Louisiana faces billions in storm damage with no new coastal projects, officials warn | Environment

Louisiana could see more than $ 31 billion annually in storm damage based on worst sea level rise predictions if it does not adopt new plans for its 2023 Coastal Master Plan, officials warned Thursday. state.

The warning came when the State Coastal Protection and Restoration Authority held an online hearing on updating its master plan, which outlines the state’s strategy to combat land loss.

And even if the state adds the more than 130 projects considered for inclusion in the master plan, the Louisiana coast remains on track for continued dramatic land loss.

The state has lost more than 2,000 square miles of its coastline since the early 20th century. That loss is due to a number of human-induced factors, including the banks of the Mississippi River preventing sediments from reaching wetlands and the dredging of thousands of miles of navigation and oil and gas exploration channels. Other causes include invasive coypu that feeds on vegetation helping to hold the swamp together.

These maps and charts show the potential loss of coastal land without further project approval as part of the 2023 update. The increased land loss is the result of higher sea level rise rates fueled by global warming a 50 years. (Authority for the protection and restoration of coasts)

Another 2,000 square miles could be lost over the next 50 years, said Stuart Brown, who is overseeing the rewrite of the plan on behalf of the authority. Much of this loss could occur if a worldwide failure to reduce greenhouse gases results in a sea level rise of about 2.3 feet. A lower level estimate used in the plan predicts 1.3 feet of sea level rise by 2073.

The master plan, first unanimously approved by the Louisiana legislature in 2007, provides the state with a $ 50 billion ongoing 50-year agenda, using the latest information on land loss, leveling of the sea, the trend of the coastal population and other factors. The plan is now updated every 6 years.

The 131 projects currently under consideration for addition to the plan include 113 for the restoration of wetlands or other land features along the coast, as well as 18 structural projects such as levees and gates that will reduce the risk of flooding from hurricane storm surges. The state is also evaluating a number of “non-structural” risk reduction projects – elevating homes, flood proofing or buying homes in flood prone areas – in more than 300 coastal communities, Brown said.

300 communities

The 2023 update is examining potential projects for effects on more than 300 local communities. (Authority for the protection and restoration of coasts)

These projects are developed from proposals submitted to the authority by local governments, individuals and authority staff since October 2018. Five regional working groups of state and local officials have developed and refined individual projects since 2018.

The state uses a suite of computer models to study and compare individual projects based on their effectiveness and cost, then the projects are re-modeled in groups to determine which ones work well with each other.

A final list of projects will be presented at eight in-person community roundtables along the coast in November, while a final draft will be the subject of public hearings in New Orleans, Houma, Baton Rouge and Lake Charles in January. The coastal authority council will vote on a final version of the plan in March before submitting it to lawmakers in April.

Flood depth in 2023

This map shows the potential floods from storm surges in 2023 for a low sea level rise scenario. (Authority for the protection and restoration of coasts)

As part of the plan’s rewrite process, scientists have updated models showing how global warming-enhanced hurricanes will affect the coast over the next 50 years. There is also a risk model to determine both the overall costs of damage caused by surges and wetland losses, and separate accounting of damage to the facility that is not weighted by construction costs, in an effort to ensure that the selections are correct. at low. income and other smaller communities, Brown said.

The authority has developed a number of predictions of what will happen without the construction of new projects. That modeling produced chilling estimates of both the potential for land loss and damage to communities.

Damage calculation.jpg

Officials are estimating the total damages, based on the actual value of the assets, and also the damages based on the type of facilities alone, in an effort to provide more equity to low-income and smaller communities in their choice of projects. (Authority for the protection and restoration of coasts)

A list of the top 10 damages after 50 years, assuming no action is taken, indicates that the Slidell-Eden Isles-Pearl River communities would be the hardest hit in 2073. The models show an estimated $ 845 million a year. possible damage there from the effects of the storm caused by a hurricane with a 1% chance of occurring in any year, a so-called 100-year storm.

The first 10 damage

This list shows the potential damage caused by storm surges without the approval of further restoration projects and levees in the Master Plan 2023 update. However, if projects are built, even while they are under construction, a significant level of damage could still occur. additional. Modeling of these totals can be released when the final plan is completed.

Even using a scenario of lower sea level rise, the 100-year heights in the Slidell area are estimated to be between 16 and 20 feet. The higher sea level scenario predicts water levels in parts of the Slidell area above 21 feet.

On Thursday, the authority was unable to provide a detailed list of coastal restoration projects, beyond a map identifying the types of projects and where they would be located.

Map of the candidate project

This map shows the candidate projects along the coast, with symbols showing which type of project. (Authority for the protection and restoration of coasts)

The structural protection projects under consideration include:

  • Ring embankments for Slidell, already considered by the Army Engineers as part of a separate study.
  • A plan to raise levees in the greater New Orleans area. State and local levee officials urged the Corps to consider raising the levels to protect itself from a surge of at least 200 years in the future. The Corps has already been authorized to spend $ 3 billion over the next 50 years to maintain the levee system at current 100-year levels.
  • A “Lake Pontchartrain Barrier” project, which would add storm protection to the Rigolets and Chef Menteur passes, reducing the height of storm surges in the lake.
  • Additional storm protection in St. James and Ascension parishes.
  • Several improvements to hurricane embankments along the Mississippi River in Plaquemines Parish.
  • Additional protection of the ring embankment for Lafitte. The area has already been funded for the lower embankments for flood protection at high tide as part of the upgrade to the existing plan.
  • Upgrades for the Larose in Golden Meadow and Morganza to the Gulf levee systems in the parishes of Lafourche and Terrebonne.
  • A New Iberia / St. Embankment of the Mary Parish Plateau.

Sea level projections

This graph shows different sea level estimates projected over 50 years, depending on the success of efforts to reduce greenhouse gases. The state’s lowest estimate is the solid blue line, around 1.3 feet, while its highest estimate is the dashed blue line, around 2.3 feet. (Authority for the protection and restoration of coasts)

CORRECTION: Previous versions of this story provided an incorrect location for one of the public hearings planned on the final draft of the master plan and an incorrect sea level elevation for a worst-case scenario of sea level rise.

This work is supported by a grant funded by the Walton Family Foundation and administered by the Society of Environmental Journalists.


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