What major landforms define and restrict New Orleans?

Answer 1

The Mississippi River is the major defining point of New Orleans. The geography of New Orleans is all dependent on the river. The East Bank of New Orleans is actually to the West, but it's called the East Bank because it's East of the river. I know that this is confusing, but that's just how the city was broken up.

The reason that New Orleans is sinking is that the river has been essentially blocked by the levees. While the levees are supposed to protect New Orleans, they have actually done more damage. Without the overflow of silt from the river, the wetlands have shrunk. These barriers no longer flow way out into the Gulf of Mexico. The wetlands would extend out and, since a hurricane would be moving onto land, it would decrease the intensity of a storm. Without these "barrier islands", hurricanes come on shore with their strength intact, increasing the chances of a deadly storm.

Without the levees, the Mississippi River would have probably long ago merged with the Atchafalaya River, making New Orleans no longer a port city.