That is an excellent point. I seem to remember reports of jams and running out of gas in TX probably from Rita or Wilma or something.
A huge city being evacuated is very touchy. People would probably run out of gas if they were able to fill up in the first place, which probably not because the stations would run out quickly.
I agree with the possibility of ordering evacuation of high-risk sections, generally. Again, weighing the risk of jams and depletion of gas.
In the age of cell phones and the internet, it's almost impossible to orchestrate a limited evacuation or a staged evacuation anymore. As soon as one group of people in a certain area is ordered to evacuate, word spreads like wildfire and you have everyone within 10 miles loading up their cars and hitting the road immediately.
Everyone keeps overlooking the timeline here.
We knew of a tropical storm/depression on Tuesday.
We knew that it had the potential to be serious on Wednesday.
It totally hit the fan on Thursday, and that’s when the stores were stripped of water and the gas stations ran out of gas.
The little tropical strom of Tuesday hit the beach as a damn Category 4 on Friday.
You could not have reasonably ordered an evacuation until Thursday. We would have been out of gas as a region four or five hours later.
Half the Metro Area would be trapped on 10, 45 and 59 five hours after that when accidents started happening and people ran out of gas. Galveston and the rest of the coast would have hit downtown Houston like a tidal wave of cars right in the middle of Thursday rush hour. By the time the people from the Eastern suburbs got home, packed, and hit the road, half a million people not from the Metro area would be bottlenecking the exchanges downtown.
This would last 24 hours at least at which point, the rain would hit, and here is the punchline:
The most dangerous place to be in Houston during a flood is the freaking interstate. Our major highways are catch basins for the heavy rains and they drain into the access roads. And the access roads would be Mad Max at this point. The highways and access roads flood first, because that is their job - to prevent the rain from drowning the neighborhoods.
An evacuation would have 2 million people trapped in their cars in a freaking outdoor bathtub.