Answer:
The lowest points in the city of New Orleans can drop to 5 feet below sea level or more. The site of the city was originally very low in relation to sea level, but human interference has caused the city to sink even lower.
When New Orleans was being constructed they ran out of good land. To make more room, engineers drained swamplands around the area so they could continue expansion.
This drainage led to subsidence. Subsidence is sinking or settling to a lower level, in this case it was the earth’s surface sinking lower in relation to sea level. This sinking effect has led to present day New Orleans being, on average, six feet below sea level