Three different views of the South Louisiana of the future

Three different views of the South Louisiana of the future

(WVUE) - Scientists tell us the coastal Louisiana of the future will look much different.

Read that, much smaller.

The state's coastline, which has already shed about 2,000 square miles since 1932, could lose another 4,000 square miles, according to planners at the Louisiana Coastal Protection and Restoration Authority.

However, that is a worst-case picture in the state's coastal master plan, the so-called "high environmental scenario."

Under the worst-case scenario, in the absence of action, Lakes Borne, Pontchartrain and Maurepas could merge, according to CPRA.

While the plan includes two other scenarios that could be seen as less dire, none of these futures is particularly attractive.

"The no-action alternative is actually not an alternative," said Bren Haase, chief of the CPRA planning and research division.  "It's simply unacceptable."

Planners estimate under the low-environmental scenario - what could be seen as the best case -  Louisiana would lose another 1,200 square miles of coast over the next 50 years unless it acts to fight the problem.

The low sea-level rise scenario is depicted above (CPRA)

The differences depend largely on the future rate of sea level rise.

On average, seas today are rising at a rate of about 3.2 millimeters a year, according to the Intergovernmental Panel on Climate Change, a rate close to double the average global increase from 1901 to 2010.

However, Louisiana's battle with the sea involves more than the politically-charged debate about global warming.  The state's problem is three dimensional.

While deltas naturally sink, geologists say the rate of subsidence along the south Louisiana coast increased dramatically as the Mississippi River was encased in levees and cut off from the marshes and swamps.

That "relative sea level rise" has contributed dramatically to Louisiana's coastal land loss. 
 
A study by the National Oceanic and Atmospheric Administration found Grand Isle, for example, subsides at a rate nine times greater than Key West, Florida.

State planners argue they can fight the rising sea-- to a degree-- by restoring key parts of the coast.

The plan includes a suite of projects: dredging to build barriers and marsh instantly; various shoreline protection measures; man-made structures; and sediment diversion projects to feed river water and mud into bays in an attempt to build land.

The low, medium and high scenarios for future land loss barring action, as depicted in the Louisiana Coastal Master Plan (CPRA)

The CPRA asserts that natural and man-made defenses included in the Coastal Master Plan would prevent $150 billion dollars in flood damage over the next half century along the coast.

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