“When one includes the anticipated costs of the Urban Water Plan, federal flood protection, and other factors excluded from the 2012 Master Plan, the cost of restoring this coast and protecting its people can be expected to exceed $100 billion over 50 years.”
A related report, Ryan, Tim. The Economic Impact of Coastal Restoration and Hurricane Protection (March 2014), points out that even the report admits that it will really take more:
“The Master Plan calls for an investment of a minimum of $50.00 billion on coastal restoration and hurricane protection over the next 50 years. This level of expenditure slows but does not stop or reverse land loss. The Master Plan recommends $100.00 billion as the optimal level, which will yield a net gain of land.”
Thus, under the rational of the first report, the realistic estimate is $200B. This does not include the known problem of agencies significantly underestimating the cost of civil engineering projects, knowing that once the project is started, the public will be unwilling to abandon it and lose the value of the sunk costs.
Craig Bond, et.al, Economic Evaluation of Coastal Land Loss in Louisiana (2015)
This paper attempts to analyze the economic costs of land loss and potential hurricane damage. The problem is that irrespective of the costs, there is no clear way to avoid the loss.