Actually, Camille did knock out a modern bridge over the back bay of Biloxi. The center span at the highest point on the bridge, a modern concrete bridge, was lifted out of position, rotated about 45 degrees and set back down into the opening. A pedestrian might have been able to climb carefully onto the resultant skewed section but it was so precarious that if he strayed from the center of balance, both he and the center span would have gone down into the water. It was considerable time before that bridge, the only one on US-90 across the back bay was repaired. The old, rickety wooden bridge that had been decommissioned a few years earlier, survived as it was completely covered by storm surge and covered during the highest wind and wave action....unfortunately, they had removed the center section when the new bridge was built and the two ends left in place as 'fishing piers'.

The damage very much reminds me of CAT-V storm surge and wave damage like that of Camille. Ivan probably was still carrying water and waves from when shortly before he had been CAT-V for quite some time. That much energy doesn't dissapate quickly even if the winds died down some before landfall. Energy stored in the greater mass of water won't change as fast as in the lower density mass of air.