Riddle me this!

I've been looking at this map Maitri made and these FEMA maps.

Jim Carrey as the Riddler

In my neighborhood existing grade elevations are between three and six feet above sea level. We are required to build at least three feet above grade, resulting in a minimum floor elevation of six feet.

Immediately across the street in Gentilly the grade elevation is generally negative one foot and lower. They are required to build 3 feet above grade or one half food below sea level, whichever is higher. That makes the floor elevation a maximum of two feet.

In Lakeview the average grade elevations are negative three to six feet. There people are required to build three feet above grade or two and one half feet below sea level. That results in a floor elevation of negative two and one half feet.

There is no significant difference in the potential flooding from any of the most likely mechanisms for catastrophic flooding, breach of the levees or over topping (which would likely lead to breaches if it were substantial enough).

Frank Gorshin as the Riddler

Does this makes sense?

I wonder who thinks up this stuff?

I realize I have generalized the conditions to illustrate the principle.