MASSIVE STORM surges destroyed large sections of two major highway bridges when Hurricane Katrina struck the Gulf coast last week.
Both were low lying structures built just above normal high water levels and were similar to the 4.6km Pensacola Bridge, which was severely damaged by Hurricane Ivan last year (NCE 23 September 2004).
The 11km Interstate 10 bridge spanning Lake Pontchartrain near New Orleans lost more than a third of its deck to the storm surge which lifted deck sections off pier supports.
And at Biloxi the Highway 90 crossing of Lake St Louis lost more than 50 spans, again to a storm surge.
Both structures are multi span viaducts made up of concrete deck sections bolted on to cross beams, supported by piers.
As NCE went to press most of the highway networks in Louisiana and neighbouring Mississippi and Alabama had reopend. The exceptions were Interstate 10 and Highway 90.
A low lying 60km section of Highway 90 hugging the coast west of Biloxi was also shut.