And if he said "evacuate" and six million people tried to hit the road? How much trouble would that have caused?
He’s supposed to have a plan for evacuating six million people on short notice.
Of late, Houston mayor’s term is 4 years, with a limit of 2 terms. That means that a reasonably optimistic mayor will serve 8 years - and that means there’s a nontrivial 8% chance that a “once in a century” disaster will occur during his term, and a “once a decade” crisis will most likely happen at least once. With those odds in place, and the sociopolitical consequences of being unable to handle major problems, you’d think he’d make a high priority of preparing for likely crises (like those associated with being at the end of a major hurricane zone).
So yeah, I do expect there be a plan for vacating millions of people in short order, or encouraging viable “shelter in place” preparations & servicing those who can’t. And certainly there should be plans for much of the city being underwater when the whole place isn’t far above it (just 80’ above sea level).