Johns Island Moratorium (copy) (copy)

Construction workers build houses on Johns Island in February. A proposed new neighborhood on the island is zoned for light industry, which allows a significant residential component under city rules.

The more we learn about the geology and hydrology of Johns Island the more we learn what really should have been obvious all along: It’s just not a very good place for intensive residential development.

The island, the fourth-largest on the East Coast, is a series of dunes that turned into barrier islands as sea levels receded millions of years ago and then fossilized into a contiguous piece of land in the relatively recent past, at least in terms of the age of the planet.

As such, it would only take a particularly strong storm or, say, the long-term prospect of significantly higher seas to turn Johns Island back into much wetter terrain. That’s an obvious risk for current and future residents.

Unfortunately, a substantial portion of undeveloped Johns Island is inside the urban growth boundary, and much of it is zoned for surprisingly high-density development.

The latest case in point is a proposed new neighborhood near the airport on Johns Island, which would put about 240 homes and some commercial properties in a critical watershed on what is now wooded land.

Looking purely at the numbers, this isn’t an especially large development compared to others planned or permitted on the island. But it could have been. And that’s perhaps the most alarming issue.

Much of the property in question is zoned light industrial. That seems reasonable enough given its proximity to the airport and the practicality of zoning for warehouses or other supporting facilities nearby.

Charleston’s zoning code, however, allows a shockingly intensive amount of residential development in light industrial zones. Developers could have asked to build up to 19 units per acre closer to 2,000 homes on the same piece of property.

Compared to that scenario, 240 houses is something of a win. And that’s, of course, part of how the developer is selling plans to city officials.

There were a couple of chances to derail this and similar messes in the past few years.

Last spring, Mayor John Tecklenburg pushed for a temporary building moratorium in flood-prone parts of Johns Island as a chance to rethink stormwater rules. City Council said no.

This year, city staff painstakingly reviewed industrial zones citywide and proposed a comprehensive overhaul that would remove any existing housing component. City Council denied it.

Get a weekly recap of South Carolina opinion and analysis from The Post and Courier in your inbox on Monday evenings.

Both opportunities would have been legally defensible ways to demand a development less likely to exacerbate flooding problems and livability concerns on Johns Island. Now, city officials have fewer options to say “no.”

And this is an issue worth attention across the entire region. Zoning may be dull, bureaucratic and impenetrable, but it’s also one of the most powerful tools for protecting ecologically sensitive and vulnerable areas from overdevelopment.

In too many cases, public officials wait until it’s far too late to address problematic zoning. Planning documents have suggested sensible adjustments to how the city manages growth on Johns Island for at least a decade, for example.

And yet, here we are.

Charleston is a growing, dynamic place with lots of mistakes to learn from and lots of new information to process. The rules have to keep up or they risk doing more harm than good.

We're improving out commenting experience.

We’ve temporarily removed comments from articles while we work on a new and better commenting experience. In the meantime, subscribers are encouraged to join the conversation at our Post and Courier Subscribers group on Facebook.