lived in New Orleans for a few years. first apartment was 11 feet below sea level - it flooded a few times. 2nd apartment was still below sea level but was on a raised foundation - hurricane (a few before Katrina) smashed a giant oak tree into the house. 3rd apartment was closer to the downtown area (ground was less reclaimed swampland and more solid) - still below sea level but not near trees. nice place, was there for a year then I gtfo before Katrina hit.
most of Louisiana is a floodplain, most of it does not have a very high elevation. most of the cities around Lake Pontchartrain are either at or below sea level - Slidell is relatively mountainous with an average elevation of 13 feet (which means basically nothing when a hurricane rips through). everyone that lives there (near Lake P) is familiar with flooding and is not under any assumptions that they are not living in a flood prone area.