Charleston Flooding (copy) (copy)

Passersby during a period of rainfall in December 2018, as seen on Vanderhorst Street. File/Brad Nettles/Staff

Homes with persistent or severe flooding problems need to either be fixed to prevent future problems or torn down. The alternative is a costly headache at best and a potentially dangerous situation at worst.

Charleston officials have a responsibility to track when a home is so severely damaged — when repairs cost 50% or more of the home’s value, a threshold referred to as “substantially damaged” — to either force improvements or start a buyout and demolition process.

As The Post and Courier’s Chloe Johnson and Stephen Hobbs reported Sunday, major flood damage sometimes slips through the cracks, which means that problems don’t get fixed and people remain in vulnerable houses.

Failure to accurately monitor flood-prone homes also ends up costing taxpayers and homeowners who buy flood insurance through the National Flood Insurance Program, which is more than $20 billion in debt, by wasting money repairing homes that will inevitably flood again.

Our reporters found five Charleston properties that likely had crossed the substantial damage threshold, but weren’t in city records for tracking flood problems.

Obviously, this is a concern.

Just as concerning is the fact that city officials can’t legally use the NFIP insurance claim data that enabled The Post and Courier to make a determination of substantial damage, despite those records easily being the single most comprehensive source about past flood problems.

Instead, city officials have to drive around after a flood and eyeball properties that they think might have been damaged. They can inspect houses if the owners let them inside. And then they use software that estimates the cost of damage based on property value, water level and other factors.

This is an incredibly imprecise way to figure out the toll from a flood, and it works about as well as one might expect.

Flood insurance claims data aren’t a perfect measure either. Some people might not file a claim after damage, or the numbers might not accurately reflect the actual cost of the repairs. But that information would still be a lot more useful than an educated guess.

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Federal privacy rules protect NFIP data on specific homes. Those rules must be loosened in order to better protect people who live in vulnerable houses — and people who might unwittingly buy one — while also helping to shore up the flood insurance program’s finances.

It’s difficult to get a completely accurate picture of specific flooding problems. Collecting the necessary information is a logistical challenge, and there are financial incentives and communication problems that likely cause under-reporting.

That’s why it’s crucial that city officials be able to use all of the information available to them. And it’s important that they aggressively track and crosscheck as much new data as possible.

Flooding is perhaps the single most serious threat Charleston faces. We can’t hope to fix it if we don’t know what needs fixing.