Climate change may be the subject of debate in some places but in South Florida it’s become a costly reality.

In Miami Beach, where prolonged flooding in low-lying neighborhoods has become the norm after heavy storms, city leaders are weighing a $206 million overhaul of an antiquated drainage system increasingly compromised by rising sea level.

The plan calls for more pumps, wells to store storm runoff, higher sea walls and “back-flow’’ preventers for drain pipes flowing into Biscayne Bay. Those devices are intended to stop the system from producing the reverse effect it often does now. During seasonal high tides, the salty bay regularly puddles up from sewer grates in dozens of spots, such as near the local westside bar Purdy Lounge. Extreme high tides — like one in October 2010 — can push in enough sea water to make streets impassable, including blocks of the prime artery of Alton Road.

“It’s the first time, as far as I know, that any community in South Florida and actually in the entire state of Florida is taking into account sea level rise as they plan their storm water infrastructure,” said Fred Beckmann, the city’s public works director, during a public hearing on the plan earlier this month.

It won’t be the last time.

South Florida counties and cities, as well as the South Florida Water Management District which oversees flood control for the region, all are beginning to draw up projects for keeping the coastline dry as sea level creeps up. The potential costs could be staggering.

The district alone has identified three flood control gates along coastal Northeast Miami-Dade — critical to draining storm water from Pembroke Pines and Miramar in southwestern Broward — in fast need of retrofitting with massive pumps. Rising seas threaten to reduce the capacity of a system that now depends on gravity, the storm water flowing downhill into the Atlantic. Cost estimates run $50 million or more for each pump alone and buying land for them could double or triple the bill. Nine other gates could need similar work down the road.

Fort Lauderdale, where high tides also push salt water up storm drains in the ritzy Las Olas Isles section, is also planning to install back-flow preventers, said Jennifer Jurado, director of Broward’s environmental protection and growth management department. Hallandale Beach already had to install pumps on storm-water injection wells, at about $10 million each, to combat increasing back-pressure, she said.

“The overall issues are so much greater, I think we’re easily looking at hundreds of millions of dollars,’’ she said. That’s just for the next 20 to 30 years, to handle a moderate three to seven inch rise.

A study last year by the Florida Atlantic University Center for Environmental Studies found that the projected rise over the next 70 to 100 years would require one city alone, Pompano Beach, to spend from $500 million to $1 billion to overhaul drainage and water supply systems, as well as coastal roads and facilities.

“If 50 years from now we’re looking at a foot and a half or two feet and rising, our region is going to be confronted with some very serious problems,’’ said Barry Heimlich, an FAU researcher who co-authored the study. “It’s going to cost hundreds of billions of dollars.’’