How Developers Are Hedging Against the Risk of Rising Sea Levels

HYPERLOCAL

Rising sea levels are predicted to impact populations around the globe, but the United States is particularly at risk of large economic losses from the phenomenon.

Without improved infrastructure for defending against floods, annual U.S. flood losses could top $200 billion by 2050, according to a CBRE report published last year.

And, the report notes, commercial real estate owners will suffer a significant portion of these losses, with damage to their holdings potentially running in the range of $1 billion per year.

These sorts of projections have property owners considering new ways of protecting themselves against the rising waters, says Quinn Eddins, author of the report and CBRE’s director of research and analysis for the state of Florida.

In and of themselves, rising sea levels aren’t an immediate problem, Eddins notes. The most pressing issue is their role in exacerbating flooding during extreme weather events like hurricanes.

“It could take, say, 100 years for sea levels to rise however many feet is expected,” he says, “but rising sea levels are going to cause storm surges to reach new heights considerably earlier than that. So we will first feel the impact of sea level rise in the form of [increased] storm surges.”

That being the case, the most common approaches property owners are taking to protect themselves against rising sea levels involve managing these storm surges. And here, the emerging thinking is focused less on repelling flooding and more on making room for it.

The big [trend] is this idea of accommodating the flooding when it occurs. 

“So in your landscaping, you lay out your site so that there is a place for water to go,” Eddins says. “So what might be a landscape feature in normal times will become a water retention area in times of flooding. Likewise, you might design your building’s first floor with the understanding that it could become flooded in times of extreme weather.”

“The big [trend] is this idea of accommodating the flooding when it occurs,” he says.

This isn’t the only tack developers are taking, however. Eddins notes that in Miami, particularly on the luxury apartment and luxury single-family home side of the business, some builders are using a more oppositional approach, raising seawalls and site infills to stay above rising sea levels.

“Developers have actually just raised seawalls or even raised the elevation of the lot infill by four or five or six feet or more, and then built the [structure] on top of the raised lot,” he says.

Eddins also cites the example of Brickell City Centre, a new mixed-use Miami development that includes a subterranean parking lot designed to be impervious to water.

“That’s important in Miami because when sea levels do rise, they don’t just come in from the bay,” Eddins says. “We have a problem here of flooding coming up through the ground as well because Miami is built on basically petrified coral reefs that are porous.”

Of course, the lot will stay dry only until the time when sea levels rise enough to come in over the sides, he notes. “But you’re still looking at a number of decades for that to happen.”

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