Charleston is on its way to enacting a flood protection measure that's already been adopted by other local jurisdictions, but some on City Council have concerns about the rule. 

On Tuesday, council voted 9-3 to require homes built in flood hazard areas be raised 2 feet above the Federal Emergency Management Agency's minimum elevation. Charleston County is among the governments that already follow that standard.

Currently, the city requires just 1 foot of additional "freeboard" above FEMA's base flood elevation, or the point it projects waters will reach in a flood zone.

The crux of the controversy is that the regulation doesn't just affect new homes — it would also apply to any existing home that has been substantially improved or substantially damaged. In both cases, the threshold to reach "substantial" is work that is equal to or more than 50 percent of the value of the home. 

Council members Keith Waring, Bill Moody and Harry Griffin opposed the proposal, and Councilman Robert Mitchell was absent. Council will have to approve it two more times before it takes effect, and at least two who voted in favor on Tuesday expressed serious concerns. 

Waring worried whether homeowners in low- to moderate-income neighborhoods would be challenged in a disaster because their homeowner insurance policies might not cover the full cost of rebuilding. He also urged that less valuable homes could reach the point of being substantially damaged more quickly. 

"Under a catastrophic loss type scenario — earthquake, Category 4, Category 5 type of thing — you’re going to have tons of people that are going to be underinsured," he said. 

Councilman Mike Seekings wondered if the requirement might lead to a rash of people raising their homes by trucking in fill dirt. Raising land with new dirt has been done increasingly in fast-growing outer edges of Charleston, but it removes the land's ability to retain water, contributing to flooding nearby.

Mayor John Tecklenburg supports the 2-foot freeboard in part because it will improve the city's flood insurance rating with FEMA, which could reduce local flood insurance premiums. Charleston property owners depend heavily on the program: Since 1978, about two-thirds of all the federal flood insurance claims made in South Carolina. 

"Long term, we’re going to have less damage, less claims, if we build higher," Tecklenburg said.

Raising homes reduces flooding risk, and a single foot can make a big difference. For example, the city of Houston found that three-quarters of the homes in its most vulnerable floodplain would have stayed dry if they had been a foot higher when Hurricane Harvey hit. 

Not all Charleston homes would be affected by the new rule: About half of the city falls into one of FEMA's special flood hazard areas where the regulation actually takes effect, said Stephen Julka, the city's floodplain manager. 

And historic homes on the peninsula already are variances, allowing owners to skip the elevation requirement. 

Some on the panel argued that was unfair to homeowners west of the Ashley River. Councilman Gary White suggested just applying the regulation to new homes.  

“If all of a sudden everybody gets a variance for the sake of not doing it when they replace, we haven't made any impact to existing structures, only new construction," White said. 

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Reach Chloe Johnson at 843-735-9985. Follow her on Twitter @_ChloeAJ.