It would be a massive, highly controversial wall sure to cost billions of dollars. But this barrier would be much closer to home — and potentially more expensive — than the one President Trump has proposed along the Mexican border.

As rising sea levels pose a growing threat to Boston’s future, city officials are exploring the feasibility of building a vast sea barrier from Hull to Deer Island, forming a protective arc around Boston Harbor.

The idea, raised in a recent city report on the local risks of climate change, sounds like a pipe dream, a project that could rival the Big Dig in complexity and cost. It’s just one of several options, but the sea wall proposal is now under serious study by a team of some of the region’s top scientists and engineers, who recently received a major grant to pursue their research.

With forecasts indicating that Boston could experience routine flooding in the coming decades, threatening some 90,000 residents and $80 billion worth of real estate, city officials say it would be foolish not to consider aggressive action, no matter how daunting.

Restricted tidal flow