A lesson from New Jersey's rebuilding following Hurricane Sandy has become a key piece of the Obama administration's sweeping plan to prepare the country for the effects of climate change.

The lesson, which is to set a uniform standard for rebuilding flood-damaged or vulnerable properties and infrastructure to new flood heights, is the first of its kind for the federal government and is aimed at reducing the cost of recovery from damage caused by future storms.

Flood and environmental experts, however, fear the height requirement - elevations in the most recent flood maps released, plus 1 foot - is not high enough, because both the speed of sea-level rise and the number of damaging storms are expected to increase.

The financial stakes of this standard, which comes with big political risk, are huge. New Jersey already is allocating $600 million of federal grant money to helping homeowners raise their houses, with more grant money expected to be announced in October.

Setting the elevation standard too low could result in all of that money being wasted. However, some experts say, setting the standard too high could be too costly for homeowners and towns to afford.

New Jersey ranks third among states that have received payments through the National Flood Insurance Program, or NFIP, since 1978. Only Louisiana and Texas rank higher, with New Jersey trailing Texas by about $500 million, or one-seventh of what Sandy flood claims have totaled in the state. New York ranks fourth and Florida ranks fifth, according to the most recent statistics.

One more storm that causes widespread coastal flooding, and New Jersey could top Texas, which long has held the No. 2 position in a competition no state wants to win.

"We can only hope and pray that when all is said and done, we will have used the best science in anticipation of the changes that are likely to occur along our coasts over the next century and beyond," said David Conrad, a flood policy expert who writes for the Brookings Institute and other Washington thinktanks. "If we are always striving to improve the situation but undershoot our marks, we're virtually guaranteeing that the long-term costs will be compounded."

report commissioned by Federal Emergency Management Agency released this month warned that not only will the number of people in flood zones increase dramatically in the coming years, those policies could cost billions in losses under the current NFIP structure.

Assuming the shoreline does not erode, the report, "The Impact of Climate Change and Population Growth on the National Flood Insurance Program Through 2100," said nationally the number of flood insurance policies for coastal areas would more than double, with the cost of the average insurance payouts increasing by 90 percent by 2100. And more than 70 percent of the number of policy increases is due to climate change, not population growth, the report stated.

What this could mean to federal taxpayers is, potentially, an unfunded liability that exceeds that of the Social Security program, Conrad said. Disaster costs borne by the federal government could reach $5.7 trillion in the next 75 years, compared with $4.9 trillion for the projected Social Security shortfall, he said.

Additionally, Conrad said, federal taxpayers are increasingly bearing more of the costs related to disasters. From 1990 to 2005, the federal government paid about 26 percent of the costs related to disaster recovery, including FEMA assistance, grants, repair programs and help to local governments, Conrad said. But since 2005, the federal government has paid on average 70 percent of the costs.

"The frequency of storms that are beginning to challenge and overwhelm (state and local governments') capability is obviously increasing," Conrad said.

And that, Conrad and others say, is due to climate change.

Climate scientists and experts agree that sea-level rise is occurring, but they don't yet agree on how fast, or how high. Sea level in Atlantic City has risen about 15 inches since 1900, or the difference between flooding during a moderate northeaster and the flooding during Hurricane Sandy.

But the rate of rise is expected to accelerate in the coming years. By 2050, sea level at Atlantic City could rise between 13 and 27 inches and, by 2100, could rise between 29 and 69 inches, Rutgers University Climatology Professor Anthony Broccoli has said.

But the standard is based on newly developed elevation data in FEMA flood insurance rate maps. These maps, including the preliminary work maps released June 17, do not calculate what climate change or sea-level rise could do, said spokesman Darrell Habisch.

"FEMA is considering including climate change in its future maps," he said.

The federal government defends the standard's current height requirements, calling it the first step toward making coastal communities better able to withstand future storms, Sandy Rebuilding Task Force spokesman Aaron Jacobs said in a statement. "This critical first step begins to take into account the future risks of climate change. The standard is just one step ... to address future flood risk."

Before the advisory maps released in December, flood maps used in New Jersey were last updated in the 1980s, using data from the 1970s. While maps in some communities were digitized around 2005, they still relied on the old data.

The revisions bring the flood risk that homeowners face up to 2012, not the future, said John Miller, of the New Jersey Floodplain Managers Association.

Incorporating future changes into flood maps and land-use plans is rare, partly because most practices to develop these plans rely on historical data, said Jordan Fischbach, a policy analyst with The RAND Corp., a national-level research and public policy group.

There also can be major tradeoffs when doing so, he said. Rebuilding to the highest level predicted under the most aggressive sea-level rise scenario may keep future damage costs lower in the long term, Fischbach said, "but that could mean much higher costs in terms of mitigation up front, and that's something that needs to be considered."

Still, some governments around the country are beginning to take climate-change preparations seriously in terms of long-term planning. Fischbach was part of a massive team that developed a long-term master plan for Louisiana, where the combination of erosion, low elevation and sinking land means sea-level rise will occur at among the fastest rates on the planet, according to the National Oceanic and Atmospheric Administration.

The plan, which looked at the standards needed to protect houses from flooding, and the types of coastal infrastructure that made physical and financial sense, considered multiple "what if" scenarios. "Although elements were very controversial, it was passed unanimously by the Louisiana state legislature," he said.

Department of Environmental Protection Commissioner Bob Martin said earlier this year that state officials discussed making New Jersey's standard, which has caused significant controversy among coastal residents as they recover from the storm, tougher but felt the elevations in the advisory base flood elevation maps released in December were "aggressive enough."

Jacobs said that as part of the Sandy Rebuilding Task Force work, NOAA and the Army Corps of Engineers earlier this month released a new mapping site to help states, towns and planners use future flood risk information in rebuilding plans. The site is similar to njfloodmapper.org, which was released earlier this year by Rutgers University and Sustainable Jersey.

The Sandy Rebuilding Task Force also will release in August a report on how lessons learned from Sandy can be applied elsewhere in the country. The rebuilding standard will be one of those recommendations, Shaun Donovan, Secretary of the U.S. Department of Housing and Urban Development, said Wednesday in a conference call with reporters.

"Too often in the past, as we've invested in rebuilding, we've gone about it in a way that hasn't protected from the next storm," he said.

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