That was standard operating procedure. Once Gretna was evacuated, the bridges were to be shut down because they would be unsafe for travel durring a hurricane. Then after the hurricane were to be closed to foot traffic until they could be inspected to see if they could hold thousands of people stampeding across them.
Stampeding? Nice "Wild Kingdom" imagery there.
That bridge could hold pedestrian traffic fine as long as they didn't march in lockstep.
Look at the story SJackson just posted in 894. Do you really believe SOP--or anything you've said above--justified halting 200 elderly and injured people who made it to the peak of the bridge?
Also, the bridge was closed to white people as well as black, but everyone involved knew that the VAST majority of those who had stayed behind in NOLA were black.