Flooding

As Charleston looks to update its Century V City Plan, rising sea levels, flooding and traffic loom as major concerns. Above, Morrison Drive during a recent high tide. Grace Beahm/Staff/File

By ORRIN H. PILKEY

Rising seas are the first truly global environmental disaster related to climate change. Millions of people will be forced from their homes as the seas drown the atoll nations, devastate much of barrier-island and river-delta civilizations and, of course, invade the world’s coastal cities including Charleston.

The general consensus among scientists is that a threefeet rise in sea level should be anticipated by 2100. But recent projections suggest a possible rise of five or six feet.

The Thwaites Glacier of West Antarctica illustrates the uncertainties of prediction. It is thinning more rapidly than originally expected, which could lead to massive sea level rise starting in this century. The potential volume of water in this single (two-mile thick) glacier system could raise the world’s sea levels by 11 feet! Another uncertainty involves how much greenhouse gas will be contributed by the accelerating melting of permafrost in polar regions. These gases released from melting permafrost will in turn lead to further warming and further melting of ice.

Two cities on the U.S. East Coast lead the way in preparing and planning for sea level rise. These are Charleston and Norfolk, Virginia. Last year, Charleston adopted a sea level rise strategy that assumes a 2.5 feet rise over the coming 50 years.

In addition, and very importantly, the plan requires keeping track of the evolving sea level rise projections and changing the plan accordingly as predicted sea levels change.

Charleston is doing the right thing. Authors of a recent article in Science magazine wrote that preparation for sea level rise should take the long view because planning, financing, building of political consensus and taking action will take years.

The authors also warned that if we defend against the maximum sea level rise the cost will be high, but if we ignore such projections the result could be disastrous.

For Charleston, responding to sea level rise will not be an easy task. A huge variety of shoreline types with widely varying exposure to waves, storm surges and tides constitute the seaward edges of the city.

Because the entire Charleston area is flat and at low elevation, it already has a flooding problem. Sea level rise will only exacerbate it.

Different solutions to the flooding problem will be needed in differing parts of the city.

When Charleston is in real trouble with a big sea level rise, the city will be competing for funding with such major municipalities as New York, Boston, Miami, St. Petersburg and San Francisco. The competition for support will be intense. So, taking “early” action to defend against a future rise before other cities start clambering for money makes sense.

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Today, storm water drainage project tunnels, some still under construction, are providing significant relief from nuisance flooding, especially in downtown Charleston, and will continue to do so in coming decades. As the water rises, downtown development may eventually have to be protected by a surrounding seawall, a costly prospect.

A variety of other options may someday be pursued in some parts of the city including moving, raising or abandoning buildings and allowing some streets and parks to be flooded. There are many details to be considered, such as maintaining safe hurricane escape routes and raising port facilities (a worldwide threat to commerce since all ocean ports are at the same low elevation).

The good news is that Charleston is stepping up to the challenge of responding to sea-level rise.

One step in this effort is Awakening V: King Tide, a month-long series of public art and events bringing scientists and artists together to shine a light on rising tides and flooding streets. You can learn more about Awakening at: www.enoughpie.org.

Orrin H. Pilkey is the James B. Duke Professor Emeritus of Geology at Duke University’s Nicholas School of the Environment.

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