, including limiting heights and elevations.

“If you’re in the floodway next to the creek, you can’t put fill there and you couldn’t put an addition in the floodway because you’d be taking up storage space for the water,” Adler said. “We just want to make sure the model we have is correct.”

Affected residents have been invited to an informational meeting with the city this week. Radcliffe, president of the Nine Mile Village Townhouse Association, said her fellow residents are as surprised as she is.

“We’re at the point of waiting to see what happens,” she said. “I’m glad the city is taking the lead on this ... looking at this, rather than just saying, ‘That’s the way it is.’ ”