Must We Abandon the Marshes to Save New Orleans?

A new study of the marshes around New Orleans suggests that the best way to save New Orleans from the "next Katrina" is to abandon the outer marshes, and focus on saving those closer to the city:

Mississippi River Mouth Must Be Abandoned to Save New Orleans from Next Hurricane Katrina

Extensive studies done after Katrina verified what lifelong residents of southeastern Louisiana already knew: Unless the rapidly disappearing wetlands are made healthy again, restoring the natural defense, New Orleans will soon lay naked against the sea (see satellite image, below).

So, how does one reengineer the entire Mississippi River delta—one of the largest in the world—on which New Orleans lies?

Three international engineering and design teams have reached a startling answer: leave the mouth of the Mississippi River to die. Let the badly failing wetlands there completely wither away, becoming open water, so that the upper parts of the delta closer to the city can be saved. The teams, winners of the Changing Course Design Competition, revealed their detailed plans on August 20. Graphics from each plan are below. . . 

 The river should be cut off (north of the number 5) to better
 save wetlands closer to the city (red “Sustainable” line), and the rest
must be left to wither away, becoming open water (brown “Historic” line).

The modern Mississippi Delta passed its "use by" date many years ago. The river wants to take a shortcut down the Atchafalaya waterway (6 on the map), and bypass the old crows foot delta, thereby robbing the delta of it's sediment source, and dooming New Orleans to becoming a sinking bywater.  The switching of the river has happened many times over in geologic history. The only reason to prevent it is because of New Orlean's importance as a seaport. This may well be another example of the "sunk costs fallacy."