However , storm surge remained high at landfall because large waves greater than 30 feet ( 9.1 m ) in height were generated beforehand ( with a buoy recording a 55 ft\/16 .7 m wave at sea ) , when Katrina was at Categories 4 and 5 on the Saffir-Simpson Hurricane Scale .
However , storm surges remained high at landfall because large waves greater than 30 feet ( 9.1 m ) in height were generated beforehand ( with a buoy recording a 55 ft\/16 .7 m wave at sea ) , when Katrina was at Categories 4 and 5 on the Saffir-Simpson Hurricane Scale .