However , the worst property damage was in coastal areas of Louisiana , Mississippi and Alabama , such as all Mississippi beachfront towns , which were flooded over 90 % in hours , as boats and casino barges rammed buildings , pushing cars and houses inland , with waters reaching 6 â `` 12 miles ( 10 â `` 19 km ) from the beach . However , the worst property damage occurred in coastal areas , such as all Mississippi beachfront towns , which were flooded over 90 % in hours , as boats and casino barges rammed buildings , pushing cars and houses inland , with waters reaching 6 â `` 12 miles ( 10 â `` 19 km ) from the beach .