Floodplain mapping makes progress in Eastern Iowa

BY DORA GROTE | MARCH 06, 2012 6:30 AM

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Iowa water-resource officials say research progress is accelerating after they established effective methods for the Iowa Floodplain Mapping Project.

"The first year was a learning experience, trying to make sure we had a good process in place, hire staff, and do other things," said Nathan Young, an associate research scientist/engineer for the Iowa Flood Center. "There was a start-up period. We were not as productive as we will be in future."

The team, established following the catastrophic 2008 floods, began digitizing Iowa floodplains last year.

Following 2008, Housing and Urban Development disaster-relief funds granted the Iowa Flood Center $8.8 million to create floodplain maps for the 85 counties declared federal disaster areas in collaboration with the Iowa Department of Natural Resources. The research team has spent $2.4 million on the project so far. Work will begin in Iowa City next year, Young said.

Last year, the Omaha District Army Corps of Engineers and Iowa Natural Resources agreed to provide roughly $4 million to fund the remaining 14 counties.

The floodplain maps — expected to be completed by 2015 — are used to show flood-hazard areas and minimize flood damage to property, said Young, who is leading the project.

"The biggest difficulty is managing such a large data set," he said. "We're covering such an enormous area and generating a lot of data, but it came as an unexpected challenge."

The project funds 13 full-time University of Iowa research staff and nine UI graduate and undergraduate students.

Project coordinators met last week to update and re-evaluate the mapping plan based on watersheds, said Scott Ralston, the Natural Resources floodplain-mapping coordinator. The project started in the southwest part of the state, he said.

"There are seven watersheds that we basically said we don't need to worry about, and they went out of the picture," Ralston said, referring to the recent agreement between the Army Corps of Engineers and Natural Resources. "We remapped the rest of it. The boundaries change between years a little bit. We moved around some areas; FEMA had some funds there to do work that it didn't have originally."

The mapping of Iowa's 56 watersheds is based on state Lidar data, an area survey of the land using lasers. The mapping uses hydrography — which measures the depth of the watersheds — and hydrologic analyses to estimate how much flow to expect on a given stream or river. Hydraulic computer modules predict the depth and extent of flooding based on the estimates.

"If you understand where you're at in association to the floodplains, it helps you make a better decision on where to live, what type of business you might own, or what the community should do with that land," said Flood Center Managing Director Carmen Langel.

Connie Wisniewski, a senior natural-hazards program specialist with FEMA, said the updated digitized floodplain maps will determine flood-insurance costs.

The collaboration between Natural Resources and the Iowa Flood Center has also sparked new projects, Young said.

"We work a lot with the engineering research, and [Natural Resources] knows more of the governmental issues," he said. "The complementary relationship has also fostered some other collaborations on other projects including the stream-sensor project."

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