Borough planning commission hears update on Tanana River flood study

The Fairbanks North Star Borough Planning Commission received an update on a major floodplain study last week from borough staff.

Adam Pruett, the borough floodplain administrator, said the Tanana River Flood study is an update to the 2020 version by the Federal Emergency Management Agency's Flood Insurance Study program.

"Fairbanks is prone to flooding," said borough planner Adam Pruett. "Local communities manage their floodplains ... it's up to the local government to enforce those rules and educate the community."

Pruett noted that borough voters approved the borough's adoption of flood control powers in an Oct. 5, 1965, election, nearly two years before the August 1967 flood.

Pruett said that the chances of another massive flood such as the 1967 flood is extremely low, but it's still possible with the Tanana and Chena Rivers.

"One of the things to keep in mind with flood management and the Flood Insurance Plan is that visualizing the damage is a big part so that people can take the information and operationalize it," Pruett said.

The updated flood study includes 523 miles of newly mapped or remapped streams and waterways

Pruett noted the 1967 flood prompted Congress to fund the Chena River Lakes Flood Control Project, built over 11 years starting in 1973. Pruett said the project was planned since the 1930s, but failed to gain traction until after the flood.

The borough is responsible for the flood control project levee's maintenance and certification. If the levee were ever removed, just over 21,200 homes and properties are in the Tanaan River's floodplain would be in a high flood-risk area.

With the levee in place, only 11,592 properties are considered in to be in a high-risk flood area, or about 21.5% of the 54,000 properties in the borough

Updating the floodplain management plan has several layers, including hydrological and weather patterns.

"People had to actually go up and down the Tanana River or anywhere there was a floodway measuring streams," Pruett said.

The floodplain plan regulates development in a floodplain zone, including minimum base flood elevation based on a 100-year flood chance. Different areas of the borough have different elevations.

"We are trying to make sure people protect their property by building above the minimum level or at least taking the methods that are in consideration," Pruett said.

A home with a 30-year mortgage still has a one in four chance of being flooded over the home loan's period.

Pruett said while participation in the flood insurance program is voluntary, it was critical for a community the size of the borough.

Homes or businesses built in a special flood hazard area require a floodplain advisory and building specs must demonstrate a base flood elevation and that it won't be negatively impacted by flood waters. The base flood elevation factors in a 100-year-flood event.

"We try to ensure that we educate owners and that they are above that base flood elevation or where that water will reach during that 100-year event," Pruett said. "You won't be in compliance unless you're at least above the base flood elevation."

Spillman, the borough's community planning director, said the borough noticed huge changes when it received updated maps from FEMA, including in the Salcha area.

"The whole community of Salcha was being brought into the flood zone and those base flood elevations were going up significantly, in some areas a 10-foot change," Spillman said.

Spillman said the FEMA maps lacked the necessary topography data needed to justify the floodplain area, prompting the borough to update the information.

"The reason why we did the entire Tanana River was because the data we had was so bad that we couldn't just do a portion of it," Spillman said. "We needed to remap the entire Tanana in the borough."

Spillman said the updated Tanana River floodplain management plan will remove significantly more areas out of the floodplain level and will lower the base flood elevation.

"We have better data and a more accurate model to map the area," Spillman said. "This will have a much more positive benefit, particularly out in the Salcha area."

Other areas, such as the Eielson Farm Road and Chena Pump Road community, could come out of the flood zone.

Pruett said about 932 homes will be removed from the high-risk flood area, while 318 will be folded into the designation.

"It is unfortunate in that flood insurance will become a requirement when people get a mortgage, but ultimately they will be able to mitigate any hazard with that knowledge," Pruett said.

Participation comes with federally-backed flood insurance, access to federal grants and loans, mortgage insurance and loan guarantees and disaster aid. Withdrawing from the program means federal assistance becomes more difficult to access.

Spillman stressed the insurance program's federal funding component.

"You cannot get a federally-backed mortgage if you own a property in a flood zone without flood insurance," Spillman said.

Spillman said that homes and businesses in high-risk flood areas must have flood insurance if owners have a federally regulated or insured lender.

Spillman said some private lenders offer flood insurance besides the national program, but it has a higher rate.

"One of the most important pieces of our economy is being able to sell those properties and having the option of that federally-backed mortgage and the Flood Insurance Program," Spillman said.

Pruett said the base flood elevation effectively drives insurance premiums. Homes built four feet below elevation have a $9,500 annual premium, while homes built at elevation have a $1,410 premium. Homes built three feet above the elevation rate average a $427 annual premium.

Spillman noted that technology has improved the floodplain accuracy over the years. Thirty years ago, the borough was using contour maps but now implements the use of LiDAR technology to generate better elevation mapping.

Spillman used the Chena Slough flood study update as an example. He said as early as the 1990s, the borough believed the flood data was overstated.

"With FEMA we initiated a study of Chena Slough and we got this detailed topography information and we got a new flood zone adopted for Chena Badger Slough," Spillman said.

For Badger Road area residents who live near Chena Slough, he said the number of impacted properties dropped from 767 to 636. The number of structures completely within the flood zone dropped from 372 to 12; those partially in the flood zone went from 524 to 33 structures.

"This is important because we are saving property owners millions of dollars because of this," Spillman said.

Spillman said his department will conduct a "roadshow" about the plan this summer as it comes close to completion, including in Salcha, Chena Pump and Moose Creek.