A misuse of economic impact analysis to argue for beach nourishment

From the Future of the NC Coast (written by my former boss [chancellor] at UNCW):

Carolina Beach, Figure Eight, Kure Beach, Masonboro Beach and Wrightsville Beach — generates $3.9 billion a year in recreational expenditures. During the past 10 years, those beaches have been renourished 23 times at a total cost of $6.8 million. In other words, for every million dollars expended in beach renourishment there has been a return of $49 million in expenditures. This does not definitively resolve the debate about beach renourishment because, among other things, there isn’t an unlimited amount of sand in some regions. But it does give us a cost to benefit ratio.

The ratio 49:1 is grossly overestimated. Economic impacts (i.e., regional GDP) ignore substitutes. If the beaches went away the recreation dollars would go to some other vacation area (e.g., the mountains). Therefore, attributing all of the recreation dollars spent in beach towns to renourishment overstates the impact.

P.S. Figure Eight is a gated community. Riff raff aren't allowed on to the island. Masonboro beach is an undeveloped island that doesn't need nourishment. It sees odd that these two are included in the beach list above.

P.S.S. Another way to think about it from a distributional perspective is this: Mountain folk are robbed two ways. We pay to renourish beaches and protect houses built on sand which reallocates tourist dollars from the mountains to the coast.