Flooding on the bay  on Chadwick Breach Island, N.J. on Tuesday, Oct. 30, 2012 after Hurricane Sandy made landfall. (AP Photo/New Jersey Governor’s Office, Tim Larsen)

President Obama issued an executive order Friday directing federal agencies to adopt stricter building and siting standards to reflect scientific projections that future flooding will be more frequent and intense due to climate change.

The order represents a major shift for the federal government: while the Federal Emergency Management Administration published a memo three years ago saying it would take global warming into account when preparing for more severe storms, most agencies continue to rely on historic data rather than future projections for building projects.

The new standard gives agencies three options for establishing the flood elevation and hazard area they use in siting, design and construction of federal projects. They can use data and methods “informed by best-available, actionable climate science”; build two feet above the 100-year flood elevation for standard projects and three feet above for critical buildings such as hospitals and evacuation centers; or build to the 500-year flood elevation.

The White House move comes just days after the U.S. Army Corps of Engineers released a massive post-Sandy report examining flood risks for 31,200 miles of the North Atlantic coast. The research explicitly took sea level rise induced by climate change into account, and finds that “Flood risk is increasing for coastal populations and supporting infrastructure.”


Figure from the new U.S. Army Corps of Engineers report on flood risks to the North Atlantic coast, showing sea level rise scenarios for Sandy Hook, N.J. Source: U.S. Army Corps of Engineers

Last month, the National Oceanic and Atmospheric Administration predicted coastal areas will face 30 or more days of flooding by mid-century due to sea level rise. According to the National Climate Assessment, more than $1 trillion of property and structures in the United States are at risk of inundation from sea level rise of two feet above current sea level — an elevation that could be reached by that same point.

Despite these threats. Americans continue to flock to the coasts: more than half the U.S. population lives in coastal counties, according to administration officials.

Jerry Howard, president and CEO of the National Association of Home Builders said in a statement that his industry recognizes “the need to prepare for and build more resilient buildings and communities” but new buildings already accommodate concerns over sea level rise.

“As a result, any new initiatives should address improving older homes, structures and infrastructure that are less resilient to flooding and other natural disasters,” Howard said. “Further, any reforms must preserve the strong partnership between state and local governments so that they, not the federal government, retains primary authority over land use decisions.”

While global warming is a contested political issue in Washington, many state and local governments — more than 350 — have already adopted flood standards along the lines of what the Obama administration is now requiring.

Perdido Beach, Ala., a small waterfront community of 581 people, adopted an ordinance in 2010 requiring any new construction be built three feet above the 100-year flood elevation for standard project. The town’s mayor, Patsy Parker, said in an interview that in April the town experienced its worst deluge of rain in a century — 25 inches within two days — which caused major damage.

“It was more severe than any of us in this area, in this county, have seen in our lifetimes,” Parker said, adding there has been no opposition to the stricter requirements. “We know these events are going to come, and we want to be prepared for them.”

Within the D.C. region, two counties–Ocean City, Md. and Stafford County, Va.–already require standard projects be built built three feet above the 100-year flood elevation. Nine counties in Maryland and Virginia demand they be built two feet above that height, and D.C. requires projects are built 1.5 feet above that level.

Building to the stricter federal standards will add between 0.25 percent and 1.25 percent to the cost of construction, senior administration officials said. In the long run the move could save taxpayers money, they said, because it could significantly cut the nation’s recovery costs.

In an interview, Georgetown Climate Center executive director Vicki Arroyo called the new policy “a positive step towards being more prepared for the threat that we’re already facing from rising sea levels and more intense storms.”

“We have to start applying what the science is telling us, and what we’re seeing from recent events, to investment decisions and codes and standards — ideally at all levels of government,” Arroyo said.

The administration has applied future climate impact estimates to rebuilding efforts once before, in the wake of Hurricane Sandy. In that instance, FEMA and the Housing and Urban Development Department developed new elevation standards for New York, New Jersey, Connecticut, Maryland and Rhode Island based on scientific projections, and required any approved projects to meet either those estimates or local elevation requirements if they were tougher.

The new policy does not make changes to the National Flood Insurance Program, which covers Americans in flood-prone areas with federally backed insurance provided they meet federal standards aimed at minimizing risks. But it will apply to grants the program provides, thereby affecting construction in flood-prone areas.