Building in N.E. coastal risk zones continues apace

From ecoRI News (ecori.org)

As the country’s coastal communities continue to build homes in flood-risk zones, a new nationwide analysis by Climate Central shows that nearly 20,000 homes built in the past decade are at significant risk of chronic coastal flooding by 2050.

If greenhouse-gas emissions go unchecked, more than 800,000 existing homes worth $451 billion will be at risk in a 10-year flood by 2050, according to Ocean at the Door: New Homes and the Rising Sea. Those numbers jump to 3.4 million existing homes worth $1.75 trillion by 2100.

The analysis paired Zillow’s housing data with Climate Central’s sea-level rise expertise to identify the number of new homes — and homes overall — in low-lying coastal areas. It then projected how many will become exposed to chronic ocean flooding over the coming decades, depending on the choices the world makes regarding greenhouse-gas pollution. It expanded on analysis done last year that showed some 386,000 U.S. homes are likely to be at risk of regular annual flooding by 2050 and that new homes are being built at striking rates in areas that face high risks of future flooding.

The recent analysis found that Connecticut (more than three times faster), Rhode Island (twice as fast), and Massachusetts are developing coastal risk zones more quickly than safer areas.

A third of the country’s coastal states have seen higher housing growth rates inside the 10 percent flood-risk zone than outside it.

As sea levels rise, the intermittent floods that coastal communities now experience once a decade on average are projected to reach farther inland than they do today. Those floods can damage and devalue homes, degrade infrastructure, wash out beaches, and interrupt transportation systems. They also put homeowners, renters, and investors in danger of steep personal and financial losses.

The results are clear. If the world makes moderate cuts to greenhouse-gas emissions — roughly in line with the Paris Agreement, whose targets the international community isn’t on track to meet — some 17,800 existing homes built after 2009 will face an at least 10 percent flood threat each year, on average, by 2050. The figures for 2100 are more than two times higher, and more than three times higher if climate pollution grows unchecked.

“For homebuyers over the next few years, the impact of climate change will be felt within the span of their 30-year mortgage,” said Skylar Olsen, Zillow’s director of economic research and outreach. “Without intervention, hundreds of thousands of coastal homes will experience regular flooding and the damage will cost billions. Given that a home is most people’s largest and longest-living asset, it takes only one major flood to wipe out a chunk of that long-growing equity. Rebuilding is expensive, so it’s doubly tragic that we continue to build brand new units in areas likely to flood.”

Coastal communities will encounter the impacts of sea-level rise to greatly varying degrees, depending on the local rate of rise, local tides and storms, the potential future development of coastal defenses, and the flatness of the landscape and where homes are built within it. Some major coastal cities sit high enough above sea level that the biggest hit will be to their beaches. Others will suffer more far-reaching and damaging effects.

Florida would have the most homes in the zone at risk from sea-level rise and 10-year floods by 2100 (1.58 million), followed by New Jersey (282,354), Virginia (167,090), Louisiana (157,050) and California (143,217) — assuming levees and other infrastructure defenses hold and emissions continue unchecked.

What’s more, 24 cities including New York, Tampa and Virginia Beach have built at least 100 homes in that risk zone since 2009.

“In many states, building on land projected by 2050 to face chronic flood risks has outpaced development in safer places,” said Benjamin Strauss, Climate Central’s CEO and chief scientist. “Failure to control climate pollution will lead to faster-rising seas and bigger coastal risk zones, but building a cleaner-running economy can still reduce these consequences.”

Flooding in Marblehead, Mass., caused by Hurricane Sandy on Oct. 29, 2012