THE LOCAL NEWS OF THE MADISON VALLEY, RUBY VALLEY AND SURROUNDING AREAS

Alex Hogle demonstrating the difference between the base flood elevation and lowest adjacent grade in his office. PHOTO BY KEELY LARSON

Not so high & dry

Recap of recent floodplain mapping public meetings

Last week, the Federal Emergency Management Agency (FEMA) and the Montana Department of Natural Resources and Conservation (DNRC) in collaboration with Gallatin, Beaverhead, Jefferson and Madison Counties presented a series of public meetings to discuss new floodplain mapping on the Madison, Jefferson, South Boulder and Ruby-Beaverhead Rivers, along with Indian and Mill Creeks that run near Sheridan, Mont.

In Madison County, many floodplain maps are dated to the seventies and eighties, created by memory and by hand. Updated maps use more accurate topographic information, updated hydrology data and modern engineering methods to map flood risk areas. These rivers and creeks were chosen due to the age of the maps before the update and, in cases like the South Boulder River, where there was no mapping to begin with.

After the public meetings, members of the public have an opportunity to provide review and opinion on the draft maps. During the March meetings, DNRC representatives encouraged members of the public to do so before the appeal period begins—which requires much more technical data to be provided to FEMA—in late 2021. After public comment and appeals are reviewed and resolved, official flood insurance rate maps (FIRM) will be issued by FEMA, estimated 2022.

According to FEMA, the federal government became involved with floodplain management in the 1800s, “when it had an interest in maintaining the navigability of rivers to facilitate interstate commerce.” Flood Control Acts of 1928 and 1936 focused government agencies on building flood control structures, like dam or levees, to mitigate potential damage. Despite these control efforts, people continued to build in floodplains.

The National Flood Insurance Program (NFIP) of 1968 established an insurance program, distributed floodplain management responsibility to all levels of government and the private sector, set a national standard for development in floodplains and began comprehensive floodplain mapping.

Under updated mapping, many preexisting structures in Madison County may end up inside the 100-year floodplain. Representatives from the DNRC during the public meetings said it is best to think about that number not as the possibility that a flood will happen once in 100 years, but that there is a 1% chance an area in the 100-year floodplain will flood each year. A 500-year floodplain represents a 0.2% annual chance of a flood and is not currently regulated.

How impactful that 1% flood may be depends on where a structure is located.

According to the Commissioner of Securities and Insurance (CSI) office for the state of Montana, in a 30-year mortgage for a home within a 100-year floodplain, property owners are 27 times more likely to experience a flood than a fire.

A floodway, inside the 100-year floodplain, is the most developmentally restrictive portion of the floodplain. During a flood, the floodway would be most directly impacted by the deluge, becoming an active channel. No new residential structures can be built in this area.

Residential structures sit in the floodway of Mill Creek in Sheridan, according to the draft maps. These structures would remain and be recognized as pre-firm structures, or those that existed before new mapping commenced. However, if they were not insured before, flood insurance will be required once draft maps are finalized.

Alex Hogle, Madison County planning director and floodplain administer, explained that contrary to what might seem obvious, these rates are not necessarily sky-high. Hogle understood the mapping of Indian Creek as more of a proactive measure—putting the FIRM panels in place due to the potential for future development.

FEMA offers cost saving insurance options for homeowners newly mapped into a floodplain and it is recommended flood insurance be purchased either before or within 11 months of a new FIRM panel going into effect.

In a 100-year floodplain, floodplain development permits (FDP) must be obtained in Madison County for new construction as well as for improvements to existing structures.

As far as Twin Bridges goes, two structures above and below Highway 41 were created to mitigate any potential flooding, an example of a type of action taken after the Flood Control Acts were signed into law. These structures are not formally recognized by FEMA.

The Town of Twin Bridges is working with Great West Engineering, who functions as the town’s floodplain administrator, to get the structures recognized. Without recognition, homes along the Jefferson River in Twin Bridges will be mapped into the 100-year floodplain and would require flood insurance once the FIRM panels are finalized.

Conversations between Twin Bridges and FEMA and the Army Corps of Engineers have begun. If recognized, the structures could be added to the draft mapping and leave flood risk and insurance rates relatively as they are.

According to current floodplain regulations, a home must be two feet above the BFE to be complaint. Hogle explained in some cases, homeowners can get a permit to fill the space between the ground and BFE, basically creating an island.

This homemade island puts one’s home above the BFE and uses specific materials that are able to handle erosive forces in-between a home and the water. Hogle expects realtors, residents, builders and insurance companies to become more familiar with this practice in Madison County as population grows.

“We have to adjust,” he said.

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The Madisonian

65 N. MT Hwy 287
Ennis, MT 59729
406-682-7755
www.madisoniannews.com

Cori Koenig, editor: editor@madisoniannews.com
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