The entire damn city is a low-lying area.
Show of hands: Who lives in Houston Metro?
If you don’t, you don’t know the geography and you don’t know the road system. By the time the Eastern suburbs which got truly hammered, hit downtown, traffic would be stalled for three days and everyone would have drowned in their cars.
And where exactly are we getting the gas for this? We ran out of gas on Thursday night when everyone starting preparing for the storm (which we truly understood on Wednesday).
The choice is not between (1) everyone trying to get out at once and (2) nobody leaving at all. The trick is to stage a controlled evacuation so as to get as many of the most vulnerable out as we can in the remaining time available.