Texas plans for evacuation

Chron.com | Statewide hurricane drill to be held Tuesday:

"The three-day drill — being staged statewide for the first time — will test the evacuation response in the first 72 hours before landfall of the worst-case scenario — a Category 5 hurricane.

Numerous improvements are being incorporated into the evacuation plan, including:

•Establishing contraflow lanes more quickly, using shoulder lanes for the first time and preventing Houston-Galveston evacuees from using U.S. 59 north.
•Using the private sector to distribute gas and food.
•Opening shelters as far away as El Paso and Lubbock.
•Providing more efficient assistance to the sick and elderly.
No extra vehicles will be used to clog the freeways to simulate the evacuation exercise."

The evacuation of Houston during Rita was a complete failure. Many just gave up. Or ran out of gas.

Is it really necessary to evacuate the whole city of Houston, after all? Is all of it subject to flooding?