Hill County floodplain study about to start

The Montana Silver Jackets, Montana Department of Natural Resources and Conservation and the Hill County government teamed up to provide a floodplain mapping update at a meeting in Havre Tuesday.

DRNC Floodplain Outreach Specialist Nadene Wadsworth said that she was was in Havre Tuesday to announce when she was in Hill County in January, Hill County applied for a grant from the Federal Emergency Management Agency and was here Tuesday to say they received it.

“What is the purpose of floodplain mapping? Essentially, it is to help identify that risk,” she said. “The risk that is identified on the maps will essentially help keep people and property out of harm’s way.”

She said they do identify these areas on the maps by working with the county and the city and FEMA to help identify areas of risk.

The Silver Jackets is an interagency team, comprising federal, state and local partners, with the goal to reduce flood risk for Montana communities, Montana Silver Jackets team leader Worby McNamee said.

“The way that we go about that is, we partner up with communities across Montana and we provide them through, (U.S. Army Corps of Engineers), funding and opportunity to take a look at various flood risks,” he said. “In this case, the Hill County commissioners sent a letter of support to the Montana Silver Jackets to submit a proposal for a flood risk project.”

McNamee said that, in March, a proposal was sent to the Army Corps’ Omaha District for funding and in August they were notified that the funding had been delayed, but later received notification that in the new fiscal year the proposal was awarded.

“To go over that project, it is a two-component project that has an end result of one model that can be used for updating emergency action plans and evacuation routes,” he said.

He provided a screenshot during his presentation showing an image of the program that the Army Corps did in Glendive, including proprietary software called LifeSim that simulates a levee breach. The program would simulate a levee breach at various points based off of any low-lying area or weaknesses the engineers might find in a levee analysis, he said

He added that what LifeSim does, instead of  giving a flood inundation map that gives depths right off the bat, is use shading to and how show, the deeper water. Also it shows the inundation of an area. Through the course of time, what areas are cut off, what the timing would be for certain evacuation scenarios and then, in the event of a catastrophe, the potential of loss of life based on those factors, he said.

He said that from start to finish the model project in Glendive took eight months to a year.

“In this case, the Hill County levee and Army Corps crews have already been out to survey it a little bit and they’ll run a hydraulic model and they’ll look at the hydrology and that’s how they get to the end result of this kind of model,” McNamee said. “The findings can be to update evacuation routes or an emergency action plan, so that in a nutshell is what the Hill County commissioners expressed interested in receiving and what the proposed Montana Silver Jackets action will be for Hill County.”

He said, besides the model, the Silver Jackets provide an all-inclusive report  that will have components that can be updated on and will point to potential legal issues for areas that the county might want to look into and will also provide steps or a framework for updating that emergency action plan.

“One of the key factors to this is because it’s working with other agencies and things like that, the Montana Silver Jackets is able to provide this to Hill County with no cost to the community,” McNamee said. “This is just merely looking at in this particular case it would be looking at the county-owned portion of the levee here in Havre.”

Other key highlights of this proposal, he said, are:

• The LifeSim model that is developed from the Corps of Engineers provides the community a look at risk areas and shows the flood event in terms of  loss-of-life

• Mitigation areas to reduce potential damage and problems can be developed through information that is evolved during the project.

People who have any questions or need more information about the Hill County Montana Silver Jackets project can contact McNamee at [email protected] or can call him at 406-444-1343.

He said he is hoping to start moving forward with this project at the beginning of next year.

Wadsworth said the floodplain maps will be focused on what is called a 100-year flood event, the worst floods likely to happen in 100 years with a 1-in-100 chance of occurring.

Hill County floodplain ,maps made in 1978, and were last revised in 1988.

Wadsworth said the new information that was incorporated in the 1988 revision was a limited study on five miles of the Milk River downstream of Highway 232 and along portions of Big Sandy and Beaver Creeks.

“Floodplains maps today are what we call flood insurance rate maps and, essentially, they are used by lots of organizations,” she said. “They are used by the county for building standards and the city because the county and the regulate to their floodplain ordinances. They are used by your local emergency management. They are used by the planners. They are used by insurance agents to help set those insurance premiums. They are also used by lenders to determine if a mortgage they are willing to finance if that structure is at risk.”

She added that the maps need to be updated periodically so that they reflect the most current risk. 

She said important things to know are: 

• A website will be developed and will be as they move through the projects, which will be online at  http://www.floodplain.mt.gov/milkriver . Wadsworth said she will announce the website release once the project begins.

• DNRC will work with communities and provide updates throughout the project.

• Physical changes to bridges/culverts and the floodplain can affect the study, and communities should keep DNRC updated of any changes during the project

• DNRC plans to work with the communities to host public open house meetings for landowners to view/draft preliminary maps once they are produced.

• Flood studies can take many years to complete.

Wadsworth said the next step is that the city of Havre should form a local levee committee that can help navigate the decision-making processes during the next mapping update.