NEW ORLEANS (WVUE) - It has become almost cliche to say Louisiana's coast loses a football field an hour.
In fact, the rate may be less than that. However, planners caution in the long term the rates are likely to rise again.
Geologist Chris McLindon believes there is confusion about the current rate of land loss stemming from a U.S. Geological Survey study released in 2010.
"What it actually said was from a period of 1985 to 2010, the rate was equivalent to a football field an hour," McLindon said. "But the rate was dropping the entire time."
The USGS released color-coded maps that depicted land loss since 1932, with the various colors representing the period of time when specific areas of the coast went under water. McLindon points out much of the loss occurred in the 1970s in subsidence hot spots.
"We may have years of net gain and then years of net loss, and we may be in a period of relative stability," McLindon said.
State planners point out that land loss rates are variable.
"While we may have lost a football field last hour, this hour we might not," said Bren Haase, assistant administrator of the Coastal Protection and Restoration Authority. "If you look at the trend over the long term, it averages out to be that amount."
Hurricanes Katrina and Rita, which devoured a couple hundred square miles of land, show that years of stability can be wiped out in a matter of hours. Since the state coastal master plan in 2012, scientists say predictions for sea level rise have worsened. Although the science behind climate change predictions remains a political controversy, state and federal planners factor those predictions in to the planning of coastal projects.
The CPRA is working with three different scenarios for sea level rise over the next 50 years: a best case scenario of 1.4 feet; a medium scenario of 2.07 feet and a worst case prediction of 2.7 feet.
That does not factor in the additional effect of subsidence, which means a higher rate of "relative" sea level rise.
"Wetlands can generally keep up with sea level rise to an extent," said Karim Belhadjali, CPRA deputy chief. "What we're trying to figure out is where that extent occurs."
State planners are trying to decide which of the proposed coastal projects can withstand a rising sea.
"It's how well it either builds or maintains land over a period of time in the face of that environmental scenario," Belhadjali said.
Building more robust restoration projects may help mitigate the effects of a rising sea. However, the new scenarios mean the state may have difficulty reaching its goal of no net loss of wetlands.