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A Barrier Could Substantially Reduce Damage in Southeastern Louisiana

• A Lake Pontchartrain barrier could provide substantial damage reduction benefits for southeastern Louisiana, with median expected annual damage reduction benefits ranging from $1.2 billion to $1.4 billion per year.
• A barrier could also lower future design height requirements for the Greater New Orleans hurricane protection system along the south shore of Lake Pontchartrain, although it could also increase design heights for the eastern face of the system or otherwise necessitate additional levee armoring in other locations.

A Barrier Could Somewhat Increase Damage Along the Mississippi Gulf Coast

• All barrier alignments considered increased flood damage in coastal Mississippi compared with a future without action but at a level several orders of magnitude lower than the damage reduction benefits estimated for southeastern Louisiana.
• Damage inducement was typically low for the best-performing alignment options compared with total flood damage risk for the three Mississippi coastal counties, with total damage increases ranging from 1 to 2 percent.

Overall, a Low Barrier Provides the Best Balance of Benefits and Induced Damage

• A barrier option that includes Highway 90 with its current crown and 2-ft. gates yields median expected annual damage reduction of $1.2 billion, nearly as high as alignments with higher crowns and higher gates.
• The low barrier also yields the least induced damage for coastal Mississippi, approximately $22 million in total across all three counties (1-percent increase).