How did Hurricaine Katrina effect the landforms of the gulf coast?

Answer 1

Many of the barrier islands that lay off the coast of Mississippi/Louisiana were washed away. Most of the wetlands in Mississippi have been restored to their pre-Katrina borders naturally.

Can't tell you about Louisiana Marshlands since they are so messed up before Katrina.

This link contains a fascinating explanation of what is happening to South Louisiana due to the USCOE, and mismanagement of the Mississippi River Basin:

http://www.nola.com/speced/lastchance/multimedia/flash.ssf?flashlandloss1.swf