They usually get added to over time.
|Animated map showing chronology of the L-28 Jetport Levee and Canal|
Here's a look a the chronology of the L-28.
Notice how big the Jetport was supposed to be (i.e. 39 square miles).
It set off an environmental movement that led to the formation of Big Cypress National Preserve in 1974 and, in the process, made the levee obsolete over night. Fifty years later the levee that levee remains intact. A new study is underway to figure out to what degree we can modify it to put it more in tune with Everglades Restoration goals.