How the flooding flows: Study reveals patterns in northern Wisconsin

Feb. 05--A two-year study of seven counties in northern Wisconsin revealed patterns in the way the region floods.

Northwest Regional Planning Commission recently completed the study with funding from the U.S. Economic Development Administration, Wisconsin Economic Development Corporation and Northwest Regional Planning in Spooner.

Using data for Ashland, Bayfield, Burnett, Douglas, Iron, Sawyer and Washburn counties, and modeling a large-scale flooding event, the study revealed where flooding would likely occur and the depths water could reach.

"It is really detailed and models the landscape quite well," said Cody Kamrowski, community development planner at Northwest Regional Planning. "We virtually mapped seven counties and then we flooded them with this Hazus (modeling) software. And then we looked at structures, facilities. What is critical with doing this study is to look at recommendations and ways to move forward."

The full 350-page report on the study includes recommendations and mitigation strategies.

The Hazus software, derived through the Federal Emergency Management Agency, can help generate the estimated losses from earthquakes, floods and wind.

For the study, a model of the land surface was created using topographic and lidar data to understand the direction of water flow. Then layers were added, including roads, bridges, culverts, homes, businesses and other structures.

The information was put together to determine where the flood inundation would occur. The study identified individual structures by class, such as a two-story residential home, and included tax parcel data to help estimate potential losses during a flood event. The models generated data for a 100-year storm and 500-year storm to determine the impact.

"If you have 4 inches of water versus 4 feet of water, that really changes up the damage on that property," Kamrowski said.

"We had seven counties that were affected in the 2016 presidential disaster declaration, and Douglas County was one of those counties affected ... on top of this 2016 event, we know we had the 2018 event, which caused a lot of damage," Kamrowski said.

In 2016, Douglas County experienced some damage to structures -- homes and business -- and there was significant road and infrastructure damage, but Iron County had the highest public infrastructure damage, largely driven by $10 million in project costs to repair Saxon Harbor, Kamrowski said.

"We're looking at several different parts and components," he said. "We have structural impacts, so we have our homes and businesses. Then we have our public infrastructure impacts. Roads and bridges is a component of this, but we have other public infrastructure -- Saxon Harbor, a wastewater treatment plant, and then transportation systems. Are roads passable or is there a disruption?"

He said the study also looked at the health consequences of flooding.

And it's data Northwest Regional Planning is making available to the public at nwrpc.com.

Clem Larson, geographic information specialist for Northwest Regional Planning, said he's also assembling a user guide to help residents in the region search for address-specific impacts. The public can research specific buildings and view aerial imagery, he said.

When compared to FEMA maps, the data generated by the study was really close, Kamrowski said, but noted that there's "no regulatory teeth" to the study.

"Insurance companies can't be using it," he said. "You can't change a zoning based off of it. The firm maps from FEMA are the supreme law of the land when it comes to flooding information."

However, the information can be used for planning -- disaster response, hazard mitigation or even in constructing infrastructure -- to inform decision-making and raise awareness, and to guide recovery, he said.

"Northwest Wisconsin has been significantly affected by flooding," Kamrowski said. "If the counties really beef up their hazard mitigation plans and put a lot of flooding information into them, Wisconsin Emergency Management, FEMA, might be more willing to throw grant funding as a way to help these counties ... they're taking it more seriously."

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