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Elevating homes can flood neighbors. Will this move by Miami-Dade fix the problem?

Two next-door homes along the Miami River
Alex Harris
The Miami Herald
Two next-door homes along the Miami River show the impact of new building and elevation standards compared to older stock housing. Both homes are only one story, but the newer house appears nearly twice as tall as the older one.

It’s an increasingly common scene in South Florida: a brand new home, elevated to the newest building standards, rising above its older neighbors, houses that may have been built before flood maps even existed.

The complaint that follows is also happening more often, that the new home built higher for better flood protection is worsening flooding to surrounding homes, draining its runoff onto the lower properties.

A new code tweak in Miami-Dade, plus more to come, is designed to address that growing concern.

The twin drivers of increased flooding from sea level rise and a relentless real estate market have made the ripple effects of raising homes a particularly acute issue in Miami-Dade. New homes can be elevated as much as 10 feet above sea level — and a new push from the county requires new roads, canal banks and empty lots to be at least six feet above sea level.

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Building codes, at least on paper, already call for homes to hold onto the rain (also known as stormwater) that falls on their property, but a new tweak to the code will add a new layer of review by county officials intended to ensure it happens.

Commissioner Kevin Cabrera, who co-sponsored the legislation, said he hopes it will address the concerns of the “numerous” residents who’ve called and complained about the issue of flooding from adjacent properties.

“Taking these precautions is a proactive step toward safeguarding our neighborhoods. We are committed to ensuring that our residents’ safety and quality of life are not compromised by the effects of stormwater runoff,” he said in a statement.

That could, for instance, result in design changes, such as adding low walls between new higher construction and neighbors to retains or direct rainwater, said Marina Blanco-Pape, director of the county’s water management division.

“The fact that runoff should not be going onto adjacent properties, it’s already been in the code,” she said. “What hadn’t been, sometimes, is an explicit way of how do you get there. Is there an explicit way that can be provided so we’re more clear at how do we arrive at that outcome.”

The new policy, approved by Miami-Dade’s commission on Tuesday, is a first regulatory attempt to address the murky rules around what counts as flooding your neighbors.

A newer home in the River Oaks neighborhood of Fort Lauderdale is visibly elevated
Alex Harris
The Miami Herald
A newer home in the River Oaks neighborhood of Fort Lauderdale is visibly elevated compared to its older neighbors. Homes like this appear to have weathered the flood much better.

In recent decades, Florida has required newly built homes to handle all the rain that falls on their property themselves, a switch from old policies that allowed properties to drain excess rain — or stormwater — into the street. New developments are not allowed to cause “adverse impacts”, like flooding, to their neighbors.

However, floodplain management experts say, that can be tough to avoid in a state where powerful rainstorms, tidal floods and backed-up drainage systems are becoming more common. And, judging from the increasing complaints surrounding new construction in older neighborhoods, builders haven’t always designed site plans that meet the old code.

The problem is basic hydrology. Water flows downhill. When you elevate half the houses on a street, the water that used to settle evenly among them now concentrates on the lower-lying properties. To those residents, that’s flooding caused by new development. But that specific impact isn’t accounted for in building codes.

So far, this policy change only applies to unincorporated Miami-Dade, but Blanco-Pape said her team has been working on an overhaul of the building codes around flooding that they hope to debut soon. Potential changes include the amount of concrete versus green space on properties and how dirty the water pouring into canals and waterways is allowed to be. And, like the county push to elevate new roads and lots, it would apply to a broader swath of Miami-Dade.

“This outcome change today is one step, and what we’re bringing back to the board in hopefully a couple of months is the next one,” she said.

This story was produced in partnership with the Florida Climate Reporting Network, a multi-newsroom initiative founded by the Miami Herald, the South Florida Sun Sentinel, The Palm Beach Post, the Orlando Sentinel, WLRN Public Media and the Tampa Bay Times.

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