Environment
 

Scientists say Louisiana’s latest projections for coastal flooding are grim, but realistic

Many Louisianans may have been shocked by grimmer forecasts in the latest edition of the state’s 50-year plan to protect its coast: There is no longer hope that more land can be built than the Gulf takes each year. Even if the plan works perfectly, the state could lose another 2,800 square miles, and 26,000 homes and other buildings may have to be elevated, flood-proofed or bought out.

And all this could happen even if the plan achieves its goals.

But some scientists who have followed the effort for years see these changes as good news. They believe the state Coastal Protection and Restoration Authority has long underestimated the rate of sea level rise.

The worst-case scenario for human-caused sea level rise in the 2012 Coastal Master Plan, 1.48 feet, has become the best-case scenario in the 2017 edition. In fact, the National Climate Assessment now estimates sea levels on U.S. coastlines could rise 4 feet by 2100.

Torbjörn Törnqvist, chairman of the Department of Earth and Environmental Sciences at Tulane University, admitted the changes “are not very uplifting,” but he welcomes them.

“Many of us in the scientific community have recognized for quite some time that the idea of reaching a ‘net gain’ situation in the future (in terms of land building) is entirely unrealistic,” he said in an email. “The best we can do is reduce the rate of loss.”

The state coastal authority, he said, “should be commended for fully embracing climate and sea-level scenarios. This is a significant update, well beyond cosmetic.”

Erika Spanger-Siegfried, senior climate analyst at the Union of Concerned Scientists, said the plan “is just way out ahead of other states in terms of the stark nature of the changes outlined to which it is trying to adapt.”

“Louisiana has the misfortune of leading the nation out there on the front line of sea level rise,” she said in an email. “And the struggle is real: no one — not even Florida — has faced the extent and pace of land loss unfolding here.”

Praise also came from Donald Boesch, president of the University of Maryland Center for Environmental Science, who said Louisiana should be lauded “particularly when some state governments, such as Wisconsin, are expunging any mention of this reality from their websites and reports.”

Boesch, a New Orleans native, once headed the Louisiana Universities Marine Consortium and is a leading authority on coastal ecosystems.

He also saw room for improvement in the coastal plan. He thinks the state’s best-case scenario of sea-level rise, about 1.5 feet, is too optimistic.

And he believes the plan should outline why the climate is warming. In order to avoid cataclysmic levels of sea-level rise and coastal erosion, the state and the world must reduce carbon emissions, he said.

“If we do that,” he said by email, “the science says that we have a good chance of avoiding the collapse of polar ice sheets and not having to deal with the worst-case, high scenario of the Master Plan.”

Residents of the North Shore of Lake Pontchartrain, long considered less vulnerable to the coastal crisis than New Orleans due to its elevation, received some of the most alarming news in the 2017 edition of the plan.

The Master Plan say future flooding may require 5,900 homes and other buildings to be elevated, flood-proofed or — in about 900 cases —bought out. That’s under the worst-case scenario for sea-level rise and would be true even if the plan achieves all of its goals.

The plan includes projects to reduce flooding on the North Shore. A U-shaped levee would be built around Slidell. Storm surge would be limited by 2-foot-high flood gates on the Chef Menteur and Rigolets passes between Lake Pontchartrain and Lake Borgne.

St. Tammany officials, while happy with those projects, said residents should take the projections in the plan as a call to action.

“If you don’t have insurance, get it, especially if you live below I-12,” said Gina Campo, chief administrative officer of St. Tammany Parish. “If you are in an area that has flooded in the past or is in a zone that now can expect flooding, there are programs you can take advantage of to address those concerns. Contact us immediately.”

Mandeville Mayor Donald Villere said his community, which has suffered flooding from storms such as hurricanes Isaac and Ike, is already preparing for the risks made clear in the new plan.

He hopes Congress will fund a proposal by the U.S. Army Corps of Engineers to elevate homes that are in flood-prone areas — anything below 7.5 feet above sea level.

“We’re a small city, so raising homes is more affordable than building levees or floodwalls,” he said.

But he said the future of his lakefront community will depend on solutions not yet found.

“We have been keeping an eye on other communities like Miami and Miami Beach that are raising streets and walkways,” he said. “I believe that breakthroughs in technology and new products will become available before we get to that stage.”

Public forums on the 2017 Coastal Master Plan

Jan. 18, New Orleans: Port of New Orleans Auditorium, 1350 Port of New Orleans Place
Jan. 25: Mandeville: David C. Treen Instructional Technology Center,‪ 2024 Livingston St.
An open house will held at 3:30 p.m. and the the meetings will start at 5:30 p.m.

Read the Master Plan

You can view the entire draft of the 2017 plan online.
Help us report this story     Report an error    
The Lens' donors and partners may be mentioned or have a stake in the stories we cover.