The city of Charleston, which worked diligently to establish an urban growth boundary for Johns Island, well, it changed its mind.

On Tuesday, City Council agreed to permit 462 units on a piece of property zoned for 350. It also said OK to adding retail, warehouse, assisted living and commercial businesses to what was initially to be residential only.

All this on a 462-acre tract near River and Plow Ground roads that is outside the urban growth boundary designed to prevent sprawl.

All this despite public support to respect the urban growth boundary as a way to maintain the rural character of Johns Island.

And all this despite the city Planning Commission’s unanimous decision to reject the additional density.

If that isn’t enough of a head-scratcher, consider this: The city of Charleston spent about five years and a lot of money in court defending the lower density of that same piece of property, which it had previously down-zoned to limit prospective development. And it won. But that was then. Now, well, things are different, it seems.

City Council, with a hard-fought court decision in its pocket, decided to go along with the property owners it had just defeated.

Chief city planner Tim Keane encouraged the change, saying the new plan would be preferable in that buildings could be clustered instead of spread out, one house on each acre and a half.

Clustering can be a better way to maintain open space, but in this case, the number of units grows by 30 percent. Adding commercial uses adds traffic and noise, and seems sure to erode the rural feel even more.

When Charleston annexed land on Johns Island, residents feared that their island would come to look like James Island, more dense and less green.

Over the years, the city has reassured Johns Islanders by first implementing and then supporting the urban growth boundary, which is intended to protect rural areas and direct development to areas that are already urbanizing.

It is understandable that some feel betrayed and angry at this recent change.

Mr. Keane said that the boundary does not say “no growth” on the rural side of the line, only that it is less dense than urban areas.

But the density that the city has served up willingly to the developer is still more dense than it needs to be — substantially so.

The city has been trying to rally support on the island for the completion of I-526, despite the development that is sure to follow that project. Its dubious action on this rezoning could shake people’s trust in city promises.

And cause the Planning Commission to question its role in city government.

And make residents think their voices aren’t been heard.

And chisel away at the rural character remaining on Johns Island.