Hundreds of Woodbury residents will have to buy flood insurance -- or take steps to prove they don't need it -- under a new federally mandated ordinance passed on a 5-0 vote by the City Council on Wednesday night.

It's a move that probably will catch many of those residents by surprise.

The new floodplain ordinance culminates a nine-year effort by the city to identify and map flood-prone properties under the Federal Emergency Management Agency's National Flood Insurance Program (NFIP), said Klayton Eckles, Woodbury's city engineer.

FEMA's mapping and study identified slightly more than 500 parcels considered to be in flood hazard zones, of which 460 are residential properties, Eckles said. The rest are utilities, commercial properties or farmland.

The vast majority of residential property, about 450 of those parcels, is well above the flood elevation, Eckles added. But the entire property doesn't have to be in the defined flood hazard zone. If even a small portion of a property is in the zone, it's considered a flood hazard.

That's why so many more properties are now falling under the floodplain ordinance -- and why homeowners may be caught off guard.

A 2009 analysis by FEMA showed there were 22 flood insurance policies in the city of Woodbury, and not a single claim had been paid dating from 1978. In all of Washington County, there were 410 policies, mostly in communities along the St. Croix River.

FEMA mandates that homeowners have flood insurance if they live in areas deemed hazardous, but there are two ways for homeowners to opt out.

The more informal of the processes verifies that no structures on a property are actually threatened by flooding. The second, a "letter of map amendment," is more involved, and may require a survey and other steps to get an exemption.

Woodbury had until next Wednesday to get the new floodplain ordinance in place, a timetable dictated by the completion of FEMA's mapping process. Failing to pass the ordinance would have led the city to be suspended from the NFIP. And getting suspended from the NFIP has serious consequences, Eckles said.

If a community is suspended, no flood insurance policies can be written or renewed within the community. That means mortgages regulated by federal agencies, which is virtually all of them (including refinancing loans and home equity loans), will stop being processed for properties considered to be in the flood hazard zone.

On the other hand, being in the NFIP is ultimately an advantage for the city and its property owners. Insurance rates are better, Eckles said, and the ordinance spelling out what can and can't be done in flood-prone areas is backed by the new maps.

Recognizing the complexities of the new floodplain ordinance, the City Council is including an information program for homeowners who are affected, along with assistance in getting the exemptions. More information will be available on the city's website: www.ci.woodbury.mn.us.

Jim Anderson • 612-673-7199