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Coastal risk: Corps of Engineers releases planning guide for future storms, flooding

By C. Todd Lopez

WASHINGTON (Jan. 28, 2015) -- The U.S. Army Corps of Engineers, or COE, released a study, Jan. 28, that frames future risks from rising oceans and increasing weather patterns along the areas affected by 2012's Hurricane Sandy.

The "North Atlantic Coast Comprehensive Study," commissioned by Congress in 2013, looks at the risk along 31,000 miles of Atlantic Ocean shoreline from North Carolina to New Hampshire.

Joseph R. Vietri, with the U.S. Army Corps of Engineers, said the United States was hit "very badly" by Hurricane Sandy, and said the storm was not the first to affect the East Coast of the United States in such a fashion -- nor would it be the last.

"In the last 100 years ... every 20 to 30 years we've had a fairly significant storm that has pretty much created havoc along the coastal communities," he said. "That includes not only civilian communities, but also Department of Defense communities."

At risk from such storms along the East Coast is a significant amount of national infrastructure, including the U.S. Atlantic Fleet in Norfolk, Virginia, Vietri said.

"The idea behind the comprehensive study, at least the congressional intent behind it, was that the Corps of Engineers, working with a large number of partners -- state and federal and local -- would identify vulnerable areas, and come up with a framework on how to address those vulnerabilities into the future," Vietri said. "Understanding the effects of climate change and sea-level rise is paramount to that."

Vietri said the Corps developed new tools to look at how storms affected coastlines, and how projected increases in sea level would change the way those storms acted on coastal communities and infrastructure.

"I think it was the largest use of Army supercomputers by any civil works activity ever," he said. "A tremendous amount of time was spent burning up supercomputer hours and trying to analyze all this data and develop these storm models that are critical to not only what happened but what will happen into the future."

Vietri said one conclusion drawn in the study is that several large areas along the East Coast did not have adequate protection from Hurricane Sandy or potential future storms. Included among those areas were Washington, D.C., New York City, Baltimore and Norfolk, for instance. He said the study calls for further, more detailed analysis of such highly developed areas.

He cited one hypothetical example from the study involving the New York City area, which he said has seen a 12-inch increase in sea level over the past 100 years.

"If you look at the high end of that curve spectrum, into the future, based upon some of the information that has come out though a lot of the work done on the international scene, you realize a change as high as two meters -- almost six feet in 100 years, could occur," he said.

Regardless of whether additional sea-rise estimates fall at the low end -- 12 more inches -- or the high end -- 6 feet -- the results will still be disastrous, he said.

"A lot of barrier island areas that are only 10 feet above sea level would be really catastrophic," he said.

Vietri said that it would be inappropriate to just assume the worst-case scenario, however.

"That would over-exaggerate what the potential damages are, and by extension potentially exaggerate what solutions might be needed," he said. But at the same time, "If you take the lowest, you could really underestimate it."

The U.S. Army Corps of Engineers' Roselle E. Henn said the 31,000 miles of shoreline that was studied includes not just oceanic shoreline, but also estuaries, and river inlets, for example -- anything that would be affected by rising flood water. The study broke that area down into multiple "reaches," or areas of beach and shore that she said were 'hydraulically separate" from one another.

"We looked at risk of flood in those areas as well as the exposure of the populations; exposure by population density, infrastructure density, and vulnerability by socio-economic factors that might make it difficult to respond to an emergency situation and flooding, as well as the vulnerability of environmental resources and cultural resources like monuments and historic locations," Henn said.

The team responsible for the study also looked at possible measures that could be used to manage the risks they assessed as part of the study, including those tools owned by the Corps.

"We looked at the traditional COE portfolio, which includes levies and breakwaters and shoreline stabilization techniques," she said. "But we also took a broad look at non-structural measures, like flood-proofing, acquisition, relocation and flood warning."

The team also factored into their risk calculations the natural protections, such as salt marshes, and also things that could be engineered to mimic such natural protections.

"Using that full array of measures, we then began to screen and aggregate them as a system, to link them together, not looking for measure alone to reduce the risk in an vulnerable area, but to see how different combinations of measures provided different levels of risk management," she said.

While the study "stopped short" of providing solutions or making recommendations -- something Henn said was outside their congressional mandate -- it does provide the information smaller jurisdictions can use to manage their own risk.

"We provided this framework as a methodology that regional partners can use at smaller scale," she said. "They can take it all the way down to the end point which is to evaluate and compare solutions ... to plan, implement plans, and then monitor and adapt. The point is this framework, what we put together, is not a COE-only document. We hope it provides a common basis for thinking about coastal risk across the region."

One of the major conclusions of the report, Vietri said, is that there is a shared responsibility for risk assessment and planning that ranges from homeowners all the way up to the federal government.

"The federal government, the Army Corps of Engineers, or any governmental body by itself is not the sole party responsible for managing or mitigating these increased risks," he said. "It starts with the local homeowner, carries into the local village or the person who has land-use controls in these vulnerable areas. It goes to the DoD on a facility on how you might look at that facility in the future, and what changes you might have to make to that facility ... so the mission of that facility is not compromised."

Partners in the study included the U.S. Army Corps of Engineers, Housing and Urban Development, the Federal Emergency Management Agency, the Department of the Interior, or DOI, and agencies within the DOI such as Fish and Wildlife Service and U.S. Geological Survey, as well as the National Oceanic and Atmospheric Administration.

Henn said partners also included state-level governments, regional groups, and tribal officials, as well as metropolitan governments in impacted areas.

Henn and Vietri said they hope the study will be used by all levels of government to improve decision making on storm preparation in the future, taking into account both possible storms and rising oceans due to climate change.